(ASTM)Significance of Tests and Properties of Concrete and Concrete-Making Materials

Significance of Tests and Properties of Concrete and Concrete-Making Materials STP 169D Joseph F. Lamond and James H. Pielert, Editors ASTM Stock No.: STP169D ASTM International 100 Barr Harbor Drive PO Box C-700 West Conshohocken, PA 19428-2959 Printed in the U.S.A. Copyright © 2006 ASTM International, West Conshohocken, PA. All rights reserved. This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher. Photocopy Rights Authorization to photocopy items for internal, personal, or educational classroom use, or the internal, personal, or educational classroom use of specific clients, is granted by ASTM International (ASTM) provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; Tel: 978-750-8400; online: http://www.copyright.com/. NOTE: The Society is not responsible, as a body, for the statements and opinions expressed in this publication. Printed in Bridgeport, NJ April 2006 Foreword THIS PUBLICATION is a revision and expansion of Significance of Tests and Properties of Concrete and Concrete-Making Materials (STP 169C) published in 1994. That publication in turn replaced editions published in 1956, 1966, and 1978. The present publication includes a number of new materials and test methods that have been developed, or materials that have increased in importance since the 1994 edition. Two most useful additions are the chapters on slag as a cementitious material and self-consolidating concrete. As in the previous editions, chapters have been authored by individuals selected on the basis of their knowledge of their subject areas, and in most cases because of their participation in the development of pertinent specifications and test methods by ASTM Committee C09 on Concrete and Concrete Aggregates and, in some cases, ASTM Committee C01 on Cement. The authors developed their chapters in conformance with general guidelines only. Each chapter has been reviewed and, where necessary, coordinated with chapters in which overlap of subject matter might occur. This latest edition has been developed under the direction of the Executive Committee of ASTM Committee C09 by coeditors Joseph F. Lamond, Consulting Engineer, and James H. Pielert, Consultant, both members of Committee C09. Contents Chapter 1: Introduction—JOSEPH F. LAMOND AND JAMES H. PIELERT ..................................1 PART I GENERAL Chapter 2: The Nature of Concrete—RICHARD A. HELMUTH AND RACHEL J. DETWILER ......5 Chapter 3: Techniques, Procedures, and Practices of Sampling of Concrete and Concrete Making Materials—TOY S. POOLE ...........................................16 Chapter 4: Statistical Considerations in Sampling and Testing— GARLAND W. STEELE ................................................................................................22 Chapter 5: Uniformity of Concrete-Making Materials—ANTHONY E. FIORATO .......30 Chapter 6: Virtual Testing of Cement and Concrete—DALE P. BENTZ, EDWARD J. GARBOCZI, JEFFREY W. BULLARD, CHIARA FERRARIS, NICOS MARTYS, AND PAUL E. STUTZMAN ...........................................................................................38 Chapter 7: Quality Cement, Concrete, and Aggregates—The Role of Testing Laboratories—JAMES H. PIELERT .....................................................51 PART II FRESHLY MIXED CONCRETE Chapter 8: Factors Influencing Concrete Workability—D. GENE DANIEL ...............59 Chapter 9: Air Content, Temperature, Density (Unit Weight), and Yield—LAWRENCE R. ROBERTS ................................................................................73 Chapter 10: Making and Curing Concrete Specimens—JOSEPH F. LAMOND ...........80 Chapter 11: Time of Setting—BRUCE J. CHRISTENSEN .....................................................86 Chapter 12: Bleed Water—STEVEN H. KOSMATKA ...........................................................99 PART III HARDENED CONCRETE Chapter 13: Concrete Strength Testing—CELIK OZYILDIRIM AND NICHOLAS J. CARINO........................................................................................125 Chapter 14: Prediction of Potential Concrete Strength at Later Ages— NICHOLAS J. CARINO ..............................................................................................141 Chapter 15: Freezing and Thawing—CHARLES K. NMAI ............................................154 Chapter 16: Corrosion of Reinforcing Steel—NEAL S. BERKE .................................164 Chapter 17: Embedded Metals and Materials Other Than Reinforcing Steel—BERNARD ERLIN ..................................................................174 Chapter 18: Abrasion Resistance—KARL J. BAKKE ....................................................184 Chapter 19: Elastic Properties, Creep, and Relaxation—JASON WEISS .................194 Chapter 20: Petrographic Examination—BERNARD ERLIN ........................................207 Chapter 21: Volume Change—FRED GOODWIN ...........................................................215 Chapter 22: Thermal Properties—STEPHEN B. TATRO .................................................226 Chapter 23: Pore Structure, Permeability, and Penetration Resistance Characteristics of Concrete—NATALIYA HEARN, R. DOUGLAS HOOTON, AND MICHELLE R. NOKKEN ......................................................................................238 Chapter 24: Chemical Resistance of Concrete—M. D. A. THOMAS AND J. SKALNY .....................................................................................................253 Chapter 25: Resistance to Fire and High Temperatures—STEPHEN S. SZOKE ........274 Chapter 26: Air Content and Density of Hardened Concrete— KENNETH C. HOVER ...............................................................................................288 Chapter 27: Analyses for Cement and Other Materials in Hardened Concrete—WILLIAM G. HIME..............................................................................309 Chapter 28: Nondestructive Tests—V. MOHAN MALHOTRA .......................................314 vi CONTENTS PART IV CONCRETE AGGREGATES Chapter 29: Grading, Shape, and Surface Texture—ROBIN E. GRAVES ..................337 Chapter 30: Bulk Density, Relative Density (Specific Gravity), Pore Structure, Absorption, and Surface Moisture—JOHN J. YZENAS, JR. ........346 Chapter 31: Soundness, Deleterious Substances, and Coatings— STEPHEN W. FORSTER ...................................................................................355 Chapter 32: Degradation Resistance, Strength, and Related Properties of Aggregates—RICHARD C. MEININGER .................................................................365 Chapter 33: Petrographic Evaluation of Concrete Aggregates— G. SAM WONG......................................................................................................377 Chapter 34: Alkali-Silica Reactions in Concrete—DAVID STARK.............................401 Chapter 35: Alkali-Carbonate Rock Reaction—MICHAEL A. OZOL ..........................410 Chapter 36: Thermal Properties of Aggregates—D. STEPHEN LANE .......................425 PART V OTHER CONCRETE MAKING MATERIALS Chapter 37: Hydraulic Cements—Physical Properties—LESLIE STRUBLE ................435 Chapter 38: Hydraulic Cement-Chemical Properties—SHARON M. DEHAYES AND PAUL D. TENNIS ....................................................................................450 Chapter 39: Mixing and Curing Water for Concrete—JAMES S. PIERCE .................462 Chapter 40: Curing and Materials Applied to New Concrete Surfaces—BEN E. EDWARDS ...............................................................................467 Chapter 41: Air-Entraining Admixtures—ARA A. JEKNAVORIAN ...............................474 Chapter 42: Chemical Admixtures—BRUCE J. CHRISTENSEN AND HAMID FARZAM ..........484 Chapter 43: Supplementary Cementitious Materials—SCOTT SCHLORHOLTZ .........495 Chapter 44: Slag as a Cementitious Material—JAN R. PRUSINSKI ...........................512 PART VI SPECIALIZED CONCRETES Chapter 45: Ready Mixed Concrete—COLIN L. LOBO AND RICHARD D. GAYNOR ..........533 Chapter 46: Lightweight Concrete and Aggregates—THOMAS A. HOLM AND JOHN P. RIES ..................................................................................................548 Chapter 47: Cellular Concrete—FOUAD H. FOUAD .....................................................561 Chapter 48: Concrete for Radiation Shielding—DOUGLAS E. VOLKMAN .................570 Chapter 49: Fiber-Reinforced Concrete—PETER C. TATNALL .....................................578 Chapter 50: Preplaced Aggregate Concrete—EDWARD P. HOLUB ...........................591 Chapter 51: Roller-Compacted Concrete (RCC)—WAYNE S. ADASKA .....................595 Chapter 52: Polymer-Modified Concrete and Mortar—D. GERRY WALTERS .........605 Chapter 53: Shotcrete—JOHN H. PYE ..........................................................................616 Chapter 54: Organic Materials for Bonding, Patching, and Sealing Concrete—RAYMOND J. SCHUTZ ..........................................................................625 Chapter 55: Packaged, Dry, Cementitious Mixtures—DENNISON FIALA ................631 Chapter 56: Self-Consolidating Concrete (SCC)—JOSEPH A. DACZKO AND MARTIN VACHON ............................................................................................637 INDEXES Index ..............................................................................................................................647 1 Introduction Joseph F. Lamond1 and James H. Pielert 2 ASTM STP 169C, SIGNIFICANCE OF TESTS AND Part II deals with the properties of freshly mixed concrete. Properties of Concrete and Concrete-Making Materials, was Part III concerns itself with the properties of hardened published in 1994. ASTM Committee C9 on Concrete and Con- concrete. crete Aggregates has once again decided the time was appro- Part IV deals with concrete aggregates. The order of the priate to update and revise this useful publication to reflect chapters has been revised. They are now presented in the or- changes in the technology of concrete and concrete-making der that most concerns concrete users: grading, density, sound- materials that have taken place since that time. New materials ness, degradation resistance, petrographic examination, reac- have appeared on the scene, along with a greater appreciation tivity, and thermal properties. Some of the chapter titles have of the capabilities of concrete as a basic construction material. changed and the previous chapter on pore systems has been in- Committee C9 and its subcommittees have made significant cluded in the chapter on density. changes in many of its specifications and test methods to re- Part V includes materials other than aggregates. The title flect these changes. New specifications and testing techniques of the chapter on curing materials was changed to reflect cur- have been developed to provide for informed use of new ma- rent technology of materials applied to new concrete surfaces. terials and new uses for concrete. The chapter on mineral admixtures has been separated into Hydraulic cement concrete is a product composed of many two chapters, one on supplementary cementitious materials materials and produced in many forms. The quality of concrete and the other on ground slag. is dependent on the quality of the constituent materials and re- Part VI, on specialized concretes, contains one new chap- lated manufacturing, testing, and installation processes. Since ter on self-consolidating concrete. The subcommittee structure 1914, ASTM Committee C9 has played a vital role in promoting of Committee C9 has been modified to accommodate this the quality of concrete by developing specifications, testing need. methods, and practices for concrete and concrete-making ma- The editors, along with ASTM Committee C9 on Concrete terials. This has been possible through the dedication and com- and Concrete Aggregates, believe this new edition will serve mitment of its volunteer members over the years. the concrete industry well. The editors selected authors and Committee C9 first published Report on Significance of their chapters were reviewed in accordance with ASTM’s peer Tests of Concrete and Concrete Aggregates, ASTM STP 22, in review procedures. C9 subcommittees having jurisdiction 1935, with an updated report published in 1943. ASTM STP over the subjects for pertinent chapters participated infor- 169 was published in 1956, followed by ASTM STP 169A in mally in the review process. The editors appreciate the help 1966, ASTM STP 169B in 1978, and ASTM STP 169C in 1994. and guidance of these people and the cooperation of ASTM Following this brief introduction, this special publication Committee C1 on Cement in providing authors for the two is organized into six parts: General, Freshly Mixed Concrete, chapters on cement. Some of the authors in ASTM 169C are Hardened Concrete, Concrete Aggregates, Concrete-Making no longer active in Committee C9. The co-editors and Com- Materials Other than Aggregates, and Specialized Concretes, mittee C9 members wish to dedicate this edition to those au- with revised and new chapters. thors who have died since ASTM STP 169C was published. In Part I, the chapters consist of general subjects on the They are Paul Klieger, Ed Abdur-Nur, Bill Dolch, Jack Scan- nature of concrete, sampling, variability, and testing laborato- lon, Bob Philleo, Bill DePuy, Bryant Mather, Ron Mills, and ries. A new chapter deals with modeling cement and concrete Owen Brown. properties. 1 Consulting engineer, Jeffersonton, VA 22724. 2 Manager, Cement and Concrete Reference Laboratory, Gaithersburg, MD 20899. 1 PART I General 2 The Nature of Concrete Richard A. Helmuth1 and Rachel J. Detwiler 2 Preface materials for making concrete and their effects on concrete properties are given in other chapters in this work. T. C. POWERS AUTHORED THE FIRST VERSION OF Typical hydraulic-cement concretes have volume fractions this chapter, which was published in ASTM STP 169A in of aggregate that range approximately from 0.7 to 0.8. The 1966. His chapter was reprinted without revision in ASTM STP remaining volume is occupied initially by a matrix of fresh 169B in 1978. In ASTM STP 169C (1994), Richard A. Helmuth cement paste consisting of water, cementitious materials, and condensed some of that work and included more recent mate- chemical admixtures, that also encloses air voids. While the ag- rial. The present version relies on the framework established by gregates occupy most of the volume, they are relatively inert the earlier authors, while updating and adding to it. and intended to be stable. It is the cement paste matrix that undergoes the remarkable transformation from nearly-fluid Introduction paste to rock-hard solid, transforms plastic concrete into an apparent monolith, and controls many important engineering For thousands of years, mankind has explored the versatility of properties of hardened concretes. materials that can be molded or cast while in a plastic state and then hardened into strong, durable products [1]. As with Scope ceramics and gypsum plasters, lime mortars and pozzolanic con- Hydraulic-cement concretes may be designed to provide prop- cretes provided engineers with economical materials for pro- erties required for widely varying applications at low life-cycle duction of diverse utilitarian and aesthetically pleasing struc- cost. If not properly designed or produced, or if exposed to tures. Modern concretes preserve these ancient virtues while service conditions not understood or unanticipated, premature greatly extending the range of technically achievable goals. failures may result. Successful use depends on understanding the nature of concrete. Concrete-Making Materials—Definitions The scope of this examination of the materials science of Concrete is defined in ASTM Terminology Relating to Concrete concrete is mainly confined to concretes made with portland and Concrete Aggregates (C 125) as “a composite material that cements, with or without supplementary cementitious materi- consists essentially of a binding medium within which are als and chemical admixtures. The focus is mainly on how we embedded particles or fragments of aggregate; in hydraulic- understand concrete performance in ordinary construction cement concrete, the binder is formed from a mixture of practice. That understanding is based on knowledge of its hydraulic cement and water.” Hydraulic-cement concretes are constituents, and their physical and chemical interactions in those most widely used in the United States and worldwide. different environments. Hydraulic cement is defined in ASTM Terminology Related to Hydraulic Cement (C 219) as “a cement that sets and hardens Freshly-Mixed Cement Paste and Concrete by chemical interaction with water and that is capable of doing so under water.” Portland cement is the most important Water in Concrete hydraulic cement. It is produced by pulverizing portland The properties of fresh cement paste and concrete depend on cement clinker, consisting essentially of hydraulic calcium the structure and properties of ordinary water, which are silicates, usually by intergrinding with small amounts of unusual for a substance of such low molecular weight. Each calcium sulfate compounds to control reaction rates. It may be molecule has a permanent dipole moment, which contributes used in combination with one or more supplementary to the strong forces of attraction between water molecules cementitious materials, such as fly ash, ground granulated blast and results in unusually high melting and boiling points, furnace slag (referred to as “slag” in the remainder of this chap- heats of fusion and vaporization, viscosity, and surface ten- ter), silica fume, or calcined clay. sion [2]. Aggregate is defined in ASTM C 125 as “granular material, In addition to dipole interactions, hydrogen bonding such as sand, gravel, crushed stone, or iron blast-furnace slag, between water molecules and thermal agitation affect the used with a cementing medium to form hydraulic-cement structure of water and aqueous solutions. Hydrogen bonding concrete or mortar.” Detailed descriptions of these and other favors formation of clusters of molecules, while thermal 1 Materials Research Consultant, Construction Technology Laboratories, Skokie, IL 60077-1030. 2 Senior Concrete Engineer, Braun Intertec, Minneapolis, MN 55438. 5 6 TESTS AND PROPERTIES OF CONCRETE agitation, including translational, rotational, and vibrational that contain small percentages of ultrafine (submicron) parti- motions, tends to disrupt the structure. cles may also aid in dispersing cement particles by adsorption In the liquid state, the molecules are easily oriented in an of the ultrafine particles on the surfaces of the larger particles. electric field so that water has a high dielectric constant (78.6 at This specific kind of fine-particle effect is responsible for the 25°C). This orientation, as well as molecular polarization, improved flow of many portland cement/fly ash mixtures [7,8]. means that the electric field strength and the forces between The average thickness of films of water separating discharged particles, such as ions in solution, are reduced to 1/78.6 persed particles in the paste depends on the water-to-cement relative to that in vacuum (or air). Because of its exceptionally ratio (w/c) and the cement fineness. A first approximation of high dielectric constant, water is an excellent solvent for salts: the average thickness of these films is given by the hydraulic the energy of separation of two ions in solution is an inverse radius: the volume of water divided by the specific surface. If function of the dielectric constant of the solvent. Ions in it is assumed that the films are thin compared with the particle solution are not separate entities but are surrounded by water sizes, the calculated thickness is 1.2 m for cement of specific molecules attracted to them by ion-dipole forces. surface of 430 m2/kg, mixed at 0.5 w/c [9]. Since the assump- A few minutes after mixing begins, about half of the tion is not valid for the finer fractions and much of the fine cement alkalies are dissolved so that the concentration of the fraction in portland cement is composed of calcium sulfates alkali and hydroxide ions may commonly be 0.1 to 0.4 mol/L, and other phases that dissolve within minutes after mixing be- depending mainly on the water-to-cement ratio and the cement gins, the average film thickness for the larger particles in that alkali content [3]. At 0.3 mol/L, each ion would be separated paste is probably about 2 m. For flocculated particles, the from like ions, on the average, by about 1.7 nm, or about five films are much thinner between adjacent particles, so that water molecules. much of the water is forced into relatively large cavities or capillary-like channels. Interparticle Forces Atoms near the surface of solids are distorted and shifted rela- Cement Hydration and Structure Formation tive to their positions in the interior because of the unsatisfied atomic bonds at the surface. These distortions of the surface Early Hydration Reactions produce net positive or negative surface charge, and elastic ex- It is convenient to divide the process of cement hydration into cess surface free energy. In aqueous solutions, solid surfaces the early (within the first 3 h), middle, and late (after 24 h) pe- may preferentially adsorb certain ions [4]. Particles with sur- riods. Soon after mixing cement with water, a gel layer forms face charges of the same sign repel each other in suspensions on the surfaces of the cement grains. Taylor [10] characterized and tend to remain dispersed. Particles of opposite sign attract this layer as “. . . probably amorphous, colloidal and rich in alu- each other and flocculate [5]. mina and silica, but also containing significant amounts of cal- In addition to these electrostatic forces, which can be at- cium and sulfate . . .” Within about ten minutes, stubby rods of tractive as well as repulsive, there are forces among adjacent calcium aluminoferrite trisulfate hydrate (AFt) begin to form. surfaces of solids, atoms, and molecules that are always attrac- They appear to nucleate in the solution and on the outer sur- tive. These van der Waals, or dispersion, forces exist because face of the gel layer. even neutral bodies constitute systems of oscillating charges During the middle period of hydration approximately 30 % that induce polarization and oscillating dipole interactions [5]. of the cement reacts. The rapid formation of calcium silicate The combined action of the different forces causes sorption of hydrate (C-S-H) and calcium hydroxide (CH) is accompanied by water molecules and ions from solution, which can neutralize significant evolution of heat. The CH forms massive crystals in surface charge and establish separation distances of minimum the originally water-filled space. The C-S-H forms a thickening potential energy between solid particles [6]. The mechanical layer around the cement grains. As the shells grow outward, properties of fresh and hardened cement pastes and concretes they begin to coalesce at about 12 h, a time coinciding with the depend on these forces. maximum rate of heat evolution (Fig. 1) and corresponding approximately to the completion of setting. The shells are Structure of Fresh Cement Paste apparently sufficiently porous to allow the passage of water in Modern portland cements have mass median particle sizes that and dissolved cement minerals out. A gap begins to appear are about 12 to 15 m (diameter of an equivalent sphere), al- between the hydration shell and the surface of the cement most all particles being smaller than 45 m, and very little of the grain. Toward the end of the middle period the growth of AFt cement being finer than 0.5 m. During grinding, calcium sul- crystals resumes; however, this time they are distinctly more fates grind faster and usually become much finer than the acicular in shape. Their formation coincides with a shoulder on clinker. After mixing with water, the solid surfaces become cov- the heat evolution curve [10]. ered by adsorbed ions and oriented water molecules forming a Like most chemical reactions, cement hydration proceeds layer of solution of different composition and properties from more rapidly with increasing temperature. Verbeck and those of the bulk aqueous phase; the layer extends out to a dis- Helmuth [11] postulated that because of the low solubility and tance at least several times the diameter of a water molecule. low diffusivity, the ions forming the cement hydration products These surface layers have the effects of simultaneously separat- would not have time to diffuse any significant distance from the ing and weakly binding the particles into a flocculated structure. cement grain, thus forming a highly nonuniform distribution of In fresh cement pastes and concretes made with high solid phases. They believed that the dense hydration shells doses of water-reducing admixtures, cement particles may be- would serve as diffusion barriers, hindering further hydration. come almost completely dispersed (deflocculated) because A consequence of the uneven distribution of the solid phases is large organic molecules are adsorbed on their surfaces, dis- a coarser pore structure. Skalny and Odler [12] found that C3S placing water films, and greatly reducing attractive forces be- pastes of a given w/c hydrated at temperatures of 50 to 100°C tween cement particles. Supplementary cementitious materials had a coarser structure and greater volume of large pores than HELMUTH AND DETWILER ON THE NATURE OF CONCRETE 7 Before setting, two, and sometimes three, kinds of volume changes occur. Sedimentation causes subsidence of the floc structure and collection of bleeding water on the top surface, if evaporation is not excessive. If the surface becomes partly dried, capillary tension in the water can cause plastic shrinkage and cracks. Chemical shrinkage is the volume change that results from formation of hydrates that have less solid volume than the volume of water and solids reacted. While the paste is plastic, the entire volume of paste undergoes chemical shrinkage. After setting, the external dimensions remain essentially fixed and additional water must be imbibed to keep the pores saturated with water. If sufficient water is not imbibed, the paste undergoes self-desiccation. Autogenous shrinkage is the volume change that results when there is no moisture loss to the surrounding environment. It is most significant for concrete in which the water-to- cement ratio is less than about 0.42. Before the concrete sets, Fig. 1—Heat evolution of Type I/II portland cement paste autogenous shrinkage is equivalent to chemical shrinkage and as measured by conduction calorimetry. The first heat peak is manifests itself as plastic settlement. Once a continuous struc- associated with the initial hydrolysis of the C3S, the hydration ture begins to form, the chemical shrinkage is restrained to of the C3A in the presence of gypsum to form ettringite, and some degree. As the internal structure of the cement paste ma- rehydration of the hemihydrate to form gypsum. It is normally completed within 15 min. Deposition of ettringite on trix becomes more rigid, autogenous shrinkage is influenced the surface hinders further hydration of the C3A. The first less by chemical shrinkage and more by self-desiccation [16]. peak is followed by a dormant period of 2 to 4 h, during Tazawa and Miyazawa [17] found that the amount of autoge- which the paste remains in the plastic state as the C3S nous shrinkage increases with increasing C3A and C4AF con- continues to dissolve slowly. The acceleration period begins tents of the cement and decreasing water-to-cement ratio. with the renewed evolution of heat (beginning of the second Bentz and Geiker [18] found that the effects of self-desiccation, peak) as the initial hydration products of the C3S begin to and thus the autogenous shrinkage, can be mitigated by the use form. Initial set coincides with the beginning of the accel- of water-saturated low-density fine aggregates or of super- eration period. The CH crystallizes from solution, while the absorbent polymer particles to provide an internal source of C-S-H deposits on the surface of the C3S, creating a diffusion water, or by the use of shrinkage-reducing admixtures. barrier. Eventually the rate of hydration slows due to the difficulty of diffusion of water and ions through this barrier Gypsum and other sulfate-bearing materials are normally [20]. Final set takes place just before the maximum point of interground with portland cement clinker in the production of the second peak. The “shoulder” of the second peak, which in cement to control the hydration of the aluminates. If little or this figure appears at about 9 h, is associated with the no gypsum is present, the cement experiences “flash set” or renewed formation of ettringite [10]. Further hydration of “quick set,” in which the cement sets rapidly with much evolu- the cement continues at a much slower rate, asymptotically tion of heat. Plasticity is not regained with further mixing, and approaching 100 % [20]. (Image courtesy of E. Shkolnik.) the subsequent development of strength is poor. It is associated with the rapid hydration of the aluminate and ferrite phases to form plates of low-sulfate AFm phases such as C4AH13 and those hydrated at 25°C. Kjellsen et al. [13] found that in cement C4AH19 throughout the paste. Some cements low in aluminate paste hydrated at 50°C to a degree of hydration of approxi- phase do not flash set even without gypsum [10]. mately 30 % the hydration shells were already sufficiently dense Flash set and quick set may be caused by insufficient to act as diffusion barriers to sulfate ions. The morphology of sulfates in the cement, or by the presence of the wrong form(s) the CH crystals was dependent on the hydration temperature, of sulfate. During milling, gypsum can dehydrate to form being more elongated in cement paste hydrated at 5°C and hemihydrate or so-called “soluble anhydrite” (-CaSO4). Some more compact in cement paste hydrated at 50°C. byproducts from various industrial processes contain calcium During the first hours of hydration, very fine supplemen- sulfite (CaSO3), known as hannebachite, rather than gypsum, tary cementitious materials such as silica fume and fine fly ash and are much less soluble than gypsum. Byproduct gypsum have some important physical effects on the development of the from flue gas desulfurization is often difficult to dispense microstructure. According to Bache [14], the principal physical uniformly due to its high moisture content; thus the quantity effect of silica fume in concrete is an enhancement of particle of gypsum in the cement can be variable. The form of sulfate packing because the silica fume particles can fit into spaces has a direct bearing on the availability of sulfates in solution at between cement grains in the same way that sand fills the the right time, since the solubility and rate of solution vary interstices between particles of coarse aggregate and cement considerably from one form to another. Very finely ground grains fill the interstices between sand grains. This analogy is cement requires more sulfate to control the reactivity of the valid only when there is sufficient superplasticizer to counter- aluminates. act the effects of attractive surface forces. As the cement begins Incompatibility among the various concrete ingredients to hydrate, the fine particles of silica fume or fly ash serve as may also contribute to flash set or quick set. Lignosulfonates in nucleation sites for the hydration products. Asaga et al. [15] water-reducing admixtures limit the solubility of sulfate and found that fly ash, silica fume, and slag all increase the rate of calcium ions. Triethanolamine (TEA) in water-reducing admix- early hydration of C3S, even though the supplementary cemen- tures makes the aluminate phases react faster while retarding titious materials do not themselves react at this stage. the hydration of the calcium silicates. Some Class C fly ashes 8 TESTS AND PROPERTIES OF CONCRETE Fig. 2—Computer-based model of the development of microstructure in hydrating portland cement pastes: (upper left) portland cement paste before hydration begins; (upper right) portland cement paste after 47 % hydration; (lower left) unhydrated portland cement paste with fly ash; (lower right) partially hydrated portland cement paste with fly ash [images courtesy of E. J. Garboczi]. All images 100 m 100 m. contain sufficient quantities of reactive aluminate phases to form inside them. The availability of sulfate ions is very lim- upset the balance between aluminates and sulfates unless ad- ited within the hydration shells, and calcium aluminoferrite ditional gypsum is added to the system. If either the cement or monosulfate hydrate (AFm) forms, replacing AFt as the alu- the fly ash has a high alkali content, it will increase the rate of minate phases continue to hydrate. After the spaces between hydration. Hot weather accelerates the hydration of the alumi- the hydration shells and the cement grains fill with hydration nates and reduces the solubility of the sulfates [19]. products, further hydration is slow and appears to occur by Another type of rapid set is called “false set,” in which lit- a topochemical rather than a through-solution mechanism tle heat is evolved. False set is associated with the rehydration [10]. of calcium sulfate hemihydrate to form secondary gypsum. Larger clinker particles in cement hydrate partly by disso- The interlocking and intergrowth of the gypsum crystals re- lution and partly by in situ reactions so that a pseudomorph sults in the stiffening observed. If the quantity of secondary of inner products is formed within the boundaries of the orig- gypsum is not too great, it redissolves on further mixing, and inal grain. The depth of reaction increases with time, but at the hydration reactions proceed normally. During milling, gyp- decreasing rates so that large particles may have unhydrated sum can dehydrate to hemihydrate; hemihydrate is sometimes cores even after years of moist curing. The dissolved portion added directly to the clinker when a more reactive form of forms outer products in the water-filled space near the grains. sulfate is desired [10]. Grinding at a higher temperature or a The calcium silicates produce crystalline calcium hydroxide lower relative humidity can often achieve the same result. and nearly amorphous calcium silicate hydrate (C-S-H gel) that engulf crystalline phases formed by the early reactions. Capil- Hardening Reactions and Microstructure lary pores remaining in mature cement paste increase in size After the first 24 h, the hydration shells surrounding the ce- with water-to-cement ratio and have diameters ranging from 10 ment grains become less permeable, and C-S-H begins to nm to 10 m [20]. HELMUTH AND DETWILER ON THE NATURE OF CONCRETE 9 Powers designated the hydration products of portland ce- monomolecular sheets, about 700 m2/g, as measured by small- ments as “cement gel,” recognizing that they contained both C- angle X-ray scattering [26]. Because of the large internal surface S-H gel and crystalline products, and micropores [21]. He area, the distances between solid surfaces of the pores in the gel found that typical cement gels had minimum porosities of approach the size of water molecules; most of the gel water is about 30 %, and specific surface areas of about 200 m2/g, as close to the surfaces. In such systems, it is not certain how much calculated by Brunauer, Emmett, Teller (BET) theory [1] from of the volume change of chemical shrinkage should be attrib- water-vapor adsorption data obtained after first drying to uted to the reaction itself, and how much to the possible change remove all of the evaporable water. These studies also showed of density of water in pores as it is adsorbed on newly created that at 0.38 water-to-cement ratio all of the capillary pore space surfaces. If it is assumed [27] that the adsorbed solution has the was just filled by maximum density gel when all the cement same density as that in large pores, the apparent specific vol- was hydrated. Mixtures made with water-to-cement ratios less umes of the nonevaporable (hydrate) water and solids were than 0.38 cannot be completely hydrated; the amount of found to be 0.74 and 0.398 cm3/g, respectively, and the mini- cement that can hydrate is less because hydration virtually mum porosity of the gel to be 30 %. The amount of chemical stops when the capillary space is filled with gel of minimum shrinkage is expressed in terms of the change in the apparent porosity. Saturated, fully hydrated cement pastes made at specific volume of the reacted water, from 0.99 to 0.74 cm3/g, water-to-cement ratios above 0.38 have remaining capillary and the amount, wn, of nonevaporable water: 0.25 wn. pore space (by definition) equal to the excess above 0.38. Hydration of each unit volume of cement produces about Partially hydrated mixtures have proportionately less gel and 2.2 volumes of gel. This value does not depend on the assump- more capillary space. Cements of different compositions tion concerning specific volumes. Although chemical shrink- behave similarly, with similar values for the constants. age slightly reduces the space filling by solid hydrates, cement Supplementary cementitious materials can alter the de- gel is an even more effective filler of the capillary space than veloping microstructure of hydrating cement paste by means the solid hydrates because of the 30 % porosity of the gel. of the pozzolanic reaction, in which silica reacts with CH and water to form additional C-S-H. The composition of the C-S-H Effects of Drying formed by pozzolanic reaction differs somewhat from that of Loss of moisture due to self-desiccation or evaporation par- C-S-H formed by hydration of cement in that the former has a tially empties the largest capillaries at exposed surfaces. Ad- lower Ca/Si ratio and a higher Al/Ca ratio [10]. In the hydration sorbed water remains on capillary walls as concave menisci of cement pastes containing slag, Al substitutes for Si in the form and progress into smaller interconnected pores. Menis- silicate chains [22]. With any supplementary cementitious cus curvature and capillary tension in the remaining water are material, the pozzolanic reaction improves both the later-age increased as the relative humidity is decreased down to about strength and the durability of concrete because it consumes 45 % RH, below which sorption effects prevail. Reductions in the relatively weak, soluble CH and generates more C-S-H, relative humidity slow the hydration rate; at 80 % RH, hydra- which further subdivides the larger pores and increases the tion is insignificant. Drying causes shrinkage of hardened ce- strength of the cement paste. The microstructure of cement ment paste and major alterations of the gel microstructure. pastes hydrated at elevated temperatures is marked by uneven Shrinkage and stabilization of cement paste by drying are com- distribution of hydration products and, consequently, a coarser plex and partially irreversible processes involving capillary, pore system. Goto and Roy found that the total porosities of sorption, and dehydration effects. pastes hydrated at 60°C were greater than those of comparable Capillary tension in the pore water increases as the rela- pastes hydrated at 27°C for the same length of time. They at- tive humidity decreases below the vapor pressure of the pore tributed the difference in porosity largely to the difference in solution. For dilute solutions, tensions increase to about 97 volume of pores of radius 75–230 nm [23]. It is the larger pores MPa (14 000 psi) at 50 % RH. At lower relative humidities, 40 that contribute most to the permeability; Mehta and Manmo- to 45 % RH, the tension exceeds the cohesive strength of water han proposed a pore radius of 50 nm as a somewhat arbitrary in capillaries and menisci can no longer exist [21]. Above 45 % dividing point between “large” pores which contribute most to RH, capillary tension in the water must be balanced by permeability and “small” pores which are much less significant compressive stresses in the solid structure, in which stress [24]. For cement pastes hydrated at low temperatures, the hy- concentrations can produce irreversible effects. When the dration products are more evenly distributed and the pores pores are nearly water-filled, the average stress is that fine and discontinuous. Hydration shells around the cement produced by surface tension in the cross-sectional area that is grains are not apparent. For cement pastes hydrated at ele- pore water; the resulting strain in the solid structure is the vated temperatures, dense hydration shells are readily appar- beginning of the drying shrinkage. As the capillaries empty the ent and the pores are coarse and interconnected [13]. cross sections of the remaining water-filled pores are smaller, Supplementary cementitious materials mitigate the dele- but the capillary tension increases and causes local collapse of terious effects of elevated-temperature curing. Cao and Det- less dense regions of the outer product, and enlargement of wiler [25] found that both silica fume and slag were effective large pores. Desorption causes shrinkage both by permitting in homogenizing the distribution of the hydrates of cement solids to come together, and by increasing solid surface pastes cured at 70°C. While the total pore volume remained tension. Well-crystallized AFm and AFt hydrated phases also de- essentially the same for pastes with and without silica fume or hydrate, decreasing lattice spacings, so that elastic restraint of slag, the average pore size was significantly reduced. the shrinking C-S-H gel is reduced. Drying and rewetting alter the microstructure, and differ- Cement paste cured for six months before drying at 47 % ent adsorbates measure different surface areas. The sheet-like RH for the first time shows both reversible and irreversible wa- crystallites are imperfectly stacked and separated by interlayer- ter loss and shrinkage [28]. Increased drying time causes in- adsorbed water at relative humidities down to 11 %. Before creased water loss, shrinkage, and greatly reduced internal sur- drying or aging, cement gels have specific surfaces of C-S-H face area. Rewetting causes sorption and swelling that only 29 psi) [9]. creep. long. . interstices between cement grains.3 They are also plastic solids with typical values for plastic viscosity that range roughly from 10 to 100 mPa s (centipoise). viscous flow of gel. Increasing the water-to-cement ratio of a cement paste reduces both the yield stress and the plastic viscosity. At low water-to-cement ratios. to disperse [7]. like the during rewetting [29]. Water reducers and superplasticizers increase the dispersion of the ag- glomerated particles of cementitious materials by adsorption on the particle surfaces. Another possibility is that.2 %. Yield stress values increase to 2 104 Pa (2. Taylor [10] discussed three mechanisms by which these admixtures cause dispersion: (1) an increase in the zeta-potential between the first adsorbed layer and the bulk solution.2 % perplasticizer to overcome the effects of surface forces. Typical values for portland cement pastes without admixtures range roughly from 10 to 100 Pa (0.9 psi) at initial set and 1 105 Pa (14 psi) at final set [9].0014 to 0. making the paste shrinkage tends to become porosity-independent at about sticky [31]. The effect at small dosages was attributed by Bache 0. indicating a rubber-like elasticity. and other factors. They are a result of redis- intensity. and stress relaxation are Rheology of Fresh Cement Paste useful in dissipating vibrational energy.2 to 0. The the air-water interface of the air voids [1] and reduces the surface irreversible component of shrinkage increases with water. at larger dosages. the particle tied during drying become closed off and are not accessible packing is no longer efficient. loss of interlayer water is accompanied by large partially to the surfaces of the cement grains. Thus the addition of water reducers and superplasticizers reduces the yield stress of the fresh paste. so that like surface charges of sufficient magnitude cause the particles to repel one another. Internal friction. the silica fume particles adhere RH.6) from 0. portland cement hydration reactions cause progressive stiffening and setting during the first few hours. reducing the cement ratio (0. and slow growth of cracks.014 psi) for w/c from 0. and (3) steric hindrance. Prior to yield. stabilizes partly reverses the first water loss and shrinkage (Fig. At ordinary temperatures.10 TESTS AND PROPERTIES OF CONCRETE trolled. dry agglomerates of fine particles are first dispersed tribution of moisture.35 [9]. which suggests that some pores emp. which is continuously solids under stress and recrystallization in pores. and solid-liquid affinity. the floc structure reforms until it becomes an essentially continuous floc. When mixing is stopped. the pastes are obviously plastic and can be deformed by moderate forces. the ori- of measurements [28]. of the particles when minute particles of silica fume can fill the cific volume to be 0. and dissolution of and then tend to form a floc structure. Numbers indicate sequence mix water than to one another. causing the cement grains irreversible shrinkage and water loss effects [30]. Even without drying. or have reduced capacity. The addition of air-entraining admixture. High water-to-cement ratio pastes seem to be liquid and may be poured easily because their yield stress values are so low. are thermally activated 3 Unpublished work done at Construction Technology Laboratories for the Portland Cement Association under Project HR 7190. small and nearly independent of porosity. on the other hand. processes.6 to 0. whereas the re. the pastes are elastic and shear deformations can reach about 20 deg. cement fineness. tion between particles. if we assume its spe. These broken down by mixing if the early reactions are well con. Below 11 % finest fraction of fly ash particles. and preventing exces- When cements are mixed with sufficient water and sufficient sive stress concentrations in concrete.4 so that even the irreversible increase both yield stress and plastic viscosity. plastic viscosity of the paste [31]. rewetting swelling. (2) an increase in the Fig. potential of the particles of cementitious material.99.4 to 0. Cement Paste Structure—Property Elasticity and Creep Relationships Hardened cement pastes are not perfectly elastic. Cement pastes in this condition are actually weak solids with measurable shear stress yield values that depend on water-to-cement ratio. In the presence of sufficient su- versible component (after stabilization by drying) is only 0. Standard test pastes made at normal consistency have w/c about 0. 3—Drying shrinkage. larger dosages of silica fume water-cement ratios above 0.25 and yield stress values of about 2000 Pa (0.4 %. The irreversible shrinkage volume is only about half of [14] to the displacement of water due to more efficient packing the volume of the irreversibly lost water. so that the particles are more attracted to the evaporable water content of a 0. but are vis- coelastic solids.6 water-to-cement ratio hardened portland cement paste. quantities of silica fume (less than approximately 5 % by mass of term aging in moist conditions causes age stabilization at cement) reduce the plastic viscosity. 3). thus reducing the amount of water needed to produce a given flow. Reprinted with permission of the ented adsorption of a nonionic polymer that weakens the attrac- Portland Cement Association. the moduli increase more rapidly.2 to 2 s and a slower component that ranges over weeks. and the volume of gel produced. in addition to the applied stress. It can can reduce the permeability by several orders of magnitude be calculated from the water-to-cement ratio.2 psi/in. short-time component was associated with redistribution of wa. concentration gradients cause friction reaches a peak at about 90°C as the gel water viscos. Water itself E E0(1 )3 may be harmful because of its ability to leach CH from the cement paste. If we consider fresh cement pastes to have strengths equal ter in capillary pores [32]. and diffusion of ions ity increases as it approaches its glass transition temperature at to lower concentrations. The changes of microstructure that cause great changes of elastic moduli and strength of cement pastes Compressive Strength during hardening cause reductions of permeability and diffu- The fraction.18. ice formation in capil. Elastic moduli can be measured precisely by dynamic Permeability and Diffusivity methods and are found to vary with porosity. and other irreversible changes are mately harden to compressive strengths of 10 to 100 MPa. and m3/(s m2 MPa/m) [4. of cement paste can be several times the elastic deformation. If the capil. which E0 is an average modulus for the solids. the believed to contribute to the slower processes. respectively [35]. 14 000 psi) at 0. The mortar data. When the cement paste is partly 119°C [34]. of 0. Diffusion co- cement particle size distributions over the range investigated. . Diffusion of strongly adsorbed and hy. determined with machined samples. at sites of adsorbed wa. internal are made for osmotic effects. The presence of supplementary cementitious materials gel at any stage of hydration is called the gel/space ratio. and the bulk modulus. If the total porosity (including that of the gel) is used.54 w/c. K1 is the permeability.3 to 0. The gel water (adsorbed solution) does not freeze dried. calculated from bleeding at different water-to-cement ratios and ages can be simply data. MPa (13 000 to 18 500 psi) in mortars made with five different The diffusion of ions in cement paste is described by Fick’s cements [21]. indicated intrinsic strengths of 134 and 97 MPa (19 400 and ter molecules. D’Arcy’s 106 psi). Thus water-saturated flow is laries increases the moduli as ice contents increase. h is the hydraulic head.3/(s in. recrystallization. were reduced to ultimate values of 4. if corrections lower temperatures. Use of this equation by Powers indi. HELMUTH AND DETWILER ON THE NATURE OF CONCRETE 11 processes in which random thermal motions provide sufficient each water-to-cement ratio when plotted against X3. permeable to gases such as oxygen and carbon dioxide. and because ice crystals that grow on freezing in which E0 is the modulus at zero porosity [33]. according to The transport properties of cement paste and concrete largely determine its durability in most environments. efficients for Na are on the order of 1011 to 1013 m2/s and although rates of strength development do.)] n has a value of about 3. This result Short-term loading tests of water-saturated cement paste show indicates that the intrinsic strength of the gel formed at that creep and creep recovery versus time curves are bimodal water-to-cement ratios above about 0. but becomes a glassy solid. to their yield stress values.38 decreases with and consist of a component with retardation times ranging from increasing water-to-cement ratio. the transport of ions may also be driven electrically or shown that intrinsic strengths of the gel do not depend on by convection (in the case of partial saturation). or solid-solid bonds. from about 0. typically 10 to 100 Pa. generate tensile stresses that may cause cracking [36]. osmotic flow to higher concentrations.1 to expressed as 22 104 in. For fully hydrated cement pastes. Equations of the same form apply for the shear and law describes the flow of water through saturated cement paste bulk moduli. Permeability coefficients of fresh pastes are about ten cated intrinsic strengths of cement gels ranging from 90 to 130 million times as great as when fully hydrated. where c is the concentration of the ion at distance x from the Testing of pastes made with both normally ground and surface after time t and Dc is the diffusion coefficient. cause of capillary tension and diffusion along surfaces and in the vapor phase. At temperatures in the cross-sectional area.36 and 0. relative humidity and moisture gradients cause flow be- to ice.5 to 60 1012 in which fcg is the intrinsic strength of the gel (at X 1). in contrast with Powers’s 0. it may be expressed as (1 Permeability coefficients of fresh portland cement pastes ). where is the capillary porosity. of the available space that is filled by cement sivity. [37]. Tests of cement pastes c/ t Dc 2c/ x2 yielded higher strengths at gel/space ratios calculated to be equal to those of mortars made with the same cement. thickness of the specimen [37]. Cement and concrete are also pastes. A is the the temperature is decreased to 0°C. Compressive strength. At still proportional to hydraulic pressure differences. Drying significantly reduces Poisson’s ratio. and l is the freezing range down to about 60°C.5 and 0. stresses are carried by dq/dt K1 A h/l at least some of the water in pores. fc . and energy. Long-term creep increase is about six orders of magnitude.7 to 20 105 m3/(s m2 MPa/m) [6. range from 5.3/(s in. However.)]. Water lary porosity is used. about may also carry harmful dissolved species such as chlorides or 34 GPa (5 106 psi) for Young’s modulus of water-saturated acids into the concrete. respectively. and ulti- drate water. mortars probably do not provide ac. second law once steady-state conditions have been reached: curate measures of intrinsic strengths of pastes because of transition zones at aggregate surfaces.2 psi/in. paste for Cl on the order of 1011 to 1012 m2/s [10]. These coefficients for hardened pastes of the same water-cement ratios fc fcg X n after prolonged moist curing. Diffusion strengths at several ages defined different straight lines for coefficients increase with increasing temperature and water-to- . However. system [10]. to exceed the bond energy.7 water-to-cement ratio. X. the fraction of as the pozzolanic reaction reduces the continuity of the pore the cement that has hydrated. E0 is the modulus of the cement gel. about 76 GPa (11 contributes to the corrosion of steel reinforcement. In prac- controlled-particle-size-distribution portland cements has tice.8 to 65 1011 in. Elastic moduli of saturated pastes increase moderately as where dq/dt is the flow rate. yielded values several orders of magnitude cooled without access to additional water. smaller than for larger specimens.38 and 0. and solid surface forces.6 106/°C [38].12 TESTS AND PROPERTIES OF CONCRETE cementitious materials ratio and decrease with degree of concrete so that the higher. and their different orientations.45) water-to-cement ratio show transient effects spite the low (less than 1 %) porosities of these rocks.7 in. free of decreases as temperatures increase. Heavyweight aggregates are used mainly for radia. Concrete Proportioning. coefficients of thermal expan. Also. and vice versa. Ten different common types of rock tested Specimens dried step-wise to 79 % RH and carefully resat. Concrete Aggregates and after compaction have sufficient strength to support their own weight. and mortar or concrete concrete. ordinary. such as sandstone. be more significant. and limited plastic deformation becomes and stresses. and organic matter.3/(s in. content is called the “basic water content” [6].4 108 ture flows into the gel. Coefficients of thermal expansion of concretes are determined mainly by those of their aggregates. thermal con.2 psi/in. This mini- tion shielding. A good average value tinuously moist cured. 1013 m3/(s m2 MPa/m) [3. Densities of ordinary concretes not below a certain limit. However. although is nearly the same as the normal consistency as defined in ASTM the effect on strength may be significant only in high-strength standards. Strength and bulking increase to a maximum as water is added. many excellent aggregates range in strength down to 80 MPa (12 000 psi) [40]. the cement paste void space is increased by the added aggregate nificant once the rock has been crushed to the sizes used in surfaces.2 to 3.4 Mg/m3 (140 to 150 lb/ft3). Mature saturated cement pastes of made at water-to-cement ratios of 0. Such changes indicate enlargement of for concrete aggregates is about 200 MPa (30 000 psi). reduce interparticle forces. because samples. The consistency of cement paste at its basic water content ductivity. slightly dried ce.) diameter) pieces of rock. Further additions of water increase void volume. de- low ( 0. have specific gravities that are compacted by ordinary means. caused by the relatively slow movement of moisture from capillary to gel pores during cooling and vice versa during warming. have slump values of about 42 mm (1. The remaining cohesive force is a result of interparti- insulation. or dolomite.3/(s in. Such weaknesses in the rock samples may not be sig. salts.71. Porosity increases permeability to fluids and diffu. mixtures made with different aggregates at their basic water sivity to ions in pore solutions. and strength of aggregates and concretes. which probably contained ment gel has a linear coefficient of thermal expansion of about flaws [32]. the resulting expansion (during or after in. void contents C 125). to 2. Values for the small specimens ranged from 3. Lightweight aggregates are used to reduce dead loads reach a minimum. quartz. Nonplastic mixtures made with relatively small amounts of water show considerable bulking as water is added. or at least average. at the Bureau of Public Roads had average compressive urated so as to avoid cracking had permeability coefficients strengths that ranged from 117 MPa (16 900 psi) for marble about 70 times those of comparable specimens that were con. chemical admixtures and higher water contents. respectively. Such concretes are much stiffer than the plastic mix- in aggregate particles in moist concrete can cause surface pop. a dense trap rock. Strength of Aggregate Particles and increase the capacity for plastic deformation.24 to 2. as described in the next section.8 1012 in. mum void space contains about 12 % air when such mixtures granite.0. Freezing of water in pores dard test. especially if the pores are open contents.)]. and to provide thermal possible. Properties Such differences between coefficients of thermal expansion of Proportioning and Consistency pastes and aggregates may cause excessive local stresses in Two basically different kinds of concrete mixtures must be dis- concretes unless relieved by creep. When visible imperfections. These values are generally above strengths of Thermal Expansion ordinary concretes. tures commonly used in American practice that usually contain outs or D-cracking in concrete pavements [20]. to 324 MPa (47 000 psi) for felsite [39]. Porosity reduces the weight. the mixture is wetted so that sur- ity into lightweight. tinguished. limestone.2 psi/in. of weakness. Permeability sions of cement paste depend strongly on their moisture Measurements of coefficients of permeability to water of contents because retention of water by surface forces in the gel selected small (25-mm (1-in. mois.5 27 106/°C.) in the stan- (interconnected) rather than closed. and heavyweight materials (ASTM face menisci and capillary tension disappear. Normal consistency pastes. and the cement content is range from about 2. At low relative humidities. cle attraction between closely spaced fine particles.2 109 m3/(s m2 MPa/m) [2. Structure. and sion decrease to about the same value as for saturated pastes. elastic modulus. Void space in such mixtures is rocks or gravels used as coarse aggregates and sands used as relatively high and filled mostly by air. and then decrease as the void Specific Gravity and Porosity space nearly fills with water and capillary tension is dimin- It is useful to classify aggregates by specific gravity and poros. such deleterious substances as clay. When cement gel is cooled in contact with suf. in some of the The total effect is not just that of volume displacement. Materials used in concrete usually need to be hesive mixture results from capillary tension under menisci processed to be of proper size grading and relatively free of bounding the water films on and between the solid particles. Ordinary aggregates. when aggregate . strengths may hydration. The water content at minimum voids range from about 2. but large pores by partial drying. The concrete block industry employs such non- The major constituents of ordinary concretes are crushed plastic but cohesive mixtures. With sufficient water. ished. thermal expan. These values are equal to cooling) produces a net coefficient of thermal expansion of those measured for mature hardened portland cement pastes about 11. especially in tall structures. Strength test results of individual samples of rock from any The main effect of adding increments of aggregate to paste one source show wide variations that are caused by planes is to reduce the volume of voids and cement per unit volume. The strength of the co- fine aggregates.)] for a granite. for ficient capillary water in cement paste or external water. the vicinity of a surface (the “wall effect”). a thin film of calcium hydroxide. the strength of the ag- each increment of aggregate. less efficient packing of particles of cementitious materials in ter requirement is proportional to the volume fraction of ag. The average values by the two different methods ranged from 26 m to 121 m for lean to rich mixtures. the aggregate must be dis. For fixed proportions. particularly those with aggregate contents the nature of the transition zone include bleeding. duced content of C-S-H. the latter having the highest percentage of fine aggregate (43 %) and being close to the minimum voids ratio. higher contents of CH and ettringite. mation under shear stress. and the “one-sided gregate in the total solids [6]. CH and ettringite). that form through solution (that is. especially very lean mixtures. Although concrete yield orientation parallel to the aggregate interface. The ratio of the volume of water gregate becomes the controlling factor. Consistency of concrete depends on consistency of cement Small crystals of calcium hydroxide begin to form on the sur- paste as well as on dispersion of aggregate by sufficient paste faces of the cement grains. re- rich in cement and paste volume. For concretes made with nearly the same voids ratios (about 0. mixtures that require excess amounts of entrapped air. the stiffer the of the transition zone as compared to the bulk cement paste: paste. with sufficient improvements in the be maintained constant if increments of water are added with strength of the paste-aggregate bond. it must contain a volume of paste and air above the minimum to disperse the aggregate. and if the same compacting force or energy improves. tion products diffusing in from the bulk cement paste (but not from the aggregate) [45]. While this film is still form- until a minimum voids content is reached. that is. If for concrete with a high water-to-cement ratio. adding increments of aggre. Factors contributing to leaner mixtures. Hadley [43] found that plus air to the total volume of solids (voids ratio) decreases with the first hydration product to form on the aggregate surface is added aggregate. paste yield stress values for concretes made with different ag.) slump. calcium silicate hydrate gel begins to appear on the film. ing. to provide some separation between particles that would otherwise be in contact. As the cementitious materials hydrate. which cre- above those at minimum voids ratios. Because persed by a sufficient volume of cement paste to permit defor. but below those very lean ates pockets of water-filled space beneath aggregate particles. In mixtures that are relatively higher void content. In ented parallel to the aggregate surface. and then increases. These crystals also have a preferred volume for each particular aggregate. of the relatively open space. at 75 to 100 mm (3 to 4 in. there is as distance from the interface. With increasing stress values can be calculated from slump values. suffer from poor workability because of particle interference to flow by the larger (. by two different methods with dissimilar results [6]. but not as much as without the added water. Such results indicate that many concretes. the orientation of the crystals be- yet no valid method of calculation of concrete slumps from come more random. HELMUTH AND DETWILER ON THE NATURE OF CONCRETE 13 is introduced. Structure the transition zone fills preferentially with hydration products For concrete to possess plasticity.20). For any aggregate size grading. the wa. that consistency can strength of the concrete. the crystals can grow large. and different aggregate finenesses. the stiffer the concrete. If the concrete is plastic. Powers calculated the minimum separation distances between aggregate particles from the excess paste volumes. the minimum voids ratio indicates the volume required to fill the voids in compacted (dry-rodded) aggregate. Fine aggregate disperses coarse aggregate but also reduces average paste film thicknesses. This range comprises much of growth effect” of dissolved cementitious materials and hydra- the concrete made for ordinary use. as the quality of the paste normal consistency. respectively. failure is con- such additions are begun using cement paste of the standard trolled by the properties of the paste. and larger crystals of CH strongly ori- gate does not greatly increase water requirements for flow. the strength of the paste-aggregate bond controls the is applied to the mixtures as to the paste. plastic strains in the paste during compaction are terms of the strength of the bond between paste and aggregate: necessarily greater and the mixture is stiffer than the paste. Figure 4 [44] illustrates the microstructural characteristics gregates and proportions. Al- though cement pastes made with cements of 30-m maximum particle size were stiffer than those made with ordinary cements. Reprinted with permission of P. improved flow was obtained using cements with controlled particle size distributions in standard mortars and ordinary (not lean) concretes [41]. the larger the maximum size of the aggregate the lower crystalline and porous microstructure than that of the bulk the strength of the concrete. Cordon and Gille. This indication has been confirmed by recent research.40. showing a more coarsely of 0. . Particle interference by large particles is also one of the reasons that some fly ashes increase water requirements of concretes [8]. The presence of the aggregates creates an anomaly in the structure of hardened concrete known as the transition zone between the cement paste and the aggregate. 4—Representation of the transition zone at a paste/ spie [42] noted that for concrete with a water-to-cement ratio aggregate interface in concrete. K. Mehta. 30 m) cement particles. Fig. They explained these results in cement paste [44]. New York.. Be- the microstructure develops and by which it affects the prop.14 TESTS AND PROPERTIES OF CONCRETE Mathematical modeling of the microstructure of concrete gates. Although the basics of good concrete practice had been long stress/strength ratios near this value produce failure in time [40]. Mortars. microcracking at paste-aggregate interfaces develops ample for the purpose of comparing life-cycle costs of various progressively with increasing strain [40]. damage the concrete. but would be paste. American replacement of calcium with alkalies or magnesium. alternative designs. Concluding Discussion ual transition zones interconnect with one another to percolate through the concrete [45]. presence of the relatively weak transition zone affects the Our understanding of the fundamental relationships between mechanical properties of concrete. F. but the main effect is that Nostrand Reinhold. These models have advanced sufficiently to allow the prediction of transport and mechanical properties and even provide insights Properties of Hardened Concrete into the reasons for the behavior observed. while those for concrete exhibit curvature with increas. magnesium..20 mm (0. No. Ion exchange. established when the first edition of this volume was published Durability of concrete depends strongly on exposure and in 1966. 1–10.. crete. for ex- strength. S. 3rd ed. The increasing emphasis on high performance concrete ments of many properties of hardened concrete. the effect on the transport properties of the concrete is significant. increasing its porosity and permeability. field. and can even. New York. in Structure and Properties of Solid Surfaces. ample. 1985. Exposure to acidic or remarkably forgiving material. S. 5th ed. except possibly those loaded at Another implication of the use of high performance con- early ages.3 to crete is that. pp. the derstanding. to continue to improve the test methods that measure the per- stress/strain relationships for aggregates and cement paste can formance and correlate them with field performance. The propagation of cracks structure and properties has been furthered by computer- preferentially through transition zones reduces both the based models simulating the development of the microstruc- strength and the modulus of elasticity of concrete. ture of hydrating cement paste and concrete [45]. R. thus it both capillary and gel pores to ice in the air voids dries the is used at higher dosages. References ride solutions react with aluminates to form Friedel’s salt and [1] Lea. Fly ash at the same dosage is less beneficial due than about 0. Van ficient to cause significant reactions. Tang. Moisture and freezing temperatures can cause damage by Gomer and C. Understanding the science behind the action with aluminate phases in the cement paste to produce practice enables us to specify and enforce the right criteria to ettringite. 1953. we need In short-term loading tests for compressive strength. 596. J. A. Concrete is a pore structure—and structural detailing. Creep of many concretes. these basics are often slighted in the interests of service conditions. and craftsmanship. de.. Journal. by diffusion of water from the gel pores. F.85. Seawater causes leaching and contains and 625. pp. concrete reaches about 0. cause of ice/water interfacial tension. practical. grow by osmotic accretion of ice transition zone and react to convert CH to C-S-H. concrete properties—especially porosity and meeting the constraints of schedule and budget. pp. 68. The Chemistry of Cement and Concrete. of erosion or loss of constituents [1]. University of Chicago Press. [45] showed that of ice crystals. and possibly controlling its behavior.8 times its ultimate strength. [4] Weyl. Calcium and sodium chlo. so that their void spacing factors are less cement paste. and to allow us to use them with confidence. there is little cracking at the interface until the Thus the use of such models is no better than extrapolation. the concrete. sufficient space to accommodate the volume expansion of that highly hydrated reaction product. Dec. we observe seemingly pending on the heterogeneity of the mixture. can also Ceramic Society. or the rate of construction. exhibit proportionality up to about 0. chloride. some of these reactions are also expansive Chemical Publishing Co. are not solidly based on empirical data.. pp. 667–673. it requires due attention to proper design waters can penetrate into concrete to cause sulfate attack by re. Chicago. Ice formation at frozen surfaces is propagated through has improved our understanding of the mechanisms by which capillaries large enough for the contained water to freeze. Eds. be sensibly linear up to near the compressive strength of the these correlations would not be merely statistical. 2311–2312. To make performance specifications truly of the cement paste/aggregate composite. M.. for ex.6. [2] “Water” in Van Nostrand’s Scientific Encyclopedia. J.4 times Some of the models used to predict field performance. diffusion of moisture from to its larger particle size and lower pozzolanic activity. 1971. Other chapters in this publication give comprehensive treat. and Weiss. predicting. particularly if the individ. However. Smith. Bentz et al. and also silica fume particles both reduce the initial thickness of the those in entrained air voids. high performance concrete is much less tually soften even the much less soluble C-S-H. Sulfates in fresh “abuser-friendly”. The structure provides continuous The materials science of concrete provides a foundation for un- pathways for the transport of fluids or ions. ice formation in large pores in the paste and in some aggre. otherwise caused by Because of the greater porosity and the connectivity of the ice formation in capillary pores [46]. paste and prevents excessive expansions. is proportional to stress/strength ratios up to 0. Similarly. In concretes. pores in the transition zone. based on the underlying physical and chemical mechanisms. Further work is needed to provide the necessary data. such as the [3] Gartner. performing amazingly well neutral waters causes leaching of calcium hydroxide from the even under the less-than-ideal conditions that prevail in the paste. For high strength con. ensure the desired performance. which can be destructively expansive if there is in.. 1976.. These crystals in frozen capillaries. however. Ideally. other complex salts. M. under some conditions. ing strain and pseudo-plasticity at stresses above about 0.. Thus the tran. as we seek to increase the strength or durability of 0.). microcracking also begins in about this same range. smaller capillaries re- erties of the concrete. sodium. W. E. 147–180. and sulfate ions in amounts suf. Some details provides an incentive for further development of performance- are noted here to relate previous sections to specific properties based specifications. By developing models and verifying quire lower temperatures to be penetrated by the growing tips them against experimental results. . for example.008 in. 12. Vol. new problems: a greater tendency to crack. 272. If entrained air voids sition zone is thinner and more closely resembles the bulk are closely spaced. Also available through Portland Cement Association as Monograph 43. No. J. 38. 4. C. 8–21. U. Thomas Telford. Hydrates. The Properties of Fresh Concrete. R. 1997.. 1029–1051. R. Cement Pastes. and Gillespie. HELMUTH AND DETWILER ON THE NATURE OF CONCRETE 15 [5] Adamson. Vol. T. Technical Report No. H. E. Institute. A.. L. Chemistry of Cement. and Berger. A. R. Detroit. D. 3. A. 1981.. pp. IL. Jan. 575–579. (Wiley. [28] Helmuth. [46] Helmuth. 2–6 June Ph..” Construc- Congress on the Chemistry of Cement. Vol. No. Highway Research Board. and Beaudoin.. 1962. [26] Winslow. Stanford. Paris Editions Concrete Science. Essex. Highway Research Board. J. J.. January 1991. 193–197. Early Age Autogenous Shrinkage of Concrete. Hayes. VI-0/1–30. Wiley. Whiting. D. J. 332. G. National Bureau Cement Pastes Cured at Elevated Temperatures. “Phase I: Energy Conservation Potential of Hydration Rate of Alite. 156. III. 1987. “Inelastic Behavior of Hardened Portland August 1972. “Avoiding Material Incompati. Properties of Concrete. 1980. E.. H. 8. N. H. J. 21. American Ceramic science Publishers. E. Septima. . DC. and Turk. 1995. of Concrete IV. Tokyo.S. L.. 5. C. 121–125. pp. 1972.. NJ.” Technical Report No. 1962. K. 462–475. 280. and Gjørv. pp. and Roy. [Rheology of London. M.” Journal of the American Concrete [22] Richardson. Kuga. Sept. R. Washington. Cement Association. 193–197. 2nd ed. “The Effect of W/C Ratio and Curing Prentice-Hall. 14–15 June 2002. Vol. 1968.” Cement and of Standards. Westerville. Silica Fume. DE86-001926. Espoo. III. and 566–567.. and Detwiler. G. “Densified Cement/Ultra Fine Particle-Based [34] Helmuth. 40. pp. the 10th International Congress on the Chemistry of Cement. [44] Mehta. Physical Chemistry of Surfaces. Proceedings. Jan Skalny and Sidney Mindess. Concrete. A. F. and Mann. S. [9] Helmuth. 14. NBS 2001. A.. Engle. [32] Sellevold. pp. p.. Gothenburg. E. Washington. pp. 77–88. pp. Copeland. p. and Odler. pp. T. W. and Diamond. 1960. 285–298. Longman Scientific and [19] Detwiler. A. [17] Tazawa. T. 855–869. 2.. O. “On the Mitigation of Early Age [39] Woolf. M. R.. Monograph 43. Fourth International Symposium. H.S.. J. D. S. 10. pp. Schlangen... 5.” Final Report to U.. Englewood Cliffs. 25. R. Vol. A. No.S. C. “Development Engineering. Journal.. [38] Helmuth. P. Malhotra. 4. Stanford University. Washington. and Young. crete Research. erties of Cement Paste.. H.” Superplasticizers in Concrete. of Microstructures in Plain Cement Pastes Hydrated at Different [33] Helmuth. Department of Commerce. lære.. “Variables in Concrete Standards. the Properties of Cement-Based Composites. 627–638. Symposium on Structure of Temperatures. J. dissertation. V. and Geiker. CR7523-4330. Sweden. Slag.. H. Proceedings. [18] Bentz. D. P. 2.” Cement and Concrete Research. D. PA. Norway. 1962. 131. OH. Vol. DC. 1995. U. 1969. Washington.. Ottawa. 2nd ed. på Betong med og uten Tilsetning av Silikastøv. R. Aggregates and Portland Cement Paste which Influence the Vol. 95–99. Washington. pp. R. Hansen. 51. A. Vol. Strength of Concrete. “Backscattered Electron Imaging of on the Chemistry of Cement. 1986. No.. Heyden. D. NJ. 1966. 723–740. D. U. pp. Vol. 9. pp. Cement and Con- 112–117. “Pore Size Distribution and Per. pp. A. K.” Roads & Bridges. R. DC.. Vol. pp. “Investigation of the Low-Temperature Materials. S. “Structure and Properties of York. F... Proceedings of the Third International Research 1966. New York. 1980. 155–199. and Shkolnik. Aug. and Natural Pozzolans Congress on the Chemistry of Cement. E. NTIS No.” Materials Science [24] Mehta.. Takahashi. F. American Concrete Institute Proceedings. Trondheim. I. J. Paris. Stanford. English preprints. pp. Department of Civil Engineering. 259. Society. Detwiler. R. O. J. A. Vol. Nov. 387–400.. Vol. S. National Bureau of [42] Cordon. O. J. R. Ceramic Society. and Manmohan. pp. VII-1–5. R... pp. Proceedings. UK. and Helmuth.. 154. VTT [36] Helmuth. paper 2ii068. Ed. No. H. in Fly Ash. July. 3. Technical Research Centre of Finland.. 11. Prentice-Hall. 60. J. Department of Civil [13] Kjellsen. A. II... July [12] Skalny. June 1981. 75.. 1984. gress on the Chemistry of Cement.. “Influence of Cement Composi. C. D. pp. Cement Paste. P. DC.” Proceedings of the 10th International Congress [43] Hadley.. Addition of Silica Fume. E.S. Vol. tion on Autogenous Shrinkage of Concrete. Fourth International Symposium on of Energy. pp. G. paper 2ii071... 1987. Cracking. A. Gothenburg. A. 1981. D. 97–110. pp. M. Distribution Control Phase II. “Pore Structure of Calcium Silicate 1990. L.. Sweden. pp. November 1982.. Den Ferske Betongens Reologi og Anvendelse [10] Taylor..” Self-Desiccation and Its Importance in Concrete ASTM STP 169A. Concrete Structure. pp. [6] Powers. [23] Goto. J. July-August Simulation of Interfacial Zone Microstructure and Its Effect on 1981. Paper II-5. “Energy [20] Mindess. 1974. MI. K. K. 577–608. 135–144. H. Proceedings of the Publication 446. Vol. Sakai. and Verbeck. E. the Chemistry of Cement. [16] Holt.” Proceedings of the 10th International Portland Cement Particle Size Distribution Control. Technical. and Gartner. A. Department of Commerce. [14] Bache. S. 647. 1980.. II. E. and Garboczi.C.” Proceedings of 1954. 76–79.. 1986. No. West Conshohocken. R.. ASTM International. LT257. Properties and Materials. and Miyazawa. 1–32. CA. tion Technology Laboratories Final Report. Seminar in Lund. Congress on the Chemistry of Cement. in Norwegian with English summary]. Gothenburg. 218–219. I. D. Special Report 90. Institutt for Bygningsmaterial- Symposium on the Chemistry of Cement. Purdue University. E. W. CA. 179–189.” Cement and Concrete Research. E. 42. M. 364. 1961.. [29] Parrott.” Proceedings of the Fifth International Doctoral dissertation 1990:45. Fresh Concrete and Application to Concrete With and Without [11] Verbeck.D. Concrete Research. 1968. 1. Eds. M. 829–833. Hardened Cement Paste. New York).” Proceedings. Feldman. Inter. No. in Principal Reports. 315–336. 4. pp. “Effect of Pozzolanic Additives in the Portland Cement on the [35] Helmuth. Vol. pp. P. Technology. 1997. Sweden.. [15] Asaga. “The Structure of C-S-H in Hardened Slag Institute. May 1974. Monograph 43.. M. Norges Tekniske Høgskole. Vol.” [45] Bentz.. SP-91. Temperature on the Permeability of Hardened Cement Paste. May 1967. 76–86. pp. Cement Chemistry. pp. Washington. 2–6 June 1997. 1960. [31] Wallevik. 209–245 and 317–379. Vol. II. Fly Ash in Cement and Concrete. Seventh International [30] Ramachandran. R. R. Paris. Skokie. 2. W.. Y. and 156–163.. Sixth International [7] Helmuth. 3rd ed. J.” presented at the 2nd International Conference on Dynamic-Mechanical Response of Hardened Cement Paste. H. to 2–6 June 1997. 293. Stanford University.. R. Department [21] Powers. 57. [41] Helmuth. [37] Powers. O. 195–203. on the Chemistry of Cement. Vol. Department of Energy. W. and 392–436. “Structures and Physical Prop.. S. and Turk. [40] Neville. in Concrete. 113. in Concrete and Concrete-Making Materials. March 1979. Portland Association. V. Harlow. A. bility Problems in Concrete.. Conservation Potential of Portland Cement Particle Size wood Cliffs.. April 2004. E. A.. Fourth International Symposium [25] Cao. Journal. Portland Cement [8] Helmuth. and 401–402.” 7th International Con. paper 3ii107. D... W. Journal.. August 1963. American Concrete Moscow. R. Philadelphia. DC.. New [27] Copeland. American meability of Hardened Cement Pastes. M. pp. No.. and Daimon. 1980. Vol. “Computer Cement and Concrete Research... E. The Nature of the Paste-Aggregate Interface. L. Portland Cement Paste and Concrete.. Vol. The erences on general sampling theory and practice. The chapter in 169C was largely written by Ed Abdun. Procedures. Army Corps of Engineers. One is that details of sampling for various terial. and to crete uniformity and is often part of the description of the outline the major features of sampling practices described in hardened concrete properties in a structure. the variation is not of particular interest. It is at least im. sampling is often a ne. both of these problems exist in a material source or in hard- Nur and contained an extensive bibliography on sampling. and by Abdun-Nur and Poole in taking of the sample. and either or STP 169C. it is important for sampling to glected part of the testing process. would plausibly be the case for some materials sources in cal importance in determining the meaning of the test results which considerable blending of material will occur prior to representing that sample. cause test results to represent the average property of the ma- tribute to this. by E. In this case. who may already sampling heterogeneous materials. E. then test results may poorly represent the ma- chapter in this edition focuses more on the details of sampling terial under examination. MS. and Practices of Sampling of Concrete and Concrete-Making Materials Toy S. but rather the aver- It is not difficult to make the argument that the details of age property of the material is the object of the testing. needed for monitoring material supplies to help control con- to discuss details critical to specific sampling problems. This information on uniformity is often cepts as they apply to concrete and concrete-making materials. concrete-making materials and of all finished concrete. If sampling is inadequate. Variation is a normal part of the production stream of all ferred to the bibliography in 169C as an excellent source for ref. At least two things con. or to smooth out this variation. The ened concrete. In some instances the purpose of the work is to de- The purpose of this chapter is to discuss general sampling con. and where samples are taken can often be of criti. challenge for sampling is to either capture the nature of this variation. The reader is re. current ASTM standards. 1 U. and therefore require knowl. In other cases. A. which include to some de- be under severe time constraints. making concrete. Proudley in STP 169. Another reason may be that gree most concrete-making materials. This how. as they are represented in current standards. Engineer Research and Development Center. uniformity of concrete production. are variation in a material or concrete structure and bias in the dun-Nur in STP 169A and 169B. Poole1 Preface Sampling Concepts THE SUBJECT COVERED IN THIS CHAPTER WAS The two major problems sampling protocols seek to address previously covered by C. Bias in the taking of a sample is particularly a problem in edge and training of the individuals involved. Vicksburg.S. pled. scribe the variation. as a minimum. when. A major source of bias in adhering to the details of standard guidance is time consuming sampling is segregation within the lot of material being sam- and expensive to execute in some situations. An exception to this would be the that. depending on the Introduction purposes for which the sampling and testing is being employed. they can develop an understanding of the case where the sampling and testing is to verify whether or not limits of interpretation of test results when sampling history is a stockpile is segregated to the point of causing a problem with unknown.3 Techniques. However. The intention of the sampling protocol is to avoid mis- portant for people responsible for the quality of construction representing a material source due to the sampling of a segre- to have some grasp of the important details of sampling so gated part of the material. materials are seldom obvious. Ab. 16 . The practice covers sampling of aggregate elements of a grid superimposed on a structure. for reason- unit (or sometimes unit). particles to become segregated at the bottom of the pile. These are the lot.” etc. All concrete aggregate is a mixture load of material. but the phrase “. . in three increment samples (grab samples). the grab sample (or sometimes incre. The problem with stockpiles is the tendency for the larger aging in the process. ment). with a Aggregate relatively small number of units being actually sampled and Practice D 75 covers sampling of aggregates. equipment is available. However. Definitions vary among standards. stockpiles. For acceptance purposes this is often the amount of amount of sampling or the amount of testing per sample de- material for which a financial payment is agreed on by contract. range with the expectation that tests would then better correlate pling sections of ASTM standards. . may represent quite a bit of averaging of properties. The former is used when may also be defined by the user as the total amount of aggregate the full properties of a lot of material are unknown. is interested in determining the properties by sampling and Mostly for purposes of economy. but all definitions contain the flowing discharge or from a conveyor belt because of the rela- concept that they are samples taken as a single effort. can occur and the difficulty in dealing with it in these cases. C 494 uses the con- some discrete quantity. In practice samples required or allowed to make a composite sample and the definition of a lot is often determined by the user for his own as to the number of composite samples that need to be ana- purposes. in the material being tested. Units are production. This is often un. The practice each grab sample represents a relatively small fraction of the discourages sampling coarse-aggregate and mixed coarse- material being sampled. Again. ably uniform materials. which tend to easily segregate concrete. be based on some time interval of production. this may be an unnecessary detail. since there is essentially no aver. material or structure being sampled and the confidence inter- A lot is the fundamental unit of material subject to sam. It is typically the amount of material in which a user lyzed to make a determination. and from in-place roadway bases. . Standards The problem with sampling conveyances is that it is diffi- covering specific materials are usually rather specific as to the cult to get to various locations in the shipment unless power amount of compositing allowed or required. Rec- The composite sample is put together by blending two or ommended sampling involves using power equipment to dig more grab samples. and the number of samples. and fine and coarse with the purposes of the testing program. val on the test. the sample with performance of a batch of concrete. Grab sam. some standards vary the testing. into the stockpile and taking samples from many locations in positing directed in a sampling program. which to the production of concrete. curred in the loading of the conveyance. depending on the knowl- project over a day. are often used. The number of samples commercial production a batch of concrete might reasonably needed to test a lot is left undefined and must be determined by . ASTM standards that cover acceptance testing and amount of material offered for sale. The practice strongly favors sampling aggregate from a ples are defined in various ways. A sampling unit may have some meaning with respect lem associated with sampling aggregate is segregation. it may be a truck can lead to a biased sample. because of the ease with which segregation samples be taken at random locations within a sampling unit. capture this with a series of grab samples. the smallest amount of material typically used is the selected at random. samples over a total amount of material approximating this Several terms and concepts consistently appear in sam. potential aggregate sources—quarries and gravel deposits. A sample unit (sometimes called simply a unit) is a subdi- vision of a lot. problem. or the during handling. but typically a lot will be subdivided into a relatively large number of sample units. Depending on the amount of such com. The major prob- tested.. . So it would be a reasonable practice to composite grab are found in the various ASTM standards. the amount used to produce a single batch of of a wide range of particle sizes. etc. For example C 183 uses A lot might reasonably be the amount of product delivered to a a normal and reduced testing concept. In the case of concrete a sample unit (called a unit in D 75) is left to the user. the composite sample. particularly if grading is one of the critical proper- with grab sample (as in D 75). It cept of quality and uniformity testing. guide the user towards solving or avoiding the problems with usually depending on the amount of variation expected in a uniformity and segregation problems typical of that material. Some standards are more specific. while others leave it to transportation units. It is normally required that the sample units dices are included that give guidance on practices for sampling to be sampled and tested be selected at random. Terms such as “one pass” or “one aggregate and fine-aggregate from stockpiles and transporta- scoop. or it may be defined as edge of the quality history of a cement source. grab samples show the maximum vari. In the latter to be used in a construction project. its exact definition is often determined by Acceptance Testing of Concrete Materials the user for his own purposes. The simplest type of sample is the grab sample. For example.” features prominently in uniformity testing vary quite a bit as to the number of grab most definitions. standards will define a sampling unit. and that tive absence of segregation at these locations. which explains much aggregate amounts might each range from 2 to 10 metric tons of of the differences in the details of sampling requirements that material. An An important concept about grab sampling is that test results appendix to the practice does give some recommendations on among grab samples will tend to show the maximum variation practices to use if sampling these is required. The The number of samples required to adequately represent guidance for each sampling problem uses these concepts to a lot of material varies considerably among testing standards. a week. The term increment is synonymous tion units. such as a barge load or a train load.. conveyor belts. A test sample is defined as a composite of amount that goes into a single batch of concrete. Appen- the user to define. It is usually required that grab ties to be tested. only those tests that are good indicators of uniformity are run. pending on the purposes of the testing. POOLE ON SAMPLING 17 So the importance of problems of variation and bias varies contain 1 to 3 metric tons (Mg) of cement. realistic because the material is rarely or never used in the small The definition of what constitutes a lot and what constitutes amounts represented by a grab sample. This can be a relatively complicated statistical pling. Some production from flowing discharges. For example. a month. composite samples hopes of overcoming the possible segregation effect. so that if some segregation has oc- As mentioned above. it may be difficult to ation in a lot or production stream of material. ples be taken.18 TESTS AND PROPERTIES OF CONCRETE the user. from bags or packages. Each sample is represented by no more that 115 Mg of . In other cases the mill certificate is only a representation This the oldest (1944) standard covering the sampling of cemen. The standard gives instructions on compositing 2. and on frequency of samples therefore. Cement plants typically take grab samples every tions on when and where grab samples can be taken. number of samples required to develop the required resolution. certificate data. dures are allowed: 2. so test values are unit because of the layer of fine cementitious dust that can set. If it is relatively uniform or mented sources. Some may represent a longer regation is not heavily covered. (due to. but many standards do caution period of averaging. these into a test sample. ered in Specification C 989. while larger composites will show the average to tively minor contamination may show up as a significant con. during transfer between storage bins. This may constitute a relatively minor contamination sometimes cause grab samples to slightly exceed the specifica- considering the amount of material in the load. such as every hour during production. the cement. from bulk storage and bulk shipment by means of a slot. In some cases. quality assurance records. A reduced sampling and testing requirement is property. 3. The pro. transferred among storage units. chaser. from bulk shipment of rail car or truck. tificates for distribution to customers. then make a 24 h composite sample many grab samples can be composited for a test sample. Standards by manufacturers for quality control and for generating mill covering these materials typically give rather specific instruc. from rail cars. tificate actually represents reasonably closely the cement being Sampling of hydraulic cement is covered by Practice C 183. sample. ing frequency to be adjusted according to the uniformity of the ples is adequate. new and established sources. Sampling and testing for acceptance typi- about sampling from the surface of a storage or transportation cally involves considerably less compositing. though not in extensive detail. Information is given on stored. from a conveyor (from process stream) to bulk storage. Small residues of erties that typically fall near the specification limit. physical tests and chemical analyses are recommended only on ted tube sampler. ent levels of compositing for testing of different properties. and for full testing. from bags. and fineness are believed to 1. Therefore. this amount of detail is required to cover all scenarios. represent at least a 24-h average. Three standard sampling proce- 1. Hydraulic cement sources typically issue mill certificates listing test data for the cements offered for sale. and shipped to a site. for example. This practice contains it is not uncommon that the same mill certificate will be issued considerable detail on the sampling of hydraulic cement for pur. from bulk storage at point of discharge. C 183 is probably different from the sampling procedures used rials must overcome is manufacturing variation. The number of samples is intentionally left undefined. Two standard methods of sampling for acceptance testing Like hydraulic cement. pozzolan is stored and shipped in purposes are allowed under all circumstances. The mill certificate typically reflects values from also relatively specific instructions on the number of test sam. These procedures cause the sampling and test- the criticality of test results is low. a specific number of grab Sampling of ground-granulated-blast-furnace slag is cov- samples are prescribed for each of these optional methods. the cer- ment will exceed normal levels or fail to meet requirements. some cement tamination if a grab sample is taken from the first material plants will sample and test for these properties at a higher fre- taken from the container. The methods are: a number of configurations. mill certificate data probably ples required to adequately represent a lot of production. As with the two standard methods. Practice E 122 is designed to assist in determining the allowed for these sources relative to an undocumented source. of typical values one can expect in the product. monthly composites. companies in the frequency with which they produce mill cer- tamination can occur) is that the insoluble residue of the ce. with shipments for quite a long time. depending on the amount of this variation. on how hour during production. but this rela. Sampling fly ash and natural pozzolans for acceptance A number of configurations exist by which hydraulic cement is testing is covered by Method C 311. more likely to reflect more of the manufacturing variation in tle there as a result of the loading or transfer process. while other 2. then a small number of sam. require daily (or at least every 360 Mg) testing. comply with the limit. from trucks (road tankers). Therefore these test data may differ from the mill cedure is typically to remove several inches of material before certificate data. the latter requiring six months of 4. Four optional methods of sampling for acceptance testing This practice prescribes different frequencies and differ- purposes are allowed contingent upon approval by the pur. Lack of agreement between a user’s test data and mill cer- Cementitious materials are sometimes carried in trucks or tificate values can be a serious source of contention for prop- rail cars used for hauling other materials. A common result of such a sample quency. required for acceptance testing. source and the proximity of a material’s properties to the spec- cality is high. taking a grab sample. size of samples. sold. titious materials and the most detailed. and Each method directs that a specific number of grab sam. These methods are: Moisture content. then more samples must be taken to capture this ification limit. In these cases. types of samples. The standard also distinguishes between 3. because the number needed to char. from conveyor delivering to bulk storage. The practice distinguishes between sources of cement that as explained in the practice. acterize a lot depends on the variability of the material in the lot Procedures are given for calculating control limits on docu- and the criticality of the test result. from bulk storage at point of discharge. poses of determining conformance with purchase specifications. loss on ignition. fly ash and cement being transported in There are also considerable differences among cement the same trucks or stored in close proximity such that con. but if the material is quite variable or the criti. Seg. such as al- these other materials may reside in the bottom of these con. kali (Na2Oe) and sulfate content. this composite sample. 1. tion limit. Manufacturing variation will tainers. Recognizing this problem. have a documented testing history and undocumented sources. Sam- with additional instructions in the standard on compositing pling is allowed to be either by grab sample or by a composite into a test sample. The user should Cementitious Materials be aware that the sampling and testing frequency described in The major problem sampling schemes for cementitious mate. although tice and not a specification. Seg. The principal precautions are to avoid sam- Curing Compounds pling the very first or the very last material delivered from a The sampling of curing compounds is covered in Specifica. C 917 predates C 1451 and is the cannot be stirred. One is that samples be taken from either the ex- Chemical Admixtures treme ends of a mixer. if concrete is sampled directly from the Sampling of chemical admixtures is covered in Specifications mixer. The solids may either settle or float getting a segregated sample due to separation of coarse aggre- on prolonged storage. One is testing to determine unit. sis should be on composite samples taken from each. can occur when the gate on the delivery stream is partially tainers to be sampled from a lot. sampling at different levels of the tank using model on which the latter was developed. as in uniformity in freshly made concrete Sampling of silica fume is covered in Specification C 1240. Therefore. on the av. In the case of large storage tanks that specific to hydraulic cement. of poor mixing. when samples A major concern in sampling liquid products is segrega. and open-top. The purpose of these precautions is to prevent particles in a liquid carrier. poses using a practice of regular sampling. These are ap- for sampling. No definition of lot is Analysis of uniformity among concrete batches is covered offered. a concrete producer’s performance criteria. POOLE ON SAMPLING 19 material. standing.6 rounded to 5) would be sampled ary mixers. hydraulic cements. If unifor. Mixer uniformity is covered in Specification C 94 on tail. The standard is not exactly clear on this. The other is testing to determine production chased. so of the total number of containers in the lot. rounded to the guidance is given to avoid these conditions. sampling of silica fume is not covered in great de. stream uniformity. The apparent purpose in C 172 is to capture the average prop- tom of the container. are taken from the discharge stream. The first precaution is the exact oppo- regation is the major source of problems in sampling curing site of the guidance given in C 94 on mixer uniformity. Instructions are also given . On standing. This detail is currently under consideration for revi. is representative of the lot under test. revolving-drum or agitating trucks. the analysis should be on grab samples. Segregation of the concrete contain specific guidance for determining the number of con. agitating and sampling from erties of the batch of concrete and not let irregularities in the the top and bottom of containers is required. so results the specification) are sampled using the same grab-sample and show the maximum variation in a material. while a user might each required to be made up as a composite of at least three want to determine uniformity of the materials according to the grab samples. Sampling of air-entraining admixtures is covered in Speci. as the metric for the analysis and determination of compliance. These standards fringes bias that determination. Current specifica- a special sampling bottle is required. mixer and to avoid practices that will cause the concrete to seg- tions C 309 and C 1315. of these grab samples. of concrete. These standards use compressive strength Uniformity may be determined using either grab or com. posite sampling. one sample is collected for each 2300 Mg of material pur. by ACI 214 and 318. or from the first and last 15 % of the batch. mixer performance as measured by uniformity within a batch erage. Sampling Fresh Concrete fication C 260. Specific instructions are given for sampling from station- tainers in a lot. ready-mixed concrete. which compound. or for other specific uses. and does not differ substantially. but left to the discretion of the user. which contain identical guidance. ACI 318 gives mini- mity among lots or sampling units is required. The standard relies heavily on Practice C 183 for guidance. Method C 917 is a similar standard stirred prior to sampling. non-agitating trucks. There are two important requirements in sampling for mixer uniformity. or in concrete-making materials. For example. This is particularly a problem if the liquid is not impede the flow of concrete from the mixer. an entire cross section of tion on storage due to settling or floating of one or more of the the discharge stream be collected and that nothing be done to components. The specification recognizes two purposes crete is sampled on discharge from the mixer. If the uniformity within a lot or sampling unit ACI 214 gives sampling and analysis procedures for determining is required. then the analy. for testing. Sampling units are chosen for testing such that. True solutions do not segregate on gate from mortar. the exact structure of the sampling the physical acquisition of the samples more resembles the scheme is not defined. Sampling from a single batch of fresh concrete is covered by Practice C 172. The sampling guidance is adapted from Speci- fication C 494. regate during sampling. when con- C 494 and C 1017. Determining uniformity of concrete-making materials is The specification directs that containers be agitated or covered by Practice C 1451. The number is the cube root closed or when only part of the delivery stream is collected. tions on concrete-making materials do not have uniformity lim- Solid-phase admixtures (called non-liquid admixtures in its. Sampling for Determination of Uniformity sion. but the general guidance is offered that These two sampling schemes could easily result in different they should be distributed to insure that the composite sample calculated levels of uniformity. The practice is based on analysis of grab samples. A techniques used for cementitious materials. materials supplier might determine uniformity for its own pur- Acceptance testing is performed on composite samples. but rather a suspension or an emulsion of solid closing the gate. then five (4. next largest whole number. As with slag. Since it is a prac- composite-sample concepts as for liquid admixtures. such as partially a true solution. The other requirement is that. the solid component of many curing is to intentionally sample the first and last part of the batch. One is for determining properties for acceptance parently the locations in a mixer most likely to show the effects testing and the other is for determining uniformity. There is no specific guidance as to the location schedue on which they are received. but apparently this mass of material represents the maximum size of a sampling Uniformity testing takes two forms. Mixer-uniformity tests are normally run although sampling frequencies are somewhat higher than for to determine the minimum mixing time required per batch. compounds will either float to the surface or settle to the bot. paving mixers. mum sampling frequencies for quality assurance purposes. if there are 100 con. calculating. It also discusses some problems en- be in two or more categories with respect to composition or countered in executing probability-sampling plans. If sampling is not done properly. Practice D 3665 lem is relatively simple if the location of the problem is known. particularly when property variation is not obvious number table. The Chi-Square test is purposes. Practice E 105 ture may result.” The meaning of this phrase is unclear. some knowledge of the variation in the material and testing The term Probability Sampling is sometimes used in this process.3. probability sampling rules. if such are found. procedures for determining unbiased estimates of experimen- is to take a preliminary round of samples to determine whether tal or measurement errors. No other guidance is given tice distinguishes two types of problems. sample sizes. This section of the practice probably ent approaches to sampling. It uses ter- samples taken. The practice recommends at least ten. identifying the cause of some kind of concrete problem. equal sections. and so requires some study to fol- pose (see below). the more samples The practice covers topics on auditing the sampling plan. It is not specific to concrete or are preferable since systematic sampling can sometimes cause concrete-making materials. . mining project specifications on strength. cance of the frequencies of each type of concrete found (if ing in-place properties is covered by Practice C 823. A useful approach. Practices E 105 and E 122 are cited for this pur. It gives minimum sampling fre- of performance by using the Chi-Square test (5). “. the practice of samples needed to give an estimate of a material property to actually recommends using random sampling methods. The practice gives examples of how not appear to have a problem. The full expression of the problem or problems is represented. Clearly. De- termining the number of sample units requires some experi. This type of calculation also requires tures in a structure. One is This practice describes recommended rules for setting up a when all of the concrete appears to be of similar condition random sampling plan. The user must determine the de- the analyst to miss or to overrepresent regularly occurring fea. The practice recognizes two conditions. if such exists. Such a test might be applied Sampling Hardened Concrete in the analysis of the data obtained from samples of a concrete of mixed types or conditions to determine the statistical signifi- Sampling concrete from structures for purposes of determin. Determining an adequate number of samples low. as long as there is no bias in the selection This practice gives guidance on how to determine the number of sampling sites. This practice was developed to assist in random sampling of Samples of problem concrete and similar concrete that does road and paving materials. and the properties of the structure. as well as sampling guidance for hardened concrete usually applied to the analysis of count or frequency data to de. termine whether the number of events in one category occur sized aggregate by wet screening. The practice gives information on how to estimate this context. is not specific to concrete or concrete-making materials. quality (called Situation 2). then. re- taken. For Situation 1. The Sampling units are chosen by some random selection practice is particularly designed to assist in one-of-a-kind stud- method. where there is no previous experience to rely on. design a more comprehensive ACI 214 plan to determine the extent of the problem in more detail. sired level of precision. The practice comments on the issue of the number of ies.” The (5) is a quencies for concrete for quality assurance and acceptance reference to a standard statistics text. if possible. there is cause to believe that there are problems in the concrete. . This standard gives guidance on sampling. each requiring differ. are usually taken to use a random number table to determine which sublots using judgment as to number and location to insure that the (sampling units) should be sampled from a lot of material. sampling plan that will be suitable for evidentiary purposes.20 TESTS AND PROPERTIES OF CONCRETE for sampling concrete containing large nominal maximum. . practice also gives information on how to determine the num- Sampling to determine the range and distribution of ber and size of sublots. “In Situation 2. and us- Practice E 141 gives guidance on how to properly sample for ing among-batch variation in a concrete production for deter- cases likely to be part of a legal dispute. It vestigation. One is sampling for purposes of needs to be revised. on sampling for Situation 2. but not less This practice gives recommendations for rules for setting up a than the number of separate areas that are included in the in. but is not specific to concrete and con- (called Situation 1). The other is when the concrete appears to crete-making materials. The practice recommends dividing the structure or from other sources if there is no such information in the actual parts of the structure under investigation into a number of testing program. Sampling for the purpose of analysis of a concrete prob. significantly more or less frequently than the number of events in one or several other categories. Paragraph 11. appears to be very confusing. on visual inspection. It gives rules for accepting or rejecting evidence based on requires some experience and judgment as to the purposes and a sample and for data collection procedures for legal purposes. The paragraph reads. samples were taken at random). economic limitations of the analysis. but no guidance is offered on how to determine minology that is unconventional relative to that commonly this number. samples Building Code ACI 318 may be taken for comparison with respect to several categories This is the Building Code. specific to Situation 2. The prac. Practice E 141 ence. is more complicated. the more detail will be developed in the description of porting formats. in cases of disputes over strength. and the other is sampling for purposes of describing the average Other Guidance and distribution of properties of concrete in a structure. an incorrect description of the state of a struc. As shown in a later paragraph. which the desired level of precision. any random or systematic sampling Practice E 122 scheme is allowed. found in concrete standards. The practice contains a large random- properties. The individual sections are sample units. ASTM C 823-00. ASTM C 42-03. ASTM E 122-00. ACI 318-99. POOLE ON SAMPLING 21 Referenced Documents ASTM C 917-98. Practice for Evaluating ASTM C 989-99. Use in Producing Flowing Concrete. Concrete. Specification for Chemical Admixtures for Concrete. ASTM D 75-03. ASTM C 1451-99. ASTM C 309-03. Practice for Random Sampling of Construc- Compounds for Curing Concrete. Specification for Ready-Mixed Concrete. Test Method for Obtaining and Testing Drilled ASTM C 1240-03a. . Specification for Air-Entraining Admixtures Ingredients of Concrete from a Single Source. ASTM C 94-03a. Specification for Liquid Membrane-forming ASTM C 172-99. Furnace Slage for Use in Concrete and Mortars. Practice for Sampling and the Amount of Test. for Use as a Mineral Admixture in Hydraulic Cement Concrete. Practice for Determining Uniformity of ASTM C 260-01. ACI 214-77 (Reapproved 1997). Test Methods for Sampling and Testing Fly ASTM E 105-58 (Reapproved 1996). Specification for Liquid Membrane-Forming ASTM D 3665-02. Practice for Examination and Sampling of ASTM E 141-91 (Reapproved 2003). Practice for Accep- Hardened Concrete in Constructions. acteristic of a Lot or Process. for Concrete. crete. ASTM C 311-02. tance of Evidence Based on the Results of Probability Sampling. Practice for Sampling Freshly Mixed Concrete. Test Method for Evaluation of Cement Strength Uniformity from a Single Source. Practice for Probability Ash or Natural Pozzolans for Use in Portland-Cement Con. Specification for Use of Silica Fume Cores and Sawed Beams of Concrete. ASTM C 1315-03. Practice for Sampling Aggregates. with a Specified Tolerable Error. Specification for Ground Granulated Blast- Strength Results of Concrete. Building Code Requirements for Structural ASTM C 1017-03. ing of Hydraulic Cement. tion Materials. Practice for Calculating Sample Size to Esti- ASTM C 494-99a. the Average for a Char- Concrete. Sampling of Materials. Specification for Chemical Admixtures for mate. Compounds Having Special Properties for Curing and Sealing ASTM C 183-02. curve can be constructed to show the probability of acceptance (or rejection) at any quality level for the acceptance plan.4 Statistical Considerations in Sampling and Testing Garland W. published in 1978. A. Cordon that first appeared in the peal to the designer of the plan. the user’s specifications. St. many sources. When a material is exactly at the rejectable quality plication of statistical probability to the field of concrete and level (RQL) as set forth in the acceptance plan for a contract. T. the probability of rejecting that material is the contributions of previous authors regarding the practical ap. Other tools that are helpful include upon statistically assessed test data applicable to concrete and computer simulation programs to be used in the development concrete-making materials is now an accepted industry prac.. tween the AQL and the RQL. A few are listed in the references. Inc. One of the most succinct papers. crete are to be determined with a known probability of meeting contained the chapter entitled “Evaluation of Data. and Walker [23]. Arni. much research and development work was done expected pay (EP) curves that are developed to show the ex- in and around the decade of the 1960s that aided in establish. Since it tion will review and update topics as addressed by the previous is possible for the quality level to vary over the entire range be- authors.. introduce new clarification of the concepts presented. The number of each is of this chapter is to provide suggestions regarding the use of recorded for use in decisions concerning the use or other dis- statistical applications that are practical. J. A. If the characteristics of concrete or of a material used in the con- pling. contained the chapter entitled “Size and Statistical Parameters [2–5] Number of Samples and Statistical Considerations in Sam. if the Introduction plan specifies accept/reject decisions based on specified numbers of tests. The for a contract. If needed. Albans. Steele Engineering. explaining the need for probability-based concrete unsatisfactory so that the relevant parameter is percent satis- strength specifications was published in 1962 [1]. valuable. Two types of risks that are often 1956 edition. testing. probability of accepting that material is the buyer’s risk. and the buyers risk (). tions to the sampling and testing of concrete and concrete- making materials has been addressed by chapters in each of General Considerations the four previous editions of ASTM STP 169. of the various pay factors is one requirement necessary for fur- tice. and appro.” by J. Many papers When a plan is designed to obtain the desired information documenting the work were published and are still available in through a process called inspection by attributes. pected average pay for given levels of quality. The fourth edition. The purpose factory or percent unsatisfactory. Zande & Associates. published in specifying authority’s risk. The third edition. 424 2nd St. The use of probability-based acceptance criteria founded ther evaluation of the risks. a plan is required. each item or various records. of percent within limit (or percent defective) acceptance plans tice in many areas. seller’s risk. Box 173. and evaluation of used on precast concrete items. Subsequent to the pioneering work by tailored to provide a predetermined buyer’s (or seller’s) risk. D. WV 25202. The second edition. F. If the acceptance plan incorporates pay adjustment The use of statistical methods to assess test data derived for the factors for various quality levels. or R. the concrete-making materials are hereby acknowledged. 1 Consulting Engineer. Construction of OC curves for each concrete-making materials is now established industry prac. published in 1966. WV 25177. The second edition also con. or the chapter entitled “Statistical Considerations in Sampling supplier’s/contractor’s risk. position of the item(s). published in 1956. monly called acceptance plans or other similar names that ap- tained the chapter by W.” by W. Hanna. ing the rational foundation for current practices. This edi. Attributes inspection is occasionally priate when used in the sampling. The first edition. by Abdun.” by the author of this chapter. When a material is exactly at the ac- 1994. contained the chapter entitled “Statistical Considerations ceptable quality level (AQL) as set forth in the acceptance plan in Sampling and Testing. Steele1 Preface concrete and concrete-making materials. group of items will usually be classified only as satisfactory or Nur. Such plans are com- McLaughlin and S.” by H. contained determined for acceptance plans are the seller’s risk (). Cordon. an operating characteristics (OC) and include appropriate references. Tornado. detailed texts on statistical methods and procedures are available from THE APPLICATION OF STATISTICAL CONSIDERA. or owner’s/ and Testing. 22 . determination of the and purpose of determining the characteristics of concrete and risks is a more complex task. to determine ness and kurtosis. How- The fundamental statistics derived from variables inspec. The range is also used occasionally to estimate the stan. as previously noted. the teristic will have values greater than. the coefficient of variation parameters needed to describe the characteristic. The two independent sets of data are from the same population) is simplest of the three statistics that are commonly encountered upheld for the variances. the average value (central tendency) of the measured behavior of another variable. in one figure. and of values tend to be grouped unequally above or below the second. and process variability. mode. The range is also the least powerful and its use is means of the two independent datasets. t-test. the range of values obtained. This is sufficiently well defined to permit rejection of the hypothesis information is conveyed by the standard deviation. F-test. usually expressed as a percentage.. a t-test is then used to compare the is the range. This spread sheet software used in construction activities have keys comparison provides information on test procedure and equip- for direct calculation of the standard deviation. etc. the comparison process is quently calculated. such as geo. acteristic of a material or product and recording the measured When the standard deviation is not reasonably constant for the value. First. It is culated t-value. the most useful statistic tractor. The purpose of tion of concrete and concrete-making materials include skew. as they are designed to do. The coefficient of variation is these comparisons provide information only on test procedure the ratio of the standard deviation to the mean of a group of and equipment variability. in addition to the stan. data gathered by a properly designed plan. either statistic may be used. is compared not uncommon to see the range used in decisions concerning to a critical t-value at the selected significance level. the second variable half will have values smaller than the average value. The d2S limit is the maximum acceptable difference be- metric mean. particularly when it is constant over the Inspection by variables is done by measuring the selected char. dif- or less than the frequency expected from a normal distribution. The values are used to calculate fundamental statistical range of values encountered. Note that it is acceptable crete and concrete-making materials are the mean and the practice to apply either statistic to subset ranges of the overall standard deviation. Such de. such as the average deviation. it does not show how far or in what way the hibited by the data when one variable is plotted against the other greater or lesser values may be distributed from the mean. If neither statistic is constant over disposition of the material or product. positive correlation {A} im- approximately one half of the measured values of the charac. the two sets of data dard deviation. The range conveys the difference between the results are to be compared. in one When the behavior of one variable is to be compared to the value.) Since d2S lim- dard deviation. and approximately one other tends to increase also. All that is indicated by a good correlation is that the trend ex- tant statistic. When more than one pair of split sample test variation (CV). a paired t-test may be used. ference two sigma percent limit (d2S % limit). range of values collected for the measured characteristic. The ratio of the variances is cal- measurement of concrete and concrete-making materials char. The calculated t-value is normally limited to specific applications (for example. not to use the range for this purpose. its appear in many ASTM standards. materials variability. based on differences within pairs.. A more powerful comparison process involves independent quently calculated for measured characteristics of concrete random samples obtained by representatives of the owner/ and concrete-making materials. control compared to a critical t-value at the selected significance level. The standard deviation indicates. culated and compared to a critical F value at the selected signif- acteristics is the arithmetic mean. plies that as one of the variables being correlated increases. Although the mean is a very impor. icance level. the F-test is used to compare the variances of the concerning the central tendency of data collected during the two independent sets of data. specifying authority and representatives of the supplier/con- Generally.2 Alternatively. If charts).e. STEELE ON STATISTICAL CONSIDERATIONS 23 The majority of plans designed for concrete and concrete. two statistics concerning dispersion are fre. . standard practice dictates otherwise. Skewness indicates whether the distribution whether the two datasets are from the same population. such comparisons will usually be twofold. in the Precision and Bias section of this chapter. First. measurements are made. words. The cal- largest and smallest value of the measured characteristic. The most useful statistic con. the preferred statistic. (Additional discussion of this limit and the d2S % limit is are usually not calculated. the standard deviation is preferred in such cases unless tion that are most useful in making decisions concerning con. the null hypothesis is upheld for the means. a powerful that there is no relationship between the two variables—in other statistic that measures variation about the mean. since many pocket calculators and are generally considered to be from the same population. should be considered. it is preferable ment variability. A good. by the supplier/contractor’s representative. to determine whether the material and completed mean (nonsymmetrical) rather than equally occurring on each work comply with the governing specifications for the con- side (symmetrical). other material using the same process followed in deriving the limit statistics concerning dispersion. This statistic is fre. how far above Other statistical terms will be encountered when an or below the mean other values will be and how many values owner/specifying authority requires comparison of test data will likely be found at any distance from the mean. are seldom calculated for concrete tween two test results obtained on a split sample of the same and concrete-making materials characteristics. Other statistics representing central tendency. 2 Letters in braces refer to the notes attached to the end of this chapter. scriptions are used in decisions concerning the use or other it would normally be used. conveys. If the null hypothesis (i. Both of the use of materials or products. values. However. when derived from set of values when said statistic is constant for the subset. ever. value. The additional terms encountered may include some or occurrence of values at any distance from the mean is greater all of the following: difference two sigma limit (d2S limit). derived by said authority’s representative with test data derived Other statistics occasionally derived from variables inspec. a correlation coefficient may be characteristic of the material or product. or significant. that the relationship is completely random. The mean (arithmetic). or dispersion. It also indicates that determined. Likewise. However. Kurtosis indicates whether the frequency of tract. If the coefficient of variation is constant. the hypothesis that the cerning the dispersion of said data is less straightforward. These are the range and the coefficient of easily followed. when may tend to decrease as the first increases (negative correlation). The standard deviation is making materials use a process called inspection by variables. the use of relation- from the sum of the squares of the deviations of the meas. . The standard errors of the slope and intercept indicate the significance of the relationship {D}. proper use requires a practical under. While both sets of measurements are affected by changes in the property of interest. system to measurements that might have been obtained by mated variance and corresponding standard error (the some other system introduces an additional degree of uncer- square root of the variance): sb12 for the slope and sb02 for tainty into the process. practical. there may be a large variation in the prediction obtained from the measured value. if any system of measurements is valid. However. b0. When a coefficient of determination. if the probability of inclusion is not the same for • There are three kinds of confidence intervals that can be all parts of the lot. the square of the coefficient of correlation.” The use of a ing included in the sampling operation. is calculated for an assumed linear relationship. If regression lines showing the relationship between data from two measurement systems are to be calculated and used for purposes other than illustrating the relationship existing in the data. this fact should be considered when evalu- calculated for a fitted regression line: the line as a whole. provide more reliable data {H}. Alternatively. Therefore. in appropriate situa- ured Ys above and below the fitted line. an equal chance of being included in any sample obtained lated and reported. are statistically related to each other and one of the test methods is used to obtain measurements that are then used to predict measurements of the other type. when a sample is used to evaluate a char- the other parameters. is to obtain samples from which an unbiased estimate of the sion was calculated and the upper and lower limits of the characteristic of interest of a lot of material or product can be data of both X and Y values should be reported along with obtained. tions. and the Y intercept of the line. In addition. Note C and the references contained therein illustrate this point. a point on the line. ships other than linear equations will. several points should be considered. 1—Regression curve and confidence limits for compressive strength versus rebound numbers [12]. new measurements are probably subject to the same degree of • Using an appropriate plan. ating data derived from the sample. When two separate measurements. data from which the equation was derived increases the degree sy2. all material in the lot • A confidence interval for the fitted line should be shown should have an equal chance of being included in the sample. This is usually accounted for by recognizing that many measurements are needed to derive a reliable line. a 100-yd3 (76-m3) concrete It should be reiterated when using regression lines that placement. the fresh concrete could be variation that characterized the original data. In addi. there is an estimated variance. then. in many situations this may not be standing of the confidence interval given {G}.e. • Derivation of a linear regression line involves determination of two parameters. would assure that all concrete had an equal chance of be- “the system must have validity within itself. Fig. on the graph of the line {E} (Fig. ures of variation (variances or their corresponding square roots) should always be given whenever a regression line Sampling is reported. Due to the departures of the data regression equation to convert measurements obtained in one points from the line. b1. r). There may or may not be a high nonlinear correlation between the variables. Consider. sy. each of these parameters has an esti. the slope of the line. sampled during the placement process in a manner that In general. the number of pairs of data from which the regres. or a future value of Y corresponding Given the preceding goal. The three meas. from the lot. and corresponding standard deviation. note that an r2 value that is closer to the value of 0 than the selected minimum only means that there is little linear correlation between the variables. Further.24 TESTS AND PROPERTIES OF CONCRETE Regression Lines The standard method of using paired data as a source in developing a process for predicting one variable from another is by calculating a linear regression line using the method of least squares [6–10]. calculated of uncertainty in the derivation. acteristic of a lot (quantity) of material.. This method is very useful in situations that involve actual calibration of a measuring device and in which the plotted points approximate the calculated regression line very closely with small scatter {B}. each obtained from different test methods. consideration should be given to selecting a minimum acceptable r2. 1). The goal of sampling concrete and concrete-making materials tion. for example. r2 (i. each is actually measuring two different quantities and each is affected by different sets of influences extraneous to the property of interest. to be a requirement that all material in the lot should have • When appropriate confidence limits are correctly calcu. the simplistic answer may seem to a given value of X {F}. Extrapolation beyond the limits of the the intercept. How- ever. Also. produce data from which unbiased estimates of certain char- ASTM Practice for Random Sampling of Construction Materi. as noted in the original example. five (or some other suitably determined number) 2000-lb (900-kg) unit will likely yield a better estimate of the randomly selected subsamples may be selected from each of characteristic being determined than would the performance the 2000-lb (900-kg) units for compositing. bility in the sampling and testing process. into a number of sublots or subquantities. the sample must be selected randomly. when the alternative provides a possible advantage in that much smaller number of subsamples obtained from the 2000-lb (900-kg) quantities of aggregate are handled in the final sample. The purpose of stratified random sam- critical stresses. as the number of subsamples samples may then be used to estimate the characteristic of the is increased. An engineer. although depending somewhat on the purpose The definition should also assist in a better understanding for which the estimates will be used. This The term “representative sample” has been used in many should include the type. Such decisions would likely be . to establish the 2000-lb (900-kg) unit may then be averaged and used in the reliability required in each case commensurate with the re- same manner as the data derived from the composited sample sources that are to be made available and with how much in- in the first alternative. consider the 2000-lb (900-kg) unit of aggregate gate is to be used to estimate that characteristic in 10 000 tons example set forth in the previous section on sampling. repre- tions for calculating sample size. a material (or process) will provide sampling direction. for example. out resorting to mathematical proof (which could be done). Final geometry. acteristics of the material can be derived. The second alterna. a particular characteris. To illustrate. tray the actual properties of the materials. using an appropriate plan for sampling hard. using procedures that Testing will allow an unbiased estimate of a particular characteristic of the material to be derived from the sample. estimates based on ten 10-lb may then be combined to form a single sample obtained from (4 1/2-kg) subsamples obtained from the 2000-lb (900-kg) unit each 2000-lb unit randomly selected for sampling. A second alternative for 200 subsamples will be far greater than that which can be compositing is available that provides the information needed derived from treating the 2000-lb (900-kg) unit as a single for estimating the variations within the 2000-lb (900-kg) units of sample.” This concept can be no samples or tests available. reinforcement. Likewise. creases. The most useful sampling. the reliability of estimates based thereon will 10 000-ton (9000-metric ton) lot of aggregate. it is likely that in most situations the hard. Note that “sample size” as senting the owner or specifying authority. The data derived from each subsample in a the cost of testing. the quantity and handling of samples definition would paraphrase the goal of sampling previously subsequent to selection should be clearly detailed [19]. the characteristic can be deter. that is. be easily determined. method. sublot or subquantity. who must rely on used in ASTM E 122 is equivalent to the “number of samples” samples or tests that do not provide reasonably unbiased esti- as commonly used in the construction industry. Then. Furthermore. it may be better to make Size to Estimate with a Specified Tolerable Error. is intuitively seen that the performance of a test on the entire Alternatively. therefore. The five randomly of a test on a 10-lb (4 1/2-kg) subsample obtained from the selected subsamples from each of the 2000-lb (900-kg) units 2000-lb (900-kg) unit. STEELE ON STATISTICAL CONSIDERATIONS 25 • In contrast. it mined from testing each of the 2000-lb (900-kg) units in total. be based on a determination of the consequences of inadver- other concrete-making materials. therefore. the information in the characteristic of interest that exist in the 2000-lb (900-kg) concerning the characteristic that can be derived from the unit of aggregate will remain unknown. mates of the properties of interest for materials or structures A useful concept when sampling concrete and concrete could probably make more appropriate decisions if there were materials is “stratified random sampling. This is called will be more reliable than the estimate derived from one 10- a composite sample. Results from the single composited lb (4 1/2-kg) subsample. a possible disadvantage to be considered is that variations However. Finally. and location of different ways in the construction industry. It is necessary. If. the Average no tests than to make tests with poor samples that do not por- for Characteristic of a Lot or Process (E 122) contains equa. a representative sample is a sample that is obtained from a lot or quantity of material. The reason for testing concrete and concrete materials is to nition is to be operant. The most conven- ened concrete in different segments of the placement ient number is usually equal to the number of samples to be would have an unequal chance of being included in the obtained. either fresh or tently accepting defective material due to a low level of relia- hardened. The number of samples needed to provide the information Similar examples could be presented for cement. other necessary for estimating a particular characteristic of a lot or concrete-making materials. very important that the circumstances in being sampled. aggregate for the characteristic of interest. ever. and concrete. With- (9000 metric tons) of material. and lack of accessibility all pling is to prevent the possibility that several samples would be contribute to the situation. If the stated defi. These decisions should also Similar types of examples could be presented for cement. It is also intuitively evident from the previous example that tive requires that each subsample be individually retained and testing additional samples or samples of greater size increases used for testing. unit equals 200. the reliability of the estimates will be equal. the reliability tends to of composite samples. noted. tic of several randomly selected 2000-lb (900-kg) units of aggre. easily implemented by dividing the lot or quantity of material ened concrete. How. this approach that of the 2000-lb (900-kg) unit. Obviously. each sampling situation be recognized and receive competent An adequate plan for evaluating specific characteristics of consideration. formation it is necessary to obtain. either fresh or hard- quantity of material with a given confidence in the results can ened. and concrete. The reliability of als (D 3665) contains a random number table that can assist these estimates improves as the number of test results in- the sampler in obtaining random samples. obtained from one segment of the lot or quantity of material It is. increase as the quantity of material undergoing test increases. frequency. Each sample is then randomly obtained from one sampling operation (or even no chance). ASTM Practice for Calculating Sample Although it is seldom articulated. ” “multi- uniformity as set forth in ASTM Test Method for Evaluation of laboratory. Precision and Bias Statements Other Useful Standards ASTM Practice for Conducting A Ruggedness or Screening One of the most important factors concerning a test method Program for Test Methods for Construction Materials (C 1067) that is used to determine acceptance and rejection of materials provides an economical procedure for the detection and re- and construction in a buyer-seller relationship is the informa. If more than two results are to be making materials tests. those noted earlier have been recommended number of test results existing for that particular process or as the most appropriate for test standards developed by ASTM lot of material. Chemicals (C 672) that uses an ordinal scale of measurement When test values from independently obtained samples and ASTM Test Method for Organic Impurities in Fine Aggre. other than editorially. lowed in deriving the value. specifications. design criteria. for a few nonparametric {K} compared. plete interlaboratory study. • Requirements for the designated number of test results terial or process is estimated from the evaluation of one set (one or more) that constitute a valid test should be stated of test results that have been obtained in accordance with in a test standard. The indices of precision used in evaluated with respect to a standard or potential standard such these standards are. C9. materials are ASTM Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials (C 670) Evaluation and ASTM Practice for Conducting an Interlaboratory Test Pro- gram to Determine the Precision of Test Methods for Con- Test data. Examples are ASTM Test Method for index. with appropriate standards. different multipliers are required to determine the tests this is not the case. However. While neither of these situations will generally data. terms preceding the value listed that will define the process fol- tion of hydraulic cement. to be useful after they have been obtained. When one of these indices is provided in a test stan- 214. properly planned interlaboratory study.” “within Cement Strength Uniformity from a Single Source (C 917). Recommended Practice for Evaluation of Strength Test dard. coefficient of variation of test results. The following items are Another consideration that may be encountered when very important in the maintenance of valid precision informa- evaluating values derived from test data is whether retesting tion in standard test methods: is appropriate. Standards {L} best suited for the determination of preci- These risks were previously defined and discussed in the Sta. ACI test. the practice of retesting is fully acceptable if all test results. split samples. cerning precision are of limited value in making acceptance or mizes the risk that the owner will accept faulty material and rejection decisions. Test values derived from independently obtained sam- such tests. provides detailed procedures for the time in 20 will the difference between two test results {M} on evaluation of concrete strength tests. obtained under approximately the same condi- The principles contained in the three cited standards tions noted in the precision information. The • When a standard test is revised. Generally. ples contain additional components of variance not present in cedures applicable to these types of test data. standard deviation or coefficient of variation obtained from a ASTM Practice for Sampling and the Amount of Testing of Hy. sion and bias of tests for concrete and concrete-making tistical Parameters section of this chapter. respectively. when the level of quality of a ma. based on standard test data. from other related tests are presented in ASTM Practice for .” “within laboratory.” etc. said estimate will be improved by in. appropriate standards.26 TESTS AND PROPERTIES OF CONCRETE based on conservative assumptions. with large safety factors. or other sigma limit (d2S) and the difference two-sigma limit in percent previously determined concepts. both precision information should be reviewed to determine original and retests. The versatile concept of moving av. in order of preference. 2(2)1/2 2.” “single operator. • Criteria used in deriving the precision information should cluding another set of test results. D4. duction of variations in test methods before initiating a com- tion contained in the precision and bias statement. Numerical limits. with appropriate standards.828 by the standard deviation of test results or the tive when commonly used statistical procedures are applied. Test standards that contain no information con- using faulty data are obvious. The indices are determined by multiplying the factor concrete-making materials will be more practical and informa. exceed the value above can be extended to many other concrete and concrete. The d2S or d2S % limit draulic Cement (C 183) utilizes control charts {I} and quality published in a test standard will generally have descriptive history to determine the frequency of testing and the evalua. the user of the standard can presume that only about one Results of Concrete {J}.” “between laboratory. Optimum cost effectiveness mini. the greater risks inherent in ing this point. and 3) the final evaluation recognizes the increased derived and used. Reference [26] should be consulted for other pro. indicated by the index. Although other indices based on different criteria can be tion. Typical descriptive terms include erages is demonstrated in the evaluation of cement strength the following: “single laboratory. the risk that the supplier will have acceptable material rejected. are 1) obtained and tested in accordance whether a new precision index should be derived. ASTM C 670 contains a table of multipliers for Scaling Resistance of Concrete Surfaces Exposed to Deicing determining indices for use in comparing up to ten test results. the F-test and t-test should be used as pre- gates for Concrete (C 40) that uses a nominal or classification viously discussed in the Statistical Parameters section of this scale. which are Procedures for determination of precision based on values included in specifications to govern acceptance decisions. the “difference two- as contract documents. Any evaluation of concrete or (d2S %). This is the Typical guidance can be obtained in numerous publications. and D18. Reference [27] provides additional information concern- yield optimum cost effectiveness. must be struction Materials (C 802). 2) included in the final evalua. obtained in accordance be outlined in the standard. Committees C1. test values derived from split samples. The median can be used to indicate central tendency for chapter. in the evaluation procedure. are to be compared. should be fully compatible with the precision and bias infor- rather than reliance on fallacious information with consequent mation contained in the test standard used for generating the unknown risks. These figures combined with the confidence cerning the appropriate inclusion of test method precision interval for the line give an approximately 90 % confidence in- values in specifications containing limits that are based on data terval for the predicted compressive strength of 27. illustrated in this case by a standard deviation of 0.e.2 MPa Procedures for deriving the variation of properties of (4530 psi). concrete strengths in the 1970s [15–18]. The water-cement ratio) results in a change in the distribution. One portion of the variation can be described as ran- {F} Reference 6 describes how to calculate these three dom or chance variation of the process and the other as the confidence intervals. Since the rebound num- ate comparisons of such derivations to precision statement bers themselves have a distribution with a characteristic scat- data are presented in ASTM Practice for Determining Unifor.6 to 35. this is not the limit of the final uncertainty Notes of the predicted result. averages of 20 rebound numbers. with only chance variation should result in some distribution propriate to use if the calculated line is to be used repeatedly of the measured characteristics. center. means of control charts. the intervals will actually contain the true average in its exact dicting what will happen in another type of test. and one should be able to pre- for predicting future values of Y from future observed values dict a range within which a certain percentage of the data of X. it is highly unlikely that the calculated line will gineering data. its size and affect on the derived measurements may be Later-Age Strength (C 918). however. confidence intervals have been plotted by multiply. Oc. rebound numbers obtained on slabs made from the same Three types of control charts that are frequently used are batches of concrete as the cylinders. MPa (4010 to 5070 psi). This use is discussed by linear equations for determining the relationship between cer- Hockersmith and Ku [11].50)]}. What it actually means. This point is illustrated in the case concerning tion of the maturity concept. this is insufficient evidence to conclude that the strength and the logarithm of a quantity called maturity of the true slope is other than zero (that is. many in-place tests on concrete tend to limits given. For any given determination of the line and its confi- relation coefficient has limited use in the field of analyzing en. toring the quality by means of regularly performed tests through- culating the relationship. The control chart became a well-established technique in ing the SY (standard error of the Y estimate) by the t value for production quality control during the World War II era. The concept goes back a long way. the concrete that is defined as the product of temperature at dom). this figure in- Other Test Methods (D 4460). each with the strength increases. tion in Specification Limits (D 6607) presents guidance con. The figure also shows the control charts for averages (or moving averages). gories. is that if the ex- show increases in the measurements obtained as concrete periment is repeated a large number of times.. STEELE ON STATISTICAL CONSIDERATIONS 27 Calculating Precision Limits Where Values are Calculated from For a hypothetical rebound number of 25. control hyperbolic curves representing the upper and lower 95 % con. for the average rebound measurement is from 24 to 26 (i.50 for mity of Ingredients of Concrete from a Single Source (C 1451). fidence limits for location of the line referred to earlier. Thus uncertainty of the predicted Y out the process of production. In fact. the 95 % confidence interval ASTM Practice for Inclusion of Precision Statement Varia. variation due to assignable causes. should fall. charts for standard deviations (or moving standard deviations). prediction of compressive strength measurements from pene. (degree-hours). then 95 % of the intervals so calculated will include itself constitute evidence that the relationship is sufficiently the true average. the relationship is ran. A 95 % confidence limit is often interpreted as meaning that 95 % of future results will be within the {A} For example. if the slope is not at least twice as large as The standard involves establishing a relationship between its standard error. which the curing is taking place and the curing time in hours {E} Calculation of the quantities needed to plot the confi. control . dicates a calculated average compression strength of 31.0 to 32. coincide exactly with the true line. dence interval is described elsewhere [6]. Unfortunately. with the 95 % confidence interval extending from concrete-making materials from a single source and appropri. but detailed work was done on its application to evaluation of tration and rebound tests in Refs [12] and [13]. and each time the 95 % confidence interval is behavior and the results of standard strength tests does not in calculated. 30. The basis of the theory arises from the fact that the gives an optimistic picture of the uncertainty of estimated Y variation of a process may be divided into two general cate- values. the average of all the X values used in cal. for Developing Early-Age Compressive Strength and Projecting nized. If some assignable cause (such as an increased {G} Figure 1 (taken from Ref [12]) illustrates the point.1 obtained by use of said test method. 25 [2(0. It is important to note that only the con. casionally. tain variables in concrete is contained in ASTM Test Method {C} Even when the existence of this uncertainty is recog. This is not correct and procedures. {B} An example is the calibration of proving rings that are {H} One example that illustrates the successful use of non- used for calibrating testing machines. Also. dence interval.5 MPa (4350 to 4710 psi). A process that is operating fidence interval for the location of the line as a whole is ap. The the number of points used and drawing parallel straight lines control chart is a combination of both graphical and analytical above and below the regression line. and control charts for ranges (or moving ranges). The best tool for doing this is by increases as the X value departs from X in either direction. {D} In general. ter. then regression line shown is based on 16 plotted points relating the values of the measured characteristic could fall outside the strengths of 28-day cylinders to the average of 20 Swiss hammer predicted range. This standard involves the applica- underestimated. the cor. A good correlation (or high correlation same materials and conditions and with the same number of coefficient) between the results of any test that exhibits such determinations. It should be noted {I} Monitoring Production-Continuous Evaluation (adapted that the upper and lower confidence limits are represented by from Ref [20])—One of the most effective means of maintaining two branches of the hyperbola that are closest together at the the quality of a manufactured product is by continuously moni- point where X X. This does not mean that any particular one of close to permit the use of one type of test as a means of pre. in the form of 6 by 12-in. (d2S) lim. a solution from the test sample is sponsible for the test method can obtain proficiency sample compared to a reference solution and judged to be lighter. re. sium volume that included seven papers presented at the The limit in a precision statement is to provide a crite- symposium. and D18 on Soil and Rock for Engineer- and ranges. Both of these standards should resulted in the publication of ACI Standard Recommended be studied and followed closely by any task group that is Practice for Evaluation of Strength Test Results of Concrete charged with writing a precision and bias statement for con- (ACI 214-03 ). a joint tical quality control [14. or the same. If appropriate. may be useful. a single iso- sometimes cause problems because of the fact that numbers lated failure to meet the criterion is not cause for alarm. both laboratories should significance. is not necessarily the same increment as that the results obtained are a valid test for the purpose. ment has undergone a number of revisions. In 1946. The appropriate action to take depends on how serious an ordinal or ranking scale [25]. or on rial. in the United States. The latter is sometimes not measurements of quantities. ing Purposes developed two practices: ASTM Practice for {J} Evaluation of Strength Tests—One of the earliest and Preparing Precision and Bias Statements for Test Methods for most widely used applications of statistics in the concrete field Construction Materials (C 670) and ASTM Practice for Con- has been in the area of evaluation of strength tests both of ducting an Interlaboratory Test Program to Determine the Pre- mortar cubes for the testing of cement strength and. most appropriate depends on various circumstances con- dard 214-65. standard deviation. In many cases. used to check the results and procedures of a single operator for instance. Test methods of the latter type the consequences of failure are. this docu. Such calculations are inappropriate when the tail more serious consequences than those connected with fail- magnitudes of the numbers indicate only order or rank and ure to meet a single-operator criterion. Adding ranking numbers of this type may occur in situations where there is a dispute about accept- and dividing by the number of measurements may have little ance of materials. tests are not unbiased samples from the same type of mate- Such tests measure on a nominal or classification scale. data from the Cement and Concrete Reference Laboratory or darker. the subcommittee re- C 40. category is higher or lower than another. ferent categories without any judgment being made that one Also note that conditions. ing precision statements when the necessary estimates (usually ders. In most cases. D4 on Road the control chart constants for averages. The latter may be treated as an ordinal propriate revisions to update a precision statement can be scale if one end of the scales is judged to be better than the drafted as shown in the ASTM C 670 appendix. Detailed treatment of this from one level to another. for the analysis of strengths of concrete specimens. more ex. Table 27 in Ref [22] contains task group of ASTM Committee C1 on Cement. and then the numbers are treated as though they watched to see if the failure persists.19. In another procedure. papers dealing with evaluation of concrete strengths [24]. laboratories. sion index was derived or that the samples used in the two its. The increment of one between scaling ratings of one operator (d2S) limit should be used to check whether or not and two. Central tendency and scatter can be indicated by obtain two results by the same operator who was used in the giving the median and the range. ASTM C 670 gives direction and a recommended form for writ- usually. The chief pioneer in this effort was Walker who published standard deviations) for precision and/or bias are in hand. operators. such as percent defective (or per. Thus the failure of a pair of results to meet the (d2S) crite- {K} Nonparametric Tests—There are some test methods rion causes concern that the conditions surrounding the two that do not provide numbers for which the customary tests may not be the same as those existing when the preci- processes of calculating means. the tests represented measurement on an interval scale. struction materials. Because of the num. however.” This symposium presented valuable information nected with the situation. and in most cases a degree of judg- on the meaning and use of ACI 214 and resulted in a sympo. ASTM etc.21]. The same amination of the materials and procedures. a reprint of ACI 214-65. and Paving Materials. Failure to meet a multilaboratory precision limit may en- cate scatter. The former between three and four. First published as a standard in 1957. cision of Test Methods for Construction Materials (C 802). C9. and reprints of two earlier rion for judging when something is wrong with the results. cylin. Which interpretation is vention on the subject “Realism in the Application of ACI Stan. {M} If two results differ by more than the (d2S) limit. change with time. specimens and even to calculate standard deviations to indi. . standard deviations. but are assigned to the different levels of quality of performance in an indication that the process under consideration should be the method. there is a temptation to average results of several which the precision statement was developed. a In 1971 a symposium was conducted at the ACI Fall Con. the American Concrete Institute (ACI) began work on an interlaboratory study and analyzing the results in order to statistical evaluation of compression tests that eventually obtain the necessary estimates. subject and tables of control chart constants for determining {L} As a result of concern about problems connected with upper and lower control limits are presented in texts on statis. which is the can be repeated. the single- spectively. test is performed in accordance with the standard from bers derived. In these cases. tensively. precision statements and how to develop and use them. for example. the difference between an object that measures 5 in a laboratory. In one procedure. and failure to meet the criterion leads to reex- cm and one that measures 6 cm is a length of 1 cm. five color stan. and use the single-operator difference as A test that provides measurement on a nominal or a check on proper performance of the test method within the classification scale is one in which results merely fall into dif. ment is involved. If the test is being difference applies to two objects that measure 9 and 10 cm. largely at the instigation of ASTM C 802 describes a recommended method for conducting Walker. and usually the procedures of the labora- type of measurement scale appropriate to most concrete or tory(s) involved should be examined to make sure that the concrete-making materials test methods. materials. apparatus. number of interpretations are possible.28 TESTS AND PROPERTIES OF CONCRETE charts for other measures. his study in 1944 [23]. used to determine compliance with a specification. When lengths are measured. multilaboratory tests. other end and the stages in between represent progression cent within limits). the AASHTO Materials Reference Laboratory from which ap- dards may be used. and other so called parametric statistics are applicable.. Vol. pp. [23] Walker. Woodward-Clyde Consultants. 1975. H. Fitting Equations to Data.” Publication Code IMQA-1. ASTM International. Engineering Statistics and Quality Control. McGraw-Hill. p. T. 1973. T. 1969. DC. Part 1B.. E. R. 1–12. S.. J. MD. (reprinted in Precision Mea. J. American Concrete Institute. No. “Evaluation of Data. PA. and Wood. ASTM International. February 1966. DC. Part 1. [9] Acton. “Impact and Penetration Tests of Portland Cement American Concrete Institute. The Analysis of Straight Line Data.” Report No. 1963. American Concrete Institute. ASTM Cement.. ASTM STP 15D. Rockville.. Washington.” SP-56.. [10] Mandell. F. F. 378. [25] Siegel. shohocken. 1959.. C. and Aggregates Journal. B. “Acceptance crete from Maturity. B. A. J. February 1966. E. [22] Manual on Presentation of Data and Control Chart Analysis. Proving Ring Calibration. New York. L. 1. Vol..” Publication Research Board. Gaithersburg. 1971. G. [17] Lew. New York.. Concrete for Strength. Washington. PA. H..” Highway Research Record No. Sciences. tion of Potential Strength of Concrete from Results of Early surance. ed.” High- [1] Abdun-Nur.. 1957. in Nonparametric Statistics for the Behavioral Concrete. S.” West Virginia Department of Highways Re- Specifications for Transportation Materials and Methods of search Project 47. “Uncertainty Associated with 1976.” Transportation Research Record No. National Bureau of Standards. May surement and Calibration. Hill. 558. Part 1B. Federal Highway Ad. Statistical Analysis in Chem- Bureau of Standards. J. New York. Quality Control and Industrial Statistics. W. New York. Sampling Plans for Highway Construction.. and Higgins. Wiley. and Steele. search Board. MI.” Signif- sis. 83–87. H. F. Wiley. IL. J. Specifications for Transportation Materials and Methods of [18] Hudson. S. Sciences.. A. T. [2] AASHTO (American Association of State Highway and Trans. 1954. pp. S. McGraw-Hill.” AASHTO Standard Cement Concrete. 1956. F. [20] McLaughlin. rev. [7] Dixon.. 3–5. No. pp. “Establishing Specification Limits for Materials. 1979.1962. 1976. Sampling and Testing. The Statistical Analysis of Experimental Data. T. S. STEELE ON STATISTICAL CONSIDERATIONS 29 [15] Hudson. FHWA-RD-73-5. National [19] Bennett. Detroit. [6] Natrella. Wiley. J.” SP-37. Highway Research Board. and Massey. 1959. Washington. W. B. C. New York.. cial Technical Publication 300. DC.. . and Franklin. to Refine Methods and Procedures for Implementing the [5] AASHTO Standard Recommended Practice R10. ASTM STP 169A. icance of Tests and Properties of Concrete and Concrete-Mak- [8] Daniel. [11] Hockersmith.” [14] Burr.. 59. pp.. No. West Conshohocken. 1972.. Jan. pp. “Application of Theory of Probability to Design of ment Society of America. 1964. [27] Philleo. [13] Arni. Jr. “Implementation Manual for Quality As. “Research Study Sampling and Testing. Introduction to Statistical Analy. pp. Wiley. “Prediction of Strength of Con- [4] AASHTO Standard Recommended Practice R9. Tests. 16–28. [16] Hudson. S. Irwin. Code QA-1. 1966. and Ku. 5. S. 1953.. Instru. Vol. New York. W. G. H. N. istry and the Chemical Industry.” Concrete. West Con- New York. McGraw. Feb. “Prediction of Potential References Strength of Concrete from the Results of Early Tests. A. 370. W. “Developments in the Predic- portation Officials). 2. Homewood. 1. 25–28.. W.. Highway Re. and Reichard. 36.1. F. F. S... way Research Record No. ing Materials. “Quality Assurance Guide Specification. Experimental Statistics. Vol. G. 1956. 1972.3-2-64. 229–248. 1971.” Proceedings. Washington.” AASHTO Standard pp. S. S.) [24] “Realism in the Application of ACI Standard 164–65. “Impact and Penetration Tests of Portland Cement [26] Siegel. in Nonparametric Statistics for the Behavioral ministration. Concrete. and Steele. Concrete. 55–67. pp. Final Report. Bowery. 1978. “Definition of Method of Early Prediction of Potential Strength of Portland Terms for Specifications and Procedures. 1964. H. DC. New York. Transportation [3] AASHTO. “How Good is Good Enough. Spe.” Reprint Number 12. 26–30. [12] Arni. Inc. and Hanna. MD. [21] Duncan. I.. Handbook 91. N. T. McGraw-Hill. 1944. 52. E. Richard D. Skokie. it is necessary to consider those factors that affect concrete properties In 1988. However.5 Uniformity of Concrete-Making Materials Anthony E. and batch water. whether these are defined in the form of prescriptive or performance Properties of Constituent Materials that specifications. aggregates. but also more complex in that the num. The question is. Presumably. ing admixture. remain unchanged today. air-entrain- which eventually became ASTM Standard Practice for Deter. And anecdotal evidence indicates these perceptions concrete that consists only of cement. Members were asked to and specification developed for the particular application. 30 . for three categories of construction (residential. mercial. properties and performance. retarder. and how uniformity from a single source of The goal of the concrete supplier is to provide a material that these materials can be controlled. identifying properties that must be controlled to achieve uni- als as well as the uniformity of batching. consistently meets requirements set out by the buyer. Today. 1. The ASTM C01/C09 Uniformity Task Group identified im- Introduction portant properties of constituent materials. However. To minimize the variability of concrete. once that is done. and water. technology. IL 60077. most mixtures also contain chemical The survey provides guidance on specific materials’ prop- admixtures or mineral admixtures (supplementary cementi. oped for a specific cement. surveyed to obtain their impressions on the relative impor- tually illustrated in Fig. and also in the context of field practices and processing of those materials in accordance with the speci. CTLGroup. ing those materials’ characteristics that affect concrete per- ber of mixture constituents has increased. the survey can be considered a valid With improvements in concrete technology. how much variation is acceptable. It was concrete mixtures to accommodate individual properties of derived from the work of the joint ASTM C01/C09 Task constituent materials. coarse ag. gregate. The Task to maintain uniformity to assure consistent concrete properties Group provided the impetus for development of guidelines and performance. The process starts with a mix design tance of concrete-making materials. cause problems with fresh or hardened concrete performance. 1 President and CEO. low-rise com- fications. tal impact on performance? This chapter will address the vari. if the design. it is essential Group on Variability of Concrete-Making Materials. the respondents are among the world’s most knowl- ability of concrete-making (constituent) materials and their edgeable and experienced individuals in concrete materials effects on performance. members of ASTM Committee C1 on Cement and and performance. tion. Within relatively broad limits. selves. no claim can be made for statistical significance. This information is valuable in it is necessary to control the uniformity of constituent materi. each con- tation steps are properly conducted. Therefore. Uniformity of properties may be as important to the concrete supplier as the individual properties them- THE SUBJECT OF VARIABILITY OF CONCRETE. However. formity of performance. “How do we define and assure Affect Concrete Performance uniformity of concrete?” To answer this question. water reducer. concrete has representation of industry experience and perceptions regard- become more versatile. it is attributes. Twenty-eight members responded to the survey. It is rare to encounter formance. and high tech/high strength). the supplier can adapt making materials was first covered in ASTM STP 169C. and curing. selection. erties and performance attributes that impact concrete tious materials) or both. In addition. Committee C9 on Concrete and Concrete Aggregates were The steps to obtaining concrete performance are concep. It is rank major constituent materials in their order of importance followed by selection and acquisition of constituent materials relative to variability. naive to assume that the steps to obtaining properties and per. fine aggregate. mixing. attempt was made to scientifically select the sample popula- But what level of variation can be accepted without detrimen. transporting. For example. Fiorato1 Preface placing. Since no formance can be achieved without accommodating variations. the concrete properties stituent material was rated relative to its own properties and and performance will meet job requirements. unanticipated mining Uniformity of Ingredients of Concrete from a Single changes in critical properties of individual components can Source (C 1451). and implemen. once a mixture has been devel- on determining uniformity of concrete-making materials. the overall importance (lower rating numbers) increased from residential to commercial to high tech. Cement was considered the most important for all construction categories. Variations in cement are identified as the most important by a significant margin. In the context of the question. Variations in batch water are identified as least important. 1—Uniformity of concrete is a function of the entire stituent materials. 2 and 3 provide a rather general picture of perceptions about the relative importance of con- Fig. “important” relates to what impact variations in the constituent material would have on concrete performance. and high tech/high strength). major constituent materials were evaluated independently of each other to identify those characteristics that are important to performance. but it is likely that strength was the most commonly considered attribute. While the results in Figs. while for high-tech/high- strength concrete. . In this part of the survey. Answers were to reflect whether the variability of the constituent material can be considered to produce few or numerous field problems. low-rise commercial. Respon- dents were asked to rate each material property or performance attribute on a scale of one to three with one being most Fig. silica fume was considered least important (not likely to be used). The relatively “unimportant” rankings given to slag and silica fume may be related to a belief that these materials have little variability. For this part. For residential and low-rise commercial construction. or to the fact that they are less frequently used than the other constituents. Figure 3 shows results when constituent materials were rated within different construction types (residential. another valuable part of the survey is sum- design and construction process. The intent of the question was to determine the overall importance of potential variability in the constituent material for selected types of construction. marized in Table 1. batch water was considered least important. Not surprisingly. FIORATO ON UNIFORMITY OF CONCRETE-MAKING MATERIALS 31 Figure 2 is a summary of responses (27 for this part) to a question that required the respondent to rank ten major constituent materials in order of importance from one being most important to ten being least important. the materials were rated (not ranked) on a scale of one (important) to ten (not important). strength. or durability—might be affected. 2—A 1988 survey of ASTM C1 and C9 committee members revealed their perceptions about the impact of variability of constituent materials on concrete performance. No distinction was made as to what performance aspect— constructibility. and ratios of 28-day to 7-day strengths were pub- With further quantification. 3—ASTM C01/C09 1988 survey of perceptions about cement at the rate of 30 samples per calendar quarter the impact of variability of constituent materials on concrete (preferably ten per month and not more than one per day). participated. Forty-six cement companies. It also provides an indication of their perceived level of importance relative to defining potential variations in concrete performance. After a pilot program in 1975. The joint committee planned a program to develop data on uniformity of cement strengths from individual cement plants [6]. or concrete. . mortar.2 They were arranged in serve as the basis for uniformity standards. specific characteristics to be con.and 28-day strengths of mortar cubes that conform to ASTM Test Method for Com- pressive Strength of Hydraulic Cement Mortars (Using 2-in. the initial impetus for development of ASTM C 917 can be traced to work by Walker [3] and Walker and Bloem [4]. In fact. 2 Data developed in 1991 were used to update the standard [7]. 2 and 3 and Table 1 from the 1988 ASTM survey. data such as listed in Table 1 lished in the appendix to ASTM C 917. terms of cumulative percentage of plants falling below the dards can be developed. It is worth reviewing the development of ASTM C 917 because it is representative of efforts that are needed to implement uniformity standards for properties or attributes of other concrete-making materials.and 28-day average incorporated in paste. Such was the case for the only existing uniformity standard for concrete-making materials. important and three being least important. but to illustrate the process of developing a uniformity standard. Performance at. 7. Evaluation of Uniformity An Example: ASTM C 917 The development of ASTM C 917 took place over a number of years. strengths. coefficients of variation. representing over 100 plants in the United States and Canada. a one-year voluntary sampling and testing program was initiated in 1976. Data from the program that includes information on stan- tributes reflect the behavior of the constituent material when dard deviations. The fact that cement strength was selected as the first attribute to be standardized is not too surprising given the earlier discussion of Figs. The joint committee selected 7.32 TESTS AND PROPERTIES OF CONCRETE example. Before such stan. the following discussion is presented not to focus on cement strength issues. and provide a refer- trolled must be identified and then quantified with respect to ence point for comparing strength uniformity results from a their impact on concrete performance variations. ten duplicate sets of cubes prepared each quarter to evaluate within-laboratory test error. This identifies critical characteristics that should be considered in uniformity standards for constituent materials. performance based on field practice for different construction Mortar cubes were prepared in each plant’s laboratory with types. Testing was conducted on grab samples representing 25 ton (23 Mg) lots of Fig. Data were submitted quarterly for statistical analysis. The key point is that a specific attribute of a constituent material for concrete was identified as important to the uniformity of concrete. Therefore. Johansen and Taylor’s summary of the effect of cement characteristics on concrete performance [1]. or 50-mm Cube Specimens) (C 109) as the reference for cement strength. This led to the establishment of a joint committee of the Portland Cement Association and the National Ready Mixed Concrete Association to address strength uniformity [5]. starting in the 1960s and culminating in its first edition in 1979 [2]. for particular source. Table 1 provides a comprehensive list of properties and attributes for the major constituents in concrete. value indicated for the statistic of interest. ASTM Test Method for Evaluation of Cement Strength Uni- formity from a Single Source (C 917). See. 82 8 17 3 2.18 23 5 0 Required Deleteriousair-entrainment dosage particles (amount 1.00 5 18 5 1.71 content 12 7 5 1. mortar.21 22 6 0 1.00 3 18 3 2.81mixing) 10 12 5 2.46 17 9 2 1.43 10 1 1.48 15 11 1 (continues) .39 17 11 0 FINEC3A.29 4 12 12 Performance Variations in attribute CaO (in paste.25 21 7 0 COARSE Slump AGGREGATE UNIFORMITY loss with admixtures 1.63 13 11 3 1.07 8 10 10 Specific gravity Autoclave 2.96 8 13 7 Attrition Strength(grinding gain beyondduring 28mixing) days 2. concrete) 1. mortar.82 7 and type) 19 2 1.43 18 8 2 1.82 Air entrainment 14 5 9 1.04 6 15 7 Absorption Loss on ignition2.54 14 7 3 1.80 8 14 3 Particles Bleeding 200 sieve (amount and type) characteristics 1. RETARDERS UNIFORMITY Temperature 2.04 6 15 7 Particle shape Air content 1.71 12 12 4 Grading Drying shrinkage 1. I.57 14 12 2 Water reducer Variations in Al2Oeffectiveness 2.46 17 9 2 Reactivity with different cements Particle shape 1.65 mortar.29 3 14 11 Material property Chemical composition 2.86 10 12 6 Moisture content dosage 1.30 19 8 0 Sensitivity to time of addition 1.82 8 17 3 Absorption Material property 2.50 15 12 1 Moisture Thermal vol.76 11 9 5 1.96 6 17 5 3 Variations COARSE in Fe2O3 UNIFORMITY AGGREGATE 2.O.96 8 13 7 Strengthproperty Material gain beyond 28 days 2.43 18 8 2 Material property Alkalies 1.07 7 12 9 2. Algravity 2O3.07 3 20 5 Specific Loss gravity(L.88 8 13 5 Absorption 2.14 5 14 9 WATER REDUCERS.72 10 12 3 Deleterious particles (amount and type) Sulfate expansion 1.32 3 13 12 FINE AGGREGATE Performance UNIFORMITY attribute (in paste. etc.86 10 12 6 Air entrainment dosage 1. O. FIORATO ON UNIFORMITY OF CONCRETE-MAKING MATERIALS 33 TABLE 1—Perceived Relative Importance of Materials Characteristics to Concrete Quality (ASTM C01/C09 1988 Survey) Number of Respons Sulfate expansion 1.37during17 mixing) 10 0 2. AGGREGATE C3S.04 6 15 7 Pozzolanic activity index Attrition (grinding during1.75 11 13 4 1.07 8 10 10 Autoclave Sulfate form expansion and content2.36 20 6 2 1.07 5 15 7 1.79 7 20 1 Particle Volume shape changes1.43 17 10 1 Material Slumpproperty loss with temperature 1.25 22 5 1 Water Early reducer age strengtheffectiveness gain 1. 1.18 4 15 9 Attrition (grinding Fineness 1.96 6 17 5 1.68 16 5 7 FLY Particle shape ASH UNIFORMITY 1.29 4 12 12 2.68 12 13 3 Deleterious particles Chemical composition 1.12 5 12 8 Chemical composition 2.content changes (cracking.26 and type) 21 5 1 1.) 1.27 4 11 11 1.58 (amount 13 and type) 11 2 1.14 25 2 1 Air entertainment Strength gain from 7–28 days 1.80 8 14 3 Number of Responsesa Bleeding characteristics 1.15 3 17 7 Attrition Specific (grinding gravity during mixing) 2.14 expansion 5 14 9 2. C2S UNIFORMITY 1.15 7 8 11 1.11 on ignition 25 1 1 2.21 22 6 0 Air entertainment Alkalies 1.04 Finishing characteristics 6 15 7 1.79 7 20 1 Volume changes 1.I.36 19 8 1 Expansion Fineness in moist storage2.68 10 17 1 Time of set200 sieve Particles 1. concrete) Material Concreteproperty strength 1.29storage 3 14 11 2.48 2 9 14 Specific gravity Material property2.18 of alkalies 23 5 0 1.39 17 11 0 Grading Water including fineness requirement modulus17 1.32 3 13 12 Sensitivity to cement composition 1.50 17 8 3 Grading including Solubility fineness modulus 1.46 3 9 16 Performance Performanceattribute attribute(in(inpaste.18 23 5 0 Deleteriousdurability Freeze-thaw particles (D-cracking) 1.36 20 6 2 Concrete in Variations strength SiO2 2.82 14 5 9 Response Absorption to admixtures 1. paste.21 22 6 0 Concrete strength Setting time 1.78 9 15 3 Particles 200 sieve Microscopically (amount and determined type) composition 1. HRWR.68 16 5 7 2.07 5 15 7 Temperature Expansion in moist 2.81 9 13 4 2.68 10 17 1 1.75 11 13 4 Reactivity Moistureat different temperatures 1.88 8 13 5 Average 1 2 3 FinishingUNIFORMITY CEMENT characteristics 1.18 4 15 9 2.26 3 13 10 Performance Grading attribute (in paste. 13 concrete) 9 4 Water requirement Variations in SO3 1.93 8 14 6 Moisture Heat of content hydration 1.11 8 9 11 Specific SiO2.57 14 12 2 1. mortar.mortar.concrete) concrete) Water requirement Strength 1.) 2.07 (L.07 7 12 9 Shrinkage Specific gravity 2. MgO 2.18 23 5 0 1.78 10 13 4 1.43 18 8 2 Particles Drying 200 sieve (amount shrinkage1.12 5 12 8 1.) 3 20 5 2.50 15 12 1 1. RETARDERS UNIFORMITY Material property Sensitivity to cement composition 1.) 1. mortar. mortar. etc.) 1.11 24 3 0 Air void system characteristics 1.26 3 13 10 Performance attribute (in paste.17 3 13 7 Performance attribute (in paste.15 7 8 11 Variations in Al2O3 2.58 13 11 2 Reactivity at different temperatures 1.81 10 12 5 Shrinkage 2.54 14 7 3 Composition (infrared spectra) 1.93 8 13 6 Performance attribute (in paste.65 13 9 4 Variations in SO3 1. concrete) Required air-entrainment dosage 1.27 4 11 11 Variations in Fe2O3 2.O. mortar.30 19 8 0 Sensitivity to time of addition 1. HRWR.81 11 10 6 Variation in alkalies (HRWR) 1.59 15 8 4 Composition and concentration 1.93 10 9 8 AIR-ENTRAINING ADMIXTURE UNIFORMITY Material property Percent solids (specific gravity) 1.00 5 18 5 FLY ASH UNIFORMITY Material property Loss on ignition (L.81 9 13 4 Pozzolanic activity index 1.78 9 15 3 Temperature stability (freezing.37 17 10 0 Variations in CaO 1.I.37 19 6 2 Sensitivity to temperature 1. concrete) Time of set 1.59 15 8 4 Sensitivity to temperature 1.62 15 6 5 Variations in chlorides 1. concrete) Concrete strength 1.50 16 7 3 Compatibility with other admixtures 1.34 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Perceived Relative Importance of Materials Characteristics to Concrete Quality (ASTM C01/C09 1988 Survey) (Continued) Number of Responsesa Average 1 2 3 Performance attribute (in paste.85 8 14 4 Stability in storage 1.11 24 3 0 Rapid stiffening 1.54 14 7 3 Time of set 1.48 15 11 1 Compatibility with other admixtures 1.43 17 10 1 Freeze-thaw durability (D-cracking) 1. concrete) Stability of air with fly ash 1.39 17 11 0 Water requirement 1. changes (cracking.) 2.76 11 9 5 Alkalies 1.48 2 9 14 Specific gravity 2.78 10 13 4 Variations in SiO2 2.63 13 11 3 Drying shrinkage 1.82 7 19 2 Thermal vol.00 7 10 7 pH in deionized water 2.85 8 15 4 Finishing characteristics 1. mortar.15 7 9 11 (continues) .26 21 5 1 Reactivity with different cements 1.48 16 9 2 Percent solids 1.71 12 7 5 Response to admixtures 1.41 17 9 1 Later-age strength 1.63 14 9 4 Sensitivity to aggregate grading 1.78 10 13 4 Sensitivity to mix water composition 2.15 23 4 0 Early-age strength 1.11 25 1 1 Fineness 1.44 16 10 1 Generation of air voids 1.00 3 18 3 WATER REDUCERS. etc.27 20 5 1 Sensitivity to cement composition 1.91 7 11 5 pH 2. sulfate resist.77 8 16 2 Attrition (grinding during mixing) 1.83 9 10 5 Sulfate content 1. concrete) Air entertainment 1..83 7 14 3 Required water reducer. mortar.40 16 8 1 Percent solids 1. FIORATO ON UNIFORMITY OF CONCRETE-MAKING MATERIALS 35 TABLE 1—Perceived Relative Importance of Materials Characteristics to Concrete Quality (ASTM C01/C09 1988 Survey) (Continued) Number of Responsesa Average 1 2 3 LIGHTWEIGHT AGGREGATE UNIFORMITY Material property Unit weight 1.) 2.60 14 7 4 Particle shape 1.68 11 7 4 Stability in storage 1.52 16 5 4 Organics content 1.38 16 10 0 Moisture content 1. concrete) Air entertainment and air void system 1.25 19 4 1 Temperature 1. etc.74 10 9 4 Specific gravity 2. Na2CO3) 1.63 13 7 4 Required air-entrainment dosage 1.48 14 10 1 Variation in chemical composition 1. mortar. HRWR dosage 2.31 20 4 2 Shrinkage and volume changes 1. mortar.24 19 6 0 Glass content 1.73 11 6 5 Specific gravity 2. concrete) Activity index 1.25 4 10 10 pH 2.27 19 7 0 Grading 1. .58 12 13 1 Air entrainment 1.46 14 9 1 Time of set (Cl.00 7 10 7 Shrinkage 2.29 3 11 10 Solids content 2.38 2 11 11 Performance attribute (in paste.81 8 15 3 Performance attribute (in paste.62 14 8 4 Alkali content 1. concrete) Concrete strength 1.96 8 10 7 SLAG UNIFORMITY Material property Fineness 1.00 7 10 7 a 1 important to 3 unimportant.92 8 11 6 Hardness 2.00 5 14 5 SILICA FUME UNIFORMITY Material property Composition 1.80 10 10 5 Durability (ASR.85 10 10 6 Absorption of admixtures 1. mortar.44 16 7 2 MIX WATER UNIFORMITY Material property Chloride content 1.72 10 12 3 Temperature 1.23 6 5 11 Performance attribute (in paste.38 19 4 3 Specific gravity 1.23 20 6 0 Absorption 1.12 5 12 8 Performance attribute (in paste. single- ever.11]. Potential properties and attributes are listed in Table 1. Walker also noted that strength was not the only concrete performance attribute of importance. mixing. the attribute being measured. the first ASTM standard for uniformity of a concrete-making material. The early work by Walker recognized that concrete strength uniformity was not solely a function of cement strength uniformity and included discussion of such factors as sampling and testing variations. the critical property or attribute of the particular constituent material must be identified. and reporting requirements. corrections for testing variations. for ASTM committees that govern standards for materials listed in Table 1. Standard for Determining Uniformity of Concrete-Making Materials Figure 4 illustrates the process for developing a uniformity standard.7 % 1 time in 20. testing criteria. the precision state- After test methods are selected. Compilation of this information into a draft recommended practice document greatly facilitated the ASTM development process for the new standard. Thus. statistical by more than 20. 4—Process for developing uniformity standards for critical must be selected. Education of both those providing and those using uniformity data is an important step once a standard is introduced [10. test method must be selected. approximately two years after completion of the test program. placing. However. particularly for between- ASTM method exists. transporting.13]. How. the effect of inherent variability of testing on the property or Once the attribute has been identified for evaluation. A final test of the standard is whether it is used. Generally. Batching. with the increasing trend toward total quality management. single This will provide data for a specific standard’s provisions on batches mixed by two different laboratories should not differ sampling frequency and protocol. Given that today’s concretes are more sophisticated. example.7 %. made in a single laboratory should give strengths that do not ing variability for the particular property should be conducted. for some attributes. particularly for material properties. it is appropriate to consider standardization of uniformity provisions for other constituent material properties and attributes that affect concrete constructibility. standard procedures may need to be laboratory testing is preferred for uniformity work.9]. and must be accommodated. However. and durability. A uniformity standard should provide a communication tool between manufacturer and customer that will improve overall concrete quality and performance [2. use has been growing. laboratory tests. and age effects [3]. so those that are most Fig. there is a continuing development and educational process that must take place to foster appropriate use. Even with approval of a document such as ASTM C 917. he recognized constructibility and durability as other critical attributes [3]. This is an appropriate responsibility concrete-making materials. It would be prohibitive and unnecessary to develop uniformity requirements for each specific property or attribute in Table 1. First.36 TESTS AND PROPERTIES OF CONCRETE In addition to comprehensive data that quantified potential strength uniformity. was approved in 1979. temperature effects. differ by more than 10. ASTM C 1451 should speed the standards development The development of comprehensive test data is considered an process because the test program data for any property or essential part of the process because it is necessary to define attribute can be “plugged in” to a standard format. as pointed out by Gaynor [12]. an appropriate Testing errors can be significant.8. The following section discusses a standard for determining uniformity of other characteristics of concrete-making materials that was developed by the ASTM C01/C09 Task Group and is now designated as ASTM C 1451. a comprehensive sampling ment in ASTM C 109 implies that duplicate batches of mortar and testing program to quantify uniformity potential and test. For developed or existing procedures modified. In most cases. It addresses . ASTM C 917. Widespread adoption of ASTM C 917 has been slow [12. the PCA/NRMCA program provided extensive information on sampling and testing procedures. and correction factors for testing variations. strength. and curing also have important implications. Sampling and the importance of total quality to concrete users.and between-laboratory testing variations are [3] Walker. Farkas and terials. uniformity of concrete. Silver Spring. it is es- (a) Sampling is performed by trained personnel. 80–11. (a) Samples are tested in accordance with standard Skokie. PA. sential that the industry be prepared to provide uniform prod- (b) Grab samples are taken at a frequency defined by uct performance. [9] Davis. 190–192. deviations of the measured values. (Available as NRMCA a “generic” approach to accommodating any property or Back Engineering Report No. D.” (b) Variations from a single source are corrected for NRMCA Publication 161. V. Rome. Evaluation Procedure [1] Johansen. Con- 4. J. Vol. D. This will lead to increasing reliance on maximum lot sizes. P. (a) Reports identify materials tested. but not sufficient.” Concrete Construction... [11] Gaynor. [10] Gaynor. West Conshohocken. 58. St. “Amemdment of Appendix X2 in ASTM C 917 Evalu- rected for testing variations. Houston. 3. D. St. E. [4] Walker.S.” (e) Between-laboratory variations are quantified by sam. Feb. With the growing sophistication of concrete mixtures. FIORATO ON UNIFORMITY OF CONCRETE-MAKING MATERIALS 37 the following components for determining the uniformity of and a protocol for developing uniformity standards is dis- properties of a material from a single source: cussed. TX. 1 April 1980. May 1986. 1995. for obtaining nar on Cement Strength Uniformity. that are considered to affect concrete uniformity are identified 1987. S. V. 76.. MD. (c) Within. Vol. and Taylor.” NRMCA Semi- making materials is necessary. and Aggregates. 77. National Ready Mixed Concrete Asso- variations inherent in the test procedures.” Modern Concrete. be a continuing process. Standards Committee Meeting. standards.. Silver Spring. tion for an ASTM C 917 Method for Evaluation of Cement (d ) Reports include specific statistical results for time Strength From a Single Source. April 1975. National Ready Mixed Concrete This format follows that of ASTM C 917 and provides Association. In addition. IL. R. plicate testing if no history is established. MO. Dec. ment. R. 2 Feb. “Effect of Cement Characteristics on Concrete Properties. p. . 2003. West Conshohocken. 2. 61. “Cement Strength Variability and Trends in Cement Specifications in the U. and Bloem.. “The PCA/NRMCA Strength Uniformity Study. D.. R. 80–10.” Research and Engineering period covered. 1958. ciation. National Ready Mixed Con- (d ) Single-laboratory test variations are established by du. 22 July 1980. (d ) A minimum rate of sampling of ten per month or two References per week is required. uniform concrete performance.) attribute. also reprinted as NRMCA Publication No. [8] Davis. E.. tion. ASTM International. Silver sensus standard it will be necessary to educate users. [13] Uniformity of Cement Strength. ASTM International. Statistical Calculations [5] Davis. uniformity standards by suppliers of constituent materials and (c) Sampling protocols are defined by existing ASTM concrete producers. No. MO. pp. p. E. ASTM procedures. 1.” Cement. (c) Equations are defined for standard deviation cor- [7] Sykora. D. “Variations in Portland Cement.) This chapter has addressed uniformity of concrete-making ma. March 1958.” National Ready Mixed Concrete Association. Louis. Proceedings.. crete Association. PA. 86–3. “Evaluating Cement Variability—The First Step. (Avail- able as NRMCA Back Engineering Report No. [2] Peters..” Re- (b) Equations are defined for testing standard deviation search and Engineering Standards Committee Meeting. twelve months. P. This will Spring. Report Requirements crete. even after the development of the con. R.” NRMCA Publication No. Eds. R. 22 July 1980. “Has There Been a Change in Strength Level? (Or How to Look at C 917 Data When It Comes In). 87. Those properties and attributes of constituent materials P. Louis. Na- and coefficient of variation. tional Ready Mixed Concrete Association.) addressed. “Uniformity of Portland Cements: Facts and Fan- (a) Equations are defined for average and total standard tasies. E. ation of Cement Uniformity from Single Source. “The Cement Producer’s Role in Providing Informa- (c) Reports include duplicate test results. Field practices must also be (Available as NRMCA Back Engineering Report No.” EB226. 1978. Klieger. Portland Cement Association. 17.. R.. Feb. “How Uniform is a Portland Cement From a Single (b) Reports cover a minimum of three and a maximum of Source. L. ple exchange or standard reference samples. ASTM STP 961. 1977. 2.. S. MD. 1976. “Use of Cement Strength Uniformity Informa- As discussed here.” European Ready Mixed Con- Summary crete Organization (ERMCO) Congress.. [6] Klieger. [12] Gaynor. MD.. “Uniformity of Concrete Strength as Affected by Ce- considered as required. and not necessarily an properties that are already covered by existing ASTM C01 (Ce- attractive one. is available for oped. materials scientist. 38 . but the general public at http://vcctl. starting materials are char. physicist.1 and Paul E.nist. but analyzing and While at first glance. material properties are measured at a companies spend millions of dollars per year on the testing of fundamental level. then. If proper. Gaithersburg.cbt. it may appear that virtual testing has predicting the materials science properties requires a level of the potential to eventually eliminate physical testing and its theory involving computational materials science. Garboczi. Cement and concrete are complex. respectively. tual” everything around us these days. terials. given the ubiquity of “vir- ties of the fresh and hardening cement or concrete. What Really is Virtual Testing? acterized in some fashion and this information is input into one or more computer models to predict a variety of proper. storage. quantitative predictions from condensed matter theory that is An additional benefit of virtual testing would be the capability based on valid mathematical principles and atomic and molec- to rapidly perform a large number of “what-if” type computa. and composite material that provides both strength the characterization of the starting materials. since the problems the consortium can be seen in three annual reports [1–3]. the properties of concrete continue to de. and disposal. 1. and (2) to highlight needs relative to existing and waiting periods of less than 28 days. the time and cost savings to mean for cement and concrete materials? In the field of con- the cement and concrete industry can be tremendous. who rently exists. The chemistry of cement is well developed predicted using the VCCTL [4] and other existing models. Having to Standards and testing are critical for validating and extending wait 28 days to assure performance compliance is another the computer models. Bullard. the truth is that a functional VCCTL places a greater burden on testing and standards than ever be- CONCRETE IS A UNIQUE MULTI-PHASE. Stutzman1 Introduction accompanying standards. necessary standards work be pursued and completed. Bentz. standardized and impermeability to engineered structures. MD 20899. who ment) and C09 (Concrete) standards.1 Chiara Ferraris.6 Virtual Testing of Cement and Concrete Dale P. but a com. it is not possible to carry out analytical calculations and based Virtual Cement and Concrete Testing Laboratory so the field of computational materials science has been devel- (VCCTL). more complex materials are studied. needed in order to empower and validate the prediction models. methods for preparing and analyzing these materials will be crit- struction materials. So the 1 Chemical engineer. in January of 2001 a joint indus. but what does it really ties can be successfully predicted. labor. physicist. the 28 day compressive strength test. The dual tive processing methodology. For many of these ma- try/government consortium was initiated to develop a web. While current models can predict several unique feature of concrete. In tions to explore new material systems and optimize existing materials science. Even though much work remains to be done on re- would prefer to avoid waiting 28 days (or more) before truly fining and extending these models.1 Nicos Martys. ical. and are analytically intractable. With this goal in mind. they can also quantitatively would prefer to directly proceed with further aspects of the predict other properties for which no standard test method cur- construction.1 Edward J. Thus. and geologist. many efforts have been objectives of this chapter. dom composites and biological materials. not eliminate them. compliance. An earlier version of the VCCTL. RANDOM. future standards for characterizing cement and concrete mate- One area of effort has been the development of computer rials and for evaluating their properties. plication in testing and quality assurance. Materials and Construction Research Division. and quite fundamental and analytically based. models to predict cement and concrete properties via virtual testing. Many densed matter physics. fore. physicist. In these models. Thus. This holds true both for the field engineer. This is clearly The VCCTL will drive the standard tests to move from empiri- exemplified by the bread-and-butter test of concrete quality cism towards a firm materials science basis. like ran- ones. These measurements are then compared to concrete. First. typically.1 Jeffrey W. in numerous examples of properties that can be successfully multiscale materials. and the industrial or academic researcher. it is just as critical that the knowing the effects of a new chemical additive or an alterna. including material costs. “Virtual testing” is an exciting name. “Simple” materials are usually studied. model property predictions can only be as good as complex. ular arrangements. are (1) to show what current made to predict (and ensure) concrete performance based on models can do. The progress of with the mathematics solved on a computer. National Institute of Standards and Technology.1.gov. Unlike most con. measurements of fundamental properties are velop over time and in place—an aid in processing. All this entails is the usual condensed matter theory. And second. aggregate shape means a lot. In dard tests that address aggregate shape (ASTM D 4971 and modeling the hydration of a cement. having more exposed surface area. a 3-D model of the particles ASTM Standard Guide for Petrographic Examination of themselves is built up. data from careful characterization of materials. More de- microstructure. can probably capture most To be able to build models using real-shape aggregates. since smaller amount of internal porosity and hence water absorption can cement grains hydrate faster and more completely than larger vary as well.10]. For example. The each particle. how the various chemical phases of the cement are the successful simulation of cement paste microstructure and distributed in the cement particles.” terized in the same way. ground granulated blast furnace slag. In a cement. The characteriza- information is needed about them as well. or are crushed to the desired sizes. does not give the distribution of sizes. the desired gradation. Their different mineralogical types imply that cement grains. and what is their shape. Aggregates for Concrete (C 295)). Elongated Particles. This is a critical step in like. A polished sec- terials users. like ness of the cement. als will prove fruitful [16]. too. are of many dif- ure the particle size distribution using some method. though further research on better with portland cement. If there are other mineral admixtures.12]. On standardization within ASTM subcommittee C01. like chloride diffusivity. a phenome. one must go to the particle level. one must first meas. this ideal model is model. can vary greatly. between its different hydrated forms. A measurement such as Blaine fineness. The per particle. both fine and coarse. or Flat and Elongated grains to measure/compute an equivalent spherical diameter for Particles in Coarse Aggregate (D 4971). information is needed as an input into the virtual hydration Even with modern-day computers. the final segmented SEM images can also be analyzed to determine phase surface frac- The Importance of Materials Characterization tions and autocorrelation functions. The fresh concrete rheology and mechanical properties. Along with a measured particle size distribution. while others are a complex input. at early ages. used does not seem to matter much. This is critical for virtual testing. ties.15]. This procedure is being investigated for ization of a cement does not give useful data for a model. BENTZ ET AL. or something else. their elastic moduli will also vary. So the rise of virtual testing in this instance tails on this procedure are available elsewhere [8. but cannot distinguish urement of cement particle size distribution. In addition to the meas- the areas of rheological properties and durability. tion technique for cement particle shape is very similar to that To characterize a cement so that one has a hope of predict. so to model the hy- needed molecules. But the hydration of a cement proportions and arrangement of atoms.23 at present on replacing the inaccurate The ideal model for concrete would start from the known Bogue calculations with more accurate X-ray diffraction chemical composition of the material. gates used in concrete. while Fig. which must be used Rietveld analysis of X-ray diffraction data. not tion is prepared. This technique shape. and a combination of back-scattered electron empirical tests. as well as the heart of its virtual testing. to understand and predict the effect of shape on properties. age for a portland cement. Figure 1(a) the other hand. these three characteristics can be utilized The heart of concrete. and eventually predict properties at the macroscale. however. careful measurement of the cement particle shows the ordinary gray-scale back-scattered electron SEM im- size distribution (PSD) does give information vital to the suc.11. ON VIRTUAL TESTING 39 definition of virtual testing of cement and concrete is just the of a cement’s hydration properties. so aggregate shape is considered first. adapting the above characterization techniques to these materi- such as fly ash. There is work in ASTM computational materials science of cement and concrete. Starting with the correct Rietveld measurements [7]. a long way away. for aggregates. Correct particle level needed. urement of bulk volume fractions. non that must be captured accurately for any model to have a one must in general use realistic aggregates. for example. could be given in tion in bulk. some science-based virtual models that do exist need good data as particles are purely C3S. Aggre- ing its hydration and general performance. By far the ferent mineralogical types. Quantitative X-ray diffrac- ples. procedure can identify calcium sulfate. A few forms of fly ash and slag have gypsum is also included since it is almost always interground been so characterized [14. For some proper- hope of being accurate. the shape of model aggregates while useful in conveying information about the relative fine. up multiscale models starting from the atomic scale. so an accurate size distribution is needed. It is still not possible to systematically build Particle level information includes the detailed breakdown. not just some measure of the average size. each pixel in the image. Analogous exam. CEMHYD3D [8–10]. measuring the Blaine fineness scanning electron microscopy (SEM) and X-ray microprobe (using ASTM Standard Test Method for Fineness of Hydraulic analysis are used to identify the chemical phase belonging to Cement by Air Permeability Apparatus (C 204)) as a character. metakaolin. to reconstruct an initial three-dimensional microstructure of ce- lies in the cement. and none that attempt to Accurate bulk measures of cement chemical phases using characterize the full 3-D aspects of shape. The mixture of clinker phases. ment powder is mixed into an epoxy and cured. and are either found naturally in most popular method among cement companies and other lab. subcommittee C01. performance properties.23. For other properties. a dry ce- models can predict physical properties of interest to actual ma. To acquire this information. By saying “cement. The VCCTL models start at the level of the ment particles in water that is a very realistic representation of cement particles. silica fume. This should drive the testing of Blaine fineness toward the meas. Their oratories is the laser diffraction method [5. but not at the particle level. the same kind of Cement particle shape is important. There are few stan- bution of sizes. it would build up the takes place at the individual particle level. Specific needs are what cement particles look the specific cement in question [8. of the various clinker phases. of the information needed for experimental characterization one must be able to treat a given aggregate particle as a . which is measured in the ASTM Standard Test Method uses optical laser light diffracting from the various cement for Flat Particles. especially hydration performance of a cement couples more to the distri. the nanostructure and microstructure dration.6]. To make a virtual concrete. 1(b) shows the image after cessful modeling of how the cement hydrates and develops all of the major chemical phases have been identified. but are based on fundamental parameters. ticle size distribution information. what their particle size dis. Mineral admixtures need to be charac- tribution is like. combined with par. in which virtual testing could push existing test methods tion or thermogravimetric analysis [13] can give this informa- toward more fundamental measurements. only the Young’s modulus is considered. through a pumping process. Virtual Testing of the Rheology of Fresh Cement and Concrete Rheology of concrete is the study of how concrete flows. Spheres are easy to so use. Figure 2 shows a VRML (virtual reality modeling language) picture of a fine and a coarse limestone aggregate. Aggregate data- bases are currently being built up for various aggregates and incorporated into the VCCTL. but the plastic ticles can also be characterized in terms of mathematical func.80 mm. an elastic solid is characterized by two parameters. After such an image is obtained. Images are 256 m 200 m. concrete flows in a given situation. investigating the aggregate particle. However. In the same way. Once this mathematical function is ob. A recent paper predict the rheology of concrete.40 TESTS AND PROPERTIES OF CONCRETE Fig. the yield stress. 2—Reconstructed images of aggregates sampled from AASHTO Materials Reference Laboratory (AMRL) proficiency sample #39. (b) False ASTM Standard Test Method for Slump of Hydraulic-Cement gray scale image of the same section. tained. Young’s modulus and Poisson’s ratio. Rheology of the . The slump test specified in the Reference Laboratory proficiency sample program. The left image is of a coarse limestone aggregate with an equivalent spherical diameter of 13. viscosity is needed as well to be able to fully understand and tions. Typically. duce an analytical function for the surface of an arbitrary Because concrete is a multi-scale material. rheology involves a multi-scale approach.46 mm. To characterize cement particle shape requires X-ray microtomography. A voxel is a small cubic or rectangular paral- lelepiped-shaped element of a 3-D digital image. and the image on the right is of a fine limestone aggregate with an equivalent spherical diameter of 1. workability and flowability of the concrete into a form or phy (CT) and spherical harmonic functional analysis could pro. although this is a little more complicated. work in the last few decades has shown clearly that concrete rheology is characterized by at least two parameters. the slump test the center of mass to the surface is a constant. before the setting point is reached. then real-shaped particles can be handled in a model with the same ease as spherical particles. Real-shaped par. only measures one parameter. the same methods used to characterize the shape of aggregates can be used for the cement particles [19]. from an American Association of State Highway and Traffic Officials (AASHTO) Materials Ref- erence Laboratory (AMRL) proficiency sample. which in turn determines the [17] showed how a combination of X-ray computed tomogra. This is important because Fig. The meaning of each gray scale is indicated in the accompanying legend. 1—(a) Backscattered electron SEM image of a cut and the concrete must be placed by some kind of pouring or pump- polished section of cement 140 from the Cement and Concrete ing into the prepared forms. since there is needed to completely understand and predict the elastic per- a simple equation that defines their surfaces: the distance from formance of an elastic solid. which can achieve the length scales of approximately 1 m/voxel necessary to capture the shape of particles the average size of which are usually about 10 m to 20 m [18]. based on X-ray micro- Concrete (C 143/143M) is an empirical measurement of how probe analysis. yield stress and plastic viscosity. but really both are mathematical object. In a similar way. concurrent with the vast increases gregate. been made in this approach. . etc. but adapted for coarse aggregate-size particles. The dispersion models of Knudsen [24. The effect of coarse ag. possible. particle dynamics (DPD) approach. Cement paste and mortar rheology is provide an excellent fit to an individual experimental dataset. BENTZ ET AL. While a complete understanding of cement hydration is still lacking. In the concrete. and the remaining on whether or not the underlying (blended) cement paste datasets are experimental data obtained using various rheometer types. An intercomparison effort is underway [21. 4—Static image from simulation of vertical flow of a more fundamental materials science basis. Several different designs are currently available. The subcommittee C09. two approaches are possible. cement PSD. Therefore. In this approach. The second approach attempts to make greater use of the ular dynamics approach for the movement of atoms and detailed characterization of the starting materials described molecules. Some of these tests concrete with real particles through a grid of four steel rein- are currently being considered for standardization in ASTM forcing bars which are separated by a distance of 200 mm. and thus could be used to predict later-age degree of hydration gregates on concrete rheology is modeled using a dissipative from early-age measurements. Figure 4 shows a DPD simulation of particles are dropping down. research is being done on measuring concrete rheology using various concrete rheometers. The two most influential parameters for the properties of cement and concrete are water-to-cement mass ratio (w/c) and degree of hydration. prediction of the performance of other systems (change Simultaneous modeling of the hydration process and in cement composition. these equations can be useful. This is similar to a molec. characterized by the process described in the previous section. we have taken a combined theoretical. depending data in the legend are the simulations. The first approach consists of utilizing some functional form to describe the relationship between degree of hydration and time. measured in a custom rheometer [20]. a significant knowledge base [23] has been accumulated in over 100 years of experimentation. To model the increase in degree of the volume fraction of coarse aggregate. The above by directly modeling the microstructure development of rheological properties of the matrix of the suspension come the cement paste. There has also been DPD modeling work of concrete flow in self-compacting concrete (SCC) empirical tests. more importantly. as they usually do experimental approach. and it may be possible to extract fundamental rheological parameters (plastic viscosity and yield stress) from these measurements. Still. this approach. many properties Fig. similar in bars. This would both enable the rheological models to be validated and. significant developments have viscosity of a concrete plotted versus the volume fraction of ag. Adding more aggregate clearly increases the apparent viscosity. dition.47. The first three sets of hydration with time. If degree of hydration (of both cement and pozzolans) can be accurately predicted.22]. PSD. thus offering the potential for putting these tests on a Fig. Virtual Testing of the Properties of Hardening Cement Paste and Concrete Hydration and Degree of Hydration To model the development of cement and concrete properties over time. phase com- from the cement paste and mortar measurements. The DPD simulations can be used to analyze flow in different rheometer designs and extract fundamental parameters from empirical test results. through the re- coarse aggregate falling through four parallel rebars.) based on the fitting of cement paste rheology is beyond current computational one (or more) set(s) of experimental data may or may not be capabilities. ON VIRTUAL TESTING 41 some ways to the SCC tests being considered for standardization. Figure 3 position and distribution. and is itself non-Newtonian and complicated. Experimentally. mental data may or may not have physical significance. as will be demonstrated in the on the dependence of relative viscosity of fresh concrete on subsections that follow. also has a very large effect on concrete rheology. having such a large volume fraction of aggregates. In the last 15 years or so. In ad- 60 % or more. See Ref [21] for detailed discussions of these microstructure is explicitly considered. the parameters obtained from fitting the experi- However. The coarse aggregate shapes were taken from the shapes of real aggregates. due to gravity. w/c. a proper understanding (and model) of the hydration process is essential. begin to allow fundamental rheological parameters to be used in analyzing and predicting concrete flow in field conditions. concrete rheometer types.25] or the use cement paste greatly influences the time-dependent rheology of of nuclei-growth models [26] are examples of this approach. 3—Comparison of DPD model to experimental data can be conveniently computed. and w/c can all be explicitly consid- shows experimental and DPD simulated plots of the plastic ered. a cellular automaton-like computer algorithm is used to simulate the hydration process. CEMHYD3D considers the cement particles at the and 1000°C (or another similar range of temperatures de- sub-particle level. An image of a portion of mined by Rietveld X-ray diffraction analysis is not known at a typical starting 3-D microstructure is provided in Fig. 1 [43] (the effect of the more correct composition as deter- particle chemical phase distribution. microstructure formation. can be determined by a simple voxel counting algorithm. The underlying hydration model. process. 6. The phase designated by each microstructures for the subsequent evaluation of degradation gray scale is indicated in the accompanying legend. applying a digital-image-based approach to pending on the preference of the researcher) relative to the the modeling of cement hydration and microstructure devel. students to predict a variety of cement and dimensional image of a portion of a hydrated CEMHYD3D mi- concrete properties. For portland cements. This model considers the cement particles to be spherical and explicitly analytically accounts for the overlap of hydration products as the cent version of CEMHYD3D also includes reactions for a vari- individual cement particles expand during the hydration ety of mineral admixtures such as silica fume. The image [36–41]. slag. In Japan.jp/en/demos/ducom (accessed input for the CEMHYD3D cement hydration model. of the cement powder or any combination of the original cement phases. while focused on heat generation and water consumption. by cement re.23]. including heat development. The model has been applied by van Breugel and his and limestone [1–3]. In the early to mid 1990s. the user is able to create an specimen by that measured for a fully hydrated cement paste initial three-dimensional cement (in water) microstructure that specimen. 5. developed the DuCOM (durability model of concrete) model. 5—Typical 3-D reconstructed microstructure used as http://concrete. hydrated for 2000 computational cycles using the searchers to predict performance properties and to generate CEMHYD3D hydration model. Degree of hydration. w/c 0.t. crostructure.29]. worldwide.D. obtained by dividing the non-evaporable water content of the Using computational algorithms. initiated research on this topic. In CEMHYD3D.4. obtained via the characterization methods outlined ment using coefficients provided by Molina and given in Table earlier in this chapter: PSD.ac. including the chemical shrinkage first highlighted by Le Chatelier over 100 years ago [35]. Unlike the other models mentioned loss of the hydrated cement paste occurring between 105°C previously. non-evaporable water content Institute of Standards and Technology (NIST) that ultimately [42] is one generally accepted method for estimating the de- culminated in the CEMHYD3D three-dimensional cement gree of hydration of the hardened paste. either on a mass or a volume Fig. and heat and mass transport [30]. In addition to cement hydration reactions. and autogenous shrinkage [31–33]. diffuse within the available capillary porosity. Degree of hydration (0. also considers the stereological aspects of the overlapping hydrating cement particles. A demonstration of the model is accessible over the Internet at Fig. fly ash.D. mass of the ignited paste (corrected for the loss on ignition of opment. A pioneering effort in this field was the work of Jennings and Johnson [27].0–1. the most re. In the Netherlands. velopment. bulk phase composition. thesis [31] on the HYMOSTRUC model for the hydration panying Fig.42 TESTS AND PROPERTIES OF CONCRETE in computer speed and available memory. all active at the present date. strength de. Experimentally. . Each digitized spherical cement particle is composed the original cement powder) provides a measure of the non- of one or more digital elements (voxels) that can be assigned evaporable water content. 6—2-D cross section of a 3-D model cement paste with basis. and microstructure development of cement paste. The phase March 2005). CEMHYD3D has been utilized. The value for a fully hydrated specimen can also be matches the following measured features of the real cement estimated based on the potential Bogue composition of the ce- powder. Maekawa et al. The algorithms are applied so as to maintain the correct volume stoichiometry for the generally accepted reactions of cement hydration [8. and intra. Individual cement phase voxels can dissolve.0) is then to be any of the possible phases of the starting cement powder. is 100 m 100 m. van Breugel published his designated by each gray scale is shown in the legend accom- Ph. u-tokyo. Figure 6 provides an example two- subsequent Ph. In this test. who modeled the cement powder as a collection of spherical particles of tricalcium silicate that resulted in the formation of calcium hydroxide and calcium silicate hydrate reaction products. The model proceeds as a series of dissolution/diffusion/ reaction cycles. and a single user-provided parameter is used to approximately convert between hydration cycles and real time. and react to form solid hydration products. Bentz and Garboczi initiated uating the degree of hydration of either portland or blended a cement hydration modeling effort [34] at the National cements. Similar models continue to be developed and utilized to this day [28. three other research groups. including modules for hydration.10. no ASTM standard method exists for eval- During the same time period. while explicitly considering the PSD of the powder. the mass hydration model [8–10]. to the experimental data for both curing conditions. algorithm measures the fraction of total solids (mainly cement Clearly. For Type I portland cements.. for determining setting. mally controlled by the formation of calcium silicate hydrates ence of the pozzolanic reactions. 7—Degree of hydration as a function of time for CCRL cement 135 with w/c 0. cured isothermally at 25°C.4.40 Cement Paste by Gillmore Needles (C 266). The or slag) cements appears to be a promising new option [46]. Both methods basically measure when the hydrating cement paste develops some finite value of resistance to penetration. . in this case. Within the VCCTL software. both hydrated at a w/c time. respectively. For blended ce.37 provide slightly different values. a typical value is on the To predict setting times using a computer model.45].0003 h/cycle2 to convert between cycles and CCRL cements 135 and 141 [48. setting degree of hydration of both portland and blended (with fly ash is assessed using a specialized percolation algorithm [10]. it is likely the aluminate hydrates that SEM/image analysis (e. some hydration product bridges them.51]. The two usually C4AF 0. present). [49. unless degrees of hydration for Cement and Concrete Reference Lab. one first order of 0. the paste self-desiccates due to the behavior of both well-dispersed and flocculated cement pastes chemical shrinkage that occurs during hydration. ettringite. ON VIRTUAL TESTING 43 Setting Time TABLE 1—Non-evaporable Water Contents Setting time is one of the most important properties of a ce- for Major Phases of Cement ment. and calcium aluminate hydrate hy- Figure 7 provides a comparison of VCCTL-predicted and dration products. as it will determine how much time is available to place Cement Phase Coefficient (g of water per g of phase) and finish the concrete. this is an area where further standardization efforts particles at this point) that are linked together by calcium sili- are needed. Two ASTM standards exist for the evaluation of setting time: ASTM Standard Test Method for Time C3S 0. The solid curve is the prediction by CEMHYD3D using saturated curing conditions. Fundamental research has indicated that setting is nor- measure of degree of hydration due to the confounding influ. which consume calcium hy. needs to decide what constitutes the physical process of set- ments.1] for the total solids as a be observed that the computer model provides an excellent fit function of either hydration time or degree of hydration.33 times for initial and final set generally being slightly greater than those obtained using the Vicat needle. two touching cement particles are not experimentally measured (via non-evaporable water content) considered to be connected. cate hydrate gel.40.23 g of water per gram of cement.24 of Setting of Hydraulic Cement by Vicat Needle (C 191) and C2S 0. one says that the structure is perco- both saturated and sealed curing conditions [47. (bridges) that link together the original cement particles droxide (and its accompanying non-evaporable water) in pro. hydrated under spans the entire system.48]. the setting sealed curing conditions.50].21 ASTM Standard Test Method for Time of Setting of Hydraulic- C3A 0. The VCCTL program returns the decreases the achieved degree of hydration at later ages. with the Gillmore needle Free lime (CaO) 0. The use of nate phases and flash set. Thus. In systems that undergo a rapid reaction of the alumi- ducing other cement hydration products [44. using saturated and sealed curing conditions. The symbols are experimental measurements. set. BENTZ ET AL. Under lated or connected or. point counting) to estimate the form these linking bridges. It can percolated (connected) fraction [0. using Figure 8 shows these percolation plots versus time for a parameter of 0. and the dashed line is the prediction using sealed curing conditions. determined by the ASTM Test Method for Normal Consis- Degree of hydration Fig. When such a structure oratory (CCRL) cement 135 with a w/c 0. The error bars indicate one standard deviation from the mean value. In this way.g. which also can be consistently evaluated. and are about the same size as the data symbols. based on nonevaporable water content. non-evaporable water content is no longer an accurate ting. the measurement of chemical shrinkage was also one of graphs.54]. Setting time will be strongly in. coarser cements re. The fluctuations in the model curves is an indication of the randomness of the model due to its relatively small size. Because the cement hydration products occupy less volume respond to percolated fractions of 0.8. This holds true except for low w/c of 0. The initial and final set. of hydration such as non-evaporable water content and heat reticle system [52].25.4 and 0. than the starting materials (cement and water). lease [8.4) after a few days of curing. w/c 0. a hydrating The Gillmore setting times are slightly longer. in which fluenced by the w/c of the cement paste and the PSD of the the depercolation of the capillary porosity may dramatically cement powder.6 and 0. with the initial cement paste will imbibe water in direct proportion to its on- and final setting times corresponding to percolated fractions going hydration [53.75. w/c 0. Chemical shrinkage has been at a lower degree of hydration. The w/c ratio of both cements was determined by the ASTM Normal Consistency test (ASTM C 187). Chemical Shrinkage ting times as determined experimentally by both the Vicat In addition to being identified by Le Chatelier over 100 years and Gillmore needle tests are shown as vertical lines on the ago. As would be expected. pastes (less than w/c 0. as noted in the caption. the ini. The sharp rise in the curves gives an indication of the setting times predicted by CEMHYD3D. the first subjects investigated by Powers early in his career [53].44 TESTS AND PROPERTIES OF CONCRETE Fig.54]. as fewer interparticle bridges shown to be in direct proportion to other measures of degree are needed to percolate the microstructure in a coarser par. It appears to provide a rapid method for assessing . tency of Hydraulic Cement (C 187). these coarser systems actually achieve set the continuing hydration [8. due to their slower bition rate below that required to maintain saturation during hydration rate. respectively. respectively. The vertical lines in each plot mark the measured initial and final setting times using the Vicat needle test and the Gilmore needle test. For the Vicat needle. But.55]. 8—Fraction of solids connected as a function of time for (a) CCRL cement #135. reduce the permeability of the cement paste and limit its imbi- quire more hydration time to achieve set. and (b) CCRL cement #141.267. tial and final setting times are shown to approximately cor. 65 OPC concrete with 50 % fly ash replacement of cement. Knowing the de- model. if the heat ca- porosity mentioned above. the mental results for CCRL cement 135 with w/c 0.3. land cements is heat of hydration. hydrated isothermally at 25°C under saturated curing conditions. crete are known [36]. for Heat of Hydration of Hydraulic Cement (C 186). gree of hydration of each individual cement phase. specific gravity. For adiabatic ation between model and experimental results at later ages boundary conditions. pacity. . early hydration rates and may provide a means for evaluating Heat Release and Adiabatic Temperature Rise cement cracking susceptibility [56]. Heat of hydration is con- ASTM C01. and mixture proportions of the con- served between model and experiment up until this time. it is straightforward to puted based on the individual heats of hydration of the vari- compute chemical shrinkage in the VCCTL CEMHYD3D ous cement clinker (and pozzolan) phases. BENTZ ET AL.. Figure 10 provides an example of the Temperature ( oC ) Fig.31 subcommittee on Volume Change is currently ventionally measured using the ASTM Standard Test Method balloting a draft standard for this test. The devi. 10—Comparison of predicted (solid line) and experimental measured (data points) adiabatic heat signature curves for a w/c 0. this heat of hydration can be readily ( 40 h) is likely due to the depercolation of the capillary converted to an adiabatic temperature rise. While no standard method Another convenient measure of degree of hydration of port- currently exists for the measurement of chemical shrinkage. and the circles are experimental measurements. Within Knowing the volume stoichiometry (e. The solid curve shows the prediction using CEMHYD3D. overall heat of hydration is easily computed. ON VIRTUAL TESTING 45 Chemical shrinkage (ml / g cement) Fig. Figure 9 provides a comparison of model and experi. molar volumes) the CEMHYD3D computer model. 9—Chemical shrinkage of CCRL cement 135 with w/c 0.g. as excellent agreement is ob. heat of hydration is com- of all ongoing hydration reactions. by mass.3. voxel counting is utilized to calculate the volume fractions of “gel” and “space. as it reduces the 28-day evaluation window Concrete Specimens (C 215). In the CEMHYD3D model. for w/c ranging from 0. a careful test of this algorithm applied to the packages that predict compressive strength development based microstructures resulting from operation of CEMHYD3D was on the measurement of heat signature curves (as a measure of carried out [60]. theory has also been used in commercially available software Recently. the upper point is the 56-day value and the lower point is the 28-day value. ital hydrated 3-D cement paste microstructure. Figure 11 shows the comparison down to either 3 days or 7 days. Therefore.46 TESTS AND PROPERTIES OF CONCRETE E. ient empirical equation relating Young’s modulus and com- tar cubes and concrete cylinders is an obvious application for pressive strength. the output of the CEMHYD3D model is a dig.25 to 0. the above of the ASTM Standard Test Method for Fundamental Trans. imens (C 39/C 39M). The most Virtual Testing of the Properties of Hardened widely used to date has been Powers’s gel-space ratio theory Cement Paste and Concrete [61]. it has been in size. in which each at least one experimental measurement of compressive voxel is occupied by a unique cement paste phase. Computationally. generally observed agreement between model and experi. The ern desktop in an hour or less. versus w/c ratio. Usually. concrete cylinders is assessed according to ASTM Standard Test mental data for the adiabatic temperature rise of a blended Method for Compressive Strength of Cylindrical Concrete Spec- cement concrete. while that of via similar kinds of equations that are microstructurally based. As stated above. Cement paste samples were prepared from a degree of hydration) [63]. It is possible that a multiscale is generally assessed based on the ASTM Standard Test Method strength of materials theory can be formulated to give accu- for Compressive Strength of Hydraulic Cement Mortars (using rate. There is excel. While using finite element techniques. microstructure-based predictions of compressive strength 2-in. for 28-day and 56-day specimens. based on many experimental results. G (GPa) Fig. between compressive strength and elastic modulus. compressive strength is a more highly utilized param. By treating strength is required to estimate the pre-factor. procedure could still result in considerable time and cost sav- verse. is to first compute elastic moduli. A typical model is 1003 voxels originally developed for portland cement systems. agreement between model predictions and measured compres- ods of 28 days and 56 days of curing. [50-mm] cube specimens) (C 109/ C 109M). development can be accurately predicted using the VCCTL lent agreement between the virtual and experimental results. 11—Comparison of elastic moduli predictions to experimental data. several approaches are possible for the prediction of compressive strength. . After peri. either a each voxel as a tri-linear finite element. the degree of hydration sive strengths for CCRL cement 133 [10].” and compres- Elastic Moduli sive strength is estimated as a function of the ratio of the two.6. prediction of the compressive strength of mor. between model and experimental results for 28-day. plied to blended cement (specifically fly ash) systems [62].and 56. and then estimate Actually. and Torsional Resonant Frequencies of ings to the industry. the overall elastic 3-day or a 7-day strength measurement is performed and the re- moduli of the cement paste model can be computed directly sulting pre-factor is used to predict the 28-day strength. software. The previous subsection has illustrated that elastic moduli day-old samples. Another approach to predicting compressive strength. compressive strength based on some functional relationship eter in the cement and concrete industries than are elastic mod. The compressive strength of mortar cubes found in the ACI standards [64]. graphed as a function of w/c. Longitudinal. so that a conjugate gradient relaxation solver must be recently verified experimentally that the theory can also be ap- used [57–59]. Figure 12 provides an example of the German cement. currently being pursued within the VCCTL consor- Compressive Strength tium. A conven- uli. is computer modeling. At each w/c ratio. This size system can routinely be done on a mod. and the elastic moduli were measured using a version ment without requiring an early-age measurement. Since a pre-factor is present in the strength prediction equation. While it would be was measured using loss on ignition (a method described preferable to directly predict compressive strength develop- above). ON VIRTUAL TESTING 47 Compressive strength (MPa) Fig. Even though the results of this test are concretes produced under carefully controlled conditions. however. us. Many of the needed new standards and test meth- hydration. The models’ performance depends Using this approach. studied using computer modeling. Diffusivity [68. one has illary pore space [73–76]. The newly An important area for virtual testing is durability. Hardened Cement and Concrete ing the test as a performance criterion for conformance to specifications is a dangerous but ever-growing practice. In the past. and so it is bility testing is still in its infancy. While they may used extensively to measure the “rapid chloride permeability” provide adequate predictions of the diffusivities of laboratory of a concrete cylinder. equations have been developed to predict As more and more concrete structures are designed for concrete diffusivity for limited ranges of these four input pa- durability as well as strength. the Modeling the Degradation and Service Life of test method may produce the correct performance ranking. a hard core/soft shell (HCSS) microstructural model of concrete has been de. The error bars indicate one standard deviation from the mean. BENTZ ET AL. While for a set of similar materials.69]. such Bulk Diffusion (C 1556) is a welcome addition that will provide as leaching of calcium [72]. It must be recognized that these equations ignore a diffusivity are becoming more important. The concrete is modeled as a three-dimensional cement and concrete properties that can be predicted and continuum volume of spherical aggregates. become a major area of focus as time goes on. dards and test methods. Degradation mecha- Chloride Diffusion Coefficient of Cementitious Mixtures by nisms at the microstructural level have been considered. 12—Experimentally measured (circles) and model-predicted compressive strengths for ASTM C 109 mortar cubes prepared from CCRL cement 133 at 25°C. Virtual dura- ionic electrolyte such as cement paste pore solution. known to be confounded by the conductivity of the pore solu. new and di- (ITZ). has been clearly shown that standards and computer model- Random walker techniques are then employed to determine ing can and should function in a synergistic relationship. degree of question.77]. and leaching (of Ability to Resist Chloride Ion Penetration (C 1202) has been calcium hydroxide) from the surface layer. how leaching affects diffusion diffusion coefficients that can be subsequently used to obtain rates via changes in the amount and connectedness of the cap- service life estimates for concrete structures. as determined in the CCRL testing program. in which each ag. computer modeling efforts of recent years have clearly ture [71]. For the case of diffusivity. . differential curing. verse applications surely will be discovered. it is still widely specified within the industry. as durability- approved ASTM Test Method for Determining the Apparent type tests are usually time consuming. Prospectus and Future Directions tar and concrete [68. successful predictions at the cement paste level have been also successfully extended to mor. As computer modeling gregate particle is surrounded by an interfacial transition zone slowly moves into the industrial mainstream. ASTM number of field concrete realities such as (micro)cracking. The diffusivity of the diffusing species is different (gen. it has been determined that the ma.69]. critically on high quality input concerning the materials in jor variables influencing concrete diffusivity are w/c. aggregate volume fraction. and how leaching affects elastic to be careful in evaluating chloride diffusion through a strong moduli via the dissolution of solid phases [41. it erally higher) in the ITZ regions than in the bulk cement paste. The previous sections have illustrated the wide variety of veloped [70]. Thus. The the diffusivity of the overall 3-D model concrete microstruc. par- Standard Test Method for Electrical Indication of Concrete’s tial saturation (drying). although it will possible that more refinements will have to be made [66. and silica fume addition ods are already being worked on by the appropriate ASTM rate (other mineral admixtures have not been considered) subcommittees. The HCSS model is currently being extended to use pointed out the need for new materials characterization stan- real-shape aggregates instead of model spheres.67]. For this application. they should be used with caution in field applications. In addition. However. transport properties such as rameters. tion and various temperature effects [65]. U. should also prove invaluable in providing guidance and direc. U. A.. chemical shrinkage. P. Department of Commerce. 303–311.. even greater predictive power and usefulness. V. S. experimental validation of the computer models.S. by com. Rightly viewed.” Cement and rent vice-chairman of ASTM C01. “The Virtual Cement and Concrete Testing ment system. J. “The Virtual Cement and Concrete Testing days and 28 days. and the members of the VCCTL consortium for their “Microanalytical and Computational Analysis of a Class F Fly financial. 2004. vide measures of reactivity at limited points in time. [1] Bentz. 2004. Even this standard only provides a Department of Commerce.” NISTIR 6485. No. No.. for his continuing enthusias. P. S. E.” NISTIR 6840. J. not [13] Blaine. pp. Biernacki. I.. 60–73..” NISTIR 6962. Depart- age to predict performance properties. A..” Proceedings physical testing towards materials science-based measure. April ments that had not been thought of previously. and useful conversations. and end-user communities. 2002. of the American Ceramic Society. and heat of hydration References are all fundamental measures of the reactivity of a (blended) ce.. Delft University of Technology. P. pp. A. physical testing and virtual testing are complementary. J. Advances in ceramics. the authors would like to thank Dr. “Three-Dimensional Computer Simulation of Cement Hydration and Microstructure Development. P.S.. U. Feng. Hackley. “Incorporation of Fly Ash into a 3-D Acknowledgments Cement Hydration Microstructure Model. for their support of this work comparison to carefully measured quality experimental results. and mech. J. September 1995.” NISTIR 7096. P. technical.. tic support for the computer modeling efforts described in this [16] Williams. 457–466. January 2003. E. models can only be proved..S. Larbi. disproved. 1994.A.S. [15] Remond. merly of Dyckerhoff Zement GmbH. 26.. pp. ASTM standard test methods would be a welcome ad. P. D. 1999. C. 1997. D. No. Version 2.. U. and Bentz.” Materials and Structures. Vol. “Phase Composition Analysis of anistic-based tests for common degradation problems such as the NIST Reference Clinkers by Optical Microscopy and X-ray sulfate attack and freeze-thaw degradation. dition to the research.” ASTM STP 1215. E. and moral support for the development of Ash. ASTM International. Rawn. Ferraris.. pp.. J. for collaborating on the crete properties. [8] Bentz.” ACI Mater. In addition to its us.. leading to im. W. [14] Bentz.. D.. Mr. The oratory (AMRL). “Prediction of Cement Physical Properties by Virtual Testing. 86–92. and polymers have been driven [10] Bentz.” NISTIR 6050. “Measurement of puting values of important parameters for which no standard Particle Size Distribution in Portland Cement Powder: Analysis measurement is available. Vol. only heat of hydration is covered by an existing Laboratory Consortium Annual Report 2001. pp. Experimental former Manager of the ASTM Cement and Concrete Reference validation is critical both during model development and Laboratory (CCRL) and the AASHTO Materials Reference Lab- during their extension to new systems/environments. computer modeling ment of Commerce. Robin Haupt of CCRL. P. Eds. “Determination of Calcium Sulfate Hydrates in Build- competitive. Hydration and Microstructure Development Modeling Package zling experimental results and point the way to new experi. West Conshohocken. Fi- As the above sections indicate.” American Laboratory. We would also like to thank Mr. C. Janssen. Sharon M.” portland cement systems) or SEM point counting (for portland Cement International. D. Vol. 2005.. provements that opened up new opportunities. J. and H. pp. 32. 1999. J.. 3–21. R. 3. standard (ASTM C 186). eas. Stutzman.48 TESTS AND PROPERTIES OF CONCRETE High quality quantitative standards are also needed for the virtual testing. pp... “Petrography of Cementitious a whole new level of control over their material. Haecker. J. C. and Buchanan Jr. 102. U. 80. D. Particles Conclusion and Property Prediction. Bentz. Department of Commerce. Concrete. A. While degree of hydration by non-evaporable water content (for [4] Haecker.. and Bai. James Pielert. 5. E.. Vol. 32. measurement Aggregates. for- ited the potential to predict a wide variety of cement and con. calorimetry can provide nearly continuous monitoring of the Department of Commerce. Distribution of Portland Cement: Phase II.S. “Effects of the The authors would like to thank Dr. But the development of virtual testing will drive ing Materials Using Thermal Analysis. of elastic moduli and creep of concrete at early ages. test data. Examples include measurement of of ASTM Round-Robin Studies. . P.. and Remond..H. and Stutzman. [6] Hackley.A. For both of these [3] Bullard. Pimienta. pp. P. 27. Vol. and Leigh. 14. 187–195. Walker. The results of virtual testing clearly point this out. 71–81. V. Virtual testing pp. P. 2002. virtual) understanding of the material gave material designers [11] Bentz. Ed. and internal relative humidity in hardened concretes. nally. P. PA. 24–28. Pietersen. U. cements and those blended with slag and fly ash) typically pro- [5] Ferraris.” NISTIR 6931. and improved based on and Mr.. computer modeling has exhib. D. While degree of hydration. Aviles. J.S. and Remond. H. 330–337. J.. D.. of the 7th Euroseminar on Microscopy Applied to Building ments that will in turn empower the material models to have Materials.” ASTM Cement. Department of Commerce.. 1997.S. chapter. P. U. S. via material samples. Powder Diffraction. changes in physical testing—there is no doubt about that. “Analysis of the ASTM Round-Robin Test on Particle Size zation efforts for these two measures are also critically needed.” NIST Technical Note 1441. W. Theoretical (or 2000. 2. C. and Stutzman. D. C.. P. terials. Concrete Research. 2003. F. for cement and concrete can do the same thing for these ma- [12] Bentz. D. Laboratory Consortium Annual Report 2003. S.. early hydration rate of cement-based systems.. P. 1. measure of heat of hydration at limited fixed times such as 7 [2] Bullard. Ed. Vol. Virtual testing will drive the development of empirical “SEM/X-ray Imaging of Cement-Based Materials.. “Modeling Cement Microstructure: Pixels. No. J. Cement Pastes and Mortars I. December 2001. Ron Holsinger of AMRL. Ray Kolos and Mr. Experimental Study. F. Standard test methods are lacking in a number of other ar. metals. production. several of which are lacking a standard test elastic work by supplying elastic and degree of hydration data. standardi- C. Department of Commerce.” Journal tion for these new standards development efforts. I. P.. X. Geoffrey Frohnsdorff.. E. Vol. [7] Stutzman. [9] Bentz. and Aviles. Both chemical shrinkage and isothermal Laboratory Consortium Annual Report 2002. Eds.S. “The Virtual Cement and Concrete Testing measures.. September 2002.0.. for- Incorporation of Municipal Solid Waste Incineration Fly Ash in mer Chief of the Building Materials Division at NIST and cur.. Ed. method for obtaining the necessary experimental data. No. L. 1.. P. “CEMHYD3D: A Three-Dimensional Cement by the development of sufficient theory to help explain puz. Materials.. Claus Haecker. DeHayes and David Stark. “Effect of Silica Fume on Cement Research. L. 1933–1937. 34. Vol. London. Procedure. “On the Origin of Portland Cement Performance: Hydration. P. May the Connectivity of the Capillary Pore Space. S. [36] Bentz. J. C. Richet.. “Cement and [29] Navi. 211–226. “Three-Dimensional Mi.” Cement and Set. E.. E. “On Predicting the Influence of Curing Conditions on the Degree of Hydration. van Breugel. 191–196. 30.. H. Vol.. Graham. Delft. Rheometers: International Tests at LCPC (Nantes. E. 565–576. Fraaij. and Hayes. Res. “Nuclei Growth Model in Kinetic Analysis of Cement Concrete Research. Technical University of Denmark. Vol. W. 1999. 1986. P. Willam. pp. 2. T. [51] Cement and Concrete Reference Laboratory. Res. Billington. A. Cement and Concrete Research..” Journal of Research of the National Institute of Standards Concrete Research. “Mon- Concretes Using a 3-D Microstructural Model. 260–264. M. pp.. “An Extension of the Dispersion Model for the Vol. Delft. P. M.631–638. and Ward. P. 1991.” Ph. W. 1996. 1990. Hydration in Low Porosity Cement Pastes.. 1999. 1953. C.. No. and Gérard. Concrete Research. J. K. F. pp. London. J.. tion) and Physical Evolution (Setting) in the Case of Tricalcium Delft University of Technology. Vail. and Baruchel. No.” Cement and Concrete Research. also ASTM Bulletin 194. Waller. Adenot. 32. Vol. Research. E.. 107. M. T. “Studies of Portland Cement Hydration: Measure- Societe d’Encoragement pour l’Industrie Nationale.” RILEM International Sympo.-H. pp. Stockholm. “The Determination of Non- ogy.” Ph.D thesis. A. Victor C. Engineering [35] Le Chatelier. and 605–609. F.” Cement and Concrete Monterrey. 2001. F.” Journal of the American Ceramic Society. F. 622–630. thesis. 33. E. Blended Cement Pastes by a Microscopical Point-Count ture Development During the Hydration of a Cement Com. A.” Gaithersburg. 1947–1954. Eds. J... 2. “Cement and ing Cement-Based Materials. Lyngby. 1991... 215–222.” Gaithersburg. Gutteridge. R.. 2000. M.. D. Prené. K. 1986. J. 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The results of these activities are important to build. and and procedures and recognize their responsibility for ensuring architectural and engineering firms in determining whether that the plans and procedures are rigorously followed. In a study conducted by the Bureau of Public Concerns in Testing Roads in the late 1960s.7 Quality Cement. or shipment. Pielert1 Preface process—poor specimens and faulty sampling techniques will defeat the purposes for which the tests are made. On completion of testing. specifies outside organizations plays a vital role in providing the con. The procurement of representative specimens through stan. contractors. For example. and reporting test results. DISE. owners. which is vital to the nation’s economic Materials (ASTM). curing. the implementation of neous conclusions about the characteristics of the concrete quality system concepts in testing laboratories. makes up a significant portion of the more than $900B prepared by the American Association of State Highway and spent annually on construction. sampling variance. J. stantly monitored if reliable results are to be obtained. variance in quality of the product can be divided used to recognize the competency of laboratory technicians. Cement and Concrete Reference Laboratory. which is frequently referenced. No matter who the This chapter discusses the role of laboratory testing in originator of the chosen standards may be. The role of field and laboratory testing in tracts are often based on the results of test methods devel- promoting the quality of construction and protecting the pub. The evaluation of testing laboratories by Institute (ACI 318). concrete producers. National Institute of Standards and Technology. in recognizing In studying quality assurance for highway construction the competency of testing laboratories. MD 20899. 169A and ASTM STP 169B. Suitable detailed sampling procedures are Introduction described in standards for concrete and concrete-making materials prepared by the American Society for Testing and Concrete construction. and testing variance. that tests of concrete materials and of concrete must be made struction community with confidence in the quality of testing. Supervisors process. These two processes must be con- sampling. in accordance with ASTM standards [1]. ating authorities. Among other requirements. est testing techniques. receives do not represent the material under consideration who prepared the chapters on Laboratory testing in ASTM STP either because they have not been taken with appropriate care. and Aggregates— The Role of Testing Laboratories James H. performing specified tests. respectively. The report should be 1 Manager. the qualities of the materials in the construction comply with Concrete specifications enumerated in construction con- contract documents. oped by ASTM. it is imperative assuring the quality of in-place construction through testing and that every effort be made to avoid the use of any but the lat- inspection activities. Employment of an unsatisfactory pro- dards-developing organizations in the United States in preparing cedure is potentially dangerous because it can lead to erro- standards which promote quality testing. the role of evalu. a laboratory is usually required dard sampling procedures is a critical step in the testing to submit a written report to its client. into material or process variance. it was found that 50 % or more of the overall variance could be attributed to two of these factors: The testing of concrete and its component materials consists of sampling and testing [2]. are acknowledged. the Building Code Require- lic safety is receiving added consideration. Field testing and inspection Transportation Officials (AASHTO) for highways and bridge (including sampling) and laboratory testing of concrete and construction. R. both nationally and ments for Structural Concrete of the American Concrete internationally. 51 . WADDELL AND J. and the existing programs materials. including accreditation bodies. Concrete. adequate training concrete-making materials are key activities in the construction and instruction of sampling personnel is essential. Gaithersburg. or have been altered by mistreatment in initial storage. Comparable national standards are also health. at all levels must also be fully acquainted with sampling plans ing officials. and the safety of the structure. Specific areas discussed are the role of stan. A laboratory cannot produce satisfactory information if the samples it THE CONTRIBUTIONS OF J. 52 TESTS AND PROPERTIES OF CONCRETE complete and factual. reference to major • ASTM Standard Guide for Surveillance of Accredited equipment and reference standards used. the client and project identification. If there is a question about the sampling or activities implemented with the quality system. specimen in the quality manual include: quality policy. processes and re- Evaluation and Accreditation has responsibility for preparing sources needed to implement quality management. both nationally and internation- of Testing ally. relations between management. with specification re. scope of testing and references to test proce- to evaluate measurement practices of laboratories and dures. test results. then the reliability of the entire report should be ques. They are as follows [5]: ing a Quality System for Construction Materials Testing Lab- • ASTM Specification for Agencies Engaged in the Testing oratories [8] provide information similar to that contained in and/or Inspection of Materials Used in Construction (E ASTM E 1187. quality system. • ASTM Standard Terminology Relating to Conformity Assessment of a laboratory by an evaluating authority is based Assessment (E 1187)—Provides definitions of terms under on the existence of a comprehensive quality manual and docu- the jurisdiction of ASTM Committee E36. arrangements for ensuring that the laboratory reviews ensures that appropriate protocols are provided for statis. it can be determined by effective and comprehensive quality system involving both the laboratory or another representative of the client whether quality assurance and quality control activities. procedures. The International Organization similar international standards.” A quality standards related to testing laboratory quality. and quality practices of an or- nition (E 994)—Provides requirements for systems that ganization. and identification of the standard test method(s) and known devia. procedures for achieving traceability of Resulting Data (E 1323)—Provides guidance for assessors measurements. ASTM E 1187 a material complies. Interlaboratory Comparisons (E 1301)—Provides guidance A quality manual is essential since it provides the basic ref- for the development and operation of proficiency sample erence to a laboratory’s quality system. reference to interlaboratory comparisons. interpretation of the results obtained. measuring. Typical topics covered programs including management structure. ratory’s quality system be documented in a quality manual. support services. 329)—Provides requirements for laboratories testing and Each of these standards concerning quality systems require inspecting construction materials. report identification and date issued. According to ASTM Standard Practice • ASTM Standard Guide for Development of a Directory of for Laboratories Testing Concrete and Concrete Aggregate for Accredited Laboratories by an Accrediting Body (E 1738)— Use in Construction and Criteria for Laboratory Evaluation Provides guidance on criteria to be used by laboratory ac- (ASTM C 1077).” In recent years. and the E36 have done much to raise all aspects of the quality of AASHTO R18 Standard Recommended Practice for Establish- testing. sources. on the need for laboratories to establish and maintain quality systems [6]. This may include to organizations that use independent auditors or asses- comments about any unusual aspects of the appearance or sors to assure the soundness of their quality systems behavior of specimens that might in any way be relevant to the and practices. description of the preparation and distribution. cedures and the extent of their duties and responsibilities. entity will fulfill requirements for quality”. there has Trends in Improving and Promoting Quality been increasing emphasis. Assignment. new work to ensure that it has appropriate facilities and retically analyzing data. technical ing of results. operations.” Such a manual provides the staff with an under- accredit organizations involved in testing. Relevant standards prepared by Committee tence of Testing and Calibration Laboratories [7]. standing of the laboratory’s quality policies and operating pro- inspecting. and practices comprising a labo- ASTM standards for specific materials. procedures for handling test items. procedure for that accredited laboratories continue to satisfy criteria and feedback and corrective action. and calibrating activities. In some techni. job • ASTM Standard Guide for Evaluating Laboratory Mea. or fails to comply. for Standardization/International Electrotechnical Commis- nizance of international work has had a beneficial influence on sion (ISO/IEC) 17025 General Requirements for the Compe- ASTM standards. cog. verification. procedures. laboratory structure. ASTM E 1187 defines a quality system as ASTM Committee E36 on Laboratory and Inspection Agency “the organizational structure. identification of the laboratory’s ap- surement Practices and the Statistical Analysis of the proved signatories. defines quality assurance as “all the planned and systematic quirements [4]. sample identification. descriptions of staff. the Monitoring of Persons to be Utilized as Assessors/ tions from the standard. procedures for protecting confidentiality and . to provide adequate confidence that an port. while in other areas. The key to competent testing is the laboratory’s use of an When a final report is available. name of credited laboratories. system must be tailored to the unique characteristics and ca- cal areas. the report should cite the name and address of crediting bodies in the development of directories of ac- the laboratory. procedures for dealing with conditions under which they were accredited. and other information Auditing Technical Experts (E 2159)—Provides guidance required by the appropriate standard [3]. and the quality system. and maintenance of equip- ratory accreditation body may use to provide assurance ment. strated as needed. • ASTM Guide for Calibration and Testing Accreditation ASTM E 1187 defines a quality manual as “a document stating Systems—General Requirements for Operation and Recog. and the analysis and report. • ASTM Standard Guide for Selection. the quality policy. and demon- testing methods used to generate results recorded in the re. mentation confirming that the laboratory operates as stated in • ASTM Standard Guide for Proficiency Testing by Use of the manual. reference to proce- Laboratories (E 1580)—Presents procedures which a labo. dures for calibration. trol as “operational techniques and activities that are used to fulfill requirements for quality. complaints. the work of the committee stimulated the drafting of pabilities of each laboratory. it references other that the policies. and quality con- tioned. A laboratory and Proficiency Sample Programs. ing organizations that have been shown to be competent [12]. and equipment requirements for cement testing laboratories [9]. der Memoranda of Agreement between the sponsoring organi- C 31/C 31M. tion (A2LA). ASTM C 1077 defines an evaluation authority as “an independent entity. ASTM C 1077 also re. C 127. reinforcing steel. mum training and experience requirements for personnel. and other oratories to perform designated ASTM tests on concrete and recognized agencies as may be established. while the AMRL Proficiency ated with its intended functions. with at least three years of supervisory experience in the test. or an engineer the four accrediting authorities referenced in ASTM C 1077. and ASTM Standard Performance Specification for laboratories in the United States and 25 other countries Hydraulic Cement (C 1157). apart from the organization being evaluated. and provide a report of tion of Laboratories Testing Hydraulic Cement (C 1222). The primary functions of the CMRL are the assessment of at least five years experience in construction materials testing. tion for integrity. maintain a quality system for cement analogous to that for con. Standard chemical and physi. portland-cement have the capability of performing all laboratory testing associ. and quality systems according Turning to cement. ASTM Specification for Masonry Cement (C 91). and ASTM Standard Specification for Expansive Hydraulic Cement for use in preparing precision statements. C 143/ are NIST Research Associate Programs that operate at NIST un- C 143M. and quality system. and procedures for assuring Building and Fire Research Laboratory (BFRL) program. though because of its reputa- crete. identifies mini. or a person with equivalent science. testing laboratories and the distribution of proficiency test sam- and that the laboratory be periodically assessed by an ples. CCRL and AMRL required for laboratories testing concrete (C 172. through use of its programs by accrediting bodies. it lists optional ASTM technical oversight of CCRL through a Joint C01/C09 Subcom- concrete and aggregate test methods for which a laboratory mittee on the CCRL. the American Association for Laboratory Accredita- laboratories. Data from these programs are provided to standards commit- dard Specification for Portland Cement (C 150). concrete. and pozzolan materials. The Evaluation Authorities actual quality system requirements depend on the standard that a laboratory is trying to meet. that Continuing Improvements in the Quality of can provide an unbiased evaluation of that organization. C 138/C 138M. (CMEC). . Accrediting bodies listed include prepare documents for use by inspection/accreditation agen. Concrete materials routinely distributed to laborato- ASTM C 1222 does not identify mandatory test methods that a ries by the CCRL Proficiency Sample Program include portland laboratory must be able to perform. performance of construction materials testing laboratories. methods. materials analyst. AASHTO Accreditation Program (AAP). procedures for providing support to the sponsoring standards committees in record keeping. and concrete. ASTM C 1077 prepared by Committee C09 pro. ASTM is the sponsor of CCRL and AASHTO dards for laboratories testing concrete aggregates (C 136. (A2LA) was formed in 1978 as a nonprofit scientific member- oriented education or experience. zations and NIST. and C 39/C 39M). Construction Materials Engineering Council vides criteria for the evaluation of the capability of testing lab. ticipation in a proficiency sample program. The scope of a testing laboratory currently participate in the CMRL Laboratory Assessment may be chemical testing. but does require that it cement. The 2003 version of C 1077 lists ratories (CMRL) [10. ASTM Stan. ASTM Committee C09 on Concrete and evaluation authority that provides laboratory inspection and Concrete Aggregates. and procedures for audit and review. procedures for equipment calibration and the preparation of test methods. procedures for which complements and benefits from interaction with the NIST handling technical complaints. ASTM Stan. certified. The American Association for Laboratory Accreditation ing of hydraulic cement. masonry cement. while AASHTO provides oversight to may request evaluation. or both. and the quality of external technical services. Over 1500 different (C 845). A periodic assessment by an ship organization dedicated to the formal recognition of test- evaluation authority is also required. physical testing. results from its programs are used by three of ratory should be a chemist. The standard establishes minimum CCRL and the AASHTO Materials Reference Laboratory requirements for the testing laboratory’s personnel. ASTM Standard Practice for Evalua. blended cement. and ASTM Committee C01 on Cement proficiency sample services. PIELERT ON THE ROLE OF TESTING LABORATORIES 53 proprietary rights. C 128. evaluate equipment.” The Concrete Testing standard lists the Cement and Concrete Reference Laboratory (CCRL) sponsored by ASTM Committees C01 and C09 as an Among other things. and C 40). masonry materials. par. pozzolans. operating a research program maintenance. as described in ASTM C 1077. or accredited by the CMRL itself. which findings to the laboratory. to the requirements of the test methods. and five mandatory ASTM stan. (AMRL) comprise the Construction Materials Reference Labo- ment. and other organizations involved in quality assess- the full-time technical direction of a professional engineer with ment. 1077 must establish and maintain a quality system that in. Sample Program distributes fine and coarse aggregate profi- cal requirements for various types of cements are listed in the ciency samples as well as samples of other highway materials. an inventory of test equipment. CCRL Laboratory Inspection Program are hydraulic cements.11] which are located at the National In- seven mandatory ASTM test methods in which competence is stitute of Standards and Technology (NIST). procedures. Further. The manager of the labo. C 1064/C 1064M. C 173/C 173M. is the sponsor of AMRL. the “National Voluntary Laboratory Accreditation Program cies or other parties on evaluating concrete and cement testing (NVLAP). determining the impact of revisions to standards. Utilization of the CMRL complying with ASTM C 1222 is required to establish and programs is voluntary and laboratories are not rated. A laboratory complying with ASTM C AMRL through the AASHTO Subcommittee on Materials. ASTM provides programmatic and C 117. Laboratory Assessors from the CMRL visit laboratories to independent evaluating authority. aggregates.” concrete aggregates [3]. tees of ASTM and AASHTO for assessing the adequacy of test dard Specification for Blended Hydraulic Cements (C 595). equip. governmen- quires that testing services offered by the laboratory be under tal agencies. Concrete materials included in the was first published by Committee C01 in 1993. CMRL promotes the quality of testing by assessing the cludes procedures for personnel evaluation and training. and implemented Certification Program. con. NIST Special Publication the Washington Area Council of Engineering Laboratories 788. nondestructive testing. cut. plays a vital role in assuring the quality of testing. with enhanced mechanical. J. concrete. American Concrete Institute. steel materials. and thermal. zations. . ASTM AASHTO in 1988 for construction materials testing laborato. of demonstrating the competency of a technician in perform- back asphalts. have a responsibility to have a means for training their crete. MI. AAP certifies the competency of testing laborato. No. ASTM International. calibration. biology. equipment. NVLAP STP 169A. T. The con. 2002. standardized.02 Concrete and tures. masonry. and testing of construction materials Conclusions through accreditation. p. soils. 2003. accredits public and private testing laboratories based on the evalua. volume stability. or of an equivalent certification program. 2003. hot-mixed asphalt. burg. ing tests on concrete materials.” Public construction materials testing field is available for selected Roads. and generally uses contract assessors who are grams are offered by independent organizations including the experts in their field for on-site assessment of laboratories.13]. and [1] Building Code Requirements for Structural Concrete and Com- the technical qualifications and competence of their staffs for mentary. qualifications to perform assigned tasks. and Halstead. “Quality Assurance in High- requirements of ISO 9002. asphalt. ASTM C 1222. and bituminous material. importance of concrete sampling and accurate testing will nually. There are [5] Annual Book of ASTM Standards. 1929. CMEC provides inspection and profi. A2LA requires laboratories to partici. PA. CMEC operates laboratory accreditation and proficiency High-quality field inspection and laboratory testing services are testing programs for cement. and Shotcrete Nozzleman Program accreditation may also be obtained for compliance with ASTM [19]. The competency of laboratory technicians conducting the tests mechanical. 105. Farmington conducting specific tests [15]. important to achieving safe. and and Concrete Laboratory Performance. 35. technician training and certification pro- and AMRL.02 General Test Methods. NICET offers four levels of certification for concrete C 1077. construction materials. Participation in the CCRL and AMRL profi. will continue to promote the quality of these services. inspection. As of June 2004. NVLAP accreditation is based Hills. hydraulic cement. and certification programs [14]. emulsified asphalts.54 TESTS AND PROPERTIES OF CONCRETE A2LA grants accreditation in the following fields of testing: Technician Competency acoustics and vibration. geotextiles. American Concrete Institute (ACI) and the National Institute The AASHTO Accreditation Program (AAP) was started by for Certification in Engineering Technologies (NICET). as a means ries in carrying out specific tests on soils. Tilt- laboratories and 68 were hydraulic cement laboratories. and The National Voluntary Laboratory Accreditation placement properties require more accurate test results. The mechanisms discussed in this chapter group for the American Concrete Institute (ACI) Technician which are being developed. NVLAP accreditation in the way Construction Part 1—Introduction and Concepts. “Quality Assurance in the Construction Materials testing laboratories include the International Accreditation Laboratory. environmental. soil and rock. Properties of Concrete and Concrete-Making Materials. West Con- construction materials testing field. Forensic Sciences. asphalt cements. ciency sample programs may be used by laboratories to meet [4] Waddell. shohocken. PA.. Gaithers- [18]. methods of testing for concrete. the Concrete Advisory Board of Georgia [17]. J. Volume 04. electrical. concrete. chemistry. geotechnical. West Conshohocken. and aggregates currently has about 100 personnel. AAP Up Certification Program. ACI 318. samples. “Quality of Testing. durability. and Aggregates. soil. admix. Conformity Assess- currently around 20 laboratories accredited by NVLAP in the ment. aggregates. West Conshohocken. Program (NVLAP). and chemical testing. test procedures. Volume 14. and is a sponsoring concrete structures.” Proceedings. on the requirements of ISO/IEC 17025 and the relevant [2] McMahon. throughout 15 states (from coast to coast) and three increase as structural design and modeling by computers foreign countries. 1969. aggregates. and documenting their laboratories accredited. J. generally uses contract assessors who are experts in their p.” Significance of Tests and the NVLAP proficiency testing requirements for aggregates. efficient. field for on-site assessments of the laboratories. ASTM International. Feb. 32. The Construction Materials Engineering Council (CMEC) was founded in 1983 for the purpose of improving the quality of production. W. as. C 1077 references compliance with programs of these organi- ries [11. Certification Program. Statistical Techniques. Laboratories struction materials field of testing which includes cement. Aggregate Technician and Canada of which 599 were portland cement concrete Certification Program. ACI currently operates eight certification programs for The Laboratory Inspection and Proficiency Sample Programs portland cement concrete and aggregates: Field Testing of CCRL and AMRL are used by AAP to evaluate the perform. Laboratory AASHTO had accredited 939 laboratories in the United States Technician Certification Program. p. CMEC does not use CMRL programs in accrediting Additionally. cement. PA. References tion of their quality systems. assessing their competency.. and ISO/IEC 17025. J. Terminology. The ciency sample programs to over 400 different laboratories an. and portland cement concrete. ance of laboratories that test these materials. the development of high-performance concretes laboratories. bituminous materials. 1975. Craftsman Certification Program. July 1991. F. National Institute of Standards and Technology. [3] Annual Book of ASTM Standards. Vol. 6. Because CMEC provides its own proficiency require that material properties be determined more precisely. ASTM cement. W. As a means of ensur- pate in the applicable proficiency sample programs of CCRL ing this competency. Inspector Certification Program. aggregates. technicians [20]. Strength Technician Certification Program. Workshop on Evaluation of Cement Service [16]. ASTM International. which is administered by NIST. education. and cost-effective phalt. Other organizations which accredit construction materials [6] Locke. soils. MD. Lime 214.cabofgeorgia. A. P.. H. PIELERT ON THE ROLE OF TESTING LABORATORIES 55 [7] General Requirements for the Competence of Testing and Cali. 34–37. 1999. and Spellerberg. ASTM International. at http://www.. pp. J. 22–28. West Conshohocken.” ASTM Stan- [17] Information on Concrete Advisory Board of Georgia is available dardization News. Farming- Board.org ods of Sampling and Testing.iasonline.net for Standardization.org tory—Promoting Quality in Laboratory Testing. “AASHTO Materials Refer. 2003.01 Cement. Transportation Research [19] ACI Certification Guide. [11] Pielert. [16] Information on the International Accreditation Service is [10] Pielert. J. 2003. [15] Information on the National Voluntary Laboratory Accredita- Washington. 2002.wacel. Part 1B: Specifications. pp. [18] Information on the Washington Area Council of Engineering ence Laboratory—Thirty Years of Service to the Transportation Laboratories is available at http://www.org Engineering Technologies is available at http://nicet.nist. ton Hills. MI. Geneva.org . tion Program is available at http://ts. [13] Information on the AASHTO Accreditation Program is available bration Laboratories.amrl. available at http://www. American Concrete Institute. Number 183. March-April 1996. “The Cement and Concrete Reference Labora. November 2002.htm and Gypsum. DC. Switzerland. ISO/IEC 17025.cmec. [12] Information on the American Association for Laboratory [20] Information on the National Institute for Certification in Accreditation is available at http://www. PA. Volume 04.” TR News. Washington. AASHTO. West Conshohocken. International Organization at http://www. H.org PA.gov/ts/htdocs/210/214/ [9] Annual Book of ASTM Standards.org Community. ASTM International. [14] Information on the Construction Materials Engineering Council [8] Standard Specifications for Transportation Materials and Meth. is available at http://www. DC.a2la. PART II Freshly Mixed Concrete . rheology as “the science dealing with flow of materials. large laboratory rheometers of several designs. ments is that it advances the industry past a single descriptive gates. Inc. Four primary terms have now be- of the beholder. and changed the title to “Factors Influenc. and placing of freshly mixed concrete. and admixtures. and the like. Smith revised ishability. properties of a concrete mixture by the yield stress and plastic ful without reasonable guidelines pertaining to the workability viscosity. Janney. rheology. pastes. and self-consolidating concrete (SCC). and Mr. includ- It is important to note that by using today’s technology. What has been shown is a reasonably definite rela- Aggregates defines workability of concrete as “that property de. Another approach is to characterize the rheological concrete construction portion of a project cannot be success. Scan. testing agency. the concrete and the equipment available to assist in the place. Gene Daniel. and pumpability. T..8 Factors Influencing Concrete Workability D. AZ 72758.” in ASTM STP 169 [1. How. These properties are currently measured by rather of the concrete for each portion of the work. Hubbard with the National Slag Association. D. there is no widely accepted test method to measure the time of initial mixing to the time of testing.1R [7]. defined as “the science dealing with the deformation and flow ability somewhat differently depending upon his or her of matter”and “the ability to flow or be deformed. the handling crete mixtures can be proportioned with practically any worka. Inc. C. and the behavior of slur- bility and retain the capabilities to develop a wide range of hard. The is zero. who is influenced by the space to be filled with come important in describing some basic concrete properties. 116R [6] as “that property of freshly mixed concrete or mortar ters on “Uniformity. ing studies of deformation of hardened concrete. Such technology may The importance of rheology technology and measure- require the use of specialty products such as nonlocal aggre. 59 .” The American Concrete Institute (ACI) defines workability in ACI I. inspectors. Smith with describe the degree of workability desired by the contractor in Marquette Cement Manufacturing. Each of the parties having a consistency. will normally provide guidance on maximum workability as as- lon revised. Mr. measurement for concrete workability. is time dependent as measured from the ever. Vollick with Sika Chemical Corporation. harshness. sociated with water content of the concrete via maximum wa- ing Concrete Workability” in ASTM STP 169C [5]. Project specifications and updated this chapter in ASTM STP 169B [4].2]. and finished to a homogeneous condition. There are a num. and at times a minimum cement content. These specified properties of the fresh concrete may not fully Mr. Mr.” As related to particular responsibilities. ment and finishing process. tionship between slump and a rheometer-determined yield termining the effort required to manipulate a freshly mixed stress [8. concrete. Scanlon was a the fulfillment of the contractor’s responsibilities. Vollick com. and updates the topics as addressed by with ASTM Test Method for Slump of Hydraulic-Cement Con- the previous authors. like slump. ACI 116R [6] defines workability of concrete. placed. Rogers. TYLER AND FRED HUBBARD PREPARED CHAP. Tyler was with the Portland Cement crete (C 143/C 143M). contractor. Rheology is responsibility for the completed concrete structure views work. The current ter-cement ratio. engineer. that determines the ease with which it can be mixed. D. revises. consolidated. which was previously defined. The rheology of ber of factors that influence the workability of concrete. Unfortunately a reliable field test has not been developed to measure the rheological ASTM C 125 Terminology Relating to Concrete and Concrete properties. Concrete senior consultant with Wiss. range of slump as measured in accordance edition reviews. updated. Information on behavior of fresh concrete during vibration and rheology on consoli- Terminology dation can be found in ACI 309. The involved parties may include concrete there is a direct relationship between shear stress and the owner. Elstner Associates. Gene Daniel 1 Preface quantity of concrete with minimum loss of homogeneity.” Work- bined. They are workability. John M. and others. ity and Plasticity. L. A. con. fin- and Workability” for ASTM STP 169A [3].9]. ries. mixture proportioning to provide greater workability then becomes an issue between the contractor and the concrete pro- Introduction ducer to determine a method to provide a greater workability and maintain concrete that in the eyes of the design engineer The workability of concrete is partially determined in the eyes meets the specified criteria. Both a field test and a greater understanding of the 1 Consulting Engineer. supplementary cementitious materials. Association. and updated these two chapters into “Uniformity ability includes such items as compactibility. the rate of shear plus a shear stress when the rate of shear stress concrete producer. revised. Segregation and Bleeding” and “Workabil.” ened properties needed by the structure. concrete materials suppliers. consistency. Mr. Product tolerances are provided by ASTM Specification for Ready-Mixed Concrete (C Uniform concrete can be obtained only through proper quality 94/C 94M) for slump and air content.60 TESTS AND PROPERTIES OF CONCRETE information provided by rheology test results and the relation. rial sources and at the batching and mixing plants and related components. mixing. content determinations. These variations may be attributed to with computerized batching and the development of moisture a buildup of hardened concrete in the drum. because the better the uniformity Water (Moisture) Content of Soil by the Calcium Carbide Pres- during production. and placing. improper loading sequence. The available methods include using ations. or microwave ovens and ASTM Test Method gation of the mixture due to a relatively high water-cement for Total Evaporable Moisture Content of Aggregate by Drying ratio or poor mixture proportions. two different formats: a “maximum” or “not to exceed” value terials through batching. ASTM and ACI definitions of consistency are virtually scribed property. All materials must be slump. After mix. or a Speedy Moisture Tester separate. hot plates. it is essential that the economic realities and not by specification requirements. and the variability from batch to batch are each important signed to maintain consistency of the product. There is great reliance on the manu. Only the fine ability and other characteristics that permit it to be mixed. or possibly overloading of Reservoir No. sistency of the product. predominately composed of minimum or maximum require- Consistency is a term related to the freshly mixed con. 22 Dam. and finished in a timely fash. the concrete quality relies on specific gravity. modulus of 0. consolidated. and curing. and density.” The word con. as measured by the slump also contain maximum variances between lots and thus are de- test. ances. such as fly ashes. silica fume. aggregate grad. The flow of the mixture. excessive wear of probes for aggregate feed bins. Chemical admixture specifica- measurements are slump for concrete. absorption. not use moisture determining probes have increased the moni- ings. Tests for aggregate to the anticipated environmental conditions. mentitious materials. but do not have specific toler- uniform products. include coarse aggregate gradings. with an appropriate ASTM specification.5 % of the kept relatively uniform. Once an acceptable level of volved typically involve residue content. Chemical admixture specifications concrete. consistency requirements in aggregate properties will also in- ened concrete. The and natural pozzolans are each specified to be in compliance criteria for these specimens is provided in ASTM Practice for . The tests in- properties for successful projects. The uniformity of product achieved is actu- identical. The concrete mixture proportions may result in segre. and bulk density. consolidation. particularly for fine aggregates. The uniformity of concrete production and delivery as described in ASTM Test Method for Field Determination of should always be evaluated. The use of improper mate. ovens. tains information on absorption and surface moisture. compared to control mixtures that do not contain the particu- sistency has multiple usages and two of these are pertinent to lar admixture being tested. As the quantities of ingredients be kept relatively uniform. a Chapman flask with ASTM Test Method for Surface rial-handling equipment may also cause a marginal mixture to Moisture in Fine Aggregate (C 70). and moisture content. relative density. where sand bins were filled 17–20 times the mixer. middle. the usual than any specified tolerances. density. Even batch plants that do variations in aggregate moisture conditions. each day with sand of widely varying moisture content. finishing. Control of aggregate moisture has steadily progressed charged from the mixer. absorp- Within-batch variations refer to variations relating to concrete tion. Concrete specimens must be properly fabricated. and tested for evaluating hardened concrete properties. Temperature and concrete density tests are facturers or producers of the raw materials for relatively useful production control tests. (C 566). ments and rarely have an allowable tolerance range for a pre- crete. GGBF slag. toring of fine aggregate moisture by the use of rapid moisture and. inaccurate weighing or volumetric dispensing equipment. Control must be maintained at the raw mate- control of variability by maintaining uniform consistency. air con- Control of Concrete Production tent. There are two distinct measurements of nonuni. or a specified target value. Equally impor. Slump tolerances are in control of all operations from selection and production of ma. all of the variations related to within-batch vari. inadequate or excessive mixing time and Van Alstine [10] attributed the uniformity obtained at Denver speed. flow for mortar or tions contain minimum and maximum limits for properties grout. sampled from the front. of course. prescribed grading ranges for each size aggregate. properties are all defined as maximum allowables except for tant is that the freshly mixed concrete should possess the work. conveying.20 from the base fineness modulus addresses con- ion without hardship under prevailing conditions. to the Batch-to-batch variations in concrete may be attributed to use of an electrical resistance meter. and penetration for neat cement paste. specified value. placed. transportation. Items that may be subject to future variation restrictions formity: within-batch variations and batch-to-batch variations. The tolerance varies by level of ing. crease. demands for more consistent concrete increase the need for Nonuniformity may be evident in freshly mixed and hard. Mixed concrete should be tested for consistency. aggregate with a specified maximum variation of the fineness transported. Uniformity of Concrete Aggregates should be tested for grading. and mixtures should be adjusted to Concrete mixture proportions should always be developed in correct for changes in these properties. the mixer blades. ASTM Specification for such a way that the finished hardened concrete will attain the Concrete Aggregates (C 33) covers the requirements for both required physical properties and be able to withstand exposure coarse and fine normal weight aggregates. transporting. To cover the wide ship to the concrete composition [8] are current research range of raw materials being dealt with these specifications are goals. Hydraulic cements and supplementary ce. temperature. The chapter in this volume by Yzenas con- opportunity to obtain desired hardened concrete properties. and end of the batch as dis. the greater the sure Tester (D 4944). moisture contents. and workability has been established. plac. cured. ACI 116R [6] defines it as “the relative mobility or ally the result of the desire for customer satisfaction rather ability of freshly mixed concrete or mortar to flow. Consistency of aggregate products is tures have been developed and the necessary characteristics driven by the need for customer satisfaction balanced against that affect workability are determined. infrared analysis. The stated tolerance for air content is 1. and the type of weigh batcher sys. ASTM C 94/C 94M. density of air-free mortar. This method has been used by Slater [17]. percent of coarse aggregate. slump determinations. limited usefulness because of sampling errors and difficulties in distinguishing between cement and very fine sand.S. concrete of satisfactory quality can be obtained if proper control is maintained. Tests are to be Cylindrical Concrete Specimens (C 39/C 39M). air content. and others to study the effects of different rates of ASTM C 94/C 94M also contains tolerances of test results rotation of truck mixers. calcu. water content by oven drying. ASTM Test Method for Slump of Hydraulic- water content. air content. Bureau of Reclamation’s mixer performance test [14] The tolerances for measuring the materials vary with the ma. The Dunagan test has concrete. U. Water added to the batch air-free mortar of two samples. The uniformity requirements They suggested that a variation of more than 16. Dunagan [16] proposed a method for measuring the propor- formity tests have been used to establish required mixing time. [15]. Hollister [18]. For batches that use more than 30 % of of freshly mixed concrete is evaluated by comparing variations scale capacity cement and cement plus other cementitious ma. and differences of more than requirement is that an acceptable mixer must meet not less 32. nonuniform distribution of water or other ingredients through- . coarse aggregate con. Methods of Measuring Uniformity Air-Free Unit Weight Test Tests for Mixer Uniformity A study designed to establish test methods and limits for variations in truck-mixed concrete was reported by Bloem et al.1 lb/ft3) corresponds to a change in water aggregate. Concrete uniformity generally has been measured in terms of compressive strength. tions of cement.S. density of air-free mortar. U. Large variations in the density of air-free mortar may indi- ter on aggregates and is measured to an accuracy of 3 % of cate that the batching procedure is incorrect or mixer blades are the specified total water quantity. performed on samples of concrete representing each of the Routine instructions for measuring. 1/2. and Measuring the uniformity of concrete mixers has been a part compressive strength of concrete obtained after approximately of ASTM Specification for Ready-Mixed Concrete (C 94/C 94M) 1/6. is essentially an indication of tent. Bureau of Reclamation Test of Mixer structions for critical segments of batching operations plus Performance maximum acceptable batching tolerances for each material. will be within prescribed limits of uniformity. and to verify efficient crete by a series of wash separations and weighing in air and batching procedures. is used to evaluate the ability of a mixer to mix concrete that terial. ables was reduced and excessive changes in this property re- The test method requires two separate samples from each end flected changes in water or in proportions of cement and sand. of about 9. The requirements of a mixer uniformity test mined. effect of time of haul. Chemical admixtures are worn. the consistency of an individual batch of concrete. and 5/6 of discharge from a truck mixer were deter- since the 1940s. slump.0 kg/m3 involve six comparison values. Uni. mixing. Annex Al. Tests by a number of investigators have water. Army Corp of Engineers Test Method for Tests for Quality Control Uniformity Within-Batch Uniformity of Freshly Mixed Concrete (CRD-C 55-92) [13] Slump This method of evaluation tests three samples of concrete for The slump test.9 L/m3 (2 gal/yd3) when the proportions of sand to lated density of air-free concrete. The tests are performed Manual of Concrete Inspection [11]. Total water includes any wash water and free wa.0 kg/m3 (2 lb/ft3) should be considered evidence of unsatis- than five of the six measured properties.6 kg/m3 (1. The ASTM C 94/C 94M tions of the mortar ingredients. and coarse aggregate in fresh con- mixing speed. seven-day compressive strength. but consistent ect specifications include limits for these various tests. Cement Concrete (C 143/C 143M). water. air content. been considered in the preparation of ASTM C 94/C 94M. and Dunagan Test content of coarse aggregate and cementitious materials. assigning a maximum variation (1 lb/ft3) in this test indicates real differences in the propor- to each tested or calculated property. mixing water. slump. of air-free mortar varies more than 24 kg/m3 (1. mixer batch capacity. in quantity of coarse aggregate. DANIEL ON CONCRETE WORKABILITY 61 Making and Curing Concrete Test Specimens in the Field (C place two samples and water content replaces concrete density 31/C 31M) and ASTM Test Method for Compressive Strength of as a sixth measurement and potential criterion. and cement were kept constant and the water alone was varied. ASTM C 94/C 94M provides specific in. the size of the batch. Some variation must be accepted. one taken from each of the first must be measured to an accuracy of 1 % of the total required and last portions of the batch. and the density of terials have a tolerance of 1 %. air content. and placing three thirds of the batch. practices that lead to better uniformity are found in the ACI The standard guide specifications that are used to prepare proj- 304R [12]. Additional mixing time may be required if the unit weight measured to a tolerance of 3 %. The uniformity tem for aggregates. Large within- The difference between this test method and the ASTM C 94/C batch variations in slump indicate incomplete mixing and 94M Annex Al mixer performance test is that three samples re.S. Cook [19]. concrete density. factory uniformity. but not the very first and very last por- concrete are given by the American Concrete Institute (ACI) tions of the batch to be discharged. and seven-day compressive strength. sand. of the middle portion of the mixer and involves determining According to their data. density. The U. Uniformity Requirements air-free density of mortar. and effect of that are requirements of uniformity of a single batch of mixing time on uniformity of concrete. They concluded that the air-free density test was an have expanded and changed but the premise of checking for improvement over the density test because the number of vari- uniformity of concrete within a batch has remained the same. Concrete Variations in slump. Additional information on also to determine the feasibility of altering the mixing time. a difference in air-free density of mor- the air content of each sample as well as the quantity of coarse tar of 17.5 lb/ft3) [15]. This water covers the concrete upon in- special pressure-tight container and accessories designed to sertion of the inner bowl. or knife blade. ASTM C 173/C 173M volumetric meter. the finger is carefully removed content. ASTM Test mences. temperature. variations in concrete This test method is described in detail in AASHTO T 199 Air Con. from the stem. it should be recalibrated.5 cm (1 in. set upright and jarred to release trapped foam. 25 mm are removed by sieving before the test procedure com- cepted methods include the pressure method. it may be the result of a . uncorrected changes in moisture indicator in a vertical position. The apparatus is inverted and shaken vigor- lightweight aggregate. If the mass of aggregate per cubic meter and the indicator is rolled from vertical to horizontal several of lightweight concrete changes. This apparatus must be calibrated peri. Within-batch variations should not exceed 1 %. mass based on the density of the materials used. in mass of aggregate.25 %. weight. consists of a inner bowl is inserted.5 cm (1 in. A correction factor. bubbles and striking off the top to produce a level surface.4-mm di- sure Method (C 231). and changes in moisture called the Chace Indicator. and. This instrument is approximately 50 % of the height of an Several methods have been developed to directly deter. ered as reliable as the pressure meter or the volumetric method ity. Density (Unit Weight) tainer. proved test methods. Results ob- concrete as well. and the liquid level is adjusted to the top line. Less air than desired will detrimentally affect workabil. After shaking. may be an isopropyl alcohol is added. The potential problem with either of these non-ASTM Due to the advent of new air-entraining admixtures and test methods is greater variability of test results than with ap- their ability to entrain much smaller air bubbles. ers of material that are each rodded 15 times with a 9.9 cm (3/4 in. The volume of air is determined from the difference in Air content of normal weight concrete may be computed by volume of the sample containing entrained air and the volume comparing the actual density of concrete with the theoretical of the sample after it has been agitated to permit the air to es.) of vide an indication of relative air content and cannot be consid- slump. The long-necked top section is then hold a precalibrated volume of concrete. to the nearest 0. ously a minimum of 15 times. ASTM Test Method for Density (Unit Weight). ple. ASTM C 231. The glass tube that comes with the device is filled especially for lightweight aggregate concrete in conjunction to the top line with isopropyl alcohol. Yield. content of aggregates. Nasser in Canada [21. tained by this method are influenced by variations in mixture A non-ASTM standard air indicator is a miniature device proportions. density of ingredients.) within a batch. quantity of air. consists of yield. It is important that the concrete contain a uniform volumetric air meter developed by K. as outlined in cape. removing air from a concrete sample by mixing it with water and isopropyl alcohol in a long-necked. ter is placed in an outer bowl before the concrete-containing The pressure meter method. or variations in temperature. Aggregates larger than mine the air content of fresh concrete. This method is recommended particularly for light. ASTM Test ameter rod before tapping the sides to remove large air Method for Air Content of Freshly Mixed Concrete by the Vol. Air entrainment increases slump with each 1 % of addi. The tent are kept constant. which uses the volumetric principle. ASTM C 173/C 173M.62 TESTS AND PROPERTIES OF CONCRETE out the batch. With the ing tolerances or errors. agitation of the sample. it is recom. mended that the results of the pressure meter tests be periodi. closed-top special con. It is most air content. grading of the aggregate. A sudden stiffening of the mixture may indicate useful as an indicator of the batch-to-batch consistency of the loss of air or a lower air content than desired while a sticky air content of the concrete.3 cm (1/2 in. the slump measurement the new liquid level gives an indication of the air content in the should not vary more than about 2. and Air weight concrete. and the volumetric method. based on the mixture proportion.) density of air-free mortar test. The principally ac. the apparatus is odically to guard against changes caused by rough usage. This method is used connected to the outer bowl and more water is added through more than any other and is considered satisfactory for all types the open neck of the top section until the apparatus is of concrete and mortar except those made with highly porous completely full. ity. mortar sample.22]. Wa- umetric Method (C 173/C 173M). The top is if the elevation of the place at which the apparatus is used opened and a measured quantity of antifoaming agent that changes by more than 183 m (600 ft). A calibrated rod is in- An aggregate correction factor should be determined with the serted through the top of the neck and the air content is read materials used and subtracted from the apparent reading to de. times until all mortar has been removed from the cup. but it may be applied to other types of Content (Gravimetric) of Concrete (C 138/C 138M). and removal of the finger from the tube. the brass tube is inserted with air determinations and slump. Batch-to-batch variations may result from batch. method of inserting the stopper. mixture or reduced bleeding is an indicator of increased air Another non-ASTM standard air indicator is a mini- content. in diameter by 1. Sudden loss of workability may indicate a major change in and should not be used to accept or reject concrete. termine the actual air content. A test is more definitive when the mass and solid volume of small sample of carefully selected mortar is obtained from the coarse aggregate and volume of air are eliminated as in the concrete and placed in a brass cup measuring 1. tional information on air content. The chapter in this publication by Roberts contains addi- cally verified by the density test. and the number of graduations from the top to In reasonably uniform concrete. The test can only pro- tional air being approximately equivalent to 2. density are difficult to evaluate as to cause or significance. a change in density indicates a change finger is placed over the stem to prevent alcohol from escaping. must be applied to convert to percent air in concrete. The aggregate correction factor This test method can be used to measure air contents of varies only slightly for the same type of aggregate and need concrete containing any type of aggregate including light- only be checked when there is a definite change in materials. Consequently.) high and compacted with a wire The density test is recommended as a job control measure. density and The volumetric method. The tent of Freshly Mixed Concrete by the Chace Indicator [20]. Air Content Meticulous care must be used in the selection of the mortar sam- Air content has an important influence on concrete workabil. The concrete is placed in an inner bowl using two lay- Method for Air Content of Freshly Mixed Concrete by the Pres. If the slump and air con- in the tube. The centrifuge test was used in the study by Bloem et al. The variation in test results is greater than with the a quick indicator of batch-to-batch consistency of the concrete ASTM C 39/C 39M compressive strength test. sistance. [15].” in ASTM in strengths of production concrete the larger the compressive STP 169C [5]. They concluded that the test is quite involved and. testing during the 1960s but was then dropped from ASTM C ful in determining the degree of uniformity of concrete. This Strength Testing liquid is used to separate the components of a carefully pre- Measured concrete strength is used widely as a criterion of pared mortar sample extracted from the concrete. The primary precaution in determining the cessive wear or excessive hardened buildup. This is a laboratory test method. DANIEL ON CONCRETE WORKABILITY 63 change in moisture content. Variations in excess of this amount must be attributed uring devise accurate to 1°F (0. based on the ture increases the time period for a given workability decreases. The dimensions of this tensile strength as a pass/fail criterion for the concrete.5 mm (112⁄ in. also known as the Willis-Hime method. ASTM C 1362 contains a precautionary note for Flexural Strength of Concrete (Using Simple Beam with that this test method may not be appropriate for use with gap. placeability. The permissible Temperature difference for the average compressive strength at seven days Workability is also effected by the temperature. This test method was ASTM C 1078 and was discontinued in tical evaluation method for control of compressive strength August 1998. In a The heat increases both the hydration rate and the rate of water well-controlled laboratory. tions in test results than with testing for compressive strength. thus Tests for Cement Content Uniformity limiting its usefulness as a quality control method. Third-Point Loading) (C 78) or ASTM Test Method for Flexural graded aggregate concrete. Other factors such as durability. ASTM 94/C 94M. ASTM C 94/C 94M lists requirements for The chapter in this publication by Roberts contains added within-batch uniformity of concrete. The measurement and to mixing variations within the batch of concrete being tested reading are performed in accordance with ASTM Test Method for uniformity. The larger the variation 13. fabricated from the same concrete sample may vary from 3 to perature is accomplished using a calibrated temperature meas. plications. thus limiting the or within-batch consistency. and handling. An excessive variation for within batch com- for Temperature of Freshly Mixed Hydraulic Cement Concrete pressive strengths may indicate a mixer containing fins with ex- (C 1064/C 1064M). sistency of very stiff concrete. is applicable for any the test method of choice unless one of the other methods is re- low-slump concrete. Not to be overlooked in an evaluation process are any grading of the aggregate are required in order to determine the improper laboratory procedures that may be a source of cause of the variation. This test method also uses cylindrical specimens. The chapter in this volume Consistency and Density of Roller-Compacted Concrete Using by Ozyildirim and Carino on concrete strength testing contains a Vibrating Table (C 1170) were approved in May 1991 and are information on quality control uniformity. concrete quality. Measurement of the freshly mixed concrete tem. compressive strength of cylinders evaporation. time and labor required. Content of Freshly Mixed Concrete Evaluation of Compressive Test Results of Concrete as a statis. curing. When strength is to be used as a measure ASTM C 39/C 39M is rily used for roller-compacted concrete. The flow testing device was originally known as a K. This test method is discussed in detail in Chapter based on the coefficient of variation. thermal properties. is described C 1170 also prescribes a method to determine the density of in detail elsewhere [25]. It is applicable for concrete with practical usefulness of this test to projects using the splitting coarse aggregate up to 37. This test method includes a vibrating table with a surcharge mass (Test Centrifuge Test Method A) or without a surcharge mass (Test Method B). 5 %. The current test method. and these are expressed as information on air content uniformity as related to density. ASTM This test. in most and compactibility may be more critical. Strength of Concrete (Using Simple Beam With Center-Point Loading) (C 293). under the jurisdiction of Subcommittee C09. dimensional stability. grading. Additional tests. Flexural specimens are sensitive to small varia- Vebe Apparatus tions in molding.45 on Roller- Compacted Concrete.5°C). moisture content. and are met. This test for cement content was an dicative of variations in other properties. strength overdesign needed to ensure strength requirements gate. Test Method for Compressive Strength of Cylindrical Concrete Specimens (C 39/C 39M) is the most-used strength test for this Rapid Analysis for Determining the Cement purpose. “Cement and Water Content of Fresh Concrete. or density of the aggre. strength variations. The result is wider varia- A modified Vebe apparatus is now used to determine the con. including density. for each sample (not less than three cylinders). ACI Committee 214 [24] has developed ACI 214R-02. The available test procedures are ASTM Test Method slump tester [23]. is 7.). the maximum permissible difference in results of samples taken from two locations in a concrete batch. but strength tests are cases. average strength of all comparative specimens.5 %. The ASTM Test Methods for Determining quired as a pass/fail test for strength. prima. the information gained is not commensurate with the easily made and variations in strength are assumed to be in. alternative to the air-free mortar density in mixer uniformity Compressive strength as a control test is particularly use. It provides a basis for within-batch the consolidated concrete specimen. comparisons of cement content of concrete and employs a liquid with a density greater than sand but less than cement. but The measurement of concrete flow by ASTM Test Method for the load is applied to the edge of the cylinder producing a ten- Flow of Freshly Mixed Hydraulic Cement Concrete (C 1362) is sile failure. strength comparisons is ASTM Test Method for Splitting Ten- sile Strength of Cylindrical Concrete Specimens (C 496/C Flow Test 496M). As the tempera. abrasion re. temperature of fresh concrete is to properly and adequately Another ASTM strength test of concrete available for cover the temperature sensor with concrete. relatively small and compact apparatus are provided in ASTM Flexural strength testing is normally limited to paving ap- C 1362. . pumpability. Accuracy lowable batching tolerances of ASTM C 94/C 94M. The degree of workability required for mately 5 min and subsequent cycles are approximately 2 min. Relative cement contents of various portions of a batch Workability is an everyday concern in concrete construction. rating coarse aggregate after the first cycle. The water content is calculated by dividing the total change An instrument small enough to be used in a field laboratory in mass by the mass of the fresh specimen. converting the results into pounds of water [26. “Cement and Water Content of Fresh Concrete. This test method is discussed in detail in Chapter could not be used and hand tamping and spading were required. The improve the test precision include the use of specimens larger calcium atoms absorb the photons in proportion to the quantity than the current 1500 g minimum plus the use of more pow- of calcium present in the concrete. As recy. Ce. Potential modifications being studied to sorption of low-energy photons emitted by the apparatus. Class C fly ash can create potential measurement errors. Concrete that can be placed readily without segregation or Rapid Analysis for Determining Water separation in a mass dam could be entirely unworkable in a thin Content of Freshly Mixed Concrete structural member. to its poor precision. is measured by the ab. consistency or fluidity. of this procedure was reported to be within about 14 kg of cement/m3 (24 lb/yd3). The test procedure does require a new cali. results of the test. None of these tests evaluate all a phenomenon that should have a profound effect on the end characteristics that are involved in this property.” Both relate to the physical char- and. The apparatus contains a fast neutron source that emits cling of mixer wash water and process water increases this water these neutrons into a concrete sample by a probe extended into becomes another source of non-cement calcium that varies and the sample. and transporting. proper placement and consolidation of concrete is governed . seg- Oven Drying regation. Field tests indicate the procedure is Workability most useful for evaluating the performance of a concrete mixer. and bleeding. A calibration curve Methods must be developed for each mixture to be tested. mixing. of each in the concrete. The test apparatus contains radioiso- permitted batching tolerances. The apparatus measures the quantity of these neutrons. Water is actually measured as hydrogen because be satisfactory for project averages but the accuracy is not suffi. at present. Calcareous aggregates and erful ovens. Properties involved in workability include finishing char- Water Content Determined by Microwave acteristics. Several calibration tests are necessary with each concrete mixture and Water Content Determined by Nuclear with each change in source of materials. dried in a microwave oven. the most applicable use of the procedure is in acteristics of the concrete alone. workability is related directly to the type Tests for Water Content Uniformity of construction and methods of placing. Workability This test procedure was apparently used on concrete that means different things to different people and for different did not contain calcareous aggregates. ASTM has not adopted this procedure due ment. portation Officials (AASHTO) has adopted this principal in Test The test apparatus contains radioisotopic materials. Workability is dependent upon the physical and chemical quent drying cycle the test specimen is stirred and its mass properties of the individual components and the proportions determined. based on experience. there was no placing conditions. there is little hydrogen in the other materials making up the con- cient for measuring batch-to-batch cement quantities. necessary to produce full compaction. The sensitivity An instrument small enough to be used in a field laboratory uses of the apparatus to the chemical make-up of other materials has nuclear technology to measure the amount of water in a sample produced variations in reported cement contents in excess of of freshly mixed concrete. methods of placing and compacting. The nuclear apparatus has not been incorporated in an fixed period of time (1 h in this procedure) has been employed ASTM test method due to precision variations larger than the al- by the California Department of Transportation [27]. primarily composed of calcium. Sev- Cement Content of Fresh Concrete eral calibration batches are required for each different concrete Constant neutralization by 3 N hydrochloric acid (HCl) for a mixture. None of the test methods proposed or A sample of the concrete is wrapped in a fiberglass cloth and in use today simultaneously measures all of these properties.” in ASTM Concrete having suitable workability for a pavement might be STP 169C [5].” Powers [31] defined it The authors of the report state in their conclusions that as “that property of the plastic concrete mixture which deter- the test was not proven to be of sufficient accuracy for routine mines the ease with which it can be placed and the degree to control of cement content during normal concrete production which it resists segregation. lose energy. Various nonstandard methods have been discussion of the reaction of HCl on the aggregates. uses nuclear technology to measure the amount of cement in The American Association of State Highway and Trans- a sample of freshly mixed concrete [26]. and it is a factor easily appreciated in practice. In actual practice. heavily reinforced section. crete. 13.29]. can be determined in about 1 h. The use of nuclear methods may topic materials. being independent of the evaluating mixer efficiency. Workable concrete compacted by means of This test method was ASTM C 1079 and was discontinued in high-frequency vibrators would be unworkable if vibrators August 1998. and this is developed for its measurement. After each subse. Method T-318 [28]. Granville [30] defined workability as “that property of the bration curve if there is any change in cement or aggregate concrete which determines the amount of useful internal work source and ordinarily a new curve each day. at least. The particulars are the use of not Consequently. Upon striking hydrogen atoms the source neutrons must be accounted for in the measurements by this apparatus. measurement of workability is determined to a less than three drying cycles with crushing of lumps and sepa.64 TESTS AND PROPERTIES OF CONCRETE Cement Content Determined by Nuclear The 2-min cycles continue until the change in mass is less than Methods 1 g. large extent by judgment. unsuitable for use in a thin. Each of the first three drying cycles is approxi. mobility. defined as particles having a ratio of width pact. cement. such as ASTM to coarse aggregate. grading and shape of coarse aggregate. than an equivalent rowest dimension between sides of forms.) pipe. and contamination of aggregate can materials may be sticky and difficult to finish. Specification for Concrete Aggregates (C 33). Training of front-end Consistency (according to ASTM C 125) and plasticity are loader operators on the use of techniques to minimize aggre- terms often used to indicate workability. Forster. but aggregate larger than 6. pumping concrete indicates that concrete containing 6. Very coarse sand can have an undesir. An increase in occur during handling and stockpiling. Plant layouts to mini- Consistency mize aggregate handling are desirable. acts as a lubricant. The consis. and other concrete properties. The chapters in this volume by Graves. finishing properties will be may be increased 9–15 kg/m3 (15–25 lb/yd3). and separation may occur because of the tendency for to thickness or length to width. Generally.S. concrete made with rounded aggregates.4 cm lar sand particles have an interlocking effect and less freedom (2 12⁄ in. ficial in establishing the fine aggregate (sand) content. cement ratio is held constant. as measured by the slump test. The MFA generally contain a greater quantity of fines than natural sands and often mask Air Entrainment their good workability with low slump test results. Yzenas. proportion of fine gates meeting standard grading requirements. If a mix is too dry.) maximum size aggregate can readily be pumped of movement in the freshly mixed concrete than smooth through a 20. tity of pozzolan or other supplementary cementitious material. . Forster. shape of sand water requirements and workability of concrete. Natural sand may give satisfactory results cm (2 12⁄ in. The maximum size of aggregate that can be used to pro- tency necessary for full compaction varies with the type of duce workable concrete is limited by practical considerations structure. more water/m3 (10–15 lb/yd3) when crushed sand is used.3 cm (8 in. Neither very fine nor very coarse crete (ACI 211. It must not be assumed that the wetter Production of workable concrete with sharp. The U. workability. Flat or face. and type of concrete. Consistency generally gate segregation will assist in avoidance of sudden changes in denotes the wetness of the concrete. maximum sizes of aggregate for various types of construc- Rounded river sand gives greater workability than crushed sand tion. It is agreed generally that con. it should be maintained within quantity of water. More formed when it is deposited. aggregate should not be larger than three- Sand fourths of the maximum clear spacing between reinforcing Concrete containing fine sand requires more water for the same bars nor larger than one-fifth of the wall thickness or nar- consistency. sulting in a demand for additional water. or the mix the more workable the concrete. Segregation is reduced and uniformity improved by separating the aggregate into several size Cement fractions and recombining these fractions when concrete is Very lean mixes tend to produce harsh concrete having poor manufactured.) may cause difficulty. Heavyweight. Factors Affecting Workability Some of the factors that affect the workability [30] of concrete Coarse Aggregate are quantity of cementitious materials. more cement is required. Manufactured fine aggregate (MFA) processed from and Meininger have additional information on factors affect- crushed stone is gaining wider use as natural sands become de. type and quan. method of consolidation. Introduction into the the fineness of cement increases the cohesiveness of the con- mixer of a large quantity of undersize material that may have crete mix as well as the rate at which the cement hydrates and accumulated will result in a sudden change in workability re- the early strength development. separation. reinforcing bars. equipment. ACI 304R [12] recommends with a coarser grading than would be permitted with crushed limiting the maximum size of angular or crushed coarse ag- manufactured sand. respectively. amount rather close tolerances to avoid sudden changes in workability and characteristics of admixtures used.1) [32] provides recommendations on the sand is desirable but both have been used satisfactorily. After the grading is established. The aggre. Coarse aggre- grains. If a mix is too wet. and Mass Con- able effect on finishing quality. It reduces bleeding are influenced by the type of crusher used in the MFA produc. increases the cohesiveness or “fattiness” of the concrete. pleted in some geographic areas. gate particle shape and subsequent finishability characteristics and improves the workability of concrete. greater than 3:1. DANIEL ON CONCRETE WORKABILITY 65 by the type of mixing equipment. ACI Practice for Se- amount of coarse sand. If the water- impaired because of the accumulation of laitance on the sur. but concrete containing a very high proportion of cementitious Breakage. Entrained air increases the paste volume. This recombined grading should then be bene- workability. lecting Proportions for Normal. In addition. and segregation during handling and placing of concrete and tion process. concrete must contain 2–3 % gregate to one-third of the smallest inside diameter of the more sand by absolute volume of total aggregate and 6–9 kg pump or pumpline. elongated particles. Bureau of Reclamation’s [33] experience in composed of sharply angular pieces with rough surfaces. characteristics of these The particle size distribution of coarse aggregate influences the materials. it may be difficult to place and com.4 rounded particles. grading of fine aggregate. and availability of materials. ured by the slump test. and water are required when the coarse aggre- crete should have the driest consistency that is practicable for gate contains flat and elongated particles. The water demand ing on the exposed surface. Angu. should be used. angular. type and size of aggregate. percentage of air entrained. amount and spacing of equipment available. placement with available consolidation equipment. and type of compaction including type and size of structure. method of placing. and time in transit. Rich mixes are more workable than lean mixes. which is commonly meas. Yzenas. crushed aggregates generally requires more sand than similar regation may occur with resulting honeycomb or sand streak. and Meininger have additional information on factors affecting workability. larger particles to roll towards the outer edge of the heap are detrimental to concrete workability and finishability. seg. sand. ing workability. size and type of placing The chapters in this volume by Graves. consistency. mixture and ambient temperatures. very dry concrete. These materials have been used to improve the grading of sands deficient in fines. Two concretes with the same slump may behave differ- placeability capabilities for high-strength. of time. permit a ure all factors contributing to workability. Slump reported by different operators on the same batch . As the temperature of the concrete increases. if the wa. Too much mortar formation on factors affecting workability. can result in a sticky mixture. or SCC. crete to be placed readily in forms and vibrated around rein- able because of poor aggregate grading or type of aggregate forcement as necessary. that is. including sand. and admixtures are uni- quency of plugged pump lines when water-reducing retarders form and aggregate gradings are within acceptable tolerances. Re- permit concrete to be handled and vibrated for a longer period peated batches of the same mix. is parabolic. Improvement is more noticeable in proportions of coarse aggregate to be used in trial mixes.) when placed at 10°C (50°F).5 in. An average change in water content of 3 % generally is considered necessary for a 25 mm (1 in. Cementitious Methods of Measuring Normal Consistency and pozzolanic materials are usually substituted volumetrically Concrete for 10–70 % of the cement. workability for placement in pavements or mass concrete. that is. but ical admixtures.0 % when the initial slump is 127 mm (5 in. are used in the concrete.). 1—Slump test. as measured by the slump tant. This is partially due to the increased Additional information on the mobility of the concrete can slump and typically an increased sand content with the use of be obtained if. It does not meas- Water-reducing admixtures. As the proportion of mortar. The first concrete may have sufficient consolidating concretes require maximum utilization of chem.1 provides a basis for estimating the workability of the concrete. It should not be more than is required for consolidation by available equipment. water. Air-entrainment and water-reducing admixtures will increase the slump of concrete if all other conditions remain the same. Each 1 % increase or decrease in air content will produce approximately the same influence as a change in water content of 3 %. produce an increase in slump.) slump when placed at 32°C (90°F). Popovics [34] has presented data indicating that the rela- ing and angularity of the coarse aggregate become less impor. in. one may fall apart after tapping and be harsh with tio concretes. lean mixes than in rich mixes. or. There should be sufficient mortar to fill the voids in the test and the water content of concrete. surplus workability. will have the same water content and water-cement ratio pro- It has been reported that there is a decrease in the fre. The slump generally is reported to the nearest 5 mm (1/4 Fig. The self. brought to the same slump. tionship between consistency values. Slump tests may be Concrete workability can be controlled by proper proportion. The quantity Finely Divided Material of mortar required to produce the desired workability with a The addition of finely divided material. nor is it always rep- reduction in mixing water with no loss in slump. The slump test (Fig. used conveniently as a control test and gives an indication of retarding admixtures reduce the early rate of hardening and the uniformity of concrete consistency from batch to batch.5 % when the initial slump is 51 mm (2 in. HRWR admixtures have been used with silica a minimum of fines. the concrete is tapped on the side with the tamping water-reducing (HRWR) admixtures have greatly increased the rod.) may vary from 2. in. (VMA) is usually needed to increase the consistency (viscosity) The slump test should be performed in strict accordance and prevent segregation. ACI 211. cement. given coarse aggregate can be determined more effectively by mentitious materials or pozzolans. It is not suitable for Chemical Admixtures very wet concrete. However. ently. low-water-cement ra. the slump. or the same concrete may have a slump of 140 mm (5. batching operations. The use of high-range. after removing the slump cone and measuring a water-reducing chemical admixture. A late generation HRWR is necessary to the other concrete may be required for more difficult place- produce good flowability and a viscosity-modifying admixture ment conditions. 1) is the most commonly used method of measuring the consistency of concrete. and air. made at the batch plant in order to check the uniformity of ing of the constituent materials.) at 21°C (70°F) may only have a 76 mm (3 in.). Set. the percentage change in water content required to increase the slump 25 mm (1 in. Workability will be improved if these materials are added as a replacement for part of the sand. An excess of mortar increases worka- used.) to approximately 4. is increased. the grad. with the requirements of ASTM C 143/C 143M. cement. Slump Test stead of substituted for part of the cement. and the other may be very cohesive with fume providing highly workable concrete mixtures.) slump change. it is ter content is held constant.66 TESTS AND PROPERTIES OF CONCRETE Improvement in workability resulting from air entrainment is coarse aggregate plus a sufficient amount to permit the con- more pronounced in lean mixes that are harsh and unwork. the slump decreases. Concrete placed at a slump of 100 mm (4 in. Tests are often made at the point of placement and should be made whenever Mixture Proportions specimens are molded for strength testing. The chapter in this volume by Roberts has additional in. but excess workability is inefficient. vided weights of aggregate. including inert or ce. when added to concrete. generally improves the laboratory tests. resentative of the placeability of the concrete. bility. This reading.2-cm (6-in. The ball is lowered gradually onto the surface of the concrete. and the minimum distance from the center of the ball to the nearest edge of the concrete is 23 cm (9 in.6 kg (30 lb) and consists of a 15. avoiding excess working. The flow tester (K-slump tester) (Fig. measure “the relative effort required to change a mass of con. and the depth of penetration read immediately on the stem to the nearest 6 mm (1/4 in. durable plastic material have been approved by ASTM C 143/C 143M after a series of comparative tests at three different slump ranges indicated no measurable difference in test results. It measures an index that is related to workability after the device is removed from the concrete. in centime. the concrete probably lacks the necessary plasticity for the slump test. The insertion of the instrument into the concrete is limited to 40 s before the measuring rod is lowered and the flow measurement read. in centimetres.). Concrete in the forms can be tested or con. 2) is reported to measure slump directly 1 min after the tester is inserted in the concrete [23]. The ball test can be performed on concrete in the forms.) is permitted in The equipment consists of a metal cylinder mounted inside a the concrete. 3) weighs 13. space permitting. method was reported in Ref 35 and ASTM STP 169C [5]. and it is claimed that tests can be performed faster and precision is greater than with the slump test. tres. or other container. a falling away or shearing off of a portion of the concrete from the mass. the legs of which rest on the concrete to be tested. Slump cones manufactured using a stiff.). If this condition exists. slump cone is removed. released.) drops required to retested later if desired. The minimum depth of concrete at testing is 175 larger cylinder and a suspended plate that fits inside the smaller mm (7 in. wheelbarrow. The number of 6 mm (1/4 in. Flow Tester The test apparatus is used to measure a concrete flow value with ASTM Test Method for Flow of Freshly Mixed Hydraulic- Cement Concrete (C 1362).) diameter ball and stem that can slide through the center of a stirrup.).5 mm (1 12⁄ in. The test was developed to provide a mold the concrete into a cylindrical form is a measure of the method of testing using a minimal concrete area and volume. This ASTM Test Method for Ball Penetration in Fresh Port- land Cement Concrete (C 360) was adopted in 1955 and discontinued by ASTM in February 1999. Ball Penetration Test The Kelly ball test [35] was developed principally as a conven- Remolding Test ient method of measuring and controlling consistency in the The remolding test apparatus was developed by Powers [31] to field. Information on this test Fig. The concrete. The apparatus (Fig. the be 75 mm (3 in.” Coarse aggregate up to 37. The most unsatisfactory form of slump is the shear slump. and the plate is placed on top of the crete may be in a pail.). Both the classic metal cones and plastic cones can now be used for the slump test. crete from one definite shape to another by means of jigging. 3—Ball penetration apparatus. DANIEL ON CONCRETE WORKABILITY 67 of concrete may vary by as much as 13 mm (1/2 in. this reading. It is filled with concrete. This method has not found wide- Studies have been made and reported on 420 concrete batches spread use and no ASTM standard has been written about it. The first reading is taken after the tester has been in place (the disk resting on the concrete surface) for 60 s.5 and 2 and is fairly constant for a given mix but varies according to the mix. by five laboratories. The depth of concrete must be at least 20 cm (8 in. is referred to as the K-slump. Statistical determinations and equations are reported elsewhere [23]. that is. represents the workability of the mix.) and the minimum distance from the tube to the cylinder. The device is removed from the concrete and the measuring rod is again lowered to rest on the surface of the concrete remaining in the tube. Fig. One disadvantage of this test is that it requires a large sample of concrete. workability of the concrete.). The flow table on which the apparatus is mounted is concrete may be retained in the original test position and then operated. 2—Flow test apparatus. The ratio of slump to the penetration of the ball is between 1. A slump cone is placed inside the smaller cylinder so nearest edge of the level surface of concrete to be tested shall that the bottom rests on the base. The surface of the concrete is struck off level. . and the number of drops required to operated compaction table. 4) is used to measure the consistency of Roller-Compacted Concrete. ter is an improvement over the slump test because work is ac- The apparatus is placed on the table and the concrete is com. but the vibration is too vigorous for concrete with a slump greater than about 5. The cone is placed in the pan.) into the concrete is is fastened to a sliding stem is mounted in the lid of the con. considered a measure of the consistency of the concrete. Wigmore Consistometer pacted by turning the handle attached to the cam at the rate of The Wigmore consistometer is described by Orchard [38]. It is claimed that the Wigmore consistome- position with the ball resting on the surface of the concrete. a sheet metal pan. free-moving rod that serves as a reference end point. This about 1 rps.) four times per apparatus consists of a galvanized container and a hand.) slump to very stiff concrete and leveled off.6–10. and 10–32 s [40] may be required for concrete with less than zero slump.68 TESTS AND PROPERTIES OF CONCRETE Truck Slump Meter Truck mixers now use the hydraulic pressure needed to turn mixing drums to measure the consistency (slump) of the concrete contained in the drum.1-cm (2-in. 0–3 s are required for concrete with a slump of 7. Guide for Selecting Proportions for No-Slump Concrete (ACI . The container is again filled with the concrete changes from a 150-mm (6 in. slump meter pressure readings were taken at various drum speeds and graphically plotted as drum speed versus hydraulic pressure. and the vibrating table is set in motion.7 cm (734⁄ in. Fig. The latter apparatus is not a true rheome.). Tests indicate that higher pressures for mixing indicate lower slump values. The plastic disk is brought into position on top of the concrete. The container is filled with concrete that is compacted The number of drops required varies by a factor of ten as on the table by eight drops. The table drops 0. but equipment manufacturers claim it is not a major factor.2 cm (3–4 in.). After several calibration comparisons of hydraulic pressure readings versus measured slump test results. then the lid and the ball are placed in no-slump concrete. The results produced the same pattern as that of a Bingham material and relative results comparable to the tests of these mixtures in an IBB rheometer [37]. and condition. The number of seconds required to remold the cone of truncated concrete to the shape of the cylinder is the measure of consistency and is reported as the number of Vebe seconds or degrees. slump cone. 5—Thaulow concrete tester.) diameter ball that lower the ball and stem 19. Methods of Measuring Consistency of No-Slump Concrete Vebe Apparatus The modified Vebe apparatus (Fig. The Vebe consistometer [39] includes a vibrating table. ter. Daczko [36] discusses the use of truck mixer slump meters as a method of measuring rheology properties of production concrete. In the ACI Fig. 4—Modified vebe apparatus. A 5. Variations in results may be expected if the ball comes in contact with large aggregate. ASTM Test Meth- ods for Determining Consistency and Density of Roller- Compacted Concrete Using a Vibrating Table (C 1170) is discussed in the chapter by Adaska in this volume. The Vebe consistometer differs from the modified Vebe Apparatus of ASTM C 1170 and the results should not be interchanged. These pressure readings will vary for each truck and mixer necessitating calibration for each mixing unit not of identical design. but is the instrumented mixer described in the Two-Point Workability Tests. the truck mixer gage can be used to closely estimate the slump of the concrete. revolution of the cam. Experimenting with two high-fluidity concrete mixtures having comparable slump values. age.1 cm (2 in. For example. filled with concrete.6 cm (7/32 in. Load size is a factor. tually done on the concrete in a way that resembles field conditions. and removed. This method is very suitable for very dry concrete. tainer. and plastic plate attached to a graduated. and the Compacting Factor A meter for measuring the consistency of grout has been de- test developed in Great Britain [30]. assembly to which a torque is applied as the sample of grout is The Compacting Factor test is considered only marginal for rotated. results. All of these test methods have a volume of grout from a standardized flow cone or funnel. and the number of seconds until the first break in the continuous flow of grout is the efflux time. Concrete with a slump of 0–2. Differences in consistency veloped at the University of California and is described else- of very dry mixes cannot be measured with the slump cone.2 cm (3–4 in.) requires on a platform that can be rotated at a constant speed of 60 14–28 revolutions of the drop table. Suspended from a music wire is a 7.6–10. meter. 6—Flow cone. The grout consistency meter is essentially a torque the Thaulow drop table is considered to have merit for this ap. 6) is mounted firmly with the top surface level. When com- Other Methods paring grouts. ger is removed. with good repeatability (single operator) and repro- Fig. the speed of mixing and the mixing time have an ACI 211. These methods are the conventional Vebe consistometer [39]. The goal of being relatively inexpensive and providing immediate flow cone (Fig. Methods of Determining Consistency of Grout Measuring Workability of Self-Consolidating Concrete (SCC) Flow Cone The general characteristics of SCC make the usual workability ASTM Test Method for Flow of Grout for Preplaced-Aggregate tests ineffective. influence on efflux time and should be kept constant. and concrete with a slump rpm. The sample of grout is placed in a metal pan mounted plication. The fin- and not the modified Vebe apparatus of ASTM C 1170.3R) [40]. 5). The angle of twist or consistency factor is read by an very dry concrete.3 kg (16 lb) paddle of 7.) requires less than seven revolutions. several tables are included referencing Vebe test the discharge tube is closed by placing the finger over the end.3R [40] provides a comparison of consistency meas. the Thaulow Concrete Tester Grout Consistency Meter developed in Norway [41] (Fig.5 cm (0–1 in. DANIEL ON CONCRETE WORKABILITY 69 211. . but where [42]. urements by three methods. results. index pointer attached to a cross strut. Some of these tests will be developed into ASTM test grout mixtures by measuring the time of efflux of a specified methods while others will not. These results are based upon the Vebe consistometer and 1725 mL of mixed grout is poured into the cone. The high flowability and variable viscosities of Concrete (Flow Cone Method) (C 939) is a method used in the SCC have caused the development of a series of new test meth- laboratory and in the field for determining the consistency of ods. that all tests Pumpability be performed in one style of rheometer. Values for yield and plastic vis- set of shearing conditions. cosity are obtained by plotting (P PE) / w against w. tercept on the torque axis. whereby measurement at all three speeds when the bowl contains a pre- only one measurement is made at one specific rate of shear or scribed quantity of concrete. but additional knowledge will be required if dures. It is nevertheless advisable. Two use coaxial cylinders. The two-point test yields more in- Tattersall also states that there is evidence to indicate that. The Concrete knowledge and technology have advanced slowly balance of this paper by Tattersall [44] discusses test proce. gies are being developed in all phases of the concrete industry point workability test and the relationships between slump. Brower and Ferraris [46] found when test- Flowability ing several different concrete mixtures in each of the five styles Compactibility of rheometers that comparisons of test results were reasonably Stability good. and conclusions. In the last ten years five rota- classifying as identical concretes that can be shown to be tional rheometers have been designed to measure the flow dissimilar. Qualitative that are not directly comparable to values from a different Workability rheometer design. and (c) to contribute to the efficient use of manufacturing processes such as vibration. The original de- Flow table spread sign of the IBB rheometer was a converted food-mixer with a III. The yield value and Conclusions plastic viscosity are constants. tions are used in these instruments. In this paper.45] further explains the rationale of a two. and the other two use rotating vanes. Tattersall [37] claims thousands of tests have proven stress to shear rate. at a rapid rate as evidenced by SCC. Two-Point Workability Tests Tattersall [43] discusses the principles of measurements of the workability of fresh concrete and a simple two-point test.43. any test based explicitly or implicitly on the assump. and an increasing use of rheology in concrete research. The test procedure consists of measuring the Yield value power required at three separate speeds to operate an 18. during the years. Quantitative fundamental planetary motion and ultimately a pressure gage and an H- Viscosity Mobility Fluidity shaped impeller. Im- . Tattersall [44] states that such a pro. terial with a yield value and a plastic viscosity. (b) to provide a method of control in the manufacture of the mixture. and that ordinary observation shows that beyond doubt that the flow properties of fresh concrete closely fresh concrete is not a Newtonian liquid and that. 7—Rheometer test results. the principals of which were developed by Vebe time Tattersall [37. is not like other rheometers.9 L The objection to the several workability tests are that. where w cedure is valid only for a simple Newtonian liquid whose flow is speed. properties of concrete [46]. Fig. and the two-point test. the author points out that an understanding of workability of fresh concrete is important for the following reasons: (a) to make possible the design of mixtures for particular purposes. and consequently controlling concrete uniformity. approximate the Bingham model and that there is a simple quently. (20 qt) food mixer when empty. Quantitative empirical Slump IBB Rheometer Compacting factor The IBB Rheometer. concrete is to maintain the position it has established as the low application of vibration. II. it may be sufficient to treat freshly-mixed concrete (Fig. al. which together describe the shear stress of the material. truck mixer slump meters. Unfortunately each rheometer produces numerical test values I. New products and new technolo- Tattersall [37. Each of the test methods is capable of able constant-speed rheometer. they are single-point tests. one uses parallel plates. straight line relationship between torque and speed with an in- tion that it is will be inadequate.47]. and PE is power when the bowl properties are completely defined by the constant ratio of is empty. results. then repeating the power most without exception. if the properties of different Finishability concrete mixture proportions are to be compared. Tattersall contends that in spite of all the efforts (papers that have been written and the many proposed tests) over the past 30 plus years. Three different types of configura- Tattersall [37] suggests the following summary of pro. Vebe time. there is no test that is fully satisfactory and Rheometers the property of workability cannot even be defined except in The basis of the two-point test to measure workability is a vari- the most general terms. universal building material. posed terminology as an effort toward standardization. P is power under load. conse. compacting factor. and finishing. pumping extrusion. 7) and appears to have good potential for determining as conforming with the Bingham model. and it follows that measurements at two shear rates are required to determine them. and further modifications to al. formation concerning the performance of a concrete mixture in practice. The chapter in this volume by Daczko and Vachon presents detailed information on self- consolidating concrete and the testing methods associated with its workability. which describes a ma.70 TESTS AND PROPERTIES OF CONCRETE ducibility (multilaboratory). pp. PA. “Testing Unifor- and corrections can be applied only to subsequent batches. Gaynor. Nasser. economy. Dept. L. PA. MI. R. DC. Mar..S. sistency can be made only after the concrete is discharged. J. and friendliness in the field. 43–46. L.” als. 1999. T. R. ASTM STP 169. S. W. F.” Journal. MD. As antiquated as it sometimes seems 1931. 8th ed. 355–362. C. Mixing. Vol. “Tests of Concrete From a Transit Mixer. July-August 1990. 2004. “Testing and Modeling of Fresh ing techniques are also being developed. 413–428. American Concrete requirement of the concrete industry.” Journal. Part 1. American Concrete Institute. 1952. and De Larrard. 558–562. 73. 31. Proceedings. but this [14] Bureau of Reclamation. Thomas Telford New methods of mixing. 9th ed. [8] Ferraris. pp. pp. D. C. with methods of mixing and placing concrete. aggregate moisture meters. B. 41 pp. P. American Concrete Institute. ASTM Inter- Perhaps future research will reach into such areas as detect. ACI Manual of Concrete Practice 2004. West Conshohocken. p. “Water Control by Use of a Moisture Meter. Making Materials. Standard References Specifications for Transportation Materials and Methods of Sampling and Testing. and Wilson. K. C. W. Tests and Properties of Concrete and Concrete-Making Materi. and Hester. 43–44. ASTM International. 74–101. ASTM STP 169B. and fin- Ltd.” Proceedings. K. and workability will improve the competi. http://www. quality. Vol. p. MS. tency of concrete while being mixed and transported. 2004. has greatly im. Some say that the slump test has already outlasted its [17] Slater. American and other tests used to measure uniformity may be replaced by Concrete Institute. PA. the slump test continues to be in demand because of its sim. gates.” Magazine of Concrete Research. Concrete Rheology. 1961. PA. and Bleeding. National Institute of Stan- more widespread use of available knowledge for controlling dards and Technology. “Evalua- Conshohocken. Civil Engineering Research Foundation.. ASTM International. H. “New and Simple Tester for Slump of Concrete. The develop. F. No.. Method to Measure Air Content in Fresh Concrete. Freshly Mixed Concrete. 1930.army. Vol. PA. [23] Nasser.. ASTM STP 169A. [2] Hubbard. No. C. Vol. pp. Proceedings. Transportation. 4. New tests and methods of quality control and Journal. tion. and Whaley. G.. 1956.. West Conshohocken. C. [27] Report No. both MTC/handbook/handbook.. California Department of [7] Behavior of Fresh Concrete During Vibration (ACI 309. updated December 2002. B. ASTM International.” Significance of Tests No.” Concrete technology is expected to become even more accurate in the Manual. ACI Journal. Denver. [13] U. 26.. [25] “Proposed Tentative Method of Test for Cement Content of [5] Scanlon. 2004. Sacramento.” Concrete International: Design & Construction. pp. 561–565. Proceedings. W. W. ASTM International.. American Concrete In. D. 47. ASTM STP [22] Khayat. Reston.. Waterways Experiment Sta- hydraulic and electrical resistance. West Conshohocken. 171–179. “A Method of Determining the Constituents batching process. p. 1998. (Designation 26). Segregation. F. M. J. but several of the new tests for SCC are being developed ing Plant. 1999. American Concrete Institute. 1978. Tests and Properties of Concrete and Concrete-Making Materi. VA. 1966.” NISTIR 6094. [4] Smith. and Properties of Concrete and Concrete Aggregates. D. Gaithersburg. Transporting. Vol. K. has improved the consis. “Uniformity and Workability. 51. Army Corps of Engineers Handbook for Concrete and Ce- proved the quality control of concrete throughout the industry. pp. The widespread use of 2004. “Factors Influencing Concrete Workability. No. delivery. 341–347. Farmington Hills.htm. Part 2.” Signifi. “Uniformity and Workability. future. ACI Manual of Concrete Practice. and Placing Con- Meters have been developed to measure moisture content crete (ACI 304R-00). ASTM International.. Revised. ASTM International. L. of sand and coarse aggregate in the bins at concrete plants and Part 2. “Variability of Constituents in Concrete (A Test of Mixer Performance). MI. The slump test [11] ACI Manual of Concrete Inspection. Farmington Hills.. 2004. Sept. Vicksburg. promote better control of mixing water.” CERF [6] Cement and Concrete Terminology (ACI 116R-00). W. “Effect of Time of Haul on Strength and Consis- crete in both the laboratory and the field remains a tency of Ready-Mixed Concrete.” AASHTO T 199. ASTM International. ASTM STP 169C. pp. Vol. crete. Washing- cance of Tests and Properties of Concrete and Concrete Aggre.S. London. DANIEL ON CONCRETE WORKABILITY 71 provements in concrete production.. nificance of Tests and Properties of Concrete and Concrete. G. MI. 61. West [26] Highway Innovative Technology Evaluation Center. A. Oct. stitute. 1988.” Pro- plicity. 1976. 239. 1956. W. The slump test and other tests used to indicate con. Vol. [15] Bloem. “Uniformity. national. Part 1. K. well. ment.. consolidating. Vol. 1952. Part II. particularly in sand. ceedings. 1976. Part II. “Workability and Plasticity. Xu. A. West Conshohocken.” Significance of [24] Evaluation of Strength Test Results of Concrete (ACI 214R-02). tion of State Highway and Transportation Officials. 3. SP-2. 24th Edition. Nov. 1955.1R-93). 49–64. uniformity.mil/SL/ The development of slump meters for equipment. Yongmo. American Concrete Institute. M. U. [12] Guide for Measuring. 10. ACI Manual Report: HITEC 96-03-F..” concrete quality. [18] Hollister.. T. “Mini Air Meter for Fresh Con- PA. pp.” Proceedings. 37. “Alternative 169. MI. pp. measurement of workability must be developed concurrently pp. P. control. D. ing Microwave Oven Drying (T 318-02). August 1996. CA. more efficient test methods in the future. [9] Domone. American Association of . ton. I. West Conshohocken. ment of improved testing procedures for freshly mixed con- [19] Cook. 28. tion of the Troxler Model 4430 Water-Cement Gauge. [28] Test Method for Water Content of Freshly Mixed Concrete Us- stitute. No.. of Fresh Concrete.. 1981. 87. CA-DOT-TL-5149-1-76-65..” Bulletin. ACI Manual of Concrete Practice. 73–89. 1994. around the slump mold. and Banfill. American Associa- [1] Tyler. Farmington Hills. At the same time. July 1959. Pro- The slump test is an old friend and has served its purpose ceedings. 39. ing changes in aggregate absorption and gradings during the [16] Dunagan. American Concrete Institute. placing... Farmington Hills. “Develop- tive position of concrete. Institute. J. 10. 3.. mity of Large Batches of Concrete.” Significance of rials Journal. CO. and plac. pp. Farmington Hills. [21] Nasser.” ACI Mate- [3] Vollick. “Tests of Concrete Conveyed from a Central Mix- time. [20] AASHTO. of the Interior. of Concrete Practice 2004. 405–417. pp.” Sig. F. “Method of Test for Air Content of Freshly Mixed Concrete by the Chace Indicator. 48. Vol. MI.. ments of the Two-Point Workability Test for High-Performance Concrete.wes. ishing concrete may permit the use of less water and improve [10] Van Alstine. American Concrete In- als. . M. 28. “A Review of Methods for Measuring Water [39] Bahrner. Resume in ACI Journal.” Report No. pp. and Mathews.. [47] Tattersall. and Mass Concrete (ACI 211. W. DC. London. L. DC. Vol. [43] Tattersall. Wiley. Vol. CO. D.. 44. 2002. American Concrete Institute. MI. G. MI.” Journal. an imprint of Chapman & Hall. [32] Practice for Selecting Proportions for Normal. Norsk Cementforen- American Concrete Institute. Aug. G. C. Oslo. and Neelands. 28.3R-02). H. [29] Monfore. 41–47. 25. Vol.. 7. R. J. of the Interior. 1973. G. . 5. V. ACI Manual of Concrete Practice. Concrete Technology. 24–26. 8. pp. Vol. 2003. Washington. tion Concrete. D. Joint Re- Record Number 342. D.” Journal. H. [30] Granville. Vol. “Report on Consistency Tests on Concrete Made by Content of Highway Components in Place. 1983. S. Denver. G. Proceedings. May 1955. Collins. March 1940. E. The Rheology of Fresh 1991. 50. R. London. Test. 10–11. Pro. Rilem Seminar Proceedings... London. No. 5. 84. and Polivka. 26 1947. 2003.. Environmental Effects on Concrete.” Magazine of Concrete Research.72 TESTS AND PROPERTIES OF CONCRETE State Highway and Transportation Officials. H. of Fresh Concrete and a Proposed Simple Two-Point Test. Her Majesty’s Stationary Office. and Banfill. Vol. Farmington Hills. p.. Heavyweight. E & FN Spon.” Journal. D.” Concrete International. Washington. “The Rationale of a Two-Point Workability Dept. T. 1962. pp. Farmington Hills. pp. Sept. “Relations Between the Change of Water Content 1973... dard Tests for Workability and the Two-Point Test. ACI Man. ing. [38] Orchard. April 1948. [45] Tattersall. “Comparison of Concrete 2000. W. American Concrete Institute. C. Vol.” Road Research (ACI211. Technical Paper No. E. and Ferraris. E. p. A. G. 1954. American [37] Tattersall. 1.. p. Vol. “A Proposal for Measuring Rheology of Produc.” Magazine [36] Daczko. Proceed- Farmington Hills. 881. July 1962. Jansen. 8th ed... Revised. American Concrete Institute. “The Grad. “The Relationships Between the British Stan- ceedings.” Magazine of Concrete [44] Tattersall. H. [33] Bureau of Reclamation.” Highway Research Means of the Vebe Consistometer. Concrete Manual. 63. Svenska Cement- way Research Board. [42] Davis. 1932. 1. F. 22. Sept. MI. Vol. Part 1. 96. May [46] Brower. 1976. Rheometers. 2.. No. crete Consistency. 51.” Concrete International. G. “Ball Test for Field Control of Con. Barker Dam. Concrete”. A. search Group on Vibration of Concrete. No. Part 1. Feb. 25. 17–26. F. Field Testing of Concrete.. New York. [41] Thaulow. G. Concrete. [34] Popovics. P. [31] Powers. foreningen.. 47–49. ings. Vol. 1952. 1970. 2004. Sven. “Principles of Measurement of the Workability Research.” Fresh [35] Kelley.S. H. London. C. No. 419. of Concrete Research. W. “Workability and Quality Control of Concrete Institute. Pitman Books Limited. 1981. Also..1-91) (Reapproved 1997). [40] Guide for Selecting Proportions for No-Slump Concrete ing of Aggregate and Workability of Concrete. U.. Concrete.. and the Consistence of Fresh Concrete. R. E. pp. Mar. F. T. “Restoration of ual of Concrete Practice. High. “Studies of Workability of Concrete. No. American Concrete Institute. due to errors in batching or contamination of materials. changes in mate- quality control of concrete construction. changes in cement alkali content and are thoroughly described in the applicable ASTM test [1. and Yield Lawrence R. and is well-covered elsewhere [3–5]. and ASTM performed to control concrete weight per se of both lightweight STP 169C. Bartel. Roberts1 Preface concrete. all other material contents being unchanged. suffice it to say that the ods. and assurance of essary safety precaution for these concretes. number of reasons. updates the language and expands on the utility of density While air content is most commonly determined to ensure measurement in conjunction with air content measurement to the presence of air entrainment for freeze-thaw durability. but imposed to control thermal gradients and possible resultant also on the accurate knowledge of the weights actually batched. admixture type or dosage. ranging from simple dis. increases in air content can have on compressive and flexural strengths. job problems. much of what is here has appeared be. The purpose of this chapter is to help the interested con. temperature. While a discussion putes over yield to complete performance failures. 2 The older term unit weight is now deprecated. checking air content and density is also a nec- portioning of mixtures. Cambridge. Density (Unit Weight). brought about by contaminations. Thus. use simple equipment. concrete to provide a control of these properties in the hardened the gravimetric determination of air is much more useful to 1 Key Accounts Technical Manager. and density (unit thereby significantly reducing the economic impact caused by weight)2 of freshly mixed concrete are the backbone of field excess air. Despite this. pro. The interrelationship between air content and density should be obvi- Overview of Significance and Use ous: an increase in volume of air results in a lower density. Further. and to determine the volume of concrete being produced from a given batch. possibility of a change due to any one factor is great enough to crete technician understand some of the key issues controlling warrant close control of the air content. Temperature. mix- methods. concrete temperature. Measurements of air content. from proportions. then the specific gravities of the aggregates imposed in cold weather to ensure adequate setting and and cement (usually taken as 3. The tests in. Tests for unit weight are also fore in ASTM STP 169B. rials. and to minimum temperature specifications. frequently of the impact of each of these is beyond the scope of this work can be attributed directly to faulty application of these meth. authored by F. The yield data so obtained are then THIS CHAPTER CONTINUES THE TRADITION OF available for the calculation of unit cement and aggregate con- previous editions of ASTM STP 169. slump. F. usually only on the correct determination of the concrete density. Due to the fundamental tents. The author would also like to acknowl. strength development. etc. improve test reliability. Grace Construction Products.9 Air Content. fine aggregate grading. If the density test is to be used to estimate air content directly bient conditions. ing intensity and duration. Without these. but is included here as reference. and air-entrained concretes can also develop significant air contents. authored by the present author. For this reason. This chapter and heavyweight concretes. hopefully to encourage more careful and frequent application. Among these are changes in air-entraining volved are relatively straightforward. Density will be used in the remainder of this document. The calculation of ma- Temperature measurement of fresh concrete is vital to ensure terial quantities per unit volume from the density depends not adherence to maximum temperature specifications.15 when portland cement is strength performance. Slight errors can result in Tests for air content and density are performed on fresh significant error in estimating the air content. control of yield.2]. required in some specifications. nominally non- the correct application and interpretation of the methods. used) must be accurately known. MA 02140. The author is aware of a number of job problems in Introduction non-air-entrained concrete that could have been prevented by air measurement or even simple density measurements. placeability. thermal cracking as the cement hydrates and then cools to am. due to the strong negative impact that unexpected many colleagues who have provided useful insight. and many others. and durability of concrete Air contents of air-entrained concretes can vary for a large exposed to freezing conditions are not possible. 73 . which are essential in mixture development and may be nature of these topics. knowledge of air content of non-air-entrained concrete is also edge the support and encouragement of his company and the important. This represents an inconsistency that needs resolution. at the job site discharge method. While some conclusions may be made Mixed Portland-Cement Concrete (C 1064). If. mometers can lose calibration. when air and the specifications allow addition of retempering water. to distinguish between large and small air voids. there is no clear dividing line even thermometers may be used. respectively. nificant heat to its surroundings during the time of testing. volumetric. and all the other directions of care gregate and other material temperatures. evaporative cooling could reduce the temperature read if the ods. if the sample is small enough to gain or lose sig- acceptable deviations from test specifications is needed. what steps are to be taken in this situation. the water is added. The with focus on the proper selection of method. Furthermore. in glass reference thermometers was required by the test at the plant for control of production. but the slump is too low. content of which is determined by other methods. contract language for “entrained air practical. using two temperatures at least 15°C concrete. ASTM Test Method own advantages and limitations. result will not be representative of the mass of the concrete. replicate readings over time are obvious changes in the concrete being discharged are noticed. for Slump of Hydraulic Cement Concrete (C 143). No guid- this must be noted and good practice indicates re-testing. This is clearly not possible if a truck is being sam. ance is given in the method as to how far apart these should solving this sampling time issue takes a clear eye for concrete. Yearly cali- content” has been interpreted to mean that the specified level bration against 0. due to the reduction of required water for equal determined. usually about 10 %. and is traceable to NIST standards. this is currently in the balloting process. crete properties. these methods Test Methods cannot in any way make such a distinction. tion being run if deviation is noted. the batch. fortunately sometimes in contract documents. with a full recalibra- These methods are regularly applied under a variety of condi. In some cases. the slump re-run and found to be within speci- density changes may be less than predicted by air content fications.2°C precision reference temperature meas- should be in addition to the base air content of non-air-entrained uring devices is required.5°C) required of the tem- voids by comparing the air contents of similar air-entrained and perature measuring devices to be used. and is sometimes a source of contention on perature remains within 1°C. at regularly spaced intervals during discharge of the middle of While the test method does not now explicitly indicate this. solely because the concrete measure the total air in the concrete. which requires that for a minimum of 75 mm of concrete to surround the temper- the concrete come from two or more portions of the load taken ature-measuring device. device were withdrawn prior to reading. if after a 5 min delay the tem- good judgment. and subsequent determinations of the hardened air the gravimetric method can be used only if all the water weights contents may not agree with the results recorded for the fresh are accurately known. apart. each have their at a job site at the same time the slump test. but. concrete properties. yet are re. a clear understanding of proper sampling procedures and size. samples must be Finally. and these are most frequently employed. all the methods to be discussed nominally re. to obtain concrete brate. ASTM C 1064 calls for the sample to be large enough Sampling Freshly Mixed Concrete (C 172). and air content. Ac- quire that concrete be sampled according to ASTM Practice for cordingly. and. as rapid which is perhaps the most common application of these meth. . Language to clarify therefore it is best if the specification documents clearly out. While the adjectives “entrapped” and “en. the For example. Thus in large aggre- described in ASTM C 172 must be adhered to. Clearly. it is obvious that the measuring device should remain embed- pled prior to discharge for compliance with specifications. and such distinctions are purely testing in many cases make metal dial thermometers more arbitrary. for practical purposes. dance with ASTM Test Methods for Temperature of Freshly- ferred to as entrained air.74 TESTS AND PROPERTIES OF CONCRETE monitor variation in air content of mixtures. Formerly. but enough concrete must the concrete to take as much as 20 min to temperature equili- be allowed to discharge. warranted to ensure that the equilibrium is reached. This test method for research purposes about the expected amount of small air describes the types and precision (0. the reference air air is found to be within specifications. but the air content of the retempered concrete is not changes alone. since no such distinction is possible. aggregate of 75 mm or greater in size may cause taken from the initial discharge. using pres- the air content methods is applied to a load of concrete arriving sure. Due to the limitations of these various loca. but now direct-reading resistance thermometers are point—to ensure compliance with specifications. line the sampling requirements. the conditions of field concrete by microscopic examination. This contents vary in concretes being controlled to a fixed slump. Concrete temperature measurement is determined in accor- thaw are uniformly the total measured air contents. subject to the limitations tested in the fresh state was altered after testing but before be- of each method. one or more of The three tests for air content of fresh concrete. is run. and gravimetric methods. In practice. point of placement. and un. ded in the concrete while the reading is being taken. Questions about the accuracy of the air It must be emphasized that all methods to be discussed here content measurements then arise. job sites. to best estimate the resulting hardened con. Also. The addition of water and further mixing alter the slump in many concrete mixtures as air content increases. We will discuss each in order. after testing. Although liquid in glass non-air-entrained concretes. The job specifications should make clear trained” are sometimes applied in technical discussion. the fresh concrete air contents specified by the American Concrete Temperature Institute (ACI) and others for concrete durability under freeze. but due to the ease with which some metal dial ther- crete methods. it is recommended that a single temperature comparison against a reference thermometer be Sampling performed daily as an equipment check. Re. Frequently. at the acceptable. Another key provision of ASTM C 1064 relates to sample tions. precision liquid tions—in the laboratory during mixture proportion development. One source of error in sampling during application of these Air Content methods deserves special mention. so long as their calibration is done at least yearly. gate concretes sampled early. ing allowed to harden. be. especially if there are large differences between the ag- representative of the load. effective equilibrium is reached. This is an inappropriate application of these fresh con. Strike-off of the concrete is possible with either a bar or a strike-off plate. rodding is required above a slump of 75 pering were significant differences seen. data included in reports of such underestimation problems [10] Vibration should cease when all the coarse aggregate is submerged and the surface takes on a smooth. but has the termination of Air-Void Content and Parameters of the Air-Void drawback that recalibration is necessary if barometric pressure System in Hardened Concrete (C 457) than was obtained using or elevation changes exceeding 183 m occur. weights is required to obtain the required answer. chamber. this is not the be sensitive to instability in dial readings that may signify leak. then coming out of solution in In the Type B air meter. and either in between. and for this reason vibration is rarely used in slumps above 25 mm. The Type A meter relies on direct measurement of the contents are high and may be to some extent dependent on the volume change. To ensure contents compared to the fresh concrete results prior to retem- proper consolidation. a strike-off plate must be used. lated to the amount of air within the concrete. since representative sampling becomes difficult with larger aggregate. a known volume of air at an es. A change of 183 the pressure method [8–12]. it is possible to not observe a leak in Ozyldirim [16] followed up on field reports of higher air in the needle valve that would normally be noticed due to air bub. quired aggregate correction factor. This is usually perceived to occur when the air (C 231). . relatively minor changes in ag- total volume of air. higher pressure at sea level. If this is done. the lack of which applica- crete is based on Boyle’s law. 1. When the air meter base is being used for determination of density. In no case did the dif- This method requires complete consolidation of the con. A common mistake is to derestimation is unlikely to exceed around 1 % air content. Only when the concrete was retempered and the hardened air tion will be measured as air content of the concrete. leading to a net increase in air vol- tablished higher pressure is allowed to equilibrate with the ume [13]. the concrete must be discarded at advantage that no knowledge of specific gravities or batch the end of the test. By applying pressure to While this correction factor will compensate for the air in the a known volume of concrete containing air voids. the hardened concrete with a thorough test program in which bles escaping the open petcocks. thus indicating a higher than from Ref 10). This would result in incor. hardened air results from ASTM C 457. Concretes containing aggregates larger than 50 mm must be screened using the 37. and the bar is acceptable. such an increase [15]. Re-examination of the mm. largely be a manifestation of the sampling problem mentioned ment of the Type A meter. crete in the bowl. as shown in Fig. This is corrected for by application of the re- The pressure method for determining air content of fresh con. TEMPERATURE. DENSITY. Other authors have failed to find pressure measured in the high-pressure air chamber can be re. aggregate correction factor exceeds about 0. Meilenz et al. larger voids. and the vol. concrete containing lightweight aggregates in which the ume change can be measured and related to the initial volume. lower pressure. any large air voids due to lack of consolida. This method Closer examination of the data indicates the problem may does not have the ambient air pressure recalibration require. ROBERTS ON AIR CONTENT. by means of a column of water above the type of air-entraining agent used. but the complexity of valves and earlier.5 %. A calibrated sight tube allows ported significantly higher air contents in hardened concrete measurement of the volume reduction directly as pressure is measured according to ASTM Practice for Microscopical De- applied. Extreme care must be taken to avoid removal of the intentionally entrained air by over-vibration. A degree of controversy has arisen regarding the ability of Two types of meters are defined in ASTM Test Method for the pressure meter to measure air content when the air voids Air Content of Freshly Mixed Concrete by the Pressure Method are very small. This method is very straightforward. which states that the volume of a tion is a common flaw in observed field testing procedures. ferences display the extreme variation previously reported. This method has the Due to the use of water. internal vibration below 25 mm. The drop in bility of very small air voids. and prised a significant portion of the air volume. AND YIELD 75 Pressure Air Measurement true air content. This principle was first applied by Klein gregate porosity will lead to significant variation in measured and Walker in 1946 [6]. even in concretes of high air content [15]. because with Knowledge of the pressure difference allows calculation of the aggregate of this high porosity. glistening appearance. the voids are aggregate. and proposed a standard test procedure. the concrete is reduced in volume. The pressure method is limited to use with concretes containing relatively dense aggregates. while Menzel [7] refined the apparatus air content. operators should underestimation could occur if the very small air voids com- be prepared with tools and replacement parts for repair. gas is inversely related to the pressure. While Hover’s calculations [14] show that significant seals make the apparatus prone to leakage. Air in the interconnected porosity within the aggregate particles will be compressed just Fig. case.5 mm sieve prior to testing. Several authors have re- known volume of concrete. Thus. pressure air voids dissolving. In the case where only a pressure air test is being run. 1—Pressure versus microscopic air content (data as air within the cement paste. it is not appropriate to apply the pressure test to compressed. this un- age and therefore incorrect results. not close the petcocks prior to pressurizing the high-pressure the 3–6 % reported by some. m is approximately equal to a 2 % change in barometric discussed the theoretical possibility of air in the smaller. as described later. Hover [14] calculated the effect of the incompressi- known volume of concrete in a sealed container. the precise volume of concrete is less critical. all types of fresh concrete air content tests were compared with rectly low air content readings. volved in agitating the filled apparatus is significant and can lead to severe operator fatigue over a work day. The apparatus is sealed. confirms the good cross- 7.69 correlation of fresh concrete methods. primarily by a rolling action. it is absolutely vi- metric method results (see Fig. The agitation must be repeated until there is no further drop in the water level. If this occurs. sticky concretes having high air Further consideration makes this unlikely. In most cases. ences reported are up to 6 %. the unit. Figure 3. as aggregate particles can lodge in the neck of the meter. this is considered to be when there is less than 0. it is frequently necessary to tip the apparatus upside down. Air Content. effectively making them seem larger.5 7. and with the ASTM C 457 gravimetric method. Measured Air Content (Data from Ref 17) and may be related to the wider application of air-entrained high cement factor concrete in recent years. This method has the advantage that air trapped in the aggregates has no impact on the test results.25 % change in the measured air content. an amount of nally read as described in the calculation section of ASTM C isopropyl alcohol appropriate to the type of concrete added. it has two significant disadvantages. These in the actual concrete from fresh to hardened state could be two factors work in opposition to each other in practice. Some preliminary A further constraint is that with high-air-content concretes data showing this effect have been presented [17]. Care must then be exer- level of isopropyl alcohol.0 7. and thus is the method of choice for lightweight aggregate concretes. During agitation. the effort in- Fig. then added to each test. cup provided. as seen in it may be very difficult to dispel residual bubbles of air in the Table 1. 173/C 173M. Second. C 457 test. When needed. Poor sample surface preparation tends to erode the neck of the apparatus. Such a leak will result in a higher air content being This would result in up to an 18 mm increase in height of a measured than actually is present in the concrete. and thus con. . The drop in water care to remember to add the different amounts to different concrete classes. further crete by the Volumetric Method (C 173/C 173M) measures air increments of isopropyl alcohol may be added using the small content by washing the air out of the concrete through agita.0 from one paper in which a lack of correspondence with hard- 8. of 2. This would seem to preclude tal for accurate measurements that the agitation indeed be re- a specific problem with the pressure test. The air differ. Such growth is not reported. the more isopropyl alcohol will be found Volumetric Method necessary to dispel the bubbles during the first rocking and The ASTM Test Method for Air Content of Freshly Mixed Con. the volume of which is equal to 1 % air content tion of the concrete with an excess of water containing some as measured in the calibrated neck. test method. Accepting that the fresh concrete The operator should be alert to any free water on or air content measurements are accurate. 2). First. % the air contents measured by pressure and volumetric methods agree with each other reasonably well. previously an option. which are covered elsewhere [3]. 2—Pressure versus gravimetric air content (data from Ref 10). espe- invoked.23 8. based on data 8. isopropyl alcohol.4 11.7 11. cially in high cement factor. contents. Generally the higher the air content and the stick- ier the concrete. although some change peated until no significant change in air content occurs. Fine parti- typical 300 mm cylinder. rolling. It is for this reason that the addition of void edges. This is in line with previous experience [18. a net growth of the around the apparatus. as described in notes 2 and 3. they usually may be dislodged by sloshing the apparatus from side to side. A cised to note the volumes added and add to the air content fi- known volume of concrete is covered by water.2 ened air contents is shown [10]. To ensure that all the concrete is dislodged from the base. very different levels of rolling until the air in the original concrete is displaced and isopropyl alcohol may be needed. cles adhering to gaskets and the cap frequently cause such swer may well lie in the difficulties associated with the ASTM leaks. As defined in ASTM C 173/C 173M. Recent reports of problems with volumetric measurement of high-air-content concretes have paralleled the prob- TABLE 1—Effect of Surface Preparation on lems attributed to the pressure method as described earlier. and water are agitated by rocking and than one class of concrete on a job site.19]. leading to the conclusion that the ASTM C 231 Good Polish Bad Polish problem is not in these test methods.76 TESTS AND PROPERTIES OF CONCRETE level from its original mark provides a measure of the air content. For a consistent class of concrete. How- ever. When the test operator is monitoring more the concrete. generally an and the water level adjusted to a zero mark in a calibrated clear ideal level of isopropyl alcohol will be found and it should be neck on the described apparatus. and it will require extreme rises to the top of the neck of the apparatus. alcohol. but this should be done briefly.8 8. indicative of a failure to properly seal concrete would be required to cause this measured difference. The fatigue factor can be reduced by using smaller apparatus with containers shows that the pressure test corresponds well with the gravi. it should be possible to hear the aggregate rolling around within the chamber.0 L capacity as are now allowed. is now required in the tributing higher measured air contents. The an. alternate methods should be employed. to the air substituting for the water needed to fill in the voids mined in accordance with ASTM Test Method for Density (Unit between the fine aggregate particles. Accordingly.0) while ASTM C 231 permits vibration at this size. an approximate 1 % er- of the bowl after completion to ensure that all the concrete was ror in the air content computed according to ASTM C 138/C loosened from the base. . the density of concrete is deter. If such attention results in unaccept. when there is a 2 % er- proper amount of isopropyl alcohol. Further.5) smallest measures cannot be used in accordance with ASTM C 150 (6) 99 (3. pressing down. 138M will result. The ability to have a simple cross-check by effects tend to bias the sampling toward lesser aggregate contents. actual cement content per unit vol- Fig. it is the author’s experi- ture proportion information is available. specific gravities and their moisture contents as batched. and air content are outlined clearly in ASTM C 138/C Ref 10). The amount of reduc- Gravimetric Method tion is greatest in the lower cement content mixtures [21]. giving a nonrepre- sentative sample. and that when used for other than density. air content Weight). it does appear that with dure for determining air content of fresh concrete is used. Rodding may be used above 25-mm slump. surface dry should be exercised in the use of this method when such con. For example. Using the known volume. and withdrawing with a sawing motion. and Air Content (Gravimetric) of Concrete (C increases measured by ASTM C 138/C 138M would be reduced 138/C 138M). Due to these uncertainties associated with direct calcula- tent and yield can be determined provided the requisite mix. edge enumerated above. density of the concrete is calculated and.5 (1 1/2) 11 (0. many of which are measures used. Yield. This cretes are encountered. Vibra- 25. The concrete is placed in a container of known by approximately one-third unless completely accurate water volumetric capacity and weighed. from this. Subsequent calculation of volume of concrete produced per batch. the 112 (4) 71 (2. to continuation of agita. due In the gravimetric procedure. and advance it over the unsmoothed portion with a sawing motion. with special attention paid to using the can lead to serious errors. This dependence on ence that the greatest value is realized when density is used as extraneous information is a major limitation of this method a cross-check to other methods of air measurement. in that regard it is extremely valuable. and will not be repeated here. mm (in. 75 (3) 28 (1.4) requires that measures smaller than 11 L be consolidated by 50 (2) 14 (0. Such situations may require two test technicians to ensure that since aggregate-specific gravities and moisture contents are fatigue does not unduly influence the willingness to ensure both subject to wide variation. for determining air contents of lightweight aggregate concrete.0 (1) 6 (0. Each calculation requires precise knowledge of batch weights and material properties not readily available in the field. Therefore. 138M. the extremely sticky concretes it can be so difficult to wash out all density of concrete as determined is compared with the theo- the air that at the very least the volumetric method takes an im. since as the aggregate increases in size. Thus. retical density of air-free concrete. The minima given in ASTM C 138/C 138M are reproduced in Table 2. due to the possibility of excessive loss of entrained air. Do not overfill the measure then push the coarse aggregate down into the measure with the strike-off plate. the air con.5) 138/C 138M for concretes of less than 25-mm slump. ASTM C 138 37. care mixture. 3—Fresh versus microscopic air content (data from ume. the relative yield. as it leads to a less precise filling.) L (ft3) and consolidation of the measure. TEMPERATURE. in some instances [20]. required water contents will be reduced in most concretes. the Nominal Maximum Size Minimum Measure results of this test are completely dependent on proper filling of Coarse Aggregate.04 in the aggregate specific gravities. When the gravimetric proce- However. as this results in mortar being squeezed out. from which it is important to note the very high volumes required when aggregate size exceeds 25 mm. ror in the moisture content of the fine aggregate or an error of tion until no air increases are registered. ASTM C 138/C 138M is not appropriate ably long test times. Striking off with a bar is specifically not permitted. DENSITY. when air contents increase.5) rodding. This is best accomplished by covering about two-thirds of the surface with the plate. Thus. Safety considerations require that means be provided for TABLE 2—Minimum Capacity of Measures movement of the buckets on and off the scales without undue for Use in ASTM C 138 strain on the individuals conducting the test. tion of air by the gravimetric method. weight and specific gravity of each ingredient of the concrete ous to the inclusion of isopropyl alcohol). AND YIELD 77 The top surface of the concrete must be obtained with a strike-off plate. As with the other air content methods discussed here. ROBERTS ON AIR CONTENT.2) tion may not be used if the slump exceeds 75 mm. that thorough separation of the concrete has taken place. Capacity. and to the checking 0. Testing of concrete air Aggregate size determines the minimum capacity of the in the field is subject to a number of errors. Then replace the plate on the smoothed two-thirds. the content information were available. and requires knowledge of the saturated. press down. vibration is required for lower slumps. This is calculated from the practically long time to complete (this information was previ. Having prepared lems led to determination of high air in the hardened concrete.78 TESTS AND PROPERTIES OF CONCRETE Fig. 5—Air versus density data from field testing of different trucks during one day of field testing. when that mix is eliminated from the dataset. Figure 4 shows data from a typical well-run field test quickly can prevent incorrect rejection of concrete. with the same base concrete mixture.9 % air. at 2. the concrete may be used in and keeping a running simple air cross-check graph as shown other testing. Fig. and also in. when strength prob. 4—Air versus density data from field testing of different trucks during one day of field testing. . 5 shows the improvement plant dosage adjustment was made. blank graphs at the job site on which the data can be plotted the faulty testing became manifest. The dotted lines illustration of such a use. Fig. represent the expected relationships. On crete ultimately had to be removed because faulty pressure close inspection. of a number of different admixtures yielding different air con- correct adjustment of air-entraining agent doses. Figure 2 is an tents. one mix. precluded in the case of pressure meter testing by the simple Since no water comes in contact with concrete tested ac- expedient of using the air pot base to determine the density. Later. is somewhat question- method air measurement at the job site indicated low air and able and would bear repeating. 3. after elimination of one data point. while the fitted regres- The author is aware of a number of cases in which con. This could have been easily makes this approach easier. sion line shows by its slope that the test is well controlled. which problems with the apparatus or method can be found in Fig. cording to ASTM C 138/C 138M. and Flack. [15] Roberts. [20] Gaynor. 305–315. R.. 4. coupled with advances in digital electronics. ASTM International. and possible biases between the results of the H. cellent quality control of fresh concrete when properly applied. A. Air Loss.” and Hardened Concretes. A. C. Manual on Control of Air in Concrete. R. “Slump Loss. B.. . Summer generally for mix qualification. R. S. 11. Oct. however. 80. Vol. [13] Meilenz. Some specifying agencies are currently Proceedings. as described [9] Gay. 67–72. pp. E. “Effect of Entrained Air on Concretes Made with So- Control of Concrete Mixtures. 47. [19] Britton.S. American Concrete Cement Association. C. p. IL. Skokie. “Air Content and Unit Weight. Cement Microscopy. 1. 211–227.. 22–36. 1947. Fort Worth. This shows promise in Microscopy Association. pp.. significant issues Concrete.. R. IL. 10.” [4] Jeknavorian. Concrete. and Gaynor. Vol.” Cement. 2002.fhwa..” It is expected that the effort to improve the convenience Proceedings. Portland Called ‘Sand Gravel’ Aggregates.” Proceedings. significant advances in the understanding of its use and appro. S. C. and Nagi.” Cement. D. Design and [21] Klieger. 11–17. 13.. p. and Nasser. L. “Origin.. p. International Cement next decade. American Concrete Institute. Vol. A. situation. ASTM International. R. has been developed [22]. No. ROBERTS ON AIR CONTENT. Fourteenth Edition. A.gov/rnt4u/ti/pdfs/airvoid. 4.. 9. TX. D. Symposium on Measurement of Entrained Air in [2] Whiting. “Comparison of Air Contents in which requires setting up the equipment remote from job sites Fresh and Hardened Concretes Using Different Airmeters. 47. [6] Klein. Evolution. “Comparison of the Air Contents of Freshly Mixed and Hardened Concretes.. “Air Entraining Admixtures. Houston.. and Aggregates. Wolkodorff.” are not well understood. Duncanville. U.” or using special vibration isolation techniques. Priority Market Ready Technologies and Innovations: Air Institute. Concrete. rently underway. Vol. 332–339. T. July using the method. Duncanville.” Cement. and Aggregates... Traverse Apparatus for Air-Void Distribution Analysis. D. 1990. Part 1—Entrained Air in Unhardened Concrete. Microscopy Association. U. Void Analyzer. No. 28 March–1 April 1982. References [17] Roberts. TX. pp. the methods discussed here provide ex. 2. with job site control still by total 1991. 1947. 6 Nov.. Vol.. carefully and care is taken to avoid procedural pitfalls or use July-Aug. “Procedures for Determining the Air Content of Freshly-Mixed Concrete by the Rolling and Pressure Methods. P. [18] Proceedings. C.dot. No. 95–122. “A Method for Direct Measurement [22] Jensen. “A Factor Which May Affect Differences in the earlier. pp.967. Summer 1991. M. Patent No. K.pdf. time delay if used as an acceptance Summer 1989. pp. Evaluation of its reproducibility is cur. and Field Performance of and useful results providing the operator follows the methods Concrete. A. Skokie. 16–19 March 1981. K. F. There are. No. the Automatic Void Analyzer. 42. R. 833. Vol. 1992. 657. Concrete. “Comparison of the Air Contents of Freshly Mixed Amount of Air-Entraining Agent in Portland Cement Mortars.. personal communication. discussion of paper by [1] Greening. and Effects of the Air Void System in method and actual hardened air parameters per ASTM C 457 Concrete. 25–28 March 1985. V. 1983. C. 1948. Vol. but this has Concrete. H. Concrete. K. Focus on this method is likely to bring Summer 1988. 29–34.588. “The Effect of Mix Temperature on Air Content are available. and are employed for maturity methods under and Spacing Factors of Hardened Concrete Mixes with Stan- ASTM C 1074.” Cement. Portland Cement Association. Las Vegas. Third International Conference on Cement and rapidity of test methods will yield significant advances in the Microscopy. L. pp. Backstrom.” Proceedings. pp. “Report of Investigation of Different Methods for [3] Hover. Kerkhoff.. B.” Journal. AND YIELD 79 Summary and Future Trends [7] Menzel. durable concrete. L. pp.” in this Pennsylvania Slag Association.. and experimental issues such as sensitivity to vibration. TX. Duncanville.. H. Vol. www. No. of Entrained Air in Concrete. and Scheiner. J. Proceedings.. Concrete. pp.. C. and Aggregates. K. N. and Aggregates. K. E. Vol. 1998. For now. 1. DENSITY. C. pp. 13. “Some Recent Problems with Air-Entrained void size in fresh concrete. J. [12] Khayat. No. Current use is Cement. and Panarese. Seventh International Conference on Cement Microscopy. H. are changing this 296–292. Numerous in situ temperature measurement systems [10] Gay. Concrete. May 1967. publication. A. W. of methods inappropriate in certain situations. but potentially valuable test known as dardized Additions of Air-Entraining Agent. T. Fourth International Conference on erators than they can provide. A complex. W. American Concrete [23] FHWA. [16] Ozyldirim. p. not always been the case. 13. G. TEMPERATURE. No. No. method. Vol. 16–17. mixes should have the AVA results calibrated against actual [14] Hover. 30. The specification writer should take cognizance of Determined Air Content of Plastic and Hardened Air-Entrained these limitations and not ask more of the methods or the op. tional Cement Microscopy Association. 1. 42. P. “Microprocessor-Based Linear priate application in the near future.. and Aggregates.. Institute.” in this publication... Vol. or AVA. Vol. Summer 1991. International Cement based on buoyancy of released air voids. 16–17. C. and Walker. allowing determination not only of air content but also of air- [11] Hover. Determining the Amount of Air Entrained in Fresh Concrete. “Some Causes for Variation in Required Ozyldirim.” Journal. R.. [5] Kosmatka. Journal. F. “Analytical Investigation of the Influence of Bubble Size on the Determination of Air Content in Fresh ASTM C 457 prior to setting ranges in specifications. 1.” Proceedings. Good practice would indicate that different 1955. Tests run in accordance with these methods will yield accurate [8] Burg. American Concrete Institute.. Interna- The growing emphasis on high quality. pp. 1. of sampling reproducibility. 1. Concrete. W. 629. 11 April 1949.” Journal. air content methods [23]. 832. E. PCA Research and Development Laboratories. In ASTM cal factor in the overall performance of the concrete. An insufficient number of tests will result in unreliable con- ten about factors that influence the strength of concrete are clusions. Accordingly. in compression. These two standards have had con. Traf- STP 169C [4]. the actual compressive strength of the designed mixture may be in excess of structural require- The 1914 Committee Report [5] is the basis for the presently ments. These include size of It is important to keep in mind that the test specimens in- the aggregate. C 31 has been revised six times and C 192 has fic loads have been found to induce critical tensile stresses in a been revised four times. this chapter was under the present authorship. tension. tered in making and curing test specimens. VA 22724. The other is other use is to determine the splitting tensile strength in accor- ASTM Practice for Making and Curing Concrete Test Speci. example. has in most cases a direct in- THIS CHAPTER COVERS THE IMPORTANCE OF PRO. C. B. In ASTM STP used. concrete is field and the laboratory. In those cases 169 [1] in the chapter Static and Fatigue Strength authored by where strength in tension or in shear is of primary importance. Statistical procedures provide tools of considerable Price [6]. The effect that any of these variables has on the ap. and shear. E. and crete in the structure. For STP 169C [4]. In most structural applications. Two ASTM Test Method for Compressive Strength of Cylindrical Concrete standards have been developed for making and curing test Specimens (C 39). To be meaningful. edges. In such cases. Method for Flexural Strength of Concrete (Using Simple Beam mens will affect the test results. Among the many who have writ. racy. Siess. relationship to estimate flexural strength. or a combination of these. with Third-Point Loading) (C 78) or ASTM Test Method for Flex- ural Strength of Concrete (Using Simple Beam with Center- Applications Point Loading) (C 293). type of mold. dance with ASTM Test Method for Splitting Tensile Strength of mens in the Laboratory (C 192) and was originally published Cylindrical Concrete Specimens (C 496). strength tests using an established correlation or empirical dicated by the specimens is affected by many variables encoun. this chapter was authored by R. Pavements are often in 1944 and updated periodically. this became empirical relationships to the compressive strength are often a separate chapter authored by T. either ASTM Test tures from the standard procedures to make and cure speci. size and shape of the test specimen. Lamond1 Preface The strength of concrete. and in the transverse direction near the longitudinal Specimens have to be made and cured properly since depar. consolidation dicate the potential rather than the actual strength of the con- of the concrete. Specimens cast in the field are most often used to accepted procedures for testing concrete cylinders and beams determine the compressive strength in accordance with ASTM to determine the compressive or flexural strength. longitudinal direction at the top of the slab near the transverse siderable use in concrete research and concrete construction. of the verification of other required properties or characteris- crete Test Specimens in the Field (C 31) and was originally tics of the concrete as delivered or designed. However. This subject was covered in ASTM STP designed primarily to resist compressive stresses. However. 80 . In ASTM STP 169A [2]. Kelser and C. strength may not necessarily be the most criti- 169B [3]. Since publication of ASTM designed for tensile stresses in flexure in the concrete slab. fluence on the load-carrying capacity of both plain and rein- perty making and curing concrete test specimens in both the forced structures. the need for acceptable durability may impose lower water-cement ratios than required to meet the strength re- Introduction quirements. must be derived from a pattern of tests from which the charac- parent strength of the specimen will often vary depending on teristics of the concrete can be estimated with reasonable accu- the particular circumstances. P. Sparkes [7]. F.10 Making and Curing Concrete Specimens Joseph F. Jeffersonton. One is ASTM Practice for Making and Curing Con. capping procedure. joint. curing. ACI Recommended Walker and Bloem [9]. value in evaluating results of strength tests. is used as an acceptance test for most pavement concrete. Practice 214 [13] discusses variations that occur in the strength 1 Consulting Engineer. a flexural strength test. due to inherent variability of the The strength of concrete is one of its most important and useful flexural strength tests many agencies rely on compressive properties and one of the most easily measured. The strength in. The most common published in 1920 and updated periodically. Kennedy. conclusions on strength temperature. Adams. ACI Manual of Concrete Inspection [8]. The test results may be used as an indication specimens. and Richardson [10]. compressive strength test results meaningful and reproducible test results. and other suitable material being used less fre- 59 000 technicians have been certified under the American quently. and the test requirements of ASTM C 470. Reusable molds are made of nonabsorptive ma. Grade I. ping and the specimens not meeting dimensional tolerances. (25 mm) would be roller- strength specimens are rectangular beams cast and hardened compacted concrete. suitable sealants must Testing Personnel be used where necessary to prevent leakage through the joints. Creep specimens are cylin. programs that test technicians’ knowledge of the standard and Richardson [10] reported on a number of studies and ob- ability to perform the test also exist and are used. use type. (2) measured by ASTM Test Method for Slump of Hydraulic Ce- nonreactive with the concrete (aluminum and magnesium are ment Concrete (C 143) is used to select the consolidation proce- examples of reactive materials). These specimens are used in various test procedures to determine a property of con- Molds crete. odically the making and curing of test specimens and the procedure to verify that it is being done correctly. consolidated by either rodding or vibration. Single curing for acceptance testing and field curing for removal of . Roller-compacted concrete would be con- with the long axis horizontal. (25 mm). was noted even in some molds made with light-gage metal side- form than those made by untrained personnel. Molds for casting cylindrical solidated using vibration procedures in ASTM Practice Making specimens are covered in ASTM Specification for Molds for Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Forming Concrete Test Cylinders Vertically (C 470). molds for laboratory-cast flexural strength and freeze-thaw Other concretes that cannot be consolidated by rodding or vi- beams are covered in ASTM C 192. They are covered in ASTM resent the product or structure are not covered by this practice. servations on the rigidity. with the length equal to twice the diameter. The assembled mold must be watertight. and expansion of Adams [3] discussed the importance that personnel are molds made with various kinds of materials. Only in this way can For high-strength concrete. The standards must be reviewed sult in out-of-shape cylinders have an effect on the proper cap- annually for any changes. There is increasing emphasis and a requirement in many build. All molds can suffer from being out of round. sonnel who make concrete test specimens be certified. The molds that re- making and curing specimens. Specimens are fabricated using concrete delivered to a project site sampled from the transportation unit prior to plac- Specifications ing. either consolidated by rodding or vibration. If the slump is less ting tensile test specimens are cast and hardened in a vertical than 1 in. Specimens are fabricated in cylindrical or beam molds and The molds for casting concrete specimens must have the fol. The significant differences between When not properly waterproofed. This can be attained with sufficient wall thickness Personnel should have the required tools and equipment for alone or in combination with a stiffened top. or brass. mation for a number of purposes. treated paper products trained and untrained personnel were reported by Wagner (cardboard molds) may suffer from absorption and elongation [14]. The reusable molds are designed to be used more than This usually occurs when initial standard curing is misinter- a single time. An example of position. The shape tends to be oval at the unsupported tops for In addition to proper training. The single-use mold may be made of any material that passes ing codes. The concrete slump lowing properties: (1) made of a nonabsorbent material. project specifications. Details for Table (C 1176) or ASTM Practice Molding Roller-Compacted field-cast beam molds are covered in ASTM C 31. gle-use mold materials are plastic with treated paper products. of round. supervising engineers and plastic and cardboard molds. particularly if it can be shown that the person making the This practice is a definitive procedure for performing specific test had not complied with all the details of the test procedure. which are not open may be lower with plastic molds than reusable steel molds [11]. The most prominent sin- ASTM Specification for Ready-Mixed Concrete (C 94) that per. Details of Concrete in Cylinder Molds Using a Vibrating Hammer (C 1435). If the slump is greater than 1 in. LAMOND ON MAKING AND CURING CONCRETE SPECIMENS 81 of concrete. Also. There have been instances There are two types of molds. be obtained. the concrete is shape. supervisors should review peri. Flexural a concrete with a slump less than 1 in. operations to produce a test specimen. Compressive strength and split. the reusable type and the single. This same concrete by trained personnel were higher and more uni. assembled molds are made of steel. (3) hold their dimensions and dure. political jurisdictions. At least three single-use molds and reusable plastic Concrete Institute’s certification program for “Concrete Field molds shall be selected at random from each shipment by the Testing Technicians. There are two separate conditions for using cylinders or beams: (1) they must be standard Types cured and (2) they must be field cured. therefore. C 192 and ASTM Test Method for Creep of Concrete in Com- pression (C 512). bration. The requirements for molds may be covered Uses in more than one standard. Reusable steel properly trained in making specimens and the details of the molds not properly sealed had a tendency to leak at the joints. the tests are almost always questioned. walls. or requiring other sizes and shapes of specimens to rep- drical specimens cast horizontally. preted as field curing. The two most frequent uses are standard terials and constructed in one piece or several pieces. where standard curing and field curing have been combined. Over metal molds.” Other equivalent certification purchaser to ensure that molds are in compliance with C 470. specimens must be vibrated. iron. therefore. (25 mm). Wagner’s study showed that strength tests made from the problems. all the requirements ASTM C 31 states that specimens may be used to develop infor- must be considered for the type of specimen being molded. The sidewalls of molds should be technicians responsible for technicians making and curing test of a sufficient stiffness to prevent the mold from becoming out specimens must be thoroughly familiar with the test procedures. various procedures are precisely followed. to question. and (4) be watertight. water absorption. When strength Making and Curing Test Specimens test results fail to meet a specification requirement and rejection in the Field (ASTM C 31) of the concrete is considered. and presents statistical procedures and control piece reusable molds are made most commonly of plastic while charts that are useful in the interpretation of these variations. For compressive strength specimens. Richardson [10] pointed out that various specifications re. Test Data on Specimens (150 mm) in diameter or width. A set of cylinders that does not come from the same that is free of vibrations and other disturbances. A larger specimen mold is used two or more portions at regularly spaced intervals during dis. required. and concrete temperature. for comparison with test results of standard cured entrained. and its properties are influenced by a large number of vari. 14. If air-entrained concrete is accidentally air- in service. explain some unusual strength results. Also. and curing. capacity compression machine. A cylinder smaller in size than Because of these many variables. Samples For evaluation of the test results by statistical procedures to be Specimen Sizes valid. The molds should be placed on a firm and level surface single truck. strength. The procedures for obtaining ders can be used when the aggregate is smaller than 1 in. or agitator. statistical methods given in ACI ing adjustments and any testing variability. The difference in strength between 4 mens can only measure the potential strength of concrete in by 8 in. Where the specimens are to be molded is important. The slump. when specified. The elapsed the diameter of the cylinder or the smaller cross-sectional time between first and final portions should not exceed 15 min.82 TESTS AND PROPERTIES OF CONCRETE forms or shoring. and density test results should be used to assure the concrete is controlled within required tolerances. wind. Chapter 8 in this volume contains workability infor- ance testing. (920 by 1830 mm) may be only 82 % short as possible and the sample should be protected from con. if slides from the scoop. (100 by 300 mm) cylinders and the specifier few tests to check uniformity and other characteristics of determines it is appropriate. Select a small truck will cause a considerable amount of consternation should tool to fill the molds with concrete that is representative of the the 14-day measured strength be lower than the 7-day strength. for example. usually 7. Chapter 9 in this vol- they are standard cured when used to check the adequacy of mix. and transport. It should fering time intervals. unless an least 20 in. have been made to the mixture proportions including addition of (50 mm) or. The time should be kept as of a cylinder 36 by 72 in. Cur. Making Specimens quire different numbers of replicate cylinders to be tested at dif. or percent increase in air content reduces the compressive to determine the adequacy of curing or protection procedures. mation on the properties of fresh concrete. (150 by 300 mm) cylinder [12]. In these cases. Additional information evaluating cylinder sizes test results based on a random pattern should be used as a has been published [18–20]. for fabricating field test specimens is a minimum of 1 ft3 (28 L). air content. The sample is collected by taking described in ASTM C 172. If the aggregate is too large for the size of mold available. be called to the fact that the size of the cylinder itself affects Molding of the specimens must begin within 15 min after the observed compressive strength. differences in mixing. it has to be known and corrected because each specimens or test results from various in-place test methods. Also. Attention must and transported to where the test specimens are to be made. multiple concrete [17]. then the air must be controlled for determination of whether a structure is capable of being put within tolerances. The advantages of 4 by 8 in. air of layers keeping the coarse aggregate from segregating as it content. trowel. recognizing mixture proportion- concrete. Concrete should be placed in After all adjustments have been made to the mix including total the mold to the required depth and with the required number mixing water and admixtures. and 4) higher strength concrete uses a smaller ents. For flexural strength specimens. The size of the sample specimens when cast in the field to be a specific size. Chapter 3 of this volume on sam. when specified and wet sieving is not permitted. 2) smaller storage space is required. Therefore. 4 by 8 in. and 28 days. (100 by 200 mm) cylin- total mixing water and admixtures. (150 by 300 mm) will yield a somewhat greater com- quality of the concrete must be employed. (100 by 300 mm) cylinders are Concrete is a hardened mass of heterogeneous materials as follows: 1) they are easier to fabricate. Select the appropriate rod for the size of the specimen using a smaller rod for specimens less than 6 in. tamination. It is important to be as near as practicable to where the specimens are to be make sure that the concrete for a set of cylinders comes from a stored. handle. sun. a 6 by 12 in. 3) less capping compound ables related to differences in types and amounts of ingredi. (150 by 300 The sampling must be made after all on-site adjustments mm) cylinder is used when the aggregate is smaller than 2 in. Also measure the density. The present C 31 permits the use basis for judging quality rather than placing reliance on only a of 4 by 8 in. the cylinders or beams must be standard cured. If the specimen is . they are field cured If concrete is air entrained. the strength fabricating the composite sample. charge of a stationary mixer.16]. For this purpose. be at least three times the nominal size of the coarse aggregate. ume contains information on the effects of various air contents ture proportions for strength or quality control. sample and the batch. And Chapter 13 in this vol- test results are used for form or shore removal requirements. and other sources of evaporation. transporting. Recommended Practice 214 [13] should be used. measure and record the slump. (500 mm). methods of checking the 6 by 12 in. the standard beam is 6 from different types of delivery equipment are covered in ASTM by 6 in. dimension of the beam should be at least three times the nom- The portions are combined and remixed to ensure uniformity inal size of the coarse aggregate in the concrete. When strength on the properties of fresh concrete. truck mixer. The concrete temperature test results may help Various in-place test methods are discussed in ACI 228 [15]. of the 6 by 12 in. Other test methods may require test alternative procedure has been approved. or shovel. The sample must be representative of the nature and condition the oversize aggregate is usually removed by wet screening as of the concrete being sampled. When strength test results are used for accept. Strength test speci. pressive strength [6. cylinders or beams must be field cured. ume contains information on properties of hardened concrete. (100 by 200 mm) and 6 by 12 in. (150 by 150 mm) in cross section with a length of at Practice for Sampling Freshly Mixed Concrete (C 172). the data must be derived from samples obtained by means It is generally accepted that the diameter of the cylinder should of a random sampling plan. ing procedures are discussed in the section on Curing Specimens. placing. pling contains information on a random sampling plan. is needed. (150 by 300 mm) the structure because of different size and curing conditions cylinders increases with an increase in the strength level of the between the specimen and the structure. (25 representative samples of concrete at a construction project mm). concrete temperature. roding materials are also permitted. This causes poor capping and dimensional tion will be different. standard initial and final temperatures. Even then. A variations can dramatically affect the concrete properties and moist room is a “walk-in” storage facility with controlled tem- test results. tained throughout the period of transportation. shall not be transported until at least 8 h after final set. If the specimens are not transported within 48 h the molds should be Curing Specimens removed within 16 to 32 h and standard final curing used un- This practice requires either standard curing or field curing til the specimens are transported. This would be the case in a relatively massive struc- concrete they represent. Care should be taken to ensure conditions of moisture and temperature from the time of that the moisture condition of field-cured specimens is main- fabrication to the time of testing. Since each condition is differ- exposed surface of a cylinder is one of the most violated ent. or [23] gives procedures for checking the adequacy of curing. Wet fabric may Specimens transported to the laboratory for standard final cur- be used to cover the specimens to help retard evaporation. Specimens concrete or cardboard molds. The exposed concrete surface should be finished to pro. field curing method must be used. Specimens should be transported in such a for checking adequacy of mixture proportions. (3 mm). LAMOND ON MAKING AND CURING CONCRETE SPECIMENS 83 rodded. when a structure may be put pickup truck could result in a 7 % loss of strength and drop- into service. In. commonly called a fog room The standard initial curing period takes place in a moist when the prescribed relative humidity is achieved by atomiza- environment with the temperature between 60 to 80°F (16 to tion of water. 11 % at three days. Continuous running wa- sufficient moisture during the initial curing can lower meas. They are not interchangeable. ASTM Specification for . comparison with standard curing. Vibration may reduce the air content of air-entrained the required storage temperature.5°F (23. Standard final laboratory curing is at a temperature of 73. carefully count the strokes for each layer. the method selected for moisture and temperature condi- requirements. The procedure is Harsh and Darwin [22] reported that wet mixtures exhibited as not expected to produce optimum consolidation but is used in much as a 5 % loss in strength through segregation as opposed order to permit reproducibility of results with different techni. If the specimen is to be vibrated. air curing could lower the strength by 8 % at one should not be used in storage tanks. when stored near 80°F (27°C). heat brator and the best uniform time of vibration for the particular generated during early ages may raise the temperature above concrete. ter or demineralized water may affect results due to excessive ured strength. They give little indication of whether a deficiency is due necessary. seal the top of the specimens with a plastic cap. the effect of the moisture and tolerances in cylinders. Water storage tanks constructed of noncor- is 6000 psi (40 MPa) or greater. Early-age re- should not strike the bottom of the mold when rodding the first sults may be lower when stored near 60°F (16°C) and higher layer. for strength. or curing or ping cylinders from waist level can lower strength at least 5 %. The water should be clean period to provide satisfactory moisture and temperature. All fog rooms should be equipped with a record- 27°C) for up to 48 h. Caps may leave depressions in the concrete surface greater than 1/8 in. For high strength concrete. then be demolded the fabric must not be in contact with the surface of the and placed in laboratory standard final curing. or quality control. For traffic-induced vibrations. ACI Standard Practice 308 specimens with a sheet of plastic. Automatic control of water perature shall be between 68 and 78°F (20 to 26°C). The specimens should be moved. temperature would not be the same as on the actual concrete Mark the specimens to positively identify them and the structure. Transportation time should methods. layer is consolidated by tapping the outside of the mold. verification can rated with calcium hydroxide may be the easiest method to be performed by determining the density of the specimen and maintain the required storage temperature. and 18 % at seven days. Immersion in water satu- concrete. If air content reduction is suspected.0 2. perature and relative humidity. (3 mm) Transporting in depth making capping for testing difficult. if ture. the standard initial curing tem. practice for rodding or vibrating specimens. protection requirements. comparing it to the calculated air-entrained concrete density at During the setting and initial hardening. Carefully follow the procedure in the be damaged by harsh treatment. One study [21] showed that even at proper leaching of calcium hydroxide from the concrete specimens and temperatures. If specimens are for determining indicated that rolling and bumping around in the back of a removal time of forms or shoring. Cover the top of the dling and curing of the specimens. These mold and that has no depressions or projections larger than specimens will reflect the influence of ambient conditions on 1/8 in. The rod day. Field curing is maintaining the specimens as nearly as possible in the same moisture and temperature conditions as Standard Final Laboratory Curing the concrete they represent.0 3. the concrete can the measured air content. and saturated with calcium hydroxide. Cylinders and beams should be cushioned during transport Standard curing is exposure of the specimens to standard and handled gently at all times. determine the best vi. Moist rooms and water Control of standard curing conditions is very important since tanks are usually used for creating the moist environment. to curing storage with a minimum amount of to the quality of the concrete as delivered or improper han- handling and immediately after finishing. and protects them from jarring. to a 4 % gain in strength in dry mixtures due to improved cians. Field Curing duce a flat even surface that is level with the rim or edge of the Field curing procedures are unique to each situation. If the specimens are not exceed 4 h. Close any holes left by rodding or vibration after each consolidation.0°C) and a moist condition with free water main- Standard Initial Curing tained on the surface of the specimens. manner that prevents moisture loss and exposure to freezing acceptance testing. but ing before 48 h should remain in the molds. When the specified compressive strength ing thermometer. Richardson [10] curing method must be used. seal them in a plastic bag. It is the author’s experience that finishing the the properties of the concrete. It may be temperature and recording thermometer with its sensing ele- necessary to create an environment during the initial curing ment is required in the storage water. Each laboratory should. The making and curing of concrete test specimens are cov- crete. and Absorption of Coarse system. Before mixing the concrete. care has to be taken that not for air-entrained or no-slump concrete. ments of ASTM C 511. Immediately sub- mine the number of batches of concrete. Perform the slump and days than those cured in a fog room at 100 % relative humidity.1 [24] and 211. and ered by two ASTM standards: ASTM C 31 for field use. and water must be known accurately prior to batching. Finish the specimens as required. for 16 to 32 h prior to the removal of the molds. (3) correlation with nonde. as part of its quality Relative Density (Specific Gravity). Scales for weighing batches of materials and con. should be verified prior to mixing the concrete. slump mitted or required. covered in C 1176 and C 1435. standard is based on data from the concrete proficiency If required. and Conclusions Absorption of Fine Aggregate (C 128). Cover and cure the specimens Some test methods require specimens that are other than cylin. The selection of the method is similar to ASTM C 31 using the slump of the concrete as guidance for the Equipment method to be used. Concrete with drical or prismatic in shape. until at least 16 to 24 h after final setting time. all the materials must be at room temperature in the range of 68 to 86°F (20 to 30°C) unless Evaluation the design is being performed at other than room tempera. They should be molded following prolonged setting time may require the molds not be removed the general procedures in this practice. rods or vibrators. is also a definitive procedure for Discard concrete used for determination of the air-content test. determine the relative density and absorption of sample program of the Cement and Concrete Reference the coarse aggregate using ASTM Test Method for Density. and the making. admixtures. A sampling pan is required to specimen as they are consolidated with external vibration. When required. Machine-mixed concrete the Testing of Hydraulic Cements and Concretes (C 511) covers should be mixed for 3 min after all the ingredients are in the the requirements for fog rooms and water storage tanks used mixer followed by a 3-min rest and 2 min of final mixing. small tools. Store the cement as required and check it for fineness. Mix the concrete in a mixer that will provide a uniform. mallet. Therefore. receive the entire batch discharged from the concrete mixer. Different tests may require different molds. Relative Density (Specific Gravity). performing specific operations that does not produce a test Make the specimens following the procedures in ASTM C 192.84 TESTS AND PROPERTIES OF CONCRETE Moist Cabinets. Price [6] stated that water-cured specimens eliminate segregation. or (4) providing specimens for research purposes. aggregates. temperature tests in accordance with ASTM C 143 and C 1064. Flexural test specimens must be stored in water saturated with calcium hydroxide at standard curing Materials Conditioning and Testing temperature for a minimum period of 20 h prior to testing. like ASTM C 31. Committee C9 has over 150 standards and C 192 is referenced Consolidation in over 40 of these standards. either internal or external vibration may be cone. curing. number of specimens ject the specimens to standard curing conditions after removal for all the various tests. To for standard curing. The failure to meet specification requirements has resulted in many investi- Mixing and Testing gations to determine the adequacy of in-place concrete. as-delivered concrete. Additional information on consolidating low-water-content Conformance of the molds to the applicable requirements specimens is in Chapter 51 of this volume. a particular method of consoli- The equipment needed in the laboratory includes the follow. Propor. When vibration is per- mixing pan. respectively. (2) evaluation ASTM C 31. The field standard is used to tioning concrete mixtures are covered in ACI Standard make specimens to comply with specification requirements Practices 211. A program to deter. especially when a laboratory regularly mixes low water contents such as roller-compacted concrete are concrete. The size concrete specimens. Aggregate (C 127) and fine aggregate using ASTM Test Method for Density. result. perform the air-content test in ac- Making and Curing Test Specimens cordance with ASTM C 231 or C 173 and the yield test in ac- in the Laboratory (ASTM C 192) cordance with ASTM Test Method for Density (Unit Weight). Moist Rooms. and Air Content (Gravimetric) of Concrete (C 138). or concrete mixer. deposit concrete onto a clean damp mix- with a water-cement ratio of 0. thermometer. analyze their data against the values in this practice. and Water Storage Tanks Used in required for molding the specimens. Care should be taken that specimens are cast and of different mixtures and materials. The dimensions of the molds also Finishing and Curing vary for different tests and usually according to aggregate size. Hand mixing is permitted but used. for concrete used on construction projects. However. air-content apparatus. When using external vibration. and testing of homogeneous mixture in the mixing times required. This practice. and scales. and various test ages needs to be of the molds in moist room or water tanks to meet the require- performed prior to laboratory mixing of the concrete. which the specimens are being made. Concrete with preferred. The laboratory standard is used to of the batch has to be about 10 % in excess of the quantity develop mixture proportions for field concrete and research . The procedures are for a wide variety of purposes.55 were about 10 % stronger at 28 ing pan and remix by shovel or trowel. structive tests. Specimens consolidated with crete should be checked for accuracy prior to use and be low water contents may require a surcharge weight on the within acceptable tolerances. when using C 192 it The specimens are consolidated by rodding or internal and necessary to coordinate with any other applicable standard. dation may be required by the test method or specification for ing: molds. ASTM C 192 for laboratory use. The weights of the cement. such taking the precautions as previously discussed in the section on as: (1) mixture proportioning for project concrete. A precision statement of all the test methods included in the ture. stored in accordance with the applicable test methods. external vibration. The moisture content of the aggregates must be known before batching the con. Machine mixing is the mold is rigidly attached to the vibrating unit. Laboratory.2 [25]. sampling pan. Yield. May 1991. “The Control of Concrete Quality: A Review of 1969.” ACI Committee Report 214. July 1981. A. B. Effects of Curing and Moisture Distribution. [13] “Recommended Practice for Evaluation of Strength Test Results of Concrete. MI. 1963. Farmington Hills. and Mass Concrete.” Signifi. Farmington Hills. MI. MI. tional.. Bureau of researcher’s results are different from those of another Reclamation.S. the Present Position. Part 2. T.” ACI Committee 211. Farmington Hills.. 1966. “Static and Fatigue Strength. and Willens. Concrete Institute.” Proceedings.15. J.. Part 2. May [8] ACI Manual of Concrete Inspection. August 1999. Concrete Association. [1] Kesler. pp. C.. American Civil Engineering. D.. researcher on the same type of study. Detroit. “Effect of Size and Shape of Test Specimens Aggregates. [19] Pistilli. N. 8. No.” Journal. No... Concrete. [5] “Report of Committee on Specifications and Methods of Test [20] Burg.” Concrete International.1. ASTM STP 169C. 1978. gates. tested to obtain accurate and representative results. MI. M. Vol. Farmington Hills. ASTM International. [10] Richardson.” MI. Significance of Tests and Properties of Concrete and Concrete [16] Gonnerman. shohocken. 3. American Concrete Institute. K. Committee 363. No. and Bloem. H. “Studies of Flexural Strength of American Concrete Institute. V. PA. 2001. ASTM C 31 [14] Wagner.. and for Concrete Materials. R. G. Vol.” ASTM Journal Cement.” Significance [18] Forstie. shohocken. D. W. American Concrete Concrete test specimens should be made. 1975. L. ASTM International. West Con.” [24] “Standard Practice for Selecting Proportions for Normal.” Cement Users (now American Concrete Institute). West Con. and Siess. Concrete Institute. S. Vol.. U. SP-2. R. Jan. . 1. London. Caldarone. MI.” National Ready Mixed 417–432.. 1976. PA. D. ASTM International. 8. 1993. and Darwin. p.” Signifi. PA. American Concrete Institute. and Institute. cance of Tests and Properties of Concrete and Concrete-Making [17] Malhotra. 25. [3] Adams. R. Jansen. 58–69. Silver Spring. Highway Research Board. MI. Strength of Concrete Test Specimens. pp. pp. “Compressive Testing of HSC: Latest Technology. “Factors Influencing Concrete Strength.. P. 36. “Making and Curing Test Specimens. [6] Price. “Effect of Curing Conditions on the Compressive ings. W. 1957. Farmington Hills. 1991. “Traffic-Induced Vibrations and Association. F. 1995. MI. 1914. and Schnormeier. N. 629. F. PA. Washington. 1951. on Compressive Strength of Concrete. 5. PA.. 53. “Review of Variables that Influence Mea.. West Con. ASTM International. J. MI. Vol. 36–42. D. DC. American Concrete Institute. C. American Society for Testing and Materials.” ACI Committee 308. American Concrete Institute. Proceedings. and Capping Methods in Compressive Strength Testing of cance of Test and Properties of Concrete and Concrete-Making Concrete. Vol. “Evaluation of Cylinder Size [4] Lamond.. F.” Proceedings.” Proceed.. MI. 237–250. [23] “Standard Practice for Curing Concrete.” Proceedings. cured. pp. G. M. [21] Bloem. Concrete International.. Research studies on test specimens made in the laboratory MI. 6 12 Cylinders for Quality Control of Concrete. pp. 47. “Making and Curing Test Specimens. Department of Interior. MD. 1994. Detroit. T.” U. National Association of Wilems.S. on the Compressive Strength of Concrete. Aug. [2] Kennedy. Farmington Hills. ASTM STP 169A. 1954. 9th ed.. The failure of the laboratory-developed mixtures to [11] “State-of-the-Art Report on High Strength Concrete” ACI perform in the field has caused considerable problems. 1999. L. shohocken. C. D. American Concrete Institute. pp. “Making and Curing Test Specimens. “Are 4 8 Inch Concrete Cylinders as Good as Materials. Publication No. Vol. H. 67–76. [25] “Standard Practice for Selecting Proportions for Structural sured Concrete Compressive Strength. 1925. West Con. have been questioned on many occasions when one [12] “Concrete Manual.2. 2002. Bridge Deck Repairs. A. West Conshohocken.. 42–45.. shohocken. Heavyweight. Concrete & Concrete Aggre- Materials.. “Effect of Sampling and Job Curing Procedures or C 192 and the standards they reference should be followed. Vol. 1997. Farmington Hills. E.” Materials Research and Standards. Government Printing Office. ASTM STP 169B. ASTM STP 169. D. LAMOND ON MAKING AND CURING CONCRETE SPECIMENS 85 studies. American 1986. 1956. F. [15] “In-Place Methods to Estimate Strength of Concrete. “Development and Use of 4 of Tests and Properties of Concrete and Concrete-Making by 8 Inch Concrete Cylinders in Arizona. T. M. Farmington Hills.” Concrete Interna- Materials. Detwiler. F.. ASTM International. Cement and Concrete [22] Harsh. S. 19. Farmington Hills. [7] Sparkes.” Journal of Materials in Lightweight Concrete.” ACI Committee 211. [9] Walker.” ACI References Committee 228. 1998. tial setting is defined to be the time at which the concrete is no timately affect the time at which finishing and curing opera. viding the applied load by the surface area of the respective pin. resistance to penetration of the mortar fraction is obtained by us- gineering properties. Periodically. Degussa Construction Chemicals. as well the previous editions were drawn upon. The mortar fraction is placed into a rigid. The The most widely used method for determining the time of setting review period has been limited primarily to contributions made of concrete is ASTM C 403/C 403M—Standard Test Method for during the last decade. cold joints is often the time at which steam-curing is applied in precast op- can be avoided. In particular. STP 169C [4]. ASTM STP 169. container and stored at a specified temperature. tration locations and at a minimum distance from the perimeter ing rise to stiffening. of initial and final setting are arbitrarily defined as 3. Christensen1 Preface History SCRIPTURE PREPARED THE ORIGINAL VERSION OF A number of methods for monitoring the time of setting of con- this document. longer mobile. erations. non-absorptive early stages they are moldable and castable materials that sub. reactions. temperature. Initial set tions can be initiated. a process referred to as hydration. which was subsequently est methods were developed in the late 50s and are discussed updated by Sprouse and Peppler in 1978 with ASTM 169B [3]. Resistance to penetration is determined by di- which is defined as “setting. a sample of mortar is ob- Introduction tained by wet sieving a portion of the concrete on a 4. The 1994. tion time and fitted by regression analysis to determine the times dration process is complex and consists of a series of chemical of initial and final setting. This structural transformation occurs as ing a series of pins of successively decreasing diameter injected the result of chemical reactions between the cementitious to a depth of 25 mm (1 in. that being ASTM intent of this document is to review the current ASTM method. As relevant research. it is important to have methods by which the rate of setting ishing operations can begin. In in detail in the previous edition of this publication [4]. These changes ul. even by the application of vibration. Bleed water is removed from the sur- material and water. Because the hy. on these definitions. respectively. In the preparation of this chapter. termined from changes in the penetration resistance of a specimen as a function of time. The British Standards Institute BS 1 Vice President. Pin penetrations dration process results in the consumption of free water and are spaced in such a way as not to be influenced by previous pene- formation of an interlocking network of hydrating particles.6 MPa (4000 psi).75 mm sieve to remove the coarse aggregate fraction or it can be a prepared Hydraulic cementitious compositions are unique in that in their mortar. water content.11 Time of Setting Bruce J. and the presence of chemical (500 psi) and 27. The hy. steam-curing can be applied. giv.” With portland cement-based com. There. positions. Dodson prepared the most recent update. and subsequently a hardening behavior. edition. in 1956 [1]. the The resistances to penetration corresponding to the times chemistry and/or the surface area of the cementitious compo. Some of the earli- work with ASTM STP 169A in 1966 [2]. the contents of noting the advantages and disadvantages of the method. face of the mortar fraction on a regular basis. R&D. the sequently are transformed into rigid structures with useful en. Kelly extended this crete have been investigated over the years. 86 . of the container. but undoubtedly important advances were not clearly stated in the title of the method. The time of ini- and mineral admixtures in concrete mixtures. but every attempt was as to highlight some of the other methods that have emerged made to minimize duplication of information from the previous or are in the process of being developed. as well as generally regarded as the time at which fin- fore. Attempts have been made to uncover all Time of Setting of Concrete by Penetration Resistance [5]. the process is affected by changes in the content. though. this process normally occurs in a matter of hours These resistance values are then plotted as a function of hydra- from the time of contact of cement and water.5 MPa nent. provide up-to-date references and focus Basics of the Method specifically on new technologies that have been developed. Current ASTM Method The current edition will review and update the topics as addressed by the previous authors. The author acknowledges the contributors of the previous editions and their summaries of the literature on this topic. and load can be applied to the structure.). the time of setting is de- covered or were unknowingly omitted in this review. There is not complete agreement of the cementitious composition can be quantified. While holding the device by the spring- is used to slowly inject the appropriate-sized pin into the plas. 1—One style of bench-top penetrometer used to with one of these two functions and removing any outliers gen- perform the ASTM C 403/C 403M method. 2—Pocket penetrometer used to perform the ASTM C The equipment typically used in the lab to determine the 403/C 403M method when a bench-top style is not available. since the pin size is fixed) are inscribed on tion step. It consists of a base platen with a vertical post. times of setting is a bench-top penetrometer like that shown in Fig. these data were plotted manually on semi-logarithmic graph paper and the times of setting determined by hand-fitting. as well as two additional samples. water. 1. Fitting a set of at least six data Fig. Fig. This signals the end of the finishing window. particularly due to the difficulty in maintaining the pen- pin with a spring-loaded head assembly and a sliding collar. The time of final setting is generally regarded as the time at which the concrete is no longer deformable. produce very reproducible results. Equations are shown for fits made using either an exponential or a power law function. Manipulation of the Data An example set of data that was obtained from a bench-top penetrometer is shown in Table 1. These instruments are fairly rugged. the device only provides information on time of initial setting and not final setting. Abel and Hover observed that the time to begin finishing operations. When the maximum achieved. the monly referred to as a pocket penetrometer. from the location of the sliding collar. shown in Fig. and. and as such produces results with a wider variability. Measurements of the compressive strength of the concrete specimens can be made at this time and have been reported to be on the order of 0. device is much more operator dependent than the bench-top ter. which is observed in practice as the time at which the boot of an adult male leaves an imprint approximately 6 mm deep in a fresh concrete surface. at which time the surface of the setting concrete can no longer be manipulated and also corresponds to the time at which curing operations can begin. As one might expect. sistance (not force. At the time of the development of the method.1 MPa (15 psi) [6]. Ad- ditionally. With the availability of personal computers and spreadsheet software. erally results in a correlation coefficient that is greater than . finishing operations on concrete slabs performed using a finishing machine are understood to begin as soon as measurable values of penetration resistance are obtained on companion mortar specimens [7]. which acts as Markings corresponding to different levels of penetration re- a marker of the maximum force delivered during the penetra. loaded head and manually inserting into the plastic mortar tic mortar sample until the maximum penetration distance is specimen. it is now a relatively easy task to plot and analytically determine the best function to fit the data. occurs at a penetration resistance of approximately 0. the mortar specimen and penetration resistance determined A smaller version that is often used in the field is com.5 MPa (72 psi) [4]. 2. since the application of sufficient force to achieve penetration at the later stages of the hardening process is very difficult. This variability is further expanded because only one diameter pin is typically used. Figure 3 shows the penetration resistance versus elapsed time for the specimen in Table 1 (control). CHRISTENSEN ON TIME OF SETTING 87 5075 defines the limit for placing and compaction at 0. wet burlap. Finally. thereby limiting the number of useful penetration events that can be executed to get a good statistical sampling. the device is extracted from if regularly calibrated. the head travels downward. A lever attached to the side of the spring mechanism the side of the device. is a small device that consists of a single unit. Nev- ertheless. this device does have the advantages of being easily transportable and can provide a quantifiable estimate of the rate of hardening under many conditions. to which is attached a spring mechanism with a meter to display the applied force.7 MPa (100 psi) [4]. such as the application of a curing compounds. etrometer in an orientation perpendicular to the surface of the specimen during penetration. The meter contains a floating needle. easy to use. penetration distance is achieved. This penetrome. evidence currently exists to suggest that finishing operations generally begin much sooner than the time corresponding to initial setting as determined by ASTM C 403/C 403M. or the like. Therefore. 4 32 12. Evaluations were performed on prepared mor.5 16 34.5 16 21. this can represent a sig- of various diameters. and is quickly understood by a technician.4 416 343 4. one dimension is used throughout the test.98. one pin size is used for determination of initial set and an- shows the results of the calculation on this dataset. solid lines and boxes represent power law fits to the data. This time of setting is that it is based on multiple quantitative meas.54 281 176 14.3 161 1. The data were collected during a penetration to that used in the field by finishers to determine round-robin test program in which five different laboratories when to begin finishing operations. while for ASTM C ance and calculating the corresponding elapsed time. in place of mortar wet-sieved from ($1–2 K). especially when the slump of the urements on the same specimen. These characteristics are in contrast to capturing vessel to be able to perform the method.1 311 370 14. where dozens of concrete mined by this method. For ASTM C 191. Table 2 266. Disadvantages of the Method Advantages of the Method The first disadvantage of the method is the requirement of wet- One of the main advantages of this method for determining the sieving the plastic concrete to obtain the mortar fraction. largest particle in the mortar specimen. because the penetrations are mixtures may be evaluated in a day.9]. The use of multiple data concrete is low and/or the water-to-cement ratio (w/c) of the points improves the precision of the time of setting. the influence of edge In the field.1 65 4. TABLE 1—Penetration Resistance Data for the Control Mixture Elapsed Time (min) Penetration Force (N) Pin diameter (mm) Surface Area of Pin (mm2) Penetration Resistance (MPa) 251 176 20.1 . Subsequently.5 MPa (initial) or 27. concrete as specified in the method. ASTM C 403/C 403M The precision and bias statistics of this method are shown is used in such specifications as ASTM C 494/C 494M to evalu- in Table 3. wet sieving requires transporting a large sieve and effects is minimized. The method is very straight- participated.3 341 299 9. a Vicat needle of 3. forward to perform.4 446 546 4. the times of ASTM C 191 or ASTM C 266 methods used to quantify the time initial and final setting can be determined by inputting either of setting of cement pastes.3 323 0. utilizes relatively inexpensive equipment tars for ease of preparation. In addition.88 TESTS AND PROPERTIES OF CONCRETE Fig. These values were obtained using the inch-pound ate the effect of chemical admixtures on the time of setting [10]. as deter. system and hand-fitting procedures in 1973 and have remained Another advantage is the fundamentally similar mechanism of unchanged since that time. 3—Penetration resistance versus elapsed time for mortar fractions from three different concrete mixtures. Once an adequate equation is determined. Dotted lines and boxes indicate exponential function fits to the data.6 386 396 6. mixture is low. 0.6 MPa (final) for the penetration resist. process can be laborious. which are significantly larger than the nificant investment in time and effort to perform the method. In the laboratory. other size for final set [8.3 161 2. while the maximum difference in the time of final setting is on dicated by the method. the specimens at five equally-spaced locations along the diameter of the same must be continuously monitored and tested at successively de. Therefore.1 5. different elapsed times between the time of mixing and the mens can remain unattended for the first few hours after con. While there is general agreement among the C09. exist and can perform the method on multiple and final setting could be determined as a function of position specimens without human intervention. and the sample was then discarded (all punches creasing time intervals until the time of final setting has been were made with the same operator on the same penetrometer exceeded. Finishing operations are ferences in the time of initial setting are small with position. As the hydration proceeded and the specimens TABLE 3—Precision of ASTM C 403/C 403M Coefficient of Variation. One observation that many practitioners have commented upon in recent years is a belief that the operator has the ability to skew the values of initial and final time of setting by varying the location at which the pin is penetrated into the specimen. Modifications to the Method The basic aspects of the current method appear to have remained essentially unchanged for more than three decades. as that of an ASTM C 494/C 494M Type F water reducer. 5. though. Three Average of Time of Setting Individual Results Three Tests Initial 7.23. no data could be found to substantiate the hypothesis.5 Fig. Automated systems. As a result. The dif- to observations with field concrete. Thereafter. and not a fundamental flaw in the method. appears to be a mat. . a plot was prepared and is shown in Fig. there is always room for improvement. One large batch of mortar was prepared and transferred into ten identical cylindrical containers (approximately 18 cm in diameter). 3 Fitting Function Time of Setting (Initial or Final) Accelerated (minutes) Control (minutes) Retarded (minutes) Exponential Initial 251 333 478 Final 336 430 583 Power Law Initial 248 337 489 Final 340 446 602 A second disadvantage is the requirement to continuously began to stiffen. Using a fit to all ten data points for each po- equipment requires a significant capital investment ($80 K as sition. the order of 40 min. Multilaboratory Multiday. which is indicative of the usefulness of the method. the time of initial shown in Fig. though. penetration measurements were made at ten monitor the specimen. Under normal conditions. generally initiated earlier than the time of initial setting as in. this in the specimen. container. The trend is of 1999) and is impractical for many users. but the magnitude briefly is the lack of correlation of the results from the method of the difference depends upon the stage of hydration. punches were made tact of cement and water. CHRISTENSEN ON TIME OF SETTING 89 TABLE 2—Calculation of Time of Setting for the Three Specimens shown in Fig. such as the robotic system using the same fitting equation).1 committee members that this is indeed true. where Hence. as expected. 4. This issue. time of final setting. % Single Operator. At each time interval.7 4. 4—Automatic penetrometer with ability to monitor eight specimens simultaneously. useful information can still be obtained by comparing the maximum allowable delay in time of setting of the admix- the relative setting characteristics of different concrete mixtures by penetration resistance.2 Final 4. towards a shorter time of setting at the center of the container Another disadvantage that has been already mentioned as compared to the perimeter. the following test was recently performed in the laboratory to investigate this phenomenon. the speci. This is significant for specifications such ter of definition. Neverthe- less. Unfortunately. 90 TESTS AND PROPERTIES OF CONCRETE Fig. 5—Time of setting of mortar specimens as a function of the punch location on cylindrical specimens. ture-treated concrete mixture is 90 min from the control. The Additional Methods for Evaluating thermal loss from the perimeter of the container is likely re- Time of Setting sulting in less activation of the hydration process than in the center of the specimen. This gradient from inside to the out- Other Penetration Methods side of the container is more significant as the hydration As mentioned previously, one of the limitations of the ASTM C process proceeds, further substantiating the observation of 403/C 403M method is that the mortar must be wet sieved from wider variation at the time nearer to final setting. the concrete. To eliminate this step, Abel and Hover proposed the As a result of these observations, additional tests are use of a modified penetrometer with a much larger surface area planned to investigate the extent of this variation in time of set- than the pins typically used in the current method [6]. The sur- ting as a function of different cements and chemical admixture face area is similar to that of the base of an adult work boot and compositions. In parallel, efforts are underway to modify the the penetrometer foot can be used directly on the surface of a method. The current proposal is to limit the locations for pene- concrete slab. This apparatus is referred to as the “Finisher’s tration measurements to a ring of a fixed distance from the Foot” and is shown in Fig. 6. Two different feet are used, the outer perimeter of the container. smallest of which is still several times larger than the diameter of Fig. 6—Finisher’s foot apparatus being using on a concrete slab to determine penetration resistance (after Abel and Hover [6]). CHRISTENSEN ON TIME OF SETTING 91 from this plot. First is the observation that the penetration measurements can be obtained much sooner on the concrete slab than on the mortar. Second is the smooth transition during the change from the large foot to the small foot, as well as during the transition from measurements on the slab to the mortar specimen. Probably of most significance, which is not apparent from the plot alone, is the authors’ observation that the time to begin finishing operations occurred at penetration resistances on the order of 0.1 to 0.2 MPa, which is prior to the first penetrations on the mortar specimens. While some of these observations are specific to the reported projects and some of the effects are likely due to the differences in sizes of the specimens, the time of “initial” setting by this method is much earlier than predicted by ASTM C 403/C 403M. Interest in standardizing this procedure is significant and is currently going through the balloting process as an ASTM Standard Test Practice. Another limitation of ASTM C 403/C 403M that has been mentioned is the need to continuously monitor the specimen during the hardening process. While this can be addressed Fig. 7—Penetration resistance versus time after batching with a sophisticated and expensive robotic system, this re- for field concrete. Open symbols are generated using the quirement can also potentially be overcome by using a continu- “finisher’s foot”; closed symbols are from C 403 measurements ous penetration measurement. Sohn and Johnson discussed an on mortar wet sieved from the same concrete (after Abel and apparatus that could be used to continuously monitor the hard- Hover [6]). ening process of cement-based materials during microwave curing [11]. Figure 8 shows the details of the arrangement. They investigated multiple penetration rates and interpreted a typical coarse aggregate. The penetration depth in this method the data in terms of hardening rate at various temperatures is modified and limited to 6 mm. This depth is chosen to simu- and hardness values. Results were limited to investigations on late the depth at which the work boot of a finisher will sink into cement pastes and mortars. a bull-floated slab when beginning subsequent finishing opera- Further evaluations of this method were carried out in the tions. The abbreviated depths may possibly result in less edge ef- laboratory on prepared mortars by modifying the orientation fect from interaction with the coarse aggregate. of the apparatus and comparing the results to those obtained In essentially the same manner as the ASTM C 403/C 403M by ASTM C 403/C 403M [12]. Different penetration rates, as method, the penetrometer foot is pressed into the plastic con- well as specimens with a range of setting times, were investi- crete to the prescribed depth, and the force necessary to achieve gated. An example comparison of the results of the two meth- the penetration is recorded and converted to penetration re- ods is shown in Fig. 9. The correlation for the mixtures inves- sistance. An example plot of penetration resistance versus batch tigated at this penetration rate was quite good; however, time is shown in Fig. 7. The open symbols on the lower left por- further work was considered necessary to fully investigate the tion of the plot are obtained on the concrete slab, while the method. Among the limitations of the method, the mortar frac- closed symbols in the upper right portion of the plot are ob- tion still needs to be sieved from the concrete mixture. While tained on companion mortar specimens sieved from the same in principle a similar system can be designed with a large pene- concrete mixture. A couple of significant features are apparent trometer for use on concrete, economically impractical loads Fig. 8—Continuous penetration apparatus discussed by Sohn and Johnson [11]. Reprinted with permission. 92 TESTS AND PROPERTIES OF CONCRETE Fig. 9—Comparison of initial and final times of setting determined by the continuous penetration versus that obtained by C 403 [12]. A penetration rate of 6.4 mm/hr was used on prepared mortar specimens. would be required. Another limitation of the method is that the alter that correlation. Equipment is now available commer- apparatus must be dedicated to one specimen throughout the cially that allows testing of multiple specimens at the same hardening process, so multiple pieces of equipment are neces- time, but the cost is significant ($20 K). This equipment is an sary for use in a development laboratory. excellent tool for laboratory investigations and for pre-qualification of field mixtures, but is not transportable to the field. Thermal Methods Another limitation of this method is that the cell size is small Because the hydration reaction of portland cement is exother- so that only pastes and mortars can be tested. mic, researchers and practitioners have used this attribute as a One of the simplest approaches is merely to embed a ther- means of assessing the state of the hardening process [13–17]. mocouple wire into the center of the concrete specimen and Isothermal calorimetry is one technique that is very useful for monitor the temperature as a function of time. This condition quantifying the energy liberated in this process, as well as a is often semi-adiabatic and the results are heavily dependent very good tool for elucidating the reactions of the calcium upon the size of the specimen, environmental conditions, and sulfate and other mineral phases. An example plot of energy mixture design. Nearly adiabatic conditions can be achieved by liberated versus hydration time is shown in Fig. 10. In general, placing the specimen in an insulating chamber, which is useful the time corresponding to the onset of the rise in the curve af- in some applications, but may not translate well to the setting ter the induction period is considered to correspond closely characteristics of a slab or other structure that is not fully with the time of initial setting, but many factors in the field can insulated. Nevertheless, portable equipment with the ability to Fig. 10—Typical isothermal calorimetry curve for hydrating cement pastes (20 °C). CHRISTENSEN ON TIME OF SETTING 93 Fig. 11—Insulating chamber with cavities for concrete specimens used in proposed thermal method. Thermocouple tips are imbedded in the base of the cavity. read multiple thermocouples and that are relatively inexpen- sulating cavities, but no insulation is placed on the top surface sive and convenient to use are now available. As such, investi- of the specimens. Thermocouples are attached permanently to gations have been performed recently to further develop the the interior base of the cavities, thereby eliminating the need of appropriate sample storage conditions, with the intent of im- embedding and removing the thermocouple wires every time a proving the correlation to ASTM C 403/C 403M [14]. specimen is tested. An example plot of temperature versus time This author has proposed a sample configuration and data for a specimen tested in this configuration is shown in Fig. 12. manipulation technique for temperature versus time measure- Determination of the first and second derivatives of tempera- ments that provides good correlation with ASTM C 403/C 403M ture versus time, and plotting the data versus time, results in the [14]. The method is intended for use in the laboratory and al- curves shown in Figs. 13 and 14. The time corresponding to the lows the use of a concrete sample, instead of mortar sieved from maximum in these plots is then compared to the times of initial plastic concrete. An example of the sample configuration is and final setting determined on companion mortar specimens shown in Fig. 11. The concrete mixture is placed into 15 cm (wet sieved from the same concrete) using ASTM C 403/C 403M. 15 cm plastic cylinders, which are subsequently placed into in- These comparisons for three different concrete mixtures are Fig. 12—Example of the temperature versus time plot obtained for a specimen placed in one of the cavities shown in Fig. 11. 94 TESTS AND PROPERTIES OF CONCRETE Fig. 13—Plot of the first derivative of temperature with time (from Fig. 11) as a function of time. Time of the maximum appears to correlate with time of final setting determined from C 403. shown in Fig. 15. Interestingly, the correlation between the time Ultrasonic Methods of final setting and the time of the maximum in the first deriv- A number of investigations have been published on the use of ative versus time is reasonable. The time of the maximum in the ultrasonic waves to follow the setting of concrete [17–27]. second derivative versus time occurs earlier than the time of ini- Some techniques rely upon the propagation of the waves tial setting by ASTM C 403/C 403M and seems to correlate bet- through the material, hence the specimen must be thin, due to ter with the time at which the penetration resistance on the mor- its lossy nature. Others utilize reflection of the wave off of the tar specimen is approximately 1.25 MPa (200 psi). Further work near surface, where the response is independent of the thick- on a range of mixture designs is necessary to further validate ness of the specimen. Typically, either shear waves or com- the method, but initial observations are very promising. Never- pression waves are used, though shear waves are only sup- theless, because this method addresses many of the operational ported in solids, so assessing the extent of shear wave deficiencies of ASTM C 403/C 403M (wet sieving and constant absorption or reflection can be used as a basis for investigating human monitoring), the consensus of the C09.23.1 committee the transition from a fluid to a solid. Subramaniam et al. have has been to move forward with standardization of the method. characterized this relationship as a wave reflection factor Fig. 14—Plot of the second derivative of temperature with time (from Fig. 11) as a function of time. Time of the maximum appears to occur slightly before the time of initial setting determined from C 403. CHRISTENSEN ON TIME OF SETTING 95 Fig. 15—Comparison of the time at the maximum in the 1st or 2nd derivative of time plot versus time of setting from ASTM C 403/C 403M. Data from three different mixtures with a range of setting times are presented, one of which is based on information in Fig. 12. (WRF), which changes with hydration time as shown in Fig. 16 Electrical Methods [20]. They have observed that the time corresponding to the de- Investigations concerning changes of the electrical character- crease in the WRF exhibits a linear relationship with the time istics of hydrating systems have continued since the last edition of initial setting determined by ASTM C 403/C 403M [19]. of this chapter [28–32]. Many of the recent investigations uti- One of the obvious advantages is that this technique is non- lize impedance spectroscopy (IS) as the technique of choice. IS destructive, thus is suitable for real concrete structures. WRF allows easy separation of electrode effects, sweeps a range of can also be used at times beyond the setting regime to charac- frequencies to find the true bulk resistance (or inversely the terize compressive strength development, and hence can be conductance), and provides a means to determine the dielec- used to characterize the concrete mixture throughout the entire tric properties of the material with time. An example plot of hydration process. Continuous data acquisition also allows for bulk resistance versus hydration time is shown in Fig. 17. A automation, so a large portion of the manual effort can be re- common feature is the inflection point, where the resistance moved. A disadvantage of the reflection method is that a trans- begins to increase significantly with time, concurrent with the ducer is required for each sample tested and the setup for mul- end of the dormant period and renewed hydration reactions. tiple specimens is somewhat costly ($10 K for an 8 channel Attempts by this author to correlate the time of the inflection system). Nevertheless, the method appears to be quite promis- point from mortars with the time of initial or final setting from ing and further development in this area could be quite fruitful. ASTM C 403/C 403M have not shown a clear relationship. An Fig. 16—Wave reflection factor (WRF) versus hydration time for a concrete specimen. Point “A” is where the WRF begins decreasing and corresponds closely with time of initial setting (after Subramaniam et al. [20]). Reprinted with permission. 96 TESTS AND PROPERTIES OF CONCRETE Fig. 17—Example of changes in bulk resistance of a mortar prism as a function of hydration time. Vertical line indicates time corresponding to the inflection point in the curve. example of the trends is shown in Fig. 18. The specimens, tion, as well as the connectivity of the pore network, both of which were retarded, exhibited significant bleed water, which which can change independently [28,29]. Therefore, this may have adversely affected the test results. Torrents et al. in- method may not be sufficiently sensitive for some applications. vestigated cement pastes with electrical means and the Vicat needle [31]. Reasonable correlation was found between the re- Rheological Methods gion defined as “beginning,” but poor correlation for the re- Struble and coworkers appear to be the primary group in- gion referred to as the “end.” vestigating the relationships between rheological changes A disadvantage of the equipment for making IS measure- and the setting characteristics of portland cement systems ments is equipment cost ($15 K), which could limit its wide- during hydration [33–35]. With the use of a constant stress spread use. Furthermore, the resistance of the specimen has rheometer in a regime below the yield stress, they observed shown to be dependent upon the resistance of the pore solu- two regions of yield stress in cement pastes. The first corre- Fig. 18—Comparison of time of setting determined by ASTM C 403/C 403M versus the time of the inflection point in the electrical resistance versus time plot. CHRISTENSEN ON TIME OF SETTING 97 lated with the induction period and the other with the ac- References celeratory period, with the time of the transition corresponding to the time of initial setting by the Vicat needle [33]. In [1] Scripture, E. W., “Setting Time,” Significance of Tests and Prop- another study, they developed a dynamic rheology test and erties of Concrete and Concrete Aggregates, ASTM STP 169, ASTM International, West Conshohocken, PA, 1956, pp. 53–60. compared the oscillatory shear behavior to the features in [2] Kelly, T. M., “Setting Time,” Significance of Tests and Properties ASTM C 403/C 403M and C 191 [34]. Good agreement was of Concrete and Concrete Aggregates, ASTM STP 169A, ASTM observed up to the torque limit of the rheometer, but they International, West Conshohocken, PA, 1966, pp. 102–115. were unable to follow the rheological behavior to the time [3] Sprouse, J. H. and Peppler, R. 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O., “Impedance [39] Apih, T., Lebar, A., Pawlig, O., and Trettin, R., “Continuous Spectroscopy of Hydrating Cement-Based Materials: Measure- Monitoring of the Zinc-Phosphate Acid-Base Cement Setting ment, Interpretation and Application,” Journal of the Ameri- Reaction by Proton NMR,” Journal of Applied Physics, Vol. 89, can Ceramic Society, Vol. 77, No. 11, 1994, pp. 2789–2804. No. 12, 2001, pp. 7784–7790. [29] Christensen, B. J., Mason, T. O., and Jennings, H. M., “Influence [40] Brooks, J. J., “Prediction of Setting Time of Fly Ash Concrete,” of Silica Fume on the Early Hydration of Portland Cements ACI Materials Journal, Vol. 99, No. 6, 2002, pp. 591–597. 12 Bleed Water Steven H. Kosmatka1 Preface and durability of the concrete near the surface. Excessive bleeding also delays finishing as finishing should not proceed with ob- THE SUBJECT OF BLEEDING WAS BRIEFLY AD- servable bleed water present. On the other hand, lack of bleed dressed in the first edition of ASTM STP 169, published in water on concrete flat work can sometimes lead to plastic 1956. Ivan L. Tyler, manager of the Field Research Section of shrinkage, cracking, or a dry surface that is difficult to finish. the Portland Cement Association, concisely described the gen- The first reported case of bleeding in North America was eral significance of tests for bleeding in his article on Unifor- in 1902 during the construction of the stadium at Harvard mity, Segregation, and Bleeding in the Freshly Mixed Concrete University [1,2]. During placement, up to 2/3 m of bleed water section of ASTM STP 169. ASTM STP 169A and ASTM STP developed. Up to 150 mm of concrete was removed from the 169B did not address bleeding. ASTM 169C had a chapter sim- top of each lift prior to the sequential placements in order to ilar to the one presented here. The effects of concrete ingredi- remove the less durable and weaker concrete. Even with the ents on bleeding as well as the significance of bleeding with high degree of bleeding, this structure survived the elements modern concretes are presented in this chapter. This chapter for over 100 years and will be serviceable for many years to also reviews the standard ASTM test methods on bleeding and come (Fig. 2). Structures in which severe exposures exist and provides data on the bleeding characteristics of a variety of ce- in which porous concrete was not adequately removed have ment pastes, mortars, and concretes. not performed as well as structures from which the bleeding- damaged concrete was properly removed. Introduction During the construction of massive structures, such as deep foundations, tall walls, or dams, bleeding became of con- Bleed water is the clear water that can gradually accumulate at cern in early concrete projects. To study and help control the surface of freshly placed concrete, mortar, grout, or paste bleeding, a variety of bleeding tests were developed. These tests (Fig. 1). Bleed water is caused by sedimentation or settlement of will be discussed later under the section on Test Methods. By solid particles (cement and any aggregate) and the simultaneous understanding the process of bleeding, Powers [3] and others upward migration of water. This upward migration of water and provided means to control bleeding and today bleeding is its accumulation at the surface is called bleeding, also referred rarely a problem. to as water gain, weeping, and sweating in some countries. A Bleeding can occur at any time during the transportation, small amount of bleeding is normal and expected on freshly handling, and placing of concrete, as well as shortly after place- placed concrete. It does not necessarily have an adverse effect ment. Most of the discussion in this chapter will focus on con- on the quality of the plastic or hardened concrete. However, ex- crete after it is placed in a form and will no longer be agitated. cessive bleeding can lead to some performance problems with This chapter will address the effects of concrete ingredients plastic or hardened concrete. With proper mix proportioning, and placing practices on bleeding and the effect of bleeding on mixture ingredients, placing equipment, and proper construc- various concrete properties. Much of the discussion pertains to tion practices, bleeding can be controlled to a desirable level. cement paste or mortar as bleeding in concrete is a direct function of the paste or mortar bleeding properties. Significance Fundamentals of Bleeding Bleeding is not necessarily a harmful property nor is excessive bleeding desirable. Because most concrete ingredients today A fresh concrete mixture is merely a mass of concrete ingredi- provide concrete with a normal and acceptable level of bleeding, ents that are temporarily suspended due to the agitation and bleeding is usually not a concern and bleeding tests are rarely mixing of the material. Once the agitation stops, the excess performed. However, there are situations in which bleeding water rises through the plastic mass to the surface or, more properties of concrete should be reviewed prior to construction. appropriately, the solid ingredients settle. Although the actual In some instances lean concretes placed in very deep forms have volume of the total ingredients does not change, the height of accumulated large amounts of bleed water at the surface. This the hardened concrete is less than the original plastic height as not only creates a placing problem but also reduces the strength the bleed water will come to the surface and evaporate away. 1 Staff Vice President, Research and Technical Services, Portland Cement Association, Skokie, IL 60077-1083. 99 100 TESTS AND PROPERTIES OF CONCRETE Fig. 1—Bleed water on the surface of a freshly placed concrete slab. The accumulation of water at the surface of a concrete As bleeding proceeds, the water layer at the surface main- mixture can occur slowly by uniform seepage over the entire tains the original height of the concrete sample in a vessel, as- surface or at localized channels carrying water to the surface. suming that there is no pronounced temperature change or Uniform seepage is referred to as normal bleeding. Localized evaporation. The surface subsides as the solids settle through channels of water coming up through the concrete, sometimes the liquid (Fig. 3). Fig. 4 illustrates a typical bleeding curve re- carrying fine particles, is termed channel bleeding and usually oc- lating subsidence of the surface to time. The initial subsidence curs only in concrete mixes with very low cement contents, high occurs at a constant rate, followed by a decreasing bleeding water contents, or concretes with very high bleeding properties. rate (Fig. 4). Fig. 2—Harvard University stadium after 90 years of service (photo courtesy of Tim Morse). KOSMATKA ON BLEED WATER 101 Fig. 3—Demonstration of bleeding or settlement of cement particles in cement paste with water-cement ratios by weight of 0.3, 0.7, and 2.2 (left to right). All cylinders contain Fig. 4—Typical bleeding curve for concrete illustrating 250 mL of paste and were photographed 1 h after the paste surface subsidence with respect to time [3]. was mixed and placed in the cylinders. Observe the accumulation of bleed water for pastes with the higher water-cement ratios. paste within the concrete is greater than it is for paste alone. This is due to the greater unit weight of the concrete. Consequently, In the interval between the beginning of subsidence the hydraulic force induced by the aggregate in the concrete dis- and setting, there are three primary zones describing the rupts the paste structure more so than in paste alone. Because nature of the bleeding process (Fig. 5). These are the zones of of this, channeled bleeding develops in concrete sooner than it (1) clear water at the sample surface, (2) constant water content does in paste alone and it develops at lower water-cement ratios or density, and (3) compression. Figure 5 is a simplified version for concrete than for paste. The rate of bleeding in a concrete of a five-zone analysis of the bleeding process of paste presented mixture is controlled by many variables that will be discussed by Powers [3]. In the zone of constant water content, the water- later under the section on Effects of Ingredients on Bleeding. to-cement ratio and density are essentially constant, even Bleeding capacity is the quantity of bleed water that a par- though some water is moving through the zone. The compres- ticular concrete, mortar, grout, or paste mixture can release to sion zone is a transition zone where the paste is being densified. the surface with respect to a certain depth. It is usually expressed The water-to-cement ratio is also being reduced and the solid in terms of the settlement or change in height of the paste- or particles represent a lesser volume than when originally placed. mortar-solid’s surface per unit of original sample height (or, in The paste densifies until it stabilizes and stops settling or bleed- other words, the ratio or percentage of the total decrease in sam- ing. At equilibrium, the paste achieves a stable volume and the ple height to the initial sample height). Bleeding capacity can degree of consolidation in this fresh state dictates the hardened also be expressed as a percent of the mix water. Figure 7 illus- properties of the paste, such as strength and durability. trates the bleeding capacity for pastes with a range of cements Bleeding is often analyzed in terms of bleeding rate and and water-cement ratios. Table 1 shows bleeding capacities for bleeding capacity. Bleeding rate is the rate at which the bleed concrete and mortar. Figure 8 demonstrates these data in com- water moves through the plastic concrete, mortar, or paste. parison to paste. Bleeding capacity is directly related to the wa- Bleeding rate can be expressed in terms of cubic centimetres ter and paste content of concrete mixtures. Higher water con- of bleed water per second per square centimetre of sample sur- tents especially increase bleeding capacity. As expected, bleeding face, centimetres per second, millimetres per second, or other capacity is closely related to bleeding rates (Fig. 9). applicable units. The bleeding rate of pastes with different cements and water-to-cement ratios is shown in Fig. 6. The rate Duration of Bleeding of bleeding is controlled by the permeability of the plastic paste. As the solid particles settle, the flow of water is con- The length of time that the concrete bleeds depends upon the trolled by the permeable space or capillaries between particles. depth of the concrete section as well as the setting properties The bleeding rate of concrete is less than that of paste alone of the cementitious materials. A thin slab of concrete will set- with the same water-cement ratio. However, this would be ex- tle or bleed for a shorter period of time than a deep section of pected as the aggregate in the concrete replaces some of the vol- concrete. Likewise, a concrete that sets up quickly will bleed ume of the paste. The velocity of the water moving through the much less than a concrete that takes many hours to set up. 102 TESTS AND PROPERTIES OF CONCRETE Fig. 5—Illustration of the process of bleeding in cement paste. Most bleeding occurs during the dormant period, when ce- Effects of Bleeding on Plastic Concrete menting materials have little to no reaction. The dormant period is commonly around an hour. However, chemical and Volume Change mineral admixtures as well as different compositions and fine- Combining cement, water, and aggregates in a mixer creates a nesses of cements can greatly affect the dormant period. Fig- disbursed and suspended state of particles in plastic concrete. ure 10 illustrates the increase in bleeding with increased paste This suspended state is not stable because the heavier particles height and dormant period. of cement and aggregate are forced downward through the Fig. 6—Range in relationship between bleeding rate and Fig. 7—Range in relationship between bleeding capacity water-cement ratio of pastes made with normal portland ce- (total settlement per unit of original paste height) and water- ment and water. The range is attributed to different cements cement ratio of pastes made with normal portland cement having different chemical compositions and finenesses [4]. and water. The range is attributed to different cements having different chemical compositions and finenesses [4]. The amount of volume reduction is clearly of physical and chemical reactions occurring during the first demonstrated in Fig.019 0.05 % to 1 % for portland cement pastes at a water-cement ratio of 0.75 mm) 1:0. However. disrupted during hydration. such as warm windy days.266 0.028 1:1.. Water-Cement Cement: Sand: Ratio by Mass. 9—Relationship between bleeding rate and bleeding unit of paste in the mix compared with the bleeding capacities capacity for cement paste using a variety of cements.009 0. the gel coating on cement grains. is to support. may exert enough pressure to cause the sample to increase in volume. In effect.9:2.688 0. the volume after bleeding will be less than void between the concrete surface and the object the concrete that of the original plastic mixture.0 0. mately 100 data points were used to develop the range [4].570 0.6 0.8 0. matter decreases.. Typical one-day expansions range from 0. Approxi- of neat pastes of the same water-cement ratio.40 119 0. expansion occurs within the evaporation is sufficient to remove the bleed water as it comes paste.042 1:1.6:2.019 0.446 0.43 203 0.304 0. 0.018 0. 0.614 0.41 . such as a machine base. 0.53 229 0. Most of this expansion occurs within the first day.45 . Expansion beyond the first Fig..012 0. Settlement can occur even though bleed water is not observed at the surface. This postbleeding expansion is caused by a combination to the surface. . applications in which concrete is being placed the disbursed solids is replaced by water.8 0. stages of setting..034 1:1.020 1:1.2:1.314 0.034 1:2.2 0. Although the total volume of materials is should have little to no bleeding to prevent the formation of a relatively constant.506 0. of the freshly placed concrete.. As the surface of tions.4:3.323 0.4 0.34 .85 0. mm Capacity. This is be. The downward movement of the solid The small amount of settlement or volume reduction is not particles continues until settlement ceases when the particles of concern for most general construction practices or applica- are in contact with one another and densify.60 0.38 by weight [5. 4 in terms of settlement of the surface.374 0. Bleeding also increases the risk of plastic settle- The total amount of settlement is proportional to the depth ment cracks over embedded items such as reinforcing steel.38 213 0.019 0.. p (H)/ p CONCRETE (AGGREGATE: 75 m TO 19 mm) 1:0. Postbleeding Expansion cause on many occasions. 0.49 203 0.4 0. ture proportions are by mass [3].. 8—Bleeding capacities of mortars and concretes per Fig. the volume of solid under an item that it must support. KOSMATKA ON BLEED WATER 103 TABLE 1—Bleeding Capacities of Concretes and Mortars [3] Mix by Mass..037 lighter water by gravity.009 0.028 1:1.8:1.2 0.38 . Approximate Bleeding Paste per Unit Gravel w/c Slump.011 0. Concrete mix.6:2.013 0.041 1:2.31 102 0.013 0.028 1:1. H Volume.6].041 MORTAR (AGGREGATE: 75 m TO 4. the rate of Following the bleeding period. 38 a Type I cement was used with a water-cement ratio of 0. The amount of bleeding and surface evaporation much less than that for paste alone or even nondetectable. plastic shrinkage occurs.10 0.05 % mixture. The bleeding period ended at 1 h and 12 min bleeding and surface evaporation as well as consumption of the and the expansion began at 1 h and 30 min.04 0. %/h Total Expansion. The age at the beginning of the expansion was 1 h 30 min. This shrinkage results from a loss of free water in the within the first day and is not likely to add more than 0.14 3 1/2 to 4 1/2 0. 10—Bleeding time versus height of paste sample for cements with different dormant periods [4].02 0. is shrinkage that occurs before the concrete has hard- day can be expected to be less than half of that which occurs ened.10 2 1/2 to 3 1/2 0.104 TESTS AND PROPERTIES OF CONCRETE TABLE 2—Post-Bleeding Expansion of Cement Pastea [5] Observed Rate of Age Interval. autogenous rate. 11—Plastic shrinkage cracks in concrete (photo courtesy of the Portland Cement Association). Fig. h Expansion. rate of evaporation at the sample surface exceeds the bleeding merged continuously during the test. If the must also be realized that the samples in Table 2 were sub.20 5 1/2 to 6 1/2 0.18 4 1/2 to 5 1/2 0. Otherwise. The age of the paste at the end of the bleeding period was 1 h 12 min.22 6 1/2 to 23 1/2 0. Plastic Shrinkage Plastic shrinkage. The water loss and resulting shrinkage is caused by a expansion. sometimes called setting shrinkage in older literature. It must be realized water by the cement during hydration (autogenous and chemi- that the amount of expected expansion for concrete would be cal shrinkage). % 0 to 1 1/2 0 0 1 1/2 to 2 1/2 0. Expansion is expressed as the percent of the depth of the sample.02 0.04 0.01 0. . cantly contributing to autogenous shrinkage are a concrete’s Fig. It predominantly control the amount of plastic shrinkage. Table 2 illustrates the postbleeding expansion of a combination of loss of free water from the concrete due to cement paste.38 by mass. The three factors most signifi- shrinkage opposes the expansion as the cement hydrates. velocity. plastic shrinkage and higher bleeding characteristics as well as the use of fibers. volume change induced by plastic shrinkage. amount of bleeding. At this stage. KOSMATKA ON BLEED WATER 105 chemical shrinkage. they often do not The disappearance of the water from the surface of the con. Plastic shrinkage cracks can pene- shrinkage cracks in the concrete that resemble parallel tears trate from one fourth to full depth of a concrete slab. concrete temperature. Plastic shrink- crete indicates when the rate of evaporation has exceeded the age cracks can also be reduced by the use of concrete with bleeding rate. Evaporation rates exceeding 1 kg/m2/h are prone to induce plastic shrinkage cracks in concrete (adapted from Ref [7]). Shortly after this time. hinder performance of nonreinforced concrete. ates tensile stresses near the surface. and wind velocity on the rate of evaporation of surface moisture from concrete. Consequently. and plastic sheets controlled by the air temperature. tion and removal of the bleeding water from the concrete cre. the concrete has obtained a contribute significantly to total plastic shrinkage for concretes small amount of rigidity yet is unable to accommodate the rapid with water-cement ratios greater than 0. Fig. and time of harden. relative humidity. windbreaks. Although (Fig. plastic shrinkage cracks may be unsightly.42 [28]. The evapora. The time required to obtain this condition is evaporation retarders. relative humidity. Autogenous shrinkage is very small and usually does not the concrete (Fig. 12—Nomograph demonstrating the effect of concrete and air temperatures. These tensile stresses can The best way to prevent plastic shrinkage cracking is to pull the concrete away from the form as well as form plastic prevent surface evaporation. shades. tensile stresses develop and plastic shrinkage cracks form. 12). cracking occur. wind or wet burlap covering the slab. 11). . and bleeding characteristics of ing. This results in a lower rate of evaporation of bleed ter-cement ratio. The paste continues to settle in between the stabilized tual water-cement ratio of most of the concrete mixture in place. and bottom of a 12-m-deep caisson had sification of particles occurs. some of the water leaves the concrete and rises to the surface at Hoshino [10] demonstrated the effect of bleeding on strength. which time it evaporates away. bituminous concrete. a den. the sections on Durability and Removing Bleed Water). bleeds noticeably more than concrete placed on a granular base. The aggregate can settle only higher water-cement ratio than the rest of the concrete. Because the degree of Concretes with high cementing materials contents consolidation or settlement is not uniform throughout the (around 500 kg/m3) or that use silica fume or low water-to. espe- admixture can be used to offset slower setting time associated cially in the lower part of the placement. they have little to no also reduces strength. The top. scaling. the concretes with water-to-cement ratios of 0. reduction of cement Thixotropic Mixtures particles. aggregate particles (Fig. Matsushita and Sue [30] demonstrated that in the occurrence creased and that particular concrete should be removed in of a cold joint. Concrete must never be finished with visible bleed water on the surface as such practices promote dusting. special care and planning should be used when differences in bleeding rates are caused by isolated vapor barrier locations.7 by weight. They exhibit a cohesive nature and. they squeeze some of the water out of the paste. be. bottom than at the top. and other surface defects [9]. cement ratio and increases the strength. Thixotropic mix. In addition. occurs.42) aggravate plastic top). and 2441 kg/m3. the water may With regular concrete. bleeding. However. effect. The use of a freezing-weather settle. densities of 2400. 13). For example. This practice. and increase in water content in the upper portion of Thixotropic mixtures of concrete. 13—Cross section view of concrete illustrating bleed bleeding-induced low-strength concrete of poor durability (see water accumulation along a coarse aggregate particle. However. such as clay. 2435. Therefore. bleeding should not be so excessive as to interfere with the finishing operation. the water and about 100 mm of surface concrete should be removed prior to placing the next lift. or vapor barriers. although not usually needed for concrete with normal bleeding. water-cement ratio of the surface concrete may actually be in. thus minimizing the differential Strength and Density between the temperature of the concrete and the ambient tem. Separation between paste and aggregate due to bleeding properties. The strength of hardened concrete is directly related to the wa- perature. 3 and 5. normal bleeding is beneficial in reducing the ac. metal-deck forms. excessive bleeding of low-cement-content mixtures may cause undesirable early segregation during transportation and placement. the accumulation of bleed water around aggregate particles cause of the ingredients in the mixture. This is illustrated in the left cylinder in Fig. An example would be in the use of supporting grout under machine base plates [8]. blisters. This lowers the water- with a cooler concrete temperature.6 and 0. This is especially prone to hap- ened concrete or mortar. aggregate particles. if the concrete is sealed or trow. As the solid particles in the paste or concrete water from the concrete surface. where excessive bleeding occurs. however. As illustrated in Figs. mortar. Paste-Aggregate Bond tures are important in applications where the volume of the Bleed water can accumulate under and alongside coarse fresh concrete or mortar must equal the volume of the hard. Placing and Finishing Normal bleeding usually does not interfere with the placing and finishing of concrete mixtures. Some minor bleed water is desirable to help keep the surface paste moist and help provide lubrication during the finishing of concrete. height of a sample (more consolidation at the bottom than the cementitious material ratios (less than 0. plastic sheeting. or grout have low the concrete. Effect of Bleeding on Hardened Concrete age cracking can be controlled in cold weather by lowering the temperature of fresh concrete. This applies to most of the illustrating strength increase with depth for normal-strength concrete depth. This phenomenon also contributes to a weakening of the paste due to bleeding. middle. eled before the bleed water comes to the surface. the strength of an element can be increased by extreme situations. If excessive bleeding occurs between lifts in a wall placement. removes Fig. As the solid material compresses. The differential consolidation effect is usually identified by Water-Cement Ratio an increase in concrete density. Concrete placed on a sub-base of low permeability. 3. . the strength can be expected to be slightly higher at the shrinkage crack development. a differential settlement between be trapped under the surface creating a weakened zone with a the paste and aggregates occurs. which contains a paste with thixotropic properties. In most until point-to-point contact (bridging) between aggregates applications. Usually bleed water is allowed to evaporate away before finishing commences.106 TESTS AND PROPERTIES OF CONCRETE Senbetta and Bury [33] demonstrated that plastic shrink. respectively [29]. a caisson place- The water-cement ratio of a concrete mixture before bleeding is ment in the Chicago area illustrates the consolidation/density higher than after bleeding. removing bleed water from the lower layer of concrete. flowing concrete expe- bleed water have a tendency to collect under large objects in riencing excessive bleeding. . small amount of small air void above the aggregate particle. Corrosion can the sides of coarse aggregate. leaving a ment to which they are exposed. Once the aggregate can no longer settle. Bleed-water channels also tend to migrate along presence of moisture. 15—The effect of concrete settlement on the bond strength of horizontally embedded deformed bars using ASTM Test Method for Comparing Concretes on the Basis of the Bond Fig. KOSMATKA ON BLEED WATER 107 pen when differential settlement occurs between the aggregate However. related to the permeability and water-cement ratio of the This can result in a condition called “mortar flaking” over the concrete. Dusting of a concrete surface can also develop. 14—Imprint in concrete illustrating the collection of Developed with Reinforcing Steels (C 234). and possibly continues to settle allowing bleed water to rise and collect under promote corrosion of the steel at void locations—especially in the the aggregate. This is because not only does demonstrated in a study of plasticized. contributed A minor collection of bleed water or settlement under rein. This reveals the poor bond at the between the top and bottom of the specimen. chlorides. and allow aggressive materials Paste-Steel Bond to enter the concrete. paste-steel bond. Concrete slump was 50 to 125 mm. acids. Another phenome. the concrete pulls away below the surface and areas of high water-cement ratio were from the steel leaving an air void and an easily accessible lo. if the concrete’s surface mortar sets faster Durability than the rest of the concrete due to hot weather conditions. Sometimes. but as the concrete settles. Bleed channels extending 12 mm concrete. The weakened surface layer cation for water to collect. induced by bleeding. A broken fracture face of a horizontally oriented For plain and deformed bars. 16). abrasion. 15). and sulfates are directly not have the strength or durability of the surrounding mortar. bond stress was reduced with crack from a vertical placement demonstrates the reduced settlement. This condition can partially be resistive paste. Fig. Bar diameter was 19 bleed water voids under a smooth steel bar held firmly in a mm. Some differential bond stress face (opposing face) will expose the socket or imprint of the can also be attributed to differential strength development aggregate in the paste. and sulfate resistance. the paste reduce bar embedment strength. Durability and concrete’s resistance to Upon rapid evaporation. An increase in water-cement ratio and permeability coarse aggregate particles. Welch and Patten [11] demonstrated the effect of reduced by revibrating the concrete after some bleeding has bleeding or settlement on the bond stress of reinforcing steel. or chlorides. this mortar dries out quickly and does aggressive chemicals. observed (Fig. excessive water collection and void development can and paste. Concrete mixtures are designed to be durable in the environ- some of the coarse aggregate particles might settle. underside of the aggregate particle. The upper portion bottom bars because more bleed water accumulated under top will have half-embedded aggregate particles. bleeding does not reduce durability. As expected. and high water-cement ratio. Weakened surface layers forcement is not detrimental to strength development in the bar can sometimes delaminate upon exposure to impact or because most of the stress is applied to the bar deformations. A normal. The top and bottom horizontal position during and after placement [2]. deicer- scaling. caused by excessive bleeding would reduce freeze-thaw. however. occurred. top bars developed less bond than paste-aggregate bond caused by bleeding. whereas the lower bars than bottom bars (Fig. to poor deicer-scaling resistance [12]. 14). Bleed water is prone to collect under reinforcing steel and The relationship between bleeding and durability is other embedded items (Fig. bars were 75 and 230 mm above the sample base [11]. excessive bleed- non is the presence of flat particles near the surface that inhibit ing can have a serious effect if special precautions are not bleed water from entering mortar that is above the aggregate. observed by petrographic analysis. carbonation. This reduction of paste-aggregate occur because the steel is not in contact with the corrosion bond reduces concrete strength. possibly resulting in popouts or surface cracking. bleed water and air. Also. carbonation. Bleeding channels can carry lightweight materials to the surface that can reduce abrasion resistance as well as allow popouts to form. and avoiding hard troweling. The corrosion mechanism is most likely a carbona. this figure illustrates that in- porous due to excessive bleeding. creased bleeding or subsidence can actually improve scale re- and moisture would more readily reach the steel. The scale resistance of a concrete surface can be jeopard- ment despite the high pH of the bleed water and low levels of ized whenever the plastic material near the surface has its wa- chlorides. had evaporated away from the surface and after maximum tack. ter content changed or its ability to transmit bleed water is tion reaction involving carbon dioxide in the air and calcium hydroxide in the grout bleed water. In this crete was wood floated after maximum subsidence [14]. increased degrees of subsidence were ter collects under reinforcement steel. This reaction creates regions of low pH at the surface of the bleed water where the passivity of the steel is lost and corrosion subsequently occurs [31]. The poor quality concrete at the lift surface was caused by excessive bleeding and deteriorated due to frost action. A chemical analysis of bleed water indicates that channeled or uniform bleeding can leach alkalies up from the concrete to near the surface [13]. chlorides. in the presence of grout bleeding had occurred [14]. Upon evaporation of the water. Corrosion of reinforcement is more likely when bleed wa. an accumulation of alkalies can develop in the upper few millimetres of the surface. It must be realized. Figure 17 illus. If alkali-aggregate-reactive particles are in this zone. and curing practices. Higher scaling values indicate more scaling. The relationship between bleeding and scaling depends upon The rate of scaling numerical scale rating divided by the num- the placing. particularly corrosion pitting. however.108 TESTS AND PROPERTIES OF CONCRETE Fig. . air. finishing. Landgren and Hadley [27] found that AAR-induced popouts can be minimized by wet curing as early as possible. centimetres of a deep concrete section become significantly Contrary to common belief. inducing corrosion. thereby sistance for this nonair-entrained concrete. Scaling Fig. Con- trates the relationship between scaling and subsidence. The corrosion occurs in a sealed environ. the increased concentration of alkalies can aggravate alkali-aggregate reactivity (AAR). 17—The relationship between scaling and subsidence. A similar accumulation of alkalies can develop if the surface is sealed too early during finishing. protecting concrete from drying prior to finishing. if the upper few formed by increasing the rate of evaporation over the concrete. ber of cycles. 16—Deterioration at top of lifts in a dam from which the porous-nondurable concrete was not adequately removed prior to sequential lift placement. particular example. that this concrete was finished after the bleed water Grouted prestressing strands can experience corrosive at. or by sprinkling dry cement onto the slab to take up excess water to facilitate finishing. This condition should not be confused with area of surface mortar from the base concrete (Fig. shrinks slightly more than more scaling. the mortar drys out. . Mortar Flaking Mortar flaking resembles scaling or a flat popout. the surface mortar crete not receiving a final finish [14]. actually creates a water void beneath the surface. as it received the necessary water for proper Surface delamination here refers to the separation of a large strength gain. The 1/4- popouts caused by aggregate that swells excessively upon to 1-cm-thick surface delamination can occur in sizes ranging water saturation or freezing. from 10 to 100 cm in diameter. 19). Further deterioration to the surrounding mortar usually does Surface Delamination not occur. does not develop adequate strength for frost resistance. more than concrete finished after bleeding stopped or con- Upon repeated freezing in a wet condition. this weakened zone or water-filled void can scale off the surface. If Fig. in some cases. due to a lack of water for hydra. and. this is achieved by reducing the water-cement ratio or increasing the cement content of the surface material. 19—Mortar flaking over coarse aggregate (photo courtesy of the Portland Cement Association). Large flat coarse aggregate particles block the migration of bleed water to the mortar over the aggregate. It cannot penetrate through and merely accumulates under the surface. usually with a flat surface parallel to the concrete surface (Fig. KOSMATKA ON BLEED WATER 109 reduced. This accumulation of water either creates a weakened zone of paste or. Figure 18 illustrates that final finishing prior to the completion of bleeding significantly increases scaling. Con- the surrounding mortar. 20). crete with a final wood finish at 50 % subsidence scaled much tion. The water rises to the surface and hits the surface stratum of more impermeable cement paste. Steel troweling early seals the surface much more than wood floating. as with an unprotected surface on a concrete after 100 cycles of test. All samples received a wood float strikeoff. deteriorates and exposes the underlying coarse aggregate. The remaining exposed surface Fig. This can be done by finishing the slab prior to the accumulation of bleed water. It is identified by a loss of mortar over flat coarse aggregate particles at the surface. Upon freezing. 18—Effect of time of final finish on scale resistance of rapid evaporation occurs. Higher scaling values indicate hot windy day. Usually. 20—Delaminated surface caused by early finishing that trapped bleed water under the surface (photo courtesy of The Aberdeen Group). In some instances. .110 TESTS AND PROPERTIES OF CONCRETE Fig. The addition of cement to fa- cause of surface delamination is the accumulation of bleed wa. This allows planes of weakness to surface delaminates in sheet-like form. lamination can occur with interior slabs not exposed to freez. as the setting time will permit. two practices both reduce the settling rate of the surface and Upon the freezing of water in the void or weakened zone. resembles a scaled surface with coarse aggregate exposed. de. 21—Illustration of weakened zone or bleed water void under a finished surface. The reducing the water-cement ratio. forming a void. cilitate finishing also reduces the water-cement ratio. develop and bleed water to accumulate under the surface. Early Fig. These ter under the surface creating a void or weakened zone (Fig. Finishing operations should be delayed as long ing simply because of the large void under the finished surface. and the sprinkling of cement on The consolidation of a surface by floating and troweling to the surface should be avoided to minimize the risk of devel- too early squeezes the water out of the top surface layer oping a plane of weakness or void beneath the surface. 21). the make it more impermeable. 22—Blisters (photo courtesy of the National Ready Mixed Concrete Association). because of a potential change in water-cement ratio. concrete placement with nonuniform bleeding can possibly re- Delaminated areas. 24). An excess of fines or a lack of adequate vibration can also trap air under the finished surface [9]. A concrete neath the surface. Consequently. 23). illustrating the bleed that have different bleeding rates or different bleeding prop. As the bleed water moves upward Concrete Bridge Decks by Sounding (D 4580). blisters are usually 1 to 10 cm in diameter. In wall place- hammering. however. 1/4 to 1 cm thick. can be located by chaining. surface will create a lighter-colored surface. but before bleeding has stopped. steel troweling is especially prone to trapping bleed water be. and visibly rise above the surface. They usually occur during or shortly after steel troweling. sand streaks can form as the bleed water collects and outlined in ASTM Practice for Measuring Delaminations in rises along the form face. concretes placed adjacent to one another Fig. Delaminated ar. a ent circumstances leading to the entrapment. . Spaced a few centimetres or decimetres apart. They can form by the accumulation of water under the surface at particular locations—often at the top end of a bleed-water channel (Fig. it washes away eas produce a hollow sound upon impact and can often be some of the paste leaving behind a somewhat sandy appear- lifted off the base concrete with a knife or screwdriver. or by electro-mechanical sounding procedures all ments. KOSMATKA ON BLEED WATER 111 Fig. ance (Fig. If punc- tured while the concrete is plastic. sult in blotchy-colored areas of light and gray. along the form in long bleed-water channels. 22). Formation of blisters is usually an indication that the surface was finished or closed up too early. water void under the surface (photo courtesy of the Portland erties can induce a color change in the surface primarily Cement Association). 23—Cross section of a blister. They are more apt to occur on interior steel-troweled floors. Blisters can also form due to an excess of air in the concrete. Jana and Erlin [34] show project examples that bleeds enough to increase the water-cement ratio at the of delamination caused by trapped bleed water and they pres. Blisters Blisters are small bubbles of water that form under the surface during finishing (Fig. water will usually squirt out. still intact. Surface Appearance Uniform bleeding on flat work should not affect the color of the surface. Increases in cement content. Fig. The correlation be- in concrete have a major effect on the bleeding characteristics tween water-soluble alkalies in the cement and bleeding is not of concrete. The trend is that an increase in alkalies reduces bleeding. periods on bleeding. Bleeding is expressed as a percent of mix ure 10 illustrates the effect of cements with different dormant water [15]. the amount of bleeding decreases (Fig. . Cement The type. and fineness of cement can all influence bleeding properties. Any increase in the amount of water or the water-to-cementitious material ratio results in more available water for bleeding. The individual ingredients and the amount of each ingredient An increase in SO3 reduces bleeding [4]. chemistry. Fig. however. Water Content and Water-Cement Ratio The water content and water-cement ratio predominantly control the bleeding of concrete (Fig. 26). Only reactions that occur during the mix. it is difficult to isolate the effect of a particular property or chemical compound.112 TESTS AND PROPERTIES OF CONCRETE Fig. other factors such as the precipitation of gypsum and SO3 content probably have an overshadowing effect. Effects of Ingredients on Bleeding The amount of SO3 that can be leached from cement in a short time has been found to correlate rather well to bleeding. As the fineness of the cement increases. 27). Both bleeding capacity and bleeding rate are increased with increased water content. A one-fifth increase in water content of a normal concrete mixture can increase bleeding rate more than two and a half times [3]. as it relates to the reduction of water- cement ratio. Because the chemical and physical properties of cement are interdependent on one another in how they affect bleeding. This section will briefly review the effects of some good. also reduces bleeding (Fig. 25—Relationship between water-cement ratio and ing period or bleeding period will affect the bleeding rate. of these common ingredients and their proportions. 25). bleeding of concrete. content. 24—Sand streaks along a wall caused by excessive bleed water rising along the form (photo courtesy of The Aberdeen Group). rice husk ash.007 0.. .61 0.080 0.42 2. KOSMATKA ON BLEED WATER 113 Fig.22 0. of initial chemical reactivity occurring with the cement shortly Fly ash usually reduces bleeding.88 0.7 F C 0.40 7.6 E F 1.34 0. decreased water-cement ratio. % Bleeding..31 0.40 7. Control mixtures contained no fly ash.0 G C 0.. Bleeding tested as per ASTM C 232.44 2. Class F 1.12 0.053 0.48 .42 2.48 0. a Concretes had a slump of 75 to 100 mm and air content between 6 and 7 %. Most of the fly ashes reduce bleeding compared to the concretes with cement only. The Fly ash. Bleeding is expressed here as a percent of mix water [15].41 .. 27—Relationship between cement content and eter on bleeding capacity of paste.41 4.004 0.3 I C 0.89 0. The correlation between bleeding and heat liberation However. bleeding of concretes containing ten different fly ashes with re- tivity and heat-producing capacity and is considered an influ. Note that Wagner values bleeding of concrete.58 0.43 0 Average of Class C 0. mL/cm2 Material Ratio by Compared to 307 Identification (ASTM C 618) of Mix Water of Surface Mass.3 H F 0.028 0. 2 282 2. based on a 307 kg/m3 cementitious material content. % A C 0.43 ..42 2.011 0.3 C F 1. Test mixtures contained 75 % cement and 25 % fly ash by mass of cementitious material.3 D F 1.11 0. W/CM kg/m3 Control. This is not always the case.051 0. Tricalcium aluminate has a high degree of reac. 26—Effect of cement fineness by Wagner turbidim.18 0.022 0.067 0.059 0.0 B F 1.004 0..42 0. Table 3 compares the after mixing.45 4.035 0. silica fume...75 0. Fig. Class C fly ashes re- Supplementary Cementing Materials duce bleeding much more than Class F ashes in this study. as can be TABLE 3—Bleeding of Concretes With and Without Fly Ash [16]a Change in Mixing Water-Cementing Water Requirement Fly Ash Class of Fly Ash Bleeding. each material and different source all have varying demonstrates that bleeding can be reduced by a higher degree effects.036 0.044 0.13 0. kg/m3 1 307 1.43 . slag. The increased cement content reflects a are a little more than half of Blaine values [4].42 2. ability to reduce the water demand in the concrete to achieve creasing the amount of cementitious materials in a mixture. a particular slump.3 J F 1. spect to their water reduction and performance in comparison ence on bleeding properties. and natural pozzolans ability of fly ashes to reduce bleeding appears to be in their can reduce bleeding by their inherent properties and by in. to two controls. Control Cement Mixtures Content. Similar results have been found by other TABLE 4—Effect of the Specific Surface Area of Sand on the Bleeding Rate of Mortars [3] Water-Cement Ratio Specific Surface Area Reference Number by Mass Bleeding Rate. Aggregate observed with Fly Ash H. 28).490 60 126 50 0. represents only a small amount of the surface area within a ing capacity and have little effect on bleeding rate compared to concrete mixture. which has no effect on wa. ciable change in the minus 75-m material. The effect of slag on bleed. and 13 kg/m3 had bleeding capacities of 12. Silica- fume concretes with very low water-to-cementing materials ratios essentially have no bleed water available to rise to the surface. such as calcined clay or ground di. The control mix with 120 kg/m3 of portland cement had 11. Fly Ash J. 28—Comparison of bleeding concrete versus fly ash proportionately with the amount of ash in the paste. ness of the material is primarily responsible for the reduction of bleeding [20]. one study demonstrated that concretes with silica fume at dosages of 3.402 37 113 59 0. has little effect on the bleeding rate of mortar at four Calcined Natural Pozzolan for Use as a Mineral Admixture in different ranges of water-cement ratio. gate is only 5 % of the total surface area of the concrete atomite. the bleeding of concrete. a di.439 48 126 49 0. 7.508 60 113 61 0.9 %. primarily due to its extreme fineness. The total surface area of the aggre- Natural pozzolans.693 113 113 62 0. such concrete mixtures are prone to plastic shrinkage cracking if proper precautions are not taken to reduce or eliminate surface evaporation while the concrete is in the plastic state.431 43 86 52 0. pozzolan dosages at 30 and 50 % by volume of cementitious material resulted in bleeding capacities of 9. Consequently. Rice husk ash (also called rice hull ash) reduces bleeding Fig.490 63 99 57 0. This assumes that there is no appre- ter.452 47 113 60 0.668 121 99 58 0. and 3 mL. 106 cm/s of Sand. For example. consider a concrete mixture mixes with portland cement only.384 30 86 51 0. However. negligible [3].668 112 126 . Compared to a control with 20 mL of bleeding in samples 40 cm high.393 36 99 55 0. The primary influence is re. The fine- mortar water requirement of ASTM C 618 [16].114 TESTS AND PROPERTIES OF CONCRETE In a study on calcined kaolin clay in mass gravel concrete. However.9 % bleeding [18]. clay. or the fine- requirement of the ASTM Specification for Fly Ash and Raw or ness. respectively [19]. or other material pass- The retardation effect of the fly ashes did not correlate with ing the 75-m sieve can have a significant effect in reducing bleeding [16]. the bleeding of concrete. that contain a high amount of silt.4 and 6. respectively. aggregates Portland Cement Concrete (C 618) mortar test exists (Fig. Table 4 demon- rect correlation between concrete bleeding and the water strates that the specific surface area of the sand. cm2/cm3 47 0.477 52 86 53 0. with proportions of one part cement to six parts aggregate ing is primarily due to the fineness of the slag [17].443 50 99 56 0. The surface area of coarse aggregate is essentially lated to the pozzolan’s fineness and its effect on water demand. This is not surprising as the aggregate Ground granulated blast furnace slags can increase bleed. usually reduce bleeding. mixture. which increased water demand and Ordinary variations in aggregate grading have little effect on yet still reduced bleeding. also demonstrated a reduction in bleeding.393 32 126 48 0.646 114 86 54 0. 8. (coarse plus fine) by mass. Silica fume can greatly reduce bleeding. 29—The effect of entrained air on bleeding rate of paste control and Mixes 1 to 4 contain HRWR admixtures inducing [3]. Mix C is the Fig. aggregate.031 Control 2 0.58 171 215 3. % by Bleeding. the concretes with high-range water reduc- Chemical Admixtures ers have slightly more bleeding than the low-slump control. At a constant water-cement ratio. Bleeding. tend to increase bleeding due to the higher water content in the mix [32]. water reductions of 13. 30—Effect of high range water reducers on concrete bleeding when used to reduce water content.36-mm to duced bleeding. These mixes had more bleeding TABLE 5—Bleeding of Concretes With and Without Plasticizers (ASTM C 232 Bleeding Test) [22] Water-Cement Water Content. they Järvenpää [32] determined the relationship between likewise dramatically decrease the bleeding of concretes as il- aggregate fineness and pore area and bleeding in conjunction lustrated in Fig. ing. Nominal cement content is 223 kg/m3 and control water content is 157 kg/m3 [15]. As the threshold for the ability of an aggregate to Table 5 illustrates the effect of plasticizers on increasing hold mixing water is passed. KOSMATKA ON BLEED WATER 115 Fig. crete. A reduction in as gap-graded aggregates.060 sulfonate Naphthalene 0. but The most predominantly used admixtures are air-entraining significantly less bleeding than the high-slump control. researchers. 10. and 17 %. it is expected that they likewise reduce the bleed. ASTM C 232 bleeding expressed in percent of mix water. 10. These data compare concretes of equal with absorption tendencies and water-retaining capacity of slump. the flowing concretes with the cations. The effect of high-range water reducers or plasticizers is Aggregates that significantly increase paste content. mm Mass of Mix Water of Surface Control 1 0. it has been observed that entrained air reduces bleed. compares a high-slump versus low-slump control. between 175 and 225 mm. respectively. ment contents. 30. especially water content through use of a water reducer results in re- if the combined aggregate grading is missing the 2.47 143 215 1.5-mm sizes. plasticizers bleed more than the control. such similar to that of normal-range water reducers.47 143 75 1. can also increase bleeding. The relationship between air content and bleeding rate for than the control of the higher water-cement ratio and high paste is illustrated in Fig.059 sulfonate .143 Melamine 0. The admixture was added to increase slump to crete mixture. the bleeding tendency quickly slump without influencing the water-cement ratio and also increases. All the concretes have the same nominal water and ce- Because water reducers reduce the water content of a con. reduce the free water content in concrete significantly.27 0. but also the air-entraining admixture it. Aggregates that increase water demand. In laboratory and field appli. equivalent water-cement ratios. air-entraining agents reduce bleeding by inducing an air-void Figure 31 illustrates the effect of plasticizers on concrete system in the concrete. but significantly less ing.47 144 225 1. Bruere found that not only do the slump [22]. bleeding with two different cements used to make flowing con- self can slightly reduce bleeding rates [21]. 29.50 0. mL/cm2 Mix Identification Ratio by Mass kg/m3 Slump.59 0. When high-range water reducers are used to 9.09 0. such as crushed rock. At admixtures and water reducers. including a negligible reduction in bleeding with reduced particle size [10]. bleeding. than the flowing concrete in Table 5 because of a higher initial Special bleed-reducing admixtures based on cellulose de- water content. struction but are very effective for special applications. Mix C is the control and Mixes N. respectively. The influence of Placement Size and Height accelerating salt such as calcium chloride may be largely due The depth of a concrete placement directly affects the amount to the effect of its acceleration of setting. Calcium chloride tends to make cement paste more served especially in placements of low-cement-content con- susceptible to channeling. The increased fluidity increased bleeding. and X contain different plasticizers [12]. in the plastic concrete to induce cracks or zones of weakness TABLE 6—Effect of Calcium Chloride on Bleeding Rate and Bleeding Capacity [4]a ASTM C 150 Admixture Bleeding Time.085 CaCl2 38 146 0. Excessive bleeding in plasticized.040 II none 71 139 0. terial selection and mixture proportioning. strates the effect of different cement and admixture combina. Sodium chloride and calcium chloride both can reduce bleeding significantly. H I none 71 163 0. This phenomenon has been ob- in Table 6. M. These admixtures make concrete mixtures very cohesive and tions on bleeding. where many centimetres ferent chemical compounds and chemical admixtures affect of water can accumulate over a lift just a few metres deep.020 a Amount of CaCl2 was 1 % of the cement mass and about 2. the slump was 175 to 25 mm. Excessive bleeding can be avoided by optimal ma. These admixtures are rarely used for normal con- sistance [12]. Calcium chloride is commonly used as an accelerator in Effects of Placement Conditions on Bleeding nonreinforced concrete. Figure 31 demonstrates that increased fluidity rivatives. and 6 1 %. after the admixture addition. The initial slump was 75 to 125 mm and. regation. and air contents for all mixes were 323 kg/m3. . crete mixtures in deep dam sections. the amount of bleeding chloride on bleeding time and bleeding capacity is illustrated increases with sample depth. Bleeding Cement Type Addition min 106 cm/s Capacity. water. Little is known about how the dif.466 by mass. The nominal cement. 161 kg/m3.1 % of water.072 CaCl2 46 103 0. The effect of calcium of bleeding. as bleeding is not a required test in ASTM admixture The shape of vertical forms can produce sufficient strain specifications. B. Bleeding Rate.049 CaCl2 26 89 0. or various other chemical for- induced by the plasticizer increased bleeding and it demon. water absorbing resins.039 III none 46 129 0. As shown in Fig. flowing thixotropic and therefore are very effective at preventing seg- concrete can reduce surface durability and deicer-scaling re. The water-cement ratio was 0.116 TESTS AND PROPERTIES OF CONCRETE Fig. 31—Effect of plasticizers on bleeding of flowing concrete. mulations can significantly reduce or eliminate bleeding. 32. The greater the bleeding capacity of the concrete the greater the tendency of such faults and arches to form. 32—Relationship between the amount of bleeding dence at temperatures of 10. faulting can develop up from the corners of the narrow form. 23. In a test on 25 different cements. The opposite situation occurs when the concrete parti. This is primarily due to the decrease in water viscosity with an increase in temperature. some studies indicate along the vertical face. cles settle away from an outward incline where a layer of water Normal field vibration would not be expected to greatly affect can develop and collect along the sloped surface. Klieger illustrated that changes in temperature for concrete did not affect the subsidence of the surface [14]. Deep and narrow placements concrete. respectively. and bleeding capacity of the con. Bleeding can be reduced by placing 50 to 75 mm of compacted granular fill on the impermeable surface. All bleed water must rise to the surface when concrete is placed on an impermeable sub-base. . In general.5 to 32°C resulted in a 20 % increase in the rate of bleeding for cement paste. and sample height for concrete [10]. These faults can be eliminated by revibration. matrix as well as the decreasing degree of dispersion of the crete. the depth of the capacity. For example. At a wind velocity of zero for nonair-entrained concrete.2 % by mass of mix water for normal due to bleeding and settlement. Figure 33 illustrates how the increase in wind velocity and.502. Impermeable Sub-bases Concrete placed on sub-bases of low permeability such as plastic sheet vapor barriers. Obviously.456 mm for this concrete. Construction in which only parts of a placement are on a vapor barrier will need special care in finishing practices due to nonuniform bleeding in order to provide a uniformly durable surface. Whiting found bleeding of concrete at 23 and 32°C to be 2 and 3. however. Such condi. KOSMATKA ON BLEED WATER 117 Weather Conditions Weather conditions can have a significant effect on bleeding. bleeding at higher temperatures [12]. if a T section is filled in one placement. 33—Effect of wind velocity on subsidence [14]. The Surface or internal vibration should not significantly affect settlement along an inward incline would be less than that the amount of bleeding. aggregate and the expulsion of some of the entrapped air.454 mm. When concrete is placed on a granular material. bleeding [23]. The wind velocity and increased evaporation greatly increase the capillary force at the surface. there was little change in bleeding capacity with the change in temperature for most of the cements studied [4]. This is partly due to the reduced volume of the placement. and 32°C was 0. Consolidation and Revibration assume that the settlement along a vertical face is constant. pulling the bleed water out of the concrete. bituminous. consequently. rate of evaporation significantly increase the amount of surface subsidence. the bleeding capacity tends to be nearly constant.to 3-s vibration period can slightly increase the ment from one side of the form to the other. The average subsidence was 0. going from 23. tions can create localized bleed channels along the form resulting in sand streaks. Settlement can also form zones of weakness in forms that have areas of significantly reduced cross section. and 0.413. The addition of plasticizers in some cases reduced in which the walls are not parallel are more prone to settle. 0. rate of filling. the use of an internal vibrator in strain and possibly faults to form depending on the angle of concretes from 20 s to 10 min tends to reduce bleeding the slope. Fig. or clay appear to bleed noticeably more than concretes placed on granular sub-bases. The bleeding rate increases with an increase in temperature. the way to avoid this problem is to fill the narrow portion first and then place the rest of the concrete after the concrete in the narrow section has settled. This practice also helps control slab curling. For example. the subsi- Fig. some of the bleed water can flow out the bottom of the slab into the granular material. These situations can create stresses within the plastic concrete upon settlement and bleeding. however. ment strain. This would create some possible move. distance between the wall faces. that a 2. However. inducing shear bleeding capacity. Table 8 illustrates that particular cement pastes or by other means are capable of reducing the bleeding of remixed within the first hour bleed about the same amount as concrete. capacities compared to the first settlement.125 57 87 45 192 0. 3. MPa Increasing Bleeding The easiest way to increase the bleeding is to increase the 0 2. revibrated. remixing of the cementitious system after it has set. Increase the amount of cement resulting in a reduced wa- would be expected as removal of some of the bleed water ter-cement ratio. b This is the period after the initial mixing. Limits on the amount TABLE 7—Effect of Revibration on Bleeding of bleeding are not available. 106 cm/s Bleeding Capacity.5°C. Remixing 5. Reduction of the water content. This 2. Interval Before Bleeding. . minimize the forma- kg/m3. Just as revibration allows bleeding to occur after concrete is slag. The final remixing was 30 s continuously. and slump. little attention need be given to controlling bleeding of bleed water from a concrete surface if normal evaporation is concretes made of normal ingredients at normal proportions. note that the compressive strength was also increased. however. min of Bleeding. The most important ways of re- and settle again upon internal revibration of the concrete. 6. The schedule for the initial mixing was: 2 min mix. H Bleeding.9 28 amount of water in the concrete mixture as well as reduce the 1h 3. Use air-entrained concrete. % of Compressive Revibration Mix Water Strength. The aggregate was natural sand and Bleeding may need to be reduced for a variety of reasons.8 29 finished in dry weather.122 55 55 15 189 0.090 47 137 120 167 0. The cement content was 307 cluding to facilitate finishing operations. Increase the amount of fines in the sand. 2 min wait.075 45 165 a The water-cement ratio was 0. tled has a similar effect with little change in bleeding charac.118 TESTS AND PROPERTIES OF CONCRETE the bleeding to solve particular problems. after remixing.4 39 terials. water-cementitious mate- bleeding were obtained for revibration intervals up to 4 h. would have resulted in a lower water-cement ratio [23]. at the end of which the final remixing was done. resume its normal bleeding characteristics.469 by mass. The results for remixed pastes are averages of two or three tests. This demonstrates that concrete in a ready mixed truck for some period of time Removing Bleed Water can. acceptable bleeding rates and Strength of Concrete [24]a can be determined by test and correlated to field experience. Use supplementary cementing materials such as fly ash. This ducing bleeding in concrete are as follows: is illustrated in Table 7 where consistent degrees of additional 1. there is little time or opportunity to change the con- Controlling Bleeding crete mixture. However. minimize bleed-related corrosion in grouted tendons.113 55 70 30 196 0. If the concrete is placed within an enclosure. followed by 2 min mix. 7. or silica fume.106 52 97 60 185 0. The temperature was 23. this section will provide some guidance as to adjusting the temperature of the air can be increased and large fans can TABLE 8—Bleeding Tests on Remixed Pastes [5]a Time Between Duration of Initial Mix and End Rest Period. in- crushed trap rock with a maximum size of 25 mm. Reducing Bleeding a The cement was an ASTM C 150 Type I. Also rial ratio. Bleeding may need to be increased to help prevent plas- 3h 3. not satisfactory. Use blended hydraulic cements.b min Bleeding Rate.5 32 amount of the fines in the sand and amount of cementing ma- 2h 3. The depth of the paste was 36 mm. before remixing with only slightly reduced bleeding rates and 8. certain techniques can be used to remove excess Usually. The slump of the concrete was 75 mm. it can bleed plastic volume of the concrete. in wall forms. Use chemical admixtures that reduce water-cement ratio teristics. Therefore. especially once the concrete is in the forms. Compressive strength was estimated tion of weak concrete at the top of lifts.2 31 tic shrinkage cracking or to improve a concrete’s ability to be 4h 2. 4.103 48 108 90 172 0. min 0 194 0. Once the observation of bleed water has become a noticeable problem. or to stabilize the hardened volume with respect to the After concrete has completed its settlement. Increase the fineness of the cementitious materials. reduce sand streaking by impact hammer. priority grouts are used for grouting base in a container with a volume of about 0. In other applications.1. the concrete can harden and will not be able ment paste. mulation of bleed water is removed from the surface (Fig. Bleeding is reported as millil. bleeding properties of paste and concrete. and ASTM Test Method for Expansion and Bleeding of Freshly Mixed Grouts for Pre. pastes. capacity is reported as cubic centimetres of water per cubic cen. within the duct. Stoke’s law was also used in empirical rela- . mines the relative ability of grout to bleed. KOSMATKA ON BLEED WATER 119 be used to evaporate away some of the water. The upper sulting in potential plastic shrinkage crack development. a squeegee float consisted of a disk of lucite or bakelite to which a or garden hose can be used to drag the water off of the surface straight glass fiber was mounted like the mast on a sailboat. mm. Many of these relationships. permeability. which the surface level of the plastic volume of concrete. thereafter until bleeding stops. Because of the thixotropic structure of the ce- to evaporate away. water readings are taken every 10 min and every 30 min models for the bleeding rate and bleeding capacity for paste. and the cylinder is covered to prevent evaporation. so that finishing can commence. The float is used Test Methods both for paste. subsidence of the small area at the top of the sample. developed several mathematical min. or retain its water. and hourly thereafter until bleeding equipment that uses a filter mat placed on the surface of the stops. and concrete samples. 34. where must be taken when using this technique to not remove so 800 mL of grout are placed into a 1000-mL graduated cylinder much bleed water that the evaporation exceeds bleeding. This would include. mor- ASTM C 243 is based on a test method published in 1949 tar. ASTM C 941 is used to determine the water retentivity of uum pump. The ASTM C 243 test apparatus is shown in Fig. 36). pertaining itres of bleed water per square centimetre of surface. Method B uses a similar sample and apparatus. Another related ASTM standard is ASTM Test Method for Water Reten. mortars. Several nonstandard test methods have also been used cal applications such as wall forms. A layer of water is tlement or bleeding problems. The final bleeding is recorded as the amount of bleed wa- concrete. and a more abrasion-resistant surface. The water depth is about 6 mm deep. the float remains in a relatively fixed position at to be finished. One of the in the form prior to concrete placement that uniformly drain first was the Powers Float Method (Fig. the construction of superflat floors where nonuniform sample container is filled with mortar or paste. bleed water is ter decanted as a percentage of the original sample volume. For verti. The float Three standard ASTM test methods can be used to analyze the method was used in most of the early major findings on the bleeding properties of concretes. the end product is a concrete with a higher strength. Poisseuille’s law. As the mat settles with the surface. care ASTM C 940 is used to test the bleeding of grout. and concrete. Mortars (C 243—discontinued in 2001). The ample. Often. the top of the paste during settlement.1-trichloroethane to the top of the burette. quate strength development within the entire mass. grout for preplaced-aggregate con- nel are filled with carbon tetrachloride or 1. re.1. was used to measure settlement of bleeding by measuring the For normal concrete slabs experiencing occasional exces. forced up through the filter and the water is removed by a vac. special liners can be placed for analyzing the bleeding properties of concrete. ASTM Test Method for Bleeding of Cement Pastes and Association in the 1930s to 1950s. mortar. several re- is drawn off to facilitate water collection. However. Grout used tles and bleed water rises through the carbon tetrachloride or in post-tensioning ducts must minimize the formation of voids 1. Grout placed under base plates for machinery Bleeding rate is reported as cubic centimetres of bleed water or column applications must not allow bleed water to form per square centimetre of sample surface per second. including Powers. Special Applications placed-Aggregate Concrete in the Laboratory (C 940). and grouts. lower under pressure. The test essentially deter- crete more than would normally occur due to normal bleed. or grout must be maintained. The sample is temporarily tilted when the water Ever since Powers’s work in the 1930s on bleeding. with vibration to help consolidate the concrete mixture.1-trichloroethane. surfaces of the grout and bleed water are recorded at 15-min Vacuum dewatering can be accomplished by special intervals for the first hour. were based on Darcy’s law and percent of the mix water. or as a to the permeability of the paste. for ex- [25]. grout under vacuum atmosphere. Bleeding voids. This test method These are ASTM Test Methods for Bleeding of Concrete (C was used in most bleeding research at the Portland Cement 232). For precast concrete elements experiencing set. The collecting bleeding would interfere with surface tolerance. ing. it is desirable to eliminate the bleeding tivity of Grout Mixtures for Preplaced-Aggregate Concrete in capacity as much as possible. can be added to grout to prevent such bleeding and actually ASTM C 232 has two procedures—one with vibration and induce a small amount of expansion to help eliminate bleed- one without. Movement of the float was measured with a micrometer pletely stopped. During the first 40 searchers. Under some conditions. The burette and fun. Certain admixtures timetres of paste or mortar. However. The sive bleeding that is not removed due to evaporation. As the grout provides the support for these elements. for concrete. 35). crete must have a low level of bleeding in order to provide ade- which are liquids that are denser than water. Finishing should continue only The disk had a diameter of about 13 mm and a thickness of 3 after it has been ascertained that bleeding has nearly or com. along with a Mathematical Models clamped-on cover. If a finisher waits too long for the bleed water microscope. The float method away the bleed water without the formation of sand streaking. the sample diameter was at least 500 mm.014 m3 and the accu. a centrifuge can be used to com. plates [8]. mortar. ring is then placed to penetrate the sample. to prevent the development of capillary forces from evaporation. Method A allows the concrete to be undisturbed water voids. As the sample set. These are usually situations in the Laboratory (C 941). bleeding must essentially be eliminated. bleeding meas. due to bleed water in order to prevent corrosion of tendons urements are taken at regular intervals until settlement stops. Because this method consolidates a slab of con. placed on the surface immediately after the float is installed pact the concrete and remove the bleeding by centrifugal force. 120 TESTS AND PROPERTIES OF CONCRETE Fig. . 34—ASTM C 243 test apparatus to determine the bleeding properties of paste and mortar. Mortar Fig. V. April 1941. The Bleeding of Portland Cement Paste. C.. constant bleeding rate.. F. “Influence of Ground Granulated Blast Furnace Slag (GGBS) Additions and Time Delay on the Bleeding of Concrete. 253–257. W. 1986. 1954. Harvard University. [17] Wainwright. M. Feb. stant bleeding rate of paste.. IL. “Relationship Between Bleeding. and Dannis. Tests of Special Cements for Basic Research Program. IL. C. and Dziedzic. aggregate shape. 1967. MA. 130–136. A. Cement Association. Paper No. IL. 36—Powers float test for measuring bleeding. A. [26] used a self-weight consoli. aggregate ment Effected by Concrete Sedimentation. Portland characteristics of the bleeding process. the early equations to deter- [7] Menzel. [15] Whiting. A. and Specimen Height of Concrete. pp. H. pp. S. M. pp. Portland Cement Association.” Concrete International. 1941. 1926. 185–190.. As opposed to Powers’s consideration of bleeding as [8] Kosmatka. ASTM International. IL. No. J. H. and Rey.” Seisan Kenkyu. Skokie. Effects of High-Range Water Reducers on Some Properties of Fresh and Hardened Concretes. B. L. diminishes with time. K. Expansion of Pastes. Skokie.. 1992. Effects of Conventional and High- Range Water Reducers on Concrete Properties. RX004. 62. the bleeding rate Portland Cement Association. Cambridge.. N. In addition.. Portland Cement Association. and Uno. J. L. 59–65. F. and Klieger. Skokie. Tokyo. March-April 1989. IL. Powers Skokie. Major Series 290.” ACI Materials Journal. W. [6] Brownyard. By understanding its influences on plastic and hardened concrete properties and by understanding the effects of ingredients and ingredient proportions on bleeding. H. 1990.” Proceedings. 128–130. RX072. Skokie. not influenced by hydration of the cement. and Steinour developed equations relating to the initial con. 1989. 1945. PA.. RD089. [2] Mardulier. References [1] Johnson. 1956.. Skokie. Järvenpää [32] developed a bleeding model that considers [11] Welch. Based on Poisseuille’s law of capillary flow. is covered to prevent evaporation of the bleed water. dation model to express the relationship between the different [9] Panarese. J. Fig. 2000. M. IL. IL. Skokie. H. The container Cement Paste.. P.. “Causes and Prevention of Crack Development in mine bleeding capacity assumed that the bleeding process was Plastic Concrete.. and Concrete. By using the consolida. [3] Powers. L. aggregate surface area.. RD107. G. Portland Cement Association.. Portland Cement Association. merely sedimentation.. N. Junior Series 354. 2. The Effect of Atmospheric Conditions During the Bleeding Period and Time of Finishing on the Scale Resistance of Concrete. Harvard Engineering School. IL. B. Vol. were able to obtain very good agreement [10] Hoshino. KOSMATKA ON BLEED WATER 121 Conclusions Bleeding is a fundamental property of concrete.. H. Method A without vibration. “Properties of Mass Concrete Containing an Active Pozzolan Made from Clay. Further Studies of the Bleeding of Portland container is filled to a height of about 255 mm. bleeding can be economically controlled. Portland Cement Association. paste content. pp. Skokie. Tan et al. pp. and Paulon. [5] Steinour. J. Portland Cement Association. Portland Cement Association.. tion model. [12] Whiting. Skokie. mixture effects. The container has an inside July 1939. Concrete Institute. T. diameter of about 255 mm and a height of about 280 mm. T. Lecture Notes on Materials of Engineering. The Bleeding of Cement: Its Significance in Concrete. P. pp. 35—ASTM C 232 test for bleeding of concrete. and Patten. West Conshohocken. RX002. July 1982. Portland Cement Association. Coarse Aggre- with the bleeding process. Unfortunately. Dec. 41.. With proper control.” 22(4) Cement and Concrete Composites. IL. [18] Saad. Effect of Fly Ash on Some of the Physical Properties of Concrete. No. H. “Chemical Composition of Bleeding Water on Fresh Concrete. PA122. 1965. [14] Klieger. [13] Kobayashi. Pacelli de Andrade. RD061. bleeding should not hinder concrete construction or adversely influence concrete strength or durability. Cementitious Grouts and Grouting EB111. 1979. 2. . tionships. Skokie.. Y. D. 251–263. fines surface area. Vol. D.” Journal. Portland Cement Association. and ad. Skokie. C. S. “Bond Strength of Reinforce- mix proportions. even beyond the period of initial gate. Mortars and Concretes During the First 24 Hours. 1990. Cement Mason’s Guide. IL. Tan et al. 67. American porosity. [16] Gebler. P. The [4] Steinour.. IL. W. 196 pp. MI. S.. London. Civil Engineering and Building Construction American Concrete Institute. Illinois. R. C.” RILEM [27] Landgren. 2001. in Grouted Post-Tensioned Tendons. Melburn.” Concrete International. 2001. and 446. IL. Affect Viscosities and Bleeding Properties of Cement Paste. Skokie. H. Espoo. G. A. ASTM International. Erika E. C. Corrosion from Bleed Water Properties of Freshly Mixed and Hardened Flowing Concrete. E. L. Controlling their Effects on Concrete. S. 721–732. Early Age Autogenous Shrinkage of Concrete. Vol. “A Study on Relationship Between Australian Journal of Applied Science. Cracking During Cold Weather Concreting Using a Freezing p. Addison. and Schmidt. Espoo. Portland Cement Association. W.” Concrete Construction. 1. pp. VTT Containing Rice Husk Ash. and Schokker... Vol. J. pp. R. 1958. Foundation Elements. “Effects of Revibrating Concrete. 349–359. Commonwealth Condition of Placing on Consolidated Fresh Concrete and Oc- Scientific and Industrial Research Organization. G. D. H.. “Properties of Cement Paste [28] Holt. 1989. March 1991. The Properties of Fresh Concrete. Tan.. P. [21] Bruere. Slag.. E. “Bleeding of Concrete. January 2005. T. 9. and Wu. Entrained Air. 1990. and Bury. D. 891. 49. A. 2005. 1982... pp.. Vol. 1949. 1. No. 4. Series. H. A. “Control of Plastic Shrinkage Mixtures. A. Finnish Academy of Technologies. C. L. C.. No.. Quality Characteristics of Fine Aggregates and York..122 TESTS AND PROPERTIES OF CONCRETE [19] Scheissl. Brussels. 1958.. S. M. [22] Gebler.” Zairyo.” Fly Ash... 733–762.. Skokie. Portland Cement Association. pp. and Sue. solidation Model for Bleeding of Cement Paste. Jr. Surface Popouts Caused by Al- Colloquium of Properties of Fresh Concrete. Ci 122. RD137. 1987. Portland Cement Association. Silica Fume. Continuous Measurement of Bleeding in Portland Cement [33] Senbetta. D. RD117. R. R.. [23] Powers. Bowling. . 24 pp. C. Detroit. Wee. 18–26. J.. R. American Concrete [29] Burg. Thomas Telford Services Ltd. New [32] Järvenpää. and Erlin.” Advances in [34] Jana. 101–107. M. T. Technical Research Centre of Finland. D. Portland Cement RD081. The Effects of High-Range Water Reducers on the [31] Bricker. H. and Lee. L. 1999. currence of Cold Joint.. Scandinavica. [20] Hwang. IL. Tam. “Delamination: The Sometime Curse of Cement Research. 2002. and Hadley.” Proceedings. 851–856. T. “The Direct and 243 pp.. The kali-Aggregate Reaction. RD121. 2001.” [30] Matsushita. B. and Fiorato. 54.. Weather Admixture. pp. Y. pp. and Blaine. S. 50. 48–53. Hanley Wood. High-Strength Concrete in Massive Institute. A. Wiley. “A Con. [26] Tan. 8. European Cement Association. 77 pp.” Proceedings. M. Oct. Acta Polytechnica [24] Vollick.. SP-114... Vol. T. Skokie. 20 pp. Illinois. [25] Valore. 1968. Vol. S. Natural Pozzolans in Concrete. Association. Paper No. “Mechanism by which Air-entraining Agents Skokie. Illinois. E. pp. PART III Hardened Concrete . or application of prestressing. E. or nondestructive tests may be performed to esti- procedures. cement paste due to mechanical property differences and the sion resistance or strength of structural members. arrest crack growth. referred to collectively as gel. preparation of test specimens. correla. Carino2 Preface crete taken at job sites. ite. when voids [5]. Caution should be exercised. tions. When a nonstrength property is of primary interest. There are three main reasons for this. Hardened paste consists of poorly crystallized used to estimate other properties based on empirical correla. mate the strength from previously established correlations. that crystals of calcium hydroxide. P. First. 2 Consultant. trol problems for the concrete supplier or changes in ambient ries by C. consisting of cement paste and aggregate. and the loading method. Charlottesville. In construc. Kesler. Carrasquillo. hydrates of various compounds. strength un. The coarse • For quality control and quality assurance. Derucher. Finally. Kesler and C. the interfacial regions between them. existing standard test methods Introduction must be followed for reliable results. Failure of concrete Strength tests of concrete specimens are used for three occurs as a result of the development of a network of micro- main purposes: cracks that grow in length with increasing load to the point • For research. “Concrete Strength Testing” [4].13 Concrete Strength Testing Celik Ozyildirim1 and Nicholas J. significant factors affecting test results. these specimens [1]. Concrete can be considered as a two-phase compos- penetrability is of concern. strength re. rather than relying on a strength under load is a result of the interaction of the two phases and correlation that can be misleading. Unfortunately. strength tests are conducted on specimens made from con. a test related directly to penetra. nondestructive and in-place strength testing in. unhydrated cement. Strength tests are used to obtain reference values when exist in concrete at the interface of coarse aggregate and other characteristics of concrete are being studied. which binds together coarse and fine aggregate to form tests. “Strength” [2]. specimen preparation. In cases previous authors by introducing new developments since STP where the strength of the in-place concrete is in doubt. When appropriately cured in place. “Static and Fatigue Strength” conditions. ing of concrete specimens are discussed in later sections. Second. by K. erty. and its behavior bility should be conducted. These pre-existing tion. or combinations of these. however. ous materials or mixture proportions on the strength of con. the strength of concrete gives a direct indication of its capacity to This section discusses the nature of concrete strength and resist loads in structural applications. This chapter provides information on the mens may be cut from existing concrete placements and tested nature of concrete strength. test for strength. Virginia. Seiss. Virginia Transportation Research Council. The current chapter augments the topics addressed by these removal of formwork. those factors involved in the fabrication of the specimens that compressive. where the concrete cannot support further load. Maryland. Therefore. Results obtained by testing a given concrete will depend der combined stresses. The most common concrete property measured by testing is Nature of Concrete Strength strength. Gaithersburg. Factors involved in the test- strength tests are relatively easy to conduct. by C. concrete strength is not an absolute prop- cluding maturity and temperature-matched curing. ture is sufficiently strong for application of construction loads. and fatigue strength. occurrence of shrinkage or thermal strains. lationships. For example. ing the brittleness of concrete. N. such as abra. “Strength” can also be used to determine when the concrete in the struc- [3]. The latter feature is beneficial in reduc- In research. tests are used to determine the effects of vari. on specimen shape and size. whether they be tensile. tions can be developed relating concrete strength to other Reaction of cement with water forms hardened cement concrete properties that are measured by more complicated paste. 125 . microcracks are responsible for the low tensile strength of 1 Principal Research Scientist. Before external load is applied to concrete. and air property should be measured directly. either to determine the adequacy of the mixture proportions developed for the particular job or to THE TOPICS OF STRENGTH AND RELATED TESTING check for changes in strength that could indicate quality con- were covered in the previous editions of the ASTM STP 169 se. fine cracks crete. when strength is a solid mass. E. aggregate particles act as inclusions that can both initiate and • For determining in-place concrete strength. influence the measured strength. speci- 169C was published. and by P. shear. M. if con- the ultimate strength of concrete is related strongly to the crete is allowed to dry prematurely. cracks rials ratio (w/cm). Various factors affect paste stable up to about 30 % of the ultimate load. The use of ground granulated blast-furnace The process of microcracking and its relationship to the stress. As the w/cm is increased.126 TESTS AND PROPERTIES OF CONCRETE Fig. be used to alter paste performance. As ultimate strength is crease in voids in the paste. As external load is applied. interfacial cracks begin to increase in length. ting and strength development. while producing higher early some point. ther. When 70–90 % of the ultimate strength is reached. Up to about 30 % of the the paste strength and strength gain. as well as its strength- crete is related to the formation and growth of microcracks. affect both strain curve is illustrated in Fig. Thus. deviation from linearity ily). When micro. water-reducing interfacial microcracks begin to propagate. The shape of the compressive stress-strain curve of con. gain characteristics. The entrainment of air without cracks penetrate into bulk cement paste. curing temperature and approached. the curve starts ing admixtures reduce paste viscosity (make it flow more read- to deviate from linear behavior. hydration will cease before . mentitious materials also affects paste strength. and other admixtures can be used to regulate time of set- increases as more interfacial cracks are formed. and so does its strength. At High early curing temperatures. Fur- required for additional strain decreases. such as fly ash and silica fume. Chemical admixtures can ultimate strength. it is clear that available for reaction with the unhydrated cement. Finally. will reduce strengths at later ages due to the forma- cannot support additional load. concrete. the density of the penetrate into the bulk paste leading to continuous larger paste decreases. and quan. When exist. and subsequently the stress tion of less dense and nonuniform hydration products [5]. Probably the most important factor is paste density. 1—Stress-strain curve of concrete in compression and stages of microcracking. slag and pozzolans. width. at which point strength. which in turn depends highly on the water-cementitious mate- tity. form continuous cracks parallel to the direction of loading. existing microcracks are strength of the cement paste. for example. interfacial and bulk paste microcracks join to moisture conditions have a marked effect on the paste strength. The nature of the ce- cracks until the concrete cannot support additional load [5]. deviation from lin. the stress-strain curve is linear. the cement type affects paste strength. 1. For example. the extent of cracking is so great that the concrete strengths. reducing the w/cm will decrease the strength due to the in- earity increases at a faster rate. hydration will continue only as long as free moisture is Based on the above microcracking process. as supplied to the job. con. In test specimens. or splitting tension. ing are used to check the adequacy of the mixture proportions dration products and increases the strength of the paste-aggre. test specimens in the laboratory and is generally used in Factors involving both the paste and aggregate will affect research and mixture proportioning studies. Beyond this. Once the proportions have cylinders (ASTM C 873) are also used to determine in-place been selected. The use of cardboard or plastic cylinder molds in into the concrete mass monitor the temperature rise as it preparing specimens has been reported to result in lower cures and control the temperature of specimens placed in a measured strengths compared with the use of rigid steel molds water bath or in molds with heating elements. Even though efforts are made to provide equivalent cur- degree of mixing of the constituent materials and consolidation ing to both the concrete in the structure and the molded speci- of the concrete. This 31/C 31M). the [13. as is done for cores. especially in the top portions of use the temperature-matched curing (TMC) technique [17]. hardened concrete are specified in ASTM Test Method for Ob- mation obtained can be quite different depending on speci. and under laboratory conditions by ASTM Practice can be due to low strength test results during construction or for Making and Curing Concrete Test Specimens in the Labo. weak planes may be less likely to exist. so that the cylinders receive cur- The strength of coarse aggregates is determined mainly by ing identical to that of the surrounding concrete in the structure mineralogy and density. as free of flaws as the particular con- Current ASTM test methods for measuring strength call for struction will allow. Molds (C 873) provides procedures for obtaining cylinders cast In most concretes.14]. the materials must be mixed adequately to concrete strength. taining and Testing Drilled Cores and Sawed Beams of Concrete men preparation and handling prior to testing. Specimens given curing similar to that of the struc- rising bleed water is often trapped beneath coarse aggregate tural component are used to indicate the in-place strength of particles. Drilled cores can be tested either in compression brief descriptions of current standard procedures for prepar. a rough. It has been found that temperature-matched curing allows for the Preparation of Test Specimens best estimation of in-place strength [18]. When concrete bleeds. and the smaller particles ASTM C 192/C 192M specifies procedures for preparing reduce stress concentration effects at paste-aggregate interfaces. In practice. sound concrete. [12]. and sawed beams are tested in flexure. Following are (C 42/C 42M). Specimens from Existing Structures mens and specimens cut from existing structures. gate interface [10. Strength of Concrete Cylinders Cast in Place in Cylindrical cured cylinders at 28 days [6–8]. In ing test specimens up to the time of testing. Also. however. the [15. thus weakening the interfacial zone. Excessive bleeding and segregation of fresh concrete can Another technique to estimate the in-place strength is to also lead to reduced strengths. Push-out ture with the desired properties. monitor the producer’s quality control. this can be the structure according to ASTM C 31/C 31M. The use of 31/C 31M have multiple uses. there is an optimum mens. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 127 desired properties are attained. however. differences in strength are expected due to differences proportion of ingredients that yields the most economical mix. Self-consolidating concrete. in consolidation and early-age temperature histories. Also. such as clay. ratory (C 192/C 192M). on the aggregate and indicate changes in materials and other conditions surface reduce interfacial strength. This procedure is the strength of the paste-aggregate interface. placed within a structural slab. ASTM Test Method for Compressive crete may never reach the strength obtained from standard. single-use plastic or cardboard ambient temperature surrounding the concrete specimens molds are used widely for economic reasons. Although Procedures for obtaining strength test specimens from existing testing procedures are similar. ders typically have length-diameter ratios (L/D) less than the tion will reduce strength. In effect. however.11]. Concrete strength tests are conducted on both molded speci. The bond between considered to be the “ideal” condition for specimen prepara- paste and aggregate particles will be stronger for smaller-sized tion. Those given standard moist cur- pozzolans such as fly ash or silica fume results in denser hy. In poorly cured members. Push-out cylin- achieved through rodding or vibration. cures. and a strength correction factor has to be does not require any consolidation effort during placement applied to the measured strength. Inadequate consolida. concrete prior to form removal or application of construction Other factors that affect the strength of concrete include loads. but the curing of push-out cylinders is more achieve a homogeneous mixture. thermocouples inserted bleed water. The concrete must then be like that of the structure than for molded specimens stored on placed in the molds and thoroughly consolidated. The standard also specifies moisture con- specimens in the shape of cylinders or beams. In some lightweight and high-strength concrete. the significance of the infor. of concrete. drilled cores or sawed beams are obtained when Making and Curing Concrete Test Specimens in the Field (C doubt exists as to the strength of the concrete as placed. addition to placing dimensional requirements on specimens. a smaller-sized until the time of test. signs of distress in the structure. aggregate strength may limit concrete strength. which have a higher surface area per unit volume. Coatings.16]. high degree of control involved. established temperature history of a structural element. Preparation of ditioning before testing (to be discussed subsequently). cut specimens are useful . Such a curing system could also be used to follow a pre- vertent application of loads may also show reduced strength. Also. and will produce the most consistent results due to the aggregates. For a given set of materials. ASTM C 873 involves cylinders that are cast in special molds however. ASTM C 42/C 42M requires that test specimens be comprised of Molded Specimens intact. concrete that matches the temperature history of the concrete mass as it has been damaged due to mishandling of specimens or inad. these specimens in the field is governed by ASTM Practice for Generally. which will have a higher w/cm due to the rise of a temperature-matched curing system. standard value of 2. Specimens made according to ASTM C 873 aggregate may have strength advantages in that internal will be referred to as push-out cylinders. aggregate strength is higher than the and cured in concrete slabs. The first two of these standards are concrete strength and does not adversely affect the strength discussed in detail in the chapter by Lamond in this publication. angular surface texture such as exists in crushed Specimens prepared in the field according to ASTM C aggregates increases interfacial bond strength [9]. 21. Bloem [22] reported that cores taken ration. due to pronounced effects on measured strengths. All jected may also affect the measured core strength. strength. The effect of reinforcement on compressive strength molded specimens. segregation. from the top of an 8-in. Studies on high- strength concrete [23] indicated no effect of core elevation on Compressive Strength Test Procedures strength test results.22]. have lower strength than those from unstressed in the structure. costly. strengths than cores with two days of moist conditioning prior tor may become more pronounced as the ratio of cut surface to testing [22]. 2—Planes of weakness due to bleeding: (a) axis of specimen vertical and (b) axis of specimen horizontal.14. Unless specified otherwise. which can be attributed to the fact that high-strength concretes generally exhibit little bleeding. Moisture conditioning of cores affects measured strengths. subjected to good curing. the process of drilling or sawing of specimens may cause Early work showed that specimens tested dry had higher some damage that may affect strength test results. when the slab was poorly cured. poor consolidation. specified in ASTM Test Method for Compressive Strength of this is attributed to the alignment of weak interfacial regions Cylindrical Concrete Specimens (C 39/C 39M). dures adopted in 2003 are intended to preserve the moisture of Besides the drilling or sawing processes. however.19. and the drilling or sawing processes may introduce variables af. The presence of reinforcement in the tensile region are likely to affect the strength of the concrete samples thus of flexural beams or in splitting tensile strength specimens has obtained. . the specimens are sealed again after surface drying.128 TESTS AND PROPERTIES OF CONCRETE if strength information is required for older structures or if The loading to which the concrete member has been sub- service loads are to be increased above original design levels. The resultant strength tioning practices has shown similar results leading to changes reductions have been reported to be greater in higher-strength in ASTM C 42/C 42M [25.21]. however. Cores are to be placed in sealed plastic bags or nonab- placement have lower strengths than those cut from the bot.24]. Cores Compressive strength testing of molded concrete cylinders drilled horizontally have been shown to yield lower strengths prepared according to ASTM C 31/C 31M or C 192/C 192M is than those drilled vertically [5. the strength of these specimens is from highly stressed regions. Recent work on the effect of moisture condi- to specimen volume increases [19]. sorbent containers after the surface drill water evaporates or tom of the placement due to bleeding. 2. The difference increased to 15 %.14. Further. Cutting of these specimens is. The inclusion of reinforcing steel in the specimen is not fecting strength test results. permitted by ASTM C 42/C 42M since there are insufficient Although the concrete in drilled or sawed specimens is data to demonstrate the effect of embedded steel on measured more likely to be representative of that in the structure than strength. Testing proce- parallel to the loading direction in cores drilled horizontally. As shown in Fig. cores are to be tested within seven days of drilling. (203-mm) slab tested approximately Cores are kept in the sealed condition for at least five days after 5 % weaker than those from the bottom when the slab was being last wetted and before testing. The moisture conditioning proce- concretes [20]. one must be aware of various factors that is variable. regions [19.19. the location and the drilled core and to minimize the effects of moisture gradi- orientation of the cut specimens in the structure will affect ents introduced by wetting during drilling and specimen prepa- strength test results. All of these standards specify tolerances on specimen Fig. If water is used for subsequent end prepa- effects [5. dures for cores (C 42/C 42M) and push-out cylinders (C 873) due to accumulation of water under coarse aggregate particles also refer to ASTM C 39/C 39M for measuring compressive due to bleeding. Excess voids in a particular concrete sample.26]. and curing within 1 h of drilling. where microcracking is likely to most likely to be representative of the strength of the concrete have occurred. will cause strength reductions. Specimens cut from the top of a concrete ration. Cores taken other factors being equal. and this fac. In addition.5°. grinding or sawing of the ends to meet the requirements. Formed surfaces of beams are to be smooth and plane such that the maximum deviation from the nominal cross section shall not exceed 1/8 in. The effect of in state of triaxial compression shown as shaded region. Hardened cylinders and drilled cores may be 1231). the effects of various factors on Unbonded caps have a thickness of 1/2 1/16 in. the tri. least as strong as the concrete. ASTM C 31/C 31M and C 192/C 192M on specimen preparation allow for depressions or projections on finished surfaces of cylinders and beams of up to 1/8 in.8 of the diameter. The plane to within 0. It is important to keep the cement paste caps ASTM Practice for Use of Unbonded Caps in Determination of moist.5 MPa). but no more than 5/16 in. (2 mm).050 mm).2 mm).3D). The stress state in tars are permitted if allowed to harden at least 2 h before testing standard compressive strength test specimens is.002 in. (13 2 mm] compressive strength test results are discussed. however. Surface irregularities will lead to local concentrations of stress even in specimens that are Fig. ments of the test procedures. (1.2 in. (152 mm) or more. At distances shall not be off-center with respect to the specimen axis by more from the specimen ends of about 0.05 mm). shall not depart from per- portion of the cross section under triaxial compressions pendicularity with the specimen axis by more than 0. and that the ends must be plane to within 0. or 1/16 in. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 129 Effect of Specimen End Conditions ASTM C 39/C 39 M states that the ends of cylindrical specimens to be tested must not depart from perpendicularity with the specimen axis by more than 0. 3 [5. or capped in accordance with either ASTM C 617 or ASTM C 1231. In general. cylinder end conditions prior to capping on strength test results has been reported by several authors [27–30]. (3. The purpose of the latter requirement is to avoid exceeding maximum cap thickness specified in ASTM C 617. (3. men end. of triaxial compression and can withstand higher stresses than the unconfined cube strength [31]. Generally. (2 mm) smaller than . Sulfur mor- withstand a uniaxial compressive force. (0.2 mm) for cross- sectional dimensions of 6 in. capping materials must be at axial effects are negligible [5]. Caps on hardened concrete Factors Affecting Compressive Strength specimens should be approximately 1/8 in. (3 mm) thick. (0. or ASTM C 617 covers procedures for capping with materials capping with bonded caps according to ASTM Practice for that bond to the cylinder ends. end conditions. where D is the average core diameter in inches (or millimetres). in 12 in. The caps shall be pression in the specimen ends as shown in Fig. If the specimen does not meet these tolerances. (8 mm) thick. Friction between concrete strengths of 5000 psi or greater.002 in. or 1 mm in 100 mm). 3—Frictional restraint at the ends of cylinders results capped to meet the planeness requirements [15]. the test methods require concretes. Thick caps can reduce the measured strength [32]. for concrete with strength less than 5000 psi (34.14]. capping material is lower than the compressive strength of the Details of this effect are covered in subsequent discussion of concrete. than 1/16 in. thereby inducing lateral com. specimen ends that do not meet the specified require- geometry. shorter time has been shown to be suitable. unless there are data showing matic specimens having an aspect ratio of two. since they are susceptible to drying shrinkage and possi- Compressive Strength of Hardened Concrete Cylinders (C ble cracking. This is possible because bonded caps are under a state the effect of length-diameter ratio. unless a restrains the specimen laterally. and the diameter is not more than 1/16 in. and specimen moisture condition at ments prior to capping cause lower strength test results. Thus. and time of testing. sulfur mortar caps the bearing faces of the testing machine and the test specimen must be allowed to harden at least 16 h before testing. ASTM C 42/ 42M allows projections of up to 0. tar.5° (approximately 1/8 in. for cylindrical or pris. The purpose of specifying end condition requirements of planeness and perpendicularity is to achieve a uniform transfer of load to the test specimen.6 mm) for smaller dimensions. the result obtained from a compressive strength and the thickness of the caps for concrete strengths below and test would be a direct indication of the concrete’s ability to above 7000 psi (50 MPa) are given in ASTM C 617. Freshly molded cylinders may Capping Cylindrical Concrete Specimens (C 617) or with be capped with a neat cement paste that is allowed to harden unbonded elastomeric caps (to be described) according to with the concrete. For more complex than uniaxial compression. if the end condition tolerances are the degree of strength reduction increases for higher-strength not met by the concrete specimens. (5 mm) from the core ends and requires that ends of cores do not depart from being perpendicular to the specimen axis by a slope of more than 1:8D or (1:0. The requirements on the strength of the capping material Ideally. the ends shall be sawed or ground to meet those tolerances. and decreases with distance from the specimen ends. All of these factors will influence measured strengths as capped with either high-strength gypsum cement or sulfur mor- discussed in following sections. cross sections satisfactory performance even though the cube strength of the at mid-height should be free of the effect of the end restraint. and well bonded to the speci- In order to understand better the significance of the require. with it has been believed that the resulting cylinder strength is re- higher-strength concrete requiring harder pads. cylin- method that produces test results comparable to those ders are used.34]. (6 mm) exhibited that has been used five times. shown. An alternative is the unbonded capping method cov. which is illustrated in Fig. ders are made at both the highest and the lowest strength lev.130 TESTS AND PROPERTIES OF CONCRETE the inside diameter of the retaining ring. cylinders. the magnitude of the size effect decreases with increasing specimen diameter [7]. With sulfur mortar caps. the capping operation is tedious and can be hazardous in the case of molten sulfur Effect of Specimen Size mortar. and one is tested after grinding or capping while the in order to maintain a diameter-aggregate size ratio of at least other is tested with unbonded caps. Research has surface of the retaining rings shall be free of gouges. The within-test variability of 4-in. the elastic These compounds have a range of melting temperatures. Equal ders in compression. it was pour [15].35–39]. In cases of includes information on the maximum uses of pads and the massive concrete placements. precision of average strength can be obtained if the number . cylinders is Fig. Drilled cores will follow the same trend of increasing strength with decreasing specimen size for larger-diameter cores.42]. It has been found that the use having increasingly higher strengths requires that testing of unbonded pads is a convenient and efficient capping machines have higher load capacities when 6 by 12-in. high-strength con- be reused until physical damage is observed. Required hardness of the capping material when bonded caps are used. requirements for compressive testing. As shown in Fig. 3 to 1. the use of large qualification of unbonded cap systems. however. diameter cylinders have only 44 % obtained with bonded caps [33.7. the ratio of cut surface to specimen volume becomes significant. modulus of the capping material should be similar to that of the above and below which they become viscous and difficult to concrete. that this strength difference can be reduced if 4-in. (5- Although bonded capping satisfies the end condition mm) thick caps. volatilization of the sulfur occurs upon found that neat cement paste caps with cube strengths of 12 000 heating. Further. 5. This smaller 4 by 8 in. however. commonly made of neoprene. on average. Historically. about 20 % greater than that of 6-in. capping material rather than strength [31]. however. It has been shown. The with compressive strengths between 1500 and 12 000 psi. and it is possible that coring damage will cause strength reduction for decreasing diameters below 4 in. ASTM C 1231 crete can be tested with existing testing machines. thus. compared with about 9 lb (4 lateral tension in the specimen ends. or wet-sieving to remove larger aggregate sizes. cylinders. grooves. ered by ASTM C 1231. ASTM C 617 restricts the reuse of any material psi (85 MPa) and thicknesses up to 1⁄4 in. In addition. reduction in strength was observed with 3/16-in. (102 by 203 mm) cylinder size is permitted system. cylinders are molded by using two layers instead of three when consolidation is by rodding [43]. els for which the unbonded caps are to be used. The reasoning behind the size effect is that the strength of a concrete specimen will be governed by the weakest part of that specimen. that can reduce the fluidity and strength of the material. It is commonly accepted that as specimen size increases. The capping mate- ping technique. cylinders [42]. which can be used for testing concrete (152 mm) in diameter and 12 in.6 kg). Traditionally. (102 mm) [19. The 4 by 8-in. precision of strength determination should not be sacrificed. Because 4-in. Ideally. At least ten pairs of cylin. confined within metal of aggregate (NMSA) does not exceed 1/3 the cylinder diame- retaining rings. A review of available data indicated that 4-in. cylinders [41. thereby reducing the kg) for a 4 by 8-in. The use of retaining rings is essential to easier to handle: a 6 by 12-in. cylinder. Sulfur capping compounds must be kept rial must have a high elastic modulus to distribute the applied molten at a temperature of approximately 265°F (130°C). such as dams. consists of elastomeric when specified and provided that the nominal maximum size pads. For small diameter cores. and that the probability of the occurrence of large flaws increases as specimen size increases. concrete is related more closely to the elastic modulus of the The use of sulfur mortar is the most common bonded cap. the measured concrete strength and the variation in test results The measured cylinder strength of concrete is affected by decrease [5. it has been reported that the strength difference due to specimen size increases as concrete strength increases [36]. the standard field molded cylinder has been 6 in. 4—Unbonded cap system for testing concrete cylin. Pairs of cylinders are aggregate sizes requires the use of larger-diameter specimens made. 4. the use of concretes apparent compressive strength. however. The elastomeric pads can of the cross-sectional area of 6-in. load uniformly to the ends of the specimen. The bearing lated to the strength of the capping material. The elastomeric pads conform under load to ter. The the specimen end surfaces. (152 by 305-mm) concrete cylin- restrict lateral flow of the pads that would otherwise induce der weighs about 30 lb (13. cylinder is being used more commonly. thereby distributing the applied smaller specimens require less material to make and are much load uniformly. Further. In a study of different capping materials [32]. that the measured cylinder strength of a given or indentations.40].14. (305 mm) in length. Retrieval of capping material strengths similar to specimens with ground ends for concrete from specimen ends introduces oil and other contaminants strengths up to 17 000 psi (120 MPa). result in about 4 % higher measured strength compared with 6-in. the pads depends on the strength level of the concrete. Although the testing of smaller specimens is more convenient. Fig. two. The Effect of Diameter-Aggregate Size Ratio actual length-diameter ratio will influence the apparent Current specifications for molded specimens and push-out strength of the specimen being tested. Fig. 6 [7]. cylinders is increased to 1. Standard test cylinders have a length-diameter (L/D) ratio of cylinders. 8—L/D strength correction factors. For example. and greater proportion of the specimen is in a state of triaxial com- thus recommended the minimum ratio of 3 to 1. For drilled cores. As shown in Fig. larger-sized aggregates may be removed by hand specimen with L/D equal to one.37.14. 7 illustrates the conditions in a specimens. tests provided the core diameter is at least twice the maximum According to these test methods. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 131 Fig. higher compressive strengths [44].5. lightweight concretes with densities between 100 and 120 lb/ft3 (1600 and 1920 kg/m3).5 picking or by wet sieving so that smaller specimen dimensions and 2. 6. For L/D values between 1. For L/D values below 1. applicable to specimens of normal-density concrete. but L/D values of capped specimens as low as one are permitted by ASTM C 39/C 39M and ASTM C 42/C 42M. measured strengths removing larger aggregate sizes from concrete will result in increase markedly as shown in Fig. As L/D decreases. He reported difficulty. Fig.5. 6—Relationship between measured compressive strength and length-diameter ratio [7]. however.75. This is attributed to the effect of the end test results were satisfactory for specimens with diameter-ag. ing blocks and the test specimen ends. . These correction factors are shown in Fig. cylinders require that the minimum specimen dimension be at measured strengths increase as the L/D value decreases least three times the NMSA. This condition may be relaxed by the specifier of 1 and 1.5 times the number of 6-in. however. the prefer. 5—Effect of cylinder size on measured compressive strength [7]. For molded pression. 7—Overlapping regions of triaxial compressive stresses in specimen with L/D 1. Gonnerman [37] reported that [5. 8. restraint due to the friction between the testing machine bear- gregate size ratio of two.45–47]. the correction factors are size of coarse aggregate. in con. concrete that is dry or soaked at the Fig. ASTM C 39/C 39M and C 42/C 42M provide correction able condition is that the core diameter is at least three times factors to be applied to strength test results obtained from the maximum nominal aggregate size used in the concrete specimens (molded or cores) having an L/D value between placement. Effect of Length-Diameter Ratio of 4-in. that the practice of for L/D 2. It has been reported. a solidating the specimens so that they were homogeneous. measured strengths are within 5 % of the strength may be used. many factors strength test results [16. however.14. then a at a constant rate of movement between the bearing blocks. On average.05 MPa/s) in direction.50. Studies showed that at the extremes of the permissible range of loading rate. if results are to ASTM C 39/C 39M requires that test specimens be loaded be compared with standard-cured cylinder test results. The compressive strength of concrete is of primary impor- minimum and maximum diameters. This would appear to be in agree- effect that the moisture condition will have on the test results. and long-term observed with no spherical seating [30]. It has been postulated that as The measured strength of concrete specimens increases as the a specimen dries. their “as received” condition. affect the measured compressive strength of concrete test The spherically seated bearing block must be free to specimens. and concrete strengths between 2000 and bearing block must not rotate when the specimen is being 6000 psi (14 and 42 MPa). that higher-strength concretes were more affected by loading which increases its apparent compressive strength [49]. however. and other features. The higher load rate shall be applied in a controlled manner so that the specimen is not subjected to shock loading. however. strength reductions of up to 20 % have been These include restraint. a standard rate [51]. field-cured cylinders and push-out cylinders are tested in further load application.30]. The designated rate of movement shall be maintained pendicular to the casting direction due to water gain under from about 50 % of the expected ultimate load until the ulti- coarse aggregate particles [5]. mate load is attained. Significance of Compressive Strength cation. rate of loading increases [5. and ASTM C 39/C 39M prohibits the use of heavy (42 MPa). specifies moisture conditioning that preserves moisture of the • For hydraulically operated machines. ing rates: men should be tested as closely as possible in the moisture • For screw-type machines. A higher rate of loading is not prohibi- ing direction may have about 8 % higher strengths than those ted up to a load that is about 50 % of the expected ultimate tested perpendicular to the casting direction [5]. if determination Prior to 2002.16. Thus results from . a dry condition [5. The user is required to establish mens tested in the same direction as cast will yield higher the rate of platen movement that will result in the prescribed strengths than those tested perpendicular to it. This will require trial and error until sufficient in Fig. concrete will eventually fail with no hand. (1.14 and 0. correction factors may have larger values [48]. As has been discussed. the faster loading rate produced Casting Direction about 2. Fail. psi/s (0. A rate. the difference in measured strength is attributed to experience is gained. of the ends.2 % greater strength. apparatus to be used in compressive strength testing. and that the ultimate strength was unaffected by rapid specimen that is wetter in the outer region will have lower loading up to 88 % of the ultimate load followed by loading at compressive strength. These findings lead to narrowing Molded concrete cylinders are tested parallel to their casting the loading rate range to 35 7 psi/s (0.49].39].05 in. A flexible The moisture condition of the specimen at the time of testing testing machine results in sudden failures of test specimens can have a significant influence on measured strengths. accurate load measurement.19. may be tested the 2004 version of ASTM C 39/C 39M. Cores tested parallel to the cast.7.21. The dependence of ultimate strength on When choosing the specimen moisture condition for test. Beams and drilled cores. ASTM C 42/C 42M mm)/min running idle. The Effect of Testing Machine Characteristics loading rate should not be adjusted as the load approaches the ASTM C 39/C 39M gives required features for the loading ultimate strength.25 0.26] intro. there. both of which must satisfy further requirements of surface planeness. version revised the requirements for screw-driven or servo- depending on the circumstances involved. non-negligible strength differences Effect of Loading Direction versus could occur [42]. ment with the observation that when subjected to a sustained Standard-cured cylinders for acceptance testing are tested in a load of approximately 75 % of its ultimate capacity obtained moist condition according to ASTM C 39/C 39M. moist condition may be preferred. and two bearing blocks. As illustrated loading rate. In general. the purpose of the test must be considered.25. as well as the and microcracking [5. In especially for high-strength concrete [42]. For strengths higher than 6000 psi loaded.132 TESTS AND PROPERTIES OF CONCRETE time of testing.34 MPa/s). In addition.39. The spherically seated effects such as creep and shrinkage. approximately 0. loading rate is thought to be related to mechanisms of creep ing. Placing the specimen off-center with respect to the loading axis by only 1⁄2 in. Abrams reported by inducing lateral compression on the specimen interior. the 2004 either parallel or perpendicular to the casting direction. There are also differences between the conditions rotate to accommodate any small deviation from parallelism that exist within a structure and those within a test specimen. 2. speci. Test Results one being spherically seated and one being solid. controlled loading machines. the speci. In core testing.3 condition that exists in the structure. does not appear to when tested in a moist condition than they would if tested in have a significant effect on measured strength [42]. Among these are the capacity for smooth and continuous load appli. Effect of Specimen Moisture Condition (13 mm) can cause strength reductions of 10 %. duced by wetting during drilling and specimen preparation.8.14. tance in structural applications because design procedures ure to meet these requirements has been shown to reduce require this property. On the other using ASTM C 39/C 39M.22. the occurrence of weak paste-aggregate interfaces aligned per. loading conditions. specimens have 5–20 % lower compressive strengths stiffness of the testing machine.51]. ASTM C 39/C 39M specified the following load- of the in-place strength of the concrete is desired. The higher strength of dry specimens is attributed to increased strength of secondary Effect of Loading Rate bonds within the paste structure. The longitudinal general. grease to lubricate the ball-seat assembly. a loading platen drilled core and provides a reproducible moisture condition movement that produces a stress rate between 20 and 50 that minimizes the effects of moisture gradients [25. the outer surface attempts to shrink. load. and surfaces in con- Drilled cores provide representative samples of in-place tact with the loading or reaction blocks should be flat. If either the upper or lower Fig. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 133 standard compressive strength tests may not represent in. These factors include. late the residual strength or toughness at specified values of sile strength of concrete. among others. however. af- strength under uniaxial tension. The spec- concrete. which is the only cross sentative of in-place concrete. The performance characteristics of edge of the tensile strength of concrete is important because fiber-reinforced concrete are determined using the flexural test. Direct Tensile Strength of Intact Rock Core Specimens (D The cylinder is placed on its side and subjected to a diametric 2936) to measure direct tensile strength of concrete. and reactions must be parallel to the direction of load applica- Tensile Strength Test Procedures tion. but not all of them For both test methods. (0. There are. in the loading configuration. dis- • ASTM Test Method for Flexural Strength of Concrete cussed in the chapter by Tatnall in this publication. This is due to the difficulty terwards. eliminates some of these limitations. however. 9—Bending moment diagrams for center-point loading and third-point loading. the loading rate is required to produce a tensile stress involved in inducing pure axial tension within a specimen between 125 and 175 psi/min (861 and 1207 kPa/min) in the ex- without introducing localized stress concentrations. however. limi. Knowl. however. failure initiates in the tensile faces of the beams. several test The load-deflection curve that is obtained can be used to calcu- procedures have been developed to indicate indirectly the ten. The first half of the load may be applied rapidly. Further requirements are specified for the testing apparatus to ensure the supports and loading blocks are free to move There are currently no standardized test procedures for deter. mixing. Flexural testing of FRC is. If the spec- drilling or saw cutting of ends. and differences in size and L/D leather shims may be used. compressive force along its length. . (Using Simple Beam with Third-Point Loading) (C 78) • ASTM Test Method for Flexural Strength of Concrete Splitting Tensile Strength (Using Simple Beam with Center-Point Loading) (C 293) ASTM C 496 gives requirements for the testing apparatus. operations. and delivery involve testing a simply supported prismatic beam. the beam is to be tested on a span because molded specimens are not consolidated the same as that is within 2 % of being three times its depth. (25-mm) tainty of measured core strength as being truly representative or longer gaps in excess of 0. If 1-in.015 in. at right angles to the top and bottom faces. As shown in and for evaluating effectiveness of admixtures and other con. treme fiber of the beam. Therefore. For both. resulting in maximum bending information on the in-place concrete. that is. imens should be tested on their sides as molded. the as tested. 9. they differ. Sides shall be in-place concrete. Tests of standard-cured specimens are used as ASTM C 78 and ASTM C 293 are similar in that they both a basis for quality control of batching. contribute to the uncer. and load application for determining drical Concrete Specimens (C 496) splitting tensile strength of cylindrical specimens. Flexural Strength Testing place behavior. specifies load application at midspan.004 in. Temperature-matched curing section subjected to maximum moment. moment in the middle third of the specimen. specimen surfaces and the loading or reaction blocks at no load. stituent materials. These include: midspan deflection. The testing Some agencies have adapted ASTM Test Method for machine should meet the requirements of ASTM C 39/C 39M.38 mm) of being plane. (0. Fig. specimen geometry. presence of moisture gradients resulting from water-cooled the specimen surfaces should be ground or capped. determination of compliance with specifications. it determines resistance to cracking. The loading apparatus must apply value compared with standard molded specimens. test • ASTM Test Method for Splitting Tensile Strength of Cylin. Several factors. ASTM C 293 tations on the ability of field-cured test specimens to be repre. to maintain uniform distribution of load over the beam width mining the direct tensile strength of concrete. by the core removal process.1 mm) exist between the of the in-place strength. undefined damage introduced imen surfaces are within 0. ASTM C 78 specifies application of load to the specimen at the Tests of field-cured specimens are intended to provide third points along the span. load perpendicular to the face of the beam without eccentricity. and the ratio of width to depth as- a nearly uniform tensile stress perpendicular to the vertical molded must not exceed 1. however. The direct tensile strength is determined by dividing the axial load at failure by the specimen cross-sectional area. This was found .001 in. (0. at least 2 in. affected by the width of the uniformly applied load [52]. flexural strength of specimens tested in third-point loading sile strength and is approximated by the following equation: decreases as the depth of the beam increases. In it. rather than compressive failure occurs because the stress state and is due to the size effect as was discussed for compressive at the loading strips is triaxial compression. (456-mm) span. cylindrical test specimens are loaded in axial tension through the use of metal caps bonded to the specimen ends. tribution over the depth of the beam is linear. the apparent value of the uniform tensile stress at failure is the splitting ten. tested on an 18-in. whereas the actual test specimens are short and deep. This has been strips are subjected to large compressive stresses. strength test specimens. The flexural stress equations apply to long. (3. Various other bearing block of the testing machine is shorter than the cylin. with increasing specimen size [57]. this approximation is not significant. larger coarse aggregate particles may be removed eter. It is likely. D cylinder diameter L cylinder length Effect of Specimen Size It is commonly agreed that as the size of the test specimen The regions of the specimen in the vicinity of the loading increases. reported no effect of span length on strength P maximum load during test for third-point loading. allowing the con. shallow beams. a bearing bar or plate shall be used that is at least as thick obtained using either third-point or center-point loading. 100 and 200 psi/min (690 and 1380 kPa/min). LD the effect of span length is unclear. on fsp splitting tensile strength the other hand. 10. and plane to within 0. by 20 in. One assumption is that the concrete be- haves as a linear-elastic material throughout the test. Care is required during specimen preparation to ensure application of a tensile load with minimum eccentricity. the end of the cylinder.61 is not pursuing standardization at this time (2004). which is not true at stresses approaching failure. mum coarse aggregate size. Reagel and Willis [54]. The actual stress distribution on the vertical plane is by hand-picking or wet-sieving. Variability of test results decreases crete to resist the high compressive stresses [52]. The minimum specimen dimen- taining the specimen axis and the applied load. that compared with the variability inherent to concrete strength. This test procedure is not widely used for concrete specimens and ASTM Subcommittee C09. Plywood bearing strips at least Effect of Specimen Dimensions as long as the cylinder and 1/8 in. the loading configuration of this test method induces of coarse aggregate. The For a constant beam width and test span. Tensile found to be true for both center-point and third-point loading. These as the distance from the edge of the machine bearing block to will be discussed.134 TESTS AND PROPERTIES OF CONCRETE test method for rock cores. flexural strengths decrease [54–57]. flex- 2P ural strengths seem to be independent of beam width for a fsp (1) given depth and span [54].5. (51 mm) wide. however. other beam dimensions are permitted depending on maxi- Failure of the cylinders occurs along a vertical plane con. The load is dard beam dimensions are 6 in. (152 mm applied so as to produce a spitting tensile stress rate between by 152 mm by 507 mm). Kellerman [55] reported where that strength decreased for both center-point and third-point loading as span length increased. factors have been found to affect flexural strength test results der. ASTM D 2936. For specimens prepared in the plane over approximately three-fourths of the specimen diam. Factors Affecting Flexural Strength The formulas in ASTM C 78 and ASTM C 293 for computing flexural strength (modulus of rupture) are based on several assumptions that are approximations when testing concrete beams to failure [53]. the flexural strength of concrete beams or mortar specimens is an adaptation of an existing standard is higher for smaller coarse aggregate sizes. The failure stress calculated using the two test methods is higher than the actual extreme Fig. As shown in sion must be at least three times the nominal maximum size Fig. (25 ASTM C 78 and ASTM C 293 require the test specimen to mm) wide are placed between the specimen and the loading have a span of three times its as-tested depth.2 mm) thick and 1 in. For a constant beam cross section. Direct Tension Test Effect of Coarse Aggregate Size A proposed test method for direct tensile strength of concrete For the same w/cm. 10—Stress distribution on diametrical plane of fiber stress due to the simplifying assumption that the stress dis- cylinder for load distributed over a width of 1/12 cylinder diameter [52]. laboratory. While the stan- faces to accommodate minor surface irregularities. by 6 in.025 mm). the flexural strength of specimens increases with loading rate [56]. ing 6-in. the tensile stresses in the near-surface specimen under the loading strips. Several factors that affect splitting ten- cause failure. The drying condition discussed occurs rapidly un. gion by a distance of more than 5 % of the span length. since the specimen surface contained third-point loading. concrete is tensile stresses approach the tensile strength of the concrete. they act as stress concentrators and strip. When the sur. stress is lower with the center-point loading compared with the third-point loading. When specimens are tested in a drying condition. requires that Effect of Loading Rate if fracture occurs outside of the maximum moment region but As with compressive strength. and strips cause significant strength reductions. the application of a line load perpendicular to the when tested in a saturated condition [5. axis of a cylinder and in a diametrical plane produces a uni- ductions of up to 33 % have been reported [58]. As a result. If fracture occurs outside of the maximum moment reapplied stress rate has been observed. This effect should be considered when removing stress is calculated using the bending moment at the fracture larger aggregate particles from concrete by hand-picking or plane. sile strength test results are discussed. (3-mm) thick plywood unless comparative test data are probability of having weak concrete in a region of highest provided. but rather is distributed within a cracks exist due to drying. does not require making note of the location of fracture. not linear elastic as is assumed in the analysis. the theoretical case [52]. the theory applies to a homo- This induces tensile stresses in the surface and. probably due to thus maximum extreme fiber stress. in. The purpose of these strips is to the load is applied at the specimen midspan. Secondly. If perpendicular to the diametrical plane.61 has rejected the use of alternative materials to maximum moment and maximum extreme fiber stress. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 135 to be true even when the use of the smaller coarse aggregate at a location other than midspan corresponds to a lower ex- resulted in a mixture with a higher w/cm to maintain worka.57]. Third. it attempts to ing of a concrete cylinder there are several departures from shrink.58. In center-point loading. . is based on the bending moment at the location of the fracture tionship between flexural strength and the logarithm of plane. Due to the significant effect of surface Effect of Specimen Length and Diameter moisture condition on test results. specimens [52]. the test results are to be discarded. Indeed. Variability of test results decreases with increasing specimen diameter. 9). the flexural strength of the specimen is lower than when wet-sieving. (3-mm) thick plywood that are 1-in. coarse aggregate size. least as long as the cylinder. Increasing the thickness of the bear- along the test span. Strength re. Effect of Specimen Moisture Condition flexural strengths obtained from third-point loading are lower It is not expected that drying of the specimen surface will than those obtained from center-point loading [55–57]. if the induced geneous material. dif. near the surface of the cracks do not develop. but this shrinkage is restrained by the specimen core.59]. their inability to conform to the specimen surface. the apparent flexural strength within a distance of 5 % of the span length. (102 mm) ture. The 1/8-in. however. the apparent flexural strength is lower than In theory. In third-point conform to the specimen surface and distribute the load loading (ASTM C 78). der normal ambient conditions if care is not taken to keep the specimen surfaces moist. but tested in a saturated condition. within the failure plane is subjected to high triaxial compres- Sometimes fracture of test specimens tested in center-point sive stresses. for a given beam size. Since the bend. In center-point loading (ASTM C 293). even if direct tensile strength val- are cumulative. Steel bearing beam span is subjected to maximum bending moment. (152-mm) diameters [52. Cylinders having a diameter of 4 in. the splitting concrete due to drying act as a preload condition. thereby resulting in a lower applied load to ues are not obtained. Variability of test results is lower with smaller calculated using the bending moment at midspan [55. the load is applied at the third points from the loading block. flexural strength specimens For a given diameter. (25-mm) wide and at tion (refer to Fig. For actual test- face of the specimen is allowed to dry rapidly. Effect of Center-Point Versus Third-Point Loading Effect of Bearing Strips As was discussed previously. The strip loading results in large compressive stresses also reduce the effective cross section of the test specimen. where ing moment distribution along the beam span varies linearly the restrained shrinkage of the outer surface induces com- from zero at the support to its maximum at midspan. only the cross section at midspan is subjected to mittee C09. the load cracks will develop in the outer surface of the specimen. more similar to that in compressive strength cylinders. affect the measured splitting tensile strength as significantly as ferences of 15 % are not unusual. Nevertheless. ASTM C 78. For the latter case. Thus. and results tensile stresses due to drying and those due to applied test load provide comparative values. the middle third of the ing strips may cause strength reductions [52]. Note that the effect of were observed to have splitting tensile strengths that were drying on flexural strength test results is opposite to that for roughly 10 % higher than those obtained from cylinders hav- compressive strength test results. cylinder length does not seem to affect that are used to indicate the strength of the concrete in-place test results. it is possible that the effect of drying is loading occurs at a location other than midspan. Subcom- however.60]. Variability is also lower for it does flexural strength. ASTM C 293. the tensile strength test is reasonably easy to conduct. First. fracture pression in the specimen interior. treme fiber stress than exists at midspan. A linear rela. on the other hand. Effect of Moisture Condition Flexural strength test results are sensitive to the specimen mois. form tensile stress perpendicular to that plane. When is not applied along a line. that is. other than possibly reducing variability for longer should be cured under conditions similar to the concrete struc. which concrete is not. the main difference between ASTM C 496 requires the use of bearing strips made of 1/8- ASTM C 78 and ASTM C 293 is the location of load applica. Factors Affecting Splitting Tensile Strength ture condition at time of testing. when failure bility [55].14. oped for a given concrete mixture. strength-maturity relationship is developed by laboratory tests on ple. Even so. higher splitting tensile strengths attained by various tension testing methods are discussed in are obtained when the specimens are loaded at a more rapid the literature [5. This application is cov- and testing. a corre. concrete is estimated. coarse tration Resistance of Hardened Concrete (C 803) and the aggregate properties. sion Test Values and Projecting Later-Age Strengths (C 918) and lation between compressive and flexural strength can be devel. Field-cured specimens (ASTM ting tensile strengths would be lower than flexural strength. These pullout strengths can be related to compressive of compressive strength tests. as well as the 1074). Finally. Thus. These in-place tests are discussed in surfaces from drying.136 TESTS AND PROPERTIES OF CONCRETE Effect of Loading Rate the type of tension test [5]. established [70]. For exam. and thus more care must be taken to prevent beam before use in the field. the results the field concrete is recorded from the time of concrete place- obtained are not direct tensile strengths.65 [60]. To avoid such limitations. or cause localized damage to the structure. and A useful and relatively simple technique to estimate in-place thus more closely resembles a direct tension test. using the calculated maturity index the structure are much more complex than can be taken into and the strength-maturity relationship. changes in properties can be monitored over tension test methods. The maturity concept can also be used to Also the variability of flexural strength test results is high estimate later-age potential strength based upon the early-age due to sensitivity to details of fabrication. As an alternative.62–64]. including concrete strength level. strength are obtained through the use of flexural and splitting location. mens that do not necessarily give direct information about the Thus. air entrainment. and may be more or ment to the time when the strength estimation is desired. or nearly the same. The pullout strength is determined by measuring the tests. splitting tensile strength is used in the design of light. curing. and compressive strength Another commonly used in-place test for strength is the testing can be used for control and acceptance of concrete. with an average ratio of cured specimens [69] are of some help in accounting for in- splitting tensile strength to flexural strength for center-point place conditions. As a result. Therefore. a obtain the values required by the design formulas. and temperature.7. rate. Tests that cause no the direct tensile strength of concrete. It is important to note that in-place strength tests do not method are particular to that method. is more sensitive to moisture nied by laboratory testing to develop the strength relationship conditions. The former. testing age. a variety of Significance of Tensile Strength Test Results in-place tests have been developed. actual concrete in the structure. Typically called “nondestructive. Indications of tensile damage allow for retesting at the same. a metal insert is either placed into fresh concrete or installed Strength Relationships into hardened concrete. cores. In addition. handling. When the in-place strength is desired. The relationship between com. temperature history is then used to calculate the maturity index similar to compressive strength test limitations. The tests described thus far involve separately made speci- where in the portion of the diametrical plane that is in tension. failure is controlled by the Nondestructive In-Place Strength Testing strength of the concrete at the tension surface of the beam. the concrete mixture to be used. conditions in of the field concrete. Strength of Hardened Concrete (C 900). is discussed in the chapter by Carino. This less sensitive to factors that affect tensile strength. but in the splitting tension test failure can be initiated any. empirical strength relationships have been developed so amount of force necessary to pull the insert from the concrete that other strength properties may be estimated from results mass.8. the strength of the field account using strength tests on small specimens. and rebound hammer test described in ASTM Test Method for . such methods either require pre- loading of 0. however. Other in-place tests include the penetra- pressive and tensile strength has been found to be influenced tion resistance test described in ASTM Test Method for Pene- by many factors. The splitting tensile strength follows a power function relationship of the compressive strength. The maturity method provides an approach for making expected use of the test results. strength of standard-cured specimens. The splitting tension test subjects the greater detail in the chapter by Malhotra in this publication.14.39. which interchangeably. the ratio Relationship of Flexural Strength to Splitting of splitting tensile strength to compressive strength is not con- Tensile Strength stant but decreases with increasing strength [65–68]. and temperature-matched This has been shown to be the case. First. use of specialized equipment. In the flexural strength tests. pullout test described in ASTM Test Method for Pullout with flexural strength data used for reference only. based on the size effect principle. age. In this method. Strengths obtained from each test time.” these tests either do not damage the concrete or There is currently no standard test method for determining result in superficial localized damage. strength test results. major portion of a diametrical plane to tensile stresses. When selec. the insert is pulled by means of a jack reacting against a bear- Due to the convenience of performing compressive strength ing ring. in-place tests should be accompa- sion test. however. as described in ASTM Practice tion of a concrete tension test is being made. C 31/C 31M or ASTM C 873). the proper test must be performed to ship between concrete strength. it is expected that split. The flexural strength test is more similar to means that relationships to other standard test results must be the loading encountered in pavements than is the splitting ten. the loading of the for Estimating Concrete Strength by the Maturity Method (C concrete in the structure should be considered. strength is the maturity method. curing. Thus flexural strength tests may be problematic ered by ASTM Test Method for Developing Early-Age Compres- for acceptance testing of concrete. General relationships between the As with testing of specimens for compressive strength and compressive strength of concrete cylinders and the strengths beams for flexural strength. and cannot be used provide direct measures of compressive strength. If the strength is to be used in reliable estimates of in-place strength by establishing a relation- design calculations. Then the temperature history of weight concrete beams to resist shear [61]. planning. 5 [72]. an average increase in tensile strain perpendicular to the plane of loading. causes a significant decrease in concrete’s compressive strength. resulting in biaxial to uniaxial strength concrete. The discontinuity point is the stress at which unstable pro- axial tests conducted using brush platens seem to have gressive microcrack growth begins. and the tensile strength is not affected significantly creases of roughly 30 % above the uniaxial compressive by the application of biaxial tensile stresses [5. unstable crack growth in higher-strength concretes would seem to provide an additional safety margin in these concretes when subjected to the same sustained stress-strength ratios as for normal-strength concrete. Research results have shown that the degree of con. ASTM C 801 was withdrawn in 2004 because the method was not being used. A common use of data obtained from triaxial compressive tests is to construct a Mohr failure envelope for determining shear strength as a function of normal compressive stress. Thus. compressive strength with biaxial compressive loading is Calixto [74] performed biaxial tension-compression tests about 30 %. Bi. tensile. limit for high-strength concrete as well as the discontinuity finement at specimen loading surfaces had a significant effect point were at higher stress-strength ratios than for normal- on biaxial stress test results. As specimens indicated that fracture was controlled by a limiting determined with these end conditions. In addition. and shear stresses. it was noted that the proportional no failure. ranging from a minimum of 26 % for 12 is an example of a biaxial stress failure envelope in which trap rock coarse aggregate to a maximum of 34 % for granite stress combinations that lie within the envelope correspond to coarse aggregate. of lateral compression had a much less pronounced effect on strength concretes. The higher stress-strength ratios required to initiate progressive. such as bridge decks and pavements. average strength in- strength. it may be important to understand the behavior of concrete under different stress states. cylindrical test specimens are subjected to a lateral confining stress in combination with an axial load. The test method is analogous to the triaxial test used for soil specimens. concrete members are often subjected to combinations of compressive. obtained from triaxial compression tests. According to the test method. Lateral tension.71]. The increased capacity of concrete under a biaxial or triaxial compressive stress state is significant in that the lateral restraint provided in reinforced concrete structures through such means as steel spirals will enhance the capacity of the concrete. Thus specimens are subjected to triaxial stress states such that two of the three principal stresses are equal.5 [72]. ASTM Test Method for Deter- mining the Mechanical Properties of Hardened Concrete Under Triaxial Loads (C 801) provided a standardized method for determining such behavior. Biaxial states of stress are more common. ratio. As with normal-strength concrete. however. Triaxial states of stress are typically of significance in massive concrete structures. In numerous Fig. the increase in compressive strength under the axial tensile capacity. OZYILDIRIM AND CARINO ON CONCRETE STRENGTH TESTING 137 Rebound Number of Hardened Concrete (C 805). and occurs at a principal stress ratio of approxi. and increased with increasing biaxial stress compressive strength ratios in the range of 1. 11—Shear strength as a function of normal stress structural applications. In biaxial compression tests performed on high. on high-strength concrete specimens. The failure modes of the removed the effect of end confinement to a great degree. concrete members are subjected to repeated applications of .14. Fatigue Strength of Concrete Fatigue strength is the greatest stress that can be sustained for a given number of stress cycles without failure. The report of ACI Committee 228 provides guidance on the proper use of these types of in-place tests [70]. 11). Strength Under Combined States of Stress In structures. In general. a biaxial stress state depended on the type of coarse aggregate axial compression is higher than its uniaxial compressive [73]. whereas the application construction. The shear strength of the concrete is estimated by drawing a tangent to the Mohr’s circles at failure obtained for various combinations of confining pressure and axial stress (see Fig. The compressive strength of concrete subjected to bi.1–3. Figure strength were observed. Fig. the applica- mately 0. tion of lateral tension caused a significant decrease in the axial Higher-strength concretes are becoming more common in compression capacity of the concrete. 12—Biaxial stress failure envelope for normal- strength concrete [71]. the fatigue life of high-strength concrete increases with short-term static strength. a ratio of ap. Furthermore.138 TESTS AND PROPERTIES OF CONCRETE Fig.61. and tural design purposes. simple. The sequence of loading cycles is also significant. Miner’s rule. ration of rest periods. strict adherence to specified procedures and toler- dition exhibit lower fatigue life compared with those tested in ances is necessary for obtaining meaningful results and ensur- a dry condition. The number of cycles of loading to failure strength concrete [77]. However. of maximum to minimum cyclic stress has an effect. usually 107. the range largely unknown under actual service conditions of the structure. a standardized test Cyclic loading of the specimens below the fatigue limit in- method is not available. Thus.14. Summary tive. specimens tested in a moist con. standard test procedures will provide useful information. influence test results be understood and controlled in accor- creased the fatigue life for maximum stress levels below 76 % dance with the applicable standards. of a specimen is different if it This chapter has reviewed the standard practices and test is subjected first to high stress-strength ratios followed by low methods used to measure concrete strength. erations for design of concrete structures subjected to fatigue tors [75]. In normal. the number of cycles to failure. that is. Similar to normal strength con- when subjected to cyclic loading of a given level but below its crete. the fatigue limit thus defined is approxi. quality control by testing specimens subjected to standard- hanced fatigue life over those subjected to a uniform stress curing conditions. Whereas normal-strength concrete is reported to have a fatigue plied stress to static ultimate strength (stress-strength ratio) be. du- As shown in Fig. which states that the effects of cyclic loads are cumula. loading frequency. it will eventually fail. and (3) for evaluating in-place properties of distribution. Therefore. possibly because the lower stressed regions concrete. The dis- sequence. Finally. most of which are associated with the details of the loading. important to understand the response of concrete to cyclic load- mately 55 % of its static ultimate strength. Concrete does not have a fatigue limit. the fatigue life. Also. strength tests have three main rest period beyond 5 min has no additional beneficial effect. creased the uniaxial static strength on the order of 40 %. merous load cycles under normal service conditions. These standards stress-strength ratios. taken as the maximum stress-strength ratio at which failure oc. Nevertheless. 13—Schematic of cyclic load history and fatigue strength curve of concrete. ing. Over 100 references are given in the ACI report on consid- The fatigue strength of concrete is sensitive to several fac. the fatigue life concrete in the structure. including references on biaxial stress states and high- applied loading. decreasing maximum stress-strength ratio and stress range. Thus. does not strictly apply to concrete. the fatigue limit of concrete is slightly lower. cycles to failure decreases. Rest periods of up to 5 min during fatigue test. It is essential that the In biaxial compression fatigue tests on high-strength con. the number of eral information about a very complex phenomenon. that is. of concrete to fatigue loading. from tests on small specimens in estimating properties of the When the frequency of load application is low. load at a level below the ultimate strength of the concrete. since factors such as the depends on the level of cyclic stress applied to the specimen. knowledge of their limitations and the factors that affect meas- cation. as the stress-strength ratio is increased. results obtained from correctly performed propagation. 13. limit of approximately 55 % of its static ultimate strength. purposes: (1) research. of the ultimate strength. creasing biaxial stress ratio. . for struc. Cycling below the fatigue limit increases both the cussion has stressed the limitations of the results obtained fatigue strength and the static strength by 5–15 % [5. and concrete moisture condition are the number of cycles to failure decreases [2]. it is desirable to establish the response wet specimens fail at less cycles compared with dry specimens. magnitude of applied load. the fatigue limit decreased with in- Like most materials.76]. increasing the length of the In concrete construction. than if subjected to the reverse are under the jurisdiction of Subcommittee C09. ing reproducibility between laboratories. (2) for acceptance of concrete and Specimens subjected to a stress gradient also exhibit en. As the information obtained from laboratory studies can only give gen- difference between the two stresses increases. the low which the concrete can withstand an infinite number of corresponding value for high-strength concrete was found to be loading cycles [5. Nelson et al. and that those factors that will crete. in the range of 47–52 %. This is probably due to mechanisms of creep and crack ured strengths. Rather. purpose of the test be defined. While the tests discussed in this chapter appear to be inhibit crack growth. ing also increase the fatigue life. with a thorough is shortened compared with a higher frequency of load appli. [75] reported that biaxial compression de. concrete exhibits fatigue behavior. Structures such as bridge decks and pavements undergo nu- curs only after a large number of cycles. it is strength concrete.14]. the stress state. “Effect of Core Diameter Versus In-Situ Evaluation.3. 1958.” Conshohocken. 2. 3 169B. and Hynes. from 6 12. M. No. D. Cylinder Sizes: A Statistical Analysis. 1998. A. 1990. Institute.” Concrete Technology Today. and Cook. ders. 1994. Dec. M. “There is More to Concrete than Cement. B. 441–464. PA. D.. PA.. Use of Current Concrete Practice in the Production of High. 607–615.. No. M. 12. 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Each of the accelerated testing procedures was conducted us- Recognizing the need for alternative test methods for as. Currently. 550. Carino1 Preface 1996. and C9 on Concrete and Concrete Aggregates formed Subcommit. expensive and program among nine laboratories to evaluate various proce- costly delays are encountered when 28-day test results are low. which was written by M. the subcommittee was discharged and jurisdiction of its standards was assigned to Subcommittee C09. uses the maturity method by including the basis of ASTM Test Method for Developing [1] and a previously established strength-maturity relationship Early-Age Compression Test Values and Projecting Later-Age to estimate later-age strength based on the early-age strength of Strengths (C 918). H. ASTM Committee Type III portland cement. In addition.) The subcommittee developed two methods for estimating the potential later-age strength of a concrete mixture mating the later-age strength of concrete specimens based based upon the compressive strength measured on cylindrical upon early-age strength tests.02. a multistory building could go up Chojnacki [5]. celerated test specimens.” The earlier text tionship between accelerated strength and standard-cured was augmented by the current author in ASTM STP 169C by the strength is used to estimate the later-age strength under stan- addition of information on the high-temperature and pressure. dard curing conditions based on the measured strength of ac- accelerated test method that was added to ASTM C 684 in 1989.14 Prediction of Potential Concrete Strength at Later Ages Nicholas J. specimens at early ages. Gaithersburg.61 on Strength THIS CHAPTER DEALS WITH METHODS FOR ESTI. The results of the cooperative research One of these methods. Testing. This review is based on procedure that is used.09 was to after placement. Further delay is certain to accelerate strength development of concrete [8]. essential for overall Experimental Program construction economy and safety. niques and provides supporting information to the standard test methods to assist persons who are contemplating specify- Introduction ing these procedures in contract documents.. Early assessment of concrete quality is. and 650 lb/yd3). and was titled “Accelerated Strength Tests. Accelerated Curing. Cement contents were 265. A previously established rela- Jr. Depending on the specific Test Specimens (C 684) are reviewed. the author expanded the chapter in ASTM STP 169C The other method. (In admixture and mixing water were used to produce air contents 1 Consultant.09 on Accelerated Strength Testing in 1964. and Testing Concrete Compression elevated curing temperatures. Sufficient air-entraining tee C09. Rapid construction practices throughout the concrete industry Accelerated Curing Methods have caused specifying agencies to require assessment of concrete strength at an age earlier than the traditional 28 days The first assignment for ASTM Subcommittee C09. During the 28-day period between the preparation dures being developed by King [2. [7]. Wills. dures (Table 1) involving immersion of specimens in hot or because a field investigation may be necessary to verify the boiling water or autogenous curing in an insulated container load-carrying capacity of the structure. therefore. 325. if the structure must be strengthened or replaced. Furthermore.02. the accelerated strength is measured at Chapter 13 of ASTM STP 169B.3]. Malhotra and Zoldners [6]. and Smith and Tiede four or more floors. ASTM C 918. ages ranging from 5 h to 48 h. ASTM C 684 and ASTM C 918 since ASTM STP 169C was pub. 141 . Akroyd [4]. This chapter reviews the background of these two tech- lished. involves testing program leading to the development of ASTM Test Method for cylinders whose strength development has been accelerated by Making. 385 kg/m3 (450. ASTM C 684. ing ASTM Type I (or Type II meeting Type I specifications) and sessing the quality of concrete at early ages. the later age is still specified for investigate the needs of the concrete industry and to study the compression tests for acceptance of concrete as delivered to suitability of standardizing several accelerated testing proce- the job site. This current version updates changes to specimens whose temperature history has been measured. Smith and and testing of the specimens. MD. A positive response to this canvass led to a cooperative test tion to proceed in this manner. Many consider it precarious for construc. and their averages The results of the cooperative testing program were summa- were used in subsequent analyses. and to examine whether these relationships were af- Procedures A. Fig. ment. compressive crete. The tops of the cylinders were covered by about 100 mm (4 in. Water volume and heater capacity were sized to prevent an appreciable reduction in the desired water a ASTM Test Method for Time of Setting of Concrete Mixtures by Penetration temperature when the specimens were immersed. B. Procedures B—Modified boiling Standard curing for 23 h E. Consequently. place in insulated tories conducted Procedure A (warm water) and Procedure B container for 46 h (modified boiling). Procedure C. 57 size. Fine and coarse aggregates were tic container and polyurethane foam insulation (Fig. they had fected by factors such as the type of accelerated procedure.) cylinder. 75°C (175°F) water for 15 h The accelerated procedures involving the use of either hot or G—Initial set and hot At initial setting.) of water. 1—Hot or boiling-water accelerated curing tank. . of one day or two days and were compared with strengths of standard-cured specimens at ages of 28 days and 364 days. all labora- D—Autogenous curing At 1-h age. Only four of C—Final set and boiling At final setting (ASTM C 403/C the nine participating laboratories conducted Procedure D 403M).0 % and slumps from 50 to 75 mm (2 to 3 in. 4). Two Results replicate specimens were tested at each age.142 TESTS AND PROPERTIES OF CONCRETE the option of conducting one or more of Procedures D through TABLE 1—Accelerated Testing Procedures G (Table 1). Additionally. E—Initial set and hot At initial setting (ASTM C 403/C water. that is. However. place in hot water for 15 h F—Initial set and hot At initial setting.a cylinders boiled for 15 h (Autogenous Curing). and only the main conclusions are cured.0 to 6. were not placed in a tank that already contained specimens. polyurethane foam retained the heat of hydration of the ce- Each laboratory used materials available in their locality with. Con. Despite the plans of the subcommittee. which was optional. and G were also abandoned because they also required followed by boiling for 3. the relationships between accelerated and standard-cured The nine participating laboratories were asked to conduct strengths.75 mm (1 in. The graded to a No. In all cases. 55°C (130°F) 403M). and C listed in Table 1. place in hot boiling water were conducted in thermostatically controlled water. which accelerated the strength development of the con- out interchange among laboratories. Once curing was initiated. involving the measurement of final setting time A—Warm water Cylinders placed immediately in followed by boiling. it was nec- Procedure Description essary to curtail some aspects of the experimental program. place in hot Accelerated Curing Apparatus water. Specimens Resistance (C 403/C 403M). 25. All highlighted here. It was made by using a plas- of a water-reducing retarder.5 h measurement of setting time and overtime work. F.). to No. had to be abandoned because it required water at 35°C (95°F) too much overtime work to conduct. All specimens were prepared. the container was not opened strengths of the accelerated specimens were measured at ages until the end of the specified curing period. The autogenous curing container for Procedure D was from 5. rized by Wills [8].0 to 4. The objective was to establish the nature of materials conformed to appropriate ASTM specifications. and tested according to applicable ASTM standards. similar to that used by Smith and Tiede [7] to cure a single 152 cretes were made without a retarder or with a normal dosage by 305-mm (6 by 12-in. 1). 90°C (195°F) water for 15 h tanks (Fig. 2). presence of set retarder. and the temperature was required to recover to cement type. it Only four laboratories performed this procedure. the sealed molds were placed in a standard moist room. 2). Most importantly. this is attributed to each laboratory using locally warm-water curing increased concrete strengths from 1. however. were immersed in boiling water. also obtained what seemed to be significantly different correla- uring compressive strength at an age of 26 h 15 min. Procedure D (Autogenous Curing) cantly different correlations. Therefore. ter the start of mixing. Cylinders were molded in light-gage steel molds. diately after casting. The two-day strengths after au- made on mixtures produced from the same materials. They were capped with sulfur corporated into the first version of ASTM C 684 in 1974. and strengths were measured at an age of 28. B.1 to 1. togenous curing ranged from 1. the cylinders were removed from the molds and al- discussed here.6 available materials. Sulfur mortar the effect of local materials. including molds and covers. except that plastic bags and placed inside the autogenous curing chambers the relationships were at a higher strength level. data were sufficient to justify including autogenous curing in gree of confidence to assess concrete quality when the tests are the subsequent ASTM standard. the molded cylinders were sealed in served with concretes made with Type III cement. and lab. where B and made with Type III cement. there were good correlations. 3—Relationships between accelerated and standard- cured strengths for Procedure A (Warm Water Method) using Type I cement.5 times those obtained . They remained there for 46 h. cement content. The trends discussed for Pro- they remained for a period of 24 h 15 min. After boiling for 3. Imme.5 h 15 min. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 143 Fig. correlations between accelerated strength and 28. on caps were applied and aged at least 1 h before strength was the relationships between accelerated strength and standard. and D are h 5 min. it appeared that each laboratory obtained signifi. Within each laboratory. the boiling point in no more than 15 min. Again. cement. the same general trends were ob. the cylinders. One hour af- Although not shown.or 364-day Figure 3 shows the relationships between accelerated strengths were obtained [8]. measured at an age of 49 h 15 min. particularly the type of cement. At 23 h 15 min from the time of cast- Fig.1 Cylinders were cast in steel molds with tight-closing lids. good times those achieved after one day of standard moist curing. Only the results of Procedures A. mortar. 2—Autogenous curing container. cured strength. Procedure B was also strength and 28-day strength for concretes made with Type I considered to have equal merit in assessing concrete quality. but their was concluded that Procedure A can be used with a high de. because these procedures were eventually in. lowed to cool for about 45 min. Procedure B (Modified Boiling) After the cylinders were cast. the results emphasized from the molds and allowed to cool for 45 min. ing.5 oratory. Since the test (Fig.1 and 2. then they were removed procedures were carefully controlled. however. The modified boil- Procedure A (Warm Water) ing procedure increased concrete strength between 1. The tions. the cylinder molds were immersed in the Figure 4 shows the results for concretes cured by Procedure water bath at a temperature of 33 to 37°C (92 to 98°F). the sulfur was allowed to age for 1 h.4 to 2. Based upon the good correlations. Sulfur mortar caps cedure A are reemphasized. however. Within a given laboratory. times that measured after one day of standard moist curing. Reduction in water temperature was limited to 3°C (5°F). the laboratories were applied to the cylinders and aged at least 1 h prior to meas. 540 0.935 2. Significance of Test Procedures The subcommittee was convinced that laboratories.905 2. test procedures.285 0.915 1.770 0.290 0. may explain the high values of accelerated strength for Procedure D. which is beneficial to early hydration reactions.34 1. cement type.69 III 23.17 1. correlation coefficients (r ). B.10 1.940 1.985 0. B0 the intercept.975 0. B1.10 III 15. With the autogenous curing proce.07 6 I 14. This previous fact.870 1. the cured strengths for Procedure B (Modified Boiling Method) best-fit values of B0 and B1 were obtained by least squares fit- using Type III cement.955 1.985 0.765 3.28 11 I 14. plus the additional fact that higher curing temperatures are attained in this procedure compared with Procedure A.44 1. Fig.10 1. the heat of hydration of the cement causes the accelera.910 2.580 0.54 1. and 4 for Procedures A.07 a See Eq 1 for meaning of B0 and B1. and residual standard deviations are summarized in Ta- bles 2. It was assumed that the correlation for each set of conditions could be represented by a straight-line relationship as follows Sˆ28 B0 B1Sa (1) where S28 the standard-cured 28-day strength. which was the tween the data and the best-fit straight line and is computed highest level of strength acceleration.a RSD.20 0.96 III 18. ting. and cement types had significant effects on the correlation between accelerated strength and standard-cured strength.525 0. and procedure.960 1.905 2.31 1.65 1. The resulting values of B0.095 0.31 1.65 0.980 1.440 0. b r correlation coefficient.375 0.65 0.915 1. n2 TABLE 2—Linear Regression Analysis Results for Procedure A Laboratory Cement B0.96 III 15. c RSD residual standard deviation.960 0. and B1 the slope. 4—Relationships between accelerated and standard- For each laboratory.825 2.320 0.86 0.96 1. The residual standard deviation (se) is a measure of the error be- after an equal length of standard moist curing.86 III 14.83 III 13.62 12 I 17. respectively.93 8 I 9. and the data were analyzed from that viewpoint [8].90 III 15. 3.62 III 24.c Number Type MPa B1a rb MPad 1 I 13.59 10 I 19.86 III 17. and D.475 0.725 3.090 0. .440 0.815 1. as follows: High concrete temperatures at early ages are detrimental n to the early hydration reactions of cement and to the developing paste microstructure.144 TESTS AND PROPERTIES OF CONCRETE tion but at a low rate of temperature increase. d 1 MPa 145 psi.48 0.31 9 I 16.76 1.925 2.120 0.86 4 I 19.76 5 I 15. se ∑i (Sai Sˆ28)2 (2) dure.13 1.905 0.515 0.27 1. Sa the accelerated strength for a particular procedure. b r correlation coefficient.55 0.03 III 14.52 1.095 0.230 1. Laboratory 11 dures A. timated standard-cured strengths is discussed subsequently. c RSD residual standard deviation.050 0.79 III 13.970 0.780 4.975 0. Further.975 1.280 0.07 tained from the data analysis are shown in Table 5 [8].830 3.82 1.28 6 I 11.970 1.875 0.58 1. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 145 TABLE 3—Linear Regression Analysis Results for Procedure B Laboratory Cement B0.66 4 I 17. only with the repeatability of the measured accelerated c RSD residual standard deviation.195 0.865 1.a RSD.17 1. A procedure for determining the precision of the es- d 1 MPa 145 psi.48 values were used to prepare precision statements. n number of pairs of strength values used in the regres- After studying the residual standard deviations. as would be expected by the close fit of the data to the linear relationships shown in Figs.13 1.34 III 16.950 2. and D.525 Sa (MPa) (3) each laboratory.86 MPa (125 psi).82 0.96 III 3.990 0.48 1.89 1. Note that the precision statements deal See Eq 1 for meaning of B0 and B1.280 0.960 1.79 1.86 III 13.015 0. B.65 0.810 0. and oratory 6. The tentative test method was approved in 1971 as ASTM C 684-71T.21 III 14.950 1.840 0. celerated and later-age strengths.96 1.55 III 13.17 5 I 9.27 1.143 0.03 1.020 0.13 1. they were combined into a single precision statement when ASTM C 684 was published as a tentative test method.810 4. the variances Laboratory Cement B0. the subcommittee started and residual standard deviation had a correspondingly low work to develop a tentative test method that included Proce- value of 0.86 0.930 0.10 procedures [8]. The within- 4 I 11.965 1.970 1.145 0.c (squares of standard deviations) of replicate strength measure- Number Type MPa B1a rb MPad ments seemed compatible and were therefore pooled across laboratories and cement types for each procedure.96 0. cluded that all three procedures were equal in correlating ac- For example.900 2. for the three 12 I 16.79 1. where had a much lower correlation coefficient and a higher residual standard deviation.86 1.24 10 I 19. it was con- sion analysis. strengths.860 2.41 1. TABLE 4—Linear Regression Analysis Results Test Precision for Procedure D While accelerated strengths measured by the nine laboratories were significantly different for a given procedure. d 1 MPa 145 psi. the data for Laboratory 11 did Sai the average accelerated strength of the ith specimens. not fit its straight-line relationship as well as the data for Lab- Sˆ28 the estimated 28-day strength corresponding to Sai. 3 and 4 for Sˆ28 14. The autogenous curing procedure was called Proce- a dure C in ASTM C 684.975 1.c Number Type MPa B1a r b MPad 1 I 12.48 12 I 18.955 2. Correlation coefficients were ing Procedure A and Type I cement was quite high in most cases.a RSD.41 batch and batch-to-batch coefficients of variation that were ob- 5 I 22.03 9 I 16. it was found that accelerated compressive strength correlated with 364-day strength as well as Note that the correlation coefficient had a high value of 0.07 8 I 15.000 0. Subsequently.93 Test Methods for Construction Materials (C 670).400 0.515 0.930 1.45 sulting statements.950 1.58 III 19.800 3.125 0.220 0.72 ASTM Practice for Preparing Precision and Bias Statements for III 9.000 0.45 1. These III 22.79 1.315 0. .96 1. the regression equation for Laboratory 6 us.17 1.000 0.86 1. according to 8 I 7.985 with 28-day strength.90 11 I 9.48 III 18. b r correlation coefficient.910 0.960 1.62 1.930 1.060 0. Because of the small differences between the re- III 9.965 1.24 III 17.07 a See Eq 1 for meaning of B0 and B1.55 0. Therefore.985 0.290 0.225 0.780 0. On the other hand. Fig. Warm water 2.). Sˆ28 B0SaB1 (4) duced useful correlations with one-day accelerated strength. The accelerated strengths were between 22 and ated strengths and two cylinders were moist-cured at 23°C (73°F) 90 % of the 28-day strengths. they are stacked in a compression testing frame. methods. After three molds are filled. or both. and with normal-density and low-density (light- 100 mm (3 to 4 in. 5—Relationship between alkali content and accel.5 are extruded from the molds and tested for compressive strength. An attempt was made to hold the slump constant at 75 to water reducer. 5). and IV cements. or gravel. 6. moreover. this caused the principal variation between laboratories in the cooperative test program since each used a different Type I cement. % Variation. power functions as follows: Several multiple correlations were also examined. water-cement ratios (w/c) between eight Type I cements mixed with the same source of sand and 0. Data were provided to the subcommittee to demon- gram was conducted to determine the chemical or physical prop. with and without fly ash. the physical and chemical standard deviations of correlations obtained with the HTP pro- properties of each cement along with the corresponding con. High Temperature and Pressure Method In 1978. in.90.2 the heaters are turned off. % crete temperature at 149 3°C (300 5°F).146 TESTS AND PROPERTIES OF CONCRETE schematic of the apparatus is shown in Fig. A cedures. Therefore. The results of the comparison are shown in Table 6. strate that the method resulted in correlations similar to the erties of cement. air-entraining agent. Undoubtedly. 6—Schematic of apparatus for high temperature and erated strength using Procedure A.9 8. After three hours.0 8. strong correlation was found between the sodium alkali (Na2O) The relationships for the HTP method were expressed as content and the one-day accelerated strengths (Fig. A task force of the subcommittee compared the residual After all cylinders were tested. III. with the strengths of standard-cured 152 by 305-mm (6 by 12- cording to ASTM C 684. Usually. a pro. the subcommittee was requested to modify the existing version of ASTM C 684 to permit the high temperature Effect of Cement Chemistry and pressure (HTP) procedure as an alternative to the other In order to explain the differences between laboratories. a different accelerated strength procedure was proposed that could produce test results within 5 h [9].6 8. only combinations involving Na2O pro. and the electrical Coefficient of Coefficient of heaters are turned on. In 1980. The accelerated strengths were compared were molded from each batch. to obtain one-day acceler.45 and 0. capping materials are not needed because the metal end caps result in sufficiently flat ends. The hardened cylinders Autogenous curing 3.) cylinders.3 0. Procedure A.5 specimens are allowed to cool for 2 h. the variation between the accelerated strengths for the different Type I cements was attributable mainly to variations in alkali content. that affect the one-day accelerated other methods [10]. pressure accelerated curing method. The heaters raise and maintain the con- Procedure Variation. cedure with those obtained by others using the standard pro- crete strengths were analyzed to search for correlations. Special molds TABLE 5—Precision of Accelerated Strength with heating wires and insulation are used to prepare 76 by 152- Tests [8] mm (3 by 6-in.) cylinders. The concrete mixtures were made with strength of concrete. Accelera- tion of strength development in the new procedure is achieved by a combination of elevated temperature and pressure.) cylinders weight) aggregates.2 MPa (1500 25 psi) is applied. a compressive stress of Within-Batch Batch-to-Batch 10. Four 152 by 305-mm (6 by 12-in. the axial stress is maintained. A Fig. Two cylinders were cured ac. and the Modified boiling 3. Similar concrete batches were made using Type I. . For two independent variables. only loss on ignition (LOI) coupled with the Na2O produced a better multiple correlation than Na2O alone. in 100 % relative humidity to obtain standard 28-day strengths. This study provided further evidence of the suitability of the HTP method.58 Bisaillon [14] Autogenous curing I Linear not given 1. private communication.77 MPa (257 psi) for Procedure B and the HTP method.4.21 MPa (175 psi) and 1. To account for the uncertainty in that the HTP method should be added to ASTM C 684. Proponents of the method noted that the data obtained by using a variety of materials showed good correlations.7. Then. the best-fit equations were very similar. 0.36 IV Power function 65 4. Malhotra. a member fidence interval for the estimated average later-age strength of the subcommittee reported on a comparative study of the can be detemined. and 0. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 147 TABLE 6—Comparison of Accelerated Strength Correlations Regression Number of RSD. for a new accelerated strength. and with Table 7. . Estimation of Later-Age Strength To estimate the potential later-age strength from a measured early-age accelerated strength. Fig.a Reference Procedure Cement Type Equation Points MPab Bickley [11] Autogenous curing I Linear 43 2. 11 Jan. erated and 28-day strengths given in the first two columns of ferent sources. 1985.. Surpris- ingly.66 I Linear 36 2. with w/c values of 0. The residual standard deviations were 1. concern was expressed that the hydration reactions due to the high temperature and pressure would not be representative of those due to normal curing. Each number is the average strength of two cylinders.48 Bisaillon et al. HTP method and the modified-boiling method (Procedure To illustrate the procedure.30 Malhotra [16] Modified boiling I Linear 336 2. 28-day strengths (Fig. the task force recommended residual standard deviation. be.54 Nasser and Beaton [10] High temperature I Power function 171 3.40 I Linear 40 2. Based on the comparisons. b 1 MPa 145 psi.82 Roadway and Lenz [13] Modified boiling I Linear 219 3. an air-entraining agent. Ont.5.51 V Linear 61 1. M.59 and pressure III Power function 99 3. [15] Autogenous curing I Linear 213 2. Thus it was felt that the accelerated strength from the HTP method might not be indicative of the potential strength under standard curing. Subsequently.34 I Linear 76 2. Power functions were fitted to the data. Canada Centre for Mineral and Energy Technology. respectively. the laboratory must first con. mixtures were made with fly ash from dif. 2 V. the HTP method was adopted as alternative Pro- cedure D in ASTM C 684. Canada.08 Lapinas [12] Modified boiling I Linear 312 1. Ottawa. the confidence interval for the line is es- cause the 5-h accelerated strength correlated reasonably tablished [17. the regression line. During the balloting process.03 a RSD residual standard deviation. In 1989. 7). 7—Comparison of relationships between accelerated duct enough tests to establish the regression equation and its and standard 28-day strengths.35 IV Linear 147 2.18]. consider the 12 pairs of accel- B). The accelerated strengths were correlated with standard-cured. the con- well with standard-cured strength.2 In this study.46 I and IV Linear 68 2. and steps were taken to incorporate this procedure into ASTM C 684.64 I Linear 265 3. 15 34. Assume that the compressive Fig.23 34. The value of Wi at each value Sa is listed in the fourth Column of Table 7. of 3.77 45.05.97 41. the 95 % confidence interval for the average 28-day strength would be 38.96 41.98 42.89 1.42 18.78 16.64 12.71 39.06 33. because the second term under the square root sign in Eq 6 equals zero.68 40.89 42.19 Sa (MPa) (5) se residual standard deviation for best-fit line (Eq 2). 8) is Wi half-width of confidence interval at Sai.67 16.148 TESTS AND PROPERTIES OF CONCRETE TABLE 7—Values Used in Sample Problem to Illustrate Estimated 95 % Confidence Interval for 28-day Strength Accelerated 28-day Estimated Lower Upper Strength.42 1.30 18.42 41.31 15.00 42. F value from F-distribution for 2 and n degrees of freedom The residual standard deviation of the line.58 1.21 38.71 40.51 1.82 1. Sˆ28 19.82 46. Suppose that the average accelerated strength of two cylinders made from similar concrete is 17.15 40.02 37.29 38.10 1. constructed by calculating Sˆ28 for selected values of Sa and Sa grand average value of accelerated strength for all data plotting Sˆ28 Wi . MPa 12.54 33.86 1.09 37. Strength.13 41.73 1.82 2.8 MPa (5610 to 5920 psi) (see the bottom of Table 7). columns five and six list the values of the lower and upper 95 % confidence limits that are shown in Fig.88 18.85 35.20 35. The 95 % confidence interval for the line [17.09 36.20 1.24 MPa and significance level 0.65 1. MPa Limit.96 35.50 44.22 39. (180 psi). From the regression equation.05 35.7 to 40. where gression equation for the data (Fig. Finally.0 %. Saa ∑(Sa)2(∑ Sa)2/n. se.78 32.96 1. the estimated average 28-day strength is 39. The third column in Table 7 lists the estimated average 28- day strengths for the accelerated strengths in Column 1. Strength.24 41.74 37. points used to establish the regression line.33 33. 8.0 MPa (2460 psi). and Wi se 2 F 1 (Sai Sa)2 n Saa (6) Sa values of average accelerated strength for each point used to establish the regression line. Therefore.76 40. MPa Wi. MPa Sˆ 28. MPaa S28. Confidence Confidence Sa.71 33.73 43.67 17.49 38.62 39. at an average . the standard deviation. the best-fit re. Note that the width of the confidence limits is narrowest when Sai equals Sa .19 37. If the accelerated strength were known without error.44 1.06 38.82 CONFIDENCE INTERVAL FOR ESTIMATED STRENGTH AT ACCELERATED STRENGTH OF 17. However.00 MPa 17.08 40.66 37.57 1.7 MPa (5760 psi). is 1. the accelerated strength has an uncertainty that is described by the within-batch standard deviation.11 21.87 17. within-batch coefficient of variation established strength relationship.92 1.26 40. Using ordinary least squares regression analysis.19] is Sai selected value of accelerated strength.16 42.21 39. 8—Confidence limits for the estimated 28-day strength strengths measured by the specific accelerated test method based on a measured accelerated strength and the previously have a single-laboratory.72 12.38 36.60 41.00 39.07 35. s.46 13.67 20.70 a 1 MPa 145 psi. MPa Limit.05 38.28 42. n number of data points used to establish regression line.03 37.12 45.67 41.99 1.33 34.76 32. history to a “maturity index” that would be indicative of strength development. therefore.” temperature histories of the early-age specimens and by using which stated that statistical methods were to be used to ac. Attempts have been made. where z0. The early-age strengths and the corresponding confidence interval (z0. the maturity index. The basic principles of the maturity method are dis- S 17. . 95 of those intervals would include the true regression line for the population. there are fixed rela- strength is 16. However.645) was used in the illustrative values of maturity index are then used to estimate the later-age example instead of the 95 % interval as presented above. The motivation for the development of ASTM C 918 is tion corresponding to 2. the “equivalent age at the temperature history of the test specimens. measured accelerated strength. comes these limitations by requiring measurement of actual A new paragraph was added under “Interpretation of Results. by multiplying the early- 6050 psi) for the approximate 95 % confidence interval for age strength by an empirical factor. that is. 95 of the intervals would include the true mean.025 17.96 0. simple approach: (1) on a construction project. Thus discussed first. age. Concrete mixtures cured at standard tempera- the 95 % confidence interval3 for the average accelerated ture gain strength predictably.7 MPa (2360 to 2570 psi). Subsequently. history and the availability of water to sustain the chemical als. The The other method developed by the original Subcommittee on reader is urged to read the appropriate section of Malhotra’s Accelerated Strength Testing to estimate the later-age strength chapter in this publication and ASTM Practice for Estimating from early-age tests is based upon the maturity method. Each laboratory must conduct enough tests with a given set reactions. except that the 90 % is recorded. It is insufficient to simply use the regression equation to convert the accelerated strength to Concrete Maturity an equivalent 28-day strength. Each different measurement of have not been found to be reliable. The maturity index from the was added to provide a recommended statistical methodology time of molding each set of cylinders until the time of testing based on the above statistical procedure. See Mendenhall and Sincich [20] for further explanations on the proper interpretation of confidence intervals.0 z0. upon accelerated strength test results. but it does require measuring pute the maturity index.7 MPa cussed by Malhotra in another chapter of this publication and 2 a more comprehensive review is also available [1].23] at the West Virginia the two cylinders is Department of Highways. the testing laboratory first establishes was recommended that estimated strength corresponding to a relationship between the strength of concrete cylinders and the lower 90 % limit could be used to compare with the speci. to relate to the level of count for the various sources of uncertainty. the term “maturity” refers to the extent procedure presented in the example may be found in the ref. cylinders made from similar fied standard-cured strength. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 149 strength of 17. of the development of those properties that depend on cement erences by Moore and Taylor [21] and in Miller [19].51 0.” rather than age. In this chapter. and (2) the early-age temperatures cannot be controlled In 1999.0 MPa (2460 psi) is 0. there are two pitfalls to practical application of this the average 28-day strength. The 95 % an outgrowth of research performed in the late 1960s and confidence interval for the average accelerated strength of early 1970s by Hudson and Steele [22. A nonmandatory Appendix X2 concrete are tested at early ages. it is not pos- mended for implementing the preceding calculations for rou. In the early 1950s.05 1. Additional information on the In concrete technology. The procedure in ASTM C 918 over- ance on using statistical methods to estimate later-age strength. age. there are no special curing ground information on the maturity functions used to com- requirements for this procedure. to estimate the average 28-day strength based maturity index relationship. sible to perform the early-age tests at precisely the specified tine use. the correct interpretation is as follows: If 100 repeated samples are taken from the same population and the 95 % confidence intervals for the mean are computed in each case.0 1. The maturity index can be displayed Overview on a self-contained unit or downloaded to a computer. a procedure is used that The following provides a brief review of the terminology accounts for the uncertainty in the regression line and in the associated with the maturity method.23]. it hydration and pozzolanic reactions. A personal computer is recom. such as at 28 days. However. and it was adopted as ASTM C 918 in 1980. In practice. While this index is not as 3 The 95 % confidence interval is often interpreted to mean that there is a 95 % probability that the true mean falls within the interval. cussed in the next section. Projecting the tionships between the strengths at early ages and at a later limits of this interval to the lower and upper confidence lim. The meaning of “maturity index” is dis- that all interested parties were to agree on the statistical pro.025 is the value from the standard normal distribu. ASTM C 684 was revised to provide explicit guid. It was also stated strength development.3 to 17.51 MPa (74 psi). strength based upon the previously established strength- In summary. It To use ASTM C 918. such estimates the average 28-day strength. Unlike Concrete Strength by the Maturity Method (C 1074) for back- the accelerated strength methods. to estimate the its of the regression line results in 37. the idea was developed that the of materials and a certain procedure to establish the regression combined effects of time and temperature could be accounted line and its confidence limits before estimates of later-age for by using a “maturity function” to convert the temperature strengths are possible. cedures to be used and the criterion for acceptance testing. As has been explained accelerated strength produces a new confidence interval for [22.5 % of the area under the curve. maturity de- is emphasized that a particular regression equation is valid pends on the previous curing history. the maturity index is ob- Later-Age Strength Estimates Using The tained by using electronic instruments that monitor the con- Maturity Method crete temperature and automatically compute the maturity index as a function of age. At any age.7 MPa (5500 to later-age strength. The method is 23°C” is used as the maturity index. The 95 % confidence interval for the regression line has a similar interpretation: If 100 groups of data are taken from the same population and the 95 % confidence intervals are computed for the regression equations.9 to 41.0 0. Finally. as accurately as needed. that is.707 17. the temperature only for a specific test procedure and combination of materi. a “maturity index. if the equivalent age at 23°C increases from one day to ten days. tory and that one of them is instrumented with a maturity me- turity index of the specimens. The purpose of the early-age results is to establish the appropriate value of a as follows: SM a b log M (7) a Sm b log m (8) where where SM compressive strength at M. is the more meaningful quantity and is expected to be used To estimate the later-age strength of a similar concrete more widely in the future. which is the slope of the line. M maturity index. This is generally a reasonable By substituting Eq 8 into Eq 7. program is applicable to the cylinders being evaluated by early- In 1956. ured early-age strength. for example. maturity index of the early-age test specimens is monitored rity as has occurred at the actual age under the actual temper. the at a specified temperature that would result in the same matu. the value of a will be a negative number that has no physical significance. This is done by preparing stan. The values of a and b are obtained by tor” (expressed in degree-hours or degree-days). and the main purpose of Strength-Maturity Relationship cylinder strength tests is to assure that the specified strength is As mentioned earlier. 4 Note that the value of a depends on the units used for the maturity index. These have been reviewed elsewhere [1] and only the assume that the value of a obtained in the laboratory testing function adopted in ASTM C 918 is discussed here. the strength increase equals M maturity index at the later age when strength is to be es- b. Assume that a set of cylinders are molded in the labora- curing procedures.4 The parameter b. the “prediction equa.6 and average strengths (two cylinders) that are obtained at different the corresponding maturity indexes are recorded along with values of the maturity index. The value of a in Eq 7 depends. the concrete-making materials will usually be the same from batch to batch. 5 In the original version of ASTM C 918. however. the average strengths. This is con- ature history. this derivation assumes that the value of b is not affected To use ASTM C 918 to estimate the potential later-age strength by small variations in w/c. 14. Sm average early-age strength measured at maturity index. It is reasonable. at 1. that is. A maturity meter is used to monitor the ma. A change in the value of a shifts the pirical equations have been proposed to represent such rela. strength. If the maturity index is expressed in terms of equivalent age at 23°C in days. as covered by ASTM C 918. represents the increase in strength for a tenfold increase in the where maturity index. The equivalent age is the curing age mixture based on the results of subsequent early-age tests. revisions in 1993 called for monitoring the actual concrete temperature. The values of the early-age strength development under different temperature histories. and proportions of the specific concrete [22–24].5 Pairs of cylinders are tested at ter that computes the equivalent age at 23°C. sensor of the maturity meter is embedded. are used along with the as is covered by ASTM C 1074. . 6 Testing at ages that are related by a factor of two will result in approximately equal strength increments. Application Again. The values of a and b depend on the materials and mixture timated. or it can be used to estimate the previously established strength-maturity relationship to esti- later-age strength under standard curing based upon a meas. Sm. 3. one obtains the following approximation for strength development between 1 and 28 days “prediction equation” for estimating the strength at a later age: under standard room temperature curing. The following example illustrates the application of ASTM C dard cylindrical specimens and subjecting them to standard 918. m. b regression constants. If the maturity index is expressed as the temperature-factor (degree-hours or degree-days). For example. mate the potential later-age strength. According to Eq 7. and 28 days). because large changes in w/c are needed to semi-logarithmic function change the value of b [23]. 7. It is not appropriate to tionships. a variety of em. However. ular maturity index. Plowman [24] proposed that the strength of con. and m maturity index at time of early-age test. SM estimated strength at maturity index M. Example tion. The instrumented crete mixture is used to relate the strength development to the cylinder is exposed to the same environment as the cylinders maturity index. however. During a project. m. equivalent age least squares fitting of Eq 7 to the data. it is first necessary to establish the strength-maturity relationship. from the time of molding until the time of testing. age testing. The availability of relatively inexpensive maturity meters justifies this more precise approach. veniently done by casting a “dummy” cylinder into which the The “strength-maturity relationship” for a specific con. the measurement of the ambient temperature history was considered adequate. to assume that the value crete could be related to the maturity index by the following of b is applicable. strength is a straight line function of the logarithm of the maturity index. and a. The parameter a represents the strength at a maturity index of 1 (the logarithm of 1 SM Sm b (log M log m) (9) equals zero).” for the concrete mixture. the value of a is the strength at one day of curing at 23°C. Over the years. at 28 days.150 TESTS AND PROPERTIES OF CONCRETE well known in the United States as the “temperature-time fac. Table 8 gives the regular intervals (for example. and maturity index. on the strength and the maturity index is a fundamental requirement water-cement ratio since it represents the strength at a partic- to apply the maturity method. knowledge of the relationship between achieved. The relationship can be used to estimate that will be tested for strength. straight line along the strength axis. 9—Example of a strength versus maturity index From such past data. capped. standard-cured strength would be n ∑ di (12) S28 10.0 14. will be eliminated in the near future. it is possible to establish an acceptance relationship. Thus TABLE 8—Equivalent Age and Compressive the 28-day strengths of standard-cured specimens will proba- Strength Values Used in Illustrative Example bly continue to be measured. of the potential strength of the concrete sample.13) d i =1 n 10. d between the measured and estimated 28-day 31/C 31M). 9). First. If the design strength is f28.0 0. two cylinders were removed from their strengths is computed molds. and arithm of the equivalent age (Fig. one can continually correct and improve the slope.0 7. future early-age test. The standard deviation for the difference between the measured and estimated strengths is calculated as follows n sd ∑ i=1 (di d )2 (13) (n 1) The upper 95 % confidence limit for the average difference between the measured and estimated 28-day strength is sd K d t0.5 where 28.5 27. the aver- Making and Curing Concrete Test Specimens in the Field (C age difference. After 24 h.n1 value from the t-distribution at the 95 % point for n 1 degrees of freedom Fig. days. The best-fit equation is Sm measured early-age strength at maturity index m.0 MPa (1450 psi). the differences between the estimated and measured 28-day strengths can be used to calculate a confi- Further assume that cylinders fabricated in the field were dence limit for future estimates.0 28. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 151 such as at 28 days.13 days based on a matu. and The intent of early-age tests is to provide an early indication n number of pairs of strength values. of the prediction equation by using the fol- 1. MPa (10) In addition. By keeping records of estimated and measured 28-day strengths of companion specimens Equivalent Age Average Strength. n mated 28-day. and the ∑ (S28 SM ) i 1 corresponding equivalent age was 1. The value of d is the “bias” of the prediction equation.28 (4250) ∑ (log M28 log m) where S28 measured standard-cured 28-day strength.29 (log 28 log 1.95. It is unreal- istic to expect that the traditional standard tests at later ages. Interpretation of Results di the difference between the ith pair of strength values.0 18.4472 0.0 3.0 13. S28 measured standard-cured 28-day strength.0 13. b. days MPa (psi) from the same batch. the slope is used in the prediction equation to criterion for the concrete based on the estimated strength of a estimate later-age strength based upon early-age strength.3 25. According to Eq 9.95. n age strength of two cylinders was 10.09 (2480) 7.5 MPa (4130 psi) SM the estimated 28-day strength. the esti.25 21.10 17. and thereby establish an ac- subjected to “standard curing” as specified in ASTM Practice for ceptance criterion for future early-age results. and it should be close to zero if the value of b is updated as new data are accumulated. The aver. the concrete . d rity meter in the dummy cylinder.25 13. and tested for compressive strength. SM 10.77 (3160) b (11) 14.29 log M.91 9.56 (3710) 29. days at 23°C. M28 maturity index corresponding to standard curing for 28- These strengths have been plotted as a function of the log.n1 (14) n where t0. Age.44 (1370) lowing relationship [22]: ∑ (S28 Sm) 3.0531) 10.29 (1. Batch-to-batch variations due to mixing on different days pp. 256–262.” Chapter 5 in Handbook standard-cured strength. 10. as dis- ASTM C 918. 3. The other method (ASTM C 918) is based on the principle of the maturity method. inherent deficiencies of the traditional practice. past experience ship is between strength and the maturity index. The results of these early-age tests can pro- and accuracy for quality control purposes. Boca Raton. 4. June 1960. Analysis of the data 50th Anniversary Conference of the Institution of Structural from that program resulted in the following conclusions [8]: Engineers. did not have significant effects on the relationships. why the procedure quire a precisely controlled curing procedure.. the nine laboratories due to the use of different local pp. the basic principle of ASTM C 918 can curing procedures in ASTM C 31/C 31M. information on in.” Journal Institution of Civil Engineers (London). accelerated strength correlated acceptable if the following condition were satisfied: with 364-day strength as well as with 28-day strength. FL and or 91 days. Significantly different relationships were obtained by [3] King. test methods are available to overcome the on strength tests at ages of 28 days or later. Before implementing ASTM C 918. ships within the same laboratory. (refer to ASTM C 1074) at the time of testing. In this case. Vol. materials. V. V. 386–387. also required to estimate the potential. ASTM C 918 does not re- up to 28 days. should be used to establish a confidence erenced for terminology related to the maturity method. and ASTM C 1074 was ref. Paper No. later-age strength. In the 1997 revision of moist curing [8]. References tablish the relationship between the accelerated strength and the [1] Carino.” Journal of Applied Chemistry (London). and Chojnacki.. “Accelerated Strength Testing retarder in the concrete did not affect the relationships. The coop- Before the 1993 version of ASTM C 918. cussed in this chapter. West Coshohocken. ing methods are specified that permit strength determinations at ages ranging from about 5 h to 48 h after preparing the specimens. the relation- that this assumption is valid. provided cannot be applied to estimate strength at ages later than 28 sufficient moisture is maintained during early ages to sustain days. [6] Malhotra. 19. Subsequent tests showed that significantly different Sm ƒ28 K (15) strength relationships were obtained by the laboratories because of variations in alkali content of the cements. changes were made in the 2002 revision of ASTM C 918. P..” Proceedings. ASTM International. velopment of ASTM C 684 was reviewed. the Use of an Accelerated Method of Estimating 28-day day standard strength ranged from good to excellent. J. J. of Concrete Cylinders. In the 1993 revision. Typically. May 1961. this information was moved into in an assessment of concrete quality at ages less than two days the body of the standard. “Accelerated Testing of Concrete.. timate the potential later-age strength of concrete specimens later-age strength could be estimated with sufficient precision tested at early ages. however. If the laboratory results reveal that the linear approxi. “The Maturity Method. Four alternative accelerated cur- duction process on major construction projects. A previously established relationship is strength is a linear function of the logarithm of the maturity in. The only additional still be applied provided an appropriate equation is used to rep. 1963. J. “Accelerated Test for Strength of Concrete. M. pp.. 376–381. later-age strength based dex.. G. Minor interval of the estimated potential. pp. M. In a statisti- This chapter has discussed the basis of two test methods to es- cally designed testing program. Vol. is measured at 28 days. W. Appropriate statistical techniques. The specimens are cured according to the standard- mation is not applicable. Examples of specimens must be monitored to determine the maturity index equations that may be applicable are given in Carino [1]. T. Unlike the ac- shows that the linear equation is usually adequate for strengths celerated strength testing methods. hydration. W. laboratory testing is required to es. the standard-cured strength on Nondestructive Testing of Concrete 2nd Edition. which relies In summary. Strength of Concrete. The cooperative testing program leading to the initial de. 1. N. There is no reason. “The Accelerated Curing of Concrete Test 2. but other ages are possible. Prior to using these measured accelerated strengths to estimate the later-age strength. 63. As was stated. The definition of the factor K in the that is as reliable as that obtained after 28 days of standard 1993 version differed from Eq 14.23].. 1958.” Proceedings ASTM. London. This method also re- vide timely information on the concrete production process quires use of statistical principles for a reliable lower-bound es- for quality control. 6441. depending on the job specifications. the user should verify on the measured early-age strength. [4] Akroyd. results pendix. N. For each cement type. 1079–1101. Oct. PA. CRC Press. Early-age strengths can be measured at any age 24 h after molding the specimens. The potential benefits arising from One of the test methods (ASTM C 684) involves subjecting early-age testing should be considered carefully prior to setting the early-age test specimens to specific curing conditions that ac- up the quality control program to monitor the concrete pro- celerate strength development. B.” Internal Report MP1 68-42. in which the early-age curing history Precautions is converted to a maturity index indicative of the level of The prediction equation given by Eq 9 assumes that concrete strength development. using the same procedure and materials. 2004. Vol. to judge the ade- deficiencies of quality control programs based on the tradi- quacy of concrete batches. Eds. H. N. The omission or addition of a normal amount of chemical [5] Smith. erative study showed that accelerated strength testing by a sin- terpretation of results was included in the non-mandatory ap. J. and Zoldners. Correlation of accelerated strength with 28-day and 364. Eq 14 was introduced. W. 1–22. These procedures attempt to overcome the timate of the potential strength. requirement is that the temperature history of the early-age resent the actual strength-maturity relationship. gle laboratory. it was shown that the potential. tional 28-day strengths. Different types of cements resulted in different relation- Cubes. such as 56 Malhotra and N. “Some Field Experience in 5. Carino. [2] King. Minerals .. Summary The basis of ASTM C 918 is research performed at the West Virginia Department of Highways [22.152 TESTS AND PROPERTIES OF CONCRETE represented by the early-age results would be considered 6. H. M. A. 259–283. pp. Record. Malhotra. Washington. 2nd ed. MI. and Dietz. 1975. Malhotra. 50–60.. and Tiede. John Wiley & Sons. New York. “Early Assessment of Concrete Quality by tion of Potential Strength of Concrete from Results of Early Accelerating Compressive Strength Development with Heat Tests. 117–128.” in ACI SP-56. M. No. M. 4. and Beaton. Short-Termed Tests at La Angostina Hydroelectric Project. Malhotra. the CN Tower. Accelerated Strength Testing. M. “Use of Modified Boiling tute. Chin. N.” in ACI SP-56.” Transportation Research Record. G. No. V. American Concrete Institute. [12] Lapinas. R. R. L.. New York. 558. NBS Handbook 91.” Journal of [24] Plowman. No.. M.. Strength Potential. pp... 95–101. 13–22. “Accelerated Strength Test Results from M. A. celerated Strength Testing. M. 1978. Vol. M. H. Ed. 51–73. T. MI. W. Concrete Practice. B. Ed. American Concrete Institute. (Results of ASTM’s Cooperative Test Program). MI. 29–44. “Statistical Properties of Accelerated Testing Procedure for the Control of Concrete During Techniques for Predicting Concrete Strength and Examples of Construction of the Tunnel ‘Emissor Central’ in Mexico City. Strength Testing of Concrete.” Highway [7] Smith.. American Concrete Institute. W.. Ed. L. Mexico. Simultaneous Statistical Inference. ACI SP-56. “Prediction of Potential Resources..” Transportation Research Record.” Accelerated Strength Testing. 1963. V.1R-81(1986).... M. 201–228. W.. 2. 179–188. and Olivan. pp. 1975. Strength of Accelerated Cured Concrete. and Lapinas. 22.. Applied Regression Analysis. 558. Accelerated Day Test for Concrete. American Concrete Institute. Zoldners. 210. .” in ACI SP-56. 25–36. Orchard.” Transportation Research Record. A. K. “Accelerated Methods of Estimating National Bureau of Standards. No. pp. K. E. “Accelerated 28- of Expanded Polystyrene Molds for Self-Cured. Farmington Hills. Method in Manitoba and Alberta. Ottawa. 1978. [9] Nasser. Ed. Highway Research Board. and Al-Rawi. Prediction of 28-day Strength of Concrete. “Accelerated Testing for pp. March 1956. Concrete Made with Slag Cement. pp. Magazine of Concrete Research. I. [18] Draper. H. [17] Natrella. “A New Method and Apparatus for Accelerated pp. Ed. Accelerated Strength Testing.. “Field Evaluation Malhotra.. 1981.. ACI SP-56. Dellen Publishing Co. S. No. pp. 51–54.. A. V. Ramakrishnan.. G. F. Kalyanasundaram. 69–76. M. M. Accelerated Strength Testing.. 1981. CA. pp. 129–146.. A. Malhotra. 1971.. R.. R. and Larason.” Transportation Research Record. “Maturity and Strength of Concrete. Malhotra. “Developments in the Predic- [8] Wills. A.. 251–262. 77–86... pp. Vol. K. 2nd 558. “Accelerated Concrete Strength Testing at Quality Control of Concrete. pp. “Use of Accelerated Strength Testing.1–12. 3rd ed. and Sincich. pp. V. pp.” Canadian Pit and Quarry. Ed. R. American Concrete Bibliography Institute.. Fãlcao Bauer.” Transportation Research pp. [15] Bisaillon.. 1968. 1978. No. P. W. 558.. 1975. Malhotra. M. V. ACI Committee [10] Nasser. American Concrete Institute. Experimental Statistics. W. “Quality Control of Concrete by Means of Concrete Institute. ACI 214. 1975.. 75–93.. pp. F. 1978. 558. P. 1967. American Concrete Institute. V. 558. Strength of Concrete from the Results of Early Tests. 1975. Strength Testing of Concrete. the Strength of Concrete. No. Sciences. 1978. “Earlier Determination of Concrete Research Record.” Journal of the American Concrete Institute. V.” Journal of Testing No.. R. pp.” Accelerated Strength Testing. and Keyser. Fréchette. “The K-5 Accelerated Strength 214. 558. [23] Hudson. B. V..” in ACI SP-56.C. July 1975. Jones. and Flores-Castro. G. V. J. and Steele. K. G. D. Springer-Verlag. Vol. R. 15–28. H. San Francisco. pp.” Ac- Their Use.. T. Brockenbrough.. 29–61. Ed. [14] Bisaillon. No. and Kurien. M. “Accelerated Concrete Strength Testing by pp. 2. pp... M. Bibliography. L.. Farmington Hills. J. V. Jr. K. 13–18. Sanchez..” Transportation Research Record. V. 29–38. 1986. G. May-June 1980. 1975.. ed... Ed.” Transportation Research Record. Malhotra. 370. R.” ACI Manual of Tester. Ed.. V. L. D. “Canadian Experience in the Use of the Properties and the Thermal Compatibility of Aggregates on the Modified Boiling Method. Ont. 1978. V. ACI SP-56. Amer- Malhotra. and Evaluation. Ed. V. [20] Mendenhall. M. American Concrete Insti- [13] Roadway. Ramakrishnan.” Testing and Evaluation. 249–258. 3. 1978. W. “The Effect of Cement [16] Malhotra.. Expanded Polystyrene Molds with Emphasis on Initial Concrete MI. M. and Smith. J.” in ACI SP-56. K. Accelerated Strength Testing. pp. No. “Experience in the Use of the [21] Moore. and Steele. 1978.” Accelerated Strength Testing. March 1974. 8. and Lenz. Aug. Farmington Hills. Statistics for Engineering and the MI. H. 3.. M. Mines and [22] Hudson. 285–312.. J. ACI SP-56. Temperature. Farmington Hills. N.. Malhotra. 77.. “Early Strength Test for [11] Bickley.” Highway Research Record. Vol. American Ferrer. M. J. Accelerated Strength Testing. J. Farmington Hills. 1975. G. ican Concrete Institute. V. No. R. Malhotra. “Accelerated Strength Testing—Annotated [19] Miller. pp. State of Chiapas. S. Modified Boiling Method: Concrete Producer’s View. and Taylor. R. 1978. “Use of Accelerated Tests for American Concrete Institute. March 1966. pp. Accelerated Strength Testing. Canada. No. CARINO ON PREDICTION OF POTENTIAL STRENGTH AT LATER AGES 153 Processing Division Department of Energy. 1992. pp. pp.. 61–68. “Strength Tests at Early Ages and at High Setting Temperatures.” in ACI SP-56. Aug.. J. A. 1978.. No. In addition. as the U. and for interpreting the results of exposure in either the labora- lished by the Highway Research Board (HRB) in 1957 [9] with tory or under field conditions. with some 600 citations. ASTM Test field exposures. available. an update of the reference list and a few re. This test. freezing and thawing. in 1975. the Portland Cement Association. methods have been discontinued. ACI symposia on durability of concrete. ASTM STP 169B. was pub. A monograph by Woods [6] presents risdiction of ASTM Committee C9 on Concrete and Concrete Ag- a comprehensive picture of durability. to freezing and thawing.2]. There are currently two standard test methods under the ju- Arni [4]. the chapters on this subject in ASTM STP 169. came commercially available for food processing in the 1930s. Degussa Admixtures.15 Freezing and Thawing Charles K. 70. the Corps of Engineers. [8]. OH 44122. 2 Attack by aggressive fluids and cement-aggregate reactions are treated elsewhere in this publication. Perhaps the most com. 66. The presently standardized rent annotated bibliography. to the version that appeared there. from the 19th century survive. A more cur. Newlon. Inc. An for predicting the resistance of concrete to freezing and thawing extensive annotated bibliography on concrete durability pub. need for rapid assessment of resistance to weathering and the tee 201 on Durability of Concrete [12] contains valuable rec. Mitchell. H. Scholer and T. difficulty of translating the results from accelerated laboratory ommendations for the production of concrete that provides testing to the varied conditions encountered in field exposures. the most widely used of those pects of producing durable concrete [13–17]. of “artificial stone” in the form of portland cement concrete ASTM STP 169A. C. cedures are standardized that provide invaluable information ance to freezing and thawing is that of Larson et al. freezing and thawing. Powers [3]. tion) constructed specialized equipment for testing concrete by rently standardized testing procedures for evaluating the re. respectively. purposes naturally gave variable results. the Bureau of Public Roads (now the Federal Highway Administra- Introduction tion). will be found in reports by the agencies [19–24]. and 1997 resulted in 17. 111. and T.S. 1994. T. Nmai 1 Preface weathering is determined by its ability to withstand the effects of freezing and thawing in the presence of moisture. on various theoretical and operational as. Method for Resistance of Concrete to Rapid Freezing and 1987. but when freezing equipment be- Newlon. this chapter includes only minor that tests conducted in a variety of freezers designed for other changes. Beachwood. 290 and C 291) and provides for two procedures: Procedure A poration of aggregates susceptible to detrimental expansion by in which both freezing and thawing occurs with the specimens reaction with alkalies in cement. several agencies such visions in the text. Jr. Few published tests authored by C. and ASTM STP 169C were would result in corresponding evaluations. resistance to the various destructive processes encountered in Of the currently standardized methods. and 81 Thawing (C 666) covers the exposure of specimens to cyclic papers. that is. Jr. H. of this special technical publication by Scholer [1. 154 . 1991. These efforts The published literature on the subject is extensive and only a marked the beginning of a systematic quest for standardization somewhat superficial treatment can be given in a brief paper. Because little has changed in this subject area since the pub. is a consolidation of two earlier methods (ASTM C In the absence of contact with aggressive fluids or incor. respectively. and Procedure B in which the specimens 1 Chief Engineer. It was only natural that the advent and properties. Arni. H. the resistance of concrete to surrounded by water. and H. and the National Sand and Gravel Association (now the National Aggregates Associa- The purpose of this paper is to discuss the significance of cur. Two older freezing and thawing a supplement in 1966 [10] contains 534 citations. several petrographic pro- prehensive treatment of the influence of aggregates on resist.. and an understanding of factors influencing the resistance of The reader should consult the similar papers in earlier editions concrete to freezing and thawing. The report of American Concrete Institute (ACI) Commit. Powers. and one by Cordon [7] gregates intended to aid in evaluating the resistance of concrete discusses freezing and thawing in detail.2 THE SUBJECT OF FREEZE-THAW DURABILITY The testing of concrete for resistance to freezing and thaw- of concrete was covered in all four previous editions of the ing had its genesis in similar tests on building stones reported ASTM Special Technical Publication on significance of tests as early as 1837 by Vicat [18]. the reporting of such testing increased. Bureau of Reclamation. Descriptions of some of this equipment sistance of concrete to weathering under service conditions. and Newlon [5]. methods as well as those discontinued have evolved over more lished by the Strategic Highway Research Program in late 1992 than 60 years and reflect the inevitable compromise between the [11].. With the recognition lication of ASTM STP 169C. 03. verse. length change was incorporated as Historical Evolution an optional. Rapid freezing was more severe than slow freezing when again in 1959 [31]. Methods involving freezing in water were more severe. brick. Freezing in Air and Thawing in Water (C 310). In 1928. In general. Good reproducibility generally was obtained only In 1951. through the freezing point with specimens that are continu. Grun [27] in 1944 and 1954 test series as follows: Europe and Scholer [28] in the United States reported results 1. that is. development of freezing and thawing tests is beyond the scope When ASTM C 666 was originally adopted. ASTM Test for Resis- tinued in 2002. initiated in 1954 and re- conducted “by substituting for the expansive force of the con. ASTM Test for Resistance of Con- Freezing (C 671). Longitudinal. one with good-quality coarse aggre- of the U. first two cooperative test series were conducted before any 4. the Highway Research Board (HRB) Com. an extensive body of freezing chamber and thawing tank. both of which provided for general characteristics of the methods are reflected in their ti- a single cycle every 24 h. mittee on Durability of Concrete reported results of coopera. from accelerated freezing and thawing of concrete in the labo. The 1944 series of tests used concrete 5. and 2. the two rapid environmental factors.15 and cur. In 1971. were dropped because of lack of use. additional means for that evaluation (length As early as 1837. that is. 13 laboratories participated using three concrete for- soda. soon after standardization of the four gealing water. Only the slow freezing in air and thawing in water method methods were standardized. In 1984. and Torsional Frequencies of Concrete Specimens (C 215). samples of marble used in the extension adequate air entrainment. also because of lack of use. the air content of the specimens. ASTM Test for Resistance of Concrete Specimens to Slow 1952 and 1953 that later became standards. deterioration of this summary. the degree of sat. laboratories. ASTM approved four tentative test methods in ods. involving freezing in air. the sulfate of methods. produced failure in fewer cycles. ASTM Test Method for Scaling rently C09. and ASTM Test for Resistance of Concrete Specimens to Slow ously wet. a brief treatment is necessary. In 1936 [29]. which employed a single cycle of cooling crete to Slow Freezing and Thawing in Water or Brine (C 292). tory testing greatly increased. The reader of specimens was evaluated only by the resonant frequency should consult the cited references for additional information method. These meth. The 1936 series concentrated on (ASTM Test C 310) was able to discriminate adequately be- the influence of cement using mortar prisms incorporating ten tween concretes of low durability.67) with the major responsibility for proposing Resistance of Concrete Surfaces Exposed to Deicing Chemicals methods for evaluating the resistance to freezing and thawing (C 672) provides a procedure for evaluating the effect of deic. These tests were In the third cooperative test series. tional freezers with manual transfer of specimens between the While much is still to be learned. commercial cements. 3. Following Scholer’s initial paper. by 50 cycles of mulations: a concrete with good-quality coarse aggregate and freezing and thawing. gate and deficient air entrainment. done in air but not when done in water. These methods were knowledge has been developed that permits evaluations of dropped in 1971 because neither was in general use nor re- concrete to aid in minimizing premature deterioration from quired by any other ASTM specification. reported the results from experiments in ASTM Specification for Apparatus for Use in Measurement by Brard [25] to distinguish the building stones that were in. phasized especially by the HRB cooperative programs was poor and the degree of saturation of the concrete at the time of repeatability and reproducibility of results within and between freezing. Rapid freezing and thawing in water (ASTM Test C 290) tive freezing and thawing tests designed to identify factors that appeared to do the best job of detecting a difference be- influence resistance of concrete to freezing and thawing. Both of these series emphasized the necessity for cretes in the same order of durability when there was a sig- carefully regulating the methods of making and curing the nificant difference. tests. various tests of stone. the 20th century. in his famous Treatise on Calcareous change measurements are made with the apparatus described Mortars and Cements. NMAI ON FREEZING AND THAWING 155 freeze in air and thaw in water. These are ASTM tance of Concrete Specimens to Rapid Freezing in Air and Test for Critical Dilation of Concrete Specimens Subjected to Thawing in Water (C 291). ASTM Committee C9 formed Subcommittee III-0 for concretes that were very high or very low in durability. of Length Change of Hardened Cement Paste (C 490). ASTM Test Method for Fundamental Trans- on these subjects.” specimens. The Air and Thawing in Water (C 310). Vicat. Capitol [26]. of aggregates in concrete and standardizing the methods of ing chemicals on concrete and the effectiveness of modifica. 1944 [30]. that of an easily crystallizable salt. concretes in the middle range. One of the difficulties with the four methods that was em- uration of the aggregates at the time of mixing the concrete. The tween concretes both of which had high durability. Drawing heavily on the results of the HRB cooperative tions of the concrete or of surface coatings in mitigating the test series and the experience of several laboratories that had detrimental influence of such chemicals. and Arni [4] summarized the general conclusions from the other porous materials were reported. These methods Freezing and Thawing in Water or Brine (C 292) and ASTM were largely representative of the methods and procedures Test for Resistance of Concrete Specimens to Slow Freezing in then in use by the membership of Subcommittee III-0. ported in 1959 [31]. and the ASTM Practice for Evaluation of Frost Re. than were those ratory. accelerated labora. tles: ASTM Test for Resistance of Concrete Specimens to Rapid Another standard and a recommended practice were discon.S. jured by frost from those that were not [18]. For on Resistance to Weathering (subsequently C09. thawing tests. Freezing and Thawing in Water (C 290). Two of the initially developed specialized equipment for conducting freezing and approved standards were discontinued in 1971.” In 1856. concrete. the four methods tended to rate different con- specimens. a wide spread in results was ob- . Joseph Henry reported testing. tests (ASTM C 290 and C 291) were combined as two proce- While an extensive discussion of the theory and historical dures (A and B) in a single test (ASTM C 666). The two slow sistance of Coarse Aggregates in Air-Entrained Concrete by tests were adopted to cover tests usually conducted in conven- Critical Dilation Procedures (C 682). and one with poor-quality During the two decades before and those after the turn of coarse aggregate and adequate air entrainment. the water content exceeds the critical saturation point. the stress is produced not by hydraulic pressure. the pressure thawing tests to be applied to the evaluation of coarse aggre. in ceeds the strength of the paste. As the concrete pavements can be identified by freezing and thawing water freezes. Browne and Cady [45] have summarized for more than a century. Such flow would occur when an unpublished report. The theory was were required [32]. and the pores of the paste causes unfrozen water to move to the site no standardized failure criterion is available.). While the variabilities were large in the middle range. thawing studies related to aggregates [8]. they were amenable to establishing a precision statement that Powers and his co-workers. ASTM C 666 continues to be the most enough to cause chemical attack. the mechanism is probably Theoretical Considerations most influenced by concentration gradients. are required to account for the behavior of con- tures of methods that had been developed and used by various crete subjected to freezing and thawing. Various theories have been advanced to explain for conducting the tests under controlled conditions. the designation “osmotic pressure hypothesis. conceived as spaces into which the excess water produced by ods. and procedures vary considerably. a value that was approximately the same as crete. led to the de.156 TESTS AND PROPERTIES OF CONCRETE tained. When freezing and thawing takes place in the presence of cated to permit ponding of water on surfaces that are sub. as discussed later. which combined fea. Since the resistance to flow at a given rate is pro- ance to freezing and thawing of coarse aggregates in concrete portional to the length of the flow path. being due to the viscous resistance of such flow through the gates. trated. In addition to the Cyclic freezing and thawing tests were developed on a prag. deicing chemicals. as well as those of this work. [37]. amplified in 1949 [39] to explain the beneficial influence of en- Lack of a standardized test method for evaluating resist. Agencies desiring of freezing in order to lower the concentration made higher at to use these procedures for accepting or rejecting aggregates the freezing site than the more dilute solution of the unfrozen develop failure criteria by relating the freeze-thaw test results water. Specialized equipment is commercially available and thawing. particularly on highway and bridge deck pavements.” Concern with surface mortar deterioration or deicer scal. scaling results from freezing widely used. This dures for using ASTM C 290 if evaluations of coarse aggregates concept is called the hydraulic pressure theory. In 1961. by the segregation of ice into layers that enlarge as unfrozen ture survey prepared by Larson et al. was reproduced artificially in the laboratory environment.. the air bubbles were coupled with theoretically based criticisms of the cyclic meth. these theories and their own experiments. of such tests was not warranted because of the high levels of when the flow path exceeds a critical length. Although definitive answers have not been obtained. The existence of solutions of various concentrations in specimen preparation. trained air. 0. that suggested by Mielenz and his co-workers from experimen- posed to continuous soaking and subjected to a cycle of cooling tal studies [40]. freezing could be expelled without generating destructive pres- velopment of methods designed to determine the length of time sures. This method was first used by the California soils did not apply to mature concrete. modification. the subcommittee reported that standardization permeable structure of the concrete. Powers. the pressure ex- variability associated with the existing methods. the subcommittee did outline proce. According to Stark even if the concrete is at a uniform temperature throughout. in a subsequent summary of his and other re- ing. nal sources but also must withstand pressure generated by wa- More recently. which provides guidelines for applying ASTM Test C 671 considered separately when explaining the resistance of con- to the evaluation of coarse aggregates. again because neither was in only may become critically saturated by moisture from exter- general use nor required by any other ASTM specification. localized failures of the exposed surfaces oc- jected to freezing and thawing in the presence of various cur that is called “scaling.01 in. sures. is water is drawn toward the region of freezing rather than a particularly valuable reference on all aspects of freezing and forced away from it. This flow generates stress somewhat like osmotic pres- to field performance. Powers’s initial studies suggested that the hy- through the freezing point exhibited dilation greater than a pothesis advanced by Taber [39] to explain frost heaving of specified value. and that this process described earlier. hence. particularly by Powers [33]. ceptible to this type of deterioration [36]. ASTM C 671 was approved in 1971 along with ASTM Powers [43]. but sively evaluated by Larson and his co-workers [35]. led in search [44]. As an outgrowth of Studies by Verbeck and Landgren [42]. pothesis. advanced the hy- As noted earlier.25 mm (0. It was assumed that the creased deicer concentration. Subcommittee III-0 was formed initially pothesis that the destructive stress is produced by the flow of in 1951 with the primary mission of developing freezing and displaced water away from the region of freezing. the structure of cement paste in 1945 [38]. Verbeck and Klieger [46]. flow of water from areas of lower destruction resulted from the 9 % volume expansion accom. Critical saturation was defined as when specimens ex. as discussed later. with some 1971 to standardization of ASTM C 672. lowering of the freezing temperature that accompanies in- matic rather than a theoretical basis. According to this theory. as part of the research. have generally found a modification of the older procedure The temperature at which water freezes in various pores (ASTM C 666) to be useful in identifying coarse aggregates sus. The litera. agencies studying “D-cracking” of concrete ter expelled from the aggregate particles during freezing. within the paste decreases with the size of the pore so that. ASTM C 671 and ASTM crete to freezing and thawing. Powers calculated a critical dimension of the order of required for an aggregate to become critically saturated in con. According to this hy- Department of Highways [34] and later was refined and exten. but the the increased severity of the damage as compared with freezing essential elements of the method are those that have been used and thawing in water. Ex- deicing agents. to those of higher concentrations generate stresses such as were panying the conversion of water to ice. The method uses blocks fabri. agencies for a number of years. concludes that all three of the theories. from their comprehensive study of has been incorporated in ASTM C 666. make clear that the paste and aggregate should be C 682. in work confirmed . the solution in the pore becomes more concen- concrete in water at a rate of two cycles per day.” or surface mortar deterioration. This is because the paste not C 682 were both dropped in 2002. Equipment. However. cept where the concentration of deicing chemicals is high Of the methods. for example. aggregates susceptible to causing distress in the water will be at various stages of conversion to ice. and thawing portion is not less than 25 % of the total cycle time. and between 275 and 405 mm tures for Concrete (C 260).) of water during the freezing and properties of concrete on the resistance of the concrete to the thawing cycles. Admixtures for Concrete (C 494). . to 37°F) shall be not less than one half of the length of the heat. sumption is not true in many cases because of disintegration. RDF relative durability factor. %. the performance eral manufacturers produce off-the-shelf or custom-built requirement is stated in terms of a “relative durability factor” freeze-thaw equipment that meets the requirements of ASTM C calculated as 666. Currently. and P does not reach 60 % prior to the end of the test n1 fundamental transverse frequency after c cycles of freez. and other parts of the equipment. and ASTM Specification for During the early years of testing by freezing and thawing. ASTM Specification for Air-Entraining Admix- mm (5 in. while in Procedure B. Thus. be achieved during a 24 h period. and ing and thawing. Some and aspects of these machines have been subject to criticism. the number of cycles at which the exposure is to be termi- specimens freeze in air and thaw in water. ASTM Specification for Chemical (11 and 16 in. a minimum of four and a maximum of 12 complete cycles may DF durability factor of the specimen. dure. While this as- movement of water between areas of varying concentrations. For Procedure A. where P relative dynamic modulus of elasticity in percent of the dynamic modulus of elasticity at zero cycles (values of Pc relative dynamic modulus of elasticity.) nor more than 125 cations: namely. DF1 durability factor of the concrete containing a reference n 12 Pc n2 100 admixture (or in the case of ASTM C 494. Capacities typically range from 18 to 80 specimens. al- PN though custom-built units have been designed for up to 120. In these admixture specifications. For Procedure A. freezing and thawing cycles specified in the particular proce- rounded completely by air during the freezing phase of the cy.6°C (41 3°F). found that deterioration was greater for intermediate The fundamental transverse frequency is determined with concentrations of deicing chemical (3 to 4 %) than for lower or the specimens at a temperature of 5. M specified number of cycles at which the exposure is to while for Procedure B. ASTM C 290 and C 291 were combined as Procedures PN A and B in ASTM C 666. n fundamental transverse frequency at 0 cycles of freezing N number of cycles at which P reaches 60 %. or 300 if and thawing. ASTM C 215. The specimens are Procedure A is currently required in three ASTM specifi- normally prisms not less than 75 mm (3 in. for thawing. Neither procedure is intended to provide a quantitative cle and by water during the thawing phase. after c cycles of P will be 60 or greater since the test is to be terminated freezing and thawing. sev. and the time required for the temperature at the nated when the relative dynamic modulus of elasticity falls center of any single specimen to be raised from 16 to 3°C (3 below 50 %. The requirements measure of the length of service that may be expected from a for Procedure A are met by confining the specimen and sur. %. NMAI ON FREEZING AND THAWING 157 by others. only an approved air-entraining admixture). whichever is less. which can be obtained in 25 to 63 N number of cycles at which P reaches the specified mini- days. testing usually is termi- ing period. RDF 100 DF1 Deterioration of specimens is determined by the resonant frequency method. each specimen is surrounded by intended for use in determining the effects of variations in the approximately 3 mm (18⁄ in. both freezing and thawing occur with mum value for discontinuing the test or the specified the specimens surrounded by water. specific type of concrete.” rounding water in a suitable container.) in width and depth. (300 cycles). the nated. DF or (DF1) 300 Some of the equipment is designed for Procedure A only. while in Procedure B. term of testing is 300 cycles. The time required for the temperature at the center of any single specimen to be reduced from 3 to 16°C (37 Because of the danger of damage to specimen containers to 3°F) shall be not less than one half of the length of the cool. the specimen is sur. The fundamental transverse where frequencies are determined at intervals not exceeding 36 cycles of exposure and are used to calculate the relative dynamic DF durability factor of the concrete containing the admix- modulus of elasticity ture under test. Chemical Admixtures for Use in Producing Flowing Concrete laboratories constructed specialized equipment. The scope of ASTM C 666 states that “both procedures are ing period. (C 1017). Such findings can be explained culation of Pc assumes that the mass and dimensions of the by generation of osmotic-like pressures accompanying the specimens remain constant throughout the test.) in length. when P falls below 60 %). not less than 20 % of the time is used be terminated.0 1. but DF they do meet the needs for rapid testing within practical limits. the test is usually used to make comparisons between the relative dy- Rapid Freezing and Thawing Tests namic moduli of specimens and Pc is adequate for the purpose. while the larger units typically can be used for both A and B. The method is designated as “rapid” DF M because it permits alternately lowering the temperature of specimens from 4 to 18°C (40 to 0°F) and raising it from 18 where to 4°C (0 to 40°F) in not less than 2 h nor more than 5 h. The durability factor is calculated as In 1971. The conventionally accepted P relative dynamic modulus of elasticity at N cycles. Cal- higher concentrations (to 16 %). For Procedure A. while de- Statistical analyses of these data.03.67) reviewed the data from major published studies. sloughing or reduction in resonant frequency may occur with- dure A are somewhat less variable than those obtained from out accompanying length change. Either mass loss due to cretes of intermediate durability and that results from Proce. as discussed by Powers [33]. therefore.0 19.7 4. limiting values for the method’s measurement quantities. durability factors or other requirements are stated.5 Above 95 0.3 0. aggregates for construction on agency projects [48]. shows durability factors of concretes containing a disruptions that are caused by unsound aggregates or deficient variety of aggregates. terminations of reductions in tensile or compressive strength showed that the variability was primarily a function of the level are used only infrequently because such testing is destructive. Values for standard deviation (1S) and the properties measured are related to freezing-and-thawing acceptable range (D2S).2 30 to 50 5. In 1976. A tion zone” reflected much greater variability of performance.” ASTM C 666 is similarly was established before levels of precision were established for listed as a method of sampling and testing in ASTM Specifica- ASTM C 666. and. measure different things.3 ASTM C 260. states that “in the absence of a proven freezing and thawing nition of the variability of the test method. tive dynamic modulus calculated from determinations of reso- In response to the requirement by ASTM for precision state.3 7. in Procedure A.8 3. and the manner and extent to which cedures A and B. an undeterminable por. and with varying cement contents. but is consistent with the now-established pre.7 4.3 6. This figure. The specification sure the same level of performance. ing or by a permanent dilation after a freezing and thawing ability is less for very good or very poor concrete than for con. 1987 survey of State and Canadian provincial highway agen- One might conclude that. C 494.8 90 to 95 0.4 1.9 0. of durability factor of the concrete for the ranges of N and P The question of which measure of deterioration is best to normally used.5 3.6 4. der test be at least 80 when compared with the reference While ASTM C 666 is specified in the ASTM Specification concrete. The tion of the variability reflects the real variability of concretes seven had “seven different specification limiting values. One criticism of rapid freezing and thawing tests has been As noted.7 80 to 90 2.4 18.8 1. but again no minimum cision values. nant transverse frequency.6 1. uniform precisions durability factor of the concrete containing the admixture un.7 13. 1. contents. the particular measure used often depends on Construction Materials (C 670).2 23. For very low and very high air face mortar deterioration.3 0. purpose for which the tests are being made.15 666 as an acceptable additional way of assessing deterioration.4 20 to 30 3.4 1. (now C09. as defined by ASTM Practice for damage. especially under natural conditions. as described by Arni [47]. water.2 5 to 10 0. based . The value of 80 test satisfactory to the purchaser. At intermediate values of air content. with appropriate recog. for intermediate levels of perform. a “transi. The value of 80 is not intended to permit poorer for Lightweight Aggregates for Structural Concrete (C 330). ASTM Subcommittee C09. are matters of dis- Preparing Precision and Bias Statements for Test Methods for agreement.158 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Within-Laboratory Precisions for Averages of Six Beams Tested in Accordance with ASTM C 666 Procedure A Procedure B Range of Average Durability Factor Standard Deviation (1S) Acceptable Range (D2S) Standard Deviation (1S) Acceptable Range (D2S) 0 to 5 0.2 70 to 80 4. companied by expansion rather than contraction during cool- These values confirm the long-recognized facts that the vari. are given in Tables 2 and 3 of the philosophy of the laboratory using it and on the particular ASTM C 666 for ranges of average durability factor in ten in. the measured durability factors showed relatively Users of ASTM C 666 have not reached a consensus on small variations.7 10 to 20 2.4 9. minimum durability factor values are given. while mass loss reflects primarily sur- cement ratios. Mass loss is also sometimes used for such assessments. would not be expected for the entire range of durability factors. An example of earlier work showing the variability loss often occurs without a reduction in resonant frequency or at different durability factors is given in Fig.3 12. a precision statement was added to use is complicated by the fact that the different available tests ASTM C 666 for expected within-batch precision for both Pro. but rather to as.4 6. mass Procedure B.2 14. Length change is noted in ASTM C ments in all test methods.7 6. cies indicated that seven used ASTM C 666 to qualify coarse ance as indicated by durability factors.3 17. C 494.9 2. Mass loss measures crements and numbers of specimens averaged from two loss of material or sloughing from the surface of the specimens.4 1. and air contents.8 2. no performance than the reference concrete.6 6. through six. Thus. and C 1017 require that the relative with such characteristics and.1 8.8 50 to 70 6. from expansion. the primary measure of deterioration is the rela- variability of the results both within and between laboratories. Resonant frequency and expansion reflect internal Cordon [7]. and C 1017) are given in Table 1. Values for six specimens (as required by ASTM C Length change is based on the fact that internal damage is ac- 260. cycle. air-void characteristics. tion for Concrete Aggregates (C 33).4 7. cement contents. can cause excessive days old “unless some other age is specified. the comparatively high degree of internal saturation and exposed with the long dimension vertical. and water-cement ratios. particularly in equipment that uses air rather says that the tests should be started when the specimens are 14 than a liquid as the heat transfer medium. who deterioration. since it is difficult to resaturate con- have been made to mitigate this problem. ing Concrete Test Specimens in the Laboratory (C 192) require tion of containers occurs should be interpreted with caution. gin after 14 days of moist curing. Strategic Highway the specimens in containers with the long dimensions horizon. three agencies used durability factor. number of cycles. The speci- damage specimens and are not permitted. as shown by Cook [49]. from Procedure A if the specimens are wrapped in terrycloth tom of containers to absorb the pressures. on the fact that each had a unique way of testing regarding reported to overcome the problem by some and not by others. drying. in containers. method of measuring tive dynamic modulus is clear.”) The mixing pro- damage to rigid metal containers. Results of tests during which bulging or other distor. fications citing the use of ASTM C 666 require that testing be- ther. This situation is particularly noticeable when the specimens are Thus. All of these have been during the test. dur. “Experience has indicated that ice or water pressure. which would include research-supported limiting values. or inclusion of a rubber ball in the bot. One agency has minimized the container tice. curing methods and the number of cycles required to reach a specified level of rela- time. One important potential influence on ASTM C 666 results Another important influence on the results is the degree of is the effect of the container used to hold the specimen during saturation of the concrete and the aggregates both at the time testing with Procedure A. Pressures from continued conversion of water drying normally occurs before exposure to freezing and thaw- to ice between the specimen and container cannot be relieved. tainers made of steel. and possibly to the specimens cedures referenced in ASTM Test Method for Making and Cur- therein. inclusion of flexible windows. Even a brief period of drying greatly improves resistance with consequent bulging of the container. cement contents. failure criteria. including exposure of crete that has undergone some drying. (A note in ASTM C 666 itself ing freezing tests. found that the number of cycles necessary to reach a given level stituting a test. Various adjustments to freezing and thawing. aggregate grading. mens were tested in rubber containers as compared with con- and one used both for specification limits. as a function of air content (after Cordon [7]).” Further. influence by using cylindrical specimens and surrounding them is clearly desirable. coarse aggregate contents. ing. this keeps the outer surface of the concrete . A standard prac. That the degree of restraint offered by the container influences air contents. 1—Durability factors for concretes containing various aggregates. cycle length. with rubber boots [48].” that coarse aggregates be immersed for 24 h prior to mixing. NMAI ON FREEZING AND THAWING 159 Fig. Research Program researchers [11] confirmed the effect of tal to provide a larger open area. They found that Procedure B results approach those or corners. A note explains fur. Rigid containers have the potential to of mixing and throughout the course of the testing. Ice forms quickly on the early age at which testing begins result in a relatively severe the open top rather than uniformly along the long dimension test when compared with field exposures in which a period of of the container. moisture conditioning. and number of specimens con. of durability factor was increased dramatically when the speci- three used length change or another measure of expansion. They cited been rejected by other conventionally accepted criteria.005 % ( 50 millionths) or less. usually conical spalls are cooled in water-saturated kerosene at a rate of 2. noted the significance of moisture conditioning of aggregates Still another influence on freezing and thawing tests is the and concretes in the test methods that generally provided for use of salt water (typically 2 % sodium chloride in water) as the only saturated concrete as compared with natural exposures freezing-and-thawing medium.7 0. isfactory air-void characteristics. similar materials as required in ASTM C 260 and C 494. because of its relationship with the methods. Concrete subject to frost damage should freezing. Prior to critical saturation. and performance amount of freezable water. the specimens lems in a concrete. sections have been his studies of salt scaling. The method was used to evaluate several aggregates was necessary to provide an acceptable degree of frost re. dilation is not critical. He points out that most concrete undergoes both drying freezing and storage in water at low temperature between and curing longer than 14 days before encountering its first freezing exposures. In 1971. a given level of maturity (strength) criteria. between dilations on successive cycles. [34]. They developed specimen preparation and conditioning ported tests indicating that. the time to critical saturation could be more gain characteristics for concrete with sound aggregates and sat. mentitious materials that gain strength more slowly than con. at or near saturation. but that expansion that occurred during a slow cooling cycle icers. Some agencies have used salt where some seasonal drying is possible. when also standardized in 1971. ASTM C 671 was standardized. The length of time required to become critical so that the most consistently reproducible condition is that cally saturated would be compared with the field exposures to of continued moist curing. after which it would ex- variations of saturation that might be encountered is impracti. This practice is based largely on the they were extended to cores or prisms cut from hardened con. accommodating the many possible reach some critical saturation level. the specimen is pressure and can be attributed to defects in the aggregate. readily interpreted for various field exposures.160 TESTS AND PROPERTIES OF CONCRETE moist. recommending that resistance to damage by freezing and thawing.) Visual examination of specimens during ASTM C 666 cy. Use of salt water in Procedure A increases the severity of when the concrete or its aggregates became critically saturated the test beyond that attained with the use of fresh water. pand on freezing. At two-week intervals. Procedures essentially in ac- crete. 1. Popouts are shallow. He stated that durability was not a measurable property tions where water ponds on structures regularly treated with de. If the period during which freezing would be Because the testing is initiated at a fixed age. In addition to the ASTM C 671 criterion for critical dilation in terms Dilation Methods of increase from one cycle to another. dilation is defined as a sharp increase (by a factor of 2 or more) perficial surface defects [53]. . in diameter and 150 mm (6 in. The aggregates sistance as indicated by a durability factor of 50 for concrete judged acceptable by the California procedure would have containing satisfactory aggregates and entrained air. be encountered. This method provides for cylindrical specimens 75 mm (3 in. the popout material would presumably only cause su. Nevertheless. a practical application of Powers’s proposed method strength at the time that exposure begins. but the of initial freezing is particularly important in testing concrete freeze-thaw performance of all of the concrete has been re- made with blended cements and pozzolanic supplementary ce. variation of strength at the time of exposure to freezing and then no damage would be expected. ported as continuing to be satisfactory. ASTM C 682 was applied only to laboratory-mixed concrete until 1975. This influence is minimized when veloped in California were extensively studied and refined by the evaluations are made by comparing concretes made with Larson and others [35]. that is. who reported similar findings in concrete is now more than 30 years old. Powers published a critical review of existing cyclic be as follows: methods for freezing and thawing tests [33]. that is. (a) If the dilation is 0. [51] re. During the cooling cycle. the length change center of a relatively small specimen could cause it to fail. any were using anything other than specimens cast to size it will show some limited initial dilation as all moist specimens specifically for freeze-thaw testing [48]. work of Larson and his coworkers. Buck et al. Critical the field. for a major highway construction project. Experience with testing of specimens from hardened cordance with ASTM C 671 have been used by Buck [54]. testing and measuring techniques. but dilation will not continue throughout the cooling. 2. the rates of from 6 to 60°C/h (10 to 100°F/h) as compared with nat.) long that are stored in water at cling may also give warnings of the likelihood of popout prob. Highly frost-resistant Cyclic freezing and thawing methods were developed and concrete may never exhibit critical dilation. the results of a 1987 survey of State and he found that a specimen that is frost resistant will not show Canadian provincial highway agencies gave no indication that increasing dilation with continuously decreasing temperature. water since that is the medium encountered in many field situa. was measurable and would provide an indication of potential Philleo has taken ASTM C 666 to task. in will proceed along the dashed curve without dilation. rather than allowing it to ural cooling rates that seldom exceed 3°C/h (5°F/h). A typical plot of length change versus temperature is because a large piece of popout-producing aggregate in the shown in Fig. He proposed it be “modified or replaced by a more realistic standard for that specimens be prepared and conditioned so as to simulate judging the acceptability of concrete for field applications” field conditions and then be subjected to periodic slow-rate [50]. He was particu. The procedures proposed by Powers and the method de- crete without such materials.8 of the concrete through aggregate particles due to internal 0. in data on the influence on resistance to freezing and thawing of 1961.9°C (35 2°F). He also dry out during the freezing-in-air portion of the test cycle.5°C/h (5 1°F/h). The earlier work by Klieger [52]. As opposed to a single thawing may be encountered with cements of different strength durability factor. do. The placed in a strain frame to permit measurement of length small size of the specimens in ASTM C 666 has been criticized change. he suggested that a criterion for critical dilation applicable to results of a single test In 1955. There is not a great body of The California Division of Highways was first to report. and concrete is limited. the larly critical of what he considered unrealistically high freezing specimen may be regarded as frost resistant. Consideration of strength at the time overlaid because they are structurally inadequate. considerable expected was less than the time to reach critical saturation. 005 and 0. met consistently and brought forth a plethora of remedial or nificant storage capacity is required. it and thawing in the presence of deicing agents. water on one surface and that could be exposed to freezing tive of that which might be expected in the field. ASTM C 671 included the state.) deep. it became apparent that the increasing use (c) If the dilation is in the range between 0.” The report of ACI Commit- their resistance to freezing and thawing for defined curing and tee 201 says. 2—Typical length change and temperature charts. were discontinued in 2002. In 1971. widespread surface scaling of pavements and bridge decks. It is intended for use in evalu- affected adversely by variability in aggregate moisture. Reproducibility of overall test results is likely to be presence of deicing chemicals. surface treatments. The 1987 survey of State has long been known that dense. This agency has riod of drying before the first application of deicing agents. surface treatment. of deicing chemicals as part of a “bare pavement” policy an additional cycle or more should be run. adopted for the nation’s highways was being reflected in ASTM C 671 and C 682 were not used extensively and.2) and be at least 75 mm (3 in. NMAI ON FREEZING AND THAWING 161 Fig. is essential in preventing damage [12]. subsequently stopped using the method. It was suggested that aggregates and concrete be who used blocks that were fabricated to permit ponding of “maintained or brought to the moisture condition representa.” However. This test method is not in- evaluation were warranted. con.020 % ( 200 millionths) or more. with and Canadian provincial highway agencies indicated that only adequate entrained air and with adequate curing and a pe- one was using ASTM C 671 to any extent [48].” However. Although the appara. tended to be used in determining the durability of aggregates ment that it “is suitable for ranking concretes according to or other ingredients of concrete. mixture” [12].045 which field conditions could be expected to correlate with m2 (72 in. on the other hand. demonstrated that all of these requirements were not being mens can be processed than with ASTM C 666 equipment. The specimens those employed in the laboratory. that is. ers determination of the resistance to scaling of a horizontal urated are very difficult to maintain during preparation of concrete surface subject to freezing and thawing cycles in the specimens.” While ating the surface resistance qualitatively by visual examina- the complexity of the evaluation procedure limited its general tion. are placed in a freezing space after moist curing for 14 days . The procedures of ASTM preventive products including admixtures. or other large projects or economic consequences of detailed aggregate variables on resistance to scaling. both ASTM C 671 and C demonstrate the acceptability or failure of a given concrete 682 warned that the significance of the results in terms of po. the Scaling Resistance specimen may be regarded as not frost resistant. high quality concrete. curing. The test “cov- was noted that “aggregate moisture states other than dry or sat. critical dilation has been exceeded. C 682 were extensive and complex. It sequently. sig.020 %. Widespread scaling tus is comparatively inexpensive and larger numbers of speci. This test method can be used to evaluate the effect of applicability. ASTM C 672 was standardized. and curing agents. (b) If the dilation is 0. the procedures may have been justified where mixture proportioning. ments designed to bracket a broad range of potential exposure The test is based on the experience of a number of agencies conditions. tential field performance would depend upon the degree to The specimens must have a surface area of at least 0. the “use of ASTM C 672 will conditioning procedures. In the early 1960s. largely because of require. MI. “Resistance to Weathering. High- such as are encountered in certain parts of nuclear construc. Dry con.” Publication SP-47. MI. Resistance to Weather- may not be subjected appropriately to analyses based on the ing—General Aspects. chemical attack and alkali-aggregate reac. and every [1] Scholer. characteristics. Provisions are included for appli.” Bibliography 20. West Conshohocken. 15. [10] “Durability of Concrete: Physical Aspects: Supplement to Bibli- creased concentration of dissolved salts. ASTM STP 169. 1978. the writers are not aware of cases where Highway Research Board.” Publication SP-100. [13] “Durability of Concrete. DC. West Conshohocken. sistance to weathering. Washington.” Report SHRP-C/UFR- Summary 92-617. all of which reduce re. DC.57]. Elevated temperatures and a Proposed Program of Research. including freezing of water and of the variety of exposures encountered. W. B.” Manual of Concrete Practice. PA. 1966. Detroit. PA. West Conshohocken. 1992. ternational. MI. As noted in the method. While adequate air entrainment with The method calls for covering the surface with approximately proper air-void parameters protects the paste. and as such [2] Scholer. tions are treated elsewhere in this publication. ASTM International. 1994. Detroit. expansion [56. [11] Snyder. pends on its ability to resist freezing and thawing. 1987. “A Critical Review of Literature Treating Methods of Identifying Aggregates Sub- believed to have at most a minor effect on concrete durability ject to Destructive Volume Change When Frozen in Concrete within the normal temperature range. 10. “Durability of Concrete. crete Institute..” Significance of Other weathering processes that have been suspected of caus. Cady. C. ASTM International. This damage tional Conference. Farmington Hills.” SP- ume of entrained air with the proper void distribution and 145. 1964. ASTM STP 169. “thermal incompatibility” is now generally [8] Larson. available from Transportation Research Board. alternate wetting and drying per se have caused deterioration.” Significance of Tests and Properties of Concrete and Con- range may be used. crete Aggregates.. method describes laboratory procedures. M.” Significance of Tests and Properties of calculation of averages and standard deviations or other tech. an adequate vol. Washing- content that influence the resistance to freezing and thawing. but this is not required by the method. MI.2R-92. it has been used for outdoor exposures as well. 1955. T. mass of the detritus.162 TESTS AND PROPERTIES OF CONCRETE and air storage for 14 days. Washington. Strategic Highway Research Program. 3. J. and exposures that reduce the opportunity for cations of protective coatings if desired at the age of 21 days. DC. American Concrete In- is more likely to occur when the air content of the concrete stitute. is at the lower end of the recommended range. H. M. H. D. [14] “Concrete Durability—Katherine and Bryant Mather Interna- tures may be severely damaged in a few cycles. and interpreted and have undoubtedly resulted in a signifi- The specimens are cycled through a freezing environment cant improvement in the resistance of concrete to weathering for 16 to 18 h. Highway Research Board. 1943. “Freezing and Thawing of Concrete— sion [55] or where the freezing and thawing resistance was Mechanisms and Control. As noted. Detroit. H. P. 1968.. 20. T. American Concrete Institute. ton. ASTM International. ing requires a low water/cement (w/c) ratio. While wetting and drying induce variations in moisture NAS-NRC Publication 493. “Freeze-Thaw Resistance of Concrete—An Annotated Bibliography.. C..” Report on Significance 25 cycles thereafter. followed by laboratory air for 6 to 8 h. DC. ASTM International. Detroit. the ratings are ranks. vere conditions such as hydraulic head or very low tempera..” Bibliography 38. and Janssen. DC. Detroit. Tests and Properties of Concrete and Concrete-Making Materi- ing deterioration include heating and cooling and wetting and als. Although cases [6] Woods. H. The resistance of concrete to weathering in the absence of [12] “Guide to Durable Concrete. drying. ASTM In- niques that assume continuous distributions. but the currently ap- addition of the solid deicer. aggregate cracking from excessive drying shrinkage. West Conshohocken..” ACI Monograph No. West Conshohocken.. PA. T. The specimens are rated visually according to a scale of 0 References (no scaling) to 5 (severe scaling) after 5. such nonparametric quantities as the median and ing. [16] “Durability of Concrete—Third International Conference. American Concrete Institute. PA. tion are beyond the scope of this paper. 1955.” Special Report 80.” Publication SP-126. Research and [15] “Durability of Concrete. Detroit. “Resistance to Weathering—Freezing and Thaw- groups. A. Some investigators have measured the of Tests of Concrete and Concrete Aggregates. and Properties of Concrete and Concrete-Making Materials. critical saturation. American influenced by aggregates with different coefficients of thermal Concrete Institute.. and an in. 1957. Direct translation of results from labo- 4 g of anhydrous calcium chloride. ASTM STP 169A. MI. American Concrete whereas highly saturated concrete exposed to particularly se. . lar specimens are to be reported or compared with other [3] Powers. If groups of simi. Part 1. gregate with an abnormally low coefficient of thermal expan. American Con- experience have shown that resistance to freezing and thaw. Jr. Institute. “Hardened Concrete. Washington. and Reed. Washing- ton. PA. ASTM STP 22A. are allowed where there is need to proved standards are very useful when properly conducted evaluate the specific effect. [5] Newlon. Concrete and Concrete Aggregates. [9] “Durability of Concrete: Physical Aspects. MI.. [7] Cordon.” ASTM STP 169B. Experience with ASTM C 672 generally has been satisfac- [4] Arni. J. H. graph No. come the effect of aggregate that is susceptible to damage by ing a concentration such that each 100 mL of solution contains freezing and thawing. 1975. While the from natural forces..) of a solution of calcium chloride and water hav. way Research Board. 4. Modifications of the deicer ratory freezing and thawing tests is difficult at best because and application procedures. C.” Significance of Tests tory for evaluating the variables for which it was developed. Franzen.. American Concrete Institute.. ography No. “Durability of Concrete Construction. “Resistance to Weathering. Other Weathering Processes 1966. ACI chemical attack or detrimental cement-aggregate reactions de- 201. crete will withstand freezing and thawing indefinitely. 1991. NAS-NRC Publication 1333. it may not over- 6 mm (14⁄ in.” ACI Mono- have been reported where deterioration was attributed to ag. 25. 1966. 1993. MI. . Vol..” Bulletin 150. 17.” Special Report No. Evolution and Effects of the Air [19] “Symposium on Freezing-and-Thawing Tests of Concrete.” NCHRP Report No. istics of Aggregate on the Frost Resistance of Concrete. 53. “Curing Requirements for Scale Resistance of Con- [33] Powers. MI. Washington. H. [54] Buck.. ASTM International.” Journal. 1959. “Identification of Frost-Suscepti. No. mal presentation. P. “Characteristics and Utilization of Coarse Aggregates stitute. lated from the French by J. Associated with D-Cracking. and Thornton. T. J.. and Oct. Detroit. 47. “Origin. C. Detroit. T. Weale. 1856. Transportation Research Board. stitute. “Thermal Expansion of Aggregates and Concrete ASTM STP 597.. Mukherjee. DC. “Investigation of Frost Resistance of Mortar and Highway Research Board. and Cook.” Proceedings. and Flack.” NCHRP Synthesis No. “Automatic Equipment for Rapid Freezing-and. and Bloem. 1952.” Proceedings.. and Kretsinger. PA. 1960. Highway Research Board. Foster...” Technical Report C-76-4. T.” Bulletin 305. “Deicer Scaling Mechanisms in [24] Cook. R. E. Publication SP-47. [56] Callan. A. West Conshohocken. Detroit. R. G. V. [43] Powers. 259. Concrete.. 1963.. ASTM International.. “Studies of ‘Salt’ Scaling of Con- [25] Hericart de Thury. DC. Hooton. J. 1936.” Pro. T. National Sand and Gravel Asso- Equipment and Comparative Test Results for the Four ASTM ciation. 1961.. Bryant Mather International Conference. Washington. MI. 3. C. “Automatic Freezing-and-Thawing Equipment crete. Detroit...S. Vol. “On the Method Proposed by Mr. T.. 24. J. 1956. H. Vol.. B.. “Freezing and Thawing Resistance of High- Strength Concrete. Highway Research Board. 66. 1945. B. Conshohocken. O. H. Vol.” Durability of Concrete. London. R. of the Marble Used in the Extension of the U.S. “Evaluation and Prediction of Concrete Durability—Ontario bility of Concrete Aggregates. 1986. Vicksburg. 55. F.” Bulletin No. Wolkodoff. 1928. Durability. 1987. P.” The Journal of ing-and-Thawing Apparatus for Concrete. tainers on the Severity of Freezing and Thawing Tests. 56. Jan.. K. Vol. C. Vol. Highway Research Board. Washington. Backstrom. West 1957. [45] Browne. C. [53] Sturrup. M. ings. Board. 1979. “Investigations of Concrete in Freezing Chambers. Concrete Institute. PA. 1960. P. MI. No. 38. ble Particles in Concrete Aggregates. D. L. “D-Cracking of Concrete Pavements. Army Engineer Water- [36] Schwartz. [18] Vicat. “Basic Considerations Pertaining to Freezing-and. ASTM Geology.” Technical Report 6-784. West Conshohocken.” Cement. 29. 1958. R. J. West Conshohocken.” Journal. PA.. D. American Concrete Institute. “Freezing Effects in Concrete. American Thawing of Concrete in Water. 1960.” Proceedings.” ment of Transportation and Other Agencies. “Durability Tests of Certain Portland Ce- ments. Aggregate in Concrete: Procedures Used by Michigan Depart- [27] Grun. “The Air-Requirement of Frost Resistant Con- 1997. “Some Accelerated Freezing and Thawing Tests. Vol.. and Landgren. National Ready-Mix Concrete Association. crete. 1987. C. Silver Spring Freezing-and-Thawing Methods for Concrete. 1930. for a Small Laboratory. “Freeze-Thaw Testing of Coarse ican Journal of Science.” Bulletin 150. 48. E. R. 134. 259. Aug. [35] Larson. A. MS. “Tests for Freeze-Thaw Dura. Waterways Experiment Station. P. [50] Philleo. B. D. p. “The Mechanism of Frost Action in Concrete. 38. P. E. ceedings. 28..” Bulletin No. [51] Buck. Highway Research Hydro’s Experience. D. L. D.” Proceedings. July 1958.. B. “Progress Report. 1946.. lication 768. American Concrete In. H.. “A Concrete Failure Attributed to Aggregate of DC. DC. MS.” Pro- ing-and-Thawing Apparatus for Testing Concrete. L. H. S. E. R. Brard for crete. 51. C. G. 1945. E. A. MI. 60. 48. 46. July 1967.. [20] Wuerpel. 1975.. Vol. American Concrete Institute. Test Program. “Prediction of Concrete Frost Resistance of Concrete. [41] Taber.” [22] Arni. 11. DC. D. DC. Concrete. Vol. [29] Mattimore. C. Lawrence Sea- Tests of Concrete. Void System in Concrete. ASTM International.” infor- Vol.. Durability from Thermal Tests of Aggregate. 1. P. PA. 768. Washington. No. [52] Klieger. 1953. H. [40] Mielenz. G.” NCHRP ways Experiment Station.. Vol. (trans. H. 4.. Thawing Tests. [32] ASTM Committee C9. H. “Report on Cooperative Freezing and Thawing of Concrete in Eisenhower and Snell Locks St. “Automatic Accelerated Freez. “Influence of Physical Character- [21] Walker. of Frost. V. T. Jr. 72.” Proceedings. Concrete. 1951. and Spellman. D. [48] Vogler. and Cady. Highway Research Board. D. Burrows. West Conshohocken.. C. A. T. J.. American Concrete In- [37] Stark. 1949. Concrete. 1989. pp. 45... and Klieger. T. Transportation [30] Withey. Low Thermal Coefficient. Synthesis No. PA. crete. Mather.” [49] Cook. Vol. [39] Powers. 1928. the Immediate Detection of Stones Unable to Resist the Action 1957. 129. ASTM International. E. American Concrete Institute. and Clevenger. International. 1975. C. and Aggregates. DC. E. [38] Powers.. and Aggregates. T.” Amer. Treatise on Calcareous Mortars and Cements. ASTM International. 1958.. 1965. [34] Tremper.. NAS-NRC Pub. Smith). “Precision Statements Without an Interlaboratory 160–192.” Proceedings. PA. DC. T.. S. and Carmichael. . Vol. Detroit. Highway Research Board. Vol. DC. [28] Scholer. 16. DC. Feb.. 1969. minutes of December 1961 Meeting.. 1976. R. C. 1958. R. T. D..” Proceed. “Investigation [31] Foster. [47] Arni. Vol. NMAI ON FREEZING AND THAWING 163 [17] SP-170. W. [46] Verbeck.” Cement.” Concrete Durability—Katherine and Board. American Concrete Insti- ceedings. Vol. 45. Publication SP-47. PA.. S.. American Concrete Institute. Annual Meeting of Highway Re- search Board. “Performance of Automatic Freez. 1952. Washington.” Annales de Chimie et de Physique. crete.. J.” Proceedings. D. tute. Washington. Highway Research way. Washington. [26] Henry. [44] Powers. “On the Mode of Building Materials and an Account 2.” Proceedings. West Conshohocken.. [42] Verbeck. West Conshohocken. 1976. U. “The Mechanics of Frost Heaving. MD. Washington. PA. Highway Research Board.. 1. ASTM International. Con- Zement. West Conshohocken. “Effects of Fluid Circulation and Specimen Con- Proceedings. J. H. K. 1955.” Proceedings. PA. Washington. and Grove. 1837. K. [55] Pearson.. Session 13. Vol. MI. Vol. Farmington Hills. NAS-NRC Publication MI. R. and Cady. Publication SP-100. H. ASTM International. ASTM International.” Durability of Con- [23] Cordon. Vicksburg. Washington. W. G. Vol.. 1944. Highway Research Board. West Conshohocken. Capitol. Committee on Durability of Research Board. “A Working Hypothesis for Further Studies of [57] Higginson. H. E. L. 1828. “Automatic Stanton Walker Lecture No.” Living with Marginal Aggregates. Sept... sealers. 1 Research and Development Fellow. which Note—as in the original versions. however. the source of the chloride is since it involves transfer or displacement of electrons. The number of references has in. separated by only small distances. including reinforcing steel. However. These and other structures have suffered concrete in the presence of chlorides [1]. Temper. it may be chemical admixtures added to the concrete where anodes and cathodes are some finite distance apart. The main value of the chapter is to provide an construction. so it should be minimized. made in recent years. Chloride marine structures in this country have been severely dam. Few metals (except for the noblest forcement earlier. How- usually deicing salts. investigative tech- sion inhibitors. However. Peren. epoxy-coated steel. as in concrete. gold. ions can disrupt the passive film through a process known as aged by corrosion of reinforcement and the resultant in. metallic (elemental) state. cathodic protection. An electrolyte is not necessary. introduction to the field and numerous references for a more in-depth understanding. that protects concrete. the anodes and cathodes are corrosion.4]. Metals tend to do this tion are not addressed as chloride is the major problem and because. are normally well sive film of tightly adhering corrosion products usually forms protected against corrosion by embedment in high-quality on steel in alkaline environments. The increased volume due to the development contained in the same bar. however. chio. Materials tend to seek lower energy levels. or moisture. making the flow of electrical current over measurable dis- Cracks are not necessary for chloride penetration into the tances a part of the process [2]. sometimes termed atmospheric corrosion amount of chloride. In this case. resulting in corrosion starting at an earlier ones: platinum. Such chloride-induced corrosion is a serious problem. all are The first three sections remained as they were with a change in expensive. Corrosion. is usually the oxide or the hydroxide. loads. that contain chlorides for set acceleration. of course. When a metal corrodes. In ASTM STP 169A. IL 02140. therefore. carrying ions and completing the voltage differentials to develop that greatly increase the rate of electrical circuit. quickly disappearing while in service. with the water in which they are dissolved. can cause of rainwater can act as one. this chapter was authored by B. bridges and parking structures. or oxygen at different points [3. the carbonation [1]. embedded metals from corrosion at the design stage have been Substantial changes are included in the following sections to re. Salts are capable of penetrating solid concrete along place on reinforcing steel that is exposed only to air and rain. Mechanisms of Corrosion creased from 28 to 53 reflecting the increase in information available today. Berke1 Preface of corrosion products can cause spalling of the concrete cover. parking garages. Cady. tendency to corrode. In ever. and remedial measures. Cambridge. the effects of carbona. even a thin film along a reinforcing bar. Significant improvements in methods of protecting Ref 1 to provide a source of more information on the subject. This chapter will discuss the mechanisms flect more knowledge that is now available on the use of corro. this chapter was authored by P. silver) are ever found in nature in the time. In marine structures. In ASTM STP 169B. in their metallic state. many of the bridges.16 Corrosion of Reinforcing Steel Neal S. typical damage caused by it. Grace Construction Products. Durable repair procedures are available. amounts to the depth of the reinforcing steel. Variations in the This is. and sufficient reduction in the cross section of the bar to THIS VERSION OF CHAPTER 17 IN ASTM STP 169C IS render a structure incapable of safely supporting its design an updated version of the chapter written by William F. it returns to its natural state. A good overall treat- damage due to the penetration of chloride in sufficient ment of the corrosion of steel in concrete is given in Ref 1. of corrosion. niques for evaluating its extent. means of preventing it in new and new steels. and the remaining steel from the corrosive conditions [1]. or between different bars. one might expect that metals would be unusable. Because of this tendency to return to the state from which Introduction they were refined. a pas- Many metals. hence. they are at a higher energy design for chloride resistance will provide protection against level. can take concrete. it is seawater. 164 . Cracking can cause chlorides to reach rein. In the case of Any chemical action can be regarded as electrochemical. pitting and this is the initiation process of corrosion of steel in creased volume. the term is sometimes applied only to cases of corrosion others. J. if no suitable cathode is available. the rate ture. if the corrosion develops conditions found in a bridge deck or a floor in a parking struc- because the cover concrete has become carbonated. Fig. “Why is a Cathode Called a Cathode. (This is called the Leclanche’ cell in physical chemistry textbooks. suggested a “one-fluid system. The difference in voltage could be increased by bubbling oxygen (or air) into the left side. 2 Although rubbing two dissimilar metals together was found to attract bits of paper or pith. producing light. leaving two electrons behind for every iron ion released. The primary reactions that take place at each electrode are shown below the cell. It becomes anodic much greater damage. but Franklin’s convention was so well established by then that we still refer to “current” as flowing in the direction opposite to electron flow. the iron that makes concrete deterioration in all types of structures along the sea up the majority of the steel composition goes into solution. and sparks had been made to jump gaps. Therefore. are low enough. June 1991. coast and in northern states where salt is used to remove ice from roads. Most chemical reactions double in rate for every 18°F (10°C) increase in temperature [3]. Because of this capacity for flow. This figure depicts the typical In the case of reinforcing steel. therefore. Benjamin Franklin. 1—Electolytic cell. or cells is given by Uhlig [2]. if either the quality or the depth of cover. for over a hundred years previously. A simplified electrolytic cell is shown in Fig. which travel to the carbon cathode in the center of more. balconies on high-rise buildings. Cl. Between them is a mixture of manganese oxide. the cell. If. The salts typically of corrosion is relatively slow. the surrounding concrete becomes inundated addition to various chemical reactions. In the figure. However. This is called anodic polarization. The common (or now. in areas where deicing salts are used. Stephan Grey found he could transfer this “force” along a damp thread several hundred feet long and attract a feather at the other end. Shortly thereafter. etc. The battery op. ammonium chloride. the corrosion is in. in ions. It is of paste consistency rather than a solution. Houston. 1. (50 mm) or behind. the concrete cover becomes carbonated. or two different fluids. 6. with more of each than does the concrete near the bottom Chloride-induced corrosion is a very common cause of steel. Vol. This type of corrosion involves voltage because it is much closer to the source of water and chloride differences and transfer of electrons and electrical current. The electrical circuit is completed through the solutions surrounding the electrodes and the semi-permeable membrane by the movement of ions such as OH.) The case of the battery is made of zinc metal and the center pole is made of carbon. but still acts as an electrolyte. K. light. BERKE ON CORROSION OF REINFORCING STEEL 165 Concrete provides protection for embedded metals. (Taken from Maxey Brooks. which becomes cathodic. 30. 2. such as metal or carbon. dropping the pH A more detailed and complete description of electrolytic from about 13 to about 9.” calling it positive or negative depending on the direction of flow. This flow of electrons excites the filament in the or both. old-fashioned) flashlight battery is an example of an electrolytic cell that produces a usable product. Oxygen and water combine with the electrons to produce hydroxyl ions. however. No.” Materials Performance.) . well known for his electrical experiments. The damage occurs at a more rapid rate in warmer climates because it is due primarily to chemical reactions. If a cathode is available and is connected to the anode by a material. National Association of Corrosion Engineers. chloride ions have penetrated into the concrete such that Extending this battery concept to a more practical prob- the concrete adjacent to the steel contains at least 1. the rate can be The top layer of steel is termed the anodic steel because many times as fast as atmospheric corrosion [2] and it causes this is where most of the corrosion occurs.2 these extra electrons can be shed by the reaction shown. that is capable of transferring electrons (carrying electrical current). corrosion of steel can occur when: flashlight bulb. Charles Dufay named these two “vitreous” and “resinous” electricity for the opposite charges produced by rubbing glass or resin. Thompson demonstrated that electrons flow from negative to positive. electricity was thought to be some kind of fluid. he arbitrarily decided it was from positive to negative. TX. and water. streets. that of corrosion of reinforcing steel in concrete.77 kg of chloride ions/m3). and Ca. Because he had no way of knowing which direction the current was flowing. the schematic diagram in Fig. consist essentially of sodium chloride. in 1729. will eventually stop the corrosion reaction. a voltage difference has been set up by a low salt content surrounding the iron electrode on the left side and a high salt content on the right. stigated by the presence of chloride ions. parking structures. consider chloride ions/yd3 (0. Na. occurs at the anode. In 1747. 2. 1. It is this difference in voltage that drives the cell and causes the corrosion to proceed rapidly. pulverized carbon. Corrosion. or the conversion of metallic iron into ferrous ions in solution. These remain within the electrode and. if it is erates by the zinc going into solution and leaving electrons high quality and if the depth of cover is about 2 in. J.3 lb of lem. One hundred years later. is a reasonable supply of water (75 % humidity appears to be ter in the concrete at that depth and below. this is slow to develop and. The only usual crystalline substance detected is magnetite Damage to concrete. Hime. This in- Microcells can be set up along a given bar. of course. in the form of cracking. All that is necessary while the bottom steel has more oxygen because there is less wa. the steel was within the concrete completes the circuit. passivated by the high pH of the concrete.3 3 William G. depending on the exter. are amorphous (no crystalline structure determinable by X-ray diffractometry) ferrous (Fe) and ferric (Fe) oxides. and at least the threshold amount of chloride ions gases) can diffuse into dry concrete much more easily than wet at the anode. solid volume of the original metal. Bits of mill scale can act as cathodes reaction of the metals with gases or liquids or dissolved solids. de- were badly stained by reinforcing steel corrosion products. personal communication with William Perenchio. it produces many types of corrosion physical differences in or on the metal can also cause small products (collectively called rust). As previously stated. delamination. can occur due to atmospheric corrosion. parts of which space that the original iron (or steel) did. the top steel has much more destructive. The electrons are then shed into the solution in rapidly. The electrons find their way to the very little deterioration was observed. separated only by crease in volume is largely due to the production of solids from tiny fractions of an inch. hy- Damage Caused by Corrosion droxides. and complexes of these. as indicated by the re. that is. Occasionally. Crystalline corrosion previous author was asked to visit Tiger Stadium at Louisiana products such as magnetite occupy two to three times the State University to inspect the football stadium. The deterioration. chlorides and hydrates. chloride. is usually chloride ion. Chloride-induced corrosion. Most of the products pit corrosion. and spalling occur in the The preceding discussion is presented as a common ex. the passivation was lost. However. concrete because.166 TESTS AND PROPERTIES OF CONCRETE Fig. quickly that cracking. with wet concrete. it is not meant to im. someone new to X-ray analysis the type brought on by carbonation of the cover concrete. while the amorphous were 70. carbonation progressed bar chairs. The oldest portions products are generally more voluminous and variable. in the case of iron. interprets the pattern as simply magnetite. But the the pores of the portland cement paste by combining with wa. Oxygen (and other sufficient). leaving electrons behind. also of the poorest quality. 2—Electrolytic corrosion inside concrete. . Before carbonation. that drive an adjacent anode in the steel [2]. It does not depend on carbonation and more water and chloride in the cement pores surrounding it. delamination. 1. 40. Such localized cells can result in serious oxygen. occurs because ample of macrocell corrosion. may never cause serious deterioration. After carbonation The voltage difference between the top and bottom mats of and the resultant drop in pH. by comparison. 50. but pending on specific conditions. and disruptive pres- action shown. allowing atmospheric corrosion to take place. and as little as 10 years old. depending primarily on voltage differences. The cathode must have good access to oxygen. etc. it must diffuse through The voltages that develop cause corrosion to advance so pore water rather than pore air. The oldest concrete was bottom mat by metallic continuity brought about by bent bars. acteristic “amorphous hump” in the pattern that indicates that nal environment. Therefore. Local chemical or When steel corrodes. the solid volume of the corrosion products is many times the ply that separations of anode and cathode are always so great. Ionic conductance sures did not soon develop. same high porosity that allowed the rapid carbonation also ter and oxygen to produce hydroxyl ions. crystalline oxides. ignoring the char- However. and oxygen. can develop even in good quality concrete. but exposure to air and slow drying produces more and spalling. the same as that in Fig. cover concrete. a much slower process. and water availability. provided space for the corrosion products. The the rust is almost entirely amorphous. (Fe3O4). steel are due in part to differences in concentration of water. The top surface spalls were “repaired” with a contract with Construction Technology Laboratories to de- open-graded asphalt. which then found termining chloride permeability of concrete. BERKE ON CORROSION OF REINFORCING STEEL 167 its way to the bottom through cracks. the most commonly used procedure embedded in concrete was in its infancy. the total current resistance is small. the chloride ion. ferrous chloride. salt. concrete prisms are continu- caused by a 4-in. 3—Concrete spall over a reinforcing bar in a parking The peculiar action of the chloride ion is not entirely garage floor. Fig. Figure 4 shows cracking. and calcium ions within Fig. Some believe that. In the past version of this chapter it was believed that concrete containing silica fume. and indeed it does not. the Federal Highway Administration entered into was much younger. understood. The Peculiar Effect of Chloride Ion Thus far. the presence concrete cover and quality. corroded galvanically due to its proximity to the steel. which allowed the entry of large quanti- velop both a rapid field and laboratory test procedure for de- ties of water and salt into the top of the slab. 2. . Certainly. more detailed look at the test procedure shows that sample 4 This stabilized layer causes “passivation” of the steel. chloride ions are the only ones of this group that are normally found in large quantities in concrete. and monly start to occur after 5–15 years of service. depending on instigating the electrochemical cell.) required. However. Being more mobile (soluble) than the oxide. or a ferrous chloride complex. normally a very derground parking structure that had been exposed to deicing poor conductor. It involves forcing chloride ions to move through a small sample of concrete by applying direct current voltage. the technology of corrosion of metals Until the late 1970s.” In this method. A version of this standard was also published in the 1992 Annual Book of ASTM Standards as ASTM Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration (C 1202). and the water that carried it in. for a wide range of concrete quality and types. potassium. Figure 3 shows a spall over the the chloride salt or complex moves away from the steel. of the chloride. scribed in AASHTO T259. therefore. However. presumably because the silica fume is such an active pozzolan. the chloride content at several depths vanic corrosion is discussed in the chapter “Embedded Metals is determined. which ously ponded with 3 % sodium chloride solution for 90 days. when the chloride ion concentration becomes large enough. we have discussed only one ion as an instigator of corrosion. increases the and spalling on the underside of a floor slab in a 27-year-old un- current-carrying capacity of the concrete. but only in an uncarbonated portland-cement paste. a garage floor. local anodes and cathodes became established within the bottom mat of steel. (100-mm) zinc alloy electrical conduit. This ties up the normally free sodium. is formed on the steel surface. this passivation is due to the formation of a very thin gamma Fe2O3 film that prevents further corrosion. The obvious disadvantage to this test is the time and Materials Other Than Reinforcing Steel” in this volume. no effective for testing concrete for chloride ion permeability was de- anti-corrosion measures had been taken. However. Subsequent work has shown that the rapid method has an excellent correlation with chloride penetration as tested by AASHTO T259. ASTM Test Method for Determining the Penetration This may not appear to follow the description that attended of Chloride Ion into Concrete by Ponding (C 1543) was ap- Fig. 3 and 4. According to some investigators. for example. After the electrical conduit corroded away. leaching. The results were to correlate well with the 90-day ponding test. expos- top reinforcing mat in a parking structure. Such spalls coming fresh iron to the now-corrosive local environment. therefore. is rated at lower permeability than it should be [7–9]. When it was built. slab did follow that description very well when the structure In 1977. 4—Severe corrosion of reinforcing steel and an insoluble calcium silicate hydrate structures. (Gal- At the end of this time. some concretes that have altered electrical properties can give false readings. “Resistance of Concrete to Chloride The very large spall near the center of the photo was Ion Penetration. The rapid test method is now described by AASHTO as the rapid chloride permeability test [6]. However. Corrosion specialists in general agree that any ion of the halogen family would also be destructive. the cross section of this proved in 2003 and is an updated version of AAHTO T259. These microcells developed rapidly because the distance that ions must travel through the concrete to complete the cell is small. replacing the ferric oxide4 film that was stabilized by the high pH of the Some examples of damage due to chloride-induced corro- cement paste. sion are shown in Figs. reducing the ca- embedded electrical conduit on the underside of a parking pacity of the concrete for conduction of electricity. effective in resisting chloride intrusion is considered to be due zolans at low w/cm. Work is currently under used. These will be discussed in more cal Admixtures for Concrete C 494. was issued in used in a concrete overlay on a bridge deck in Michigan in the 2003.30 by weight. first identified in the 1930s by Tucker [13].168 TESTS AND PROPERTIES OF CONCRETE heating occurs. develop the technology of the physical properties of latex-mod- ment of Rate of Absorption of Water by Hydraulic Cement ified concrete. Types F and G). with good workability. required to make concrete workable is the addition of a high- mixtures and additives are very effective in reducing further range water reducer (HRWR) (ASTM Specification for Chemi- the permeability of concrete. developed for use in concrete almost simultaneously in proximately three-quarters of the volume of concrete. the heating and several other issues. For the first time. do not heat up over the testing period so to the fact that 3/4-in. portant effects of cover and low water/cement ratios in resist- Thus. The physical presence of a lattice of latex (or rubber) within the concrete presents a more torturous route to water at- Precautionary Steps Against Corrosion tempting to penetrate the concrete. The test is an tance between the concrete surface and the steel. and their Germany and Japan. made possible by the solids portion of the latex that im- Concrete water-cement ratio is especially important in deter. and three is. They are extremely effective in reducing permeabilities can be as much as 1000 times greater than that water requirements. Some recently introduced ad. done why two inches (50 mm) of cover is so much more effective under artificial conditions of high saturation and applied volt. These detail in a later section. ASTM Test Method for Measure. And the reduction in mix water. is now available to add additional ability to Latex reduces the permeability of concrete in two ways. . and therefore dissolved permeability due to a decreased water/cement ratio paste. than one. A synthetic latex admixture was first A new bulk diffusion test. became The effect of aggregates on the permeability of concrete is available in the United States in the mid-1970s. crete cover are available. results in lower mining the rate of ingress of water. so that higher steel against corrosion. Its speed. Work [11] has shown the extremely impermeability concretes look worse than they really are [10]. All of the physical Fig. parts workability of its own to the concrete. This method allows for a more accurate determination early 1960s. comparatively. as shown in concretes due to the heating effect. 5—Chloride content profiles at 44 weeks for different w/c ratio concretes. little better than two. because the latex proved to be so of the diffusion coefficient for chloride into concrete. however. model the ingress of chloride. materials. This ratio above all else in plain concrete is Another method of greatly reducing the amount of water the most important factor [11]. salts. effective in resisting moisture and chloride penetration. (19-mm) maximum size aggregate was their currents don’t increase over time. concrete could be supplied with water/cement ratios as low found effect on the protection concrete offers to reinforcing as 0. Very low permeability Fig. Because of its intrinsically higher permeability and the way to develop a modified version of ASTM C 1202 to address high permeability of the paste adjacent to some aggregates. age. Concretes (C 1585). into concrete. but re. 5. (25 mm) of cover was relatively in- concretes such as those containing silica fume or other poz. the test tends to overestimate the permeability of ordinary ing the ingress of the chloride ion into concrete. commercially prepared of a high quality portland cement paste [12]. The reason that 1 in. makes the method attractive to those Other methods of decreasing the permeability of the con- who need such information. ASTM C 1556. Since that time. having been generally to increase it. Because the aggregates occupy ap. This explains indirect method for determining chloride permeability. a great quires a minimum of three months to get results. increasing current passed. they have a pro. Because of such situations. Another new deal of work has been done in the laboratory [7] and field to method on water absorption. one large aggregate particle can easily “short-circuit” the dis- it is best to interpret the test results carefully. However. and is somewhat ef. used as an additive by itself it would cause such a black steel. it is still capable of Soon after the HRWRs were introduced. in combination with a coating thickness for new reinforcement [31]. Recent crete containing the zinc. and the coating can be damaged by (GGBFS) reduce the permeability of concrete [15. Two of these that can be present in concrete are outstanding.16]. corrosion in prestressing strand can occur at low chloride lev- Another approach to preventing corrosion is to coat the els in the bulk concrete due to cracking or at the anchorage steel. however. at a fraction of the cost. the A different approach to the prevention of penetration of same percentage loss of metal can cause catastrophic failures water and dissolved salts into concrete is to apply a surface in prestressed structures. In one need to be reapplied on a routine basis (every 3 to 5 years) as study [11]. of the steel is fusion-bonded epoxy [11. al- boxylates. prestressing steel is subject to stress corrosion cracking. performance [29]. and a Cases have been reported [36] where chloride levels have methyl methacrylate as the best performers. A study [37] of pretensioned and post-tensioned prestress- The usual product that results from corrosion of zinc is zinc ing systems evaluated grouts. This testing at high temperatures. Chloride wetting and drying. leaving a silane. The protection systems mentioned above can be combined ica fume would slow the entry of water and the chloride ion. Some of these have dampproofing capabilities that help to reduce chloride ingress. a bridges were subjected regularly to deicer salts for more than byproduct of the manufacture of silicon metal and ferro-silicon 25 years and chloride concentration measured at the level of alloys.26]. 50 to 100 times finer than port. pounds are used during the manufacturing process.8] as that of latex-modified concrete. (3 mm) into the concrete. and anchorage systems. it is initiation [17–19]. This was silica Field evaluation of bridge decks reinforced with galva- fume. Zinc has been used for this purpose. The use of such effective sealers as those or 1. an extremely fine form of silica (“finer than tobacco nized reinforcing steel showed good performance. Based inhibitor. prestressing steel as in mild reinforcing steel. Several organic based inhibitors are now commercialized Prestressed Concrete [25. Generally. times brought about.30]. They are especially more and the calcium nitrite would slow the corrosion rate after the effective at lower w/cm values [1]. Silanes can be effective but Research [11. often appear to be innocuous [35. appeared. anodic [11. it is generally accepted that corrosion of 1/8 in. zones for post-tensioned structures [38]. However. are Another additive available as an anti-corrosion agent is minimized. and it did not restrict the prestressing steel is instigated by chloride ions. with or without metal. the rate of metal loss is moderate. extremely active as a pozzolan. chloride concentration reached the threshold level at the steel. steel were scientifically higher than the corrosion threshold for land cement. solid rather than liquid. concrete can be produced with permeabilities as low A more widely used material to use for surface protection [7. zinc hydroxy chloride can also form. BERKE ON CORROSION OF REINFORCING STEEL 169 properties of concrete with equal proportions. Although high corrosion densities may occur at calcium nitrite. developments in HRWRs include the introduction of polycar. The silane had the been high in prestressed concrete members. This is some- concrete cubes in salt water for three weeks. These materials are predomi. Because of its fineness. in this case. one study indicated longer steel was found to be approximately six times that for mild steel. as indicated in the SHRP study reapplication is this was the finding of only one study and that chloride induced necessary under field conditions. calcium nitrite and silica fume. HRWR. to increase the chloride threshold level for corrosion upon field experience in Florida and elsewhere [32–34]. These were tested further by subjecting them to the nitrate and bisulfide ions (NO3 and HS) [35]. The philosophy was that the sil. now realized that defects should be minimized and that con- sion rates after initiation [20. oxide.37] has shed some light on this subject. the corrosion threshold of chloride for prestressing found in SHRP [28]. while causing nothing more than sealer after the concrete has hardened. investigated 22 materials used for this purpose. resulting in decreased permeability. which are more effective at lower dosages [14]. though this is less than the iron products. the same factors are involved in the corrosion of nantly amine and amine and fatty acid derivatives. to provide improved performance. it can do a very good poration of such materials in cement paste reduces the pore job of protecting the steel. Incor. Evaluated smoke”) and.36]. Early work showed The use of other supplementary cementing materials that. material. an epoxy. but no corrosion added advantages that it could not be seen. outward movement of water vapor. ducts. structure is coated and the number of holes. are essentially identical. or holidays. it penetrated about is evident. another type of producing large expansive forces. was used to deter. it must be used on all the steel within the steel is more susceptible to embrittlement and failure if the structure rather than only that which is expected to become concrete or mortar pH drops [1]. or at least is associated with.5 times the volume of the metal and. Note that prestressing fective. and either freezing and thawing cycles ions. Also. except or extremely severe exposure to ultraviolet light. This material acts as an anodic or passivating breaks in the coating. a amounting to nothing more than immersion of 4-in. (100-mm) phenomenon that does not occur in mild steel. rough handling or bending of the bars. Note that However. therefore.2 % by weight of the cement. stant wet conditions can be more severe than laboratory expo- Several papers [22–24] suggest using a combination of this sures with drying cycles. However. particularly if all the steel in the sizes. Remaining coating thicknesses of steel samples great increase in concrete water requirement that the material taken from the bridges were within the range of recommended would be of very low quality. However. the presence mine which of these appeared to have merit.17]. A 1981 study [27] spalls and delaminations in normally reinforced structures. This occupies about 3. Later work showed that it can reduce corro. A screening test. eliminated two materials. which occupies only 50 % more space than the original Highlights of the results were that polyethylene ducts were more . Five were of certain ions. However. if large amounts of chloride are present in con- the presence of a HRWR.21]. Part or all of the reason for identified by this study is sometimes more effective against the greater resistance to corrosion may be that stearate com- corrosion than producing a very impermeable concrete [11]. although the epoxy typically has small holes or holidays (SCM) such as fly ash and ground granulated blast-furnace slag in the finished coating. and by the length and temperature of leaching [43]. By measuring these potentials with a half-cell When concrete cores are not removed. The results of water-soluble tests Cell Potentials of Uncoated Reinforcing Steel in Concrete (C are greatly affected by the degree of grinding of the sample 876). It can also be used to locate tional dry-pack mortar. Historically. Cover profiles can be obtained by scanning the Assessing the Severity of Corrosion in Existing radar antenna along the surface of reinforced structures [42]. with full awareness of the fact that all of this sus CSE. but it was autopsy or corrosion rate measurements. and junction potentials can cause corrosion were. spalls. but the plastic tended to wear through at bends during potentials to vary significantly for essentially the same corro- stressing of the steel. half-cell badly under chloride exposure. allowing chloride to enter the potentials are best used in contour maps and with subsequent grout. or compressive strength tests. Closely spaced lines are and slightly beyond the depth of the steel. and other features of deterioration. etc. The petrographic.23 V versus CSE [18]. 6—Relationship between corrosion current and half-cell potential. the acid-soluble technique (AASHTO T260 or ASTM C 1152) ever the half-cell potential is more negative than 0. concrete cores cracks. epoxy. due to chemi- to actual corrosion current that was determined in this study. the oxygen content. and damage caused by that are typical of the worst. ASTM Practice for Petrographic surface with a metallic object and listening for hollow sounds. However. Traditional bare and galvanized steel ducts deteriorated lower half-cells than 0. study [11] has shown that active corrosion is indicated wher. corrosion. usually related to the wa. ment is useful in determining the potential for future corro- The anchorages proved to be vulnerable behind the tradi. cal combination with the cement or because it is tightly held The test method is described in ASTM Test Method for Half. Examination of Hardened Concrete (C 856).170 TESTS AND PROPERTIES OF CONCRETE effective in shielding the strand from corrosion than steel ducts ter saturation. Joints in duct material were a serious problem. These should be coated or covered with a near-surface bar for grounding the half-cell voltmeter.23 V ver. moderate. can yield infor- The visual and delamination survey results can be used to select mation on the quality of the cement paste. netic wave principle can be used to measure concrete cover more effectively. chloride ion de- survey data can be used to produce maps that show locations of termination. This is usually done with a ro- contour maps can be constructed. diagrams that resemble be taken for chloride analyses. Half-cell potential surveys are very useful in determining which areas are actively corroding [40]. Analysis can be typically observed near areas of high corrosion activity. This instru- cover possible within the duct at the inside surfaces of bends. Structures Concrete Cores The simplest technique for assessing the present condition of a structure deteriorated by corrosion is a visual survey [39]. done by striking the concrete microscopical. Figure 6 shows the relationship of half-cell potential chloride is not available to support corrosion. The Fig. down to points of equal potential. because of the minimal grout amount of concrete cover over reinforcing steel. One done on an acid-soluble or water-soluble basis. which is based on electromag- even within the wedge grips. freezing and thawing. The epoxy coating on the strand was never breached. powder samples can and a voltmeter on a grid pattern. Samples are taken at various depths. exposing the steel to the surrounding con. overcome by the use of shrink-fit tubing. usually those areas stability of the aggregates. air content. Providing an excellent A magnetic rebar locator may be used to assess the grout was largely unsuccessful. chemical attack. Indeed. or voltage. sion rate [41]. Visual For detailed petrographic examination. Ground penetrating radar. Thus. within aggregate particles. The action of an Chloride Samples electrochemical cell produces differences in electrical potential of the steel. or followed by a delamination survey. has been used. and best conditions. sion in various parts of a structure. . degree of curing. areas for the in-depth studies described later. no corrosion has been found at much crete. examination. with lines connecting tary hammer. This is usually removed from the structure can be useful. hundreds of needing repair and rehabilitation. M. A. they are Steel processed to have untransformed nano-sheets of expensive and must be maintained. A similar system was used crete (C 1218). Chin. a major Concrete—Fundamental and Civil Engineering Practice. can be used. H. W. 1983. these repairs con.. Detroit. Additional information can be found After the deteriorated concrete has been removed and in a paper by Broomfield and a SHRP Review [52. low-water ce.53]. S. [7] Whiting. Boston Society of Civil Engineers. 1998. pp. and Berke. and Berke.. in a research project a decade ago [47] to protect a deteriorating interstate highway bridge deck. Corrosion and Corrosion Protection volatile organic compound concerns. An anode of zinc or magnesium Fly Ash Upon the Microstructure and Permeability of is connected to the reinforcing cage through a lead wire.” Report No. Since that time. F. These materials polymerize within the concrete and also combine with the siliceous portions of the References cement and aggregates. Washington. In extreme cases. but they are is working on a standard. The version penetrate the surface more readily [44] and. Difficulties in achieving bond with the substrate over standard reinforcing bars in testing. Though corrosion is reduced. becoming chemically bound adjuncts. Florida. expected to last longer. Over- lays of specialty concretes. “Corrosion Protection for Concrete Structures: wet exposures. has been used for many years on concrete piles by the state of 1. Typically. while not ex- Bridges and parking structures in areas of deicer use. in chloride-contaminated concrete. remain [49]. E & FN disintegrator of organic molecules. K. 195–222. have met with somewhat better success.. It was considered a success by the researchers.. cannot reach them. “Evaluation of Portland Cement Concrete for shrinkage can help to improve performance. bridge decks have been so treated. pp. long-term durability of prestressed structures due to the possibility of hydrogen gen- such repairs has not been evaluated. SP-108. Steel Corrosion in Because they are inside the concrete. but dependent upon are sometimes encountered. 1991. are constantly exposed to first instance of the use of such a system was in 1974. D.. New York. rather [2] Uhlig.. cathodes to the open circuit potential of the anodes [46]. The Corrosion Handbook. so cathodic a penetrating sealer such as a silane or a siloxane. “Rapid Determination of the Chloride Permeabil- pletely preventing corrosion of reinforcing steel embedded ity of Concrete.” AASHTO T277. it polyurethane alone.. are with the most promise contains over 8 % chromium [57]. New York. 1948.C. Permanent Bridge Deck Repair. Silanes reaction rates are claimed to be low on this steel. Diamond. C. York. course. 1987. A metal is cathodically [8] Whiting. London. are the usual structures bridge deck in California [48].” Final Report No. New terials as they are restrained by concrete around the patch [45]. In others. ultraviolet light. and some means for restricting the entry of water current systems have not been put to use commercially on and salt solutions. uniform potentials continue to be basic problems. some form of waterproofing must be applied.. 211. Cathodic protection is truly the only known method of com. MI. The technique The Past and the Future. Corrosion of the anode supplies electrons scribed in ASTM Water-Soluble Chloride in Mortar and Con. with a sacrificial anode system. BERKE ON CORROSION OF REINFORCING STEEL 171 currently accepted test for water-soluble chloride is de. or silica fume-containing. Corrosion Mechanisms. [1] Bentur. Marcel Dekker. Wiley. HWA/RD-81/119. Systems that employ impressed current. 6. therefore. S. 31 and 502. “Permeability of Selected Concretes. [4] Mansfield. such as latex-modified. but serious difficulties sist of removal of spalled and delaminated concrete (suffi.” Civil Engineering Practice. However. austenite sandwiching dislocated martensite laths is available. This can be accomplished easily and safely. therefore. replacement of the several viable anode systems have been developed. preventing its corrosion. Thin proprietary membranes of which alloys are used [55. FHWA-RD-74-5. Federal Highway Administration. but the technique has not gained popular Repairs to Deteriorated Structures acceptance among transportation agencies. In most instances. new delaminations will soon form in the original concrete on cathodic protection [54].. immersed in the sea. Results are significantly improved expensive. August 1981. Impressed concrete.. Marcel Dekker. H. cathodic protection general early review of cathodic protection was presented by may be a viable alternate. J. then Concrete. This is called the “ring anode effect. which can give rise to hydrogen embrittlement. outside of cathodic protection. or combined with an epoxy-sand wearing is not necessarily prevented [57]. Federal Highway Administration. Reducing the strength of the concrete in the patch or reducing [5] Clear. p. If it is the proceedings from several NACE annual meeting symposia not. D. two British authors [51]. P.. Vol. surrounding the repairs. than the more traditional alcohol solutions. N. No. doing away with [3] Schweitzer. American Concrete Institute.. Silanes Spon. D. D. are also used with good success. A simpler and less expensive method is the application of There are no carbon containing phases present. Patch areas often fail due to shrinkage of the patching ma. as well as replaced..” Proceedings of the 9th International Conference on . in constantly [9] Pfeifer. February 1974. “Effect of Microsilica and for offshore drilling platforms. A structure must be demolished. S.56]. D. and as part of the overall corrosion protection systems [10] Scali. are now available as water emulsions or as 100 % silane. the eration [50]. American Association of State Highway and Transportation Officials. 1988. on a corrosive conditions and.” Starving the concrete for water is the most effective way to New Steels reduce the corrosion rate. Controlling current densities and maintaining ciently below the top reinforcing steel so that it will be encap. Handbook. N. A. [6] “Rapid Determination of the Chloride Permeability of Cathodic Protection Concrete. The with marine structures of all sorts. Stainless steel bars and cladding are now available and ASTM ment ratio. although sulated within the repair concrete). to the steel.” Permeability protected when sufficient current is applied to polarize the of Concrete.. along tremely popular. Washington. K. P. D. “Corrosion Evaluation of Reinforced Concrete Understanding Corrosion Mechanisms in Concrete: A Key to Bridges. [45] Poston. L. pp.. “Corrosion Inhibitors for Steel in Concrete. “Protection Against Chloride Content of Concrete. Nagi. 1983. 234. K. M.” Supple. pp. Ed. P. J.” Report No. Institute of Technology... H.” BRI/Reports/287PD010. 35. Institute.. “Experimental Cathodic Protection of a Bridge of Bridge Structures.. D. “Epoxy-Coated Reinforcement International Conference on Superplasticizers and Other in Highway Structures. 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American Bridges. Browning. Pierre. May 1995. No. D.” SM Report of the Art Report. Nguyen.. B. 28–33. J. “The Resistance of Stainless Steel Association of Corrosion Engineers. J. S. Hydrogen Generation... 65–70. TX. Vol. Strategic Highway Research Pro. and Cox. 31 gram.” [51] Wyatt. and Virmani. 87. BERKE ON CORROSION OF REINFORCING STEEL 173 [50] Hope. P. National [56] Flint. Sherman.. “Stainless Steel Reinforcing as Corrosion Protection. 9. D. No. T. No.. B.” 1987.. pp. and Irvine. R. B. N.. pp. March. and Locke. D.” Materials Performance. 5. TX. 13–27. R. V. Vol.. S. 40. National Research Council. September 1992. 1993. Houston. 469–472. W. 12–21. 1988. High [53] “Cathodic Protection of Reinforced Concrete Elements—State Chromium Reinforcing Steel for Concrete. J. M. Houston. G. “Field Survey of Cathodic Protection on North pp. DC. “Mechanical and Corrosion Properties of a High-Strength. September–October 1990. December Partly Embedded in Concrete to Corrosion by Seawater.” ACI Materials Journal.” Materials Performance. . Pfeifer. N. pp. B. “A Review of Cathodic Protection Concrete International. [55] McDonald. 142.. and Poland. J.... Jr. of Reinforced Concrete. [52] Broomfield. Magazine of Concrete Research. [57] Darwin. South Dakota DOT Office of Research. The rate of drying also depends on ambient humidity of air in contact with the concrete. calcium hydroxide. of course. An understanding and caution should always be exercised Concrete is wet when mixed and completely saturated with wa- in material usages. and recycled concrete. remains water to be lost to the environment. and. any material. copper and copper alloys. may be relatively dry. and chlorides. sufficient in many cases. materials. and among lies. special alloys of por form or as pore solutions that facilitate transport of soluble iron. It also lar cellulose materials. alka- materials are glass. PA 15650. [1]. concrete that will eventually be dry may be at an internal given here to the possible degradable aspects relative to their relative humidity long enough to cause corrosion of susceptible use and conditions that may render them unserviceable. 169B pletely dry because it contains air voids and capillary voids that and 169C. If that is the case. and tin. 36 in. The response of materials to their environment is the the following: same now as it was when this chapter was originally written. There usually is more mois- has guided the use of embedded materials other than rein. And. but Introduction even at low ambient humidities. Fiber-reinforced concrete is gaining in increases the electrical conductivity of concrete.) slabs of normal-weight concrete are shown in Table 1 terial behavior. 174 . in the subsequent two volumes. CaSiO2xH2O CO3 → CaCO3 SiO2 xH2O ronmental exposure. silver. liquid water. Among the metals are alu. The distance ance reported in the literature. Perhaps that understanding and caution ter for some time after hardening. stellite. sion of embedded materials is slowed dramatically or stopped. thus aiding any use. What has equilibrium of the paste. any soluble corrosion products away from the materials. quently to a damp environment may remain moist enough to organic and organic substances. a material may perform in an unusual way. The free moisture in concrete can stay in va- minum. support corrosion. tain a relative humidity of about 80 %. The chapter was published 27 years ago in ASTM STP 169A and. because of a peculiar envi. concrete exposed continuously or fre- The materials to be described include metals and other in. the concrete at any given time. ture than needed to hydrate the cementitious materials so there forcing steel so that there is little about their adverse perform. which is the moisture formation than reported previously in this chapter. The table shows that at an environmental relative humidity 1 Petrographer. so information about some fibers has been included. to main- concrete on embedded nonferrous metals reveals little new in. or solutions where water is the solvent. It can be in the form of water vapor. as shown by change. times used in conjunction with concrete. although a concrete been located is now included. monel metal. Emphasis will be Thus.17 Embedded Metals and Materials Other Than Reinforcing Steel Bernard Erlin1 Preface General Condition THE INITIAL WORK ON THIS CHAPTER WAS DONE Moisture is usually necessary for the chemical degradation of by Hubert Woods. tendency for electrochemical corrosion of metals. carbonation of the portland-cement The basic principals of chemistry and physics do not paste will release water when carbonation occurs. A general condition necessary for the chemical degrada. such as oxygen. a concrete consultant who is now deceased. asbestos. Furthermore. sulfates. lead. and a appreciated. then a value through which free water must move to an external surface of the principals that extend the service life of those embedded where it can evaporate dictates the residual moisture content of materials has become a code of use. The Erlin Company. Latrobe. Concrete is never com- with some modifications. zinc. a long drying time may be needed to lower the concrete humidity to a point where corro- Metals other than conventional reinforcing steel are some. in spite of lessons learned or. A current search of the literature for the effects of hold moisture in vapor form. toward embedded materials and of the organic materials are a variety of plastics and wood and simi. The relatively long drying time of concrete is not usually tion of any material in concrete is exposure to moisture. Among the inorganic chemical substances. The rates of drying of 15 90 90 cm (6 36 short discussion on that aspect precedes the discussions of ma. nominal 1. It has also been shown that the compound. other conditions being favorable.) Slabs of Normal-Weight Concretea Drying Time to Reach Various Relative Humidities in the Concrete Slab Environmental at Middepth. 15-cm (6-in. in these cubes were as high as. The laboratory investigations by Monfore and Ost [6] show kali hydroxides derived from hydration of portland cement. for bedding machinery base plates. such as walls or elevated floor slabs. but metal losses spalling over aluminum conduit in the Washington D. Addi- tional tests show that when the mid-depth relative humidity reaches 90 %. the aluminum pieces were removed. Indeed. In smaller amounts. severity to cause collapse of aluminum conduit in reinforced • Cubes containing 1 % flake calcium chloride (CaCl2 concrete made using calcium chloride. C-shaped sheets of mild steel were also metal because of the lesser surface area exposed to the alkalies. sion of the aluminum and the subsequent cracking of concrete.25-cm (1⁄ 2-in. those in . but it seems almost certain that such corrosion could proceed. aluminum reacts principally with the al. Several direct contact with the embedded aluminum. electrical coupling of steel and aluminum. An ratory studies designed to describe conditions necessary for its example of concrete spalled over corroded aluminum conduit corrosion and methods for circumventing its distress. connected in some tests and not connected in others. or higher than. sheet. coated with a curing der unfavorable circumstances. Thicker sections. Sta. important findings were noted: Wright [3] described a case of corrosion of sufficient • All cubes that cracked contained calcium chloride. and weighed.25 or pipe form reacts much less vigorously than the powdered cm (1⁄ 2 in. These prompted labo. and for this reason aluminum cement. One that calcium chloride concentration. 1. and then stored at 23°C (73°F) and 50 % relative situation can be worse if concrete contains purposefully intro. who de. though at a much lower rate.C.) concrete cubes were prepared us- provides slight expansion of grout and has been used.9 cm (3/4 in. ERLIN ON EMBEDDED METALS 175 TABLE 1—Rates of Drying 15 90 90 cm (6 36 36-in. the relative humidity at a point only 1. cleaned.) from an exposed surface is 87 %. alkali content of portland reaction product is hydrogen gas. at 90 % relative humidity and probably also at 60 % relative humidity. will dry more slowly than thin sections.) from one face. Concrete made with lightweight aggregates dries more slowly than concrete made with normal-weight aggregates. today lightweight aggregate is used for internal curing. for exam. Several dozen additional cases of concrete cracking due to corrosion of embedded alu- Aluminum has been given widespread attention because it has minum conduit.) aluminum conduit was embedded 1. Aluminum in rod. The steel and aluminum were externally and the reactions will continue until the metal is totally reacted. days. The cubes the corrosion of embedded aluminum can crack concrete un. veloped it for insulation purposes). concrete have occurred. ing cements of high and low alkali contents in which pieces of ple. 1—Concrete spalled by corroding aluminum conduit (from Ref 5). of 50 %. In fresh concrete. is shown in Fig. such as beams and columns. posts. days Relative Humidity (RH) 90 % RH 75 % RH 50 % RH 10 18 80 620 35 30 110 840 50 36 240 … 75 36 … … a From [1]. The moisture condition of concrete required to support active electrochemical corrosion of aluminum and other susceptible metals is not known with any accuracy. Edison. In every case. the gas In their studies. humidity for 28 days and observed regularly for cracks. and window frames in contact with been the cause of problems in the past. Fig. 36 days are needed to lower the mid-depth relative humidity to 90 %. After 28 duced calcium chloride (chloride ions are a strong electrolyte). were removed from their molds at 24 h. and 240 days are needed to reach 75 %. Various Tests carried out by Jones and Tarleton [2] indicate that amounts of calcium chloride additions were used. and much worse if it also contains reinforcing steel that is in The principal results of the studies are given in Table 2. embedded in the cubes. Extensive concrete 2H2O) by weight of cement did not crack. chloride was present. and the ratio powder sometimes is used to form lightweight cellular concrete of steel area to aluminum area are all interrelated in the corro- (an invention usually attributed to Thomas A. dium [4] and corrosion of aluminum balusters embedded in Aluminum concrete have been reported [5]. .09 2 14 uncoupled no crack 0.7 % flake calcium chloride by currents occurred in the circuit connecting the aluminum and weight of cement.16 2 14 coupled 5 0.07 4 28 uncoupled no crack 0.04 D 0. steel.1 % flake calcium chloride by weight of In the case of coupled metals. Area to Surface Alkalies as % by weight of Aluminum Days to Thickness. cor.) Concrete Cubes Stored at 50 % Relative Humidity for 28 Daysa Ratio of Steel Loss in Cement CaCl2 2H2O. b Calculated from weight losses.) concrete cubes by Wright and rosion generally increased with increasing ratio of steel Jenks [7].0 2 7 coupled 3 1. The steeper slopes occurred for als electrically coupled. cracks did occur at various ages.06 4 7 uncoupled no crack 0. varying shapes were obtained with the slopes depending on the • With a 2 or 4 % calcium chloride addition..07 4 14 uncoupled no crack 0.3 4 28 coupled 3 2.54 1 7 coupled no crack 0. no crack 0. the of corrosion measured as loss in thickness. after 61 days with 1. (b) the cause of .17 4 0 .92 2 28 coupled 4 1. tions were not used.2 4 28 coupled 7 3. With electrically coupled steel and aluminum (area area to aluminum area and invariably increased as the ratio 10:1). % cement Area Electrodes Cracking milsb C 0.5 coupled 3 1.176 TESTS AND PROPERTIES OF CONCRETE TABLE 2—Corrosion of 6063 Aluminum Conduit Embedded in 15-cm (6-in. a From [5]. cracks did not occur in the encasing progressively increased with increasing calcium chloride concrete when chlorides were not present. no crack 0.4 2 28 coupled 4 1..54 105 m.04 0 0 . Current flow trically coupled to steel.. other cubes that cracked.85 2 3. Some measured currents are shown in Fig..10 4 7 uncoupled no crack 0.5 coupled no crack 0.7 4 14 coupled 2 2. Tests somewhat similar to those reported by Monfore and • With calcium chloride and metals electrically coupled.5 coupled 2 1. when the higher alkali cement was used.6 4 3. straight curves of corrosion was greatest with the high alkali cement.0 1 28 coupled no crack 0.12 1 3.24 0 28 uncoupled no crack 0.07 4 14 uncoupled no crack 0. amount of calcium chloride.33 2 14 uncoupled no crack 0. no crack 0. no crack 0. cracks did not occur when calcium chloride addi- amount of calcium chloride increased.08 0 0 . (Exposure to a damper environ. contents up to the end of the 28-day tests.4 2 14 coupled 4 1.3 0 28 uncoupled no crack 0.09 4 0 .05 NOTE—Conversion factor: 1 mil 2. corrosion was slightly greater the higher amounts of calcium chloride. Ost were done on 31-cm (12-in..77 1 14 coupled no crack 1.89 0 28 coupled no crack 0.4 0 28 uncoupled no crack 0. 2 as a McGeary [8] also found that: (a) for aluminum conduit elec- function of time and calcium chloride content.2 4 7 coupled 3 1. Cement Na2O.06 2 28 uncoupled no crack 0. considerable galvanic cement to eight days with 5. However.6 4 14 coupled 3 2.5 4 7 coupled 2 1. and with met.09 4 28 uncoupled no crack 0.07 2 28 uncoupled no crack 0..) electrical flow during 28 days was plotted against the amount • With no calcium chloride and no electrical coupling.. When the total ment might have caused cracking to occur. • Cubes that cracked did so within seven days. 5 cm. cells activated when chlorides were present in the concrete. which are themselves TABLE 3—Effect of Protective Coatings on Corrosion of Aluminum Conduit Embedded for 28 Days in 15-cm (6-in. content of 0. Sodium chloride is the principal constituent of sea salt. mil Days to Cracking Thickness. 1 in. steel and aluminum in electrical contact) are present is that of an electrolyte. flu. a necessary part of a galvanic cell. (c) and other organic coatings or sleeves. the resistance to galvanic corrosion: certain bitumens. A galvanic cell forms. or both. in which case the rate of corro- permitted some corrosion.. and thus partially ex- corrosion and cracking. Lead has a high resistance to certain chemical actions. weight of cement. which is also Lead referred to as intergranular corrosion. 2—Effect of calcium chloride on galvanic current (from Ref 5). The data for example. In view of chemical similarities between calcium chloride and sodium chloride.) Concrete Cubes Containing 4 % Calcium Chloride and Steel Electrically Coupled to the Aluminuma Protective Loss in Surface Coating Material Thickness.. 2 2. and (d) there was an enrichment of chloride at the aluminum conduit surface. .. (b) removal of all corrosion nous coatings have been used successfully.) concrete cubes made with cement having an alkali comes converted to lead oxide or to a mixture of lead oxides. (c) corrosion of the aluminum was of the cubic type. may be destroyed in a few years. and corrosion and deterioration of the embedded lead result. the attack will continue. In the presence of water. Fig. Synthetic plastic products adjacent to the embedded aluminum surface. The results are shown in Table 3. it is prudent not to use calcium chloride in concrete in which aluminum will be used or where concrete will be exposed to corrosion of the aluminum was due unquestionably to galvanic chlorides.1 Lacquer B 1 no crack 0.5 Silicone .. and (d) engagement of an experienced patching specialist to complete the repairs. and bedded portion that becomes an anode. certain metallic pigmented coatings. alkyd and phenolic materials. air-exposed portion becomes a cathode with respect to the em- idized-bed plastics.47 Lacquer C 2 no crack nil Bitumen A 5 no crack nil Bitumen D 15 no crack nil NOTE—Conversion factors: 1 mil 2. If the lead is elec- demonstrate that a silicone coating was ineffective. and coatings that insulate the aluminum from the concrete are commercially available and practical for use.g. The role of chloride when galvanic cells (e. A lead pipe. but in Tests [6] were done to determine the effectiveness of contact with damp concrete it is attacked by the calcium hy- several different coatings on aluminum embedded in 1. seawater. or near. that a trically coupled to reinforcing steel in concrete. ERLIN ON EMBEDDED METALS 177 patching using epoxy or epoxy polysulfide systems. epoxies. Coatings A and D were each effective in preventing both Lead partially embedded in concrete.. it seems evident that the latter would also facilitate corrosion of aluminum. Bitumi- (a) removal of all loose concrete. posed to air. A protective coating or covering should be used when lead cedures for concrete cracked because of corroded aluminum: pipe or cable sheaths are to be embedded in concrete. is susceptible to corrosion because of the differen- Other tests [8] indicate that the following coatings provide tial electrical potential that results.89 % and containing 4 % calcium chloride by If the dampness persists. galvanic action lacquer (Lacquer B) prevented cracking within 28 days but may accelerate the attack [9a]. milb None . and it therefore seems prudent not to use aluminum in concrete exposed in. The results of these various investigations and of field experience show that reinforced concrete is likely to crack and spall from corrosion of embedded aluminum if calcium chloride was used. Based upon laboratory studies and field experiences. a From [5]. and that Lacquer C and Bituminous sion may be several millimeters per year.54 105 m. 2. McGeary [8] found the following to be effective repair pro.25-cm droxide component of portland cement hydration and be- (1⁄ 2-in. 3 2. b Calculated from weight losses. Other salts that hydrolyze and provide strong electrolytes should also be damaging. damaging stresses ances have been reported. Galvanized wall ties of brick masonry with calcium hydroxide is facade construction can undergo similar corrosion when chlo- Zn Ca(OH)2 → CaZnO2 H2↑ (1) rides are present.) were of the steel due to galvanic action is likely to occur. Figure 3 shows one instance of mul- are not created. Stark copper-silicon alloys embedded in concrete have good resist. and manganese bronze bolts have sheared below their ultimate strength. The amount of galvanized coating remaining was 92–100 %. bronzes. and possibly nitrates. crete cores examined were from mean tide and above high tide ment and an electrolyte such as chloride is present. embedded galvanized steel reinforcement has been used in crete. red brass. and thus there are conflicting Copper. Galvanized corrugated steel sheets often are used as per- When zinc is used in concrete. Also. bridge deck. galvanized bars was from 5..3 cm (214⁄ –514⁄ in. Lead in contact with concrete should be protected by suitable coatings or otherwise isolated from contact with the concrete [9b]. The reaction is self-limiting. Chloride concentrations to depths of 10. Concrete cover over the with suitable coatings.7–13.7–4. but normally in with mortar of 12-year-old masonry facades containing exceed- concrete the reaction is superficial and may be beneficial to ingly high chloride contents revealed that the galvanize coating bond zinc (galvanized) to steel. which explains 10 96 the observed acidity of the corrosion product. aluminum-bronze. likelihood of concrete itself being damaged by corrosion of lead because of the softness of the metal and its capability for absorbing stress. if any. It is probable that 10 99 this reaction takes place only after local depletion of calcium hy- 12 92 droxide by the reaction expressed in Eq 1.178 TESTS AND PROPERTIES OF CONCRETE unaffected by damp concrete. Copper and Copper Alloys Copper will not corrode in concrete unless soluble chlorides are present. The chemical reaction is probably Years of Age Galvanize Coating Remaining. it is desirable to insulate the copper [from 1.4 kg/m3 (3. failed by stress corrosion. un. There appears little. and products of construction. % 7 98 Zn CaCl2 2H2O → CaZnO2 2HCl H2↑ (2) 8 100 10 95 This chemical action produces hydrochloric acid. 3—Corrosion and perforation of galvanized steel cause stress corrosion cracking. Very small amounts of ammonia. ter-exposed concretes that were from 7–23 years old. or floor coating for steel. bridge decks and columns.1 cm (4 in. Other reported zinc 23 98 corrosion products are zinc oxide and zinc hydroxy-chloride. corrosion zones. if any. However. Both satisfactory and unsatisfactory perform- reaction are not voluminous. always exceedingly high at about the level of the galvanized bars der such circumstances. and chloride. and docks). some were moist and had acidic pH values of 2. Admixtures containing major amounts of chloride should not be used in concrete that will be exposed to moisture and . The primary chemical reaction was completely corroded. Further investigation of this and other similar cases showed that in each instance calcium chloride was TABLE 4—Galvanize Coating Remaining on used in the concrete so that chlorides were in direct contact Reinforcing Bars After Indicated Years of with the galvanized sheets. The con- When copper is connected or adjacent to steel reinforce. Thus. Copper pipes are used successfully in concrete except under unusual circumstances where ammonia is present [10]. because such phenomena can occur under circumstances unrelated to con.9–6. Analysis of the corrosion protuberances indicated the presence of iron.12].7 lb/yd3)].g. This abetted the corrosion by Concrete Exposure to Seawater chemical action on the zinc and by increased electrical conductivity of the concrete. lead and lead salts very strongly retard portland cement hydration. brass. [16] investigated embedded galvanized reinforcement in seawa- ance to corrosion [11.2–10. stopping corrosion of the steel. it is not clear what role. A summary of Zinc the data is given in Table 4. zinc. probably because these Galvanized reinforcing steel has not always been successful in metals have given satisfactory service under such conditions. if any. concrete exposed in marine and other environments where chlo- tle systematic work has been reported on the behavior of copper rides are present (e. of the coating [13–15]. but environment for protecting embedded steel from corroding. Unpublished data by Hime and Erlin for galvanized bars threaded through brick hollow cores packed Zinc reacts chemically with alkaline materials. Brass wall ties have reportedly from under concrete slab (from Ref 11). the concrete plays.). and its alloys in contact with concrete. Very lit. are also appropriate. consequently. can Fig. it is generally as a galvanized manent bottom forms for concrete roof. tiple perforation and corrosion of such sheets under a roof Although good concrete normally provides a nearly ideal slab [10]. and reports about the benefit. Most of the corroded spots were dry to the touch.8. chrome-nickel Further. as wall blocks or or used to circumvent the influence of wood constituents on set- tiles. was found the zinc surface due to reactions of the zinc and alkalies in the to be deleteriously reactive. in cated the deleterious behavior of reactive glass. proposed for use in concrete is wood (including bamboo. Chromate dips on galvanized bars or Nondeleterious reactive glass is manufactured and is avail- 400 ppm chromate in the mixing water also prevent hydrogen able for use in concrete. fibers. fied with sulfuric acid. iron-chrome. and Paragraph X1. and trolytes can cause galvanic corrosion. are possible ways for improving their utilization. The amount of such Glass substances differs with wood species and from time-to-time with place-of-origin within a single species. Monel metal and Type 316 stainless steel are well and subsequent shrinkage after drying. tions. A chromate treatment. With woods of high to alkali-silica reaction. an amount equivalent to one third to one half of the cement by silica gel. or fibers in concrete commonly results in very slow setting and able if chlorides are present in the concrete or in solutions that abnormally low strength because of interference with normal permeate the concrete [18]. of ASTM Specification for Concrete Aggregates (C 33). The glass aggregate removed from the concrete. and possibly other substances in the wood. rated in mortars and concretes. Special circumstances might justify the use of these Sawdust. high differential thermal coefficients of expansion of steels. waste bottle glass used as tannin or carbohydrate contents. bark. the glass or the concrete or both [21]. has been Current trends in the use of new or unusual materials in con- used as a method for avoiding that problem. stellite. may cause concrete surface Before glass is used in portland-cement concrete. ERLIN ON EMBEDDED METALS 179 contains. galvanized steel.3 of the ASTM Test Method for Potential ported to be effective in protecting galvanized products. Softwoods generally give Glass sometimes is embedded in mortar or concrete as artifi. moistening the wood with 1 % sulfuric acid for 4–14 h which was bonded to a non-expansive concrete backing.20] used for decorative or aesthetic pur. and timbers have been embed- Nickel and cadmium-coated steel will not corrode in chlo. cial aggregate [19. The treatment is usually effective with mixed softwoods. The in precluding the use of many cellulosic materials. cut from the panels and tested using accelerated methods in able to keep chloride-containing solutions from permeating the laboratory had expansions of 0. Among the materials proves the corrosion resistance of zinc in concrete [10a]. as reinforcing as a substitute for steel. specifically those given in Paragraph X1. Some glasses are re. Concrete in which galvanized reinforcing steel is located Wood close to galvanized forms has a tendency to stick to the forms. Other reports [21] have also indi- cement paste.” and treating it with 37 % . the corrosion resistance of these materials becomes question. These factors are perhaps foremost nickel alloys. and chemical degrada- known for their resistance to the effects of sodium chloride tion due to contact with calcium hydroxide solutions. ting and hardening. in active with alkalies in portland cement paste and form alkali.2 of ASTM C 289 Passivation of zinc by use of chromate dips has been re. wood pulp. cotton. wood chips.1. im. The resulting expansion may cause severe damage to volume. nickel. It is also advis. the addition of lime with or aggregate in a decorative concrete facing of outside-exposed without calcium chloride is not effective. jute. (60°C). cast silicon-iron. constructions. or is in contact with. The corrosion phenomenon results in pitting of Reactivity of Aggregates (Chemical Method) (C 289). Other treatments that pre-cast concrete panels caused sufficient expansion to warp have been suggested include soaking in sodium silicate solu- the panels. such as previously described. as well as hydrated lime. Prisms then neutralizing with “milk of lime. For example. it should always when a high proportion of larch or Douglas fir is present. be tested to ensure that it would be chemically stable in the al. for example. setting and hardening processes by carbohydrates.2 % after three months of the concrete. Other Metals Problems incidental to the use of natural cellulosic materials have included adverse effects of sugars on concrete setting The following metals have been reported to have good resist. some of these materials and unaccommodative volume changes alloyed cast iron. precast or cast-in-place concrete. Prior and other constituents of seawater and should work well in treatment of the cellulosic materials. Many admixtures and wood treatments have been proposed poses. has been found effective in overcoming this action [23]. and tin [12]. testing. Five percent calcium chloride by weight of the cement is kaline concrete environment and not cause deterioration due sometimes added. can cause cracks to develop.1. or carbonation of the portland-cement presence of chloride and when temperatures are above 140°F paste [22]. and degradation of fibers due to the high concrete alkalinity. such as calcium nitrite. crete are due to the emphasis on conservation of energy and Use of corrosion inhibitors. The use of fresh untreated sawdust. and wood fibers have been incorpo- more costly metals. Bar Method) (C 227). tannins. silver. resistance of some of these metals to corrosion may be affected Additional problems incidental to the use of natural- by the presence of “corrosion promoters” such as soluble cellulosic materials include swelling upon moisture absorption chlorides. zinc-coated steel forms. ded in or placed in intimate contact with concrete in composite ride-free concrete if the coatings are continuous [17]. Contact of galvanize to should be tested using the methods provided in the Appendix steel in concrete in the presence of chloride and other elec. The warping was due to expansion of the facing. it disfiguration due to contact of the zinc. and as frameless windows or lights. tested Zinc galvanize can corrode when in contact with relatively using the procedures in the ASTM Test Method for Potential fresh concrete. ance to corrosion in concrete: stainless steels. chromium-aluminum-silicon steels. However. such as impregnation or concrete. except Whenever glass is to be used in concrete. The Alkali Reactivity of Cement-Aggregate Combinations (Mortar- dips are solutions of sodium or potassium dichromate acidi. chrome-nickel alloys. monel metal. Thus. less trouble in this respect than hardwoods. The 300 series of stainless steel will corrode in the coating techniques. evolution in fresh concrete. utilization of wastes and by-products. Addition of hydrated lime to the mixture. and rice stalks and hulls). rock slope stabilization. steel and polypropylene bridges. which create a minimum pH of 12. etc. overlays. Plastic products are now being used as eral aggregates. culverts. dolosse. chiefly of rotary barrel with beater. waterstops. sheets. in general. If drying is not uniform. A treatment found by Parker [23] to pentosans. glass cellulose. and airfield pavements. conduit shields.180 TESTS AND PROPERTIES OF CONCRETE TABLE 5—Resistance of Plastics to Strong Alkalies [26] Class of Material Resistance Polyethylene excellent Polymethyl methacrylate poor Polypropylene excellent to good Polystyrene excellent Polystyrene acrylonitrile excellent to good Polytetrafluoroethylene excellent Polytrifluorochloroethylene excellent Polyvinyl chloride and polyvinyl chloride vinyl acetate excellent (rigid) Polyvinyl chloride and polyvinyl chloride vinyl acetate fair to good (plasticized) Saran (monofilament grade) fair to good Epoxy (unfilled) excellent Melamine (formaldehyde) poor Phenol (formaldehyde) poor Polyester styrene-alkyd poor Urea (formaldehyde) poor aluminum chloride solution or 50 % zinc-chloride solution in a which causes dissolution of lipins. pile caps. or simply with The use of plastics in concrete and concrete construction has changes in external humidity. drying may lead to pipes. the element may warp.4. boards. sluices. than concrete made with min. styrene copolymer permeability to moisture. and polypropylene Miscellaneous small precast items (burial vaults. boats. tunnel linings. sistance of plastics to strong alkalies (Table 5). pavements. Ref [26]. highway. to a smaller extent of lignin. (c) reboiling with a 2 % water solution of ferrous sulfate. slabs. steps. Their compatibility with concrete is thus important. poles. and least of all to be effective with all sawdust woods evaluated consists of the cellulose. and joint cracking. preferably of a type with high resin content [24]. glass and polypropylene garden units. and and the results achieved have not. chairs. and (d) draining and rewashing. If the element is restrained. moisture. Some of these methods involve encasement of the The following plastic groups have excellent resistance to these wood particles or of the finished product in a material of low alkalies at 24°C (75°F) [25]: polyethylene. increased significantly. and building panels polypropylene . piles. pavement. slab overlays. Timbers embedded in concrete sometimes have been Another source.) Pipes. provides information on the re- observed to deteriorate. sheaths. and washing with water. and decomposition. TABLE 6—Some Applications of Fibers in Concrete Type of Use Type of Fiber Cast-in-place and precast bridge deck units. panels. sodium hydroxide. pavements steel. been revealed. etc. The harm is done by calcium hydroxide. glass. Plastics Concrete made with wood aggregate has considerably greater volume change on wetting and drying. The most suitable wood for embedment is said to be following consecutive steps: (a) boiling in water. steel and polypropylene structural bridge deck elements. but the details of such treatments rubber-resin blends poly (vinyl chlorides). (b) draining pine or fir. industrial floors Maintenance and repairs to dams. polytetrafluoroethylene. Types I and II. Various methods have ably attack plastics are calcium hydroxide. The fillers. been used to reduce the changes in volume with changes in and potassium hydroxide. Industrial floors. pretreatments mentioned previously have only a small The principal chemicals in concrete that could conceiv- influence on these volume changes. street. asbestos. fence posts. steel fibers are subject to the same type of corrosion as reinforcing steel. such as that due to plastic shrinkage.31]. and alkalies— tions where the fibers are exposed in the cracks. They increase impact strength discussed in the section on Glass Fibers. The volume percentage of metal used is significantly restricted to fiber surfaces. Corrosion products are electrical continuity between the steel fibers. to develop adhesion to the cement matrix. and its modulus of elasticity is about 60 % of that for conven- kali-silica reactivity [33]. but not tensile or flexural strengths. The ride-deicing agents are used. ERLIN ON EMBEDDED METALS 181 Fibers Glass fibers formulated with zirconia were thought to be resistant to alkali degradation [34. loss phenomenon. tional concrete [43]. ment is enhanced and failures are due to fracture rather than ance. The polypropy- Some glass fibers can corrode and also cause embrittlement as lene fibers are in common use. crete are steel. The alteration of the asbestos fibers does not adversely toppings to enhance wear characteristics desirable in ware. Steel Good durability of steel-fiber reinforced concrete has been re. . thing of the past because of its potential carcinogenic effect. However. The chemical seawater environment for eight years. rusting of fibers to reactions have been found to be topo-chemical and occur on depths of 0. However. aggregates. and minimize the concrete potential for early cracking. However. Because of the lack of fiber surfaces and on cleavage planes. Glass Fibers The workability of concrete made with recycled concrete aggregates is about that of concrete made with conventional Glass fibers can be sensitive to alkalis in portland cement paste. Deterioration of surfaces has resulted because of rusting of the fibers. use. and increased fracture resist. polyethylene. and further research is American Concrete Institute [27] provides little information re. Asbestos minerals are naturally been reported that steel-fiber reinforced concrete used for occurring and include a variety of different materials that fall pavements.29]. increased re.35]. the loss of In a broad sense. rusting will be initiated at loca. however. because they have a low modulus of elasticity. fibers used for reinforcing concrete are small fracture resistance caused by chemical changes within glass- versions of conventional steel reinforcement. mag- corrosion cannot develop on a large scale. as deicing alone or blended with other aggregates [40–42]. and carbon. is thought to result from reformation of cement hydration part to concrete are increased flexural strength. glass. they posures in wet environments) was as dramatic as previously must enhance the physical attributes of concrete and be experienced. The embrittlement associated with that exposure durable. and they provide fiber reinforced concrete (which occurs prior to five-year ex- a similar service. bridge decks. For such using calcium chloride. nesium silicate hydrates. products in and tightly around the fibers so that fiber encase- sistance to fatigue and impact. needed [37. such as nylon and polypropylene. concrete has had principal use as a base for concrete made with conventional aggregates.34 cm (11⁄ 6 in. Early work using glass fibers reflected the adverse effects of al. That explanation does not entirely satisfy Table 6. The de. after prolonged periods because of chemical reactions with In studies of steel-fiber reinforced beams in a simulated calcium hydroxide in the portland-cement paste. and thus the durability The use of asbestos in portland cement-based products is a of concrete made with steel fibers and exposed in environ. chloride equivalent to a purposeful calcium chloride addition (1 % by mass of portland cement) was present in the The current emphasis on recycling of materials and the razing concrete on which a topping shake containing steel fibers had of old concrete structures and pavements have resulted in the been applied. and low lime calcium silicate hydrates Steel fibers and steel filings are used in proprietary floor [39]. For fibers to be useful and effective. In one Concrete such case. the old concrete is crushed and graded and used either tures or. This situation points out the desirability of not use of old concrete as aggregates for new concrete. along with sodium chloride (rock salt). Organic fibers are considered to rely upon Organic Materials mechanical interlock. either as an admixture to concrete mix. greater than for steel fiber-reinforced concrete. However.38]. particularly by chlorides. and the concrete should have as considered a problem. and steel and glass upon chemical interactions. ments chemically aggressive to the steel may be poor. It has cement since about 1900. polypropylene. nylon. Crushed chemicals. electro-chemical probably magnesium hydroxide. Asbestos ported [28. some corrosion of the fibers may occur low a permeability as workability and water-ratio will permit. Steel fibers Polymer fibers. chlorides should not be a component of admixtures used in Although the durability of embedded asbestos fibers is not steel fiber-reinforced concrete. improve im- have also been produced as crimped or deformed fibers so that pact strength of concrete. its compressive strength is about 75 %. affect properties of the concrete because the alteration is houses. Obviously.) occurred [32]. asbestos. asbestos has been used in conjunction with portland terioration of steel is enhanced. can suffer reductions in strength asbestos minerals may differ in composition but have the [30. common composition of magnesium silicate. A report on fiber-reinforced concrete prepared by the all aspects of the situation. New glass fibers coated with chemically inert garding their corrosion characteristics. into two mineral groups: amphibole and chrysotile. and other similar usages where chlo. Applications of fiber-reinforced concrete are shown in pullout of fibers [36]. magnesium and iron may freely substitute for each other. coating have been used in an attempt to overcome the strength- Among the materials that have been used as fibers in con. magnesium carbonate. Among the desirable characteristics that fibers can im. If cracks are present. they mechanically interlock in addition to chemically bond. “The Effect of a Corrosive Environment on the 1965. L. Properties of Steel Fiber Reinforced Portland Cement. and Tarleton. 42–44. 13th Annual Conference. Great in concrete must possess certain necessary physical and Britain Cement and Concrete Association. 1951. Sept. 28–29.” Journal. S. Concrete Containing Calcium Chloride. No. E. P. 348.” Portland Cement necessarily mean that it will perform similarly as concrete ag- Association. 10–22.” HRB NCHRP. 22. H. 9 corrosion of reinforcing steel. K. E. No. St. New York. 31–34. and Rosenburg. Research Laboratory.. A. “The Performance of Galvanized Reinforcement in Concrete Bridge Decks. Feb.” [6] Monfore. 1964. American Society Sept. H. pp. 593–596..” Concrete Construction No. G. No. [32] Lankard. 117–132. Feb. 1949. 11. 38. T..” (unpublished). 95–97.” Journal. 9. [10b] Berke. Chemical Rubber terials Protection and Performance. Journal Structural Division. Division of Building Research.. minum Alloy Balusters in a Reinforced Concrete Bridge. and Steiner. “Stronger Market Seen for Glass-Fiber Concrete. 10. A. 1938.369. Portland Cement Association. 1964. March 1976. pp. 36.” Nitrite Corrosion Inhibitor in Concrete.” Notice. Urbana.. W. The Corrosion gate had resistance to cyclic freezing [44].” Modern Concrete. R. References [20] Johnson. Concrete made with a calcium chloride addition.” Materials ing Reactions of the Corrosion of Lead in Cement. 1971. National As.. et al. E. J. Jan.” Journal of Testing and Evaluation. Dodero “Accelerat. 1966. Budapest. 1977. No. “An Unusual Case of Corrosion of Aluminum [23] Parker. [3] Wright.415. 1955. 1956. Construction. D. No. Aggregates for use of Metals in Contact with Concrete. Washington. L. and Ost.. Australia Commonwealth Scientific and Industrial [2] Jones. Paper [9a] “Corrosion of Lead by Cement. G. F. Vol.. “Galvanized Reinforcement in Concrete Containing and requirements to ensure that concrete made with recycled Chlorides. Oct. Re. [28] Shroff. 1963. [24] Dominik. 5. pp. Containing Calcium Chloride. J. now with Materials Laboratory. Morrison. “Strength of Steel Fiber Containing Chlorides. [35] Tallentire. H. D. Vol. 27.. 1975.” Engineering Journal. No.. [1] Abrams. 1977. W. and Orals. p. “Technical Review of Calcium [34] Ironman.” Proceedings.” Journal. July 1977. “Waste Glass as Coarse Aggregate for Con- crete. Vol. Inc. exposure and environment for lengthy periods does not [13] Stark.. “Concrete Corrosion and Concrete Protection. “Concrete Drying Methods and pp.. J. I. March 1964.” [4] “Spalled Concrete Traced to Conduit. W. F. Naval Civil Engineering Laboratory. [31] “Corrosion Behavior of Cracked Fibrous Concrete. 1963.. 70-65. M. No. 1965. and Costello. Project No. search Record 1211. These are two examples that July 1976. G. 5. [21] Waters. Potsdam.” Ma. could promote 140. of Corrosion Engineers. Materials Performance. Vol. pp.” Reprint No.182 TESTS AND PROPERTIES OF CONCRETE Buck reported that concrete made with recycled aggre. 729–744. T. Their Effect on Fire Resistance. New York. private communications. 14 Aug.. Jan. 9. [11] Halstead. 247–264. Title No. American in Concrete. Record. 48. such as those required in ASTM C Chemistry and Industry. pp. Akadimiai Kiado. 1. C. pp. MI. U. Vol. Technical Note. No. Note N-1032. Washing. Aggregates for Highway Use. Because the concrete has seen prior service in a given [12] Rabald. 89. 9. July 1969. 1957. “Corrosion of Nonferrous Metals in Contact with as for concrete aggregate. pp... “Corrosion of Galvanized Steel in Contact with Memorial Institute. Corrosion Guide. pp. 1132–1137. Oct.” Research and Development Bulletin 181. “Corrosion of Metals in Buildings. 25. B. 1. pp. B. Skokie. D. Cleveland. 2. American Concrete Institute. 591–592. London. demonstrate the need for establishing suitable specifications [16] Stark. DC. 11. S. D. 282. minum and Aluminum Alloys in Building Materials. reprinted from chemical characteristics. Concrete. 1973.. April 1978. pp. and Obszarski. Vol. D. 24 Aug. Great Britain Department of Scientific and Industrial [22] “Fiber Reinforced Concrete. T. 74–82. J. pp. Research Paper 36. “Corrosion of Aluminum Conduit Journal.. 1970. Canada. N. “Performance of Aluminum in Concrete [30] Bateson. Vol. E. Portland Cement Association..” Precast ton. “Action of Cement on Wood. and Perenchio. I. 372–376. Dec. Elsevier.” Technical elevated structure where the exposure has been dry will prob. IL. Reinhold.” Chemistry and Industry. pp. Concrete. [8] McGeary. IL. Nov. search and Development Laboratories. and Hans. pp. crete aggregate by adhering gypsum plaster from plastered [18] “Guide to Durable Concrete. 44. 18 pp. 1357–1362. Vol. 1975 [9b] Biczok. Clarkson College of Technology. 344–350. No. 50–56. MO. R. E. 1959–1960.. “Galvanic Corrosion in Concrete thesis. [26] Handbook of Chemistry and Physics. Houston. ST [29] “A Status Report on Fiber Reinforced Concretes. Oct.. A. Vol. pp. 1971. walls can cause internal sulfate attack.. [25] Seymour. “Glass Fibre Cement Applications. Products. E. W. 1970.. R. Final Report. D. University of Illinois. Engineering. IL. Jan. June 1970. American Concrete Institute. R. pp. . Project 4–10.. Company. Port ably respond differently when used in a moist environment.” Report S-41. building construction has been used for fill material as well [17] Freedman. “Effect of Embedding Alu- Research Organization. “Attack on Glass Wall Tiles by Portland Cement.” Engineering News— Przemsyl Cheniczny. C. 7. Task 03. Concrete Products. 63. Work Unit 006. formerly Battelle [10a] Mange. DC. pp. 33. E.10. Vol. and June 1971. 1974. Hueneme. gregate in other service and exposures. if used in [15] “Use of Galvanized Rebars in Bridge Decks.. Jan. Portland Cement Association. Reinforced Concrete Exposed to a Salt Water Environment. reinforced nonchloride-containing concrete. Federal Highway Administration. “Promising Replacements for Conventional sociation of Corrosion Engineers. ACI Committee 201. 1966. Applications. Vol. IL. and Jenks. Skokie.” Construction Technology Laboratories. D... 1957. NACE Annual Conference. 1947. Vol. 1955. B.” Concrete Construction.” Preprint. 1977.. Feb.” Concrete 5. concrete will provide adequate service. [27] “State-of-the-Art Report on Fiber Reinforced Concrete.” Centre de Recherches de Pont-a- Research. p.. “Effectiveness of Zinc Coatings on Reinforcing made using chemically unstable aggregate and used in an Steel in Concrete Exposed to a Marine Environment.” Proceedings. “Corrosion of Alu. Sept. concrete [14] Griffin. [33] Marek. M. New York. Louis. 16.S. Plastics for Corrosion-Resistant [5] Copenhagen. 1949. 172.” Metaux & Systems and Science Division of the Construction Engineering Corrosion. 1976. Project OK1. Building Research Station. Concrete from ZE-247. R.” Transportation Re. S. M. ACI Committee 544. 13–16.” Masters [7] Wright. Contamination of the crushed con. Concrete Institute. 41st ed. E. Transportation Research Board. 1976. [19] “Waste Materials in Concrete. F. For example. Detroit. French Patent No. Skokie. “Sawdust-Cement and Other Sawdust Building Conduit in Concrete. 38. 1989. 1973. 15. ERLIN ON EMBEDDED METALS 183 [36] Grimer. F. No. pp. Concrete. No. 373–376. and Concrete. A. . American Concrete Institute. 108. 107–108. Paris. 74. [38] Cohen. 23–30. Symposium on Fiber Reinforced Cement and [41] “Reusing Concrete.” Highway and Heavy Reduction as an Indication of Alkali Attack on Glass in Fibre Construction. 269–276. S.. RILEM. March 1969.. Energy. RILEM. 186. pp. E. 5. 66. p.. “The Strengths of Cements Times. pp. July 1977.” Proceedings. J. pp.” Highway Research Record No. 7. pp. 1975. 80. Proceedings.” [37] Majundar. Symposium on [43] Frondistou-Yamas. Vol. A. and Ali. L. p. Vol. 1977. Vol. [39] Opoczky. “Validity of Flexural Strength [42] “Recycled Slab is New Runway Base.. J. Paris. and Pentek. No. L. “Investigation on the ‘Corrosion’ of [44] Buck. No. Aug. pp. and the Environment. June 1971. 1975. May 1977. RILEM. 30–33. S. 315–325. 22. 8. “Properties of Fiber Cement Composites. A. M.. Vol. 120. D.” Rock Products. Reinforced Cement Composites.” Magazine of Concrete Research.” Proceedings. “Waste Concrete as Aggregate for New Fiber Reinforced Cement and Concrete. “Recycled Concrete. Vol. 279–313. Symposium on Fiber Reinforced Cement Reinforced with Glass Fibers. pp. 1975. and Diamond. Paris. No. Asbestos Fibers in Asbestos Cement Sheets Weathered for Long 430. B. 21. Concrete. [40] “Rubble Recycling Saves Time.” Journal..” Engineering News-Record. impact. inadequate chains (attrition. and abutments due to the action of abrasive ing discussion of significant factors relative to concrete resist- materials carried by flowing water (erosion). ACI 302.18 Abrasion Resistance Karl J. An excellent source of information on cavitation erosion ASTM Terminology Relating to Erosion and Wear (G 40) defines can be found in Refs 4 and 5. E. scouring. or cutting from mechanical or hydraulic forces. Evergreen. metal scraps. composition. granite. the quality of the coarse aggregate as determined by ASTM Test pact. tunnels. or be increased appreciably by the use of maximum amount of similar materials. M. ance to abrasion illustrates the importance of the proper • Wear on concrete dams. crete containing limestone aggregate has approximately twice bing action. Kalman Floor Company. introduce new technology that has so created. • Wear on concrete road surfaces due to heavy trucking. it will not be covered. The abrasion resistance can introduction of foreign particles. therefore. As the wheel revolves. The fourth type of wear. is the Factors that may affect the resistance of concrete to abrasive “ability of a surface to resist being worn away by rubbing and action should be considered in the design and construction of friction” [1]. The Method for Resistance to Degradation of Small-Size Coarse 1 Sales Engineer. CO 80439. The action of the abrasive particles carried by the flowing water. H. is controlled largely by the velocity of the water. Abrasion Testing. E.” Abrasion re. the type of abrasive material. Bakke1 Preface third type of wear is primarily grinding and cutting actions. For example. upon entering areas of high pressure. percussion. and application of concrete based on ter-carrying systems where high velocities and negative the specific type of service condition. a great impact. sliding. pressure are present. according to American Concrete Institute (ACI) Com- mittee on Cement and Concrete Terminology (ACI 116). attrition. IN PREPARATION OF THIS CHAPTER. Liu. and include up-to-date references. gouging. R. the abrasion loss of con- intended use [3]. including design and construction considerations based on the or metallic aggregate. [7] indicated that the from a rubbing action to high impact and hard-wheel traffic of abrasion resistance of concrete is strongly influenced by the forklifts. the failure of concrete to resist abrasion can be automobiles.1 classifies floors. tion. a process that tends to cut the surface of the concrete. O. Quality of Aggregates The first type of wear to concrete floors can vary widely Studies by Liu [6] and Laplante et al. Subcommittee Chairman ASTM C09. The vapor pockets by the previous authors. spillways. and Tony C. is caused by the abrupt change in direction and velocity Prior. and Frequently. Prior. selection. and other wa. about by the use of chains on automobile and truck tires or Abrasion tests carried out by Liu [6] indicated that no cor- metal vehicle wheels. concrete surfaces that are to withstand abrasion due to rub- Wear of concrete surface can be classified as follows [2]: bing.1R-04. The follow- bridge piers. plus scraping and percussion). chert. This is brought as much as that of the concrete containing chert [6]. cavita- authors of the first four editions. L. of course. Lane. respectively. with and without studded snow tires or traced to cumulative effects such as soft aggregate. • Wear on concrete floors. dense. manipulation during finishing of concrete surface. The of a liquid to such a degree that the pressure at some point is current edition will review and update the topics as addressed reduced to the vapor pressure of the liquid. and the gen- of the 4th edition were drawn up. spillways. Concrete floor wear is greatly increased by the hardness of its coarse aggregate. improper curing or finishing. The second type of wear is caused by a rub. collapse with been developed. hard coarse aggregates such as traprock. The author acknowledges the eral surrounding conditions. such as sand. or over- • Wear on hydraulic structures such as dams. Factors Affecting Abrasion Resistance sistance. which eventually causes pits or holes in the concrete surface. plus an impact-cutting type of wear. THE CONTENTS the angle of contact. This is generally known as cavitation erosion (cavitation). compressive strength.62. Table 2. Discussion of cavitation resistance of concrete is Definitions and Types of Abrasion beyond the scope of this paper. it brings the metal relation existed between abrasion resistance of concrete and into contact with the concrete surface with considerable im. scraping. 184 . abrasion as “wear due to hard particles or hard protuberances forced against and moving along a solid surface. Kennedy and M. 45 has been specified by the U. However. in turn. so will the resistance of concrete to abrasion.S. such as limestone. A similar finding was increases with a decrease in water-cement ratio [6]. and finishing and has a direct influence on the abrasion resist. the abrasion loss of the limestone concrete is that. tend to produce a concrete of improved abrasion resistance. concrete. the hardened cement paste assumes a greater role in However. good studies reflects an increase in abrasion loss proportional to in- quality aggregates meeting the requirements of ASTM Spe. the Los Angeles abrasion slab surface strength [12]. such as chert. conventional concrete mixture containing a very hard chert mately 44 % as the compressive strength increases from 20. and relatively hard aggregate. usually resulting in increased abra. which. [13] and Laplante [7] indicated that important factors responsible for the abrasion resistance of adding condensed silica fume and high-range water-reducing concrete. 1—Relationship between resistance of aggregate to abrasion and concrete abrasion loss. the admixture to a concrete mixture greatly increases compressive abrasion resistance of concrete increases with an increase in strength. Compressive Strength Witte and Backstrom [10]. the abrasion resistance of concrete much more than that containing chert. As can be seen from Fig. as shown in Fig. BAKKE ON ABRASION RESISTANCE 185 Aggregate by Abrasion and Impact in the Los Angeles Machine tested to measure compressive strength is not a measure of the (C 131). crease in air content for any given water-cement ratio (w/c). A maxi- reported by Smith [8]. For the same aggregate and finishing procedure.1 MPa (9000 psi) [6]. including air-entraining ance of concrete. These very high-strength compressive strength of concrete [11]. the basis of the literature review. Mixture Proportioning the abrasion losses of the concrete containing these aggregates Abrasion test results by many researchers clearly indicated vary widely. abrasion resistance is a function of the water-ratio resisting abrasion and as such the aggregate quality becomes at the surface and of the quantity of quality aggregate. For example. for the high-strength silica-fume MPa (3000 psi) to 62. the av. The compressive strength. The general trend in most For concrete subject to light-to-medium abrasion. The effects of various admixtures. Schuman and Tucker [9] pointed out that the shape of ag. Angular to subangular-shaped aggregate is and water-reducing admixtures and retarders. considered the compressive strength as one of the most Studies by Holland et al. . 2. for a given aggregate. as researchers before and after Concrete Types them. abrasion resistance of silica-fume concrete containing erage abrasion resistance (the reciprocal of abrasion-erosion relatively soft limestone is similar to that of a high-strength loss) for concrete containing limestone increases approxi. not of the correspondingly less important. The 6-in. mum water-cement ratio of 0. by virtue of their positive effect on the aggregates [2]. cylinder concretes appear to offer an economical solution to abrasion Fig. increases abrasion resistance. resistance of concrete could not be established conclusively on sion resistance. Army Corps of Engineers for concrete subject to abrasion in gregate particles regulates the water requirements for placing hydraulic structures. on the abrasion known to improve bond. As cification for Concrete Aggregates (C 33) are generally the compressive strength is adversely affected by increased air acceptable. Apparently. losses are approximately equal for soft aggregate. Heavy-duty floors and slabs exposed to more contents. Water- severe abrasive action demand well-graded hard mineral reducing admixtures. 1.7 aggregate [13]. w/c and consequently on increases in strength. 12-in. Krukar and Cook [19]. crete. methyl methacrylate poly- gregate otherwise might not be acceptable. This is finishing. closing any existing imperfections than comparable conventional concrete. The abrasion losses of fiber-reinforced compared with abrasion resistance of concrete in a study by concrete as determined by ASTM C 1138 were consistently Fentress [23]. was investigated by Liu [21]. Combining these demands in one application. and the U. treated with polymer showed considerable Ytterberg demonstrated that a deferred topping finish from increase in abrasion resistance.5. and polymer portland cement concrete. the w/c [24]. polymer portland cement concrete.S. This is attributed to surface compaction and would be expected to increase the impact resistance of con. Army Corps of The relative abrasion resistance of four different types of Engineers [21] confirmed that vacuum-treated concrete surfaces polymer concretes (that is. to power finishing is significantly higher than that subjected to While the addition of steel fibers in the concrete mixture hand finishing. Concrete achieved by proper finishing procedures and in a reduction in of 34. and providing excellent resistance to abrasion.8-MPa (5000. U. mer concrete. The technique remarkable improvements in concrete properties. particularly in those areas where locally available ag. particularly requires that after the water of workability has been removed. are also ter-cement ratio [17]. problems. procedures used. and upon stiffening.186 TESTS AND PROPERTIES OF CONCRETE Fig. are considerably more resistant to abrasion than surfaces with . fiber-reinforced concrete is less resistant to abrasion Finishing techniques. Abrasion tests carried out by Kettle and Sadegzadeh [22]. Other studies with shrinkage compensating ce. and hard-steel trowel finishes. the abrasion resistance of concrete containing fly ash is Among these polymer concretes tested. non-air-entrained. as long as the concrete ranked first in abrasion resistance. including wood float. Abrasion resistance of concrete is affected by the finishing portions [14]. steel trowel. float. Army Corps of Engineers indicated that tained limestone aggregates. magnesium than conventional concrete of the same aggregate type and wa. which all con- Tests by the U.to 6500-psi) compressive strength. in strength and abrasion resistance due to impregnation and the surface is blade-floated. and Dikeou [20] also demonstrated process yields highest abrasion resistance [24]. has an abrasion resistance from 30 to 40 % Finishing Procedures higher than portland cement concrete of comparable mix pro. Polymer-impregnated concrete for highway bridges was The key to durable. Bureau of Reclamation [25]. despite ease of ranges of water-cement ratio and compressive strength. Both the steel trowel and hard-steel trowel generally has less coarse aggregate per unit volume of concrete produce smooth surfaces. The wood float tends to tear the surface and to higher than those of the conventional concrete over wide displace the aggregate. polymer-impregnated comparable compressive strength at the time of tests. when properly proportioned and cured. the ture concrete.to 44. troweled. cleanable concrete slabs can be investigated by Fowler of the University of Texas [18]. the vinyl ester polymer comparable to that of concrete without fly ash. Tests by Kettle and Sadegzadeh [22] indi- ment have indicated similar results: Nagataki and Yoneyama cated that the abrasion resistance of concrete subjected [15] and Klieger and Greening [16].S. and vinyl ester polymer concrete). to reduction of the w/c of the surface matrix. in-place polymerization of monomers in overlays and in ma. concrete. The magnesium float. polymer-impregnated concrete. Shrinkage compensating concrete. followed by concretes contain the same type of aggregate and have methyl methacrylate polymer concrete. Experimental studies by Liu which surface water is removed by a vibratory absorption [6]. 2—Relationship between abrasion resistance and compressive strength.S. causes a rough-textured surface and a lowering in attributed primarily to the fact that fiber-reinforced concrete abrasion resistance. curing. components of the concrete. sodium silicate. some coatings. over a century to evaluate the abrasion resistance of concrete out the use of additional water to produce a hard. The pact-type wear as imposed by the dressing-wheel-type machine. This rubbing action simulated best by a revolving-disk-type abrasion procedure was revised in 1964 calling for the explicit use of sil- machine. gregate mixtures. ica sand that allows for closer control of the abrasive action. loss. Adjustments in the pressure used and the type of abrasive permit a variation in the sever- Surface Treatment ity of abrasion that may be used to simulate other types of Certain chemicals (magnesium and zinc fluorosilicates. After the dry shake is Abrasion Test Methods applied to the concrete. BAKKE ON ABRASION RESISTANCE 187 either nontreated lean or richer concrete. finishing. Preceding any stan- demonstrated that abrasion resistance is significantly improved dardization of laboratory methods or of testing machines. More recently. addition to cold rolled steel and hardened tool steel. especially for evaluating the resistance of concrete subjected to various types surfaces composed of leaner concrete. This proper surface preparation or thermal incompatibility be- treatment is most effective on concrete with a high w/c. Once the dry shake has absorbed water.13 on Methods of Testing Concrete for Resistance to treatment of deficiencies in relatively pervious and soft Abrasion from the original Ruemelin blast cabinet equipped surfaces that wear and dust rapidly [29]. Several types of ASTM C 779 surface coatings including polyurethane. Rushing [36] compared the 1958 and 1964 proce- protect the concrete from the attack of the environment or dures of ASTM C 418 in a laboratory study and found the later chemicals [32] possess only limited abrasion resistance and revision permits a more accurate determination of abrasion any test simulation to evaluate their effectiveness is difficult. tween coatings and concrete. From this study. The background. abrasive action based on the tumbling of steel balls impacting a test surface [33]. and iron-aggregate toppings For almost two decades. w/c. Sandblasting (C 418) dates back to 1958 and is based on the For concrete floor and slab construction using Type I principle of producing abrasion by sandblasting. beneficial known specific gravity for the filling of voids in the abraded con- effects from treatment with linseed oil were demonstrated by crete surface. and incremental curing. Numerous modified versions of the rattler Curing principle continued to be the dominant test procedure along Efficient curing increases the abrasion resistance. While the magnesium fluorosilicate is more resistant to The 1958 standard specified carborundum or silica sand. furan-resin mortar. that the greatest abrasion losses encountered were ASTM Test Method for Abrasion Resistance of Concrete by associated with less-than-adequate curing procedures. These have been due primarily to im- to the reduction of water content in the concrete mixture. and waxes) serve to prolong the life of This test method was modified by ASTM Subcommittee older floors and are considered an emergency measure for C09. some popularity because of its simple design. However. The improvement in [21]. Pockets of bleed water should be removed prior to the application of the dry shake. with the revolving metal disk pressed against a small concrete tion of curing time and abrasion resistance reported by Sawyer specimen [34]. problems in field application of surface coat- abrasion resistance of vacuum-treated concrete is due principally ings have been reported. fluorosilicates densifies and hardens surfaces and improves The control over such variables as gradation of the silica sand. of abrasive actions. The techniques and test methods that have been employed for it is power-floated and then steel troweled into the surface with. formulations have Concrete wearing surfaces can be improved by the use of been developed that have coefficients of thermal expansion cast-on hardeners or “dry shakes” consisting of cement/hard-ag. it should be given enough time to absorb water prior to floating. [30]. steel-trowel. dense topping have attempted with varied success to reproduce the typical layer. and applica- A laboratory program conducted by the California Divi. Test data indicated. This permits accurate measurement of abrasion an increase in abrasion resistance of as much as 30 % [31]. A correla. there are four standard ASTM test methods for can be expected with extended curing time. epoxy-resin mortar. acrylic mortar. The current revision now allows for a ceramic nozzle in However. rate of feed of the abrasive. abrasion resistance of old. Treatment with with an injector-type blast gun with high-velocity air jet (Fig. Testing by the Portland Cement Association in 1970 forces detrimental to concrete surfaces. more similar to that of the concrete substrate [4]. It performs a cutting seven days at temperatures of 10–21°C (50–70°F) are required action that tends to abrade more severely the less resistant to assure adequate abrasion resistance [3]. finish as liance was placed initially on the use of rattlers that provide compared to ordinary concrete without surface hardeners [26]. reusing cast-on surface hardeners with hard. 1976 revision specifies the use of oil-base modeling clay of For poorly cured or porous concrete surfaces. gums. it is apparent that marked improvement in abrasion resistance Currently. bilities of these ASTM test methods are presented here. worn floors. by volume displacement and replaces the old weight-loss deter- Paints and coatings used to seal concrete surfaces and to mination. significance. and surface ASTM C 418 treatments using linseed oil. among these variables. ASTM C 418 remained the only speci- have exhibited good abrasion resistance in laboratory tests fied standard for testing concrete resistance to abrasion. abrasion. distance of the nozzle by the two types of fluorosilicates is not of equal magnitude from the surface.03. among them vinyl and heavy rubber. the zinc fluorosilicate shows greater resistance to im. sion of Highways [28] considered the effect on abrasion of such variables as slump. The drill-press-type abrasion machine [35] in [27] involved a series of tests comprising a wide range of modified form still is used by highway departments and enjoys cement contents. if properly bonded remain fairly resilient and effective in protecting concrete from abrasive actions. From . 3). and the area of the shielded surface is critical. but the improvement air pressure. at least five days of curing at concrete dure simulates the action of waterborne abrasives and abra- temperatures of 21°C (70°F) or higher and a minimum of sives under traffic on concrete surface. This proce- portland cement. ASTM Test Method for Abrasion Resis. accomplished by rotating steel disks in conjunction with abra- tance of Horizontal Concrete Surfaces (C 779) covers three sive grit. All number of major test programs conducted by independent lab. three machines are portable and adaptable for laboratory and oratories. 4) introduces frictional to the selection of three abrasion machines and their inclusion forces by rubbing and grinding. leading The revolving-disk machine (Fig.03.13 initiated a dressing-wheel machine. The revolving-disk machine was redesigned by Mas- testing procedures: (a) the revolving-disk machine. Cleveland. and was essentially Fig. 3—Sand blast cabinet. Sliding and scuffing is in one ASTM standard. in-place field abrasion testing. 1964 through 1971. The results of these comparative programs estab.188 TESTS AND PROPERTIES OF CONCRETE Fig. . and (c) the ball-bearing machine. 4—Revolving-disk abrasion test machine. (b) the ter Builders Company. Ohio. ASTM Subcommittee C09. lished such parameters as severity and reproducibility. A supply of No. Yet. In its abrasive severity. On ordinary-finished concrete slabs. etc. BAKKE ON ABRASION RESISTANCE 189 patterned after a machine developed by the National Institute of Standards and Technology. 6—Ball-bearing abrasion test machine. 6).0 mm (0. and cutting action of steel wheels or the effect of studded tires. no abrasive material is employed with this machine. bringing the ball bearing in contact with sand and stone particles still bonded to the concrete surface. also producing the highest coefficient of variation among the three procedures (Table 1). Water is used to flush out loose particles from the test path. and high-speed rolling constitutes the abrasive action of the ball-bearing machine (Fig. A plane surface resulted in either case regardless of the variation in the quality of the hardened cement paste or the toughness of the aggregate that became exposed as the depth of wear increased. compressive forces. the dressing-wheel machine (Fig. 60 silicon carbide abrasive is fed to the disks at a rate of 4–6 g/min.12 in. due to soft and hard spots causing the core barrel to . The abrasive mode of this procedure best simulates wear by light- to-moderate foot traffic and light-to-medium tire-wheeled traffic or moving of light steel racks. the ball-bearing machine exceeds both the revolving disk and the dressing wheel. In contrast to the disks. but it is recommended to extend the test period to 60 min if information on the longtime abrasion resistance is desired. Abrasion of concrete induced by the dressing-wheel machine closely simulates the rolling. abrasion readings are taken every 50 s with a dial micrometer mounted directly to the supporting shaft allowing readings “on the fly. continues. Tracking of the dressing wheel normally leaves a grooved path with the test surface being irregular and fairly rough as harder aggregate particles stand out from the softer aggregate particles and mortar that are abraded more quickly. However. the dressing wheels produce a depth of wear more than double that obtained with the revolving-disk machine for the same test duration.” Readings are continued for a total of 1200 s or until a maximum depth of 3. The dressing-wheel machine is similar to the revolving-disk machine in appearance. The effects of the ball-bearing machine on concrete surfaces indicate abrasive action becomes progressively more severe as the test Fig. pounding. These results are essentially concurrent with a parallel study conducted in the Portland Cement Association laboratories [26]. except for three sets of seven dressing wheels mounted on horizontal shafts that take the place of the three rotating steel disks. the revolving-disk machine provides the most reproducible results. Davis and Troxell [37] reported that the depth of wear for periods of 30–60 min is about the same for ordinary slabs as for heavy-duty concrete surfaces. The coefficient of variation established by the Berkeley study [37] for slabs abraded with the dressing-wheel machine is several times as great as that for the revolving-disk machine. 5) imparts high concentrated compressive forces with high impact stresses. Initial and intermediate measurements of the test path are taken with a Fig. The ball-bearing machine operates on the principle of a series of eight ball bearings rotating under load at a speed of 1000 rpm on a wet concrete test surface. Repeated dynamic loading through strong impact. depth micrometer. Among the three standard methods. thus providing impact as well as sliding friction.) is reached. During the test. 5—Dressing-wheel abrasion test machine. approximately equal depths of wear are obtained from both machines for the same test period when hard troweled finished floors are tested. A test period of 30 min generally produces significant wear on most concrete surfaces. The detailed cross-sectional view of Procedure of meana percent of meana the test apparatus is shown in Fig. or other samples of concrete of insufficient test area to dust off the test specimen. More severe abrasion due to percussion. for instance. and 70 steel grind- Variation. clean the surface occasionally during the test by blowing the mens. The These numbers represent respectively the 1S % and D2S % limits as described in ASTM Practice for Preparing Precision and Bias Statements for Test Methods for standard test consists of six 12-h test periods for a total of 72 Construction Materials (C 670). in turn. impact.) diameter concrete cores. General practice is to ends of 152-mm (6-in. an agitation paddle. ASTM C 944 ASTM Test Method for Abrasion Resistance of Concrete or Fig. The C. Additional testing time may be required for concrete that Statement. This has been poor. The apparatus consists of essentially a drill press.2 circulating water. with the single-operator coefficient of varia- test method produces a much more rapid abrasive effect than tion of more than 20 %. This test method can duplicate . 8. generally a produces significant abrasion in most concrete surfaces. mortar speci. • Failure to remove dust and loose-abraded material regularly from the test surface. is highly resistant to abrasion.74 50.6 B. cutting. The difficulty in maintain. ing a constant load on the abrading cutter when using the mens. revolving disks. Mortar Surfaces by the Rotating-Cutter Method (C 944) gives an indication of the relative abrasion resistance of mortar and concrete based on testing of cored or fabricated speci. and steel balls and failure to replace them regularly as specified. TABLE 1—Within-Laboratory Precision for ASTM adopted this test procedure with some minor modifi- Single Operator. The test apparatus is a fairly simple piece of equipment consisting of a rotating cutter and a drill ASTM C 1138 press or similar device with a chuck capable of holding and rotating the abrading cutter at a speed of 200 rpm. increasing in order with dressing wheels and ball bearings. a cylindrical steel container that Coefficient of Acceptable Range houses a disk-shaped concrete specimen. in the section on Alternative Form of the Precision h. The reproducibility of test results permit the conduct of tests by ASTM C 418 and C 779. This test method has been successfully used in the lever. derwater Method) (C 1138) was originally developed by Liu [21] in 1980 for evaluating the resistance of concrete surfaces subjected to the abrasive action of waterborne particles on hydraulic structures such as stilling basins and outlet works. Excluding these variables.69 33. ing balls of various sizes.51 15. producing the abrasion effects. percent of Two Results. In general. loss in test accuracy may develop due to the following factors: • Rapid wear of dressing wheels. • Arbitrary increase in the length of test or flow of sand.1 is powered by the drill press rotating at 1200 rpm. • Differences in age levels of concrete at which test results are compared. or rolling creates erratic action and is less conducive to reproducibility. Dressing wheel 11. the within-laboratory precision shown in Table 1 indicates the lowest coefficient of variation is obtained with the revolving-disk method. Experience with testing of abrasion by ASTM C 779 demonstrates relatively good reproducibility over a fairly wide range of concrete surface types and conditions when the abrasive action is moderate. the other test methods. 7—Rotating-cutter drill press. and spring system of a drill press has been elimi- quality control of highway and concrete bridges subject to nated by placing a constant load of 98 N (22 lbf) directly traffic. gear. Testing. totaling 24 h. This method is primarily intended for use on the top upon the spindle that turns the cutter.190 TESTS AND PROPERTIES OF CONCRETE bounce to high angular speed. • Improper selection of a representative test area or specimen. ASTM C 779 cations in 1989. Revolving disk 5. and • Insufficient number of wear readings. Figure 7 ASTM Test Method for Abrasion Resistance of Concrete (Un- shows a rotating-cutter drill press. This test procedure has merit in that the ball bearings are similar to rolling wheels and are more typical of actual loadings by steel-wheel traffic to which a concrete floor may be exposed. moves the abrasive charges (steel grinding balls) on the surface on the concrete specimen. through attrition. Ball bearing 17. The water in the container is circulated by the immersed agitation paddle that A. 8—Test apparatus. XX X Abrasive erosion of waterborne particles on hydraulic structures X X . overlap in the type of abrasion imparted by these test applica- efficient of variation made from a single batch of concrete is tions and that a specific service condition may be reproduced 14 %. was expressed as a percentage of Table 2 serves as a general guide for possible applications of the original mass of the specimen. it is necessary to bear in mind that there is allowable variations in specimen size. or studded tires. etc. as determined by the original Corps of degrees of severity and types of abrasive or erosive forces. and C 1138 offer six distinct procedures that simulate various The abrasion loss. Engineers’ test method [21]. The single laboratory co.03. However. heavy steel-wheeled traffic. This method is not. at the end of the test time wear with the abrasive action particular to each of the test increment to eliminate differences in results resulting from the methods. ASTM C 1138. etc. well the abrasive action of waterborne particles in the stilling Application of Test Methods basins. C09. heavy tire-wheeled traffic. by more than one procedure. intended to provide a quantitative measurement of length of service that may be As discussed in the previous section. BAKKE ON ABRASION RESISTANCE 191 Fig. C 779. ASTM C 418. X X Forklift. C 944. automobile with chains. however. expected from a specific concrete.13 revised the method by calculating the volume loss. ASTM Subcommittee the six standard procedures for various categories of abrasion. TABLE 2—Application of Test Procedures ASTM C 779 Type of Abrasion ASTM C 418 ABC ASTM C 944 ASTM C 1138 Foot traffic or light-to-medium tire-wheeled traffic. This tabulation attempts to correlate the severity of in-place or the average depth of wear. Farmington Hills. [22] Kettle. February 1956. and Cook. “Properties of Expansive resisting abrasion while the remainder gives satisfactory Cement Concretes. [24] Ytterberg. A. Research Paper No. January 1970. M.. “A Portable Apparatus for of Concrete Surfaces. Abrasion Resistance of Air-Entrained Concrete. D. tional. abrasion resistance. Luther. June 1987. D. U. 19–28. Protective. E. PA.S. American Concrete Institute. 1986. Farmington Hills. References [21] Liu. and Natural Pozzolans abrasive action of environmental and man-made factors. May. “Abrasion Resistance of Concrete. R. terials. IL.. September 1971. Japan.” Proceedings. C. Manual of Concrete Practice. Guide to Concrete Floor and Slab Construction. C. predict.. DC. C. 1939. 2.” [7] Laplante. C 819.. Part 1.. Farmington Hills. M.. R. types of concrete surfaces under simulated abrasion condi. 439–379. J. ter. Vol.. 1143–1153. J. April. Effects of variables on reduced abrasion resistance of Expansive Cement Concretes. 2001. National Bureau of Standards. 131–163. Slag. University of Texas. C. T. 57. C. P.S. or accept the quality of [18] Fowler. MI. 2. Reinforced Concrete and Prestressed Concrete Pavements jected to abrasion from vehicular traffic or water-borne par. “Polymer Impreg- concrete surfaces. pp. N. “Radiation Polymerization of Monomers. Tokyo. curing. MI. surface hardeners. 1990. Farmington Hills. MI. Determining the Relative Wear Resistance of Concrete Floors. Engineers. ASTM C 418. addition. P. “Cooperative Study on September–October 1981. Silica Fume. DC. Washington. mixture proportion. American Waterways Experiment Station. C 944.” ACI Journal. E.” Materials and Research Department. Erosion of Concrete in Hydraulic Structures. 1967. 3. P. MI.. and McDonald. Methods of Testing for Abrasion of Concrete Floor Surfaces. and Brinkerhoff. C. In in Concrete. curing. [3] ACI 302. 341–350. Washington. “Use of Sil- ica-Fume Concrete to Repair Abrasion-Erosion Damage in the Kinzua Dam Stilling Basin.. “Factors Affecting Durability [9] Schuman.. ACI Manual of Procedures on Abrasion Resistance. and Decorative Barrier . [12] ACI 360R-92 (Reapproved 1997) Design of Slabs on Grade. February 1952.” Proceedings.. Proper selection of concrete-making ma. American Concrete [23] Fentress. or coating materials. Part 5. ACI Peoria. Bureau of Reclamation. Madrid. Houston. M. Paper IV -132. 2.1R-79. R.. Concrete Laboratory Report No. J. MI. pp. B. C [17] Liu... 1969. ACI Committee 201. Winter 1981. ASTM STP 205. Department of Agriculture. and Backstrom. Vol. “Studies on Continually are the basic requirements applying to any concrete sub. [19] Krukar. American Concrete Institute. Cement and Concrete Terminology. ASTM International.” Proceedings. L. West Conshohocken.C. D. finishing procedures. “The Effect of Studded Tires on tions. R. DC. Association. Farmington Hills. Report 3. Civil Engineering.2R-01.” Laboratory Report No. [30] “The Effect of Various Surface Treatments Using Magnesium ASTM International. Farmington Hills. 2001. Concrete Surfaces.” Klein Symposium on ticles. 51. Portland Cement Concrete.” Proceedings. ACI Committee 210.. Krysa.1R-04.S.” Journal. “The Influence of Construction [2] ACI 201. [29] “Surface Treatments for Concrete Floors. Concrete Practice.. Concrete Institute. RP 1252. U. and finishing procedures [15] Nagataki. pp. for evaluating the resistance of con- Fiber-Reinforced Concrete. F. J. Made with Expansive Cement Concretes. ACI SP-100. and (4) verify products or systems to meet specifications. Vol. Revised 1985. F. [25] “Erosion Resistance Tests of Concrete and Protective Coatings... 3-Part Series. M&R 250908-1.. Aitcin. proofing.” U. American Concrete Institute.S. that is. July 1980. Dampproofing.S.. A Guide to the Use of Water- Farmington Hills. 1.. 78. Skokie. p. (2) evaluate specific effects of variables such nated Concrete for Highway Application. (3) compare various TX. July 1973. IL. WA. No.. Durability. “Some Properties Affecting the tion ST-37. American Concrete concrete have proved to be cumulative. W. and Greening. C. Standard Practice for the Use of Shrinkage and construction techniques contribute to the reduction in Compensating Concrete. Reclamation. “Slab Construction Practices Compared by Wear Institute. which may explain Institute.. “Linseed Oil Emulsion for Bridge Decks. Katharine Concrete Practice. There are four ASTM test methods.192 TESTS AND PROPERTIES OF CONCRETE Conclusion [13] Holland T. C. J. [28] Spellman. West Conshohocken. 1957. Concrete International Design & Construction. L. T. PA. and Zinc Fluorosilicate Crystals on Abrasion Resistance of 1141. “Wear Resistance of Industrial Floors of American Concrete Institute. American Concrete Institute. crete subjected to various types of abrasive actions. and Ames. American Concrete Institute. Manual of Concrete Practice. R. [27] Sawyer.” Cement and Concrete. D. PA. K. BRPD-3-7. and Vezina. [26] Klieger. [20] Dikeou. U. Farmington Hills. 1987. ACI Manual of Concrete Practice. L.. P. as concrete-making materials. “Shrinkage and Curling of Slabs on Grade. Jr.” Washington..” Technical [1] ACI 116R-00. and Tucker.” ASTM Cement and Aggregate. 5th International Symposium on Chemistry of Cement (Tokyo 1968). MI. D. methods serve to (1) evaluate. “Wear Test on Concrete Using the German Stan- [8] Smith. “Abrasion-Erosion Resistance of 779. Pullman. ASTM Interna- Concrete to Abrasion. “Abrasion Resis. J. Bureau of [6] Liu. S. ACI Manual of Report C-78-4. February 1991. Vol. pp. American Society of Civil [5] “Erosion of Concrete by Cavitation and Solids in Flowing Wa.” California Division of Highways. “Abrasion-Erosion Resistance of Concrete. [4] ACI 210R-87. Center for Highway Research. Research and Development Laboratories. Guide to Durable Concrete.” Journal. ACI MI.” Proceedings. January 1971. T. 5. T. ACI Committee 116. Part 1. Part 1. [31] Mayberry. F. why only certain portions of a concrete surface may fail in [16] Klieger.. T. Sacramento. Vol.” Research Report No.” Concrete Informa- [10] Witte. W. No. Manual of Concrete Practice. 1951.S. Farmington Hills. C. “The Effect of Aggregate Quality on Resistance of dard Method of Test and Machine. D. J. Report No. Farmington Hills. P. C 445. February 1973. 1947. Cement Association of performance. L. p...” Concrete Laboratory Report No. U.” Washington State University.. Part I. Vicksburg. Tests. 1956. Army Corps of Engineers. H. and Sadegzadeh. Austin. 1141. Washington. March 1970. Part 2. and C 1138.” Journal of Materials in Civil Engineering.” Bureau of Reclamation. Second International Concrete materials are susceptible to deterioration due to the Conference on Fly Ash. DC. MI. 1973. Portland Cement tance of Concrete. ACI SP-38.. and Yoneyama. Agriculture Research Service. Washington. [32] ACI 515. CA. T. Portland Cement Association. These test 3. L. pp. [11] Ytterberg. February 1973. C-342. Bureau of Reclamation. No. American and Bryant Mather International Conference on Concrete Concrete Institute. Proceedings. D. MI. intrinsic conditions related to properties of concrete [14] ACI 223-98. MS. Vol. H.” U. and Paul. West Conshohocken. Different Pavement and Surface Texture. and Liu. MI. Spain. R. Part 5. American Concrete Institute. H. ACI Manual of Concrete Practice.. 5750. Berkeley. E. Highway Research 1968. “Methods of Testing Concrete for [34] Guttman. Resistance to Abrasion—Cooperative Testing Program. University of California... D. 30. DC. H. Vol. Board. BAKKE ON ABRASION RESISTANCE 193 Systems for Concrete.” Chemical Abstract. p.” Proceedings. p.” Chemical Abstract. 38.. “Apparatus for Testing the Hardness of ACI Committee 515. Hills. CA. and Troxell. E. [36] Rushing. October 1964. June Concrete in Road Slabs. Baton Rouge. 127. 1990. [37] Davis. 1944. “Abrasion Tests on Concrete. A.” Report PB 183410. H. Washington. MI. . 1936. 1338. G. 1925. “Concrete Wear Study. [35] Harris.” Vol. H. LA. p. B. Farmington Materials.. [33] Scofield. “Significance of Talbot Jones Rattler as Test for Louisiana Department of Highways. where Importance of Elastic Properties and Creep F the applied force or load Engineers need to be able to compute deflections of structures. to proportion the deformation sections. Relaxation describes material property. and Relaxation Jason Weiss1 Preface the load is removed. concrete can exhibit in. discuss creep and relaxation. (i. Hooke proposed this concept in Philleo authored the chapters appearing in ASTM STP 169A 1678 by stating that the deformation of a body () was linearly (1966) and ASTM STP 169B (1978) under the title “Elastic Prop. “stiffness” of the material/structure that is dependent on the These properties are commonly referred to as the elastic prop. 194 . Bureau of Public Roads (now FHWA).S. and early age creep and relaxation measurements. This chapter will review some of the basic elastic properties. In this linear relationship the elastic gives rise to the more familiar form of Hooke’s Law for uni- modulus describes the ratio of the change in stress and change axial loading where stress is related to strain through a pro- in strain.. . Creep describes the slow. While the elastic properties can be used to describe portionality constant which is referred to as the elastic modu- the initial deformation under loading. this chapter has been modified to include information on non. there are changes When a load is applied to a material body it deforms. the applied stress E the elastic modulus Background Information About Elastic the strain Constants and Properties When stress is applied in a given direction. given geometry of body that is loaded as well as the properties erties. in its simplest form. illustrate why concrete may or may not be elastic. compare these properties with other construction materials.e. Teller changes length and when sthe load is removed it returns to its of the U. however. essentially only a function of the material and as such it is in- tained load. where L is the original specimen length) which L ing a linear relationship. the slow reduction in stress over time due to a system displacement. 1b). This. it is frequently assumed that written in terms of the stress (i. thereby making it a of a material under a sustained loading. original position (Fig. The magni- materials the body will return to its original dimensions after tudes of the lateral strains are different for different materials. When the spring is pushed or pulled it first appeared in ASTM STP 169 (1956) authored by L. F K destructive testing. 1 Associate Professor. Over time this pro- erties and Creep. To overcome this limitation the force can be F nonlinear and inelastic.. The elastic modulus is creased deformations over time due to the presence of a sus. Strictly speaking.e. discuss common test methods for obtaining elastic properties and the where stress strain response. Purdue University. . where A is the cross- for low load levels (stresses less than 50 % of the strength and A sectional area) and the deformation can be written as a strain strains less than 1000 in compression and 100 in tension) the relationship between stress and strain can be described us. Robert E. progressive deformation dependent of specimen size and geometry. Creep. the stress-strain response of concrete is of the material. however. 1a). the spring coefficient can be thought of as a neers need material properties that can relate stress and strain. West Lafayette. For many in the dimension of the perpendicular directions.19 Elastic Properties. and discuss potential applications and future needs. K the spring constant to compute stresses from observed strains. In each of these calculations engi. In actuality. proportional to the force that is applied (F ). elastic modulus inferred from other test methods. lus or Young’s Modulus (Fig. describes a material’s elasticity and the concept can be simply illustrated by A CHAPTER ON ELASTIC PROPERTIES OF CONCRETE considering a spring. W. Indiana.” The chapter on elastic properties was portionality constant (K ) was termed as a spring constant that reprinted in ASTM STP 169C as it appeared in ASTM STP 169B. and to determine the quantity of steel required in reinforced concrete members. can be written mathematically as This version is based largely on these earlier chapters. 10 0. son’s ratio. also called the modu- Table 1 shows typical values for the elastic modulus and lus of rigidity or torsional modulus.26 to 0. AND RELAXATION 195 Fig. E and ) are generally used to describe the re- as “the absolute value of the ratio of transverse strain to the sponse of many materials since a more general relationship corresponding axial strain resulting from uniformly distrib. and b) the linear relationship between stress and strain using the elastic modulus (E).31 Aluminum 10 to 10.6 to 2.” When an element is subjected to simultaneous normal stresses The transverse strains are opposite in direction to the axial in each of three axial directions (x.8 Wood. CREEP. ) is introduced in where the subscripts refer to actions in a specific direction. Shear stress is defined in ASTM E 6 as “the stress construction materials. Poisson’s ratio are known they can be used to calculate the shear modulus (G ).18 Wood. the following equation to relate the axial and lateral strains: 1 [ (y z)] Axial E Lateral Axial E 1 y [y (x z)] E where 1 z [ (x y)] E Axial the applied stress in the axial direction Poisson’s Ratio It is also important to note that once two elastic properties Axial the strain in the axial direction are known (i. in this case E and ) any other elastic property E the elastic modulus. It can be seen that the elastic modulus or component of stress acting tangential to a plane..6 to 25 66 to 169 0. 1—a) Conceptual illustration of the relationship between force and deformation using a stiffness constant (K).5 0.55 to 0.. since the elastic modulus and Lateral the strain in the lateral direction. z ). uted axial stress below the proportional limit of the material. Poisson’s ratio falls between 0 and two lines originally perpendicular to each other.3 Iron 9. WEISS ON ELASTIC PROPERTIES. for concrete is lower than that of most metals and it is consis- but the two most commonly used are elastic modulus and Pois. Perpindicular to Grain 0.0 11 to 13. The parameters may take many forms. can be written to account for cases of multi-axial loading. is the ratio of shear stress Possion’s ratio for mature concrete and other commonly used to shear strain. y.35 Concrete 3 to 6 21 to 42 0.5 69 to 72. the resulting strain strains and can be described using the following relationship. tent with many ceramic materials.08 to 0.” It can be TABLE 1—Elastic Modulus and Poisson’s Ratio of Commonly Used Construction Materials Elastic Modulus Poisson’s Ratio Material x106 psi GPa Steel. It can be seen that Poisson’s ratio behavior of a material.e.33 Copper 14 to 22 97 to 150 0.30 to 0. For example. Grade A36 30 207 0. components can be obtained from the following equations A new material property (Poissons Ratio. The shear modulus.5 for nearly all materials. Poisson’s ratio is defined in ASTM Standard It is important to note at this time that these two elastic Terminology Relating to Methods of Mechanical Testing (E 6) properties (i.” and shear for concrete is lower than that of most metals while it is slightly strain is defined as “the tangent of the angular change between higher than that of wood. Parallel to Grain 1.69 . two parameters are required to describe the elastic 0. Thus.e. and can be determined. ASTM C 469. curve at the origin. properties of concrete has been done on concrete in compres- rameters to describe a material even though many materials do sion. ural Strength of Concrete (Using Simple Beam with Third. concrete in compression. No standard test currently exists ASTM E 6 defines several different moduli as follows: to assess direct tensile strength. Flexural Strength of Concrete (Using Simple Beam with 3. the modulus are illustrated on the stress-strain curve in Fig.196 TESTS AND PROPERTIES OF CONCRETE shown that for an elastic material the following relationship exists between Young’s modulus of elasticity in shear. The upper . Two addi.e.” The at the time of loading. Secant Modulus—The slope of the secant drawn from the Center-Point Loading) (C 293). ticity of concrete. and Pois- son’s ratio: E 1 2G where Poisson’s ratio E Young’s modulus of elasticity G modulus of elasticity in shear In addition to measuring elastic properties by applying a mechanical load and measuring the deformation it is important to note that the elastic properties can describe the natural frequency of vibration. The only ASTM test method for the static modulus of elas- not exhibit a truly linear stress-strain relationship. While instantaneous effects are referred to as the elastic re. It can be seen sponse. 3. various forms of Concrete in Compression (C 469) to determine the static elas.” machine platens and strain measuring devices. however. depending on the mode of vibration. by far the greatest amount of work on the elastic The elastic modulus is one of the most commonly used pa. strain curve defined as follows: the lower point corresponds to portional limit is defined in ASTM E 6 as “the greatest stress a strain of 50 millionths (i. As a result. comes nonlinear due to the development of cracks between the sponse of concrete. After the stress reaches a mined in accordance with ASTM Standard Test Method for maximum value. the stress strain curve is observed to begin to Compressive Strength of Cylindrical Concrete Specimens (C soften due to the opening of cracks in Region III [2]. sive stresses. Test Method for Flexural Toughness and First-Crack Strength 4. the flexural strength 1. Also it should be noted that the deformation exhibited by many materials depends on numerous factors including the A typical compressive stress-strain response of concrete is magnitude of the load. stress and strain is relatively linear. It tional terms are generally used to describe the limits of elastic stipulates a chord modulus between two points on the stress behavior: (1) proportional limit and (2) elastic limit. 50 ) and the upper point cor- which a material is capable of sustaining without any deviation responds to a stress equal to 40 % of the strength of concrete from proportionality of stress to strain (Hooke’s law). The lower point is near the origin but elastic limit is “the greatest stress which a material is capable far enough removed from the origin to be free of possible ir- of sustaining without any permanent strain remaining upon regularities in strain readings caused by seating of the testing complete release of the stress. Modulus of Elasticity in Compression though it would also be possible to use this test to determine Since structural concrete is designed principally for compres- the elastic modulus. time-dependent deformations are commonly referred that in Region I of this diagram the relationship between the to as creep or relaxation. Initial Tangent Modulus—The slope of the stress-strain can be determined using ASTM Standard Test Method for Flex. and the illustrated in Fig.. 2 [1]. Additionally. ASTM Standard origin to any specified point on the stress-strain curve. The pro. 2—A stress-strain response of a normal strength square root of the elastic modulus. the rate at which it is applied. This can be seen to occur at stress levels below approximately 50 % of the peak strength Elastic Properties of Concrete and at strains lower than approximately 1000 . aggregates and cracks in the paste. Tangent Modulus—The slope of the stress-strain curve at Point Loading) (C 78) and ASTM Standard Test Method for any specified stress or strain. is a compressive test method. Compressive testing is typically deter. It can be seen that at higher stresses and strains (Region II) the response be- Several standard tests exist to determine the mechanical re. Chord Modulus—The slope of the chord drawn between of Fiber-Reinforced Concrete (Using Beam with Third-Point any two specified points on the stress-strain curve. quickly becomes apparent that the manner in which its modu- ior. the velocity with which a compression wave travels through an elastic body is proportional to the Fig. 2. Loading) (C 1018) is commonly used to test the flexural toughness and first crack strength of fiber-reinforced concrete. The natural frequency of vibration in an elastic body is proportional to the square root of either the elastic modulus or the shear modulus. tic modulus in compression. In addition. This response is generally known as rheological behav. While a line has been superimposed on elapsed time after the load application that the observation is the stress-strain diagram for low stress and strain values it made. lus of elasticity is defined is somewhat arbitrary. 39) to determine the peak strength and ASTM Standard Test It should be noted that concrete has neither a definite pro- Method for Static Modulus of Elasticity and Poisson’s Ratio of portional limit nor an elastic limit. and it must be large enough the steel to obtain the complete stress-strain response of con- Fig. and (b) geometric relation for calculating strain [3]. [9] utilized U-shaped specimens where the central portion of formly spaced around the cylinder. however. the behavior of concrete at stresses above 40 % of the strength. A convenient device for measuring the strains is a compressometer. The upper yoke is rigidly attached to the specimen. only time-dependent strains. For this purpose. indicated and recorded. AND RELAXATION 197 to span an adequate sample of the material. strains should be measured along complete stress strain response of concrete. It must not. Hognestad et al. shortly after the maximum load be common for concretes with smaller aggregates. As a result the strains near the ends of the specimen may differ somewhat from strains elsewhere in the specimen. The 150 by 300-mm (6 by 12-in.6]. however. an automatic stress-strain recorder is helpful but not essential. such as the one illustrated in Fig. Half the specimen height is said to be the preferred gage length. 4. This limitation is established because restraint occurs where the specimen is in contact with the steel platens of the testing machine. The pivot rod and dial gage are arranged so that twice the average shortening of the specimen is read on the dial. The selection of the gage the specimen was loaded eccentrically to back calculate the length is important. encroach on the ends of the specimen.) cylinder is the specimen the shape of the stress-strain curve at high stresses is of signifi- size. it concrete member [7–9]. In order to has been attained. the axis of the specimen or along two or more gage lines uni. Shah et al. the deformation. ASTM C 469 specifies that the gage length shall be not less than three times the maximum size of aggregate nor more than two thirds the height of the specimen. When tested under load control. is signs. whereas the lower yoke is free to rotate as the specimen shortens. it is important that the specimen be loaded expeditiously and without interruption. CREEP. cance in determining the ultimate load-carrying capacity of a tion of the modulus of elasticity in compression. [10] tested steel in parallel maximum aggregate size so that local strain discontinuities do with a concrete cylinder and subtracted the linear response of not unduly influence the results. Thus. however. a commonly used specimen geometry for the determina. . It must be large in comparison with the stress-strain response. the determined modulus is approximately the av. It should be noted. This type of device was used in the first comprehensive investigation of modulus of elasticity by Walker [4]. instead of being observed on a dial gage. and it is cited in ASTM C 469 as an acceptable device.) cylinders may crete cylinders fail suddenly. 4—Compressometer testing details: (a) compressometer testing apparatus. compensate for the effect of eccentric loading or nonuniform Several different approaches have been used to assess the response by the specimen. 3—Various forms of static modulus of elasticity. Because the test is intended to measure Fig. Figure 4 illustrates the use of a linear variable differ- point is taken near the upper end of the linear behavior and ential transformer (LVDT) displacement transducer in which near the maximum working stress that is assumed in most de. WEISS ON ELASTIC PROPERTIES. erage modulus of elasticity in compression throughout the Although the standard test method is not concerned with working stress range. con- should be noted that 100 by 200-mm (4 by 8-in. that other procedures may exist [5. The circumferential control was used to illustrate the stress-strain curves of concrete of various strengths (Fig. Figure 6 can also Modulus of Elasticity in Tension and Flexure be used to show the influence of testing specimens of different Substantially less work has been done to determine the elastic length [14–16]. deformation is grinding the specimen ends and using friction reducing substances or brush plattens [13]. Several different approaches have been ad- appears to be constant irrespective of specimen size. the larger specimens demonstrate a specimens in tension.21]. medium strength. It is important to understand how the end conditions of the cylinder influence the results. that the span-to-depth ratios of concrete beams normally used for such tests are so large that shear deflection comprises a significant part of the total deflection.5) 0. however. This approach takes advantage of the fact that as damage develops in the specimen (at high stress levels and in the post- peak region) the circumferential (lateral) deformation increases much more rapidly than the lateral deformation.4 1. The higher strength materials show a steeper response in the post peak region that corresponds with a more brittle material. it can be subject to errors in the later portions of the post-peak stress- strain response since the large contribution of the steel is being subtracted from the large composite response. associated with eccentricity [20. For example. low strains at failure. capping compounds may demonstrate a disproportionate deformation and friction at the plattens may result in a confining effect. An obvious approach is to measure deflections caused by known loads and to calculate the modulus of elasticity from well-known beam deflection formulas. After the complicated by the problems associated with gripping the peak is reached. 5—Typical stress versus axial strain plots for a normal P applied central load strength. 23P l3 216h 2(1 ) 1 1296EI 115l2 where maximum deflection Fig. certain other corrections must be made to take care of discontinuities in the shear deflection curves at load points. 5) [12]. however. To overcome these limitations a closed-loop testing control method was developed in which the expansion of the cylinder in the circumferential deformation was controlled at a constant rate [11]. One common Fig. l distance between supports . It can be observed that as the strength of the concrete increases the pre- peak behavior is linear up to a higher level of stress. and the need to more brittle response. 6—Influence of specimen size on the measured method that is used to overcome end confinement or excessive compressive stress-strain response. and high strength concrete. Newer vocated over the last three to four decades mainly aimed at de- testing procedures are being developed in which closed-loop veloping procedures for improving the stress distributions at testing enables the stress strain diagram to be measured on the specimen ends for different grips and removing difficulties specimens of different size [15].198 TESTS AND PROPERTIES OF CONCRETE crete. While the testing of two materials in parallel provides a simple approach for obtaining the stress strain response. The test is is relatively similar irrespective of specimen length. For center-point loading. In the pre-peak region the stress-strain response modulus when concrete is tested in tension [17–19]. Since a principal use of concrete is in flexural members.84 48EI l l While the deflection for third-point loading can be computed using the following expression from ASTM C 1018. Seewald [25] gives the following deflection formula: P l3 2 3 h h 1 (2. It should be noted. Much of the research has not focused specifically at only assessing the elastic modulus. This occurs since the zone of damage avoid eccentricity. but rather much of the work has focused on assessing the softening response that occurs when cracking begins to develop [22–24]. several investigators have determined the elastic modulus on specimens loaded as beams. In applying shear corrections. the influence of aggregate fracturing in strength related prop- tion and translation is permitted at the other end. CREEP. elastic properties can be determined nonde- ture. AND RELAXATION 199 E modulus of elasticity I moment of inertia of the section with respect to the centroidal section Poisson’s ratio h depth of the beam The portion of the expression outside the brackets is the simple beam formula without considering the effects of shear. erties while this does not occur for modulus measurements tion frame provides a reference location which does not move due to the low level of stress that is applied. This can be primarily attributed to crushing of the specimen at the load points and Fig. The deflec. mechanical load. WEISS ON ELASTIC PROPERTIES.” which is a frame that is attached to the neutral axis of the beams directly over the supports. Researchers have illustrated that substantial errors can occur if deformations are not measured correctly. This is illustrated in Fig. 7 in which the deflection of the machine (i.e. 8—Rate of material property development as a deflections of the testing fixtures and machine itself. It can be seen that the measured machine deflection can be much higher than the deflections measured on the specimen. is commonly measured at the center point of the beam using a “Japanese Yoke. In addition to measuring elastic properties by applying a A large number of results have been reported in the litera. Deflection function of degree of hydration. stroke or ram deflection) is compared with the deflection measured directly on the specimen [26]. The range of results has been from 7 to 40 GPa (1 to 6 .. during the test and to which the measurement device is attached so that it can react off of a smaller element that is at. Elastic Modulus from Ultrasonic Measurements tached to the beam. It should be noted that the deflections used in determining the elastic modulus should be carefully measured on the flexural specimens. The frame is designed so that rotations are permitted at one end while rota. The main premise of the ultransonic pulse velocity test is re- It is also interesting to note that Olken and Rostasy [28] lated to the concept that the velocity with which a compression presented relationships for the development of various me. [30] recently demonstrated that differences in flex. 9—An illustration of the ultrasonic pulse velocity measuring deflections on the specimen. While all of the reasons for the A schematic illustration of the testing equipment is illustrated differences in the rate are not completely understood [29]. high voltage pulse. Of all the nondestructive methods. 8 shows this relationship as a function square root of the elastic modulus. The second transducer is held on the opposite side and used to record the time that it takes this wave to reach the second transducer. interfacial transition piezo-electric crystal inside the transmitting transducer with a zone. the wave speed (or pulse velocity) can be determined using the following equation: L V t Fig. This testing procedure relies on the development of appears that this may be related to the composite nature of compression wave pulses that are generated by exciting a concrete and the fact that the aggregate. The transmitting transducer is held in con- Barde et al. measurement procedure. wave travels through an elastic body is proportional to the chanical properties (Fig. tact with one end of a specimen (usually a coupling agent is ural strength and elastic modulus development may be due to applied between the specimen and the transducer). . ASTM C 597. Using information obtained from the test. ultrasonic meth- 106 psi) [27]. ASTM Standard Test of the degree of hydration). 9. or compressive strength. and paste influence each of these properties differently. It should be noted that the elastic modulus in ten. 7—Conceptual illustration of the importance of Fig. it in Fig. from the elastic modulus in compression at low stress levels. ods offer a distinct advantage in that they can be conducted sion or flexure does not appear to be substantially different with a relatively low cost and without causing any new damage. It can be seen that the elastic Method for Pulse Velocity Through Concrete (C 597) can be modulus develops at a much faster rate than either the tensile used for the determination of the compressional wave speeds. structively. 3). This test method is commonly used in the lab for assessing freeze-thaw It should be noted that while this equation is useful. wc unit weight.200 TESTS AND PROPERTIES OF CONCRETE where Poisson’s Ratio Static determinations of Poisson’s ratio are made by adding a V the compressional wave speed (i. information on the elastic modulus is re- urated concretes may be 5 % higher than that in dry concrete quired for many aspects of civil engineering design.20. Further details on this testing procedure tic modulus is highly sensitive to the modulus of the aggre- and its use for determining elastic properties are available in gate and as such the measured modulus may be expected to ASTM C 215. the elas- damage in prisms. This test is generally conducted either by E modulus of elasticity. that at high stresses or under where conditions of rapidly alternating loads. for most concretes the values fall between 0. The modulus of elasticity deter.. An alternative nondestructive test is based on the concept For concrete with a hardened unit weight between 90 and 155 that the natural frequency of vibration of an elastic body is pro.5 c ƒc (in psi and lb/ft3) Standard Test Method for Fundamental Transverse. the measured value of Poisson’s ratio can change dramatically. It should be noted. lb/ft3 (1440 to 2885 kg/m3) the modulus can be taken as portional to the square root of either the elastic modulus or the shear modulus. It should be noted that alternative ASTM test methods can be used for measuring the compres. Procedures for determination of Poisson’s ratio of the compression wave through concrete if a value for Pois. It should be noted that the elastic modulus in sat. Loads applied at a higher rate result in a higher elas. inforced composites) to increase the stiffness of the overall ond.e.25.20–0.5 c (in MPa and kg/m3) nal. taken for normal weight concrete as port from ACI 228. a vibration that is recorded by an accelerometer. the ultrasonic test tion and low creep. the dynamic Poisson’s ratio at higher loads cracking develops which results in an increase E the dynamic modulus of elasticity in the volume of concrete and an increase in Poisons ratio [33]. Typical values of the ultrasonic wave speed can range Property Specification and Estimation from 3500 to 5500 m/s depending on the strength of the con. The elastic modu. ASTM E 33w1. The same considerations apply to gage length for lateral strain measurement as for longitudinal strain The elastic modulus can be determined using the velocity measurement. The static value at stresses below following expression: 40 % of the ultimate strength is essentially constant. concrete strength. It should be noted however that in some structures where mined from the ultrasonic test (typically referred to as the dy. longitudinal. The ACI [31].043w1. of Elastic Properties crete or age at which the concrete is tested. This occurs for two reasons. vary by approximately 20 % of the computed value. First. and Torsional Resonant Frequencies of Concrete Speci- mens (C 215) was developed for determining the fundamental where transverse. Poisson’s ratio is also commonly son’s ratio is assumed (typically 0.22–0. where ness of Concrete Plates Using the Impact-Echo Method (C 1383). sign. Other structures may specify the use com- is conducted at low stress levels and as such the test results posite sections (of concrete and steel or concrete and fiber re- more closely resemble an initial tangent modulus (Fig.e.1R [32]. Longitudi. and mechanical driving unit or using a small impactor to generate ƒc specified comprehensive strength. Further information on the method for measuring pulse Building Code [34] permits the modulus of elasticity to be velocity can be found in ASTM C 597 or in the committee re. is applied. compressive strength) to estimate these properties for their de- erly calibrated before a test. or torsional resonant frequencies of concrete specimens. Sec. The dynamic [(1 )(1 2)] E V 2 (1 ) values are usually in the vicinity of 0.15 and 0. the time it takes the wave to travel strain gages on the surface of a specimen perpendicular to the between the transducers) direction of loading. the elastic modulus is dependent on the rate at which load structure.. However. deflections need to be minimized aggregates may be restricted namic modulus) can be up to 25 % higher than the static to those that can economically produce low elastic deforma- modulus. or by mounting t is the transit time (i. Results from this test can provide an alternative method E modulus of elasticity to measure the wave speed which can be used in the preceed. To improve the Frequently designers do not specify elastic modulus but rather accuracy of the results the wave speed of a known material is they rely on approximations using other properties (namely typically measured to enable the testing apparatus to be prop. ƒc specified comprehensive strength ing equation to estimate the elastic properties.24). E 57000 ƒ c (in psi) 473 ƒ c (in MPa) sional wave speed (P-wave) in concrete such as ASTM Standard Test Method for Measuring the P-Wave Speed and the Thick. It has . are included in ASTM C 469. forcing the specimen into resonant vibration using an electro. Although code specifications are primarily associated with tic modulus. however. the pulse velocity) third yoke and second dial gage to a compressometer so that a L the distance between the transducers magnified transverse strain may be measured. When the applied density stress is below 50 % of the peak strength there is a decrease in V the pulse velocity volume of the body as a compressive load is applied. c ƒ 0. depending on the mode of vibration. computed from results of the elastic modulus and shear mod- lus can be determined using the pulse velocity from the ulus determined dynamically. est in creep once again increased due to applications in nu- lowing empirical relationship can be used for concretes with clear structures.5 c ƒ c 1. pressions overestimate the elastic modulus for higher plates and shells. AND RELAXATION 201 been also been noted by ACI 363 that the aforementioned ex.5 E 23w1. In the 1980s concerns with creep in higher compressive strengths between 3000 psi (21 MPa) and 12 000 strength concretes emerged since these materials were being psi (83 MPa) [35]: used in offshore oil structures and high-rise buildings. to an improved understanding of creep for prestressed beams. CREEP. In the 1970s inter- strength concretes. it has been suggested that the fol. As such. WEISS ON ELASTIC PROPERTIES. and long-span structures. In the 1990s interest in creep once again increased due to problems w1c . duce low elastic deformation and low creep.106 (in psi and lb/ft3) 145 associated with early age cracking and the desire to understand how stress relaxation influences the behavior of concrete at very early ages. 10—A conceptual illustration: a) creep. Since that time over Strictly speaking. creep is generally used to describe all aspects of the rheologi- The creep of concrete appears to have been first described cal response) of concrete are frequently less than precise. Unlike aggregates play no role. in the United States in 1907 by Hatt [36]. This complexity is called aging which generally conditions. Furthermore. when information is desired at early ages since the Creep is defined in ASTM E 6 as “the time-dependent increase cement is hydrating relatively rapidly. aggregates (especially other materials. refers to the fact that cement pastes continue hydration which means that the pore structure and elastic properties are chang- Rheologic Properties: Creep and Relaxation ing over time or with age. however. This frequently results in problems. creep and microcracking. In the 1930s the rise in dam construction was driv. Over time this - ing research in creep. In since it is observed under normal service conditions at all some structures. Although creep is a paste in strain in a solid resulting from force. . and this gave way over the next 20 years deformation increases (c) due to the effect of creep. however. time (to) the specimen is loaded with a stress (o) and the speci- plications. however. ture concrete in compression) and it appears to increase at At this point it should also be noted that the names applied higher stresses presumably due to the cumulative effects of to the rheological response (often. and b) relaxation. creep of concrete is approximately gregates may be restricted to those that can economically pro- a linear function of stress up to 50 % of its strength (on ma. the creep of concrete is unique stiff aggregates) substantially reduce the creep of a material.20 for cement paste adds a particular complexity to the problem of static measurements while values are usually assumed to be trying to describe creep that does not appear in many other 0. It cur under a constant stress.22 for dynamic measurements or rapid loading materials. If the load Fig.18–0. It should be noted. The cement paste exhibits creep due to its porous struc- where ture with a large internal surface area (nearly 500 m2/cm3) that is sensitive to water movements. as done in this document.20–0.5 c ƒ c 6895 (in MPa and kg/m3) 2325 First it should be noted that creep is a property of the paste.” Nearly all materials property it is important to note that this does not mean that the undergo creep under some conditions of loading. At some high at various times over the last century due to various ap. that the interest in creep has been can be seen that initially the specimen is unloaded (a). w1c .5 E 0. The fact that creep is associated primarily with the Poisson’s ratio is also commonly assumed to be 0. ag- stress levels. Creep is illustrated in Fig. On the contrary. It appears reasonable to con- E modulus of elasticity clude that the movement of water in the paste structure is re- wc unit weight sponsible in large part for creep in concrete elements. creep describes the deformation that may oc- 1000 papers have been written on various aspects of creep. men exhibits an initial elastic deformation. In fact. ƒc specified comprehensive strength Mullen and Dolch [37] found no creep when pastes were oven dried. 10a.030w1. where deflections need to be minimized. ASTM C 512 are applicable to all types of concrete sealed to tically at time (to) to a strain of (o). [42] and Bissonette and Pigeon [43] have conducted uniaxial tensile creep tests where a specimen Measurement of Creep in Compression is loaded using a dead-weight that is attached to a lever arm. Hansen and Mattock to zero while some permanent deformation may remain in the [41]. This creep coefficient (CCU) can be thought “basic creep” and to label the additional deformation not ac. the testing procedures fall into a few distinct categories. creep and relaxation properties have been heavily investigated. terials. it is evident that there must be a size effect over time if this deformation is maintained constant the stress associated with the moisture gradients within the specimen. Toward this end early-age materials vary from location to location making it very diffi. cult to “predict the effects of creep” with a high level of Although no standardized testing procedures have been devel- accuracy without having testing information on the local ma. paragraph indicate that the techniques and specimens of An initial specimen can be considered (a) that is deformed elas.202 TESTS AND PROPERTIES OF CONCRETE is removed at some time (d) the specimen unloads elastically counted for by shrinkage “drying creep” [38]. found that shrinkage and creep were dependent only on the ra- Creep and relaxation properties are not frequently de. If the applied deformation It should be noted that the creep of a structure may be is then released (d) the stress in the specimen will be reduced only a fraction of that in a test specimen. drying creep. loop test provides the total stress history of a specimen and is Limitations on gage lengths similar to those in the test for quite useful [48–53]. and Relaxation Parameters erances. 10b. Early-age cracking sensitivity of concrete recently has been a ing the amount of creep that can be expected. under a longer duration of loading. of as simply the ratio of the long-term (ultimate) strain. It should be noted that in each of these modulus of elasticity apply. gle age of loading is satisfactory for this purpose. long-term strain to immediate strain can be as high as 3. and to the strength of the ume change. tio of surface to volume. Information of this sort may make it fined in specifications. although gory of testing devices consists of horizontal testing frames provision is made for other storage conditions or other ages that use a closed-loop control to rapidly adjust the force on a of loading. stress level (at least to 50 % of the peak strength). to the duration of loading with more creep in materials eliminate the effects of shrinkage and other autogenous vol. Further. The age at which creep tests begin and the stress level to The second category of tests consists of a pressurized cylindri- which specimens are loaded are usually dependent on how cal specimen that applies a constant pressure on the inner sur- the data will be used. The stress is restricted to the range throughout specimen to maintain a specified displacement. material. to apply either a constant load or constant displacement to a mens at an age of 28 days to a stress not exceeding 40 % of single specimen or series of specimens [45–47]. nature of many of the calculations may be traced to the fact that the composition and size of the cement and composition Measurement of Tensile Creep or Relaxation and size of the aggregate play such a large role in determin. re. The ratio of measured and adjusted frequently. Testing at a sin. It is required in the test method that the stress remain constant Property Specification and Estimation of Creep throughout the one-year duration of the test within close tol. most modern theories deny the inde. these topic receiving much attention. however. Thus. pendence of shrinkage and creep and thus indicate that the A simple method for computing the effects of creep at two effects are not additive as assumed in the test. will decrease (c) due to relaxation. The closed which creep has been found to be proportional to stress. This observation plus occur due to the movement of water in the microstructure un. The reason for the approximate structure. tests the entire testing frame or specimen is generally placed in pare the creep potential of various concretes. On the other hand stress relaxation describes the reduction in stress that occurs when a Effect of Specimen Size specimen is deformed and this deformation is maintained con. a controlled environment. amount of creep exhibited is generally proportional to the Length changes of these specimens are measured and sub. The ASTM C 512 requires companion unloaded specimens. drying atmosphere. the total and continues to unload over some time (creep recovery) shortening at any time may be considered the sum of elastic though it should be noted that only two thirds of the original strain. For unsealed specimens exposed to a the specimen to develop an initial elastic stress (b). and shrinkage. While this correction is qualitatively correct and material being tested with higher strength materials showing yields usable results. the time under loading influences system or by springs.40] that creep of sealed speci- stant. The final cate- the strength of the concrete at the time of loading. oped. Rather designers often use very possible to apply correction factors to the data obtained from approximate calculation procedures or apply larger safety ASTM C 512 to determine the creep in any size and shape of factors to account for them. to the age at tracted from the length changes of the loaded specimens to loading with materials loaded at an earlier age showing more determine creep due to load. The method is intended to com. basic creep. A test procedure has been standardized face of a hollow cylinder [3. It is now various times under loading was defined by ACI-209R-92 using common to label creep which occurs in the absence of drying a creep coefficient.0. This deformation causes prevent loss of moisture. Finally creep tests are frequently labor intensive. creep deformation is recovered. weight. in an investigation of both size and shape of specimens. and take a test that relies on the application of load through a dead substantial amount of time to perform. This correction is intended to creep.44]. The third category of tests con- in ASTM Test Method for Creep of Concrete in Compression sists of using an electric or hydraulic mechanical testing device (C 512). The first category of tests consists of a uniaxial tensile creep quire a conditioned space to perform the tests. The method stipulates loading moist-cured speci. stress relaxation is illustrated in Fig. The load may be applied by a controlled hydraulic As previously mentioned. It has been demonstrated [39. which . less creep. the observation concerning mass concrete in the preceding der an applied stress. provided in the latter case the load is the corresponding deformation of the concrete. Umehara et al. While stress relaxation is related to creep because both mens is independent of specimen size. however. girders. of L (ii). 11a as the uments for further information on predictive creep models point at which these two lines intersect. Residual Stress Calculations and surface to volume ratio. and b) a schematic description of stress development. These models are commonly referred to as the Gardner. AND RELAXATION 203 includes both elastic and creep effects (CU).6 Loss of Prestressing Force where In contrast to the lack of precision needed for deflection measurements. After the prestressing force is applied. 30–70 %. Shrinkage strains can be converted to stresses with knowledge of the elas- Deflection of Compressive and tic and creep (relaxation) behavior of concrete. 11—An illustration of the restrained shrinkage cracking problem: a) residual stress development.56]. can be expected to crack. Relatively little creep testing is directed to predicting deflec- tic strain (CI): tions of specific structures. member size.e.35. 11b in which It is not uncommon for a reinforced concrete flexural member a specimen of original length (i) is exposed to shrinkage. This is illustrated in Fig. Hooke’s Law) since load and continue to deflect with the passage of time.e. point of analysis. Since the initial pre- to be 2. if the strength of the concrete is always greater than the developed stresses. This may stress relaxation (creep) can substantially reduce the stress by be of interest for reinforced beams. the Bazant Models (BP or B3) strength of the material. an accurate knowledge of the early-age rheological CCT coefficient at any time properties of concrete is valuable to the prestressed concrete t time in days industry.15 but the recom. will occur if the residual stresses that develop exceed the tensile Lockman Model (GL2000) [54]. and Relaxation restraint may sometimes be difficult to quantify. or autoge- posed to overcome the shortcomings of the creep coefficient nous shrinkage. drying. a knowledge of the factors governing loss of mended value is 2. it follows that and their application [58–60]. It should be noted that ACI-209 provides prestressing force has important economic implications. WEISS ON ELASTIC PROPERTIES. The residual stress that develops in concrete as a result of Creep. slabs. t0. Similarly. Although numerous factors influence whether approach to predict the response of concrete under sustained a concrete will crack [61]. or the CEB model (CEB-90) [57]. As a first the most accurate models are commonly believed to be accu. Recently it has become increasingly common to see concrete Over the last three decades several models have been pro. while a precise prediction of these deflections is cause the specimen to undergo a change in length (shrinkage) possible only if the elastic and creep properties are known. there is a loss d is a constant (typically assumed to be 10) in days of prestressing force resulting from creep (and shrinkage) of CCU is the long-term on creep coefficient (typically assumed the concrete and relaxation of the steel. . structures developing cracks due to thermal. the applied shrinkage would tial deflection. duration of moist curing. relative humidity. Due to space limitations the velopment exceeds the strength of the specimen the concrete reader is referred to the original documents or summary doc. This reduction can be described by Fig. Fig. prestressing force. or columns. it can be simply stated that cracking loads.6 CCT (t) CCU d t0. specimen were unrestrained.3 to 4.. no cracking will occur. CREEP. it can be argued that if the residual stress de- rate to only approximately 35 %. If the eventually to reach a deflection three times as great as its ini. to the initial elas. Figure 11a illustrates how one can [55. predictive equations and approximations are frequently used. an approach to correct CCU to account for moist or steam curing.. Significance and Use of Elastic Properties. To maintain the condition of perfect restraint (i. This residual Flexural Members stress cannot be computed directly by multiplying the free Concrete members undergo deflection upon application of shrinkage by the elastic modulus (i. It should be noted compare the time dependent strength development with the that there is no universally accepted model for creep and even time dependent residual stresses that develop [62].35) stressing force is limited by the strength of the steel and the load-carrying capacity of the member is limited by the residual Typical values for CCU range from 1. U. American Concrete Institute.69]. dependent elastic properties. • Standardized testing practices exist for determining the [3] Weiss. may be changing dramatically due to hydration. S.. 584–2 to 584–6. p. Poisson’s Ratio. Bureau of Reclamation. and McHenry. [2] Puri. 21–27. 635. • Standardized practices are needed for conducting early plied (iii). PA. 111. Summer 1981. consider recommendations of model developers that will (iv). P. it is suggested that engineers begin to discuss how No. Concrete and Aggregates. Vol. 1. “Digest of Tests in the United States for the De- RILEM SSC (strain softening in concrete) committee [67]. S.. this shrinkage is re.S. Part 1. a wide range of material properties. and Weiss. This illustrates that creep • It currently appears that predictive models may be needed (relaxation) can play a very significant role in determining the that are capable of meeting the needs of two distinct au- magnitude of stresses that develop at early ages. PA. however.” International creased use of nondestructive testing procedures to assess Journal of Cement Composites and Lightweight Concrete. This places the concrete in ten. 1. Dissertation. no length change) enable this data to be utilized in future model develop- an opposing fictitious stress is applied (v) resulting in an over. As a result sub.. [7] Whitney. concrete. Other organizations have assembled substantial [4] Walker. different maturities). March 1947. consider the addition of an appendix that would define stricted by the restraining steel.” Cement. Part 1. Jensen. prestressed concrete.204 TESTS AND PROPERTIES OF CONCRETE no length change) a fictitious load can be envisioned to be ap.. Vol. and relaxation tests that is sim- crete ring to cause cracking. “Concrete be compared to ultrasonic. Vol. “Stress-Strain Curves for Con- define how these properties should be defined [68. Further re. Vol.. Research linking ultrasonic. and Anasari. 15–25. Ongoing Efforts and Future Needs References [1] Puri. Purdue University.” Journal. termination of the Modulus of Elasticity of Portland Cement Mortar and Concrete. however. ASTM Interna- which require elastic properties at early ages when they tional. 455–479. SP-12. standard reporting procedures for reporting data from the sion and compresses the steel. L.e. pp.. that research and standardized procedures be developed to [8] Ramaley. measurements which may measure fundamentally differ. S. While the test is primarily used test and the development of a data bank for elastic modu- to determine if sufficient tensile stresses develop in the con. it is sug. W. Feb. This fre- [6] “Bibliographies on Modulus of Elasticity. “Assessment of Localized Damage in cretes.” Ph. [10] Shah. how this test method could be used to determine the residual stresses and effect of creep [64–66].. and behavior of high-strength low-water-to-cement ratio con. 377. S.. of development as well as “time-zero” and it is suggested Supplement. pp. Vol.” Journal.. W. Denver. This includes both rate of Beams. p. pp. 510. As the concrete dries (or experiences autogenous • It is recommended that future standard test procedures shrinkage) it attempts to shrink. simple test method was recently added as an ASTM standard (C The second audience for these models are users that may 1581) to assess the behavior of restrained concrete elements. ciples. It should also be noted that a complicated calculations can be performed in the models. D.. 1928. age cracking. calorimetric measurements of property development can [9] Hognestad. The following list provides an outline of ongoing efforts Concrete under Compression Using Acoustic Emission. “The Plas- search is needed to define how elastic properties develop ticity Ratio of Concrete and Its Effect on the Ultimate Strength over time (i. electrical. it should be noted that if the specimen age creep and relaxation tests. diences. Vol. early-age creep. p. pp.. 1943. U. and Moreno. West Conshohocken. standardized tests do not exist Concrete Elements. A. 1983. For fur. Vol. “Effect of Confine- • Interesting work is being performed in the area of the in- ment on the Ductility of Lightweight Concrete. PA. May 2003. It would be anticipated that these models would be ther information on early age stress development the reader is incorporated by the computer modeling community since referred to RILEM TC-181 [63]. 1930. want to be able to perform approximate calculations very This test consists of casting an annulus of concrete around a quickly using hand calculations. CO. 1919. 28. In ASTM International. E. “Modulus of Elasticity of Concrete. Dec. 39. C. especially the age.. [11] Shah. West • Significant advancements are taking place in attempting to Conshohocken. to maintain perfect restraint (i. 5. Northwestern Univer- for determining the complete stress-strain response for sity. Hanson. all reduction in shrinkage stress (vi). E. behavior of thin elements..” Proceedings. J. Proceedings. Namaan. W. American Concrete Institute. The first audience desires a model that includes a stantial research has been conducted over the last decade to description of material behavior from first scientific prin- better determine how stresses develop at early ages. . the absence of ASTM standards on the subject. and electrical measurements with rheological nique for Obtaining the Complete Stress Strain Curves for High properties should be further developed and validated over Strength Concrete. J. Evanston. and mechanical Stress Distribution in Ultimate Strength Design. F. West Lafayette.” Proceedings. 1955. discussion of a paper by V. data for assessing the stress-strain response of concrete. “An Experimental Tech- acoustic. the elastic properties of concrete. Nov.. S.” Under in the area of rheological properties as well as future needs: review by the ASCE Journal of Civil Engineering Materials. p. “Prediction of Early-Age Shrinkage Cracking in elastic modulus. ments [70]. W. S. P. Gokoz..” Laboratory Report ther. 21. P. 1999.e. creep. and McHenry. and quently includes computation of deformations and stresses Volume Changes of Concrete. 52.. No. N..” Proceedings. 30. J. “Assessing the Development of Localized Damage in Interest in more accurately assessing rheological properties of Concrete Under Compressive Loading Using Acoustic Emission. IN. Part 2. As these tests are developed were free to displace under this fictitious loading the length of and standardized it is recommended that experimentalists the specimen would increase (due to creep) by an amount L. steel ring. additional research has described ilar to that RILEM Shrinkage and Compliance Data Bank. gested that readers review the practices advocated by the [5] Teller. Proceedings. No. Again.D. ent aspects of the system. lus. 3. crete Strained Beyond the Ultimate Load. Fur. D. D. ASTM International. West Conshohocken. However. describe the behavior of concrete at early ages.” hardened concrete is increasing due to concerns related to early MSCE Thesis. 1954. Chapman and Hall. American Concrete Insti- Testing. [37] Mullen. N.. P. pp. C. 123. Bureau of Reclamation. Ø. M. pp.. Sept. E. M. 11th Edition. S. 9.. pp. 65. Jul. IA. A. 289–296. [17] Davis. Holland and E.. K. pp. A.S. W. pp. 92. J.. 419–428... Vol. [31] Bungey. B.. J.” Maga- Institute. 1997. Lafayette IN. WEISS ON ELASTIC PROPERTIES. No. [20] U. E&FN Spon. D. No. PA. pp. Z. 2001. 1966.” Journal of the American Concrete of Concrete under Restrained Shrinkage at Early Age.S.” ACI Materials Journal. F. I. “Tests of Concrete in Tension.. and Jiang. 1995. [43] Bissonnette. W. pp. RILEM 148-SSC. Kanstad. 2002. “Risk of Cracking in Massive Con- [24] Li.. 25. “Studies of Creep in Size-Dependent Response of Reinforced Concrete Beams.. J. Jan.. “Effect of Length on Compressive Paste. West Conshohocken. 1989. 1994. P. and Okuda. ASTM Interna- [14] Van Mier..” Ordinary. dition on the Autogenous Shrinkage of Silica Fume Concrete. H. ceedings of the International Symposium Thermal Cracking in pp. Vol.” Pro- under Uniaxial Tension. and Hammer. Shape of Member on the Shrinkage and Creep of Concrete. Vol. Utilization of High Strength/High Per- [30] Barde. E. Ed.” ACI Materials Journal. [36] Hatt.” Materials and Structures. 1997.. Strength.” Pur. MI. W. H. M. and Shah. 4th ed. 1956... and Didry. 1999. 79–86.. A.. 5. P. V. K. pp. Normal and High Strength Concretes. 4.. S. Thermal Cracking in Concrete at Early Ages. ing Reinforced Concrete Beams. S. “Abhandlungen. 1964. . 2002. [22] Ueda. M. C.. “Fracture Toughness of Fiber Rein.. S. Vol. Vol. 1994. and Sugiyama.” ACI Mass Concrete. and Shah. Mazzotta. Second Edition. G. J.. [48] Springenschmidt. H. 324–330. 2. No. September 1968.. 1989..” Proceedings. p. Vol. ASTM International. S. Detroit.. T.. 25–35... 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Volume Change. 86.” I. “Plastic Flow and Vol. Springenschmidt. P.. H. J. Vol. Ames. Amer- Structures Journal. Sande- Strength: The Role of Aggregates and Their Influence on Ma. U. pp. J. Influence of Different Cements. Chemical Admixtures. J. pp. Vol. [40] Karapetrin. 195–209. R. J. HPC at Very Early Ages. “Tensile Creep at Early Ages of O. J. Simulation of Thermal Stresses and for the Prediction of Early 57–72. MI.. pp. K. “Influence of Size upon Creep and Shrinkage ume Changes in Concrete. 30. 317. Hasebe. Sellevold. Kulkarni. Wiley. “Early Age Flexural formance Concrete. Den. et al. and Shah. June Library of JSCE.” Proceedings. and Lange. Farmington Hills. “Localization and the [39] Polivka.” Magazine of Concrete Research. S.. and Adams. Springenschmid. No. M. pp. McGraw Hill. J. C. No. 92. and Weiss. et al. and Shah. axial Compression. 372–381. 257–283. Vol. 1985.. and [53] Pigeon.. [29] Graveen. T. Mechanics.. 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Munich Germany.. Iisaka. 2.” No. of Fiber Reinforced Concrete for Airfield Pavement. Vol. C. July-Aug. 52. Ammouche. No... Technischen Hochschule. tute.” Public Roads. and Rostasy. “Strain Softening of Concrete in Uni. “Testing System for Determining the Mechanical [32] “In-Place Methods to Estimate Concrete Strength” (ACI 228. “Cracking and Permeability of Concrete under Tension. American [51] Bloom. [44] Ross. R4. “Concrete Dimensional Stressing. Davis. and Winter. Fiziko—Mathematicheskie. 27(170). 1991. Tekhiniceskie Nauki. D. E. U. [25] Seewald. No. Inc. “Ther- [27] State-of-the-Art Report on High Strength Concrete (ACI 363. Manual of Concrete Practice. et al. W. Güler.K.” Proceedings of the 15th Inter- [28] Olken. A. 247–264. MI. Feb. 1928. No. Bureau of Reclamation. Aachen. M. S. pp. 31–45. P. 1995. Farmington Hills. 3–10. 1075–1085. turity Predictions. W. 1994. Breysse. 1993. and Kernozycki. Part axial Shrinkage. 249–265.. “Notes on the Effect of the Time Element in Load- Vol.” Cement Materials and Structures.... pp. Farmington Hills. 29.. Houdusse. H. 33. Testing of Concrete in Structures. May 2001. 4.... A. Creep in Concrete at Early Ages on Thermal Stress. Vol. 88. M.” Proceedings.” in Thermal [49] Altoubat. [47] Parillere. fjord Norway. PA. [21] Gérard. D. 1994. 1. A. J. pp. Stress-Inducing Deformations and Mechanical Properties of due University. Part 2.. “The Use of Nondestructive Test Methods to Assess [50] Bjøntegaard. G. R.1R).” American Concrete Institute Materials Jour. [18] Johnson. 229–243. 2000. American Concrete Institute..” ACI SP-173- under Uniaxial Tension. Vol. M. and Rossow. Vol.. 64.. Sato. Lausanne.. 1997. RILEM. [16] Weiss. pp.. R. pp. Uehara. No.” in RILEM crete Manual.S. p.” Materials Science of Concrete VII. Static Modulus of Elasticity. 98. and Bentur. Eds. CRC Press © tional. A. Ed... and Dolch.” Symposium on Mass Concrete.. A. E. 1146–1171. 37. MI. G. “Early-Age Creep and Shrinkage Cracking in Concrete At Early-Ages. Part 2. 7. II. 421–433. T.” Bulletin No. Vol. H. 27–36. Early Age Shrinkage Induced Stresses and Cracking in Ce. M. Dilger. [63] Early Age Cracking in Cementitious Systems.” Materials and Structures.. The Impact of Specimen Geometry on Quality Control Testing [56] Bazant. pp.. Concrete: Structure. Vol. Elsevier... “Tensile Shrinkage and Creep of Normal-Strength Concrete. 1–19. RILEM 148-SSC.. P.” Concreep 6: Creep. “Strain-Softening of Concrete in Uni- tures: A Precis of Recent Developments. Bentur. and Brooks. pp. and Curability Mechanics of Concrete and Other and Structures. 98. Vol.. March-April 2001. J.. Formulation. 195–209. J. J. and [65] Weiss. et al. P. J. 26. “Creep and Shrinkage Prediction Model for Analy.” Concreep 6: Creep. L. [69] Weiss. “Chapter 3. [59] Bazant. Materials and Structures. don 1983. August 26–29. [66] Hossain.” ACI SP 135-1. W. Vol. Bazant. 1979. J. P. Quasi-Brittle Materials. MA. Wittman. 169–183. S. H. 425–434.. Bazant.” Mechanics Today. 645–651. 159–167. pp. H. 307–316. G. A. of Concrete. RILEM TC-181 [70] “Guidelines for Characterizing Concrete Creep and Shrinkage EAS. Ed. pp. pp. J. Creep in Restrained Shrinkage. and Durability Mechanics of Concrete and Other Quasi-Brittle [55] Bazant. and Miltenberger. Bentur. Z. Ed. P. Z.. J. Cambridge. Prop. See. “Design Provisions for Drying [64] Attiogbe. W. pp. J. W. and Panula. pp. Z. 1995. 20. and Monterio. 1978. 28. H.206 TESTS AND PROPERTIES OF CONCRETE [54] Gardner.. 1992. M. Z. [57] Müller. J. pendent Deformations of Concrete. Structures.” Construction Press. “Creep of Plain and velopment and Stress Relaxation in Restrained Concrete Ring Structural Concrete.. for Material Performance Assessment. ‘Time-Zero. M.” [62] Mehta.3 – Evolution of Solid Behavior. 30. P. and Yang. Specimens. 1997. P. F. and Weiss.” Materials and Elsevier. 28. J.. J.” Z. “Shrinkage Cracking— Systems State of the Art Report..” ACI Mate. 1986. W. Cambridge. Ulm. “Practical Prediction of Time De.. S. 651–656. W. [67] Van Mier. A. K. A. 12... and Materials. and Lockman. J. Wittman. “New Prediction Models for Creep and Shrinkage Eds. 107: Creep and Shrinkage Prediction Models: Principles of their 2003. 51–55. Englewood Cracking in Cementitious Systems State of the Art Report. Cliffs. “Restrained Shrinkage Testing: Vol. 196–206. Vol. 2nd Edition. 2001. No.. 11. Axial Compression.. RILEM TC-181 EAS Early Age Shrinkage Induced Stresses and erties. Prentice Hall. 531–540. 1975. pp. P.” Materials Shrinkage.” RILEM TC mentitious Systems State of the Art Report. 2. Ed. 52–55.. M. Parts I–IV. 4. pp. Ed. Vol..” Journal of Cement and Concrete Composites. Shrinkage.1 – Experimental Determination of the 1998. pp. Early age of Concrete: Mathematical Modeling. A. pp. Z. and F. N. 1–93. [68] Bisschop. Lon. B. 2004. Eds.” RILEM TC-181 EAS Early Northwestern University.. A. pp. Materials. and Ferguson. Longman Group. “Assessing Residual Stress De- [58] Neville. 2003. Weiss. . “Chapter 6.. pp. K. Ulm. Can It Be Prevented?” Concrete International. P. “Theory of Creep and Shrinkage in Concrete Struc. in Structural Design Codes or Recommendations. Bentur. E. © 1993.. Age Shrinkage Induced Stresses and Cracking in Cementitious [61] Shah. S. A. sis and Design of Concrete Structures – Model B3. Bazant. P. 2001. Vol. [60] “Fourth RILEM International Symposium on Creep and Shrink. 2003. W. rials Journal... M..’ Early Age Cracking In Cementitious Systems. Age Cracking In Cementitious Systems. 317–378. F. T. MA. Vol.. J. and F. New Jersey. 1995. His work was published in a ALMOST 50 YEARS HAVE PASSED SINCE THE PUBLICA.” But then. in which this chapter was first published. only concrete of inferior strength is scientific description of the composition and texture of mate- commonly produced. During these times. which includes the use of a of what makes inferior concrete inferior. Petrography [18]. while doing petrography for the purpose of provid. foretold the potential ad- tendant elemental analysis. was published in 1998. clude Refs 2–15. extends even further. including the systematic classification of rocks. Today. scanning electron microscopy with at.65 on petrography has been working to standardize types of instrumentation and techniques that cover subjects that approach. Paul was not panded and now includes work on many aspects of concrete. “wet” The closing remarks of Katherine Mather. That organization. has ex- not made of things which do appear.” There were trailblazers before Johnson. ASTM Practice for proaches. quoted. ACI sponsored a symposium on determining the water- ence material available on petrography of concrete. In 169B was published. there was little refer. and it is gratifying that her visions are in In the history of petrography of concrete as we know it to. sis is used so frequently for petrographic work that ASTM Com- croscopes. the imagination and other analytical tools. who It also provides publications of interest to concrete petrogra- died in 1991. cement ratio and durability aspects of concrete [17] that in- there are literature references to petrographic examinations cluded a number of papers on petrographic methods.20 Petrographic Examination Bernard Erlin1 Preface but his work was. whose St. St. ASTM STP 169A and ASTM STP 169B. day. 207 . was the work of Johnson who described and related microscopical observations of the Petrography composition and texture of deteriorated concrete to its performance. About three years ago the Society of Con- raphy. “even with broad variety of analytical and physical methods. more stringent qualification requirements for petrographers ing links connecting “activity” within concrete to its behavior doing petrographic examinations and more detailed informa- and performance is indeed a fulfillment of the science. from light optical microscopy to specimen preparation. the first symposium specifically directed toward presenting information on petrography of concrete and Almost 50 years have passed since the inception of ASTM STP concrete aggregates was sponsored by ASTM. Once con. and 27 years have passed since the updated ASTM STP sented at that symposium resulted in ASTM STP 1061 [16]. tion of ASTM STP 169A. He further applied what he saw toward a philosophy Within the realm of petrography. 1999. Paul is not with us—neither is Katherine. is the the very best of materials. Much of this paper is still her “quote” on petrog. from ation (ICMA) was founded in 1978. vances in the science of petrography. six-part series from January through March 1915 [1]. however. differential scanning calorimetry. are needed because doing petrography Petrographic Examination of Hardened Concrete (C 856) has solely for the sake of providing information can be an exercise been modified throughout the years and now provides for in futility. tion on a number of aspects of petrographic examinations. It also in- 1 Petrographer. Subsequent and more recent informative documents in- Katherine Mather. Latrobe. who wrote the first two versions of this chap. A book available in which the focus is on petrography as a tool used to devoted entirely to details of concrete petrography and corre- provide information about concrete instead of petrography lations to field concrete performance. phers and others. a petrographer. dispersive spectroscopical (EDS) method for elemental analy- sidered by many to principally revolve around light optical mi. and aptly titled Concrete that is incidental to the main subject of a paper. in her closing. at least from published papers. the first widespread enough so that it truly reached out to engineers. The Significant advances in petrography and petrographic scanning electron microscope (SEM) and its ancillary energy methods have been published related to concrete. X-ray diffractome. but with changes and additions that update the subject. the initial versions on petrographic examination of concrete in try and spectroscopy. The Erlin Company. crete Petrographers (SCP) was founded and now provides a home base to concrete petrographers. PA 15650. The International Cement Microscopy Associ- ter in ASTM STP 169A and 169B. “Things which are seen”—concrete and mortar—“were main emphasis originally was on portland cement. Today. Paul. Introduction In June 1989. St. perhaps. use and being extended. who authored chemical analyses to infrared spectroscopy. Both ap. The papers pre- 169A. rials. and said. the science has greatly expanded to include new mittee C09. tests. allow projections of its future serviceability. examination by analytical techniques that will identify proce. Paster [19] comments that the water- concrete’s past as it really was—to identify. as may be nal and existing conditions. Secretary (dcong@wje. to answer the question that prompted his need for the petro- Petrographic analysis of concrete—a man-made rock—is its graphic study. water-cement ratios. architects. a number of methods for doing so are discussed. engineers. Useful background information that cially immediately and shortly after it is made. To background information upon which to make that kind of be effective. are a physical may help the petrographer direct his work and evaluate the pet- wonder. how will it behave in use? (c) why did it behave the way it did? and (d) what can be anticipated in the future? The most useful Methods—Standardization and Description method for developing practical information from which to answer these questions is to study the concrete in the laboratory ASTM C 856 was adopted in 1977. complicated than was expected because there are different Petrographic examination of hardened concrete is among purposes for examining concrete. beyond all of the ob. be used. in light of research and prac. excessive wear. and allow its classification as to type. measurable in terms of days. and way of establishing the relationship of concrete composition to samples from newly cast laboratory and field structures. rographic data may be from plans. resent exposures to different environments for different peri- tional information on what is in concrete and provides another ods of time. portland cement and other cemen. number of concrete petrographers and their limitations in ex- tions. reports of the petrographic data. should be demonstrable. concrete is a “mirror” with a the needs and economic restrictions imposed by his client. and reactions.com). specimens from laboratory test programs. ASTM concrete performance. Within a very short time. origi. from of the petrographer for obtaining the information necessary its mineralogy to its strength and volume stability. It is re-created “rock” akin to the rock conglomerate most anyone involved in the concrete. essential facts about its manufacture and performance. gotten or neglected. C 856 does the following: (1) serves those who request a petrographic examination and want more understanding of what Responsibilities they are getting and why. grapher. A petrographer’s responsibilities include not only of each concrete-making material. and other features. His reliance is on the background and experience on steps to be taken before laboratory examinations. The Society recognizes the weak- describing information it can produce. depending titious materials. Its strength originates within itself by complex chemical the concrete-making components. bleeding. the influence of environmental exposure on its stability and and interpretations of the data. performance. and training. phers2 was formed as a means of getting together hands-on lems inherent in its applications. and pre- 2 Derek Cong. Recently. memory. (2) provides information to petrographers conducting petrographic examinations. where it is vital for supplying factual information. Standard procedures should usually internal structure. air contents. outlining what it involves. or modifications of standard procedures. methods. . That tical experiences. petrographer has a low comfort level of evaluation does not ing. noting prob. cement hydration. adverse chemical and physical reactions result. comment brings up the competence of the now relatively large Petrography is used frequently to assist in forensic evalua. The petrographer should not expect his petrographic re- dures and the sequence of its production. concrete petrographers. crack. and it does delamination. The for Concrete (C 295) was first published in 1952. and future serviceability. Usually the discussions include a summary of the ASTM Guide for Petrographic Examination of Aggregates situation that prompted the need for the examinations. goals of the Society is to provide a meeting ground for General questions that petrography tries to answer are: (a) petrographers to discuss issues of mutual interest so that they does the concrete conform to specification requirements? (b) can better perform and interpret their work. contractors. Bernard Erlin. However. inspectors.com). its composition and sults to be taken on faith. blistering. materials it becomes hard and strong and usually endures for long peri. The Society of Concrete Petrogra- examinations for evaluating hardened concrete. ASTM C 856 establishes minimum requirements for concrete This chapter provides insight into the use of petrographic petrographers. in ACI SP 191 [17] and in dozens of other Its makeup and past performance. spalling. upon their education. specifications. espe. ASTM Prac- person requesting the examinations may not be familiar with tice for Examination and Sampling of Hardened Concrete in techniques petrographers use or petrographic approaches Constructions (C 823) was adopted in 1975. finishing. not speak highly of anyone that apparently does not have ing from internal and external sources. examine concrete with all available means commensurate with Like rocks and minerals. mixing. the petrographer must have a good understanding statement. experience. The concrete also may rep- the subjects in this volume because it provides direct observa. mean all petrographers are at that same low level. curing. scaling. appropriate—the rationality of the techniques that are used The physical and chemical properties of concrete. level does indeed vary between petrographers. but also data that are qualified. low strength. suppliers of ods. President ([email protected] TESTS AND PROPERTIES OF CONCRETE cludes almost anything that can be said about a concrete. concrete manufacture. It turned out to be more and correlate what is found to its field performance. papers. Because one placing. That comfort coarse and fine aggregates. That amining and interpreting what they find in concrete and their information can relate to mixture proportions that include comfort level in estimating water-cement ratios. and showing how this nesses of some petrographers in areas of their work—one of the information can be applied. It gives guidance available. cement ratio (w/c) cannot be determined using petrographic scurities. and (3) serves A petrographic examination usually begins with discussions as a reminder to petrographers of things they may have for- between someone who requests the examination and a petro. concrete producers. and petrographic examinations. The petrographer should that Mother Nature has made. Petrographic examinations allow us to interpret the In a recent article. and infrared absorption spectroscopy. vide direction for the petrographic examinations. Sampling hardened concrete is discussed along with each part of the study. However. X-ray diffraction samples that understanding is in hand. dures for detailed investigations of the concrete in-place are de. varies depending on the problem and . Transportation Research Circular No. and (4) textural characteristics resulting thick and immersion preparations even smaller examined us. Thus. better examination. and users of the construction. and (4) the selection of additional methods that will pro. differen. the number and size of samples. prejudice the petrographer in his examination and interpreta- mission electron microscopes. be augmented. and finishing. ASTM C 823 was prepared to tributed to or be part of a problem. the problem is purposely not defined because of a desire to not probes. faces. 176 [20] was pub. Another publication for help in petrographic examination of Analytical techniques offer a means for understanding in- hardened concrete is Highway Research Board Special Report ternal chemical reactions in detail so that it is possible to char- No. the appropriateness of each item and may be milligrams of material hand-picked under the stereo. scales. and (2) the usefulness of interviews with con. used in final analyses and interpretations of the data. A better petrographic examination is one that re- microscopy. and others who have ent analyses should be taken to represent inherent parts of the reasons for a need to examine concrete. Once that ing petrographic microscopes. supple- core samples with dimensions in hundreds of millimetres that mentary cementing materials. (3) air-void systems including the size and microscopes. Today. picking paste or aggregate from carefully broken concrete sur. from individual concrete components to its manufacture in paste. physical or chemical alteration. when his report is finalized. and interpretation of the manufacturing history of clinker. These methods can Purpose bring with them the danger of losing touch with the primary The purpose of a petrographic examination is initially to under- purposes of an examination due to great differences in scale. of deterioration requires knowledge of many aspects of con- lished. vide ancillary information needed to properly evaluate the ability of assembling reports and legal documents concerning problem that prompted the studies. to the things that affect cement hydration.64 1011 cm3). and other reactions. concrete needed to understand its original makeup and subse- ASTM Quantitative Determination of Phases in Portland quent physical or chemical alteration. A stimulating publication originating reasonable clarity so that detailed information is available to in 1971 [24] covers a wide field of cement and concrete topics decipher a concrete’s history. The sam- phases. alteration to the original concrete can be identified. Sometimes single crystals of a few angstroms examined using micro.to 30-m distribution of air voids. which includes: (1) aggre- Those differences include concrete elements with dimensions gates—their grading. (2) is the one that provides enough information to resolve the evaluating samples using the naked eye and low-power stereo. Proce. The transition from the the construction. consolidation. In Sorting out major from minor causes or secondary effects 1976. the end result is what is important. from its placement. and effects of the tial thermal analysis. tion of why the concrete malperformed can then be identified. and any in hundreds of metres (kilometres in the case of pavements). Other publications of interest are in volumes of acterize cement hydration and hydration products. followed by (3) the selection of microscopical solves the problem with maximum economy in minimum time. It also provides information that assists in an evaluation pling should include unaltered concrete for comparison. (2) portland cement. Field samples may include examples of the preparation of appropriate sampling plans and selection of different outwardly appearing concretes. methods that allow greater insight into the makeup of the con. few cases will be tion of the analytical data or to test his skillfulness. sophisticated analytical instrumentation is bringing about a breakthrough by orders of magnitude in our abil. stand the original concrete makeup. chemical and physical environment on concrete performance. the the Fifth International Symposium on the Chemistry of Cement chemical reactions of normal hydration or of abnormal [22] and those of the Sixth International Symposium on the deterioration and alteration to concrete can be detected with Chemistry of Cement [23]. Approach mental analysis using EDX methods of material volumes The concrete problem must usually be defined in order to pro- equivalent to one-trillionth of a cubic inch (1. and anything else that may have con- company samples is described. The number of samples 1356) provides a standard systematic procedure used to iden. pozzolans. It provides help in (1) identifying alite and belite residues crete. The basic microscopical techniques parts of the world where cement and concrete research is used for petrographic examinations of hardened concrete can carried out. by other techniques. efflorescence. but not replaced. Purpose and Approach ity to decipher and interpret (and sometimes misinterpret) the composition and performance of concrete. Care is needed to ensure that proper sampling is done for scribed. ERLIN ON PETROGRAPHIC EXAMINATION 209 liminary investigations are outlined and include: (1) the desir. problem. and their hydration can be examined with great advantage using low-power stereo. engineers. macro to the micro scale and the information from each unit tractors and others connected with the construction and with of effort provides separate and complimentary data that can be the owners. A good petrographic examination nation can include: (1) observing the concrete construction. and (2) examining paste by X-ray diffraction. needed is dependent upon the specific problem—and should be tify the volumetric properties of portland cement clinker representative of the various features of the concrete. scanning electron microscope specimens that may be 200 mm3 down to micro-picked specimens—and ancillary ele. if suitable. and distribution. The good. The ques- microscope or a few grams of material concentrated by hand. or items that may have Cement Clinker by Microscopical Point-Count Procedure (C contributed to its current condition. The relative roles of chemical and has the advantage of being truly international because the attack and physical attack that dictate concrete performance editorial board and contributing authors come from various are usually decipherable. thin sections about 800 mm2 by 15. Information needed to ac. or crete. The latter found in which all of these will be needed. with cracks. spalls. and nanometer-sized material examined using trans. Specimens for the differ- be useful to petrographers. occupants. In both cases. and appropriate analytical techniques can be used. 127 [21]. composition. is unneeded because his prowess ultimately becomes known The sequence of steps involved in a petrographic exami. specific times of cracking could not unless paste interfaces. there may have been undesirable chemical reac. Petrography is the science of observation. transportation. changes to cement manufacture. The petrographic effort becomes valuable on a To progress from consideration of simple petrographic exami- micro scale. regional geology—as it determines quantity and uni- taminants may be present. duction. and knowledge—not nation to the petrographic examination of concrete that has only about microscopes. and wet chemical methods information about concrete than any other technique because . a scanning electron microscope and an ancillary elemental probe. a main hydration Recently. Petrographic examinations provide the most direct and more struments for elemental analysis. For example. servation is of particular importance when in other 15-year-old. Texture is the way in which concrete components are finally similarly exposed field concretes from the region calcium sul- allied and aligned. On a micro formance. the differential settlement of compo. the features that are usually undesirable. and may also include a metallurgical though compositions of pastes and nature of the environments microscope. The petrographer should be familiar with petrographer’s skills include deftness in obtaining data and in specimen preparation..210 TESTS AND PROPERTIES OF CONCRETE particularly the skill and adeptness of the petrographer. example. or significantly affect the ef- Observations ficacy of air-entraining and other admixtures. the concrete. Today. The sulfoaluminate (ettringite) found in many voids as far as 130 processes of batching. there is a tions of the aggregates. tion of. That ob- independent factors that control its final makeup and texture. texture can be reflected by the uniformity of distribu. it is peculiar. cement hydration environmental conditions vary both locally and regionally. and crack patterns. position and environment of any field concrete. or preferably located along the bottom side the cracks occurred very early (e. calcium components. The may also be needed. plastic shrinkage cracks). as most people recognize. is probably of less practical importance. ods of time on the constituents present in several cement pastes mentation viewpoint. grinding and lapping equipment. and limitations of their use. Supplementary equipment may include lated blast-furnace slag. even graphic microscope. a variety of in. area can change the previous “immunity” of some siliceous aggregates to alkali-silica reactivity. discharging. petro.g. honeycombing. However. where ment and supplies needed to make each of the preceding effec. titious materials. Sources of Concrete tural and compositional characteristics. to provide resistance against damage by cyclic freezing. must include: (1) a series of light-optical of known w/c stored under laboratory conditions have been in- instruments that includes a low-power stereomicroscope. foaluminate is not abundant. calcium hydroxide. coarse and fine aggregates. What is most desirable difference probably justifies some concern about its future per- is a uniform distribution of concrete components. texture. lift lines. mixing. and due to material shortages. poor with longer-range shipment of concrete-making materials. anomalies remain in the results. if it is 15 years old. at aggregate. skill. On a macro scale. unknown age and of high flexural and compressive strength nents (among the results is bleeding). been common to a regional area because of local cement pro- phering the texture and composition of concrete is where pet. A variety of analytical instrumental methods that include Composition X-ray diffractometry. consolidating. (2) specimen preparation equipment that includes were known and controlled far more thoroughly than the com- saws. finishing may have created incipient delaminations in the sur. use of supplemental cemen- face region. whereas low alkali cements may have once terms of composition. and poor mixing or inadequate consolidation. the kind of information each of these can interpreting the data. and curing are may be of importance relative to projected service. Although relative ages nonuniformly distributed throughout the paste. con. Some examples are: low strength resulting because the Knowing the concrete background and its geographic location physical structure (texture) is inadequate can be caused by is sometimes of importance because aggregates. For example. Petrographic examinations are useful for identifying tex. increased shipment of higher-alkali cements into an rography shines. vestigated. of aggregate particles. there is extensive use of fly ash. Texture and Composition Age of Concrete Under Study Concrete is a very heterogeneous material because it is made The age of the concrete may be important for judging the sig- up of a variety of coarse and fine materials in terms of its basic nificance of petrographic observations. may arise in areas previously thought immune to some prob- Each concrete and each part of a concrete is unique in lems. infrared spectroscopy. whether on a macro Reconstruction of History of Field Concrete or micro scale. there are even more anomalies. mm (5 in. finishing. If the concrete of unknown age is and stratification of components are examples of textural in fact five or seven years old and it differs conspicuously. and exposure. but the peculiarity scale. air-void systems may be inadequate formity of aggregates—may be of importance. silica fume. The effects of the passage of relatively short peri- The cupboard of a petrographic laboratory. history. Neville [25] reviewed dating the age of cracks us- component of cement hydration that can be uniformly or ing depths of carbonation as signposts. Deci. differential thermal analysis. for example. However. cements. today. could be identified. and ground granu- tive (see ASTM C 856). In a sense. from an instru. but also aged and perhaps deteriorated in service introduces two im- about ancillary techniques to which attention is directed based portant new unknowns—time and the precise environment of upon microscopical evaluations. which requires patience. and air. For may have been curtailed because of a number of factors. provide. paste. and (3) accessory equip. everyone is a petrographer on a macro scale.) from the outer surfaces of a concrete pavement of placing. and aggressive chemicals may have broader overlap of different materials so that new problems been introduced from the environment. cracks. differential scanning calorimetry. 02 when estimated using a manual mentally controlled exposure.47 versus the mix design crete is the water-cementitious materials ratio. cent [29]. the products that have ASTM Practice for Use of the Terms Precision and Bias in formed as a consequence of their chemical reactions. which means that the variation from the concrete. many key factors controlling its technique.44. If the petrographic ful of people over which there has been controversy about its examination is of laboratory-made concrete from an environ- claimed accuracy of 0. the results of a petrographic study can 0. (2) the validity of all field and other conditions and exposures are included. whether non-air-entrained or air-entrained. (4) the purpose rarely controversial. Although average or mean val- rapher and his or her experience and expertise in interpreting ues may look good. may well be narrowed. tual. and cracks. depth of carbonation. have been using a variety of techniques for estimating the w/c However. Environment ture of how to translate what is observed to assessing the w/c using these methods.03 to 0. in ASTM formation about their chemical and physical stability or insta. The degree of interpretation of data from each method Sometimes an answer to the specific questions posed is is based upon the comfort of the petrographer in extending not interpretable from the data initially uncovered even though his or her expertise to provide that estimate.01 and other approaches. mineral surface estimating the w/c. (2) scratch hardness [26] and indentation hardness crete is currently assessing different methods petrographers [27] techniques. their rock and a statistical viewpoint it is virtually impossible to have an ac- mineralogical types. Field concrete examined by a petrographer is concrete hence. Petrographers w/c of 0. That doesn’t sound too bad. the greatest influence on its performance. and in.65 on petrography of hardened con- nique [26]. of cementitious materials present. premature carbona. ratory test specimens of concrete. Sometimes combinations of methods are used. There is nothing in the literature ciphered than if the examination were of field concrete. All of them are subjective and rely upon the petrog. As a result. Unfortunately. Things that can be deciphered include: (1) the types whatever reason. Complicating the interpretation is the fact that the deterio- fort level)—and some petrographers even decline to provide rated field concrete may have performed abnormally because an estimate. (2) aggregates. and ASTM Test Methods (E 177) says. in about the accuracy of the scratch hardness. used round robin tests to provide informa- hardeners. there is a bility. sometimes confounding that in. ASTM Committee C09. Test Series has a mean w/c value of 0. and (4) features an average or mean value of a number of estimates can be. ERLIN ON PETROGRAPHIC EXAMINATION 211 it can be used for identifying its physical and chemical makeup. Their “E” Round Robin One of the many items of interest and concern about con. there is a decrease of available background in- combined optical and physical paste properties technique is formation compared to examinations of new concrete or labo- reported to cover a 0. That Singularly.52 for those values is more realistic for industry. The w/c estimate using the field concrete. (3) the ability of the petrographer to is a built-in bias in the sampling process—good concrete is qualify the techniques used for the estimates. expressing the variance of values of a method than the mean There are four general methods among petrographers or average. and they are generally accepted by the concrete standard deviation of 0. for samples of absorption. skill. Unless samples representing on: (1) the competency of the petrographer. for sent for petrographic examination is “controversial” concrete. [29]. the distance to the estimate two techniques in which the dye is either blue [26] or fluores. and blue tone methods. their uniformity throughout a concrete. mean is from 0. of more than one cause. in a paper on the fluorescence method for tion. rapher will usually dictate his or her comfort zone and. the six w/c values reported are from 0.08. finishing. and (5) the needs of those who and its proportions and factors leading to an understanding of either want to accept the estimates or debunk the estimates—for its behavior. . Usually concrete terpretation is the existing concrete condition.40 to 0. this usually means that sampling was from the poor that the concrete has undergone. the degree of interpretation of the items used to that has worried a responsible person enough to put forth the estimate the w/c. and the results are frequently extrapolated to the en- The acceptability of the petrographic estimates depends tire area of concrete in a project. depending.10 (a low com. test documents where numerical values are obtained. ers. to which the data will be used. (4) air-void character. distribution Here is an example of how deceptive the w/c expressed as of the voids and parameters of air-void systems. but perhaps when that assessment is completed and made from concrete having known w/c’s. curing. true reference to base accuracy on. water droplet which many variables are unknown. be used to express accuracy. (3) a combination of 12 or so microscopical use for estimating the w/c of hardened concrete.29]. (3) estimates of water-cementitious materials ratios and mandate that precision and bias statements. The latter includes some verification studies are done. the environment to which concrete is exposed has method originated in Europe and has been evolved by a hand. surface dusting. a difference of 0. that are popular today: (1) a water-droplet absorption tech. Jakobsen et al. However. istics. the range of values is hidden. related to consolidation. effort and expense of sampling and testing. uniformity of distribution. in so many words.07 to 0. The reported the data. The methods and physical observations of the paste technique [28.06 be used to eliminate certain factors or direct attention to oth- (a range of intermediate comfort levels) to 0. The deftness.03. on the varieties of chemical and physical alteration In practice.15). aggregate coatings. suitably qualified. Usually. that from estimates of amounts present. there the techniques involved. concrete. there are few specific details in the litera. example. and and techniques used for estimating the elusive w/c and w/cm (4) methods where thin sections of concrete are impregnated of hardened concrete may never be developed to the satisfac- with dyed epoxy and are compared to thin reference sections tion of all. and an accuracy of 0.02 range. grading. Yet.01 when estimated using a performance and consequent alteration can be more easily de- semi-automatic technique. and experience of the petrog. tion on the accuracy of the method.02 (a relatively high degree of comfort) to 0.55 (a and water-cementitious materials ratio (w/cm) of hardened difference of 0. That comfort the petrographer has recovered evidence not accessible by zone is from no interpretation (no comfort) to 0. except for the fluorescence method. the cement content was low. teristic loss of surface mortar that is unlike the condition of surface distress due to improper finishing. ened Hydraulic-Cement Concrete (C 1084) provides for petro- terior. of portland cement that have led to bulk concrete expansion ronments. Maine [33]. niques is sometimes essential for proper interpretation of the Evaluations of data from laboratory test exposure samples analytical data. when examined by optical graphic examinations as a means of understanding chemical in- methods. for example. on the mean-tide rack at East. however. and inade- specimens exposed. the causes of concrete failure to set. however. ASTM Standard Test Method for make the interpretative process easier because the materials Analysis of Hardened Masonry Mortar (C 1324) (also applicable and mixture design are known compared to natural exposures to portland cement-based plaster and stucco) has an initial de- where many factors are unknown and environmental condi.. That constituent of secondary calcium carbonate [30]. and poor performance due to compo- port.2 m) in diameter and 2 ft (0. the alkali content distress may not always be similar. Consequently. The kinds of information about hardened concrete that pet- centrates from field concrete has revealed that vaterite (not rographic examinations reveal can be used to identify a great easily identified using optical methods) is frequently a major variety of data about its physical and chemical makeup. or coffin vault located anywhere . Field concrete that is not air-entrained and has sition. even today. That calcium carbonate. on the analysis. laboratory-induced proce. concrete electrical insu- cretes. according to ASTM C 227. wall. in Charlevoix. sidewalk. early and late concrete instability Concrete exposed to accelerated freezing and thawing in due to a variety of causes. tailed section that deals exclusively with petrography and that tions are variable. conformance to specifications. samples of materials are made using portland cement and other calcare- field concrete. ASTM are frequently found to contain secondary calcium carbonate Standard Test Method for Portland-Cement Content of Hard- near outer surfaces. cite containing interstitial water). poor proportioning and batching. features symptomatic of specific types of or inadequate. rarely aragonite. some field It makes no difference if the concrete is a 10 ton cherry concretes regarded as undeteriorated have shown a range of pie 14 ft (4. curing. of the cementitious materials cannot usually be reconstructed although it may have helped direct the performance of the Petrographic Assistance in Other Types of concrete. improprieties of aggregates that can cause low laboratory specimens stored at room conditions. However. ous and siliceous materials that skew the chemical data.35]. almost never vaterite (the birefringent spherulitic form of cal. and inconspicuous degrees of reaction may be the only lator. from a variety of ASTM tests involving alkali-silica or alkali-car- activity of Cement-Aggregate Combinations (Mortar-Bar bonate reactivity. For example. deteriorated field concrete usually shows superimposed traces of several processes. and mineral admixtures. general quality of workmanship was good exposure conditions. with Field concrete that has deteriorated because of alkali-silica new and exciting methods and techniques being constantly reactions usually has much more advanced and conspicuous developed. concurrently in varying degrees of development in some con. can be used to identify unsound aspects on samples from seawater exposures or from other wet envi. Vaterite. water using Procedure A of ASTM C 666 can produce a charac. etc. in turn. foundation. pavement. fly ash or other supplementary cementing materials were Because of varying specimen orientation and variable or were not present. Vaterite is known to persist for several months in [34. with at least one in an ad. recognizable peculiarities in cases of unsatisfactory service with graphic examinations of old outdoor-exposed concrete that the possibly expensive consequences. bridge. nuclear reactor facility. by optical methods to be common in mortar bars that had been Petrographic analysis of post-test specimens. Conclusion ing and Thawing (C 666). The use of X-ray diffraction to examine cement paste con. or a dam. rapid slump clarified based upon work in Ref 31 that identified naturally loss. high. the factors that led to good or be reproduced in accelerated freezing and thawing in water. is generally found to be calcite. it can be deduced from petro. manufacture. and sometimes in the in. quate air entrainment. Alkali-carbonate and alkali- w/c was high or low. along old cracks. tested for resistance to freezing and thawing according to ASTM Test Method for Resistance of Concrete to Rapid Freez. large concrete shrinkage. supplements the second section on chemical analysis and al- dures often result in different diagnostic “symptoms” than lows suitable interpretation of the chemical data because these evidenced by field-exposed concrete. Examinations Finally. especially information. is mentioned in those test standards as a Method) (C 227) and had been found in concrete specimens means of providing supplemental assessment of damage. The identification of compositional properties of portland vanced stage. poor concrete performance were unclear. pozzolans. The most advanced process may conceal evidence cement-based products analyzed using other methods and tech- of others that had a more important effect. was found supplementary cementing materials. for example. there is no need to view our analytical level bars of expansive combinations examined after they are tested of understanding as insignificant. or silica reactions are described in other papers in this publication. we still have some ignorance concerning these internal symptoms of this reaction than are found in mortar factors. stray naturally occurring organic conversion of aragonite and the poorly crystallized vaterite to chemicals in aggregates that can cause variable concrete air well-crystallized calcite in pastes and mortars has been contents [8]. when examined using light optical microscopy. the liner of a bank safe. On the other hand. These materials include aggregates. and exposure to aggressive environments deteriorated because of natural freezing and thawing usually for which it is not designed.6 m) deep constructed evidence of alkali-silica reaction. Michigan to commemorate the birthday of Alkali-carbonate and alkali-silica reactions sometimes exist George Washington. malperformance due to chemical reactions of aggregate.212 TESTS AND PROPERTIES OF CONCRETE Although. and fluences of constituent materials. other than portland cement. factors resulting in occurring vaterite [32]. such as specimens tested according to ASTM Test Method for Potential Alkali Re. For example. concrete strength [36]. medium. develops sets of sub-parallel cracks normal to the direction of Before the petrographic trail was blazed and during its the freezing front (because of directional freezing) that may not early adventuresome period. finishing was improper. “Petrography: New Man on the Construction sciences. Part 1. Eriksen. “Comparison of Known and Portland Cement Association.. Farmington Hills. “Correlation Between Labora- Research Board. MI. B. John. M.” Concrete International. and 13 March 1915. 1966. R. the basic constituents are similar at any age.” Observations of the Perfor. 1981. [5] Mielenz.. 3. [8] Erlin. 1967. Research and Development Determined Water-Cement Ratios Using Petrography. K.. 1966. PA. “Cooperative Examination of [7] Dreizler. examination. SP-191.” Journal. B.” Rock Products. I. 535–544. why it functioned as expected.. W. [17] “Water-Cement Ratio and other Durability Parameters.. 6 Feb. I–IV...” Mineralogical Magazine. CO.” Concrete Con. 1990. Sept. 8. G. “Petrography for Contractors. Larne. T. 3–17.” Nature. pp. placing. Sept.” Concrete Construc- tion. “The Role of Petrography in the Investigation of causes of concrete performance and malperformance.. Carbonation. [18] St. moderate and justifiable costs. Research Board. S. [24] Cement and Concrete Research. R. MD. pp. [1] Johnson. R. B. Cores from the McPherson Test Road. ACI Interna- 1962. and Kahn. ASTM International.. B. pp.. W. [32] McConnell. Vol. 125–143.. B. There is a need West Conshohocken. National Research Council. Special Report 106.. F. M. February land.” blended cements..” Proceedings. 216–222. Concrete Society. Washington. C. R. West Conshohocken. 1964. C. July Along with improvements in analytical methods and 1987. S. A. pp. Roy. rographic methods are ideal for evaluating how concrete has Technical University of Denmark. was installed. 156–170. the techniques and particu. Highway [33] Kennedy. M. the development of new methods and techniques of Team. 1960.. and provides an understanding of its behavior “Cement Research: Boon or Boondoggle. pp. in part. more laboratories available to complete work. SP-191.” Transportation Research Circular No. A. pp.” Water-Cement Ratio and Other and Properties of Concrete and Concrete-Making Materials. 1960.” Significance of Tests Fluorescence Microscopy.. Significance of [27] Erlin. Northern 1966.57.” Reviews in Engineering Geology. for hands-on appreciation of mixtures of portland cements. 2000. A. and the [19] Paster. P. D. “The Microscopy of Concrete. Vol. “Other Viewpoints on Petrographic Reports..” Special Report No. [16] Petrography Applied to Concrete and Concrete Aggregates. “Can We Determine the Age of Cracks by Measuring Concrete. B. Ed. L. 6 March. pp. varieties of coarse and fine aggregates. 127. 5–7. “Application of the Microscope to the Study of [25] Neville. T. Moscow Stroyizdat 1976. The cost of Research. Farmington ASTM STP 169A. 1972.” Lecture Series on the Materials Sciences. DC. Vol. R.” Stanton Walker [28] Erlin. 80. less often.. and Hammersley. Portland Cement. “Petrographic Analysis of Concrete.. Eds. 176. [10] Idorn. equipment comes a new problem—the development of petrog. “Petrography Applied to Portland-Cement International. Chatterji. Boulder. others in understanding why it failed to function as expected [12] Porvar. B.. pp. the analyst becomes a specialist who operates Paste. ERLIN ON PETROGRAPHIC EXAMINATION 213 in the world.” Journal. DC. ASTM STP 395. R. 1968. and Campbell. J... Dolch. New York. and Thaulow. 1971. J. “Petrography of Cement and Concrete.. Concrete Petrography. [26] Liu.” Water-Cement Materials. K. Stark. happens to and within plastic and hardened concrete. also have the background to interpret the data. L. L. N. W. March 2003. 13 Feb. an International Journal References (bimonthly). 1–38. 1969. Ireland. Fifth International Symposium on the Chemistry of However.. Sept. U. 1. W.A.” [31] Cole.” Engineering Record. ASTM International. Addison IL. 1998. methods of mixing. Hawkins. “Petrographic Examination. University of Mary. [4] Mielenz. G.. A. Highway No. 23 Jan. 250. “Vaterite from Ballycraigy.. Ltd. “Why Do Some Concretes Fail. isolationism.. No. J. Transportation Research Board... Concrete Society.” Zement-Kalk-Gips. Highway Research Board. of concrete now make possible better interpretations of the [15] Pitts. and Mather. 1974. O. Vol.. Tokyo. P. 1970. Vol. December 2003. 585–587.. M.. Jan. Sixth International Symposium on the Chemistry of Cement. 1959. Hills. DC. of Water-Cement Ratio in Hardened Concrete by Optical [6] Mather. Farmington Hills. C. p. S. the physics and chemistry of what John Wiley & Sons. PA.. petrographers. Durability Parameters. tory Accelerated Freezing and Thawing and Weathering at . Nov. [30] Mather. American Concrete Institute. DC. Ratio and Other Durability Parameters. pp. [9] Erlin. 32. Vol. N. SP-191. J.” Concrete Construction. G. pp. Reader Response. and Brandt. P. New York. College Park. Pergamon Press.or organization-imposed semi. D. PA. 1978. there is still a lot of information obtainable at Cement. and Mielenz. raphers who are able to obtain the “right” analytical data and ASTM STP 1061. C. and Kroone. Petrography of concrete is flourishing.. been put together and changes that have occurred to it since it [11] Klemm. SP-191. C. H. “Practical Concrete Petrog- raphy. Concrete and Its Constituents. 1972. [29] Jakobsen. pp. Skalny. “Methods Used in Petrographic Studies of Concrete. 1984. In this day of specialization. Concrete Construction. West Conshohocken. 1959. Cement Ratio and Other Durability Parameters. K. Poole. ACI International.. water. No. No.. I. ASTM International. [20] “Evaluation of Methods of Identifying Phases of Cement Too frequently. 12. “Carbonate Minerals in Hydrated Analytical Techniques for Hydraulic Cement and Concrete. available in English preprints. England. mance of Concrete in Service. [2] Brown. Durability of Concrete Structures in Denmark. Pet. 27–31.. Erlin and D. E. D.. Geological Society of America.. Laugesen.. MI. Washington. “Analytical Techniques. 2000. and Sims. Vols. A.” Danish Building Export and better understanding of the physical and chemical makeup Council. 5. mineral and chemical admixtures. [23] Proceedings.” Water- Laboratories. I..” Journal. in a narrow walkway of self. It is invaluable in assisting engineers and Cement International. more sophisticated equipment. 27 Feb. [22] Proceedings. “Determination struction. 23–24. 1977. B. Washington. 2000. and consolidation. C. C. and. 184. MI. 4. pp. Washington. Ed.. Addison IL. and Copeland. Concrete. “Paste Microhardness—Promising Tests and Properties of Concrete and Concrete-Making Technique for Estimating Water-Cement Ratio.. N. getting petrographic information dramatically increases as the National Research Council. tional. Thaulow.. ACI [3] Mielenz. 1. D. “Diagnosing Concrete Failures. 29–37. effects of time and environmental exposure on performance. T. more qualified [14] Jensen. 2000.. Like in other [13] Bennitt. J.. 205–216. and performance. size and scale of what is analyzed progressively decreases. Part 2. January 2004. Denmark. J. No. Copenhagen. 2000. June 1976. [21] “Guide to Compounds of Interest in Cement and Concrete larly the analytical equipment are very expensive. 214 TESTS AND PROPERTIES OF CONCRETE Treat Island.. 461–486. Basis for Resolving Concrete Problems.. ASTM International. 171–181.. pp. [35] Erlin. D. American Concrete Institute. Mielenz. R. Vol. 25. 1953. B. No.” Journal of Materials.. . 50. and Jana.” Proceedings. Eds. B.” Concrete International. No. “Forces of Hydration That Can Cause Vol. [34] Erlin. pp. M. pp. Vol. PA. Erlin Petrographic Analysis and Special Tests Not Usually Required in and D. and Polivka. 11. 3. “The Magic of Investigative Petrography: The Practical November 2003.. Stark. R. 1990. B. “Importance of to Concrete and Concrete Aggregates. Sept..” Petrography Applied [36] Davis. 141–172. E. 1967. Judging Quality of Concrete Sand. ASTM STP 1061. 2. West Conshohocken. Havoc in Concrete. Maine. C. and Mehta [1]. the cement cause another expansive mechanism as the Freshly mixed concrete remains plastic for a relatively hydroxides of these minerals form during hydration.3]. These types of volume other references produces expansive reaction products changes. introduce new technology that has been ettringite (calcium sulfo-aluminate). more commonly. restrained expansions or contractions can easily exceed the Washa [2. sential format as well as many of the fundamental aspects of Ingress of sulfate ions from the environment or an excess the earlier publications are retained in this paper. nonuniform changes in hardened concrete was authored by George W. result of concrete’s response to environmental effects such as were drawn upon. The cur. respectively. The magnitude of volume change is generally dration product. and include up-to-date references. drying shrinkage. still results in cracking and spalling of therefore is a dimensionless quantity.” are discussed causing cracking and potential disintegration of the concrete. 215 . 1 Principal Scientist.21 Volume Change Fred Goodwin1 Preface are discussed elsewhere in this publication and therefore are not covered by this chapter. of sulfate intermixed within the concrete causes an expansive rent edition will review and update the topics as addressed by reaction known as sulfate attack resulting in the formation of the previous authors. ASTM STP 169C. face on the area that is exposed to the carbon dioxide [5]. which is not completely reversible on unloading. OH 44122. This expansive mecha- developed. the material shows nonlinear stress-strain behavior. One microstrain is 1 millionth of a unit length change per Uncombined crystalline calcium oxide (CaO) and magne- unit length change (i. Sawyer [4]. which can occur in sealed and unloaded load. and expansion due to hy- plied stress level is 50 % or more of the ultimate strength of dration of free CaO and MgO in hardened concrete. In ASTM STP 169B. short period of time. the chapter on volume to the relatively low tensile strength of concrete. Degussa Construction Systems. During this period. 1 millionth of a metre per metre or sium oxide (MgO) present in the cement or intermixed within 1 106 inch per inch). Carbonation that occurs during the first few stated in linear rather than volumetric units. dusty sur- are generally evaluated in these terms. freezing. especially when the ap. Also dis- concrete. Concrete’s reaction with carbon dioxide from the environ- Introduction ment (carbonation) lowers the pH (thereby lowering the corrosion threshold of imbedded reinforcing steel) as well as Concrete is subject to several types of volume changes during causes shrinkage due to chemical reaction with the cement hy- its service life. while not a volume change of the which is defined as the change in length per unit length and concrete constituents.” rosion of imbedded steel.. Kumar mal volume changes are discussed in the chapter by Tatro. Cleveland. versible and also is proportional to the applied stress is called Volume changes that are not covered elsewhere include car- “elastic strain. the es. The author acknowledges the author of wetting. as well as those in the previous editions. Cor- tice. Due STP 169 and ASTM STP 169A. IN THE PREPARATION OF THIS CHAPTER. Ther- the volume change chapter in the 4th edition. The last section of this chapter contains a brief termed “creep strain” or. cussed in this chapter is the autogenous shrinkage associated The gradual increase in strain with time under a constant with cement hydration.” On sustained loading. P. cooling. THE There are other types of volume change that occur as a contents of the 4th edition of this series.” The description of volume change in expansive cements that are strains resulting from concrete’s response to applied stress used in the production of shrinkage-compensating concrete. water evaporation. commonly called “plastic shrinkage. volume changes can The reaction of alkalis (sodium and potassium) with occur due to cement hydration. absorption.e. the chapter was authored cohesive tensile strain capacity of the concrete resulting in the by James L. drying. is specimens. and bleeding. steel oxidation products within the rigid concrete matrix. This topic is covered in more detail in the chapters on The instantaneous strain on loading that is fully re. In the interest of consistency. heating. In engineering prac. bonation shrinkage. nism is discussed in the chapters by Forster and Meininger. petrographic examination by Erlin and Wong. The term “microstrain” the concrete due to the expansive nature of the formation of is frequently used to quantify the magnitude of shrinkage. thermal certain types of aggregates as described in ASTM C 295 and change. formation of cracks. the volume change is generally expressed as “strain. elsewhere in this book. “creep. and thawing. In ASTM moisture effects are covered in the chapter by Hearn et al. since test data hours following concrete placement causes a soft. 216 TESTS AND PROPERTIES OF CONCRETE Under conditions of restraint. it is still undesirable for a variety of reasons.30 water-cement ratio. Air fills the pore structure of Many of these mechanisms rely on attempts to control the concrete resulting in a decrease of internal humidity within otherwise deleterious reactions such as ettringite formation. toppings. that is. for a given consistency increases as the fineness of cement and Cracks create a plane of weakness within the formerly the cement content are increased. shrinkage to the attention of researchers again [21.010 to the liquid phase from which the ions migrate to the CaCO3 %. The factors affecting chemical shrink- standards are only now beginning to be developed [6. replaced with 10 or 20 % condensed silica fume by weight. the particle size distribution of the ce- members.7].22]. Occasionally. Self-desiccation importantly. (namely. F Fe2O3. foundations. as well as D-cracking in freezing environments. voids and micro cracks that are always present in concrete. while the ultimate shrink. Carbonation shrinkage occurs as a result of chemical interac- nomena: (a) the increase in the disjoining pressure in poorly tion between atmospheric carbon dioxide (CO2) and hydration crystalline C-S-H2 and ettringite due to water adsorption and products of cement. a Autogenous Volume Changes high early-strength portland cement (430 m2/kg. This phenomenon is likely the most common cause of correlation with C3A. process [8]. the volume changes involving less absolute volume than the volumes of the reactants. Autogenous deforma. [16–18]. can the adjacent concrete due to point loading of the crack edges therefore also increase the amount of autogenous shrinkage. penetrate with relative ease into the interior of the concrete This appears to be due to the formation of ettringite as some mass. in stress imposed by drying shrinkage and the subsequent depo- most instances the initial expansions obtained during the first sition of CaCO3 in spaces free from stress [24].003 %. Continuing movement of cracks to be somewhat greater for high C-S-H forming cements frequently causes problems with coatings. According to Washa [2]. ments of autogenous deformation have been reported by Since it takes place concurrently with drying shrinkage. to exceed the tensile strain capacity. The formation controlled volume changes are used to shrinkage-compensate of a rigid structure of decreasing permeability as hydration concrete and mortars in an attempt to produce expansion at progresses decreases the migration of water to the hydrating rates and magnitudes approximately equal to the shrinkage. Chemical shrinkage has been determined by ity of the concrete. The autogeneous volume change with ordinary portland cement concrete is usually small.010 % or 100-microstrain expansion or shrinkage. where the crystal growth takes place. ment (Type I). most reported data do not distinguish between the two and Chemical shrinkage results from the chemical reaction of designate both as drying shrinkage. Carbonation shrinkage is probably caused (b) the reduction in the disjoining pressure due to removal of by dissolving crystals of Ca(OH)2 while under compressive adsorbed water by desiccation. The magnitude is dependent on the overall effect of two opposing phe. the kinetics of the hydration reaction.23 or 0. If condi. particularly architectural concrete.20]. This autogenous shrink- variation in moisture and temperature. S SO3. and a superplasticizer. expansive volume changes also cause Self-desiccation results from the consumption of the in- cracking and are therefore harmful. internal fractures can develop cement ratios has brought the phenomenon of autogenous within the concrete causing failure. Drying shrinkage is 2 Cement chemistry abbreviations are used: C CaO. and metal oxidation. or over. creep. Using cement pastes made with a 0. less than Carbonation Shrinkage 0. ucts near the pore dissolve continuously to furnish Ca ions age obtained after several years usually does not exceed 0. A Al2O3. subgrade friction. C4AF. and gases to ginning a few hours after initial mixing and lasting up to 20 h. The magnitude of chemical volume change in concrete element. Hydration can cease to occur when the relative hu- uncombined calcium oxide. autogenous shrinkage of sealed specimens at an age of 70 days dration alone and do not include environmental effects due to was of the order of 1000 microstrain. [9]. Hydration prod- few months do not exceed 0. nucleating site. Tazawa and Miyazawa [23] reported that the Autogenous volume changes are associated with cement hy. and H H2O. Differences between volume and length change measure. . and modulus of elasticity.13]. Barcelo et al. As the cement hydrate is car- the cement with water. the system. Blaine). Frequently. Unrestrained. age value increased to almost double when the cement was tion combines the mechanisms of chemical shrinkage and self. and the use of etc. however. Cracks also Chemical shrinkage is the dominant factor in autogenous look bad and are the most frequent subject of complaints shrinkage during the time prior to setting or the formation of a about concrete. While cracking may not supplemental cementing materials and other admixtures be serious enough to jeopardize the structural integrity of an [12. The tions exist in which insufficient restraint or inhomogeneous development of high-strength systems with very low water- uncontrolled expansion occurs. desiccation [8]. tensile strength. ment [11]. restrained ternal water due to the hydration of the cement. steel reinforcement. which produces hydration products of bonated. suspended in water [10].15]. harmful chemicals. interlinking with internal becomes dominant after setting [14. More self-supporting skeleton of hydration products. large external cracks. ASTM Type IV cement) than for normal portland ce- lays installed as barriers to protect the underlying concrete. regions near the cement particles. age of hydrating cement systems include the mineralogical com- Concrete typically is under sufficient restraint due to connecting position of the cement. which increase the amount of CSH formation. Ultimate contraction appears homogeneous structure. The addition of pozzolans such as silica fume and Cracks in structures subjected to traffic can rapidly deteriorate metakaolin. and gypsum levels has been found numerous concrete durability problems with field structures. a period of swelling has been observed be- make it possible for water. midity of the pore structure falls below 75–80 % [19. resulting shrinkage commonly produce cracking through the generated in the densification of the solid phases during the hydration tensile stress from shrinkage exceeding the tensile strain capac. the mass of the sample increases. dilatometry and by the change in weight of a hydrating sample age. Significant work is underway to relate shrink. S SiO2. Paillere et al. carbonation depths of pozzolanic cements were similar to those ity of blocks cured in steam at atmospheric pressure. Mineralogical analysis of the carbon- nm increased the carbonation coefficient greatly. While au. meability. This in. it did not help against carbonation shrinkage near 50 % relative humidity [26]. Paillere et al. of portland cements provided that concretes having similar Ying-yu and Qui-dong [27] investigated the mechanism of strengths were compared. with 30 MPa compressive strength at 28 midity. not in volume of drying concrete is not equal to the volume of wa- the water-binder. Since the gaseous-phase carbonation curing period was too short. paste. whereas the ettringite phase in the expansive ce- concrete types were discussed in several studies. such as the one shown here. the CO2 to form carbonic acid and react with the alkaline ce. Malhotra et al. Whereas the presence of entrained air improved the blocks cured in steam at atmospheric pressure show maximum resistance to freezing and thawing cycles. Cements with Drying Shrinkage unusually low lime contents (that is. the au. ated material confirmed that C-S-H was decomposed to calcite Factors influencing the depth of carbonation in different and silica gel.and epoxy-modified mortars showed no 50–65 % relative humidity [26]. Sakuta et al. size of the member. Schubert [28] ment concrete decomposed to calcite. Concrete that has been sub. days. showed only 3 mm carbonation in one year and 7 mm in method of curing. carbonation depths were toclaved blocks are relatively free from carbonation. Further evaporation of adsorbed water is on depth of carbonation in 20 years. tend water absorption of the cement paste. The carbonation behavior of blended carbonation of cement mortars and the dependence of car. are soluble glycol ether derivative as an anti-foaming agent reduced eventually subject to carbonation. between the carbonation rate and the 28-day compressive strength. Carbonation depths of mortar When plain. With permeable concrete.57 water-to-cement ratio were found to have carbonation is porosity. cements was inferior to portland cement only when the moist- bonation on pore size. CH. Massazza and Oberti [36] reported that it is reported that precarbonation improves the volume stabil. was usually an improvement in carbonation resistance of thors suggest “prediction of the carbonation coefficient” by the blended cements. using an accelerated test reversible upon resorbtion of additional moisture [38]. With increased F-T cycles. [37] compared the carbonation characteristics of a Type K expansive cement concrete with ordinary portland a1(2C1/kP)1/2 cement concrete from a 22-year-old building in Nigata Prefec- ture. [35] found that the addition of amino alcohol and glycol ether deriv- Ca(OH)2 CO2 → CaCO3 H2O atives was effective in controlling carbonation. C-S-H. mass is used to determine the equilibrium point of drying [25]. concrete increased. Amino alcohol derivatives that are used for desulfurization and deoxidation pos- All of the constituents of hydrated portland cement. the penetration of CO2. hardened concrete is dried from a specimens moist-cured for 28 days were much less than the 7. the carbona- magnitude of drying shrinkage in a CO2-rich environment at tion resistance of latex. [31] reported that a superplasticized. sess the ability to absorb atmospheric CO2. ment hydrates. Core samples with 58 MPa compressive strength where C1 is the partial pressure of CO2. blast furnace slag showed similar behavior to carbonation as At low humidities. [30] studied the effect of 28-day concrete strength of the concrete.04–0. GOODWIN ON VOLUME CHANGE 217 accompanied by a loss of water resulting in a mass loss. and monosulfate hydrate. Also. Oye and Justness [33] investigated the carbonation resist- the diffusion rate of CO2 decreases. five years at 50 5 % relative humidity. As the pore humidity approaches saturation. however. The porosity of the cement the size of air bubbles in concrete thereby decreasing the per- paste and the specimen size are controlling factors in carbon. [32] investigated the effect of freezing ation because they determine the diffusion rates of CO2 ingress and thawing (F-T) cycles on air-entrained concrete containing fly and the egress of moisture released by CO2 reacting. there process is a chemical reaction controlled by diffusion. Ho and Lewis [29] found that in the range of 0. Aimin and Chandra [34] investigated the effect of acrylic with changes in relative humidity. CO2 concentration. The change carbonation depth depended mainly on the water-cement. (1/fc ). It was found that superplasticized concrete had a lower verse relationship can prove misleading when the specimen depth of carbonation than the corresponding normal concrete. but the rate of carbonation to release moisture reached maximum at 10–15 % polymer loading. time of exposure. [32] found Carbonation proceeds slowly and usually produces little that portland cements containing up to 29 % Class F fly ash or shrinkage at relative humidities below 25 % or near saturation. found an inverse relationship. ash or slag. 70 % slag cement) showed increases in carbonation rates. The initial loss of water causes little or no shrink- in their study. Increasing the polymer content reduced the porosity and Carbonation reactions. With prolonged moist curing. and the sequence of drying and carbonation. relative hu. The authors found that pores with radii above 32 depths of about 12 mm.08 % (400 to 800 microstrain). normal-weight. At higher levels of cement replacement. con- the magnitude of carbonation shrinkage may approach the trary to a general improvement in other properties. age since the most easily evaporable water resides in large pores Dhir et al. ance of latex-modified cement mortars and reported that. and P and 0. and Al(OH)3 gel. the carbonation of concrete increased. ettringite. The use of a water-in- namely. One . temperature. the shrinkage associated with moisture loss is days of standard moist curing. For fly ash concretes with seven relative humidity. ratio regardless of the mix constituents used ter removed. reported the carbonation behavior of mortars and concretes The authors observed that the decomposition rate of ettringite containing different types of cements and fly ashes. there is insufficient water in the pores for neat portland cements. gypsum. saturated condition to a state of equilibrium with air at 50 % day moist-cured specimens. Japan. significant improvement when compared to unmodified mor- jected earlier to carbonation shrinkage will still shrink or swell tars. The author by carbonation was somewhat slower than that of C-S-H. equation Sakai et al. high- The rate of carbonation is dependent on several factors volume fly ash concrete containing 56 % fly ash by weight of the such as porosity of concrete. k is a constant. the magnitude of polymer additions on the rate of carbonation of portland cement these volume changes will be smaller than before carbonation. cementitious material. method. Powers [44] achieved [47]. Most of these materials reportedly work cement paste and the water held by capillary tension takes place by changing the capillary water surface tension [40]. orien- aggregate. Portland cements with high-C3A and high-alkali water held in small capillary pores of the hydrated cement paste contents tend to give high drying shrinkage. and low relative humidity. the factors leading to a greater high cement contents to obtain the specified strength. finer cements usually show greater shrinkage cement and weighing 10–20 lb/ft3 (0. It has been suggested that the evaporation of capillary wa. but theoreti- shrinkage of concrete (Sc) is related to the drying shrinkage cally the ultimate shrinkage may be independent of size of cement paste (S). tation and edge effects complicate this relationship.15 cement as well as the curing time. (water-cement ratio) and the degree of hydration. in massive concrete members differential drying (1 g). The former shrinks and the latter restrains shrink. it has been suggested that the water calcined clays) generally increase drying shrinkage but many meniscus in small capillaries (5–50 nm) exerts hydrostatic water-reducing admixtures that reduce the water content do tension. it seems that slower drying developed the following expression showing how the drying conditions yield lower ultimate shrinkage values. the degree of hydration. reduces the disjoining pressure and brings about the shrinkage Admixtures that increase the water requirement of con- of hydrated cement paste on exposure to drying conditions. modulus of aggregate: This gives rise to tensile stresses at and near the surface while compressive stresses are developed in the interior. shrinkage of concrete are the content of cement paste. reducing admixtures has allowed a reduction in drying Atmospheric diffusion of the adsorbed water present within shrinkage of up to 50 %. the wa. For a wide range of concrete mixtures only 20–25 % of the 20- ter-cement ratio. By in- more than twice for the low-elastic-modulus aggregates than creasing the amount of reinforcement. Since unhydrated cement particles can offer containing aggregates that have high rates of absorption. which in According to Washa [2]. the size drying shrinkage is obtained at 45 % relative humidity as and shape of the concrete mass. Conse- Sc Sp(1 g)n quently. controlled by using optimum gypsum content via ettringite for- ter causes a disjoining pressure when confined to narrow spaces mation and the associated shrinkage-compensating effect (see between two solid surfaces. Reinforced concrete elements aggregates. and about 75 % in one year. over a long period of time and is accelerated by high environ- Among the more important factors influencing the drying mental temperatures. ratio and the logarithm of shrinkage. and humidity %. There ap- age. tion of internal reinforcement (such as steel and fibers [41]). the volume fraction of the cement paste [48. The introduction of shrinkage. Similarly. In crete for a given consistency (namely. In full-sized concrete members.35 or 0. the characteristics and amounts of admixtures three months. To the extent that the water requirement for a with normal amounts of reinforcing steel may show drying given consistency of concrete is influenced by the maximum shrinkages of the order of 0. and removal of this water tends to induce a compressive not reduce drying shrinkage. drying shrinkage values for turn depends on the fineness and chemical composition of structural lightweight concrete may vary between 0. temperature. high porosity.03 %. Concrete made with correspondingly reduced but it will increase the tensile dirty sand or with unwashed aggregates containing silt and stresses in concrete such that it is likely to crack when exces- clay shrinks significantly more than concrete made with clean sive reinforcement is used. the effect of aggregate type on drying shrinkage [45] showed Shrinkage of reinforced unrestrained structures pro- that with a given concrete mixture the 23-year shrinkage was duces tension in concrete and compression in steel. and the amount and distribu. and/or require manner as aggregate particles. shrinkage. Thus. these reinforcement will cause cracks at a closer spacing and also factors also affect drying shrinkage. a high proportion of fineness. thus contributing to the calcium chloride and triethanolamine tend to increase drying overall contraction of the system.49]. restraint to shrinkage of hydrated cement paste in the same low modulus. The size and shape of the concrete mass have a consider- Drying shrinkage of concrete and the factors influencing it are able effect on the rate and total amount of drying shrinkage. 50–60 % in of aggregate. An increase in steel size.218 TESTS AND PROPERTIES OF CONCRETE source of irreversible drying shrinkage in concrete is the loss of values. al- factors follows. degree of hydration generally contribute to a higher drying Moist-cured. which can be [39]. and surface texture of the aggregate. long-term studies on redistribution of internal stresses. discussed in numerous reports.22–0. Also. though the shrinkage process continues over a longer period Concrete is made up of two constituents: cement paste and for the large mass [46]. In realistic terms. and a constant (n) that is dependent on the elastic conditions produce larger shrinkage at and near the surface. The effectiveness of aggregate to restrain the shrinkage of pears to be a linear correlation between the volume-to-surface cement paste is related to the elastic modulus of the aggregate. diatomaceous earth or regard to capillary water. The removal of the capillary water the last section of this chapter that deals with testing methods). cellular (foamed) products made with neat shrinkage. grading. as well as to the loga- From the data obtained by an experimental study of concrete rithm of time required for half of the ultimate shrinkage to be mixtures with water-cement ratios of 0. surface cracking may occur if the tensile stresses exceed the tensile strength of the material and the stress relax- Thus.50. Higher shrinkage values generally result from concretes conditions. shape. Almost twice as much used.44 kg/m3) may . the elastic modulus year drying shrinkage was realized in two weeks. compared to 80 % relative humidity exposure. reduce the crack widths. These cracks then increase the shrinkage may be doubled when the aggregate volume fraction available surface area for evaporation of water. the shrinkage can be for the high-elastic-modulus aggregates. Accelerating admixtures such as stress on the walls of the capillary pores.04–0. the time and the relative humidity of exposure. as well as cause is decreased from 80 to 50 %. Fibers added to concrete also redis- The quality of the cement paste is primarily a function of tribute the stresses resulting in a similar reduction in crack the water content for a given cement content in concrete width and closer spacing of the cracks [41]. for a given aggregate and cement paste the drying ation provided by creep. such as those authored by The rate and ultimate shrinkage of a large mass of concrete are Ytterberg [42] and Meininger [43].02–0. A brief discussion of these smaller than the values for small-size concrete elements. which were made at much lower temperatures weigh 40 lb/ft3 (0. and ferrite (Lime saturation factor 1) [56]. During the last 20 years. Data from moisture or too slow to hydrate under ambient temperature ACI 234R indicate that the drying shrinkage of silica fume conditions. Autoclaved In regard to crystalline MgO or periclase.S. prac- stochiometric requirement for combination with silica. Fss). when compared to normal portland cement. clinker constituents determine the reactivity of both CaO and the cements of this type have been commercially used for mak- MgO in cement. ment is known as shrinkage-compensating. The cement produced by which caused cracking of the unrestrained paste [57]. 3CaOSiO2. the steel will go into tension and concrete into 3 Fss stands for the calcium aluminoferrite solid solution phase. The crystalline size. the concrete will bond to the reinforcing steel and under restraint in shrinkage-compensating concretes. Concrete shrinkage is influenced little by tional discussion).7 MPa). In addition to analytical verification of the ment. cements due to better manufacturing controls. Under these are described in the next section of this chapter. which any expansion will be restrained by the steel.3–0. as well as ena have been harnessed to produce shrinkage-stress- clinker composition containing calcium levels above the compensating concretes. if and MgO the expansion is adequately restrained.02–0. a graphical representation is given of the con- which is that the content of uncombined or crystalline CaO cept showing how a Type K shrinkage-stress-compensating ce- seldom exceeds 1 %. the range of 0. C3A. The blending this additive with normal portland cement is called phenomenon is virtually unknown in modern portland Type K expansive cement. a result of In Fig. it is additives for cement containing a large amount of crystalline observed that large amounts of ettringite start forming.1 %. It is now decrease in shrinkage [50]. the lower the reactivity.88 kg/m3) and have drying shrinkage in than used today. clinker at a kiln temperature of 1400–1500°C is either inert to tary cementing material for concrete elements. Conversely. 1.60) and for high silica fume contents test. This amount of ex- sion and cracking. Only under autoclaving conditions. in accelerated concrete is generally comparable to that of a control concrete laboratory tests such as ASTM Test Method for Autoclave Ex- after 28 days of moist curing regardless of the water-to. physical verification using the ASTM C 151 reduce the risk of drying shrinkage cracking [61]. Immedi- [58] autoclave expansion test is now also conducted. internal curing occurs The expansion and cracking of cement pastes and concretes when saturated lightweight aggregate is used. Note that approximately 2–5 % MgO goes into the solid solu- lated blast furnace slag in the concrete mixture are reported tion of portland cement clinker compounds (C3S. and the solubility of the material within the other due to subsequent drying shrinkage. pansion of Portland Cement (C 151). and post-tensioned concrete members for parking cement. accepted that the periclase formed in modern portland cement Silica fume is being used increasingly as a supplemen. Incorporation of silica Volume Changes in Expansive Cements fume leads to reduced pore sizes in the cement paste. Fly ash and ground granu. Large expansion occurring in Expansion Due to Hydration of Free CaO an unrestrained cement paste can cause cracking. airport taxiways. and 4CaOAl2O3Fe2O3. thus increasing the surface tension in small capillary pores and ASTM Specification for Expansive Hydraulic Cement (C 845) therefore the autogenous shrinkage. The expansive additive in U.6 %. when present in concrete is on the order of 25–100 psi (0. When the magnitude of ex- It has been often reported in the published literature that pansion is sufficiently small such that the prestress developed hydration of crystalline MgO (periclase) or CaO. The silica fume drate and cause considerable expansion in unrestrained pastes quantity and curing regimen prior to drying were found to be (see the section on test methods and specification for addi- important factors. creased gel formation of the pozzolanic reaction products) as well as to have minimal effect [53–55]. water-storage with water and likely are consumed in the plastic state of the tanks. over 3 % free (crystalline) CaO gave considerable expansion. Early Specification for Portland Cement (C 150) [59] are required to drying increases shrinkage for lean silica fume mixtures comply with the maximum limits of expansion in the autoclave (w/cm greater than 0. significant amounts of anhydrous calcium aluminosulfate Laboratory tests on early portland cements showed that (4CaO3Al2O3SO3) and calcium sulfate in addition to the the cement pastes made with low-MgO cements containing cementitious compounds of portland cement. 2CaOSiO2. Low burning temperatures can leave are capable of causing disruptive expansion. MgO. The higher the calcining temperature of both CaO and garages. as the crystalline structure The formation of ettringite and hydration of crystalline becomes denser. works to free CaO content. . Expansive ately following the start of hydration of Type K cement. Since portland cements meeting ASTM silica fume content up to 10 % by mass of cement [52]. GOODWIN ON VOLUME CHANGE 219 have drying shrinkage as high as 0. it is one of the chemical requirements of ASTM C 150 that (greater than 10 % by mass of cement) because early drying the total MgO content of portland cement shall not exceed 6 %. conditions. C2S. the thermal history of pansion is generally enough to offset the effect of tensile stress the material. contained large amounts of this compound. some early port- concrete products containing fine siliceous additives may land cements. its magnitude will be reduced but a self-stress will develop.2–0. Very fine particles react rapidly after mixing ing crack-free industrial floors. [60] covers hydraulic cements that expand during the early hardening period after setting.3 and the remainder shows up in the form of periclase. After CaO are being used in Japan to obtain controlled expansions initial set. resulting in a containing these cements were attributed to periclase. tice is a modified portland-cement clinker that contains alumina. Both phenom- unreacted calcium oxide present in the cement. the ce- in significant amounts in a portland cement. is periclase known to hy- cementitious materials ratio (w/c m) [51]. can cause expan. CaO and MgO are both chemically combined CaO are two mechanisms known in concrete technology that within the clinker phases. inhibits the pozzolanic reaction. and to both increase drying shrinkage (probably due to the in. However. 6. However. Since the do show almost the same amount of drying shrinkage as nor. With a water-cement ratio of 0. the shrinkage will first relieve the precom. 1a). the rate and crete. As with normal portland cement concrete. and (b) illustration showing why Type K cement concrete is resistant to cracking from drying shrinkage (Ref 38). the magni- sometimes called nonshrinking cements. This. the expansion during stresses. therefore. the residual dimensional change after the drying shrinkage age. magnitude of expansion and degree of precompression is mal portland cement concrete (Fig. Due to their ability to produce reinforced concrete changes from positive to negative at high water-cement ratios. it will drying. With the former the reduced considerably with water-cement ratios above 0.6 be used . Thus by preventing the development of large tensile tent. 2. is tude of initial expansion was large enough to ensure a residual misleading because concretes made with expansive cements expansion after two months of drying shrinkage. magnitude of drying shrinkage with Type K cement concrete is pression in concrete before tensile stresses have a chance to influenced by the aggregate content and type and water con- develop. compression. the expansive cements can become instrumental in this moist-curing period is reduced proportionately.220 TESTS AND PROPERTIES OF CONCRETE Fig. members that suffer little or no dimensional change during This effect is shown by test data from Polivka and Willson [62] their service life. it is overall dimensional change is negligible because of expan. With increasing water-cement ratio. which precedes the shrinkage on element is exposed to environmental drying conditions. reducing the risk of cracking in concrete from drying shrink. At the end of the moist-curing period when the sion during moist curing. shrink in the same manner as normal portland cement con. however.53 or less. 1—(a) Comparison of length change characteristics between portland cement and Type K cement concretes. recommended that water-cement ratios lower than 0. the shrinkage-compensating cements are in Fig. 8 mm) that are moist cured for 24 1 ⁄ 2 h and then chapter.e. The critics of the test say that the measured expansion has no significance because: (1) exaggerated expansion values are obtained by destroying the cohesive forces that would be present in normally hardened cement pastes. (2) the test conditions force the crystalline MgO present to hydrate and expand. even when it is not needed Concrete under Restrained Shrinkage (C 1581) [72] from the standpoint of structural strength.80 %. Cylindrical Specimens from Hydraulic-Cement Grout (C age of a Type K expansive cement concrete (Ref 39). Kesler [63] found that good moist-curing conditions are absolutely essential (Fig. Portland Cement ASTM C 151 provides an index of potential delayed expansion Test Methods of Determining Volume caused by the hydration of CaO or MgO. (3) the magnitudes of expansion in neat cement paste bars due to hydration of the free CaO normally present may be high (that is. ASTM offers several methods that are listed here: exposed to the action of steam under a pressure of 2 0. but in corresponding concretes it will not be high enough to cause significant expansion and cracking (due to the restraining effect of the aggregate). 2. ASTM Test Method for Autoclave Expansion of Portland MPa for 3 h. ASTM Test Method for Drying Shrinkage of Mortar Containing Portland Cement (C 596) [66] 5. 3—Effect of curing conditions on restrained expan.4 by 25.80 % expansion). ASTM Test Method for Determining Age at Cracking and Induced Tensile Stress Characteristics of Mortar and with Type K expansive cements. Standard Test Method for Change in Height at Early Ages of Cylindrical Specimens of Cementitious Mixtures (C 827) [68] 7. ASTM Test Method for Length Change of Hardened Linear expansion is measured by a micrometer comparator Hydraulic Cement Mortar and Concrete (C 157) [64] over an effective gage length of 254 mm. and (4) no correlation has ever been shown between the autoclave test specification limit and the soundness (cracking potential) of concrete. The method Changes covers determination of the autoclave expansion of portland cement by testing neat cement paste specimens (25. ASTM C 150 for portland cement permits a maximum expansion of 0. the MgO present is either inert or hydrates at a rate that is too slow to be of any consequence. The Le Chatelier apparatus is a 30-mm. Standard Practice for Length Change of Drilled or Sawed Specimens of Hydraulic-Cement Mortar and Concrete (C 341) [65] 4. 3).4 For evaluation of volume changes discussed in this by 285. including the scope To develop adequate expansion and precompression in and significance of each. whereas in normally cured commercial portland cements. deleterious expansion problems caused by uncombined CaO and MgO are not issues with cements manufactured according to C 150 and C 1157 standards. 2—Effect of w/c on restrained expansion and shrink. GOODWIN ON VOLUME CHANGE 221 3. 1090) [71] 10. ASTM Test Method for Expansion and Bleeding of Freshly Mixed Grouts for Preplaced-Aggregate Concrete in the Laboratory (C 940) [70] 9. Fig. ASTM Test Method for Measuring Changes in Height of Fig. or both.07 1. Another commonly used test serving this purpose is Le sion of expansive cement concrete (Ref 40). A brief description of these methods. The author of this chapter in STP 169C [1] (the previous edition) expressed his opinion that “The autoclave test for expansion is able to provide a quantitative measure of the expansion caused by delayed hydration of free CaO and crystalline MgO.” The fact remains that although the C 151 test may be overly severe. Chatelier’s method. Test Method for Restrained Expansion of Shrinkage- Compensating Concrete (C 878) [69] 8. ASTM Test Method for Restrained Expansion of Expansive Cement Mortar (C 806) [67] 6. within permissible chemical limits (i. The rates at which pressure is increased in the Cement (C 151) [58] beginning of the test and released at the end are specified. maximum 6 % total MgO). follows. . concrete.. high enough not to meet the requirements of the ASTM C 150 specification limit of maximum 0. cylindrical mold with indicator needles. The specimens The procedure can be used to determine the effects of varia- are kept in molds for 23. The practice is essentially a modification of ASTM C density of the mixture floats on the surface of the specimen and 157 utilizing specimens that have either been cast for freeze. the rate of and specimens that are to be directly compared with each tensile stress development at the time the test is terminated other shall be subjected to the same conditions. Since drying shrinkage of concrete is greatly influenced by the aggregate content. 14. This test method is not intended for expansive mate- 4 % relative humidity. Any specification limit based tion on induced tensile stresses and cracking potential. adapted. mixture that will continue to fill the same space at time of hard- nally applied forces and temperature changes. During the test. At ASTM C 596 covers determination of the effect of portland the end of a 24-h normal moist-curing period.5 h. A small ball selected to be 55 5 % of the bias data. it was revised into a standard (depending upon aggregate size) with the freshly mixed ce- practice in 2003 due to the lack of applicable precision and mentitious material. relative atmospheric pressure for a period of 3 h. Comparator readings (19 mm). patching.7°C in water or in air at 50 dration. and rate of evaporation in the environment [66]. mortar or concrete specimens under restrained shrinkage. Originally writ. ing methods. 7. For upon this method shall be applied to a specified specimen size materials that have not cracked during the test. concrete on cracking due to both drying shrinkage and def- ments are taken. and after 8. rate of property development. to studies of length change involving It is particularly applicable to grouting. aggregate stiffness. 32. and form- different schedules or environmental treatments than the stan. and Portland Cement Mortar and Concrete water content. especially when the tests are of potential unrestrained expansion or shrinkage in different concluded at early ages. Much greater variability decrease in the steel ring strain. and 64 the steel ring caused by the restrained shrinkage of the mor- weeks. The test consists of filling a 100 to 300 mm high cylinder ten as a standard test method. 32. and environmental conditions. many researchers question the validity of ASTM C 157 provides a method for potential volumetric ex. the European Committee for Standardization has ap. its image is magnified using a light source and lenses calibrated thaw testing or removed from field-applied concrete or mortar. It can be readily age or expansion of cementitious mixtures prior to final set [68]. After ormations caused by autogenous shrinkage and heat of hy- curing. the demolding time of the speci. the behavior of either neat pastes or rich mortars to predict the The method is particularly useful for comparative evaluation ultimate shrinkage of concrete. The test allows different sized prisms to be used without based materials that are less likely to crack under retrained compensation for the different surface-to-volume ratios and shrinkage.4 by 25. The specimens in air storage have a rials or concretes containing aggregates coarser than 3/4 in. ASTM C 341 covers the determination of the length changes of drilled or sawed specimens of hydraulic-cement Expansive Cement Mortar and Concrete mortar and concrete due to causes other than externally ASTM C 827 affords a means for comparing the relative shrink- applied forces and temperature changes [65]. then they are demolded. A qualifying statement is imbedded many variables including type of structure. and 28 days. This test method men. higher drying shrinkage values result when rate of tensile stress development in the test specimen are in- specimens are cast in the field under temperature and humid. The specification for humidity. As volume changes occur.222 TESTS AND PROPERTIES OF CONCRETE longitudinally split. The compressive strain developed in water storage readings are taken at the age of 8. Similarly. ening. hydraulic-cement mortar or concrete mixtures. to a known magnification. the drying shrinkage of mortar as determined by this method Recently. cal specimen and the projected magnified image is read from a . in some cases. and that specimens to be compared shall have the same can be used to determine the relative effects of material varia- dimensions and demolding time.2 age at cracking and induced tensile stress characteristics of by 280-mm concrete prisms with 25. gregate and 254-mm gage length in both cases. and they are moist-cured for 28 days. their initial measure. extrapolating the data on mortar shrinkage to concrete shrink- pansion or contraction of mortar or concrete due to various age. Swayze [74] found it inconsistent to rely on causes other than applied stress or temperature change [64]. provides a basis for comparison of the materials. Actual cracking tendency in service depends on subsequent drying rates.0 1. clearance of at least 25 mm on all sides. In cement soundness according to the Le Chatelier test permits a regard to significance and use of the method. the A provision is made for application of gage studs to hardened position of the ball moves relative to the height of the cylindri- specimens. has a linear relationship to the drying shrinkage of concrete proved the use of the Le Chatelier method for testing cement made with the same cement and exposed to the same drying soundness (EN 197) [73]. This test method is useful for determining changes occurring prior to demolding at 24 h (or longer in the the relative likelihood of early-age cracking of different ce- case of slow-hardening cements) are not captured during the mentitious mixtures and for aiding in the selection of cement- test. The age at cracking and the and. they are stored at 23. or longer if necessary to pre. filling operations in which the objective is to completely fill a dard procedures for sawed specimens of hydraulic-cement cavity or other defined space with a freshly mixed cementitious mortar and concrete due to various causes other than exter. 16.4-mm maximum size ag. or concrete is compacted in a circular mold around an in- 16. Volume strained shrinkage. tar or concrete specimen is measured from the time of cast- It may be pointed out that ASTM C 157 is intended for use ing.4 by 280-mm mortar prisms or 76. dicators of the material’s resistance to cracking under re- ity conditions that are different from the laboratory. conditions. For instance. if desired.2 by 76. strumented steel ring. a sample of freshly mixed mortar after air storage are taken at 4. tions in the proportions and material properties of mortar or vent damage. and 64 weeks unless otherwise specified. The test utilizes ASTM C 1581 covers the laboratory determination of the triplicate 25. it is stated that maximum distance of 10 mm between the indicator points. degree of re- within the test method that length change may be influenced straint. construction and cur- by the size of the specimen. the mold cement on the drying shrinkage of a graded standard sand containing the cement paste is exposed to boiling water at mortar subjected to stated conditions of temperature. Cracking of the test specimen is indicated by a sudden in a standard laboratory environment.5 0. pp. et al. ASTM International. 3. “Volume Changes and Creep. “The Chemical Shrinkage of Pozzolanic Reaction oration so as to cause drying. cement [67]. J. or environmental treatments Barcelo. moved from the molds at the age of 6 h and exposed to curing [3] Washa.. “Reaction Mechanisms of Concrete Admixtures. This test method is intended to provide a means of [14] Hua. Vol. Since the potential for expansion under conditions of 1998. pp.. Material Behavior or Experimental Artifact?” Proceedings of the Second International Research Seminar on Self-Desiccation and ASTM C 940 determines the amount of expansion and its Importance in Concrete Technology. 20. S. a need has been recognized for a test method in [7] Hossain. D. standard restraining cage. 6. Vol. No. ASTM C 878 covers the determination of the expansion 1978. A. Attiogbe. which is restrained by using a Tests and Properties of Concrete and Concrete Aggregates.. E. 189–201. and Clavaud. L. Lund. The test face to minimize the effects of bleed water evaporation. T. E. [5] “What. ences in degree of restraint. No. P. Lamond. “Retrait d’Autodessicca- assessing the ability of a hydraulic-cement grout to retain a tion du Ciment: Analyse et Modelisation.” Proceedings of the Second Interna- height of hydraulic-cement grout by the use of cast 3 by 6-in. conditions. The method uses visual Assessment of Chemical Shrinkage of Hydrating Cement observation of the plastic volume change and bleeding in an Pastes. then water-cured until the age “Linear vs.. 219–228. carbonation. 910–918. pp. “Chemical Shrinkage of Cementitious Pastes ASTM C 1090 covers measurement of the changes in With Mineral Additives.” Bulletin Liaison stable volume during the stipulated testing period of 28 days. West Conshohocken. Klieger and J. 1998. pp. “Volume Change.0 1. and the mixing procedure are specified.04–0. ASTM International. However.. GOODWIN ON VOLUME CHANGE 223 calibrated chart. test method. 81–92.. mixture proportions.. and content.. Sweden. 243–262.. or both. 1966. K. and Acker. and Weiss. Drops of oil may be used on the specimen sur. G.. the length change ASTM STP 169A. B. Marchand. 100. measurement is taken and percent expansion is calculated. B. 115–128. Measurements are performed using a depth [13] Paulini. Rigaud. ASTM International.” predicted from test mortars made in accordance with ASTM ACI Materials Journal. 1999. The test specimen is a 50 by 50 by 260-mm prism [2] Washa.. J. 196. At the end of the water-curing period. and Clavaud.. “Shrinkage compensating cement cannot always be satisfactorily Cracking Characteristics of Concrete Using Ring Specimens.” CIP 1. K. Eds. Why and How – Dusting Concrete Surfaces... Silver Spring. P. hydraulic-cement grout used in the production of preplaced. . B. (In Press). MD. “Experimental aggregate (PA) concrete [70]. the portion of the grout providing either the change before the mixture becomes hard. The specimens are re.. method is primarily intended for use in evaluating mixtures The method affords a means for comparing the relative of materials intended to be used in producing “nonshrink shrinkage or expansion of cementitious mixtures prior to set. 1999. “Volume Changes. Slag & Natural Pozzolans in Concrete.. pp. development of internal forces resulting from hydration of the West Conshohocken. 191–205. [11] Justness. ting.. controlled restraint of concrete made with shrinkage- [6] See.” that vary from the standard procedures prescribed by this Materials Science of Concrete VI. tional Research Seminar on Self-Desiccation and Its Importance cylinders [71]. C.” in Significance of Tests and of expansive cement mortar while under restraint due to the Properties of Concrete and Concrete-Making Materials. West Conshohocken.” Fly Ash. The mix components of the mortar ASTM STP 169. that the measurements are primarily useful for comparative purposes rather than as absolute values and the degree of restraint to which the specimen is subjected varies with the vis. Acker. and Van so that the tendency to change in height does not include evap. L.. P. A. A. 1999. C 806... E&FN Spon. B. and a reference micrometer bridge. H. the speci. Sweden. 2002. Ardoullie. PA. H. [10] Boivin.” in Significance of having a 250-mm gage length. SP 178. MI. 1994. PA. ASTM International. the glass plate during the first 24 h of the test. Lund. In these for prescribing mixtures having restricted or specified volume applications.. The cylinders are covered by a restrained glass in Concrete Technology.10 %. Gemert.” micrometre to measure the distance between the grout surface Cement and Concrete Research. Boivin.. Volumetric Autogeneous Shrinkage Measurement: of seven days when the length change is measured. pp. the grout will pull away from (in French). Acker. Specimens. J. References cosity and degree of hardening of the mixture. cylinder during the first 3 h after mixing. Farmington or exposure to temperatures outside the range of standard Hills.” in Significance of Tests and in lime-saturated water at 23.. pp. P. “Early Age Behavior of Cement-Based Materials. S. “Volume Change. F. A. Delagrave. West Conshohocken. PA.. M. accumulation of bleed water at the surface of freshly mixed 109–126. Charron. and Miltenberger..” Autogeneous Shrinkage of Concrete.” in Significance of Tests and requires the seven-day retrained expansion to range between Properties of Concrete and Concrete-Making Materials.. Cement and Concrete Composites 2003. May 2003. plate for the first 24 h after mixing and subsequently protected [12] Justness. ASTM STP 169C. cement composition. G.. pp. 1990. American Concrete Institute.. 35–41 If settlement shrinkage occurs. B.. demolded at the age of 6 h. American Ceramic Society. Sellevold. pp. 226–241.. W. The procedure calls for a standard restraining Westerville. bearing support or bolt anchorage. cage for a 76 by 76 by 254-mm concrete prism that is [9] Barcelo. Assessing Residual Stress Devel- which concrete specimens are tested. PA. ASTM STP 169B. will set and men used in this test method is not completely unrestrained so harden under confinement. 1999. ASTM Specification for Expansive Hydraulic Cement (C 845) [4] Sawyer. pp. Hendrix. and for similar applications. grouts” for use either under machine bases or column bases. E.. H. P.. National Ready Mixed Concrete Association. P.. Ehrlacher. 2 pp. Laboratoire des Ponts et Chaussees. OH. Rigaud. 73–84. Products. Vol. ASTM C 878 can be opment and Stress Relaxation in Restrained Concrete Ring adopted readily to studies of expansion involving differ. S. W. of concrete made with shrinkage-compensating cement [69]. J. 1956. P. Silica Fume. L. It would be appropriate to use this test method as a basis for bolt anchorages. J. W. Lon- 800 mL sample of grout confined in a 1000 mL graduated don. ASTM C 806 covers the determination of length changes [1] Mehta. pp. cement [8] Bissonnette. 0. uptake of moisture.7°C until an age of seven Properties of Concrete and Concrete-Making Materials. days. 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John Scanlon and James McDonald. watts per meter concrete engineering and construction industry. density. who retired Definition and Units in 1980 as chief of the Concrete Branch. Typically. Results are given in weight concrete. The unique ability of concrete The amount of free water in concrete.0 Btu in. and the even more favorable properties of light. a measure of the ability of a material to neers. Bureau of Reclamation in conjunction with consistency exist. Office Chief of Engi. Other As with most construction materials. and tem- hydration of cement could be responsible for volumetric perature) significantly influence the thermal conductivity of a changes that would affect the integrity of a structure. whether joules per second square meter degree Celsius per meter. is defined as the ratio of the rate of heat flow to from the Corps of Engineers. or negligible.S. and per hour square foot degree Fahrenheit per inch. under ordinary circumstances. steady-state heat flow is needed. WA 99362.S. and buildings. expansion (or contraction).1441314. Colorado. and specific concrete. Denver. U. both within and between systems of units [2]. entrained air.S. with w/c ranging from 0. both of whom retired conduct heat. The thermal Kelvin. exhibit a fairly constant characteristics vary from those under normal conditions. and users of conductiv- the fundamental thermal properties of concrete was carried ity values are cautioned to assure that compatibility and out by the U. importance in their effect on tionship between a change in temperature of concrete and its conductivity are cement type and content. regardless of density. specific heat. The mineralogical character of the aggre- that this heat. areas. Tatro1 Preface time periods has been utilized by designers to control volume changes and consequent concrete cracking. multiplying by 0. provided the last update. Army. The investigations were stimulated Parameters and Values by the realization that in massive structures heat generated by Three principal conditions (water content. the approved SI that are most ignored and the least understood by the general (Systéme International) units are obtained. Thermal Conductivity Mitchell. for such structures as highways. and British units. while with lightweight concretes air voids and the Boulder Canyon Reports [1].3 to 0. By the concrete is massive or in thin sections. frequently express temperature gradients. This fact has been long recognized water/cement (w/c). conductivity is frequently expressed in Btu tivity. Rhodes. Values of heat of hydration of cementitious materials. and age. originally written in 1965 by L. ambient moisture conditions has little meaning because the struction and for other applications in which resistance to specimens suffer extensive cracking because of drying. A. walls. a supervisory engineer with the Bureau of Reclamation. Thermal conductivity measured under reduced weight concretes have been used effectively in building con. Neat cement pastes. the design and construction of Boulder (Hoover) Dam between 1930 and 1935. While water (unsteady state) and to store or release heat over significant is a relatively poor conductor of heat as compared to rock. there is a direct rela. J. to dampen annual and daily ambient temperature variations has a major influence on the thermal conductivity. Walla Walla. IT IS AN HONOR TO REVIEW AND UPDATE THIS chapter on thermal properties.22 Thermal Properties Stephen B. its 1 Senior Concrete Materials Engineer. could take as gates largely determines the thermal conductivity for normal- much as a century or more to dissipate. are the properties dimensional manipulation and substitution. factors of slight. it can be considered to be the number of kilocalories passing between Introduction opposite faces of a 1-m cube per unit of time when the temperature difference is 1°C. In U. An alternate set of dimensions is The thermal properties of hydraulic cement concrete. and time in One of the earliest and most comprehensive studies of units of measure most useful to them. Corps of Engineers. and later updated by J.6 and Only at very high and very low temperatures do the expansion ages from three days to one year [3]. customary characteristics of concrete covered in this chapter are conduc. bridges. condition. This last property conductivity in these units may be converted to the SI units by is included because of its influence on the thermal and physi. Thermal conductivities [6. Thermal conductivity of the conductivity can be determined directly with any of concrete varies directly with moisture content [4.8].4 10. 18 0 2.3 16. Conductivity values at about 400°C (7500°F) are given in Table 6 [5].6 18. and a wide at normal temperatures [3]. the conductivity at the measurement of a wide variety of specimens.5]. However. the mineralogical characteristics of the ag.56 3. specific portion of the temperature range between the freezing those with densities less than 960 kg/m3 (60 lb/ft3)./h ft2 °F expansion [9].3 23.0 QUARTZ GRAVEL CONCRETE Moist 3.0 EXPANDED SHALE CONCRETE Moist 0. Water Temperature Conductivity This decrease has been attributed to disruption of the inter- crystalline bonds in the aggregate caused by excessive thermal °C °F W/m K Btu in. may have and boiling points of water and to saturated or near-saturated been aerated (foamed) or may contain a very lightweight concrete. moist condition (not necessarily saturated) is given in Table 2. Insulating lightweight concretes. conductivities of cement pastes.2 36.0 SANDSTONE CONCRETE Moist 2.9 20. For moist normal-weight concrete.0 Dry 1.0 157 250 5. At elevated temperatures.7 19. TATRO ON THERMAL PROPERTIES 227 about 750°C (1380°F). grad- 20 68 0.2 15.9 50% relative humidity 0. 0 32 0. porous aggregate.2 15. cylinders subjected to steady heat flow conditions.0 Values for the thermal conductivity of concrete are usually calculated from the diffusivity and specific heat because they are easier to measure.3 23./h ft2 °F LIMESTONE CONCRETE Moist 2.7] given in Table 5 The discontinued ASTM Test Method for Steady-State Heat are for air-dry or low moisture contents.0 50% relative humidity 1.85 5.0 50% relative humidity 2. Use of wa- gregate markedly affect the conductivity of the concrete. achievement and measurement of steady-state heat flux mal-weight and lightweight concrete is essentially constant through flat-slab specimens.0 59 75 2.5 Dry 0. the thermal conductivity of oven-dry. as ter as the heating and cooling mediums limited the results to a shown in Tables 3 and 4. TABLE 2—Typical Variations in Thermal Conduc- tivity with Moisture at Normal Temperatures Conductivity Moisture Condition W/m K Btu in.62 4.0 Dry 1. ranging from 157°C (250°F) has been found to be about 50% greater than opaque solids to porous or transparent materials. the Boulder Canyon Project [1] used 200-mm (8-in. and structural light. The test method for thermal conductivity developed for For heavyweight. up to range of environmental conditions.7 11. nor.4 10.9 resulting in further decreases in conductivity [9].59 4.79 5. and concrete decrease in a consistently uniform manner. which it replaces in concrete [3].0 Test Methods 101 150 3.1 ual disintegration of the fully hydrated cement paste occurs. normal-weight.0 50% relative humidity 2. mor- TABLE 1—Thermal Conductivity of Water tars.0 Dry 2. air.3 16. Flux Measurements and Thermal Transmission Properties by Over a temperature range from room temperature to Means of the Guarded-Hot-Plate Apparatus (C 177) covered the 157°C (250°F).3 . Above temperatures of 400°C (70°F). The effect the steady-state or transient (nonsteady-state) test methods of moisture on thermal conductivity values from oven-dry to a described in the following. The Corps of Engineers [10] Method for Calculation of Thermal Conductivity of Concrete (CRD-C 44) is suitable for calculating the thermal conductivity of concrete thermal conductivity as shown in Table 1 is many times that of from results of tests for diffusivity and specific heat.) diameter weight concretes. This test method was applicable to [3. 1 Quartzite 152 2440 24 3.85 .6 Marble 152 2440 15 2. The speci- (C 518) was a comparative method of measurement since spec./h ft2 °F W/m K Hematite 179 2870 18 2.0 Barite 190 3040 14 2.6 Limestone 151 2420 18 2.3 Quartzite . men.0 Dolerite 147 2350 14 2.4 Limestone 126 2020 10 1. and temperature men) measures temperature response to a measured alternating differential through the oven-dry specimen is from 32 to 60°C current input.6 1. was coated with mercury imens of known thermal transmission properties must be used on all surfaces to retain moisture and electrically heated inter- to calibrate the apparatus.46 Expanded slag 60 960 1.9 0.).5 0./h ft2 °F W/m K Hematite 190 3040 28 4..5 Dolomite 156 2500 23 3.2 0.9 Expanded shale 99 1590 5. Its acceptability or modifications conditions of 10 to 40°C (50 to 104°F) with flat slab thicknesses are not known..4 Dolerite 136 2180 8.. ASTM Test Method for For experimental work.9 Granite 151 2420 18 2.1 Sandstone 133 2130 20 2.2 Limestone 152 2440 15 2.22 Another discontinued test method. Lentz and Monfore. developed a hollow-cylinder.).3 Limestone 153 2450 22 3. steady-state system for measuring sion Properties by Means of the Heat Flow Meter Apparatus conductivity at temperatures up to 200°C (392°F).3 0.1 Quartzite 150 2400 28 4. up to approximately 250 mm (10 in.7 Sandstone 120 1920 10 1. There are no moisture or density restrictions.62 Expanded slag 103 1650 3. The method was used at ambient nally and cooled externally. 23 3. with the Portland Cement Association The Corps of Engineers [10] Method of Test for Thermal [8]. and (90 to 140°F).5 1. Campbell-Allen and Thorne [5] Steady-State Heat Flux Measurements and Thermal Transmis.2 Quartzite 147 2350 21 3. developed a transient hot-wire method for determining ther- Conductivity of Lightweight Insulating Concrete (CRD-C 45) mal conductivity of concrete or rock.2 Expanded shale 89 1430 4.0 Basalt 158 2350 13 1. the axis of a prism (or in the center of a split and lapped speci- Nominal specimen thickness is 25 mm (1 in.228 TESTS AND PROPERTIES OF CONCRETE TABLE 3—Effect of Aggregate Type on Conductivity of Dry Concrete at Normal Temperatures Dry Density Conductivity Aggregate Type lb/ft3 kg/m3 Btu in. TABLE 4—Effect of Aggregate Type on Conductivity of Moist Concrete at Normal Temperatures Moist Density Conductivity Aggregate Type lb/ft3 kg/m3 Btu in. A thermocouple cast along measures conductivity directly under steady-state conditions.2 Basalt 157 2520 14 2. measurements are completed within a few minutes time.. at a selected moisture content.6 Marble 143 2290 12 1.9 Sandstone 150 2400 20 2. .0 Rhyolite 146 2340 14 2.2 Barite 180 2880 8. 232 320 20 0.248 480 30 0.72 also increases up to at least 600°C (1110°F). These values represent mass concrete from the consolidation of three other properties that appear mixtures and several aggregate types [11]. In this procedure. according Definition and Units to the Boulder Canyon studies [1]. specific heat is those of water.58064 105 m2/s W/m K Btu in.8 VERMICULITE that of normal-weight concrete at ordinary temperatures and 400 25 0.219 AERATED 38 100 971 0.4 960 60 0. or k/(c p).22 and 0. The most suitable procedure is the Corps of Engineers [10] Method of Test for Specific Heat of Aggregates. The actual values found were 0. one must take tions by Harmathy and Allen [12] indicate the specific heat of care to assure that the dimensional units of the three con- expanded aggregate lightweight concrete differs little from stituents are compatible.2 Some type of calorimeter apparatus is employed in all procedures to measure the specific heat (heat capacity) of hardened concrete. the specific heat (and media whose physical or chemical properties differ from heat capacity) values are the same. The mineralogical differences among such aggregates as generally used have little effect on specific heat of the concrete. with no particles larger Definition and Units than 25 mm (1 in. age under unsteady-state conditions. Specific heats of in differential equations that define heat flow and heat stor- most rock types tend to increase up to at least 400°C (750°F).14 1. and hydrated cement pastes up to 1000°C (1830°F). tended to increase the spe. diffusivity values are usually small.0 800 50 0.9 tivity. Specific Heat of Aggregates.75 640 40 0.2 Both thermal conductivity and density are sensitive to moisture content of the concrete. In SI units. The following formulas are used to convert British to SI units. Thermal Diffusivity with values at normal temperatures ranging between 0. and Other Materials.) in size. which would to the amount of heat required to raise the same mass of water react with water. The diffusivity property is described as a measure of the fa- cific heat of the concrete.75 5.2 Those variables and conditions that influence thermal conduc- Sandstone concrete 1. These are shown in Table 8. and Specific Heat Other Materials (CRD-C 124)./h ft2 °F Cement paste 0. that can be found in the Bureau’s Con- Parameters and Values crete Manual [13]. Concrete.24 cal/g °C (Btu/lb °F). Thus.0 (either Btu/lb °F or cal/g °C).1868 103.07 0. TATRO ON THERMAL PROPERTIES 229 TABLE 5—Thermal Conductivity of Insulating TABLE 7—Typical Specific Heats of Concrete Concrete Temperature Specific Heat Density Thermal Conductivity °C °F J/kg K cal/g °C kg/m3 lb/ft3 W/m K Btu in.11 0.17 1. TABLE 6—Conductivity Values ft2/h 2. aggregates.5 66 150 1038 0. and density also affect thermal diffusivity. In approved SI base units. Investiga. EXPANDED CLAY Testing Methods 825 52 0. The ASTM Test Method The rigorous definition of specific heat is the ratio of the for Specific Heat of Liquids and Solids (D 2766) is applicable amount of heat required to raise a unit mass of the material 1° to materials.10 0. expressed in joules/kilogram K. Concrete. Procedure No. and cement pastes.24 mass of material. which is obtained from cal/g The Bureau of Reclamation uses a procedure described as °C by multiplying by 4. Increased water content. 4907. approximately 1 kg (2 lb) of the material. When calculating diffusivity from its parts. and derived thermal diffusivity values should be based on conductivities and densities that .56 3. diffusivity results as indicated in Table 7.20 1. The test requires smaller samples (up to 100 1°. Ilmenite concrete 1.26 1. specific heat.22 cility with which temperature changes take place within a cal/g °C at 4 % of mixing water by weight of concrete and 0. heat and density. such as cement and cement pastes.2 8.9 Parameters and Values 1:3 mortar 0.6 10./h ft2 °F 10 50 917 0. In those systems of units in which the heat capacity of water g in weight) and provides for selection of nonreactive cooling is 1. is tested. as thermal conductivity divided by the product of specific Specific heat varies directly with concrete temperatures. Thermal diffusivity is defined numerically cal/g °C at 7 % mixing water by weight and higher. cement. show the general range that can be expected for nor.085 2.42 0. temperature individually and together. Quartzites and other determining the thermal diffusivity of partially saturated con- siliceous aggregates exhibit high thermal expansion properties. the thermal expansion coefficient was found to increase significantly with age when the aggregate was all quartzite and less when only the fine aggregate was quartzite a Convenient when computing heat flow in large structures. most of the capillary water Diffusivity of Mass Concrete (CRD-C 37) determines diffusivity and essentially all of the absorbed water is contained within with large moist concrete cube specimens. which occurred at about 60 % relative humidity. Density kg/m3 and diffusivity values are applicable to dry environments only. crete. .017 ft2/h) at and somewhat above normal room temperatures.65 0. change in linear dimension per unit length divided by the tem- Thermal diffusivity of concrete is determined largely by perature change. from the relationship between time and the temperature Cement paste occupies only about 15 to 20 % of the con- differential between the interior and the surface of the speci- crete volume.23-m3 (8-ft3) the gel pore system.132 thermal expansion with age up to three months but a general Basalt 0. ously.1 106/°F) that Thermal Diffusivity occurred at 75 % relative humidity. which can be defined as the ated with concrete that heats or cools most easily.0012 to 0.0015 0.” While the results of both tests are applicable only Specific heat Btu/lb °F to moderate temperature ranges. Generally. The 0. The Corps of Engineers [10] Method of Test for Thermal Dif- Thermal expansion can vary widely among aggregates because fusivity of Concrete (CRD-C 36) outlines a procedure for of differences in mineralogical content. but its expansion coefficient ranges from 9 to 22 men as it cools. specimens of other sizes and up to 13 106/°C (7. which may be several times that The Corps of Engineers [10] Method of Test for Thermal of the aggregate itself.38 0. (Table 10). they are quite reliable. there is a hygrothermal expansion or contrac- mal-weight and structural lightweight concrete. A test specimen is heated in Some limestone aggregate concretes exhibit expansion values of boiling water and then transferred to a bath of running cold 5. taken from Refs 1. Within As with most construction materials.065 1. Density lb/ft3 Another standard procedure (USBR Procedure 4909) for Thus ft2/h determining thermal diffusivity can be found in Ref 13.036 Dam in Brazil. The thermal diffusivity of the concrete is determined other natural rock types usually have values between these two.0025 0. except that the dry and saturated condition in Concrete m2/h ft2/h ft2/daya m2/day values were from 65 to 80 % of the maximum value. concrete has a positive the same system of units. and for a specific concrete will decrease as the concrete tempera. expansion is the net result of two actions occurring simultane- Typical diffusivity values in Table 9. change in length is a specific heat varies directly with temperature.0061 0. and the concrete British system units mass is considered to be “moist” rather than either “dry” or Conductivity Btu/h ft2 °F per ft “saturated. Since millionths/°F) has been widely used. The first is a normal expansion typical of anhydrous and 12.059 1. One practice. A similar relationship was Type of Aggregate found for concrete. In addition. coefficient of thermal expansion.) cylinder. Quartzite 0. Parameters and Values Since aggregate comprises from 80 to 85 % of concrete. ranging from 0.190 ficient of expansion increases with decrease in the w/c. the coef- Quartz 0. in which the expansion coefficients for oven-dry and saturated conditions were half the maximum TABLE 9—Typical Thermal Diffusivity Values expansion coefficient of 11 106/°C (6. 106/°C (5 to12 106/°F).0079 0. This method is directly applicable to a 152.0016 m2/h (0.6 106/°C (3.5 the mineralogical characteristics of the coarse aggregate.016 0. Powers [14] thermal equilibrium at 38°C (100°F). and Conductivity W/m K density as determined from laboratory tests. then a water spray cools showed one aspect of the significance of the moisture content of paste specimens.by 12-in. 11.0055 0. The actual thermal ture increases. While a general value of 10 millionths/°C (5.04 0. The cooling procedure creates a moisture gradi- TABLE 8—Diffusivity Calculations ent from the surface of the specimen inward. where W J/s Thermal Expansion Definition and Units correspond to the condition of the concrete in service. Thus m2/s. however.230 TESTS AND PROPERTIES OF CONCRETE the surfaces. and water.56 0. diffusivity values complex process reflecting principally materials.013 to 0. which makes the paste sensitive to water test specimen is heated by hot air until the specimen is in movements caused by temperature changes. higher diffusivity values are associ.146 Some sources report a slight increase in the coefficient of Limestone 0. For concretes used in Ilha Solteira Expanded shale 0. Second.027 0. its ther- Tests Methods mal properties greatly influence the behavior of the concrete. solids. shapes may be accommodated.2 106/°F) at normal temperatures. is to cal- SI units culate thermal diffusivity from conductivity.060 decreasing trend thereafter.by 305-mm and concrete containing such aggregates frequently show values (6. Test methods for Specific heat J/kg K conductivity are essentially limited to an oven-dry condition. moisture. not necessarily always preferable.1 106/°F) for comparable conditions. The Bureau of tion associated with the movement of internal moisture from Reclamation [1] reported diffusivities for neat cement pastes capillaries or from gel pores. specific heat. 0 millionths/°C (2.62) 10. ture of about 38°C (100°F). the magnitude of thermal only the original dry ingredients remain.8 expansion coefficients do not lend themselves to unique millionths/°C(5.2 6.65) 14.67) 12. and the [16] showed a similar typical decrease from 9.4(7.0(8.6 4. respectively.34) 10.5 5.64) 12.7 millionths/°F) below 260°C change.4 to 6.2(5. and Monfore and Lentz complex in terms of type and mineralogical content.2(6.2 to 3.96) 15.8(7. The slowing rate of contraction at low millionths/°C (4.6(5.0(8. the Bureau of Reclamation and (and of the ice already formed) and an opposite expansion re. As stated previously. temperatures results in continued contraction of the concrete Over a number of years. c Basalt coarse aggregate and quartzite sand.90) a Results are from University of California (Berkeley) tests with Ilha Solteria (Brazil) materials. use.98) 15.1 6.18) 10.75) 9 12. Corps of Engineers have conducted thermal expansion coeffi- sulting from the formation of additional ice. d Quartzite natural sand. millionths/°C (4. are frequently and below 0°C (32°F). Some typical results are listed in Table that the coefficient continues to decrease with further 11.33) 48 13. so the thermal expansion values were 5. For expanded shale aggregate concrete.69) 62 13.0(7.2 Grand Coulee basalt 7. (°F) Quartzite days Quartzite Concreteb Basalt Concretec Mortard 4 12. Berwanger and cient tests of specimens composed of concrete mixtures that Sarker [15] found the coefficient decreased from 7.0 6.12) 17 13.9 millionths/°F) for similar temperature levels. mental conditions to which concrete is exposed have pre- and at higher temperatures starts to shrink [17]. continuing to cluded development of a standard test method for general do so up to about 500 or 600°C (930 or 1100°F). Philleo [17] reported a thermal expansion co- about 65°C (150°F) is the same for each unit temperature efficient of 8.8(5. TATRO ON THERMAL PROPERTIES 231 TABLE 10—Effect of Age on Thermal Expansiona (Units Are Millionths/K) (Millionths/°F) Units are millionths/K Approximate Age.9(7. b All natural quartzite aggregate.8 millionths/°F) and 8.7 to 5.5 .42) 10. the are smaller per unit of temperature.5 millionths/°C (4.9 5.75) 30 13.14) 10.3 to 2.5 millionths/°F) above figure. from the actual job sources. The significant effect that moisture and temperature have on grothermal volume change of the cement paste. so the coefficient of thermal expansion is a constant (500°F).5 millionths/°C (12. The values therein are applicable for an average tempera- decreases in temperatures. Physical measurement of specimen length change with TABLE 11—Thermal Expansion Coefficients for Mass Concrete Coefficient of Thermal Expansion Dam Name Aggregate Type millionths/K millionths/°F Hoover limestone and granite 9. For a given concrete mixture.7 Dworshak granite-gneiss 9.8 coefficient decreases.2 Greers Ferry quartz 12.5 Libby quartzite and argillite 11.3 Hungry Horse sandstone 11.6 7. Test Methods mal expansion property of the aggregate and a complex hy.89) 16.51) 10. the length changes 425°C (800°F).9 4.8 millionths/°F). the expansion of concrete exposed to increasing temperature is the net result of the inherent ther.9(7.4 Table Rock limestone and chert 7.7(5.2(7. There is some evidence groupings by rock type.2(5.7(7.5(7.1 have moderate to low cement factors and large-size aggregates. Up to about the behavior of concrete and the wide variety of environ- 100°C (212°F).2(5. For calcareous ag- expansion or contraction at temperatures from freezing to gregate concrete.6(8. Below the freezing point of water. the paste has achieved its natural expansion. At this level. and 22.1 Jupia (Brazil) quartzite 13.8 millionths/°F) for temperatures above The aggregates. the fineness of a cement was a major TABLE 12—Typical Compound Contribution factor in the rate and amount of heat developed during hydration. tent or controversial (the reader is referred to Lea [6] or other mal coefficient of concrete varies with moisture condition. followed by 140°F) water baths.8 had only a slight effect on followed by tricalcium silicate (C3S) and tetracalcium alumi. When the amount of The w/c in pastes has a significant influence on the this heat and the heat capacity of the paste. mortar. or concrete amount of heat generated at ages of three days and greater.4 to 0. However.4 to 0. At and below 0°C (32°F). slow decline in rate thereafter. high-early strength cements are finer than other types to the C3S 58 117 122 degree that their extra fineness works with their more active C2S 12 54 59 chemical compounds to produce earlier strength and more C3A 212 279 324 rapid release of heat.or 2-h delay. The nature and interrelationships of the chem- along the longitudinal axes of 152. ical reactions are complex. The differences over the range 0. (cal/g) or kilojoules per kilogram (kj/kg). Prior to about 1935.9 cal/g (6660 J/kg) for Type III at one year of age. when in contact ucts and hydration of the remaining cement will cease. corresponding to normal placement and curing temperatures. The finer cements presented much more surface area to to Heat of Hydration [18] be wetted and.) cylin. Although the data cal/g (4770 J/kg) for Type II (moderate-heat) cement to 15. hydration increases with temperature. and sometimes inconsis- ders are used in lieu of the length comparator.17]. alkalies.by 16-in. C4AF 69 90 102 Pozzolans are defined in ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618) as siliceous or . thereby substantially retarding Definition and Units subsequent hydration. Verbeck [19] suggests this slowing is the result of a dense Heat of Hydration hydration product created by high temperatures at early ages surrounding the cement grains. are known. about 70 % saturated. There is high w/c will tend to result in more complete hydration and in general agreement that the tricalcium aluminate (C3A) is the more heat developed. the resulting temperature rise can be calculated. More recently all cements are so finely ground that the moderate variation in fineness of different cements is no Compound 3 Day 1 Year 13 Year longer an important factor in cement hydration. The increases in heat of hydration principal calculated compounds in 0. a extended period of time. other minor compounds. the rate of cement ture condition for the tests to be made. heat liberation for Type IV (low-heat) cements but produced an noferrite (C4AF) with about equal contributions. caused more rapid and complete Heat Evolved in cal/g hydration. the reaction is exothermic. Many test procedures. apparently indicate progressive increases in the total heats gen- tioning of the specimen and control of the conditions during erated by each compound. This degradation in hydration is gener- When water is added to cement. The accelerating effect The Bureau of Reclamation has a procedure (No. being comparable texts for a comprehensive presentation on the at a minimum when saturated or oven dry and at a maximum at chemistry of cements). variable. or 14 %. the hydration product steadily Parameters and Values increases in volume. The heat liberated up to a specific sharp drop in rate of hydration occurs.and later-age laboratory molded specimens are used. strain meters embedded hydration rates. and sub- that can be found in Ref 13 for determining the linear thermal sequently the hydration process slows to a rate less than that expansion for concrete. Data reported by Verbeck [19] show that largest single compound contributor to the evolved heat. a gradually increasing hydration rate to about 6 or 8 h.8 w/c are greatest at assuming no heat loss to the surroundings. If the capillary void space is small (low w/c). cance of the regression characteristics are discussed in Ref 18.2 of a specimen alternately immersed in 5 and 40°C (40 and joules/g/min). intermediate ages but continue to be evident at up to six years. There then occurs a 1. Thus.8 cal/g (4520 J/kg). a with water. able space will become filled completely with hydration prod- pounds present in cement are anhydrous and.232 TESTS AND PROPERTIES OF CONCRETE the necessary accuracy is not a major obstacle. 4910) of high curing temperatures is limited to early ages.40 w/c cement pastes caused by an increase in w/c from 0. According to Verbeck [19]. All the com. Relative proportions of the four surement of Length Change of Hardened Cement Paste. some quite C3A and C4AF deviate from this pattern by generating a higher sophisticated. Possible causes and signifi- research studies [8.4 cured at 21°C (70°F) are given in Table 12. ally true for temperatures above 24°C (75°F) and becomes sig- and a considerable amount of heat is generated over an nificant at 52°C (125°F) and above.by 405-mm (6. Because the ther. and between 10 and time or age is measured in calories per unit mass of cement 15°C (14 and 5°F) hydration ceases. an increase in w/c from 0. values at intermediate ages for both the test may be difficult. The Corps of Engineers [10] Test Method for Coefficient of When water is first brought into contact with portland cement. and finally increase of 10. Approximate contributions of the four early) at three days of age. Mortar. but condi. Linear Thermal Expansion for Concrete (CRD-C 39) determines there is a very rapid and very brief heat evolution with the evo- the thermal coefficient of concrete by measuring length changes lution of heat reaching possibly a rate of 1 cal/g/min (4. for Type III (high- dicalcium silicate (C2S). major compounds. it is important to select the relevant mois. the avail- and reported by many authors for many years. react at various rates and at varying times. and a scribed in ASTM Specification for Apparatus for Use in Mea. and and Concrete (C 490) is used to measure length changes. have been developed in conjunction with proportion of heat after one year.4 to 0. therefore. A length comparator similar to that de. filling the capillary void space in the The hydration reactions of portland cement have been studied paste.8 ranged from 11. As with most chemical reactions. When gypsum content cause variations in both early. temperature rise tests etary products. devel. which relaxation. a minimum fineness limit admixtures to the cements. com- in a concrete construction. at later ages up to one year. TATRO ON THERMAL PROPERTIES 233 siliceous and aluminous materials that in themselves possess method is sensitive to the initial starting temperature and is little or no cementitious value but will.) cylindrical metal heat generated for a specific cement or cement blend. water-reducing admixtures will affect the rate of hydra. is that ation and subsequent cooling. and in the presence of moisture. determined the amount of heat developed the hydration of portland cement and other cementitious prod- by a 0. The Bureau of Reclamation uses Procedure No. hydration rate is very low. The procedure is not recommended for pozzolan occurs when the magnitude of these strains exceeds the tensile blends nor for slag cements in which a portion of the strain capacity of the concrete. 4911 for tion of the cement. Generally. refers to nearly adiabatic conditions existing in the interior of a massive materials added in relatively small amounts to mortar or concrete structure. The significant. and maintained in a temper- and Isberner [21] found no consistent difference in heat of ature environment corresponding to its own temperature his- hydration up to three days of age between Type I and Type IS tory for a period of 28 days. and. These volume changes may be due to heat gener- nificant to the user. Klieger cylinder that is sealed. The most widely used method for determining the heat of which keeps an electrical resistance thermometer exposed to hydration of a hydraulic cement over long periods of time is the chamber air in balance with a resistance thermometer in a by heat of solution. The magnitude of required. as well as properties of specific considerably above the portland cement value is imposed. the Type IS (a) cement-pozzolan blends may be used. insulated. There is little if any evidence that air-entraining are conducted on 318-kg (700-lb) concrete specimens sealed in admixtures influence either the rate or the total amount of 546. also classified as a pozzolan. change [24]. The procedure requires several corrections All concrete elements and structures are subject to volume and Lea [6] discusses a number of possible errors. expansion and the amount of temperature change. A minor difficulty is maintaining an concrete during mixing to modify some characteristic of the adequate insulation condition at the later stages when cement product.40 w/c cement paste by measuring the rate of heat flow ucts and from heat added by environmental factors. Cracking struction. In this procedure.by 546-mm (21 1/2. to some ex. this procedure can and will differ significantly with different cements and propri. as is used here. (b) the aggregates cements exhibited slightly to moderately lower heat genera. usually is limited to a three-day duration.by 762-mm (30. and. tent.40 is pressive. regardless of size or procedure. The advantages of this method are: cements. in finely divided form neither adiabatic nor isothermal. cement. may range in fineness clude the immediate heat of hydration (0 to 1 h). The method before processing from below to well above that of portland is well suited to determining the effects of additions and cement. but the processes are not well delineated determining temperature rise of concrete. the temperature pozzolans (sometimes used to replace a portion of cement in rise of a sample of hydrating cement weighing up to 8 g (0. the difference between Significance of Thermal Properties these values being the heat of hydration for the respective hydrating period.) In a study of portland blast-furnace slag cements. reaction between the siliceous glass in the fly ash and the lime The Corps of Engineers [10] Method of Test for Tempera- in the cement is particularly sensitive to heat. thus producing the total heat evolved by a value up to one half of the replace. creep or stress the storage temperature is standardized at 23°C (73°F). purpose. and (c) the temperature rise approximates the The term chemical admixtures. retarding. chemically react with calcium Monfore and Ost [22] developed a refined calorimeter for hydroxide at ordinary temperatures to form compounds measuring early rates of heat liberation that ideally is suited possessing cementitious properties. containers and placed in a calorimeter chamber. but this ratio will result in an understatement of the these strains is determined primarily by the coefficient of heat generated where higher ratios are encountered in con. either by internal or external forces. ASTM Test Method for Heat of Hydration well extending to the center of the concrete specimen. or flexural strains will develop. the heat of result. tensile. The temperature of the air within the chamber is maintained at the same Test Methods temperature as the specimen by automatic control equipment. When used in concrete. Raw or calcined natural for laboratory research. nearly isothermal conditions at any temperature level. Most sig. and adiabatic ture Rise in Concrete (CRD-C 38) covers a procedure for curing of concrete containing a fly ash replacement will serve determining the temperature rise in concrete under adiabatic to increase substantially the chemical activity of the fly ash conditions primarily due to heat liberated on hydration of component. any heat generated by the cement or pozzolan or both hydration of a hydraulic cement is determined by measuring results in a temperature rise in the concrete and a correspond- the heat of solution of the dry cement and the heat of solu. rated in the test. must include provisions to accommodate restrained The Carlson-Forbrich vane conduction calorimeter. The cement compounds or other similar materials. When these changes are is usually not representative of the environment experienced restrained. test sample usually remains insoluble at the end of the test The design of concrete structures. shrinkage. volume changes resulting from heat generated internally from oped prior to 1940. A standard paste w/c of 0. In this calorimeter. ing rise in chamber temperature.by 21 1/2-in. measures are implemented to minimize the . the test period usually was limited to three days. tion of a separate portion of the cement that has been partially hydrated for 7 and 28 days. but the results in- Fly ash. accelerating. Because of difficulties in controlling extraneous heat width of joints to allow movement.by 30-in. be found in Ref 13.3 mass concrete) vary widely in their composition but will reduce oz) can be held to less than 0.5°C (0. other than laboratory techniques. The test specimen is a 762. The test ment percentage figure [20]. In this procedure.9°F). As a of Hydraulic Cement (C 186). or other mechanisms. Such from the paste receptacle through cooling vanes into a water designs often include considerations for the frequency and bath. Where internal heat can be transfer. proposed for use in the prototype structure may be incorpo- tion characteristics. heat is gained from the V [ ( Ti Tad Tf ) Tenv ] K CTE (1) surrounding air. temperature depending on the member geometry and envi- ature decline as heat is dissipated. This is temperatures about 50°C (90°F) above initial concrete placing also true for large foundation mats. the heat Heat of hydration (Tad). and the Tennessee Valley Tf the final stable temperature of the concrete Authority. values for specific heat of concrete is relatively narrow. as a result of heat loss or gain. ification for Portland Cement (C 150) and ASTM Specification humidity. Aggregate adjustments and admixture usage are other Type II (C 150) 70 80 means to attain required performance with less cementitious Type III (C 150) 84 to 95 101 to 107 materials. bridge piers. This Type P (C 595) 60 70 practice reduces the peak temperature that subsequently will be attained. which . However. crete. The ultimate volume below the ambient air temperature during the normal construc- change can be conceptualized by the following simplified tion season. temperature change. and other temperature required exterior insulation to control gradients relatively large placements. discussed previously. CTE the coefficient of thermal expansion Pier footings and heavily reinforced raft foundation slabs up to 2 m (7 ft) thick and totaling 2000 m3 (2616 yd3) with ce- Heat Generation and Temperature Rise ment contents of 400 kg/m3 (675 lb/yd3) have been successfully The importance of heat generation and disposal of that heat placed with no cracking detected [5]. or is specified frequently for large concrete dams. source of heat for a concrete structure. In lieu of established specification products. Peak interior concrete has long been recognized by designers of large dams. but during the period the concrete is at a temperature below air temperature. This is usually the hydration of the cement may be imposed through ASTM Spec. tures should be monolithic and in intimate contact with the Conventional concrete structures are routinely con- foundation in order to achieve the design stress distribution structed using mixtures with cement contents in excess of 350 and stability. The use of ground granulated blast-furnace 7 Days 28 Days slag is becoming popular in certain regions to replace or supplement portland cement in mixtures to reduce heat from hy. is one generation characteristics of the cementitious materials avail. This low placing temperature reduces the rate of expression: cement hydration initially. upper limits on the heat of environmental conditions (Tenv in Eq 1). cementitious materials. Cracks that disrupt the stress pattern and de. through. and cooling rates for prevention of thermal cracking. higher pozzolan to cement ratios. depends perature rise (Tad in Eq 1) when the specific heat value for the also on the heat capacity and is measured by the thermal paste. mortar. these cementitious materials and typical ranges for Types I and Cooling of concrete by embedded cooling pipes or water III not subject to specification restriction are indicated in Table 13. restricting the amount of heat that Heat Flow causes the temperature rise is a fundamental and certain The rate at which heat flows into. this period of time is short as compared to the time the concrete is warmer than the surroundings. Type I (C 150) 63 to 88 83 to 109 dration. Peak temperatures in these concrete mix- crease stability are caused principally by thermal tensile stress tures can be as much as 36°C (65°F) above the initial placing created by concrete volume changes associated with a temper. construction practices are available to deal with temperature changes that tend to occur. A maximum placing temperature of 10°C (50°F). Type IV (C 150) 60 70 The practice of precooling concrete materials to lower the Type IS (C 595) 70 80 initial temperature of the concrete at the time of placing is Type IP (C 595) 70 80 resorted to frequently in massive concrete construction. Another common able for use in concrete are quite broad. or out of a concrete scheme for mitigating the thermal stress problem.234 TESTS AND PROPERTIES OF CONCRETE amount of heat generated. lower the initial temperatures. Precipitation. measured as linear large mass concrete dams constructed by the Bureau of Recla- length change mation. When positive control source is heat added or removed from the structure due to over temperature rise is desired. While the range of diffusivity of the concrete. While several design and ronmental conditions. The advent of Tenv the heat added or subtracted from the concrete due to roller-compacted concrete in mass concrete construction has environmental conditions resulted in mixtures with significantly lower proportions of K restraint coefficient(s) that factor the effect of struc. result of high or low ambient air temperatures. partial replacement of the cement in a mixture by natural or processed pozzolans or one of the several types of fly ashes will reduce TABLE 13—Specification Limits for Types I significantly both the hydration rate and the total amount of and II heat generated. The favorable trend toward lower peak concrete Ti the initial placing temperature of the concrete temperatures (Ti Tad in Eq 1) has allowed the use of larger Tad the adiabatic temperature rise of the concrete monolith lengths without serious consequences. and ture geometry and foundation elasticity consequently lower temperature rise. and consequently less heat generated. the Corps of Engineers. and solar gain are additional environmental for Blended Hydraulic Cements (C 595). where Waugh and Rhodes [23] have listed experiences at several V volume change of the concrete. kg/m3 (590 lb/yd3). is usually well lower the generated temperatures. structure is governed by the thermal conductivity of the con- The heat resulting from the exothermic water-cement re. with values in calories per gram. wind. Specification limits for factors that contribute to heat flow into or out of the structure. or concrete mixture is known. Upon final completion. these struc. The ease or difficulty with which the concrete undergoes action over a given time interval is expressed in terms of tem. of level. and cracking in mass con- and gravity dams. (c) mechanical the concrete and restraining material and upon the geometry properties (strength. in mathematical description of the applied heat flux (adiabatic addition to their lower dead-weight structural advantage. concrete ideally combines strength and durability with a The effects of time-dependency and temperature on modulus. fied manual computation processes to a complex modeling tion of calcium chloride or similar admixture will reduce the approach that requires finite element methods [24]. Construction parameters include: of the lift provides restraint as the concrete in the periphery of (a) lift height. because many remove much of the heat generated during hydration of the of the properties of concrete depend on the degree of hydra- cement. Such heat losses create adverse ther. then computed by combining the heat dissipation from the zontal lifts from 0. favorable thermal diffusivity property that is most effective in strength. A number of parameters may be con- first few days after the placement of the concrete when the trolled to limit cracking caused by restrained volume changes. such as elastic modulus. . with the user-supplied material model [26]. specific heat. strains. including heat generation materials. and restraint factors and the coefficient of thermal stresses by restricting lift thickness and placement frequency is expansion as shown in the formula above. modulus of elasticity.3 m (2. location and size of inclu- ditional factor that influences restraint is the relative elasticity sions such as galleries. struction schedules. equation for heat transfer. minimum strength requirements. expressed by thermal diffusivity. and tensile strain of the section. capacity). embedded pipe cooling is used frequently to crete at early times presents special problems. Volume change. Calculations are carried out in consideration of heat and energy costs. placement temperature. and capacity of the re.5 to 7. The analysis of these early-age and time-dependent prop- vent freezing of the uncombined free water in saturated new erties is complex. crete. Surface-applied insulation is cially available software is not necessarily suitable for these commonly used during cool and cold weather conditions to problems involving concrete materials and long-term con- regulate the loss of heat. (d) ambient temperature. and density. element program with a user-defined material model to the Besides being important in the dissipation of internal heat. thermal properties of concrete contribute to damping ambient The heat-transfer capability of this program uses the finite ele- cyclic variations. of hydration. maintained for long periods of time in the center of mass Equally significant is the flow of heat that can lead to concrete structures and affect mechanical properties that are accelerated cooling of the mass or excessive cooling of the sur. (b) thermal properties (coefficient of external restraint depends upon the stiffness and strength of of expansion. designers now utilize time steps to model the incremental construction of mass con- the damping effect. are ment method to numerically solve the governing differential designed without consideration for thermal insulation. crete structures. Concrete material parameters underlying lifts cause external restraint (K in Eq 1). Water is circulated through pipe coils placed at the tion of the cementitious materials. initial temperature of the water. the internal environment of frigeration-pumping plant are determined primarily from the mass concrete is affected by the hydration of the cementitious thermal properties of the concrete. Analytical Methods In exceptionally large concrete structures. essential in determining the stress/strain condition of the con- face. and (d) time-dependent deformations (shrinkage and dients within the concrete. The thermal and incremental construction analysis proce- Restraint and Volume Changes dures have been used to develop specific recommendations to Restrained volume changes that cause tensile strains are a pri.). heat transfer and structural analysis finite or the entire structure. etc. At the same time. principally arch The prediction of stresses. An ad.75 to 2. The de. Normal-weight heat-transfer analysis is used as the loading in a stress analysis.5 ft) in thickness. specific heat. Bond or These parameters can be generally classified as either material frictional forces between the concrete and the foundation or or construction parameters. Control of thermal ture. limit thermal-related cracking during construction of mass mary concern in mass concrete structures. The rate of hydration of the bottom of each new lift of concrete. and accelerating the hydration process by the addi. tensile capacity of the concrete can be quite low [31]. The Corps of Engineers adapted a mal gradients that may lead to cracking of the surface concrete general-purpose. monolith length. and creep compliance along with interactive cracking reducing the heating and cooling requirements of the building criteria for concrete are incorporated into the calculations interior. (c) concrete the lift cools due to heat transfer to its surroundings. creep. compressive strength. culverts. The warmer concrete in the interior creep or stress relaxation). Few buildings. problem of thermal analysis of mass concrete structures [25]. duration of the cooling operation. Commer- duration of protection required. ture levels that will facilitate hydration and development of and volumetric changes associated with hydration. (e) use of gree of restraint varies depending on the shape of the structure insulation. The analytical methods range from simpli- concrete. the peak temperature of the structure to its final stable tempera- shallower lifts facilitate the loss of heat. Spacing of the cooling cementitious materials is affected by the type of materials used pipes. in the form of a linear length change. (b) time between placement of lifts. TATRO ON THERMAL PROPERTIES 235 immersion and spraying are means to force an increased of the restraining structure compared to the restrained struc- environmental heat flow change. ture. is Concrete in massive structures is usually placed in hori. (f) use of cooling coils. a provide a measurable degree of insulation for the interior. Material properties necessary for in- weight aggregate concrete and foamed or cellular concretes put to the program are thermal conductivity. (section thickness. Internal restraint is caused by temperature gra. especially effective for concrete that must be cast at a high initial temperature. The degree include: (a) heat generation. The temperature-time history obtained in the ing out the cyclic air temperature variation. particularly in the concrete projects [27]. Light. and conductivity). Elevated temperatures generated by hydration are characteristics of the cement. rate of water circula. In temperature rise). and by the temperature and moisture history during the period tion. Protection is required to pre. residential or industrial. and (g) monolith geometry and where in that structure stresses are being evaluated. Newly placed concrete must be maintained at tempera. 1992. Engineer Research and Develop- [3] Lentz. A.” Technical Report SL- [6] Lea. New York. MI.. M. Washington. Army Engineer Waterways Experi- [4] Brewer. Portland Cement Association. 2.S. Vicksburg. and Hawkins. of Civil Engineers. faced with cast-in-place concrete. “Some Physical Properties of Concrete at High of thermal expansion caused by the amplitude of the ambient Temperatures. Concrete. T. Weight of Concrete. Skokie. 70. and Monfore. Feb. Properties of Concrete... P. The principal thermal property to be considered in rigid American Concrete Institute. U. National Bureau of Standards. Research Department. Waterways Experiment Station.. R. Jan. Research Depart- cyclic variations in ambient temperature. 3. IL. “Development and Imple- ratories. P. Portland sulting thermal expansion or contraction can be determined ana. and Bombich.” Bulletin 145. Proceedings.. IL. thermal stress analysis [7] Neville.. New York. 9. Conventional building construction. and Lentz. PO 5.. American Concrete In- joint grouting is contained in Ref 30. Vol. G. 15. Adding fillers or aggregate to polymers will improve [20] “Investigation of Cement-Replacement Materials. nical Report SL-87-21. Farmington Hills. 4th ed. Association.S. warrants consideration of thermal ex. I.. . D. [15] Behavior of Concrete Under Temperature Extremes. CO.S.. and Ost.” Journal. Vol. G. C. R. S. G. B. D.” or continuous structures. perature gradients during operation as well as during shutdowns. pavement design is coefficient of thermal expansion under the [16] Monfore. Oct. Monograph 43.” Corps of Engineers. Vol.” Bulletin 207. E. Sept.” Journal. Wexham Springs. A. U. “Cement Hydration Reactions at Early Ages. American Society Reports. Depending on the type of poly. F. Thermal Stress Analysis. [27] Garner. 1.” Jour- mer. For arch dams and similar massive structures containing [10] Handbook for Concrete and Cement. this thermal mismatch. May 1965. A minimum opening of this Part I. ties of Concrete. MS. U. Skokie. U. Vol. mentation of Time-Dependent Cracking Material Model for [5] Campbell-Allen. May 1966. E. April 1955. mm (0. Vicksburg. Fourth International Symposium on the Chemistry pansion coefficients as they may affect either joints or stresses.S.. Oct.. “General Relations of Heat Flow Factors to the Unit ment Station. 3. 8. and Thorne. (September 2000).. 1962. E. No. Research and and construction procedures resulting from these studies have Development Laboratories. Skokie. “Thermal Properties of Se- grouting. Improvements in material properties and new design Concrete at Very Low Temperatures. The Chemistry of Cement and Concrete. ACI Manual of Concrete Practice. “Thermal Temperatures. “Case Histories of Mass [2] Jakob. MP No. SP-25. 7. and Jones. Cement and terways Experiment Station.08 in. W. the coefficient of expansion for unfilled polymers is 6 to nal. neers.” Magazine of Concrete Research.. pp. and Isberner. Studies. A. No. New York. Skokie. 90-8. 1998. Calorimeter for Study of the Early Hydration Reactions of Portland Cements. Research and Development Labo- ratories. [19] Verbeck. July 1958. 1940. 6-123. 9th ed. W. ment Center.” Journal. Research Department. IL. G. ley. the polymer and the thickness of the repair will also affect the Research and Development Laboratories. SP-39. Bureau of Reclamation. Proceedings. Denver. Wiley. Bulletin No. W. Wiley. Portland Cement magnitude of the stresses caused by thermal incompatibility. 7. Dec.” Bulletin 90. procedures have also been used to address thermal cracking 1995.ccb. Denver. principally rigid frame [18] Verbeck. significantly reduced the extent of cracking in lock walls resur- [9] Temperature and Concrete. 9. 1971.. Report 2.S. T. Army Corps of Engineers.” Tech- Cement Association. A. 1959. H. Research and Development Labo.. Report No. “Thermal Conductivity of [28.” Journal. [24] Tatro. M.S.. U. “Laboratory Studies of Blended Cements-Portland Blast-Furnace Slag Cements. March 1963 (and subsequent discussions). Portland Cement 14 times higher than that for conventional portland cement Association. width of expansion joints is determined mainly by the amount [17] Philleo. “Thermal Conductivities of Port.29]. Detroit. M. No. “Red River Thermal 43. Concrete Thermal Studies.. 1960. MI..” Bulletin 97.. stitute..236 TESTS AND PROPERTIES OF CONCRETE In addition to new construction. E. Portland Cement Association.. A. “Control of Cracking in Con- [1] “Thermal Properties of Concrete. magnitude is required to permit successful and complete [12] Harmathy. 1958. 4th ed. Spacing with the ment. Vol. and Rhodes. DC. Cement Association.” Boulder Canyon Project Final crete Gravity Dams. No. A. Part VII. A. C. and Hammons. J. Thick repairs with stiff materials present the greatest potential [22] Monfore.” Technical Report SL-91-7. traction) should be such that joint openings of at least 1 to 2 [11] Mass Concrete.. MI. Wi. times more than that of concrete. 1973. MS. MS. G. Bombich. A. S. 1. IL. Portland Stress Analyses of Mississippi River Lock and Dams 26 (R). The modulus of elasticity of [21] Klieger. 1973. Department of the Inte- clude consideration of stresses or strains originating from tem. G. and Hess. Vol. “Physical Properties of Concrete at Very Low Temperatures. U. M.04 to 0.” Journal. 2004. lytically for introduction into the stress and strain patterns. Portland Cement Association. “The Thermal Conductiv. ONLINE AVAILABLE WORLDWIDE WEB: http://www uct of temperature drop and coefficient of expansion (or con. Elements of Heat Transfer and In. the prod. Portland temperature cycle and solar heating of the pavement slab. 2. Vicksburg.) will occur. Army Corps of Engi- joints that must be subsequently closed by grouting. New York. Z. Research Department. sulation.S. H. E. 75 pp. “An ‘Isothermal’ Conduction for failure.” Technical Report ERDC/SL TR-00-8. Norman. W. S. 1950. Vol.. July 1987. Aggregate and Concrete Down to Very Low [25] Bombich. concrete with polymer mortars. C. E. April 1991.. rior. [13] Concrete Manual. of Cement.1R. B. 132–142. Cement Association. MS. and Monfore. Bureau of Reclamation. References [23] Waugh. 1967. 1991.5 to 5 burg. B. Vicksburg. 2. American Concrete Institute.. No. Hammons. A. Detroit. Sept. but the coefficient of expansion for the 1. L. concrete. 1966. Research and Development Laboratories. A. CO. A recent example of thermal evaluation to assist in lected Masonry Unit Concrete.. UK. 1967. G. M. Part 2. Concrete Association. J. [14] Powers. W. Thermal incompatibility is a primary concern in repair of 1. No.. problems in rehabilitation of existing navigation lock walls [8] Lentz.96. U. ACI207. 1965.org. “The Physical Structure and Engineering Proper- Thermal conductivity at higher temperature levels and the re. Vol. The design of prestressed concrete reactor vessels should in. A. MS. Power Division. land Cement Paste. W. American Concrete Institute. [26] Garner.. and Allen. E. Army Engineer Waterways Experiment Station. . Vicks- polymer-aggregate combinations will still be about 1. Portland Cement Association. “Energetics of the Hydration of Portland Cement. No. Slough. Army Engineer Wa- ity of Concrete.” Journal. Vicksburg. Aug.. and Smith. Sr.S. Fryingpan-Arkasas Project. randum No.. Colorado. MI. Volume Change. June 1989.95. “Thermal Stress [31] “Effect of Restraint. Army Engineer Waterways Experiment crete Practice. M. Campbell. Nuss. “Analysis of [30] “Temperature Studies of the Roller Compacted Concrete Place- Concrete Cracking in Lock Wall Resurfacing.. D. Bureau of Reclamation. Vicksburg. Dashields Locks.” Technical Cracking of Mass Concrete. MS. and Garner.2R. S. Army Engineer Waterways Experiment Sta.. Larry tion. D. B. R. I.S.” Technical Report ments for the Modifications at Pueblo Dam. Ohio River.. Garner. U. ACI207. S. MS. M..” Technical Memo- REMR-CS-15. TATRO ON THERMAL PROPERTIES 237 [28] Norman. 2000. U. K. American Concrete Institute.. Farmington Station. Part I. [29] Hammons. PUE-D8110-FD-98-4. and Reinforcement on Analyses of Lock Wall. 1988. 2004. . December 12.” ACI Manual of Con- Report SL-89-6. C. Hills. L. The engineering properties. Mills. The per- Permeation characteristics of concrete have been studied meability is influenced by the volume. Canada (formerly Ph. Irreversible drying shrinkage may involve capil- concept of durability encompasses both porosity and perme. at the solid-to-pore interface and. Measurements of mass transfer through this measuring and characterizing the pore structure and perme- continually changing pore structure become a function of ability of concrete and in elucidating the various mechanisms testing parameters and the type of transport that is being by which they influence the properties of the concrete. 3 Assistant Professor.and air-filled voids after consolidation and final set. University of Toronto. Concrete porosity is complex. therefore. are viewed. Concordia University. The following sections will review the fundamental pe. Since publication there of pores in the concrete. 2 Professor. and ac- etration resistance. Ontario. and ionic resistance of deleterious substances (e. Canada. Department of Civil Engineering. with one of the first publications on the the pores. Water.23 Pore Structure. Douglas Hooton. Permeability.2 and Michelle R. Canada.. space between cement grains and around aggregates. and Penetration Resistance Characteristics of Concrete Nataliya Hearn. thawing and deicer scaling is controlled by the volume. Porosity of the aggregates. who original grain boundary and partly in the original water-filled made significant contributions on porosity and permeability. Most of the important properties of hardened concrete are re- vious edition ASTM STP 169C [1] under the authorship of N. In regard to the strength and elas- need to improve mechanical properties and subsequently to ticity of the concrete. lary phenomena. such as have been significant developments in modeling of penetration strength. size. Ontario. durability can be defined as the ability of a nature of the solid surface and the total surface area of the material to withstand the intended exposure conditions. Therefore. Department of Civil Engineering. Even the word “permeability” is more cautiously The initial porosity of concrete is determined by the sum of used and is frequently replaced by the more general term “pen. H. as it is not a static system and can simultaneously undergo and spacing of air voids. Civil and Environmental Engineering. Nokken3 Preface Porosity of Concrete THIS CHAPTER WAS FIRST PUBLISHED IN THE PRE. permeability.and air-filled voids after partial hydration of the Introduction cement. Hooton and R. 2. Thus. 1. [2]).D.1 R. but potentially similar permeability depending on rock type and 1 Associate Professor. pore structure and permeability. not their size or continuity. it is primarily the total volume of the ensure sufficient durability to meet the specified design life. there has been considerable interest in developing ways of ing exposure. R. depends upon the In general. the volume of mixing water. durability. lated to the quantity and the characteristics of the various types Hearn. 238 . pores that is important.” The new version of this chapter explores cidental voids due to incomplete compaction (aggregate voids the changes associated with defining and measuring concrete are discussed in Chapter 38). The pore system. it is not surprising that evolution during the hydration process and deterioration dur. Department of Building. creep. University of Windsor. the new solids (cement hydrates) occupy space partly within the This chapter is dedicated to the late Ronald H. and continuity of for over 100 years. is largely a function of changes in surface energy Smith [3]. at least that part of drying shrinkage that water permeability of concrete published in 1889 by Hyde and is reversible. and in the way diffusion are directly influenced or controlled by the relative pore structure and permeability of the cementitious systems amounts of the different types and sizes of pores.g. As the cement reacts with water. tested. Water. The resistance of concrete to freezing and ability properties of concrete. the and who was a co-author of the previous version of this chapter porosity of concrete may be classified as follows: in ASTM STP 169C. intentionally entrained air. shrinkage. D. size. The pores can exert their influence on the properties of The evolution of modern concrete has been propelled by the the concrete in various ways. Montreal. candidate at University of Toronto). The constituents of concrete—hardened cement paste (HCP) culiarities of the cementitious pore systems and mass transfer and aggregates—are characterized by widely different porosity within them. Shrinkage. Mills. 3. Microcracking as they are isolated and do not form continuous flow paths in can result from drying shrinkage. For instance. concrete.001 to 0. the mortar surrounding the coarse aggregate.93] Rock Cement Paste Permeability Coefficient.71 Limestone 3.6 3. it suffers from a number of problems when applied to the complex pore structure in cementitious systems [9–11]. indicating the possible contribution of Porosity is affected by the curing and the exposure of concrete the accidental flaws to increased permeability.66 Fine-grained marble 1. or honeycombing (large irregular a lack of hydration or due to microcracking in the HCP and in voids due to poor compaction) are less damaging than bleeding. Workability can be controlled by the quantity. This indicates that water can enter into space that other fluids can- TABLE 2—Size Distribution Pores and Cracks not and this is likely the interlayer space described by Feldman [6] and Sereda [8]. air voids in hardened concrete and the characteristics of the air- void system (void size. Potentially. between C-S-H sheets Because of the ease of the test and the wide range of effective Capillary voids 0. the resulting concrete has lower amount of air-entraining agent used. and pure cement paste. to the environment.0 1013 28 0. voids per inch of traverse. larger air voids discussed above. durability can be seen and studied using a microscope at a mag- tween about 7 % and 15 % (respectively) by volume. The cracks are formation of bleed water channels creates continuous flow larger than most capillary cavities (Table 2) and generally pro- paths and as the upward movement of the bleed water is im. Few normal nification of approximately 50 to 125 times. Liquid Displacement Techniques Those purposely entrained voids. such as by air-entrainment. Other than the tentional voids. ther- the cement matrix.1 8.3 1. Methods of Porosity Measurement The latter. When cement volume and size depending upon several factors including the paste is mixed with aggregates. The air voids may constitute from less than Hardened Concrete (C 642).03 1 to 60 mentitious systems was reported by Winslow and Diamond [5].3 1014 15 0. in particular. entrapped air. zones of low density occur below the aggregates. within the solid hydrates and often capillary pores. or it can stem from faulty construction practices allowing excessive bleeding. Both effects enhance continuity of the pores. aggregate. and duration of mixing [5]. AND PENETRATION RESISTANCE 239 TABLE 1—Comparison of Permeability and Capillary Porosity Between Well-Hydrated Cement Paste and Natural Rocks [4. peded by aggregate particles. en. cement paste contains pores size. vide continuous flow paths throughout the cement matrix [6]. 1 % to occasionally more than 10 % of the concrete volume.38 water to cement ratio of the paste (Table 1 [4]). ASTM Method for Specific Gravity. the The porosity measured using water as a displacement fluid is always higher than that using isopropanol. Absorption. ON PORE STRUCTURE. or even mercury intrusion [7] or initial helium displacement. range from a few to several hundred mi. Unfortunately. Type Porosity. .7 1011 30 0. Bleeding has more serious effects [5]. which is mixed with cement paste having 25 % to 50 % by vol. will have a final porosity be. Typical Dimensions Micro-Crack Mercury Intrusion Porosimetry of Pores (m) Dimensions (m) The early use of mercury intrusion porosimetry (MIP) for ce- Interparticle spacing 0. % w/c Sandstone 4. w/c ratio. depending dicious use of admixtures. or from voids Porosity in Hardened Concrete such as entrapped air or honeycombing due to incomplete com.8 3. and ju. Porosity decreases with time due to continuing cement hydra- paction. and surface characteristics of aggregate. A liquid (water) displacement technique for measuring total fect on the resistance of the concrete to freezing and thawing porosity of cementitious systems has been standardized in and deicer scaling. and externally applied loads. concrete consistency. this test has Entrained air bubbles 1 to 50 become very widely used to study the pore structure of con- Entrapped air voids 1000 to 3000 crete. The small air voids having a significant effect on concrete ume of pores (depending on w/c).48 Dense trap 0. % m/s (rock and paste) Porosity. and spacing Porosity Formed During Concrete Production factor) can be determined in accordance with ASTM Practice Porosity can be introduced into concrete at the time of mixing for Microscopical Determination of Air-Void Content and Para- and placing purposely to improve the concrete’s performance. are compared in Table 2. tion if the pores have a high degree of saturation. The sizes of the various pore types on the water to cementitious ratio and degree of hydration. The mal shrinkage. contributes to the difference in permeability between concrete. size distribution of fine porosity than the original cement paste. carbonation shrinkage. that have a significant ef. and Voids in crometres in size. methanol. The volume of the density aggregates have porosities greater then 5 % by volume. Continuous channels can form due to either trained air. PERMEABILITY. Adequate workability is the key to reduction of unin. HEARN ET AL. meters of the Air-Void System in Hardened Concrete (C 457).01 to 50 pore sizes that can be measured (200 m to 2 nm).5 1015 6 0. mortar. The biggest problem is with the assumption lecting the required number of points takes about 6 min and that the voids are conical in shape and decrease in diameter the standard C 457 calculations are used to calculate air-void from the surface to the core. the pore structure indeed was the case with blended cement pastes where.22]. the air voids are normally the coars- as the maximum of the dV/dP plot. Factors that govern the mass transfer of fluids include clear magnetic resonance. will not be correctly measured in the ished surfaces after different preparation steps [24. the aggregates are. which high resolution flat-bed scanners and multiple scans of pol- HCP almost certainly have. Recent work by Diamond [15] suggests that the only accurate pieces of information that can be Summary of Porosity obtained from MIP are the threshold pore radius (the radius Concrete can be visualized as consisting of a heterogeneous mix- where the pore system becomes percolated. recorded pore-size distribution. which often hydrate after the initial pore structure is es. the properties of the hardened cement paste (HCP) because in One problem with using image analysis to automate ASTM most cases. which gives numerical val. not all agreed with his interpretation [14]. These methods have been reviewed pore structure. The method of sample drying can influence pore-size dis. by comparison. (This section was adapted from a paper by Hearn and Figg lary condensation. Moreover. drying and wet- Portland cement pastes. low-angle X-ray scattering. 1. are largely research techniques [21. were postulated by Bakker [19] to result in blockages from almost 0 to 20 % or more (most commonly about 1 to 5 %).240 TESTS AND PROPERTIES OF CONCRETE (cm3) ) Fig. Excepting compaction porosity from Some authors prefer the use of the critical pore diameter. Over the life-cycle of concrete. Bet. The presence of so-called ink-bottle parameters [23]. with an internal pore volume varying tablished. developments are taking place using pores. in order to . ash. he. provides data for a particular mixture at a particular time. perature. and boundary conditions. nitrogen or water vapor adsorption. BET. as suggested by ture of components. each component having its own character- Bentz and Garboczi [16. hydration and changing solubility of the constituent materials. effectively C 457 has been in distinguishing between entrained air voids impervious. Col- contact angle [14].17]) and the total intruded porosity. plicated by changes in its pore structure due to continued ter sample preparation techniques and shape factor analysis. unlike undergoes changes due to continued hydration. and deterioration processes.25]. microscope and a motorized X-Y stage to perform a modified tributions [12] as can sample-size effects [13] and selection of point count on a contrast-enhanced polished specimen. taken poor placement practices. image analysis. or chemical gradient will affect the state of water Commercial equipment is now available which uses a digital held in the HCP. moisture content. Thus. The cement paste component usually contains both extremely These would certainly be examples of ink-bottle pores. showed that this spaces [26]. est of all pores and may constitute from less than 1 % to occa- ues smaller than the threshold diameter [18] shown in Fig. are needed to allow ASTM C 457 to be fully automated. the movement of water in HCP is com- in the paste. sionally more than 10 % of the total volume of the concrete. fine gel pores and the coarser but submicroscopic capillary man [20]. and cracks as well as voids in the aggregates. threshold. ever. resulting in damage to the pore system. using double intrusions of mercury. such as pressure. 1—Determination of total porosity. Ap- Supplementary cementing materials such as slag or fly proximately 65 to 75 % of the volume of concrete is aggregate.) lium inflow. and critical pore radii from MIP curve [33]. Transport Mechanisms in Concrete Other Methods Other methods. include capil. porosity analysis only these blockages. The adjustment to such changes. Also. the mercury forced its way through ting. the movement of water is controlled by cracking and image analysis. which are not discussed in detail. In by Diamond [9] and by Feldman [10] and. as well as continuous pores with narrow openings. How. Feld. tem- voids. istic pore dimensions. [27]. with the exception of concrete. and nu. of capillary pores without a huge reduction of total porosity. frequently heterogeneous. which automatically separate out the spherical entrained air Changes in the boundary conditions. ing rapid moisture transfer without coherent flow. PERMEABILITY. Conceptually. the energy vapor. Five primary measured on the bulk specimen. 2—Idealized model of movement of water and ions within concrete (adapted from [28]). but acts as a driving force along the pores. while liquid-assisted vapor transfer mechanisms can be defined: transfer occurs on micro-scale within the hydrate structure. In assessment of dura. uid form allows movement of dissolved. Darcian flow is a direct 3. allow- flow is driven by a static applied head. e. it is obvious that some and 100 %. pore widths are not uniform. vapor diffusion. saturated liquid flow. and at the evaporative front precipitation and crystal- kJ/kg of H2O. At relative humidities (RH) ionic diffusion are defined by Fick’s law. but all the possible transfer also has been termed wick action. through concrete driven by concentration gradients and fol- cule layers are further away from the hydration product sur. dration products. any external source of water will be initially quently the most significant transport phenomenon that deter- adsorbed onto highly hydrophilic surfaces of the cement hy. In liquid conditions. with increasing RH transport mechanisms will be more effective than others at Fig. For relative humidity between 45 ious flow mechanisms. where water [31] (Fig. at 11 % RH a sin. not only Darcian flow. saturated pore systems will pore walls transmitting the flow ahead of the meniscus at undergo tensile stresses due to expansion of the forming ice. except wick action is means of water transport must be evaluated. surface diffusion. and as part of the water movement at the initiation of bulk fluid flow in a dry pore [30]. 2). Under freezing conditions. 1. According to BET theory. has been done to compare permeation rates obtained using var- ular diffusion [31] (Fig.. is controlled through corresponding to increasing pore sizes forming menisci. very little work on the pore surfaces. AND PENETRATION RESISTANCE 241 restore thermodynamic equilibrium. At saturation. faces. lowing Fick’s law of diffusion.29]. Ionic diffusion is fre- approaching zero. The rates of the driving forces behind them. If an evaporation front exists. which includes adsorption. adsorption. The result is that a short circuit is created. so that the transfer is propelled by condensation at the Historically the effectiveness of concrete containment higher pressure side and evaporation at the lower pressure side structures was measured assuming Darcian flow. mines the rates of physical and chemical deterioration. ionic diffusion under saturated conditions. a capillary meniscus cannot be There is a considerable body of work on the measurement of sustained inside the pores. HEARN ET AL.g. 2). higher relative humidity. ON PORE STRUCTURE. ionic species driven by Figure 2 [28] shows the various transport mechanisms and the molecular concentration gradient (Fig. With the thin film of adsorbed water permeation characteristics of concrete. liquid assisted vapor transfer (film transfer). Inter-Relationship of Transport Mechanisms Below 40 to 45 % RH. and The presence of water within the cement structure in liq- 5. 4. dissolved species can migrate of surface adsorption decreases as the subsequent water mole. With increasing relative humidity. Most deterioration in aggressive exposures occurs under gle monolayer of water molecules will exist on all the hydrated conditions where water is present in a liquid form rather than surfaces [10. the mass transfer is in the form of molec. ity of the fluid and the pressure gradient. the fluid transport is controlled by the viscos- 2. when the energy of surface adsorption of the first the aqueous solution is pulled into concrete through capillary and fourth monolayers of water molecules are 1523 and 8 suction. of pores. This type of bility of concrete. 2). menisci are formed in the necks vapor diffusion. and bulk flow. however. Adsorption is not only important at lization of dissolved species can create tensile stresses in the low relative humidities. respectively. . As the humidity flux. relationship between pressure gradient and resulting flow. menisci form in the pore system. 42 5. and dissolution and precipi- tious system. controlled by viscosity 0. presence or introduction of water into the concrete’s pore sys- por. . curing and conditioning. continued hydration. for partial vapor pressures below 0.242 TESTS AND PROPERTIES OF CONCRETE Summary TABLE 3—Comparison of Mass Transfer Three stages of moisture front propagation in concrete can be of Water through Various OPC Pastes using defined: Darcian Flow Measured under High Pressure 1.24 fer is mainly due to laminar flow.0024 2. Transport Test Methods and Standards Figure 3 relates depth of penetration achieved through externally applied pressure and the size of the pore radius. or ionic species. Mixes (g/day) 2. A study by Leong compared transmission rates of tation of alkalis. from the real environment. and Aldred [36]. 3—Influence of external pressure (Pe) on penetration ( contact angle of water) [51]. dt dL Fig. in saturated or nearly-saturated material. Moreover.45. The following sections discuss pro- Nokken [33] also found that flow due to wicking was orders of cedures for measuring mass transfer in concrete and their ad- magnitude greater than in saturated permeability. Other papers vantages or disadvantages over direct measurement of satu- showing the effect of wick action are Nokken et al. rated flow. as swelling. key elements of the cementitious mi. the moisture movement is controlled by ad- Rate of Water Transmission sorption and surface diffusion. moisture transfer is achieved through vapor diffusion and Darcian Permeability Wick action capillary tension. The complexity of the pore structure of concrete. Gas the smaller the pore radius the greater the pressure required to achieve a given depth of penetration. For low permeability materials the Methods of measuring multi-phase moisture flux in con- effect of wick action on liquid ingress was 1000 times greater crete suffer from variability or simplistic modeling divorced than transmission driven by pressure head as shown in Table 3. creates difficulties in numerical analysis even when only one flow mechanism is examined.5 1. Thus. and 0. before a meniscus 10 MPa (1450psi) and by Wick Action [32] is formed. and the porous solid is often characterized by the illary suction become less significant and transmission may intrinsic permeability coefficient. Flow into unsaturated concrete may be supported by all of the preceding mechanisms. dq g dh KA (1) crostructure must be examined. feld et al. its variation with mix proportions. In concrete.90 and defined by Darcy’s law. these rates of transmission are tem obscures analysis even further. become diffusion controlled. [34]. where both Darcian flow and cap- Darcy’s law. In concrete.3 0. water va. K. moisture trans- 0.32 3. [35]. Buen. the trans- Gas Flow mission rates are further complicated.4 0.041 5. for partial vapor pressures between 0. due to possible discon- Pressure-induced gas flow through a sample appears to follow tinuity of the pore structure. OPC and blended pastes [32]. In order to better comprehend the interaction between transmission rates and microstructural characteristics. the transmitting a unit mass per unit time of liquid water. Hong and Hooton [37] showed that cyclic absorption will also accelerate ingress of chlorides. because of processes such a function of the microstructural characteristics of the cementi.45 and close to 1. Ca(OH)2 CO2 CaCO3 H2O Equation 1 incorporates Carman’s findings [38] (which show an inverse relationship between the rate of flow and viscosity The hydrates (C-S-H) are also affected once the pH drops and of the permeant) with Darcy’s equation. because of changes to the microstructure. This test is most useful for rapid is an effective barrier to gas flow. Dp. and this area. the so-called “moisture dome test. ing the rate of drying of a sample. rated and unsaturated flow take place. it can al. ASTM subcommittee F06. Water-Vapor Diffusion ter the microstructure and cause extensive cracking. Pe- riodic weighing of the sample and the desiccant monitors the b Ka K 1 Pm (2) movement of moisture through the sample. Carbon dioxide initially reacts with calcium viscosity of the permeant (Pa s). however. a nitrogen stream is initially maintained at equal Kv vapor diffusion coefficient (m/s). and of oxygen is applied at the upstream face and the resultant gas dp/dx vapor pressure gradient (m/m). to nearly saturated.40]. under which both satu- Ka gas permeability (m2). This test. A slight over-pressure A cross-sectional area (m2). PERMEABILITY. The rate of water vapor diffusion is governed by the Bamforth [42] derived a relationship. or by creating a vapor pres- meabilities. are common in concrete K actual intrinsic permeability (m2). of course. face. transfer is detected by means of a gas chromatograph on the downstream side [43]. The altera. gas permeability is sure gradient and then monitoring moisture transfer [31]. and the carbonation front is often taken to pendent of the properties of the permeant. ON PORE STRUCTURE. water retaining structures. controlled humidity environment. capillary action. HEARN ET AL. He proposed downstream side of the specimen and storing the whole in a the following relationship between gas and liquid permeabili. and has also been used to predict carbonation rates and Standard Test Method for Measuring Moisture Vapor Emission reinforcement corrosion rates.40 dealing with flooring developed cretes. Q KvAdp/dx (3) Gas Diffusion where Gas diffusion measures the concentration of a chosen gas (usually oxygen) across the sample. For materials of low porosity. The diffusion coefficient. The always greater than that of water. is calculated using Eq 3. The common isopropanol [12. (F 1869). The moisture and the possible onset of corrosion in reinforcing steel. and vapor diffusion is well known [30]. of saturated flow. and hydroxide as shown below: K intrinsic permeability coefficient (m2). which . This technique is useful for dense con. because water not exclusively carbonation. Water-vapor diffusion refers to the movement of water vapor tion of pore structure and flow can be minimized by drying across the sample driven by a difference in partial pressure be- techniques such as freeze-drying or solvent replacement using tween the upstream and downstream faces. cium chloride is placed inside a known area of concrete. for concrete.81 m/s2). The limitations discussed with Rate of Concrete Subfloor Using Anhydrous Calcium Chloride regard to gas flow also apply to gas diffusion testing and inter. AND PENETRATION RESISTANCE 243 where Depth of Carbonation Depth of carbonation is taken as a measure of the rate of re- density of the permeant (kg/m3).39. breaks down into hydrous silica and calcium carbonate. that accompany drying. This discrepancy was attrib. Estimating the wetted surface on-site evaluation where the depth of acidity together with the area and calculating the hydraulic mean radius can estimate the age of the structure is used to estimate the rate of carbonation permeable porosity at various moisture levels. but only if the mois. Not much research has been done in b constant (m). due to exposure at the upstream Q vapor transport rate (m3/s). using Eq 2. some doubt regarding the application of men and can be described by Fick’s first law: Eq 2 to cementitious materials. detects the advance of controlled. vapor pressure gradient and the microstructure of the speci- There is. into the concrete. latter is achieved by using a dry cup filled with desiccant on the uted by Klinkenberg [41] to the gas-slippage effect. including cracking. A container of cal- same effect as a solid barrier. as in ASTM Standard Test ties for a porous medium: Methods for Water Vapor Transmission of Materials (E 96). As the moisture content may vary from surface dry a pH change and indicates acidity from all possible sources. must be constant throughout the specimen. methods of testing water vapor diffusion are either by measur- There is no direct relationship between gas and water per. action between carbon dioxide from the atmosphere and the g acceleration due to gravity (9. however. especially for thick samples. The intrinsic perme.” for measurement pretation because water in a partially saturated system has the of moisture loss from a concrete surface. Conditioning of the test samples to a constant moisture content Water is a lengthy process. These conditions. The ability coefficient thus depends only on the microstructural rate of reaction depends on the diffusion of carbon dioxide properties of the porous medium and is supposed to be inde. based on Fick’s law. of a phenolphthalein indicator onto the freshly exposed con- ture condition of the concrete sample is known and carefully crete cross section. Typically. so will intrinsic permeability. level. but the intractability of analyzing the combined effect Pm mean pressure (m). Though oven drying is a quick and uniform method of conditioning. The rate of water vapor transmission has its most practical application where when the sample is in contact with water on one side and a desiccant on the other. cement paste. pressure on either side of the specimen. be revealed by the color change resulting from the application The test can be rapid and reproducible. Floor Slabs Using in situ Probes (F 2170). filled with water. This is followed by sealing the samples in. however. and the volume of absorbed water is calculated at this “nick Absorption and Rate of Absorption point” in the curve. which has been discontinued. and compacted concrete. The test face is exposed to water and mary can be found in Emerson [50]). The advantage of this test is that absorption is one- illary absorption rather than either water permeability or ion dimensional. The C09. then the rate of moisture emit. involves subjecting one end of the unsaturated and provides a method to evaluate the rate of absorption of concrete to a pressure head. The new ASTM Test Method for Water Penetration Measurement of Rate of Absorption of Water by Hydraulic. In British Standard 1881. that committee The water uptake in volume per unit of surface area is has also developed a relative humidity test. concrete mixture. In penetration tests . volume of water entering the sample. 30. Although in all these [47–49]. The difference in absorptiv. also give an indication of mean pore radius Gravity. the are small compared to that of capillary tension. the sorptivity varies a great devices exist. There are sides of the specimen are sealed and the top face is fitted with many equations used to model water penetration (a good sum- a loose fitting plastic film. r mean pore radius (m). for example. or a combination thereof.66 subcommittee is currently considering an in- ther measured at a single.46]. the rate of absorption drops off sharply. the calcium chloride desiccant. and in Australia: AS1342). In ASTM C 1151. Absorption is ei. the change in mass is measured at various time intervals from ted from the concrete is measured by the increase in mass of 1 min up to 192 h. rate-of-absorption test suitable for evaluation of the effects of tration. the differences in the test limits and procedures create consid- r P dt 0 (4) erable variation in sorptivity measurements [44]. where entrapped air voids do not get d depth of penetration (m). After several hours. P0 atmospheric pressure (Pa). fects sorptivity measurements [30. In ASTM C 642. in poorly A area of penetration (m2). Slices of concrete cylinders or cores is achieved either by measuring the volume of water entering are conditioned at 80 % RH and 50°C for three days either in the sample or by splitting open the cylinder and measuring the a humidity-controlled chamber. from a splitting test contact of one surface with water. rate of absorption (by change in mass). The major difficulty in the assessment of absorption tests v porosity is the determination of the initial moisture condition. Absorption. a closed reservoir is sealed onto 1000 M v (5) the concrete surface. The Concrete Society [43] in their ASTM Test Method for Evaluating the Effectiveness of Materi. Moreover. A secondary rate of absorption at times Most concrete is only partly saturated and the initial ingress of beyond the nick points is also calculated. Then. the usual external hydraulic forces in structures side closed containers at 23°C for another 15 days. The water penetration test. arbitrary time or by measuring the situ rate of absorption test. besides measuring degree of Concrete. based on the work of DeSouza et al. by cap. and porosity of the sample. the absorptivity of 10-by-25-mm. water and dissolved salts is dominated. M gain in mass (g). molded t time (s). These tests measure the weight gain of a averaged over the thickness of the specimen. This makes the sample. at least initially. and ity between the top. on Bulk Flow. The reservoir is flooded with water and Ad sealed except for an open-ended capillary tube that is used to monitor the volume of surface absorption after 10. A wide variety of water absorption tests on concrete measured. (m). BS1881 Test for Determining the Initial Surface Absorption of Capillary absorption tests. which af. ASTM Standard plotted against the square root of time. by either complete immer. assessing and correcting for in-situ moisture con- deal between test methods. The absorption tests have been tents is the most important issue with respect to interpreting standardized in many countries (for example. standardized in Germany as the Cement Concretes (C 1558-04) addresses some of these issues DIN 1048 test. unlike other tests where rates of transport are have been developed. 60. and ASTM Test Method for tion of mean pore radius and porosity Measurement of Rate of Absorption of Water by Hydraulic Ce- 4 ment Concretes (C 1585). The measure of water penetration concrete in the laboratory.45. depth of pene. sorbed to the dry weight is the absorption. summary has provided the following equations for determina- als for Curing Concrete (C 1151). where men is measured after a 48 h immersion or after such immersion followed by 5 h in boiling water. exposing only one face to water. and where 120 min. As discussed earlier in the section potassium bromide. diameter. which also makes use of in situ moisture data to cor- tests the absorption process is proportional to the square root rect the measured absorptions. or by drying in an oven with average depth of discoloration (due to wetting) taken as equal the samples sealed in a desiccator over a saturated solution of to the depth of penetration. viscosity of water (Pa s). the water absorbed by an oven-dried speci. the initial Test Method for Determining Relative Humidity in Concrete rate of absorption is plotted as the initial slope of this graph. and Voids in Hardened Concrete (C 642). curing on a surface in addition to assessing the quality of the sion of dry samples in water. More recently. The ratio of the water ab. in Great Britain: in-situ test results [46]. Absorption from a single face of interest can be diffusion. the absorption may be lower than for a thoroughly compacted sample. While a number of commercial of time over a specified time period. surface is taken as a measure of the effectiveness of curing.244 TESTS AND PROPERTIES OF CONCRETE is sealed from the environment. or spraying the specimen surface with water. methanol-dried cores are measured after 60 s of d depth of penetration. cured surface and the bottom. From this. in North America: ASTM Test Method for Specific imperviousness. the equations 2. The conditioning process for saturated flow (water r Pe Pc saturation of the sample) does not damage the existing 1/2 B (6) 2 microstructure. HEARN ET AL. Saturated flow has only one fluid transport mechanism— must be modified. If a concrete surface is not saturated at the time it is ex- dq 1 . sulfate Pressure-induced water flow through a saturated sample ions can also be of relevance for ionic diffusion as well as other follows Darcy’s law. While concrete can be penetrated by many aggressive ions. The major disadvantages of saturated water permeability where B is equivalent to sorptivity (S). Establishing equilibrium flow conditions [60]. several in-situ tests utilize water 1. PERMEABILITY. mechanisms of ionic transport. main concern with ionic diffusion is chloride ion migration into concrete. absorption. as defined by Hall [52]. However. The water penetration results are often complicated by the initial moisture state of the specimen and the nonuniformity of moisture distribution. because of the extent of reinforcement corro- Saturated Flow sion damage due to deicing and marine salts. of concrete. 3. Figg’s tests [53] and several modified 3. Decrease in flow with the progress of the test (the self-seal- versions (see Refs [54. Reinhardt [51] presented the combined flow of water through voids—while unsaturated flow effects of capillary tension (Pc) and hydraulic pressure (Pe) on encompasses diffusion. for estimating the quality 2. the modifying the pore size distribution of the matrix. penetration or absorption. the microstructural char- Ionic Diffusion and Chloride Ingress acteristics in concrete change with the introduction of water. AND PENETRATION RESISTANCE 245 where artificially high pressures are applied. capillary. Potential problems with saturation of specimens [57–59].55]). ON PORE STRUCTURE. ing phenomenon [61]). testing are: Besides the DIN 1048 test. and satu- the fluid penetration coefficient (B). or both. in the following form rated flows. Moreover. for example. h posed to ionic solutions. This is a very common mechanism where of chloride ingress. the cap- A cross-sectional area of the sample (m3) illarity will continue to absorb chlorides. concentrating them . then capillary tension will rapidly K (7) dt A L draw the solutions into the surface layer until the surface layer becomes saturated. If the concrete surface is exposed to wetting and drying cy- dq/dt rate of flow (m3/s) cles and is intermittently exposed to chloride solutions. Wick action can occur where relatively thin structural elements are exposed on one side to ionic solutions and on k 9. parking deck soffits or the inside of tunnel liners or for slabs- The intrinsic permeability is solely a function of the pore struc. The magnitude of the concentration gradient is the where driving force for diffusion as solutions seek to come to an equi- density of the permeant (kg/m3). For the de-icing salt exposure. zones in marine structures. This will result in an in- One of the major objections of the saturated water flow creased ionic concentration inside the concrete at the depth test is that the boundary conditions are not representative of of evaporation. alone.81 m/s2).g. Saturated flow gives intrinsic permeability as defined by rate of chloride ingress beyond that predicted by diffusion Darcy’s law. The effect of wick action will be to increase the usual concrete environment. causing the ionic solutions to be drawn toward the ture. K. and at least one surface is exposed to a chloride solution (for example). The measurement of the out. for example. This is the scenario for bridge or park- flow enables the determination of the permeability coefficient. Hearn. For water at 23°C. and is constant then the surface concentration builds up rapidly. or the intrinsic permeability coefficient. ing decks subject to de-icer salts or for the tidal and splash k (described in Eq 2). For tunnel linings and other elements under hydrostatic The major attractions of this test are: head. In viscosity (Pa s) the case of de-icing salts. which are related by: When concrete is saturated. . on-grade). air-exposed surface and evaporated. it has drawn consid. librium concentration. and Sosoro [56]. the chloride concentration in the outer convection zone will Saturated water permeability testing involves subjecting the build up during the winter and reduce due to rain washout in sample to a pressure gradient. When the external source of chlorides g gravitational acceleration (9. the surface concentration will build up slowly over many years and only then will the surface con- so that conversion factors can be calculated for the various flu. Even so. not of the permeating fluid.h drop in hydraulic head across the sample (m) and building up an interior “surface” concentration at the L thickness of specimen (m) depth of the convection zone. [3] to Reinhardt. then a chloride concentration gradient exists be- K k (8) g tween the surface and the pore solutions and pure diffusion will result. centration become constant.. warmer weather [62]. ids at various temperatures. both surfaces are inundated.75 106K (9) the other to air at a relative humidity less than 100 % (e. pressure-driven fluid movement will also increase the 1. the rate of chloride ingress beyond that predicted by diffu- erable attention over the past century (from Hyde and Smith sion alone [63]. [66]. The tops of the slabs are then ponded with a 3 % NaCl solution. fusion coefficient is one where only the free chlorides in the No standard method of analyzing the results is given but pores are measured with depth. An effective chloride dif. The ments over the previous method are provided. NaCl solution for at least 35 days. and an equation is fitted of such a migration test method are given by McGrath and to the chloride concentration versus depth and using Eq 10. m. Dc diffusion coefficient (m2/s). concrete slabs parameters for chloride service-life prediction models [65]. is also often used in service-life prediction models. but this chloride exposure and the length of chloride ponding are is not always consistent with a lower integrated chloride con- important parameters when Da values are calculated. has been the concrete at that age of test. option for precision grinding of millimetre-thick layers and use typically with values between 0 and 1 (see Eq 11). including the ef- taken at 28 days) fects of all dissolved ions.246 TESTS AND PROPERTIES OF CONCRETE Ionic Diffusion Tests Other methods involve the use of a concrete slice as a mem- Chloride diffusion of in-situ concrete is usually determined by brane between two salt solutions. most commonly measured some have adopted an integrated chloride content (the sum of using steady-state migration tests. . often taking several weeks. centration and diffusion coefficient are constant with time. consuming. The sides of the slab are sealed.8N Planck equation to determine migration-diffusion coefficients. These values can be used as input AASHTO T259 chloride ponding test. are cast and moist-cured for 14 days. Dc. dc/dx concentration gradient of the ion (mol/m3/m). a log-log Ion into Concrete by Ponding. Thomas and Bamforth [67]. The driving force is provided by 60-V of direct D(t) diffusion coefficient at time t. The sample is then profile A review of related issues is given by Andrade [72] and details ground inward from the exposed face. numerous improve- plot of bulk diffusion versus age should yield a straight line.71]. then titrated to determine the chloride content. and This solution to Fick’s second law assumes both surface con. ASTM Test Method for Determining the Apparent Chloride However. high chloride content but the chlorides did not penetrate illary pore network is altered. Once steady state has been estab- profile in order to first establish an estimate of the surface lished. after fitting an equation to the chloride concentration side [70. so an electric potential is often simultaneously ap- sion (C 1556-03) is based on the Nordtest NT Build 443 [64]. Cs used to calculate an effective ionic diffusion coefficient C(x. where Cs surface chloride concentration (%). [69]. In this test. the value of its comparing concretes where in one case. in acid. This provides a chloride bulk diffusion coefficient for the Another test. known as the Rapid Chloride Permeabil- ity Test. the conductivity of the saturated sample. cient.t) chloride concentration at depth x (m) at age t (years). the chloride content multiplied by thickness of the slice for all Another issue is that as a particular concrete matures. It involves measurement of the total charge where passed in 6 h across a sample sandwiched between NaOH and NaCl solutions. of penetration depth as a figure of merit. chloride binding midity. such static or steady state tests are very time Diffusion Coefficient of Cementitious Mixtures by Bulk Diffu. slices from concrete cylinders or cores are sealed termed migration tests and require the use of the Nernst- except on one face. From this. Hooton [73]. used by highway agencies. including the slope of this line can be taken as the time-dependent coefficient. thin slice of paste or mortar. Since the total chloride content (free plus bound chlo. and Nokken et al. is often calculated by using Crank’s solution (Eq 10) by the analyses of the ion concentration change on the lower to Fick’s second law. At the end of this exposure. this bulk diffusion typically for 90 days. but the bot- coefficient is an apparent chloride diffusion coefficient. then immersed in a 2. The diffusion coeffi. concentration gradient of a salt as a driving potential across a ing a chloride ion concentration profile. tent. Stanish and trated deeper but the concentrations in each slice are not as Thomas [68]. For tom of the slab is exposed to laboratory air at 50 % relative hu- use of this value in service-life modeling. then air-dried for 14 days. The effect of this was considered deeper. These have been this test. tref (often test. Having a lower depth of penetration is desirable. Recently. Test Method for Determining the Penetration of Chloride 1556 test on a concrete at a series of ages. In this D(ref) diffusion coefficient at a reference time. the outer slice has a apparent diffusion coefficient will reduce with age as the cap. current applied between the two sides of the sample.t) Cs [1 erf (x/2 D ) ct (10) dc Q Dc (12) dx where C(x. AASHTO T277 and also ASTM Method for Electrical tref m Indication of Concrete’s Ability to Resist Chloride Ion Pene- D(t) Dref (11) tration (C 1202). is measured without emphasis on a m constant (slope of line) particular ion. due the slices). has become widely used in North America t and abroad. and erf error function (from standard tables). Each slice is crushed and digested to penetrate further into the concrete. One of these methods uses the analyzing a concrete core at successive depths. relative to another case where the chloride has pene- by Maage et al. a version of T259 was adopted as ASTM C 1543- This effect can be evaluated by performing the ASTM C 02. vacuum saturated. cores are taken and sliced needs to be considered since not all of the chlorides will be free at about 10–12 mm intervals. Q mass transport rate (mol/m2s). the age at high. A rapid method. Therefore. In this test. rides) is measured at each depth in this test. Fick’s first law (Eq 12) can be chloride concentration. The rate of diffusion is monitored cient. This value has been found to be misleading [74] in to reasons including continued hydration. In plied to accelerate the rate of chloride ingress. thus establish. This coeffi. The ce- come.66 subcommittee is conducting tests to develop such a sim. Above about log1012 K 2. porosity. it is likely that this test will casting. vantage that the results are not influenced by the pore fluid conductivity. the other considers viscous rent flows will result in heating of the sample and solutions drag of moving fluid on a particle. such as silt and that some of the lack of correlation found by others is in and clay. sis. tended to hardened cement paste since it is a porous solid with plified procedure. Many tests that directly measure transport properties require specialized equipment and long periods of time to p (1 C ) 0. permeability experiments were America and internationally. [86] took the second approach. The experiments were designed to minimize variations remain as an index test for permeability for many years to due to osmotic pressure by using leached specimens. In spite of its shortcomings. The depth of penetration is measured by splitting the specimens open after the test and spraying the C fracture surfaces with a 0. Four water-to-cement based on the procedure developed by Tang and Nilsson [80] ratio pastes were tested at four different temperatures. the capillary pores become disconnected to as the Rapid Chloride Permeability Test. In the course of or inverse-resistivity test. the capillary pore system presents the pathway for the ingress ous researchers have pointed this out [75–77]. noted in the standard. curing water placed on top of the cement paste at the time of fore. in spite of other developments. it does not measure and the permeability is controlled by the “gel pores. A nonsteady state migration-diffusion value can be cal- 539 C 0.. The alkali was leached into the highway bridges.” Given that the “permeability” or “chloride diffusion” of concrete. dependent on initial current reading to calculate a resistivity value. calcium nitrate corrosion inhibitors) and this is point of achieving discontinuity is of little value.. The particle concentration and temperature. saturated water permeability). admixtures which continuous capillary pore system is highly desirable. How. this nonsteady state migration test involves inverse of the hydraulic radius to a function of permeability. p. Powers result in large changes in conductivity are unfairly judged by [84] also suggests that moist curing of field concrete past the this test (e. Predicting Chloride Penetration of Hydraulic C particle concentration. Hooton. PERMEABILITY. it has leagues “observed that the degree of permeability was con- also been criticized. and in spite of it often being referred further hydration. at complete hydration is given by: lar interest. and Thomas [81.3 T 1C culated from the depth of penetration together with knowledge of the magnitude and period of the applied potential. The theories of permeability in porous media arise from Others have criticized it for apparent lack of relationship two schools of thought. AND PENETRATION RESISTANCE 247 While this test has become widely used as an index of con. the AgNO3 will covert to AgCl2 (13) and turn white in color. it follows that the formation of a dis- flow is a function of pore fluid conductivity. do relate to salt ponding data [74. volume of specimen. tribution of small particles using sedimentation. i.g. ASTM C 1202 test is found in numerous laboratories in North To define discontinuity. Because current of deleterious substances. the relationship becomes: nitrite corrosion inhibitor.. One is the application of the Poiseuille- with salt ponding test data [78] and for the fact that high cur. the large part due to poor sampling and analysis procedures used Stoke’s velocity decreases. ment is described as ultrafine with a Blaine of 8000 cm2/g. Fine An alternate rapid index test to ASTM C 1202 for chloride cement hydrated for an extended period led to completely hy- penetration resistance of concrete is a rapid migration test drated specimens free of capillary pores. volume of solids per unit Cement Concrete. leading to the following relationship: plied DC potential.79]. it is easy to envisage substitution of the ASTM from tapioca suspended in oil. based on the development work of Stanish. Numer. The theory was ex- C09.. was fit to the four data points at each temperature relating the Similar to C 1202. Test as TP164-03. Hagen law (used by Hughes [85]). AASHTO has adopted a version of this Rapid Migration K coefficient of permeability in cm/s. leached of all alkalis [83]. measurement of the depth of chloride ingress under an ap. it is simply a conductivity trolled mainly by the capillary porosity” [83]. complete (e. and continues to be specified for performed on cement paste specimens approximately 600 days evaluating the quality of supplied and in-place concrete for old.097 1C (14) and Permeability Given that porosity of the gel pores is 26 %.2 2. particle connections involving a small fraction of the surface. Steinour [87] determined a function in salt ponding tests (i.g. others have found that ASTM C 1202 test data.) As the concentration of particles increases. Powers and his coworkers during the 6 h test.26 (15) . the capillary The relationship between porosity and transport is of particu. for the variation in particle concentration using data derived Regardless.1N AgNO3 solution.e. after over 20 years of use. Fundamentally. (Stoke’s law is also used when determining particle size dis- rected for temperature.e. This makes it applicable to concrete with calcium At 27°C.07N chloride concentration. A line and recently adopted as a Nordtest standard (NT Build 492). which uses Stoke’s law as a ba- ever. Powers and col- crete quality by highway and other specifying agencies. if cor.82]. HEARN ET AL. ON PORE STRUCTURE. dure and gives a very similar ranking of results. tunnel liners. There. The nonchloride areas will turn brown. Relationship Between Porosity log1012 K C (1 C)2 C 4. The actual function used is pro- C 1202 test with a simpler resistivity test or simply to take the portional to the inverse of the hydraulic radius. raising the measured conductivity. () viscosity of the fluid [poises] as a function of tempera- The test is of similar rapidity to the ASTM C 1202 proce- ture (°C). but has the ad- T temperature (K ). and parking structures.13154 log() (1 C )2 0. AASHTO T259) [74]. Based on where this. the and can be thought of as a collection of particles. Although the chemistry and fineness of Figure 4 shows Eq 16 plotted with data from Powers et al.70. study showing that capillary discontinuity will not occur with ing Eq 14 for 18°C. The paste was produced using cement with a data to an equation for the permeability based on the assump- fineness of 1800 cm2/g Wagner. a dashed line is shown in Fig. The highest permeability cor.74 p (0. Figure 5 shows the results of this along it. 5—Discontinuity of concrete [89] compared with Powers [83]. The particle concentration was calculated by non- log 0.64 water to cement ratio can be capillaries rests on conformity or lack of conformity of the seen in the figure. it will continue to move mentary cementing materials. 4 solv. It can be seen that temperature differences water to cement ratio greater than approximately 0. . tion that resistance to flow through a granular body is deter- responds to the permeability calculated from bleeding rates.74 0. However. low the law. the terminal points for the paste made with the coarser cement would likely lie on (16) the line. it is assumed that continuous capillary pores exist. are minimal.26 p specimens been leached of all alkalis. When the flow through the paste does not fol- point on the 24th day after casting. Later permeability meas. cement has changed significantly since the time of Powers.097 0. The line defines discontinuity. the [84] for cement pastes of various water to cement ratios (shown discontinuity relationship was recently validated in concrete by in the figure). Once the paste has Nokken and Hooton [89] using modern cements and supple- hydrated enough to reach this line. urements yielded points slightly below the line signifying The assumption that no continuous capillary pores existed was Fig.26 p)2 12 evaporable water content (hydration) of pastes. Solving for K (in cm/s) in terms of p yields: capillary discontinuity. For comparison.74 p 4. Mercury intrusion porosimetry only became available commercially after the work of Powers [88].248 TESTS AND PROPERTIES OF CONCRETE Fig. The decrease in porosity and permeability with “The conclusion about continuity or lack of continuity of time for a cement paste with 0. mined by viscous drags on the individual particles composing The next point was established on the fourth day and the final that body” [83]. alkali remaining in the specimens accounted for the somewhat lesser permeability.2 2. 4—Definition of discontinuity. Had the K 10exp 0. 568[1 (C /1 C )] (17) these samples. by the surface forces and the Darcian flow becomes less effec- ments of permeability with time for pastes at two water to tive as a mass transfer mechanism. complete discontinuity of the pore system is The degree of hydration. from low to high porosity and the 0. while w/c 0. various flow mechanisms have different rates Approximate degree W/C Time Required of hydration required of transmission in a singular pore structure. Table 5 classifies the 0. In this system. In this system. The presence of continuous capillaries would not flow would provide the highest transmission rates.65 w/c 0. and 17 days.3. are well cured. resulting in the following relationship: showed that the time required to reach zero flow conditions for w/c 0. required to achieve measurable flow.00 levels of hydration.00 Table 5 represent increasing cementitious content and/or 0.45 7 days 0.45 to continuity of pastes under standard laboratory conditions. curing regime.64 and 0.5 had tion for autogenous shrinkage that can be thought of as achiev.70 Impossible 1. 0.001–0. Under these conditions.40 3 days 0. and 0.45 to 0. permeability of 17 2 1016 m/s and 780 150 1016 ing discontinuity [17].4 and 0.15 w/c (C /1 C ) 1 MPa were 2.50 samples are exactly alike. Subsequent tests on 0. the pressure-induced absorption. and concrete pore structures undergo dynamic changes. so that ( 37 %) are similar and diverge at 60 % hydration.) In concrete.45 w/c Continuous Large Medium Small pore radius Pore sizes (nm) 10–100 0. Larger cement particle size distribution m/s.7) and/or low levels of hydration. Higher pressures are cement ratios (0. respectively. most of the water is free and unaffected by the surface forces of the hydration products.3 had achieved zero flow conditions (i..70 1 year 1. Work done by Leong [32] nuity.0 3. capillaries.50 14 days 0.45. ability less than 1 1016 m/s). Darcian permeability of gel has been determined TABLE 5—Three Cementitious Systems Based on the Porosity/Permeation models [27] System 1 System 2 System 3 w/c 0. perme- Geiker [90] showed that there is a critical degree of hydra. using a higher pressure of 13 MPa.71) with the line signifying disconti. requires a larger degree of hydration to achieve depercolation High performance cementitious systems have w/c ratio [91].60 to categorize concrete into three groups. The 0.70 porosity-permeation system. or maturity. pore structure. The discontinuity of the pore struc- verified by confirming that the solid surface area calculated by ture is never achieved. AND PENETRATION RESISTANCE 249 Characterizing Pore Systems TABLE 4—Time Required to Achieve a (This section was largely taken from a paper by Hearn and Figg Discontinuous Pore Structure [83] [27]. which permeability is a function of the transmission through gel seems to indicate that pore continuity is the overriding factor and tortuous pathways through small poorly connected at early ages. The three systems in 0.65. and often incorporate supple- Winslow and Liu [92] found that pore size distributions of mentary cementing materials. under a proper is certainly of lower C3S and coarse particle size distribution). ON PORE STRUCTURE. a broad classification was developed 0. 5. below 0. showed that only w/c 0. Table 4 lists the estimated time required to achieve dis.60 6 months 0.70 0. As no two concrete 0. The most porous system corresponds to high w/c ratios (above w/c 0.95 corresponding transfer mechanisms. respectively. The existing porosity (as determined by the initial w/c) is time was based on hydration of ordinary Type I cement (which divided into a multitude of finer pores and.e. the water is affected discontinuity was estimated from the intersection of measure. As the the permeability relationship matched that measured by water internal flow paths are unobstructed. the pore struc- the paste. and concrete at lower degrees of hydration ture is mostly that of the internal C-S-H gel porosity. where high porosity is compounded by high connectivity.1 Controlling Darcian flow Capillary suction Vapor diffusion transmission Ionic diffusion Evaporation mechanisms Ionic diffusion . mortar. through the produce the same result. as discussed by Powers (Table 4). Most structural concretes are cast at w/c ratios of 0.5 hardened cement pastes tested at 1.4.1–10 0. PERMEABILITY. required to achieve possible (Table 4). HEARN ET AL. Rate of absorption measurements. Mindess and J.. wick action and. Cement Paste as Deduced from Sorption-Length Change and ration in extreme exposures. J. “Sample Mass and Dimension into unsaturated concretes. L.” Cement and from one face. is a theoretical determina. m/s. K. R.250 TESTS AND PROPERTIES OF CONCRETE by Powers [93] to be 2 1017 m/s. Determine the Permeability of Cements and Cement Mortars. Vol. 509–520.. 15. 22..” Pore Structure and Permeability of Absorption of Water by Hydraulic-Cement Concretes (C 1558. the governing mass their service lives. E96 can be used. For low pressure systems (less resistance. transfer mechanism becomes diffusion of aqueous and ionic species instead of pressure-induced flow.. “Mercury Porosimetry. As rapid indices of penetration dient during the experiment. F. although other tests. N. F 1869 has [15] Diamond. 1517–1525. the cracks. due to the impetus to produce highly meable to any aqueous transmission. Peculiarities and Problems. “Mercury Porosimetry Study of the Evolution of Porosity in Portland Cement. 2001. Concrete porosity is complex and covers pores ranging from [7] Bonzel. rather than the original mix design. L. R. pp. Sept. Vol. concrete porosity is not a static value and can simultaneously [8] Feldman. and Measurement of Rate of Intrusion Porosimetry. pp. J. when run for a range of tion. “Measurement of Porosity in 642 is commonly used. W. P. L. References With the onset of a deterioration process. Westerville. these systems [1] ASTM STP 169C. 3.” Journal of Materials. Der Einfluss des Zements. Vol. mechanisms and porosity in the intervening years since the last [10] Feldman. F. Other test methods are under development.. R. they are useful for evaluation of the combined Concrete Research. 137. Under these conditions. D. Skalny. 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R. pp. “Capillary Con- tional Conference on Deterioration and Repair of Reinforced tinuity or Discontinuity in Cement Pastes. and Tumidajski. 137.1. “Permeability Specifications for High-Performance ment of High Performance Concrete Using a High Pressure Concrete Decks. and Copeland. Vol.” Cement and Concrete Research. Oct. pp. and Nilsson. 2000. Vol.” ACI [61] Hearn.. M.. Porosity in Concrete–Does it Exist?”. 2004.. 1994. “Chloride Ingress tion. USDOE Report DOE/METC-85/6018. D. D. B.. “Influence of Voltage on [92] Winslow. T.” ACI Materials [57] Day. Journal. H.” Ph. pp. II. D. 3rd Interna. W.. 1998. Vol.252 TESTS AND PROPERTIES OF CONCRETE 1982. No. surement of the Permeability of Concretes Containing Fly Ash. and Hooton.. D.” Cement and Cements in High-Performance Concretes. Bentz. “A Discussion of Cement Hydration in Relation to Espoo. Rilem Report 16.. 827–838. and Leek. R. pp. pp. P. A. 213–264. A. 227–235. C. 141–150. [78] Pfeifer. 15 pp. [80] Tang. No. pp. “Studies of Portland Cement Hydration. “A Re-Evaluation of the 1982. and Vennesland. pp. “Discontinuous Capillary crete Research. Chan. “The Rapid [59] Denno. Vol. and Anderson.” Cement and Concrete Research. K... No. and Bamforth. [75] Feldman. D. L-O. L. 49–53. “The Permeability of High Strength Lightweight Chloride Permeability Test and its Correlation to the 90-Day Aggregate Concrete. A. “What is Needed in a Permeability Test for Rapid Chloride Permeability Test of Concrete with and Without Evaluation of Concrete Quality. T. 91.. “Quality Inspection of Shore [86] Powers. and Helland.” Portland Cement Association. 2. 1999. 1999. “Pore Structure of Paste in Concrete. No. N. 1959. H.” Cement and Orlando. M.. D.. “Transport Proper. Concrete Research. 615–618. of Concrete. Accelerated Chloride Penetration. Reinhardt.. L-O. J. 1959. Vol. Vol.. R. P.” PCI Journal. PCA. 487–495. pp. 1993. Hearn. Vol.” Transportation Research Record. F. G.” Portland Cement 126. Vol. M. Concentrated Flocculated Suspensions of [68] Stanish. W. C. D. E. and Hooton. L. H. D... [60] El-Dieb. B. D.” Proceedings of the Highway Research [65] Boddy. pp... 2004 (MS#5444). Ed. R.... accepted March 22. Mann. [84] Powers. AASHTO T259-90 Day Salt Ponding Test. SP-108. Whiting and A. 6.. A. ACI SP Water in Hardened Portland Cement Paste. Vol.. R. D. Walitt. Materials and Structures. 179–88. 29. Copeland. the Curing of Concrete. R. pp. P. C. “Rate of Sedimentation: I. Suspensions of Uniform-Size Concrete Composites. Multimechanistic Chloride Transport Model: An Overview and [85] Hughes. 609–624. R. E. 1993.” Magazine of Concrete Research.” Concrete Durability. “An Argument for Using Coarse Concrete From Ionic Diffusion Measurements. 29. D. and Hooton.. 563–567.D.. M. “Pore Solution Composition and Advances in Concrete through Science and Engineering.. “Self-Sealing. “Mea. Hooton.. Concrete in a Marine Environment... “A Review of the Pore Structure of Cement Paste Gradient in Concrete. pp.” Materials and Structures. C. Vol. for Describing Chloride Ion Transport Due to an Electrical [88] Young.. R. RILEM.. B. A... [67] Thomas. A. 23. T. pp. D. J. Vol.. Roberts and J. “A Board. Vol. pp. Vol. Mineral Admixtures. No. F. “Evaluation Testing and Modelling the Chloride Ingress into Concrete.. Imperial College. “Calculation of Chloride Diffusion Coefficients in Proceedings. Institute of Mineral Industry. 67–76. Paris. on Durability of Building ity of Cementitious Materials. ties of Concrete. M. 23. D. of Four Short-Term Methods for Determining Chloride 11–12 September 2000. pp. 5 pp. H. Thaulow. L. S. B. Finland.S. International Symposium: [70] Page. Boddy... Nonflocculated Sus- Diffusion in Concrete—Effect of Fly Ash and Slag. A. D. Vol.. III. from De-Icing Salt.. [72] Andrade. S. 1947. and Nilsson. . [77] Geiker. Vol. thesis.. Box 116. “A Novel Method Powders. J. Denmark.. 1–18. D. U. Publication No. Bulletin 106.” CD-ROM proceedings. H.. 1983. R. 724–742. C. “Prediction Vol. pp.. Precast/Prestressed 1992.34. Detroit.” Cement and and Concrete and its Influence on Permeability. Concrete from Ionic Diffusion Measurements. of Chloride Penetration in Concrete. 25. Cement Paste. 1989. P. ties in Concrete. and Sosoro. American [69] Nokken. 81–98. R.” Proceedings. pp. Triaxial Cell. 89. and Stanish. R. Part 2: Experimental Study. K.” Permeability Concrete Research. 26. 8. [79] Ozyildirim. R. [90] Geiker. G. 29.1–28.D. P..” Penetration and Permeability of Concrete. “The Flow of Approach High Strength Concrete. Oct. 91.K. pp. 41. No. 724–742. W. 1199–1208. appears unusual situations where concrete is exposed to high tempera- again here. concrete faces a wider forcing steel and other embedded metals. introduce new technology as in hazardous waste containment or nuclear waste storage [1]. regard to concrete exposed to aggressive agents are how long will including temperature. access of water and external chemical reactions so that appropriate protective strategies can be devel. however. The two questions most commonly faced by engineers with supply of the reactants. may occur and cause damage simultaneously. The common forms of chemical attack discussed are Concrete may be thought of as a man-made rock. oxidation. that has been developed. the attack in a specific Due to the fundamental nature of the subject. Canada. and acid hydrolysis) that cal reactions. The more commonly occurring situations involving exposure to aggressive chemicals have been extensively investigated THIS CHAPTER BUILDS UPON CHAPTERS ON THE over the years and some general guidelines have been developed same topic from previous editions of the ASTM STP 169 series. as is the redox and acid-base reactions) to ion exchange (substitution of case with carbonation. prop. In addition to being a strong the deterioration of concrete from chemical reactions: (1) me- and versatile material with good constructability and low cost. Tuthill. chanical expansive forces arising from the chemical reactions the durability of concrete should be the main reason for concrete leading to formation of expansive reaction products or prod- being the material of choice. constituents. are discussed in variety of chemical reactions. This is particularly true in Lewis H. and include updated references. the physical configuration of the information on the specific exposure conditions and chemical reaction site (e. DePuy. Most chemicals in a dry and the physical properties of the compound). alkali-aggregate reaction and corrosion of rein. University of New Brunswick. In these instances. and the dura. (dissolution.g. and (3) dissolution and leaching of soluble jected to chemical attack by aggressive substances. ucts that have a larger volume than the original materials. FL. A. addressed by the previous authors. attack rock [2].24 Chemical Resistance of Concrete M. and 169C. and decomposition (dissociation of one or more compounds such as pozzolanic reactions. some may be beneficial. hydrolysis. authored by the variables governing the reaction. much of what ap. ranging from dissolution other chapters of this volume. and well-made concrete resists deterioration for (2) chemical alterations that weaken or soften the concrete many years. the above mechanisms bility of concrete may become a serious concern. inhibit. ble material. and subject to the same natural chemical weathering processes exposure to saline water. 253 . such as effects of other substances that alter. 2 President. Materials Service Life. There are three main types of mechanisms involved in pected to have a long service life. one ion for another in a molecular structure that may change cals in a liquid or gaseous form. erly designed concrete is a very durable material and may be ex. such as in some circumstances but harmful at other times. of reaction.. permeability). This chapter will review and update the topic as tures or where the performance of concrete is especially critical. Skalny2 Preface oped. Under certain conditions. factors governing the rate Under ordinary processing and environmental conditions. substances). Holmes Beach. for dealing with these situations. Chemical reactions per se in (dissolving of a solid substance into a solvent such as water) concrete are not necessarily harmful. the general guidelines that have served so well in the past may not adequately cover the situation and it becomes Introduction increasingly more important that the engineer have a good understanding of the chemical reactions. reactivity of the reactants.. authored by G. 169A. In industrial exposures. various forms of sulfate this context concrete structures exposed to the elements are attack. and in leaching by soft water. acid attack. Other reactions may be beneficial and chemical combination into other compounds. there are instances where concrete is sub. solid form are not harmful to concrete until they are brought The rate and severity of attack is governed by the quality into contact with water or other solvents. However. Thomas1 and J. D. exposure to industrial chemicals. components. W. and mechanisms causing deterioration in concrete. and whether 1 Professor of Civil Engineering. of concrete (e. Two other types of destructive chemi. The reaction is also affected by other the structure stand up to the exposure and what can be done to factors. In most situations concrete is a sta. Most harmful reactions involve chemi. situation is a complex matter and may vary greatly depending on peared before in ASTM STP 169. carbonation. and severity of exposure conditions. prolong the service life? The answers to these questions require or promote the reaction.g. and 169B. the nature of the reaction products. subsequently evaporates on exposed surfaces. the passage of mole. Design measures may also include the provision of sacrificial Mineral deposits may form on exposed surfaces where wa- concrete (using sections with added thickness to compensate ter seeps through concrete along joints and cracks of concrete for the chemical attack). particles may be involved in harmful chemical reactions. and Leaching replacing part of the portland cement with pozzolans that will react with calcium hydroxide to form more stable calcium sili. Diffusion. selection of an optimum amount of a well-graded. powdery-to-hard deposit eliminate the water migrating through concrete or ponding (commonly calcium carbonate or sodium sulfate hydrate. or poly- soluble in water and more chemically reactive than the other hy. . multiple admixtures are used. including groundwater. other reactions form products that may 1. Use of properly selected chemically resistant materials. the to the selection and proportioning of concrete materials. One strategy to improve the chemical resist. Permeability. sometimes only temporarily. the use of supplementary ce. well-consoli- produce a physical blocking or passivation effect and tend to dated. Special surface treatments to produce a hard.254 TESTS AND PROPERTIES OF CONCRETE the reaction goes to equilibrium or completion. Leaching refers to the chemical dissolution water and aggressive agents. which includes: laries in concrete. such as and sulfate ions. well-designed. and the provision of a physical barrier to exclude formation of incrustation and efflorescence. Leaching and deposition are as a partial replacement for portland cement. admixture or high-range water reducer) to reduce Although both the hydrated cement paste and aggregate shrinkage. The best strategy starts with the design of the structure. mer concretes. of structures under the threat of chemical attack. and minimal cracking. finishing and curing to produce a diffusion [3]. or magnesium salts. In surface. It reacts readily with acids and with carbonate 5. portland cement concrete calcium hydroxide constitutes about 4. or water contained in or transported by concrete the design of the structure to avoid or minimize contact with structures [7–12]. impervious also referred to as lime. and removal of water-soluble constituents in concrete. both strength and durability need to be considered. generally is linearly related to pressure and a. mize permeability. In addition to good workmanship. position of mineral deposits includes both scaling or the - ble concrete. Production of high-quality. the term “scaling” is used more often in an entirely different sense to refer to the physical process of the removal of thin layers of surface concrete. voids. Efflorescence refers to a white. structures. proper selection and use of chemical admixtures. blending the cement with pozzolan or slag to mini- attention will be given to reactions with cement hydration prod. Use of properly selected impermeable barriers. actants into concrete is its quality. well-cured. layered precipitates of calcium sulfate. impermeable concrete that requires impede. calcium carbonate. but damaging reactions often hard. if their analogs. low permeability. good mix design to obtain a workable and com- crostructure of the cement hydration products. and ucts such as a variety of calcium sulfoaluminate hydrates or f. 3. further deterioration. containing dissolved minerals migrates through concrete and diate cracking. low density (low 2. such as produced This would include avoiding or minimizing contact with by the heating or evaporation of water containing dissolved aggressive agents. pipelines and tunnels. The velocity of the aggressive agent coming into which can be easily provided by using a water-reducing contact with concrete is a key factor in surface reactions. optimum cement type and content for the intended use. and chemically resistant relate to formation of varying amounts of other reaction prod. specifically. attention must be given w/c). and permeability. most d. the production of high-quality impermea. and attention to details to control cracking. chemically resistant membranes and protective coatings ance of portland cement is to minimize the calcium hydroxide [4–6]. crack-free concrete with a hard and dense surface. Concrete exposed to water is subject to leaching and the cate hydrates. content of the hydrated cement by using a “low-lime” cement (contains more dicalcium silicate and less tricalcium silicate). 25–30 % by mass of the hydrated cement paste and is more such as chemical-resistant cement and aggregates.40 or lower root of time. the concentration gradient and is generally related to the square c. effect on concrete properties should be known. by Scaling. and capil. b. using contraction and construction joints may consist of other salts). clean. cance to chemical resistance is calcium hydroxide (Ca(OH)2. proper mixture The supply of aggressive agents for reaction is governed by design. providing good drainage to intercept or salts. This the velocity that the reactants are brought into contact with con. selection of the appropriate materials. aggregate. involves good workmanship throughout the entire crete and the penetration of the reactants into the concrete. and good quality control and workmanship. capillarity. The de- menting materials. their interactions and The portland cement hydration product of greatest signifi. penetration of a substance through fractures. related effects produced by the dissolution and precipitation of Four general strategies are used to improve the service life minerals in water from any source. production process from batching and mixing. physically sound. such as is formed when water that are water tight and frequent enough to prevent interme. Efflorescence. are generally hard. hydrates and calcium hydroxide. The primary defense against the penetration of re. placing which is generally considered in terms of permeability and and consolidation. dration products. hydrated lime. cules or ions of an aggressive substance through the mi. a low water-cement (w/c) ratio (usually 0. such as dissolution and leaching may tend to accelerate the following: future deterioration. Some reac. is a function of pactable mix. or portlandite). such as dam faces. The intrinsic durability of concrete may be improved by tions. These are surface water. retaining 3 In regards to concrete technology. or by using ground granulated blast furnace slag deposition of mineral deposits. The main cement hydration products are calcium silicate e. ucts.3 Scale deposits aggressive agents. viscosity of the aggressive agent. but behind structures. Use sacrificial concrete. as calcium usually precipitates in the form of leaching concrete and create the sandy appearance sometimes calcium carbonate. leaching increases as temperature increases. to the absorption of carbon dioxide (CO2) gas from the air. water seeps through the concrete.S. Rela. lime-saturated water migrating through concrete. This is applicable to voirs. Leaching water becomes exposed to the atmosphere. 1. Geological Survey’s WATEQ model. The rate of in- These kinds of deposits may be objectionable for several crease or decrease may be taken as evidence of whether the reasons—they are unsightly. factors governing solubility. 23 % fly ash was not effective in reducing the leaching by warm and iron salts) will not dissolve calcium hydroxide to any to hot distilled water. and building foundations. and the other surfaces. precipitation occurs as a result of a shift in equilibrium of CO2 c. Stop or divert the flow of water. the processes tend surface evaporation leads to transport of water containing to diminish. Most commonly. such as water/cement ratio. On this basis. that concrete was not suitable in exposure to flowing distilled droxide is more soluble in cold water than in hot water. rather than continue on at a silicate and less tricalcium silicate). concrete. and the concentration of other soluble materials in the little good-quality concrete has actually been destroyed or water. are capable of concrete. leading to deposition the internal chemistry of concrete as well as on the (often of salts on horizontal slabs or stem walls close to the soil line. calcium carbonate is content of the water. and very ture. dissolved solids. and slight changes in conditions can quickly result b. Pretreat the water to saturate it with calcium before it in solution due to a decrease in pressure. In dissolved is dependent upon the pH of the water. The Bureau of Reclamation investigated the effects of The solubility of CO2 in water increases with pressure and warm to hot distilled water on portland-cement concrete in a decreases with temperature. A common indicator of the or internally in the case of water migrating through more tendency of a particular water to dissolve or precipitate porous paste. and evaporation. dition. total alkalinity. the appearance is worse than the damage. tively cold and pure water from mountain streams and reser. The observable differences in resistance to leaching due to water immediately upstream of the structure to obtain a the use of different types of portland cements are very minor Langlier. a. Mineral deposits Saturated lime water is in a delicate equilibrium con. The pH of natural water low in dissolved solids is related made unserviceable by leaching of lime [21]. as in the case of water flowing in canals and pipelines. or using a protective coating as an aid). and that severity of factors governing the dissolution of lime in concrete by water. When the 2. models. more or less constant rate. At times. or on whether with leaching or mineral deposition is Ca(OH)2 (calcium leaching is damaging to a particular concrete structure. Use of special cements. Occasionally. but the The tendency of water to dissolve or to form a precipi- leaching in such cases is often relatively minor. and they may adversely affect the problem is becoming worse or is solving itself. and temperature [15]. Other factors affecting the upstream of the structure and also at the location where the permeability of the concrete. A in concrete is sometimes suspected of creating voids and more definitive answer would require a chemical mass bal- weakening the concrete. in temperature. or preferably a WATEQ saturation index. cold water is more study on the use of concrete in desalting plants. Ca(OH)2 is soluble to a certain extent in water and difficult to answer as usually there is insufficient information is the main cement hydration product susceptible to leaching. however. such as aluminous cement. calcium carbonate a. These processes are complex and depend on various ions through permeable concrete. other means to consider include: become quickly saturated with calcium.17].14]. chemical equilibrium observed in some concrete conduits. and the presence of be required to determine if leaching has weakened the microfractures and cracks. times taken as evidence of leaching in the concrete. and product water from desalting plants. most cases. for the water to dissolve lime could be obtained by testing the ble. The use of up to Hard water (water containing dissolved calcium. appreciable extent. Removal by physical or chemical means (such as in the formation of a precipitate. An indication of the potential hydrates and calcium aluminate hydrates) are much less solu. tate of a calcium salt is an issue related to the degree of Leaching may erode concrete either externally on exposed saturation of the salt in a particular situation. The amount of Ca(OH)2 that can be defective workmanship in the construction of the structure. changing) environmental conditions of use. some caution in interpretation should be Ca(OH)2 dissolves in water by dissolution and by acid-base exercised since internal voids can also be produced by reaction in acidic water. on the chemical equilibrium condition of the water before and The other principal hydration products (calcium silicate after exposure to the concrete. leaks performance of a structure by reducing the effectiveness of are observed to plug themselves through the formation of cal- heat exchanger surfaces or by obstructing the passage of water cium carbonate precipitates—the so-called autogenous crack in drain holes and water tunnels [13. and flumes. its tempera. The principal constituent of concrete usually involved Questions on the cause of mineral deposits. healing sometimes observed in concrete pipes and canals. are much more important. and concluded aggressive towards concrete than warm water as calcium hy. More recently. frequently precipitates on the surface of the concrete. The deposits are some. canals. This may be and usually attributed to differing amounts of Ca(OH)2 formed difficult to do as it would require sampling of the water from the hydration of the cement. Drilling and coring may also the appropriate use of pozzolans or slag. and joints in a concrete structure. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 255 walls and abutments. A common example is that of sulfamic acid. are hydroxide). d. The studies showed that concrete does not resist The effects of other dissolved salts in water are major leaching in warm to hot distilled water. cracks. water [22]. pH. such the U. a polymer modified . The b. a probable increase comes into contact with the concrete. but soft water (water relatively free of the In addition to the general steps to improve chemical dissolved salts) readily dissolves calcium hydroxide and may resistance. Stop the water seeps and leaks. ance approach [18–20]. Internal leaching by water seeping through cracks and joints have been developed to evaluate mineral saturation [16. magnesium. Leaching and deposition processes usually tend to either “low-lime” portland cement (contains more dicalcium increase or decrease with time. sulfate anion. and ground in contact with the structures. foundations.5–4 % as SO3 to control setting character. within the concrete mixture may vary according to the situation. reaction product from the hydration of portland cement. the water may contain other aggressive canal structures may completely disintegrate in only a very anions and cations that attack hydrated cement constituents by few years when exposed to water containing dissolved sul. and in industrial situations where and mechanistic aspects of the problem are known. and possibly reaction products of sulfate ion with calcium hydroxide and from sulfates in the portland cement. which affects the course and the severity of the reaction. In the case of external attack. Deterioration due to sulfate attack is generally attributed creases. the northern may change and influence the course of the reaction. yet in actual practice the situation is published by Skalny et al. little apparent change in volume [34. as not water).” is a groundwater. and (4) the exposure conditions Sulfate Resistance (i.256 TESTS AND PROPERTIES OF CONCRETE cement. reaction with sulfates. and a high The gypsum normally added to portland cement to control sulfate form called calcium trisulfoaluminate or ettringite setting characteristics is not sufficient to cause sulfate attack. The severity of the attack can be affected by the pres. ence of other dissolved substances in the water. If . and becomes even more severe if the concrete is sub. Sulfate solutions may also react reaction may be either external or internal to the concrete with the cement paste to form products that have little ce- [23–30]. may produce expansive forces and a subsequent physical The source for the sulfates involved in the chemical disruption of the concrete. Calcium sulfoaluminate hydrate oc- to have a chemical analysis of the ingredients of the concrete curs in two forms. all cement hydration products are equally susceptible to such as 20–30 % of a good natural pozzolan or fly ash. which is a control e. and thereby turn the concrete into mush with originate from groundwater or from sulfates leached from ad. reaction that is considered the main destructive force in sulfate The main constituents of hardened portland-cement paste attack. chemical reactions other than those associated strictly with the fates. At times these reactions may impede the attack. drainage pipe. or concrete exposed to moisture gradient will be more vulnerable than External Sulfate Attack concrete continually immersed in sulfate-contaminated Sulfate attack. Calcium sulfoaluminates form during fates may come from minerals in the aggregates. admixtures and additives. and lower parts of portions. minate or monosulfate (3CaOAl2O3CaSO412H2O). including the western United States.38].35.. Use of mineral admixtures blended with portland on the rate at which the reactants are brought together. (2) the cement (may not be effective against hot distilled composition of the hydrated phases of the cement paste. The situation is not as straightforward The attack is particularly prevalent in arid regions where as might be expected since several different chemical reactions naturally occurring sulfate minerals are present in the water rather than a single reaction may be involved simultaneously.e. the sul. Spain. Other cement The presence of ettringite alone is insufficient evidence of a hydration products can also be attacked in more severe sulfate destructive sulfate attack. A comprehensive description of the different from laboratory studies involving relatively simple chemical forms of sulfate attack and methods of prevention was recently systems of pure materials. which is added in converted to ettringite when exposed to sulfate solutions. tricalcium aluminate (3CaOAl2O3 or C3A) phase. [23]. such as ground blast furnace slag.40]. and formation through solution On the other hand. the Middle East. measures can be taken to eliminate or minimize the risk of Most of the knowledge on sulfate attack has been developed sulfate attack. the sulfates may menting value. completely understood. more complicated as the exposures may involve varying and Without taking adequate precautions. There are several particularly severe type of deterioration resulting from chemi. These options are The major factors governing the sulfate reactions are (1) usually unavailable. calcium sulfoaluminates. different sulfate reaction mechanisms depending on the com- cal reactions occurring when concrete components react with position of the sulfate water and the environmental condition. it is still not concrete has been exposed to solutions containing sulfates. It is therefore necessary calcium aluminate hydrate. In the case of internal attack. The course of the reaction and the mechanism for deterioration crete or. This soils will not be attacked. pozzolans. Great Plains area of the United States and Canada. is the the cement hydration process. under certain conditions. but generally and at other times may aggravate the attack.39. concrete exposed to dry sulfate-bearing and precipitation of less soluble reaction product [31–37]. the associated volume increase is potentially destructive. However. istics. the permeability of the concrete to water. increases as the concentration of sulfates in the water in. jacent soil as the reaction progresses from the surface into the The main reaction products involved in sulfate attack are interior of the concrete. the composition of the pore water the world. (3) the chemical composition and con- or silica fume. often from monosulfate. and also form as solved in the mix water. concrete exposed to cyclic wetting and drying. sulfate ions (SO42) present in solutions in contact with con. The monosulfate form may be Portland cement normally contains gypsum. as ettringite is also a secondary environments. centration of the sulfate-laden water. Sulfate attack has been reported in many parts of inward into the concrete. sulfates dis. sometimes called “sulfate corrosion. In such cases. temperature is also important). to chemical decomposition of certain portland-cement hydra- jected to frequently alternating periods of wetting and drying. As the reaction proceeds itself. tion products after hardening. The necessary Some controversy still remains over the mechanism responsi- conditions for sulfate attack are known and preventive ble for producing expansion and deterioration of the concrete. concrete structures changing combinations of impure materials in different pro- such as floors. (3CaOAl2O33CaSO432H2O). Great Although sulfate attack has been extensively investigated Britain. depending largely upon the supply of sulfate and of the groundwater and soil surrounding the structure in and alumina: a low sulfate form called calcium monosulfoalu- order to assess the probability of sulfate attack. This gypsum is consumed during the normal course of Formation of ettringite. and amounts of about 2. there is some controversy over the formation susceptible to sulfate attack are the hydration products of the of ettringite and the deterioration of the concrete [23. or a polymer concrete. the normal hydration of portland cement. In and Mg. recrystallization. the cement paste. Ettringite as a normal cement hydration product is such as ambient and internal temperature and wetting and usually not considered to be destructive. possibly affected by aggregate or a cement addition or can be supplied as carbonate cement composition) [28–30]. how. either ameliorate or intensify the destructiveness of the reac- tallize into the space provided by the fractures (secondary tion.61]. mechanical silicon substitutions. The course of the reaction but the latter reaction (2) is today considered to be the primary . c) damage caused by magnesium sulfate—namely. finally. high surface area cement. exposed to sulfate solutions under wetting and drying condi- cording to Brown and Taylor. by Cohen [45]. Sulfate attack is also affected by environmental factors ettringite). components leading to formation of gypsum (the so-called tions is associated with producing a deterioration effect on con. and rare excessive addition of calcium V cement would not necessarily provide protection against the sulfate) or b) heat-induced internal sulfate attack (also referred formation of thaumasite. and (2) so-called physical sulfate attack of thenardite-to-mirabilite a sulfate reaction with calcium aluminate hydrate to form et. among other effects. This type of mechanism involves or bicarbonate ions dissolved in the soil or groundwater. hydroxide and involving the alumina-containing phases of cium hydroxide to form gypsum (sometimes called gypsum at. that is. Calcium sulfate (most commonly occurring as gypsum. high ambient from sources within the concrete such as limestone used as an temperature during placing and curing. Per this view. ac. sulfate. gypsum attack).42]. The reactions are more complex. the so-called “physical” form of sulfate attack is unconfirmed theories: a) that there is more than one type of sometimes included under the general category of sulfate at- ettringite. of correlation between the amount of ettringite formed and In addition to the chemical form of attack involving chemi- the amount of expansion observed. ettringite forms typically by tions. admixtures. the reaction may intensify into acid attack that forms a calcium aluminate hydrate (4CaOAl2O319H2O) and calcium different reaction product [10. physical.33. in reality. The cations affect the solubility of sulfate minerals concentrations approaching saturation (2000 mg/L water). and even some types of aggregate particles such Calcium Sulfate Reaction as weathered feldspars. to thermal conditions during concrete processing (high heat of tures around 5°C [49. These reactions will be dis.52]. a chemical process of tringite (sometimes called sulfoaluminate attack or corrosion) repeated through-solution recrystallization leading to physical [5]. such as calcium silicate hydrate. gypsum dissolved in water in contact with the concrete. and appears to form rather quickly at tempera. and also the cium sulfate becomes reactive with calcium aluminate hydrates course of the reaction. thaumasite formation. and frequency of their changes. such as Na2SO4 or MgSO4. caused by an that the presence of C3A is not necessarily a prerequisite for excess of sulfate ions in the concrete itself (from clinker. cussed in the following paragraphs. depending upon the amount of sulfates in solution. caused by thermal temperatures due to the higher solubility of calcium salts at low decomposition and subsequent reformation of ettringite due temperatures. Ping and Beaudoin [46]. and.58]. Even so. In more severe forms of the reaction. CaSO42H2O) is not highly soluble in water. ditions when there is a supply of alumina.52]. nism is employed in ASTM Test Method for Soundness of Ag- Mechanisms for the expansion of ettringite have been reviewed gregates by Use of Sodium Sulfate or Magnesium Sulfate (C 88).43]. However. but there is some of deterioration caused by external sources of sulfate anions. and others [23]. as may occur when concrete is formed by through-solution reactions [35. ever. sulfate attack involves same disruptive effect as is attributed to ettringite formation mechanisms such as a) reactions of sulfates with cement paste [42]. and therefore such precautions as a Type aggregate. may lead to com- form as a conversion product from ettringite by carbonate and positional. K. Gypsum is also considered External sulfate attack relates to all chemical mechanisms by some to be an expansive reaction product. gypsum (CaSO42H2O) and silica gel. There are some other cal reactions. Na. there may be a and destructive effects are also affected by the presence of question of whether the fracture was caused by crystal growth other dissolved constituents in the system that can tend to itself (primary ettringite) or if the crystals happened to recrys. monosulfoaluminate have been described [10. It would appear a) composition induced internal sulfate attack.42]. which most commonly are Ca. and acid type of sulfate attack). as both anions and cations are involved. under concrete attacked by sulfate solutions [47–57]. sulfate attack Thaumasite (CaCO3CaSO4CaSiO315H2O) is structurally involves all deleterious reaction mechanisms that involve sul- similar to ettringite and was observed by numerous authors in fate ions. The reactions of calcium sulfate with sulfate. This mecha- through-solution rather than by topochemical mechanism [44]. other constituents of damage [23]. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 257 ettringite crystals are found in fractures.41. microstructural. gypsum corrosion. concrete are susceptible to sulfate attack. Thaumasite may certain processing and ambient conditions. b) that the tack [23.62–64]. other reaction products are formed such as cussed in the next section. and subse- formed by solid-state reactions is more expansive than that quent growth of crystals. attack). b) expansion by primary ettringite formation crete as it involves the conversion of cementitious constituents (the “classical” sulfate attack characterized as sulfoaluminate into products having little cementing properties [34]. and e) even the tack. a The American Concrete Institute (ACI) divides sulfate combined attack on calcium-silicate-hydrate and calcium attack into two general categories: (1) a sulfate reaction with cal. only monosulfate and ettringite (tri-sulfate) and will be dis- In some cases. question as to whether the formation of gypsum produces the independent of the cation.38. ettringite cipitation of sulfate salts. to the cations associated with the from negligible to severe. and sulfate attack The type of chemical reaction that will be prevalent is on concrete in contact with soils containing gypsum may range related. changes in the concrete material structure [23. calcium silicates or Internal sulfate attack should be then categorized as either free silica gel. Thaumasite forms preferentially at low to as delayed ettringite formation or DEF). can cause destruction of concrete [58–60]. d) thaumasite sulfate attack. or may form directly under favorable con. and carbonate [49.36. There is also a lack drying. All such reactions are chemical in nature and. With extremely high concentrations of present in the system. In the view of some contemporary authors. gypsum formation under sulfate attack condi. cal- and the concentration of the sulfates in solution. Crystallization pressures resulting from the pre- mode of formation may also have an effect. The carbonate ions can be derived hydration cement. and not all types are expansive [38. which is. cements. especially close to evaporative surfaces. to dangerous levels • At high concentrations (above 6000 mg SO4/L or above even if the original concentration of sulfate in groundwater or 7500 mg MgSO4/L). ettringite does not form. formation of magnesium hydroxide. and because it enters into two types of reactions with the hydrated cement phases in the hardened cement paste. the reaction is characterized by the soil were within the limits assumed to be safe. gypsum from cement has been already ence of MgSO4. sulfates—independently of the cation they were origi- oration and cracking may slow down and may be hardly nally associated with—may concentrate in the concrete matrix. 2H2O → 4(CaSO42H2O) Na2SO4 Ca(OH)2 2H2O → CaSO42H2O 2NaOH 3Mg(OH)2 Al2O33H2O (8) sodium sulfate calcium hydroxide water (3) magnesium sulfate calcium monosulfoaluminate → gypsum sodium hydroxide hydrate → gypsum magnesium hydroxide and aluminum hydroxide 3(CaSO42H2O) 4CaOAl2O319H2O 8H2O 3MgSO4 3CaO2SiO2nH2O zH2O → 3CaOAl2O33CaSO432H2O Ca(OH)2 → 3(CaSO42H2O) 3Mg(OH)2 2SiO2xH2O (4) (9) gypsum calcium aluminate hydrate water magnesium sulfate calcium silicate hydrate → ettringite calcium hydroxide water → gypsum magnesium hydroxide silica gel 2Na2SO4 3CaOAl2O3CaSO412H2O 2Ca(OH)2 Magnesium silicate hydrate may also be produced from 2H2O → 3CaOAl2O33CaSO432H2O 4NaOH this reaction.34. scribed elsewhere [10. the reaction is changes leading to evaporation of water from the concrete characterized by ettringite and gypsum formation. gypsum calcium aluminate hydrate water Strong solutions of magnesium sulfate are capable of reacting → ettringite calcium hydroxide with the calcium silicate hydrate phases as well as calcium hydroxide and calcium aluminate hydrate phases. but one should not rely on this sodium hydroxide process as a prevention against sulfate attack. the attack is characterized by Usually. Magnesium hydroxide may have a beneficial ef- (5) fect as it is highly insoluble and forms surface deposits. Sodium sulfate is potentially more destructive than gypsum as The various magnesium sulfate reactions have been de- it is more soluble (40 000 mg/L water) than calcium sulfate. Deteri- surface. in the continued pres- bearing solutions. • At intermediate concentrations (between 3200 and 6000 Under some conditions. Magne- → 3CaOAl2O33CaSO432H2O Ca(OH)2 sium sulfate is highly soluble (70 000 ppm) and can form more (1) highly concentrated sulfate solutions than sodium sulfate.64.66]. . Deterioration becomes very Sodium Sulfate Reaction severe as the magnesium concentration increases. MgSO4 Ca(OH)2 2H2O → CaSO42H2O Mg(OH)2 Sodium sulfate reacts with calcium hydroxide as well as the calcium aluminate hydrate phases.67]. when mature concrete is exposed to sulfate- ettringite formation. and hydrated alumina calcium aluminate and alumino-ferrite phases present in most [36].65. but there is → 3(CaSO42H2O) 3Mg(OH)2 2Al(OH)3 some controversy as to whether the formation of gypsum magnesium sulfate calcium aluminate hydrate (7) produces a harmful expansion in concrete. such as periodical temperature mg SO4/L or 4000 to 7500 mg MgSO4/L). The evidence for → gypsum magnesium hydroxide gypsum producing expansion and deterioration of the concrete does not appear as straightforward as does the case aluminum hydroxide for ettringite formation [42]. sulfate reacts with the → gypsum magnesium hydroxide hydrated calcium aluminate phases to produce ettringite and subsequent deterioration.36. at higher concentrations. sodium sulfate reacts with calcium hydroxide to produce gypsum [10]. and silica gel. gypsum.258 TESTS AND PROPERTIES OF CONCRETE deleterious reaction in the unlikely case when excess gypsum Magnesium Sulfate Reaction from cement is still present in the system: Magnesium compounds are potentially more destructive to concrete as the magnesium ion is capable of completely 3(CaSO42H2O) 4CaOAl2O319H2O 17H2O replacing the calcium in hydrated portland cement. At lower concentrations magnesium sulfate calcium hydroxide water (6) (SO4 content less than 1000 mg/L). which sodium sulfate calcium monosulfoaluminate tend to block pores and hinder the further penetration of sul- calcium hydroxide water → ettringite fate solutions into the concrete. perceptible. 3MgSO4 3CaOAl2O3CaSO412H2O scribed [10. However. magnesium hydroxide. ettringite is eventually decomposed to consumed in the normal hydration reactions between the gypsum. The con- 2CaSO42H2O 3CaOAl2O3CaSO412H2O 18H2O centration of magnesium sulfate may affect the course of → 3CaOAl2O33CaSO432H2O (2) the reaction [10]: gypsum calcium monosulfoaluminate water → ettringite • At low concentrations (less than 3200 mg SO4/L—or less than 4000 mg MgSO4/L). 3MgSO4 3CaOAl2O36H2O 6H2O Gypsum formation results in a volume increase. The sodium sulfate reactions have been variously de.36.63. yet seawater. consolidation water (800 g/L) and is highly aggressive towards concrete. Also. In some cases. England. solutions and to bisulfate solutions (HSO4 ). There is conflicting evidence concerning the effects of action of the calcium-silicate hydrates (C-S-H) with sulfates in solutions containing mixtures of sulfate salts and other dissolved the presence of carbonate ions [23]: substances. California Division of Highways [45]. or both. or even seawater [74]. which contains these → 3CaOSiO2CO2SO315H2O substances. and good finishing and curing Sulfates of copper. been many studies in many parts of the world and an extensive ment-based material). uncracked and dense surface. It has been argued that the apparent Most of these investigations seem to reach (or confirm) scarcity of TSA is partly attributed to the following: 1) the the same conclusions on the resistance of concrete to sulfate conditions of most standardized sulfate resistance tests do not attack: favor thaumasite formation. Ammonium sulfate is highly soluble in mixture proportioning and selection of materials. (2) preventing or limiting. (CaSiO3CaCO3CaSO415H2O) that can form in concrete by re. or by converting the Ca(OH)2 to a more stable concentrations chloride is thought to temper sulfate attack as form either as C-S-H or CaCO3. It should Control of External Sulfate Attack be noted that in all of the laboratory and field cases reported.82]. the access of sulfate TSA was recently diagnosed as the cause of damage to an solutions to concrete. barriers to prevent sulfate solutions from coming into contact ments are from calcium. are also aggressive The sulfate resistance of portland cements may be im- towards concrete [77. Russia. (3) using a sulfate-resistant cement (limi- aqueduct where previous investigations had wrongly tations mentioned above). and to produce a hard. cobalt. and other workers have provided Bureau of Reclamation [94]. in concrete stored at temperatures above 15°C world such as in Canada. is not as aggressive as might be expected based upon magnesium and sulfate contents [36. The process only occurs in very wet environments and the rate of formation is increased at low temperatures.110–112]. those conducted by the Metropolitan Water District [31]. Chloride ions react permeability of concrete and improving sulfate resistance . In some industrial there is no guarantee the barriers will perform effectively over situations. proved by limiting the C3A content in the cement clinker. the • Presence of mobile groundwater. sodium. The led to many investigations over the years into the mechanism for conversion of C-S-H into thaumasite results in a loss of binding the deterioration and means to combat the reaction. and at the University of California for the tions being fully met [69].69. the Bureau of Reclama- which TSA had occurred without all four of the above condi.81].41. The aggressiveness of various sulfate salts a low water-cement ratio and a reasonably high cement content towards concrete is partly related to solubility in water. by In low concentrations. which are moderately soluble in water. For example. and occasionally with the concrete. generally in the concrete aggregates. This includes good are relatively harmless. of the concrete during placement. see Refs 10. 33–36.105. and Israel (for sulfate [72]. 37. sulfate solutions containing chloride. Carbonation of the surface chloride increases the solubility and decreases the stability layer.36. There have material and hence the integrity of the concrete (or other ce. impermeable concrete. aluminum. zinc. the service life of ettringite formation [76]. the Corps of Engineers [88. and (4) using pozzolans or slag [5].63. iron. Potassium sulfate reacts with concrete in a as a long-term solution to an aggressive sulfate condition as manner similar to that of sodium sulfate. Hungary.84–86]. France. the use of pozzolans or slag (or both). and 99–109). yet in high cement paste. and also good sulfates of very low solubility (barium sulfate and lead sulfate) workmanship and construction techniques. and air entrainment also may aid by reducing the of ettringite and gypsum [10. conditions are met [68]: Some of the earlier studies in the United States include • Presence of sulfates and/or sulfides in the ground. and possibly even concrete with no access to external Africa. chlorides have been shown to limiting the amount of Ca(OH)2 formed in the hydrated decrease the sulfate resistance of concrete [79. the Portland Cement Association [32. and more recently Refs 23. nesota [83]. The thaumasite form of sulfate attack body of knowledge on sulfate attack has been developed. If attributed the deterioration to classical sulfate attack involving access of sulfate cannot be easily prevented. evidence that TSA may occur in concrete containing siliceous Extensive studies have been conducted elsewhere in the aggregates [70].90–93].S. 38. Department of Agriculture and the University of Min- • Presence of carbonate. the • Low temperatures (generally below 15°C). a series of cases were recently presented in [87]. manganese. and may even aggravate the situation. and 95–98 for brief summaries. 66. 2) forensic examinations may The four main strategies for improving resistance to sulfate have failed to detect TSA in deteriorated concrete. Impermeable barriers are not recommended potassium sulfate. been identified as acidic. sodium bicarbonate. Australia. in that in the mix. 3) buried concrete is rarely inspected [75].89]. U. carbonate-bearing groundwater [73]. the Bureau of Standards However. Belgium. in some cases the source of carbonate has example.78]. and carbon dioxide are highly 3Ca2 SiO32 CO32 SO42 15H2O aggressive towards concrete. The widespread occurrence and destructiveness of sulfate attack the sulfates for this reaction come from external sources. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 259 Thaumasite Form of Sulfate Attack with hydrated aluminates and monosulfoaluminate to form Thaumasite is a calcium-silicate-sulfate-carbonate hydrate chloroaluminates. Bisulfate solutions It is essential to have a high-quality impervious concrete to tend to be more acidic and can contribute to acid attack as well improve sulfate resistance [104. magnesium. 40. Sweden. concrete also may be increased by protecting the concrete from exposure to sulfates by limiting the sulfate content of the Other Reactions materials used to make the concrete and using impermeable The most common types of sulfate attack in natural environ. 42. concrete may be exposed to other types of sulfate a long term. and solutions are (1) making a high quality. South [71]. tion [79. magnesium.80].34. This involves using as sulfate attack. 27. It is not (TSA) is a relatively rare form of sulfate attack and risk of its possible to adequately recognize the many contributions and occurrence is thought to be negligible unless the following only a few of the contributions can be mentioned in passing. This can be ac. resistance as there are other issues involved. but high calcium Class C (e. under some environmental . the addition of signates Type II cements containing no more than 8 % C3A as a pozzolan or slag does not automatically guarantee sulfate re. Slags have been shown to be ef. and matrix. however.. It may be noted ticular pozzolan is used as a replacement or as an addition to that the development of high alumina cements (which contain the cement. or by combining Mortars Exposed to a Sulfate Solution (C 1012). sulfate resistance: tioned above. 10–20 % CaO) are ably related to the reactivity of alumina present in other often good. or slag.g. be specified in lieu of a chemical composition specification. be considered to be a secondary defense against sulfate waters. some ashes with high alumina amount of tricalcium aluminate (C3A) in the cement increases.g.113–115].. mullite).28–30.g. This is most prob. and in several instances zero C3A cements stable crystalline compounds (e. Some Class C controlled to a certain extent by increasing the amount of C2S ashes must be used at replacement levels greater than 75 and decreasing the C3S phase in the portland cement as the % to achieve sulfate resistance or may be used at moder- C2S phase liberates less Ca(OH)2 than C3S during hydration. some exceptions have been noted.133]. In these cases. sulfate resistance [36].129–131]. as mentioned earlier. ASTM Test portland cement with active siliceous mineral admixtures such Method for Potential Expansion of Portland-Cement Mortars as natural or calcined pozzolans.. Some having a beneficial effect due to a reaction with C3S to form differences in performance may depend upon whether a par- carboaluminate (C3ACaCO312H2O) [116].117].. Other differences may arise depending upon the calcium aluminates in forms other than C3A) was in part stimu. ASTM C 150 de- as the Al2O3 content is limited [122].260 TESTS AND PROPERTIES OF CONCRETE [87. There are some cases where a speci- lead to delayed formation of ettringite (DEF). In general. the following general- One means to reduce the C3A content of the cement is to izations may be made regarding the effectiveness of poz- convert the C3A phase to C4AF and CF by the addition of iron zolans classified according to ASTM C 618 for improving oxide during the cement manufacturing process. The use of calcareous fillers has been reported as and the amount and type of cement in the mixture. performance tests may other concrete products [26. Also. but this should not be used alone as a prevention fineness of the pozzolans. Please note that use of ASTM Type introducing additional calcium ions into the system V sulfate-resisting cements is not a remedy against sulfate [93. which in some fication based on chemical composition alone would exclude a cases has been proven to cause deterioration in precast and sulfate-resistant cement.96]. • Low calcium Class C fly ashes (e. However. But. ate levels in combination with silica fume [127. In Exposed to Sulfate (C 452). C2F) as having high sulfate resistance. chemical reactivity (e. low C3A The influence of the alumina in fly ash will depend on cements were observed to have poor sulfate resistance. the hydrated ferrite phases are ultimately sus. silica fume. content are not effective in improving sulfate resistance. Sulfate resistance cements should pozzolans are equally effective in improving sulfate resistance. as men. and tests should be made to determine effectiveness (containing less than 5 % C3A and 25 % C4AF 2(C3A) or C4AF in improving sulfate resistance. it should be noted that excessive heat may Exposed to Alkali Sulfates. • Class N pozzolans are variable but generally good espe- ceptible to sulfate attack in severe environments. perhaps even more so than fly ash or ground proportion of C2S with respect to C3S is effective in controlling slag [128.g. These cements are rarely used today for sulfate does not guarantee effectiveness for sulfate resistance [123].106].134–137].118–121].g. and generally are help in the presence of magnesium sulfate.127. and also to the amount of pozzolan technique. Two general approaches have been taken for the specifica- The Ca(OH)2 formed during the hydration of portland ce. 20 % CaO) hydrated phases. Again. specifications for highly sulfate-resistant cements place a limit • Most Class F fly ashes generally improve the sulfate resist- on the total amount of C3A and C4AF CF. and may reduce sulfate resistance by (calcium aluminate ferrite). but at the risk of over simplification. such as those formed by hydration of C4AF ashes are variable. or Bureau of Reclamation (USBR regards to heat-treated or low-temperature steam-cured concrete 4908) Procedure for Length Change of Hardened Concrete (around 75 or 80°C). the efficacy of fly ash in waters containing magnesium cations (MgSO4).125. low-permeability concrete the composition. In some cases. tion of sulfate-resistant cements: (1) base specification on the ment can be converted to a more stable C-S-H form through a chemical composition of the cement such as ASTM Specifica- chemical reaction with reactive forms of SiO2. tion for Portland Cement (C 150). terms of increasing sulfate resistance increases as the cal- The Ca(OH)2 content of the hardened cement paste can be cium content of the fly ash decreases [132]. Portland cement with a C3A content below 5 % is generally fective when substituted for at least 50 % of the cement as long considered to be sulfate resistant [34. However. this is of no ance of Type II and Type V cements. criteria selected to base performance (comparison with other lated by a search for sulfate-resistant cements. thermal history). However. Not all guarantee sulfate resistance. or (2) performance tests such complished by adding finely ground SiO2 to the mix followed by as ASTM Test Method for Length Change of Hydraulic-Cement high pressure steam curing at 100°C or higher. alu- moderately high C3A cements were observed to have good mina present as C3A or in glass) or whether it is tied up in sulfate resistance. production of low-C2S cements is uncommon and the • Silica fume is generally very effective in improving sulfate evidence does not clearly indicate that increasing the relative resistance. some whether it is available for reaction with sulfate (e.. fly ash. have shown poor sulfate resistance [37. alumina cements generally have very good sulfate resistance A pozzolan that meets a specification such as ASTM C 618 [36. having moderate sulfate resistance and Type V cements sistance. the relevant cially those of higher reactivity such as metakaolin [124]. be stated that the designated type of cement by itself does not fectiveness of pozzolans in improving sulfate resistance. Pozzolans and slag improve sulfate resistance by chemi. The high mixes or against an absolute scale). The apparent inconsistencies are due in part to differences in the primary being good quality. it needs to There are some apparent inconsistencies regarding the ef. permeability of the concrete. more efficient in improving sulfate resistance than Class C Although the deterioration generally increases as the ashes [125–128]. Performance tests should be specified for combinations of cally reacting with Ca(OH)2 to form C-S-H and by reducing the portland cements and pozzolans or slags. However. Tests for Sulfate Resistance • If a pozzolan or slag is to be used. especially when air entrainment is of materials. more than 6000 ppm SO4 (equivalent to 0. or for mega year service aggressive environment.g.59. The lower the C3A content indicates the groundwater or soil to have a low sulfate content.128].140]. used today.114. the curing period provided prior to sulfate exposure also improves sulfate resistance.40 or below for severe and [10. having less than 50 situations. These recommenda- directly take into account the alumina content of the fly ash. sulfate attack condition may exist even though a sulfate analysis • Use ample amounts of cement. Table 1 [5] shows the resistance [123. carbonation occurring during this period mens to sulfate. processing temperature. surface area-heat of hydration) may lead to internal sulfate specifications based on chemical composition and mineralogi. the amount required It should be noted that there is no perfect test for sulfate attack.141]: exceptionally severe conditions such as magnesium-sulfate ex- • When long-range durability of concrete is at stake in an posures. For replacement mixed in the 15–25 severity of sulfate attack to be expected from the sulfate % range. high cement cifications for sulfate-resistant fly ashes. unless the decompose and re-crystallize. the quality extremely severe exposures [4. Good the effects from the composition of the cement are less judgment must be exercised as the table lists only the concen- apparent. The table is intended for use in concrete construction under The recommendations for sulfate resistance developed ordinary service life conditions. leading to physical destruction of Type II cement contains less than 5. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 261 and processing circumstances—such as excessively high heat • Steam curing at high temperatures may increase the input or presence in ground water of magnesium sulfate—using sulfate resistance of concrete if the concrete is dense and sulfate-resisting type of cement is useless. reason.37]. it is more important to specify life. the best protective measure is % C3S and less than 12 % C3A C4AF.5 % C3A. These tests include field exposures under used to advantage in reducing the water-cement ratio natural conditions. that provided by Type V cement with 4. makes the most sulfate-resistant portland ce. reliable for the ultimate protection of concrete in exposures to dated as follows [31. temperature. such as may be encountered in severe industrial exposures performance limits that will provide the most sulfate or hazardous waste containment [42. Tests for sulfate resistance are made to study the sulfate • Air entrainment is generally recognized as being beneficial resistance of different cements and various combinations to sulfate resistance. 0. Laboratory tests involve exposing mortar or concrete speci- Presumably. or externally by soaking the specimen in a solution reduce permeability. rather than to require compositional limits on containing magnesium sulfate. ment assuming the concrete quality is good. For example.80]. or where at least 50 %. As the exposure conditions vary. cal composition [138]. At very low w/c ratios. Extending the concrete matrix [34.5.145]. an additional sack of Type II ce.50 is capable of attacking all portland cement hydration products recommended for mild exposures.75 % MgSO4).5 % of C3A. ASTM C 1012). water resistance.142]. and resistance. there cannot exist a single test that applies to all • A low-lime and low-aluminate cement. in which less than quality concrete. thus testing of cements and other concrete 4 % is C3A. under severe and repeated wetting and drying conditions..96. Sulfate exposure conditions are accelerated .60. attack problems (see section on DEF). an “R value” based on Two aspects of controlling sulfate attack are identification chemical composition of fly ash (where R %CaO 5 of the severity of the exposure conditions and selection of %Fe2O3) has been proposed as a method to estimate sulfate appropriate precautionary measures. and the Portland alumina combined with lime is available for attack and not Cement Association [128]. tions are generally consistent with those given by the Bureau however. which has to be taken into consideration if mag. the better will be the These are situations where the exposure conditions may cause resistance of concrete to sulfate attack. The R values has been questioned as it does not recommended precautionary measures. uncracked [83. and laboratory tests of concrete or mortar [113.139. high temperature exposures. tration of the sulfate anion (SO4) as a criterion for potential nesium sulfate in aggressive water is an issue [83]. severity of sulfate attack and does not include cations that also • Use a portland cement with the lowest possible C3A have an effect on the conditions and severity of the reaction. either internally by adding the sulfate to the contributes to improved sulfate resistance. In this case. These have included . containing sulfate. even more than in other cases. ingredients is important but of only limited value. For example. An additional sack the water in contact with the structure to become more concen- of Type V sulfate-resistant cement will increase resistance trated in sulfates due to ponding and evaporation. of several weeks of drying following good curing.146]. and 0. water ment will not provide additional sulfate resistance equal to may evaporate and crystals of sulfate salts may crystallize. For the same testing (e. especially in concentrations of ingredients that most manufacturers can not meet. However. specimens exposed to artificial and generally accelerated • Precast units such as concrete pipe and block can be exposure conditions. R values below three indicate improved sulfate concentrations encountered in both soil and in water. is • Use as low as possible w/c ratio. as it may mixture. with a particular cement to produce the desired level of the known sulfate reaction mechanisms are numerous and sulfate resistance should be determined by appropriate complex and they may occur simultaneously.45 or below for regardless of cement type or combination of pozzolan or slag moderate exposure. high heat input (ambient Studies have been made for the development of spe. A w/c ratio below 0. the Corps of Engineers. the R value indirectly allows for alumina since of Reclamation [80]. of concrete rather than the cement type is crucial.42. As discussed above.143]. of the cement and the richer the mix. R values are not commonly the ACI 318 Building Code [144]. some made appreciably more resistant by introducing a period differences in the rate and severity of attack may be expected. but have yet to be fully adopted by when combined with iron [140]. It content [83. but may not necessarily be originally by Tuthill are fairly well accepted and can be up. Consider the availability of alumina is also possible to have cases where a potentially destructive originating from the hydrated ferrite phases. 4°F) and measuring (usually at early age) leading to thermal decomposition and length change.20 to 2. It was and Method C consists of alternating wetting and drying tests postulated that the normal early formation of ettringite was .9. magnesium sulfate exposure. blends of portland cements with pozzolans or slags. subsequent reformation of ettringite. concrete railway ties in the early 1980s in Germany [151]. by using high sulfate concentrations.5. and 2. 2. the sulfates may come from posed to aggressive sulfates and with predictions based on the minerals in the aggregates.3 requirements Class 0 exposure 0. and slag recommendations are described in Sections 2.5. uations.4 See section 2.45.2.10 and 0. as given in reports of chemical analysis of portland cements as follows: SO3 % 1. the maximum w/cm should be that specified in ACI 318.50 C 150 Type II or 1500 equivalent4 Class 2 exposure 0.7. Method B consists of continuous soaking of test used to describe a form of deterioration in heat-cured precast specimens in a 10 % Na2SO4 solution at room temperature. % in water. Methods B sulfate solutions.2R-01) Severity of potential Water-soluble sulfate Sulfate (SO4)1 Cementitious material exposure (SO4)1.40 C 150 Type V plus greater pozzolan or slag4 Seawater exposure . max.2 SO4 %. includes requirements for special exposure conditions such as steel-reinforced concrete that may be exposed to chlorides.3. such as the thaumasite destruction mechanism or ured over time.4 (ACI (ACI 201. Method A consists of continuous soak.262 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Requirements to Protect Against Damage to Concrete by Sulfate Attack from External Sources (ACI 201.2. The test is considered suitable for portland ce. 0.2R-01). Prevention of delayed lution of a given composition is desired.147–149]. 2. Chapter 4.40 should be replaced by specified 28 day compressive strengths of 26. 3 These values are applicable to normal-weight concrete. The test is considered suitable for portland ce. The latter process is ments. (76 by 152-mm) cylindrical specimens.50.9.5. An expansion of 0. . but not for blended cements or blends of portland cement with pozzolans or slags.2. or DEF. or the materials used for con- The Bureau of Reclamation Procedure 4908 [150] de.6. The test does not simulate sulfate The presence of excessive sulfates in the concrete can be attack by solutions of sulfate compositions other than that prevented by the appropriate selection and testing of the used. and 0. In the case of internal attack. and 2.2. blended hydraulic cements.00 to 0.2. 4250.9 (of ACI 201. attack are high-heat processing of concrete or other specific sit- The specimens are stored in water and length changes are meas.10 0 to 150 No special requirements No special requirements for sulfate resistance for sulfate resistance Class 1 exposure 0. For concrete likely to be subjected to these exposure conditions. was first temperature.115. pozzolan. A failure criterion of a 40 % reduction in dynamic ASTM C 452 involves adding gypsum to a mortar bar (1 by modulus of elasticity has also been used.0 or greater 10 000 or 0.26. and 4750 psi). or 25 by 25 by 250-mm size prism) in amounts so that These test methods are irrelevant if the reasons for sulfate the total sulfur trioxide content of the specimen is 7 % by mass.1 % Na2SO4 solution. The sulfate resistance of concrete is Internal sulfate attack may be induced by either (1) an excess not guaranteed. equivalents are described in Sections 2.2R-01) 201. or by using a wet-dry exposure cycle.106. materials used to produce concrete. Chapter 4. ments. admixtures and additives. however. For Class 2 exposure. They are also applicable to structural lightweight concrete except that the maximum w/cm ratios 0. equivalents are described in Sections 2. This test is used to establish that a water. by using magnesium of specimens soaked in a 2. none of them is absolute in Method A. sulfates dissolved in the mix C3A content of the cement.5 % is considered failure in [10.8.2. crete production. See section 2. 2. Delayed Ettringite Formation ing of test specimens in a 2.2. of sulfate ions in the concrete (contributed by one or more ASTM C 1012 involves expansion of mortar specimens in of its ingredients) or (2) exposure to an elevated temperature a 5 % Na2SO4 solution (50 g/L) at 23°C (73. Results of this test generally Internal Sulfate Attack conform with the long-term behavior of cements in concrete ex.2.2R-01) 1 Sulfate expressed as SO4 is related to sulfate expressed as SO3. and commonly referred to as delayed ettringite formation (DEF). 2. the test. and 2. scribes three methods for testing 3 by 6-in.90. For Class 3 exposure. respectively. the portland cement or supplementary cementing materials. or both.45 C 150 Type V or 10 000 equivalent4 Class 3 exposure 2. 1 by 10-in. if the concrete is of inferior quality.0 1500 and 0. quirements of ASTM C 150. 4 For Class 1 exposure.2. and 33 MPa (3750. and possibly from sulfates in sulfate-resisting portland cement meets the performance re. 2 ACI 318. and C produce failure in about one-sixth the time required ety of test methods have been devised. ppm w/cm by mass.1 % Na2SO4 solution at room The term delayed ettringite formation. if it is lower than that stated in Table 2. 29.20 150 and 0. and if evaluation of behavior in exposure to a sulfate so. turing and curing processes. A vari. then that solution ettringite formation requires either control of the manufac- should be used in the test. 162–164]. and increased availability of sulfate results in a conversion of ultimately all cement hydration products may be attacked. it has susceptible to this form of deterioration with cases involving not been possible to extend the models developed for one set ties being reported in Germany [119. [173]. and cement (particularly alkali content) and. Ex. but only a dissolved by even relatively mild acid solutions. high-alkali cements [168. Fortunately. These restrictions include between studies and is likely affected by the composition of the limits placed on pre-set times.158]. base chemical reactions. [151. The concrete. During subsequent exposure to moisture at reaction with acid is Ca(OH)2. railway ties appear to be particularly portland cement [119.152]. delayed formation of ettringite may under some circumstances Certain types of aggregates. long after the concrete has hardened).164–171]. This process may occur many example.165–169]. rial and production parameters.151. sulfate and alumina concentration in the pore solution of Acid solutions attack concrete through dissolution and acid- concrete. concrete. may also attack certain types of crystalline monosulfate appears to be the main sulfate-bearing aggregate particles. Most studies have indicated perience with the German recommendations dates back to that a temperature somewhere above 70°C is required.. South Africa [155]. 1977 and there is evidence that these and similar practices although expansion has been observed both in the field and in Europe have been successful in eliminating damage due the laboratory at somewhat lower temperatures ( 60°C) with to DEF [157. hence the term “delayed ettringite formation. react with acids. It has been demonstrated by numerous studies that expan- The occurrence of these problems and the apparent role sion due to DEF cannot be induced in the laboratory without an of elevated-temperature curing have led many countries to im.170. The during manufacture and that ettringite formed during subse. However. other mate- the maximum allowable concrete (or curing) temperature. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 263 postponed as a result of exposure to excessive temperatures small pores ( 100 nm) of the cement paste [164. This delayed formation around aggregate particles and cracking of the cement paste of ettringite in the hardened concrete led to deleterious expan. either A number of comprehensive reviews on the DEF phe. ASTM Test Method for Portland Cement Content of months or years following the exposure to elevated tempera. In The solubility of ettringite increases with temperature and industrial exposures. DEF process rather than a cause of damage [173]. ers.165–167. rates of heating and cooling.168.175]. most natural waters that damage due to DEF can occur without an excursion to are neutral or only slightly acidic and do not present a prob- elevated temperature (i. excursion to an elevated temperature [162. The reaction attacks concrete on the ex- lated by the rapidly forming calcium-silicate hydrates (C-S-H). through natural processes or from contamination. For some reason. Such incorporation of sufficient quantities of pozzolans or slag cases apparently involve certain modern-day high-sulfate clink. it is subject to deterioration rise effects). expansion of the cement results in the formation of gaps quent exposure to moisture in service. mine drainage. and generally involves removal Immediately after the early excursion to elevated temperature. As an the monosulfate into ettringite. The hydration product most susceptible to phase [164]. [154]. More aggressive small amount of the alumina. of soluble reaction products. Fly ash. and attack nomenon have been published recently [27–30. and poorly products and.e. such as limestone and dolomite that result in expansion of the paste and consequent cracking of the contain carbonate minerals. The acid attacks cement hydration little or no ettringite is detected in the concrete. However. Finland [118]. and exposure to elevated temperatures increases both the variety of acidic solutions.163. of cements and test conditions to the results of other studies the former Czechoslovakia [153].. there is no laboratory evidence to confirm in exposure to acid solutions. lem. elements where it has not been possible to prove unequivocally that DEF is the primary cause of deterioration or that the Acid Attack concrete had not been exposed to elevated temperature either deliberately or adventitiously (due to autogenous temperature As concrete is an alkaline material. which reportedly result in a slow or late release of sulfate metakaolin) are all effective in this role whereas silica over time (i. Much of this sulfate and alumina becomes encapsu.162. It is now generally believed that the paste expansion The two main factors involved in the chemical reactivity results from the growth of ettringite crystals in the very of an acid are the concentration and strength of the acid. posed surface and works inward. . and Australia [120. Since this time DEF has been the cracks. possibly. concrete may be exposed to a wide pH.e.” This dissolution of all hydrated cement paste in hydrochloric acid.156]. Natural processes for acidifying water include the mechanisms of DEF are now fairly well established as are decay of organic matter in marshes and swamps. somewhere above 60–70°C). but this process is harmless being a symptom of the implicated as a cause of deterioration in numerous other cases. All of the fume is not. is released by the C-S-H.g.174]. slag and natural pozzolans (e.171]. and agricultural and industrial wastes. in some cases.172]. natural waters can become acidic. It has also been claimed that concrete that has not been Damaging expansion can be prevented in mortars exposed to elevated temperatures may suffer deterioration due and concretes cured at temperatures up to at least 95°C by the to so-called “ambient-temperature” DEF [154. Natural waters can also be contaminated by acid pozzolans or slag [151. the United States using different materials and test conditions [164].159–161]. To date. Ettringite eventually reprecipitates into these gaps and sion and cracking of the concrete. It appears that the alumina content of the poz- evidence to support this viewpoint comes from investigations of zolan is artly responsible for mitigating the damaging effects of damaged nonheat-cured precast and cast-in-place concrete DEF [168–171]. Canada. The pose restrictions on the heat-curing process used during the precise temperature necessary to produce expansion varies manufacture of precast concrete. which is readily attacked and normal ambient temperatures most of the sulfate. Most of these cases have involved precast concrete elements A number of workers have attempted to develop models to that have been subjected to heat curing during the production predict the expansion due to DEF from the composition of the process.151. The acid solutions react with other cement hydration products. Hardened Hydraulic-Cement Concrete (C 1084) is based on ture.. and absorp- means for minimizing the risk by controlling the maximum tion of gases and pollutants from the atmosphere such as CO2 temperature reached within the concrete or by incorporating and SO2. Ka. rather than below where the sewage is in than an acid solution of pH 6. from highly to slightly reactive.1-normal solution has a pH of Concrete sewer lines are susceptible to acid attack al- 1. the HCO3= alent weight of a completely dissociated acid per litre of water) ionizes to H CO3=. weak acids do not due to carbonic acid (H2CO3) which forms when the water completely ionize.77. and is a strong acid. terms of pH. and reactivity increases as the H concentration mosphere and inversely proportional to temperature. the CO2 combines related to both the strength and concentration of the acid in the with water to form carbonic acid. calcium hardness. A neutral solution has a pH of 7. The intrinsic reactive and oxalic acid is only slightly reactive. Vinegar is dilute acetic acid.177. most engineers are interested in rules of thumb tion products. the transport of the acid into the concrete if industrial wastes are discharged into sewage lines. but on an equal volume basis. When sewage is stagnant or in addition to the strength and concentration of acid. As acid solutions are commonly described in concrete and as the flowing solutions tend to remove the reac. step. Strong acids have a large dissociation constant and a small The leaching of concrete ascribed to soft water is largely pKa. may tend to seal the concrete surface from the acid resistant slag cements or supersulfated cement).5). The extent of the attack is governed by the rate regarding the resistance of concrete to acids at various pH the acid penetrates into the concrete. and sulfuric protected [4.5 that form insoluble reaction products. Ka).180].5 acid attack may range from slight to and form insoluble reaction products that are not readily somewhat aggressive if the acid is replenished and some removed. pKa log concrete to various acids [4. and below pH and impede further reaction of the acid with the concrete. Most exposed aggregate surfaces. soluble products. Although pH by itself is not necessarily a good indicator reaction products are generally more aggressive than acids of aggressiveness. battery acid is concentrated absorbs carbon dioxide (CO2) from the atmosphere. and may show some recommended for these purposes as the reaction is difficult to inconsistencies as the acid is consumed during the test. Organic acids range expressed either in terms of normality or molarity. Strong acids ionize completely in water. Ka. The gas rises and combines with oxygen and with moisture have the same pH as a concentrated solution of a weak acid. such as SiO2 gel. which is a function of the sulfate ions it contains are also available for sulfate attack pH. acidic. For neutral to moderately acidic acid are among the more common acids and are highly reac. acids. which produces hydrogen sulfide ample. A 1-normal solution of a strong acid (one gram equiv. as more CO2 is dissolved and the pH decreases. The deterioration of concrete in sewer lines is observed that is.10.182–184]. running full or with ventilation at higher velocities. but may be misleading. precautionary measures may be advisable (such as chemically or CaSO4.178]. In the first step.264 TESTS AND PROPERTIES OF CONCRETE The concentration of a particular acid solution refers to the control and as it is difficult to make sure the surfaces have weight of acid per unit volume of water and is commonly been washed clean and all acid removed. citric acid. These moves slowly. the nature of the reaction product tion may significantly change and present a special problem.12. Flowing solutions are more aggressive than whether concrete will be resistant to acidic solutions of varying static solutions as more acid is brought into contact with the concentrations. As the increases. bacterial creation of the sulfide may be too rapid factors include exposure conditions (exposure to static or for the sulfide to be oxidized by air dissolved in the sewage. dissociates to a much lesser extent The effect of CO2 on the pH of soft water is quite complex (pKa 4. most investigators seem to feel above pH 5. theoretically has a pH of 0. Oxalic acid is property of a particular acid to dissociate in water is indicated sometimes beneficial as it has been used as a floor treatment by the dissociation constant. the situa- (diffusion and permeation). natural waters. and tartaric acid are highly to moderately dissociate in water and form protons (H ions). Acids that form soluble levels. the American Water Works Association recom- tive with concrete. Insoluble reaction products. is highly ionized (pKa 1. formed. For example. acetic acid (vine- The strength of an acid is determined by its tendency to gar). and is a weak acid. an acid solution of pH 4 is 100 times more concentrated above the water line. a given volume of the weak corrosion problems in the crown portions may be reduced by acid ultimately will be more destructive to concrete than an design or operating modifications that results in the sewers equal volume of the stronger acid as the weaker solution con. For ex. Lactic acid.92). The amount of CO2 that can be dissolved in water is The chemical reactivity of an acid is due to the hydrogen directly proportional to the partial pressure of CO2 in the ation (H). [179. 3.77. reactions. and in some cases. Problems of acid attack above pH measurements are commonly used as an indicator of the water level in sewers arise indirectly from the bacterial the aggressiveness of a solution. Sulfuric acid is particularly aggressive since mends using an Aggressiveness Index. H2CO3 dissociates to defined as equal to the negative logarithm of the H concen. Lower tains more acid [77]. Such H2SO4. Most acids react to form the prospective severity of acid attack is zero to very slight.36. Carbonic acid dissociates to solution. decomposition of sewage. the rate at which the reaction prod. however. it is possible for a dilute solution of a strong acid to gas.176]. and total alkalinity [185]. oxalic and phosphoric acids are exceptions from about pH 4 to 5. and a 0. CaCO3. But running solutions). form H HCO3. In the second tration). The literature contains tabulations on the exposure of rithm of the equilibrium constant. for the acid. for the acid.5 acid attack may be severe and the concrete should be Hydrochloric acid (muriatic acid). waters are quite aggressive towards concrete [9. Dilute hydrochloric acid has been used to clean Testing for acid resistance usually consists of soaking test concrete surfaces and for architectural purposes in making specimens in acid solutions followed by periodic testing. condensed on upper surfaces of the sewer conduit to form Both solutions may initially attack concrete at about the same sulfuric acid where it reacts with the cement paste [181]. A decrease of a full pH unit though the sewage itself is usually neutral or only slightly represents a 10 times increase in the concentration of the acid.10. temperatures also tend to reduce the production of acid- The rate and extent of attack is governed by several factors forming hydrogen sulfide gas. nitric acid. hydrochloric acid is not tests are run under static conditions. lowering the pH of the water. ASTM . The H concentration of a particular solution is dissolved CO2 content of the water increases.6. Acid rate. which also may to improve the resistance of the floors to other weak organic be expressed in terms of pKa (defined as the negative loga. direct contact with the concrete. and is commonly expressed in terms of pH (originally produce H in two steps. which further lowers the pH. Engineers are often faced with questions concerning uct is removed. Generally speaking. The role of chloride appears weight loss. the concrete cement concrete is considered suitable for use in exposures generally deteriorates from erosion and loss of concrete con. reinforcement. Ettringite is also more soluble in solutions con- There are several mechanisms involved in the deterioration: taining chloride [194]. Leaching and subsequent erosion of concrete is more severe in seawater as Seawater and Brines calcium hydroxide and gypsum are more soluble in seawater than in ordinary water.43. the solubility of Ca(OH)2 is increased. Bureau of nesium sulfate and sodium chloride. The use of pozzolans such as fly ash corrosion of reinforcement and freezing and thawing. The fact that plain concrete (nonreinforced) of good quality can Chloride reactions appear to have three main effects on have good resistance to seawater is amply demonstrated by the the cement paste: lowering of pH and dissolution of Ca(OH)2 many examples of structures showing good service life af.64. weight structive to concrete as the total sulfate content of the water loss. The permeability of concrete Ca(OH)2 is only very slight at pH 13.81. . and below the water line by chemical cements and polymer concretes work well [199]. and in tions involved in seawater attack may vary according to the saline water conversion projects involving the use of concrete exposure and temperature conditions and according to structures. frost action. and as the pH is low- involve the deterioration of poor quality. but increases as pH is is one of the key factors in seawater attack [81].186–190]. presence of sufficient sulfate the chloroaluminate will con- freezing and thawing.5. The most commonly Reclamation in a study on the use of portland-cement concrete described reaction of seawater with cement paste is sulfate in saline water distillation plants [22. but usually the course of chemical attack may vary with depth within the there is no guarantee as to their long-term effectiveness concrete according to rate the reactive species penetrate into [4. good consoli- crete exposed above the high tide line is subject to attack from dation. and showed only slight surface deteriora- reaction is somewhat different than ordinary sulfate attack tion at exposures up to 250°F (121°C). under investigation over a period of time. Conventional portland in that the reactions seem to be more complex. and the cial concrete is provided. These investigations attack although other reactions involving chloride and magne.192]. formation of chloroaluminate over ettringite.5 % dissolved salts. Chloride ions penetrate cement paste Surface treatments or protective coatings are sometimes more readily than sulfate and other ions. If the exposure is severe.36. Concrete exposed to seawater at chemical composition of the cement seems to play only a 290°F (143°C) for 40 months showed surface deterioration to minor role if at all [36.43. Most of these examples tend to reduce the pH of the system. low water/cement ratio. Chloride and dissolved CO2 in the seawater also resistant cement than to rely on a protective coating system. con. however. a high cement content. reactions between seawater and cement paste that soften The question of the durability of concrete in exposure to the concrete and make it susceptible to erosion [81. vert to ettringite. and wave action [8. in the corrosion of steel reinforcement. with the result that prescribed for concrete exposed to various acids. wetting and drying effects. Specimens are Most investigators observe that seawater is not as de- removed periodically and tested for visual appearance. especially at high temperatures. concrete and silica fume. Hot seawater exposure stud- types of ettringite have been observed: one type is associated ies performed on concrete made with a crushed limestone with Type I and II cements and is considered expansive4 and coarse aggregate showed that the limestone is susceptible to 4 This does not mean all ettringite in concrete made with Types I and II cements has caused expansion. reaction with calcium aluminate to form ter many years exposure to seawater. The leaching of the corrosion of reinforcing steel.S. corrosion of the resistance of the concrete to chlorides [10. the depth of penetration of the various seawater constituents The durability of concrete exposed to distilled water and into the concrete. and up to 250°F (121°C) if sacrifi- stituents rather than by expansion and cracking.200].36]. and loss of compressive strength. has been investigated fairly extensively by the U. In very severe cases. act to dissolve Ca(OH)2 in the cement paste. ranging up to 200°F (93°C).195–198]. and suggest this is due to the effects of dis- should be conducted on a depth of scaling basis rather than solved chloride on the reactions. But there are also many examples of concrete permeability of the cement paste [36. This generally means using conditions of the concrete to seawater. and enlargement of pores and increase in the also be found. The presence of chloride favors the leaching and chemical attack of the cement paste by seawater. and workmanship. Two long-term use at this temperature. THOMAS AND SKALNY ON CHEMICAL RESISTANCE OF CONCRETE 265 Test Method for Chemical Resistance of Mortars (C 267) the other type is associated with Type V cement and does not consists of immersing test specimens in the particular solution appear to be expansive [41].95. showed that conventional portland-cement concrete is not af- sium ions and carbonation also occur (see discussion of MgSO4 fected by exposure to seawater for four years at temperatures reactions under the section on sulfate attack) [10. to be quite complex. permeable concrete or ered.176].9. or slag cements can result in substantial rein the tidal zone or splash zone is susceptible to cracking and ductions to the permeability of concrete and hence increase spalling from wetting and drying. special cements such as high alumina tions by wave action. the concrete.193. mainly mag. brines and seawater.194]. The main line of defense against seawater attack is making The type of attack on concrete depends on the exposure good quality impervious concrete. synthetic seawater brine at normal and elevated temperatures Seawater contains about 3. Examples of good chloroaluminate and suppression of the formation of calcium performance of concrete made using seawater as mix water can sulfoaluminate.36. industrial situations. it is better to use an acid. Chlorides deterioration in exposure to seawater. Biological attack has also been identified [191]. lowered [193]. and gypsum. arises in The mechanisms for deterioration are complicated as the reac. Some feel such tests would indicate. The observed deterioration does a depth of about 15 mm and was not considered suitable for not seem to be related to the presence of ettringite per se. The up to 200°F (93°C). hazardous waste containment.87]. and erosion of material from chemical reac. of strong bases. decrease permeability and improve frost posures is not recommended. or both. when 201–205].5. such as chemical attack or freeze-thaw cement concrete under ordinary circumstances. and that the concrete undergoes abnormally [202. The Metals and Materials Other Than Reinforcing Steel).216]. may result in an carbon dioxide dissolved in water is discussed in the sections increased rate of carbonation in concrete. but also as a means to control shrink. Consideration should Carbon dioxide gas reacts with calcium hydroxide in the be given to extending the period of moist curing or reducing hydrated cement paste to form calcium carbonate [36. der prolonged exposure conditions or at elevated temperatures. especially in poorly on Scaling. glycol. most alkalies. temperature. called “carbonation. These oils form hardened films and have that may produce cracking or surface crazing of concrete been used as protective coatings on concrete. and over long periods of time will be ultimately converted to calcium carbonate and hydrated silica Attack by Other Chemicals [65. while beneficial and detrimental effects in concrete (the reactions of improving many properties of concrete. Salt attack treatments are reported to harden surfaces. and glycerides are saponified by the lime in hydrated sumes calcium hydroxide.213]. and reactivity of the particular chemical must also be bonation becomes of interest not only in studies to separate the considered. particular situations may cause damage in other ways.217–219]. salts of acid hydroxide carbonate weak bases. The literature The long-term exposure of concrete to the atmosphere of. The use of limestone aggregates in such ex. The severity and rate of attack may vary appear to be around 50 % RH. is recommended to assess the potential for deterioration. Examples of these materials are vegetation that may at 100 % RH. Carbonation reaction con. concentrated solutions of Carbonic calcium calcium water strong bases such as NaOH.176. The shrinkage is generally Such generalities on the resistance or susceptibility of con- attributed to two main causes: (1) a gradual loss of moisture crete to chemical attack should be taken with some caution as (drying shrinkage). phenol. may have indicated that carbonation does not occur in dry cement react with other substances in the environment and become or cement at 100 % relative humidity (RH) [204]. and creosote.10. Many salts are not particularly harmful to plain portland structive mechanisms. parapets. and (2) carbonation. The process has been used as a means to large expansions. Some chemicals ordinarily considered as not par- two causes for shrinkage. and imperviousness of concrete [207]. the corrosion of reinforcing steel. undergo oxidization and polymerize curs. drying oils steel. ing if the shrinkage is great enough. concrete made with resistance. vegetable and animal oils. Vegetable and animal oils usually contain fatty acids that though these problems do not appear to be quite so wide may be oxidized to form more acid during the exposure and spread in North America [208]. control dusting and increase wear resistance.203.” These forms . The deterioration is caused by become even more aggressive towards concrete. using high levels of pozzolans or slag. their effects on concrete [4. Carbonation often acts in concert with other de. but in some action [212]. terioration of concrete balconies. sulfates. and ultimately may prove to be aggressive towards concrete. prevent crazing. ble to carbonation. and processes have been developed to use car. and to control aggressive chemical reactions including sulfate attack. aggressive. further carbonation and alkali-aggregate reaction. and Leaching and Acid Attack). Apparently. con- the long-term volume stability of concrete is important. animal wastes.204.” is known to produce both than normal levels of pozzolans (such as fly ash) or slag. chlorides. nitrates. Intentional carbonation of freshly placed concrete is an ef. In situations where the length of exposure. These include acid-producing substances. sugar. of the natural siliceous aggregates did not show signs of deleterious surface. increase compres. increase imperviousness. Moisture is an important factor in carbonation. fective means to control shrinkage and also to improve and progressively attack concrete over a period of many years. car. Studies Some substances. such as on sive strength. However.266 TESTS AND PROPERTIES OF CONCRETE dissolution when directly exposed to hot brines. Carbonation also causes shrinkage of the cement paste when exposed to air. neutral carbon water Carbonic salts and many salts. destroys the passivation effect of cement to form alcohols that can react with more lime to fur- calcium hydroxide in preventing the corrosion of reinforcing ther deteriorate the concrete. (linseed oil and tung oil). although it is susceptible dioxide acid to varying degrees of attack by other chemicals not already covered in this chapter. al. which by themselves may be harmless. etc. On the other hand. centration. attack” (corrosion is discussed in the chapter on Embedded bonation as a treatment to produce beneficial effects. Many oils.. facades. fats. Efflorescence.209–211]. glycerol. the water-to-cementing-materials ratio (W/CM). magnesium salts. All calcium silicate hydration products are suscepti.207. fats.206]. such as Both fresh and hardened concrete are susceptible to by accelerating the corrosion of reinforcing steel or by “salt carbonation. exposure conditions.36. [205. The basic reactions are Concrete has good resistance to attack by dry chemicals. However. includes both “salt scaling” and “salt weathering. the moisture blocks carbon dioxide from passing decompose to form organic acids and sulfides that may oxidize through the pores. The reaction of carbon dioxide gas with hydrated portland The partial replacement of portland cement with higher cement. ticularly aggressive towards concrete may react very slowly un- age. The optimum conditions for carbonation to form sulfuric acid.77.64. contains fairly comprehensive lists of various substances and ten results in shrinkage of the concrete and sometimes crack. dry CO2 H2O → H2CO3 soils containing chemicals. H2CO3 Ca(OH)2 → CaCO3 2H2O ammonia salts. mineral oils. and reduce shrinkage sawed surfaces. carbonation of low-strength concrete with a high water-to- Carbonation cementing-materials ratio (W/CM) can result in considerable weakening of the cement matrix [214]. and lowers the pH to a point where corrosion readily oc. cured. greatly and an actual test under anticipated exposure conditions Carbonation is of concern in Europe in regard to the de. hardness. strength. low-strength concrete [215. usually sodium or calcium chloride. on concrete in freezing New York. [5] “Guide to Durable Concrete. and Liss. freeze-thaw resistance: use a high quality..231. Idaho. 67. West Conshohocken. “Evaluation of Concrete for Desalina- [2] Raiswell. 4. including silica fume and [15] Langlier. and adsorption effects that cause swelling and shrink- Chemistry Series No. Inhibition.. A. Detroit. H. J.” Report REC-ERC-71-15.. R. Scheetz. Denver. R.. N. International. F. [7] Terzaghi. J. L. American Scott. A.. Model WATEQ2 with Revised Data Base. B. L. 1989. R... Nordstrom.” PCA Concrete Information Sheet. [11] Stumm. Ed. J. been fairly well established [40. and Glasser. Journal. Feb. and Chang. although the process is fairly widespread [58–60. Admixtures Are Used. New York. “Concrete Deterioration Due to Carbonic Acid.S. VA.146. “WATEQ4F— A Personal Computer Fortran Translation of the Geochemical Surfaces Exposed to Deicing Chemicals (C 672) [226... 1989. osmotic pressures. American Concrete Institute. 1949. Detroit. P. J. W. 1950. “Internal Sulfate Attack in Concrete Related to SP-131. as by ASTM Test Method for Scaling Resistance of Concrete [16] Ball. 17th ed. P. J. [3] Roy. Facultad de Ingenieria Civil.. and Brown. P.. [20] Plummer. T. Bureau of attack to expansive pressures generated by the formation of Reclamation.. W. dense. air-entrained [14] Schaffer.. The crystal growth mechanism for salt attack has Washington.. E. such 69. and salt heaving. M.. 217 pp. Eds.. J. and therefore Journal. I. 1950... 1998. 1980.” Betonwerk Fertigteil- such as corrosion of reinforcing steel. C. “Proceedings of Symposium D of the and Concrete-Making Materials.. Washington.. Jenkins. B. of concrete surfaces associated with the use of deicing salts. Concrete. 1989. Duggan. 2. American Concrete Institute.. tion Plants. W. “Leaching of Lime in from Concrete” (Discussion). 2002. 6.. No.. P. and also in regards to historic preserva. Vol.. weather [220–227].2R. London. APHA-AWWA-WPCF. 1992. 1987. 1986.” Cement and Concrete Research.229.” Bulletin. Mexico. 1967. 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Vol. Geological Society of America. 1990. 79. P. “Elusive Solution to Pastes. L. 19. American Concrete Institute. 4.” Proceedings. G. “Growth and Dissolution of Crystals Under Nov. 1916.. 1963.” tion. are well estab. crete mixtures. Fire Testing. the fire resistance of structural and fire pro- provide much information about the effect of specific high tection components of buildings are usually based on the fire temperatures on the properties of concrete. IL. including fire resistance. temperatures. endurance as determined by ASTM Method for Fire Tests of terials. To Building Construction and Materials (E 119). building materials when exposed to fire. such tests do not In North America. 60077.” Peter Smith authored the chapter in STP 169B entitled measuring techniques. It is relatively easy to determine the residual properties by standard test THE FUNDAMENTALS OF CONCRETE PERFORMANCE methods and the results provide much of the information at high temperatures. or reinforcing steel except in a very general way. By selection of the appropriate combination of ments based on a combination of knowledge of the physical these for a particular application. including fire. Accordingly. A standard fire ex- improve fire resistance in building design. posure is defined by a time-temperature curve in which 538°C dition and possibilities of repair of a structure damaged by fire. as new concrete constituents and propor- combustible and a reasonable insulator against the transmis. Szoke1 Preface residual properties after slow or quench cooling. Portland Cement Association. H. applications. While some industrial and military applications properties of the body of the concrete remain intact. 274 . such as those arising from the use modeling offers promise for extending the results of fire tests of high-strength concrete. (1000°F) is attained in 5 min. In many require special concrete that is resistant to specific service tem- applications. and the design of con- Building codes contain minimum fire protection require. 927°C (1700°F) in 1 h. and re. and demonstrating the beneficial effects of restraint and support from Introduction unaffected cooler parts of the structure. causing excessive structural deflections that structural system and design details chosen. in particular for nuclear reactors. three of any embedded steel for as long as possible against a rise in tem. and upon fire endurance ratings specified by the survival times of specific struc. Third. Computer search results are addressed.25 Resistance to Fire and High Temperatures Stephen S. These qualities alone are considered in design for specified compressive strengths in excess of 83 MPa [12 000 fire containment and limiting the extent of the damage. the main role of concrete in a fire is to protect perature regimes. tural assemblies or components in standard laboratory fire and Modeling tests. information is needed to determine if and what modifica- Though portions of the surface of concrete elements may tions should be made to methods for determining fire crumble or spall. the desired resistance to high properties and past experience of the behavior of various temperatures. Endurance Standards. it is needed for with the present title. Concrete is non. advanced industrial applications. such has concrete with sion of heat. Second. fortunately for most constructions. Usually only the ambient temperature regime to a maximum is controlled in these tests. techniques of heat flow and structural behavior. the cardinal need for public safety in the face of the hazards of mechanical and thermal stress regimes at moderately high fire better than most alternative materials. Peterson under the title “Resistance to Fire and Radi. lished. require One of the main reasons why portland cement concrete is so a greater knowledge of the physical properties of various types widely used in building construction is that it can help satisfy of concrete when subject to complex. the thickness of might lead ultimately to collapse. or to assess the con. its constituent ma. psi]. However. needed to determine what can be saved after a fire. sustained or repetitive. Codes and Standards Department. the most important factors are within the control of the de- perature to the point where its physical properties are reduced signer and specifier prior to placing concrete. First. though new products. This kind of information has become in- “Resistance to High Temperature” and the one in STP 169C creasingly in demand for several reasons. Exposure to the furnace temperature is on one side 1 Director. on discrete assemblies to the more general cases. These are: the significantly. Skokie. more often than not the essential engineering endurance. can be achieved. and 1260°C more needs to be known about the thermal and mechanical (2300°F) in 8 h (assuming an end point has not yet been properties of steel and concrete at elevated temperatures and reached). This subject was authored in ASTM STP 169 and 169A experiments to determine the same properties at sustained or by P. tions continue to become available. cyclical high temperature require special equipment and ation. major revisions have not the development and validation of computer-based modeling been necessary. cover provided to any embedded steel. Therefore. Three other factors may significantly influence the reported on thermal factors arising from moisture content and fire endurance of concrete elements. measured at room temperatures. and columns are exposed on all vertical surfaces. Tests reviewed by Benjamin [3] sug- addressed the special problems of prestressed concrete sec. (2) that symposium provide a good opening to present-day think. or 4-h rating). Further guidance 119 requires load combinations that result in the maximum on determining the fire endurance of concrete elements is pro- load. The proceedings of performance of structural concrete: (1) type of aggregate. some degree of conservatism is (ACI 216. ditions as having particular influence on the high-temperature crete Institute (ACI) Symposium was held. sistance. elasticity. resistance to the passage of a hose stream. specimen. Load factors are assigned for specific com. (3) stress levels in both steel and ing on fire resistance through four comprehensive papers. sistance of Concrete and Masonry Construction Assemblies binations of loads. and a rapid significance of standard fire test procedures and the influence worsening in most mechanical properties of structural value. [10] also found that (9) the use of silica While the results are specific and particular to the component fume in the concrete mix influences the performance of con- or assembly tested. and placement of reinforc- strength. The requirements and leads to high thermal stresses. beams are exposed from beneath and concrete elements having similar configurations. when an American Con. Carl. with building code provisions. Generally speaking. gest that (8) the volume and relationship of volume to surface tions. vided in a report of ACI 216 [9] and is beyond the scope of this sign criteria. load carrying ability during the structural behavior at high temperatures. the en- in the applicable building code along with related design crite. Alternative superimposed loads and restraint may be added to simulate in. be used to determine the applied load on the test chapter to further discuss fire-resistant structural design. Uddin and Culver [1] cite 149 historic references cov. parameters into account. are prescribed as free water starts to be driven off. which list six interrelated material properties and con- ering the period from 1884 to 1961. concrete exposed to high-temperatures begins at a lower The appropriate fire endurance requirements. The almost limitless number of constituents and their pro- • For walls. In general. Test Methods dance with ASTM Practice for Application of Hose Stream (E 2226). ASTM E 29) [8] are based on ASTM E 119 test data. They include the following: dict the heat flow process in concrete elements to establish • Transmission of heat. microcracking. Lin et construction and improve fundamental knowledge. with improvements being crete does not occur suddenly at a specific temperature. The mathematical models tend to pre- modes of failure in an actual fire. [11. concrete. introduced as the development of knowledge and experience Previous chapters focused on the review by Uddin and Cul- dictated. the end of structural usefulness of a particular con- have been debated for over 100 years. test exposure. the progressive continuum of cement dehydration re- not to ensure structural survival or ease of repair after the fire actions. Fire endurance is then stated in terms of time to reach For most applications. bound temperature of 100°C (212°F) and immediately above sure safety in a particular set of circumstances. in accordance with nationally recognized structural de. These design criteria consider factored loads in. However. specific surface temperature criteria. configuration. cover to reinforcing steel. and details for concrete elements de- For load bearing elements. portions. the assembly must also resist the passage of a Factors Influencing Behavior and Affecting stream of water when subjected to a hose stream test in accor. interest in the behavior of structural whichever end point occurs first (such as 1. fire endurance without the expense of full scale testing con- End point criteria in the test are intended to simulate tinue to be developed. the gate. Kodur et al. taking material and structural • Transmission of hot gases sufficient to ignite cotton waste. It is difficult and much more expen- Minimum specimen sizes (areas or lengths exposed) and a mois. It must be emphasized that the prime purposes of fire tests peratures vary by only a few percentage points from those and related criteria are to ensure life safety of the building oc. ver [1]. etc. researchers and fire testing laboratories area of the concrete elements also has a significant influence around the world have worked actively to evaluate new types of as temperature drop from the exposed surface is steep. For walls.12] found that increasing the cross section size of The establishment of fire endurance ratings by means of columns. Benjamin [3] heat. sive to simulate the effects of restraint by cooler parts of a con- ture condition requirement prior to testing are specified and crete structure that are clear of the actual fire [6]. mathematical modeling methods to more precisely determine service conditions. gineering properties and behavior of concrete at these tem- ria. 2. [10] found type of aggregate. on structural factors such as concrete that (7) the amount. 3. thermal incompatibilities between paste and aggre- (though often the more fire resistant the construction is. concrete. and (6) thermal conductivity. and physical-chemical deterioration of some aggregates more likely that it will be salvageable). and radiant heat. the results are generally extended to other crete having a specified compressive strength greater than 83 . even in one direction significantly increases fire re- standard fire tests is both expensive and time consuming. configurations. of structural design and material parameters on fire endurance However. the maximum load condition is manded the development of analytical methods to determine defined as that allowed under nationally recognized structural the fire resistance rating of concrete elements for compliance design criteria. diffusivity. from the sides. above about 149°C cupants and to provide property protection in case of fire and (300°F). Troxell [5] than 83 MPa (12 000 psi). constituents. to then predict fire endurance and • For load bearing elements. al. Since then. specimen size. Sheridan [4] dis. and thermal properties. (5) modulus of son [2] looked at the effect of moisture. necessary to en. spalling. Methods such as the American creasing the load to account for potential variations over the Concrete Institute Standard Method for Determining Fire Re- life of the building. and lateral ing steel ties has a significant influence in high-strength restraint as affecting fire endurance ratings. (4) cover over reinforcing steel. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 275 only for slabs and walls. restraint. Kodur et al.1) [7] and American Society of Civil Engineers Stan- provided because the maximum load experienced is less than dard Calculation Methods for Structural Fire Protection (ASCE the maximum load conditions during the fire tests. temperature distributions and. when the specified compressive strength is greater cussed concrete as a protection for structural steel. free moisture in the concrete. Then. In the [15]. This. are not representative of actual concrete ele- adopted of first considering the influences of component ma. such as Most of the factors interrelate and the format has been Kodur et al. bonate aggregate and the chemical stability of lightweight or The development of distress and the change for the worse in instability of siliceous aggregate concretes are very evident in the thermal and mechanical properties of portland cement their loss-of-weight test data. While a case may be made for using fly ash or blast fur- port a general observation that a property easily be determined nace slag cements mainly because these produce lesser at normal temperatures by standard tests often can only be de. The corresponding cooling curves oxide is a relatively simple process occurring above 400°C demonstrate that most of the reactions and events that occur (752°F). The stage reached at any given exposure and specimens are not representative of actual con. chemically bound wa- tributed to the accommodating plasticity of the cement paste ter (nonevaporable) is released progressively from the complex at high temperatures. graphical displays of test results in the references discussed. high range water reducer was incorporated. The overall pattern of their length system of low crystalline order. and change data confirms the complex superposition of dehydra. are specific to experimental techniques and sup. in practice these are little used for such benefit alone. Most of these . where this is mina cements are used in refractory concretes but may not be not essential. there was a great re- Two tests have proved useful in obtaining an understand. through any intermediate stages. Bertero et al. Desorption of what in volume in siliceous aggregates. Dehydration is complete phenomena occurring at specific temperature exposures. However. One important result from the pastes that occur with increasing temperature are the result of an change-of-length test is to show that the - quartz transfor. On the other hand. it is not possible to reproduce the many rently used in typical building design practice today. it decomposed re- cific chemical and physical changes that occur with increasing leasing ammonia gas. is commonly called evaporable water first takes place as the tem- ding change in the concrete. then the mechanical and thermal properties of ordinary strength concrete columns tested was less than one-half the concretes and. Dougill [14]. concretes in special applications. among other investigators. including but with a disruptive 14 % increase in volume. many of the differences attributed an increase in compressive strength and decrease in reported in measured values of various properties may be the modulus of elasticity in the temperature range of ascribed to differences in test conditions. Two references. and Philleo [19] involved small specimens present. Such limitations may not be representative of typical during curing. Hertz [16]. perature range of 177–232°C (350–450°F). duction in structural properties of fly ash concrete. All the essential ones covering steel properties. while the 121–149°C (250–300°F) to the formation of tobermorite that is actual numbers may differ. calcium silicate hydrates. Choosing one portland cement over another will do little to im- Throughout the discussion. High alu- measure various properties will be identified or. will rehydrate to calcium hydroxide Many of the tests discussed in this chapter.276 TESTS AND PROPERTIES OF CONCRETE MPa (12 000 psi). [13] and Purkiss and phenomena that may occur under normal service conditions. experimental techniques to prove the properties of concrete at high temperature. The use of silica fume appears to reduce the mens or coupons are used the maximum aggregate size is also permeability of the concrete restricting the loss of moisture limited. Silica fume additions have been shown to increase the risk essarily accompanied by loss of weight. there is a usually good agreement much stronger than tobermorite gel. Frequently when small speci. Zoldners [18]. Cement dehydration or the decomposition of car. factors such as dif. temperature is dependent also upon the rate of heating since crete elements used in structures. At lower temperatures such as those that might be experienced ods is often required to determine some relevant properties at in mass concrete in nuclear reactors. after cooling and in during heating are irreversible. The dehydration of calcium hydroxide itself to form the formance of concrete. As a result. the largest cross-sectional area of the high terials. While silica aggregate in contact with cement paste is larger and the fume and other changes in the basic constituent of structural smaller aggregate typically results with an increase in concrete may influence the fire endurance. and the fire test. the at 800°C (1472°F) and above. are of much less importance. Within cross-sectional area of high strength concrete columns cur- the space available. other hydrates in the cement paste and from the calcium hy- tion shrinkage in the cement paste and expansion of the droxide crystals formed when the cement originally hydrated. Nasser and Marzouk [20] elevated temperatures. Malhotra the dehydration of the silicate hydrates and other compounds [17]. while certainly causing an increase companied by shrinkage and microcracking. and temperature distribution across various sections can be found in the references. amounts of calcium oxide as a result of dehydration in the heat termined at elevated temperatures with difficulty. measure change of length may detect other reactions not nec. drying. of existing standard methods or the development of new meth. and overlapping. Harmathy and Allen [15] at. used these to examine the same investigation. the amount of paste for a given volume. Both may exaggerate ferent types of portland cements. Subsequently. it was noted that when a melamine-based overall stability of a variety of concretes and to pin-point spe. mechanical and Influence of Cement Paste Component thermal properties of concrete. the calcium oxide. left to the details provided by the referenced appropriate for structural purposes because of the conversion sources. the presence of moisture. admixtures appear to have no temperature. Even “full-scale” tests. be due to the formation of crystalline alpha dicalcium silicates Thermogravimetry tests provide insight into chemical that are poor binders. Modification of a fire. Fly ash as it affects lightweight concrete reactions involving loss of weight while dilatometry tests that is discussed under that section. Harmathy and Allen of explosive spalling in very high strength concrete [16]. ments. Otherwise. finally. unusual effects. not limited to Purkiss and Dougill [14]. [10]. the effects of the cement paste. uninterrupted series of physical-chemical reactions that are ac- mation at 573°C (1063°F). perature increases. thought to ing of the observed behavior of concrete at high temperatures. In the latter. After six months in a tem- on the general trends reported. This latter concept has concrete used in structural members as the surface area of the not been thoroughly researched or evaluated. did not cause a correspon. aggregate as being a major factor in high-temperature per. is more complicated or coupons of concrete and while the tests identify the and gradual and not fully understood. all the reactions are not instantaneous. ect.) columns with 38-mm (1 1/2-in. Many investigators have con. The consequence in concrete is firmed that cement paste expands up to 100°C (212°F). Many findings that carbonate aggregate increases the fire endurance of these events are evident in thermogravimetric. the thermal conductivity is only half the and a high specific heat to absorb heat. in the concrete. basalt. [10] supports the ter cooling. though. Structural Systems basic. studies at CANMET that give exhaustive data on rock thermal In addition to the effects of thermal incompatibilities. Furthermore. and (2) an is the transformation of the quartz crystal from the to poly- apparent thermal expansion that is a hygrothermal contraction morph at 573°C (1063°F) with an increase in volume. aggregate and hence greater internal thermal stresses. Lin et al. This requires keeping any embedded steel as cool as pos- sium carbonate is likewise decomposed between 741 and sible to avoid loss of tensile yield strength and to minimize 838°C (1365 and 1540°F). There appear to be two components to thermal vol. of concrete columns compared to that of siliceous aggregate. calcium carbonate breaks down the building code and the specific requirements for the proj- into calcium oxide with the release of carbon dioxide. [11. the selection of one aggre. and the practical end point is probably about 538°C the surface of the concrete in considerable volume. air-cooled slag. concrete is friable. requirements are primarily for life safety. to prevent collapse in accordance with the provisions of and 979°C (1220 and 1795°F). gregates. and more porous. in particular thermal volume change. is a This research further identified that increasing the cross sec- very important component to the overall behavior of concrete tion size even in one direction and use of carbonate rather than because of incompatibility with the same properties in the ag. For most rock. This connection between thermal conductivity and ex- Unlike the situation with cements. (1112°F) than most other rock. quartz. and. the rate of thermal gressive dehydration of the paste modifies the physical bonds elongation is many times greater above 500°C (932°F) than at existing initially in the concrete and promotes micro-cracking. Though not entirely justified and loosening of grains resulting in increased rock porosity by data. as notably happens with siliceous crete with increasing temperature is clear. Attention naturally centers on A prime objective in the design of fire-resistant structural con- the reasons for the significantly different behavior of calcare. one of the causative mechanisms. and clay. Mirkovich [23] found the greatest decrease in thermal data related to the paste component alone are sparse.21]. and greater thermal incompatibility between the cement paste and then with further heating and loss of moisture. and hence decreased thermal conductivity. many building codes fire resistance calculation proce. porous. cur at specific temperatures. Both reactions are endothermic. . the apparent coefficient of contraction or expansion are time as later discussed. Thermal expansion is additive to much greater coefficient of thermal expansion up to 600°C shrinkage due to dehydration. the expansions up to 1000°C (1832°F) and confirm the dominance decrease in evaporable and chemically bound water with pro. require an amorphous microstructure and porous macrostruc- crete. The work by Kodur et al. of mineral composition. room temperatures and abrupt increases or decreases may oc- The resulting influence in the mechanical properties of con. quartz has a shrinkage that is irreversible. af. though separate rocks. slate. with temperature. finely grained igneous rock such as basalt. Above 500°C searchers have ascribed a greater tendency to spalling for these (932°F) shrinkage again changes to expansion. but may also be Carbonate aggregates are decomposed chemically by heat required to provide property protection and for many build- whereas siliceous aggregates generally are not. and differential thermal analysis [15. Furthermore. escaping from nent. forms an (1000°F). they ume change of paste prior to decomposition: (1) a true thermal have deleterious properties at high temperatures. The “ideal” aggre- dures group concretes into two to four classes of aggregate gate from a thermal conductivity point of view seems to type as a basis for determining fire resistance ratings of con. where the paste is much drier order to minimize development of parasitic thermal stresses. by 12- Zoldners’ review of experimental thermal data [22] shows in.12] found that 305-mm by 305-mm (12-in. that is. a thermal pendent: the lower the moisture content the lower the thermal expansion as close to that of the cement paste as possible in conductivity. Influence of Aggregate Component while anorthosite. other internal volume changes occur and the various states in the capillaries and gel pores. The calcined material is also less dense and hence a bet- this cause at sustained high temperatures is essentially perma. ter insulator. conductivity occurs with those rock types that show the greatest thermal expansions. dependent as is dehydration. deleterious amounts of differential thermal expansion between thus absorbing heat and delaying temperature rise in the con. Magne. calcareous aggregate. thermal conductivity that delays temperature rise. and siliceous aggregate. dilatometric. the crystal form transformation. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 277 decompositions are irreversible so damage to concrete from crete. crete are to maintain structural integrity. a specification best met by many lightweight aggregates. dum) and other special aggregates used in refractory concretes perform best. sandstone. pansion is ascribed by Zoldners [22] to the fact that higher ther- gate over another can have a great influence on the resistance mal expansion stresses cause more micro-cracking of crystals of concrete to high temperature. in particular. Actual values of reasons. the carbon dioxide.) cover made with 34–53 that the variation of thermal properties of the cement paste MPa (4950–7680 psi) concrete will have at least 3 h resistance. Zoldners [22] reviewed value measured at room temperature. The desirable thermal properties of aggregate are low Thermal conductivity of cement paste is also dehydration de. and granite. and limestone show relatively little change. At higher dependent on the internal transportation of moisture between temperatures. usually can be taken apart with the fingers. resulting in crystal form may be meta-stable. Between 660 ings. it contracts rap. shale. other mechanisms may dominate. After exposure to sustained temperatures of inert insulation layer thus further retarding temperature rise 649–816°C (1200–1500°F). Many re- idly to more than cancel the initial expansion. Crushed firebrick and fused aluminum oxide (corun. Structural integrity ous and siliceous aggregates that are the most widely used. Then in descending order of fire endurance Influence of Embedded Steel and come expanded slag. Most striking expansion that is essentially constant and reversible. siliceous aggregate significantly increases fire resistance. At 750°C (1382°F). ture. the concrete and steel. Though siliceous aggregates may be chemically stable. There. coefficient of thermal expansion of steel varies with tempera. For the same normalweight con. the steel and on the insulation properties of the concrete. are taken as one of the end points in standard fire of concrete elements to continue to support loads after the tests. Lin et al. Chana and Price [6] observed the ability (800°F). or slightly higher than. and some stress relaxation losses may remain after the outcome in terms of the distortion. Effect of Experimental Conditions on with 50-mm (2-in. the steel. However in the design of complex frames and of thermal expansion may adversely affect the local bond of continuous or restrained members.) by 200 mm (8 in. This is further substantiated by the actual plied moment.) cover. testing at high temperatures in universal testing machines. Less than 20 % of the original yield strength remains reinforcement. The cantly decrease the fire resistance. only the are related to changes in the phase and crystal composition of more recent and significant studies have been referenced. ASTM Test Method for Compressive after. on the circumstances and superimposed conditions. about 423°C determinacy. The thermal conductivity Effect on Compressive Strength of steel is much greater than that of concrete and sometimes after a fire a thin. The such as the 1973 fire in the Military Personnel Record Center influence of cover is striking. that is. Where splice lengths. Research by Sozen and Moehle [25] showed there are ditions. tures may be an important structural consideration Usually. which concrete is judged. [11. Bond strength between concrete and steel and compatibility is critical at lower temperatures. MO [28]. or structural steel) at 760°C (1400°F). it declines. Compressive and flexural concrete strengths at elevated ture in a dissimilar manner to that of concrete at very high tem. Louis. load is applied from the testing machine platens differences in the performance of bars with epoxy coatings as through cement-asbestos disks above and beneath steel cylin- compared to black bars with regard to development and lap. Steel that has remained en.) cover would reach over 427°C (800°F) whereas. whitish.) length to 100 mm (4 organic coating on fire resistance. Benjamin [3] observed the effect of both specimen area • whether it is quenched or allowed to cool slowly. temperatures have been studied widely. Variables cased in concrete will recover much of its lost strength on cool. each concrete.) cover.278 TESTS AND PROPERTIES OF CONCRETE Typical reinforcing steel used in reinforcing bars shows a [27] indicate that the epoxy coating has little detrimental effect linear decrease in yield strength with increase in temperature on the performance of concrete elements in fire exposures. deflection. and the steel differences in the strength of concrete in the compressive zone temperature then rapidly becomes high enough to dehydrate have relatively minor consequences and do not affect fire the cement paste. [26] and Lin and Burg length changes as well as strength are to be measured. and cover noting that the temperature drop from the exposed In addition. steel with only 25- mm (1-in. it is probably the most investigated crete. continuity. exposed to the heat source (as by loss of cover).12] conductivity of steel influence the performance of the sur. include the following: ing and only exposed reinforcement that has become distorted • whether the concrete is restrained or not during heating. concrete structure. Fire • whether free moisture is contained or not during heating. concrete are covered in Sheridan [4] and Harmathy and Allen • whether it is tested while hot or after cooling. The length of time before the steel reaches a critical tem. will have different strength and Both the coefficient of thermal expansion and the thermal moduli values at different temperatures. Because compressive strength is one of the prime qualities by rounding reinforcing steel embedded in otherwise sound con. porous layer may be evident sur. 593°C (1100°F) and 423°C collapse of a member. protection requirements relating to structural steel encased in • whether the concrete is subject to thermal cycling. temperatures.) diameter and 100 mm (4 in. Prestressing wire and strand reach the 50 % suddenly fails. After that. the steel temperature would be about Mechanical Properties 204°C (400°F). With 75-mm (3-in. endpoint of the fire exposure criteria in a full-scale test of a perature is when the moment capacity is reduced to the ap. the specimen is heated by means of an electrical or gas The use of epoxy-coated reinforcing steel as a defense furnace that jackets a concrete cylinder varying in size from 50 against corrosion raised the question of the effect of the mm (2 in. and [15]. The coefficient increases with temperature up to Access to earlier work is provided by Uddin and Culver [1]. and twisted will usually need replacing or supplementing. ders abutting flat machined faces of the specimens. cement paste and aggregates. In simply supported members. depends other periods of fire exposure [9]. tensile and shear peratures. 649°C (1200°F). crete exposed in a standard fire test for 1 h. the compressive strength is concrete to steel at higher temperatures. the bond strength between steel and concrete is the compressive strength testing procedure used at normal same as. depending on the behavior of the surface is steep. and member restraint all influence (800°F). up to about 370°C (700°F) totaling about 15 %. Various techniques have been used to modify the (600°F). and then increases again.). For purposes of a general understanding. The dead and live load intensity. structural in- loss of yield strength at a lower temperature. Up to about 316°C important. To maintain uniform temperature con- strength. but is generally close to that of concrete where strength less so. decreases to zero in the range up to 816°C (1500°F). This effect and the difference in coefficients endurance. in particular on bond in. or after heating and cooling. then . in St. and ultimate cooling. the It should be emphasized that there is not one critical tem- decrease is more rapid and reaches 50 % by about 593°C perature or condition at which embedded steel (conventional (1100°F). prestressing strands. This tends to happen if part of the bar has become property at high temperature. found that full restraint of concrete columns did not signifi- rounding concrete when exposed to high temperatures. but the work of Lin et al. the steel would probably be hardly warm to the touch. and work by Diederichs and Schneider [24] Strength of Cylindrical Concrete Specimens (C 39) to permit and others shows that the bond strength at elevated tempera. These temperatures. In a fire this depends on the amount of cover to performance of concrete structures during and after fires. at room temperature. Similar orders of limitation The observed strength of the same concrete when heated to a on steel temperature with increased cover are applicable to particular temperature. Changes in the cement paste and aggregates has been discussed in preceding coefficient of thermal expansion of steel at high temperatures sections. His conclusions provide three additional pieces of infor. his results showed the following: (1) carbonate and sanded lightweight aggregate concrete retained more Effect on Flexural Strength than 75 % of original strength up to 649°C (1200°F) when heated unstressed and tested hot—for siliceous aggregate con. only 85 % of the ini. found in low w/c ratios and air drying. Marechal [31] looked at • The sandstone aggregate concrete showed a significant the variation of E with temperature for expanded clay. or by displacement measurements as by Sullivan compressive strength than when specimens were slowly and Poucher [30] on concrete specimens heated within a fur- cooled.) siliceous ag. and testing after slowly cooling. a relatively pure sand. siliceous. up to 400°C (752°F) that for a given mortar or concrete (with tures [18]. Zoldners attributed this to thermal shock and noted (1) nace. curing regime.20 to 7. The most common procedure for determining flexural strength crete.) concrete cylinders made of 10 mm (3/8-in. Abrams [29] determined the compressive strength of con. temperature is a permanent one. and containing the same constituents [18].30 106 psi). Zoldners design parameter.65 had lit. sive strength. stone. Poisson’s when heated. and Bulk Modulus strength of about 20 % in specimens tested after cooling. and light-weight (expanded shale) aggre. may be obtained dynamically as by about 500°C (932°F). the corresponding temperature was 427°C (800°F). by 538°C (1000°F) it is only half or less than half of that before Zoldners’s results include the effect of four different heating. Temperatures are measured and crete out-performed the others whereas below that tem- controlled by surface or embedded thermocouples. age. the strength range of 23–45 MPa (3300–6500 psi) that contain The effects of the aggregate itself and the contact areas with ce- carbonate. Sullivan and Poucher [30] noted in their tests. ners [18] obtained similar results. Using such apparatus and 75 by 150-mm (3 by 6-in. some benefit was limestone. They were a gravel comprised mainly of a mixture of siliceous aggregates). and gravel rioration was rapid.37–0. as may happen to The ratio of stress to strain is an important structural concrete concrete that is hosed down with water during a fire. ment paste may be important for accurately determining the gates. as discussed by testing while hot.91 to 2. Philleo [19] noted that the mation in addition to generally agreeing with Abrams [29]. 400°C (752°F) (a reduction level that he found to occur at over ature lean mixes showed a proportionally smaller reduction in 600°C (1112°F) in the case of compression). rock aggregate (mainly porphyry and quartzite). those of Abrams [29] with respect to the benefit of the concrete being under compressive stress (in the order of design stress) Effect on Modulus of Elasticity. compressive strengths were 5–25 beams along the lines of ASTM Test Method for Flexural % higher but were not affected by the applied stress level. The decreases observed in flexural strength are than the corresponding hot compressive strength. flexural strength of a siliceous aggregate concrete at 400°C tioning at 24°C (75°F) and 55 to 60 % relative humidity. who tested 50 by 100-mm (2 by cline of flexural strength is much greater than that of compres- 4-in. At high temperatures.06 108 MPa (3. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 279 extension rods or optical devices may be used to bring the gage • Above 525°C (977°F). (2) appears to be a modification of three-point loading of small when loaded during heating. gate size used in the small cylinder and beam specimens to the crete between 93 and 871°C (200 and 1600°F) for concretes in performance of concrete with typical aggregate size is lacking. provides (752°F) varied from 25 % to 0 % of the original strength. made aggregate types on compressive strength at elevated tempera.) cylin. a high-calcium fine-grained limestone.34 aggregate concrete. ural strength after exposure to 400°C (752°F). These tests also confirmed mens were tested at elevated temperatures and slowly cooled. there is a decrease in E in the order of a harder outer shell in quenched cylinders due to rehydration 10–15 % between initial values at room temperature and those of the cement. ural strength reduction with limestone aggregate concrete at sive strength up to 204°C (400°F). and found that expanded shale only retained 16 % of its original flex- (2) water-cement (w/c) ratios in the range of 0. at 400°C (752°F). heating at three stress levels and testing while Zoldners [18]. The testing regimes included heating without load and performance of concrete elements. fluence. the expanded slag aggregate con- points outside the furnace. the specimen size is likely to be a significant in- hot. quenching tle influence on the order of reduction of compressive strength resulted in greater strength losses than occurred when speci- of concrete up to 593°C (1100°F). Sullivan and Poucher [30] found the gregate cylinders with maturities of from 7 to 42 days condi. the de- Turning to Malhotra [17]. but found only a 50 % flex- gregate/cement ratio had little bearing on changes in compres. Between unheated values for calcareous gravel aggregate gregate deteriorated more rapidly than did the limestone concrete ranging from 2. crushed strength gain up to about 300°C (572°F) after which dete. the value of E after cooling was essen- metamorphic and granitic igneous rock. and (4) the not necessarily of the same order and magnitude as those for original strength of the concrete had little effect on the percent compressive strength of concrete of the same mix proportions reductions in strength observed. 106 psi) and final values at 760°C (1400°F) of from 0. perature it was equal or inferior in compressive strength. value of E depended on initial w/c ratio. In summary. In general terms. If concrete specimens are quenched.62 to tial strength remained as compared with over 95 % for the 1. Generally. above this temper. Research on the relationship of the reduced maximum aggre- ders. Zold- the following observations on some additional factors: (1) ag. there is a larger reduction in residual Philleo [19]. For example. Further. and an expanded thus determining that the reduction in E with increasing slag. aggregate (siliceous and siliceous limestone) at one cement . (3) Strength of Concrete (Using Simple Beam with Third-Point residual strengths determined after cooling were a little lower Loading) (C 78). the [18] showed that for specimens exposure to temperatures of modulus of elasticity.21 to 5. and • The crystalline igneous and metamorphic rock gravel ag. the value of E. Again.59 108 MPa (0. and (2) at higher temperatures the difference in at 100°C (212°F). however. tially the same as that prevailing at the high test temperature. Zoldners [18] also compressive strength than occurred with richer mixtures. Also recorded was a reduction of compressive Ratio. E then remains relatively constant up to strength between quenched and slowly cooled specimens was 300°C (572°F) after which a progressive decline sets in so that largely eliminated. 600. but must be taken creep increased very rapidly at low stress levels as a plastic into account if reasonably accurate results are to be attained stage was reached. It is therefore not surprising that is stressed by Marechal [36]. Thompson [38] for E. a ratio of the flux of the thermal expansion. and rated or sealed specimens for which a fully accepted explana. At 300°C (572°F). ties with many of the test procedures at elevated temperatures. Stress was reduced by 2. and prior ex. Dependence of creep on moisture content in heat flow model studies. which declined with temperature in a curve paralleling that physical-chemical changes also contribute. However. but did so directly from the lon. Cruz [34] also carried out ex. Higher creep rates occur in satu. up to 400°C (752°F). ent. in the preceding order. data from Harmathy [21]. He also found that (1) the latter af. and (3) Difficulties also plague direct measurement of true spe- with a lower w/c ratio. respectively. at which temperature changes can take place). specific heat appears In addition to creep tests. Because of sensitivity complications in the test pro. companying moisture migration-desorption. while the re. are larger. Such latent heat effects are overridden to some extent they measured creep rates in concrete at three times those at by the larger contribution of the aggregate fraction to the 125°C (257°F). vibration. Both are accompanied by the fects the creep rate more than the temperature. A first step in overcoming the continuing elusiveness of constant flux and the initial temperature rise in the wire at a creep at high temperature was to devise apparatus for meas. Marechal [31] Thermal conductivity and diffusivity of a mixture such as con- also calculated Poisson’s ratio. as will be discussed. [33] found that lightweight concrete masonry unit more widely understood parameters of specific heat and the wall specimens experienced less bowing than normalweight coefficient of thermal expansion. but a general tendency to decline with increasing temperature was apparent. If inelastic behavior is not ture equilibrium is reached. and chemical dehydration reac- verse was true below 200°C (392°F). but the creep rate was higher suming linear heat flow) to determine all thermal properties. confirm that a very complex pattern of behav. He found the reduction in this modulus to be aggregate Determining Thermal Properties dependent. A high ture conditions. also present problems. including the contribution from moisture pres- and relaxation. higher values of specific heat with higher temperature. Values reported by Harmathy and Allen h period. One is (200 to 800°F) showed that the shape of creep-time curves was based on fitting a temperature distribution curve used (as- the same as at room temperature. Philleo [19] was able to compute Poisson’s ratio because he measured both flexural and torsional frequencies of Thermal Conductivity. there are difficul- tures up to 900°C (1652°F). since the hot wire does not present a surface of cur. 32. crete are not additives of the properties of the constituents gitudinal axial load and measured transverse strain data and a and there are difficulties in experimental determination at a similar decline was found after the evaporable water had been given elevated temperature. lower modulus of elasticity. creep was less. 316. and Specific Heat cedure. location of high conductivity will be less than at a location of uring it as reported by Cruz [34]. . Equilibrium at the test [30] attributed the fact that creep rates for concrete above temperature is disturbed in making the determination by 200°C (392°F) were higher than those for mortar. and 74 % at 24. the specific heat of concrete. Experimental errors are used. (2) there was necessary mathematical interpretations. Diffusivity. heat to the temperature gradient. and 1200°F). Zoldners [22] provides ex- concrete masonry unit wall specimens subjected to tempera. standard physical methods. such as the taken into account and if only data secured on small specimens hot wire method. and above 400°C (752°F). has the advantage of taking up more heat and delaying ior probably exists [37]. Brem. Transient methods. tions of the concrete. heat. temperature rise in a fire. both of which exist in near proximity in a A study by Wang [35] of moderately high-strength con. and [15] for a variety of concretes over a temperature range from 649°C (75. Holm and Bremner [32] found that for individual con. and the two ner et al. though other K. other investigators show considerable dispersion in values for tion does not exist. tions take place in the cement phase that may add or subtract crocracking between aggregate and paste. over-estimations of the affected parameters will oc. heterogeneous material such as concrete. a nonlinear relationship between creep and stress level. discusses the shortcomings of steady-state methods such as ASTM Test Method for Steady-State Heat Flux Measurements Effect on Creep and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus (C 177) or ASTM Test Method Data on inelastic behavior of concrete at high temperature are for Steady-State Thermal Performance of Building Assemblies essential for nuclear applications. normal ambient to 650°C (1202°F) show a slight trend to Investigations of concrete under transient high-tempera. pulses to determine diffusivity. Sullivan and Poucher cific heat at elevated temperatures.280 TESTS AND PROPERTIES OF CONCRETE factor. and is meaningful determination would only be possible after mois- important for fire resistance design. perimental values but. low conductivity. Harmathy and Allen [15]. thermal diffusivity (the rate posure to elevated temperatures during manufacture. since long-term behavior by Means of the Guarded Hot Box (C 236) and indicates that under complex mechanical thermal loadings is involved. to the development of mi. He made further calculations for the bulk modulus. crete at elevated temperatures are: thermal conductivity (the sulted in low residual deformations due to the lower rate of ability of the material to conduct heat). These are due principally to ac- driven off. In general. The basic thermal properties of concern to the behavior of concrete masonry units develop lower thermal expansions re. when the concrete was subject to both high temperature and a and the other on the time-temperature rise response to heat high stress-to-strength ratio. Har- cretes 38 and 46 MPa (5500 and 6700 psi) containing quartz mathy [39] offers two variable state methods that appear to gravel aggregate over the temperature range from 93 to 427°C overcome problems associated with other methods. they observed that overall apparent specific heat of concrete. the results were erratic. to be insensitive to the aggregate used or to the mix propor- ploratory stress relaxation tests under constant strain over a 5. including time-dependent effects such as creep specific heat. where p is density. whereas at lower temperatures there very close to that of mild steel over the temperature range up was considerable difference between lightweight aggregate and to 700°C (1292°F). porous. and specific heat (c) are simply related by the expression: result in differential strains and hence stresses between some k hcp. clear of the fusivity show considerable decrease at high temperatures. atures to consider: thermal volume changes. clear. diffusivity. a slight overall contraction with an almost constant into concrete and the rate and degree of temperature rise that coefficient up to 900°C (1652°F). As a result. good performance as a structural concrete for nuclear reactor ture content while that of the aggregate is highly dependent on pressure vessels at high temperature under thermal cycling. and igneous gravel aggregate concrete and for a sand-stone ag- ity. For a that show that the thermal coefficient of expansion of concrete lean concrete as compared with a rich one. the now dry. dried) had little effect. After dehydration is complete. Andesite. Philleo’s ex- becomes a much better heat insulator than at lower tempera. Density of the con. and specific heat) are important to over all gregate concrete. while showing a similar trend. if not as yet fully explained. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 281 Fortunately. variables affected the coefficient values to a greater extent. decomposition of cal. Considerable hypothesizing . and one ag- example. a 20 % increase in is in approximate proportion to the weighted value of those of thermal conductivity was noted assuming both were consoli. types of aggregate particles and paste and between the con- Conductivity and diffusivity vary with the relatively small stituent minerals of each. Moisture content (500°F). moisture tion in quartz crystals. all these ential thermal volume changes. concrete. The larger the moisture content the larger the thermal secure such data. but at a higher coefficient. they influence the thermal incompatibilities that 427°C (800°F). [41]. crete beam is measured at the test temperatures. one w/c ratio. an initial shrinkage up to about 300°C (572°F) is noted. From an examination of 16 concrete specimens paste due to dehydration has occurred. and with decomposition of 538°C (1000°F). are expanding. However. These tures for performance at elevated service temperatures as. As mineral composition. The horizontal displacement between two conductivity according to data summarized by Zoldners [22]. Harada et al. however. Unless relieved by creep or plasticity variation in specific heat with temperature. tends to approach asymptotically that of the mineral type in Harmathy and Allen [15] confirm this order of reduction and the aggregate [40]. probably due to the constituents. crete and. furnace containing the specimen. On the three cement factors and corresponding w/c ratios. above about 400°C (752°F) for a predominantly metamorphic The three thermal properties so far discussed (conductiv. A point of particular interest in this data is find that all thermal diffusivities became approximately equal that the expansion curve for limestone aggregate concrete is at about 600°C (1112°F). both thermal conductivity and dif. the constituent aggregates once initial shrinkage of the cement dated fully. ity to about 427°C (800°F). these parasitic thermal stresses may be very high. ported similar findings for concrete masonry units. The lightweight aggregate concrete Harada et al. They are also impor. served thermal expansion in concrete is an additive of concrete The importance of thermal incompatibilities and the re- moisture content and aggregate mineral composition. below 260°C (500°F). though at different rates. then after a transition period there is a further linear- has a significant role in heat conduction in concrete until de. the transi. Zoldners’s own data [18] show a very rapid expansion These findings are supported by VanGeem et al. Specimens having a higher w/c ratio and lower cement factor Thermal Volume Change and Thermal tended to have the higher coefficients. as compared with limestone aggregate con- behavior of concrete at elevated temperature because they es. There is limited research referenced on compared with concretes containing limestone aggregate and the influence of moisture content and moisture retention of a variety of portland and high-alumina cements. had about half the showed lower diffusivities and less reduction with increase in coefficient of thermal expansion of limestone or sand-stone temperature than did concretes of normalweight aggregate. did aggregate as a factor. as will be discussed. he found lightweight aggregates on the expansion of concrete. properties of concrete in which. normalweight concrete a permanent dilation as a result of decomposition. Philleo’s work [19] did include gradients are a feature of normal operations. these variables and initial curing (moist or air occur between the cement paste and aggregates due to differ. for example. [40] cite a 50 % decrease at 800°C (1472°F) as com. crete is an important overall parameter when low density is due Looking at Philleo’s data [19] for a calcareous aggregate to air voids. there is a cium hydroxide or rehydration of the lime. effect on the mechanical ical form of the component materials. The ob. for example. The coefficient of ther- made with Type I portland cement and a range of aggregates mal expansion of concrete with increasing temperature thus and processes used to manufacture concrete masonry units. the “best” natural rock aggregate normalweight aggregate concrete. and changes in phys. This is most apparent between a dry lightweight concrete shows thermal expansion is linear up to about 260°C concrete and a dry normalweight concrete. Holm and Bremner [32] re- may occur to steel or concrete in a fire. the coefficient is again lower. The term “thermal incompatibility” is effects may play a substantial role. Incompatibilities Crispino [42] pursued an investigation to find the best combination of thermally compatible materials that would give The thermal expansion of the paste is highly dependent on mois. thermal conductivity (k). in the case of an expanded slag or shale lightweight sentially determine the inward progression of temperature rise concrete. wires hung vertically from gage points on a horizontal con- For normalweight concrete. three aspects of volume change in concrete at elevated temper. volume changes the aggregate is expanding. Zoldners [22] summarizes data from other investigations pared with thermal conductivity at room temperature. While the cement paste is shrinking as dehydration proceeds. in nuclear reactors where significant temperature gregate-cement ratio. In all cases tant in heat flow calculations necessary in the design of struc. perimental technique seems fairly typical of those used to tures. both due to chemical reactions. for data are for only one cement factor. thermal diffusivity used widely to describe those differential volume changes that (h). barytes aggregate with portland cement far superior. Above microscale. [40] investigated. not merge for the aggregate groups at the upper temperatures. Philleo [19] identifies decarbonation of calcareous Their data on conductivity. Above hydration is complete after which. in the paste. There are sulting thermal strains and stresses cannot be overemphasized. to observed microcracking [30. these have usually likewise been put down to thermal incom- cape or sealed it in. cracking in the cement paste. [46] examined concrete that allowed moisture a controlled es. A larger perma. moisture content.45].282 TESTS AND PROPERTIES OF CONCRETE continues toward a full explanation of the behavior of concrete Thus. 260°C (500°F) (and in some cases may even increase) provided cling occurs. al. water. It also adds to the . and probably most important. mens at elevated temperatures from which moisture could its thermal coefficient of expansion decreased during ther. also true for concrete specimens that were permitted to • For concrete that is heated slowly at atmospheric pres- lose moisture during thermal exposure. strength at moderately high temperatures has been attributed The effect of thermal cycling on strength has been investi. Partial loss of ture contents than for those of lower moisture contents. Similar effects are observed with flexural micro-cracking. Thermal strain incompatibilities and the resulting that in the original concrete. interrelated tials in the concrete on heating (for example. possibly not as bad as moduli. use of very large specimens. when added to those arising content in influencing mechanical properties of concrete at from mechanical loadings and restraint. compressive or tensile. Zoldners [18] at- (575°F) and noted a progressive deterioration with increasing tributed the greater reductions in flexural strength as com- number of thermal cycles though most of the loss occurred in pared with compressive strength at the same temperature to the first few cycles. of Moisture Content • Deterioration of structural properties under both moisture conditions (sealed and unsealed) can be expected from any The mechanical and thermal performance of concrete at ele. and the increase in compressive chanical and thermal properties are affected [42]. and bulk modulus. encing the measured thermal and mechanical properties the primary factor influencing changes in the structural including the internal transport or the expulsion of water. posure cycling up to 143°C (300°F). they noted the micro-crack sys- the effect on other mechanical properties such as the various tem was no worse after careful heating. A similar decrease was ob. they would immediately show up as dimensional changes between cement paste and aggregate and a reduction in flexural strength. quench heat- physical-chemical behavior and strongly influenced by mois. thermal challenge to the views expressed by others on the role of micro- stresses on a smaller scale between particles determine the cracking. of the concrete and For unsealed specimens.” panded shale. determine the im. the primary factor influencing changes in the struc- nent expansion was observed for concretes of high mois. • For concrete slowly heated at saturated steam pressures.). etc. ing and cooling. The advantage in sistance. patibilities. imens up to 260°C (500°F). by Zoldners [18] to “a heat-stimulated cement hydration and gated by Campbell-Allen and Desai [44] and Campbell-Allen et al. and this expansion suc. Poisson’s ra- thermal cycling. investigators have explained their observations on at all temperatures with respect to thermal properties. with increase in temperature follow is also important in nuclear applications of concrete. chemically combined water (dehydration of hydrated In examining the significance of data from thermal cycling and cement phases) occurs above 121°C (250°F) and primarily sustained high-temperature tests. resisting strength. all the free water is removed on heating. especially where thermal cy. made their own tests on both sealed and unsealed spec- mal cycling to 143°C (300°F). are properties is the hydrothermal reactions that can occur in dependent on time or the rate of temperature increase. micro-cracking. Both me. Abrams [29] draws attention to micro-cracking and de- Since most investigations in the past have addressed fire re. This was pared to concrete sealed against moisture loss. K. sure. it is not surprising that the effect of more than one compressive strength where the concrete is preloaded in com- thermal cycle has only really been addressed after interest pression is ascribed to the suppression of thermal micro- arose in using concrete in nuclear reactor vessels. test variable that can produce large temperature differen- vated temperatures is determined by complex. and firebrick aggregate concretes up to 302°C From his pulse velocity measurements. However. and relaxation of bonds. moderately high temperatures. From petrographic examination. regime must be considered since many of the reactions influ. The interrelationship of Since the reductions in modulus of elasticity. [47] reviewed existing data secured on speci- • For a constant moisture condition (sealed) of the concrete. ex.44. the nature of the thermal affects the flexural strength. Polivka et the general pattern for reduction in compressive strength. and thermal volume change tio. Further compressive strength changes with temperature in general reading is provided by Dougill [43]. terioration in the aggregate-to-paste bond. escape. This observation helps to explain parasitic thermal stresses are thus critical to performance of that compressive strength decline is not significant below concrete at high temperature. terms of the changes in physical properties of the cement and aggregate and the thermal incompatibilities between these Thermal Cycling components with temperature. they do provide somewhat of a posed total stress levels in the concrete. the influence of heat thermal exposure. concrete in which the moisture is free to evaporate as com- cessively increased with the number of cycles. a significant concrete at the time of heating and is quite different for residual expansion was observed. exposure per se on the structural properties of concrete is • After the first thermal cycle (21 to 143 to 21°C) (70 to 300 critically dependent on the moisture content of the to 70°F) of the concrete in a moist condition. over durations up to 14 days of thermal ex. The stresses from thermal loadings due to over. and provided this summary: served for concretes that successively dried out during • First. the cement phase and that convert the original highly cementitious calcium silicate hydrates into crystalline. Whereas small defects would have little effect strengths and modulus of elasticity attributable to incompatible on compressive strength. ture content. They showed the following: Lankard et al. lime- Review of Behavior Mechanisms and Influence rich calcium silicate hydrates producing lower strength. tural properties is the loss of free water. who compared the compressive strengths of limestone. While their data strongly support the role of moisture all expansion or contraction. densification of the cement gel due to the loss of absorbed [45]. or pores if the the disruptive pressure causing spalling is the result of rapid water was not present. with to the heat source. ter in the concrete. [51] and Harmathy [49] as predominant. Spalling of concrete elements may contribute to pre- properties of concrete than occurs when the moisture is freely maturely reaching a temperature rise endpoint of ASTM E 119 driven off. as work by Shirley et al. conducted on a specimen conditioned in a manner such as to ity with temperature at moderately high temperatures. more dense high strength concrete using silica fume or similar served behavior. and save time and money. regime of relative humidity and temperature and moisture sile strength being greater than that for compressive strength. [46] established that at 143°C (300°F) a endurance of high-strength concrete slabs with and without sil- maximum reduction in strength and stiffness. both of which are discussed of free water is the controlling parameter at lower tempera. on the exposed surface nor any explosive behavior. In observations of the composition of the hydrated ce. including spalling. direct thermal causes. the exposure conditions surfaces of concrete elements is that it opens up fresh surfaces may be quite akin to autoclaving mature concrete and. How- most tests at normal temperature are made on small speci.4 % increase in volume of quartz at 573°C value. once dehydration proceeds to a significant loss of other compares to that of similar material after several years of serv- forms of water and to decomposition of the cement hydration ice. The contraction of cement outs of siliceous aggregate particles at or near the surface will paste is due to the expulsion of free water and. The prestressed Spalling of concrete surfaces. were considered a main contributing factor. even where it is cool and quence of this process. suggest that the actual fire test should be observed independence of the reduction in modulus of elastic. However. cantly differ and none of the test specimens exhibited spalling ture content corresponding to about a 50 % loss of the free wa. sometimes accompanied by spalls and sometimes it does not. bedded steel being adversely affected. is an evi- concrete sections tend to be massive and concrete may be hot dent feature of most fire-damaged concrete. plausible explanation in some detail. quartz expansion to occur the plasticity of the paste is great The amount of free water in concrete also has a major in. (1063°F). if they occur in autoclaved products. In hot sealed areas. especially if it becomes there is a greater reduction with temperature in the physical exposed. capillaries. enough to accommodate the expansion. and it is worthwhile to examine a more modify ASTM E 119 by preconditioning the specimens [48]. Experienced investigators such as Harmathy crystalline. probably lime-rich calcium silicate hydrates. ever. Moisture entrapment now is identified by Meyer a relatively poor direct conductor of heat as compared with ag. it is a many times better conductor of heat than is the stages of spalling deterioration. How- ment phases under these sealed heated conditions. standard test. . in the order of ica fume and normal strength concrete slabs did not signifi- 75 and 55 %. in particular such while the modulus of elasticity fell to only 31 % of the original things as the 2. There may be a need for further research and testing of products. spalling in which moisture expulsion plays a significant role. For many years. control and uniformity of mois. when it occurs on the fire exposed open on the other. [47] found sponding reduction in thermal resistance of the concrete ele- a continual and much greater decline in compressive strength ment. content at the start of the test. Polivka et al. they deter. nuclear reactor shields and primary containment Spalling and Cracking vessels present a different set of conditions in which the concrete essentially is sealed against moisture loss. concrete elements. strength and other properties in the referenced investigations chanical properties of concrete have been secured by testing are probably explained by lack of control of the moisture pa- small unsealed specimens. some and Allen state they have never identified spalling due to this of which. The justifications for this are that rameter and the temperature gradient in the concrete. this does not appear to be an ad- standing concern. closely bound water in capillaries behavior. at least in the earlier gregate. This led to investigations and proposals to equate explanation. though sudden pop- fluence on thermal properties. the present requirements are an improvement duces the critical stress requirements for tensile failure. they considered that the benefit of free water cover every circumstance of possible moisture condition in a removal is offset by the loss of chemically bound water that re. this apparent lack of control is the real situation when mens and. moisture is usually free to be progressively mature or young concrete is exposed to fire and sometimes it driven off from the concrete. Most investigations addressed two possible causes of and modulus of elasticity up to 260°C (500°F). How. are known to cause [15]. Many of the disparities in the results of physical tests for Most of the data so far discussed on the thermal and me. Carlson and Abrams. However. Compressive such spalling: thermal incompatibilities and moisture entrap- strength at the upper temperature was only 50 % of original ment. ever. Natural drying has been replaced with a specified conditioning centrations around flaws to account for the reduction in ten. especially with regard to the moisture con- compatibilities increase with increasing temperature. respectively. particularly at an arris. later. the quartz volume change may not be as significant as mined from X-ray analysis the presence of new. in a fire. Lankard et al. on the unexposed side due to the loss of section and corre- In “saturated steam” conditions. and once aggregate deterioration and thermal in. But it does appear that the presence or lack materials for increased strength. and gel pores will produce saturated or superheated steam ture content in the concrete prior to fire tests has been of long with explosive force. in discussion The removal of free water also appears to account for the on Harmathy [49]. It seems that by the temperature necessary for lead to lower strengths. more highly earlier thought. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 283 usual explanation of the development of flaws and stress con. A commonly held view is that air that would be occupying voids. produce a microstructure within component material which ever. thus making for more rapid progression of chemical and mineralogical changes in the component phases heat into the concrete and increasing the probability of em- of the concrete and restriction on the mobility of moisture. heating with sufficient moisture present so that. then tent and retention involved with lightweight aggregates and the these latter mechanisms appear to account fully for the ob. while water is likely occur. The worst conse- and sealed by a steel liner on one side. even after the Because it influences almost every parameter of concrete evaporable water escapes. occurred at an intermediate mois. While it is still not possible to In this case. [50] found that the fire tures. these processes are not rapid and develops across the dry layer resulting in a high rate of heat most likely the apparent spalling is simply the falling away of flow. pressure buildup would level off). in fire tests of prestressed con. the concrete. and concrete emphasize the thermal contraction and ex. As moisture is desorped in a layer adjacent to and compressive stresses (from the longitudinal prestress). intensified desorption at the frontal plane. As the thickness of the dry layer and moisture expulsion. The ap- to develop. the vapor can only leave through the dry layer. if one can call it (1112°F) to buff at about 900°C (1652°F). the color of siliceous or limestone aggregate con- to restraint of thermal expansion citing that: for thin slabs crete changes through pink or red to gray at about 600°C within a heavy restraining frame the spalling. Where doubt still exists after the 149°C (300°F). Carlson and duration and hence a first estimate of the likely remaining Abrams advise that when a specimen is dried to an equilibrium properties of the concrete. observed some cases of longitudinal tensile split. aggre. Smith [59] described the investigative. if the structure formations or thermal stresses exceed the tensile capacity of should be demolished or can be repaired. can be incorporated in the appropriate structural structural significance at locations where overall structural de. fine cracks and surface blemishes into the hot furnace. material. Planes of weakness may also develop at the level Confirmation of the residual engineering properties of the of the reinforcing steel. While the normal contractions are front forms between the two layers. the available data on the engineering properties of the con- Thermal cracking may range from crazing on the surface and crete and steel. Harmathy [55] pro- spalling. in situ nondestructive testing such as ultrasonic pulse velocity crete beams. In 1980. resulting thermal stresses may be sufficient to induce cracking. As the temperature of the opposed by a volume increase if moisture is present to rehy- exposed surface increases. Permanent color changes may of water was also observed in column tests by Kodur et al. If the permeability of the material is low. between the hotter and cooler parts of the concrete itself.284 TESTS AND PROPERTIES OF CONCRETE Harmathy [49] (including his work with Shorter) devel. pressure buildup. [50] did not observe any secured within a day or two of the fire as a means of deter- spalling on the exposed surface nor any explosive behavior in mining a temperature history inwardly into the concrete. temperature marker can be identified. sociated with desorption of moisture checks the rise in tem. they established that the differen. in discussion of Harmathy [49]. Placid [56] pro- cause. can be a source of tangential tensile (bursting) stresses of con. a completely saturated layer builds up at some Sometimes it appears as though additional spalling occurs distance in from the exposed face and later a sharply defined as the concrete cools down. expanding and Investigation and Repair of Fire Damage meeting increasing flow resistance as it goes. However. approach is based on the fact that the continuum of reactions In establishing an overall picture of the effects of moisture in the cement paste remains frozen at the temperature level on the fire resistance of concrete. The slabs made of high-strength and normal-strength concrete. analysis to determine the mode of failure. structural analysis or repairs have been completed. has been sufficiently violent to fail the specimen in a poses thermogravimetric and dilatometric testing of samples single occurrence. (1) a high available to examine concrete damaged in construction fires. modulus of elasticity and (2) reduced tensile and compressive oped an explanation called “moisture clog spalling” along the strength of concrete when simultaneously exposed to tensile following lines. rographic analysis of thin sections to assess damage. Abrams and Erlin [58] provide a method based on exam- perature in the concrete. together with factors originating from the steel arrangement gion and is reabsorbed. because of thermal shock. By analysis. this are conducive to spalling but if spalling did not take place (be. Many circumstantial clues may be relative humidity of 70 %. at either the elevated temperature reached or micro-cracking to deeper and substantial spalling or cracks of after cooling. by comparison with a ref- very important practical points. . [10]. within and between the constituents. Because the concrete to the rear is saturated. The Once the likely temperature regime has been established. Once the structure is safe to enter after the fire. a first step is tinues until a tensile spall occurs separating the dry layers from to try to obtain an estimate of the temperature reached and its the rest. the existing large vapor pressure differential would move small samples and is sensitive to the thermal exposure experi- the “moisture clog region” towards the colder region and the enced rather than just the maximum temperature reached. Escape as described by Bessey [53. the pressure build up at the front con. the absorption of heat as. if the concrete and steel after cooling can be determined by securing surface of the concrete is quenched with water. and vapor already loosened pieces of concrete. Shirley et al. hence it’s remaining tensile strength. then the moisture in the More recently. First. Standard methods for Selvaggio and Carlson [52]. and siderable magnitude. samples for standard laboratory testing. sim- temperature. and ilar metallographic methods may be useful. Though the effect of the pansion strain incompatibilities that develop with increasing temperature on normal reinforcing steel is not so critical. Two concrete factors were considered to structural evaluation techniques and restoration methods contribute to lack of resistance to these stresses. They observed liquid water being discharged from pearance of the concrete can also provide important evidence. a very steep temperature gradient drate the calcium hydroxide. measurements can be used to help delineate the damaged ar- ting through the full depth of the flanges and webs when the eas and compare the properties of the affected concrete with temperature at the level of the steel tendons was as low as that untouched by the fire. steel for estimating the temperature it reached in a fire and gates. Second. Harmathy [49] stressed two reached (for at least a few days) and. increases. the vapor migrates toward the colder re. ining the microstructure and micro-hardness of prestressing Data on the thermal properties of cement paste. high moisture contents erence sample of unaffected concrete or standard data.54]. confirma- tial thermal expansion between concrete and embedded steel tory full-scale load tests can be made. accompany dehydration of the cement paste. the heated surface. the condensation and re-evaporation found by sifting through the debris and identifying the remains process is such that dangerous steam pressures are not likely of common objects that have known melting points. As temperature Carlson and Abrams observed that thermal spalling is related increases. Riley [57] has explored the potential of the pet- concrete is most beneficial. if resistance of the pores to moisture flow was not too posed a test based on thermo-luminescence that requires only high. pressive strength of portland cement concrete containing medial work undertaken and reviewed developments in inves. The account by Fruchtbaum tween 3 and 7 h. residual strengths stable and retain considerable strength at dry heat temperatures were negligible. this increases the risk of damage from fire at an to 300°C (212 to 572°F). serpentine. [41] found that the thermal slag) concrete stood up to the effects of high temperature better conductivity and thermal diffusivity of high strength concrete than did semi-lightweight concrete. and are limited to concrete columns. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 285 Twenty-five years later he evaluated the performance of the re. fractory concrete can be as high as 1800°C (3272°F). land blast-furnace slag) cement as compared with a normal Type Currently most applications of very high strength concrete I cement. After heating to 1000°C (1832°F). and combi- tigative techniques over the intervening years [60]. or proposed for use. Lightweight aggregates (manmade expanded shale. (25 000 psi) have been used. there reactors. By using rather than portland or blended cements. Otherwise the mechanical properties appear to de- velocity. warm-up aprons. the decomposition of the cement paste with the residual engineering properties of lightweight concretes af. It has been observed in labora- thermal conductivities (at all temperatures). [50] calcined shale dust) as 20 or 40 % cement replacements did im. these effects [61] in 1941 remains a classic. Very lightweight (cellular. temperatures of 677°C triaxial stresses can occur. was considerable concern that the hot blast might be damaging der or sphere. high-strength concrete slabs with prove the heat resistance of the concretes up to 500°C (932°F). have a tendency to spall explosively when heated and glassy (amorphous) composition are also advantageous. Research by Shirley et al. They also found that. made with normalweight aggregate were similar to those for though there was no advantage in using Type IS (blended port. fly ash. and thermal studies made Most of the data and their significance so far discussed have by Harmathy and Allen [15] on concrete used in masonry units been from tests on concrete in the normal strength range used confirm the reasons why concretes made from lightweight in general constructions. Holm and Bremner [32]. 700. as aggregate [64]. and steel punchings. In summarizing the results of com. of ACI Committee 547 [65] provides a definitive discussion of re- ing applications. [62] reported reductions of up to 40 accounts of investigations and repair of fire damage to mature % in hot-tested specimens after heating to 350°C (662°F) for be- concrete have been published. perlite. Since failure is largely because of the deteriora. conventional strength normalweight aggregate concrete. the improvement in were tested for 4 h.63]. enhance fire endurance [9]. such as to 700°C (1292°F) as compared with the unheated reference crushed firebrick. and complex ends. temperature rise is a critical factor in fire resistance. and 1832°F) and after cycling 5 or 25 times from 100 crostructure. cement paste and aggregates. similar improvements were not always noted in compressive strength. the addition of micro-fillers (fly ash. magnetite. VanGeem et al. clay. insulating lightweight aggregates such as fused aluminum oxide with a cement that is refractory concretes good up to about 950°C (1742°F) can be essentially calcium aluminate. addressed slabs. and 1000°C (572. especially aggregate to retain moisture and its chemically stable vesicular if saturated. As with normalweight concrete. Heavyweight Aggregate Concrete Elevated Temperature Coupled with Air Blast Heavyweight concrete is used for radiation shielding in nuclear At the time of the introduction of jet aircraft into service.16. and to the dehydration of the paste. point out denser cement paste matrix obtained by use of high cement fac- that the compatibility in relative stiffnesses between the cement tors. cretes. vermiculite. This shielding is usually in the shape of a hollow cylin. The report ing) concretes. Lightweight Aggregate Concrete Very High Strength Concrete The thermogravimetric. Very high strength concretes ranging aggregates have superior heat resistance to normalweight con. with the slower drying out of moisture due to the less porous mi- 932. among others. Since the cement paste and lightweight aggregates is also beneficial. Resid. Refractory Concrete cator of porosity and micro-cracking in the matrix. and Ref 54 provides an excellent were ascribed to differences in thermal expansion between the general review. Numerous nations thereof. for ual strengths for all lightweight concretes were reduced to about example. The pulse velocity measurements. in strength from 80 MPa (12 000 psi) to as high as 170 MPa cretes. can be made with high 80 % by heating to 300°C (572°F) and to about 45 % by heating alumina cements and common refractory materials. or perlite insulat. and flexural strength determinations cline with increasing temperature in a similar trend to normal made after cooling that all the lightweight (expanded shale and strength concretes. Concretes used to withstand prolonged high temperatures. Immediately at the jet exhaust. (1250°F) occur and this may be as high as 1927°C (3500°F) . compressive. silica fume. silica flour. as used in roof or other build. generally supported the conclusions drawn from the strength data. 1292. dilatometric. taken to be an indi. The capacity of the tory investigations that very high strength concretes. of up to 1300°C (2372°F) because ceramic bonds have replaced tion of the cement paste matrix. None of the five specimens exhibited residual flexural strength was in the range of 10–20 % though spalling on the exposed surface nor any explosive behavior. and without silica fume and a normal strength concrete slab In all cases where micro-fillers were used. rapidly [6. to concrete in engine test cells. ings or off-shore structures where enhanced mechanical prop- nificantly lower thermal diffusivities (up to 600°C (1112°F)) and erties lead to cost effectiveness. This type of concrete will be concretes. Under moderately high operating temperatures. service temperatures for a re- made. al. They further paste matrix will carry higher loads than in normal-strength con- noted a good bond strength between paste and aggregate. maintaining a more homogeneous stress distribution Zoldners [18] (with Wilson in subsequent work) looked at with the aggregate. These concretes are more “brittle” with a Abrams [29]. by using high alumina cement the hydraulic bonds that were lost during desiccation. 480 kg/m3 (30 pcf). slag. They concluded from ultrasonic pulse early age. Coupled ter exposure to temperatures of 300. In this work. in tall build- slate. and super-plasticizers. fractory concrete properties for those having deeper interest. Desov et al. limonite. and runway thermal gradients induce moisture migrations. or mica and natural pumice or scoria) have sig. 500. in monolithic linings for kilns. R. American [30] Sullivan. ASTM Inter- ing advances have been made. MI. ties. However. “Fire Endurance Experiments on High Strength Concrete Columns. A. I..” Journal V70. age of Temperatures. Tail and higher wing mountings in more recent planes 1989. Detroit. pp. De. 102. IL. T.” Magazine of Concrete Research. 89. 3–22. 2003..” Serial No. “Fire Endurance Testing Procedures. 1. Serial No. G. [14] Purkiss. Jan. The launching of rockets from pads or underground silos [11] Lin. Discus. Containing Fly Ash at High Temperatures. and Schneider. 5. American Concrete Institute. L. G. and Dougill. 101. Leroux. D.” Proceedings. P. J. 23. 33–58. Reston. “Thermal Properties of Concrete under gests that this should be expanded to include size. American Society of Civil Engineers.. 47–74. 85–94. R. “Apparatus for Compression Tests on Concrete at High Temperatures.. Skokie. design against the extremes of fire and for moderately high [18] Zoldners. p. Proceedings. 5–9. Vol.” ACI Materials Journal. known that the solutions tried include sacrificial concrete and “Fire Resistance of Reinforced Concrete Columns. N. Selected Masonry Concrete Units.. American Concrete Institute. 102. W. 2376. N. [10] sug. Institute. [6] Chana. concrete has a long-standing and justified reputation as a [16] Hertz. type of aggregate. IL. J..” Journal of Materials.” ACI American Concrete Institute. and Latour. Shirley. G. J. 1971.. 1962. 4. and Corley. [15] Harmathy. 205–218. pp. 60. McGrath.286 TESTS AND PROPERTIES OF CONCRETE where afterburners are used. T. H. “The Effect of Temperature on the Compressive and greater understanding of thermal and mechanical proper. April fits to additional work correlating the many variables in con. G. June 1973. have largely removed the problem from the practical sphere [10] Kodur. T. [3] Benjamin. G. Incorporating Different Aggregates. “Fire Resistance of Reinforced Concrete. American Society of Civil Engineers. 537–550. May 1974. A. 25–39. 156–162. J.. Work by Kodur et al. E. [23] Mirkovich.. 1975. MI... Z. Dec. 83. R. [22] Zoldners. ST7. 1087–1108. and Price B. G. 132–142. shape of the [21] Harmathy. MI. No. [9] Guide for Determining the Fire Endurance of Concrete ward inclination and low slung engines on many early jet Elements (216 R-89). and Culver. [29] Abrams.” SP-25.. Vol. 1962. 1891. crete elements including mass of the specimen.. 59–86. Vol. Proceedings..” Journal. “Fire Loading for space exploration or military purposes presents another of Modern Reinfroced Concrete Columns. Vol. ment. MI. K. No.. M. 102–108. 1973. 115.” SP-5. J.. 1956. R. Lie. August 1990. Detroit. pp. April 1958. J. Z. full physical-chemical.. 1924. T. Portland Cement Association. velopment of temperature regime-structural behavior models [17] Malhotra. “The Effect of High Temperatures on Concrete temperature applications such as nuclear reactors. T. pp. Vol. S. “Fire Resistance with Concrete as Protection. “Thermal Properties of Concrete at Elevated specimen. “Effects of Elevated Temperatures on peratures. P... While strik. T. March 1976.” Bulletin protective shields including ceramic ablative shields. C.. Detroit.” Concrete. R. Skokie. “The Influence of Tempera- Concrete Institute. 2. Portland Cement Association. p. 2004.” SP-34. Detroit. M. 28–33. [28] Sharry. C. “Thermal Properties of Despite potential deficiencies in performance at elevated tem. pp. G. for better means of testing and specifying endurance [1. T. G.” Magazine of Concrete Research.. IL. 1976. “Instrumentation about 2760°C (5000°F) and velocities over 2438 m/s (8000 ft/s). J. R. M. and Burg. References [24] Diederichs. dynamic explanations that tie together all the aspects of the very [19] Philleo. and Moehle. ties are leading to significant improvements in specification and No.. K. [26] Lin. MI. 25. the conditions though extreme. 685. and Allen. Structural Division. S. 1962. Farmington Hills. C. and Sustained Elevated Temperatures. and McGrath. “Some Physical Properties of Concrete at High Tem- peratures. and Hillelson. complex visco-elastic. K. No. American Concrete Institute. 8.” Magazine of Concluding Remarks Concrete Research. “Compressive Strength of Concrete at Tempera- British Cement Association. answers have not yet reached the public domain. and Masonry Construction Assemblies (ACI 216. [25] Sozen. American peratures arising from dehydration and thermal incompatibili. pp. and Techniques for Study of Concrete Properties at Elevated last for only a few seconds and the choice between sacrificing Temperatures. 1377–1419. (ASCE 29-99). Vol. American Concrete Institute. W. July 1975.” ACI Journal. Skokie. Portland Cement Association. No. moisture-dependent behavior pattern of Vol. R. pp. G. Zwiers. R. pp.. W. and Poucher.. Reinforced with Epoxy-Coated Bars.. Vol. “Development and Lap-Splice pp. March 1970. RD101B. No. pp. 1992. 857–864. I. V. 2212a. P. concrete at elevated temperatures are still awaited. MI. notwithstanding a long-recognized need Elevated Temperatures. pp. aspect of the hot blast problem and is one for which all the Portland Cement Association. Detroit. R. Burg. 1992. 1–32.” SP-5. T.” SP.. R. T. Strength of Concrete. design of the concrete mix. V.. J... D. Vol.. physio-chemical changes. M. T. C.” SP-5. pp. V. “Experimental Study Relating Thermal Con- ductivity to Thermal Piercing of Rocks.” Journal. T. 1962.01T.. “Fire Resistance of Prestressed Concrete.” International Journal of Rock Mechanics in Mining Sciences. L. V. 2463–2464. pp. Skokie. pp. Cement Association. 54. pp. Culver. Skokie. 33. ment on the concrete was particularly exaggerated by the down. Detroit. Errata ST11.. Crist. Vol. Personnel Records Center Fire. B. 1968.” and a 1953 paper by Bishop [66] remains definitive. [27] Lin. “Danish Investigations on Silica Fume Concretes at fire-resistant material.” SP-25. specimen. Vol. A. and Burg.. 5.” Serial No. A. pp. involving temperatures of [13] Bertero.67]. V. the concrete or trying to shield it is one of cost and convenience. No. ST6. pp. IL. American Concrete configuration of reinforcing steel. “Properties of Mass Concrete As discussed by Abrams and Orels [48] there may be bene. thermo. July–August 1992. 1972. T.. Structural Journal. Zwiers. June 1981. I. and Marzouk. 1979. Detroit. Serial No. P. ture on the Physical Properties of Concrete and Mortar in the . March–April 1989. V. P. Nov.. D.. MI. W. Lie.” Fire Journal. “Military American Concrete Institute.. 10. H. 1971. 5. VA. it is [12] Lin.. Vol. Concrete Institute. 1531–1549. pp. “Fire Tests of Concrete Beams [4] Sheridan. pp. MI. conditioning and drying procedures and environ. Burg. Lengths for Deformed Reinforcing Bars in Concrete. However.. IL. and ST12. American Concrete Institute. Structural Members. [5] Troxell. “The Cardington Fire Test. Feb. Detroit. The velocity of the attendant hot [8] Standard Calculation Methods for Structural Fire Protection blast has been estimated at 1067 m/s (3500 ft/s) and impinge. [7] Standard Method for Determining Fire Resistance of Concrete MI. 86. 1960. 1994. Vol. 43–55.. 1268. “Bond Strength at High Tem- [1] Uddin.. national. of Concrete Slab Reinforced with Epoxy-Coated Bars. P. Bresler.. spacing. R. 102. RP321. “Fire Tests [2] Carlson. D. R. M. p.. and Polivka. tures of 1600°F.. No.” Portland sion ST3. [20] Nasser. pp. June 1976. R.. D. American Concrete Institute. V. C.1-97). aircraft. G. Vol. R. L.. pp. “Physical Properties of Concrete under Non..” SP-25. Investigation Conducted by the Bureau of Yards and Docks.. [64] Zoldners. C. 1535–1566. Detroit. J. G. W. ture. ble Changes in Concrete or Mortar Exposed to High Tempera- 27.” National Building Studies. pp. E. [48] Abrams. M. Detroit. V. W. pp.. No. 1964. pp. “Strength.” Proceedings of Stahlbeton..” Magazine of Concrete Research.. and Wilson. “Creep of Concrete at Elevated Temperatures. A. T. Portland Cement Association. No. port. Vol.” Cement. Nov. No. pp. “Fire Damage to General Mills Building and Its [44] Campbell-Allen. pp. C. Poisson’s Ratio with Temperature. Exposure Temperature of Prestressing Steel by a Metallo- [41] VanGeem.. Concrete.. pp.. [39] Harmathy. IV.. De. American Concrete Institute.. 879–888. Her [36] Marechal. pp... W. and Bremner. Oct. West Conshohocken. Aug. MI. pp. 1967. 1968. and Fiorato. 52–73.. T. 1953. Vol. De. 11. Sept. American Society ence on Mechanical Behaviour of Material. 11. Z. American Concrete PA. Proceedings. SZOKE ON RESISTANCE TO FIRE AND HIGH TEMPERATURES 287 Range 20°C to 400°C. L. C. American Concrete Institute. 1963. 17. [63] Castillo.” Vol. Holm. E.” Journal. March- Concrete Masonry Walls. No.” Proceed- shohocken. “Some Effects of Thermal Volume Changes on the [60] Smith. Vol. London. 74–94.” SP. Concrete Institute.. 1986. E. “Estimating Post Fire Strength and troit. May. and Carlson. Jan. 1964. 1972. troit. C. Influence of Aggregate and Load In- [34] Cruz. American Concrete Institute. 6. Burg. Part 2—The Visi- [35] Wang. 201–252. MI. pp. Concrete Constructions Following Fire Exposure. 10. pp. pp. 1. 1968.–Feb. Vol. P. 443–479. A. “Tests of the Fire Resistance and Thermal Prop- tion to Fire Tests. [65] “Refractory Concrete State-of-the-Art. Takeda. International Confer. PA. 9.” 547 R-79 (83)(87) Re- [47] Lankard.” [37] Schneider.. and Furumura.” ACI Materials Journal.. Malhotra. perature on High Strength Concrete. pp. T. Institute.” Proceedings. [46] Polivka. [55] Harmathy. J. T. M. No. S. Z.. 1971. American Concrete Institute. O. and Gjorv. 1971. Study B. ASTM International.. for Testing and Materials. Vol. M. 60–64. MI. J. pp. 37. and Desai. Prestressed Concrete Structural Members of Normal Dense Con- [33] Bremner. April 1964. L. 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F. West Con. 1964.. and Snyder. 423–434. C. “Apparatus for Measuring Creep of Concrete at tensity.. The beneficial consequences of air come evident that the further in time that the industry has come voids are obtained by using air-entraining admixtures and ap- from the landmark contributions of the early workers in air. which was once ex. however. and the air introduced as a result the kneading and fold. irregularly are the subjects of this chapter. Introduction The presence of these air voids initially suspended in the Incorporating air voids into concrete influences the behavior mix water among the solid particulate constituents of the of the material in both the fresh and hardened states. consistency. 288 . propriate concrete production and construction procedures to void systems and frost resistance in concrete. the air voids explain the origins of today’s state of the art.26 Air Content and Density of Hardened Concrete Kenneth C. coa- appears when there is a proliferation of the use of the ASTM lesce. “air-void system. become larger or smaller. NY 14853. Finally. and Introduction to estimate the relevant characteristics to various degrees of The air content within a given volume of concrete is the cu. strength. While expan. this edition have an opportunity to move. and the interpretation of the results obtained sizes ranging from microscopic bubbles to larger. measurement was taken. dissolved air in the Influence of Air Content on the Behavior and water. Following the pattern set by Helms. as the 4th edition had drawn nificant of these effects is the influence of air voids in mitigat- upon Samuel Helms’s clear and concise work in the previous ing the damaging effects of freezing and thawing of absorbed three editions of this ASTM Special Technical Publication. and the density. or change shape. however. The most sig- of the 4th edition were drawn upon. are often referred to as the and sources of error in performing and interpreting the test. by using ef- derstood are the fundamental principles laid down in the late fective placing and consolidation procedures to reduce the 1940s and early 1950s. and analysis. or origin. Performance of Concrete ing action of mixing and trapped in the mix while depositing the concrete in the forms [1]. sion of the use of the test has produced more data. the less well un. bleeding tendency and yield of the fresh concrete. placement. Hover1 Preface concrete influences the workability. test- mulative volume of a large number of air voids of multiple ing. shape. present edition therefore reviews much of this key literature to While the concrete is still plastic. The total air content and other air-void char- and Parameters of the Air-Void System in Hardened Concrete acteristics therefore depend on the stage in the mixing. shaped air pockets. preserving the size cases produced more confusion where less experienced opera. and shape of those air bubbles present at the time of setting. IN PREPARATION OF THIS CHAPTER THE CONTENTS and frost resistance of the hardened concrete. tors have used nonstandard equipment and procedures. not only the total volume of these air voids. regard- chapter has therefore been written in part to point out pitfalls less of their size. The mag- 1 Professor of Structural Engineering. Once the concrete has hardened. and consolidation processes at which the clusively performed by a small cadre of experts. The magnitude and utility of these effects depends on discussion of air content is more extensive here. encourage the retention of the smallest voids. perform a statistical analysis on a fraction of the exposed voids observed through a microscope. The water. Cornell University. the hardened concrete. the number and volume of the largest voids. Ithaca. Some voids can be removed from the Practice for Microscopical Determination of Air-Void Content concrete entirely. and. The All air voids remaining within a given concrete mass. but on the entire largely in response to the continuing interest and research in size-distribution of voids and on their dispersion throughout air-entrained concrete and freeze-thaw durability. it has in some however. it is presently necessary to obtain a sample of Part I: Air Content the hardened concrete. trans- (C 457) microscopical analysis procedure.” In order to evaluate the characteristics of the air-void system. accuracy and precision. It has also be. port. permanent void spaces remain. These voids have their origins in the air initially trapped among the dry constituents. The significance of such sampling. movement of unfrozen water es- crete. and on the strength of the concrete. osmotic pressure caused by tent decreases compressive strength. and on subsequent curing conditions. depending on frost-resistance afforded to the hardened cementitious paste. making steel-troweled floors and high air Workability contents typically mutually exclusive [12]. the “capillary pores” of the hardened cementitious paste [13–15]. In some mixes. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 289 nitude and degree of utility of these influences depends on the on concrete with air content higher than about 3 %. and reducing the density of the ing agents are present. duction in 28-day compressive strength [1]. moving towards the is apparently more severe the earlier the troweling is applied. and thus increase the number of cycles to failure. with various rules of differential salt concentrations. aggregate gradation and other constituents. This problem water remains in the smaller capillaries.) absorbed crete slabs when a steel-trowel finish is applied. In proportioning the primary reason for accepting side-effects such as strength concrete mixes. Blisters or shallow delaminations (2–3 mm thick) can develop on the finished surface of slabs due to the generally inadvisable Influence of Air Voids combination of a steel-troweled finish and air-entrained con.10. ciently low temperatures. and resistance to seg- air bubbles can separate solid particles in the mix [2]. gether by a hardened cementitious paste whose porosity de- and bleeding [1]. the density test. in the next section. and Air Content (Gravi. This attrac. reduced bleeding. a mutual attraction develops between microscopic bubbles and the grains of portland cement. A large number of microscopically small voids. this water freezes and expands in ASTM Test Method for Density. Since the largest of the cap- not clear.8]. this can also cause air-en. and finishing complications is the increased ability by reducing the water content by 6–12 %. the actual expansion of ice. part of the potential strength loss occurs depends on the level of stress and the frequency of these can be compensated for with the water reduction due to air fatigue cycles. or by differences between the thumb equating each 1 % increase in air content to a 3–5 % re. while maintaining This is accomplished through several mechanisms as described slump [3–5]. By displacing heavier components in the concrete mixture. will generally increase workabil. water and ice move towards the va- higher. settlement. generally desirable where the concrete is routinely exposed to freezing conditions. Air voids in concrete intersect the network of capillary pores in crete [4.11]. More significant Since these pressures are generated with the onset of freezing strength reductions have been reported [6].020 mm or 0. the impact of air con. Yield. acting as regation are useful characteristics of air-entrained concrete. there is an alarming coincidence of blisters or shal. the expansive pressure can originate in hardened concrete. consolidation. Under normal conditions. held to- ficial cohesion to the mix that reduces segregation. Cohesion Nature of Concrete and the Mechanism of When air-entraining admixtures are used to stabilize the Freeze-Thaw Damage smaller air voids. conditions is apparently more difficult as air content gets Upon rapid freezing. creating a which the freezing takes place and whether salt water or deic- more porous cement paste. sizes. variable yield. at equal water-cement ratios. but imparts a bene. cannot accommodate expansion of the ice. and on the specific exceptions. volume by 9 %. Frost Resistance ity at any given water content.5]. non-slip. especially when and ultimately relaxed upon complete thawing. multiple freeze- the air bubbles cluster at the paste-aggregate interface [7. the appropriate timing of main empty and able to accept either ice or unfrozen water finishing relative to bleeding. This is because sufficiently small While water reduction. can therefore be a useful means laries to the point where the remaining empty pore space of measuring air content in fresh concrete. the effectiveness of trained concrete mixes to become “sticky” with increased ad. When absorption of water has filled the capil- metric) of Concrete (C 138). and ambient when a freezing cycle begins.010–0. well-dispersed throughout the cement paste. surface-stiffening. one can take advantage of this increased work. illary pores are typically smaller than the minimum diameter low delaminations formed on the surface of air-entrained con. intentionally incorporated into the cementitious paste to reduce (but not eliminate) the stresses generated with each freeze- Finishing and Blistering thaw cycle. Although the mechanism of blister formation is the hardened cementitious paste. and dispersion of the air voids. of an air void (0. thaw cycles “fatigue” the concrete. the as influenced by residual. It is therefore difficult to achieve a steel-troweled finish cant air voids under a pressure gradient that is highest at the .0004–0. caping the advancing ice front [16]. air voids will reduce the strength of con.17–24]. high friction floor surfaces are material properties of the concrete. Whether physical damage Except in these latter cases. Depending on the rate at By occupying space between the cement grains. non-evaporated mix water or the sub- air voids reduce the density of the mix. the volume of the hardened concrete itself will be forced to expand with accom- Strength Reduction panying tensile or bursting stresses. Water can hesion to construction equipment and increased drag on be absorbed into the pores in the aggregate particles and into finishing tools [4.0008 in. With a few total volume. Mechanism of Freeze-Thaw Damage tion not only “anchors” the air bubbles to inhibit their loss Concrete is fundamentally a porous material composed of from the fresh concrete due to buoyancy. Density and Yield These capillary pores can be saturated to various degrees. As described in the sequent absorption of water from the environment. coarse and fine aggregate particles of varying porosity. Thus. the air voids therefore re- floors with air-entrained concrete. Air voids are entrainment [9]. pends on the original water-cement ratio. loss. thermal volume changes in ice and in paste [13–15. air voids only when under the pressure generated by rapid While there are many examples of successful hard-troweled freezing. air-cushions to reduce inter-particle friction. At suffi- chapter by Daniel and Part II of this chapter. wards from the periphery of the void. Origin and Geometric Characteristics of Air-Void ously dry would need no air at all. 15.) showing rate of freezing effects to be more complicated. water can move from coarser to finer pores because the vapor pressure over the surface of liquid water in small pores is greater than the vapor pressure of water over ice in the larger pores at the same temperature [5. [30. but tends to be so from the expansion of absorbed water in the aggregates. tem of air voids intersecting the capillary network at many points. or is therefore not independent of bubble size. one can theo. Mattimore and sorbed water in a portion of the concrete must move further Arni et al. and as a result of transporting and depositing the concrete in the forms [1.26. the velocity at which the water or ice must tensile strength of the concrete [16. Obtaining frost-resistant concrete therefore re- Air-Void System quires the selection of frost-resistant aggregates combined with To effectively provide frost resistance. to induce the movement of ice [13. concentrating on air voids “ignores 75 % of the tiveness.31] demonstrated reduced freeze-thaw damage than this critical distance to arrive at the nearest air void. Meeting initially present in and among the dry mix ingredients [16]. porosity. and such requirements will not eliminate the stress that accompa. on the rate of freezing. The additional component of osmotic pres- void can provide frost protection to only the hardened cemen. and the exposure. moves towards the air voids increases with a reduction in paste cally encountered in nature [15.26. 2 Under slower freezing conditions. in the capillary pore system.290 TESTS AND PROPERTIES OF CONCRETE freezing site and lowest at the air void. as does the cumulative [16. of mixing. volume of the protected paste shells around the bubbles. As will be discussed. while Flack [32] produced data ers calculated this theoretical distance as 0.27]. Fagerlund [29] further suggests The air voids protect only the hardened cement paste and do not that the smallest air voids.25.26. or both. another environmental variable. (Unsaturated concrete would need less air than saturated concrete.26].26].25 mm (0. permeability and with an increase in fluid viscosity As a consequence of the critical distance.25. As Pow- not be dry at the onset of freezing.2 and Air-Void Dispersion Just how far the water or ice can travel without generating The volume of freezable water initially present in the pores. ers described it. air is requirements for volume. As retically compute a critical distance (Powers’s term was pointed out earlier.23. .25. thus reducing their effec. Influence of Frost Resistance of Aggregates tion that the volume of freezable water in the shell must be no Freezing and thawing damage (frost damage) to concrete can re- greater than the volume of the bubble [25. Damage results when ab. move through the capillaries enroute to the air voids depends ment paste and set of environmental conditions. or damaging pressures depends on degree of saturation.17. degree of hydration of the and age of the concrete.33]. often much larger of a large number of small bubbles.28]. 19]. Shell thickness sult from the mechanisms of paste destruction described. curing conditions.26]. and environmental hardened cementitious paste. and the limiting condi. the System in Concrete air voids must be dispersed throughout the cement paste so that nearly all of the paste is within the protective shell of one Introduction or more air voids [16.16. permeability. For any given ce. The pressure difference is subdivided into smaller and smaller bubbles. at slower rates of freezing. rate of the “degree of saturation” will depend on the initial porosity freezing. properties of the paste.17. While the regular action of con- Principle of Achieving Dispersion and trolled mixing can stimulate formation and entrapment of a Acceptably Small Bubble Spacing fairly well-defined grading of predominantly small air voids. and spacing of the voids unavoidably present in fresh concrete as a remnant of the air depend on both the concrete and on the environment. Pow. rapid freezing conditions probably induce “critical thickness”) beyond which movement of ice or water water movement. material paste occupies a “shell” surrounding the air void with a thick.28]. as the bubbles become larger. sure is influenced chiefly by the presence of deicing salts and titious paste falling within a sphere of influence radiating out. the air-void system must the incorporation of appropriately sized and dispersed air voids have a total volume of empty air voids that equals or exceeds in the paste. subsequently incorporated by the kneading and folding action nies freezing but will maintain it at tolerable levels. providing a minimum travel distance from any point in Influence of Factors Other than Air Volume the paste to the nearest air void. and concrete that is continu. The zone of protected Details of the interaction of air-void geometry. (Among the scribed in detail by multiple researchers [13–17. “or thereabouts” for commonly encountered pastes and for It can also be shown that the pressure developed as water freezing conditions that are markedly more severe than typi. the total bubble required to move water or ice increases with distance of travel surface area increases geometrically. other dissolved solids.26].) Of equal importance. viscosity of the water.17.010 in. mathematical details of the development of the “protected 33–38]. the precise With or without the use of an air-entraining admixture. This pressure is minimized by a well-dispersed sys. As the same volume of air than those stabilized during the mixing process. Achieving dispersion and an acceptably small spacing for a the more random activity of depositing the concrete in the given air content requires that the air-void system be comprised forms tends to trap randomly sized voids.25.16. and environmental conditions are de- ness approximately equal to the critical distance. Similarly. may improve the inherent frost resistance of the aggregates. any given air [13.25. dispersion. while slow-freeze conditions are more likely will generate damaging pressures.25. paste shell” concept is a reduction in the critical distance due to the curvature of the bubble surface. similar in size to the capillaries.) problem” of the frost resistance of concrete (assuming 75 % of the volume of the material is composed of coarse and fine ag- Requirements for an Effective gregates) [26].28. The selection or testing of frost-resistant aggregates the volume of water or ice not accommodated by empty space is discussed in other chapters of this publication. The resulting air-void system is therefore a “compos- ineffective. kneading. This latter mechanism provides some The Composite Air-Void Gradation resistance to bubble loss due to buoyancy [1. The problem with this is not that the larger air As reported by Powers [26]. In the coarser of the two air-void gradings.44]. therefore to augment the coarser or “natural” air voids with a tected paste relative to the volume of the air voids themselves large number of the smaller voids stabilized during the mixing increases for smaller air voids. crete during mixing combined with the much larger voids pying the same total air volume. Coarse and fine aggregate grading bands are from ASTM C 33. leaving primarily larger voids in the hardened Air-Entraining Admixture concrete. The problem is that training agent is not used are also present when the agent is unless the air content is extraordinarily high. lescence. trapped in the concrete as a result of handling and placing.40–43]. since a protected paste concrete made of the same materials. with and without an air- shell exists around the periphery of all air voids in concrete entraining agent. the air-entraining admixture In ordinary concrete mixed without the stabilizing effects of merely stabilizes these bubbles once they are formed.39]. 1—Example grading curves of concrete constituents.) Large voids are therefore not process. Fly ash and silica fume examples are taken from Ref 45. In confusing contrast. “Comparison of sections of voids do not provide frost resistance. but also anchors the bubbles to cement grains and other charged particles. the term “entrapped air” is generally intended to apply to those These admixtures. they are simply less effective in providing frost re. related to soaps. retention. As While not implied in the literature. however. Vertical axis represents the mass or volume “finer than” the size indicated on the horizontal axis. it is normally advantageous to remove them from the that not only causes mutual repulsion and thus impedes coa. In the fine air-void grading. An air-entraining admixture is normally required to stabilize the air bubbles in such a mix. and dispersion. and the general voids trapped in the concrete during handling and placement. detergents. Cement gradings are examples of coarse and fine grinds. .17]. so-called “entrapped” air voids reduce smaller bubbles by a combination of surface tension effects the density and strength of the concrete to a greater degree and precipitates at the bubble wall [5. ite” [26] of the smaller voids stabilized and trapped in the con- sistance than a much greater number of smaller voids occu. indicates that the voids present when an en- regardless of their size or origin [5.15. a common industry misin- pointed out by Whiting and Stark [1]. 90 % of the total air content is contained in voids smaller than 1 mm in diameter. class of chemicals known as “surface active agents” stabilize Given that these larger. an air-entraining admixture. fresh concrete by appropriate consolidation techniques. the large voids used. a large number of the smaller air bubbles initially formed in the mixing process are lost from Air-Void System Resulting from the Use of an the system.” The consequence of using an air-entraining admixture is offer too little volume of protected paste. “entrained air terpretation of the terms entrained and entrapped is that air Fig. 90 % of the total air volume is contained in voids larger than 1 mm in diameter. These admixtures than is justified by their limited contribution to frost resistance also induce electrical charges on the outside of the bubbles [13. mix by promoting their formation. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 291 Air-Void Systems without Benefit of an is produced by the mechanical stirring. and infold- Air-Entraining Admixture ing actions of the concrete mixer”. (The volume of pro. Mass or volume percent is shown as a fraction of the total mass or volume of that particular constituent. The term “entrained air” as conventionally used is in- Function of Air-Entraining Admixtures tended to apply to those voids trapped during mixing and sta- Air-entraining admixtures stabilize the smaller air voids in the bilized by the air-entraining admixture. critical information is lost con- air-filled cavities the smaller the total volume of air required. the larger voids are often The specific surface () of the air-void system is analogous in seen to be non-spherical and irregularly formed. by the Turbidimeter (C 115) and ASTM Test Method for Fine- ness of Portland Cement by Air Permeability Apparatus (C Caveat Concerning Terminology 204). the simplest When calculating the spacing factor of the air-void system (as way to describe the size distribution of bubbles. the air-void grading can range from 10 this nominal limit. and placing the concrete. As has been discussed. air voids of greater rently done much more simply and approximately. Under. For air voids. smaller voids was stated by example.2/in. coarse voids” [26]. Such Parameters indices do not uniquely define the size distribution. It is observed that the voids actu.” based on the ratio of total air void surface area to total air volume. Despite this continuous grading of air voids. It is observed. istic size. “For a given degree of protection.49] developed mathe- tion of a significant number of air bubbles much less than 1 matical techniques for estimating the complete grading curve mm in diameter is unlikely without the stabilizing influence of for air voids in concrete. will be discussed). however. Finally. Given that air voids of more than a factor of 1000. Alternatively. the smaller the to represent an entire grading. that the air-void system typically produced in concrete “entrapped” when used correctly to denote void size is analo. broadly different size distributions could be described by Measurements of Air Content the same index value. since a protected paste shell exists around an Index to Void Size their periphery. in units of mm2/mm3 or 1/mm (in. higher val- trained air voids are in fact the result of air having been “en. ing its utility only for air-void distributions without “extremely stituents of the concrete including the total volume of air. voids. cific surface of 25–45 mm2/mm3 (or about 600–1100 in. The The “fineness modulus” of sand (see ASTM C 125) is another advantage of the more efficient. In each of these cases where a single number is used Powers [16]. These fineness of the air voids. ues correspond to a finer air-void system. where the specific surface is defined same terms can be misleading when used to imply the origin. ASTM Test Method for Fineness of Portland Cement to the effectiveness of the air voids in providing frost protection. m to more than 20 mm—a spread of more than three orders lying this definition by size may be the observation that reten. by dividing the total air volume by larger than. Higher fineness values indicate finer.47] found that it can be more informative to express the breadth or overall shape of their size distributions.04 in. Quantitative Description of Air-Void System in they provide no information about the actual number of parti- Hardened Concrete—The Air-Void System cles or air voids with a fineness near the average value.3) or (1/in. This same approach is used to describe the average ing only in regard to the size and shape of the voids. When air-void systems vary considerably in Klieger [9. incorporating an air-entraining admixture will result in a spe- gous to the term “coarse” when describing an aggregate gra. water. cit- pressed as a percentage of the combined volume of all con. the air content must be expressed as a frac- gregates is to report the number or volume of constituent parts tion of the “air-free” paste. The size of than 1 mm in diameter or so can be present with or without the air voids is typically defined by a statistical parameter the influence of an air-entraining admixture [26]. Further. Large or irregularly shaped voids are not altogether without benefit Limitations of the Specific Surface Alone as to frost resistance. While single-number indices may imply an “average” fineness of sorts. for ex- trapped” in the mix and stabilized via the admixture. more efficient voids. the air voids contribute to the frost-resistance of the hardened cement paste occupy the broadest range of sizes of all the constituents of only. [26. 1.3) dation. and small “entrained” voids. unit mass. The Shape of Air Voids While the smaller air voids in concrete are generally observed The Specific Surface to be spherical in shape or nearly so. it can be useful to express the air content as a percentage concrete. or ag.” cerning the range and distribution of sizes included. and smaller than. since their protected two examples of the industry’s need to characterize the behav- paste volume as a fraction of the void volume itself is many ior of multi-size systems with a single.292 TESTS AND PROPERTIES OF CONCRETE voids in concrete are of two sizes only: large “entrapped” voids the air volume as a percentage of the mortar volume (that is. since multiple. the spe- . mulative volume (rather than cumulative mass).34] (see also ASTM C 457). some ways to the “fineness” of cement. for necessarily related to the use of an air-entraining admixture or example). of the paste (volume of cementitious materials.) and defines “entrapped” air voids as those above As pointed out earlier. characterization of void size is cur- an air-entraining admixture. or effectiveness of the voids. The term ample. known as the “specific surface. and is not ment (300 m2 of cement surface per kilogram of cement. mortar volume concrete volume minus the volume of coarse ally occupy a broad grading ranging from 10 m to several or aggregate). smaller-grained ce- As described earlier.). which is expressed as tion that void shape becomes increasingly irregular with void the estimated total cement surface area per unit mass of the ce- size is observed in many other physical systems [46]. While Willis and Lord [48. The air content of hardened concrete is most commonly ex. of magnitude. and air). as the cumulative surface area of the voids divided by their cu- evolution. The observa. the volume of cement and water only. Such large voids are relatively inefficient in re.2/in. The specific surface of air voids and the fineness of cement are gard to proving frost resistance. As shown in Fig. the smaller voids classified as the en. times less than for the smaller. The specific “air-entraining admixtures” do not strictly “entrain” air into surface is expressed as surface area per unit volume resulting fresh concrete. and “entrained” air as those below. ment since smaller particles have a greater surface area per trapped air void” as defined in ASTM C 125 have specific mean. some predetermined character. observing that frost resistance consistently resulted hundreds of millimetres—a size range from smallest to largest from 9 1 % air content in the mortar. Powers recognized this limitation of specific surface. ASTM Terminology Relating to Con- crete and Concrete Aggregates (C 125) sets a size criterion of 1 Measures of Air-Void Size and Size Distribution mm (0. mixing. large or “entrapped” voids are the natural con. numerical size-index. sequence of batching. the terms “entrained air void” and “en. 25. Mather [52] observed an points in the paste to the nearest air void. pothetical set of air voids. paste content. however.” as shown in Fig. the so-called “spacing factor. Every void is equidistant from paste to the nearest air void. A less accurate but far simpler approach mensional grid. The dimensions of less than this computed value.” the grid system are determined so that the volume of the air Fig. arranged in paste in a putes a theoretical maximum distance from any point in the cubic. one needs to Arrangement first determine the air content. and specific sur- As observed through the microscope.) Air voids arranged in a simple cubic lattice. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 293 – cific surface loses much of its value as a comparative index. as generally designated by L . Under the assumption that a ma. 2.51] (see ASTM C 457).57–61]. To those not familiar with the derivation of these While both the air content (expressed as the volume of air per equations. formed relative to observed distances between voids or from tion [33. Next. studies [53–56]. the random dispersion of air voids in the actual mining the relative proportion of the hardened cementitious cement paste is replaced in the model with a geometrically reg- paste within the beneficial zone of influence of one or more air ular pattern of single-size voids arranged in a uniform. three-di- voids [28.50. representing the farthest that water or ice would have to travel through paste to get to the nearest air void in the hypothetical air-void system. 2—(After Ref 15. No measurements are required or per- crete are randomly dispersed in regard to both size and loca. and a characteristic void size on the spatial distribution of the air voids. As described by Walker [44]. 2). in which one com. To compute the spacing Characteristics of Actual Geometric factor in accordance with the ASTM equations. and (2) arranged in a simple cubic lattice where each void is equidistant from its nearest neighbor. their apparent complexity may imply a level of unit volume of air-free paste) and the air-void size (as charac.26]. The void size in the behave differently with respect to resistance to freezing and simplified system is chosen to have the same total volume and thawing. “Consider a hy- has been adopted by the industry. The ratio of the volume of the unit cube to the volume of the air voids is set to be equal to the ratio of the paste volume to the total air volume in the paste. The rele- paste within the “critical distance” of an air void are assumed vant equations for determining the spacing factor are given in to be able to tolerate the pressure generated during freezing. inhomogeneity in bubble size and dispersion such that “Many After having obtained the relevant input data. six other voids. however. As pointed out by Willis [48] and by Powers [25] the “number” of air voids in the actual versus simplified systems may be Spacing Factor significantly different. actual air voids in con. assess the dispersion or spacing of those voids and so deter. and one cannot es. face of the air voids.37. The spacing factor (L) is the distance along the interior diagonal from the center of the unit cube to the periphery of the nearest void. the first sim- samples show variations from area to area. ASTM C 457. can serve as an index to the effec- do any other indices calculated from the specific surface. all one size.” This inhomogeneity has been observed in multiple same total void surface area as in the actual concrete (see Fig. three-dimensional array. and imaginary lines connecting the voids are jority of the maximum paste-to-void spacings in the paste are mutually perpendicular. Calculation of the spacing factor (L) is based on the assumptions that all air voids are (1) the same size. only those saturated portions of cement tribution of air-void spacing in concrete [16. . tiveness of the air-void system in contributing to frost resistance. mathematical rigor beyond the intent of the developer. as the terized by the specific surface) will jointly be used to estimate relationships bypass the complexity of the real air-void system the number of air voids within a volume of paste. close to one or more air voids.50]. the specific surface can be a useful indicator of the The Simplified Model of Air-Void Spacing: relative void fineness [15. Among air-void systems with similar distributions of void sizes. total air-free paste content. it remains to and substitute a very simplified model of reality. plifying step is to replace the multi-sized voids in the actual cape the conclusion that different parts of such concrete would system with a system of single-size voids. Powers’s Spacing Factor Powers developed the concept of the spacing factor as a sim- Air-Void Dispersion and Spacing plified approach to the complex mathematics of the actual dis- As discussed earlier. Mathematically rigorous approaches are available for deter. The basis for the utility of the spacing factor is that it takes mine whether substantial portions of the paste are sufficiently into account the combined influence of the “total” air content. Sandberg and Collis [56] have pointed out factor is “related to the maximum distance in the cement paste that the most common field sample is a core extracted from a from the periphery of an air void. “first. nor is it necessarily related to the actual ther. The thickness of this hypothetical paste layer is as. strongly influenced by the air-void system remote from ilar void size distributions and. method is greatly improved when the average results of at least tor so obtained is obviously not the actual average spacing in a three samples are reported [15. Powers himself pointed out that the method Although often only one sample is used. Conduct of the Test ers [16.21. Willis [48]. a random sample comprised of only those air voids that come When it has been determined that air content in the actual into a narrow field of view. A sample of hardened concrete is sawn to expose a plane alent to the measured volume of air relative to the measured surface that is then ground to provide an “extremely smooth volume of hardened cement paste. stating that “The traditional way of calculating the air requirement. ing this model. level of magnification used. even if the average spac. although alternative and the air-void system.” Actual performance of the test. Characteristics of the air-void derived from total void volume and surface area.294 TESTS AND PROPERTIES OF CONCRETE voids relative to volume of “grid space” between them is equiv.50]. air-void size distribution. an even simpler model is used to determine the spacing factor (ASTM C 457-98. It cannot be applied universally. They recommend that observation of a ASTM C 457 Microscopical Analysis “finely ground” surface. the performance of a particular uating the frost resistance of the exposed surface. ASTM C 457 recommends at sumed to be equivalent to the spacing factor [25. requires only one sample. This sim. one simply Sampling assumes that the total paste volume is evenly distributed over Samples submitted for microscopical analysis are often cores the combined surface area of the air voids as a uniformly thick extracted from concrete in service. that surface.26]. such as required by ASTM C 457. how. and makes a series of measurements or counts on spacing factor (ASTM C 457-98. quirements of ASTM C 457 can be met by the single specimen. Statistical estimates of air content. frost load. by use of Specimen Preparation Powers spacing factor. and Lord and Willis [49]. will concrete might be determined by a much larger spacing factor be confined to the top 5 mm or so of the core. least three samples per determination when the tests are being plified model likewise ignores the complexity of the actual void performed for “referee purposes or to determine the compli- sizes and random dispersion. Unfortunately. of voids are computed on the basis of these measurements. the more optically flat must be the specimen surface. tual measurements of the air-void system.65–67]. cussed by St John et al. the frost-resistance of the The current procedure recommends grinding the surface aggregates. the orientation of cores relative to the exposed concrete spacing in the same way. as will be discussed. (These depressions are made more Methods of Evaluating the Geometry of the visible under the microscope by side-lighting with a harsh. cast specifically for the purpose. (ASTM C 457). erator must be able to clearly distinguish among the various and air-pore system. Procedure B). it [Powers’s system determined are therefore an average over the depth of spacing factor] is strictly applicable only to concretes with sim.” This vital issue is dis- tal conditions. methods have been used with success [51. being to the exposed concrete surface. move in a systematic pattern under the crosshairs of a stereo try just described are embodied in the standard equation for microscope. the core.62].) The less distinct the edges of these depressions the less accurate are the measurements. to microscopical evaluation. the op- used for normal situations as regards moisture load. These assumptions and the simplified geome. Fur- system of graded sizes.” ASTM C 457 reports that the spacing surface is important. [69]. Thus two concretes with the is difficult to extract a specimen that offers a statistically rele- same calculated spacing factor might not behave the same. Eq 12). and key ASTM C 457 describes two alternative methods: (1) the Rosiwal modifications were made by Mielenz et al. or may be hardened samples coating. whereby the axis of the core is perpendicular primary limitations of the Powers spacing factor. In this case. provided the minimum area re- Due to the nature of the simplifying assumptions in construct. . it that occurs less than half the time. coupled with although Brown and Pierson [63] and Mather [68] recom- assumptions concerning material properties and environmen. with successively smaller abrasive grits. the modified point-count method (ASTM C 457.” vant area of concrete within this critical surface zone. and spatial dispersion (normally occurring in only high air content/low paste con.25]. The air-void system of greatest interest when eval- ing is determined accurately. how- Approximate Nature of the Spacing Factor ever. material properties of the hardened cement paste. who observed that the higher the void system of hardened concrete is ASTM C 457. The spacing factor is then and plane section” suitable for microscopical inspection determined as half of the greatest distance between any two ad.” Philleo [58] summarized two concrete surface. ance of hardened concrete with requirements of specifications for the air-void system. sult should be an “extremely smooth” semi-polished surface. second.” constituents. [36] based on linear traverse technique (ASTM C 457 Procedure A) and (2) work by Chayes [64]. mended stopping short of “polishing. with the air voids appearing as sharply defined depressions in the surface. the accuracy of the “does not give actual spacing” [26]. however. low- Air-Void System in Hardened Concrete angle light. Once the concrete has hardened. He later wrote [5]. Fagerlund [29] reached a similar conclusion. The end re- ever. “The fac. Eq 13) [15. frost resistance is normally estimated on the basis of ac. The current procedure for evaluating the air. “is ASTM C 457 was originally proposed by Brown and Pierson best restricted to low-power stereo microscopy using magnifi- [63] on the basis of earlier developments in geological cation not exceeding 100. is an approximation that can only be When observing the specimen through the microscope. and sharpness of the void Introduction edges depends on the quality of the surface preparation prior As previously discussed the frost resistance of concrete de. with modifications for use on concrete. The mathematical foundation for the technique was laid down by Pow. The operator causes the prepared sample to jacent air voids.” sciences. cretes). pends on environmental conditions. system is more than about 23 % of the air-free paste volume paste content. Eq 6). but the ultimate results are essentially equivalent. Of these only about 1000 will be evaluated through the microscope. Using these principles. Both methods are statistical survey procedures in which inferences about the air-void system of the sample as a whole are made on the basis of measurements of only a fraction of the air voids visible on the specimen surface. or the “void frequency. Paste or aggregate con.) Schematic diagram of linear as the plane of the surface could have randomly cut the origi. (In practice. No where is the expected value or “most-probable” estimate of attempt is made to direct the lines through the diameters of the the specific surface of the population of voids with an average – circles. It has been shown choose a nonstandard procedure based on measuring void di. Irregularly shaped air voids in the concrete appear as depressions with an irregular outline. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 295 The nature of the measurements differs somewhat between the two methods as will be described. It can be demonstrated mathematically.70]. sliced near its periphery. void frequency is equal to the number of chords divided by the . and the number and length of these intercepts are recorded as the test continues. that small circles are more likely to have originated in small rather than large spheres. Neither of these steps are generally taken. Having obtained values for the air content. however. tribution of air-void sizes from the distribution of diameters of mate of the distribution of the original bubble sizes. a typical 100 mm (4 in. which permits the use of statistical theory combined with a sufficiently large number of observations to tent is similarly estimated by dividing the cumulative chord project an estimate of the original bubble sizes [33. intercepts are measured that do not coincide with diameters ter of the original void. dimensional void depressions does not necessarily indicate fact of a small void cut near its center. can take 2–6 h of microscopical observation to complete.65]. verse length. Eq 8) the depressions on the plane surface. mathemati. one computes the spacing length of 1400–4000 mm per specimen distributed over about factor in accordance with Eqs 12 or 13 of ASTM C 457-98. Since the number of voids encoun- length of the traverse. that can be estimated from the average of the lengths of the ameters in lieu of chords to compute air-void system parame.2) of sample surface depending on paste One additional air-void system parameter in common use content as suggested by aggregate size (see ASTM C 457). although with less certainty. . a simpler operation is performed in lieu of meas.) The cumulative length of chord intercepts divided by the number of chords intercepted produces the average chord in- – Linear Traverse Method tercept.63. The microscope moves in parallel.49. The diameters of these circles are only indirectly related to the diameters of the original voids.) diameter core taken from concrete in which an air- entraining admixture was used may contain something on the order of 20 million air voids.” generally designated by n. A small circular depression on the of the air voids. as void-size distributions are usually neglected in fa- cal corrections would be required for microscopists who vor of determining the specific surface. For example. 3 [63]. the age measure (Eq 4 of ASTM C 457-98). done. which are in turn only a fraction of the total number of air voids present in the sample. ters [61]. one could pain. (Note: Since the ASTM chord intercepts. 3—(After Ref 15. As demonstrated by Willis The linear traverse method requires that a series of “preferably [48] the average chord intercept or average chord length is sta- parallel and equally spaced” lines be traced across the surface tistically related to the specific surface of the air-void distribu- of the specimen as shown in Fig. making the void length of chord intercepts across air voids. closely nal void at any point [48. This can also be discussed. Only a coincidental and unlikely spaced paths across the prepared concrete surface. it is possible to estimate the dis- the specimen and from these measurements project an esti.” A typical test may consist of total traverse paste content. or of a much larger void the spherical diameter of the voids. and specific surface. divided by the total frequency a useful index. Fig. while those voids that were spherical or nearly so are represented by depressions that are clearly circular. The greater The total air content is estimated from the cumulative this number. Note also that the size of the two- specimen surface could therefore be the two-dimensional arti. however. As will be the depressions on the plane of the specimen. The inspected surface is a two-dimensional plane cut and ground from the three-dimensional concrete. C 457 equations are not based on void diameters.) These traverse lines randomly intercept a fraction of 4 /l (ASTM 457-98. tered is equivalent to the number of chords intercepted. Three- dimensional air voids intersected by this plane are represented by depressions of various shape and depth in the plane of the sample. however. intercept across the constituents of interest by the total tra- 59–61. l .65. 50–1600 cm2 (7–250 in. individual chord intercepts [48. multiplied by 100 to convert to percent. and is the number of voids encountered per unit length of traverse. the intercepts are therefore random “chord lengths” or chord length of l .49]. this is done tion via the expression by moving the specimen through the microscope in a regular – pattern. the more voids per unit volume. (ASTM C 457-98. “chord intercepts.49. stakingly measure the diameters of the circles on the plane of As previously discussed. Chord cut at mid-depth of a void would leave a circle with the diame. traverse procedure. from the distribution of the uring the diameters of the depressions.48. This average chord length is then used as perimposed on the sample surface in a manner similar to that explained earlier to estimate specific surface and subsequently just described in Fig. and can tent on the same specimen would be less than 1. After completing each tra. equally spaced traverse lines form a rectangular grid of 457 includes the results of two studies on precision [51]. A typical test difference would be less than or equal to 1.) The air content is estimated as the number tests sponsored by the ASTM subcommittee responsible for the of points falling on an air void divided by the total number of test method and using one set of prepared specimens.82 % air if the reverses the direction of travel over the same line. Average chord length may also be determined point-count technique. and less than 2. regularly spaced stops are made and the constituent directly under the cross hairs is Precision and Bias identified at each stop [36]. theoretically would be greater than these reported values if based on analy- equivalent to that determined by the linear traverse method. ASTM C 457. the expected difference between two measurements of air con- face depending on aggregate size (see ASTM C 457).296 TESTS AND PROPERTIES OF CONCRETE Fig. The discussion of precision and bias that accompanies ASTM C allel. for example. The microscope moves in a grid pattern over the prepared concrete surface. relates void fre. (Regularly spaced stops along par. timated that in 95 % of all cases the expected difference stituents can be estimated similarly. The volume proportions of all other con. the operator then single specimen would be less than or equal to 0. counting the two tests were performed in the same laboratory. between two independent measurements of air content on a verse line in this point-to-point manner. ses of different samples from the same batch.) Schematic diagram of modified point count procedure. tributed over about 50–1600 cm2 (7–250 in. . the same laboratory. The expected total number of air voids intersecting the traverse. Variations in estimated air content traverse provides an estimated total chord length. Fig. in which a series of traverse lines are su. Air content is determined by the number of points identified as falling on air voids divided by the total number of points counted. 3.16 % air if tested in may consist of 1000–2400 points counted per specimen. and cumulative chord lengths. 4. can complicate the procedure. In Sommer’s independent tests [51]. Rather than measuring the individual the spacing factor. Eq 7. from void frequency.61 % air within take 2–6 h of microscopical observation to complete.” also theoretically equivalent to that determined by lin- The alternative to the linear traverse method is the modified ear traverse.2) of sample sur. 4—(After Ref 15. two different laboratories. In points. dis. total length of traverse.01 % air if performed in The computed air content multiplied by the total length of different laboratories. Note that points falling on the edge between air and paste. however. it was es- points in the grid. recorded) is then divided by the total number of voids encountered on the traverse to determine an “average chord Modified Point-Count Method length. This “cumulative chord length” (even though no chords were quency and air content to average chord length. Both these minimum values increase with in- content ranged between 6. ASTM C 457 requires a minimum length of tra- prepared specimens were sent to various labs for evaluation by verse for Procedure A.170 mm (0.). It would Sampling therefore be expected that the same operator would obtain If the concrete placement being evaluated were homogeneous somewhat different results for each analysis of the same spec. one laboratory to and Variability another. concrete in question. and spacing fac.2/in. The discussion on precision and bias has demonstrated that the results of the microscopical analysis procedure are not Procedural Sources of Uncertainty only variable from one sample to another. yet the lower the air content the less certain are the re- tor. Note that whether a sufficiently 21. is of interest to note that a microscopical analysis of hardened prehensive. the voids observed would rep. tainty in air content is primarily a function of the length of the ing factor. specific surface.005 to 0. the characteristics of the air-void system vary servations. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 297 ASTM C 457-90 reports Sommer’s precision data for spac. If the studies were done in different laborato. and one operator to another.77].2/in.01 % of the voids in the 1 CY sample.011 in. [76] have shown that when tainties are reduced by about 1/3 when the results are the aver. and between 2.89 % on the other.14–9.) The un.63. have shown broad variations in air content.079 to 0. respectively.” paste content. and equipment. ratories would increase the coefficient of variation. Among other results they report uncertainty of 27. For the specimen nizing that mixes with larger aggregates normally have a with the higher air content.63.9 to 46. and Van der in Test Results Plas and Tobi [69. local variations in procedures. independent from the variability caused by opera.6 mm2/mm3 (556 to 701 in. verse length as necessary until about 1000 voids have been form concrete combined with variable surface preparation and intercepted. however. but being statistical estimates the results are fundamentally uncertain as well. For their specimen with the lower air content.63. consolidation. tainty in the estimates of specific surface and spacing factor. Snyder et al. pected. and 20 % for air content.50. While these references crete slabs. been completed. and computed values for spacing factor ranged from fewer total voids will have been intercepted even when the 0.71. Since the re- detailed subsequently. spacing factor. while the uncertainty in estimating the spacing to sample selection and surface preparation in different labo. The subsequent measurements of spacing factor within the same longer the traverse or the greater number of points the more laboratory could vary by as much as 22. the error inherent in the reported values “decreases exponentially” Inherent Statistical Uncertainty with the number of samples [50].) of one another within the same con- tional factors [36. placement. .3–2.80]. None of these studies have replicated mized by running the traverse beyond the ASTM minimum tra- the typical industrial conditions of random sampling of nonuni. It Pleau and Pigeon [77] have presented perhaps the most com. 125–250 mm (5–10 in. For example. The fundamental uncertainty in computing percent composition on the Sources of Variability and Uncertainty basis of point-count is discussed by St John et al. sults of the test are statistical estimates of the true values. Such variations can be intensified by the localized should be consulted for details. showing that at the 95 % confidence level two traverse or the number of points counted [36.007 sonable estimate of void size depends not only on the traverse in. To increase the probability of having traversed sufficient ries. Results reported for air Procedure B. the number of voids measured.71.003 to 0. for analysis of a single sample.). from one cubic yard of concrete. the results from a single sample to the balance of the volume of area of cement paste available. the specific length but on the void frequency. factor depends on the combined uncertainties in air content.79–81]. in. and values for large number of voids has been intercepted to permit a rea- spacing factor ranged from 0. ASTM Fundamental statistical uncertainty in estimating the spe- C 457 therefore advises that “The variability of the test method cific surface depends on both the uncertainty in the air content would be higher in actual practice for specimens sampled and and the uncertainty in establishing the average chord length or prepared from in-place concrete since additional variation due void frequency.71–77]. sults of the analysis. concrete is most often called-for when a low air content is sus- 24. creasing nominal or observed maximum aggregate size.9 %.3). (If 1000 voids were observed in one core extracted with location due to variations in batching. the error in estimating the specific surface can based on random statistical sampling of a small fraction of the drop from 25 % to about 15 % by examining three rather than air voids within a small fraction of the concrete so that test re. Simon et al. and finishing [53.63].135 to 0.77]. it is observed that the uncer.9 to 27.76. and average chord length [71. the variation could be as much as 56.5 mm2/mm3 (556 to 1180 content and a correspondingly small number of air voids. the area of concrete sampled.76]. actual structures. In this context. Specific sources of this variability and uncertainty are still depend on the number of samples examined. assuming that the concrete is homogeneous. one specimen. concrete surface to have a representative estimate of air and Langan and Ward [71] conducted a study in which two paste content. using the linear traverse method this problem may be mini- age of three samples [15].49–51. Multiple studies have been conducted on these sources of and spacing factor among multiple samples taken from within uncertainty. at the 95 % con- The linear traverse and modified point-count procedures are fidence level.3).76. the accuracy of the microscopical analysis would imen. ASTM C 457 minimum traverse length or number of points has Among the multiple studies of the variability and uncer. and a minimum number of points for various operators within those labs. For concrete with a low air surface ranged from 21. sampling substantially more influential and complex. the specific surface ranged from reduced paste content [36. In sults are statistical estimates based on a limited number of ob. operators.6 % of the value of the accurate will be the estimate of air content. recog- mens. throughout.284 mm (0.76]. [53] and on the breadth of the distribution of void sizes [50.78]. certainty in these statistical estimates depends on the inherent No guidance is provided by ASTM C 457 for applying the variability of the concrete. specific surface. mixing. This condition tends to increase the uncertainty inherent in the ASTM C 457 procedures [36. These uncer. effects of consolidation [53.45 % air for one of the speci. making the issue of resent only 0. “Low trapped” air voids and the finer. Image Analysis Techniques ability [71]. on the accuracy of the paste content aries unclear. if than is normally performed for ASTM C 457 samples [69]. in some cases. towards improving ac- documented operator subjectivity as the cause of variability in curacy and precision and reducing the time and effort required . it is the human operator were aggregates. There have been multiple suggestions for keeping this Pleau et al. with an inexperienced operator re- Faulty or incomplete specimen preparation has been cited as a porting about 0. and to delete the con- In light of such observations. shape.25 mm (0. Langan and Ward reported the identical effect [71]. because the various types of ence on total air content. fine Several potential errors in the air-void system calculations are aggregate. To delete large voids. value will depend.008 in. coarser voids are arbitrarily deleted from the air void analysis.87]. tion of the finer voids included in the analysis. and whether the con. It can be meaningful to simply always underestimates paste content. In many cases these decisions are not worth noting. In comparing test results ob. it is clear that operators must be A closely related source of error is the common mistake of well-trained and well-experienced. Sommer reports error due to the operator’s subjectivity will always remain.” similar errors stemming from surface preparation [51]. Pleau et al. or when the presence of aggregates or pozzolans (see Refs 69 and 78 for paste content errors using point-count). will merely assume a value for Given the subjective nature of these decisions and the paste content. and may be determined from either point is a subjective choice that can significantly affect the test the linear traverse or the point-count technique. Counting this as an “air” or “non-air” paste content is essential. using a value for paste content that includes the volume of the tained with experienced operators. – however. Other agencies have determined such practices to very small bubbles could not be seen clearly. when poor surface preparation makes bound.65. an accurate estimate of the edge of an air void. In less obvious cases. so-called “en- reported that in comparison to tests performed at 120. (However. paragraph 5. automated and semi-automated image analysis techniques for ator is trained properly.) and three experienced op- source of error by many researchers [33–36.86. The effect of discounting the larger chords is con- also the earlier statements that magnifications higher than sistently to decrease the reported value of air content and to in- about 100 require a more sophisticated surface preparation crease the reported value of specific surface.15]. the equation for spacing factor requires a easy. need for informed judgment. who makes the decisions about where to stop and start the individual measurements of chord length.50. such as when the crosshairs or line of traverse is nearly value for the paste content. The value required in computing spacing factor is the ratic” results from the inexperienced operators using modified fractional volume of “air-free” paste.” In one test series. quired in the microscopical analysis of air-void systems in con. Arbitrary Deletion of Large Voids Level of Magnification of the Microscope ASTM C 457 states that “no provision is made for distinguishing At higher levels of magnification the operator can see and among entrapped air voids. Thus for calcu- spite the mechanically rote aspects of the test (which can be lation purposes ignored air voids should be counted as if they streamlined with modern equipment). such that A in the ratio p/A reflects only the finer voids.51. While emphasizing the “paramount importance” of specimen preparation alone can skew the results of the ASTM training new operators.145 mm (0. results. Detailed discussions are In some cases the computed value for the spacing factor is ei- found in Ref 50 and in the text and notes in ASTM C 457.210 mm (0. or an air void.298 TESTS AND PROPERTIES OF CONCRETE Surface Preparation computed spacing factor. with human eyes as input devices and discount their small contribution to frost resistance but also ig- the human frame as a support system. tribution and calculated specific surface. Pleau et al. Rodway [85] reported “er. coarse aggregate. tribution made by the large voids to air content and protected mum magnification of 100 and a maximum of 125. conclude that “an intrinsic C 457 test by as much as 3 % on air content. they have significant impact on spe. and water voids. as well. erators averaging about 0. interpreting this as a confirmation of Langan and Ward’s previous findings relative to operator vari. and a magnification of 100 instead of 50 cific surface as discussed earlier [5. not as paste. Bruere [84] theless distinguish at least between the coarse. A common error is to ignore the coarse voids altogether. ther so great or so small that appropriate conclusions may be Operator bias can be particularly important in the modi. At a minimum. Each of these is severely noring the fact that their volume does not require the protec- taxed by the tedious and time-consuming process described. Some testing agencies never- C 457 requires a minimum magnification of 50. the paste Operator Subjectivity volume p must likewise exclude the volume of the coarse voids The most sensitive and sophisticated piece of equipment re. [50] suggested a mini. One reason for discounting the that spacing factor was always decreased by magnification of larger voids is to avoid their possible impact on skewing the spe- more than 50. point-count procedure. entrained air voids.51. Calculations stituent under the crosshairs is paste. Recall paste volume.006 in. [36] reported that “the results of the There has been a great deal of research and development into linear traverse are adequately reproducible provided the oper.) Some laboratories use keep track of the questionable points and report their number the paste content determined from the mix design or reported along with the number of clearly identifiable points.) by at least 10 % [51].3). and therefore on spacing factor [83]. and other characteristics” cific surface. First. [50] have observed that microscopical examination error from accumulating [50]. Pleau et al. measure smaller voids. air itself. consign their volume to the paste. Mielenz et al. While ASTM (ASTM C 457-98. and in the process not only crete is a human brain.63. De. voids intergrade in size. While such small voids have little influ. mimic the appearance of an air void. in part. drawn without much concern for the accuracy of the estimated fied point-count procedure when the crosshairs fall directly on paste content. batch weights or. so-called “entrained” air voids magnifications (40 and 60) gave erroneous results since [44.) on the same spec- Roberts and Gaynor [82] have reported that the effects of imen.82]. [50] air void systems in hardened concrete.” Sommer reported produce misleading results [72]. Any such distinction is arbitrary. and the accuracy of the computed tangent to a void. is to artificially modify the recorded air-void size dis- can be assumed to reduce an L of 0.010 in. fore alerts the user that “The air content of hardened concrete tems can nevertheless provide important information for evalu. the fresh concrete. When differences exist between the mixing. and the appearance sure.107]. • The incorporation of a beneficial air-void system in con- ing. however. or the effects of admixtures or construction op. • Some of the difficulty in interpreting frost resistance on gardless of the size or distribution of the air voids.) environmental exposure. Powers reported. A related challenge is how to evaluate any handling have desirable consequences” [5]..” (Examples of the variation between fresh and hard- erations on air-entrained concrete. if used. i. While multiple semi-automated systems are air voids can change in size. Ostensibly this is a simple matter comment may be an over-generalization in some cases.) The ASTM C 231 pro- fast. Natesaiyer and Hover [28. re. standard test methods indicate the total air content only. This tainly moderates the alarm that can accompany the observation is complicated. the human and discharge in the process of placing the concrete in the operator-based C 457 method. when interpreting the air-void system parameters obtained Comparing Air-Void System Parameters in Fresh using the procedures already described: and Hardened Concrete • The test results themselves are variable and subject to un- Total air content is the only air-void system parameter that can certainty. it is likely that the critical is. can be equally uncertain. pend upon “the methods and amount of consolidation effort One consequence of the development of automated tech.106. It may be that more rapid turn-around on test results or a reduced General Comments cost per test will permit a larger number of samples to be ex. may be either higher or lower than that determined by this ating mixtures. crete does not eliminate the pressure caused by freezing. This is because the [15. it is only a matter of time until one the concrete is to remove air from the concrete. accurate. marginal zone or “gray area” in which mation about void size or dispersion in fresh concrete. shape. and may in fact reduce the need for the the difference between fresh and hardened air contents will de- more time-consuming standard C 457 analysis. applied to the concrete from which the hardened concrete spec- niques is a more thorough appreciation of the difficulties faced imen is taken. stage in the delivery. These frost resistance is difficult to judge.58. and reliable information can prevent serious cedure goes on to explain that the magnitude and direction of problems in the field. crete using conventional methods. the reason for vibrating coming into the marketplace.101–105]. handling. plac. method. and the broader range Interpretation of Test Results of results from the same specimen by different operators. the range of results that can be obtained over multiple runs on the same specimen by the same operator. and volume within presently marketed.89–99].53. however. ing and that losses of air from air-entrained concrete during rienced operator. (The Air the basis of air-void system parameters that are neither Void Analyzer (AVA) is a relatively new technique for estimat. and not all of or more of these become an accepted standard test method. environmental expo- ment calls based on color. “clearly acceptable” nor “clearly unacceptable” is due to ing air bubble size in fresh concrete.37] cluding ASTM Test Method for Air Content of Freshly Mixed have shown that while present criteria (to be discussed) Concrete by the Pressure Method (C 231). resulting decrease in overall uncertainty and variability.” In 1968 T. In fact. pressure. tirely under the influence of mixing. and ASTM C 138 (density) to provide infor. by the variability of the C 457 test and that hardened air content is less than fresh air content. Any method than provides ened air contents are shown in Ref 108. resistance. and the concrete sam- preceded the current techniques [65. ASTM Test Method can identify concrete that is almost certainly frost-resistant for Air Content of Freshly Mixed Concrete by the Volumetric and concrete that is almost certainly nonfrost-resistant. in. accuracy of the microscopic ex- operator make a large number of subtle distinctions and judg. may not be standardized. This is because of the • The criteria against which the results are to be compared fundamental inability of any of the standard test methods in. and quirements of that method. amination.86. the air removable by the vibrator became trapped after mixing terchangeable with. number. Depending on the direction taken by the developing tech. such sys.e. complicating any inference concerning frost be directly compared between the fresh and hardened con. and an indication of the value of a skilled.88] and have been subse. or perhaps as a replacement for. uniformity and stability of the air bubbles in the by the skilled C 457 operator. pled for later microscopic determination of air content. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 299 to perform the microscopical analysis. C. and thus might not be a valid means The procedure for the ASTM C 231 pressure method thereof determining compliance with some specifications. or consolidation of the concrete sampled for the deter. before or after the concrete goes through a ming a computer to make the same judgments and distinctions pump and other factors. and can be removed from the system en- cerns the air voids in accordance with ASTM C 457 meet the re. but it is not yet a standard the fact that frost resistance depends also on the mix pro- test method [100]. It is useful to keep the following principles in mind. Method (C 173). it cer- of comparing automated results to standard C 457 results. Image-based methods mination of air content in the fresh state. While the latter given image analysis system. placement and consolidation of the feature in question compared to its background (about processes at which the air content of the unhardened concrete 1000 such judgments per analysis). expe. and on beyond the scope of this chapter. As more image analysis systems are temperature [1.79. with a sistance is included in the chapter in this publication by Nmai. shadow. is determined.80. only those in which a human operator dis. Discussion of this useful technology is portions and material properties of the concrete. “the air is a measure of the power of the human eye coupled with the content of fresh concrete may not be the same as after harden- human brain. there exists a broad. on Hardened Concrete sues of sampling and surface preparation will remain. The current test requires that the fresh and hardened concrete. vibration. differ- quently attempted to various levels of effectiveness ences in the two test results are expected. The challenge of program. Interpreting the Results of Tests nology and the industry response. texture. . time of comparison. While any given analysis system forms [36. A more detailed discussion of criteria for obtaining frost re- amined or each sample examined more thoroughly. resistance can be obtained in many cases at spacing factors in rectly result in higher mortar content in mixes using smaller the area of 0. In two independent studies. Void frequency and ognized that the spacing factor required for frost resistance specific surface are therefore not independent variables and depended on material and environmental factors.250 content. specific surface is about 16 mm2/mm3 (400 in. with no single test concrete. which is mass per unit volume.118.) when a severe but natural freez- coarse aggregates. longer sub-freez- while a particular value of air content is necessary to provide ing periods. or air-void system parameters determined on greater than 260 m (0.008 in. As Saucier et al. the number of voids encountered [28.0 % in the hardened concrete. Klieger’s observations are reflected in the While it is likely that concrete with a spacing factor in such mix design recommendations of ACI 211. eral assessment appears to remain valid. periments. [0. consolidated.3).” . void frequency. ues of specific surface greater than 25 mm2/mm3 (or about 600 (0.020 in. by the incorporation of air [85]. when it comes to scaling resistance “it is not possible to find any well-defined value of LCR. the average conclusions about frost resistance. he less than 170 m to have reasonable assurance that the 230 m demonstrated that when the coarse aggregate volume (which is requirements of this clause will be met.010 in.” Philleo [120] reported that “Data suggest that at wa- crete at values as low as about 16 mm2/mm3 (400 in. or when resistance to deicer salt scaling is required. Thus. however. and coincides with braic relationships among the air content. the specific sur. Spacing factor values on the order of 0.).0098 in.1 [3]. This is not because smaller coarse ag. ments for scaling resistance. In a practical in.72.) or thereabouts” were generally indicative of When void frequency is 1.) are required at faster freezing rates.). frost resistance for a given concrete.0102 in. spacing factor shall not exceed 250 m (0. is a function of water-cement ratio.122]. (0. ant.3). frost-resistant concrete [25]. or fin.121.” In- could have an air-void system composed of acceptably small terpretation of frost resistance on the basis of spacing factor is bubbles as indicted by specific surface. while Fagerlund [29] reports that propriately sized and distributed air-void system [105].113].). it is not equally likely that concrete gested air content increases as the nominal maximum coarse with a larger spacing factor will necessarily be nonfrost resist- aggregate size decreases. obtaining such air content Pinto and Hover [119] also observed more stringent require- is not by itself sufficient because of the need to obtain an ap. the required spacing providing no information about volume or dispersion. It is because the ACI 211 mix design method will cor. variations.50 by mass the required spacing factor Specific surface is merely an indicator of bubble size. Neville [111] reports frost resistance for certain con. Pigeon and Pleau [15] and Pigeon and Gagné [118] have gregate particles are less frost-resistant (the reverse is generally demonstrated that when deicer salt scaling is not an issue.” This gen- 5–7. it is recommended that the target spacing factor be ent on mix proportions [9. risk of frost damage is minimized.500 mm (0. Part II: Density3 (Unit Weight) Spacing Factor Various agencies and organizations.3). with no single value greater than 300 m (0. mm (0.2/in. therefore. frost true) [109].47]. ranges will be frost resistant. and air content greater than concrete samples not handled.37. Ivey and Torrans [121] concluded per unit length of traverse is generally expected to be “one to that for conventional concretes “the transition between one and a half times the numerical value of air content” durable and nondurable concrete seems to be somewhere be- [112. not eliminated [112. The Canadian Standards Association [117] specifies entirely.200 mm by Siggelokow [110]. The term density when used to 3 As noted in the 2001a edition of ASTM C 138.2/in. This conclusion was independently reached ing rate is used. ter-cement ratio below 0. but there may be too not without difficulty. “Unit Weight was the previous terminology used to describe the property determined by this test method. and are shown within air content for frost resistance was consistently 9 % 1 % of the quotations for convenience. if the air content is 5 %. pointed out.5 times air content.008 in. Powers also rec- face is about 25 mm2/mm3 (600 in. placed. such as ACI Committee Introduction 212 on concrete admixtures [114] and ACI Committee 201 on The term “density” as used here refers to the weight per unit durability [115] have recommended a spacing factor of 0. spacing factor is the most commonly used.” It is further noted Air Content that “Considering that the ASTM C 457 test is subject to large Klieger recognized that the necessary air content was depend.008 and 0. or equal to 3.25 mm].” and that in comparison to criteria such as 0.) volume of the mortar. putable. only one of the two can be specified. (0.008 volume of hardened concrete. one would expect tween an L of 0.5 voids per inch. in spite of the fact that of the few of these bubbles or they may be nonuniformly spaced so indices available. In this proposal. that “The concrete will be considered to have a satisfactory air- • The frost resistance of concrete in-service depends on its void system when the average of all tests shows a spacing fac- properties in-place.118 in.200 mm) “quite other values have been found in other ex- in. Thus.3). This rule of thumb arises from the alge.300 TESTS AND PROPERTIES OF CONCRETE but merely reduces it to tolerable levels.).20 to 0.” Fagerlund went on to write that “The Specific Surface values of the critical spacing factor are by no means indis- While frost-resistant concrete is generally characterized by val. Measures of air content in the fresh tor not exceeding 230 m (0. and Powers’s original proposal that “for typical concretes and en- specific surface.0091 in.116].” (Conversions to not protected by air voids in concrete) is ignored.2/in. Multiple studies correlating freeze-thaw durability with computed spacing factor have shown a scattered but general Void Frequency trend of increased durability with decreasing spacing factor For frost-resistant concrete. For concrete with ished in a representative manner may lead to incorrect a water-to-cementing materials ratio of 0:36 or less.113. when void frequency is about equal to the air vironmental conditions spacing factors not exceeding 0. One factor becomes larger as the water-cement ratio decreases.2/in.200 mm) as being indicative of frost-resistant concrete sense.010 in. in which the sug. as to leave large gaps of unprotected paste. the optimum inches are not part of CSA Standard. however. meability tests and density of hardened concrete [131–133]. and a fraction of the system tion. Routine vapor.4 4 Note that density measurements can be misleading when evaluating the effectiveness of consolidation by means of an immersion vibrator due to the tendency to displace aggregates leaving a high mortar content at the point of vibrator insertion. observed density and some value taken for the “maximum” or tained. A significant change in or flow channel volume. sampling.” For a given set of raw materials of fixed densities. and carbon dioxide can permeate the concrete. are termed “impermeable pores. content. a basic characteristic of concrete that influences to be maximized for structural stability or for nuclear shielding. between oven-dry density and voids content. immersion. [130]. and Testing water/cement ratio. and curing. While the densities of fresh and subse. of air voids. which may approximate a minimum un- microcracks. density signals a change somewhere in the process.5 lb/ft3). While the porosity of concrete can be related to unit weight and tive indicator of the uniformity of raw materials. among other Permeability factors. Because this useful information is so readily ob. voids content. is discussed in the chapter in this voids that communicate directly with the exterior surface of the publication by Roberts. water gain voids. This is because the density of hard. The re. In fact. is the lower the density of the mixture the greater will be the voids critical to the performance of the structure or facility.” the voids/cement ratio (volume of voids in the sample divided by the volume of the cement) well before the more currently Uniformity or Consistency of Materials. Helms [123] has reported a similar relationship even dients. sent the pore space measured by drying followed by immersion. nonuniform consolidation. The total volume of permeable voids of a sample is related or setting a minimum density requirement when self weight is to porosity. variability in the constituent materials or Such relationships. and hydraulic characteristics of the channels. The volume of some.” and repre- lationship between the fresh and hardened densities for a par. recognized relationship was established between strength and Construction Operations. in this sit. linkage between the density and durability. since the durability uation variable density could mean nonuniform batching or of concrete can be related to the degree to which water. and rapid chloride permeability. strength applied equally well to a wide variety of concrete mixes ened concrete is a function of the densities of the initial ingre. hardened concrete all of the internal voids are air-filled. certainty for density tests. if the density is seen to vary among samples relations have been demonstrated between certain types of per- of hardened concrete that had been cast at the point of con. permeability depends not only on the total pore ing. weighing of standard compressive strength specimens before testing is recommended to quickly approximate density and to Degree of Consolidation indicate sample uniformity. In some cases. bond strength. degree of consolidation. the degree of consolida. bleed water channels. Feret [124] estab- librium density of structural lightweight concrete determines lished a clear relationship between the strength of mortars and whether specified density requirements have been met.” These spaces do not fill with water upon immersion and cannot be measured by Significance of Density as a Characteristic these techniques. ticular concrete mixture will depend on the mix proportions Other voids. but not all. Analogous to routine measurements in soil mechanics and bi- Alternatively. the density of hardened concrete. many of its properties. tuminous materials. Bureau of Recla- Consistent densities normally indicate consistency in all phases mation confirmed that the relationship between voids and of concreting operations. mixing. and testing. routine density testing for all cores extracted in the field “optimum” density. Numerous studies.) Whiting went on to correlate the de- corporated into the mixture. suggest a proportions could be indicated. Data published by the U. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 301 describe the weight of fresh concrete per unit volume. initial and final water content. “The measured or calculated equi. plored these relationships [124–129]. some of the aggregate pores. degree of hydration. the maximum density was that obtained from hardened samples Voids Content that had been consolidated on a vibrating table. In Whiting’s work [131]. cor- For example. Helms [123] has documented an empirical relationship include setting a maximum density requirement when light. and air voids intentionally or unintentionally in. Dependence on these factors makes density an effec. density tests performed on samples of hard. absorb water upon be related. These are called the “permeable pores. or nonuniform casting of test specimens. tortuosity. water mixing. Because one cannot discriminate among the of Concrete various types of voids present when determining voids content by absorption methods. placing. regardless of the primary purpose for obtaining tion as the density of the hardened concrete divided by the those cores. . crete delivery. mix proportions. air when lightweight aggregate concretes were tested. and subsequent gain or loss of water. sampling. sample or are connected to the surface via capillary channels or quently hardened samples of a particular mix are expected to via cracks formed by drying or shrinkage. the final result is termed “total perme- Density able voids. one can estimate the degree of consolida- ened concrete extracted from the structure can be useful for tion from density measurements of hardened concrete. Olsen [134] defined degree of consolida- is often useful. oxygen. as when a dried specimen is immersed for a period of time. which include a portion of the capillary void sys- and characteristics of the aggregate. of gree of consolidation (or “relative unit weight”) to compressive these voids can be determined by the weight of absorbed water strength. weight aggregate concrete is used to limit structure self-weight. 40 kg/m3 (2. voids in the standard deviation on measured density was approximately the aggregate particles. beginning with those As described by ASTM Test Method for Density of Structural of Feret and continuing more recently to Popovics. Examples content. per se. (It is interest- In dried. volume changes. ing to note that within Whiting’s laboratory testing program including capillary pores in the hardened cement paste. age. tem. the values are not expected to be identical. density of the fresh concrete. Degree indicating segregation. have ex- Lightweight Concrete (C 567).S. Nevertheless. batch. On the other hand. Those determined by ASTM C 138. volume changes. but also on the connectivity. even if only empirical in nature. or other of consolidation is generally expressed as the ratio between the problems. the better is its Shielding Properties shielding ability.138] displays the approximate range of den- lus or the pulse velocity tests. The effects of Both the modulus of elasticity of concrete and the ultrasonic composition on density will be discussed. of the sample is theoretically possible as well. concrete. tenuating the transmission of atomic particles is to put as many atomic nuclei in the path of the radiation as possible. and Fig. the key issue in at- of concrete. and Nuclear means that. Valore [135] and Brewer Just as the density test can lead to estimates of the voids con- [136] separately demonstrated the relationship between den. The density test is a simple means of deter- Density is a key parameter in defining the ease of transmis. nuclear-shielding con- improved consolidation in reducing the hydraulic permeability crete is beyond the scope of this chapter. pulse velocity can be shown to be dependent on density. it is often necessary to determine the density of Typical Values concrete in order to interpret the results of dynamic modu. sities and air contents represented by aggregates. some information about the composition of the balance sity of hardened concrete and its ability to transmit heat. mining whether the required density has been achieved. in general. sion of energy through the concrete. the denser the mass. For that reason. tent. This Thermal. and when such properties are of interest it may be more appropriate to measure Inferring Batch Weights and Composition density than compressive strength. Acoustic.302 TESTS AND PROPERTIES OF CONCRETE Bisaillon and Malhotra [133] also demonstrated the benefits of Although the topic of heavyweight. 5—Density block diagram (after Helms [123]).137. . Figure 5 [123. It is reasonable The issue of sample size is briefly addressed in ASTM C to require density by displacement measurement to be re.” in which the dif- The measurement of density of hardened concrete is based on ference between weighing in air and weighing in water is at- procedures that are simple and direct. cally and horizontally within a given concrete member. yet nonstandard techniques for determin. Weight measurements are re.1 %. picts concretes with compressive strengths ranging from 0. or portions taken from hard. particularly racy of 0. the density of hardened concrete is obtained just Reclamation [142] and show a 6–7 % variation in density for as the density. mm (in.S. specific gravity. SSD Size of Water. Bureau of In principle. 642. The specimens are then immersed in water so that is highly regular and the dimensions accurately obtained. The low. HOVER ON AIR CONTENT AND DENSITY OF HARDENED CONCRETE 303 cementitious materials. ASTM C 567 makes special note of Methods of Determining the Density of establishing in-service and “equilibrium” moisture conditions Hardened Concrete in the sample. the volume of the specimen is frequently cal- cient size to be representative. This latter otherwise conditioned. ported to the nearest 1. The range is bounded at the high-den. The Procedural Factors Influencing the Results data shown in Table 1 were collected by the U. Reference is made to the detailed provisions of given the variations in degree of compaction that exist verti- ASTM C 567 and ASTM Test Method for Density. the aggregate has considerable influence on density of hardened concrete.70 2. etc. (Exceptions to the variations are well documented in work by Simon et al. In ened structures and trimmed to cylinders or prisms of suffi. methods described in ASTM Test Method for Density of Un- hardened and Hardened Concrete in Place by Nuclear Influence of Composition on Density Methods (C 1040).75 19 (3/4) 6. The moisture condition to be used for weight determina- Litvin and Fiorato [139] have independently prepared the tion depends on the purpose of the measurement and the in- “Lightweight Aggregate Spectrum” that also graphically de. steel punchings.1 lb/ft3) and within an accu. the volume of the sample General is determined by the “displacement method. In both ASTM C 567 and C 642. which in turn is molded specimens. Since the density of lightweight aggregate concrete in- service is a critical issue. are obtained for mixes using aggregates of various specific gravities but identi- aggregates. Air Content. gregate particles.0 168 (283) 336 (566) 2200 (137) 2230 (139) 2260 (141) 2290 (143) 2330 (145) 38 (11/2) 4. Other concretes are more absorptive than nor- density end of the range is occupied by cellular concretes with mal-weight aggregates and therefore can take on water at a densities less than 1000 kg/m3 (60 lb/ft3) and with air contents faster rate.7 to when specimens are obtained by extracting cores from a 40 MPa (100 to 6000 psi) with concrete densities from 240 to structure. [53] general simplicity of density measurements are the nuclear and by Kagaya et al. absorption. however. This is more difficult than it may at first appear.) % (lb/yd3) kg/m3 (lb/yd3) 2. service condition of the concrete in question. and the same concerns apply to proper moisture cal proportions. Since aggregate can occupy 60–80 % of the volume of most nometry [140]. when deal- sity end with steel shot. although such methods are more appropriate concrete mixes and the specific gravity of normal-weight for very small samples of hardened concrete. mortar. above 25 %. pointing out the need to have a representative sample. [141]. the unevenness of uncapped peated after immersion and from these data one determines ends and the tendency to out-of-roundness can introduce sig- the volume of the permeable pores and weight/volume rela. Absorption.) More advanced. conditioning. tionships for the dry and saturated specimens. This is made more difficult. related to the density of the water and the displaced volume. more slowly. ing with concrete samples that are many times larger than ag- gate used for radiation shielding concretes and counterweights. care is required to retain the “as-is” moisture con- 2000 kg/m3 (15 to 120 lb/ft3). Such and Voids in Hardened Concrete (C 642). generally less than 20 cm3). and weight and volume measurements approach can be useful only when the shape of the specimen are taken.60 2. and magnetite aggre. or paste coarse and fine aggregate is approximately one-third greater (that is.0 97 (164) 167 (282) 2360 (147) 2389 (149) 2440 (152) 2470 (154) 2520 (157) . Even the permeable pores are filled. TABLE 1—Observed Average Density (adapted from Ref 142) Density.55 2. Hardened samples are dried or culated from the physical dimensions of the sample. using samples such as tributed to the buoyant effect of the water. For example. drilled cores.5 121 (204) 242 (408) 2310 (144) 2357 (147) 2390 (149) 2440 (152) 2470 (154) 152 (6) 3. and therefore come to moisture equilibrium with densities above 5000 kg/m3 (above 310 lb/ft3). informal testing. dition. kg/m3 Cement. Effect of Aggregate Density ing the density of hardened concrete include mercury pyc.65 2. with standard concrete cylinders.6 kg/m3 (0. Aggregate. kg/m3 (lb/ft3) Maximum Average Values Specific Gravity of Aggregate. nificant errors. than that of the hardened cement paste.5 145 (245) 291 (490) 2260 (141) 2290 (143) 2340 (146) 2370 (148) 2405 (150) 76 (3) 3. American Society for Testing and Materials. C. MN.L.. P. pp. Discussion by M. M. [13] Powers. 1991. Eds. 11. tent in Concrete. and Stark. PRO 24. Auberg. 0. 85. RILEM Publications [6] Gutmann.22 1220 76 national. E&FN Spon. regardless of Auberg. Eds.. [11] Guide to the Construction of Concrete Floors. C. 2. 2000. 1953. 18–19 April.A. or distribution of the air voids. 213–221. 1989.R. 2002. “Development of the Micro-Ice-Lens Model. -J.. 1968. 2002. 2002.” and national RILEM Workshop. “Theory of Volume Changes ties of normal aggregates usually range from about 2560 to in Hardened Portland Cement Paste During Freezing. and Aggregates. ACI Committee 302. Setzer. Silver Spring. Design and Construction.. [14] Powers. Feb. T. 1132–1155.A. Proceedings of the International RILEM the pores.2002. The results are shown in Table 2. RILEM Publications S. M. Concrete. A. For these reasons. R. H.. Highway Research Board.L. paste content had a density of 2533 kg/m3 (137 and 155 [17] Powers. [1] Whiting. Duke.. Structural Concrete. DC. 133–145.L. “The Function of Entrained Air in Concrete. 32. Skokie. 42 pp.. R. “Is Delamination Really a Mystery?” Concrete Inter- 0. Final Report. Germany. PRO 24. M. 0.” Pro- 2800 kg/m3 (160 to 175 lb/ft3). The Properties of Fresh Concrete. Vol.” Cement. 1983.. in and Practice. Further data from the Bureau of Reclamation [143] mates. Louis. SD Depart- Ratio of Paste kg/m3 lb/ft3 ment of Transportation. T. T. J. and Helmuth. pp. V.. “Freeze-Thaw and Deicing Salt Resistance of Journal. C.” Frost Resistance of tute. 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Considerations on Judging Adequacy of Consolidation in Fresh [138] Helms, B., “Air Content and Unit Weight,” Significance of Concrete,” Consolidation of Concrete, SP-96, S. Gebler, Ed., Tests and Properties of Concrete and Concrete-Making Mate- American Concrete Institute, Detroit, MI, 1987, pp. 161–178. rials, ASTM STP 169A, ASTM International, West Con- [142] Concrete Manual, 7th ed., U.S. Department of the Interior, Bu- shohocken, PA, 1966, pp. 309–325. reau of Reclamation, Denver, CO, p. 34. [139] Litvin, A. and Fiorato, A. E., “Lightweight Aggregate Spec- [143] “Cement and Concrete Investigations,” Bulletin 4, U.S. De- trum,” Concrete International, Design & Construction, Vol. 3, partment of the Interior, Bureau of Reclamation, Boulder No. 3, 1981, p. 49. Canyon Project; as noted by Helms, S. B., “Air Content and Unit [140] Cook, R. A., “Advanced Mercury Porosimetry for the Investi- Weight,” Significance and Properties of Concrete and Con- gation of Cement Paste, Mortar, and Concrete,” Ph.D. thesis, crete-Making Materials, ASTM STP 169B, ASTM International, Cornell University, Ithaca, NY, Aug. 1992. West Conshohocken, PA, 1978, p. 441. 27 Analyses for Cement and Other Materials in Hardened Concrete William G. Hime1 Preface The presence of organic components is not generally revealed by optical procedures. At times, the properties of the THE CHEMICAL ANALYSIS OF CONCRETE FOR PORT- concrete may suggest such substances: delayed set suggests an land cement content was covered by H. F. Kriege in the first organic sugar derivative, while a hydrophobic nature suggests edition of ASTM STP 169. Dr. L. John Minnick provided an ex- a stearate compound or a polymeric coating. Infrared spec- cellent discussion of methods of analysis for portland cement troscopy is a powerful technique for identifying such materi- content in ASTM 169A. The present writer extended the dis- als, as noted below. cussions in ASTM 169B and ASTM 169C to include analytical Methods of analysis of grouts and mortars generally are methods for other concrete components, and broadened the ti- the same as, or are similar to those used for portland cement tle from the “Cement Content” of the first two editions. This concrete, and thus are discussed herein. chapter in ASTM 169D extends analytical developments to the twenty-first century. Chemical Analysis Procedures for Cement Content Introduction Analyses for portland cement are usually based on two of its features: a calcium oxide content, regardless of manufacturer, In the period of time since ASTM 169C, there have been few of about 63 %, and an acid-soluble silica content of about 21 %. advances in analytical procedures for cement and concrete Thus, if the aggregate is non-calcareous, analysis for calcium components other than in instrumentation. Indeed, “wet chem- usually provides an excellent result. If the aggregate is lime- istry,” the use of gravimetric and volumetric techniques, is no stone, analyses for acid-soluble silica are generally applicable, longer used in many laboratories, nor often taught in college. as is a procedure using maleic acid dissolution of an uncar- Nevertheless, wet chemistry is the standard for many proce- bonated fraction of the concrete sample. However, if a dures used to analyze concrete. siliceous aggregate is alkali reactive, neither the silica nor the Minnick [1], in ASTM STP 169A, and Hime [2,3], in maleic acid procedure is applicable. ASTM STP 169B and 169C, discussed the analysis of concrete The three procedures are well presented in ASTM C 1084. for portland cement content, and the latter also provided Although that designation primarily provides wet chemical methods for other concrete components in those publications procedures, the analyses for calcium or for soluble silica can and in Ref 4. Unfortunately there are no accepted procedures be done by instrumental techniques such as atomic absorption for many components in concrete made with blended hy- spectroscopy. For such analyses, several standard samples, as draulic cements or with supplementary cementitious materi- available from NIST and other organizations, should be used to als. Unless the original components of such concretes are calibrate the instrument. available, estimation of component concentrations is often Analyses for the sulfate content of the concrete are some- best done by an experienced petrographer, as discussed by times made to determine cement content. Although portland Erlin in Chapter 22. Indeed, a petrographer is often a neces- cement contains sulfate and most, but not all, aggregates do not, sity to direct the chemical analyst in the recognition of po- such analyses may suffer greatly because present-day portland tential interfering concrete components. The detection of sup- cements have sulfate contents ranging from about 1.5 % to over plementary cementitious materials (e.g., fly ash and slag) in 5 %. This wide variance, and the huge multiplication factor to concrete is also usually a task requiring a petrographer. The convert to cement content, can produce enormous errors. situation is even more complicated when components such as The percentage of cement found in the analytical sample silica fume are present. Neither the chemist nor the petrog- can be converted to pounds per cubic yard on two bases. One rapher will often detect silica fume and thus a cement con- uses the unit weight determined on a saturated-surface-dry tent analysis by a silica procedure may provide erroneously basis, and correlates well with the batched concrete. The other high results. uses a dry unit weight and correlates with the in-place concrete. 1 Principal Emeritus, Wiss, Janey, Elstner Associates, Inc., Northbrook, IL. 309 310 TESTS AND PROPERTIES OF CONCRETE Petrographic Analysis Procedures for if a petrographer confirms that such a process does not re- Cement Content move aggregate components such as magnetite. Experienced petrographers often estimate cement content based on: point-count or linear traverse measurements of paste ASTM C 1084 Analysis content, “measured” or estimated water-cement ratio, and, if fly ash or slag is present, visual estimates of their volume. The Soluble Silica Procedure accuracy of such estimates depends on the complexity of the ASTM C 1084 requires analyses by a prescribed procedure. In concrete system, its age and exposure to carbon dioxide or contrast to the earlier ASTM C 85, ice-cold hydrochloric acid is other aggressive agents, and curing. Further, conversion of employed to dissolve the cement, thus minimizing dissolution volume percentages to weight percentages are necessary, but of silicates in aggregates, fly ash, or slag. It is useful to examine densities of such components as fly ash may vary greatly. Stan- the acid-insoluble residue so that the presence of fly ash may dards greatly increase reliability, provided that they duplicate be revealed. components and exposure, and therefore are particularly applicable for early-age quality control of concrete production. Calcium Oxide Procedure ASTM C 856, Standard Practice for Petrographic Exami- A wet chemical procedure for calcium is lengthy and difficult. nation of Hardened Concrete, and ASTM C 457, Standard Test Alternatively, any determination method may be employed if Method for Microscopical Determination of Air-Void Content the method can be shown to provide accurate analyses of NIST and Parameters of the Air-Void System in Hardened Concrete, or other Standard Cements. Atomic absorption spectroscopy are useful adjuncts to the determination of cement content, or X-ray emission spectroscopy is employed by many laborato- but provide no specific procedure for such analysis. Chapter ries to determine calcium rapidly. 22 of this book discusses petrographic methods of analysis that augment the procedures in C 856. Maleic Acid Procedure Maleic acid determinations of cement content were first sug- Procedure Details gested by Tabikh [5], with modifications by Clemena [6], Pistilli [7], and Marusin [8]. These vary primarily in the concentration Sample Selection of the maleic acid solution and the length of digestion time. All Proper sample selection is of extreme importance in attaining are designed to minimize solution of both calcareous and meaningful cement content data, but is often not achieved. siliceous aggregates, but to allow nearly complete dissolution Although ASTM C 85 (replaced by ASTM C 1084) required of the portland cement component. For a particular aggregate, three 10-lb concrete pieces, experience indicates that a smaller one of the versions of the test may be better than the others, sample, carefully chosen, can be sufficient and will present but most laboratories do not have the luxury of allowing a test fewer laboratory problems. As indicated in ASTM C 1084, a sin- variance for each sample. gle core may be satisfactory for the cement content determi- It is imperative that the analyst minimize carbonation of nation. It should have a diameter of at least four times the max- the sample because carbonation converts soluble cement imum aggregate size and be taken through the entire vertical hydration products to insoluble calcium carbonate. If highly depth of a concrete slab. For thicker concrete members, the se- fractured concrete is the subject of the analysis, either a petrog- lection must consider that concrete composition may vary with rapher should confirm that carbonation is minimal or another depth or with structural feature. In such cases, several cores an- procedure should be employed. ASTM C 1084 now includes a alyzed separately will disclose the degree of uniformity of ce- maleic acid procedure. If the portland cement incorporates ment distribution. limestone as a processing aid (up to 5 % is allowed by ASTM C A second core or sample, or a larger core, is generally also 150), the maleic acid procedure will provide a lower cement required to perform a determination of unit weight to allow content than will the calcium and silica procedures. petrographic examination, or to allow horizontal sampling for components such as chloride, so that concentrations can be Interferences determined as a function of depth. ASTM C 1084 discusses interferences to those procedures. If a concrete cylinder is being analyzed, the sides will be paste rich. To best represent the concrete, the entire cylinder Cement Type Analysis should be pulverized before sampling. At times an investigation requires a determination of the type of cement used in the concrete: for example, concern may have Sample Preparation been expressed that a concrete structure has not been made If a second core or sample has not been obtained, it is desirable with the specified Type V cement. Dissolution of the cement to cut off (longitudinally) a portion of the sample for unit paste by the maleic acid procedure provides an avenue to a weight determination, petrographic examination, or such fur- successful approach if the aggregate is insoluble and fly ash is ther analyses as might be suggested by the problem or the ce- not a component of the concrete. The maleic acid is then ment content results. The major portion should be crushed to destroyed by evaporating with nitric acid, and aluminum and quarter-inch size (or as directed), quartered, and a representa- iron determined by chemical or instrumental methods. From tive portion pulverized as required. Since very fine particles these data the tricalcium aluminate (C3A) content may be interfere with many of the analysis procedures, the sample determined and compared to ASTM Specification for Portland should be pulverized for short intervals, with sieving after each Cement (C 150) limits. so that most particles just pass the designated sieve. Similar methods may be used to determine if the cement Significant amounts of iron may be introduced by some was “low-alkali,” but interference by the aggregate may occur pulverization and grinding equipment. A magnet may be if it contains alkalies (for example, a feldspar), and it will occur passed through the sample to remove the iron before analysis if fly ash is present. Of course, no study of the concrete will HIME ON ANALYSES FOR MATERIALS IN HARDENED CONCRETE 311 reveal if the cement satisfied other chemical or any physical re- Connolly et al. [10] and, earlier, by Hime et al. [11]. Unfortu- quirements. nately, there have been few publications in this area since ASTM STP 169B. In addition to the methods of Connolly and Calculations and Report Hime, methods have been presented by other investigators for Perhaps the greatest error in the cement content analysis is the specific compounds or admixture types: assumption that the result represents the cement content as Lignosulfonates—Kroome [12], Reul [13], Rixom [14] delivered. Two factors can cause serious divergence between Sugars—Shima and Mishi [15], Rixom [14] determined and delivered cement factor. First, because the Polycarboxylic Acids—Frederick and Ellis [16], Rixom [14] calculation is in terms of pounds per cubic yard, poor consoli- Triethanolamine—Connolly and Hime [17], Reul [13], dation of the concrete leads to a lowered cement content. Rixom [14] And second, even under good placement practice, cement con- Vinsol Resin—Kroome [12], Reul [13] centration may vary with height of placement (for example, in Retarders—Halstead and Chaiken [18], Reul [13], Rixom columns and walls), or with location in a heavily reinforced [14] structure. To partially account for such occurrences, ASTM C Waterproofers—Reul [13], Rixom [14] 1084 provides two methods for density determination: oven- Procedures for supplementary cementitious materials such dry and saturated surface-dry. The latter relates better to as- as fly ash, silica fume, and slag are almost completely proprie- delivered concrete. tary to a producer or an analytical laboratory. If the particular fly ash or slag used in a concrete is available for analysis, some Analysis of Masonry Mortars, Grouts, Stucco, element not present in significant amounts in the cement or ag- and Other Portland-Cement-Based Materials gregate may be found, thus allowing elemental analyses for it in the concrete. Among the elements found useful in this connec- The cement content methods detailed earlier have been em- tion for some fly ashes and slags are barium, manganese, and ployed by various laboratories to analyze mortars and other titanium. Petrographic examination usually will allow approxi- portland-cement-based materials, usually on the mistaken belief mation of the fly ash or slag concentration, generally as related that they are made without coarse aggregate. Such materials of- to the cement content. No generally accepted procedure for sil- ten contain, in addition to portland cement and sand, hydrated ica fume content has been developed. Indeed, successful meth- lime, finely ground limestone, or other substances. Fine lime- ods for detection of silica fume in concrete have not been stone, for example, is the major component of most masonry reported except when lumps of silica fume are present. In that cement. Therefore, analyses based on calcium will overestimate case, optical petrography has proven successful. portland cement content, analyses based only on soluble silica For the determination of chloride in concrete, published underestimate total cementitious material, and analyses based procedures employ either water extraction or acid extraction. on the maleic acid procedure usually cannot differentiate The former relates best to present-time corrosion potential, but between the cementitious components. the latter is more conservative. In either case, currently used Portland cement products should generally be analyzed procedures generally pulverize the concrete so that any chlo- only in conjunction with microscopic studies by an experienced ride originally embedded in the aggregate is determined, thus petrographer who meets the requirements of ASTM C 856. With often over-estimating potential for corrosion. ASTM proce- the guidance of the petrographer, successful analyses are often dures for acid-soluble chloride in cement in C 114 and ASTM possible by determining portland cement through the soluble Test Methods for Acid-Soluble Chloride in Mortar and Con- silica data, and hydrated lime or calcium carbonate from the crete (C 1152) are widely used, but most governmental agen- calcium data after subtracting off the portland cement contri- cies use the AASHTO method (T 260), Sampling and Testing for bution. Such analyses are in error to the extent that the aggre- Chloride Ion in Concrete and Concrete Raw Materials. The gate contains soluble calcium or silica. A procedure was out- method provides for water-soluble and acid-soluble chloride lined by Erlin and Hime [9], and is the basis for ASTM C 1324. analyses of portland cement, concrete, mortar, and aggregate. The methods described herein are usually applicable to For nitrite, a component of a commercial corrosion such materials as those used for patching, dry packing, floor inhibitor, a colorimetric procedure such as that of Jeknavorian leveling, and the like. et al. [26] is recommended. The air void content of hardened concrete is determined Determination of Other Concrete Constituents by the procedures of ASTM C 457. Details are discussed by Hover in Chapter 26 of this book. The analysis of concrete for cement content alone usually provides insufficient information to adequately determine cause for distress. In many cases, determinations of the pres- Aggregates ence of cement additives, concrete admixtures, and of water The aggregate content of concrete can be determined by the content will provide more useful information. These determi- linear traverse or point count procedures of ASTM C 457, nations are outlined in the following paragraphs. which follow those of Polivka et al. [19] and Axon [20]. Aggre- gate content can usually be determined as the residue from the Additives and Admixtures maleic acid cement content procedure. With some siliceous ag- Organic additives to cement and admixtures to concrete are gregates, the aggregate content is determined by an insoluble often present in concentrations of a few thousandths of a residue procedure such as in ASTM C 114. percent. In general, appropriate extraction and spectroscopic analysis procedures allow determination of most of the Water commercially available products. The determination of the water content of hardened concrete is Spectroscopic procedures applicable to the active organic readily made by ignition to 1000°C and correction for carbon components of most commercial products were described by dioxide by any usual procedure. In contrast, there is no gener- 312 TESTS AND PROPERTIES OF CONCRETE ally applicable method for the much more useful determination X-ray fluorescence (XRF) allows analysis for all except the of the amount of water that was present in the fresh concrete. lightest elements, depending upon the instrument. Computeri- For non-air-entrained concrete, the procedures of Blackman zation that corrects for interferences allows quantification to [21] and Brown [22] can be employed, but are difficult to per- levels often matching those attained by most “wet chemical” form and may not be accurate. An estimation procedure by procedures. Axon [20] employs microscopic techniques. Many petrographers estimate water-cement ratio by petrographic techniques General Reference Works and experience. However, water “bleed,” settlement, and other Methods of analysis for cement content, as presented in the factors may lead to significant error. Substitution of cement con- two previous editions of this book, provide considerable infor- tent data determined by chemical methods in that water-cement mation about the effect of aggregate on the calcium and silica ratio value allows at least an estimate of water content. procedures, and other useful historical background. General methods for analysis of cement and concrete were presented Instrumental Methods of Analysis by Hime in Refs 2, 3, 4, and 23. Methods of analysis of concrete The rapid development of instrumental methods of analysis and other cement products are presented in books by the during the last half century, and the remarkable improvement Society of Chemical Industry [24], and by Figg and Bowden of the capabilities of such instruments during the last decade [25]. The latter contains a bibliography of 193 references. or two, now allow analyses not possible before and greatly im- Chemical and instrumental methods of analysis of concrete by proved rapidity, sensitivity, and accuracy. As used in studies of many techniques are provided in the Handbook of Analytical concrete, such methods of analysis are detailed in Ref 4. A few Techniques in Concrete Science and Technology [4]. comments on their particular advantage in certain analyses are given below. Infrared spectroscopy (IR) allows analyses for organic References components, generally as extracted from the concrete by [1] Minnick, L. J., “Cement Content,” in Significance of Tests and selective solvents, and for some inorganic substances. Fourier Properties of Concrete and Concrete-Making Materials, ASTM transform infrared spectroscopy (FTIR) permits very rapid STP 169A, ASTM International, West Conshohocken, PA, 1966, pp. 326–339. analyses or use of a very small sample. An attenuated total [2] Hime, W. G., “Cement Content,” Chapter 28 in Significance of reflectance (ATR) attachment allows surface analyses, often Tests and Properties of Concrete and Concrete Making Materi- without special sample preparation. als, ASTM STP 169B, ASTM International, West Conshohocken, Scanning electron microscopy (SEM), when coupled with PA, 1978, pp. 462–470. an X-ray fluorescence analyzer (“EDS” or “EDX”), is a power- [3] Hime, W. G., “Analyses for Cement and Other Materials in Hard- ful technique for determining the structure and components of ened Concrete,” Chapter 29 in Significance of Tests and Proper- such materials as concrete, or indeed of most nonorganic ties of Concrete and Concrete-making Materials, ASTM STP 169C, substances. Elements of an atomic number as low as three can ASTM International, West Conshohocken, PA, 1994, pp. 315–319. be detected. Furthermore, the volume analyzed by usual EDS [4] Hime, W. G., “Chemical Methods of Analysis of Concrete,” techniques can be as small as a trillionth of a cubic inch. The Chapter 3 in Handbook of Analytical Techniques in Concrete technique is thus enormously powerful. However, because the Science and Technology, V. S. Ramachandran and James J. volume is so low, misinterpretation of the significance of Beaudoin, Eds., William Andrew Publishing, Norwich, 2001. findings has been an occasional result. [5] Tabikh, A. A., Balchunas, M. J., and Schaefer, D. M., “A Method Thermal methods of analysis include differential scanning for the Determination of Cement Content in Concrete,” Highway Research Record 370, Highway Research Board, calorimetry (DSC), differential thermal analysis (DTA), and Washington, DC, 1971, pp. 1–7. thermogravimetric analysis (TGA), and various modifications [6] Clemena, G. G., “Determination of the Cement Content of of these. These procedures usually require little sample prepa- Hardened Concrete by Selective Solution,” Final Report, VHRC ration except grinding, and allow single-scan detection and 72-R7, Virginia Highway Research Council, Charlottesville, VA, quantification of many inorganic components of concrete, Sept. 1972. including calcium silicate hydrates, gypsum, plaster (calcium [7] Pistili, M. F., “Cement Content of Hardened Concrete,” sulfate hemihydrate), calcium and magnesium hydroxide, et- presented at Cement Chemist’s Seminar, Portland Cement As- tringite, and various carbonates. sociation, Skokie, IL, 1976. A disadvantage of some of these procedures is that the [8] Marusin, S. L., “Use of the Maleic Acid Method for the Deter- temperature of occurrence of a thermal event depends upon mination of the Cement Content of Concrete,” Cement, Con- the particular instrument and sample holder. Ettringite ther- crete, and Aggregates, Winter 1981, pp. 89–92. mally decomposes between about 52°C and 100°C, depending [9] Erlin, B. and Hime, W. G., “Methods for Analyzing Mortar,” upon relative humidity and pressure, but when using DTA, for Proceedings, Third North American Masonry Conference, The example, the temperature recorded may be 150°C or higher. Masonry Society, University of Texas at Arlington, Arlington, TX, Paper 63, 1985, pp. 1–6. X-ray diffraction (XRD) allows rapid detection of crys- [10] Connolly, J. D., Hime, W. G., and Erlin, B., “Analysis for talline components of portland cement or concrete. Usual Admixtures in Hardened Concrete,” Admixtures, Concrete In- instrumentation and techniques do not allow detection of ternational 1980, The Construction Press, Lancaster, UK, 1980, components present in amounts less than a few percent. Fur- pp. 114–129. thermore, in a very finely ground sample even a major [11] Hime, W. G., Mivelaz, W. F., and Connolly, J. D., Analytical component may not be detectable. For example, modern day Techniques for Hydraulic Cement and Concrete, ASTM STP 395, portland cements are often very finely ground, and the soft ASTM International, West Conshohocken, PA, 1966, pp. 132–134. particles of gypsum reduced to a few crystal layers. Gypsum in [12] Kroome, B., “A Method of Detecting and Determining Lignin several percent amounts may be clearly revealed by DTA, but Compounds in Mortars and Concrete,” Magazine of Concrete not detected by XRD. Research, Vol. 23, No. 76, June-Sept. 1971, pp. 132–134. HIME ON ANALYSES FOR MATERIALS IN HARDENED CONCRETE 313 [13] Reul, H., “Detection of Admixtures in Hardened Concrete,” [20] Axon, E. O., “A Method of Estimating the Original Mix Compo- Zement-Kalk-Gips, Vol. 33, No. 3, 1980 (translation of article). sition of Hardened Concrete Using Physical Tests,” Proceedings, [14] Rixom, R. R., Chemical Admixtures for Concrete, E. & F. N. Spon, ASTM International, West Conshohocken, PA, Vol. 62, 1962, pp. London, 1978. 1068–1080. [15] Shima, I. and Nishi, T., “Determination of Saccharose in [21] Blackman, J. S., “Method for Estimating Water Content of Hydrated Cement,” Semento Gijutsu Nempo, Vol. 17, 1963, Concrete at the Time of Hardening,” Proceedings, American pp. 106–109; Chemical Abstracts, Vol. 61, 1964, 5344b. Concrete Institute, Vol. 50, 1954, pp. 533–541. [16] Frederick, W. L. and Ellis, J. T., “Determination of a [22] Brown, A. W., “A Tentative Method for the Determination of the Polyhydroxy Carboxylic Acid Retarder in Hardened Concrete,” Original Water-Cement Ratio of Hardened Concrete,” Journal of Materials Research and Standards, Vol. 8, March 1968, Applied Chemistry, Vol. 7, Oct. 1957, pp. 565–572. pp. 14–18. [23] Hime, W. G., “Cements, Mortars and Concrete,” Encyclopedia [17] Connolly, J. D. and Hime, W. G., “Analysis of Concrete for of Industrial Chemical Analysis, Vol. 9, Wiley, New York, 1970, Triethanolamine,” Cement and Concrete Research, Vol. 6, 1976, pp. 94–155. pp. 741–746. [24] “Analysis of Calcareous Materials, SCI Monograph No. 18, Society [18] Halstead, W. J. and Chaiken, B., “Water-Reducing Retarders for of Chemical Industry, London, 1964. Concrete-Chemical and Spectral Analysis,” Public Roads, Vol. [25] Figg, J. W. and Bowden, S. R., The Analysis of Concretes, Her 31, No. 6, 1961, pp. 126–135. Majesty’s Stationery Office, London, 1971. [19] Polivka, M., Kelly, J. W., and Best, C. H., “A Physical Method for [26] Jeknavorian, A. A., Chin, D., and Saidha, L., “Determination of Determining the Composition of Hardened Concrete,” Papers a Nitrite-Based Corrosion Inhibitor in Plastic and Hardened on Cement and Concrete, ASTM STP 205, ASTM International, Concrete,” Cement, Concrete, and Aggregates, Vol. 17, No. 1, West Conshohocken, PA, 1956, pp. 135–152 June 1995, pp. 48–54. 28 Nondestructive Tests V. Mohan Malhotra1 Preface Resonant and Pulse Velocity Methods THE SUBJECT OF NONDESTRUCTIVE TESTING OF Resonant Frequency Methods concrete was covered in ASTM STP 169A, ASTM STP 169B, and Natural frequency of vibration is a dynamic property of an ASTM STP 169C. The chapter in ASTM STP 169 was entitled “Dy- elastic system and is primarily related to the dynamic modulus namic Tests” and was authored by E. A. Whitehurst, whereas the of elasticity and density in the case of a vibrating beam. There- chapter in ASTM STP 169B was entitled “Nondestructive Tests” fore, the natural frequency of vibration of a beam can be used and was authored by E. A. Whitehurst and V. M. Malhotra. The to determine its dynamic modulus of elasticity. Although the chapter in ASTM STP 169C was authored by V. M. Malhotra. relationship between the two is valid for homogenous solid me- This chapter updates the information presented in the previous dia that are isotropic and perfectly elastic, they may be applied publications. to concrete when the size of a specimen is large in relation to the size of its constituent materials. Introduction For flexural vibrations of a long, thin, unrestrained rod, the following equation or its equivalent may be found in any In the inspection and testing of concrete, the use of nonde- complete textbook on sound [1]: structive testing (NDT) has been making slow but steady E m2k progress since the 1950s. The slow development of these N (1) 2L2 testing methods for concrete is due to the fact that, unlike steel, concrete is a highly nonhomogenous composite material, and and solving for E most concrete is produced in ready-mixed plants and delivered 42L 4N 2 to the construction site. The in-place concrete is, by its very na- E (2) ture and construction methods, highly variable, and does not m4k 2 lend itself to testing by traditional NDT methods as easily as where steel products. E dynamic modulus of elasticity, Notwithstanding the preceding, there has been considerable density of the material, progress in the development of NDT methods for testing con- L length of the specimen, crete in recent years. A number of these methods have been stan- N fundamental flexural frequency, dardized by ASTM International, the International Standards k radius of gyration of the section about an axis perpen- Organization (ISO), and the British Standards Institute (BSI). 2 dicular to the plane of bending (k = t /1 for rectan- For the purposes of this chapter, tests that are identified gular cross section where t thickness), and generally as nondestructive may be subdivided into two main m a constant (4.73 for the fundamental mode of types. The first type includes those identified as sonic and vibration). pulse velocity tests, which involve the determination of the The dynamic modulus of elasticity can also be computed resonant frequency and the measurement of the velocity of a from the fundamental longitudinal frequency of vibration of compressional pulse traveling through the concrete. Also in- an unrestrained specimen, according to the following equa- cluded in this category are stress wave tests for locating the tion [2]: flaws or discontinuities that may be present, or measuring the thickness of concrete. The second type includes those tests E 4L 2N 2 (3) that are used to estimate strength properties and include the surface hardness, penetration, pullout, maturity, pulloff, and Equations 1 and 3 were obtained by solving the respec- combined methods. Some of these methods are not truly non- tive differential equations for the motion of a bar vibrating: destructive because they cause some surface damage that is (1) in flexure in the free-free mode, and (2) in the longitudi- generally insignificant. nal mode. 1 Scientist Emeritus, Canada Center for Mineral and Energy Technology (CANMET), Ottawa, Canada K1A 0G1. 314 MALHOTRA ON NONDESTRUCTIVE TESTS 315 Thus, the resonant frequency of vibration of a concrete specimen directly relates to its dynamic modulus of elasticity. If the concrete undergoes degradation, the modulus of elasticity will be altered and so will the resonant frequency of the specimen. Therefore, monitoring the change in resonant frequency allows one to infer changes in the integrity of concrete. The method of determining the dynamic elastic moduli of solid bodies from their resonant frequencies has been in use for the past 45 years. However, until recently, resonant frequency methods had been used almost exclusively in laboratory studies. In these studies, natural frequencies of vibration are determined on concrete prisms and cylinders to calculate the dynamic moduli of elasticity and rigidity, the Poisson’s ratio, and to monitor the degradation of concrete during durability tests. The resonant frequency method was first developed by Powers [3] in the United States in 1938. He determined the resonant frequency by matching the musical tone created by con- Fig. 1—Schematic of apparatus for forced resonance test. crete specimens, usually 51 by 51 by 241-mm prisms, when tapped by a hammer with the tone created by one of a set of sponding to different modes of vibration. Specimens having orchestra bells calibrated according to frequency. The error either very small or very large ratios of length to maximum likely to occur in matching the frequency of the concrete speci- transverse direction are frequently difficult to excite in the fun- mens to the calibrated bells was of the order of 3 %. The short- damental mode of transverse vibration. It has been suggested comings of this approach, such as the subjective nature of the that the best results are obtained when this ratio is between test, are obvious. But this method laid the groundwork for the three and five (ASTM C 215). subsequent development of more sophisticated methods. The supports for the specimen under test should be of a In 1939, Hornibrook [4] refined the method by using elec- material having a fundamental frequency outside the requency tronic equipment to measure resonant frequency. Other early range being investigated, and should permit the specimen to vi- investigations on the development of this method included brate without significant restriction. Ideally, the specimens those by Thomson [5] in 1940, by Obert and Duvall [2] in 1941, should be held at the nodal points, but a sheet of soft sponge and by Stanton [6] in 1944. In all the tests that followed the rubber is quite satisfactory and is preferred if the specimens work of Hornibrook, the specimens were excited by a vibrating are being used for freezing and thawing studies. force. Resonance was indicated by the attainment of vibrations The fundamental transverse vibration of a specimen has having maximum amplitude as the driving frequency was two nodal points, at distances from each end of 0.224 times the changed. The resonant frequency was read accurately from the length. The vibration amplitude is maximum at the ends, about graduated scale of the variable driving audio oscillator. The three fifths of the maximum at the center, and zero at the nodal equipment is usually known as a sonometer and the technique points. Therefore, movement of the pickup along the length of is known as forced resonance. the specimen and observation of the meter reading will show The forced resonance testing apparatus, as described in whether the specimen is vibrating at its fundamental fre- ASTM Test Method for Fundamental Transverse, Longitudinal, quency. For fundamental longitudinal and torsional vibrations, and Torsional Frequencies of Concrete Specimens (C 215), there is a point of zero vibration (node) at the midpoint of the consists primarily of two sections—one that generates mechan- specimen and the maximum amplitude is at the ends. ical vibrations and another that senses these vibrations [7]. The Sometimes in resonance testing of prismatic concrete principal part of the vibration generation section is an elec- specimens, two resonant frequencies may appear that are close tronic audio-frequency oscillator that generates audio- together. Kesler and Higuchi [8] believed this to be caused by frequency voltages. The oscillator output is amplified and fed a nonsymmetrical shape of the specimen that causes interfer- to the driver unit for conversion into mechanical vibrations ence due to vibration of the specimen in some direction other (see Fig. 1). than that intended. Proper choice of specimen size and shape The mechanical vibrations of the specimen are sensed by a should practically eliminate this problem; for example, in a piezoelectric transducer. The transducer is contained in a sep- specimen of rectangular cross section the problem can be elim- arate unit and converts mechanical vibrations to electrical volt- inated by vibrating the specimen in the direction parallel to the age of the same frequencies. These voltages are amplified for short side. the operation of a panel-mounted meter that indicates the am- In performing resonant frequency tests, it is helpful to plitude of the transducer output. As the frequency of the driver have an estimate of the expected fundamental frequency. oscillator is varied, maximum deflection of the meter needle in- Approximate ranges of fundamental longitudinal and flexural dicates when resonance is attained. Visible indications that driv- resonant frequencies of standard concrete specimens have ing frequency equals the fundamental frequency can be been given by Jones [9]. obtained easily through the use of an auxiliary cathode-ray oscilloscope. This is because a resonance condition can be Calculation of Dynamic Moduli of Elasticity established at driving frequencies that are fractions of the and Rigidity and Poisson’s Ratio fundamental frequency. The dynamic moduli of elasticity and rigidity (or shear modu- Some skill and experience are needed to determine the lus of elasticity) and the dynamic Poisson’s ratio of the concrete fundamental resonant frequency using a meter-type indicator can be calculated by equations given in ASTM C 215. These are because several resonant frequencies may be obtained corre- modifications of theoretical equations applicable to specimens 316 TESTS AND PROPERTIES OF CONCRETE that are very long in relation to their cross section and were de- Damping Properties of Concrete veloped and verified by Pickett [10], and Spinner and Teftt [11]. Damping is the property of a material that causes free vibra- The corrections to the theoretical equations involve Poisson’s tions in a specimen to decrease in amplitude as a function of ratio and are considerably greater for transverse resonant fre- time. Several investigators, particularly Thomson [5], Obert quency than for longitudinal resonant frequency. For example, and Duvall [2], Kesler and Higuchi [16], Shrivastava and Sen a standard 102 by 102 by 510-mm prism requires a correction [17], and Swamy and Rigby [14], have shown that certain prop- factor of about 27 % at fundamental transverse resonance, as erties of concrete can be related to its damping ability. compared with less than 0.5 % at fundamental longitudinal res- There are several methods of determining the damping onance [12]. The longitudinal and flexural modes of vibration characteristics of a material, but two common methods used give nearly the same value for the dynamic modulus of elastic- for concrete are [18]: ity. The dynamic modulus of elasticity may range from 14.0 GPa 1. The determination of logarithmic decrement, , which is for low-quality concretes at early ages to 48.0 GPa for good-qual- the natural logarithm of the ratio of any two successive ity concrete at later ages [13]. The dynamic modulus of rigidity amplitudes in the free vibration of the specimen. is about 40 % of the modulus of elasticity [14]. It should be men- 2. Calculation of the damping constant, Q, from the ampli- tioned that more input energy is needed for longitudinal reso- tude versus resonance curve of the test specimen. nance and, therefore, the transverse resonance mode is used The measurement of the damping properties of concrete more often in laboratory investigations. specimens has not been standardized by ASTM, but research continues toward gaining a better understanding of the signif- Other Methods of Resonant icance of these measurements. Frequency Testing A new method for determining fundamental frequencies has Factors Affecting Resonant Frequency and been proposed by Gaidis and Rosenberg [15] as an alternative Dynamic Modulus of Elasticity to the forced resonance method. In this method, the concrete Several factors influence the resonant frequency measure- specimen is struck with a small hammer. The impact causes ments, the dynamic modulus of elasticity, or both. These the specimen to vibrate at its natural frequencies. Hence the include the influence of mixture proportions and properties technique is known as impact resonance and the specimen re- of aggregates, specimen size effect, and the influence of sponse is measured by a lightweight accelerometer mounted curing conditions. These have been discussed in detail else- on the specimen (see Fig. 2). where [18]. The amplitude and frequency of the resonant vibrations are obtained using a spectrum analyzer that determines the Standardization of Resonant Frequency component frequencies via the fast Fourier transform. The am- Methods plitude of the specimen response versus frequency is displayed ASTM C 215 was published in 1947 and since then has been re- on the screen of a frequency analyzer, and the frequencies of vised more than seven times. The last revision to this standard major peaks can be read directly. was in 2002. In operation, the pick-up accelerometer is coupled to the The significance and use statement of the resonant end of the specimen with microcrystalline wax or a similar ma- frequency method as given in ASTM C 215 is as follows: terial, and the specimen is struck lightly with a hammer. The output of the accelerometer is recorded digitally by the wave- 5.1 This test method is intended primarily for detecting form analyzer and the recorded signal is processed to obtain significant changes in the dynamic modulus of elas- the frequency response. On the resulting amplitude versus fre- ticity of laboratory or field test specimens that are un- quency curve, a dot marker (cursor) may be moved to coincide dergoing exposure to weathering or other types of po- with the peak, and the frequency value of the peak is displayed tentially deteriorating influences. on the screen. The advantages of this method over the forced- 5.2 The value of the dynamic modulus of elasticity ob- resonance procedure are the greater speed of testing, the tained by this test method will, in general, be greater capability of testing specimens having a wide range of dimen- than the static modulus of elasticity obtained by using sions, and the ability to measure readily the longitudinal fre- Test Method C 469. The difference depends, in part, quency. However, the initial high cost of equipment appears to on the strength level of the concrete. be a disadvantage. This impact resonance procedure was 5.3 The conditions of manufacture, the moisture content, adopted by ASTM in 1991 as an alternative to the existing and other characteristics of the test specimens (see procedure. The various modes of vibration are obtained by the section on Test Specimens) materially influence the proper location of the impact point and an accelerometer. results obtained. 5.4 Different computed values for the dynamic modulus of elasticity may result from widely different resonant frequencies of specimens of different sizes and shapes of the same concrete. Therefore, it is not advisable to compare results from specimens of different sizes or shapes. Limitations and Usefulness of Resonant Frequency Methods Although the basic equipment and testing procedures associated with the resonant frequency techniques have been Fig. 2—Schematic of apparatus for impact resonance test. standardized in various countries, and commercial testing MALHOTRA ON NONDESTRUCTIVE TESTS 317 equipment is easily available, the usefulness of the tests is seri- two amplifiers, two thyratron tube circuits, and a ballistic ously limited because of the following two points: galvanometer circuit. The concrete was struck with a hammer 1. Generally, these tests are carried out on small-sized speci- approximately in line with the two pickups. The propagating mens in a laboratory rather than on structural members in pulse actuated the first pickup, the voltage from which ener- the field because resonant frequency is affected consider- gized the first thyratron and started a flow of current through ably by boundary conditions and the properties of the galvanometer. When the energy impulse reached the sec- concrete. The size of specimens in these tests are usually ond pickup, the voltage from its amplifier ionized the second 152 by 305-mm cylinders or 76 by 76 by 305-mm prisms. thyratron and cut off the flow of current. The deflection of the 2. The equations for the calculation of dynamic elastic mod- galvanometer was directly proportional to the time required for ulus involve “shape factor” corrections. This necessarily the wave to travel the distance between the two pickups. limits the shape of the specimens to cylinders or prisms. In a discussion of this paper, the substitution of an elec- Any deviation from the standard shapes can render the tronic interval timer for the ballistic galvanometer was sug- application of shape factor corrections rather complex. gested. This device consists of a capacitor that begins to charge Notwithstanding the preceding limitations, the resonance when the first thyratron is ionized and stops charging when the tests provide an excellent means for studying the deterioration second is ionized and a vacuum-tube voltmeter measures the of concrete specimens subjected to repeated cycles of freezing charge. The meter may be calibrated directly in units of time, and thawing and to deterioration due to aggressive media. The thus eliminating the necessity for computations involving the use of resonance tests in the determination of damage by fire magnitude of the current flowing through the galvanometer. and the deterioration due to alkali-aggregate reaction have also This device was found to be more reliable than the ballistic gal- been reported by Chefdeville [19] and Swamy and Al-Asali [20]. vanometer for field use. The resonant frequency test results are often used to cal- Subsequent investigations in North America and Europe culate the dynamic modulus of elasticity of concrete but the have resulted in the development of a number of other devices values obtained are somewhat higher than those obtained with quite similar in most respects. These include the Micro-timer standard static tests carried out at lower rates of loading and developed by the U.S. Bureau of Reclamation, and the Con- to higher strain levels. The use of dynamic modulus of elastic- denser Chronograph developed by the Danish National Insti- ity of concrete in design calculations is not recommended. tute of Building Research. Various investigators have published correlations between In 1946, the Hydro-Electric Power Commission of Ontario, the strength of concrete and its dynamic modulus of elasticity. Canada, in an effort to develop a technique for examining Such correlations should not be used to predict strength prop- cracks in monolithic concrete structures, began a series of stud- erties of concrete unless similar relationships have been devel- ies that resulted in the construction of an instrument known as oped in the laboratory for the concrete under investigation [18]. the Soniscope. The device developed by Leslie and Cheesman [24] consists basically of a stress transmitter using piezoelectric Pulse Velocity Method crystals, a similar pulse receiver, and electronic circuits that The application of pulse transmission techniques to the testing actuate the pulse transmitter, provide visual presentation of of concrete is believed to have had its origin with Obert [21]. transmitted and received signals on a cathode-ray tube, and ac- Tests were made on concrete replacement pillars in mines and curately measure the time interval between the two. involved the use of two geophones, two high-gain amplifiers, The physical and electrical features of the Soniscope and a camera with a moving film strip. Two holes, approxi- passed through several stages of improvement, and a number mately 6.09 m (20 ft) apart vertically, were drilled into the pil- of these instruments have been built by various laboratories in lars. The geophones were placed in the backs of the holes and the United States and Canada. The instrument was used exten- the holes filled with cotton waste. A hammer blow was struck sively in Canada [24,25] and the United States [26]. at the base of the pillar, and at the same time the camera lens During approximately the same time that the Soniscope was opened and the moving film strip exposed. After the film was being developed in Canada and the United States, work of a was developed, the transit time of the impulse in traveling similar nature was being conducted in England. These investi- from one geophone to the other was determined by measuring gations resulted in the development of an instrument known as the distance between the two signals on the film, the speed of the Ultrasonic Concrete Tester. This instrument and its applica- motion of the film having been controlled carefully. The ve- tions have been described at length by Jones [27,28]. The Ultra- locity of the stress pulse could then be calculated. sonic Concrete Tester differed from the Soniscope primarily in Long and Kurtz [22] reported performing somewhat simi- the higher frequency of the transmitted pulse and the pulse rep- lar experiments with a seismograph in which the longitudinal etition rate, which was about three times greater than that of the velocity of the stress pulse created by a single impact was meas- Soniscope. These changes improved the accuracy of measure- ured between arbitrarily placed geophones. They stated that ment on very small specimens but limited the usefulness of the only very limited experiments of this nature had been instrument for field testing, since the high frequencies suffer conducted but the method appeared to hold great promise pro- much greater attenuation in passing through concrete than do viding the apparatus could be adapted to measure much shorter the lower ones. The maximum range of the Ultrasonic Concrete time intervals than could be measured with the seismograph. Tester was about 2 m, whereas that of the Soniscope in testing Long et al. [23] undertook further investigations along reasonably good concrete was 15 m or more. these lines and in 1945 reported on the instrument and tech- Portable, battery-powered ultrasonic testing units have nique that resulted from their work. The apparatus consisted of become available worldwide. One of the units available in the two vibration pickups (in the form of phonograph cartridges), United States is called the V-Meter.2 2 This is the same unit that is manufactured in England and is known as PUNDIT. 318 TESTS AND PROPERTIES OF CONCRETE The pulse travel time is displayed in three numerical dig- cracks in concrete, although it has been suggested that if the its that can be varied for three different ranges: (1) 0.1 to 99.9 cracks are fully water-filled their locations may be more diffi- s with an accuracy of 0.1 s, (2) 1 to 999 s with an accuracy cult to ascertain. In all of the other fields of investigation, of 1 s, and (3) 10 to 9990 s with an accuracy of 10 s. independent investigators have reported widely different de- Whereas the use of the resonant frequency tests has been grees of success through the use of these techniques [26]. restricted primarily to the evaluation of specimens undergoing A comprehensive report of the early experiences of users natural or artificial weathering, pulse velocity techniques have of pulse velocity techniques in the United States and Canada been applied to concrete for many purposes and, in most areas may be found in Ref 30. Sturrup et al. [31] have published data of investigation, only limited agreement has been reached con- dealing with the experiences of Ontario Hydro, Toronto, in the cerning the significance of test results. The quantity measured use of pulse velocity for strength evaluation. by all of these instruments is the travel time of stress pulses pass- Experiences in the use of pulse velocity measurements for ing through the concrete under test. If the path length between evaluating concrete quality have been reported in many other transmitter and receiver is known, or can be determined, the ve- countries, notably Great Britain and Russia. In some instances, locity of the pulse can be computed. It is in the interpretation investigators in these countries have appeared to have greater of the meaning of this velocity and in its use for determining confidence in the use of such techniques for acceptance test- various properties of concrete that agreement is incomplete. ing than has been the case in the United States. The technique is as applicable to in-place concrete as to labora- It is generally agreed that very high velocities of 4570 m/s tory-type specimens, and results appear to be unaffected by the are indicative of very good concrete and that very low velocities size and shape of the concrete tested, within the limits of trans- of 3050 m/s are indicative of poor concrete. It is further mission of the instrument employed, provided care is taken agreed that periodic, systematic changes in velocity are indica- when testing very small specimens. This, of course, is a highly tive of similar changes in the quality of the concrete. Beyond desirable attribute and, in many respects, makes the pulse ve- these areas of agreement, however, it appears that the investi- locity techniques more useful than those involved in resonant gator must have a rather intimate knowledge of the concrete in- frequency testing. volved before attempting to interpret velocity as a measure of Because of the fundamental theoretical relationship strength or other properties of the concrete. This is particularly between pulse velocity techniques and resonant frequency true if the aggregate involved is a lightweight aggregate. techniques, there is a strong inclination for users of the pulse technique to endeavor to compute the dynamic modulus of Standardization of Pulse Velocity Method elasticity from the results of the tests. Theoretically, such ASTM Committee C9 initiated the development of a test values of modulus should be the same as those determined by method for pulse velocity in the late 1960s. A tentative stan- resonant frequency tests upon the same specimens. It has been dard was issued in 1968. A standard test method was issued in shown that on some occasions this is true and on others it is 1971 and the current edition was approved in 2002. See Fig. 3. not [29]. Because of these unexplainable differences, most of The significance and use statement of the test method, as those experienced in the use of pulse velocity techniques are given in the ASTM Test Method for Pulse Velocity Through inclined to leave their results in the form of velocity without Concrete (C 597), is as follows: attempting to calculate elastic moduli therefrom. If the modulus of elasticity is to be computed from the 5.1 The pulse velocity, V, of longitudinal stress waves in a pulse velocity, the relationship generally recommended is concrete mass is related to its elastic properties and density according to the following relationship: (1 + ) (1 2) E V 2 (4) E (1 ) (1 ) V= (5) (1 ) (1 2) where E dynamic modulus of elasticity, V longitudinal pulse velocity, mass density, and Poisson’s ratio. This equation relates modulus to pulse velocity and density in an infinite medium and presumably should apply only to mass concrete. However, the experience of most investigators has been that, even for very small laboratory specimens, this relationship gives better results than do those applying to either slabs or long slender members. Leslie and Cheesman [24] have suggested that the best results are obtained if, for concretes having unit weights in excess of approximately 2240 kg/m3, the value of Poisson’s ratio is assumed to be 0.24. The use of pulse velocity techniques has been suggested for evaluating the strength of concrete, its uniformity, its setting characteristics, its modulus of elasticity, and the presence or absence of cracks within the concrete. There appears to be little question as to the suitability of such techniques to determine the presence and, to some extent, the magnitude of Fig. 3—Schematic of pulse velocity apparatus. MALHOTRA ON NONDESTRUCTIVE TESTS 319 where tablished by the determination of pulse velocity and compressive strength (or modulus of elasticity) on a E dynamic modulus of elasticity, number of samples of a concrete. This relationship dynamic Poisson’s ratio, and may serve as a basis for the estimation of strength (or density modulus of elasticity) by further pulse-velocity tests on that concrete. Refer to ACI 228.1R [33] for guid- 5.2 This test method is applicable to the assessment of the ance on the procedures for developing and using such uniformity and relative quality of concrete, to indicate a relationship. the presence of voids and cracks, and to evluate the ef- 5.7 The procedure is applicable in both field and labora- fectiveness of crack repairs. It is also applicable to in- tory testing regardless of size or shape of the speci- dicate changes in the properties of concrete, and in men within the limitations of available pulse-generat- the survey of structures, to estimate the severity of de- ing sources. terioration or cracking. When used to monitor NOTE 5: Presently available test equipment limits path changes in condition over time, test locations are to length to approximately 50 mm minimum and 15 m be marked on the structure to ensure that tests are re- maximum, depending, in part, upon the frequency and peated at the same positions. intensity of the generated signal. The upper limit of the 5.3 The degree of saturation of the concrete affects the path length depends partly on surface conditions and pulse velocity, and this factor must be considered partly on the characteristics of the interior concrete when evaluating test results (Note 1). In addition, the under investigation. A preamplifier at the receiving pulse velocity in saturated concrete is less sensitive to transducer may be used to increase the maximum path changes in its relative quality. length that can be tested. The maximum path length is NOTE 1: The pulse velocity in saturated concrete may obtained by using transducers of relatively low reso- be up to 5 % higher than in dry concrete [32]. nant frequencies (20 to 30 kHz) to minimize the atten- 5.4 The pulse velocity is independent of the dimensions of uation of the signal in the concrete. (The resonant fre- the test object provided reflected waves from bound- quency of the transducer assembly determines the aries do not complicate the determination of the ar- frequency of vibration in the concrete.) For the shorter rival time of the directly transmitted pulse. The least di- path lengths where loss of signal is not the governing mension of the test object must exceed the wavelength factor,, it is preferable to use resonant frequencies of of the ultrasonic vibrations (Note 2). 50 kHz or higher to achieve more accurate transit-time NOTE 2: The wavelength of the vibrations equals the measurements and hence greater sensitivity. pulse velocity divided by the frequency of vibrations. 5.8 Since the pulse velocity in steel is up to double that in For example, for a frequency of 54 kHz and a pulse concrete, the pulse-velocity measured in the vicinity of velocity of 3500 m/s, the wavelength is 3500/54 000 the reinforcing steel will be higher than in plain con- 0.065 m. crete of the same composition. Where possible, avoid 5.5 The accuracy of the measurement depends upon the measurements close to steel parallel to the direction ability of the operator to determine precisely the dis- of pulse propagation. tance between the transducers and of the equipment to measure precisely the pulse transit time. The re- Stress Wave Propagation Methods ceived signal strength and measured transit time are In recent years, considerable research has been undertaken in affected by the coupling of the transducers to the con- Canada [34] by CANMET and in the United States [35,36] by crete surfaces. Sufficient coupling agent and pressure NIST to develop methods to determine flaws and discontinu- must be applied to the transducers to ensure stable ities in concrete. These methods are classified as stress wave transit times. The strength of the received signal is propagation methods and the common feature of the various also affected by the travel path length and by the pres- methods under development is that stress waves are introduced ence and degree of cracking or deterioration in the into concrete and their surface response is monitored using a concrete tested. receiving transducer connected to a digital data acquisition sys- NOTE 3: Proper coupling can be verified by viewing tem capable of performing frequency analysis. One of the most the shape and magnitude of the received waveform. attractive features of the stress wave propagation methods is The waveform should have a decaying sinusoidal that access to only one surface of concrete is required. shape. The shape can be viewed by means of outputs Two main types of stress wave methods being used are the to an oscilloscope or digitized display inherent in the echo method and the impulse response method. Carino has device. published a detailed review of the principles involved in the de- 5.6 The results obtained by the use of this test method are velopment of the methods [37]. not to be considered as a means of measuring strength nor as an adequate test for establishing compliance of Echo Method the modulus of elasticity of field concrete with that as- In the echo method, a stress pulse is introduced into concrete by sumed in the design. The longitudinal resonance a transducer and its reflection by flaws or discontinuities is moni- method in Test Method C 215 is recommended for de- tored by the same transducer that transmits the wave or by a sep- termining the dynamic modulus of elasticity of test arate transducer located near the transmitting transducer. In the specimens obtained from field concrete because Pois- former case, the technique is called pulse-echo and in the latter son’s ratio does not have to be known. case the technique is known as pitch-catch. See Fig. 4. NOTE 4: When circumstances permit, a velocity- The receiver output is displayed on an oscilloscope. If the strength (or velocity-modulus) relationship may be es- compressional wave speed is known, time-domain analysis, 320 TESTS AND PROPERTIES OF CONCRETE stiffness profile of the concrete being tested can be developed. The technique was named spectral analysis of surface waves [37]. According to Carino, SAWS is the most complex of all the stress wave propogation methods and needs the services of high- strained technologists. To date the use of the SAWS method has been limited to the evaluation of concrete pavements. Infrared-Thermographic Techniques The use of infrared-techniques to measure delaminations in concrete bridge decks was first investigated by the Ontario Ministry of Transportation and Communications, Toronto, Canada, in the early 1970s. This technique is based on the principle that discontinuities in concrete such as delaminations in reinforced concrete caused by corrosion of reinforcement af- Fig. 4—Schematic of pulse-echo and pitch-catch techniques. fect heat flow through concrete, and thus result in localized differences in surface temperature. By measuring these differences in surface temperature, engineers can determine the location of the delaminations. Following the original investiga- that is, measuring the travel time of the pulse to and from the tions in Canada, research was undertaken by various organiza- flaw in the concrete, can be used to determine the depth of the tions in the United States, and the technique, enhanced with flaw or discontinuity. more sophisticated and computerized systems, was used to In the impact-echo method, instead of a transducer, me- determine the delaminations in concrete pavements in various chanical impact is used to generate a lower frequency stress parts of the United States. According to Weil [38] one of the wave that can penetrate into concrete. The stress waves are largest individual infrared thermographic inspections was car- reflected by the discontinuities, and the surface motion caused ried out in 1987 at the Lambert St. Louis International Airport, by the arrival of reflected waves is measured by a receiving and he describes the details as follows: transducer and recorded on a digital oscilloscope. Frequency analysis of the recorded signal permits measurement of the This involved testing concrete taxiways. The concrete depth of the reflecting interface. slabs ranged from 14 to 18 in. (360 to 460 mm) in These methods are being used for thickness measure- thickness. The rules set up by the airport engineering ments, flaw detection, and integrity testing of piles. ASTM C department dictated that the testing had to be per- 1383-98a entitled Standard Test Method for Measuring the formed during low air traffic period (11:00 p.m. to P-wave Speed and the Thickness of Concrete Plates Using the 5:00 a.m.) and no loading gates could be blocked. The Impact-Echo Method describes the use of this method. field inspection was completed in five working nights. Ap-proximately 2 000 000 ft2 (186 000 m2) of con- Impulse Response Method crete was inspected with production rates approaching This method is somewhat similar to the impact-echo method. 1 000 000 ft2 (93 000 m2) per night. In addition to de- An instrumented hammer is used to generate a stress wave. termining individual slab conditions, the use of an The arrival of the reflected echos causes the concrete surface infrared thermography-based system with computer to vibrate, and the velocity of this vibration is measured by a enhancements allowed the determination of damage transducer located near the point of impact. A dynamic signal caused by traffic patterns and underground erosion analyzer is used to analyze the force-time history of the impact caused by soil migration and subsurface moisture and the recorded velocity. From the analysis, information is problems. obtained about the location of the reflecting interface and the dynamic stiffness of the test object. This method is primarily being used to test the integrity of the piles. ASTM D 5882 entitled “Standard Test Method for Low Strain Integrity Testing of the Piles” issued in 2000 covers the use of this method. Impact-echo has also proven to be useful for other applications such as subgrade contact and crack depth. Spectral Analysis of Surface Waves Method (SASW) This method is based on the principle that when surface waves (R Waves) are created by an impact on a concrete surface, the various wavelength components of the generated surface waves penetrate to different depths in the concrete. The surface motion is monitored at two locations at a fixed distance apart, and from this information the speed of various wavelength components is extracted (Fig. 5). The data are analyzed using digital signal processing techniques and the Fig. 5—Schematic of the SASW test method. and a power source (Fig. the equipment needed to perform infrared-thermographic investigations consists primarily of an infrared sensor. The surface ments and bridge decks. the equipment is mounted on a van and taken to the site under inspection. Al. The sur. Another limitation of the test method is that when corresponding reflecting interface and the dielectric this technique is used to determine voids in concrete. ambient temperature. a real-time microprocessor coupled to a monitor. but primarily delaminations in con. stant of concrete and most materials will vary because crete and its thickness. This lim. the previously cited reference) as follows: Ground Penetrating Radar (GPR) When a beam of microwave energy is directed at a reinforced concrete slab (Fig. rial being examined. an antenna As the remaining microwave energy propagates that is used for both transmitting and receiving. which has been reported to range solids have different scattering and reflection response to the from 6 when dry to about 12 when saturated. 6—Components of a typical GPR system. The resulting pulse is then radiated into the mate- whereas most other nondestructive methods are “point test. Thermographic Technique which is then electrically discharged from the antenna The advantages of the infrared thermographic technique are in the transducer as a short burst of electromagnetic en- obvious. cloud cover. The speed of the vehicle can range anywhere up to 50 km/h. It is nondestructive and is an area testing method. and image recording and retrieving devices. (It must patterns can be used to determine various properties of fresh be noted that the actual in situ relative dielectric con- and hardened concrete. a of distress in the concrete. Each trigger pulse. 6). tromagnetic pulse arrives back at the receiving antenna its the available time during which inspections can be per. reconstructs the reflected pulses at an expanded time most all of the reported case histories deal with inspection of scale by a time-domain sampling technique. Cleména [39] de- the motor vehicle carrying the equipment described above is scribes the operation of the system as follows: moved as rapidly as images can be taken. etc. into the concrete. ing. a portion of the energy Ground Penetrating Radar3 (GPR) is a nondestructive detec. graphic recorder.. which is 1. 7). a portion of the beam will be 3 Radio detection and ranging. a circuit within the radar control unit gen- images are then subjected to detailed analysis to define areas erates a trigger pulse signal at a rate of 50 kHz. Each reflected elec- speed. remaining energy penetrates this interface. Standardization of Infrared-Thermographic Technique ASTM D 4788 Test Method for Detecting Delaminations in Detecting Delaminations in Concrete Bridge Decks Using Infrared Thermography was issued in The principle underlying the use of GPR for determining the 1988. and the tion tool for determining delaminations in concrete pave. and surface moisture condition of concrete. A receiver circuit method cannot determine depth or thickness of the void.e. Testing Procedure The infrared-thermographic investigations on pavements and Fig. ergy. bridge decks are performed by establishing control areas of sound and poor concrete using chain dragging or coring. pulse at every 20 s. and for estimating the thickness of reflection has a negative polarity since the dielectric concrete pavements.) A simple radar system consists of a control unit. it is affected to varying degrees by not only its water content but also by its conductivity. in turn. As the radiated pulses travel through the material. MALHOTRA ON NONDESTRUCTIVE TESTS 321 Testing Equipment According to Weil (see previously cited reference). i. a data acquisition and analysis system. and describes in detail the test procedures associated delaminations in concrete is best described by Cleména (see with this technique. somewhat like a portable video camera. It is based on the principle that different constant of concrete. and these response siderably higher than that of air. wind sent changing dielectric properties. . is reflected from the surface of the concrete. this method has serious limitations. Once these reference areas have been established on the pavements and images have been taken for future reference. the test constant of the intervening material. an oscillo. is con- transmission of electro-magnetic waves. at a different time that is governed by the depth of the formed. and further conditioned in the control unit before they are fed to an output. face temperature of the area being inspected is affected by different reflections will occur at interfaces that repre- solar radiation. For pavements and bridge deck investigations.” However. mineral composi- Equipment tion. The result- bridge decks and pavements indicating its limited use in the ing replicas of the received radar signals are amplified concrete building industry. causes a solid-state impulse generator in the transmitting an- Advantages and Limitations of the Infrared tenna to produce a pulse with a very fast rise time. The acquired In operation. thick sections. These methods consist of the indentation type and ditional reflection. Further. the concrete slab until a portion of it strikes the second According to Cleména.2 to 0. ASTM D 4748 issued in 1987 describes in detail the crete. or both. the plunger is released from its locked position by pushing the plunger against the concrete and slowly moving the body away from the concrete. The indentation meth- an indicator of the presence of a delamination in the ods consist principally of impacting the surface of concrete by concrete slab. since the dielectric constant of metal GPR has been used to determine the thickness of concrete is infinite compared with that of the surrounding con. a surface hardness tester with little apparent theoretical rela- and these are subjected to detailed analysis later. there is an addi. This causes the plunger to extend from the body and the latch engages the hammer mass to the plunger rod.8 kg and is suitable for use both in a laboratory and in the field. the principle of the test method is mat of reinforcement and the same reflection and scat. This ad. and some of it will be reflected of the slabs. some portion of the and known. through the concrete is directly proportional to the thickness tom of the concrete slab. the slide indicator travels with the hammer mass and additional reflection of the incident energy. property. has led to the development of test methods to measure this tional reflection from the deteriorated section. 7—Radar echoes from the cross section of a rein. Ernst Schmidt [40–42]. the latch is automatically released. relations have been established between strength properties and the rebound number. However. The bound principle.3 m from the surface of the concrete. A button on the side of the body . a Swiss engineer. pacts the shoulder of the plunger rod and rebounds. the antenna is In 1948. When a concrete slab is delaminated. the hammer mass. empirical cor- delaminations in concrete bridge decks covered with asphalt. Surface Hardness Methods face and be lost from the receiving antenna. of the resulting indentation. serves as those based on the rebound principle. pavements. The Schmidt rebound hammer is principally A tape recorder keeps a continuous record of the radar signals. the antenna is The methods based on the rebound principle consist of meas- placed with its transmitting face parallel to and at a distance of uring the rebound of a spring-driven hammer mass after its im- 0. and the energy stored in the spring pro- pels the hammer mass toward the plunger tip. the two-way transit time of microwave pulses original beam of microwave energy will reach the bot. During forced concrete deck. the plunger. Other features include a latching mechanism that locks the hammer mass to the plunger rod and a sliding rider to measure the rebound of the hammer mass. In cases of very pact with the concrete. Kolek [43] has attempted to establish a correlation between the hammer rebound number and the hardness as measured by the Brinell method. Description The Schmidt rebound hammer weighs about 1. The rebound distance is recorded as a “rebound number” corresponding to the position of the rider on the scale. and the main spring. The main components include the outer body. As the body is pushed. The presence of a delamination causes rebound. The remaining energy will continue deeper into test procedures. Method of Testing To prepare the instrument for a test. The remainder will penetrate through this inter. The plunger is then held perpendicular to the concrete surface and slowly the body is pushed towards the test object. The rebound distance is measured on an arbitrary scale marked from 10 to 100. the antenna may be placed directly above the concrete. When inspecting small areas of concrete. When the body is pushed to the limit. developed a mounted on the front or rear of the inspection van which has test hammer for measuring the hardness of concrete by the re- the instrumentation for measuring the horizontal distance. Rebound Method When inspecting large areas of concrete. within limits.322 TESTS AND PROPERTIES OF CONCRETE completely reflected and scattered as it strikes the top Measurement of Thickness of mat of reinforcement. Eventually. tionship between the strength of concrete and the rebound ASTM D 6087 issued in 1997 deals with the detection of number of the hammer. usually of negative polarity. at the concrete/air interface to give a positive reflection signal. This reflection will also have a Concrete Pavement negative polarity. The mass im- Fig. means of a given mass having a given kinetic energy and measuring the width or depth. records the rebound distance. usually at the The increase in the hardness of concrete with age and strength level of the top mat of reinforcement. the main spring connecting the hammer mass to the body is stretched. that when the dielectric constant of a concrete slab is uniform tering process occurs. However. of the amplitudes of these waves and the time. mented with strain gages. the rebound 5. 300 by 1270 by 1. or at any intermediate angle. and rigidity of specimens. three days and have studied the ability of the test to determine sive means of checking the uniformity of concrete.45]. high alumina. 8. general correlation between compressive strength of concrete Fig. and According to Kolek [43] and Malhotra [44. The Each hammer is furnished with correlation curves developed ratio. at the center of the plunger. From the analyses of the test data. Due to different ef. 7. tween their appearance was found to depend upon the surface the use of these curves is not recommended because material hardness of concrete. The results of moval purposes. and Correlation with Strength a large reflected stress wave. it has seri. early-age strength development of concrete for formwork re- ous limitations and these must be recognized.45] there is a 8. and the These limitations are discussed in detail elsewhere (Ref 18. r/i. the authors concluded 4. inexpen. was not significantly affected by the moisture condition of the A typical curve established by Zoldners [46] for limestone concrete [47]. shape. The test can be conducted horizontally. T. MALHOTRA ON NONDESTRUCTIVE TESTS 323 is pushed to lock the plunger in the retracted position. that because of the large within-test variation. from the slabs were tested in compression. hammer test was not a satisfactory method for reliable esti- 6. be- by the manufacturer using standard cube specimens. and three days on plain concrete slabs. 3. vertically upward To gain a basic understanding of the complex phenomena or downward. The rebound tests were performed at one. r. mates of strength development of concrete at early ages. size. This curve was based on Carette and Malhotra [48] have investigated the within-test tests performed at 28 days using different concrete mixtures. age of test specimens. . The rebound number was found to be ap- and testing conditions may not be similar to those in effect proximately proportional to the ratio of the two stresses and when the calibration of the instrument was performed. i. type of cement (portland. 1220-mm in size. Also. the ied the stress waves in the plunger of a rebound hammer at the rebound number will be different for the same concrete and time of impact. Using a specially designed plunger instru- require separate calibration or correlation charts [44. super sulfated). 8—Relationship between 28-day cylinder compressive strength and rebound number for limestone aggregate concrete obtained with Type N2 hammer (from Ref 46). variability of the rebound hammer test at test ages of one to Although the rebound hammer provides a quick. carbonation of the concrete surface. Chapter 1). aggregate concrete is shown in Fig. the authors showed that the impact of the hammer mass produces a large compressive wave. rebound number is read from the scale. the Schmidt rebound hammer test are affected by: two. Akashi and Amasaki [47] have stud- fects of gravity on the rebound as the test angle is changed. surface and internal moisture conditions of the concrete. type of mold. type of coarse aggregate. involved in the rebound test. companion cylinders and cores taken 2. smoothness of test surface. narrowed down considerably by developing a proper correla. the accuracy of estimation of one hammer is to be used. and the accuracy of the estimation of strength from the rebound the depth of carbonation. If more than discussed earlier. the method used to obtain the test sur- degree of disagreement among various researchers concerning face (type of form material or type of finishing). Therefore. However. there is a wide test surface. perform tests on a range of compressive strength of test specimens cast. The large deviations in strength can be give rebound numbers differing from 1 to 3 units. These factors need to be readings and the empirical relationship. lies between .8 % and exceeded 30 % for some 5. and tested typical concrete surfaces so as to determine the mag- under laboratory conditions by a properly calibrated hammer nitude of the differences to be expected.4 Different hammers of the same nominal design may groups of specimens. specimens averaged 18. considered in preparing the strength relationship and tion for estimated compressive strength for a wide variety of interpreting test results. tests should be made with the same tion curve for the hammer. cured.324 TESTS AND PROPERTIES OF CONCRETE and the hammer rebound number. By consensus. Coefficients of varia. which allows for various variables hammer in order to compare results. 15 and . 5 This test method is not intended as the basis for ac- of estimation of concrete strength in a structure is . 20 %. However. the probable accuracy 5. The relationship shall be established Windsor probe test system had been made in investigations of for a given concrete mixture and given apparatus. the significance and use closely related to studies reported by Kopf [52]. Results of the statement of the test method as given in ASTM C 805-02 is as investigations carried out by the New York Port Authority were follows: presented by Cantor [53] in 1970. hardened alloy-steel probes. herent uncertainty in the estimated strength. establish the relationship by Swamy and Al Hamed [68] in the United Kingdom published correlating rebound numbers measured on the struc. and a few years later Arni [57. They have found that the Probe Penetration Test relationships are similar to those obtained for compressive Penetration resistance methods are based on the determination strength. The concrete. It cannot be acceptance in Europe or elsewhere. In 1972. The in-place compressive strength of concrete and in determina- relationship shall be established over the range of tions of concrete quality. and In the 1960s. establish the relation. device was meant to estimate the quality and compressive strength of in-situ concrete by measuring the depth of pene- Standardization of Rebound Test Method tration of probes driven into the concrete by means of a pow- ASTM Test Method for Rebound Number of Hardened Con. results of a study on the use of the Windsor probe system to ture with the strengths of cores taken from corre. Apart from the Limitations data reported by Voellmy. ship by performing rebound number tests on molded several U. loaded cartridges. ceptance or rejection of concrete because of the in- Greene [49] and Klieger et al. the rebound number is The Windsor probe consists of a powder-actuated gun or affected by factors such as moisture content of the driver. determining the uniformity of concrete in the structures. der-actuated driver. Perhaps the introduction over-stressed that the hammer must not be regarded as a sub. and they appear to have received little and taken into account when using the hammer. the results of a detailed investigation on the evaluation of the ture of poor quality or deteriorated concrete. 25 %. Fur.58] reported uniformity of concrete. in an existing structure. The Windsor probe had been used to concrete strength that is of interest. Description of Test 5.1R [33] for additional weight concretes. ments. and standards have been issued both by ASTM and ISO and by The Windsor probe test system was advanced for penetra- several countries for determining the rebound number of tion testing of concrete in the laboratory as well as in-situ. while Malhotra [59–61] reported the results of estimate in-place strength development. of the rebound method around 1950 was one of the reasons for stitute for standard compression tests but as a method for the failure of these tests to achieve general acceptance [18]. establishing a relationship between strength and re. of the depth of penetration of probes (steel rods or pins) into con- ther. his investigations on both 150 by 300-mm cylinders and 610 by 5. In the 1970s. See ACI 228. and concrete damaged by fire. abut- strength during construction. the Windsor probe test system was intro- comparing one concrete against another.S. estimate the in situ strength of both lightweight and normal- sponding locations. information on developing the relationship and on using the relationship to estimate in-place strength.3 For a given concrete mixture. The development of this technique was crete (C 805) was revised in 2002. there is little other published work The limitations of the Schmidt hammer should be recognized available on these tests. to delineate regions in a struc. Meanwhile. duced in North America. and to Windsor probe. highway bridge piers. Klotz [62] stated that extensive application of the bound number. tration test in the 1980s.2 To use this test method to estimate strength requires 610 by 200-mm concrete slabs. they found that the rebound numbers for tests conducted crete. The measurement of concrete hardness by probing techniques was reported by Voellmy [51] in 1954. To estimate test reinforced concrete pipes.1 This test method is applicable to assess the in-place technique [54–56]. This provides a measure of the hardness or penetration re- on the top of a finished surface of a beam were 5 to 15 % lower sistance of the material that can be related to its strength [18]. In 1984. a depth . a number of other organizations had initiated exploratory studies of this 5. and this was followed by a pin pene- The rebound method has won considerable acceptance. federal agencies and state highway departments re- specimens and measuring the strength of the same or ported investigations on the assessment of the Windsor probe companion molded specimens. except that the scatter of the results is greater. [50] have established corre. lation relationships between the flexural strength of concrete and the hammer rebound number. pavements. To estimate strength for in-situ testing of hardened concrete [63–67]. than those conducted on the sides of the same beam. and three probes are driven into the concrete. For concrete to fracture within a cone-shaped zone below the sur- testing structures with curved surfaces. individually using the single probe locating template. A practical ish or a smooth surface. Probes 7. Briefly. elsewhere [72]. 9—Relationship between exposed probe length and 28-day compressive strength of concrete as obtained by different investigators (from Ref 72). However. If flat surfaces are to be tested. MALHOTRA ON NONDESTRUCTIVE TESTS 325 gage for measuring the penetration of probes. The dis. giving the mechanical average of the concrete and in lesser part through friction between the exposed lengths of the three probes. The tables are based on empirical re- and fits snugly into the bore of the driver. turer’s tables do not always give satisfactory results. 10). the and several others [56.18]. . times they considerably overestimate the actual strength and The method of testing is relatively simple and is given in in other instances they underestimate the strength. in large part through crushing and fracturing of tance between the two plates. For testing of relatively low-strength concrete. investiga- into the concrete by the firing of a precision powder charge tions carried out by Gaynor [55]. not be easy to posed length of the three probes fired in the triangular pattern.5 mm. The manufacturer also supplies a There is no rigorous theoretical analysis of the probe pene- mechanical averaging device for measuring the average ex. Such analysis may. test results with the type of concrete being used.69–71] indicate that the manufac- power level can be reduced by pushing the driver head fur. [7. published tables relating exposed length of the probe with a length of 79. penetration. 9. The exposed lengths of the individual probes are Mohs’ hardness numbers. value. Some- ther into the barrel.7 mm in diameter Mohs’ scale of hardness. which makes it possible to then be used to estimate the compressive strength of concrete establish useful empirical relationships between the depth of by means of appropriate correlation data.64. For each exposed length diameter are also available for the testing of lightweight ag. The probe is driven lationships established in his laboratory. and a conical point. chert. In either The probe penetrations relate to some strength parameter case. tration test available. Malhotra [59–61]. To test structures with coarse finishes. penetration and compressive strength. different values for compressive strength are given. the measured average value of exposed probe length may of the concrete below the surface. Note that different relationships have pattern. is measured by a depth probe and the concrete. one at been obtained for concretes with aggregates having similar each corner. the powder-actuated driver is used to drive a probe into The correlation published by several investigators for con- concrete. in fact. a suitable locating cretes made with limestone gravel. The area to be tested must have a brush fin. It is there- ASTM Test Method for Penetration Resistance of Hardened fore imperative for each user of the probe to correlate probe Concrete (C 803). de- gregate concrete.9 mm in compressive strength of concrete. Arni [57]. The test involves a given initial probes and rests on the surface of the concrete. and other re. achieve in view of the complex combinations of dynamic The mechanical averaging device consists of two triangular stresses developed during penetration of the probe and the het- plates.3 mm. The rear of the probe is threaded and pending on the hardness of the aggregate as measured by the screws into a probe-driving head that is 12. procedure for developing such a relationship is described the surface first must be ground smooth in the area of the test. The manufacturer of the Windsor probe test system has lated equipment. The other tri. and traprock aggre- template is used to provide a 178-mm equilateral triangular gates are shown in Fig. The probes have a tip diameter of 6. amount of kinetic energy of the probe that is absorbed during angular plate rests against the tops of the three probes. Penetration of the probe causes the gage inserted through a hole in the center of the top plate. Fig. The reference plate with three legs slips over the three erogeneous nature of concrete. measured by a depth gage. three probes are driven face with cracks propagating up to the surface (Fig. 9 tend to support the belief in the importance of the aggregate type.66 5. 19 250 by 300 by 45 3 7 and 28 1.4 by 1690-mm prisms 19 610 by 610 48 3 7 and 28 2.326 TESTS AND PROPERTIES OF CONCRETE There appear to have been no systematic attempts to determine the relative influences of these factors that could affect the probe penetration test results. 2. 14. mm Tested Probes per Test days Deviation..7 cylinders gravel 19 150 by 150 48 3 7 and 28 1.62 7.05 . 1210-mm walls semi. size of 19 mm. curing regime. The considerable differences shown in Fig.70]. Fig.14 7.21 5. 2..91 3. except for value in parentheses that is based on depth of penetration. However. it is generally agreed that the largest influence comes from the coarse aggregate. a typical value for the within-test coefficient of TABLE 1—Within-Batch Standard Deviation and Coefficient of Variation of Probe Penetration Measurements Type of Maximum Type of Total Number Age of Average Average Investigation Aggregate Aggregate Specimens Number of of Probes Test.4) Malhotra [48] 1220-mm slabs and 3 Keiller [69] limestone.30 .4 by 200-mm slabs 19 150 by 150 28 2 35 1.. 10—Typical failure of mature concrete during probe These data show that for concrete with a maximum aggregate penetration (from Ref 72).37 3. 50 410 by 510 136 9 3. However. moisture content. .4 by 200-mm and 28 slabs Malhotra [72] limestone 19 152 by 305-mm 20 2 7 and 28 3. 7. the type and size of coarse aggregate used have been reported to have a significant effect on probe penetration [57.68. by 200-mm and 28 trap rock slabs 25 410 by 510 198 9 3.5 by 200-mm slabs Gaynor [55] quartz 25 150 by 580 by 384 16 3 and 91 4. is shown in Table 1. and surface conditions are likely to have affected these correlations to some extent and could explain some of the observed differences. although more correctly they should be based on the embedded lengths of the probe.2 (5. 7. Apart from its hardness. lightweight by 1210-mm expanded walls shale as coarse aggregate Carette. Standard Coefficient of Reported by Used Size.1 limestone. other parameters such as mixture proportions. Variability is reported in terms of standard deviations and coefficients of variation with values in the latter case being calculated from the exposed length of the probe readings. 2. The within-batch variability in the probe test results. as obtained by various investigators.52 8. limestone 19 300 by 1220 by 72 6 1.. mm Variation %a Arni [57] gravel.5 gravel 1500-mm prisms a Based on exposed length of probe. 3. 25 150 by 580 256 9 3 and 91 4.57 3. 14. the cores may tions. and cast-in-place tests on standard cylinders and cores taken from the slabs. should be of interest in this regard: age standard cylinder strength (assuming a coefficient of variation of 4 % based on two cylinders) would be three. simplicity. strength of marginal concretes. accuracy.75]. along with compression penetration. whereas cores. enough that the probe test can be used as a satisfactory sub- Carette and Malhotra [48] have investigated in the labo. for such concrete. a survey of concrete testing laboratories days of the probe penetration test. tures that prevent accidental discharge of the probe from the gun. method for in-situ strength testing of concrete (see ASTM C 42). These include minimum size requirements for the be investigated. has been found possible to establish. and the following statement by Gaynor [55] tion is known with the same degree of confidence as the aver. penetration especially when the distance is less than about 100 native to the latter for estimating the compressive strength of mm [76]. by the late 1970s. pulse velocity. The importance of aggregate type and aggregate con- concrete. and of requiring only one surface for the test. cylinder. wearing safety glasses is required. If the material composition and testing conditions. in general. In these instances. manner that the rebound hammer is useful. From the analysis of the test data. would not ensure that the in-situ strength is the accuracy required if it is to replace conventional known with the same degree of confidence. of its test results. the uncertainty of the estimated they have to be tested in accordance with ASTM Test Method strength value. In the field. der or cube strength is strictly the parameter of interest be- However. it had been reported that the probe cause of the specifications being expressed primarily in these penetration test was probably the most widely used nonde. the authors con. it test: “One simply fires the probes into the concrete and com. the advantages of the tistically. The penetration tests were per. ratory the within-test variability at the ages of one to three In the early 1980s. The survey included methods such as rebound hammer.or relatively high-strength destructive techniques is in the estimation of early-age strength concretes in structures. It may also be required in the case of older However. of concrete for the determination of safe form-removal times. stitute for the core test [75]. the probe system does not supply number. formed at one. terms. The system has a number of built-in safety fea- of formwork in concrete construction. obviously. maturity. However. however. about three times the expected depth of penetration. also. delay in getting the results. which also affects the reliability of the provides precise quantitative estimates of compressive estimated strength. This Based on these tests. concrete with a reasonable degree of accuracy. probe 300 by 1220 by 1220-mm in size. matter of minutes. the minimum number of individual probe penetration test should be judged against the precision penetration tests required to ensure that the average penetra. or the quality of the tively small number of variables is an advantage over some concrete is being questioned because of inadequate placing or other methods for in-situ strength testing. the most direct and common concrete member to be tested.74. and three days on plain concrete slabs. In these tration test does not take into account the uncertainty of the tests. and the ability of the test in Canada and the United States indicated that the Windsor to indicate the early-age strength development of concrete for probe penetration technique was the second most often used formwork removal purposes. pullout. must be soaked for 40 h. In terms of reliability. However. The test is limited to a certain range of strength ( 40 have to be transported to a testing laboratory. the core test that provides a direct measure of com- structive method for the determination of safe stripping times pressive strength clearly remains the most reliable means of [66]. One main advantage cited was the great simplicity of the estimating in-situ strength. the core tests. neither the probe system nor the rebound hammer correlation relationship. Advantages and Disadvantages of the Probe cluded that unlike the rebound method. Distance It has been claimed that the probe penetration test is from reinforcement can also have an effect on depth of probe superior to core testing and should be considered as an alter. if from exposed areas and if As previously indicated. relationships be- probes penetrate too far. and thus can and needs little maintenance except for occasional cleaning of be applied to determine safe stripping times for the removal the gun barrel. locate areas of relatively low. the contractor knows the concrete is tween probe penetration and strength that are accurate not yet strong enough” [66]. Relatively little information has been published in regard to It must be stressed that in cases in which standard cylin- the performance of the probe penetration test at early ages. however. The minimum acceptable dis- method of determining the strength of concrete is through tance from a test location to any edges of the concrete mem- drilled core testing. curing procedures. the probe test has limitations that must be rec- structures in which changes in the quality of the concrete must ognized. However. and the use of two different power levels to accommo- . rugged. Penetration Test tion test can estimate the early-age strength development of The probe penetration test system is simple to operate. probe penetration were observed at these ages for each concrete. It is true that the probe test can be carried out in a tent on the correlation is emphasized. In new construction. however. it will be useful in much the same preceding within-test coefficient of variation for the probe pene. Sta. Both should be used to An increasingly important area of the application of non. within certain limits of pares penetration to previously established criteria. MALHOTRA ON NONDESTRUCTIVE TESTS 327 variation (based on depth of penetration) is about 5 % [73]. is relatively large and the test results for Obtaining and Testing Drilled Cores and Sawed Beams of may lack the degree of accuracy required for certain applica- Concrete (C 42). some nondestructive techniques ber or between two given test locations is of the order of 150 such as the probe penetration test have been gaining acceptance to 200 mm. and econ- Excellent correlations between compressive strength and omy. while the minimum thickness of the members is as a means to estimate the in-situ strength of concrete [66. since. causing further MPa). the probe test was given one of the best combined ratings. two. become necessary when standard cylinder strength test results That its correlation with concrete strength is affected by a rela- fail to comply with specified values. the probe penetra. Probe Penetration Test Versus Core Testing the probe penetration test offers the main advantages of speed The determination of the strength of concrete in a structure may and simplicity. In 1968. Pins are intended to penetrate the mortar fraction and a tip machined at an angle of 22. and probes may penetrate some aggre- In the late 1980s. and sion and in shear. wooden forms versus steel forms). Use the procedures and statistical methods in ACI 228. Calibration of the equipment is important to ensure a covering strengths up to 35. this apparatus consists of a device that and are driven by a low energy. Briefly. the latest Carino [87] has summarized analytical and experimental stud- edition was issued in 2003. and the pin penetration method was added as an alternative penetration test. Because of its shape. but the equipment is rather heavy for field of Soviet Socialist Republics [80] since 1935. are relatively new use and. ASTM C 900). 10. faces similar to those to be used during construction. . A specially shaped insert whose enlarged end has been cast into depth gage is used to measure the penetration depth. necessary. the insert is pulled out with The test. The simplicity of the test strength by means of a previously established relationship. in the United States. Tassios [84].78] reported the gate particles.4 This test method results in surface damage to the con- compressed when the device is prepared for a test.56 mm. because of the nature of the spring mechanism. and Richards [86]. grips a pin having a length of 30.5°. which may require repair in exposed architec- is reported to have a stiffness of 49. correlation testing Fig. The a cone of the concrete. makes it possible to obtain as many readings as necessary at The pullout techniques. A pullout test. The pullout force is then related to compressive when an aggregate particle is struck. gation complicates the correlation procedures. reported the development of a nail pullout test. using similar concrete materials and mixture proportions as in the structure. as Additional information on the factors affecting pene- noted earlier. the concrete. the test causes minor damage to the surface that tration test results and summaries of past research are generally needs to be repaired. A number of re- Resistance Techniques searchers including Malhotra [81]. though simple in concept. The spring crete. Fol. though in use in the former Union little extra cost. aggregate. advocated the use of pull- Standardization of Penetration out tests on structural concrete members. Finally. can. elsewhere [81. spring-actuated driver. a diameter of 3. In the 1970s Kierkegaard-Hansen [85]. the apparatus is removed.1R for developing and using the strength relationship [33]. ring. Carino [87]. Such a relationship must be established for a given test apparatus (see also 9. 11—Schematic cross section of pullout test (from should be performed on specimens with formed sur. available [79]. measures the force required to pull out from concrete a ted in the concrete is cleared by means of an air blower.7 N/mm and stores about tural finishes. The significance and use statement of the test method as given in the 2003 standard is as follows: 5.1. in consistent level of energy and its frequent verification may be Greece. therefore. In 1944 in the United States. the apparatus is held against the Pullout Test surface of the concrete to be tested.2 MPa. a test in which a pin strikes a coarse ag- a shaft that is encased within the main body of the tester. in Denmark. The concrete is simultaneously in ten- pin penetrates only a small depth into the concrete.2 This test method is applicable to estimate in-place strength. The test results are invalid (Fig.5). powder-ac- Pin Penetration Test tuated driver. A pullout system known as LOK-Test based on method covering its use was issued in 1975. pin is driven into the concrete by a spring that is mechanically 5. The gregate particle is disregarded. Steel pins are smaller in size than probes crete formwork.3 J of energy when compressed. has limitations.1 This test method is applicable to assess the uniformity of concrete and to delineate zones of poor quality or deteriorated concrete in structures. Tremper [83] not be used for concrete with strength greater than about 30 reported results of laboratory studies dealing with pullout tests MPa. 5. 5. A standard test Kierkegaard-Hansen’s work is now available commercially. provided that a relationship has been experimentally established between penetration resistance and concrete strength.328 TESTS AND PROPERTIES OF CONCRETE date a larger range of concrete strength within a given investi. defined by the key dimensions of the insert and bearing ring tions of the material at the surface. by concrete strength as well as the nature of the coarse nation of early-age strength of concrete for removal of con. and others [82] ASTM Committee C9 initiated the development of a standard have published data dealing with laboratory studies and field for the probe penetration technique in 1972 and a tentative test testing. Nasser and Al-Manaseer [77. 11). and the small hole crea.5 mm. When ready for testing. NOTE 1: Since penetration results may be affected by the nature of the formed surfaces (for example. Probe penetration resistance is affected development of a simple pin penetration test for the determi.82]. and the generating lines of the cone are therefore the results can be seriously affected by the condi. The pin is held within only. by using a dynamometer and a reaction bearing lowing this. method designated ASTM C 803 was issued in 1982. and a triggering device is used to release the spring forcing the pin into the concrete.3 Steel probes are driven with a high-energy. and level of strength Fig. The pullout insert is either cast into the fresh concrete or installed in hardened concrete.1 For a given concrete and a given test apparatus. relation with compressive strength of concrete. pullout force corresponding to a given minimum strength is Another pullout method studied by Mailhot et al. which refers to references given at the end of the chapter and to an appendix in the standard: 4. the within-test variability was reported to be high. sert need not be stressed to failure. An expandable steel ring is placed into the hole. three-dimensional state of stress. there is not a consensus on the failure mechanism at the ultimate load. How- The main advantage of the pullout test is that it provides a ever. The method high variability associated with the test data in the field tests is relatively simple and testing can be done in the field in a mat- [87]. It is understood that the pullout test subjects the concrete to a nonuniform. However. it is argued that good correlation Other forms of the pullout tests include the core and pull- exists between pullout strength and compressive strength out (CAPO) test and the drilled-in pullout tests [18]. An example of the correlation between compressive The development of other drilled-in pullout tests have strength and pullout strength or load is shown in Fig. Others believe that the ultimate failure is governed by aggregate interlock across the secondary Fig. There is a high degree of variability in the test results. 13—The CAPO test by undercutting and using an crack system. and a standard was issued in 1982 and the last revision was in 1999. 12. it has been shown that pullout strength has good cor- ring is expanded into the slot using a special device (Fig. it may be assumed that a minimum volved epoxy grouting a 16-mm-long threaded rod to a depth of strength has been reached in the concrete and the pullout in- 38 mm in a 19-mm-diameter hole. The revised standard is designated as ASTM Test Method for Pullout Strength of Hardened Concrete (C 900). and the nism. a hole is drilled into concrete and a special milling the mortar. the test has found very limited acceptance because of the direct measure of the in-situ strength of concrete. and a pullout force is applied to cause failure in con- age to the concrete surface must be repaired. depth of embedment. the rod was pulled out using a tension jack reacting against a bearing ring. [89]. The significance and use statement as given in ASTM C 900 is reproduced here except Note 1. Pior to use. MALHOTRA ON NONDESTRUCTIVE TESTS 329 ies to gain an understanding of the fundamental failure mechanisms of the pullout test and he concluded as follows: 1. Such been reported by the Building Research Establishment (BRE) correlations depend on the geometry of the pullout test con- (United Kingdom) [88] and by Mailhot et al. This could explain why good correlation exists between pullout strength and compressive strength. Some believe that ultimate load occurs as a result of compressive failure of concrete along a line from the bottom of the bearing ring to the top face of the insert head. In the BRE figuration and the coarse aggregate characteristics. [89] in- applied without failure. neath the bearing ring. and a secondary system which defines the shape of the extracted cone. bearing ring dimensions. Standardization of Pullout Tests ASTM Committee C9 initiated the development of a standard for the pullout tests in the early 1970s. In the latter case. 12—Correlation data by Khoo and best-fit linear and development in that concrete. expandable ring. It also has been demonstrated that there are at least two circumferential crack systems involved: a stable primary system which initiates at the insert head at about 13⁄ of the ultimate load and propagates into the concrete at a large apex angle. these rela- power function relationship (from Ref 87). In the because both properties are controlled by the strength of CAPO test. tool is used to undercut a 25-mm-diameter slot at a depth of 25 2. and the ultimate load is reached when suffi. tests. Variability may be reduced by assuring a flat surface be- ter of minutes. Once again. an anchor bolt is placed in a hole drilled in hardened con- A major disadvantage of the pullout test is that minor dam- crete. 13). However. After the epoxy had cured. pullout strengths can be related to compressive strength test results. tionships must be established for each system and . Despite the lack of agreement on the exact failure mecha- mm. if a crete. Such strength relationships depend on the configuration of the embedded insert. cient aggregate particles have been pulled out of the matrix. out of the concrete using the LOK test loading system. and that The entire assembly used to expand the ring is then pulled the test has good repeatability. Standardization of the Maturity Method gree-hours. where sults. K. the most im. These prima- The Nurse-Saul maturity function is as follows: rily consist of a glass tube containing a liquid that has an activation energy for evaporation that is similar to the activation M (t ) ∑(Ta T0)∆t (6) energy for strength gain in concrete.2°C (10°F). M (t ) the temperature-time factor at age t. Naik [98]. potential strength of concrete based upon early-age tests. and strength-maturity relationships were pub. in the 1950s. The measured pullout strength is t. For typical surface installations. days or hours. which de- ity of the outer zone of concrete members and can be scribes the influence of temperature on the rate of chemical re- of benefit in evaluating the cover zone of reinforced action. expected decrease of concrete strength with increas- Q activation energy divided by the gas constant. days or hours. Carino [99. oping Early Age Compression Test Values and Projecting Later crete strength and maturity and attempted to establish a rational Age Strengths (C 918). ASTM Committee C9 initiated the development of a standard on t a time interval. 4. post-installed pullout tests may be used to estimate the strength of concrete in existing construc. turity as the temperature at which the strength gain of hardened The maturity of in-situ concrete can be monitored by ther- concrete ceases. °C. consideration should be given to the normally t equivalent age at a specified temperature Ts. t. However.330 TESTS AND PROPERTIES OF CONCRETE each new combination of concreting materials. formulated in early years. (1) post-tensioning may proceed. Then. the concept of ma. and cured under similar conditions. In the United States. disposable mini-maturity meters based on the strength development. He defined the datum temperature for ma. Plowman [94] examined relationships between con. Maturity was defined as the product of time and temper. K. the amount of evaporation from the capillary tube at a given time is indicative of where strength development in the concrete. Such Ta average concrete temperature during time interval. and out test specimens and compressive strength test speci. The temperature-time Maturity functions are mathematical expressions that convert factor or equivalent age is automatically computed and dis- the temperature history of concrete to an index indicative of its played. Also. and is applicable over a wider temperature range than the crete increases with time. results have been incorporated into ASTM Method for Devel- In 1956.3 When planning pullout tests and analyzing test re. . One of the first engineering applications of the maturity portant being the concrete temperature and the availability of method was by Swenson [103] in Canada who used it in foren- moisture. compacted to similar density. ing height within a given concrete placement in a Ta average temperature of concrete during time interval structural element. days or hours. accurately represent time-temperature effects because it is place strength of concrete has reached a specified based on the assumption that the rate of strength development level so that. It has been shown that the Nurse-Saul function does not 4. °C. insert head and bearing ring. Saul [92]. the maturity function proposed by (3) winter protection and curing may be termi. Malhotra [105] attempted to relate com- basis for the datum temperature used for maturity to calculate pressive strengths using accelerated-strength tests with the ma- the maturity index. and gion represented by the conic frustum defined by the t time interval. relationships tend to be less variable where both pull.100].2 Pullout tests are used to determine whether the in. and Carino and Tank [102] have shown that the equiva- Maturity Method lent age maturity function based on the Arrhenius equation accounts better for the effects of temperature on strength gain It is well known that the compressive strength of well-cured con. Tank and Carino [101]. The combined effect of time and temperature has been sic investigations to estimate the strength gain of concrete in studied by several investigators since 1904. others [93–95]. T0 datum temperature. te = ∑e [Q ((1/Ta )(1/Ts ))]∆t (7) tions. concrete members. Basically. or Saul maturity function. for example: is a linear function of temperature. and a standard was issued in 1987. mens are of similar size. that the datum temperature was 12. indicative of the strength of concrete within the re- Ts specified temperature. K. From his investigations. the increase in strength is Nurse-Saul maturity function. Freiesleben Hansen and Pederson [96] can be used to compute nated. perature as a function of time using thermocouples or ther- mistors embedded in the fresh concrete and connected to strip- Maturity Functions chart recorders or digital data recorders. the maturity method in 1984. Nurse [91]. Their ature above a datum temperature of 10°C (14°F). equivalent-age at a specified temperature as follows: In addition. These earlier these maturity meters monitor and record the concrete tem- studies have been extensively reviewed by Malhotra [95]. Hudson and Steele [104] used the maturity approach to predict lished. pullout strengths are indicative of the qual- Equation 7 is based on the Arrhenius equation. degree-days or de. Byfors [97]. In order to overcome some of the limitations of the Nurse- (2) forms and shores may be removed. turities for these tests. but no hypothesis was structures. Arrhenius equation have also become available. governed by many factors other than curing time. and strength of concrete during construction. The maturity method has been used to estimate the in-situ turity was advanced by McIntosh [90]. Plowman concluded mocouples or by instruments called maturity meters. 113. (2) post-tensioning of tendons.. F. ASTM International. E. I. research is needed to standard- ratory specimens cured under non-standard temperature ize those tests that determine properties other than strength. pulse velocity techniques. 1053. ASTM International. conditions. H. Vol. p. strength of the concrete mixture. p. 1221. [11] Spinner. organizations. “A Method of Determining Me- porting this claim. p. and time requirements. “Measuring Changes in Physical Properties of and the force applied at failure. 17. West Conshohocken. International Symposium on improve the accuracy of prediction of strength parameters of Nondestructive Testing of Material and Structures.108].” Proceedings. 1938. researchers in the United Kingdom developed [1] Rayleigh. disadvantage of the test is that it is confined to the testing of 1944. Some [9] Jones. PA. Dover Press. 1939.” Proceedings. . “Testing of Hardened Concrete: Nondestruc- Combined Methods tive Methods. PA. T. This procedure can be used to estimate the in-place strength of concrete to allow the start of critical construc. data disputing this claim are also available. but should be count the effects of early-age concrete temperature on the considered as additional techniques. When performed in con- long-term ultimate strength. accuracy of predicting compressive strength is only marginal. C. of one method. 52. Vol. Vol. Radar scanning and impact/pulse echo techniques appear to 3. Some case histories have been published sup. chanical Resonance Frequencies and for Calculating Elastic The use of more than one method to predict compressive Moduli from these Frequencies. 460. 1945. while others have suggested the use [10] Pickett. the surface of the concrete to remove laitance. “Problems in the Sonic Testing of more than one in situ/nondestructive testing technique to Plain Concrete. However. West Conshohocken. A number of these of cold weather protection. 1123–1129. 38. p. 131. the latter fails in tension. E. The cur. West Conshohocken. 846. pp. 41. PA.. concrete. and stress discussion by T. American Concrete Institute. C. L. New York. Pulloff Tests References In the mid-1970s. PA. West property.. G. also. Witte and W. RILEM. R. 1961.” Proceedings. 40.. PA. greasing the surface using a suitable solvent.. “Measuring Young’s Modulus of Elasticity by epoxy resin. the pulloff test involves bonding a circular steel 1941. p. The pulloff test is relatively simple to perform. 1. and Thawing Studies of Concrete. Non-Destructive Testing of Concrete. V. each measuring a different Prisms and Cylinders. P.. a tensile force is then applied to the steel disk. 45. PA. The major limitations of the maturity method are: (1) the be the most promising of these types of tests.. Prior to this bonding. 101. Although some test data have been published. No. Unless comprehensive correlations have been established 4. it is possible to obtain a Concrete by the Dynamic Method.” ASTM Bulletin. Theory of Sound. Considerable progress has been made over the past four tion activities such as: (1) removal of formwork and decades in the development and use of nondestructive meth- reshoring. and Higuchi. the use of the latter to concrete mixture. 1962. (3) termination ods for estimating strength of concrete. West Conshohocken. the surface layers of concrete. West Conshohocken. predict strength properties of concrete is not recommended. 20–22. “Discussion of Dynamic Methods of [106]. This procedure can be used to estimate strength of labo. T. methods have been standardized by ASTM. 2nd ed.” Proceedings. and Duvall. and Teftt. Willis and M. F. Paris.” Proceedings. concrete must be maintained in a condition that permits In-situ/nondestructive tests may not be considered as re- cement hydration. Vol. [7] Malhotra. 1940. Vol. and other ways to traffic. the use of [8] Kesler. the test has Testing Concrete with Suggestions for Standardization. After the epoxy [4] Hornibrook. 1976. W. [6] Stanton. West Conshohocken.. MALHOTRA ON NONDESTRUCTIVE TESTS 331 This standard is designated as ASTM Practice for Estimating instances but in general it is not advocated because of economy Concrete Strength by the Maturity Method (C 1074). and (3) this method needs to juction with standard core tests. de Reus.. PA. placements for the standard cylinder test. E. Y. 61. The significance and use statement as given in ASTM C 1074 is reproduced here: Concluding Remarks 1. J. Dec. p. 1954. and several new methods are in the process of 2. London. T. a surface pulloff test to estimate the in situ strength of concrete [2] Obert. MI. 9. “Application of Sonic Method to Freezing has cured. E.” Monograph No. Vol. Dec.” Pro- found little acceptance outside the United Kingdom. The proponents of this approach Flexural and Torsional Resonant Frequencies of Vibration of claim that the use of two methods. However. sandpaper is used to abrade Means of Sonic Vibrations.. W. between the strength parameters to be predicted and the erly determining the maturity function for the particular results of in-situ/nondestructive tests. In Europe in general and in Romania in particular.. Price. followed by de. W. B. M. The accuracy of the estimated strength depends on prop. ISO. 5. national. p. Because the tensile strength of the bond is greater than that of ASTM International. pp. ceedings. disk to the surface of the concrete under test by means of an [3] Powers. Detroit. ASTM Inter- measure of the tensile strength of concrete. 1945. (2) the method does not take into ac. ASTM International. S. discussion by L. also.” ASTM Bulletin.. ASTM Interna- strength of concrete may provide useful information in some tional. and (4) opening of the road. at failure is a direct measure of the tensile strength of concrete. Part II. can overcome the limitation associated with the use Conshohocken. they can provide additional be supplemented by other indications of the potential information and reduce the number of cores required for testing. and because the possible increase in the rent edition was approved in 1998 and published in 1999. W. ASTM International. p. From the area of the disk [5] Thomson. Cambridge Uni- researchers have suggested the use of rebound hammer and versity Press. “Equations for Computing Elastic Constants from of other combined methods. concrete has gained some credibility [107. the serious No. Briefly. “Tests Comparing the Modulus of Elasticity of Portland Cement Concrete as Determined by the Dynamic (Sonic) The test gives reproducible results and does not require plan- and Compression (Secant at 1000 psi) Methods. ning in advance of placing the concrete. being standardized. 32. G. Structures. Vol. 1988. No.. and Concrete. and Vol. No.” Proceedings. and Sandenaw. 1051. Wash- American Concrete Institute. PA.” man and Hall. A. and Kurtz. V.. T. CRC Press. 5. 1963. R. J. [43] Kolek. p. 433.. J. 2. p. Schlintz.. 14. J. Bureau of Mines. J. “Status Report on Windsor Probe Test System. and Cheesman.” Cement. M. N.332 TESTS AND PROPERTIES OF CONCRETE [12] Jones. Paris. H. [34] Cummings. “Non-destructive Method for Testing Con- Dynamic Modulus of Elasticity. Chapter 13 in [17] Shrivastava. p.” ACI SP- pp. perficial Hardness. “Powder Actuated Fastening Tools for Use in the Malhotra. American Concrete Institute. No.. American Concrete Institute. 1970. FL. 1951. Eds. Vol. M. E. J. ing Testing of Concrete.. 3. M. N. 201–228. [27] Jones. 1984. [24] Leslie. 1957. Vol. M. G. 47–68. “Dynamic Properties of Hardened [36] Carino. M. M. 1971. 2. 367.. Detroit. 9.” RI.. M. No. search Board. 27. “Dynamic Testing of Concrete with the Sonis. Gordon 29. P. Eds. “An Ultrasonic Method of [46] Zoldners. and Damping Coefficient of Concrete. Vol. E. the Quality of Concrete. R. 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CRC Press. V. Carino. G. W.. and Tank. American Concrete Strength Development of Concrete. PART IV Concrete Aggregates . 6 (No. lightweight. For in. and surface texture. Additionally. would have an FM of Grading about 7. In 1937 ASTM Committee D-4 methods and new test methods developed since publication of adopted ASTM D 448. way. in mil- to change. 4. The fineness modulus (FM) is an empirical figure derived tant and can lessen problems later in the concrete-making by adding the cumulative percentages retained on a specified process. Graves1 Preface ranges for each sieve size.375 in. Using such a system of its natural tendency to segregate during stockpiling. because and all openings are expressed in SI units. authored by materials from different localities and to allow for economical J. Size No. Jr. and each size is usually assigned an arbitrary number. 1 Senior Materials Scientist. 33. even slight changes can have an for Wire Cloth and Sieves for Testing Purposes.5 this chapter. These grading sizes are reflected to a great degree in ASTM C ing. 1.3 (No. [1]. and Surface Texture Robin E.). Introduction Test Method The basic procedure for determining grading is ASTM C 136. These size numbers are widely remain relevant to current concrete mixture technology. 337 . gregate in an attempt to bring uniformity within the industry. Unlike grading. the FM on coarse aggregate is less commonly used than the FM for fine aggregate where the eye may Definition not easily discern changes in grading.29 Grading.00.). 150 (6 in.75 in. which is largely used today for coarse aggregate by lation techniques for concrete mixture design. 30). THE CONTENTS gregates. lines on a graph can be spaced at porting. Shape. 19 (0. 100). the ASTM STP 169 editions. but the changes that can occur will be discussed in limetres.20 for a sizes of a given aggregate. A typical computation for the The items discussed here pertain to normal. 100 % have will be discussed in this chapter. However. and other forms of handling. 0. Shape and surface texture properties are not as likely series of sieves and dividing by 100. discussion is provided on recent Road and Bridge Construction.). because the aggregate as well as The FM of a coarse aggregate is computed in a similar other ingredients fit together as absolute volumes in the con. attention to constant intervals to represent the successive sizes. Specification for Concrete Ag- IN PREPARATION OF THIS CHAPTER. AL 35238. Note that each successive Grading changes are perhaps more prevalent than shape sieve is approximately one-half the opening of its predecessor and surface texture. chapter may be considered benign features because even a This is done basically by separating the material on a nest of well-trained eye may not be able to discern changes unless they sieves meeting the requirements of ASTM E 11. and heavyweight aggregates. would be retained on the smaller sieve sizes so a typical coarse aggregate. Chapter 35 of ASTM STP 169C.15 (No. Specification are in the extreme. This edition has been updated to include changes to test ing or producing aggregate. Until the early 1920s. ing the percent of each size present. Vulcan Materials Company.5 in. and determin- effect on the characteristics of concrete mixtures. ASTM C 33 states that Grading is simply the frequency distribution of the particle the FM shall not vary from the base by more than 0. gives a wide range for each sieve to accommodate of the prior edition. 8). new imaging technologies for characterization of particle grad. specifiers of concrete mixtures. these two attributes are not within (0. It should be noted that all sieves in the series are always crete mixture and in no other way [2]. time of introduction into the concrete mixture is very impor. Table 2. 0. 50). in the case of a coarse aggregate. used but other specifiers may have a different number formation on historical development of this subject area within assigned for virtually the same material. and 0.).). Obviously. E. that listed standard sizes of ag- research related to grading of manufactured fine aggregates. and the every detail of these phases from the time of processing to the fineness modulus can be computed [2].36 (No. trans. the reader is referred to the prior aggregate “sizes” were concocted by almost everyone specify- edition. The three attributes of concrete aggregates discussed in this Test Method for Sieve Analysis of Fine and Coarse Aggregates. 57 from ASTM C 33. Birmingham. the direct control of the user. However. have been retained since they continue to production considerations. This distribution is given in certain given source. Galloway. FM of a fine aggregate is shown in Table 1. 76 (3 in. and emerging computer simu. Therefore. The effect these changes considered.75 (No. 16).5 (1. Classification for Sizes of Aggregate for the prior edition. ASTM C 33. These sieves are. shape. and employing a log scale. 4). in the case of a coarse aggregate. 9. 2.18 (No. 37. lar aggregate from the same source has a demonstrated Figure 1 is a particle size distribution chart of combined performance record or. necessarily conform to one of the sizes in ASTM C 33. Fig. or coarse aggregate having a large deficiency or excess of any size fraction.18 (16) 23 39 0. provided it can be done in an economical manner. designer’s need to stay with one coarse aggregate size.36 (8) 15 16 1. 1—Particle size distribution of combined coarse and 0. improve workability. searched for in other areas or. Production at either extreme may statistically cause to achieve the desired combined grading. This succeeding paragraphs modify these limits considerably even would allow any grading the specifier chose and would not to the point of discarding the grading limits.) Retained Retained 4.15 (100) 11 fine aggregate showing a gap-graded aggregate mixture. to insure plier and the user. The scarcity of a particular sieve size could result Since the FM of the fine aggregate is used in computing the in poor workability and even poor durability of the concrete. signer from modifying the grading range. 2—Particle size distribution of combined coarse and gregates with discontinuous or gap grading have sometimes fine aggregate. the grading limits in ASTM C 33 are graded combinations of aggregate. mixture design in the solid volume process. and gregate in question has shown equal relevant properties. specifying Figure 2 is an example of a combined grading plotted on an more than one coarse aggregate size to be used. These gradings generally very broad to accommodate a wide variety of conditions. in many cases.77 FM circumstances and should only be considered by someone familiar with gap grading.3 (50) 16 74 0. gate meets the requirements of ASTM C 33. differences in particle shape and texture of the aggregates. This but the trend is to consider the aggregate as a composite in the fact is often overlooked and problems with workability are concrete mixture. There has decision. Size No.15 (100) 15 89 Fig. improve long-term performance of concrete mixtures [30]. are special showing a well-graded aggregate mixture [30]. the supplier should strive to produce to the midpoint of gradings often requires blending of three or more aggregates that range. (usually No. plotted on an “8 to 18” grading control chart. decrease susceptibility to shrinkage. but assumed.6 (30) 19 58 0.45 power curves. whether they are ASTM C 33 ranges or some well-graded aggregate combinations. In any are believed to decrease water demand. However. modification. although ag. is usually undesirable. 57) can easily lead to a gap-graded aggregate. and the effects of entrained air and amount of cementitious material contained in the concrete [3–26]. or any other “8 to 18” percent retained chart that is in use by some agencies. . been a move by some specifying agencies to require more well- As previously noted. the actual FM There have been efforts within ASTM to de-emphasize the was not determined originally. particular area. Percent Percent mm (No. A well-graded material is the closest to ideal with a representative amount on each standard sieve size listed in that size Significance specification. often in conjunction with other guidelines such as coarseness Once the ranges on each sieve are agreed upon by the sup. There the concrete fine aggregate also meets C 33 requirements. What then is the ideal grading? The influence of aggregate on the properties of concrete has been extensively discussed in the technical literature during the past 125 years and many methods for arriving at “optimum” or “ideal” gradings have been presented. and the local conditions. Experience has demonstrated that either very fine or very coarse sand. provided simi. none of these has been accepted as being universally applicable because of economic considerations.338 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Computation for the Fineness Modulus Cumulative Sieve Size.75 (4) 1 1 2. the 0. that is. That size While ASTM C 33 contains fine aggregate grading limits. These. however. if it can coarse and fine aggregate grading. Achieving these types of other.20 value would necessitate a redesign of the mixture. A proposed standard the product to fall out of the specification limits and result in problems with the concrete mixture. the are many qualifying adjectives in these statements and only combination in this example results in a gap-graded aggregate someone qualified to judge these equals should make the (notice the significant peak-valley arrangement). 277 277 divided by 100 2. It is not meant to prohibit the concrete de. changes beyond The following paragraphs address coarse and fine aggregates. adjustments should be made to accommodate reduce segregation. Although the coarse aggre- be shown that concrete of the class specified made with the ag. and workability factors [31] and 0. in the absence of such record. been used to advantage [27–29]. 57. the less handling.5 mm (0. maximum aggregate size [37].5 mm 50 mm 76 mm 150 mm NON-AIR-ENTRAINED CONCRETE Water.5 1 0. 19 mm (0.3.) for the 42 MPa prohibits more than 45 % passing any one sieve and retained (6092 psi) level.5 in. spacing of reinforcement.34]. Because it is not practical to produce aggregate that is per- gate “size” to be used and is dependent on thickness of sec.5 0. Working in conjunc- . The grading in MPa (4061 psi) level. harshness.36]. it is not possible to obtain ments other than grading.3 and 3. %c 100 62 54 49 44 40 37 34 28 Entrapped air. Quantities listed can be reduced significantly through the addition of water-reducing admixture. proper attention needs to be given to the smallest sieve opening through which the entire amount of those procedures to avoid problems in the concrete mixture. using aggregate above 76 mm (3 in.5 in.3 0. The coarse aggregate was not des. Simply put. smaller maximum aggregate sizes must be tive material containing these sizes. ASTM C 125.) for strength on the next consecutive sieve shown in the standard grading.) in size.2 AIR-ENTRAINED CONCRETE Water. the fine aggregate cannot be too coarse or cementitious content of the concrete can be progressively re. and some- placement procedures (aggregates greater than 63 mm (2.5 mm 19 mm 25 mm 37.) become more difficult to pump).5 in. tion. Also. b Cement required in kilograms per cubic metre for 0. entrained air contents listed in Table 2 [38].53 water/cement ratio by weight. strengths above a practical level of 35 MPa (5076 psi) with the ignated by size number but rather by maximum size [33]. and segregation may occur. kg/m3b 520 430 406 382 360 334 316 302 262 Fine aggregate.5 mm 12. SHAPE. and nominal maximum size as Obviously. therefore. Terminology Relating to problem mentioned earlier due to poor stockpiling or handling Concrete and Concrete Aggregates.75 in. aggregate particles and retain sufficient fluidity for placement For compressive strengths below 21 MPa (3046 psi). and There will be some finer material due to breakage. Therefore. no cementitious material can be saved by ASTM C 33 is usually satisfactory.1. %c 100 58 50 45 40 37 34 31 25 Total air. These deviations The terms “maximum size” and “nominal maximum size” are not normally significant when compared to the segregation should be understood.5 4 3. d Recommended average total percentage of entrained air required for frost resistance from Table 5. availability. in some cases. the purposes.3 of ACI Recommended Practice for Selecting Proportions for Normal and Heavy Weight Concrete (ACI 211. c Approximate percentage of fine aggregate of total aggregate by absolute volume. This matrix needs to coat the coarse where this does not hold true. and 9.5 2 1. the more mortar needed in the mix to sur. AND SURFACE TEXTURE 339 TABLE 2—Mortar Requirements for Workable Concrete With Various Maximum Aggregate Sizes Maximum Size 4. ranges are given in grading specifications.375–0. defines maximum size as practices. This is still the “starting point” of selecting the coarse aggre. There are limits on both ends coarse aggregate resides. Along with aggregate size the more surface area is present for a given the water and cement (and. time. kg/m3a 245 201 192 177 169 157 148 139 118 Cement. and it is for this rea- The importance of grading has long been recognized. Thus.5–12. but as previously mentioned. bleeding. At the same duced as the maximum aggregate size is increased while main. % 6 3 2.5 3 a Approximate amount of mixing in kilograms per cubic metre required for 75-mm slump with well-shaped angular coarse aggregate. At the 28 ditional water and also may result in segregation. kg/m3b 462 380 362 334 318 296 279 262 222 Fine aggregate. the additional surface area will require ad- taining a constant water/cement ratio and strength.5 mm (0. the less likely segregation will the smallest sieve opening through which the entire amount of occur.1). The son that it is not possible to obtain high strengths with large original issue of ASTM C 33 in 1921 had very few require. aggregate is required to pass. practice from the Strategic Highway Research Program [32] In the production of high-strength concrete above 42 MPa will result in the most densely packed system and minimum (6092 psi).75 Aggregate (sand) 9. ASTM C 33 also for the 35 MPa (5076 psi) level. there seems to be no advantage in using maximum void content for the aggregates under consideration. mixtures). the smaller the of concrete than does coarse aggregate grading [39].5 times some coarser material due to screen wear or the use of in.5 mm (1. %d 13 8 7 6 5 4. also limits its FM to between 2. A large particle of aggregate has less area for bonding with the mortar than an Coarse Aggregate equal mass of smaller aggregate particles. the fine aggregate comprises the matrix in which the round the aggregate particle. It above the 42 MPa (6092 psi) level [29. aggregate size below 12. other mineral ad- value and. aggregate is permitted to pass. As the strength deviations are permitted because certain areas do not have na- level is increased. The importance of maximum size is illustrated in Table 2 Fine Aggregate that shows the relationship to aggregate size and the amount Fine aggregate grading has a much greater effect on workability of water and cement needed [2]. kg/m3a 276 228 216 202 192 177 168 160 139 Cement. GRAVES ON GRADING. if it is too fine.) In addition to the grading requirement. economics. screens slightly larger than the specified size.) [35. fectly separated. used for the most efficient use of cement with 37. 15-mm (No. but of different axial proportions. medium. other agencies such as the American Railway workability will probably result. and obtain concrete of satisfactory workability roundness and sphericity of 1—the maximum value. If the grading varies considerably. at least 15 % should be passing the 0. and form. A more thorough discussion of how these dimensions interrelate is provided by Ozol [46]. matical sense. promote or inhibit development of the graded and somewhat on the fine side. 100) sieve will cause a sig. tinguishes between particles of the same numerical sphericity nificant reduction in air content [41]. However. with the proper amounts of entrained air. good control calls for a Association and the various State transportation departments constant check on the grading and computation of the FM. its coincidence to the outer sphere. depositional environments.15-mm (No. Significant the smallest circumscribing ellipsoid. and short axes of the particle. corners of a fragment.2 allowed in ASTM C 33. However. but not defined rigorously.3-mm (No.6-mm (No. and bleeding of concrete. erty may. or can affect the air entrainment of the concrete. The fine aggregate must be well. Sphericity is a measure of how nearly equal are the three The amount passing the 0. Test Method for Flat Particles. crushing equipment used. or the degree to which the contour of a ever. The material may well stay particular grading by a different size number. 50) and 0. ASTM C 33 is the docu- Regardless of the grading used. 50) sieve. Thus. and potential for increased shrinkage continue to Particles. The spheres may may be realized through the use of air entrainment in concrete. manufactured sands re.3-mm (No. fluctuations in these sieve sizes portions of the long.0 produced the best workability and highest ideas. sphericity. The form of Folk [44] or the alternative shape factor of Fine aggregate particles passing the 0. factors such as fication being followed. Manufactured Fine Aggregate Research The shape of natural coarse and fine aggregates is influ- A substantial amount of research has been conducted in recent enced by geologic factors such as transport mechanisms and years to evaluate alternative gradings of manufactured fine ag. by the type of (up to 18 %) can benefit concrete mixture rheology and work. it has been found that a coarse sand with The concept of particle shape incorporates three geometrical an FM of around 3. or a spheres coincide. roundness. namely. As noted throughout this discussion.340 TESTS AND PROPERTIES OF CONCRETE tion with the fine aggregate grading is its particle shape that Specifications will be discussed later. For the high cement contents used in the production of Definition high-strength concrete. The shape of manufactured coarse gregate for use in concrete mixtures [42]. A desirable shape is one utilizing high fines manufactured fine aggregate in concrete that is round or a near perfect cube. proper characterization methods provides definitions for particle shape. 30) to Ashenbrenner [45] is a measure of the relationship between the 0. How. Poorly shaped aggregate pavement sections have shown good potential for successful is more difficult to define and depends largely on the speci- use of these materials [43]. appropriate admixture type and dosage to offset increased wa. Form or shape factor dis- amounts passing the 0. sion) exceeds the width by a specified ratio. or may not be concentric. 200) particles particle during mining (blasting) operations. In general.15-mm (No. thickness by a specified ratio. Additionally. particle fits the curvature of the largest sphere that can be con- sired. 100) sieve [39]. The congruence of the particle In addition to a reduction in the amount of fine aggregate that boundary to the inner sphere is an indication of roundness and may be accomplished for a given set of materials and grading. and a minimum of 3 % passing the 0. Field trials as the speed of feed to the crusher. within the grading limits. ment used to specify grading by most architects and engi- portant. A flat particle is one to insure that the fine particles primarily are composed of dust in which the width (intermediate dimension) exceeds the of fracture without deleterious clay mineral components are thickness (minimum dimension) by a specified ratio. in that a process that affects the expression of one prop- fine aggregate contents. The ASTM subcommittee with jurisdiction gated particle is one in which the length (maximum dimen- over C 33 currently is reviewing these research results and con. be researched. Roundness is a measure of the sharpness of the edges and where mechanical finishing is used such as in pavements. by the analogy of an irregular solid Grading Effect on Air Entrainment within which is a sphere of the largest possible size and around Table 2 shows the reduction in fine aggregate percentages that which is a sphere of the smallest possible size. 100) sieves entrain more air than either the finer three dimensions of a particle based on ratios between the pro- or coarser particles. Sphericity and roundness can be visualized conveniently. The lower limit of 10 % in ASTM sphere whose diameter is the maximum dimension of the par- C 33 may be satisfactory where placing conditions are easy or ticle. Therefore.3-mm (No. that are distinct compressive strength [35]. based on the degree to which 100) sieves have a greater influence on workability. This research has and fine aggregates is influenced by the natural breakage of the shown that increased levels of minus 75-m (No. Elongated ter demand. Many of these This is particularly true with fine aggregate where changes can specifications are very similar to ASTM C 33 but may call a occur without it being obvious. the 0. consistency is most im. the volume of a particle fills the volume of a circumscribed ture. but the FM may vary more than the 0. 50) sieve tained within the particle. When the it is sometimes possible to use a coarser or finer grading. They may be linked properties in the geological Concrete for pumping must be very workable. axes or dimensions of a particle. ASTM D 4791. the sphericity. the particle itself is a sphere with both a jump grading. with high sense. An elon- being evaluated. Changes have been noted over a Shape range as much as 1. surface tex. concurrently. or Flat and Elongated Particles in Coarse Aggregate. Specifications typically use . may have their own grading specifications. or by the processing techniques such ability without compromising concrete properties. with 15 to 30 % passing others.15-mm (No. where hand finishing is used and a smooth texture is de. A flat and sidering adoption of alternative manufactured fine aggregate elongated particle is one in which the length exceeds the grading specifications. and separately definable properties in the abstract or mathe- quire more fines than natural sands for equal workability [22].0 in FM in a day’s production [40]. problems with neers. Those shapes are a If the number of poorly shaped particles is not too great. handling. and the use of less on the part of the operator. distribution of stresses. the use of crushed stone ticles above the prescribed ratio. the strength of the concrete 4791 are under the jurisdiction of ASTM Committee D 4 and might be significantly lowered because of the lack of this thin are used primarily on aggregates for asphaltic concrete. large use of good gravel aggregate in the past method used by the U. Test Method for Uncompacted Void Con. may cle shape changing after trial mixtures are made or during the yield particles more elongated or flatter than equidimensional. ding. such as joints. Therefore. This is especially critical in pumped concrete where With crushed stone. are a function of the ter-reducing admixtures. aggregate particle shape should be one of the areas to be investigated. cur. The question then becomes what size and frequency of the cracks initiated by the action of shock quantity is considered too great? ASTM C 33 does not have any waves on the smaller-scale flaws and discontinuities of the rock requirements with regard to this attribute. the original would have an ideal shape factor. and current research is focusing on correla. features of the bedrock. the particle orientation may in- There are no ASTM test methods at the present time for deter. of the natural deposits. GRAVES ON GRADING. or Rounded gravels that were rounded by eons of rolling to the as-received grading. schistosity. and the final have limits generally ranging between 8 and 20 % maximum shapes of the particles are influenced strongly by preferred ori- allowable on a 3:1 ratio. however. stream action. There are other methods that have than ideal-shaped material will increase [54]. shape and surface texture [48–52]. have joined together to limit the use of what is still left method is effective in determining the mass or number of par. that were then exploited The shape of the aggregate particle influences the fresh and by glacial action. ing to find a source of relatively round to cubical-shaped ag- tent of Fine Aggregate (as Influenced by Particle Shape. but additionally. entations of any sort contributing to anisotropy. naturally occurring materials is less pronounced than with Considerable research has been conducted in recent years crushed materials [46]. Rocks with bed- One of the problems related to particle shape is the parti. The form and sphericity of aggregates are primarily the re- gates in concrete mixtures. coupled with stricter zoning laws. tions of these improved techniques with performance of aggre.. Test Method In the hardened concrete. If all particles were spheres or cubes. and comparing the resultant mass with the product. the ease with which they move in the probably most strongly controlled by its mineral grain shape in mixing and handling processes become increasingly more dif. the case of gravels. For instance. the method becomes tedious and. These 50 years. In the case of natural sands. the analogous “original” particle shape workability is of extreme importance. The characteristics of crush- . Some other speci. As the particles become particle shape. the original particle shape is controlled by larger-scale structural features of the bed rock. While the rying. that is. Therefore. face Texture. 3:1. been developed (see Ozol [46]). easily than fine ones and roundness increases with size [56]. elasticity. Similarly. the importance of try- ASTM C 1252. its shape prior to transportation. In computer simulation techniques [53]. Significance fractures. Relationships between these Conway [55] found that the sphericity in all cases increased with characterization techniques and existing ASTM methods have increasing sieve size [46]. the use of designing techniques. The test may be con. for more economic gain than quar- specification on a 2:1. ficult. lower elevations along stream or river banks will not be re- With regard to coarse aggregate. the use of synthetic or reclaimed material and time-consuming and can lead to carelessness or lethargy as aggregates will become more prevalent. mineral cleavage. ASTM D 4791 may be placed in the foreseeable future. research into effects of sult of the degree of anisotropy of the material and the origi- aggregate shape and texture on concrete mixtures properties is nal shape of the particle. when workability problems oc- shapes. individual size fractions. AND SURFACE TEXTURE 341 limiting ratios of either 3:1 or 5:1 to describe undesirable unauthorized water. It consists of drop. Army Corps of Engineers [47]. Some state transportation agencies follow a similar and. we chemical weathering. if such a thin. Additionally. and transporting [46].S. more critically. The rapid development used. shale partings. as-sup- on digital imaging techniques for characterization of aggregate plied coarse aggregates (two gravels and three crushed stones). SHAPE. is that produced by blasting of the bedrock. and use of land. can still produce a quality end known volume. with respect to this property. the parent material. The need for increased workability is Equigranular rocks with no preferred orientations tend to yield solved many times on the job by the addition of unwanted and more cubical particles on crushing. was more elongated or flatter. ducted using a standard grading. should the source be marginal measuring particle shape of fine aggregate. particle’s ability to carry the stress. and the mining particle shape directly. ping the test material from a prescribed height into a vessel of including the use of admixtures. although the relationship in herein are those in more common use. difficult. that is. on the order of magnitude of the grain sizes. or 5:1 limiting ratio basis. This method and D were introduced on that particle. the ones described Sphericity increases with size. therefore. the shape prior to the outside being conducted using X-ray tomography and sophisticated influence of blasting. Test Method for Index was oriented in the hardened concrete where outside stresses of Aggregate Particle Shape and Texture. provides an indirect method of As previously mentioned. Most of the shot fying agencies such as State transportation departments do rock requires further size reduction by crushing. flat particle lishes a particle index is ASTM D 3398. Sur. etc. complex function of the influence of the large-scale structural the workability problems may be overcome with the use of wa. and mechanical (frost) and hardened concrete. course of the project. sizing. and bedding planes. faults. coarser grains round more been investigated. This may become necessary because in some areas lo- theoretical solid mass of material filling the vessel’s volume to cating good naturally occurring aggregates is becoming more calculate the uncompacted void content. In a study of the shape of various. noise and dust pol- methods require that the technician measure each individual lution laws. and Grading). stricter permit requirements. particle in a set of proportional calipers set up according to the particularly in urban areas. An indirect method that estab. Thus. gregates is vital. fluence compressive and flexural strengths. or impeller-type machines. Additional elements of surface days to 27 % difference at six months. the characteristic Significance should be taken into account in the concrete design. the strength of the bondless concrete de- asperities) or coarse grained or fine grained (loosely referring creased with age from 19 % difference (or reduction) at seven to the spacing of the grains). or cone crusher) type. R A/a. There are several methods for measuring surface texture [59]. with an av- definition. the statistics of the height distribution of the of the bondless concrete increased with age as a percent of population of asperities and their frequency of occurrence the control. Under conditions of tension. The elimination of ad- The surface texture of an aggregate particle is the degree to hesion between the mortar and the coarse aggregate reduced which the surface may be defined relative to arbitrary numbers compressive strength by an average of about 23 %. other work by Kaplan [61] found that among the factors of angularity. Darwin and Slate [63] and others [64. texture. This ASTM C 33 does not have any limitation on particle shape for probably can be attributed to the extra mechanical interlock either fine or coarse aggregates. X-ray tomography and com- of cleavage or cracks. hesion and “keying” (or mechanical interlock) by compressive lized in asphaltic concrete specifications. simulations will lead to improved aggregate characterization It is obvious that it certainly does not affect the workability of and better understanding of their effects on concrete mixtures the concrete to the degree that grading and particle shape do. rubbing. it was concluded that surface tex- edly. A bond strength have endeavored to test the interface in as rough surface (in the sense of degree of relief) does not neces. Various specimen configurations and techniques lent dimensions—it may or may not. The two properties are not for measuring aggregate-cement bond strength have been re- related functionally but depend on the relative amplitude and viewed by Alexander et al. and elongation indexes. and (2) the amount of surface Investigations along similar lines have been conducted by area per unit of dimensional or projected area. and (2) the amount of surface area available for . However. Studies focusing further on the components of the adhe- zel [57. as well as their morphology. in the future. and (possibly) solution incident to cles. while universally recognized methods of measurement are not at hand. There are no laboratory opera- lent throughputs. That ef. that is. The round.342 TESTS AND PROPERTIES OF CONCRETE ing equipment also influence the particle shape of the rock be. urement will be affected by the relative textures. chipping. the over an area. These are research methods. include the lateral and vertical irregularity of the erage reduction of about 17 %. is variously defined de. [66]. to all aspects of the concrete and. variably involves some measure of the deviation of a profile of ing crushed. The latter prop. Compared as being rough or smooth (loosely referring to the height of the to the control. tributions. ability of particular mineral rock fragments depends directly As mentioned previously under the discussion of particle on their hardness and toughness and inversely on the presence shape. terization of aggregate surface textures and their effects on The shape then becomes an important factor with regard concrete properties. which would produce more nearly cubical particles at equiva. for particle shape of fine aggregate. untreated aggregate. At six months. the greater the reduction ratio. although it is the ratio of areas. the strength roughness. and a is the apparent or projected area. and ASTM D 4791 for Patten [62] investigated the relative contributions of ad- coarse aggregate. in both a “bondless” (or surface-treated) and an untreated condition. However. ranging from 6 to 28 % difference.58] as the roughness factor. flakiness. Generally. which tend to induce fracturing.65]. whereas at seven days. the more the surface from a hypothetical reference surface [46]. advances in digital imaging. any flow test using time as a part of the meas- their transportation and to the site of deposition. in the high-strength series. aggregate was 92 % of the strength of the concrete with the ponent of surface texture: (1) the degree of the surface relief. pure a state of tension as possible to avoid mechanical con- sarily have more surface area than a smooth surface of equiva. derives. technological advances in imaging methods and computer ture has no appreciable effect on the workability of concrete. where A is the true sive force making up the percent contribution of adhesion to (real) surface area. these methods primarily are uti. The criterion by which one surface is designated rougher hesion. erty. and increased surface area available for bond in the rough ASTM C 1252 has been developed and an indirect test method texture. but almost in. Therefore. has been defined by Wen. puter simulation techniques also are being utilized for charac- ing what rounding had been accomplished [46]. but in this case. a rough-textured particle will rub against contributing to their form and sphericity. negat. not easily incorporated into a concise comprehensive less affected. tional procedures. In work done by Kaplan [60]. gyrator. that is. The object was to eliminate adhesive bonds with- Surface Texture out affecting the mechanical interlock (or physical keying) between the aggregate and the mortar. it was 79 %. Tensile strength was texture. in terms of their reliefs. other similar particles and not flow as readily as smooth parti- attrition. the abrasion. and no limitations and tensile strength measurements of concrete at five differ- are under consideration for fine or coarse aggregate particle ent ages in which the same coarse aggregate had been used shape within the ASTM C 33 specification. Test Method fect is less pronounced with impact. Undoubt. The coarse aggregate Definition was coated with a mold release agent. frequency of the asperities on the surfaces being compared the total adhesive force is the product of: (1) the specific ad- [46]. except that the tests measuring shape by one Rounding of sand and gravel particles is chiefly the result of the flow tests are indirectly influenced by the particle tex- of those geologic factors that were of secondary importance in ture. flat or elongated the product—slightly more so if the machine is of the compression (jaw. For example. area of surface from whatever physicochemical mechanism it pending on the intended use of the information. the strength of the adhesive force per unit than another. that is. As previously mentioned. splitting tensile strength of the concrete with the bondless Two independent geometric properties are the bias com. Specification the texture had the largest effect on compressive strength. also called roughness or rugosity. not affecting point of interfering with the production of quality concrete the bond. If the water-cement ratio is to be maintained (and this part of the soil on which the stockpile rests is picked up. coatings are for the most part unde. there is more interface with which the mortar may inter- finer than the 75-m (No. because this is done during the desirable because they interfere with the bond between the ag. and can be re- whether it be foreign or fine material of the same mineralogy combined at the time they are introduced into the mixer or can as the parent particle. If such adherence is strong. no specifications cur- does not increase the chances of contamination. washing or scrubbing may be necessary. act. Many Coatings are defined as any material adhering to the particle times. GRAVES ON GRADING. There are no standard ASTM test methods cessing. plants now use a dust suppressant for ecological reasons. a rough texture increases the propensity to gate. 200) Sieve in Mineral Aggregates by Washing. 200) sieve for fine and coarse aggre. vation. un- other factors will have come into play. efflorescence. However. two coarse aggregate sizes are preferable. adheres to the material. processing procedures or may be due to a natural weathering Variations in the grading can change the surface area that is to of the rock. . Coatings can result as an inherent feature of the parent rock. depending on the economics involved. washing the aggregate usually removes coat. Continuous attention to grad- stockpiles where the material may be stored in a wet condition ing is of paramount importance. If process and. may be necessary. Choosing sizes that do not Coatings range at the extremes of the grading scale will help. the loader scoop gets too low and sistency. One The texture of aggregate particles has no appreciable effect common coating is iron sulfide that stains the concrete. particles could affect the stresses in the concrete mass leading sulting from fracture and may be eliminated during the pro. sign and trial mix stages. with an increased surface ASTM C 33 contains limits for the amount of material area. Segregation of coarse aggregate during the handling process can be a major problem. within ASTM C 33. gate particle shape. therefore. and dust from passing traffic. cal interlock with the matrix and. This. with retain undesirable coatings. SHAPE. This is rides and sulfates can also cause staining. and probably because the rough texture presents a better mechani- premature corrosion of imbedded reinforcing steel. present different true surface areas fine aggregate grading that is not discernable by casual obser- available for bonding [73]. From either of alternative gradings for these materials in the future. A possible explanation is Grading has a significant effect on concrete mixture propor- that the bond is chemical and its specific adhesion differs sig. or formance can be demonstrated. This amount is determined by sieving procedures. be coated with mortar and. ASTM D 4791 may be used to evaluate flat and elongated par- Therefore. require more water for the same con- the operator is not careful. generally satisfactory and may be used in several different eral surface [70. Alternative gradings bond is chemical but its specific adhesion on the smallest are permitted by C 33 provided that acceptable concrete per- unit area basis does not differ greatly between minerals. Alternative possibilities are that (1) the combinations to achieve desired results. ing has a strong adherence. therefore. the orientation of the coarse is not generally washed. Flat and elongated particles do not operator loading the material (usually with a front-end loader) “roll” as well as rounded or cubical particles during the mixing into trucks for transportation to the concrete holding bins. The fine ag- plastic soils. In the hardened concrete. gregate particle shape is just as important as the coarse aggre- Fortunately. Recent and ongoing research (2) the bond is physical [72]. variations in the grading (surface gregate and cement paste. in the case of gravels that have been washed during by ASTM C 1252 requires about one additional gallon of water the grading process. thus becoming less economical. is usually mandatory). all other things being main- cessing presents a problem. In the case of crushed stone that tained. surfaces of different lithologies have different roughness fac. or wind-borne dust coats the top Particle shape also has a significant effect on both fresh layer. AND SURFACE TEXTURE 343 bonding over which the adhesive force acts. If the coating is something that is tightly adhering. come dissolved in the matrix with undesirable results. The fineness modulus is one way to maintain a check on the tors [46] and. area) change the amount of optimum mortar and can lead to One of the more common forms of coatings occurs in the addition of unwanted water. Some coatings are a result of mining or be added separately. only careless contamination after pro. coated aggregate is important to ensure a good quality concrete. Different rock Summary types have been observed to have different tensile bond strengths to cement paste [67–69]. but adding fines to the matrix. to reduced strength. measure texture and the fact that when texture reaches the Also. The gradings listed in ASTM C 33 are nificantly according to the particular chemistry of the min. Test Method for Materials Finer than handling. probably due to the fact that there is no easy way to may be chemically reactive to the point of staining the concrete. Unfortunately. particularly with fine aggregate. any coatings are usually the dust re. The main these possibilities. but more often coatings are a result of care- Specification lessness during the stockpiling or handling phases. on workability but does affect compressive strength. then more cement needs to be used for in turn. an alternative hypothesis to explain differ. In any case. Another common problem can be the carelessness of an and hardened concrete. At the same time. per cubic yard for the same slump. rently are provided for either fine or coarse aggregate shape Soluble coatings also present a problem because they be. in the case of clay or the same strength. A 1 % increase in void content as measured ings and. tioning and workability. precautions should be taken so that this material ticles within coarse aggregate. Therefore. unless the coat- more accurate values obtained by wet sieving in accor. concern with regard to aggregate grading is inconsistency and ences in bond strength between different rock types is that the ability to detect changes. Coatings can ASTM C 33 is silent with regard to requirements for surface prevent the matrix from adhering to the aggregate particle and texture. it may loosen during processing or dance with ASTM C 117. at this time that measure the particle shape of fine aggregate. clean. Chlo. washing or scrubbing the 75-m (No. coating fines may simply mix into the matrix. deriving from the same sorts of on manufactured fine aggregate may lead to specifications for forces that hold materials together in general. contaminates the aggregate and. attention must be directed to void content tests. Most crushed-stone Therefore.71]. 92. Ameri. Properties of Concrete and Concrete-Making Materials. E. 62. Army Corps of Grand Barrages. and Grading of properties in the future. 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Grading and bulk density are typically easily deter- of the volume of the mixture. moisture. It is substantially a revision of the work of Land. absorption. physical and mechanical properties. Pore Structure. size. with an update of the terminol. Absorption. the American Associa- Introduction tion of State Highway and Transportation Officials. bulk density. but absolute volumes of the cement. For some and/or irregular surfaces. This value usually is Absolute Volume not required until after mixture proportions have been estab- Mass of Material lished. Aggregate physical properties can vary by aggregate source. Levy Company. and 227 kg (500 lb). size. The volume of solids in the mixture. and air. such as “relative the particle surfaces (free moisture). Aggregate surface moisture. and surface 2. mineralogy. Relative Density (Specific Gravity). The aggregate is a collection of mined for almost all aggregates. by Timms [2] in ASTM STP 169 and the revised articles by 5. Fortunately. the aggregate will occupy approximately 80 % grading. C. aggregates. materials. type. Edw. ogy and the addition of a discussion on the importance of 4. When these properties change significantly. For most aggregates. because of its effect upon the volume of mix pore structure. and prior to batching concrete. and Surface Moisture John J. and others. with a cementitious content of ally identified are relative density. ASTM STP 169B remains pertinent and is included in the Aggregates used in concrete are usually identified by their chapter. it will be The absolute volume is computed from a materials mass and necessary to make adjustments to the concrete mixture. Because the particles do not sorption may not be readily determined because of surface fit together well. In this method the vol. rive at workable concrete mixture proportions for these aggre- ter in the pores of individual particles (absorbed water) and on gates through the use of alternative means. 1.1 Preface To determine the proportions of ingredients in a concrete mixture. absorption. the relative density and ab- ternal pores that will hold water. a useful factor in concrete mix- gren [1] in ASTM STP 169C. since most mixtures are designed with the aggregate in Relative Density of Material Bulk Density of Water a saturated surface dry condition. Absorption. the aggregate particles are coated with a paste film. while the determination of the various sizes of irregularly shaped particles often with rough relative density and absorption can be more difficult.30 Bulk Density. A common procedure for proportioning concrete mix. The particles almost always have in. tures is the Absolute Volume Method. relative density as follows [5]: The primary variable in most concrete production is the surface moisture content of the aggregate. admixtures (when applicable). and surface texture for some aggregate). Aggregate relative density. which constitutes part of the Brink and Timms [3] in ASTM STP 169A and by Mullen [4] in mixing water. the physical properties that are usu- In a typical concrete mixture. porous or lightweight aggregates. Jr. These properties are defined by standard specifications and test methods adopted by agencies such as ASTM International. density factors” [6]. the following factors THIS CHAPTER DISCUSSES THE APPLICATION AND should be known: provides some insight into the background of the test proce. water (exclusive of that in the can vary by ledge. Typi- ume (yield) of freshly mixed concrete is equal to the sum of the cally these values are relatively stable for a given aggregate. 3. ture proportioning and control. The volume of voids that will be filled with paste such that dures for the basic aggregate properties of bulk density. spaces are left between them called voids. roughness and high porosity. and surface texture. relative density (specific gravity). it is possible to ar- Even in desert conditions the aggregate probably contains wa. pit location. Yzenas. The information from the original article water added. Corrections for changes in 1 Director—Technical Services/Steel Mill Services Group. Indiana 46368. 346 . shape. grading. while that per- gregate mobility between particles of different shapes and centage may exceed 50 % for compacted single-size angular texture is shown in Fig. son [10] and by Weymouth [11]. Fig. It is possible to form a pile of un. compacted single-size spheres may have a void volume of aggregate bulk density. highly porous particles. For exam- or of concrete aggregate when making a standard test for ple. such as slag or lightweight aggregates can have extremely rough surfaces. It is well known that a compacted sample past one another when manipulated. ticles. roundness. Their larger surface area per unit volume (Fig. used the terms sphericity. It is also recognized that aggregates having the same grading may vary widely in shape. in ASTM STP 169A. and short pore of coarse aggregate. The maximum size of the ume to solids volume affects the workability of fresh concrete aggregate used in a mixture and its range of individual sizes as well as the proportion of coarse aggregate that may be both affect bulk density significantly and can slightly affect ab- used in a mixture. subangular. that is. natural sands or gravels have smooth surfaces. The last “b/b0” procedure for concrete mixture proportioning. the ease with which aggregate particles move shape and grading. The particle shape and texture of the aggregate affect its Aggregate packing can also be affected by both particle mobility. containing a range of particle sizes will result in a void content fects the energy required for compaction either of concrete smaller than one comprised of single-size particles. small particles fit into the voids between larger parti- fined glass marbles can be piled only one particle deep. applied three properties can change because small particles have a packing concepts to concrete mixture proportioning. Ozol [8] also expanded on the discussion of shape and texture in ASTM STP 169B. 1—Aggregate mobility affected by shape and surface texture. angularity. When graded particles with several sizes are com- confined crushed stone several particles deep while uncon. highly porous particles of lightweight aggregate Fig. PORE STRUCTURE. a greater exposure measure of packing density was the dry rodded bulk density of pore openings to the entrance of water. or angular. Visual evidence of differences in ag. and surface texture or roughness. Generally. Aggregate Shape and Texture It is generally recognized that aggregate particles come in various sizes that are described for engineering identification purposes by separation on square-opening sieves. ABSORPTION. They have been abraded and polished by wind. Mather [7]. and relative density. free or surface moisture. The shapes within the grading may vary between rounded. smoothness. water. and roughness as descriptors in discussing shape and surface texture of aggregate par. . pacted. Crushed. Aggregate mobility af. The cles. lengths. or glacial transportation. AND MOISTURE 347 the surface moisture content are made routinely without changing the basic concrete mixture. 1. Classic studies in this area are those by Fuller and Thomp- mobility of an aggregate and the ratio of aggregate voids vol. Goldbeck and Gray [9]. 2—Surface area versus particle size at equal volumes. Small. YZENAS ON DENSITY. Crushed or manufactured aggregates generally have rougher surfaces and greater angularity than natural sands and gravels. particles. 2). less than 30 % of the total aggregate volume. Mineralogy and porosity of the source rock as well as natural polishing all contribute to the final surface texture. in their landmark sorption. The surface of aggregate particles can vary from smooth to rough and irregular. above. 110 5°C (230 9°F) prior to testing. inal maximum size greater than 37. ASTM Specification for Concrete Aggregates (C 33). Skokie. un- The test method outlines procedures for compacted and derwater. The bulk density. Graded aggregates pack more densely than one-sized ag- gates is required. by means of a shovel or scoop. ASTM C 29c Heavyweight 1760 to 4640 (110 to 290) compacted PCAb a ASTM Specification for Lightweight Aggregates for Insulating Concrete (C 332). hence they are particularly useful in showing the need being 100 L (3 12⁄ ft3) for a 125 mm (5 in. the distribution of the themselves in a densely compacted condition replaces the particles. the other decreases. The compact bulk density is Aggregates are sometimes classified in terms of their bulk determined by the rodding (as described in the next para.8 L (11⁄ 0 ft3) for fine aggregate with a lations of grout quantities required for pre-placed aggregate maximum size of less than 12. and 2. friable lightweight aggregate that may be broken by tain aggregate packings. and Compaction usually is accomplished by rodding aggre. kg/m3 (lb/ft3) Compaction Mode Bulk density Source Insulating 96 to196 (6 to 12) dry loose ASTM C 332a Lightweight for masonry 880 to 1120 (55 to 70) dry loose ASTM C 331a Lightweight for concrete 880 to 1120 (55 to 70) dry loose ASTM C 330a Air cooled slag 1120 (70) compacted ASTM C 33a Normal weight 1200 to 1760 (75 to 110) compacted PCAb. The volume of the required measuring container de. arrangement of the particles as discussed previously. Finally the measure is filled to overflowing and rodded again in the manner previously mentioned. than angular particles. in such a way as to in ASTM Test Method for Bulk Density and Voids in Aggregate balance projections and depressions in the upper surface.” is directly lating the ratio of void volume to the volume of a bulk density. Compaction is accomplished by filling the gregates because small particles fill the voids between measure one-third full and then leveling the surface with the fin. concrete where work must be completely underground. when one increases.5 mm (1 12⁄ in. TABLE 1—Bulk Density Classification for Aggregates Aggregate Classification Relative density Range. larger particles. Bulk density changes in smaller. and ASTM C 29. For cer.” The top surface is Methods to determine bulk density and void content are given leveled using a straightedge.) maximum size and smaller.5 mm (12⁄ in. The shape of dropping or agitating the mold to allow the particles to arrange the particles affects the volume of voids. tively by rodding. 14 L (12⁄ ft3) for a 37. For a given source ASTM C 29 provides for the determination of bulk density of normal-weight aggregate. and/or grading. 1. “Jigging compaction” Bulk product particles do not fit together perfectly with the re. due to particle tamping rod evenly distributed over the surface.5 mm (112⁄ in. or by jigging for aggregates having a nom. compaction effort. ASTM Specification for Lightweight Aggregates for Structural Concrete (C 330). until equilibrium is achieved.” The lated. with the minimum measure size density. The layer of aggregate is rodded with 25 strokes of the 3. density into categories such as nonstructural or insulating graph) for aggregates having a nominal maximum size of 37. grading. air-cooled slag.). Some rules of thumb relate aggregate shape. gers. Rounded particles pack more closely and have fewer voids while aggregates larger than that cannot be compacted effec. bulk density and voids are inversely re. The surface of the Bulk Density and Voids aggregate is then leveled with the fingers or a straightedge in such a way that any slight projections of the larger pieces of the Bulk density and measures of bulk products.) and not ex. the aggregate is dried to essentially constant mass at voids will vary inversely as the bulk density. (C 29). hence “jigging” compaction of these aggre. into a standard as “the mass of a unit volume of representative particles.13] are used. c Inferred from balance capacity required by ASTM C 29. Portland Cement Association. Bulk density measurements are also essential for calcu- coarse aggregate. normal mm (1 12⁄ in. That standard defines void content as a percentage re. changes in bulk density indicate of aggregates with a maximum size of 125 mm (5 in.5 mm (1 12⁄ in. surface below the surface of the measure. 2. bulk density measure is filled to overflowing by gently shovel- Aggregate bulk density is defined by Brink and Timms [3] ing the material.) and changes in angularity. or obscured from visual control of grout level [4]. have been with us almost since recorded history. either “dry rodded” or “loose. loose bulk density determinations. compaction as follows: gates that are 37. and heavyweight. The measure breakdown or consolidation. Voids will decrease with compaction effort. lightweight aggregate may signal changes in aggregate relative creases with aggregate size. follows the same procedure for filling the mold except that sult being that voids exist between the particles. or loose. Weak. b Design and Control of Concrete Mixtures.5 lightweight.). and the orientation or packing rodding. Table 1 contains such a classification. such as grain or coarse aggregate approximately balance the larger voids in the aggregates.) maximum size tures. Aggregate void contents are calculated with equations ceeding 125 mm (5 in.) or less.” measure to obtain a “dry-loose bulk density. useful in proportioning concrete mixtures where the b/b0 measuring container just filled with the granular material.) maximum size coarse for possible corrections to lightweight aggregate concrete mix- aggregate.348 TESTS AND PROPERTIES OF CONCRETE or slag have less pore volume and higher specific gravities than is then filled to two-thirds full and again leveled and rodded as larger particles of the same aggregate. weight. For aggregate of a given relative density. July 1968. IL. or the fingers. structural lightweight. Whether the bulk density is compacted given in ASTM C 29. method [9] or its variations [12. rodding can be tested using the “Shoveling Procedure. . ASTM Specification for Lightweight Aggregates for Concrete Masonry Units (C 331). 3. 3—ASTM C 127. (5) the mold Depending upon the procedure used the relative density. aggregate to the density of distilled water at a stated tem- where. “bulk” or expand to a volume larger than it would be if it were 2. stockpiles are dry they can tend to be prone to segregation. (this is the SSD condition). Relative Density (OD) A / (B C) The relative density for coarse aggregate. making it more dif. AND MOISTURE 349 The bulk density procedures described here are laboratory both C 127 and C 128. between the mass and volume of a substance. (4) placed into a conical mold. hours or until the aggregate has cooled to a temperature that B Mass saturated-surface-dry sample in air. Care should be exercised when 1. It is impor- C Apparent mass of saturated sample in water. where (2) Cool the sample in air at room temperature for 1 to 3 A Mass of oven-dry sample in air. Apparent relative density is the ratio of the apparent density of the aggregate to the density of distilled water at a Aggregate Relative Density (Specific Gravity) stated temperature. The final step saturated-surface-dry (SSD). (2) immersed in water for 24 h. g. Conversely. The ASTM C 127 relative density defini- methods for determining aggregate properties useful in con. cates that it has reached a surface dry condition. The surface tension of water in the damp ag. is determined as follows: (1) Dry the sample to constant mass. 3 illustrate the “mass in air and (4) Remove the sample and roll it in a large absorbent cloth mass in water” procedure used by ASTM C 127 to determine until all visible films of water are removed. Relative density (OD) is the ratio of the density (OD) of the applying laboratory dry bulk density to aggregate volumes else. relative density will be used here. This in water. (3) Immerse the aggregate in water for 24 h 4 h. (3) dried back to a sur- aggregate sample. when calculating volumes of aggregate perature. PORE STRUCTURE. Relative density (SSD) is the ratio of the density (SSD) (sat- in a dry condition. ASTM C 127. Dampness causes masses of aggregate to sity (OD). and (6) when the aggregate slumps slightly it indi- a dimensionless quantity. The difference between of this determination will be further discussed in the water these two masses is the buoyancy afforded the aggregate by wa- absorption section. urated-surface dry) of the aggregate to the density of dis- gregate binds individual particles together. g. absorption affect the value of the calculated relative den- formly compacted. Inaccuracies in the measurement of aggregate stockpiles. for example. The apparent relative density can be determined absolutely and is not affected by inaccuracies The terms relative density and density describe the relationship in measurement of aggregate absorption. The importance relative density of coarse aggregate. when aggregate the calculated aggregate bulk relative density (SSD). YZENAS ON DENSITY. or apparent relative density in may require you to make moisture adjustments until the A B Fig. tions are as follows: crete proportioning and control. g. The apparent loss of mass of the immersed sample procedure requires that (1) the specimen be dried to a constant is equal to the mass of the volume of water displaced by the mass. (5) Determine the mass of the sample ter equal in volume to that of the aggregate. ABSORPTION. . face dry condition. tilled water at a stated temperature. Inaccuracies in the ficult to compact or consolidate the aggregate than it would if measurement of aggregate absorption affect the value of the aggregate particles were dry. removed. tant for the aggregate to have cooled since this can affect the results. can be expressed as oven-dry (OD). The illustrations in Fig. Because ASTM An example of the formula for calculating the relative den- C 127 and C 128 use the term “relative density” to express the sity (OD) from ASTM C 127 follows: ratio of the mass of an aggregate to the mass of an equal volume of water. (6) Immediately place the SSD test In ASTM C 128 the Saturated Surface Dry (SSD) condition sample in a container and determine the mass of the sample can be determined by use of the Cone Test (see Fig. 4). is comfortable to handle (approximately 50°C). Aggregate stockpiles are usually wet and not uni. and (b) the mass of the pycnometer containing aggregate and filled to the mark with water. to calibration mark. 5). That difference is the weight of water displaced by the aggregate. or a Le Chate. closed cavities) or permeable (interconnected and extending to cedure in ASTM C 128 for the determination of the relative the surface of the particle). and this adjustment is more dif. may gregate particle. “the size. Virtually all aggregates contain pores. 5—Relative density. Aggregate relative density values measured after 24 h of water absorption are significant properties of the aggregate. g. that is. Pores and Pore Distribution While ASTM C 29 Test Method for Bulk Density and Voids in C Aggregate allows a concrete mix designer to assess the space Fig. or void. density of the fine aggregate. Equations relating specific gravities with absorption are given in Appendix to ASTM C 127 and C 128. space within the individual particles. Pores can be either impermeable (isolated. g. As noted ASTM C 127 and C 128 define three relative density values. 350 TESTS AND PROPERTIES OF CONCRETE A Fig. 4—ASTM C 128 determining SSD condition. ASTM C 128 test alternatives. Aggre- gate with a moisture content different than found after 24 h of soaking will have a different relative density. Continuous and interconnected. and shape of the void spaces within an ag- lier flask (Fig. and freeze-thaw durability. This material is then used in the The Aggregate Handbook [14] defines pore structure as fixed volume portion of the test. g. number and distribution influence water absorption. one of the most important features of an aggregate particle is the pore. mobility as discussed earlier. en- be used. . The procedure determines the difference between (a) the mass of the aggregate plus the pycnometer filled to the mark only with water. the mass of water displaced by the aggregate. ficult when testing manufactured sands since angularity affects relative density. B Mass of pycnometer filled with water. 7) complicates relative density determination. The presence of water-filled pores inside aggregate particles (Fig. volume. g. Figure 6 depicts the pycnometer (fixed volume) pro. A pycnometer. Both C 127 and C 128 yield exactly the same information. their size. for an approximately 55 g test sample. B C Mass of pycnometer filled with sample and water to calibration mark. The formula for determining the relative density (OD) using the Gravimetric Procedure in C 128 is: Relative Density (OD) A / (B S C) where A Mass of oven-dry sample. S Mass of the saturated surface-dry specimen. between the aggregate particles. appropriate slump is observed. 6—ASTM C 128. large permeable pores can form large passageways through from molecules (angstroms) to holes visible to the unaided eye the aggregate. YZENAS ON DENSITY. AND MOISTURE 351 A B C Fig. such as in slag or lightweight aggre- ambiguity between pore space immediately adjacent to the sur.5 mm). elastic modulii. but not in- termined by their size and distribution. Impermeable pores typically influence the ther.. Some aggregates have mal properties. ABSORPTION. aggregate due to water in the pores of the material. Mercury intrusion functional differentiation might be to consider the pore space techniques have been used to measure pore distribution rang- of an aggregate to be that non-solid volume that will not be filled ing from 0. Aggregate Water Absorption ities become an issue. Pores may range in size cluding water adhering to the outside surface of the particles. PORE STRUCTURE. Winslow in ASTM STP 169C [15] notes “there may be some When the pores are large. (micrometres and millimetres) [16]. with cement hydration products when the aggregate is used in portland cement concrete. ASTM C 127 defines absorption as the increase in the mass of The influence of the pores on freezing and thawing is de.” A any hydraulic pressure to easily dissipate. the determination of the saturated surface dry condition also becomes a problem (as discussed later). move. The water in these pores will freeze and cause damage. etc. they typically do not become highly saturated. gate. of the aggregate and are pores that are too small and that do not allow water to freely not of concern in this section. In aggregates where these irregular.003 to 500 micrometres (0. allowing face and major depressions or irregularities in the surface. pycnometer method. . cle cohesion produced by surface moisture is lost. An ASTM water. Concrete fine aggregate generally con- . Eventually. The primary difficulty in determining absorption in some Figure 7 shows factors differentiating three aggregate aggregate. The moisture condition of aggregates in Aggregate Surface Moisture field stockpiles usually brackets that of the SSD state. absorption. Absorption test procedures are given air trapped deep inside aggregate particles can only be dis- in ASTM Test Method for Relative Density and Absorption of placed by dissolving that air in pore water and transporting Coarse Aggregate (C 127) or ASTM Test Method for Relative it out of the aggregate by slow diffusion through the pore Density and Absorption of Fine Aggregate (C 128). tor in concrete operations. tion and other factors that are a function of aggregate porosity In normal concrete operations. Surface moisture on batched con- tially dry aggregate. is the determination moisture conditions: oven-dry. The primary difference between have been proposed will be discussed later. This accounts for the rapid initial absorption of pore absorption value may be regarded as an aggregate property water and the slow. the piles have been watered. aggregate stockpiles can contain a significantly higher per- urated surface dry” (SSD) mass of the aggregate after it has centage of absorbed water than that determined by the ASTM been soaked in water for 24 h. these two moisture states is a pore-filling combination of water and entrapped air. SSD. ods for measuring absorption. bubbles out from the larger pore channels. ASTM C 127 requires that satu. absorbed in the pores of stockpiled aggregates might approxi- gate and of concrete made with the aggregate. but measurable absorption long after the that is a function of aggregate porosity and pore size. of the ini. in water. Absorp. a few are “air-dry” and contain Aggregate surface moisture is defined as all moisture in the less pore moisture than the SSD condition. expressed as a percentage of the dry mass of the aggregate. unless there has been recent rainfall or to surface dryness by air-drying the aggregate until interparti. for a 24-h period in water. Aggregate surface moisture is a critical fac- will generally increase with the time of immersion. 7—Aggregate moisture conditions. However. These processes sorption is determined after soaking an initially dry aggregate occur quickly. This difficulty and alternative face moisture). of the “surface dry” condition. In the the concrete mix. forcing air proper mixture control. those with irregular surfaces. and wet (containing sur. aggregate except that absorbed inside the pores of individual The mass of absorbed water in the pores of an aggregate aggregate particles. The ASTM absorption testing involves oven-dry methods of measuring concrete aggregate absorption that and SSD conditions only. Typically stockpiled aggregates are wet. procedure because the stockpiled aggregate usually has been rated coarse aggregate surface dryness be accomplished by kept wet for long periods of time before it is incorporated in wiping the aggregate particles with an absorbent cloth. the amount of water are critical in determining freeze-thaw durability of an aggre. and initial absorption rates are high. mate the 24-h absorption determined by standard ASTM meth- The mass of water absorbed by the aggregate is the differ. Ab.352 TESTS AND PROPERTIES OF CONCRETE Fig. During the initial phases of crete aggregates is part of the water in the concrete mixture. some active fine ence between the mass of the oven-dry aggregate and the “sat. the introduction of water into aggregate pores Aggregate surface moisture compensation is necessary for compresses air originally occupying the pore space. Alternately coarse aggregate stockpiles are ASTM C 128 method. dry aggregate is immersed in water. water-saturated fine aggregate is reduced typically less than SSD. Method for Total Moisture Content of Aggregate by Drying (C 566) and the less widely used ASTM Test Method for Surface The Accuracy of the Measurements Moisture in Fine Aggregate (C 70). A patient. proach performance specifications that will require better gregate approximating surface dryness can be weighed. and decreasing interparticle cohesion signal approaching sur. Stockpiled aggre. One such method is ASTM C 128 for fine aggregate occurs when the mold is raised the proprietary “Speedy Moisture Test” in which gas pressure and the sample slumps. Intuition aside. illustrated for coarse materials measurement is based upon the wet mass of the sample and in Fig. or 127 and C 128 approaches to measure aggregate absorption a microwave oven. Expedient methods. not accepted by ASTM. rounded river-sands to irregular. surface moisture is blot- Precautions given in the ASTM Standard should be observed if ted with a towel. continuous measurement of aggregate Tests of moist aggregate displacement in water have been surface moisture. of wet aggregate. gregates begin to change appearance and color. In the case The last two methods accelerate drying but can be dangerous. a normal racy. have been uti. at or near the ASTM points of surface dryness the aggregate pores. Alternatively. dures are incorrect must be addressed. structure becomes larger and/or the surface texture of the The water-immersion test method of ASTM C 70 determines coarse aggregate becomes more irregular. proficient technician can utilize In concrete plants. and the approximate water absorption percentage of the ag- centages of moisture. confirm or discount the precision of ASTM relative density The slower surface moisture evaporation from the cooling ag. At this control of the concrete mixtures. crushed “manufac- termined and related to surface moisture percentage.” Particle mobility. same. of the coarse aggregate (ASTM C 127). there is little experimental evidence to face dryness. the sample can be further dried to obtain the mass in water immediately after the soaking pe- . to reduce the variability determinations is where a Depart- gregate can be calculated on the basis of an assumed aggregate ment of Transportation modified the AASHTO procedure to absorption. One critical feature and mix water when changes occur in the total moisture con- in plant management is to utilize sand stocks that have been in. such as bin used successfully to adjust directly the batching of aggregate filling and stockpiling. and absorption measurements. changes in aggregate surface moisture. 1. AND MOISTURE 353 tains the greatest quantity of surface moisture. As the pore by the methods of ASTM C 128 or C 127. since the voids constant mass. Concrete mix water control may suffer if sand stock. surface contemplating their use. Consequently. a towel during surface drying. provided the actual bulk relative density (SSD) of typical weight aggregate with fine pores will not lose absorbed water to stockpiled material is used in the calculation. Conversely. ment permits accurate. the ASTM C a hot plate together with alcohol additions to the aggregate. The difficulty is that concrete sands generated by the reaction between acetylene crystals and the have different surface textures and shapes ranging from surface moisture of a weighed quantity of wet aggregate is de. and permit adjust- ASTM standard methods of doing this are the ASTM Test ments to these changes to be calculated. face-dryness when those manifestations disappear. Manu- ation of ASTM C 566. at which time the dry aggregate can be weighed between particles are small and capable of retaining large per. As discussed previously. more. The mass of surface moisture in the moisture is removed by air-drying until the aggregate particles aggregate sample is determined as the total mass of evaporated lose the cohesion afforded by the surface moisture. gregate calculated. YZENAS ON DENSITY. and dry condition with ac- Proper placement and maintenance of moisture meter equip. they can detect changes in aggregate volume caused by Moisture meter performance should be checked routinely. the percentage of surface moisture in terms of dry ag. but does not include water gate surface moisture and arrive at a point of aggregate sur- that is chemically combined with the minerals in the aggregate. ABSORPTION. termination becomes more subjective. In the “frying pan moisture” test. of near-surface dried sands once the sand cone is raised from Another nonstandard meter calibration procedure is a vari. These procedures work well be- active long enough that most excess water has drained from cause displacement methods accurately measure total volume the pile. a factured sands. surface dry. may well have lower measured ab- heated and stirred continuously until incipient color change sorptions simply because of their lack of particle mobility. Further- water minus the calculated mass of water absorbed in the ag. are done properly. the compacted sand during the test for surface dryness. curacy sufficient for the control of concrete batching. smooth. appear correct. presumably sorbed in the pores of aggregate from typical plant stockpiles because one is no longer looking at the particles through a film in that calculation. and with reasonable accu. the methods just described to determine the mass of an aggre- tored by moisture meters installed on batching equipment. This tured sands. the aggregate surfaces removes some of the internal pore water. provided other plant operations. stockpile that has been wet a long time may contain signifi. An example of one attempt point. The determination of the “Surface Dry” condition using lized to determine sand surface moisture. Evaporable water includes surface mois. Intuitively. tent of aggregates [17–19]. if other factors remain the piles are too wet or if the moisture content is not uniform. must have similar variable effects upon the collapse should be corrected to the dry basis. which hold their shape better than rounded weighed sample of wet sand in a pan on a hot plate is lightly sands when compacted. the surface dry de- aggregate surface moisture quickly. For example. ASTM C 566 covers the determination of total evaporable The possibility that the ASTM absorption measurement proce- water in an aggregate by forced drying using either a hot plate. Utilize the percentage of water actually ab. gate sample in the wet. PORE STRUCTURE. they monitor real manifestations of wet aggre- ture and moisture within the pores. sand surface moisture is usually moni. In the case of sand (ASTM C 128). a few lightweight ag- gate may have a relative density (OD) that is different than that gregates [20] have such large interconnected pores that toweling determined for dry aggregate immersed in water only 24 h. and the pan is promptly removed from the burner. The interest in refining these gregate sample permits determination of the precise time at measurements continues as both producers and specifiers ap- which surface moisture appears to be lost and the sample of ag. aggregate from a of surface water. The pore structure as well as the surface texture of both the cantly more absorbed water than the same aggregate that has fine and coarse aggregate play a major role in the determination been soaked in water for 24 h and then tested for absorption of when the “Surface Dry” condition is achieved. 354 TESTS AND PROPERTIES OF CONCRETE riod instead of after attaining SSD. H. 646. D. Heavy- Present ASTM relative density and absorption procedures have weight and Mass Concrete. PA. p. West Conshohocken. 645. 25 Feb.. B. sistency and repeatability for most of the concrete aggregates [13] Dolch. “Porosity. 1966. ASTM In. ASTM International. and Concrete. and Aggregates.. Absorption. ASTM In- ternational.. ries. W. 1986. ture. M. p. C. “Aggregate Particles Have Holes in Them. American Concrete Institute. G. Skokie. and Surface Mois. 1978.” Rock Prod- [3] Brink. 11. L. 1978. 1956. Density. G. troduced. PA. have been made. p. ASTM STP 169B. R. 46. ASTM International. PA. MI..” Portland Cement Association. T.. Materials. [2] Timms. West Conshohocken. would be best to stay with the ASTM methods. A. W. West Con- sorption. May 1956. ASTM STP 169B. PA.. September 2003. such as concrete water-cement ratio. Dec. and Gray. p 11. Detroit. [11] Weymouth. 1992. C. W. “Weight. they have contributed to an enormous database of infor.. ASTM STP 169B. and Timms. This Concrete for Strength. “Determining the Water Absorption of Coarse crete and Concrete-Making Materials. R. ASTM International. West Con- consistency across the broad range of aggregates utilized. Lightweight Aggregates for Concrete. E. 421–428. p. Surface Area. pp. Workability. ASTM In. limits and the ultimate effect on the enormous database of in.” Significance of Tests and Properties of currently in use. 1907.. and another that uses a calibrated pycnometer and a cance of Tests and Properties of Concrete and Concrete-Making vacuum sealing device to determine relative density and ab.. [14] National Stone Association. E. and Pfeifer. L. “The Pore System of Coarse Aggregate. “Unit Weight. ASTM International. [8] Ozol. the procedure may appear to increase the repeatability of the West Conshohocken. 67. [17] Landgren.” Cement. Density. 3–7.. Surface Texture.” Significance of Tests and Properties of Concrete and Con- that occur when a new procedure is discussed is that while crete-Making Materials. pp. 432.1-91. [18] Black. 1992. Concrete. Significance of Tests and Properties of Concrete and Con- of air being entrapped within the pores between towel drying crete-Making Materials”. and Coatings. Only time and increased usage will tell if these pro. and Surface Mois- more consistent water weight since it reduces the possibility ture”. and ucts.” Transactions. PA.” Significance of Tests and Properties of Con. 1994.. [15] Winslow. shohocken. p. 84. A. IL. West Conshohocken. Surface Texture. Surface Moisture. West Conshohocken. PA. p. “A Method of Proportioning from those achieved using ASTM or AASHTO methods. May 1965.. Skokie. 629. ASTM STP 169A. J. A.2-91. PA. crete-Making Materials. Specific Gravity. PCA Research and Development Laborato- Surface Moisture. [7] Mather.” Signifi- quently. National Crushed Stone Association. p. American Concrete Institute. crete Practice. ASTM International. 1991. R. ASTM STP 169. Relative Density (Specific Gravity) of Aggregates. unless current or future research. MI. formation that has been collected over the years. The Aggregate Handbook. p. provides cance of Tests and Properties of Concrete and Concrete-Making realistic alternatives that will improve both the accuracy and Material. 1964. and Durability. E. PA.. West Conshohocken. 846. ASTM International. W. it may also yield results that are different [9] Goldbeck. R. Part 1. ASTM STP 169C. [12] “Standard Practice for Selecting Proportions for Normal. p. 47. 415. cedures are effective across the broad range of aggregate par. [19] Saxer. “Effect of Particle Interference in Mortars Summary and Concrete. Barksdale. Density. 1978. p. Hanson. Gravity) Using the Siphon-Can Method. and the submergence of the sample into the water. ASTM STP 169C. it shohocken. 297. 1990. measurements. G. PA.” Proceedings. This appears to provide a [4] Mullen. “Shape. Richard mation derived from these tests upon which many calculations D. 26. “Weight.. “Shape. 1942. ACI Manual of Con- been utilized for a very long time.” Signifi- tion. p. “The Determination of Relative Density (Specific ternational.” Journal.. While it appears that they may become more Concrete and Concrete-Making Materials. New York. Ed. Conse. There West Conshohocken. lar. “Weight. B. crete and Concrete-Making Materials. [20] Landgren. 1933.. A. ACI Manual of Concrete utilizes an automated vacuum device to remove entrapped air Practice. . American Society of Civil Engineers. G. they provide a level of con. R. and Thompson. p. S. ASTM International. Absorption. or both.. D. 78. A. that intend to improve the consistency of the [6] “Standard Practice for Selecting Proportions for Structural measurements by the use of proprietary equipment: one that Lightweight Concrete. which have recently been in. Part 1. J.” Significance of Tests and Properties of Concrete and Con. are also two new procedures. “The Laws of Proportioning Concrete. PA. R. Detroit. 584. Absorption. “A Direct Method of Determining Absorption and West Conshohocken. [5] “Design and Control of Concrete Mixtures. Portland Cement Association. A. p.” ACI 211. Absorption.. 1978.” Rock Products. p. ternational. subjective as particle shape and texture becomes more irregu.. “An Improved References Procedure for Proportioning Mixes of Structural Lightweight [1] Landgren. [16] Meininger. 1966. W.” Significance of Tests and Properties of Con.” Rock Products.” Engineer- brings up the prospect of potentially changing specification ing Bulletin No. One of the concerns ings. ASTM STP 169A.” ACI 211. [10] Fuller. and Coat- ticle shape and textures currently used. and infrared reflectance detection for moisture determina. Swenson and Chaly [6] devel- in concrete. A final section presents a summary chert (less than 2. strongly or weakly cemented to the aggregate particle’s sur- ues to do so. As is often the case. the same term can have face. “This test method covers the testing of ag- them for their work. heating and cooling. this chapter is devoted to dis- aggregate characteristic being discussed. revision and update of the chapter by the same author in the previous edition (169C). the characteristics of specifically lists the following as deleterious substances: the aggregate that are being assessed. Forster1 Preface different meanings to different people. clay lumps and friable particles. freezing and thawing. While their chapter is organized in three major headings according to the definition of deleterious is correct. Bloem authored the section on soundness and deleterious In the scope section of the ASTM Test Method for Soundness substances in ASTM STP 169A and L. whether bound in concrete or not. material finer than the 75 m sieve. soundness. there is a discussion of a series of aggregate quality tests. This description is certainly appropriate for this chapter.40 saturated surface dry (SSD) specific and conclusions based on the preceding discussions. the published literature. many tests have been devel. the chapter has been or. 355 . On the material continues to be based on the work of the chapter other hand. Ozol in ASTM STP ering. plication of the test results. or any combination thereof. Nomenclature Coatings Terminology that is used in the description and assessment of Ozol [7] described “coatings” as adhering materials that may be aggregate quality has evolved with time and usage. the subject of aggregate coatings ering action in concrete or other applications. innocuous.” herein defined as any material deleterious substances. that is. and coatings. While a number of changes have been Soundness made in this chapter (including the significantly expanded dis. and contin. 1 Consultant. the relevant terms will be discussed THE MATERIAL PRESENTED IN THIS CHAPTER IS A and defined here. For instance. Dolar-Mantuani did the of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate chapter of the same name in ASTM STP 169B. cussing “deleterious substances.” This statement was grouped with soundness and deleterious substances in this indicates that soundness is an aggregate’s resistance to weath- chapter. and they used deleterious to mean any terials. gravity). and the meaning and ap. The discussion of coatings by M. Mather and Mather [1] provide some historical oped a detailed classification of harmful substances based on background on the early use and evaluation of aggregate ma. and Coatings Stephen W.5] used During the past 100 plus years. gregates to estimate their soundness when subjected to weath- ginning with ASTM STP 169C. Thus. VA 20121. the remainder of this quality of an aggregate that is harmful to concrete. in. Bloem [2] used “soundness” as a general term to describe the cussion of unconfined freeze-thaw testing). most of which remains very valid today. ASTM STP 169C. 6505 White Post Road. Be. deleterious and its antonym. I am indebted to (C 88). Rhoades and Mielenz [3] and Mielenz [4. to refer to chemical oped to assess the quality and suitability of aggregates for use properties of aggregate particles. Deleterious Substances. Under each heading in the aggregate that is detrimental to concrete. sound to chemical properties or mineralogy of the aggregate. In order to make the rest of the chapter clearer. A. soundness in- 169B was used as a basis for the inclusion of that subject. As with cludes resistance to wetting and drying. This is the ganized to concentrate on relevant ASTM standards and their context in which soundness is discussed in this chapter. some literature limits the terms sound and un- authors in the two editions of ASTM STP 169 previous to 169C. the previous edition. After a section on nomenclature.31 Soundness. use in dealing with these three aspects of aggregate quality. Deleterious Substances Introduction Bloem [2] used “deleterious substances” to describe individual particles or contaminants that are detrimental to the aggregate’s Standards Development use in concrete. L. a great deal of the durability characteristics of an aggregate as a whole. Table 3 of ASTM Specification for Concrete Aggregates (C 33) cluding a brief overview of each method. and coal and lignite. D. it is stated. Centreville. Magne. and others laboratories use five cycles. since the soundness loss can be defined only in terms ducted by repeated immersions of the aggregate sample in sat. and openings five-sixths the size of those in the original sieves used Woolf [14. ticles in each class of distress after the test. and (2) deviations from the pre- particles in each category recorded for comparison with a scribed method. many lier. Table 1 lists only the plus 19. ing the test according to the method: (1) differences in materials sually with or without the aid of magnification. and. Even with the contin- determined by sieving using the same size sieves and method ual search for and addition of improvements. On the other urated solutions of sodium or magnesium sulfate alternating hand. Precision was re- sizes may help define the type of distress that is occurring. Although the method calls for examining the years by the laboratory conducting the test. For ported to improve [16] with tighter control on a number of these further insight as to the type and progression of distress that is factors noted in Table 1.20 recently equal to the weighted sum of the difference between the initial conducted a carefully controlled round-robin test series on the and “after test” size fraction weights. the test samples may be visually examined after representative test sample is critical to getting good results.0 mm (3/4 in. This expansion is two tests. available information on the “precision” of the Description test (that is. avenues are open. As with any test method. Aggregate particles may show flaking. or between- sium sulfate is generally more destructive than sodium sulfate. Early studies [8–11] indi- After the required number of cycles of soaking and drying. Precision is further broken down into within- said to simulate the expansion of water upon freezing. the scope of the method tematic error in the results that is inherent in the test method) indicates that the test is a means to estimate the soundness of must be carefully considered. ASTM C 88. maximum allowable difference between the results The sulfate soundness test. Although many laboratories feel that they pro- the distress caused by the procedure may be manifested in a duce repeatable results within their individual laboratories. obtaining a occurring. the percent loss for each size fraction. with respect to aggregate soundness. bias cannot be determined. The failure to get results of thereof.0 mm particles in the ments or allowable changes made to the way the test is run over original test sample. with closely spaced planes of weak. greatly reducing the sieve sizes of the particles. examination of the other some of the main factors affecting precision. continued to be added to the to separate the sample.356 TESTS AND PROPERTIES OF CONCRETE although the use of “bound” rather than “cemented” may bet. flexibility in the number of immersion and drying cycles. single-operator precision (repeatability). split. Coatings may be should be included. In reporting the results of the test. It is the aggregate.15]. for the plus 19. was first published as a of two tests. ASTM C 88 is most frequently applied. that have been used to evaluate soundness. procedures and equipment were not well enough defined to cles is estimated. a number of items ter express the range of adherence included. This test. Improvements suggested by Wuerpel [12]. difficulty in obtaining a representative sample is especially high ness. both related to the wide latitude allowed in conduct- fraction retained on the 19. the number of ways. data that correlate well with the quality of concrete made from Since the method currently allows flexibility in the number of the aggregate. or procedures used to conduct the test that are allowed under cles are categorized by type of distress. laboratory precision (reproducibility). and (2) the difference between of the salt when the sample is re-immersed. several non should be watched for. gravel. the number of particles before the test and the number of par- Although individual particles may behave differently in con. Shaley particles. the mass of each sample fraction before and and may be produced by either chemical or physical processes. and the number of the current standard method.0 mm size fraction. To better categorize the type of distress that occurred even comparable magnitude appears to stem from two groups after completing the required number of cycles. Although there is this However. this material loss is method in the interest of better precision. Expansive (tensile) forces are Precision is normally defined in terms of two variables: exerted within the individual aggregate pieces by rehydration (1) the coefficient of variation. by two different laboratories) and the “bias” of the test (a sys- dard method in 1963. either due to misunderstanding of the require- count taken on the number of plus 19. in yet another effort to better define the causes Examination of the test samples after testing reveals that of poor precision. properly conducted either by a single operator or tentative test method in 1931. precision has been investigated and determined in a with oven drying to precipitate the salt in accessible pore number of studies. This phenome. the weighted percent loss for each size fraction and for the fine and coarse Soundness aggregate portions. ASTM Subcommittee C9. Information on the crete. In order to improve the precision of the results. of solution used. round-robin series indicated that poor precision persists within ting. among others. In the case of the sulfate sound- the aggregate in concrete or other applications. cycles run. the precision of as was originally used to separate the aggregate. and additional information on and acceptance of an aggregate source for use in concrete. are discussed below. the sample of factors. the most obvious being to more closely . such as a general description and past perform- convenient to test representative aggregate samples to obtain ance. The actual test results will provide the kind found on sand. may split a number of times during the test without for sand and gravel deposits of variable composition. the cated that numerous portions of the sulfate soundness test amount of material that has been lost from the original parti. of the test method. laboratory. as defined ear. and noted in the report if detected. The each cycle. it is desirable to have general criteria for the overall rating source of the sample is needed. Paul [13]. after test. crumbling. this must also be reported. or artificial aggregate. particularly between laborato- size fractions retained as a result of hand sieving on sieves with ries.0 mm size fractions. would prove useful in interpretation of the test results. or some combination as well as between laboratories [16]. This is done by weighing the coarse aggregate yield results with good precision. The test is con. The loss is the method remains poor. spaces in the aggregate particles. As noted earlier. ness test. Precision and Bias Sulfate Soundness Test Before attempting to interpret the results of the soundness test (or any test).) sieve is examined vi. soundness test. and finally approved as a stan. crushed stone. Affected parti. For fine aggregate. granular disintegration. No individual test method accomplishes this. Temperature variation and rate of drying in oven At this point. As would be expected. Magnesium sulfate results in a greater loss than sodium sulfate because a saturated solution of it contains more material. as the number of cycles of immer- Hudec and Rodgers [19] found that disintegration was influ- sion and drying is increased. These results may be tential influence of heating and cooling. and a greater ex- define the conditions under which the test may be conducted pansion potential (tensile stress in the particles) during each and the equipment and materials used in the test. and freeze-thaw resistance Soundness Test (ASTM C 88) of concrete are discussed in other chapters of this volume. Various authors have pointed out that Interpretation of Sulfate Test Results there is little theoretical basis for equating/relating the results In order to correctly interpret the results of this test. The amount of scatter in the data indicates that there certainly were other major influencing factors. How ac- sults on 70 samples. This theory may hold for some aggregate uses. the loss also increases. both in mass and volume [2]. some aggregates that fail the sulfate soundness test have shown good freeze-thaw resistance in portland cement concrete. For example. However. indicating that wetting and drying or heating and cooling more severe. porosity of aggregates. It has been found that continuing the oven drying be- sion indices given in the latest version of ASTM C 88 indicate yond the time required to dehydrate the sulfate crystals results that much better precision can be obtained with magnesium sul- in greater disintegration of the aggregate. it was suggested that the resulting disintegration was more close temperature control of the immersion bath less critical to the result of the number of pores in the aggregate than their size the precision of results with magnesium sulfate). DELETERIOUS SUBSTANCES. in a statistical analysis of test re- soundness is an aggregate’s resistance to weathering. depending on the susceptibility of the aggregate parti- Temperature of samples at time of immersion after oven drying cle. particles in addition to those exerted by rehydration of the salt fine aggregates have a loss from the test about twice as large during immersion. are factors in the test results [10]. but the trend is not so clear. The test is most often related to that portion of weather- TABLE 1—Factors Affecting the Precision of ing due to frost action. cause concrete to fail under freeze-thaw conditions [26]. Vollick and Skillman [26] did find limited curately the sulfate test measures soundness is the subject of correlation between the sulfate soundness test results and the debate that has continued unabated since the inception of the freeze-thaw resistance of concrete containing the same coarse aggregates. For coarse aggregate. but not to reject those that fail it [15]. and can be reversed. (1S%). see ASTM Practice for Preparing that have performed very well in the sulfate soundness test Precision and Bias Statements for Test Methods for Construction Materials (C 670). it can easily be seen that interpretation of the results must proceed with cau- Multilaboratory tion. The reasoning is that Magnesium sulfate 25 71 the test is severe and. the Sulfate Soundness Test (ASTM C 88) There have been a number of explanations of the process that occurs during the sulfate test that causes the disintegra- Design of containers used for immersing samples tion of the aggregate particles [8–10. In view of the level of precision of the test method as just Coefficient Difference Between discussed. Porosity TABLE 2—Precision Indices for the Sulfate of concrete. In spite of the and distribution [11. For carbonate aggregates. investigated the impact of using various options available in Evidence suggests that there are other forces acting on the the method and discovered a number of trends. however. Magnesium sulfate 11 31 but not for others. After some variable number of Age of the solution cycles. disruptive forces are exerted within the particle.18]. It should be pointed out. and the uncertainty as to what performance charac- of Variation Two Tests (D2S%). laboratories that that this early work was mostly done prior to the era of air-en- have traditionally used sodium sulfate are reluctant to switch be- trained concrete and the development of some understanding cause direct comparison to past test results would then be lost. . while conversely. Bloem [17] subsequent immersion cycle. Preci- results. other aggregates NOTE—For further explanation of 1S% and D2S%. This losses average about 50 % higher than five cycle losses for both result points to wetting and drying as being a factor in the test coarse and fine aggregate tested with either type of salt. FORSTER ON SOUNDNESS. therefore. Ten cycle enced by the quantity of water adsorbed on the particles.” but those that deteriorate under test may or Sodium sulfate 24 68 may not be good. For instance. of the role that the characteristics of a void system can have on freeze-thaw resistance. due to magnesium sulfate having a solubility with a lower tem- During the early development and experiments with the perature sensitivity than that of sodium sulfate (thus making test. Experiments run with distilled water in when magnesium sulfate is used as when sodium sulfate is place of the solution resulted in significant disintegration and used. As stated in the definition. indicating the po- fate than with sodium sulfate (see Table 2). magnesium sulfate is also usually loss.20–25]. There is general Temperature of the solution Temperature variation of the solution during test agreement that the cycles of soaking in the sulfate solution and Chemical grade of the sulfate used oven drying cause the salt to accumulate in the cracks and Purity of the water used to make the solution pores in the aggregate particles. aggregates that survive it are Single-operator certainly “good. apparent advantage of magnesium sulfate. its signifi- of the sulfate soundness test with freeze-thaw disintegration/re- cance must be clearly understood. One suggestion was to accept aggregates that passed the Sodium sulfate 41 116 test. the quantity of salt in these spaces becomes more than can (should match solution temperature) be accommodated during hydration in the next soaking phase.12. sistance in the field. thus resulting in a more rapid accumulation of salt during each drying cycle. AND COATINGS 357 test. % % of Average teristics of the aggregate the test actually relates. states. the samples are drained and sealed. numbers of cycles.25]. then of this specification well realized the shortcomings of the put through five cycles of freezing and thawing.2 mm 9. After the five cycles. especially when test results are considered in and ASTM Test Method for Specific Gravity and Absorption of concert with aggregate absorption values (see Fig. it was felt that since comfortable using a laboratory freeze-thaw test as a part of the absorption was a direct measure of accessible pore space in the process of aggregate acceptance. and the Ontario Ministry of limits for the soundness test can easily be seen. 19. specification is written allows the specifiers to apply the sound. This relationship has not proven to be reliable.” For coarse A brief description of the MTO test. Sieving should wetting and drying. ASTM C 33 allows use of fine aggregate that has alcohol solution. dried. definitive tests. 2). York DOT procedure. In order to continually calibrate the equipment Because of the imperfect prediction of soundness by the sul. For each cycle sulfate soundness test to unfailingly discriminate between they are frozen for 16 h at 18 °C. After the 24 h. and application lend more credence to any conclusions reached. Currently a number of In view of the preceding discussions on precision and inter. has given satisfactory service when tion. The similar manner to that to be encountered. it would be closely related to the freeze-thaw behav.” ples are then soaked for 24 h in a 3 % sodium chloride solu- These statements thoroughly demonstrate that the authors tion. ideally. collaborative evidence environment that will often be encountered in practice.5 % water- an aggregate. ASTM C 33 similarly allows the use of aggregate that Thaw Test for Coarse Aggregate (MTO LS-614) [27] is provided has exceeded specified limits of the soundness test results herein as an example. then thawed at room tem- sound and unsound aggregate for use in concrete. ing will affect test result (loss) in this test. Thaw Test Sample gregate. the test can identify marginal (fair per- It has been suggested that results of ASTM Test Method for forming) aggregates. or.2 mm 1250 Freeze-Thaw Testing of Unconfined 13.75 mm 500 Since the sulfate soundness test is often considered a simulation of the action on aggregate particles due to freezing and thawing. prior to the completion of more reliable. Unconfined Freeze- aggregate.0 mm 13. alternatively. MTO experience with the test [27] indicates that based on Absorption Tests field performance. Vari- from other tests.358 TESTS AND PROPERTIES OF CONCRETE In summary. For more details on the New aggregate. and re-sieved on the same sieves as initially ness test as an acceptance test to the degree of strictness they used. interpreters of the soundness test results of loose (unconfined) aggregate by actual freeze-thaw action. and separate them from good and poor Specific Gravity and Absorption of Coarse Aggregate (C 127) performers. . and procedure used. The being tested. The New York State DOT also feels soundness of aggregate. or to supplement. the samples are drained. sample conditionings. The New York “concrete of comparable properties. washed. The use of either of these solutions increases the damage exposed to weathering similar to that to be encountered” or. the results of the sulfate test. absorption can serve as an TABLE 3—Gradation and Mass of Freeze- initial general indicator of the soundness tendency of an ag. that is. Each sieve fraction is tested and reported as the weighted av- Other Tests as Indicators of Soundness erage loss [27]. a standard control material (with an av- fate soundness test. “provided it gives satisfactory results number of cycles needed to achieve definitive losses. A low soundness loss will “usually” Such tests have the virtue of exposing the aggregate to an indicate a durable aggregate. Transportation (MTO) have some version of an unconfined ifications provide some flexibility to the user to consider other freeze-thaw test on their books. Normally. as well as other tests These tests often address only one aspect of soundness as that depend on sieving for results. however. or in the absence of test is conducted by placing three size fractions of the aggre- a demonstrable service record. in concrete subject to freezing and thawing tests. It has been found that intensity and length of siev- more commonly used tests are briefly discussed subsequently.5 mm 4. for example. resistance to either freezing and thawing. 1) or micro- Fine Aggregate (C 128) might be useful as indicators of the Deval losses (see Fig. types of additives to the freezing water have been tried in an attempt to more closely duplicate actual field performance in Specification Limits concrete (see. see Ref 29. ior of the aggregate in concrete [24.5 or 1 L jars [27]. a logical extension of the soundness test is the testing NOTE—Information after Ref 26. The way the perature for 8 h. For exceeded the specified limits of the soundness test results if either test the aggregates are vacuum saturated. a number of other tests have been used in erage loss of 24. The sam- produces concrete having satisfactory relevant properties. there have been some efforts to combine absorption Passing Retained Mass (g) with other tests to reach a more definitive conclusion [27]. spec. must proceed with caution. or. terial through the sieve on which the aggregate was first sieved.5 %) is routinely run along with the aggregate lieu of. however. or heating and cooling. DOT and the MTO both use tests with a sodium chloride solu- gate from the same source. provided that the aggregate gate (see Table 3) in three separate 0.5 mm 1000 Aggregate 9. thus accelerating the test by reducing the lacking a service record. made from similar aggre. the difficulty in setting specification portation Officials (AASHTO). The test was under development for ten “provided that concrete made with similar aggregate from the years. or down during sieving of the weakened particles. due to continued break- defined. Ref 28). with the objective of simulating the conditions of freeze- same source has given satisfactory service when exposed in a thaw cycling in the presence of moisture and de-icing salts. Originally. the American Association of State Highway and Trans- pretation of results. caused by each cycle. 25 cycles in plain water. The Iowa DOT tests aggregate evidence when making final determination of the suitability of using either 16 cycles of freezing and thawing in a 0. Loss in the test is expressed as percent mass loss of ma- are comfortable with. Also. be closely monitored to produce consistent results. prior service records in the same ous cycling rates. The freezing and freeze-thaw methods are discussed in detail in another chapter of this volume. and something equally applicable to any withdrawn in 2003. other laboratory method of predicting the field performance of an tests is an invaluable tool in correctly predicting the soundness aggregate in concrete exposed to freeze-thaw conditions. 1—Freeze-thaw test results and water absorption Large-Size Coarse Aggregate by Abrasion and Impact in the Los versus field performance (after Ref 27). has a similar effect on shaley or argillaceous particles as the sulfate soundness test. First. ASTM Guide for Petrographic Exami- have been a number of ASTM freeze-thaw tests on the books nation of Aggregates for Concrete (C 295) provides a good out- over the years. The procedure is discussed in detail in Chapter 22 of Resistance of Coarse Aggregates in Air-Entrained Concrete by this publication. Sorting of the aggregate by a petrographer into homogeneous fractions prior to testing will improve the precision of the test results. versus field performance (after Ref 27). along with the conditioning of the test specimens prior to the start of the test. Although now withdrawn. Angeles Machine (C 535)). experienced concrete of the proposed mix design is the most satisfactory petrographer both independent of. ASTM C 682 points out several areas of concern when interpreting test results that bear repeating because of their applicability to other tests. perhaps because of the potential water loss from the specimens during the freezing step. This thought will be revisited at the end of this chapter. Therefore. . including ASTM Test Method for Resistance of line for conducting a systematic evaluation. and per. Other Tests A number of other tests are or have been used as indicators of aggregate soundness. ASTM C 666 is a current test. Fig. were balloted for withdrawal (due to lack of use) and graphic examination. or other steps in sample preparation and curing that lead to some drying of the test specimens. and has optional Procedures A and B. ASTM Test Method for Lightweight Pieces in Aggregate (C 123). There of an aggregate source. repeatability of test results should be one of the factors used in choosing a conditioning procedure. Even if it is decided to test the heterogeneous aggregate sample as a whole. which. as noted earlier. and ASTM Test Method for Clay Lumps and Friable Particles in Aggregates (C 142). These tests include the copper nitrate test as described by Dolar-Mantuani [30]. This test. ASTM Test type) and state of weathering are two important factors that Method for Critical Dilation of Concrete Specimens Subjected must be considered when evaluating the soundness of an to Freezing (C 671). and in concert with. 2—Freeze-thaw test results and micro-Deval loss centage of each fraction will provide insight for the interpre. Any one test cannot serve as the definitive answer for all aggregates. These effects all relate to the moisture content of the concrete (and aggregates) during testing. the basic Critical Dilation Procedures (C 682). including C 666. Even concrete that is not resistant to distress due to freeze- thaw cycling will not be adversely affected by the C 666 test if it is not critically saturated. identifying the lithologies present. For example. it is generally agreed that ASTM C 666 Procedure B (freezing in air) is less severe than Pro- cedure A (freezing in water). minor changes in the conditioning of the specimens can have major effects on the test results. DELETERIOUS SUBSTANCES. The last two. condition. C 671 and lesson to be learned from the general approach of the petro- C682. and ASTM Practice for Evaluation of Frost aggregate. Freezing and Freeze-Thaw Tests in Concrete Petrographic Examination for Soundness Application of freeze-thaw tests to aggregate contained in The evaluation of an aggregate sample by a trained. Beyond the specifics of the practice. A combination of tests and evaluation by a trained petrographer is the best approach. Other tests that may be indicative of soundness and that are described elsewhere in this volume include the two impact and abrasion tests using the Los Angeles machine (ASTM Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine (C 131) and ASTM Test Method for Resistance to Degradation of Fig. AND COATINGS 359 tation of the test results. FORSTER ON SOUNDNESS. The lithology (rock Concrete to Rapid Freezing and Thawing (C 666). conducted by immersing the test sample in copper nitrate solution overnight. This low moisture level may occur because of air storage of the specimens prior to test. can have major effects on the results obtained. excess water also leads to lower strengths. abrasion during the mixing and. this exami. be subject to some surface material. If this material is essentially free of clay “minerals” test. they also will usually survive nally durable rock.” Particles that pass the 75 m sieve are generally referred to as As was noted earlier. They will. and or shale (as is usually the case with dust of fracture). twigs.0 mm for cate. increases drying shrinkage and the likelihood of cracking. chert particles with an SSD away leaving a pitted or pock-marked surface.40 specific gravity but still cause these problems mixing. however. If the deterio- mechanical action of processing or concrete mixing and plac. If they survive the geologic sense) weathering and chemical alteration of origi- aggregate processing procedures. Once in place. sand and gravel deposits as well as the dust of fracture that gorizing the types of distress present. or both. a deleteri- derived through contamination from another source. a lowering matrix. (Examination of the smaller may result from the crushing and mechanical processing of ag- sizes will often add additional insight on the aggregate’s per. often contribute additional.40) lower its abrasion resistance and will often quickly weather Based on empirical evidence. According to ASTM used in concrete. They are often the result of long-term (in a cally broken up to be effectively dispersed. the particles may aggregate results in high water demand by the concrete for be above the 2. how. something not normally the aggregate that is detrimental to concrete. a better predic. Fine material from crushed stone production (dust of service can be made. benefit to strength for lean concrete mixes [31]. and Description organic impurities other than coal and lignite. Soft parti- The term. chert (less than 2. it can create problems if it provides too nation. This can result in popouts near particles. The individual minerals may or may not be soft. specific gravity of less than 2.360 TESTS AND PROPERTIES OF CONCRETE type of evaluation. These particles often lack durability. coal and ous substance (as used in this chapter) refers to any material in lignite are often associated with shale. If of quartz grains weakly cemented together by a clay or calcite soft particles are present in sufficient percentages. the excess water due to the chert. and a poorly indurated shale.) If conducted by a qualified petrographer.40 SSD specific gravity). Where individual the aggregates are located just below the concrete surface. clay lumps (or clay balls). abrasion and wear. silt and clay. the fact that the bond between grains is weak results in surface where the clay lumps have weathered away. and other vegetable and animal of concrete. This includes the fine material that can occur in amination of the sample particles larger than 19. however.40 are considered to be usually Low specific gravity chert particles are susceptible to frost objectionable as aggregate in concrete due to frost suscepti. placing.0. If not As noted in the preceding section on nomenclature. Effect of Deleterious Substances on Concrete When clay lumps survive the processing of the aggregate. the aggregate particles breaking down into smaller pieces or Friable particles and soft pieces are easily broken down rapidly losing grains. Organic particles other than coal and lig- the mechanical action associated with the mixing and placing nite include plant roots. as distinguished from friable particles. of the concrete strength and durability will result. soft particles. The amined carefully. Soft or friable particles exposed at the concrete surface will certainly Chert (SSD Specific Gravity Less Than 2. and may even be of and practicality of benefication of the aggregate. in concert with a petrographic examination of the sample much unanticipated fines to the concrete during mixing or re- prior to testing. If the fines include . The lumps would have to be mechani. as well as recommendations on the need fracture) is reported to not be detrimental. is to “take advantage of all available pertinent Material Finer Than the 75 mm Sieve information prior to reaching a conclusion. in concrete can result in cracking of the concrete or popouts if tion of popouts at the concrete surface. it may be their overall percentage in the aggregate source. aggregate particles are composed of some lightweight chert An excessive amount of minus 75 m material in the and the parent rock (limestone or dolomite). Other deleterious substances not specifically mentioned earlier include lightweight pieces other than chert. ASTM C 88 requires the qualitative ex. Each of these categories will be briefly described. cles during processing. and finishing. unaccounted-for fines to the mix. Knowing the causes of distress in the affected particles. ration of the friable particles continues once the concrete is in ing. and freezing and thaw- bond between the mineral grains that compose the aggregate ing of the hardened concrete. it may result in freeze-thaw damage to the concrete. These aggregates will therefore have to be ex. Examples of friable aggregates are a sandstone composed place. the concrete surface and also the appearance of a pock-marked ever. as a consequence. from their surface during the into smaller particles or create additional fines. are composed of fine sand-sized particles that are present during and after the minerals that are soft and therefore are very susceptible to aggregate processing. Coal and Lignite Deleterious Substances Coal and lignite may occur as discrete coarse particles in the aggregate or as fine material disseminated throughout. material finer than the 75 m sieve. clay lumps and friable particles. refers to lumps of clay to cles. and Friable Particles also the mixing and placing of the concrete. action due to their internal pore structure. will provide great insight as to the causes for the sults in a poor coarse aggregate-to-paste bond in the hardened aggregate being susceptible to the conditions of the soundness concrete. they are subject to Friable particles are those aggregate pieces that have little breakdown during wetting and drying. gregate. Lightweight pieces include highly porous aggregates that float on a liquid Clay Lumps of density 2. present in greater amounts without adverse effect on the con- tion of the actual performance of the aggregate in concrete in crete. and coal Other Deleterious Substances and lignite. If this material adheres to the coarser aggregate parti- formance. Their deterioration bility and the resulting cracking of the concrete or the forma. deleterious substances include the following categories: associated with other rock types. coal and lignite may also be found C 33. 40) techniques. As is often the case. A small percentage of this material may have strength. The test procedure itself con. If the fines is subjected to ASTM C 666. soft particles in an aggregate seemed to have little correlation Then it is simply a matter of placing the test aggregate in the with concrete strength.62 % for two different laboratories. chert that has the potential for Soft Particles physical disruption of concrete under freeze-thaw conditions Although often confused. lignite are usually present in larger-sized pieces and often result in pits or popouts at the surface of the concrete due to Material Finer Than 75 m Sieve subsequent weathering. moved in the water) is the amount of minus 75 m material in the sample. it may be necessary to run X-ray diffraction or other analysis Chert (SSD Specific Gravity Less Than 2. however. that there was little correlation between the manual manipulation by the fingers to break any susceptible amount of minus 75 m material in the sample and the results particles into smaller sizes. the ASTM Test Method for Sand determine the amount of minus 75 m material in the aggre. wood. tall oil residues. a poor freeze-thaw damage depends on a number of interrelated fac- coarse aggregate-to-paste bond may develop. Staining of the surface may also result ASTM C 117 is the method used to determine the amount of this from coal/lignite. the sample is of the sand-equivalent test. 2. including the characteristics of the pore system and the par- strengths. examined by a petrographer. material over a 75 m sieve. and this distinct. higher percentages crete paste. It has been reported [35] that sand-sized particles of chert smectite. FORSTER ON SOUNDNESS. or nontronite). The procedure employs a heavy Book of Standards followed a number of years of debate in liquid that can be mixed to possess the specific gravity required committee meetings as to the merits of the test. the difference should be no greater than 0. if the aggregate is rather it is the weak bond holding the grain together that de- predominantly chert.82 % for two different laboratories. natural volcanic rocks that perform well in concrete may float entraining or other admixtures used in the concrete. if the minus 75 m material is ticle size. soft particles and friable particles are usually has an SSD specific gravity of less than 2. whereas the It should be noted that this criteria applies only when the chert component grains of a friable particle may or may not be soft. any clay lumps or friable particles (or portions most notable. ASTM C 142.40. Others have reported some corre- wet-sieved over a designated sieve according to the size range lation between the sand-equivalent test and the water demand of the original sample. volume change during wetting and dry. After manipulation. The vulnerability of the chert to remain adhered to the coarse aggregate during mixing. Ref 32 and Ref 33). as ASTM C 851) was used for some time as a means of identi- sure. Tests conducted by Gaynor [36] on 130 samples sample has undergone the ASTM C 117 test) followed by showed. This low correlation may have been heavy liquid. for fine ag- Testing for these two classes of deleterious substances is com. of this material in the coarse and fine aggregate must be con.43 % for a bined in one ASTM test. the particles should be workability. resulting in lower tors. Equivalent Value of Soils and Fine Aggregate (D 2419) is the gate. As a result. structure. Of these. to an aggregate sample after it has undergone a washed gra. the results of two properly conducted tests should differ by no more than 0. the component mineral grains that characteristic is used as a distinguishing criteria in ASTM C 33. directly comparable service may be allowable (see ASTM C 33). material in an aggregate sample. In order to determine the mineralogy friable particles is the change in mass of the sample due to the of the minus 75 m material. and density benefits for lean concrete mixes. and friable particles using the test method. this test provides a rapid indication of the relative measured in the ASTM C 142 test. Discontinued ASTM Test for Scratch the aggregate must be determined by other means. The precision statement for ASTM C 117 indicates Tests for Deleterious Substances that for coarse aggregate. and expo. By means of water suspension and settlement thereof) that break down in the wet sieving process will not be procedures. Similarly. and Other Lightweight Pieces Due to its pore structure. mental clay minerals or dust of fracture or other material. gregate. The percentage of clay lumps and of a concrete mix [34]. Percentages of as the separation value (2. Coal and in the test. Other tests have been developed that are reported to indi- dation (ASTM Test Method for Material Finer Than 75-m (No. In addition to the detrimental Finely divided organic material may retard the hardening materials noted earlier and deeply weathered soft (nondur- of the concrete and reduce the concrete strength. If there is any doubt about the composition of the light- sidered. is present in the aggregate in small amounts. the total amount records are the surest means to predict performance. The test involves washing the and pine oil contain materials that readily disperse in the alka.28 % for a single operator Clay Lumps and Friable Particles or 0. Brown lignite coal. make up a soft particle are soft (often weathered). and calculating their percentage of the total sample. ASTM C 123 is used to separate aggregate pieces of fying soft particles. as well as the characteristics of the surrounding con- essentially free of clay minerals and shale. Deletion of ASTM C 851 from the ASTM different specific gravity. .0 for coal and lignite). weight pieces identified by ASTM C 123. proportion of “clay-like or plastic fines and dusts” in a fine ag- sists of a 24-h soak of the sample in distilled water (after the gregate or soil. however. A petrographer should be consulted in this regard. AND COATINGS 361 one or more of the swelling clay minerals (montmorillonite. preferably Hardness of Coarse Aggregate Particles (C 235) (later included prior service record in similar concrete. This material able) aggregate particles. As noted earlier. cate the amount or proportion of clay-sized fines in concrete 200) Sieve in Mineral Aggregates by Washing (C 117)) to aggregate [32]. As noted earlier. This method is applied single operator or 0. and any material carried through line solution present in concrete and may cause dark brown the sieve by the wash water (or less frequently dissolved and re- stains and zones of weakness [34]. certain man-made aggregates and may also interact with or affect the effectiveness of any air. its potential effect on the durability of fines a friable particle. with the formation gregate sizes) do not damage concrete containing them when it of microcracks (see ASTM C 295. DELETERIOUS SUBSTANCES.40 for chert. and whether it is potentially detri- soaking manipulation and sieving processes. (which are detrimental to the durability of concrete in coarse aging in the hardened state can be increased. skimming off the lightweight (reject) pieces that due to the difficulty in differentiating between soft particles float. Coat- rather than being dissolved. There ample) may react with the alkalis in the cement. if the dust of fracture occurs not as a coarse aggregate ica. if necessary. Since the test solution reacts with all types of organic from the aggregate during mixing. This coating may lution is compared to a standard solution or standard color have to be dealt with either by additional aggregate washing to glass plates to qualitatively determine the amount of organic remove it or. the concrete occurrence in sand and gravel deposits. pending on the nature of the material being identified and other In addition to strength and setting time. gypsum. ASTM C 295. crete strength when present in small amounts. some organic mat. and then ings composed of iron compounds may result in staining of the precipitated as in the chemical coatings process. A soft. sion during handling. other sulfates. and stockpiling all produce a certain amount of fines (often called Organic Impurities “dust of fracture”). opal. this class of coatings is limited to ing to the aggregate particles. The procedure consists of . polish. concrete surface. Aggregates resulting in colors darker than the Identification standard should be further evaluated by other tests such as The usual approach used for identifying the composition and ex- mortar strength and setting time. namely. by compensation for the ad- matter. or Air entrainment is a particular area of concern [37] in that the easily soluble salt) likely to be deleterious when the aggregate is organic material may act as an air-entraining agent of variable used in concrete. they are derived from these particles through impact and abra- acteristics that led to the test results obtained. As with the scratch test. and compres- take place. susceptible to swelling in the presence of moisture. sand and gravel deposits may have either chemi- (C 87) compares strength results of mortar samples containing cally or physically deposited coatings. These coatings usually consist of fine materi- the particles can influence the test results. such as coarse or tion. unloading sizing. and polish-susceptible aggregate source the solution after 24 h due to reaction of the solution with any material. the results should be inter. amounts of fines during processing.362 TESTS AND PROPERTIES OF CONCRETE Two test methods. same deleterious results in the concrete as they would if ticles on which they precipitate are often of the same composi. the coatings and the aggregate par. Other possible chemically precipitated coatings include fine aggregate particles. it is only a screening test. the amount dependent on the characteris- ASTM Test Method for Organic Impurities in Fine Aggregates tics of the source material being processed. In this regard. but dispersed in the mix in small quantities. iron oxide.5 %. and for Concrete (C 40) is a simple screening test for determining wear-resistant source material will produce only small the presence of organic material. Certain siliceous coatings (opal. wear. by Coatings conducting strength tests on concrete containing the aggregate. on the other hand. first qualitatively during the petrographic examination. where. if the coating of fines is shown to be removed matter. As noted else- chemically precipitated coatings are calcium carbonate and sil. whereas a crushed stone the subject aggregate as received with strength results of can have only a physically deposited coating. aggregate coatings may be detri- Naturally occurring coatings are those that are deposited on the mental to the strength properties of concrete if the bond of the surfaces of the aggregate particles by means of natural cement paste to the coating is greater than the bond of the coat- processes. including post-test examination of the break surfaces. Deposition of these coatings often results from solution of coating. The color of the so. and additional factors [39]. to contain materials (such as opal. transported in solution. ASTM C 131 and ASTM C 535. The strength of the bond of the coating to the particles should also be determined. to form a coating on the coarse aggregate. Description Effect of Coatings on Concrete Naturally Occurring Coatings From a physical standpoint. As of Organic Impurities in Fine Aggregate on Strength of Mortar noted earlier. Goldbeck [38] reported for the requisite period of time for these natural processes to that flexural strength reductions of up to 1. The products of this reaction are These coatings are also transported by the moving groundwa. including bits of wood and twigs that do not affect con. as well as a weakening of the aggregate/paste . have also Artificially Generated Coatings been used as a measure of the presence and amount of soft Coatings on aggregate particles may also result from one or particles. depending on also are physically deposited coatings in sand and gravel de. may produce enough fine material organic material present in the aggregate. and phosphates. the amount of alkalis present. Loading. portion of the deposit. since only this type of will fail at the coating/aggregate interface at a smaller load than aggregate source has the aggregate particle surfaces exposed it would otherwise fail. whatever necessary means. Within this context. a layer or layers of silt and clay-sized particles. producing ter in the sand and gravel deposit. When this occurs. more of the steps necessary to produce an aggregate from a preted carefully since many factors other than the softness of source material. Petrographic als of the same composition as the particles they coat because examination of the material will help in identifying the char. posits. characteristics to be determined. crushing. If the coatings are considered ter may reinforce or detract from the efficiency of admixtures. ditional fines in the mix during the design of the concrete. ASTM Test Method for Effect tent of coatings is a petrographic examination. The two most important cent of dust of fracture included in the aggregate. organic material. and then. included in the concrete in any other form. for ex- gypsum. Since the source of the coatings is the Soluble or chemically reactive coatings will cause the particles in the deposit itself. it may not the minerals from one portion of the deposit (by percolating be detrimental to the concrete and may in fact be of benefit to groundwater) and redeposition in another (usually lower) some properties of the plastic and hardened concrete. can occur for every per- coating can vary over a wide range. but migrate as solid particles tensile stresses in the concrete that can lead to cracking. other components in the mix. The chemical and mineralogical composition of the sive strength reductions of up to 2 %. the coatings must be positively identified by efficiency. usually not nearly enough immersing a given amount of fine aggregate in a standard to produce any undesirable coating of the larger aggregate solution of sodium hydroxide and noting the color change in pieces. This practice al- mortar samples made using the subject aggregate after it has lows a wide latitude in the equipment and procedures used de- been washed to remove the organic matter. A hard. 15. 42. West Conshohocken. and the effect that any fine particles derived from Engineering Geology. ASTM C 88 certainly can be a useful indicator ings. Concrete-Making Materials. West Conshohocken. V. Because it is so complex. and Mielenz. S. p. are reported to be not detri. 77. ASTM from crushed stone production. West Conshohocken. G. C. O. and hardened concrete.” The Heritage of bond to them. a petrographic evaluation... “Magnesium Sulfate Accelerated Soundness Test on Coatings may be subdivided into naturally occurring coat. p. ASTM STP 169A. International. 213. “The Significance of Sodium Sulfate and Freezing environment. “Improvement in the Uniformity of the Acceler- included under coatings.” “Significance of Tests and Properties of Concrete and of soundness and. B. 1946. pp. “Soundness and Deleterious Substances. Magnesium Sulfate Soundness Tests. and should be subject to the same [18] McCown. Deleterious substances include clay lumps p.” Report to gregate (often just the same source is not specific enough). as defined herein. the service record should involve the same ag. stances on concrete. service-record is different from the intended use and. and the Association. wetting and drying. R. “Petrographic Examination Concrete Aggre- ance to all aspects of weathering when used in concrete or gate. F. and friable particles. ASTM International. p. ASTM International.. L. MD. [17] Bloem. engineering judgment must be employed. Highway Research Board. 312. PA. Vol. Highway Research Board. Results of ASTM C 88 are often considered to be [6] Swenson. Highway Research Board. ASTM International. 1956. major components. pp. Surface Area. D. ASTM Committee C9. PA. Boulder. [3] Rhoades. “Petrography of Concrete Conclusions Aggregates. a reliable tional. Vol. and after strength testing) made during the mix design process [2] Bloem. 3. L. West Conshohocken. Certain types of fine material. the Subcommittee III-e. 1953. Materials. pp. although several als. . and Proudley. “Basis for Classifying Deleterious an aggregate’s soundness without considering all that the Characteristics of Concrete Aggregate Materials. PA. West Con- shohocken. Vol. 213. Part 1. 35. ASTM STP 169A. 12. 1938.” Proceedings. p. AND COATINGS 363 bond mentioned earlier. pp. 882. [16] ASTM Subcommittee C09. same concrete mix design and components. and good lead to corrosion of reinforcing steel [7]. 39.” Proceedings. V. It is at this point that staining and efflorescence at the concrete surface and may also examination of test results. Chlorides and sulfates can cause some interpretation will be necessary. West Conshohocken. the term deleterious substance usually refers to ac. pp.. L. ing of the aggregate. 319. 381–403.. fications for Physical Characteristics of Concrete Aggregates. E. incorporation into West Conshohocken. 1936. Silver Spring. By [9] Walker. F. the amount of the constituent present. no one test adequately Tests and Properties of Concrete and Concrete-Making Materi- measures the soundness of an aggregate. “Modified Procedure for Testing Aggregate placed. “An Improved Sulfate Soundness Test for may be prescribed depending on the identity. 584–628. “Shape. FORSTER ON SOUNDNESS... Geological Society of America. [10] Wuerpel. the same type of structure. The effect of deleterious sub. National Sand and Gravel consideration.. E. 1966. H. 36. 581. 23 Sept. Vol. D. Weathering may include any combination PA.” Bulletin No. Following identification of the coatings involved. ASTM International.. West Conshohocken. PA. C. R. D. Journal. C. also beginning to be used more widely as an indicator of [7] Ozol. R. Because of the wide variety of materials [14] Woolf. 1931.. most reliable. cance of Tests and Properties of Concrete and Concrete-Making ing the petrographic examination of the aggregate. other applications. ASTM STP 169A. and Aggregates. S. “Aggregates. and Kriege. I. Surface Texture. R. PA. [4] Mielenz. In summary. [13] Paul. 497–512. M. quantity of the coating. “The Problem of Deleterious Parti- ence and amount.” Proceedings. and the tests used to determine their pres- [11] Walker. ated Soundness Test of Coarse Aggregate. pp. 323–332. Vol.” Proceedings. C. material in the aggregate (other than coatings) that may be 1935. and Chaly. assessment of soundness can be made. mental and even beneficial in some instances [31].” Proceedings. The First Hundred Years.” Circular No. tests certainly provide good insight as to how an aggregate PA.. the surest means of prediction of performance of an aggregate minutes for the years 1990 and 1991.” Proceedings. ASTM Interna- tion (preferably including a prior service record). Aggregate Durability. C. therefore. West Conshohocken. 1954. American Concrete Institute. April 1956. p.05. 11. [8] Garrity.. or freezing and [5] Mielenz. p. p.” Signifi- will often help to verify conclusions reached about coatings dur. ings and those generated by artificial means through process. K. Centennial them have on the properties and characteristics of the plastic Special Vol. DELETERIOUS SUBSTANCES. L. will behave. Methods for Testing and Speci- In all three of these areas of aggregate quality assessment. Jan. and Bloem. their bond to the aggregate relative to the cement paste’s [1] Mather. West in concrete is the availability of a prior service record. PA. CO. pher using ASTM C 295 is the most practical approach. To be Conshohocken. Vol. of heating and cooling. Usually. Concrete Aggregates. ASTM International. “Factors Affecting the Testing of Concrete rial. 1932. E. aggregate coatings may be innocuous or deleterious to concrete depending on their solubility in the concrete and their effect on any chemical reaction that might References occur. and others. specific tests [15] Woolf. 1958.. 54. Examination of specimens (both before 1991. The unconfined freeze-thaw test of aggregate is American Concrete Institute.. 42. ASTM cessory or minor constituents in the aggregate rather than International.” Bulletin No. p.” Significance of thawing.” Proceedings. A. low SSD specific gravity chert. ASTM International. 38. “Petrographic Examination. PA. and Mather. Vol. 1950. such as dust of fracture Soundness by Use of Magnesium Sulfate. one or more of these components of the and Thawing Tests on Mineral Aggregates. structure and environment in which the concrete will be [12] Wuerpel. 52. 327. “Studies of Sodium and convention. 1966. coal and lignite.” Proceedings.. when used along with other informa. 327. and Coat- soundness. O. “Studies of Accelerated Sound- A deleterious substance.. 1188–1218. term implies. West Conshohocken. V. Part 1. ASTM International. 1939. PA. will depend on the type of substance under cles in Aggregates. “Sulfate Soundness Test Relationship. ASTM International. evaluation by a qualified petrogra. PA. C.03.” Proceedings. detrimental to the concrete in which the aggregate is used. nature. Vol. An aggregate’s “soundness” may be best equated to its resist.. Vol. 987–1002. D. fine mate. 1966. May 1956. D. 237. refers to any ness Tests. DC. 24. K. Feb.. 20. O. 1939.. Vol. 1966. Materials Content and Dominant Cation on the Water Sorption Capacity of Bureau. Feb.” Proceed. West Association and National Ready Mixed Concrete Association. Jan. F.. “Factors Affecting Freezing-and-Thawing [25] Sweet. 599. A. ASTM Interna- Research Record No. Vol. “A Comparison of Absorption and ity of Concrete Aggregates. May 1976. lines for Using Higher Contents of Aggregate Microfines in Port- [21] Cantrill.. Highway Research Board. Concrete.” Proceedings. Vol. “Accidental Air in ings. M.” Proceedings. Noyes [20] Woolf. 744–761. Edmonton. International.” Public Roads.” Abstract of paper presented at Geological Materials Method 29. Washington. p. West Conshohocken. ASTM search. 39. Tests and Absorption of Sedimentary Rock. 1958. B. An Experimental Study on the Guide- 1927.” California Highways and Public Soundness Tests on Main Sands. 1991. 1945. Compressive Strength of Air-Entrained Concrete. Park Ridge. 273–284.” Bulletin No. pp.. NYState DOT. Conshohocken. P. [31] Ahn. TX. D. 201. Clay [29] New York State Department of Transportation. 34. ASTM Interna. p. 1929. 1983. 113.. D. pp. and Herbich. Vol. Silver Spring. 1956. “Soundness and Deleterious Substances. 26. 771. Vol. C. and Campbell. Conshohocken. A. PA.” Research Report No. DC. J. 1159.” Technical [26] Vollick. 30. H. K. Nov. 144. p. P. American Concrete Institute.. A. “Relation of Absorption and Sulfate Test Results of [33] Lyse. Highway Research Abstracts. 13 May 1968. West Conshohocken. Chicago. 51. [34] Dolar-Mantuani. Aggregate Acceptance Procedures. “Rapid Freezing and Thawing Test for Aggregate. W. 2.. [37] MacNaughton. Society of Canada. 301. “Relation Between Sodium Sulfate Soundness Publications.. Dec. PA. NJ. p. DC.” Transportation on the Properties of Concrete. S. Part 1. 1966. 225. E. Albany. L. “Selected Aggregates for Concrete land Cement Concrete. E. [27] Senior. Vol. [39] Hansen. ASTM International. 1947. 18. 23 Aug. PA. [36] Gaynor. tional. pp. “Chert as a Deleterious Constituent in Indiana Resistance of Chert Gravel Concrete. West Conshohocken. 26.” [24] Bloem. PA. 2000. 2001. C... 1960. “A Digest of a Report on Effect of Stone Dust Coarse Aggregate Performance in Ontario. and Rogers. Vol. 233. 1940. West Conshohocken. International Center for Aggregates Re- Pavement Based on Service Records. D. 487–496. L. C. “Review of Current and Projected Researches. 48–60. PA. p.. Austin. R. C.” Proceedings. D. [32] Temper. 1952.” Significance of Tests and Properties of Concrete and Concrete- Report to Annual Convention.. NY.” Proceedings. W. A. 52. T. A. West Conshohocken. A. Carbonate Rocks. R. 435 p. Transportation Research Board. 1963. B. Annual Meeting. “Correlation of Sodium Information Letter No. No. ASTM STP 169A. October. ASTM International. [23] Mather. L.” and Properties of Concrete and Concrete-Making Materials. 1955–1956.. Vol. I. 1934.. Aggregates. Highway Research Board. National Sand and Gravel Associa- Sulfate Soundness of Coarse Aggregate with Durability and tion.. ASTM STP 169A. H. W. PA. L. “The Influence of Rock Type. Washington. West Engineering News Record. and Pratt. ASTM International. I. Report ICAR 102-1F. tional. Handbook of Concrete Aggregates. and Haskel. p.. 937. .. C. H. Works.364 TESTS AND PROPERTIES OF CONCRETE [19] Hudec. “The Chemical Reactions. 45. [30] Dolar-Mantuani. and Rogers.” Proceedings. A. 1301. 1955. 266. “Tests Indicate Effect of Fine Clay in Concrete.. PA. L.-Dec. D. MD. p. and Skillman. p. Vol. p. 29. National Sand and Gravel Making Materials. “Laboratory Tests for Predicting [38] Goldbeck. [35] Bloem.” Concrete Sands. “The Effect of Clay on the Qual- [22] Adams. Dec.” Significance of Tests [28] Brink. Washington. “Investigation of Concrete Sands. pp. ASTM International. Highway Research Board. and Fowler.. p. Bulletin No. columns. and Elastic Properties. High-strength aggregate mechanical forces and attrition is in the concrete production materials will probably be required in the production of very process. the lithology of the particles and. ticles present. In many uses of concrete. conse- author [1. In many crushed stone aggregates and some The two previous editions of this chapter by the same sands and gravels. walls. In end uses such as MPa (20 000 psi).32 Degradation Resistance. the roughest concrete. includes a discussion of the effect of aggregate strength on Some recognition must be given to the consideration of an concrete. strength and very accurate surface alignment is needed to resist O. and volcanic cinders sometimes used in concrete. In some cases. In other instances.” Concrete carrying a distributed static or dynamic load. the particles are expected to possess enough vidual constituent particles. mineral. casional surface imperfections not particularly harmful to over- so it is not discussed in any detail here. 365 . It is recommended that all performance. usually much stronger in compression or tension than the in concrete in service. D. of magnitude as the concrete in which they are used. their mechanical properties show little variation. A small percentage of weak particles in methods and research. tenacity. Abrasion. stresses. covered slabs. necessary to give the concrete enough strength to resist the dis. aggregate materials beams. and stability to resist. and therefore they are not aggregates in tests and information on hardness. Strength. cavitation damage that can spread rapidly once started. some porous marine limestones. Federal Highway Administration. and to a large extent the indi. Meininger1 Preface stresses that will be of overriding importance in aggregate evaluation and selection. Here. That method is rarely used now. this is not a problem. and not subjected to local stress concentrations. Turner-Fairbank Highway Research Center. and the weakest link in the system is the bond treatment to which an aggregate may be subjected in terms of between the paste and aggregate. Hardness. The 1994 version included information on ASTM sion resistant particles allowed in small percentages may cause Method C 1137 on degradation of fine aggregate in water in a a slight increase of fines during mixing or may contribute to oc- vane-type attrition chamber. In earlier is high-velocity hydraulic structures where high surface editions of this book. ASTM STP 169 and ASTM STP 169A. These tributed service loads. In concerning research on strength and abrasion properties of other cases. footings. The rock. Strength. These weaker or less abra- toughness. requires Introduction aggregate that will bond with the surrounding cement paste permitting the transfer of stress through the aggregate Aggregates for use in concrete. impact. The 1978 version included material quently. ultimately. and Related Properties of Aggregates Richard C. It also included additional references most instances is not objectionable and may be thought of as an and discussion of the mineralogic nature of the breakdown of impurity or deleterious substance. the static and dynamic typical stress levels in concrete. the only real strength prop. impacts. however. or synthetic materials making up aggregates are posed both in concrete production operations and. and the proper subject of this discussion. Also. Examples include pavements and THIS CHAPTER CONCENTRATES ON TESTS RELATING slabs exposed to heavy traffic and hydraulic structures subject to degradation of aggregates—both wet and dry tests—and to eroding forces of moving water and sediment material. McLean. Other uses may expose aggregate near or weaker materials are used because of economic reasons or to at the surface to a variety of localized impact and abrasive produce concrete of lighter unit weight. Woolf covered this topic in his chapter on “Toughness. Actions involved in production are fairly predictable. and other mostly are used that possess compressive strength of the same order structural or architectural elements. in the range 70 MPa (10 000 psi) to 140 those in service may be less predictable. and wearing actions to which they may be ex. An example ASTM STP 169 B and C editions referenced above.2] were longer. eliminating even very small engineers or researchers interested in these topics refer to the percentages of friable or weak particles is desired. the effect of aggregates on wear and frictional aggregate as a whole versus the properties of the individual par- properties of concrete in service is briefly covered. Examples erty needed of the aggregate after the concrete is in place is that are lightweight aggregates. 1 Highway Research Engineer. VA. particles. great variations may exist among the mineral and aggregates and a review of North American and European rock particles involved. must possess a reasonably high strength and rigidity to carry the stresses without mechanical degree of inherent strength. breakdown or excessive deformation—for usual aggregates and without detrimental degradation. high-strength concrete. can be important factors. These loadings or actions usually are Polishing Machine (E 660) applied to the surface of the concrete so that only the properties 14. aggregates that allow rapid polishing visions such as the following have been included in many spec- can contribute to poor frictional properties of wet surfaces. The Micro-Deval test of the concrete will be acceptable. but it can cause a pol. due to the movement occurs. Crushed air-cooled blast-furnace slag is ex- Large-Size Coarse Aggregate by Abrasion and Impact in cluded from the L.366 TESTS AND PROPERTIES OF CONCRETE Impact. ASTM Test Method for Aggregate Durability Index (D 3744) The test methods listed here are discussed in subsequent 5. the amount of material removed by such C 131 or C 535). ASTM Test Method for Accelerated Polishing of Aggre- gates Using the British Wheel (D 3319) Degradation of Coarse Aggregate 10. aggregate test. Scratches and gouges from relatively large lack of enough significantly explicit data relating concrete per- particles or objects are on a macroscopic scale and are termed formance with degradation in the Los Angeles Machine (ASTM wear. ASTM Practice for Accelerated Polishing of Aggregates or tions. abrasion. or coatings may be used at the coarse or fine aggregate for construction. and other wearing ac. Proce. abrasion. machine is to be determined using the the Los Angeles Machine (C 131) grading most nearly corresponding to the grading to be used 3. In the rubbing or scratching mode. ASTM Test Method for Skid Resistance Measurements Us. 13. that the aggregate produces concrete having satisfactory rele- and others relate to properties of concrete in which the per. specifies requirements for a wide range of aggregate sizes. yielding. scuffing. Some relate directly to aggregate properties. However. Procedure C—Ball Bearings) frictional properties of pavement surfaces after being sub- (C 779) jected to traffic [3]. either in a dry environment or in the presence of water. at 50 % for all categories. Other than the Sandblasting (C 418) percent loss limits for degradation of coarse aggregate by abra- 6. Circular Track. as measured by ASTM C 131 or C 535. Impact is where hard particles or objects impinge against 6928)—ASTM and AASHTO have standardized the coarse the concrete surface with enough momentum to cause shat.” however.A. In some cases.” “L. vant properties. ASTM Test Method for Resistance of Coarse Aggregate to Surface actions are of two basic modes—impact and rub. surface to improve the surface properties locally. ized both the fine and coarse aggregate Micro-Deval tests. . gregates are varied depending on severity of exposure to ness involved. 2. (Note: ASTM C 131 and C 535 now nificant quantity of surface mortar. ASTM Test Method for Abrasion Resistance of Concrete by sections relating to the properties measured. damage can be in. if repeated over and over again. judgment pro- other types of service.” and “L.or in the absence of a demonstrable service record provided of this chapter.” when tested in the laboratory. abrasion requirement in ASTM C 33. attrition. ASTM Specification for Concrete Aggregates (C 33) determination of which grading to use in ASTM C 131 or C 535. Pavement Surfaces Using a Small-Wheel. 9. limiting abrasion resist- Concrete Surfaces (Procedure A—Revolving Disks.” “abrasion loss. In highway uses. exposing more and more properly refer to “degradation” in the tests by “abrasion and coarse aggregate with time.A.A. Materials fine aggregate Micro-Deval procedure. ness. machine. 4. Rubbing or scratching action from impact in the Los Angeles machine. . The ASTM standards given here fall under the general purview . ASTM Test Method for Abrasion Resistance of Horizontal aggregates in handling and mixing. ifications to allow use of known satisfactory materials: “Coarse aggregates having test results exceeding the limits specified. ASTM C 33 formance of different aggregates can be compared. ASTM Test Method for Skid Resistance of Paved Surfaces ASTM C 131 and C 535 are accepted and used almost univer- Using a Full-Scale Tire (Locked Wheel Skid Trailer) (E 274) sally in the United States as specification qualification tests for 12. often used to refer to the percentage loss in these tests and as ishing action at the surface. concrete mixtures. . ASTM Test Method for Abrasion Resistance of Concrete sion in the L. is based on the requirement that Small-Size Coarse Aggregate by Abrasion and Impact in degradation in the L. for the relative hard. . ASTM Test Method for Resistance to Degradation of in the concrete. and ASTM is working on standardizing the tering. the “abrasion” limit in ASTM C 33 has been set action. ASTM Test Method for Insoluble Residue in Carbonate (Los Angeles Abrasion) Aggregates (D 3042) 11. ance of concrete surfaces. Degradation by Abrasion in the Micro-Deval Apparatus (D bing. to Attrition (C 1137)—This test is rarely used and has not portance in determining whether the long-term performance been recently reapproved or revised. a minimum compact unit weight is required. They are also used widely ing the North Carolina State University Variable-Speed around the world to evaluate coarse aggregates for various Friction Tester (E 707) applications. or debonding of aggregate particles. ASTM Test Method for Abrasion Resistance of Concrete or effect of coarse or fine aggregate as measured in the other tests Mortar Surfaces by the Rotating-Cutter Method (C 944) unless there are special requirements limiting degradation of 8.) In addition. The 1. and occasionally an abbreviated name for the tests.may be accepted provided that concrete made with similar aggregate from the same source has given satisfactory service. or requirements pertaining to the dure B—Dressing Wheels. wear” are the capacity to remove much material. 15. In other words.A. coarse aggregate for concrete.A. ASTM Test Method for Resistance to Degradation of to test an aggregate product. special is now considered best for testing the wet degradation of aggregates. will wear away a sig. . the terms: much smaller particles—on a microscopic scale—does not have “abrasion. (Underwater Method) (C 1138) there are generally no other specified limits with respect to the 7. ASTM C 33 for concrete aggregates includes a modular flicted by the movement of particles or objects on the surface format where many of the required properties of coarse ag- under enough load to cause indentation. ASTM Test Method for Degradation of Fine Aggregate Due of the aggregate at or near the surface are of any substantial im. In the Los Angeles Machine (C 535) its place. Applicable ASTM Standards . and therefore cause scratching or gouging as weather and the end use of the concrete. CSA has standard- with good impact resistance are said to possess good tough. The product of the degradation action in that case may tires on coarse aggregates as measured in the Nordic ball be more of a dust rather than the larger angular pieces resulting mill test.75-mm (No. High variation of results was found revolutions of the drum are used. EN 1097-1:1996 includes the Micro-Deval test of coarse be needed for the smaller sizes of coarse aggregate.” Good correlation was found between all the whereas the charge varies with grading in C 131. They may give different results developed for aggregates under CEN/TC 154. ASTM C 535. Also. strengths below 50 MPa (7200 psi). Jumper [8] and Walker and Bloem [9] conducted re- involves placing a sample of aggregate and a charge of steel search where aggregates of high and low abrasion loss were balls into a hollow steel cylinder that is 508 mm (20 in. 2. These simulated coarse ag- and 711 mm (28 in. These data are tested by the German Impact Test. narrower 37. the tests characterize “the same or at least similar properties of quired charge of steel spheres is 12 for all three gradings. For this reason. However. gregates tested in concrete specimens. at least during early rev.) into the in abrasion values with increased strength. from the shattering. fer only in minor respects for this particular test. EN 1097-9:1998 includes the resistance to wear of studded wearing.A. the method is a dry abrasion and impact test that strength. abrasion test. abrasion with concrete should not greatly exceed 0. With respect to the freezing and thawing durability of ag- gated pieces might cause this ratio to increase. sample size from 5000 to 10 000 g and a doubling of the num. Correlation of L. harder rocks resistance to fragmentation. European Standards have been from ASTM C 131 and C 535.5-mm (1 1/2-in. With one exception he degrade readily during handling. Caution should be exercised in comparing values obtained Over the past several years.) Percent loss is ob. expressed as a percentage of the original mass. F. it is a provide a cushioning effect. with the strength of concrete prepared with a wide va- 1964 and 1965.2. Walker the amount of the final sample coarser than the 1. Often pressive strength on abrasion loss. Over that range. The same equipment is used for ASTM C 535. laboratory studies reported by and a new test method.A. dust produced early in the test may In spite of the drawbacks of the L. is closed on the ends.0 %. In Woolf [6]. or brittle material or a large number of flat or elon. and a modified Marshall Impact Test. fossiliferrous lime- three more gradings for large aggregate sizes—75-mm (3-in. Of those for me- for similar materials. abrasion and German Impact Tests when tests were ing the 1. In another pre. 4) sizes were added relations with concrete abrasion resistance were with concrete (Gradings C and D). the ratio of the drop-off of compressive and flexural strength with increased loss after 100 revolutions to the loss after 500 revolutions abrasion losses. 12) sieve. the aggregates. On the coarse aggregate that is similar to the British wheel test. freezing and thawing data.A.). the larger sizes were deleted from ASTM C 131. [12] did not find a relationship between concrete durability mm (3/4-in. the L. 9. One soft. and as a general test. dardization of procedures may be necessary. ranging in abrasion loss the AASHTO Materials Reference Laboratory. loss and the in 1937.0-mm abrasion resistance of concrete containing the aggregates (1 1/2 or 3/4-in. and single Highway Research Board. Loss is again determined us.) max.A. aggregate using a 500-g specimen. In C 535.5-mm (3/8-in. decrease in compressive strength for constant cement factor tained as the difference between the original sample mass and concrete was from about 27–23 MPa (3900–3300 psi).A.). compared the results of aggregates operator coefficient of variation was 2. the British Impact Test (British Stan- cision investigation within one state. For a material degrading at a uniform rate. In 1947. The loss in the L. specification limits for chanical and physical properties of aggregates are the following: larger sizes may not necessarily be the same as those judged to 1.70-mm (No. To some extent. a small percentage of very soft. and Bloem did not detect any dependence of concrete com- 12) sieve. EN 1097-2:1998 includes the L. Above that strength.A. 1000 tests run in one laboratory. the data show a higher dard 812). Gaynor [13] also reports this and other were tested by both ASTM and AASHTO procedures. Bartel and Walker [10] and Walker [11] showed a slight loss.) and 4. was adopted for them. fairly fast test with known variability. abrasion test has been correlated by ber of revolutions from 500 to 1000 for these larger sizes. no imum size grading (Gradings E. The samples from about 15–65 %. for the L. abrasion test and a drop- olutions of the drum before any fines are created that might hammer impact test of coarse aggregate to determine tend to cushion the impact forces. MEININGER ON PROPERTIES OF AGGREGATES 367 ASTM C 131 was first adopted as a tentative standard test found no significant correlation between L.A. Bloem and Gaynor [7] failed to show such a relationship with Briefly.5 or 19. a revision was prepared to add strength and water-cement ratio.0. other hand. using three different test procedures. it Smith [5] used coarse aggregates in concrete with L. and has gregate combinations did show some correlation of reductions a single rigid steel shelf extending 89 mm (3 1/2 in. suggesting that further strict stan- the development of a precision statement for ASTM C 535. Kohler [14]. Impact probably causes more loss. tend to shatter more 3. gregate to obtain loss values from 42–58 %.) long blended to produce a range of values. The most significant cor- Later.5 %. the based on samples ranging in loss from 10–45 %. riety of aggregates. EN 1097-8:1999 includes the polished stone value of than softer materials that can better absorb the force. even though they are strong. even though the methods use different loads and procedures. and a second. but they did find that high the loss is determined at 100 and 500 revolutions (200 and abrasion losses had lower flexural strength with the aggregates 1000 revolutions for C 535) to give an indication of the rate of studied. older Deval Abrasion Test. stone did decrease the concrete abrasion resistance at 50-mm (2-in. and minerals. softer minerals will be more susceptible to surface 4. in a comprehensive study reported to the tory coefficient of variation was found to be 4.) maximum size aggregate samples distributed to a and abrasion loss at 500 revolutions or 100 revolutions. giving possible misleading results.) in diameter.A. At first. . does provide a means of identifying coarse aggregate that may abrasion losses ranging from 13–39 %. the tions in C 131 (1000 revolutions for C 535. No data are available to use in run in different laboratories. which dif.70-mm (No. strength is inconclusive. it provided for testing only 37. Gaynor and Meininger The precision statement in ASTM C 131 is based on 19.) maximum size aggregates (Gradings A and B). and G)—with an increased coarse aggregate effect could be detected. Multilabora. Jumper blended ag- chamber. He found that level of variability on samples having a loss of 13–18 % [4]. friable. The cylinder is rotated at 30–33 rpm for 500 revolu. The re. abrasion test. This large number of laboratories throughout the United States by study included 56 coarse aggregates. which measures the ten. abrasion strength and water requirement. However. abrasion test and an extended 4-h test without the steel balls. The value obtained is very de- structures. abrasion test ranging from 12–50. that may create undesirable fines during handling. Breese [18] gives a history of the development of wet abrasion tests in the Western United States. was found to be a potentially useful tool in identifying hard cedures run in a wet environment. In studies at the Pennsylvania DOT and at Purdue University in Indiana [21. dane [23] looked into sources of variation. Liu [16] reported on research that led to the development In work with the Washington degradation test. has been standardized as ASTM D 3744. the Washington degradation test was one of the tests that interested these researchers. and a crushed river gravel all from sources in the State of Washington.A.A. A few relied on petrographic analysis to identify mineral constituents that are associated with rapid weathering. He concluded that Nevada had a number of degradation susceptible aggregates and that the California durability index test is not as harsh as some of the other procedures. the struction and normal use under traffic conditions.8. Nevada Air Test. The durability index tests start with a washed sample and cance for base courses and aggregate surfaced roads where the then measure the quality of the fines generated from interpar- possibility of interparticle movement in the presence of water ticle abrasion during a wet agitation period. the problems were termed moderate. For concrete aggregates.0. finer samples will correlated with concrete strength and the hardness of the indicate more degradation.A. It is in- principal value of such tests are identification of aggregates tended to complement the sand equivalent. In addition to the Washington test. abrasion loss versus California durability index the Corps of Engineers (CRD-C 148. The California durability in. a number also indicated use of some type of wet abrasion or attrition procedure including: Durability Index.A. Plasticity index of the fines produced from the extended test were respectively 6. that showed less than 40 % loss in the L. a pit-run river gravel. He concluded that signed to assess the abrasive effect of waterborne gravel. Fines from the standard L. At Purdue. abrasion. not related to the L. He concluded that the results of this test were pendent on the surface area of the charge. 1—L.22] to help identify the properties of shales that might help determine suitability for its use in embankment or as a granular material. Method of Testing Stone [24]. batching. however. the underwater abrasion of concrete was repeated agitation cycles as found by Hveem and Smith [24].A. and modified L. shales.A. He experimented with different procedures designed to detect comminution degradation and alteration degradation.A. Some aggregates de.A. The durability index for fine and coarse aggregate (ASTM grade in a different manner in the presence of water than D 3744) was developed to measure breakdown during con- those in dry test methods [15]. Idaho Degradation. such as correlation between the durability index and the L. . Ekse and Morris [19] compared properties of fines produced from a standard L. abrasion. There is little and mixing that could affect concrete properties. abrasion test were found to be nonplastic. Goodewar- of an underwater abrasion test method (ASTM C 1138) de. test. the Oregon Air Test.0. Wash- ington Degradation Procedure. that gave good results in the Washington Test. The L. The aggregates were crushed basalt. Highway Research Board Circular 144 [17] indicates use by state transportation agencies of various test methods relating to aggregate durability (other than freezing and thawing). and sulfate soundness procedures. rocks. Minor [20] describes the development of the Washington degradation test that was prompted by the poor performance of several basalt crushed stones and volcanic gravels that gave losses in the standard L. abrasion of the coarse aggregate.368 TESTS AND PROPERTIES OF CONCRETE Wet Degradation and Attrition Tests for Expansive Breakdown on Soaking in Ethylene Glycol) were good indicators of performance. High rebound readings were obtained for two shales dex test for fine and coarse aggregate. abrasion (a dry test) was used by the great majority. abrasion test and dency of an aggregate to break down into plastic clay-like fines. abrasion tests using water. cleanness value. Figure 1 shows may occur over the period of service of the material. These tests also have signifi. the ultrasonic disaggregation test and the ethylene glycol soak test used by Fig. Almost all agencies reported some degradation problems. and 1.A. These aggregates contained altered minerals that contributed to rapid weathering.A. L. 2. in most cases. durability index values versus L. both surface attrition and leaching of clays from the aggregate and other debris traveling over concrete surfaces in hydraulic pores were involved in the test. Aggregate quality improved with aggregate. the Swiss Hammer There has been increased interest in abrasion and attrition pro.A. 2-23A for fine performance of aggregates in asphalt concrete and in unbound TABLE 1—Within-Laboratory Variability of Attrition and Micro-Deval Tests of Fine Aggregatea Natural Sand Shaley Limestone Screenings Mean Loss Coefficient of Variation Mean Loss Coefficient of Variation Micro-Deval 13. Subsequent soundness. Rogers [33] discusses the available. in the test. the magnesium sulfate soundness test. NCHRP. In studies by Slater [25] and more recently by Gaynor to freezing and thawing and/or to chlorides in service. attrition. and it was relatively in- using a vane-type attrition chamber. 2). It is a wet attrition test developed in France during the value. the Micro-Deval test was found terial of almost 12 % in 2 h in one study. In the Ontario study.0 % 38. Loss is expressed depended on aggregate hardness. ject to weathering and abrasive action and has been included abrasion tests. ASTM is now considering the fine aggregate test for tended to break down by attrition much more readily than the standardization. For coarse aggregate agitating of concrete has been the subject of several investiga. coarse aggregate.3 % 11. It is being used in Ontario and turned at 800 rpm. ASTM C 1137 was approved. However. bust impeller and a reduction in the rpm from 850 to 390 rpm A number of tests have been used to measure the propen. The equipment is readily formance for marginal aggregates.1 % ASTM attrition 13. In 1990. Hard quartz sand only test and a similar Ontario (MTO) attrition test with a more ro- caused an increase of 1 % in the same 160-min mixing period. 100) ma. but it had lower variation (see Fig. Europe. they are better predictors of field persion in the Micro-Deval Apparatus.S.S. In a similar Ontario study of coarse aggregate tests.4 % 1. both amount of fines produced and the coeffi- crete mixing [28–31]. For fine aggregate. Also included in the research were the with steel balls in the presence of water.) steel aggregate to improve the repeatability of the test [33]. . and grinding mm (No. CSA also has included sults than fresh basalt. alternative specification limits for Micro-Deval loss of a Degradation or attrition of aggregates during mixing and maximum of 20 % loss for fine aggregate.9 % 23. and 2 h and 40 min in another case. and it is has been standardized as ASTM D 6928 when used in conjunction with water absorption and petro- for the Resistance of Coarse Aggregate to Degradation by Abra. The test for 2 h. fine aggregate.8 % MTO attrition 4. polished stone value. the Mi- The Micro-Deval test is now being used in Canada.1 % 5. and in the U. the Ministry of Trans. 100) material generated from the fine aggregate and water and rotated at 100 rpm for 15 min. it was identified that during prolonged other exposures.1 % 14.S. In 2 h of mixing in a laboratory mixer in one The fine aggregate Micro-Deval test uses a 700-g sample of case. and a number of state transportation departments maximum loss specifications used in Ontario for the Micro- are evaluating its use. 1500 g of a graded tions were made in Canada to a larger 1500-g sample of coarse sample are soaked and then placed with 9.8 % 1. The sample is placed in a steel jar mill with steel balls 150-m (No. has shown its potential relationship to the cluded that the Micro-Deval and unconfined freeze-thaw tests performance of different types of coarse aggregate in highway approximate the deterioration due to weathering and that. the coarse aggregate Micro-Deval loss limit is mixing the fine aggregate with its much greater surface area 17 %. It has gained popu. 200) material generated break down. mounted in a drill press sensitive to fine aggregate grading.A. The loss is measured by the amount passing the 1. It was found that the Micro-Deval test had method is based on work reported in the preceding references the lowest within-laboratory variability. the test is not used much.1 % 20. little change was sand washed to remove material passing the 75-m (No.8 % 6. [35. For [26] and McKisson [27]. cro-Deval coarse aggregate test was evaluated and compared to and the U.36]. Table 1 shows a comparison of sity of fine aggregates to degrade due to attrition during con. graphic examination. 16) sieve. the Micro-Deval loss limit is 14 % for use in concrete exposed tions. and base course applications portation in Ontario (MTO) modified the test. re- The Micro-Deval tests have been standardized by the search has been conducted relating the Micro-Deval test to the Canadian Standards Association as CSA A23. the Micro-Deval test for coarse aggregate.S. and to evaluate fine aggregate.5 mm (3/8-in. The Micro-Deval test correlated with sulfate as an alternative test for aggregates for concrete. A fine aggregate known to as the percentage of minus 75-m (No.4 % a Number of replicates 10. and balls and water in a 5-L steel jar mill that is rotated at 100 rpm these procedures have been used in the U. In 1960s using a 500-g specimen for coarse aggregates. The amount of minus sieve. Ontario Test Method for unconfined freeze-thaw of coarse larity in Canada in evaluating the suitability of aggregates sub. It was con- research in the U. caused an increase in minus 150-m (No. In the other study. the three tests. of both coarse and fine aggregate. aggregate. has not been recently reapproved or revised. and the L. asphalt. MEININGER ON PROPERTIES OF AGGREGATES 369 Weathered basalt was found to produce lower durability re. Modifica. aggregate and 29A for coarse aggregate. They also included the ASTM C 1137 attrition 100) size of about 6 % in 160 min. and aggregate abrasion value. 200) noted in the coarse aggregate grading. for the evaluation of coarse and fine aggregates three British Standard Tests (BS 812) for aggregate impact [31–34]. Deval tests for concrete.18- provides a combination of abrasion. applications. The cient of variation. to reduce splashing problems. a to correlate with sulfate soundness and water absorption of soft limestone sand caused an increase in minus 150-m (No. for rock from which crushed stone coarse robin testing using six sources of crushed stone ballast coarse aggregates are made. and basalt aggregates and obtained North American railroads have been using mill abrasion compressive strengths ranging from about 160 MPa (23 000 psi) tests of coarse aggregate for ballast. and for a quartzite source.2 MPa (300–900 psi). Certain inferences can be drawn from these data as to the nature and distribution of the strengths of the materials constituting aggregate particles.6–15. cracks. and usually the material is less variable than gravel deposits. [40] yielded. 105–235 MPa (15 000–34 000 psi). Compressive strength increases with confinement. and granite ranged from about In an effort to standardize the procedure and look at sources 6. 3).A. whereas in concrete. 85–275 MPa (12 000–40 000 psi). 200) material in the shaker test. However. (2) strength tests of rock Fig. granite. tunnels. Tests of two types of rocks used as aggregate by Iyer et al. The basalt had a tensile strength of of testing variability. Udd [38] gives a review of the methods used in testing rock and some examples of the range and variability of results. compressive strengths of 105–200 MPa (15 000–29 000 psi) and tensile strengths of 2. and for granite. for a limestone source. These sands also had high magnesium sulfate soundness losses. compres- bases [35. For limestone. 200 sieve after the test. the values ranged from 90–270 MPa (13 000–39 000 psi). nesium sulfate soundness of coarse aggregates [32]. the British aggregate sive strengths of 340–470 MPa (49 000–68 000 psi) and tensile impact value test was seen as a practical substitute for the L.36].1–6.2–11. but the strength of an individual aggregate particle can be influenced greatly by such defects. for traprock. limestone. and fissures. Fig. and various mining applications. only aggregate tested in seven different laboratories. with procedures differing for the gravel and the granite on the low end to 305 MPa (44 000 from the Micro-Deval test and with the mill abrasion loss re. localized stress concentrations may develop due to the nonho- mogeneous nature of the concrete. strengths of 7. there are several problems involved in translating this information to the behavior of aggregate in concrete: (1) conditions of confinement in concrete are certainly different than those of unconfined tests. ured for the gravel. Higgs [29] reported another fine aggregate wet attrition test using a paint shaker to attrition a 1000-g regraded sample of fine aggregate. a railway engineering group published 15. psi) for the basalt on the high end. He investigated a number of basalt fine aggregates and found that those causing rapid slump loss in concrete yielded more than 8 or 9 % minus 75-m (No. These values represent ranges from a number of sources. and both elastic and plastic deformations occur. Kaplan [41] tested abrasion test (see Fig. He also reports compressive strength results from one gravel source ranging from 165–235 MPa (24 000–34 000 psi).7 MPa (900–1700 psi). 3—Relationship between loss in the Los Angeles test specimens usually involve measures to distribute the stress and aggregate impact value of coarse aggregates [32]. or in some instances cobbles or boulders from gravel deposits. Of the almost 1000 compressive strengths the Mill Abrasion Test Method [37] and the results of round. Bond [39] shows compressive strengths of small cubes and cylinders cut from rock material. 2—Correlation of Micro-Deval abrasion against mag. are quite often made in connection with rock mechanics investigations for foundations. limestone. The great bulk of the strength data available is for stone materials where specimens of the required size can be obtained.370 TESTS AND PROPERTIES OF CONCRETE evenly over the entire cross section. Strength of Aggregate Material Measurements of unconfined and confined compressive (or crushing) strength of rock and mineral specimens drilled or sawn from rock ledges. In the Ontario work [32]. . and triaxial tests may not truly represent the situation in concrete. in his state-by-state summary [42]. gravel. The tensile strength meas- ported as the amount passing the No. reported by Woolf. There are many sources for data on compressive strength of rock and in some cases tensile strength or modulus of elasticity.8 MPa (1100–2300 psi). and (3) rock properties are most often reported for specimens that have a minimum of flaws.2 MPa (2200 psi). Concrete and mortar. There has been a good deal of activity in From the foregoing. timate when stress is applied over long periods. There is also a proportion of aggre. The usual practice is to evaluate the The equations advanced by Hirsch and others are complex and aggregate’s performance in concrete to see if it will produce include. Mineral and can be inferred from tests of parent rock material.57] are normally fairly coarse aggregate in concrete.” requirements in this area. These data suggest. MEININGER ON PROPERTIES OF AGGREGATES 371 about 60 results indicated compressive strength levels less than in connection with researches of aggregate and concrete prop- 70 MPa (10 000 psi). volcanic cinders [46]. and 30 of fine aggregate on concrete strength is almost exclusively 106 psi) were used in different proportions in concrete indi- through its shape. the resulting modulus of elasticity of a composite material sion. the matrix [52–56]. Generally. were reasonably elastic. ulus of elasticity will increase the E of the concrete even if the tremely important to concrete strength and that a reasonably properties of the paste are held relatively constant. indicating that the aggregate and matrix are a 28 MPa (4000 psi) oolite coarse aggregate in concrete. Creep is a third factor that enters into the es- source on concrete modulus of elasticity is determined nor. erties [40. shows data where aggregates with E values of because of its large surface area-to-volume ratio. Wear. A between the strength of the coarse aggregate and the strength direct linear relationship has also been found between rock of concrete was established. Because of this and because un- his model analysis with various aggregate and mortar strengths known factors can affect the influence of the paste-aggregate concluded that the best results in terms of delay in formation bond on the stress-strain curve. 9. 62. principally so that it does not break with an E of about 62 000 MPa (9 106 psi) that produced con- down and create excess fines and surface area during concrete crete with an E of 21 000–28 000 MPa (3–4 106 psi). scratching. 34. gates used for concrete that are weak enough.” Johnston [43].” according to Stiffler [60]. As is the case for compressive strength. the modulus of elasticity computed [47]. a good deal Hardness. ulus of elasticity for various rock types. the dynamic values these materials. on the other hand. Johnston [43. using straight lines.41. and there are no ASTM aggregate test methods ity enter into the determination of strain capacity for rapidly designed to yield this information. of the elastic moduli of the constituents. of necessity. as does broad experience with 30 % of ultimate strength. The influence about 14. 5.51]. less than 70 MPa Figure 4 gives an indication of the range of Young’s mod- (10 000 psi). particularly with the aid of an abrasive.59] gives values of tensile modulus of not been established. where natural is necessary in the production of very high-strength concrete rounded aggregate with an E of about 41 400 MPa (6 106 psi) over 55 MPa (8000 psi). There are no ASTM test methods or specification stituent will produce a corresponding effect on the concrete. produced concrete with E ranging from 28 000–34 000 MPa gate particles is apparently not too important as long as some (4–5 106 psi) at 90 days compared to a quarried aggregate minimum level is achieved. using a 48 MPa (6900 psi) sandstone stone [49] and for cement paste [43.44]. The values are somewhat lower than the corresponding compression values. and grading effects on mixing water cating “that the modulus of elasticity of concrete is a function demand needed for workability. Houghton [58] discusses the Elastic Properties concept of predicting the tensile strain capacity of mass concrete so that tensile strains caused by thermal volume changes Modulus of elasticity and related values such as the Poisson’s can be accommodated by the concrete without cracking. and goug- of investigators has also determined rock modulus of elasticity ing actions. are higher. 11. A number rock materials when subjected to rubbing. that their strength characteristic may be an im. Kaplan [41]. elasticity of rock. Aggregate strength may be an Less work has been done on the tensile modulus of indicator of other aggregate properties. but little is known about the “Hardness is the single most important characteristic that con- elastic properties of gravel or sand particles other than what trols aggregate wear. and like all brittle materials from a knowledge of the elastic properties of the aggregate and relatively weak in tension. in using a number of strong ag. Bond is not as important with fine aggregate [56].43. and 207 103 MPa (2. The influence of aggregate loaded concrete. An example high-strength aggregate with excellent bonding characteristics of this is contained in Houghton’s paper [58]. This is due to the formation of bond lightweight structural aggregates and experience using Florida cracks and slipping at the aggregate paste interface. Frictional Properties of information from rock mechanics investigations is available concerning rock deposits [49–51]. and coral in concrete curved stress-strain plot. mally by testing concrete mixtures containing each of the aggregates. The strength of individual fine aggre. It does not always hold that an increase in aggregate mod- It is recognized that coarse aggregate-to-mortar bond is ex. however. it is apparent that the great majorities the more theoretical area of developing equations to predict of the aggregate-making rock materials are strong in compres. texture. over 70 MPa (10 000 psi). concrete of the needed strength. various assumptions. concluded that “no relationship dynamic and static values determined in the laboratory. With a limestone [45]. strength. there is no simple relationship of bond cracks at the coarse aggregate-mortar interface were between aggregate modulus of elasticity and concrete modulus obtained when the aggregate and mortar were about the same of elasticity. Both static and portant limitation on the properties of concrete made with dynamic E data are included. but relationships have elasticity. stress-strain plots for strength. that aggregate strength need only be of the same order of for the concrete will vary depending on which of the several magnitude as the concrete strength needed. This finding should not be taken compressive strength and modulus of elasticity [50. both able to produce concrete over 40 MPa (6000 psi) at 28 have a curved stress-strain plot when the stress exceeds about days age. 76. An increase or de- The significance of strength tests of aggregates is not well crease in the modulus of either the aggregate or matrix con- established. Tanigawa [48] in recognized definitions is used. Rela- ratio of concrete aggregates are not included in aggregate tionships with age for tensile strength and modulus of elastic- specifications. and there is a good linear relationship between gregate materials in concrete. are worn . to mean that aggregates of low strength will not affect concrete Both in compression and tension. Hirsch production. and Collins and Hsu [44]. This is apparently due to min. in concrete abrasion tests using the steel balls or dressing . Initially. and the ac- ing horizontal wheel [63] and British aggregate abrasion tion is such that any texture such as existing pits. Rate of cutting or drilling. of fine or coarse aggregate particles. This can hap- 5. down due to the scratching and pitting that occurs. pen particularly to exposed cement paste and the top surfaces Hardness is a term used often in describing desirable ag. particularly lower-strength concrete. which are just scratched when sub. percussion or the like. 4. load. Rebound Hardness—Shore scleroscope and Swiss rebound the hardness of the fine aggregate is important. Scratch Hardness—Moh’s hardness scale. 4—Relationship between rock type and Young’s modulus: 1 psi 106 6895 MPa [50]. abrasive forces. It is any removal of particles that produces shape changes should be a property that is specified for concrete aggregates. Wear or Abrasion Hardness—Dorry hardness where a core Polishing is a special form of wear where abrasive size is of rock is subjected to wear with an abrasive on a revolv. ASTM had a scratch hardness test. minerals are pitted as well. fine and coarse aggregate may be an important factor in some 1. ASTM C 33 has no limits on soft particles and no jected to the movement of an abrasive on the surface under a other provisions referring to hardness. At one time. The coarse hammer. unlike metals. on a microscopic or macroscopic scale [60]. but it was with. but many potential ways of measuring the hardness [61]. 2. surface to expose a significant amount of the coarse particles. scratches are smoothed and polished gradually. For exam- drawn because of the high variability of the results. formance. and the inability to correlate results with per- observed that. aggregate will become involved only if there is enough loss of 3.” how measurements should be made and whether hardness [65]. Indention Hardness—Vickers hardness and Rockwell instances for concrete surfaces subjected to heavy traffic or hardness [62]. scraping. Wear is “waste or dimin- gregate properties. The mechanism of concrete wear can vary [6]. Stiffler has correct the test. As a general rule. gouges. or value (British Standard 812). concrete strength has been found to be eral grains or particles being pulled from the matrix. such as typical road grit at 10–40 m. but there has been little agreement as to ish by continual attrition. quite small. There are the most significant factor in rate of wear of concrete [64].372 TESTS AND PROPERTIES OF CONCRETE Fig. no way to ple. clay or siliceous material. [69] show photos of stud wear marks. the ture is controlled by the polishing tendency of the exposed friction numbers of the pavement surfaces containing the soft cement paste or aggregate surfaces. rubber tire running against the specimens that are mounted porting test track studies. cular track with a rubber-tired wheel for evaluating pavement In a review of pavement wear testing. stone. A softer limestone aggregate. Studded tires of the pavement. Several other laboratory procedures use a cir- grooves in softer material. used in concrete. and (4) a carbonate and the surface is made up of materials of similar hardness. Some highway agencies [74] have advocated the use of nism was somewhat different. They con. The ASTM D 3319 nificant factors in studded tire wear studies. residue. With For a granite aggregate. De- even when sand and salt were applied to the surface. and it is important in removing and since portland cement paste polishes more during the dry excess water from between the tire and pavement. . In re. Macrotexture is controlled initially by worn flush with the cement paste during the dry wearing cycle. harder aggregates retard abrasion loss and stand out limestone coarse aggregates. uti. in using fine aggregate were lowest after dry wearing and improved a number of concrete finishing textures. Rosen. cycle and gains frictional properties during wet polishing. For carbonate aggregates. Weller and Maynard [75] at the British Road Research softer material wear faster.5 mm) if significant from the surface and show higher frictional properties after speeds are involved. there was an inverse relationship be- harder aggregates. ing characteristics of a number of aggregate sources. for soft ASTM Definitions of Terms Relating to Traveled Surface dolomite and limestone fine aggregates. or rub. gree of polish is measured using ASTM Method of Measuring thal et al. after pol- In Canada and the United States. Polishing occurs when fine abrasive is used sistance. ment samples. Smith and Schonfeld [66] found that in an fixed concrete specimen decreased markedly as the siliceous area where almost one-third of the passenger vehicles was particle count in the fine aggregate was decreased below equipped with studs. that sliding movement between rubber and pavement of up to Franklin and Calder [72] report results of frictional prop- 6. that the energy needed to turn a rubber tire against a studied intensively. Pavements with aggregates of found no general correlation of properties for all aggregates. fine aggregate with both poor polishing and abrasion per- Regeneration of the surface can occur when two components formance. found good frictional properties in all cases. wore at about the same overall rate even though the mecha. around the perimeter of a second wheel. of differing hardness are present and particles of the weaker. the matrix was preferentially worn down tween wear resistance and frictional properties. fines with both good polishing and abrasion resistance. [71]. the particles were Characteristics (E 867). similar hardness to the matrix showed uniform wear. friction cause of lack of embedment. it is the fine aggregate that tends to control have also been an important factor in road wear. gritty sandstone material with good polish resistance. (2) a lize a wearing mode of rubber on pavement specimens. low frictional properties have been found tle aggregate. Abrasive and water duced more than 100 times as much wear as regular tires are fed onto the tire-specimen interface at a constant rate. for sand- around them until the particles were dislodged by the studs be. They proached 5–8 mm in one season. many erties research using several types of fine aggregate that are pavement-wear researchers. but ber on mineral aggregate samples. Colley et al. and. the polishing rate and microtexture [72]. wears along with the paste in these tests. Mullen and Dahir [73] studied the wearing and polish- portland cement concrete and bituminous concrete ap. between sand-size. Other aggregate (British wheel) procedure involves polishing oriented coarse types. on the other gregate. studded tire wear was ishing. The definitions for texture are taken from dry wearing than after wet polishing. over the winter of 1969–70. perhaps more polish resistant minerals. with an abrasive supplied to poor abrasion resistance. leaving an un. concrete finishing operations. Laboratory developed an accelerated wear machine for pave- trude and eventually be undercut and torn out. MEININGER ON PROPERTIES OF AGGREGATES 373 wheel. wear on both 25 %. The light- hand. a direct relationship containing a sand with a substantial amount of soft minerals. For concrete pavements exposed to normal traffic wear Wear of highway pavements is due in large measure to the that does not expose much coarse aggregate during the life fine mineral abrasive present on the pavements. Meyer [70]. (3) a flint sand with poor polish re- simulate road grit. as well as ASTM D 3319 (British in decreasing order of performance: (1) calcined bauxite wheel) and ASTM E 660 (circular track polishing machine). Conversely.) occur in normal rolling tires. and one mountain gravel. but good abrasion resistance. Therefore. The reverse is weight fine aggregate did wear faster. and friction prop- pavements with traprock and limestone coarse aggregates erties was implied. [71] in ing out of the studs in many areas. Insoluble material may be overall pavement was reduced. true for a shot blast test where the limestone cushioned the In other studies where calcareous fine aggregates were abrasive shot and decreased the wear compared to more brit. size of coarse aggregate. synthetic aggregate. acid-insolubility.4-mm (1/4-in. Surface Frictional Properties Using the British Pendulum firmed that studs tend to skid over hard aggregate and leave Tester (E 303). causing the harder material to pro. It was determined that studded increased as absorption and surface capacity of the particles tires did not change the frictional properties much. With the phas. this factor has diminished. small flint gravel as an abrasive followed by 5 h of wet polish- Frictional properties of pavement surfaces in wet weather ing with a fine emery abrasive. Harder sands stand out on macrotexture (amplitude more than 0. and concrete compressive aggregate particles held by an epoxy backing using a rotating strength were not significant for the materials used. Microtex. The most important character- depend on microtexture (amplitude less than 0. A higher insoluble residue retained Keyser [67] found that the age of the mortar and on the 75-m sieve indicates a higher percentage of harder and whether or not limestone coarse aggregate was used were sig. silica gravel and during wet polishing. When a 100 % silica sand was ASTM D 3042 as a tool in selecting fine or coarse carbonate ag- used with the harder traprock. Stiffler [60] reports materials and mixtures for polishing. wear of both the matrix and the gregates for use in surface courses. tests at the Portland Cement Association showed. and silica or lightweight fine ag- from the surface.5 mm) and also istic of the sands tested is hardness. In concrete increased. Preus [68] showed that studs pro. They use a dry wearing cycle of 50 h with a polished surface. Strength. American Concrete Insti.” Series 62. R. NSGA TIL No.. D. Tests that directly measure degradation resistance.. 1949. [17] Hendrickson. S. Mielenz. D. and Related Properties.” Journal. G. Bureau of Materials. p. 72. L. 1958.. DC. “A Durability Test for Aggre- Committee 221. National Ready Mixed Concrete ASTM International. and several [16] Liu. Oct.. IN.. Silver Spring. 1996. and Meininger. D. L. R. June 1975. Bureau of Reclamation. DC. DC... “Effect of Aggregate Quality on Resistance of [26] Gaynor. Comparative Study. 1963. tempts to relate these properties with concrete properties.. Highway Research Board. factorily. 510. F.76]. the evaluation and testing of concrete containing in the Process of Degradation of Mineral Aggregates. [3] “Guide for Use of Normal Weight Aggregates in Concrete. 5. Others use petrographic or Proceedings. H. 1994. [22] Chapman. Vol.” HRB Record No. p. “Effect of Prolonged Mixing on the Properties of Concrete to Abrasion. National Sand and Gravel Association. ASTM STP 205. Vol.. Gravels from Southwestern United States. Project. 101. 1975.. [18] Breese. 48.. p. toughness characteristics of an aggregate are not generally ref- [9] Walker.” Publication No. DC. “Laboratory Freezing and Thawing Tests— Structural Concrete (C 330) requires the aggregate to be of suf- Method of Evaluating Aggregates?” Circular No. 1967. and Beardsley. F.” gregate classifications on that basis. DC.” Engineering Report No. and Shumway. E. performance when special abrasion resistance. and judgment for those aggregates that have performed satis.” Journal of Testing and Evaluation. No. Highway Concluding Remarks Research Board. P.. 1948. MI. Reno. and Bloem.. PA. 28. R. Washington. R. R. 25. C.. [4] Benson. K. tute. MD. S. Washington.. . E. Highway Research Board. Herbert. “Effect of Soft Sandstone in Coarse erenced in specifications for concrete aggregates in the United Aggregate on Properties of Concrete. “The Flexural Strength of Concrete. “Shale Classification Tests and Systems—A 1978. 111. p. D. Purdue University. Aggregates for Radiation-Shielding Concrete (C 637) as well as [10] Bartel. NSGA gregate that is used in ASTM C 33 and ASTM Specification for TIL No. C.” Journal of Materials. ASTM Specification for Lightweight Aggregates for [13] Gaynor. April 1974. ASTM International. [5] Smith. ASTM Degradation Test. “Weathering Study of Some Aggregates. R. 75-11.” HRB Record No. PA. “Rattler Losses Correlated with Compressive Strength of Concrete. “Analysis of Question- naire on Aggregate Degradation. [19] Ekse. 144.” Series 88 and 107. Concrete Mixer. C. National Sand and Gravel Association. 1972. PA. p.” Journal. ASTM Interna- tional. R. West Conshohocken. 119.” alternative materials remains the best approach to assuring Symposium on Road and Paving Materials. 1931. p. American Concrete Institute. p. MD. 1959. West Research Board. G. Detroit. University of Nevada. 461. S. PA.. “Behavior of Aggregate in the Washington Properties of Concrete and Concrete-Making Materials. C. 238. and Howe. ASTM STP 277.. With respect to aggregate Durability in Concrete. Jan. Jr. DC. PA. [28] Davis. No.. Jan. acid solubility data or both to classify aggregates.” Circular No. T. 3. DC. STP 169C. C. C. W. abrasion test for coarse ag.. DC. F. R. Suitability-Phase-Final Report. D. Washington. W. ASTM International. 109. R. D. “Effects of Aggregate Properties Petrographic Analysis and Special Tests Not Usually Required in on Strength of Concrete. 2. 350. ASTM STP 277. strength. M. and Walker. and Ames. 1967. “Tests of Concrete Conveyed from a Central Aggregate Test Methods. second. “A Test for Production of Plastic Fines However. L. to test the properties of concrete made [11] Walker. The one exception is the L. American states use the British wheel (ASTM D 3319) as a specification Concrete Institute. Methods for Small-Sized Coarse Aggregates. “Aggregate Abrasion Resistance. “Shale [1] Meininger.. A.” Pennsylvania Department of Toughness.. P. Transportation Mixing Plant. C. ASTM STP 169B. 196. “Investigation of Aggregate well as various mix proportions.” Symposium on Road and Paving Materials. [15] Melville. Highway Research Board. and Gaynor.. L. F. 1. D.” ACI [24] Hveem. and Smith. D. ceedings. gates. [6] Woolf. L. NV. Sept. 122. p. “Comparative Investigations of International Test With respect to an aggregate’s effect on frictional proper. W. Detroit. p.” Proceedings. R. States. West Conshohocken. Civil the measurement of physical properties of aggregates and at. sile splitting values when tested in concrete.. Concrete. many state highway agencies rely on friction 412. R.. tool for aggregates for highway surfaces [74. 91.” TRB Record No.374 TESTS AND PROPERTIES OF CONCRETE Impact on Specifications [8] Jumper.” Pro. G. R. D. ton. E. Denver. PA. Aggregates Association. Highway Research Board. 1977.” Cement and Concrete.” HRB Record No.. and Research. impact. Report ACI 221R-96. Washington. Vol. E. D. 1966. “Abrasion Resistance of Concrete. West Conshohocken. “Aggregate Degradation Resistance. “Degradation Characteristics of Selected Nevada There is a good deal of history and data available concerning Mineral Aggregates. 1956. 4. 1969. strength properties are required. J. ness. Detroit.” Significance of Tests and [23] Goodewardane.” Significance of Tests Transportation. “Importance of [7] Bloem. 1959. References [21] Reidenouer. O.. “Degradation of Mineral Aggregate. trailer performance history of highway surfaces and assign ag. 539. or 563.. “The Relation Between Los Angeles Abrasion Test [27] McKisson.. National ficient strength to yield certain minimum compressive and ten. C. ASTM International. R. D. Washington.. R. Association. These methods can be used 1944.–Oct. or Talk. Geiger. 1937. H. p. Washing- tute. Engineering Department.” Convention with the aggregate in question if special abrasion. MI. ASTM International. “Degrading of Aggregate by Attrition in a Results and the Service Records of Coarse Aggregates. [14] Kohler. American Concrete Insti.. strength. West Conshohocken. Joint Highway Research [2] Meininger. 1981. A. 1964.” Report No. Harrisburg. R. MI. 85. Detroit. DC. 1963. C-1308. and Related Properties. p. p. M.. Washington. and Morris. West Conshohocken. Judging Quality of Concrete Sand. CO. “The Precision of Selected [25] Slater.. 62. Highway Research Board. Washington.” Journal. July 1973.” Report No. H. 16. 1946. and. A.A. tough. 341. Sept. “Concrete-Making Properties of in a large number of agency specifications. C. Conshohocken. Washington. W. Silver Spring. E. West Lafayette. L. N. [20] Minor.. ties of pavements. 1967. Part 2. and Polivka. p. Testing. National The practice is first to rely more on past service record Sand and Gravel Association. Nov. and Properties of Concrete and Concrete-Making Materials. to evaluate the performance of alternative aggregate sources as [12] Gaynor. Strength. strength. or frictional properties are needed. 5. 1193. Conducted by 1968.. Latham. FL. “Arizona Volcanic Cinder and Performance in Ontario During the Winter of 1969–70. American Institute of Mining and Metal. Bailey... 1975.. Technical Report 90-01. p. F. D. New York. DC. and Barker. Aggregate Volume Concentration. UK. pp.. DC. Journal of Engineering Geology. and Senior. 8th [54] Hobbs. CO. Silver Spring.. ASTM STP 169A.” Concrete—A Comparative Study. [65] Prior. K. P. J.” Journal. 12. March 1970. Detroit. Cement Mortar. Orlando. Mittelacher. tion Rocks. NY.” and Properties of Concrete and Concrete-Making Materials. Vol. 97. DC. and Price. Pennsylvania State University Joint Road Publication No... [43] Johnston. 97. p. as Affected by the Properties of Coarse Aggregate. 1971.. 1. J.. and Haas. National Cooperative Highway Research Program. U. W. E. Detroit. J. p. F. Mross.” Proceedings. No. Composite Material. Detroit. American Concrete Institute. G. A.. L. E. Aggregate. Concrete. “Montmorillonite in Concrete Aggregate Sands. 1990. 1966. J. Washington. C. [62] Harvey. P. p. Dec. DC. Illinois State Geological Survey. “Modulus of Elasticity of Concrete Affected by Elas- Tests of Aggregates for Use in Unbound Pavement Layers. MI. [45] McCaulley. p. J. for Aggregates. Pergamon Press.” Technical ness. Florida Concrete and Products Associa. 1301. American Concrete Institute. Conshohocken. Geological Society. Shrinkage and Thermal Expansion of Concrete Upon Research. Naval Civil Engineering Laboratory. Transportation Research Board. C. MI. H.. 1967. Program. Jr. 1977. Dec. Journal. New York. Roebuck. Asphalt Concrete Performance in Pavements. Vol. May 1959.” Journal. 1954. No. Washington.. Washington.. Pergamon Press. H. pp.” Significance of Tests and Winemberg. E. 2000. Sept.” International Journal of Rock Mechanics 139–147. CO. C. Jr.” Record No. AZ. C. 1969. “Florida Aggregates in Construction.” Testing Techniques Evaluating the Quality of Fine Aggregate for Concrete and for Rock Mechanics. J..” HRB . M. Elmsford. Ed. MD. tion and the Concrete Materials Engineering Council. Fraser. 69. “Coral and Coral Concrete.” SP-20. Washington. 1946. 7. W. and Bryant. C. 114–126. “Crushing Tests by Pressure and Impact. S. p. lurgical Engineers.. “Resistance of Various Types of Bituminous No. 679..” HRB Special Report 90. [52] Lott.. Minerals Note 54. Amer. “Floor Concrete. 1960. “Laboratory Tests for Predicting Mechanical Properties of Road Surface Aggregates. Feb. McGraw-Hill. E. C. Transportation Research Board.. Stiffler. S. and Parker. Washing. W. D. American Railway Engineering [58] Houghton. PA. 55 pp. M.. “Model Analysis of Fracture and Failure of Con- Bulletin. p.” Bureau of Public Roads. DC. A. Highway Materials. “Durability Tests on Some Properties of Roadstones. W. and Winter. 204. “Deformation Moduli of Rock. [44] Collins. p.. and Remarkrishnam. April. J. [31] Rogers. West Conshohocken. NCHRP Report 453. C. G.. C... “The Micro-Deval p. S. 068. C. S. Detroit. ton. Denver. DC. National Academy Press. 1965. “Inelastic Behavior and Fracture of [37] Lynch. “Properties of Florida-Oolite [64] Scripture. 1.” Journal.” Crushed Stone Journal. Friction Program and Automotive Safety Research Program. J.” Journal. R.” Record No. and Hsu. Test for Aggregates in Asphalt Pavements. K. 1970. Detroit. MI. L. “Physical Properties of Rocks and Probable Applica. J. ASTM STP 402. W. 1966. [60] Stiffler. PA. Feb. Research Board.. 1998. 1972. Y. “Deformation of Concrete and Its Constituent tions. ASTM International. 13. “A Review of the Geological Factors Influencing the [32] Senior.. DC. Benedict. 691. “Determining the Tensile Strain Capacity of Association. International Center for Aggregates Modulus. “Abrasion Resistance.” Magazine of Concrete [63] Woolf. C. B. 13. T. P.. “Properties of [42] Woolf. MI. Winter crete as a Composite Material. Troxell.” NCHRP Report [55] Hansen. pp. A. Denver. National Ready Mixed Concrete Association. 1966. A.” HRB Special Report 101. “Performance-Related [56] Hirsch.. 1998. p. “Mineral Wear in Relation to Pavement Slipperi- [39] Bond.. MI. N... K. 1951. B. Young’s Annual ICAR Symposium. “Aggregate Degradation During Mixing. and Wiskocil. Rogers. 1974. NY. “Studies of Studded-Tire Damage [46] Ross.. National Cooperative Highway Research American Concrete Institute. and Kienow. “Crack Propagation in Plain [33] Rogers. J. Vol. 1976. and Rogers. West Asphalt. p. 141. Vol. 1969. American Concrete Institute. 1965..” [48] Tanigawa. [38] Udd. C. p. AREA Bulletin. American Concrete Institute. Hall. Aggregates. “Rock Mechanics Properties of Typical Founda- Convention Talk. G. Uniaxial Tension and Compression. S. R. [35] Kandhal. Transportation Research Board. F. “Aggregate Tests Related to Cement and Concrete Association. March 1977.” Technical Report TRA 437. 2001. March 1962. p. also. 1975. Tucson. [47] Lorman. L.. [30] Meininger. Washington. 1996. MI.” Published as Informa. and Baxter. p. “Flexural and Compressive Strength of Concrete Inspection of Engineering Materials. P. ASTM International. B. “Canadian Experience with the Micro-Deval Test Concrete.. S.. R. J... D. 427. A. M. Engineering Geology [53] Ko.. C. R. J. 9. 133.” Cement and Concrete Research. 531. D. D. tion by Committee 1 on Roadway and Ballast. D. T.. E. 1974. 1976.. “The Effective Modulus of Rock as a Special Publications.. 68. 1964.” Journal.” Quarterly Coarse Aggregate Performance in Ontario.. “Relation Between Wear and Physical [40] Iyer. MEININGER ON PROPERTIES OF AGGREGATES 375 [29] Higgs. “Results of Physical Tests of Road-Building Carbonate Rocks Affecting Soundness of Aggregate. and Schonfeld. 1991. J. National Academy p. [36] Saeed. A.. 593. Concrete and Cement Concrete to Wear by Studded Tires. A. Dec. O.. 18. Association of Engineering Geologists. J. K.. Trans. p. Jr. W. West Research Board. p. 193.” Bulletin No. B. T. Subcommittee 2 on Ballast. and Mineral Sciences. and Cement Paste. B. T. Highway Research Board. W. 1991. Press. p. Highway Research Board. “Micro-Deval Test for [50] Clark. [66] Smith.. “Strength and Deformation of Concrete in IL.. D. E.. Conshohocken. Champaign.S. T. May. ASTM International.” Illinois Aggregate. C. P. of Elasticity of Concrete. Engineering Experiment Station. [57] Shah. W. Rahn. D. A. Detroit. R. [51] Hartley. 57.. C. 419–423. [61] Davis..” Journal of Testing and Evaluation. Elmsford. 324.” [49] Brandon. 103 pp. London. 756. E.. Sept. 1959. Highway Aggregates for Concrete. Construction Division. E. C. G.. D. p. 1301. American Concrete Institute. “The Dependence of the Bulk Modulus. K. University HRB Record No. ASTM STP 373. ican Society of Civil Engineers. Evaluation. 1953. R. “Methods for the Determination of Soft Pieces in Research.” Application of Advanced Nuclear Physics to Testing Materials in Uniaxial Tension. London.” Report REC-ERC-74-10. and Kesler...” Advances in Aggregates and Armourstone Washington.” Technical Report [67] Keyser. p. 1895. of Arizona. 305. “Mill Abrasion Test Study.. [34] Lane. M. 1953.” tic Moduli of Cement Paste Matrix and Aggregate. “Influence of Aggregate and Voids on Modulus 405.” HRB Record No. 5. PA.” Report J-15. 352. O.. [59] Johnston. K. The Testing and [41] Kaplan..” portation Research Board. Bureau of Reclamation. Mass Concrete. 1974. 101.” Concrete—The Effect of Materials Under Site Conditions.” Aggregate Requirements for Highway Surfaces of State Transportation Engineering Journal... “Factors [75] Weller. 719.. UK. 1969. E. NCHRP Report No. British Road Research Labora- ington. J. “Skid Resistance and Wear Research Board. S. Aug. “The Skidding Resistance of [76] Meininger. DC. June 2003. R. and Nowlen. . W. 1971. K. P. P.” Mix Design on the Skid Resistance Value and Texture Depth of HRB Special Report No. D. C. Christensen. DC. A. D. 1970. tory. DC.. [71] Colley. Concrete. et al. p. Highway Research Board. “Evaluation of Studded Tires. J.. Washington. “Influence of Materials and Affecting Skid Resistance and Safety of Concrete Pavements. LR 334. 1974. June 1970 (PB 197 625). C. Highway [73] Mullen. [72] Franklin.. and Calder. M. Wash. Report of ASTM Committee D-4 Survey of [70] Meyer.. Highway Research Board.” Report No. p.. 1969. Information Letter No. National Aggregates Association.” HRB Record No. E. [74] Meininger. “Wearability of P C Concrete Pavement Finishes..376 TESTS AND PROPERTIES OF CONCRETE Record No. p. H. A. 1986.” North Carolina [69] Rosenthal. Properties of Aggregates for Paving Mixtures. C. 61. R.” Technically Speaking.” HRB State University Highway Research Program Interim Report. Washington. Aug. Transportation and Road Research 1971. Highway Research Board. Technical Engineers. “Aggregates Provide Pavement Friction. G. 80. B. “Discussion. 352. p. Laboratory. DC. Washington.. 31. H. London. 352. New York. E. A. J. Rock Products Magazine. 386. W. Laboratory Report 640.. 16. and Dahir. R. [68] Preus. P. American Society of Civil Highway Agencies.. and Maynard. selection [1. of transportation. Minor modi- qualifications of personnel performing petrographic examina. and and engineering laboratories. ASTM STP 169. Mielenz for his long and dedicated service to Book of ASTM Standards. Petrographic examination is also ASTM Committee C9 on Concrete and Concrete Aggregates. [4].S. U. Among the revisions to this addition. The abundant data obtained and the rapidity with which Introduction petrographic examination can be completed justify more general use of the method in investigation. Richard C. ture. By petrographic examination. the most com- the relative abundance of specific types of rocks and minerals mon types of lightweight aggregates. and potential chemical reactivity are described. selection. Army Corps of Engineers. Dif- proposed for use in either portland-cement concrete or bitu. cited in ASTM Specification for Concrete Aggregates (C 33). Petrographic examination is performed also by several graphic examination of concrete aggregate were included in other agencies of the U. differential thermal analysis. and may be obtained through some testing lication. MS 39180. manufac- Petrographic examination of concrete aggregate is visual ex. testing. The procedure requires the use tion on the conditions of service to which the concrete is to of a hand lens and petrographic and stereoscopic microscopes. U. be exposed. selection.S. However. physics. and specifications governing acceptance are based upon the results CHAPTERS AUTHORED BY R. the petrographer should be supplied with available informa- ties of the individual particles. the physical and chemical attributes of each. Since The petrographic examination of aggregate is a forensic treat- 1936. In 1952. and monitoring of aggregate uniformity. ASTM STP 169A. fications were made subsequently. Experience and literature pertinent to exami. have brings to use many forms of analysis to provide an overall been examined petrographically as part of the basis for their estimation of the quality of the aggregate. 377 . ment of material for potential use as concrete aggregate and reau of Reclamation. and use of concrete aggregates. crushed stone. examination are treated briefly because instructions have been nating substances is determined—each in relation to proposed published elsewhere [3–11] and are included in ASTM C 295. sand. a major section on accepted and was adopted as a standard in 1954. Vicksburg. Education the method is progressively being applied more widely. ASTM STP 169C. the publication of ASTM STP 169C in 1994. rographic Examination of Aggregates for Concrete (C 295) was ate. Department of the Interior. As will be discussed subsequently. cial attention has been given to developments in this field since hardness. This paper summarizes the objectives and applications of or electron microscopy are used to supplement the examina. Spe- such as particle shape. fering educational backgrounds can provide the basic tools minous concrete are examined by petrographic methods in required to perform a petrographic examination of aggregate 1 Certified Geologist. Techniques of the ings are identified and described. by the recycling of hardened concrete from constructions. petrographic examina. amination and analysis in terms of both lithology and proper. petrographic examination of aggregates with reference to tion using optical microscopes. Sam Wong1 Preface laboratories of the Ministry of Transportation–Ontario. or prospective conditions of service in concrete constructions. Coarse aggregates ments that are addressed in a typical petrographic report.S. X-ray diffraction. government and state departments the four previous editions of this ASTM Special Technical Pub.33 Petrographic Evaluation of Concrete Aggregates G. and geochemistry are ele- Corps of Engineers since before 1940 [3]. This chapter is dedicated to Examination of Aggregates for Concrete in the 1991 Annual Dr. MIELENZ ON PETRO. Less commonly. pore characteristics. gravel. ASTM STP 169B. all aggregates used in concrete construction by the Bu. Qualification for Concrete Petrographers tion contributes in several ways to the investigation. Chemistry. and aggregates produced is established. coat.2]. Consequently. The tion for the purposes of qualifying aggregate for use in portland document has been published as the Guide for Petrographic cement concrete has been added. most recently in 2004. and the presence of contami. in all cases. blast-furnace slag. The method has been applied similarly by the engineering properties of materials. ASTM Tentative Recommended Practice for Pet- nation of all types of concrete aggregate are cited as appropri. surface texture. By relating the sample to aggregates previously used in tory directors to have a minimum of five years of experience.378 TESTS AND PROPERTIES OF CONCRETE for use in the production of concrete. heating-cooling. in mixing adding fines and reducing workability. aggregate to such phenomena as attack by cement alkalis. the preliminary petrographic minimum size required for failure. They basically rely on ASTM methods. have fallen from the basic BS geology requirements in many insti. consolidation. or high tem- gate investigation. mapping. even though the materials come from new Concrete and Concrete Aggregates for Use in Construction and sources. for two winters (Fig. By revealing variations in the material. the examination reveals the composition and physical and Petrographic examination provides a consolidated interpreta. 1). exami- rographic examination. angular particles increas- may require different sampling or sample sizes for the testing. sedimentary petrography. Petrographic examination of the The examination assists the geologist or materials engineer in gravel and of individual particles producing popouts during determining the extent to which consideration of an undevel. ing flexural strength in concrete. absorption by sometimes use standard specifications and test methods. and the pres- ments. abrasion resistance. placing. or. aggregate Purpose of the Petrographic Examination of indicated to be sound in standard tests might be found un- Concrete Aggregates satisfactory for the intended use. placement include organics in the aggregate affecting air- tural concrete. is discussed subsequently. Experience First. soluble salt affecting setting time. data and experience qualified petrographer should meet the same experience re. thus it is Correlation of Samples with Aggregates very important that this individual have the experience neces. exploration. This working knowledge Detailed petrographic examination is the only procedure that is best obtained while working in the field of petrography un. Previously Tested or Used sary to make these critical decisions. This application ments and recommendations. Criteria for Laboratory Evaluation (C 1077) requires labora. metamorphic petrography. The petrographic examination performance and the potential use of the aggregate source. chemical characteristics of the constituents. Agencies fine aggregate affecting bleeding characteristics. yet performed either in the field or in the laboratory as an adjunct produces objectionable popouts in pavements after exposure to geologic examination. angularity in any unusual details in test requirements of a project. aggregate determined to be unsound by standard tests may be found adequate. wetting-drying. and sampling. gregates upon which information is available. service has identified the unsound rock types and the critical oped deposit is justified. permits comparison and correlation of samples with aggre- der the guidance of an experienced concrete petrographer. soft particles breaking down An example is the military specifications for airfield pave. required by realistic tests of concrete or mortar. igneous petrography. The petrographer must aggregate is especially valuable because of the widespread have working knowledge of all tests associated with the per. occurrence of this condition and the long time commonly formance of aggregate. Probable performance of concrete aggregate is estimated in two general ways by petrographic examination. ASTM Standard Practice for Laboratories Testing for current work. The petrographer must remain vigilant as to entrainment. The petrographer may be the only individual in the organization that has this unique ability and knowledge. construction. and content of soft particles. gregates from unfamiliar sources can be compared with ag- perience that is expected of the petrographer in making judg. ceptance tests. nation of exposures or cores from pilot drill holes establishes zation in undergraduate education. freezing-thawing. alternate sites. Preliminary Determination of Quality Michigan meets usual specification requirements for sound- Preliminary petrographic examination of concrete aggregate is ness. Thus. conversely. For example. traditionally required the minimum program of exploration and sampling necessary courses such as optical mineralogy. amination are often to recommend more definitive testing The second way the petrographic examination helps to es- such as ASTM C 1260 for alkali-silica reactivity or ASTM C 586 timate performance is to provide a basis of comparison with for alkali-carbonate reactivity or recommendations as to the aggregates from other sources. Historically a BS degree examination indicates the relative quality of aggregates from in geology provided the basic tools required to execute the pet. for acceptance or rejection of the deposit. state the aggregate that affect long term durability. A gates previously used or tested. The requirements are often different for the various early-age properties. highway departments focus on pavements and slabs. Often the petrographer is the central figure in the aggre. establishes the fundamental nature of aggregates so that ag- These additional tests are part of the knowledge base and ex. The conclusions of a petrographic ex. The petrographer interprets the results and peratures usually can be estimated. Establishing Properties and tutions. For example. Examination of proposed . An individual should have basic geological background Probable Performance and specific knowledge on techniques to perform an examina. and development of sources. etc. previously obtained by use and long-time tests of similar ag- quirements in his or her field as those required of laboratory gregates can be applied in the selection of materials proposed directors. Also. This examination also identifies features of clients depending on their specific needs. but with the advent of more speciali. Petrographic examination is primarily a supplement to the action as outlined in ASTM C 295. one can estimate how these properties of the aggregates of any program designed to investigate potential aggregate will affect mixing. Long-term effects including the probable response of the small amounts of deleterious materials. but porous particles causing slump loss. gravel in certain deposits near Jackson. The rapidity with which the draws conclusions as to the acceptability of an aggregate petrographic examination predicts potential alkali reactivity of source for use in the intended project. but sample sizes ence of expansive clays causing stiffening of the concrete mix- are much larger in order to insure the detection of relatively ture. while Some aggregate features that may affect concrete some customers may focus on marine concrete or architec. From this infor- tion of all data produced in the testing and examination phase mation. or refractories containing free calcium or magnesium oxides are especially important. Petrographic examination aids in the production and processing of aggregate. U. such as overburden or contaminants from trucks or railroad cars not properly cleaned of previous cargo. the undesirable particles can be identified and separated. The properties can be evaluated and compared with properties of examination may be applied to determine the source of aggre. properties and volume change with wetting-drying rarely are X-ray diffraction analysis is the most dependable means of determined. the remainder of the aggregate. Petrographic examination aids interpretation of other tests. sound or chemically reactive constituents. separation may be feasible on a commercial scale. Fig. or production of rock dust. Petrographic examination of aggregate may be a part of The feasibility of beneficiation by removal of unsound or an investigation of concrete constructions as described in deleterious constituents depends on the properties of the parti- ASTM Practice for Examination and Sampling of Hardened cles and their abundance. or high in magnetic from an approved or an unapproved source. If the undesirable particles are gate used in the constructions and whether it was obtained unusually soft. plant remains. amount of microfracturing. lightweight. jected to special tests. or sub. and other types. The relative merit of alternative processing methods and equipment can be determined quickly by com- materials will demonstrate the presence or absence of such parison of the original material with the processed aggregate. . Fig. coal. slag. 2). Department of the Interior). in the light of other data. Contamination by containers may invalidate samples. 2—Coal in sintered clay before crushing (courtesy of tially deleterious and extraneous substances can be detected Bureau of Reclamation. and contaminants such as coal (Fig. chemical fertilizers. 1—Popouts produced by claystone. Through petrographic examination. friable. such as expanded shale or concrete in service ordinarily are not evaluated by test before clay. Inadvertent contamination with natural substances. and soluble salts. cause of the cost and time required. rejected. vegetable matter. Selecting and Interpreting Other Tests Petrographic examination can be used to control the All of the properties of aggregates influencing performance of manufacture of synthetic aggregate. are detected easily and can be determined quantitatively by petrographic methods or by other procedures that can be selected most definitively pursuant to petrographic identification. WONG ON PETROGRAPHIC EVALUATION 379 and determined quantitatively. it is worthwhile to apply a procedure by which the relative significance of such properties can be determined and the need for supplementary quantitative tests indicated. Other properties. such as coatings. Incomplete processing of synthetic aggregates may contaminate the finished product with raw or partly fired materials or coal. content of un- whether the aggregate should be accepted. Comparison can be based on particle shape. industrial products. petroleum products. are the particles identified as clay lumps in accordance with ASTM Test Method for Clay Lumps and Fri- able Particles in Aggregates (C 142) indeed clay lumps or are they merely friable or pulverulent particles of some other composition? What is the cause of unexpected failure of concrete specimens in freezing and thawing? Is it the presence of unsound particles that do not disintegrate in the sulfate soundness test yet expand in freezing and thawing? Is it the result of an alkali-aggregate reaction? Is failure in the soundness or abrasion test the result of a complete breakdown of a small proportion of unsound or soft particles or partial disintegration of the greater proportion of the aggregate? Detection of Contamination Petrographic examination is the best method by which poten. Microscopical examination selection of the aggregate to be used in the work. Undesirable substances inherent in the material. soil. removal of coatings. Michigan (courtesy of Determining Effects of Processing Michigan Department of Transportation). clay. Their rographic Examination of Hardened Concrete (C 856). shale. coal. Consequently. or wastes. may markedly decrease the quality of aggregate. will reveal the presence of raw or underburned materials. primarily be. and chert in concrete pavement near Jackson. particles and will thus indicate. such as chemical reactivity or effect of the aggregate on the freeze-thaw resistance of concrete are usually not determined. Such substances as clay. dense. Such factors as thermal alkali-reactive phases.S. perlite. For example. susceptibility. Concrete in Constructions (C 823) and ASTM Practice for Pet. 30–0. shales.30 (No. unsuit. capillary suction against the tongue. and similar 90–38 (3–11⁄2) 13 kg (20 lb) materials have been fired. slaking.5 lb) curves for the raw and fired product will coincide above the 19–9. 30) sieve are best fractured. and TABLE 1—Minimum Representative Sample Size clays whose crystal structure was not destroyed by the calcina- Size Fraction. slag. These notes scope.14 g Samples for Petrographic Examination 0. sand. or swelling. crushed stone. (b) stone in quarried blocks and irregularly shaped pieces or drilled cores. the point-count procedure according to ASTM Practice for Mi- able. identified. sawed pieces. and veinlets.3 kg (9.5 (3⁄4–3⁄8) 0.17 kg (0. as absorption of droplets on fresh fracture.18–0. Differential thermal analysis can be used to estimate the effective temperature to which clays.3 lb) effective temperature achieved in the firing operation. Fractions retained on the 600-m (No. are quartered or. 3—Performing petrographic examination of fine ASTM Test Method for Material Finer Than 75-m (No. mechanical stage. (2) resonance (3 in. croscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457) (Fig. and other technical literature [12]. Brief examination indicates the relative merit of materials from alternate sources and supplies justifi- cation for abandonment or continued investigation of undevel- oped deposits or other exposures. such should be taken to the laboratory for further study. Examination in the Laboratory The mineralogical composition of finer fractions usually is Petrographic examination of aggregate in the laboratory may determined most easily and accurately in immersion oils or be brief or detailed. (4) nature of the fracture tative sample of this size fraction may weigh a 100 kg or more surface and fracture fillings.36 (No. seams. such as poros- Chips from cobbles not adequately identified in the field ity. helpful information on identity and detailed work difficult. free lime (CaO). granularity. inasmuch as a represen. 30–50) 0. Samples of the aggregate for petrographic examination are obtained by sieving in accordance with ASTM Method for Sieve Analysis of Fine and Coarse Aggregates (C 136) and Fig. and (10) reaction with various stains. (8) reaction to water. when struck. Examination in the Field Details of the procedure are outlined by Mather and Petrographic analysis of samples in the field is usually qualita. the minimum representative samples are shown in Table 1. (9) differential attack by acids or other should relate each sample to a particular zone and portion of chemicals.6 kg (1. or both) that is of interest. The fractions and tally counter.017 g Samples of aggregate for petrographic examination should be 0. 4–8) 7. For fully graded granular materials. ASTM C 295.38 lb) 4. the trace of the differential thermal 38–19 (11⁄2–3⁄4) 4. 3). tive or only semiquantitative because lack of facilities makes During the analysis.60–0. Recommended procedures for sampling and for preparation of the sample for analysis are covered by ASTM Practices for Sampling Aggregates (D 75). The sample of each size fraction should comprise at least 150 particles.18 (No. or drilled cores of concrete that contain the aggregate (coarse. soft- be selected from each zone and detailed notes made at the site ening. or chemically deleterious materials should be esti. The preliminary examination should not replace the quantitative analysis included in the program of acceptance tests.1 g 1.0033 g representative of the source. (3) ease of fracturing. split repeatedly on an appropriate riffle. samples should immersion. mm (in. and (c) fragments.380 TESTS AND PROPERTIES OF CONCRETE identifying and determining quantitatively the proportion of crystalline phases such as periclase (MgO). However. 200) aggregate with stereoscopic microscope.36–1. For natural sand and gravel and crushed stone.15 (No. The analysis can be made conveniently by traversing a and the results of the tests on the samples will be the basis for representative portion of each fraction by means of a mechan- operation of the deposit inasmuch as it may be desirable to ical stage and microscope assembly such as that employed in waste or avoid zones or portions containing inferior.60 (No. evolution of air on If the deposit or rock exposure is variable. Samples supplied to the laboratory comprise (a) granular materials such as gravel. the deposit or rock ledge. 16–30) 0. fine. Mather [3] and in ASTM C 295.) Mass of 150 Particles tion. (5) odor on fresh fracture. The relative proportion of unsound.) sieve is to be used in the work.75–2.5 g Performance of the Petrographic Examination 2. 9. (6) color and its variation. 50–100) 0.5–4. and transportation of the sample to the laboratory is costly. examined. (7) internal structure.7 (3⁄8–3⁄16) 0. or synthetic aggregate. and counted using a stereoscopic micro- mated from measurements made at exposures. detailed examination in physical condition can be obtained by recording such features the field may be warranted if aggregate retained on the 75 mm as (1) friability or pulverulence in the fingers. Sieve in Mineral Aggregates by Washing (C 117). or alkali-reactive materials. slate. for fine aggregate. . the examination should be performed on at least three size fractions included in the aggregate. 8–16) 1. of grains unless a correction factor is applied. is performed on at least three coarse fractions and five fine Material passing the 75 m (No. Consequently. However. composition and description of the physical condition. 30) sieve. Observations Included in the Petrographic Examination In reporting the results of the petrographic examination. with or without etching or staining. supplemented technically the more appropriate determination because the in- by use of oil immersion mounts of granular material. However. The examination of the fines will reveal some information on the breakdown and mineral constituents of the aggregate. Analysis of aggregate enclosed in concrete usually is confined to determination of the proportional volume of individual selected types of particles relative to the proportional volume of the total aggregate (see subsequent discussion). FeS2) develops Porosity.S. Department of the Interior). X-ray diffraction analysis is commonly used in the analysis of fine grain particles to determine the presence of mineral phases such as clays and zeolites. aggregate can be reported only by count. as required and appropriate. 4). and absorption a marked exotherm at 400–485°C (courtesy of the Bureau of Volume change. bet. Illite produces the small endotherms at 100–200°C and 500–615°C. and mi. softening. such analysis. U. petrographic analysis of concrete aggregates percentage by count of particles. 200) sieve does not usu- fractions. When applied to coarse aggregate to identify or determine quantitatively constituents that are only. portion of the several rock types or facies is determined by gate (Fig. the petrographer should supply information on the following subjects as necessary for evaluation of the aggregate for service under the anticipated conditions of exposure in the concrete: Fig. are affected adversely by unavoidable loss of portions of the par- gate can be examined while enclosed in hardened concrete. The bulk composition of a concrete particles is obtained if analysis of fractions passing the 600-m sand may vary widely with fineness modulus. Nontronite is Surface texture revealed by endotherms at 100–350°C and 450–550°C. drying . Internal fracturing Organic matter produces large exotherms (upward shifts) at Coatings 430–500°C or 440–600°C. usually fluence of particles of a given type upon performance of con- are used in the analysis of blast-furnace slag aggregates. Occasionally the amount of fines and its constituents can affect the workability of concrete. composition of the aggregate in any gradation comprising the ter continuity in description of physical characteristics of the analyzed size fraction. (No. are expressed as percent by volume of the concrete or percent by volume of total aggregate. the accuracy and precision of analysis by mass Any of the previously noted types of coarse or fine aggre. Pyrite (ferrous sulfide. However. The results may be used to compute the lithologic ally enter into the overall estimation of the quality of the aggregate for use in the production of portland concrete since the volume is limited. amination or analysis. commonly for the finer fractions. Thin sections or polished surfaces. permeability. WONG ON PETROGRAPHIC EVALUATION 381 thin sections using a petrographic microscope. The presence of expansive clays can easily be detected by X-ray diffraction examination of oriented particle samples that have been treated with glycerol or ethylene glycol observing peak shift to about 17 Angstroms. Such examination should be supple. or count of particles retained on the 600-m (No. ticles when they must be broken to allow identification of the using broken fragments. For performed using a stereoscopic microscope. 30) sieve and retained on the 150-m (No. but ing and lapping. Analysis by count is mersion oils. Kaolinite is indicated by the Particle shape endotherm (downward shift) at 990–1025°C. Details of calculating and reporting of results of petrographic examination and analysis of concrete aggregates are summarized in ASTM C 295. mass. consistent analyses of all fractions of fine aggregate and coarse mented by microscopical examination of grain mounts in im. the petrographic analysis is more rapid if the relative pro- very finely divided or dispersed through particles of the aggre. The results of the analysis of composition of aggregates enclosed in hardened concrete. the results are based only upon the count is preferable because of the large area made available for ex. preparation of plane sections by saw. the composition by count may differ greatly Thin sections occasionally are necessary in examination of from the composition by mass. and disintegration with wetting- Reclamation. 100) sieve is one analysis may be performed on a graded aggregate. sawed and lapped sections. natural aggregate. Occasionally. X-ray crete in test or service depends primarily upon their frequency diffraction and differential thermal analysis may be required and distribution in the mass. They usually are employed in the study of Numerical results of the analysis may be expressed by mass quarried stone. such as by point-count analysis on sawed and lapped surfaces. 4—Typical differential thermal analysis (DTA) records Mineralogical and lithologic composition obtained on concrete aggregates. Specifi- croscopical thin sections. cations on lithologic composition are preferably expressed as Ordinarily. techniques and simple tests. as appropri- porated in concrete that will be subjected to sustained high ate.42]. The loging the physical and chemical condition of particles consti- release appears to involve ion-exchange phenomena and possi. Similar effects can be pro. potassium from phlogopite mica [25] and from particles of bentonite clay in natural sand [26] has been shown to promote an Satisfactory alkali-carbonate reaction in concrete. compared petrographically with previously tested materials. Shayan [22] reported popout formation and de. The petrographer should participate in the formulation Stark and Bhatty [24] concluded that significant amounts of of any supplementary studies that are contemplated. the properties can be evaluated semiquantitatively or quantita- and the like. bers and slabs to be included in or to support furnaces. Mielenz [14]. clots.11. moderately fractured. which the pyrite and crystallization of iron and calcium sulfates take are widespread in natural aggregates of that region [43]. and fis- Effects of contaminants sures in contrast to a disseminated condition in the rock. These observa. citing work by Davis et Alkali-carbonate reactivity al. in alkali-silica reaction involving other siliceous constituents of the aggregate [27]. and graywackes. Investigators of concrete affected by aggregate. Mantuani [11]. Particles are hard to firm and relatively free of fractures. surface relatively smooth and impermeable. Frost resistance is reduced proaching zero or being negative in one or more directions. coefficient of thermal expansion ap- concrete is reduced as much as 5 %. and others [15–19]. Bachiorrini and Montanaro [40] re- sulfides that are likely to oxidize while enclosed in concrete ported the occurrence of alkali-silica reaction in non-dolomitic was devised by Midgley [21] and is discussed more generally by carbonate rocks containing disseminated. plagioclase feldspars. and amination of aggregates for very high-strength concrete.382 TESTS AND PROPERTIES OF CONCRETE Thermal properties and drying shrinkage is increased by increasing content of bio- Strength and elasticity tite. and feldspathic sand. the compressive strength of the low compressibility. texture and internal structure of the particles by petrographic tions are pertinent to the evaluation of aggregates to be incor. The deterio. The present author has observed similar effects when It is intended that the preceding properties be determined compact pyritiferous shales constitute appreciable proportions qualitatively by observation of mineralogical composition and in gravel and sand coarse and fine aggregate. Swenson and Gillott [34]. Hansen [13]. The following classification of properties is useful in cata- kalies engage in expansive alkali-silica reaction in concrete. Chemical stability lies include glassy volcanic rocks. Dolar-Mantuani [39] described the alkali-silica reactivity of A simple test to detect forms of pyrite and similar ferrous argillites and graywackes. (2) fair. terms: (1) satisfactory. argillites. Dolar-Mantuani [11]. alkalies (sodium and potassium) can be released from certain alkali-bearing rocks and minerals when in contact with a satu. he described the effect of chlorite in ag- Sulfate attack on cementitious matrix gregate relative to its effect on the freeze-thaw durability of Staining concrete [32]. cap- duced by montmorillonite-type clays and zeolites from which illary absorption is very small or negligible. substantially by an alkali-aggregate reaction involving vermicu- ration is a result of expansion of the particles as oxidation of lite that is present in phyllites. Elsewhere. such as structural mem. Swenson and that are potentially susceptible to a deleterious degree of the Chaly [9]. and the surface sodium or potassium released by cation exchange may engage texture is relatively rough. capillary absorption small to England. Hadley [33]. When other tests are available. cially regarding internal texture and structure of the particles. Fair Schmitt [28] recently summarized information on micas as Particles exhibit one or two of the following qualities: firm to constituents of fine aggregate in concrete. The significance of these properties is discussed by Petrographic criteria useful in detecting dolomitic rocks Rhoades and Mielenz [7. . The release of (2) potentially deleterious. alkali-silica reaction in many structures in Nova Scotia have Soles [23] found that pyritiferous dolomite used as coarse concluded that alkali-silica reaction in which strained quartz is aggregate produces distress when the concrete is heated to the primary alkali-reactive constituent has been augmented about 150°C (300°F) but less than 300°C (575°F). alkali-carbonate reaction in concrete are described by Dolar- Sarkar and Aitcin [20] emphasize the need for petrographic ex. He commented also on applicable specifications on Density allowable quantities of mica in coarse and fine aggregate. potas. He concluded that for each 1 % of mica in fine aggre. finely divided sili- Mielenz [14]. in concrete is designated by two terms: (1) innocuous and sium feldspar (microcline). and (3) poor. Condition of the Particles rated solution of calcium hydroxide and that such released al. [31]. place. citing work done in friable. such as those noted. cate minerals. Sources of alka.8]. Oxidation Higgs [30] reported a correlation between methylene blue Hydration adsorption and the amount of smectite (montmorillonite type) Carbonation clay in natural sand that was the cause of undue slump loss and Alkali-silica reactivity increased drying shrinkage of concrete. tively. very gate by mass of total aggregate. Oc- Hardness currence of mica in concrete sands from numerous sources in Chemical activity the continental United States is reported by Gaynor and Solubility Meininger [29]. moderate. Physical condition is defined by three bly dissolution of silicates within the aggregate. others [35–38]. espe. tuting an aggregate. The alkali reactivity of strained quartz and terioration of the surface of a concrete floor by oxidation and quartzose rocks has been described and discussed by Buck [41] hydration of pyrite included in exposed particles of coarse and others [6. The critical criteria required for poor durability Cation-exchange reactions were found to be chlorite content of volcanic rocks in excess of Reactions of organic substances 20 % and distribution of the mineral in seams. kilns. or if the particles can be temperatures in the indicated range. The area to be traversed should be .” The measurement temperature service should be made in accordance with definitions of these terms Hydration of free lime (CaO) or magnesia (MgO) in slag as they appear in ASTM Terminology Relating to Concrete aggregates or contaminants and Concrete Aggregates (C 125) or as defined by the speci. The parti- pavements in service or from test specimens can be subjected cles of coarse or fine aggregates are accordingly identified by to petrographic examination for many reasons. interfere with the normal course mixing of concrete of hydration of portland cement. who note in particular the Presence of gypsum or anhydrite unfavorable effect of elongated or flaky pieces on the workability of concrete. re- to identify the nature of the aggregates in older structures gardless of particle size. Staining of cement paste matrix by organic matter. or other substances cussed by Sarker and Aitcin [20]. 1. Effects of attrition during handling of aggregates and produce significant expansion. Analysis of composition ties listed under “fair. Schmitt [28] Decarbonation of carbonate aggregates in high-temperature recently summarized information concerning petrographic service or fire features of aggregate coatings and their significance. particles whose length is five or more times Oxidation and hydration of ferrous sulfides in normal their width should be designated as “elongated pieces. Particles are stable at high temperature or de. coarse and fine aggregates tions ordinarily prevailing (or applicable in the present instance) Concentration of unsound particles at exterior surfaces in portland-cement concrete or mortar in such a manner as to 4. Particle shape relative to coarse aggregate is dis. D-cracking cause coatings usually are confined to portions of a deposit Thermal expansion at high temperature in service expo- and.4 % by vol. Contamination by foreign substances mosphere. quartz and highly quartzose rock types that are subject Deleterious effects to disruption as the quartz crystal expands about 2. Composition and physical characteristics posed to high temperatures as a part of the planned service—for Frequency and extent example. particle shape should be considered apart exposure from other aspects of physical quality because particle shape Alkali-silica reaction is commonly subject to control or modification by processing Alkali-carbonate reaction of the aggregate. Sand-aggregate ratio 3. water. Involvement in scaling Coatings should be reported and evaluated separately be. particles. the nature and abundance of coatings sure or fire vary with processing methods and equipment. highly tivity. or hydrating portland cement while enclosed Identification of sources of coarse and fine aggregate in concrete or mortar under ordinary conditions of service in Proportioning of blended aggregates constructions. Aggregate fines within the cement-paste matrix stituents that produce notable expansion under conditions that 5.to the -polymorph Relationship of lithology and particle size to popouts at 573°C (1063°F) [44]. WONG ON PETROGRAPHIC EVALUATION 383 Poor under investigation or to determine the involvement of the ag- Particles exhibit one or more of the following qualities: friable gregates in either satisfactory performance or deleterious ac- to soft or pulverulent. capillary absorption high. The task is straightforward if the lithology of the coarse and fine aggregates is unam- General biguously distinctive such that no mutually common con- Aggregates enclosed in hardened concrete from structures or stituents are included in the respective materials. 7. Coatings on aggregate particles are expected in the proposed work. Segregation Potentially Deleterious Homogeneity of distribution of coarse and fine aggregates Particles contain one or more constituents in significant pro. such as in concrete to be ex. sul- fying agency. Proportions of coarse and fine aggregates compose without expansion. Chemical reactivity of constituents during service or test Similarly. 6. 2. Unless otherwise defined by applicable Dissolution of soluble constituents specifications. marked volume change an examination: with wetting and drying.” and service those having a ratio of width to thickness greater than five Oxidation and hydration of ferrous sulfides in high- should be designated as “flat pieces. such as initially composition and relegated to the appropriate category. slaking when wetted and dried. See Gaynor and Meininger [29] and Mass Proportions of Coarse and Fine Aggregates [45] for helpful discussions of the significance of the particle The proportions of coarse and fine aggregates within hard- shape of concrete sands. a combination of three or more quali. By ex. this category is extended to include individual con. The following features can be investigated during such fractured. for crushed stone. ened concrete can be determined fairly readily on sawed and lapped sections by means of the microscopical point-count Petrographic Examination of Aggregates in method or the linear-traverse method in general accord with Hardened Concrete the requirements of ASTM C 457. Unsoundness of constituents during service or test exposure ume while inversion takes place from the . or supply substances that Rounding of edges and corners might produce harmful effects upon mortar or concrete.” Identification and qualitative or quantitative determination of proportions of constituents Innocuous Proportions of physically unsound or chemically reactive Particles contain no constituents that will dissolve or react constituents chemically to a significant extent with constituents of the at. Differential distribution of lightweight and heavyweight portion that are known either to react chemically under condi. Coatings of dust of fracture trapolation. fides. Of course. sand and gravel presence of secondary deposits. or secondary mineralization. The manifestations of re. Tables 2–6 exemplify a variety of forms in which the petrologic formations that are operated as sources of crushed stone graphic analysis may be reported.75 m). received as a part of engineering investigations. gravels and sands contain high propor. the dimensions of the cross priate for the description of synthetic lightweight aggregates. particle as cast in the concrete. but the aggregate and the mixing of concrete. will demark the 4. namely.) in diameter and in. A condition that is more frequent and more readily the respective nominal maximum size of aggregate. moderately weathered and inter- more dimensions greater than 31⁄ 6 in. Consequently. Moreover. Table 3 is the analysis of the sand produced with the gravel The measurement is made conveniently if the reticle of whose composition is summarized in Table 2. deposits of sand and gravel usually tial and most frequent indication of cement-aggregate reac. The concrete-making qualities of the aggregate are within the concrete rather than a result of prior weathering. or by wind or within the particles and adjacent cement-paste matrix. It departs ners by attrition incidental to the processing and handling of somewhat from the format recommended in ASTM C 295. Darkened or clarified rims are more or less complex mixtures of different kinds of rocks within the peripheral border of aggregate particles are the ini. crushed stone or crushed natural aggregate can be taken as be.384 TESTS AND PROPERTIES OF CONCRETE at least three times that shown in Table 1 of ASTM C 457 for space [47]. presumably produc- aggregate and manufactured sand or natural sand or a ing a real or incipient separation at this location or a more di- crushed stone coarse aggregate and a natural sand. interstitial clay.75-m (31⁄ 6-in. deposition of mineral matter from ground water or by weath- duced by cement-aggregate reaction will be seen to thin or ering of particles. the remainder being classified as fine sical and chemical quality is included in a separate tabulation. gates in hardened concrete. lapped sections or fracture surfaces. rims pro. Examination in the field also A decision on this matter is made readily if a bonafide should reveal the variability of the sand and gravel with sample of the unused aggregate is available for separate study. adjacent void space is the thinning or disappearance of the pe- gregate whose nominal maximum size is larger than 37. wherein lute cement paste of higher water-cement ratio and lower one or more constituents are found in both the coarse and fine alkalinity.) sieve. microcracking ticles along streams. of a crushed stone and natural sand.). designations of quality are not used because they are inappro- sion in the field of view. the discovered than the relationship between peripheral rims and method is of doubtful practicality for concrete containing ag. The tabula- Although the natural aggregates characteristically are rounded tions are always accompanied by appropriate discussions and because of the only moderate hardness of the rock. The tabulation could be simplified by cata- mated by classifying as coarse aggregate all particles whose loging the rock types into major and secondary classifications. Summarizing the Petrographic Examination tions of dolomites and calcitic dolomites originating in geo. other considerations are required. for optimum workability. Examination in the field should indicate disappear where the aggregate particle is bordered by a void the lateral and vertical extent and the physical nature and . been employed by the Bureau of Reclamation [48]. and the glaciers on the earth’s surface.) dimen. Table 6 is an example of petrographic analysis of aggre- These determinations permit estimation of the sand-aggre. these strength by the concrete under certain conditions. the opening of the U. reference to unsound or deleterious particles. the denotations “innocuous” and “deleterious” are re- irregularly shaped particles of requisite lithology whose size is stricted to potentially deleterious alkali-silica reactivity because less than 4. cross section on sawed and lapped surfaces includes one or for example.. of the analysis. a circumstance related to bleed- For concrete containing natural or crushed gravel coarse ing and settlement of the fresh concrete. Table 5 is an analysis of a sample representing a commer- cle. and deeply weathered. In the tabu- effects tend to be self-compensating. in southern Michigan. All are based upon samples coarse aggregate for use in structural concrete and pavements.75 m (31⁄ 6 in.5 mm ripheral reaction rim along the bottom side of the aggregate (112⁄ in. an important factor in the proportioning of concrete aggregate and a natural sand containing particles of shale. Table 2 is in the form that has cles of crushed stone typically are rounded at edges and cor. vary vertically by stratification and laterally because of the tion. or because of facies the rims are. In this instance.) [46]. in lakes or marine basins. the the inclusion of pertinent descriptions facilitates interpretation distinction between coarse and fine particles can be approxi.5-mm (112⁄ - of the particle may be less than 4. a consequence of processes occurring changes. For example. Table 4 is similar except that the that. when calibrated. 4 (4.75 m (31⁄ 6 in. supplementary descriptions. However. and minerals. a crushed stone coarse gate ratio.” The summary of phy- Sieve No. the parti. section so revealed are not a measure of the size of the parti. Sections of coarse aggregate adjacent to edges and corners cial crushed stone coarse aggregate passing the 37. nally fractured. The analysis was obtained because the aggregate the maximum dimension of flat or elongated particles of fine apparently delayed or prevented development of specified aggregate may be greater than 4. influenced by these changes. The format one eyepiece of the stereoscopic microscope includes a scale conforms with ASTM C 295.S. Completely angular and lation. Deposits of sand and gravel are commonly changed by ing a product of cement-aggregate reaction.75 m (31⁄ 6 in. aggregate. Peripheral rims occurring adjacent to fractured faces of organic matter. and impacting of rock and the deposition of the resulting par- activity include such features as rim formation. The presence of such rims requires determination that lenticular nature of zones and strata. “granite: fresh. natural abrasion. in fact. Petrographic Examination of Alkali Reactivity of Aggregate Constituents Natural Aggregates Examination of hardened concrete from service or test exposure allows determination of alkali reactivity of siliceous or Examination of Natural Aggregates in the Field dolomitic rock types through observations made on sawed and Sand and gravel result from weathering. aggregates.) would appropriately be relegated to the significance of the sulfides and organic matter in the stone the coarse-aggregate fraction if the aggregate is a combination was not evaluated. Also. some free quartz grained granite Rhyolite 0. fair innocuous black. poor innocuous gray Rhyolite 0.. rounded.. 0. hard. 0.0 fine-grained. 6.to satisfactory innocuous medium-grained Weathered 10.3 7.4 0. 3 Description of Rock Types Quality Quality Granite 29. rounded.4 6. massive satisfactory innocuous to schistose Milky quartz 0. firm satisfactory innocuous sandstone to hard Ferruginous .6 medium. .5 massive.4 .7 17.7 lb of 3⁄4–3⁄8-in.2 1.. porphyritic. platy.. fine. poor innocuous weathered rounded to fragmental granite Coarse.4 0.9 . hard. satisfactory deleterious pink to gray NOTE: Conversion factors—1 in.6 1. .1 microcrystalline. 0. ________________ Size Fraction.6 weathered.. satisfactory innocuous porphyry white to brown Andesite 2..2 . pink.8 0.2 2.2 . weathered.. porous. 2. satisfactory innocuous porphyry tan to green Weathered . satisfactory innocuous hard.2 fractured. porphyritic. fair innocuous granite rounded to fragmental Deeply . includes fair innocuous coarse. Near Denver. ___________________ Company. porphyritic. % by massa Physical Chemical Rock Types 11⁄2–3⁄4 in.3 15...1 medium.. absorptive.. fractured. fair innocuous dense. ⁄8–3⁄16in. includes satisfactory innocuous grained some free quartz granite Fractured .5 . a Based upon analysis of 19.. 0.0 48.. fractured to fair innocuous gneiss slightly friable Deeply 0.2 1. fractured and fair innocuous andesite weathered porphyry Basalt 0. smooth Quartzose . 25. rounded. massive.2 0..2 as above. cryptocrystalline. brittle. and 0. 3 ⁄4–3⁄8 in.0 0...to fine-grained.to fine-grained.4 mm and 1 lb 0.2 0. Colorado Sample No.2 . hard. brown.8 2. aggregate.. intensely poor innocuous weathered fractured to friable gneiss Schist 2.4 0. 0.3 .. satisfactory innocuous rounded Fractured .5 soft... fine-grained..2 hornblende schists. satisfactory innocuous rounded to fragmental Weathered 12...4 pink.... as above.0 17. slightly friable.8 hard.2 14. fractured.. 0..1 .. 0.45 kg..1 8.3 2. . 0.7 as above.. microcrystalline Diorite 0.1 microcrystalline.0 lb of 11⁄2–3⁄4-in. banded..2 2..5 40... massive Granite gneiss 32.80 lb of 3⁄8–3⁄16-in.. as above. fair innocuous sandstone quartzose Shale . WONG ON PETROGRAPHIC EVALUATION 385 TABLE 2—Example of Tabulation of a Petrographic Analysis of Gravel _______________________ Plant. fractured fair innocuous schist Quartzite 2.8 6. 2 59.5 1.3 .2 Chalcedonic . 0.. and the ease with which the coatings are and physical nature of coatings. Weathering in the deposit is especially the laboratory with samples of the gravel and sand.. alkali.. 51. iron oxides....4 .0 17...0 ... .3 16.0 100. or may be developed by weather- thawing should be packaged separately and transmitted to ing in the deposit.0 100.28]. and outwash. 0..6 3.. 2. dacites. Areas of the deposit that are free texture. Identification of such particles will aid evaluation of similar composition and physical condition might be com- the petrographic examination performed in the laboratory. . opal... 4. T total of constituent in whole sample. (2) the abundance of particles in various conditions [8.0 100. Total 100...5 . 0. and altered particles may be original con- resentative specimens of particles affected by freezing and stituents of sand and gravel..8 .. (3) the composition. ..7 . Natural aggregate may contain more than 20 rock and Weathering of gravel and sand after formation of the mineral types.1 18. 3..2 1.. Water. The petrographic examination should reveal the com- of alteration and internal texture and structure and degrees of position...4 Claystone 0..9 0. .8 .. No. etc. . .8 Hornblende..0 43. 1.6 2... 9..0 100.6 . . c S satisfactory.. 4. 0. probable potential chemical reactivity.2 chert Mica . portion of the particles... commonly can be combined into a single category with con- Close observation of gravel and sand exposed on the sur.6 21.. earth sulfates. 2...4 0.. petrographic examination is com- deposit is common on terraces and at lower levels along existing monly time consuming..8 0. 15.....2 65. .______________ Company Near Denver. 11. % In Size Fractions Indicateda In Whole Sampleb No.. This action decreases both the bond Their presence forewarns of the need for their identification with the cementitious matrix and the strength. 3. . I chemically innocuous.1 granite gneiss Pegmatite 34. 200 Sc Fc Pc Ic Dc Tc Granite and 34..3 .. 13...0 1. abundance. siderable savings in time and without loss in the validity of the face of the deposit commonly will reveal unsound particles analysis. granodiorites.2 . .6 . .. aggregate. No. . granites.. (4) particle shape and surface removed by impact and abrasion.2 . F fair... abundance.5 1. Samples and data from the field should be examined to deter. 11..3 51.2 8.9 16. thus eliminating the need for tedious examination suffi- interpreting the effects of natural freezing and thawing.4 . In bined. 9.8 ... .0 .5 . . b Based on gradation of the sample received and on the distribution of constituents by size fractions shown at the left above... ... 3. Coatings usually are composed of in the Laboratory fine sand. P poor.. . .3 Basalt . .0 82. .2 Sericite schist 2.. .. 0.2 ...0 100. clude processing as aggregate should be delineated.2 1. 0....1 .2 Rhyolite tuff 0. two or more rock types should define the extent and distribution of such weathering.________________ Amount..2 28.. consequences of particle size should be evaluated [49]..5 11.. significant because the alteration affects most or all particles. physical properties.0 4.7 23. and (5) the possible qualitative contribution of particles from coatings and zones that are so heavily coated as to pre.3 . . The examination and probable performance in concrete... No.. . 1. glacial deposits.8 9. 3. Based upon similarity in composition stream channels. 5)..1 ... and soluble phosphates have been identified cal types.. D potentially chemically deleterious. soluble salts in coatings or ground water also may be re. 0. manganiferous substances.. as Number of Particles..7 .. durability.6 quartzite Feldspar 2.. that slake or fracture with freezing-thawing or wetting-drying and quartz monzonites—or rhyolites.3 .. Consequently..7 . .3 garnet..5 100.7 11..2 0.2 0.8 0. chemical reactivity.2 9. composition of the coatings.2 . . clay. . and latites—of (Fig...0 100. ..and alkali- mine (1) the abundance of individual lithologic or mineralogi. .....7 Quartz and 24.2 ..0 0.. silt.. Rep.. 16.3 10. 0.6 41. zircon.6 15.8 51.. 11. frequency... ... 1..6 .. the cient to effect a separation.. possibly causing softening and absorptivity in the superficial vealed by efflorescence at or near the surface of the deposit... . For example.. .8 28.7 2.3 0. and and quantitative determination of their concentration in the volume stability of the concrete.. 1.0 48... Soft. No. Passing Physical Quality Chemical Quality Constituents 4–8 8–16 16–30 30–50 50–100 100–200 No. 0..8 10.... of the several types to properties of concrete (Tables 1 and 2).2 .9 33. .. friable.8 6. but organic matter.3 . 4.386 TESTS AND PROPERTIES OF CONCRETE TABLE 3—Example of Tabulation of a Petrographic Analysis of Natural Sand __________________ Plant.. No. and calcium carbonate.....1 . quartz diorites.. Colorado Sample No. 8.0 98... Coatings on gravel and sand vary from minute spots and films to a cement that produces zones of sandstone or con- Examination of Natural Aggregates glomerate in the deposit. ..... 51.0 a Based on count of 500 particles in each sieve fraction. ... at least certain artificial of dispersed silica.2 36.0 100.. as Number of Particles. 0.1 29... . 1.0 100. 0....0 100. .9 2... argillites.1 7.6 12..0 100.. results in alkali-carbonate reaction does not preclude the pos- pending on composition. . .. .. Fraser et al.4 . .0 100.. Gravel and sand potentially susceptible to the alkali-silica glasses may be identified by refractive indices below 1. slates. 0.8 0. hard vesicular particles Black to gray.2 25. The location of many known deposits of alkali. Any aggregate containing a significant tents between 55 and 65 %) are commonly reactive.0 1. hard vesicular particles Red to tan. and strained or very finely divided alkali silica reactivity leading to serious distress have been ob- quartz.1 0. No... 44. [51] (Fig... No. served with limestone aggregate that contains small amounts and andesites. 0.6 23. 2...0 21.4 24..8 7. friable contain coal particles Granite 0. friable vesicular particles Red to brown. often skeletal remains of small organisms. more proportion of these substances is potentially deleteriously al- basic glasses (silica content below 55 %) are less so.1 hard. 26. ..8 .0 NOTE: 1 in.3 .. fine- grained Coal . Passing Whole Constituent in. The known alkali-reactive lutions. brick-like firm to particles fragile Gray to pink.0 not vesicular.. 4–8 8–16 16–30 30–50 50–100 No.3 not vesicular.0 15..8 hard to friable Total 100. siliceous glasses. friable vesicular particles Red to tan. 6). brick-like fragile..1 46. Particles of volcanic glass or sometimes teristic dolomitic composition and impurity content that devitrified volcanic glass in aggregates may be reactive.5 20.... a Based on count of 500 particles in each size fraction.1 not vesicular. _____________________ Amount. Oc- reaction occur along many important rivers in the United casionally basalts contain glass whose index of refraction is States and have been responsible for serious distress in many less than 1. No.. in. . No.1 1.9 23.8 vesicular. 25. .4 not vesicular. including highway pavements such types are potentially alkali reactive.2 0...7 2.. many particles slake in water Gray to pink.6 1. de.0 100. cristobalite. chalcedony... and certain phyllites.. 4..7 7.9 21.. 7. ... many particles slake in water Gray to black.8 20.4 hard. concrete structures of all types.7 8..4 7. 7).8 0.. Reactive kali reactive in concrete in service.4 . glassy to cryptocrystalline rhyolites.. .0 . have provided a detailed study of the composition of chal- reactive natural aggregate in the western United States was cedonic cherts in relation to their reactivity with alkaline so- reported by Holland and Cook [50]. and on the distribution of constituents by size fractions shown at left above.. stituents of natural aggregates.0 0.2 64. .2 ..5 vesicular. b Based on gradation of the sample received. and The fact that limestone aggregates may not have the charac- graywackes (Fig...0 1. 1.535 and palagonite may be partly altered to opal. .6 1.4 mm.4 42..7 .8 9.0 100..0 100. percent In Size Fractions Indicated a In ⁄4–3⁄8 3 3 ⁄8–3⁄16 No. WONG ON PETROGRAPHIC EVALUATION 387 TABLE 4—Example of Tabulation of a Petrographic Analysis of Expanded Clay Aggregate _________________________ Plant. latites.. 0..7 1. 1. .1 2. opal.5 55..3 22.6 32.57. Alkali-reactive dolomitic rocks may occur as con- substances are the silica minerals. .6 30. exists in the material... . dense Sandstone .... .8 4. A number of instances of tridymite..5 1.8 9.0 25. .8 4.. 0.1 1. . . . and their tuffs.0 62.4 0. 1. brick-like friable.2 3. dacites. 100 Sampleb Remarks Black to gray. 13.. .4 vesicular.0 0.. 0. Acid glasses (those with a silica sibility of alkali-silica reaction if disseminated reactive silica content above 65 %) and intermediate glasses (with silica con. _______________ Company Sample No.2 vesicular.2 44.4 2. SW corner of __________ Street and _________ Street...96 a Microscopical point-count method. 2...1 ... 33... c S satisfactory. 1 Core No. I not deleteriously alkali reactive. dense .2 limestone with pyrite and marcasite Soft dolomitic limestone gray to buff. slightly porous.. contains sparse organic matter 56.9 lb of aggregate split from the sample (1 lb 0.____________________ Company Sample No.________________ Amount. 4.1 0.. 0..0 a Sample graded in accordance with specifications of the _____ State Highway Dept. 2. 4. % by volume of sand fine aggregate 11. in. ... 2: Sidewalk. .0 . 2 Coarse aggregate. particles of zones of chalcedony 1. .7 40.. 4 aggregate for concrete highway pavement (1 in..70 Sand fine aggregate.. _____________________.Washington Street. P poor..9 1. iron sulfides and . organic dolomitic same as above except containing one or more .. 25. for 11/2 in.4 Laminated limestone laminated. Michigan Core No.0 evident Chalcedonic chert conchoidal fracture.388 TESTS AND PROPERTIES OF CONCRETE TABLE 5—Example of Tabulation of a Petrographic Analysis of Crushed Stone Coarse Aggregate. 2. .. 0. 33. .9 . 56. TABLE 6—Microscopical Analysis of Aggregate in Hardened Concretea Core No.2 .1 Total 59..2 ..1 .99 54. b Based upon analysis of 25. ASTM C 457.4 mm)..–No..1 .4 .... . 2..9 sparse organic matter with pyrite and marcasite Soft. 33.. 1: Street pavement in front of _________________________.1 organic matter abundant Chalcedonic limestone white to gray. % by volume of total aggregate 54.2 .. Michigan Item Core No. Number of Counts Area Traversed.9 .a________________ Plant.3 . __________. 98.. F fair. ..4 .. 2.45 kg).. based on the following criteria: Core No. % by weight b Physical Quality Chemical Quality Rock Type or Facies Description of the Rock Type or Facies Sc Fc Pc Ic Dc Tc Dense dolomitic gray to buff. soft to friable.. 4.. coarse. % by volume of total aggregate 45.. 0.4 mm).2 .9 2 2838 24..1 Sandstone includes also grains of quartz and feldspar 0. . 1.. 56.2b 1 1944 35..1 ...35 8..30 Shale particles..0 1..9 b Maximum area available in submitted samples (1 in..1 .2 limestone seams of iron sulfides and organic matter Limestone white to gray.. 25. T total of constituent in the sample. D potentially deleteriously alkali reactive..to medium-grained 2. fine-grained... 0..1 100.01 45. sources of sand or gravel subject to alkali-silica reaction. silica reaction in mass concrete. and radial cracking of enclosing difficulty in service as concrete aggregate (courtesy of mortar matrix. Fig. Michigan. near Charlesvoix. 6—Location of structures in the United States (other than Alaska and Hawaii) known to be affected by alkali-aggregate reaction in concrete. A millimetre scale is shown. internal microcracking. 5—Cobbles of argillaceous limestone disrupted by Fig. WONG ON PETROGRAPHIC EVALUATION 389 Fig. 7—Metasubgraywacke exhibiting advanced alkali- freezing-thawing in the deposit. . The internal microcracks are characteristically Michigan Department of Transportation). open in the interior of the particle and closed at the periphery. and sources of crushed stone subject to alkali-carbonate reaction. Note white deposits in external microcracks. including darkened peripheral Observation of natural disintegration forewarns of possible rim. 61 %. from the crushing of boulders and cobbles recovered from drothermal alteration in igneous or metamorphic formations in gravel. The physical of such disintegration indicates unsoundness of stone in at quality was indicated as follows: satisfactory. ballast. ing. These features should be discovered by geologic and pet.34]. degree of fracturing. tail as required for natural aggregates (Table 5). This technique can be applied to Shale. of the entire sample. riprap. Similar effects occur if the zeo. Thirty seconds of immersion in oxidation and hydration (Fig. depending on lo. Quantitative petrographic analysis can be performed on vey may reveal lithologic varieties that have failed during calcareous rocks by preparing plane surfaces by sawing and natural exposure to freezing-thawing or wetting-drying or to lapping. Kansas. zeolites. . Certain zones may contain deleteri- As indicated earlier. such as clay. joint. 8—Disintegration of argillaceous facies of limestone Fig. including deeply calcareous aggregates in hardened concrete (Fig. toughness. rock formations Petrographic examination of stone in the form of quarried commonly are fractured. Fig.S. least portions of a quarry (courtesy of the Bureau of poor. Reclamation. where or chemical reactivity. pyrite or marcasite. etching by 112⁄ to 2 min immersion in hydrofluoric acid (HF) lites leonardite-laumontite constitute a significant proportion (Fig. cedures given in ASTM C 457. porosity. fair. and masonry. Quantitative analysis can be performed similarly on pre- may slake and fracture during brief exposure even though they pared surfaces of quartzose and feldspathic rocks following appear sound when excavated. Consequently. as discussed previously. and commonly does not coincide with results of the sulfate sound. 11). cobbles. these specimens provide other excavations. Procedures for obtaining representative samples are de- and stone used in the area for fill. Specimens representative of each type should be obtained by rographic examination of natural exposures.390 390 TESTS AND TESTS AND PROPERTIES PROPERTIES OF OF CONCRETE CONCRETE Petrographic Examination of Crushed Stone of the rock or occur as seams or veinlets in the formation. quartz gabbros. Disintegration of rock on natural exposures constituents. Especially in warm and humid areas. 10). altered basalts and diabases (traprock) containing nontronite. Observation and pieces of illite shale. Webster Dam. claystone. ative abundance of individual rock types or facies (Fig. 5 % by mass (courtesy of the Bureau of Reclamation. or zones of hy. Soluble salts usually will be re- Examination of Stone in the Field vealed by efflorescence at exposed surfaces. quartz diorites. scribed by Abdun-Nur [12]. Petrographic examination for special tests. Excavation of trenches or test pits may be required. Department of the Interior). and partially decomposed by blocks or irregularly shaped pieces should include inspection weathering near the surface to varying depths. and argillaceous rocks. the alkali reactivity of substantially all of the faces of the particles have resulted from dolomitic limestones typically varies widely even within the the crushing operation (ASTM C 125). or lithology. 8). Tennessee. quarried faces or the sawing or coring of typical pieces. U. This sur. such sources is analogous to that applied to natural aggregates Rock formations commonly contain zones of faulting. or local shearing. U. such as chalcedonic or opaline complex petrographically and not only when they are derived chert and clay or shale in limestone or dolomite.S. they are especially common in granodiorites. detailed petrographic examination. hardness. crushed stone aggregates are commonly ous or unsound substances. they should be examined in the same de- which sulfides. they may be derived from deposits of gravel and sand. 9—Crushed limestone aggregate containing seams used as riprap at Chickamauga Dam. within which the materials are fractured Examination of Crushed Stone in the Laboratory or chemically decomposed. 34 %. leached. and the like as widely in porosity. The significance of the size of 10 % hydrochloric acid (HCl) will provide adequate differential fragments should be recognized in any evaluation of such attack on calcite and dolomite and will expose non-calcareous observations [49]. and rock may vary duced by the processing of boulders. Department of the Interior). or clay-like minerals are promi. and anorthosites. and drilled core. Rock formations are massive or stratified. and refer- in the field should include exposures of geologic formations ence. siliceous sand or silt. chert. For example. Field examination of same quarry when deleterious facies are present [33. 9). The examination should establish the rel- calized differences in fracture. nent. the strata can occur Note that the term “crushed stone” covers aggregates pro- in any attitude relative to the horizontal. followed by etching. clays. The etched surface can be analyzed by ness test ASTM Test Method for Soundness of Aggregates by point-count or linear traverse in general accordance with pro- Use of Sodium Sulfate or Magnesium Sulfate (C 88) [52]. dark areas are augite in the etched surface. and (b) after 11/2 min etching in concentrated HF. 10—Concrete containing dolomitic limestone coarse aggregate (a) before. 11—Augite gabbro (a) before. WONG ON PETROGRAPHIC EVALUATION 391 Fig. and (b) after etching for 30 s in 10 % HCl. . Scattered crystals in the etched areas on the lapped surface of the aggregate particles are dolomite. Fig. White areas are plagioclase feldspar. if unsound or deleterious particles constitute 10 % of the finished aggregate. a compound of variable of Blast-Furnace Slag composition between akermanite (2CaOMgO2SiO2) and gehlenite (2CaOAl2O3SiO2). depending by sawing and lapping of the core along the length. forsterite. is established. Crystals oc- laboratory. Note the vesicles (bubbles) in glass phase (white). crushed or forms of 2CaOSiO2). For example. and microchemical tests can be used to identify or other soft materials. 12). graphic examination of aggregate produced from cores in the Well-granulated slag is substantially all glass. portion. The slag constituent usu- Blast-furnace slag is the nonmetallic product. Magnesium-containing blast-furnace stone. crys- cations. air-cooled slag. and light. chemically reactive substances. Petrographic examination of lightweight or More than 20 compounds have been identified in blast- expanded slag will be discussed in a later section. vesicularity. jointing. or merwinite. consisting essen. furnace slag (Table 7). frequency of fractures and seams within the particles. Crystals range from submicroscopic to The quality of the rock to be expected from the formation several millimetres in size. with or with- primarily upon the method of disposal employed at the steel out etching or staining. or the presence of products of weathering. Pseudowollastonite and anorthite The procedure for petrographic examination of blast-furnace are also common occurrences. the rock. Evaluation furnace (see ASTM C 125). the entire dark areas are concentrations of microcrystalline melilite and length of the core should be examined and compared with logs merwinite (courtesy of the Bureau of Reclamation. available from the driller and geologist. as necessary. inasmuch as such zones commonly represent fractured. frequency and intensity of fracturing. and presence of various phases in the surface under study. Such slag crushes to angular and approximately equidi- from hole to hole so that the variation in lithology or quality of mensional pieces. Fig. U. Special attention must Department of the Interior). and petro- to prepare in sizes larger than standard thin sections. High-lime blast-furnace slags slag is not included specifically in ASTM C 295. the manufactured aggregate produced should be examined to determine the effects of natural fracturing. cur individually or in clusters scattered through the glass matrix. In addition to slags commonly include monticellite. The typical con- Performance of the Petrographic Examination stituent of blast-furnace slag is melilite. or deposits or fill are being exploited. Each type should be stud- Three general types of blast-furnace slag are used for concrete ied in sufficient detail to assure identification of potentially aggregate. the graphic microscope.392 TESTS AND PROPERTIES OF CONCRETE If the sample of stone was submitted for crushing tests in the laboratory. Properties of blast furnace slag as of effects of weathering is especially important when old pits concrete aggregate have been reported by Gutt et al. However. stereoscopic microscope. the surface textures of which are pitted. The examination is facilitated Air-cooled slag is more or less well-crystallized.S. was this proportion derived from approximately one piece in ten of the original sample or does a typical piece of the stone contain approximately 10 % of unsound material? The former possibility suggests that the quarry should be examined to determine whether the unsound zones can be avoided or wasted. color. both in depth and laterally. Incipient crystallization produces brown or opaque areas Petrographic Examination of in thin sections (Fig. Blast-Furnace Slag The petrographic examination of blast-furnace slag aggregate should include descriptions of the various types of slag as Blast-Furnace Slag well as of contaminating substances. weight slag [54]. namely. and the abundance and composition of crusher dust. These observations should be correlated plant. rough. The core should be examined by preferred by some petrographers because the surfaces are easy means of the hand lens. be given to sections in which core loss was high or complete. but even well-crystallized slag rarely contains more than five compounds (Table 8). 12—Photomicrograph of granulated blast-furnace slag. examination of polished Calcium sulfide (CaS) is almost always present in small pro- and etched surfaces in reflected light is a valuable technique. or otherwise unsound rock. to establish variations in two-dimensional aspect simplifies quantitative estimation of lithology. instructions provided for examination of ledge rock. the latter suggests that the material should not be used as aggregate in concrete for permanent construction. altered. The If the samples are in the form of drilled core. the indicated microscopical methods. and internal texture on particle size and shape. regardless of rock type. deleterious compounds. and manufactured sand are applicable. content of clay composition. distribution of unsound or deleterious substances in the size fractions. depending tially of silicates and aluminosilicates of calcium and other upon particle shape. Inspection of the stone prior to processing is important because only thus can the examination of the finished aggregate be interpreted fully. that is developed simultaneously with iron in a blast tallinity. . granulated slag. Abrasion resistance relates to glass represented by the cores also will be revealed by petro- content and the condition of internal stress [54]. [53]. ally can be segregated into two or more varieties. surface texture. Sulfides of manganous manganese and ferrous iron . the usually contain one or more forms of dicalcium silicate (. or conchoidal. These features should be correlated with the processing equipment and methods employed. causes “dusting” or “blowing” of slag [54. and American Concrete Institute Committee 201 [60]. with accompanying 10 % increase in volume of the crys- Several constituents of blast-furnace slag may be deleteri. Fe)O SiO2 Merwinite 3CaO MgO 2SiO2 cristobalite SiO2 Rankinite 3CaO 2SiO2 calcium aluminate CaO Al2O3 Monticellite CaO MgO SiO2 cordierite 2MgO 2Al2O3 5SiO2 Pyroxene Diopside CaO (Mg.60]. and in attack on the cement-paste matrix of concrete in service. WONG ON PETROGRAPHIC EVALUATION 393 TABLE 7—Compounds Occurring in Blast-Furnace Slaga Compound Chemical Formula Compound Chemical Formula Gehlenite 2CaO Al2O3 SiO2 oldhamite CaS Akermanite 2CaO MgO 2SiO2 ferrous sulfide FeS Pseudowollastonite CaO SiO2 manganous sulfide MnS Wollastonite CaO SiO2 spinel (Mg. and Snow [58]. but the coloration rences. CaSO42H2O) commonly forms in these compounds are summarized by Rigby [55]. X-ray diffraction methods are ulated slag is most susceptible to the formation of gypsum dur- necessary if crystalline phases are submicroscopic and are a ing weathering exposure. b Key: C2AS gehlenite C3S2 rankinite CAS2 anorthite } melilite C2MS2 akermanite C3MS2 merwinite M2S forsterite C2S dicalcium silicate MA spinel MS enstatite CS wollastonite or pseudowollastonite CMS2 diopside MgO periclase CMS monticellite . Gran- standard works on mineralogy. are common. producing pieces fades to a homogeneous shade of gray on drying and exposure that are partly or wholly weak and friable. Fe)O Al2O3 Bredigite 2CaO SiO2 anorthite CaO Al2O3 2SiO2 Larnite 2CaO SiO2 periclase MgO -dicalcium silicate 2CaO SiO2 lime CaO Olivine 2(Mg. In less severe occur- duced on the surface of damp concrete [14]. ing the production of coarse aggregate. tal.59. and thus unsuit- to the atmosphere. Properties and techniques for identification of (calcium sulfate dihydrate. a mottled aspect is pro. McCaffery et al. cement-paste matrix produce innocuous green staining of the and the disintegrated material is removed by screening dur- interior of the concrete. This action of dicalcium silicate by yellow or brown coloration of the glass phase [53]. Inversion of -dicalcium silicate to the -dicalcium sili- dependently in this field. primarily Nurse and Midgley [56]. Occasionally. The ous to the performance of concrete. [62]. Presence of colloidal sulfides is suggested able for concrete aggregate. cate. great aid to a petrographer who is developing experience in. Sulfides released into the inversion ordinarily takes place before the slag has cooled. Insley and Frechette [57]. Gypsum can be avoided by maintaining a ratio of CaO to SiO2 in the TABLE 8—Most Frequently Occurring Combinations of Compounds of CaOMgOAl2O3SiO2 Produced by Crystallization of Blast-Furnace Slaga Combination of Compoundsb Flux Stone C2AS C2MS2 C2S CS C3S2 C3MS2 MA CMS2 CMS CAS2 M2S MS MgO X X X X X X X X Limestone X X X X X X X X X X X X X X X X X X X X X X X X X Dolomite X X X X X X X X X X X X X X X a After Nurse and Midgley [56]. the disintegration takes place slowly. Nurse and blast-furnace slag by weathering and may result in sulfate Midgley [56]. Fe)O 2SiO2 sillimanite Al2O3 SiO2 Enstatite MgO SiO2 mullite 3Al2O3 2SiO2 Clinoenstatite MgO SiO2 madisonite 2CaO 2MgO Al2O3 3SiO2 a Compiled from several sources. should describe the aggregate in terms of the nature of the fied. Department of magnesia may not be neutralized by such treatment. and volcanic cinders used for lightweight and hydration if exposed at the surface of the concrete. and coke. Scoria. particle shape. Particles of expanded material may be segregated on the basis of particle shape. U. These compounds result mainly from decomposition of calcite and dolomite in the feed during firing. and miscellaneous rock particles. and content of contaminating substances. 13).or steam-cured prior to use [63]. Scoria is a highly porous and vesicular rock in which the vesicles typically are Expanded Clay. trial furnaces. softness. slaking. including their particle shape. the Interior). Scattered crystals of Industrial cinders used as concrete aggregate are the residue -dicalcium silicate commonly are stable in blast-furnace slag from high-temperature combustion of coal and coke in indus- and therefore are innocuous. If air-cooled slag is poured in thin layers. namely.61]. shale. The composition and content of raw materials commonly can be established most easily and accurately by X-ray diffraction or differential thermal analysis. a solid solution of magnesium oxide (MgO). if identi. Such particles usually represent sandstone or siltstone that was in- tercalated within the clay. rapid cooling ordinarily arrests the compound in the - modification. Petrographic examination should determine the Free lime (CaO) and magnesia (MgO) are extremely rare physical nature of the cinder particles on the basis of compo- as constituents of air-cooled blast-furnace slag and are not sition. Expanded Blast-Furnace Slag tion and carbonation in place. Metallic iron and iron carbides rust by oxidation Pumice. Dicalcium silicate can be identified microscopi- Industrial Cinders cally in slag by special techniques [59]. manganese oxide (MnO). and reddish brown.2 Nevertheless. surface texture. The individual types of particles also should be analyzed petrographically to establish the presence of free lime or magnesia. Petrographic examination also assists in the selection of or by chilling the molten slag so that the compound does not raw materials. and ferrous oxide (FeO). Tuff is a general term designat- clude segregation of the particles into as many categories as required to describe the sample adequately (Table 4). This compound is potentially subject to one of several ways [54]. Incompletely expanded particles and particles not expanded should be distinguished from vesicular ones.S. the interstitial glass oc- Petrographic examination of lightweight aggregate should in. occurrence of efflorescence. development of a coating or “skin. gray. The source of concrete aggregate. absence or presence and abundance should be established by petrographic examination. black. scoria. likely to form either as a primary phase or devitrification prod- Particular attention should be given to identification of sul- uct in granulated blast-furnace slag [56. Shale. effects of weathering in stockpiles. its abundance should be determined. tuff. development of manufacturing equipment and crystallize [53]. Tuff. basic open-hearth slags commonly contain free oxides that are subject to hydration and carbonation in portland-cement concrete.394 TESTS AND PROPERTIES OF CONCRETE slag sufficiently low to prevent formation of the compound. methods. absorptivity. friability. ture. and surface texture. Note the rounded vesicles gregate is water. Pumice is a very highly porous and vesicular rock com- Petrographic Examination of Lightweight posed largely of natural glass drawn into approximately paral- Concrete Aggregates lel or loosely intertwined fibers and tubes. coal. softness. These compounds are deleterious because of the increase in solid volume resulting from hydra. and Volcanic Cinders and popouts. density. They should be separated on the basis of porosity.” and vesicularity. 2 Unlike blast-furnace slags. The petrographic examination supplements standard tests in distinguishing clayey particles from “clay lumps” determined in accordance with ASTM C 142. 13—Typical basaltic scoria aggregate. expanded particles. active with cement alkalies. surface tex- The glass phase of blast-furnace slag is not deleteriously re. last is important because hydration and carbonation of free lime and magnesia may produce expansion of the concrete Pumice. curring as thin films (Fig. and Slate rounded or elliptical in cross section. their fides. Fig. such as dense slag. friability. Other materials to be identified and determined quantitatively are underburned or raw material. and process control. free lime (CaO) and magnesiowustite. aggregate are naturally occurring porous or vesicular lava and ash. friability or softness. Expanded blast-furnace slag is produced by carefully con- Cristobalite (SiO2) has been reported as a constituent of trolled intermingling of molten slag and water or steam in blast-furnace slag [62]. coke. or swelling). The pieces are tress or popouts in concrete or concrete products unless the ag. iron carbide. coal. or slate. They may produce dis. . and reaction to water (softening. Contaminating substances whose presence or absence The petrographic examination is especially important when should be determined by petrographic methods are metallic fill or waste deposits are later contemplated for use as a iron. sulfates. and incompletely fused fluxstone. Hard-burned (courtesy of the Bureau of Reclamation. The petrographic examination the alkali-silica reaction in portland-cement concrete. cement ratio of the original concrete is equal to or lower than that of the new concrete containing the recycled aggregate as Exfoliated Vermiculite coarse aggregate only. However. intermixture of the vermiculite with particles of rocks and min- canic rock and organic matter. cant expansion may not occur because of the porosity of the particles. it has been investigated in the United States.” and in ASTM C 33 without development of excessive stress in the mortar. with both high. containing abundant tridymite caused only 0. a highly porous rhyolite tuff from Hideaway Park. they observed that the strength of the Exfoliated vermiculite is produced by rapid heating of the mi. certain obsidians and pitch- union Internationale des Laboratoires D’Essais et de stones release gases that. A similar but dense rhyolite tuff short supply. secondary deposits in sources. such as masonry units or precast panels. gregate. vermiculite. of 1945–1985 [70]. Fine sand. The product is known commercially as perlite. tridymite. Compressive Strength cordance with ASTM C 227 in combination with either high. usually as aggregate. and elsewhere as a partial or complete re- tential Alkali Reactivity of Cement-Aggregate Combinations placement for conventional aggregates for purposes of econ- (Mortar-Bar Method) (C 227). yet the specimen contained omy. aggregates. chalcedony. crete. ab- by petrographic examination. Colorado. depending upon mineralogical properties and vesicular (scoriaceous) fragments of lava. from near Castle Rock. more re- pansion of a high-alkali cement mortar during one year of cently. although signifi- rographic examination of samples of such materials.535–1. Petrographic examination should indicate the composi- The following summary of the properties of concrete tion of the aggregate in terms of particle shape. Such volume change will strength of concrete containing recycled concrete is controlled not necessarily cause structural distress if appropriately ac. Canada. . and potential rographer in decisions on (1) features to be considered in ex- alkali reactivity.16 to 1.) in diameter. However. that the concrete will be reclaimed for production of concrete Being composed of rhyolitic volcanic glass. the particles of vermicu- Petrographic examination of these types of aggregate in. Perlite may contain particles of dense volcanic amination of constructions to be demolished with the intent rock or individual crystals. Extraneous or lite grades into hydrobiotite or biotite. Also to be reported is the contaminating substances are primarily dense particles of vol.400 % under the same conditions. sorptive. and potential alkali reactivity. These surface texture. ness of the flakes. At least certain diatomites pro- ably is alkali reactive. and ranges from firm to pulverulent. widely differing proportions. re- glass.26 in. typical perlite aggregate and (2) observations that should be included in pet- is potentially reactive with cement alkalies. and volcanic ash are present in whose index of refraction is in the range of 1. coatings. duce significant expansion of mortars stored in accordance balite are also common alkali-reactive constituents of volcanic with ASTM C 227. predominantly rang. crete from structures and pavements was used widely in Great orado. The degree of expansion character. friability or fragility. two types of volcanic materials occasionally are intermixed for economy or to control gradation or unit weight. In production of lightweight ag. and environmental benefits. silt. being trapped within the molten Recherches sur les Materiaux et les Constructions (RILEM). largely by the water-cement ratio of the original concrete when commodated in the design of the constructions or concrete other conditions are essentially identical. Finely divided Volcanic glass with an index of refraction less than 1. new concrete is equal to or higher than that of the original con- caceous mineral. ing from 4 to 32 mm (0. Britain and Germany following World War II and. gregate in new concrete is feasible and may become routine.535 opal and opaline skeletons of diatoms are the predominant con- is potentially deleteriously reactive with cement alkalies. substitution for natural or crushed stone aggregates in abundant alkalic silica gel [64]. For ex. Release of combined water ex. as “crushed hydraulic-cement concrete. specific gravity. Volcanic cinder is a loose accumulation of highly varies widely. Recycled concrete is defined in the report of the American ica gel in highly porous vesicular lavas and tuffs. These minerals are especially common as altera- Petrographic Examination of Recycled Concrete tion products of volcanic rocks of acidic to intermediate com- for Use as Concrete Aggregate position. erals occurring with the vermiculite in the ore deposit. laboratory tests demonstrate that certain perlites produce significant expansion of mortar stored in ac.570 prob. purity and the conditions of firing. surface texture. lite are segregated by degree of expansion. clay. The Diatomite type and relative proportion of the materials can be established Crushed and sized natural diatomite typically is soft. Re- When heated rapidly to fusion. Opal.66]. and cristo. Recycled Concrete In spite of alkali-silica reaction and formation of alkalic sil. WONG ON PETROGRAPHIC EVALUATION 395 ing consolidated volcanic ash of any lithologic type or physical as much as 30 times its original size. Great moist storage in accordance with ASTM Test Method for Po. vesiculate the rock and cause disruption into small ported on the state of the art in this technology for the period pieces. friability or differ significantly within individual samples from some softness. opal may occur as an alteration product of palagonite in basaltic lavas. and vice versa. containing recycled concrete as aggregate may assist the pet- rock classification. expansion Concrete Institute (ACI) Committee 117 on Cement and Con- and cracking of the enclosing concrete usually is prevented by crete Terminology [67] as “hardened concrete that has been the abundant voids into which the hydrating gel can escape processed for reuse. Hansen and Narud [71] concluded that the compressive alkali or low-alkali cement [65. During petrographic examination. and fragility of the expanded crystals.66]. density. porous. porosity or vesicularity. Committee 37-DRC. weathering. When the water- product. fracturing. provided the fine aggregate is a natural pands the crystals—like an accordion—increasing the volume to sand or manufactured sand of suitable quality. glass stituents. Forster [69] reported on extensive studies of such applications Perlite by state departments of transportation. elasticity or brittle- cludes segregation of the particles on the basis of particle shape. Britain.and low-alkali cement [65. especially from marginal deposits where the vermicu- voids.041 % ex. Col.” Such reclaimed con- ample. produced an expansion of Buck [68] concluded that use of recycled concrete as ag- 0. may or may not affect air entrainment of the Presence of Mineral Admixtures new concrete [69]. for quality of the cementitious matrix. Chemical Contamination or Radioactivity tarding. use of recycled concrete as coarse aggregate only. there is no reason to believe that the recycled concrete sion of the particles by oxidation and hydration of the pyrite should not be required to meet generally accepted standards and subsequent crystallization of iron and calcium sulfates. but elimination of the con- calcined). including use of lar concern is recycled concrete that contains aggregates recycled concrete as coarse aggregate alone or as both coarse including disseminated pyrite (ferrous sulfide. natural pozzolans (raw or use of an air-detraining admixture. such as and fine aggregate. increases the water requirement for a given consistency. air en- the water-cement ratio usually is not known and is not readily trainment of both the original and the new concrete. or air-entraining admixtures in recycled concrete have Concrete contaminated by noxious. recycled as concrete aggregate. or radioactive sub- no significant effect on slump. deicing chemicals. Prospective sources of recycled concrete may be unsound or have been rendered unsound in service as a result of the pres. ice was maintained for long periods at temperatures in the frost resistance of the aggregates included in the recycled con. be isolated and disposed of separately. set-re. damage screening operations and magnetic separation usually will be by fire or service at high temperatures. Enhanced entrainment of air may require Mineral admixtures such as fly ash. toxic. such as [72]. Freeze-Thaw Resistance The utility of concrete damaged by fire or high-tempera- Widely varying results have been obtained in tests of freeze. The results relate to many factors. As noted previously [23]. presumably in part because of pressive strength of the concrete to be recycled is a more prac. or alkali-carbonate reaction. The possibility of the introduction of additional al- increases drying shrinkage at a given water content. minated. and re. and so on. taminant is preferable. reactivity should be rejected as a source of recycled concrete The RILEM report [70] concludes that all material below 2 mm unless it can be shown that the expansive processes have ter- in recycled concrete should be screened out and wasted. reduction determined in practice. say 70 % or less. Tests and experience Ferrous particles may cause staining where they lie adjacent to . presence of alkali-silica in acceptable proportions in the finished recycled concrete. and the like during the course of Unsound Recycled Concrete demolition and processing of the recycled aggregate. plasticizing. tration of alkaline solutions from an external source. the com. tures used at ordinary rates as normal-setting or accelerating admixtures in the recycled concrete will influence the setting Contamination by Bituminous Materials time of the new concrete. the quality of the original concrete in terms certain dolomites and firm shales. air content. crete. These effects are greatest when the recycled concrete is from the cementitious binder of the new concrete or by pene- used as both coarse and fine aggregate. crete derived from concrete exposed to temperatures in this in- posed to severe conditions of weathering. be brought to acceptable levels by specifications on removal of overlayments. It is not expected that the chloride-containing admix. mixtures. when the conventional fine aggregate is replaced in whole or Concrete affected by a harmful degree of alkali-aggregate in part by fine aggregate derived from the recycled concrete. where the concrete in serv- of water-cement ratio and parameters of the air-void system. deterioration by sulfate attack. and presence or absence of purposeful air entrainment pyritiferous dolomite or shales in aggregate can produce dis- in the new concrete containing the recycled concrete. the reduction in maximum size of the offending coarse aggre- tical measure of quality than is the water-cement ratio because gate. Available data [73] indicate that. such as bituminous concrete. or industrial media. or silica fume included in recycled concrete are un. In any tress when the concrete is heated in that range due to expan- event. range of 150–300°C (370–575°F). They Presence of Chemical or Air-Entraining pertain also to the use of such recycled aggregates in new con- Admixtures crete intended for these applications. such as structural members adjacent to kilns and furnaces or constituting the frame of such facilities. of chloride or water-soluble sodium are found. High concentrations of water-soluble chloride excessively contaminated portions of the concrete if they can ion in recycled concrete have been shown to contribute to ac. found in appropriately extended tests of the proposed concrete crete. FeS2). Portions thaw resistance of concrete containing recycled concrete as of the constructions may be suitable for such use. Metallic Contaminants ence of finely porous aggregate that is susceptible to disruption Metallic particles or fragments that survive the crushing and by freezing and thawing. Of particu- aggregate.396 TESTS AND PROPERTIES OF CONCRETE In evaluating the probable influence of recycled concrete show that concrete disrupted by D-cracking can be successfully from a given source on the strength of new concrete. termediate range. and These observations are pertinent to evaluation of recycled con- soundness of aggregates when the new concrete is to be ex. and introduction of fly ash as a partial A substantial reduction in compressive strength may result replacement of the portland cement [69]. alkaline soils. air entrainment. the new concrete will serve under conditions in which the internal relative humidity will be maintained at very Water Requirement low levels. kalies into the particles of recycled concrete during the service duces the modulus of elasticity at a given water-cement ratio exposure of the new concrete should be recognized. when used at generally recommended rates in the original concrete. of the water-cement ratio. or setting time of stances should be rejected for use as recycled aggregate. such as sea water. ture service must be examined on an individual basis. such as portions of celerated corrosion of steel embedments included in the new pavements or marine structures in which high concentrations concrete. Recycled concrete containing asphaltic materials. joint fillers. An the new concrete or compressive strength of the new concrete otherwise desirable source may be salvaged by elimination of after hardening. The proportions of such materials can likely to modify the properties of the new concrete. or that no deleterious effects are Use of recycled concrete decreases workability of fresh con. structively designate those locations or portions of concrete crete aggregate. as paint. taminants for New Concrete to be Subjected to The petrographic examination should be carried out with Wetting and Drying or Freezing and Thawing recognition of the possibility that the aggregate was derived as Reported by Committee 37-RDC. and load and to various types of en- Lime plaster 7 Gypsum plaster 3 vironmental exposure. and where extensive fenestration. Coatings of dust of fracture . bottle glass. use of the concrete in production of recycled concrete aggregate would be brought into question. impact. such as when Similar avoidance of difficulties may relate to installations of recycled concrete is obtained from facilities that include fur. and tunnel alkali-carbonate reactions or severe corrosion of steel embed- linings. such bricks included in conventional aggregates are known to Such inspection should reveal the existence of portions of create cracking. As scat. gates. spalling.15 % by mass of the recycled-concrete reaction. such as portions highly contami- brick lie adjacent to surfaces that are exposed to freezing and nated by sea water. WONG ON PETROGRAPHIC EVALUATION 397 exposed surfaces. This evaluation might con- tolerated in building rubble for production of recycled-con. Interna. On the other hand. The effects of the alkali-silica reaction may develop in the pres.) the installations that are seriously affected by the alkali-silica or in portland-cement structural concrete. Soil 5 The following features should be observed. such as that of aluminum metal or galvanized iron may produce blisters or derived from gypsum plaster or plasterboard. possibly from more than Materials and Structures one source. Recycled Concrete ASTM C 295 does not contemplate petrographic examination of recycled-concrete aggregate. and Wood 4 reported relative to the effectiveness of operations that consti- Asphalt 2 tute the production of the recycled concrete: Vinyl acetate paint 0. The report recommends that particles of tivity. or freezing and thawing. recorded. or glassware may be pres. lightweight and porous brickwork or potentially deleterious re- naces or kilns lined by such masonry. expressed as the SO3 con- with the alkalies within the cementitious matrix. industrial chemicals or wastes.95 g/cm3 be rejected gypsum plaster or wallboard. tent by mass of the entire concrete. Miscellaneous Contaminants A Japanese standard for use of recycled concrete limits various Performance of Petrographic Examination of impurities as shown in Table 9 [70]. crushed stone. The RILEM shallow cracking on surfaces of fresh or “green” concrete as a Committee report [70] recommends that the sulfate content of result of the release of hydrogen formed by the interaction the new concrete be limited to 4 %.2 Grading Particle shape Surface texture a Amount that reduced compressive strength 15 % compared to the control Angularity concrete containing recycled concrete. they can pro. or radioac- thawing while wet. they recom- duce popouts and local cracking as a result of the alkali-silica mend a limit of 0. the procedures for examination of ledge rock. and unsightly and annoying bulges may develop on aggregate for organic particles. and manufactured sand may be employed as appropriate. especially in the presence of appreciable Stringent limits are required on the allowable concentra- concentrations of water-soluble chloride salts. Objectives of the examination may include evaluation of Maximum Allowable % processing procedures and facilities as well as determination by Volume of of composition. gregate containing acceptable levels of deleterious substances. highly porous. Nevertheless. quality. be placed on allowable amounts of the contaminants listed in ent in demolished concrete structures and difficult to avoid or Table 9 for new concrete to be subjected to wetting and drying to extract during production of recycled aggregate. Noting that organic substances. coatings or overlayments will make difficult the securing of ag- Refractory bricks having a high content of crystalline mag. periclase) present special problems. from rubble that comprises two or more classes of concrete of tional Union of Testing Laboratories for differing composition and condition. ments. such tered particles lying adjacent to exposed surfaces. and that the same limit be applied to the recycled-concrete aggregate. fired-clay placements that are unsuitable or of questionable quality for brick may be susceptible to disruption when particles of such use as concrete aggregate. pavements. Examination of Prospective Sources of Recycled ence of either low. lightweight aggre- TABLE 9—Recommended Limits on Con. and may include contaminants of divergent types. installations of brick rubble having a density less than 1. floors where the eruptions are confined by flexible coverings. Small particles tion of water-soluble sulfates in recycled concrete. and popouts as deep as 50 mm (2 in.or high-alkali cements. may entrain excessive amounts of air. Glass as a Contaminant The Committee recommended further that stringent limits Fragments of plate glass. or applications of paints or other as lightweight particles in accordance with ASTM C 33. and anticipated performance of the ag- Material Recycled Concretea gregate in one or more concretes to be subjected to differing levels of attrition. Large-size fragments of fractory bricks. In each instance. Concrete in the Field The petrographer can assist in evaluation of prospective Contamination by Brickwork sources of recycled concrete by examining the intact structures The report of RILEM Committee 37-RDC [70] concludes that or pavements at the site of demolition prior to initiation of pro- up to 5 % by mass of fragmented brick masonry usually can be cedures for aggregate production. nesia (MgO. the previous extent Secondary chemical deposits in included aggregate. weak. Applied in the field. cement-aggregate reactivity other than Petrographic examination should be included in the investiga- alkali-aggregate reaction) tion and testing of concrete aggregate for use in permanent Damage to original concrete during service (freezing before construction and in the manufacture of concrete products and setting. natural and synthetic lightweight aggre- blended with a suitable red iron-oxide pigment so as to allow gates. and C 856. the chemi.75 mm (3/16 in. luster on fresh frac. 1288–1312.. leaching. in situ precast structural elements. (3) explaining results of analysis of the recycled concrete or portions thereof. the availability of alkalies in the voids. the method of Hansen and Narud can be em. sulfate attack. with proper training gate and mortar in the recycled concrete used in their tests by and the adoption of uniform techniques and nomenclature. slag. identified by them as “red cement. tional. West Conshohocken. ab.” Presumably. bond to fine aggregate. “Petrographic Examination of Aggregate and ployed to determine the relative proportions of coarse aggre. C. and other sources). ASTM STP 1061. actions is seen. tests and justifying special tests as required. West Con- shohocken. and amount of alkali-reactive aggregate. Erlin and D. L. P. In any event. other information. moderately hard. fire damage. pp. ance of concrete containing recycled concrete. [1] Mielenz. Reclamation for Identifying Reactive Concrete Aggregates. estimated water. Concrete Aggregates at the Bureau of Reclamation. and new concrete subjected to moderate or severe conditions of reported relative to the composition and condition of the weathering exposure.. ASTM International. unsound. 1990. Vol. including the kind Alteration of the cementitious matrix (carbonation. moisture to the new concrete during the service exposure. soft) ticles susceptible to the alkali-silica reaction or the alkali- Relative proportion of mortar and coarse aggregate carbonate reaction in recycled concrete presents two general Bond of mortar to coarse aggregate problems: (1) if pre-existing manifestations of one or both of Characteristics of the cement-paste matrix (firmness. sulfate attack. recorded. leach. alkali reactive. air of development of distress. thermal stability. Vol. 1948. freeze-thaw.. Concrete in Ontario. these being features important to the performance of The following features should be observed. However. G. This writer has employed the point-count method of ASTM [2] DePuy. PA. “Tests Used by the Bureau of plicit criteria applied to distinguish sections of coarse aggre. Stark. . and the availability of ural. to determine air-void content and other parameters of the air. gravel. pp. C 457. acceptance tests. the relative proportions of coarse aggregate and mortar in the recycled concrete were determined on sawed and lapped surfaces by the References linear traverse method. Erlin and D. and Mather B. W. especially by (1) detecting adverse properties. K. cracks. 48. 5–31. presence of a mineral admixture. R. than 4.. merit of processing and manufacturing methods for aggregate Because of its great effect on the properties and perform- production. “Method of Petrographic Examina- vious section on Petrographic Examination of Aggregates in tion of Aggregates for Concrete. The same type of specimen can be used Eds. Hansen and Validity of the results depends upon the training and ex- Narud [71] determined the volumetric ratio of coarse aggre- perience of the petrographer. crushed nat. PA. the concentration of ing. ASTM STP coarse aggregate all particles that include a dimension greater 1061. and cement-aggregate interface new concrete (including those derived from the cement. crushed stone. staining) available alkalies in the recycled concrete.” Petrogra- guishing coarse aggregate from fine aggregate by classifying as phy Applied to Concrete and Concrete Aggregates. pp. min- Nature of coarse and fine aggregates (natural.398 TESTS AND PROPERTIES OF CONCRETE Variability among nominally similar production lots void system of the recycled concrete in accordance with ASTM Contamination by foreign materials C 457. C. ASTM Interna- Hardened Concrete). 50. Stark. B. calcined or sintered light. “Petrographic Investigations of Concrete and C 457 in analysis of ordinary portland-cement concrete. 32–46. Eds. No details were provided as to the ex. or instructions by (2) comparing the aggregate with aggregates for which service the purchaser or supervisor show the need for partial chemical records or previous tests are available.” Proceedings.” gate from those of larger particles of fine aggregate. and aggregates produced from recycled concrete. will the composition and environmental expo- cement ratio or water-to-cementitious materials ratio. cementitious matrix. A. specimens could be prepared with the portland cement crushed stone. other) ation of materials from alternative sources. slag. will they proceed sufficiently to sorptivity. 1071–1103. high-temperature aids exploration and sampling and permits preliminary evalu- exposure. and Concrete Aggregates.” Petrography Applied to Concrete and gate and mortar and of coarse aggregate. and (5) determining the efficiency and relative closely coordinated and the data mutually exchanged. the method hydration of iron sulfides.. ASTM International. satisfactory The method can be applied effectively to sand. and Witte. sure of the new concrete be such as to initiate and propagate microcracking) these reactions to a deleterious extent? These questions require Air-void content and parameters of the air-void system careful analysis of all factors concerned. eral admixtures. detection of rock types or other par- Hardness (hard. Proceedings. ASTM International. B. fine aggregate. distin. Where the examination. casting specimens of a mixture of the aggregate and a binder subjective elements in the examination are not significant. damage the new concrete? and (2) if no evidence of these re- ture. other) Lithologic composition of aggregate and foreign materials Conclusion Quality of aggregates (sound. weight aggregate. easy distinction between the particles of recycled concrete and the binder.) in the plane of the section (see the pre- [3] Mather. 1990.. particles: As noted previously. After hardening of the specimen. [4] Roberts. (4) detecting con- cal analytical work and petrographic examination should be tamination. 1950. Detailed examina- Techniques of the petrographic examination directed to tion of aggregates in the laboratory supplements the standard these objectives are covered by ASTM C 295. these reactions are found. pp. ” Cement [14] Mielenz. Transportation Concrete and Concrete Aggregates. and Newlon. San Francisco. 1982. American Concrete Institute.S. 70–72. “Alkali-Silica and Alkali-Carbonate Reactivity of a South 1188–1218.” Highway Sands. Duncan. Vicksburg. C. PA. C. “Alkali Reactivity of Dolomitic can Concrete Institute. Vol. Vol. 1990.. Waterways Experiment Station. 20–48. Concrete. 9.. “Alkali-Silica-Reactive Rocks in the Cana- gates in Very High-Strength Concrete. 92–94. [26] Buck. B.. Maiza..” Journal of Materials. 52. 10. pp. shohocken. Sources of Distress in Concrete...” Highway Research Record No.” shohocken. E. 1981. “Alkali-Aggre- STP 930.. West Conshohocken.” Concrete International. Promoted by Alkali-Carbonate Reaction: A Documented Exam- lies in Cement—Considerations for Preventing Alkali-Silica ple. Transporta- gates as Related to Durability. 40. DC. 4. R. H. NJ. Noyes Concrete Failure. Army Corps of Engineers. National Vol. American Concrete Institute. J. 1980. and Mineralogical Characteristics of Aggre. 1963. Vol. 29–35. [40] Bachiorrini. ASTM International.. Wash. gates.. G.” Alkalies in Concrete. Ameri. 1974. L. 19. 3. pp. and Characteristics of Concrete Aggregate Materials. R. S. [27] Mielenz. ASTM STP 83. 1983. pp. 17. R. A.. Handbook of Concrete Aggregates. Geological Society of America. D. 1973. C.. J. “Correlating Water-Soluble Alkalies to Total Alka.. 99–102. Concrete Research. Eds. M. 1990. “Effect of Phlogopite gates. 789–797. T. 1975.” Alkalies in Concrete. E. Vol. and Bhatty. 1946. [21] Midgley. Transportation Re- Popouts on Slabs. Jr. and Mielenz. Cement and Concrete Research. “Deterioration of a Concrete Surface Due to the Ox. “Alkali-Silica Reactivity: Some Reconsiderations. gregate. and plied to Concrete and Concrete Aggregates. and Montanaro. Washington. pp. “Methylene Blue Testing of Smectite as Related to [11] Dolar-Mantuani. Dodson. [29] Gaynor. Concrete.. pp. Highway Research Board. R. ASTM International. Army Corps of [7] Rhoades. Engineers. Concrete Research.. 1–7. search Board. 793–804. 3. “Importance of Pet- pp. ASTM Inter- [12] Abdun-Nur. pp. 462–474. Wash. 521–535.. C. [30] Higgs.. A. N. ASTM [43] Gillott. E.” Cement. [32] Higgs. as Judging the Quality of a Concrete Sand.. 75–78. 525. pp. P. [36] Ryell.. Vol.. ASTM International. L.. Chojnacki. Stark. ASTM STP 1061. “Basis for Classifying Deleterious [28] Schmitt. No. Sulfates or Sulfides. pp. National Research Council. Vol. ASTM International. 5. Board. State of California. tion Research Board. pp. M. Eds. “Lithologic Characteristics of Concrete Aggre. pp. Washington. ASTM International. P. 1983. “The Importance of Petrological. P. Vol.. West Con. “Thermally Destructive Particles in Sound Dolostone Quartz in Relation to Alkali-Silica Reaction. 1974. 1990. H. E. No. W. Vol. R.” Cement and pp. 8. Water- [20] Sarkar. American Concrete Institute. K. D. 1990. ASTM STP 930. P. F. V. No. and Aggregates. Washington. pp. 54. N. “Petrographic Examination of Concrete Aggre.” Highway Research Record No. portation Research Board. T. “15 Years of Living at Kingston with a Reactive Car- [17] Robinson. “Evaluating Concrete gate to Determine Potential Alkali Reactivity. C. 12. “Control of Reactive Carbonate Rocks in Concrete. P. 43. and Swenson. Washington. Washington. pp. Vol. 525. W. E. pp. C..” Petrography Ap- Aggregate from an Ontario Quarry. Water-Soluble Impurities on Concrete. Performance Study. “Anhydrous Minerals and Organic Materials. “Alkali Reactivity of Strained Quartz as a Con- [22] Shayan. PA. 987–1002. stituent of Concrete Aggregate.. IV. PA. C. pp.. American Concrete Institute.. R. 47–54. E. [35] Smith. 1958. pp. R.” 1985. 525. Vol. DC. Vol. P.” 95–104. [10] Mielenz. “The Staining of Concrete by Pyrite. J.. pp. J. Oxidation.” Highway Research Record No.” Bulletin 1969. Research Report 18-C. pp. 1974. “Investigation and Repair of Damage to Concrete 1961. pp. pp. P. bonate Rock. 103–107.” Proceedings. and Aggre. F. A. 16–30. Technical Report C-75-3. [25] Grattan-Bellew. A. 1964. 1990. D.. R. L. Cement... 99–117. Park Ridge. A. DC. gate Reaction in Nova Scotia. DC. Vol. R. pp. Ed. B. Research. 1962. gate. “Physical-Chemical Properties [8] Rhoades. 1980.. [34] Swenson. 3. 66–70.. Erlin and D. and Concrete Research. and Engineering Performance of Clays. B.” Highway Research Record No. and D. “Alkali-Silica Reaction (ASR) PA. 461–479. D. 1969. 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Through the Use of A Review. B. K. H.. J. pp. [70] Hansen.. W. 1967. 2167. 1975. Bureau of Mines. Detroit. British Ceramic Research Association. 21P-51P. R. Vol. “Identification of CaOMgO Orthosilicate Crystals. Vol.” Journal. Vol. 1. pp. Illinois State Geological Survey. G. 1948. (ACI Slag as Aggregate for Concrete. 1978.” Concrete In- Cements. 183 and 661. A. H.. 1962. 1942. H. [63] Nordberg. C. 19. [64] Mielenz. and Schapiro. Vol. Sillers. 1960. 1035–1040. pp. and Narud. . p. P. and Uses. nace Slag. Amer- ceedings. 10. and Hedegard. ” Such characteristics Characteristic features resulting from ASR are shown in were the major. activity (ASR). re. and early in-service failure of the concrete occurrence of associated distress. It should be noted that rims may be due only to ical or mineralogical composition of the aggregate. updates the topics as addressed in cement and concrete articles reinforcement. The ASR may develop in hardened concrete and may appear with third version. detailing. shown in Figs. became identified in most areas of the world. Figure 1 illustrates typical fine pattern crack- The shifting emphasis in this chapter since 1966 reflects ing due to ASR. detected a previously unknown deleterious chemi. restraints. Rather. published in rials to avoid deleterious ASR. Accordingly. 401 . cracks are generally random in many the predominating concern with alkali-silica reactivity in pres. if any. hardness. Here. and ASR gel in the mi- volume stability. together 1966. pore solutions usually exceed pH values of 13. it denotes only that structure. veloped standards to identify and evaluate construction mate- Hansen and was included in ASTM STP 169A. The important point is that the greatest cracking due to ASR can develop in the direction of least resist- The selection of aggregates for use in concrete was based pri. particle exceed the tensile strength in the concrete structure. Stanton. maximum more detail and emphasis than previously included are pro.” It specifically excluded alkali-carbonate reactivity and emphasized alkali-silica reactivity. written by the present author. despite the weathering in natural gravels and. The presence of alkali silica gel can be confirmed by de- By the 1940s. The first ver. ing along a pavement highway. It is a reaction product Highways. if not the only. which swells and tain compositions of siliceous aggregates [1]. The fact that aggregates must be evaluated for chemical stability in con- THIS CHAPTER IS THE FOURTH OF A SERIES DEALING crete as well as for physical competence thus became evident with chemical reactions of aggregates in concrete. are given in the time to occur in concrete. together with applying uranium acetate solution and 1 CTL Group. The second version was written in 1978 by Sidney Diamond for ASTM STP 169B and was entitled “Chemical Reactions Other Symptoms of Alkali-Silica Reactivity Than Carbonate Reactions. It should be emphasized that resulting expansion could lead to abnormal cracking. of the California Division of ASR is the presence of alkali silica gel. this chapter. consideration of the technolo. This phenomenon became known as alkali-silica re. He determined expands with the uptake of moisture. the reaction had developed. termination of refractive indices using the petrographic mi- spread areas of the United States. Virtually no attention was given to the chem. Salient features of ASR. and through the following croscope. IL. directions and with little. It dealt with several types of chemical reactions known at with a summary of methods of preventing ASR. restraint to expansion extends parallel to the longitudinal pave- vided for the practicing technologist responsible for providing ment direction. The best evidence on which to confirm the development of In the late 1930s. transverse direction of the pavement. C. shape. Here. ance. crocracks. Figure 3 reveals cracking in a generally horizontal plane in which little restraint develops Introduction in the vertical direction. depending on the design of the structure. Fig. that simply the presence of gel deposits does not confirm the duction in strength. ASR was known to have developed in wide. microcracks in the concrete. including alkali-silica reactivity. with costly realization. as such. ASTM de- sion. thereby resulting in greater expansion in the long-term durable concrete. of alkaline solutions in the concrete and reactive forms of sil- cal reaction involving pore solutions in the concrete and cer. and exposure conditions. provided uniform restraint on the concrete does not marily on physical characteristics such as grading. They include reaction rims in peripheries of aggregate gist in achieving long-term specified concrete strengths and particles. caused by ASR. preferred directional restraint ent-day construction and reflects our updated knowledge of to expansion. and “cleanness. In response to this situation. entitled “Chemical Reactions. ica or siliceous components of the aggregate. Figure 2 illustrates well-defined longitudinal crack- how to deal more effectively with the problem. 5400 Old Orchard Road. as and introduces new technology that has been developed. Skokie.” was written by W. 1–3. covers only “Alkali. Abnormal cracking may develop Silica Reactions in Concrete.” This fourth edition reviews and in a variety of patterns.34 Alkali-Silica Reactions in Concrete David Stark1 Preface decades. density. one or more characteristics [2]. are not necessarily known fact that concrete is a highly alkaline system in which related to ASR. 4. viewing using ultraviolet light in the stereomicroscope. if any. particularly near transverse joints. depending on composition. A longitudinal crack pattern prevails in this pavement. 2—Longitudinal cracking initiated by ASR in a jointed. as de. opal and volcanic tuff the reaction can be described as a two-step process as follows: materials are often highly reactive while certain chert or Step 1—Aggregate particle alkali hydroxide solution → silicate minerals are essentially innocuous. Fig. and mois- sible expansion ture availability. . It may be somewhat accentuated by drying shrinkage. viscosity. formance as noted below: 1. 1—Fine pattern or random cracking initiated by ASR in a parapet wall of a dam. concrete. Hydroxyl ion concentration in the concrete solution is the Mechanism of Reactions and Distress in crucial factor in potential for ASR. for example. slab-on-grade pavement. There is little. cracking relating to differential restraint to expansion. Voluminous literature [3. For example. not the amount of Concrete sodium or potassium in.402 TESTS AND PROPERTIES OF CONCRETE Fig. Numerous siliceous aggregate materials are not equally aspects of ASR.4] has been produced dealing with all 2. Each of these factors variably can affect concrete per- scribed in the annex of C 856 [2]. Gel reaction product 3. together with minor random cracking. deleteriously reactive. cementitious materials. In its simplest and most straightforward form. ASR gel may exert variable pressure and expansion in the Step 2—Gel reaction product Water → Swelling and pos. STARK ON ALKALI-SILICA REACTIONS 403 Overall. Con- versely. a higher alkali content gel forms. According to Powers and Steinour. The diameter of the hydrated calcium ion is substantially larger than that of the hydrated sodium or potassium ion. an expansive reaction occurs when alkali concentrations in pore solutions are higher. a low-calcium. The lower solubility of calcium in solution and the which major cracking due to ASR developed primarily in a lower diffusion rate of calcium to reaction sites within the par- horizontal orientation. it is assumed that consumption of alkali in the reaction results in greater solubility and availability of calcium at subsequent reaction sites. ever.6 % equivalent sodium oxide (Na2O). Accordingly. Coarse aggregate particles were quarried and composed of shistose to mylonitic composition with the largest aggregate particle having a maximum size of 2 in. and the calcium ion cannot diffuse to the reaction site at a sufficient rate to prevent formation of a swelling gel. The horizontal cracking developed normal to the ticle both serve to reduce its participation in the reaction. 4—Evidence of ASR in sample of concrete from gravity dam. the Powers and Steinour [5] model best fits published results. with the result that they diffuse more readily than the calcium ion to the internal reaction sites within a particle of reactive ag- Fig. It therefore produces essentially a non-swelling reaction product. or its fineness.4 normal sodium hydroxide (0. How- general direction of least resistance to cracking. thereby continuing to produce a high calcium non-swelling gel reaction product. high-alkali unlimited-swelling gel reaction product is formed. Lesser cracking is evident vertically and diagonally. In this case. 3—Vertical concrete core from jointed pavement in gregate.50 water-cement ratio (w/c) by mass. thus reducing the concentration of calcium ion. These safe reactions were believed to begin and continue without expansion if the initial alkali concentration is not greater than that produced by cements of about 0. is increased Fig. ASR-related features include well-defined. dark reaction rims and microcracks through aggregate particles and cement paste matrix that contain white- colored ASR gel deposits. or about 0. the reacted layer in the aggregate becomes too thick. which has a greater capacity to swell with absorption of moisture. They proposed that safe reactions are those in which sufficient calcium ion is available in alkaline pore solutions to produce limited-swelling high-calcium-content gel. . if the amount of reactive silica. The initial surface reaction in this model is assumed to occur in contact with the pore solution in the cement paste. For a safe reaction to continue. which is saturated with respect to calcium hydroxide.4N NaOH) concentration in pore solutions at 0. when less calcium ion is available. such as metarhy- calcium ion concentrations. the belief that the cause of distress observed in concrete made torted. Probably the most widely used of such aggregates are 3. ASTM Standard Test Method for Determination of Length is found as microscopic veinlets or finely disseminated in other. ASTM Standard Guide for Petrographic Examination of every state in the United States and in most countries through. Moisture Availability and Environmental Effects Another aspect of the Powers and Steinour model is the As indicated. also are known to have reacted deleteriously in con- can form. which conditioned exposures. “Standard Descriptive rial. and southeastern Wyoming.60 % equivalent Na2O. and girders. moisture must be sufficiently available in the con- diffusion of silica away from reaction sites and out of reacted crete to permit expansive ASR to occur. at least on a cyclic basis. The Another procedure. residual mixing water may be sufficient silicate hydrate phase of relatively narrow composition and a to support expansive ASR in mass concrete. re- to a safe level so that a higher calcium. ceed the 80 % RH level. cal. ASTM Standard Test Method for Potential Alkali-Silica have reacted deleteriously with the highly alkaline solutions in Reactivity of Aggregates (Chemical Method) (C 289) concrete. concrete. This with these aggregates was more or less unique to those areas imperfectly crystallized quartz has been recognized as the re. that alkali-silica reactivity is the major cause of distress in those metagraywacke. such as bridge decks. but on other factors such as on an almost continuous basis. limited-swelling gel spectively. Where high water- are two-phase composites consisting of the swelling alkali. Slightly metamorphosed volcanic rocks. The author believes active component of such metamorphic rocks as gneiss. In these cases. ASTM C 295. Mis- rocks where it is classified as strained quartz and microcrys. are also known to produce expansive ASR. Kansas. and moisture availabilities exist and result in intermediate conditions in which ASR develops. especially tuff. Basically. Obviously. cement ratios are used. This standard active and are known to have exhibited deleterious reactivity was discontinued in 2001. This mate. Reactive silica of this type also 5. regardless of climate. also ex- solved silica from reactive particles. reactive aggregates. diffusion rates. referenced to 23 1°C.404 TESTS AND PROPERTIES OF CONCRETE sufficiently. was intended to identify expansive cement-aggregate and produce popouts within one day of placing the concrete [8]. Reactive Aggregate sures generated in concrete. souri. before expansion due expansion-controlling processes were diffusion rates of alkali to ASR can develop [9]. The basis for this test was talline quartz. crystal structures are variously dis. it provides some rigidity to the paste structure. Near-surface concrete experi- distance from the reaction site and movement along cracks [7]. permeabilities of olite. Weathered volcanic rock is particularly troublesome It can be done rapidly but is somewhat subjective in nature. They proposed that silica was able to diffuse out cate that relative humidity (RH) values in the concrete must ex- through the reaction layer in the aggregate particle and that ceed about 80 %. Laboratory data indi- particles. areas and that the test is of little additional value. ences major RH fluctuations that support expansive ASR on an Electron microprobe and X-ray studies suggest that ASR gels intermittent basis. They are: Potentially deleteriously reactive rock types probably exist in 1. Nebraska. depending not only be expected to be sufficiently damp to support expansive ASR on circumstances just indicated. and quartzite. Iowa. thus rendering them susceptible to deleterious ASR. reactions involving so-called sand-gravel aggregates that occur Deleteriously reactive silica also is present in metamorphic primarily in eastern Colorado. regardless of climate. support columns. Change of Concrete Due to Alkali-Silica Reaction (C 1293) wise innocuous rock types such as limestone and dolomite. results depend on the . of Cement-Aggregate Combinations (Mortar-Bar Method) These include opaline and chalcedonic silica that are found in (C 227) such rock types as chert and flint. which have reacted deleteriously (C 342). ASTM Standard Test Method for most highly reactive rock types known to the writer are shales Potential Volume Change of Cement-Aggregate Combinations that contain opaline diatoms. ASTM Standard Test Method for Potential Alkali Reactivity in. Methods of Identifying Potentially Viscosity of the gel is a major factor affecting swelling pres. together with ASTM C 294. which are very dense or very porous volcanic glasses. de- in that it has produced ASR-associated distress when used with pending on the experience and capabilities of the petrographer cements with less than 0. for example. concrete climates can ASR gels vary widely in composition. even in interior air- limited swelling calcium-alkali silicate hydrate phase. Chatterji [6] suggested that slab-on-grade concrete. The other general reactive component of siliceous aggre. ASTM has five standards available to identify potentially reac- Types of Reactive Aggregate tive siliceous aggregates. with high-alkali cements only after five or more years of service. as secondary fillings in voids 4. and as interstitial and interlayer material of Aggregates (Mortar Bar Method) (C 1260) in rock types such as sandstone. basalt. and so was given a separate test procedure. intermediate-alkali and corresponding crete. varies in both proportion in the gel and composition. a guide recommended for identifying and describing con- etration of alkaline solutions into the aggregate particle in the stituents of aggregate by petrographic examination of concrete. This condition is easily met in outdoor and calcium to reaction sites. In this circumstance. Being calcium-bearing. ASTM C 295–Petrographic Examination gates is the glassy to cryptocrystalline matrix of volcanic rocks of Aggregates of approximately rhyolitic to andesitic composition.” is types and is commonly altered by weathering that facilitates pen. cause or increase expansions by impeding the escape of dis. the alkali content of the solution is rapidly reduced pumice. including desert calcium hydroxide plays an additional role in ASR in that it can conditions. Many natural siliceous rock types are known to 2. Except for near- escape of other reaction products out of the particle. Interior portions of elevated concrete members. even where cium reacts to form a calcium-alkali silica gel that blocks the prolonged severe drying conditions prevail. ASTM Standard Test Method for Potential Alkali Reactivity those that contain noncrystalline or poorly crystalline silica. Aggregates for Concrete (C 295) out the world. surface concrete in elevated structures. Obsidian and examining the aggregate. These rock types are slowly re. constitutes a major proportion of these rock Nomenclature for Constituents of Concrete Aggregates. schist. Method).05 % af- C 227 mortar-bar test results. scribed grading as well. talline volcanics of rhyolitic to andesitic composition. C 33 leaves open which “Aggregate Considered Innocuous” is located on one to the engineer’s discretion the option of extending the test pe- side of the curve. and quartzite. and washed to the pre. graywackes. These aggregate types tion in alkalinity is accompanied by relatively little dissolution include certain gneisses. or quartzite. Even when used with cements with 1. thereby underestimating Sc found to be a serious limitation on expansion [12. A high-alkali cement. such as opa- silica (Sc) in millimoles per liter is plotted logarithmically on line-bearing materials and weathered glassy to cryptocrys- the abscissa and reduction in alkalinity (Rc) is plotted on a lin.60 For this method. many cases exist perature (80°C). where the procedure falls short of expectations. Today. the aggregate is sized and washed to meet % as equivalent Na2O. good field service records where it was attributed to the fine Overall. respectively. crete Aggregates (C 33) states that in C 227. it rapidly identify slowly and highly reactive aggregates. The result is plotted on a graph where dissolved arbitrarily defined as rapidly reactive aggregates. and in the classification of An aggregate may be judged to be innocuous when used with known reactive aggregates as innocuous. and “Aggregate Considered Deleterious” or riod to. On the other hand. iron carbonates. schist. A curve is drawn on the graph in they are tested with cement with 1.47 water-cement ratio by mass.25 parts of aggregate. with the mortar bar criterion ter two to three. and is highly recommended for use in The Appendix of the ASTM Standard Specification for Con- conjunction with other tests and field performance evaluations. such as glassy volcanics or tuffs. values or overestimating Rc values. calcium. schists. then three 25-g samples criterion. or more. gypsum. Location of the innocuous-deleterious curve on the canics. of Cement-Aggregate Combinations graywacke. and zeolites. deleteriously reactive in field structures. greater than 0.0 % alkali. schist.” The Appendix also states that combinations showing ex- tially deleteriously reactive is ASTM C 289. such as gneiss.10 %. tion to use low-alkali cement (less than 0. tivity. It fails to identify slowly if an aggregate is judged to be potentially deleteriously reac- reactive aggregates. gates as deleteriously reactive.13] in C 227.10 % or greater linear expansion. C 227 may be useful for identifying certain aggre- particle size of the material (150–300 m) and high test tem. Testing field performance record.05 % and 0.05 % criterion at three months is consid- of the material are immersed in 1N NaOH solution in sealed ered innocuous if the six months criterion is less than 0. based on simulated what might actually occur in concrete [1]. This then was a stricter test is sized to the 300–150 micron sieves. However.05 % at three months should be considered to as the Quick Chemical Test. As such. in some cases.” During the 1950s. and metavol- of silica. Field and laboratory studies [11] have revealed that reactivity results from strained or microcrystalline quartz. it had to be crushed. tional Building Research Institute [14] and was designed to ing safe or unsafe cement-aggregate combinations.60 % equivalent Na2O) tries in their practices and standards. reports have shown that mineral phases. practical in these cases. cement and 2. such as riously reactive with low as well as high-alkali cements. have resulted in misleading con- the original hydroxyl ion concentration caused by reaction clusions with eventual deterioration of concrete. which was 1980s. or those for which a significant reduc. This method was originally “potentially capable of harmful reactivity. However. The resulting suspensions Many years of experience with C 227 have revealed short- are then filtered. expan- graph presumably is based on field performance and on ASTM sions for these rock types may reach no more than 0. magnesium. STARK ON ALKALI-SILICA REACTIONS 405 judgment of the petrographer in contrast to fixed measuring for the duration of the test period.10 % at six ASTM C 289–Chemical Method months “usually should be considered capable of harmful reac- One procedure used to identify whether an aggregate is poten.10 % expansion levels were applied to test ages of Reclamation [10]. and stored in a moist . ASTM C 227 has been an ASTM mortar bar standard since 1950 Thus. or the contemplated job cement. it may be delete- the test was found to be severe for several aggregates with riously reactive. The suggested with the test sample and for the amount of silica dissolved in expansion criteria appear to be valid for rock or mineral types the solution. commonly referred pansions of at least 0. sized. then biweekly materials engineers to the presence of potentially reactive rock to bimonthly to a suggested test period of six months. the test could be used as a quality control tool for aggregate procedures only if results of the test are confirmed ASTM C 1260–Potential Alkali Reactivity of by more reliable laboratory tests or field performance records. extending “Potentially Deleterious” is located on the other. If a coarse aggregate was to the Potential Alkali Reactivity of Aggregates (Mortar Bar be evaluated. in fact. A zero reference compara- procedures for classifying aggregate. the 0. years [11]. containers held at 80 1°C for 24 h. certain aggregates. was to the specified grading. With some modifications in the late was carried out using the aggregate in question. A major use is for alerting tor reading was made the day following casting. and mineral types. the developed by Mielenz and co-workers at the U. the aggregate in question six and twelve months. some siliceous limestones. when ear scale on the ordinate.S. cement-aggregate combinations showing expansions greater than 0. 12 or more months. ASTM C 289 appears to have some serious limitations and A further limitation from C 227 results is a recommenda- is seldom recommended by various organizations and coun. cement of a certain alkali level when. then cast into mortar bars then stored over water in a sealed container held at 38 2°C of 0. are delete- Furthermore. it became an ASTM standard in 1990 and is known as sized to a fine aggregate grading. a test method was developed in South Africa at the Na- and was initially conceived by Stanton as a means of identify. Aggregates It is evident that limitations exist in ASTM C 227 and C 289 for ASTM C 227–Potential Alkali Reactivity identifying known slowly reactive aggregates such as gneiss. Four companion mortar bars were made.0 % alkali. then used at a proportion of one part of be used in the test. for example. In this procedure. Such a timeframe is not being 0. Leaching of alkalies from the concrete also has been interfere in the results of the test. Bureau of 0. Overall. and the filtrates are analyzed for reduction in comings that. Innocuous the test period to more than 12 months still may result in fail- aggregates are considered to be those that produce little or no ure to define so-called slowly reactive aggregates as potentially reduction in alkalinity. where tive. Second. schists. the test result in. One rapid procedure that has • Expansions not greater than 0. cement alkali levels and environments that can reproduce • Expansions between 0. NaOH solution added to the mixture should be 1. recent work has shown transferred to 1N NaOH solution and again stored at 80 2°C the potential for an accelerated version of the test to be per- in sealed containers for 14 days. Coarse aggregate can be the service record is based. An ad. an alkali level of 1. tive aggregate source. alkali level be known for the existing concrete.42 and 0.20 % at 16 Overall. for example. Use of an alternate source of a durable stones. ASTM C 1293 is considered by some to be the most reliable If a field service record is to be used. However. Several limitations exist in the C 1293 standard. cured. cantly not only vertically from bed to bed. schists. formed at 60°C at greater than 95 % relative humidity over a for example. First. or fine aggregates can be ered. Second. on economics and the local availability of suitable materials. This in- depending on the nature of the aggregate in question. source is of similar petrographic character as that on which gates as they are used in concrete. while being three-month period. this presumes ASTM C 1293–Length Change of Concrete Due that the innocuous aggregate has a proven service record and to Alkali-Silica Reaction has been evaluated properly using pertinent ASTM standards. at 1. Total time required between making the mortar bars and crete prisms up to 42 days in 1N NaOH solution at 80°C showed obtaining the final measurement of length change is 16 days. it A second major factor in evaluating field service record is may require a year or more to obtain a meaningful result. rock strata. Use pozzolans or other admixtures in the fresh concrete. also with some success. the test has successfully identified. Overall. and some sandstones and lime. and quartzites.45. 1. They are: overwhelming control on reactions. one must be sure to evaluate for use in job applications can be tested. cludes temperature. thus exerting due to ASR. Avoid the use of reactive aggregate. Several important points must be emphasized in this procedure. Existing tests are either too lenient.25 % as Na2O. materials from. Periodic comparator readings. If water-laid deposits from a given source of sand or where combinations of coarse and fine aggregates proposed gravel are being considered. concentration of alkali in solution in the concrete. The use of field service record also requires that cement and the w/c should range between 0. such as used. for example. Other specimens were cast with the same alkali Test criteria suggested in the Appendix of C 33 are as follows: level as that used for the immersion test. propor- rocks. certain gneisses. then the bars are To help resolve any of these issues. as well as the slowly reactive aggregates such as granite tion. such as opaline-bearing. assurance must be made procedure among ASTM test methods to evaluate aggregates that the prospective aggregate from a commercial or lithologic for alkali silica reaction. It also is the only method inclined. and restraint. [15] used fine and careful to prevent cooling and drying while taking the read.20 % are uncertain but given cement-aggregate combinations that exactly prevent or are known to include aggregates that can be deleterious or allow deleterious ASR. the specimens are NaOH solution is much greater than most alkali levels in field removed from the molds. too innocuous in field concrete. Third. At first glance. the test is effective in recognizing the potential Petrologic character of the source material can vary signifi- alkali silica reactivity of both the rapidly reactive aggregates. in confor. 10. may then become innocuous due to the remaining lower more at 12 months. the alkali content of the cement used in making Avoiding Expansive Alkali-Silica Reaction the mortar bars may be comparatively low because a much greater NaOH concentration is used in the immersion Three methods are used today to prevent abnormal expansions solution and diffuses into the mortar bars. Earlier. In mance with field observations. concrete and therefore cannot provide realistic safe cement then it is stored for 24 h in water brought to 80 2°C. • Expansions in NaOH solution greater than 0. the environment to which the concrete is exposed. glassy cryptocrystalline volcanic Variations often develop in mineralogic composition. One day after casting. one must be careful to evaluate the same tested without sieving and recombining according to pre. combinations of the various methods have been reactivity with most slowly reactive aggregates. First. In general. graywackes. but also laterally. alkali level and environment exert control on field perform. If quarried stone is being consid- evaluated without crushing them.10 % represent innocuous been developed. and particle size of individual rock types in the prospec- gneiss.406 TESTS AND PROPERTIES OF CONCRETE cabinet at 23 2°C. 2. Three com. this procedure is rapid but may overstate the shortcomings found in Use Innocuous Aggregate ASTM C 227 and C 289. an ASTM Standard [16]. ditional comparator reading is obtained. it would seem a simple matter to use innocuous aggregates to avoid expansive ASR. and can include mineral admixtures. received as concrete aggregate. is not yet aggregate. moisture accessibility. particularly where bedding is convoluted or scribed particle size distributions. when used with a more rapidly reactive aggre- be considered deleterious if expansion reaches 0. Limit the cement alkali level. Cement 3. aggregate may result in major transportation costs for In this procedure. or too time-consuming. An aggregate that is known to be months or more as needed. and 14 days. equivalent alkali in the cement plus shipment to the job site. a comparator reading is obtained. The most feasible method for a particular job will depend ance. alkali levels for the aggregate tested. Tests of con- ings. severe. regardless of panion concrete prisms are cast. 7. the same river terrace level. some success. are made. none of the existing ASTM test methods provide days indicate potentially deleterious expansion. Stark et al. Each of the three methods is discussed below.040 % or gate. coarse aggregate.10 % and 0. It allows for the evaluation of aggre. not that it will react deleteriously in field concrete. and stored in a moist whether low or high alkali cement was used previously and will environment in a sealed container at 38 2°C for up to 12 be used in new construction. dicates only that the aggregate may be potentially reactive. C 33 indicates the concrete would slowly reactive.25 % as equivalent Na2O of the cement plus Elevated temperatures and ready availability of moisture are . the deleterious nature of some cases. 3. possibly ash is 50 %. meeting the C 618 expansion criterion at 14 days for greatest expansion when the cement alkali level was high. STARK ON ALKALI-SILICA REACTIONS 407 known to exacerbate alkali-silica reactivity. available for absorption by and resulting expansion of ASR gel.. either by altering diffusion rates of alkali and lime to reaction sites. Calculations tinction is the minimum permissible proportion of SiO2 suggest that many times the quantity of alkali present in the ce. less temperature are accompanied by reductions in relative commonly used materials include ground granulated blast- humidity with possible offsetting effects on ASR. inter- is field performance record where all pertinent factors are feres with proper evaluation of the pozzolan. purposes of preventing expansive ASR. Simply specifying low-alkali cement (less than 0.60 % Pyrex glass is used as fine aggregate in a specified grading. Of much greater properly considered. in a practical sense. and seawater. Commonly. while in field concrete containing thodic connection or stray current systems develop [17. including hot and cool damp regions react in the normal course of cement hydration by complexing where the concrete is exposed directly to the ambient outdoor alkalies to reduce hydroxyl ion concentrations in concrete. A12O3 Fe2O3. For example. which for Class F ash is 70 % and for Class C ment can diffuse into concrete from external sources. . to meet. ods described in Standard Test Methods for Sampling and Test- Results of laboratory research have alluded to so-called ing Fly Ash or Natural Pozzolans for Use in Portland Cement pessimum (intermediate) proportions of reactive aggregate at Concrete (C 311). the higher the ce. How. In some cases. In this regard. serves only to change tion products. C 441 has been criticized for a number of reasons. Moisture usually is sufficiently available. NaOH). Ex- where partially weathered glassy to cryptocrystalline volcanic pansion using the fly ash is determined at 14 days. Inspection must consider all such factors in reactivity [19]. Com- successful. In general.18]. often exceeding 10 % and even 20 %. alkalies from.5 % any assessment of field performance relating to potential for maximum limit on “available” alkalies as determined by meth- deleterious ASR. cement alkali level is a major factor deter.g. The use and testing of these Water-cement ratio also will affect reactivity. even ever. and silica fume. faster than many fly ashes. but drying would remove water that might otherwise be tremely effective in reducing expansions in experimental work. An optional requirement of fly ash is a 1. Fly Ash A third factor that has been attributed to field perform. the greater will be expansion due to reactiv. or conditions. furnace slag. cement alkali levels as low as panion mortars are made with and without the fly ash. there was no expansion when the cement alkali level was though the fly ash might effectively suppress expansive alkali- low. specifically. The alkali ment alkali level. which have been found to be ex- action. sodium sulfate (Na2SO4]. tor presently available to determine a safe cement alkali level It contains appreciable alkali that. ASTM provides several testing procedures to determine sulted. crete to permit the safe use of otherwise potentially reactive ce- Deleterious ASR has been observed in concrete structures ment-aggregate combinations. The best indica. This total alkali content of cement fly ash may result in the equiv- appears to be largely of academic interest except to explain alent of very high alkali levels that may convert an otherwise some case histories in which all of the aggregate was reactive innocuous cement-aggregate combination into a deleterious but no damage resulted. It natural aggregate.g. increases in ambient outdoor is fly ash obtained from power plants burning coal. The latter restriction is important because which maximum expansion rates and levels develop [5]. Certain finely divided ground materials may be added to con- induced distress. materials are discussed below. Highly reactive ity. Attempting to specify aggregates for field concrete on the suitability of a fly ash for controlling expansive ASR in con- the basis of avoiding pessimum ratios should be avoided. continuously or cyclically. if not impossible. Test 0. For this same appeared that current densities of at least 25mA/m2 caused the reason. while in related cases only a relatively one [20]. content of the cement should be about 1. These materials are intended to in all habitable climates. by mass. First. sulting in the development of expansive ASR. with residual mix.50 % or less have failed to prevent expansive reactivity storage is over water in sealed containers held at 38 2°C. Specification for Coal Fly Ash and Raw or Calcined Natural Examples include sodium chloride (NaCl) deicer salts. the most important dis- industrial solutions (e. alkali Pozzolan for Use in Concrete (C 618): Class F and Class C. thus re. importance is the fact that Pyrex glass reacts significantly Deleterious ASR also can occur in concrete in which ca. silica reaction. feldspars or noncrystalline volcanic aggregates can exceed 100 % at 14 days when using low alkali cement. High lime contents otherwise innocuous cement-aggregate combination into a adversely affect the capability of a fly ash to prevent expansive deleterious one. the test mortar will be difficult. Class C ashes usually have greater lime (CaO) con- increase hydroxyl ion concentration.0 %. are contemplated for the future. and that This results in the formation of harmless nonexpansive reac- temperature change. and perhaps convert an tents. volves replacing 25 % of the cement. to support expansive ASR. be released by water or calcium hydroxide solutions. whereas restraint Use Admixed Materials or confining pressure reduces expansion and reactivity. finely ground volcanic glass. addition. small proportion of reactive material was used and damage re. the reverse is probably true.. and the ab- rock of rhyolitic to andesitic composition constitute no more solute expansion level of the test mortar is evaluated. lithium solutions. Other. For salts occurring naturally in soils [e. hydroxyl ion. The Standard Test Method for Effectiveness of Pozzolans or Ground Blast-Furnace Slag in Preventing Excessive Expan- Limit Cement Alkali Level sion of Concrete Due to the Alkali-Silica Reaction (C 441) in- As noted earlier. crete. In increase in temperature may increase the rate of chemical re. with an amount mining expansion due to ASR. and equivalent Na2O) to avoid expansive ASR has not always been the water content is gauged to meet a flow requirement. it has been argued. The most widely used material for this purpose the rate of reaction. specific Pyrex glass is used as the standard reactive aggregate. than 5 % of the aggregate [11].45–0. Two categories of fly ash are recognized in ASTM Standard ance is extraneous sources of alkali. for ASTM C 618 requires expansion of the test mixture to not example. ing water possibly being the only source of moisture available to support expansive reactions. of fly ash equal to the volume of cement replaced. Okada. Vol. 8th International Conference on Alkali- Metakaolin Aggregate Reaction in Concrete. thus re- cined natural pozzolans. reaction sites. Japan. thereby reducing of Research. pp. could prevent expansion when used with high-alkali cement Second International Conference. The concrete technologist has at his disposal broad knowl- except that 50 % by mass of portland cement is replaced by slag edge and guidelines to produce concrete that is not susceptible equal to the volume of cement replaced. 1989. D. and diatomaceous earths.. American Concrete Institute. 193–219. user [27]. [6] Chatterji. D.. and Steinour. but the experimental laboratory International. Kyoto. American Concrete Institute. Mortar. They found [9] Stark. Society of Materials Science. Dec. there are no speci- Cement. 8th International often used to reduce potential hazardous effects from the Conference on Alkali-Aggregate Reaction in Concrete. Research and Development Bulletin RD 121. should ensure that deleterious reac- expansion should be at least 75 %. “The Moisture Condition of Field Concrete Exhibiting that small threshold quantities of any of several such salts Alkali-Silica Reactivity. S. the hydroxyl-ion concentration in the pore solution in the con- [5] Powers. SHRP-C/FR-91-101. DC. mixed materials is the fixed composition of the salt. Greene. This would [2] Stark. 445–456. and Aggregates. R. Here. K. 974–987.. “Chemical Test used because it is soluble in tap water. 8th ICAAR Local Organizing Committee. 1992.. and Benton. Montreal. and Pyrex glass. Proceedings. and Metakaolin is a relatively recent material developed to prevent M..” Proceedings. Today. thereby minimizing the rate of ASR. That is. Nishibayashi. bility of lithium salts to inhibit expansive ASR. “Products of Reaction and Petrographic calcining the kaolin to a temperature range of 700–800°C. 2. 1940.” American Society of Civil Engineers. From laboratory investigations [21]. H.” Strategic Highway Silica fume is occasionally used to prevent expansive ASR. C. C. pp. J. C. To prevent ASR. Canada. It Research Program. Kawamura. 51. pp. Nishibayashi. K. Okada. The mechanism by which slags inhibit expansive reactivity is purported to be different than that by which fly ashes References prevent expansion. the calcium silicate [4] Helmuth. and American Concrete Institute. Currently. “Leaching of Alkalies in Alkali- alent Na2O in the portland cement. Kawamura.27] verified these findings Vol. 8th International Conference on After grinding to pozzolan fineness. such as some volcanic ashes. ering of feldspar in granitic rock types and manufactured by [7] Moranville-Regourd. “Expansion of Concrete Through Reaction between concluded that slag hydration in portland cement-water Cement and Aggregate. However. Japan. 10 % silica fume by pp. SHRP-C342... pp. “Alkali Aggregate Reactions in Concrete: An Silica Fume Annotated Bibliography 1939–1991.. This explanation needs way Research Program.” Portland Cement Association McCoy and Caldwell [25] first reported the exceptional capa.. Nishibayashi.. 8th ICAAR Local Organizing Committee.. Detroit. using highly reactive commercially available aggregate. 1948. The 10 % of the portland cement with metakaolin [24]. A very beneficial but. “Alkali Silica Reactivity: Some Reconsiderations. as noted earlier.. Vol. Kawamura. mass of cementitious material will be used [22. shales. K. S. pp. Council. “Alkali-Silica Reactivity in Concrete—An Overview hydrate reaction product complexes alkali. R.. “Mechanism of Alkali-Silica Reaction and Expan- sion. and Hooton. Examination. unlike lithium fluoride for Reactivity of Aggregates with Cement Alkalies: Chemical or lithium carbonate. 1980. The deleterious ASR in concrete [27]. ASTM Standard to deleterious ASR. 1991. Grout (C 1240) is used. Ground Granulated Blast-Furnace Slag (GGBFS) Concluding Remarks Ground granulated blast-furnace slag can be used to prevent expansive ASR. 101–105. ducing expansions due to reactivity. Strategic High- nonexpansive gel reaction product. R. 13 pp. 1989. National Research Council. R. 1781–1811. 92–94. eral Admixture in Hydraulic Cement Concrete. 1993. Washington. it is used to replace up to Alkali-Aggregate Reaction. T. DC. if used prudently with other informa- Use in Concrete and Mortar (C 989) suggests that reduction in tion noted in this chapter. A.” mental field concrete pavement. T. work suggests a dosage rate of about 1:1 LiOH H2O: equiv. S. Proceedings. it was recommended that lithium hydroxide (LiOH) salt be [10] Mielenz. Eds. lithium nitrate is Aggregate Reaction Testing. “Surface Popouts Caused by Lithium Salts Alkali-Aggregate Reaction. [12] Rogers.. [8] Landgren. T. 497–516 and 785–812. Washington. C 618 recommends ASTM presently does not address this means of preventing 75 % reduction in expansion after 14 days under C 441 test expansive ASR.. SP-126. It is derived from the weath. and Hadley. M. National Research appears to function in much the same manner as fly ash in re. II.” Proceedings. and M. D. ASTM provides various test procedures and Specification for Ground Granulated Blast-Furnace Slag for recommendations that. ASTM fication guidelines for its use. PA.. Concrete. National Research Council. SHRP C/VWP-92-601. it was [1] Stanton.” Journal. 1955. Society of Materials Science. 1991. 105 pp. Handbook for The Identification of Alkali-Silica Reac- have the effect of producing a potentially less expansive or tivity In Highway Structures. No. Vol. thereby permitting better dispersal in Processes in Cement-Aggregate Reaction. It also has been included in experi- [11] Stark. DC. 2. “An Interpretation of Published crete. 44. not practical use for conditions. S.” Journal. Washing- further confirmation. Kyoto. Okada.” Proceedings. large concrete batches. W. S.. [3] Diamond. E. C 441 is used to evaluate slag as well as fly ash. C. ton. and M. lithium solution would be its penetration to uncracked hardened concrete to prevent or mitigate distress due to ASR [27].408 TESTS AND PROPERTIES OF CONCRETE Raw or Calcined Natural Pozzolan An important advantage of lithium salts over other ad- Remarks presented for fly ash apply generally to raw or cal. pp. Standard Specification for Use of Silica Fume as a Min- Researches on the Alkali-Aggregate Reaction. opaline quiring no testing for individual concrete mix materials [21].” Strategic Highway Research Program. systems serves to reduce diffusion rates of alkali to aggregate New York. today. tions can be avoided in future construction. D.” Durability of Concrete.. Eds. Later work [26. MI. West Conshohocken. 8th ICAAR . Proceedings.23]. Eds. K. ” Portland Cement Association. J. and Möller. 11th International Conference. S. and Ishii. pp. 693–706.. D. 1985.. July 2003.. Concrete and International Conference on Alkali-Aggregate Reactions in Aggregates. 643–651. pp. S252/29. “Influence 2000. furnace Cement Concrete to the Alkali-Silica Reaction. D. 16–30. G. “Effect of gic Highway Research Program 343. 1996. Matsumoto. Melbourne. S. 1989. 18–23 August 1996. Reaction in Concrete. 1993. M. Fifth International Conference on Alkali-Aggregate Alkali in Aggregate on Expansion. Silica Fume Properties on Mitigation of ASR Reactivity in [16] Stark. Conference on Alkali Aggregate Reactions in Concrete. pp. 2. June [18] Tarii. and Industrial Research. Y. pp. NBRI of the Council for Scientific tional. and Davies. 1985. G.” Publication No. “Investigation into the Effects of [17] Shayan. Ahmad. pp. 1987. W. and Caldwell.. P.” Alkali-Aggregate Reaction in Concrete. G. E.. The Society of Materials Science. K. Quebec 2000. 266 pp. “Combined Effects of Alkali-Aggregate Reac. 16.. J.” Proceedings.. 1981. West Conshohocken.. South Africa. ing or Minimizing Alkali-Silica Reactivity. “Immersion Test to Identify Cement Alkali Levels and Concrete. of Cathodic Protection on Cracking and Expansion of the Beams [25] McCoy. and Nixon. M. Thomas. Quebec City. 11th International Conference. Alkali-Aggregate Reaction in Concrete. STARK ON ALKALI-SILICA REACTIONS 409 Local Organizing Committee.. Japan. 763–772. pp. Canada. 47. [26] Stark. “Considerations in the Use of Fly Ash to Control for the Use of Lithium to Mitigate or Prevent Alkali-Silica Alkali-Silica Reactivity.” 11th ICAAR CIRAG. M.” Proceedings of the 10th Inter- Cement and Concrete Research. Kawamwa. [21] Bakker.. [24] Sibbick. . Quebec City. H. 10th International Alkali-Aggregate Reaction. J. pp.” Cement. pp. London. 7. and Kurtis. and Bhatty. 229–238. QC. M. Y. “About the Cause of the Resistance of Blast- Kyoto. 562–569. D. “An Accelerated Method for [22] Gudmundsson. R. G. 1992... QC. J. [23] Gundmundsson. 78 pp. D. Strate. Vol.. West Concrete. 1951. PA... Metakaolin as a Cement Replacement in ASR Reactive Con- tion (AAR) and Cathodic Protection on Currents in Reinforced crete. 1986. G. A... 1017–1025. Serial Reaction (ASR). Vol. Vol. D. “Alkali Silica Reactivity: Effect of ceedings.” Pro- [13] Stark. pp. R. M. 43 pp. 186–189. K.. ASTM Interna. F. and Diamond. B. R. 10th International ings. Concrete. [27] Folliard.” Final Report. pp. 69–77. [15] Stark. 355–361. Pretoria. ASTM International. “Guidelines [20] Stark. national Conference on Alkali-Aggregate Reaction in Concrete. “Silica Fume in Concrete–16 Testing the Potential Alkali Reactivity of Siliceous Aggregates. Okamoto. J. 1996. Proceed- Pozzolans to Prevent ASR. No. 355–361.” Years of Experience in Iceland. and Olafsson.. Halfdanarson.” STP 930. “Eliminat. Institute. 1995. K. K.. “Mechanisms of Pozzolanic Reactions and Prevent Expansive Alkali-Silica Reactivity. “Lithium Salt Admixtures—An Alternative Method to [19] Bhatty. P. pp. Australia... K. pp.” Proceedings. No.” Journal. PA.” Proceedings. Melbourne. A. 327–332. American Concrete Conference on Alkali Aggregate Reactions in Concrete. D. Melbourne. Morgan. Conshohocken.” Proceedings. E.. 9th Control of Alkali-Aggregate Expansion. “New Approach to Inhibiting Due to Alkali-Silica Reaction. S. June 2000. [14] Oberholster. Proceedings. Canada. FHWA-RD-03-047. and ASTM STP 22. Aggregates (C 294) 2. more than 0. of chemical reactions. The general availability of low-alkali cement that was fur. began to and Properties of Concrete and Concrete-Making Materials be returned to the product. cracked. W. Thus. well as new “greensite” quarry sources. in moisture-exposed concrete made with cement containing and elsewhere in the world in Iraq. favored by such factors as: 1. geologist/photographer. it is expected that the coarse and fine aggregate will not Aggregates for Concrete (C 295) participate in any chemical reactions with components of the States that petrographic examinations should identify and call cement paste that will cause the aggregate particles to crack or attention to potentially alkali-carbonate reactive constituents. describes the petrographic characteristics of potentially reactive carbon- Introduction ate rocks and. those materials that had performed without prob.60 % total alkalies and. under the general heading economic and environmental constraints. C. Ontario. in response to reactivity of other rocks and minerals. These topics are of particular importance deterioration. cement kiln dust. Illinois. In addition to the now numerous occurrences of reactive ASTM Standard Specification for Concrete carbonate rock in concrete in Ontario. Walker oped strata or portions of old operating limestone quarries as [1]. Iowa. and China. sources for aggregates were necessarily developed. the reasons for that deterioration were ascribed since it is more often the case that alkali-carbonate reactive to causes other than deleteriously reactive aggregates. the same language as is in ASTM C 33. Canada. and New York. texture. to become otherwise dimensionally unstable. new THE SUBJECT OF ALKALI-CARBONATE ROCK REAC. notation as to their particular relevance. Hansen. the preceding Factors 1 and 2 (ASTM STP 169. at around the discussed the reactivity of dolomitic limestones. It should be tivity (ACR) was discussed for the first time as a distinct and sep. Describes the characteristics. Concrete and Materials. how to evaluate them. Baltimore. noted that new sources include previously unused or undevel- arate chapter-length topic in ASTM STP 169B by H. did not treat the subject of dele. in the Appendix. When a portland cement concrete mixture is designed and ASTM Guide for Petrographic Examination of placed. in the late 1960s and early 1970s. in no longer favored so much the satisfactorily innocuous behav- 1943. rock comprises a relatively small stratigraphic portion of a pro- The satisfactorily innocuous. the subject of alkali-carbonate reactivity and are listed with a and buckled concrete in the vicinity of Kingston. Ozol1 Preface As demand for concrete increased. Directs that deleteriously reactive aggregates shall not be used tucky. at that time. ior of aggregates with respect to alkalies in the cement. England. Ken. or at any rate believed to have been sat. 410 . in the United States there Aggregates (C 33) have been affected concretes in Virginia. because for certain instances of concrete core and ledge rock. Missouri. 1956) and its predecessors ASTM STP 22A. in 1935. based on his investigations of expanded. there was a time when that expectation was determine whether those amounts are capable of deleteriously satisfactorily fulfilled. determine their amounts. Prior to that. ducing quarry. affecting concrete. along with the same time. in large part to meet the requirements of transportation-related construction. and composition of car- nished as a matter of course during the years when kiln bonate rocks that are potentially alkali-reactive.35 Alkali-Carbonate Rock Reaction Michael A. or “inert. The following ASTM documents are directly applicable to son in 1957 [3]. Tennessee. in part. and recommend additional tests to Historically. and in- terious carbonate rock reactions because such reactions were not stances of deleterious behavior became more numerous. 1 Consultant.” behavior of aggre. West Virginia. N. Constituents of Natural Mineral lems over years of consumption. in ASTM STP 169A in 1966 [2]. Previous editions of Significance of Tests which is richer in alkalies than the cement product. Indiana. MD 21209. recognized as a distinct problem until identified as such by Swen. Bahrain. in essentially dust was not included in the product. And. gates was. Reference is made to examination of drilled isfactorily fulfilled. Continued availability of aggregate materials from “old” ASTM Descriptive Nomenclature for sources. as represented. a fea- samples for petrographic examination by ASTM C 856. be- portant to have information on the alkali content of the ce. with ASTM C 856 providing preliminary information for detailed and rig. availability of moisture and alkali content in the concrete.38 in. Other reactions. hence. it is im. only one. Alterna. and garding the aggregate may be drawn. ASTM ture common to all such limestones is that there will be small C 823 is of particular relevance when evaluating an aggregate dolomite crystals present in the matrix of the rock that will resource for alkali-carbonate reactivity based on its service act with the alkaline solutions in a manner such that the record in previous constructions.” as reported by 2 Alkalies from deicing materials such as sodium chloride (NaCl) may augment the alkalies supplied by the cement. C 586. the expansive dedolomitization reaction. is that the reaction causes the af- lish whether alkali-carbonate reactions have taken place. 1. line solutions (almost always sodium and potassium hydroxides derived from the cement2) in the cement paste matrix and with which it may be used in an interactive way. calcium magnesium carbonate (Dolomite) ASTM Practice for Petrographic Examination of alkali hydroxide solution → magnesium hydroxide Hardened Concrete (C 856) calcium carbonate alkali carbonate Provides the general method for how to go about examining The chief physical result of dedolomitization. causing the production of rim zones and stored at 23°C and 95 % RH. dolomitic and nondolomitic. in concrete or mortar have been recognized. simply. both to evaluate the behavior of the rock in concrete. dolomite crystals. by themselves. Information regard. and any other expands and cracks. by the alkali-carbonate reaction. it is possible that the small cores (1. . Katayama [6] gives a detailed review of rim formation. other internal changes in carbonate rocks of various composi- using up to 19. The rock sample is scribed in ASTM C 702. be used Types of Carbonate Rock Reactions as an accurate predictor of the damage that the rock will cause in concrete. 2 in. Directly measures the expansion produced in concrete prisms. of original composition CaMg (CO3)2. cussed in Refs 1. here. OZOL ON ALKALI-CARBONATE ROCK REACTION 411 ASTM Test Method for Potential Alkali ASTM Method for Reducing Field Samples of Reactivity of Carbonate Rocks for Concrete Aggregate to Testing Size (C 702) Aggregates (Rock Cylinder Method) (C 586) Samples taken in accordance with ASTM D 75 may be reduced Directly measures the expansion of small cylinders of rock dur.. Some other reactions are dis- job cement. Manifestations of Distress ASTM Practice for Sampling Aggregates (D 75) Gives the procedure for obtaining samples for examination Concrete that is affected by the alkali-carbonate rock reaction and testing by ASTM C 295. the ally perpendicular small rock cylinders. cracking accompanied by closing of joints. 4. in the event that ledge rock samples cannot be Canada by Swenson [3]. important among which are rock samples that will permit the preparation of three mutu. (50 mm) or larger—of aggregate obtained combine to produce near-ideal conditions for causing the reac- from stock pile or conveyor belt. This reaction may or may not produce rim (C 1105) zones on particles of reacting rock in concrete. in size by quartering or by use of a mechanical splitter as de- ing exposure in sodium-hydroxide solution. “spectacular expansion and deterioration. Depending on the perfection of the petro- tests and examinations from which general conclusions re.0 mm (3/4 in. and 5. and the cement content of the concrete in the dedolomitization. is of importance ASTM Test Method for Length Change of with respect to having produced significant damage in con- Concrete Due to Alkali-Carbonate Rock Reaction crete constructions. the term ment used. cussed in greater detail in subsequent sections. come other minerals and compounds. Pattern cracking after three years of obtained.) maximum size aggregate. and fected aggregate particles to expand and crack and thereby to gives some specific criteria for recognizing the effects of alkali- extend the cracks into the enclosing mortar matrix. and most conveniently. which dis- field and laboratory concrete chiefly microscopically to estab- tresses and damages concrete. needed for ASTM C 586 can be drilled out of larger particles— When all of the factors favoring alkali-carbonate reaction for example. ASTM Practice for Examination and Sampling of Hardened Concrete in Constructions (C 823) Expansive Dedolomitization Reaction Provides general and specific guidance for evaluating constructions in the field and for obtaining samples for labora. Positive test results cannot. and as dis- constructions. C 1105. However. as was reported in tively. secured in accordance with the applicable requirements of ASTM D 75. and the tions are of scientific interest. logical characteristics of the rock that promote expansion. It should be noted that the convergence of the environmental and materials-related ASTM C 586 is best. which is the principal subject of this chapter. done on ledge factors that promote expansion. limestone aggregate particles of particular but nevertheless orous application of ASTM C 823 to provide a second set of somewhat variable compositions and textures. In that connection. 35 mm) exposure is shown in Fig. The expansive dedolomitization reaction occurs between alka- tory examination as by ASTM C 856 (see next paragraph). tion. carbonate reactions. concrete may in a matter of months exhibit severe surface ing obtaining ledge rock samples is in ASTM D 75. ASTM C 1105 (see next paragraph) should be used Although various reactions involving carbonate rock. gel deposits. It is reported that the ture of the concrete or of the geometry of the cracking that alkali content of the cement was about 1.2 % (500 lb/yd3). the and the cement content of the concrete was about 300 kg/m3 concrete in sidewalks. 1. Conclusive evidence that the observed distress has been caused by alkali-carbonate reaction is best obtained by detailed examination of the concrete following ASTM C 856. and gutters expanded about 1. or crushing of adjacent weaker concretes. precisely identifies the cause of the cracking as being alkali carbonate-rock reaction. (In contrast.) The crack geometry. Expansion was measured at In at least one particular type of exposure condition. 2) with consequent compressive failures. elongate prestressed or post-tensioned reaction (upper portion of photo) that has moved 9 cm to the pieces typically develop long cracks parallel to the direction of right relative to the concrete in the lower portion of the photo tensioning or prestressing. and other kinds of prefabricated concrete can develop individualized cracking responses to internal expansion that may not be similar to those produced in slabs on Fig.2 % in three years. or pattern. Reinforced and post-tensioned concrete. Generally. the 1. For example. expansion of ordinary. and that internal cracking in the aggregate extends into the mortar. slabs. floors. 2—Concrete slab affected by alkali-carbonate grade. may provide a strong indication that cracking is due to alkali-silica reaction but not exclude the possibility that both reactions can be present. can occur within three years. Rogers [8]. extrusion of filler material. curbs. plain. manifestation of distress due to ACR does not involve gross ex- . decks. In that instance. Where moisture conditions are uniform or where the concrete elements are thick. that has nonreactive aggregate. bulk expansion of the concrete is evidenced by closing of joints. cast-in-place concrete as in sidewalks. during which it will be observed that the aggregate exhibits the characteristic microscopic texture and composition of alkali- reactive carbonate rock (see the section on Characteristics of Alkali-Reactive Carbonate Rocks). shoving or buck- ling of adjacent materials. Ontario. blow-ups.412 TESTS AND PROPERTIES OF CONCRETE Fig. produced is the response of the concrete to internal expansive force based on its particular size and shape and the direction of maximum moisture availability. precast and prestressed concrete. there is no definitive fea- shoving of adjacent asphalt pavement. Ontario. (Fig. or of low surface area- to-volume ratio. and footings where there is a moisture gradient from top to bottom or from side to side results in pattern cracking similar to that shown in Fig. and In ACR-affected field concrete. 1—Typical cracking of concrete slab by alkali-carbonate reaction after three years. Canada [48]. Canada [7]. if present.0 % Na2O equivalent. Cracks may be prominent or faint—visible only following wetting of the surface to produce some contrast—and concrete between the cracks can be hard and intact. 16] and discussed subsequently. OZOL ON ALKALI-CARBONATE ROCK REACTION 413 pansion of the concrete and widespread cracking. Ontario) about 27 years later. How- damage is confined to the surface region and is the result of the ever. The initial. typical. more commonly than not. gate (e. That is. the first damage to the concrete grained matrix is consistent. due to the where cyclical freezing and thawing occurs [12]. an open question. not before one year) and that may not show man- Generation of Crack Damage ifestations in concrete after five years in moist storage. Smith [9] has presented experimental data showing the ex. showing rock prism expansions (ASTM C 586) of a few tenths Gillott and Rogers [11] showed that alkali contributed by percent in a matter of weeks. microscopic texture and structure is characterized by tured coarse aggregate particles in the scaled surface. and that there are only two tial cracks produced by the alkali-carbonate reaction are then ex. that is usually observed. The same concrete stored in pure water at the same The grain sizes of the calcite and clay matrix in which the temperature showed 0. away ferences in internal textural restraint. A modification of the typical texture is found in reactive carbonate rocks identified as late expanders that may not show no- Comparison of Alkali Carbonate Rock Reaction ticeable rock prism test expansions until approximately 25 with Alkali-Silica Reaction as Regards weeks (rarely. he recorded about 0. opaque section in concrete or rock samples. generated within the reactive coarse aggregate particle itself. was insufficient to sustain the reaction significant amount of clay.14]. the ini.03 mm) dolomite Carbonate Rocks with 10–20 % clay minerals but with no calcite. necessary petrographic conditions: the presence of fine- ploited by saturation of the cracks and subsequent freezing. the reactive texture can be identified in in Canada. dedolomitizing. porous. crete within perhaps one year after construction. as will be noted subsequently. as shown in Table 1. And. ex- the ultimate damage to the concrete can be of the same order as tensive studies on ACR rocks in China [13] concluded that the produced by ASR if the concrete is exposed in an environment prototypical texture was less frequently observed. the which. The classic. fine-grained (0. the rocks were first identified and described. The alkali-carbonate reactive limestones that were first studied Alternatively. grained dolomite crystals and a pore structure allowing alkali solution to penetrate the rock. although bulk expan. In those rocks. And. concrete after many years of exposure should be disregarded is tar.13 % alkali cement The typical texture that is described here is found in those stored in 5 % NaCl at 23°C. and extending cracks into the mortar to connect with similar cracks (commonly) silt-sized quartz. stones known to be alkali-carbonate reactive are shown in Fig. rhombic crystals of dolomite [CaMg (CO3)2] coarse aggregate particles in the near-surface region had cracked. the case that silt-sized quartz grains are also disseminated [10] recorded comparable results. and (b) calcite. the alkali content of the concrete. or direct. It is often quarry at Kingston. application of deicing salts. the descrip- sions of concrete produced solely by the alkali-carbonate reaction tion has historically served well as a prototype for recognizing may be lower than those produced in severe alkali-silica reaction. as investigated from the particles and into cracks and voids in the concrete. but instead. by precedent. the typical feature of dolomite rhombs in a clayey fine- In alkali silica reaction (ASR). and shortly thereafter in the United States. clay. initially produced by the reacting particles. 300 days. alkali-carbonate reactive rocks that do not con- gated by the author containing reactive carbonate aggregate form to the historical prototype [13. The rhombic crystals of dolomite occurring in the matrix acerbating effect of sodium chloride (NaCl) on alkali-carbonate of the reactive rock may be relatively sparsely distributed and reactivity. or pattern cracking. Milanesi et al. and to develop the overall expansion and tensile cracks produc. The characteristic composition is from other reactive coarse aggregate particles. variable character of the matrices. Only the relatively larger. by Hilton [15. 3. or proto- throughout was deeply scaled exposing numerous cross-frac. dawsonite) can exacerbate the ACR. have been regarded as prototypical.1 % alkali ce.155 % expansion at 275 days. set in a finer-grained matrix of calcite [CaCO3]. and field manifestations in con- certain rare types of mineral components in the coarse aggre. Using concrete prisms. Examples of typical microstructures of dolomitic lime- ing the map. with the result that in which the carbonate-mineral components of the rock that the surface concrete was lost. [14] report on a Characteristics of Alkali-Reactive very expansive. Field E). it should be recognized that. measuring 0.01–0. Although the deck has reactive consist of substantial amounts of both dolomite and calcite. Field A) or ment and a known reactive aggregate. Alasali et al. direct damage due to alkali carbonate reaction sibility of late (rock prism) expanders causing distress in field is produced by the cracking. and. 38°C measured 0. silica minerals. damage produced in both ASR and ACR The above description of the alkali-carbonate reactive tex- may then be exacerbated by the action of cyclical freezing and ture derives from the “type locality” in Ontario. at 275 days on concrete prisms made with 1. Whether the pos- In contrast. or rigidity. stored in saturated NaCl may be more crowded together with dolomite rhombs adja- solution at 70°F (21°C).23 % expansion throughout the matrix. made with a 1. However.g. a parking deck investi. 3. dolomite rhombs are set is typically 2 to 6 m for the calcite Using reactive aggregate from the same quarry (Pittsburgh with smaller clay particles disseminated throughout.19 % expansion at cent or touching (Fig. appear to be “floating” in the background (Fig. and extension of cracks into the mor. Canada where thawing. A similar prism stored in water at reactive carbonate rocks that are identified as early expanders. For example. The best technique for identifying reactive texture is by Petrographic use of thin sections with a petrographic microscope. but the matrix is coarser-grained can be produced by both (a) internal cracking of aggregate and is composed of interlocking dolomite grains together with particles extending cracks into the paste and mortar. and in dif- the ASR gel.12 % at 300 days. clay. 3.. the ACR texture in North America and elsewhere. in the the dilute hydrochloric acid (HCl) insoluble residue contains a absence of deicing salts. extension of existing cracks and production of new cracks as a Those differences between early and late expanders are re- consequence of the migration and subsequent expansion of flected in the bulk compositions. have char. using a highly pol- acteristic microscopic textures and mineralogical compositions ished specimen and manipulation of the illumination to get the . there are expansive. and aggregate throughout. Illinois. and F are from the same quarry.414 TESTS AND PROPERTIES OF CONCRETE Fig. E. % Carbonate Kingston. 5 to 15 about 50 early expanders [3.17.18] Iowa. B. Fields A. and Indiana 10 to 20 40 to 60 early expanders [19. Scale bar is 0.25 mm.20] Virginia early expanders [21. Ontario. and C are from different quarries. 21 to 49 75 to 87 late expanders [18] Virginia late expander [23] 33 90 . Ontario. Fields D.22] 13 to 29 46 to 73 Gull River. D and F from the same bed [48]. 3—Photomicrographs of thin sections of alkali-carbonate reactive limestones from quarries in eastern Canada. TABLE 1—Composition of Early and Late Expansive Carbonate Rocks (Adapted From Ref 1) Dolomite Acid Insoluble % of Total Residue. This is in contrast to alkali-silica reactivity where reactive siliceous components can derive from both gravel and crushed stone sources. there will be less of it in the total limestone section—as less expansive. Chemical and Mineralogical Composition Typical compositions of early and late expanding alkali-reac- proper contrast and reflectance. A light etching of the speci. Consequently. generally. the presence of reaction rims calls for closer inspec. As such. or within a bed. 5. with the alternating bands being several inches thick. restrained in a steel frame in 1N sodium hydroxide 3 W. and. Rock by Itself Broadly speaking. or possibly diagenetic. Rogers. of reaction rims on ACR rock particles is incidental to their propensity for reaction and generation of crack damage. . Northern Virginia. Affecting Expansion of Reactive Carbonate ways. that that texture is of re. the most expansive To put reactive carbonate rocks in perspective with rock. infer that. The formation A23. experimentally or within concrete. because such particles are limestones. field is approximately 2 mm across. In Hilton’s experimental work [15. since the production of the reactive texture requires A reactive carbonate rock with low textural restraint can special conditions subsequent to deposition and not obtaining be highly expansive unrestrained. Reactive Carbonate Rock and Factors tion of those coarse aggregate particles. expanded 7. alkali-carbonate reactive particles in gravel deposits. They cylinder test (ASTM C 586) may exhibit a very different expansion may occur in carbonate rocks of any age but. Carbonate rocks displaying reactive texture can comprise In an extended study of the composition of reactive and a substantial or a small portion of a bed in a limestone quarry. French. tive expansive carbonate rocks are shown in Table 1. nonreactive Ontario limestones and their expansion in the Or. 4). either as components of the ordinary depositional regime for lime. of the carbonate rock in question. are less likely to be found in gravels than alkali-silica reactive particles. with their men surface with dilute HCl can be very helpful. Factors Affecting Expansion of Concrete with However. A. and occur. unrestrained in ASTM C 586.2-26A. and the internal resulting from primary deposition. since often. Based on It is clear from the microtexture of reactive carbonate Hilton’s work [15] the degree to which reactive carbonate rocks rocks. J. OZOL ON ALKALI-CARBONATE ROCK REACTION 415 abundant in the overall category of siliceous aggregates (crushed stone together with sand and gravel) that might be used in concrete than are reactive carbonate rocks in the category of all carbonate rocks. Those empirical relationships are the basis for the Canadian Alkali-carbonate reactive coarse aggregate particles in Standard Chemical Method screening test for ACR. The plot versus insoluble residue is shown in Fig. causing damage. on the other. reactive siliceous rocks are far more and. personal communication. to the placement. considering earth’s gravels as a whole. 4—Vein of reactive carbonate texture in limestone containing reactive carbonate rock exist and are reported to displaying alternating bands of reactive and nonreactive have been used in concrete in England in the M 50 Motorway3 texture. and they are not hibit varying degrees of (unrestrained) expansion in the rock abundant in the volume of limestone that exists on earth. That is. but not entirely. to rence as veins of reactive texture. or rigidity.16] found most often in carbonate rocks of Ordovician age. in The same type of structure can also exist on a larger scale.8 % at 14 weeks reactive siliceous rocks. gravel deposits Fig. will cause expansion in concrete is related. have been ranking when tested “in restraint” in the rock cylinder test [15. CSA concrete may or may not display reaction rims. on the one hand.4 bed to bed. or when restrained by incorporation in concrete [23]. it appears to be the case geologically that the conditions for formation of alkali-expansive carbonate rocks A suite of carbonate rocks that have reactive texture and that ex- are more restricted than for other limestones. it is more compressible and stones. but when restrained. it is reasonable to textural restraint.16]. And. up to a point. limestone-bearing gravels. field experience thus far seems to indicate. Canada. personal communication. the carbonate aggregates that participate in alkali-carbonate reaction are crushed stones from limestone quarries. [8] found that the compositions of potentially expansive rocks The occurrence of the reactive carbonate rock texture is a fell within a fairly distinct field when the CaO:MgO ratio is reliable diagnostic guide. Rogers bed that does not otherwise display the reactive texture (Fig. near their bedrock source. origin rather than one volume of dolomite in the rock. geographic location and publication reference indicated. and under conditions of rapid erosion and deposition. except near their bedrock source. with the commonly sharp-edged rhombs. their presence is indicative of alkali-carbonate reaction. 4 C. Rocks which exhibit the texture plotted against either the Al2O3 content or the insoluble should be tested further to determine their expansive potential residue. with the contemplated job cement. are not as abundant as siliceous gravels because limestones are less able than siliceous rocks to survive the weathering and transportation necessary to put them in gravel deposits as hard and sound particles suitable for use as concrete aggregate. the restraint imposed by the concrete. thus far. However. but not al. and have been found and used in concrete. from Ontario. the reactive texture may occur as veins within a limestone Rock Cylinder and Concrete Prism Expansion Tests. .5 % calcite. 6). (NaOH).416 TESTS AND PROPERTIES OF CONCRETE Fig.275 % at 14 weeks. However. It had 94 % dolomite by volume. [24] obtained similar results using autoclaved tightly packed but with abundant voids between the masses of concrete microbars (150°C in 10 % KOH solution) incorporat- tightly packed rhombs (Fig. 40 weeks of continuous soaking in the NaOH solution.6 % by 6 % calcite. Fig. with sufficiently long reaction nonporous structure (Fig.18 % porosity. The rock has 58. It is a typical “crystalline” dolomite com. They The least expansive sample did not expand at all after eight concluded that these rocks do undergo dedolomitization but weeks in 1N NaOH. expanded 0. Petro. High content of dolomite rhombs in porous matrix. It did begin to expand after volume dolomite.63 % porosity. 7). the rock has a high volume of dolomite rhombs Qian et al.8 % in 14 weeks in ASTM C 586. and 5. graphically. and 0. 5—CaO:MgO ratio versus insoluble residue for a suite of alkali-carbonate reactive and nonreactive carbonate rocks [8]. ing mosaic-textured. 6—Expansive rock from Missouri. 23. that early expansion is very low compared to rocks with the posed of a mosaic of equant dolomite grains in a tight virtually typical ACR texture. “crystalline” dolomites. time significant expansion could develop. almost pure. 7. 4 % at 14 weeks. and almost two times greater mechanical explanation for the expansion. in expansive rocks from Virginia. 36. Using STEM and EDAX to observe the locations of the . a rock. such as potassium. A further reaction that occurs is that the alkali carbonate crete “floating” rhombs and no interstitial matrix. as such. Structural framework of equant dolomite grains with no dis. which may possibly help promote water absorption and consequent expansion. in the rocks that they studied. or dedolomitized. of the reaction products is smaller than that of the reactants Thus. Walker [29] and Buck [30] found minerals of the alkali content of the concrete and high pH of the liquid phase hydrotalcite-sjogrenite group. in reacted rock. in the range of 5–25 %. (5) high proportion of reactive stone in the coarse aggregate. The explanation was sought in behavior of the reactive cal/mineralogical composition could have vastly different rock and alkali system with respect to indirect mechanisms expansion characteristics in concrete if their structural fabrics and secondary reaction products that had been identified in differ to such an extent that their elastic properties are quite various investigations. work by Hadley [4]. Mechanism of Reaction and Expansion Following the first recognition of the alkali-carbonate reaction by Swenson [3]. 8—Expansive rock from northwest Virginia with expansion results directly from dedolomitization and not from typical reactive texture. That is. secondary mineral products gaylus- The expansion of concrete containing alkali-reactive car- site and buetschliite. or insoluble residue content. Therefore. Feldman and Sereda [28] found trace bonate rocks is increased by: (1) increasing coarse aggregate amounts. rhombs. does not translate into a greater unrestrained expansion. produced in the initial reaction may then react with the Ca(OH)2. showed that the main chemical reaction that occurred in the rock was that the dolomite [CaMg(CO3)2] decomposed. reaction was considered to be the prerequisite that enabled The petrological factors leading to the optimization of the other processes to work to produce the expansion. the expanded more under restraint than the rock with five times dedolomitization reaction. (2) one way or another. dolomite volume up to the point at which interlocking texture Sherwood and Newlon [27] proposed that expansion becomes a restraining factor. in ASTM C 586. 3 (Fields A. [32] conclude that the expansion due to ACR is caused by ions and water molecules migrating into restricted spaces created by the growth and rearrangement of the products of dedolomitization. For example: Further in Hilton’s work. of a material that expands when it ab- size. and restrained 0. and F). lithology for producing expansion in concrete are: (1) clay con- An idea common to some proposed mechanisms is that. because the volume dolomite volume.25]. Clay inclusions within the dolomite rhombs of expansive rocks have not been universally reported. (4) high sorbs water.4 % by vol- Although the starting and end products of the reaction ume dolomite. with the typical alkali-carbonate reactive texture (Fig. carbonate rocks with different or equivalent chemi- [26]. representative of several. for example. in tent. (3) increase in portant in producing the expansion. or lithium: CaMg(CO3)2 2MOH → Mg(OH)2 CaCO3 M2CO3 Fig. (2) moisture availability. 8) and Na2CO3 Ca(OH)2 → 2 NaOH CaCO3 similar to Fig. it is the “active” clay released during dedolomitization that contributes to the expansion. expanded unrestrained 1. as represented by the following reaction in which M represents an alkali element.7 % calcite. the Fig. Swenson and Gillott [31] proposed that dedolomitization exposes “active” clay minerals that are present as inclusions. and later investigators. to calcite (CaCO3) and brucite Mg(OH)2. sodium.4 % at water uptake of clay mineral inclusions within dolomite 14 weeks. water absorption and incorporation is im- calcite to dolomite ratio of approximately 1:1. and water uptake by the “new” clay results in swelling. OZOL ON ALKALI-CARBONATE ROCK REACTION 417 in cement pores. Tang et al. high-volume. 7—Nonexpansive rock. B. low-density. They have not been observed. Thus. produced as a normal product of cement hydration. and (6) lower concrete strength [23. Expansion in ASTM C 586 was 1. Ex- change sites on the clay surface adsorb sodium ions. within the dolomite euhedra. to regenerate the alkali hydroxide.25 % porosity. have been well documented and establish the overall bulk The rock with the lesser value of unrestrained expansion chemical and mineralogical changes that take place. from Virginia. the primary dedolomitization different. and (4) small size of the discrete could be related to the formation of the hydrated. relatively “floating” dolomite rhombs.31 %. particularly brucite. It has 32. (3) higher temperature. and 1. dolomite Hadley [4] are adequate to explain dedolomitization in concrete mineral powders. mechanically promoting expansion when formation of brucite and calcite. al. cylinders of dolomitic rocks.205 %) of the most expansive sample. Examination of the cylinder before and after immersion in microcrystalline quartz. the uptake of water. have been con. The most expansive that contain more than 5–10 % insoluble residue. by that means. microstructure of the matrix enclosing the dolomite rhombs. discussed below.33] using mortar site. 1 N NaOH solution showed strong dedolomitization had oc- ticle. mained within the interior of the dedolomitized crystal. characteristics. 40°C in a saturated atmosphere and the reaction products The role of the clay minerals in the fabric of the rock may monitored by XRD. in turn. (2) whether absorption of water by clay exposed by chief reaction products of calcite and brucite and that the first dedolomitization causes the expansion. dolomite with a minor amount of quartz. is consid. with portland cement. shrank in the rock cylinder test and confirmed the presence of the products of both reactions. [37] confirmed the basic dedolomitization stone and high-purity. The reasons for this are ders of the three rocks completely dedolomitized in 1 N NaOH discussed subsequently. powdered dolo- Randonjic et al. Prince and Perami [38] showed that dedolomitization is Later work. thus tion occurred in the absence of any alkali. or magnesite. expanded only about 6 to 7 % of the 5-year prism expansion Investigators have noted that brucite may not always be (0. was kali-silica reactivity of cryptocrystalline quartz hidden in the a porous. was that the particular reaction products depend on the ratio sential to the chemistry of the dedolomitization reaction but is of calcium to sodium ions. (4) whether the presence of the matrix of vironment such as Ca2 and Si4. dolomite rhombs of the typical reactive texture. calcium chloride. while lower values promote dedolomitization occurs. Their actually an alkali-silica reaction due to the reactivity of cryp- results suggest that the brucite would be susceptible to further tocrystalline quartz hidden in the matrix enclosing the chemical change by reacting with species from the alkaline en. are present in the same aggregate par. With introduction of weakening the carbonate matrix and. and rhyolite clasts. action occurred in a 2-m-thick ring of parallel-oriented 25Å Tong [13] states that it is feasible for brucite to react with crystals. with space between them. brucite and pirssonite [CaNa2 (CO3)2H2O]. line solutions at elevated temperatures performed experiments ter immersion in NaOH solution. but with no evident calcite. Thus. high-purity dolostone. to form gel-like materials. of iron-rich phases from ferroan dolomite. only brucite and calcite were formed—the dedolomitiza- by disrupting the structural framework of the rock. and others to confirm this expansion lime. The calcite of the dedolomitized rhomb re. using environmental scanning aimed at addressing the following questions: (1) whether the electron microscopy (ESEM). compacts of powdered. using compacts of cement possible in the absence of alkali by experiments on pastes com- and dolomite.2-14A. A calcitic dolomite and a in rapidly expansive concrete microbars cured at either 60°C dolomitic limestone. crystals were. They conclude that the equations proposed by ducted using single crystals of mineral dolomite. small amount produced and its poor crystallinity. forming calcite and brucite with no detectable Experiments aimed at establishing and reconfirming the dolomite. Both dedolomitization and silica gel formation occurred curred. they would be expected to involve expansive volume particles in a matrix of cement paste simulates the spatial rela- changes. using XRD. both of coarser grain size and lower poros- or 150°C in 10 % KOH solution. Tang. that this should also be calcite. and mortar under normal service conditions. changes occurring during dedolomitization involve surface re. powdered magnesite immersed in alka- reaction by examining single crystals of dolomite. fine-grained. Pow- concrete that has expanded [13. rock in both the rock cylinder test (ASTM C 586 but using 1975 kali-carbonate reaction should be reviewed in light of the al. atomic force microscopy (AFM). CSA A23. After immersion in NaOH they observed the expansion. clay. Katayama [6]. soda. The pastes were cured 24 h at mechanism [26. dolomite rhombs. producing calcite and brucite. and of magne. and that strong alkaline solutions. in various proportions. products being less than the volume of the reactants) can cause troscopy (XPS). and optical mi- deleterious expansion is confined to impure carbonate rocks croscopy to identify the reaction products. [34] and Tong and Tang [26. mm cylinders) and the concrete prism test. and in powdered samples of the same three rocks immersed in ing ACR texture than with their dolomite content. The brucite and that it is therefore sensible that it would not be detected. [14] related expansion of concrete prisms suggests that there is a stronger correlation between expansion and rock cylinders to dedolomitization in both types of samples and silica (insoluble residue) content of carbonate rocks hav. as .418 TESTS AND PROPERTIES OF CONCRETE reaction products in expanded samples of Kingston. Milanesi et al. And. The use of compacted cylinders of dolomite or magnesite actions. The general conclusion to promote expansion. and ered by Tong. XRD and SEM/EDAX results ity than the expansive rock. SEM. and the formation reacted rock. based largely on a review of the literature. to simulate ACR rocks. they found that the brucite produced by the re. Therefore. The authors propose that since the chemical tion for expansion by dedolomitization.35–37]. High values of the ratio promote the an enabling factor. (3) whether the ACR is reaction product to form was brucite. Ontario. Processes which may contribute to expansion include tion of dolomite rhombs enclosed in a fine-grained matrix. Previ- For several Chinese aggregates. followed by calcite. volume-reducing alkali-carbonate reaction (the volume of the and the surface analytical technique X-ray photoelectron spec. feldspar. and fine-grained quartz enclosing the dolomite true for magnesium and iron rich phases formed during rhombs in the prototypical ACR texture is a necessary condi- dedolomitization. the presence of clays is not es.33. the formation of brucite. and the three dolomitic rocks to differences in their microstructural the expansion associated with the reaction. Tong and Tang [35] found ous work showed the rock to be definitely not alkali-silica reac- that both alkali-reactive dolomite and alkali-reactive silica. as tive. In paste composed of only dolomite and be to provide mechanical pathways to the dolomite rhombs lime. after four days. Those samples showed detectable as evidence that dedolomitization has occurred in no evidence of dedolomitization in the rock cylinder test. compacts of portland cement with high-purity. Tang et al. The authors attribute the differences in expansion of chemistry and products of the dedolomitization reaction. posed of dolomite mineral powder. dedolomitization was enhanced. He notes also that brucite can be difficult to detect due to the ticles of the matrix. before and af. helping soda. surrounded by the calcite and clay par. surrounding the euhedral silica in the alkaline environment.34]. tal aggregate. kali level per unit volume may equal or exceed that of concrete high purity alumina. the test is accelerated and is then generally similar of the potential for aggregate reactivity based on the investiga. with a total alkali content. it can be used for investigational or re- are intended to provide information on which.4 % total alkalies [23]. the conclusion that the aggre- products in relation to the surface of the dolomite rhombs. A threshold guideline. in essence. size may cause distress when used in the larger size with the gether with the migration of alkali and hydroxyl ions. in or out of concrete. nor clay in. in which the cement content was low but the alkali content of ples. and the storage temperature able and certain exposure conditions are fulfilled. ticular cement-aggregate combination prior to use in concrete. using When investigating and sampling a concrete structure cement of 0. in view of the dolomite or magnesite particles in the cement paste. The greater the proportion of reactive aggregate of the to- It is reasonable that the compacts are a good. the al- Compacts were also made with limestone powder [34]. clay. And that. interfaces of the dolomite or magnesite particles with the en. swer indirectly. of 1. and indirect infor. functional. In addition to the expansions of the compacts. focusing instead on the reaction tion of the aggregate with high alkali cement. or between. the expan. The control samples produced negligible expansions while If the structure shows no distress and it has been estab- the magnesite and dolomite compacts exhibited considerable lished that the alkali content of the concrete would be suffi- expansions which correlated well with the dolomite consump.6 % total alkalies as per eliminates the effects of cryptocrystalline quartz in the matrix. and crete cannot provide information on the propensity for reac- quartz comprising the matrix. OZOL ON ALKALI-CARBONATE ROCK REACTION 419 is the case in natural alkali-reactive dolomitic limestones. tests on the rock. A reactive aggregate proxy.3). tress when used in larger proportion with the same cement. adding NaOH to the mixing water. if the cement content of the concrete was high. aggregate under consideration can furnish direct answers to ASTM C 1105 is intended primarily for evaluating a par- the questions that the laboratory evaluation tests attempt to an. less than 0.2-14A alkali content of the cement and the cement content per cubic which is intended to accelerate the expansion by maximizing yard must be known. Reaction products were determined by tablished for judging whether the aggregate should be consid- X-ray diffraction. and (2) the more important measure is the alkali content per tion in which the brucite is the unique solid product. Larger-sized reactive aggregate causes greater expansion closing cement paste matrix. logically. therefore. artificial aggregate for the ACR limestone in which that has not caused distress as a small portion of the coarse ag- dolomite crystals are enclosed in a fine-grained matrix. for example. not the alkali content of the cement ing the expansion mechanism.2-14A. and it is also a solid volume per se. or clay in the matrix. Evaluating the Potential for Alkali Concrete Prism Expansion Test Carbonate Reactivity The surest measure of the potential for deleterious expansion of a carbonate aggregate in concrete is the measurement of the Field Service Record length change (for percent expansion) of concrete prisms.33] deleterious expansion with cement of 0. amounts of expansion if the concrete is protected and in a rela- Rather. then. exposure to sodium-chloride-containing deicing salts. which be related to the accumulation and positioning of the reaction are known to exacerbate ACR. the Potentially reactive aggregates will not cause deleterious dolomite rhombs is related to the expansion-causing process. because it also reacts to produce brucite in an expansive reac. the conditions for the detection of slowly reactive rocks and for .85 lb/yd3). of the facts. lated at 420 kg/m3 (708 lb/yd3). noted later. the expansion is directly proportional to the dedolomiti. gate is non-deleteriously expansive is strengthened.4°F) and the cement content is stipu- ocal and economic way of accomplishing the evaluation. 5. in which the storage tion of concrete structures in the field can be the most unequiv. and water. tion/calcite production and the magnesite consumption/brucite then the effects of aggregate size. gregate in a structure with “high” alkali level may cause dis- clusion may then be drawn from the experiments that neither cal.9 % alkali augmented by NaOH in the mixing wa- (ASTM C 823) known to contain aggregate from the source in ter. or. an expansive force is generated by has not caused distress with “high” alkali cement in small top the growth and rearrangement of the reaction products. However. question. then the con- clay in. alkalies. although. silica. and the storage con- from the field. the greater the expansion. and moisture availability to the concrete must also be that the results provide a powerful confirmation that the ex. that is best. based on pounds sions of rock prisms and concrete microbars of the same ma. When it is used for its primary purpose the alkali content crete construction. ASTM Specification for Portland Cement (C 150). cite. ditions will be at 23°C and 95 % relative humidity. as control sam. tively dry condition. base a prediction on what will happen if the rock is used in con. if the cement used in the con. (1) the most reactive carbonate rocks can produce Magnesite was used as a cross reference material [26.25 % by mass of cement. Where exposure to moisture also includes zation of the dolomite enclosed in the matrix and must.25/kg/m3 (8. However. proportion of reactive ag- production in the respective compacts. the dolomite rhombs. and calcite. A reactive aggregate that volume reducing reaction. considered singly and in combination before concluding that pansion was directly caused by the reactions occurring at the the aggregate is non-deleteriously expansive. must be es- terials were measured.2–14A and ASTM C 1293. by prior petrographic examination. of sodium oxide (Na2O) equivalent per cubic yard. and cement paste by itself.6 % total reducing process. if “good” information is available of the cement will be that of the job cement. or between. The con. to. the C 1105 is closer to field conditions than is CSA A 23. simplify. the cement was high. If the al- mation to predict what can be observed directly is second best. ered to have been used in a “high” or “low” alkali concrete. and crete was low alkali cement. an evaluation is raised. Then even if the cement used was less than 0. temperature is 38°C (100. into the confined space of the particle/matrix interface. cient to cause reaction if the aggregate is potentially reactive. as Field performance information on concrete incorporating the by ASTM C 1105 or Canadian Standard CSA A23. kali content is raised by using a higher alkali cement and/or Provided certain essential information. That is.5 and 6. In general. same cement. unit volume of concrete. although it is a solid than smaller-sized reactive aggregate. to CSA A 23. The authors conclude gregate. is avail. as noted. to search purposes (Paragraphs 4. in Fig. that the rock prism expansion and are. Fig. therefore. based on information from that are continuously immersed in 1 N NaOH solution has petrographic examination or rock cylinder tests (ASTM C 586) been used as a direct indication of expansive alkali-carbonate or both. total water soluble alkalies. they place greater values plotted are the average of 20 specimens. despite good correlations between the average val- factors promoting expansion due to alkali-carbonate reactivity ues of rock prism and concrete prism expansions. etc. 9. oversize between rock cylinder (or rock prism) expansion and concrete and undersize material discarded. How- three sizes recombined.2-14A. the coarse ag. the plus 19-mm material differs from the minus 19. and equal masses of the prism expansion has been substantiated (Figs. based on correlation with longer term tests and field performance. Rock Cylinder Expansion Test sumption that the plus 19-mm material does not differ in com.25% . aggregate ratio. the three-month concrete (for example. variability inherent in the rock. is the approximate level at which cracking and distress are first In C 1105 the grading of the job-proposed aggregate can observed on the prisms. 10—Relationship between one-year length change of (ASTM C 157) concrete prisms (average of three) with high Fig. 0.95 %) and length change of (ASTM C 586) correlates well with expansion of concretes using these rocks rock prisms at eight weeks. lithology. prism length changes are shown for each sample [23]. it shall not be used. for example.040 % used in the CSA standard same aggregate grading and alkali level.015 0. The expansion of small (approximately 1. 10-. specifies that if the job-proposed aggregate has material larger than 19 mm (3/4 in.4 in. If. As such. 9—Expansion of small rock prisms in alkaline solution alkali cement (0.025 0. and presumed expansive characteristics in.4 position.5 by 10 mm) cylinders of carbonate rock from the minus 19-mm material.2-14A 1. reactivity of the rock since the method. in length by 0. and 5-mm sieves.030 CSA A23.). due to the versus the service environment of the concrete. In CSA A23.015 % expansion at three months will produce deleterious expansion in field concrete at a later age. and the other factors governing expansion in It may be noted with respect to. ever. paste to C 1105 limit.. originally using square mm material in those respects. a rock which produces 0. the differences that can exist The expansion limit for the CSA prism test is specified and between restrained (in concrete) and unrestrained (in ASTM C tabulated in Table 2 with the suggested ASTM C 1105 limits. nonmandatory. that fifteen-thousandths of one percent is not a dele. 586) behavior. 14-.). based on the as. 35. 9 and 10). responsibility on the specifier of the concrete to understand the Thus. C 1105 performance [39]. But. Expansion Limits. w/c.. then instructions are given for cross section specimens. Average and range of six rock as aggregate [4]. in diameter. And since its earliest use. note in Fig. the situation is such that ASTM C 586 is terious degree of expansion. 10 the spread of the six rock prism expansion Expansion limits for ASTM C 1105 have not been adopted values corresponding to the concrete prism expansion value in ASTM C 33 but are suggested in the Appendix to ASTM C 1105 (average of three) and. . the correlation gregate is separated on 20-. was first described and used by testing the coarser fraction. Hadley in 1961 [20].040 facilitating comparisons among aggregates by using exactly the The expansion limit of 0. But the logic of the test is such that. and Alkali Content Expansion Limit at Indicated Time.420 TESTS AND PROPERTIES OF CONCRETE TABLE 2—Concrete Prism Test. Percent Na2O Equivalent Test Alkali Content 3 months 6 months 1 year ASTM C 1105 job cement 0. and it relates well to observed field be used if it is not coarser than 19 mm (3/4 in). 5 % Na2O eq. And. A typical alkali rious level of expansion is demonstrated by service record or carbonate reactive rock producing on the order of 0. stones by running two tests. general. They state also that siliceous described in ASTM C 294 and discussed elsewhere in this ASR limestones can be differentiated from dolomitic ACR lime- chapter. eventually peaking at 0. one with 100 % portland cement. with cement (boosted by addition of KOH) of pects of the testing program and interpretation of the results 1.5 % at 44 weeks. If the limestone is alkali-silica reactive the expansion will be sig- pansion of a rock cylinder (ASTM C 586) or concrete beam nificantly reduced. determination of potential alkali-carbonate reactivity of car- pansion when used in concrete.2-26A. gave average rock cylinder expansions of greater than 0. also considered applicable by several researchers in view of the For example.1 % expansion at 28 days is the implied limit field structures. For example. ment. prism expansion at one year with high alkali cement might expand on the order of 0. Canada.20 % at 16 weeks is the alumina (Al2O3) content or the insoluble residue content. petrographic examination is rographic examination should recognize that the characteristic valuable during successive steps of the evaluation to guide the reactive texture and composition are only subtly and indirectly understanding of the behavior of samples in. as reported by bonate rocks by chemical composition—Canadian standard Rogers [8]. of 1:1. and as regards ASTM C 1105. Petrographic examination speaks directly to the concerns and an effective tool for screening aggregate sources. microbar test. used is 5–10 mm. and the CaO:MgO ratio of the limestone versus given in ASTM C 586. cluster. based on comparing Petrographic Examination the behavior of aggregates in the test and in field concrete. it is desirable to prepare three mutually perpendicular specimens. origin and may or may not conform faithfully to lithologic or .1 % concrete by a concrete prism expansion test. using insoluble residue. one perpendicular to Determination of Potential Alkali the bedding and two at right angles parallel to the bedding. on the amount and distribution Selection of Samples for Testing and for of the reactive lithology within the stratigraphic section pro. it is strongly recommended that all as.1 % at The test is based on work by Rogers [8] and uses relation- four weeks also caused excessive expansion and cracking when ships based on a correlation between expansion of concrete used in concrete. or late expanding. prisms at the conclusion of the test can furnish information quired by the method. the perfection of the type lithology. Rocks with compositions in these regions should be [23] contracted 0. et al. as regards ASTM C 586. and 10. using 4040160 or 286 mm bars. but it of Paragraphs 10. when tested.1. that CSA A 23. 5. regions are fact that some rocks contract before they begin to expand delineated in which the potentially expansive carbonate rocks [23. OZOL ON ALKALI-CARBONATE ROCK REACTION 421 a relatively rapid indicator of potential expansive reactivity. as alkali-silica reactive aggregates. behavior of samples in solution at 80°C for four weeks. The Canadian Standard notes the usefulness of petrographic then three mutually perpendicular specimens are made.” ing potential alkali-carbonate reactivity using concrete micro- In view of the requirements of specimen selection and the bars 202080 mm and 4040160 mm stored in 1 N NaOH occasional irregular. Canada.5 % at four weeks in ASTM C 586.1 % at four weeks but expanded to 0. an alternate limit of 0. the test limits. Of Carbonate Reactivity of Carbonate Rocks three such specimens. prisms and rock cylinders. The aggregate particle size the rock cylinder test. For example. although not specifically called for in used as an acceptance test. It should be taken normal to the bed. even if bedding is discernible. The reactive texture is of secondary.2. Whether.3. petrographic examination of the concrete One test specimen per sample of rock is the minimum re. whereas the fly ash will have little effect on (ASTM C 1105).30 and aggregate to cement ratio be guided by petrographic information. the characteristic reactive texture. and performance of aggregates in Although 0. and the interpre. Petrographic examination of dolomitic carbonate rocks Grattan-Bellew et al.1 % at four weeks. ding if bedding is discernible. most quarry faces sampled in Ontario. 10. a delayed expander tested by Newlon. depends on the expansion of the ACR limestone aggregate. the reaction will produce ex. Ministry of Transportation and Commu- An expansion of 0. at a w/c of 0. The Ontario. dergo reaction or dedolomitization in an alkaline environ. in Fig.25 % at 16 considered to be potentially deleterious until their nondelete- weeks. for alkali- crete will detect the presence of the characteristic reactive carbonate reactive aggregates [41] which is also applicable to lithologic texture. In examination at this stage. ASTM C 1105. the other replacing a portion of the cement with 30 % fly ash.10 % at 28 days is considered to indicate nications has developed a quick chemical screening test for the the presence of material with a potential for deleterious ex. insofar as the rock is concerned. An expansion of 0.2 % at 16 weeks” than there were in the Xu et al. [41] developed an accelerated method for determin- category “ 0. [42] propose a modification of the (ASTM C 295) proposed for use as coarse aggregate in con. the concrete prism test (ASTM C 1105). or replacement. If bedding is not discernible.40]. related to the primary factors of sedimentation that produce tation of results from. by Chemical Composition sion is the one on which to base the test result. the one exhibiting the greatest expan. or near.1 % at four weeks is judged to be appropriate for recognizing ACR limestones. Other Methods and Approaches In the suite of sample test results reported by Rogers [8] there were considerably fewer samples in the category “ 0. will un. And. “Interpretation of Results” does not predict in-concrete expansion of the rock and is not of ASTM C 586.1 % Concrete Microbars at four weeks but 0. Following the initial use of petrographic examination for Quarry Sampling detecting the reactive carbonate rock texture (see Quarry Sampling of the stratigraphic section in limestone quarries for Sampling) in order to identify candidate samples for further detecting the presence of alkali-carbonate reactive rock by pet- testing by ASTM C 586 or C 1105. helpful for interpretation of results at. Concrete Aggregate posed for use as concrete aggregate. the rock cylinder test (ASTM C 586) and bedding. when it occurs in a dolomitic limestone. Thomas and Innis [44]. 48–51. West Con- nomically feasible and the lowest alkali cement. an acceptable level of dilution Properties of Concrete and Concrete-Making Materials. ASTM was reached when the reactive rock did not exceed 20 % of the STP 169A. cured at 40°C and 100 % RH. pp. then the objective of the Stage II sampling will the LiOH. Lithologies representing less pansion than the control. Ontario. tal aggregate. national. PA. or otherwise minimized. ing using ASTM C 1105. and that the use of LiOH could be an effective means to dif- ous experience suggests that the results of the more extensive ferentiate alkali-carbonate from alkali-silica reaction. 487–496.. H. and technical information. and Gillott [45]. Rogers and Hooton [43] in a five year even a minor area of reactive texture should. at nine months. “Chemical Reactions. restrict availability of moisture to the concrete by barriers or by design of the construction if possible. if both fractions contained reactive material [25].. If the “natural” dilution approach is infeasible. Canada. or mappable. thin beds of varying lithology. The author is grateful to Christopher A. that the aggregate from the produced section. level can produce alkali-carbonate reaction. Stark [46] recommends that the pre- than 10 % can be combined and sampled at random locations ferred compound for ASR mitigation is LiOH due to its greater in the combined thickness. the precise beds and their amounts of reactive ma. Downsview. guided by petrographic examination using as many thin or pol. Ministry of Trans- avoid the reactive rock by selective quarrying. prohibit the use of Potentially Expansive Rock the reactive rock in portland-cement concrete. reactive aggregate. aggregate and alkali. . to the same extent that the variations in rock prism by ASTM C 1105. “Chemical Reactions of Carbonate Aggregates in resulting mixture does not produce a potentially deleterious Cement Paste. ASTM Inter- level of concrete expansion by ASTM C 1105. ASTM STP 169B. pp. was ef- to select samples for further tests. C. It is gregate could be safely used. because of the varia. N.” Bulletin No. bars treated at 150°C in water and in 10 % LiOH and KOH. at the first sam. Results of Wang the total aggregate that can be established by subsequent test. using understood that the establishment of 100 % absolute absence the same aggregate in concrete prism tests (CSA A23. tent per unit volume of the concrete is the important measure. and finer-scale sampling can end up delineating a lesser volume In the use of the concrete in constructions that will con- of reactive material in the quarry face than may have been in. amounts of reactive dicated from the results of the Stage I sampling [25].” Significance of Tests and Properties of Concrete and Concrete-Making Materials. PA.50 %) alkali cement. Tang et al. Using Coarse Aggregate from a Quarry with If no mitigating approach is feasible. dilute the produced aggregate with nonreactive stone such that the [1] Walker. bearing in shohocken.422 TESTS AND PROPERTIES OF CONCRETE stratigraphic units. Each lithology representing more than 10 % of the trol prism.25 %) alkali and 50 % should be considered in a way that samples are located with due replacement of low (0. the follow.04 %) with GGBFS did not reduce The objective of the first (Stage I) sampling is to establish expansion sufficiently so that the Kingston. Therefore.43 alkalies. similar to the reactions with Na and K hydroxides. [47]. G. quence of beds comprising a definable. ON. and that alkali con- ture may vary laterally and vertically within beds or within a se. use the smallest aggregate size that is eco. may Unlike the alkali-silica reaction. Perhaps from 50 to 100 samples may be required. coarse aggregate. using the Kingston. the proposed job concrete mixture should be tested graphic unit. as precisely as the limitations of time and budget thors note that LiOH produced dedolomitization and brucite will permit. it should be sampled at a mini. The au- be to identify. “A Reactive Aggregate Undetected by ASTM In the concrete. when tested in concrete by ASTM C 1105. require the field sampling unit that it rep. or 90 % by slag. or individual beds as observable in the field. a minimum of five showed that concrete prisms (CSA A23. And. and in sufficient detail to permit a calculated “weighting” for Also. If the reactive portation. strati. does not produce a deletrious ex. and lowest for the water (control) sample. 722–743. Previ. Research and experience with a group of Virginia quarries [2] Hansen. West Conshohocken. intermediate for within a quarry. pp. ASTM International. comparison study of laboratory and field concrete with and pling stage (Stage I). References pansion.4 % The amount of reactive texture and the expansivity of that tex. If potentially expansive rock is present in a quarry. 1966. Rogers. high alkali cement (1. the alkali carbonate re- be as large or larger than those between lithologies [23]. for those sources. ON. unlike the ASR. formation. In Stage I sampling. fectively reduced only at 70 % replacement of cement by fly bility that can exist. W. (ASTM C 586) expansions within a given bed. Tests.2-14A) requires examination of every bed. utilize selective quarrying such portant graphs. had the same expansion as the con- in a quarry. slag did not effectively control expansion. without GGBFS concluded that up to 50 % replacement of resents to be considered suspect [23]. E. expansion ished sections as necessary to delineate the reactive rock and of concrete at one year. or 15 % of the to. West Conshohocken. action is not very well controlled by the use of fly ash or Sampling for the reactive lithology should therefore be ground granulated blast furnace slag (GGBFS).. ASTM International. found that the regard to their relationship to the quarry production horizons. terial. ON. PA. the use of lithium compounds does comparison with the maximum “allowable” reactive content of not mitigate the expansion caused by ACR. mind that cement with total Na2O equivalent alkali at the 0. any thin or polished section that shows ash. Tang et al. 20 % of the fine aggregate.” Significance of Tests and indicated that. [34] found that even with cement of 0. tain diluted. Where the face exhibits relatively solubility than either lithium fluoride or lithium carbonate. If the stratigraphy of the producing section is favorable. 1978. or lithology. 226. ob- If Stage I sampling establishes the presence of reactive rock tained the greatest expansion for the KOH.2-14A) with either LiCL and an average of approximately ten samples should be taken or LiOH. reactive ag- the presence or absence of reactive rock within a quarry. using the Kingston. 1957. who kindly provided im- rock cannot be totally avoided. and the prism with LiNO3 had significantly more ex- production should be sampled. Acknowledgment ing courses of action should be considered. aggregate in concrete mum of ten systematically located stations [25]. Lithology and structure and up to 65 % replacement of high (1. photographs. [3] Swenson. . 1994. W. Marfil.” Journal.” Record No. E. Highway Re. Transportation Research Board. 1962. bonate Rock Reaction. Vol. Highway zation in Alkali-Carbonate Reaction.. M. and Tang. DC.” Alkali-Aggregate Reac- Research Board. R. ence on Alkali-Aggregate Reaction in Concrete.. Vol. 31–37. [25] Newlon.” ACI Materials Journal. “Mechanism of the Alkali-Dolomite Research Board. M. Highway Research [10] Alasali. No.” ACI Materials and Expansion Isotherms of Reactive Limestone Aggregate. 126–133. Reaction. 45. H. 1964. Reaction. and Tang. “Alkali-Carbonate Rock [13] Tong Liang. A. 1964. Army Engineer Waterways Record 525. 1–20... [9] Smith.. A. G. Proceedings. U. 27. and Newlon. “Expansion of Gull River Carbonate [36] Tong. S.. Virginia Highway Research Council. C. Highway Highway Research Board. M. Rock Reactions.. E. [30] Buck. H.” Magazine of Concrete Research. A.. Jr. 742–749. 1992. Concrete. H. 1. VA. 613–619. Vol. M. of Carbonate Aggregate. “Alkali Reactivity of Carbonate Rocks— 2000. 275. Record No. and Han Sufen. A. Carbonate Aggregates in Virginia. H.. M. C. W. Transportation [33] Tong... Washington. of Damage Due to Alkali-Aggregate Reaction (AAR) in .. W. VA. “A Survey for Reactive Proceedings. Char. Summer 1986.” [23] Newlon. Bulletin No. Symposium on “Novel Techniques in a Study of the Mechanism of Dedolomiti- Alkali-Carbonate Rock Reactions. D. Ed. Ottawa Canada.. pp..” Proceedings. 329–396. Aggregate Proceedings of the 10th International Conference on Alkali- Characteristics and the Cement Aggregate Reaction. W. Reactive Carbonate Rock in Virginia. 2.” Concrete Alkali-Aggregate Reactions. L. Transportation Research Technical Report C-75-3. Highway [14] Milanesi.” An Evaluation of Several Methods 525. pp.. Symposium on Alkali-Carbonate Rock Reactions. “Mechanism of Alkali-Carbonate Experience with Argentinean Dolomite Rocks.. L. Washington. National Expansion of Alkali-Carbonate Reaction. and Soles. Quebec City. 470–476. 5. No. pp. Materials Information Report 99. and Perami.” Progress “Studies on Alkali-Carbonate Reaction. Vol. Research Board. pp. 71-R33. Vol. R. Vol. No. and Aggregates. Part I. Concrete Society Publication CS. 46. 1968. C. pp. “Developments in Specification and Control. pp. “Characteristics of Kingston Car. and Sherwood. U. 508–518. L. “Potentially Cement-Aggregate Reactions. W. Restraint. pp. G. Vol. M. tion in Concrete. [35] Tong. Affected by Alkali-Carbonate Reaction. Symposium on Alkali Carbonate Rock Reactions. A. 1987. 45. Bulletin No. H. “A Critical Review of Carbonate Rock Reactions— May 1972. H. S. 462–474. Concrete Society Publica.” Cement. Noyes Publications. 26–29.. on the Expansion of Reactive Carbonate Aggregates. “Concurrence of Alkali-Silica and Aklali- [17] Swenson. June [8] Rogers. and Sherwood. Canada. 1974. “Bridge Deck Deterioration National Research Council. pp.. search Board. Chemical Reac- Record No. A. No. 1. Highway Research Board.S. Toronto. Highway Research Record No. A Aggregate Reaction. 6. Promoted by Alkali-Carbonate Reaction: A Documented Exam. 1996. O. 1964. Z. No. P. “The Alkali-Carbonate Reaction and its Reaction Products an [32] Tang. A.” Alkali-Aggregate Reaction in Concrete. Cracking of Concrete Caused by the Alkali-Carbonate [26] Tong. [20] Hadley. pp. H. and Gillott. Transportation Research Board.” Cement. C.” Cement and Reaction.. 41–56. 27–44. P. 1. 1964... Washington. pp. J. [18] Dolar-Mantuani. January.. Transportation Research Board. H. National Research Experiment Station. [11] Gillott. 1964.” Magazine of Concrete Research. 1986. 1997. 1964. Jr. 1997. “Learning to Live with a Reactive Carbonate Rock. and Steam Curing of Concrete. C. W. Charlottesville. C. Washington. Report No. 25. Poten- [7] Field Trip Guidebook. No. 88. 58. DC. A Pilot Regional Investigation.” Conference Papers of the [24] Qian.. pp. 1579–1591. DC. R. F. and Maiza. Vol. 1964. No. “Control of Reactive Carbonate Rocks in Concrete. No. DC. Highway [39] Thomas. Sherwood.. Record No. 3. 355. H.” Cement-Aggregate Reactions. Is Their Reactivity Useful or Harmful.. P. “Alkali-Carbonate Rock Reaction. China. Symposium on Al. 222–233. Liu. 38–42. “Performance of Board. “Prevention Research Board. “Correlation Between Reaction and Research Record 525. “An Occurrence of Alkali. 7th International Conference on Alkali. and Gillott.” Highway Research Record No. VA. Proceedings. 45. Concrete..D. 99–112.” ple. DC. [6] Katayama. [12] Ozol. tions. Symposium on Alkali-Carbonate Nanjing Institute of Chemical Technology. Concrete. Lan Xianghi. Various Test Methods for Assessing the Potential Alkali [28] Feldman. D. M.. Hooton. A. M.. 1986. 13–23. OZOL ON ALKALI-CARBONATE ROCK REACTION 423 [4] Hadley. Charlottesville. Engi. G.. 40. 91. P. G. “Expansion of Reactive Carbonate Rocks under Grattan-Bellew. D. H. “Reaction Products in Expansion Test Specimens Vol.. 104. and Rogers.” Ph.” Transportation Research Record 525. “Characteristics of Sorption Reactivity of Some Canadian Aggregates. Progress Report No. August 1996.. Nov. [5] Mather... M. Proceedings. 3.” Proceedings. M. M. Progress Report No.” Proceedings. Dolomite Reaction. Deng. M. N. pp.” Proceedings. tural Investigations. Corps of Engineers. NJ. 7th International Conference. [19] Hadley. W. Vol.” Cement and Con- Research Council.. M. Vol. 45. 5. and Rogers. J. Concrete Research. Vol. A. “Studies on the Mech- Proceedings. Record No. Australia. Ontario Ministry of Transportation. pp. and Newlon. C. American Concrete Institute. 11th International Conference. No. Washington. pp. C.-Dec. 45. 1995. pp. Internal Release of Alkalis. [29] Walker. Shayan.. and Newlon. Highway [38] Prince. Council. Virginia Highway Research Council.. 167. Washington. Batic. [31] Swenson. 1961. Ed. Washington... Washington.” Cement and Concrete Research.. 10.” Carbonate Aggregate pp. and Sereda. Park Ridge. 178–195. Strategy for Use and Control of Carbonate Rocks Including an neering Materials Office. 8. pp. crete Research. Washington. Thesis. Reactions of Alkali-Magnesite and Alkali-Dolmite. B. “Expandability of Solid-Volume-Reducing Reaction.. January-February 1994. 1961. 1.. Ragnarsdottir. VHRC 71-R41. L. Journal. R. pp. MS. M. for Detecting Alkali-Carbonate Reaction. L. 26. DC. M. 327–336. Annotated Bibliography of Virginia Research. 7b. H... E. and Tang. 99–108.K. J. and Han. A. M. Ozol. 1991. H. E. V. J. Vicksburg. 1974. pp. tion CS.. Malhotra. pp. pp. 1974. H. DC. “The Effects of Textural and External Restraints [34] Tang Mingshu. Part Two: Microstruc- kali-Carbonate Rock Reactions. 1992. Washington. 2001. P.” Concrete Quality Control. 9–21. C. and Tang. Virginia Highway Research Council. J. W.. Sept. 19. and Tang. pp. DC. M. W.. H. 45. “Alkali-Aggregate Reaction and 2. Canada. A. and Aggregates. M. Deng Min.. Washington. Vol.” [27] Sherwood. A. 203–214. Transportation Research Record Reactive Carbonate Rocks. pp.. V. pp. Research Board. 53.. 45.. 104. Jr. Expansion and Dedolomitization.” Conference Papers of the 9th International Confer- [21] Newlon. [16] Hilton. Allen. 1994. “ACR Expansion of Dolomites 9th International Conference on Alkali-Aggregate Reaction in with Mosaic Textures. 1975.. [15] Hilton. “A Case Study of Two Airport Runways Rocks in Sodium Hydroxide. No. J. lottesville.. pp. D. “Alkali Reactivity of Dolomitic Carbonate Rocks. D. pp. DC. M. H. DC. 8. E. tially Reactive Carbonate Rocks. Jr. Melbourne.. anisms of Alkali-Carbonate Reaction. D. 18–31. E. 1960. and Ozol.. 196–221. Highway Research Board. 799–806. and Livesey.” Cement-Aggregate Reactions. T. 55–63.” [22] Sherwood.. “Evaluation of the Potential for Expansion and 1972.. DC. Aggregate Reaction in Concrete. 1974. “Alkali-Reactive Carbonate Rocks in Indiana— [37] Radonjic. H. M. 851–857. pp. M.. Lan. and Xu.. 104. 47.. 170. “A New Accelerated [46] Stark. A. D. Deng. [41] Xu. Due to Alkali-Aggregate Reaction in Concrete.. Vol. 9th Reactivity. and 11th International Conference on Alkali-Aggregate Reaction in Aggregates.” Cement. [44] Thomas. pp. 19. National Resarch Council.. and Mitchell. 2002. A. P. November/December 1998. Reaction: The Concrete Microbar Test. pp.” Proceedings. and Hooton. “Comparison Between Labora. pp.. 32. 1. [48] Rogers. London.. “The Journal. 69–75. Transportation Research Board.. 1017–1025. Vol. Concrete Research.. D. Vol.. 2. Concrete Aggre- tory and Field Expansion of Alkali-Carbonate Reactive gate Testing and Problem Aggregates in Ontario—A Review. “Lithium Salt Admixtures—An Alternative Method to Method for Determining the Potential Alkali-Carbonate Prevent Expansive Alkali-Silica Reactivity. D. 95. 109–118. cance of Chemical and Mineral Admixtures. G. G. 1974.” Transportation Research Record [45] Wang. 26–30. Ontario Ministry of Transportation and Communications. 1995. ence on Alkali-Aggregate Reaction in Concrete. B. 1997. Concrete Society Publication CS. Uhthoff Quarry Alkali Carbonate Rock Reaction: A Laboratory 716–724.” Magazine of Washington. C. and Koniuszy. Z. X. . R. B.424 TESTS AND PROPERTIES OF CONCRETE Concrete Construction—Canadian Approach. 2. pp. Alkali Aggregate Reactions. M. F.” Conference Papers of the 9th International Confer. Z. 5th rev.. 1992. Fournier. 25. J... E. Woda. Report EM-31. Concrete. Vol. M. J. C. ed. [43] Rogers. “Alkali-Carbonate Reaction: Signifi- 525. No. No. Cybanski.. A.” Proceedings. A. DC. Engineering Materials Office. Quebec. L. 2000. Deng. and Gillott. E.” Cement. Concrete. “Comparison Between Alkali- “Proposed Universal Accelerated Test for Alkali-Aggregate Silica Reaction and Alkali-Carbonate Reaction. Concrete. Vol.. and Field Performance Study. 43–54. 877–884. “Effect of Slag on Expansion Concrete and Aggregates.. [42] Grattan-Bellew. pp. pp. pp..” ACI Materials [40] Ryell. [47] Tang. Concrete. 29–34. M. 1992.. 1985.. International Conference on Alkali-Aggregate Reactions in pp. No. Chojnacki.. and Tang.. 2003. No.” Cement and Concrete Research. Vol. 6. and Innis. D. Z. importance of the thermal expansion of concrete in the de. S solidity (1 decimal porosity). the signifi- of concrete. Virginia Transportation Research Council. The need fourth. The design However. Woolf [2]. Pt(rock) S(n*1 Pt1 n*2 Pt2 n*3Pt3. The most obvious of these is massive struc. The mode of an aggregate can be determined petrograph- tures where the dissipation of heat generated by cement hy. percent by volume) of the rock is known using the of the individual constituents may be important. and others. Pt1 thermal property value of Mineral 1. Because little has changed in this subject area since the for a better understanding of the effects of the thermal publication of ASTM STP 169C. 1 Research Scientist. Scholer [3]. diffusivity of a rock can be calculated if the mode (mineral peratures or temperature cycles. This is probably because in many in- concrete aggregates was authored by H. Mineral 1. ties of their constituents. properties of the constituent minerals in proportion to their mal properties are important in the design of massive struc. The conductivity. Cook in the first stances the effects do not appear to be as important as the ef- three editions of Significance of Tests and Properties of Con. or composite are important. diffusivity. following formula [4] weight concrete structures where insulating value of the composite is a primary factor. ically using ASTM Guide for Petrographic Examination of dration is important to control thermal cracking. diffusivity..) (1) The thermal properties of aggregates that are of general concern are the coefficient of thermal expansion. with only minor revisions thermal expansion on the durability of concrete. in concretes exposed to extreme tem. conductivity. in Chapter 24 of this publication. The value thus calculated for stances include insulating concrete and the durability of a given aggregate will not be as accurate as could be measured. and in light. and sign of all concrete structures. such as dams. where the relative properties content. a calculated value particular concrete application to estimate the importance may prove acceptable for many general applications. While this necessarily requires discussion of the thermal prop- Aggregates typically compose 65–70 % or more of the volume erties of the concrete as affected by the aggregates. properties of rocks and minerals. concrete exposed to cyclical temperature changes. and specific heat of aggregates are usually of concern only in special instances. A reasonably good approximation of the tures. Other in. Robert- that thermal properties of aggregates will have on concrete son [4] has compiled a large volume of data on the thermal performance. specific heat. VA 22923 425 . and by the current author in the significance of thermal properties is not as apparent. the aggregates have a great influence on the thermal properties of concrete. Knowledge of ther. particularly the coefficient of the same as in the previous edition. and specific heat. consequently. relative abundance. given the considerable care and skill necessary to engineer should carefully evaluate the circumstances of a accurately measure these properties. the crete and Concrete Aggregates. The degree to which General Concepts of Thermal Properties thermal properties of concrete aggregates are of concern to the user depends upon the nature of the concrete structure Thermal properties of rocks are related directly to the thermal and the exposure to which it is subjected.36 Thermal Properties of Aggregates D. Stephen Lane1 Preface The attention that has been given to the thermal properties of concrete aggregates is not as great as that given to other THE CHAPTER ON THERMAL PROPERTIES OF properties of aggregates. Charlottesville. has been and additions to the text and reference list. Aggregates for Concrete (C 295). Of these. expressed by Allen [1]. the thermal expansion of aggregates is by far the most important because of the n1 percent by volume. Because the thermal properties of composite ma. conductiv. fects of other properties of aggregates and. where ity.. The discussion in this paper is primarily confined to the Introduction significance of tests and thermal properties of the aggregates. K. where thermal and volume stability of the value of thermal expansion. cance of tests and thermal properties of concrete is discussed terials such as concrete are dependent on the thermal proper. this chapter is substantially characteristics of aggregates. gates of low thermal coefficient failed much more rapidly in The paper by Meyers [17] is concerned completely with the freezing-and-thawing test than the concretes containing thermal coefficient of expansion of portland cement rather aggregates of high thermal coefficient. Given the aggregate’s freezing to their quartz content.5 thermal expansion will produce concretes of low thermal vol- Syenite.7 106/°C perpendicular to this di. Potassium feldspars are another group of minerals ex. dolomitic marble with a coefficient of thermal expansion of 3.5 to 11.3 106/°C for some samples of neat cement specimens. magnesite 7. andesine 3 to 4 pansion of concrete may be taken as 9. aggregate of high thermal coefficient of expansion similar to ported coefficients of thermal expansion for common rock. Pearson speculated that tensile stresses developed when the nificance except when the differences are great. Thus.8 106/°C parallel to its sufficient to cause fine cracking of the concrete providing path- C-axis and as low as 4. Bytownite 3 to 4 Anorthite 2. ways for water into the concrete and subsequent freezing and rection. Pearson conducted a laboratory investigation hibiting rather extreme anisotropy [19] with concretes containing aggregates of both low and high For this reason. diabase. It is included because a discussion of the ther- TABLE 1—Average Linear Coefficient of mal properties of concrete aggregates would not be complete Thermal Expansion of Some Common Rocks without some information on the thermal properties of the and Minerals [5] cements with which they are used. crystalline. or at least better understood. the cubical expansion of rocks and min.5 ages or at certain critical saturations the linear thermal coeffi- Pyroxenes.9 106/°C.5 to 7. 106/°C was reported to be very resistant to freezing and efficient of thermal expansion of the common minerals. porous limestones 3.5 to 3 range may be from about 5. The most no. thermal coefficients. effect is that on the vol- Dolomite. Quartzite. 5. andesite.5 cient of expansion of cement pastes may be somewhat higher Olivine 6 to 9 than those reported earlier. which can have a linear thermal coef. gate at extremely low winter temperatures. Concretes containing the aggre- thermal properties of aggregates. and thawing durability and because the deterioration occurred While most minerals will exhibit some degree of much more rapidly than would have been expected from freez- anisotropy by expanding more in a direction parallel to one ing and thawing action alone. particularly under severe exposure conditions or The coefficient of thermal expansion of aggregates is directly de.5 to 6. in Table 1.0 the structure and is further discussed in Chapter 24 on Thermal Properties in this publication.5 to 7. Refs 4–16 list more values than most of the others.5 to 5 An average value for the linear thermal coefficient of ex- Oligoclase.0 The significance of the coefficient of thermal expansion of ag- Quartz sands and pebbles 10. that of the cement paste or with an aggregate of low thermal forming minerals and some common rocks that are presented coefficient. Pearson [18] expansion of aggregates from specific locations are contained in attributes a case of rapid concrete deterioration to the use of many of the references listed and are available from many other an aggregate of low thermal coefficient. The other effect is the development of internal stresses as a result of large differences between the coefficients of thermal expansion of the various components of concrete subjected to temperature extremes or thermal Coefficient of Thermal Expansion cycling and the impact this may have on concrete durability. Although values for the thermal coefficients of In one of the earliest papers on the subject. diorite. having been subjected to very low tempera- coefficients of rocks vary to a large degree in direct proportion tures and to severe frost action. thawing damage. phonolite. amphiboles 6.5 to 12 106/°C to 12.3°C before being subjected this possibility should be kept in mind when investigating the to freezing-and-thawing tests. These stresses were ficient of expansion as great as 25. depending upon the type and quantities of the aggregates. basalt expansion of concrete should be accounted for in the design of Marbles 4. matrix contracted three to four times that of the coarse aggre- table example is calcite. and other factors. the the first winter. Calcite 4. chert 11. The thermal gabbro. Mitchell [7] has found that at early Orthoclase.2 106/°C and mortars from about 7.8 106/°C to 16. The Argillaceous shales 9.5 to 12. microcline 6.0 to 12. .5 gregates with respect to its effect on concrete is two-fold.0 primary.6 106/°C. The concretes were subjected to 100 ther- erals is not always related directly to the linear expansion.9 Quartz 11.0 to 7. but the Labradorite.9 and 21.0 to 12.5 Effect of Thermal Expansion Sandstones 10. silica shale.0 106/°C. Aggregates with high coefficients of Granites and gneisses 6. The concrete was severely cracked after calcite and high calcium feldspars exhibit the lowest.6 As will be noted from the table.0 to 10. this is generally not of sig. There is less agreement on pendent on the coefficients of the constituent minerals and thus whether more durable concrete will be produced with an on the mineral composition of the rock. a sources.0 ume change of concrete.5 to 8.0 Dense. crystallographic axis than another. Zoldners [5] has re. There seems to be fairly general agreement that the ther- Numerical Values for Thermal Coefficients of mal expansion of the aggregate has an effect on the durability Expansion of concrete. and mal cycles between 28. He reports values as high as Albite 5 to 6 22.8 106/°C to 14. while thawing deterioration. The aggregate. under rapid temperature changes. all other things equal.5 to 8. other causes were suspected. quartz has the highest co.426 TESTS AND PROPERTIES OF CONCRETE than aggregates.0 ume stability and vice versa. the Rock 106/°C mixture proportions. The coefficient of thermal Mineral 106/°C expansion of hydrated cement pastes may range from 10. but heating and cooling concrete specimens over the temperature are discussed further in Chapter 25. different aggregates varied approximately in proportion to the Most of the test methods are based on the measurement of lin- thermal coefficient and quantity of aggregate in the mixture. Several ingenious methods have been developed for determin- efficients of expansion of concrete and mortar containing ing the thermal coefficient of expansion of coarse aggregate. The specimens used by Willis and DeReus were 25.19].6 107/°C. 50 mm long. measurements to be made over a considerable temperature However. having a 25. Other researchers [29. Maine.S. state among other conclusions that. Pearson. The method described by Willis and DeReus [32] allows tions of test. aggregate with low thermal coefficient and a high degree of ceptance tests.2 106/°C change. drilled from the aggregate ing. this means of multiplying the change in unit length to 88°C. He suggests that differences between these co. the resulting lower thermal the measurements indicates that the calculated coefficients are expansion apparently introduced no adverse effects. aggregates containing quartz should be Treat Island. ear expansion over a temperature range. and the multiplication of the change over a aggregates with low coefficients of thermal expansion com.4 106/°C should be considered large subfreezing winter temperatures. Resistance to Fire and range of 4. in both moist and dry conditions. the greatest variation being caused by freezing. report the results of specialized conditions and are not discussed further here. The preceding discussion has dealt with the effects of ous effects if large differences are observed. LANE ON THERMAL PROPERTIES OF AGGREGATES 427 Callan [20. However. mm-diameter cores.” It also was determined that the thermal co.7°C quartz changes state there appears to be a correlation between the resistance of and suddenly expands 0.21]. concrete durability and caution against the possible deleteri. [25] stand in contrast to those 55°C or more because the change in unit length per degree is of Pearson [18.7°C. that will be subjected to extreme elevated temperatures. This range is usually The findings of Walker et al.21] statistically analyzed 78 combinations of More recently.24] that extremely small. Bureau of Reclamation produced range with the use of an optical lever. [27] to evaluate the potential stresses developed between ferences between the coefficients of expansion of coarse ag. anisotropy [28]. They found that “changes in High Temperature. Zoldners [5] physical incompatibility of the matrix and aggregate in indicates that thermally stable aggregates such as fine-grained concrete based on differences in thermal expansion. Callan [20. used temperatures as low as 28. while avoided since at a temperature of 572.8°C. binders and aggregates of different thermal coefficients and gregate and mortar may considerably reduce the durability of attributed abnormal cracking in several bridges to a limestone concrete from that predicted by the results of the usual ac. on a vertical scale the purpose of inhibiting alkali-aggregate reaction and the placed 6.28] has renewed interest in aggregate in concrete with respect to durability in freezing and the durability of concrete produced with aggregates of low thawing and differences in thermal expansion between the thermal coefficient of expansion. by means of a precise level. probably accurate to 3. temperature were destructive to the concrete with sudden changes in temperature being much more severe than slower Methods of Determining Thermal Expansion ones.85 %. Except in the point. expansion properties for any one material vary with the condi. and the others [22.4 sand sizes. It is improvement in durability probably was primarily because of reported that consideration of the possible errors involved in the inhibition of this reaction. For accelerated freezing and thawing with natural weathering at such applications. and 12.7°C to 60 2.9°C. Venecanin [27. The optical lever has also concrete at Grand Coulee Dam using a predominately basalt been used to obtain additional multiplication of the length aggregate with a thermal expansion of about 7.5 movement of the specimen as the temperature was varied was 106/°C.4- that showed an extremely high resistance to freezing and thaw.78 1. The Bureau of Reclamation also found [8] in the Kansas.1 m from the mirror. and concretes having higher coefficients of expansion of Aggregates were less resistant to temperature changes than concretes with lower coefficients. He has derived equations coarse aggregate and the mortar. Smith [23] thermal expansion of aggregates over temperature ranges that presents calculations to indicate the potential magnitude of can occur under natural exposure conditions. in this publication. on the other hand. greatly increased the durability of the concrete in measured by reading the image reflected by the mirror of the which it was used. aggregates that exhibit extreme anisotropic thermal character- Swenson and Chaly [22] include some discussion on the effect istics can adversely affect concrete durability even in environ- of thermal coefficient of expansion of the aggregates on ments not subject to sub-freezing temperatures. These are considered to be highly Walker et al. specimens to be tested and placed in a controlled-temperature Nebraska area that replacement of part of the aggregate with oil bath with a range of 2. the has reported the results of experiments to determine the correlation is probably usually of lesser importance than other structural and expansion changes of concrete aggregates with characteristics of the concrete.460°C at various rates. substantial temperature range greatly increases the facility and pared to the cement paste may reduce concrete durability.4-mm lever arm.8 to 88°C. One precision of the determination. temperatures up to 1200°C. the U. 29. case of a crushed aggregate of sufficient uniformity to permit Koenitzeer [26] subjected several concretes and the aggregates obtaining a larger specimen that will be representative of the used in them over temperature ranges of 12. is not available for determining the linear expansion of fine One of Koenitzer’s conclusions was that the elastic and thermal aggregate. . He concludes that large dif. The bridges are in areas subject to extreme efficients exceeding 5. Kennedy rocks of anorthositic composition are best suited for concretes and Mather [24]. Although the addition of limestone was for optical lever. [25]. Endell [31] expansion between the coarse aggregate and the mortar. usually producing a disruptive concrete to freezing and thawing and differences in thermal effect at the surface of concrete in which it is used.30] enough to warrant caution in the selection of materials for following Venecanin’s lead have concluded that limestone highly durable concrete exposed to temperature extremes.8 to 26. in attempting to correlate laboratory. the size of a repre- explanation for the difference in finding is that Walker’s study sentative specimen that can be obtained from a coarse aggre- did not subject specimens to temperatures below the freezing gate rapidly approaches a practical maximum. The vertical limestone. however. which had a thermal expansion averaging 4. normally is expressed in calculations as watts per metre kelvin (W/mK). Granodiorite (Nevada) 2. cal thermal coefficient of expansion from which the linear ex. presence of a small amount of moisture in the interior of a crum-type extensometer frames. Diabase 3. posure to moisture.0 perature difference between two surfaces.8 to 3. the results obtained include the effects of characteristics of the aggregate. which is impacted by the aggregate moisture mine if anisotropy or preferred crystal orientation exist. Measurements are made with lightweight concrete greatly increases its thermal conductiv- electromagnetic strain gages with electronic indicators while ity. from 0–5 % increases the conductivity by 23 %. Its units are square Johnson and Parsons [10]. but more good conductor of heat.6 to 3. Of course. The strain their abundance and relatively low conductivity. The porosity gages are then mounted so as to measure strain in each of the of an aggregate also plays a significant role in determining its three directions. the preparation of specimens.9 Thermal conductivity.6 4. Davis and Kelly [42] state that “the from 25. The usual approach has been to deter.4 Dolomite 4. The exception is barite. hence. The method determines the cubi. a sulfate mineral with a thermal conductivity somewhat lower pansion may be calculated. conductivity.0 to 3.7 5.8 apply equally to other massive structures. Tyner [41] reports that in a 1:5 mix- elaborate setup. thermal conductivities will be high. Its units are joules per kilogram kelvin (J/kgK).9 to 3. Detailed descriptions of the ap. Thermal Diffusivity. quartz monzonite 3.2 2. The Bureau of Recla. TABLE 2—Thermal Conductivity Values for Thermal Conductivity. two of these directions to lie in the major structural feldspars on the other hand are also important because of plane of the rock.3 2.6 2. content since air is a very good insulator and water a very cently. thermal diffusivity. lution held at the desired temperature. none of the preceding methods are readily also have found pronounced reductions in the thermal con- adaptable to the determination of the coefficient of expansion ductivity of concrete containing lightweight aggregate. but of this type of material.4 reducing thermal volume change and thus cracking in large Granite.” Kluge et al. Description of modern dilatometer than normal concrete aggregate [46].0 to 3. Although one rections on each of the six faces of a cube of rock. divided by the specific heat and density and is a physical prop- paratus. if a high degree of insulation is desired. Thermal conductivity values the length change contributed by the cement.0 2. and all three normally are determined only for concrete as used in massive structures. ure with their mineral content.0 ing cooling systems.4 poses.5 is also of importance in lightweight concrete for insulating pur.6 to 4. Venecanin [28] has reported on a similar.9 2.9 to 7. if such a plane can be located.8 2. of the more useful properties of lightweight concrete is its Mitchell [7] describes a method that employs specimens low thermal conductivity. The directions. parallel to foliation 3. It has been indicated by some [38–40] that thermal diffu. Amphibolite 2. Some Common Rocks (Data From Clark [45]) and Specific Heat Thermal Conductivity Thermal conductivity.8 sivity may have an important effect on concrete durability. ture.6 dams. The same type of measurements and calculations would Granite 3. . ASTM Test Method for Linear metres per second (m2/s).35] describes a method for measuring the thermal coefficient of expansion of coarse Thermal Conductivity aggregate particles in which an SR-4 strain gage is bonded to a The thermal conductivity of aggregates varies in large meas- prepared piece of aggregate and readings are taken over a tem.476. thermal coefficient of expansion that is particularly adaptable For most heavy-weight aggregates used in radiation shield- for use with fine aggregate. Thermal Expansion of Rigid Solids with Interferometry (E 289) Specific heat is the amount of heat required to raise the covers the use of Michelson interferometers for which the temperature of a unit mass of material one unit of tempera- typical specimen will possess either blunt or rounded ends.6 2.7 to 57. Limestone 2. Thermal conductivity Granodiorite (California) 3.6 to 3.428 TESTS AND PROPERTIES OF CONCRETE The use of an interferometer is described by Merritt [33] Thermal diffusivity is defined as the thermal conductivity and modified by Saunders [34].0 to 5.2 mm in size coated with wax and held in ful.2°C. where strain gages are mounted to obtain ture of Florida limerock concrete. Rock Mean Range of Values mation [37] indicates the application of these data in connection with computing concrete placement temperatures and design. This method requires that the portant minerals to consider in evaluating the conductivity of piece of aggregate be sliced in three mutually perpendicular an aggregate as it exhibits a relatively high conductivity. and the test procedure erty of the material that determines the time rate of change of with specific application to concrete aggregates is given by temperature of any point within a body. Quartzite 6. The Corps of Engineers [21. measured as the rate of heat flow Gneiss. under conditions of continuous or intermittent ex- the specimen is immersed in a circulating ethylene glycol so. Re. Verbeck and for some common rock types reported by Clark [45] are pre- Hass [36] developed a dilatometer method for determining the sented in Table 2. an increase of moisture measurements parallel to the edges and in both diagonal di. an aggregate (and concrete) of relatively low absorption Because of the size and usually heterogeneous nature of should be used. The purpose of this requirement is to deter.6 to 3.5 2.2 2. Quartz is one of the more im- perature range of 1. [43] and Price and Condon [44] fine aggregate. and specific heat are (W/mK) largely interrelated. and in other thermal calculations aimed at Gneiss. they indicate that the reduction seems to be influenced more mine the linear expansion of mortar bars containing the fine by the reduction in the density of the concrete than by the aggregate. perpendicular to foliation 2.6 through a body of unit thickness and unit area with a unit tem. equipment can be found in ASTM Test Method for Linear Ther- mal Expansion of Solid Materials With a Vitreous Silica Dilatometer (E 228). ing.6 to 2. 70 … 0. Quartz 0.01 degree of saturation. This is possible because the formula in- TABLE 3—Calculated Diffusivities of Some cludes all three values.71 … 1.80 0. Diffusivity. it is believed that such a combination would result in higher thermal Rock 0°C 50 to 65°C 200°C stresses than those existing in homogenous bodies.95 Since a difference in diffusivities would result in different rates Dolomite 0.77 0.00 temperature changes. which is Diorite 0.3 k thermal conductivity in W/mK.70 0. In a ho. Thomson [38] states that for a given body with specified boundary conditions the thermal stresses Fayalite 0. and specific heat. The specific heat of as a matter of practical convenience.00 that. it is customary to determine diffusivity and specific heat and to calculate conductivity or to determine conductivity and specific heat and to calculate diffusivity.00 … a large change in the thermal diffusivity with a relatively small Granitic gneiss 0.72 depend on certain physical properties of the materials. exposed to natural freezing and thawing ac. specific heat. TABLE 4—Specific Heat of Some Common tional to conductivity.74 0. Rhyolite 1.92 tivity. Methods are available for the direct determination of thermal crete. Dolomite 2. Minerals and Rocks (Data From Robertson [4]) weight aggregate is thus primarily dependent on its quartz con- 103J/kgK tent. such physical properties as thermal conduc. to the specific heat of the concrete [37]. Nothstine [39] and Weiner [40] have reported the results of their approach Diabase 0.99 responsible for surface stress.6 h thermal diffusivity in m2/s. Muscovite 0.77 0. or vice versa.6 Whether conductivity is determined directly and diffusivity is calculated. Peridotite 1.04 20–59 % for saturations of less than 5 %.92 the body can be thought of as being thermally homogenous. Fox and Dolch [47] found Limestone … 1. permits solving the equation for the unknown property.80 0. thermal diffusivity is directly propor.95 a gravel concrete. The thermal diffusivity of a normal. and Specific Heat tures and the limiting of thermal volume change of mass con. thermal diffusivity. Investigations have indicated that the normal diffusivity of the aggregate may have an influence on the durability of the Mineral 27°C 127°C concrete in which it is used.86 0.1 Gabbro 1.95 diffusivities and conductivities are the same for each material.95 companied by thermal shock and characterized by bond failure Granodiorite 0. and to the diffusivity of the gravel Gabbro 0. The specific heat of the aggregate contributes materially conductivity. The increases in diffusivity ranged from Basalt 0. However.85 1. Pyroxene 0.95 and internal expansion. but that further work is needed to determine the significance of the effect and to find a practical means for using this rocks can be calculated from the mineral composition of the knowledge to improve concrete durability.77 0.70 0.77 0.75 0. The effect of temperature on specific heat is ties for some rocks are presented in Table 3.6 p density in kg/m3.71 0.77 0.65 … 0.2 Sandstone 1.85 1.88 mogenous body. and knowing the values and density Common Rocks (Data From Robertson [4]) for any two. Limestone … 0. He attributes the failure to the relatively Quartzite 0. considerable and should be considered. is largely a matter of the most .79 1. Sanidine 0.92 thermal diffusivity.95 Calcite 0.87 to the problem.81 0. Calculated diffusivi.0 where Limestone 1.88 transient period only in a certain combination known as the Phlogopite 0.86 0. Table 4 presents values of specific heat for some common minerals and rocks.81 0. rock using Eq 1. The formula is Rock Diffusivity.97 high thermal coefficient of expansion of the concrete.64 0.72 … 0.99 Slate 0. Weiner’s work was instigated by the failure of Granite 0. and Quartzite 2.79 0. Albite 0. resulting in differential volume change.98 of diffusion of heat through the aggregate and paste.7 c specific heat in J/kgK. the calculations involved in the control of placement tempera. responds more quickly to Marble 0. Specific Heat of Aggregates Specific heat is of considerable importance in connection with Methods of Test for Conductivity. being higher than the mortar. 106m2/s k hcp (2) Basalt 0. Granite 0.77 0. and the density of the material influence the Microcline.9 Marble 1. The authors of the references cited essentially agreed that the thermal diffusivity of the aggregates apparently has an effect on the durability of concrete.75 0.83 … In an investigation of four limestones. LANE ON THERMAL PROPERTIES OF AGGREGATES 429 Thermal Diffusivity As mentioned earlier. If in a mixture such as concrete the thermal Forsterite 0.85 temperature distribution and the thermal stresses during the Anorthite 0. Proceedings. Vol. VA. to improve concrete further as a construction material. Vicksburg. ASTM STP 22A. ventional needle probe to measure the thermal conductivity of [7] Mitchell. MI. particularly thermal expansion. 6–370. and by refining the instrumentation. Sept.” Bulletin No. All of the methods depend ASTM International. West Conshohocken. have an effect [18] Pearson. Proceedings.49]. C. Vol. C. the conductivity of aggregates. p. N. references may be found appended to many of the references [14] Rhodes. the new surface temperature. ASTM International.. The determina. but in most cases.” Mineral Aggregates. W. “Preliminary Notes on the Coefficients of Thermal experimentation. L. W. work on the subject. J. mation on the theory and mathematics of thermal tests. 36–41. and Mielenz. refine- [5] Zoldners. 581. Bureau of Reclamation. 504–511.” lar methods [41. specimen.” Technical Memorandum No.S. “Thermal Coefficient of Expansion of Portland shape. “Thermal Expansion of Typical American Rocks. of Tests of Concrete and Concrete Aggregates.. Denver. p. p. Aug. PA. H. 29. 32. Vols. p. American Concrete Institute. [12] “Laboratory Investigations of Certain Limestones Aggregates The specific heat of aggregate usually is determined by a for Concrete.. 1953. 153. Thermal conductivity can also [8] “A Study of Cement-Aggregate-Incompatibility in the Kansas- be measured directly by ASTM Test Method for Steady-State Nebraska Area. ASTM STP 83. Sass et al. April 1944.” Report C-964. 101. 1948. West Conshohocken. specimen size and [17] Meyers. American Concrete Institute. C. Reston. H. Vol. Detroit. “Thermal Properties of Concrete Under ments can be made by grinding the specimen to a sphere. 1107. 48. “Supplementary Data on the Effect of Concrete that might be expected. 1891. tions made on concrete specimens. 1936. “Durability of Concrete. VA.. “Needed Research. Waterways procedure known as the method of mixtures [35]. Feb.” Open-File Report 88–441. ASTM STP between the temperatures at the center and the surface of a 83. Proceedings. O. H. [4] Robertson. Investigations Institute. 1963. Vol.” Mineral Aggregates. p. “Thermal Expansion of Concrete Aggregate Material. 40. June 1946. States. the temperature of a specimen of known weight.S. This procedure probably Thermal Expansion of Concrete Aggregate Materials. West Conshohocken. Neat machined. determination of the thermal properties of aggregates when CO.” Journal. Vol. 221. Depending upon the degree of accuracy desired. Expansion of Certain Rocks. drilled.. ASTM International. both to resolve existing controversy and cluded in the references to this paper are based on determina. instrumentation. R. 60. Vol. J. for Sustained Elevated Temperatures. 78. method offers a simplified and versatile means for measuring West Conshohocken. J.) [11] Parsons. dure using this methodology to measure the thermal properties IA. temperature curve until equilibrium conditions are obtained at ASTM International. 1944.” controversial. 128.. precise equipment. References The Corps of Engineers [35]. SP 25. Iowa Engineering Experiment Station. p. or unconsolidated rock material. Geological Survey. Waterways Experiment Station.” Journal of Research. “A Concrete Failure Attributed to Aggregate of Low Thermal Coefficient. 7th ed. H. and Parsons. This Cements and Concrete.430 TESTS AND PROPERTIES OF CONCRETE convenient equipment setup available and the preference of in the concrete.. and Mielenz.. Geological Recently.” Technical Memorandum No.” Industrial and Engineering Chemistry. American Concrete Institute. of aggregates. R. “Petrography of Concrete Aggregate. J. J. could be used for coarse aggregate.” Journal.. 1953. p. and Johnson. W. ASTM International. 1953. tion is by no means routine in nature and requires careful [6] Hallock.” Temperature and Concrete. and technique. “Thermal Expansion Tests on Aggregates. C. The ultimate solution must be based on the Journal. and some aspects of the problem are Aggregate Having a Low Thermal Coefficient of Expansion.. cited here. U. reported to date do not present a clear-cut picture of the effects [19] Pearson. ductivity of concrete by the use of a 203 406-mm (8 16-in. p. 1–5. specimen by starting at essentially equilibrium temperature. U. There is a real need for additional research the laboratory doing the work. diffusivity of stone and concrete. [50] present a laboratory proce.” Journal. Bureau of Reclamation. they may be used with aggregates if properly modified with respect to specimen size and shape. MS. as is normal in this field of investigation. Tan et al. required size and shape could be fabricated from a large rock p. H. 1952. PA. Army Corps of Engineers.” Mineral Aggregates. Other Vicksburg. PA. There appears to be no doubt that the normal properties 1940.” Report on Significance then changing the surface temperature. E. W. Vol. 1948. 6–371. pp. and. Oct. “Petrographic and Mineralogic Conclusions Characteristics of Aggregates. Ames. H. Proceedings. West Conshohocken. C. Army Corps of Engineers. “Thermal Expansion of Aggregates and Concrete jor difficulty is to separate the effects of the thermal properties Durability.. References 44–60 provide additional background infor. C. Survey. Test methods are available that are entirely adequate for the [16] Concrete Manual..S. of unbound aggregates.” Proceedings. 32. Thomson [38]. [20] Callan. 457. 53. [9] Griffith. of the aggregates from the numerous other variables existing Proceedings. 1988. L. R. R. 38. by Means of the Guarded-Hot-Plate Apparatus (C 177) or simi. p. 33. veloped a method for the determination of the thermal con- National Bureau of Standards. C. PA. performance of aggregates of known thermal properties in Vol. PA. the ma.. It is a Experiment Station. W. Some of the test methods in. H. 40. S. “Factors Affecting the hollow cylindrical concrete specimen. 20. “Influence of Mineral Aggregates on the Strength Dolch [47] describe methods for the direct determination of and Durability of Concrete. a given [13] “Test Data on Concrete Aggregates in Continental United amount is measured. example. [15] Rhodes. Bulletin No. U. used with proper attention to procedure.S. Sept. Reston. U. ASTM STP 83. pp. G. Heat Flux Measurements and Thermal Transmission Properties Denver. D. and a capable operator.. [3] Scholer. 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Part 3. and Kelly. “Basis for Classifying Deleterious the Durability of Concrete. p.. M. ASTM Measurements and Factors Affecting Thermal Conductivity of International. Nov. H. R. Manhattan. 2. McGraw-Hill. 987. [28] Venecanin. 625. Vol. London.. Heat Transmission. C. Conshohocken. 9. ASTM International.” Journal. S. 39.” M. 1940. American Concrete Institute. Part 2. E. p. p. Vol. PART V Other Concrete Making Materials . University of Illinois. and recom. most of the key aspects of concrete—its workability. creep. The properties reviewed in this of these properties lies in how well they predict the concrete chapter are summarized in Table 2 and their test methods are behavior. The objective of this chapter is to the Portland Cement Association recently suggested revisions to review those properties that are included in the standard speci. and optimum Cements (C 595). density to calculate fine- of this chapter included properties of expansive cements. is were covered for the first time in the previous edition of ASTM an example of a hydraulic cement. with greater emphasis on performance than prescriptive. IL 61801-2352. quantitatively or in detail. one from the American Concrete Institute [6] and the strength by chemical interaction with water. Most of the properties attempt to predict how cement this edition does not.3]. These terms are also discussed in a separate properties—fineness. C 150. The specification for hydraulic cements. Hydraulic cement is a books on cement chemistry [4. The previous edition other cement property (for example. two text- hardening and strength gain in concrete. cement is defined by its chemical composition. 435 . The focus of this chapter is on these physical difficult because the relationships between cement properties properties—their significance. C 1157. The core of C 150 remains prescriptive. formance specifications. fications for hydraulic cements. land cement and hydraulic cement. The types of cements in each specification influences the performance of concrete. at least not mendations about ways the tests might be improved. the portland ce- vant new technology and attempts to clarify certain issues. in which per- that earlier chapter (excluding expansive cement) were formance in certain standard tests is required. and two publications on more general term for any cement that hardens and gains cement. but ness). There is a general trend in ASTM C01 (and elsewhere) to significance of the standards. is similarly a mix of prescriptive and performance require- cement and its reactions with water are largely responsible for ments. increase its acceptance [1]. shrinkage. and concrete behavior are often not understood.5]. chapter of this book (Hydraulic Cements—Chemical Properties). Unfortunately. The specification for blended cements. is prescriptive. is entirely based on performance tests. Most performance requirements in C 150 are optional. and the significance are summarized in Table 1. Slag by itself may be a hy- STP 169 in a chapter that covered the full range of physical draulic cement. The current edition introduces rele. sulfate content). first published strength. fineness. Some are used to control quality during bles 2 and 3 of the ASTM Specification for Blended Hydraulic cement production (for example. into a rigid chemical properties. these are found in Tables 3 and The physical tests covered in this chapter vary in their 4 of the ASTM Specification for Portland Cement (C 150). shift from prescriptive specifications. predicting this behavior is often very listed in Table 3. other from the Portland Cement Association [7]. There are numerous references on cement and concrete. and how they might be im. Blended cement. set. Thus portland ce. and a Task Hydraulic cements and their components have a wide Group of the National Ready Mixed Concrete Association and range of physical properties. in which a certain compo- proved. and durability. and Table 1 of the ASTM Performance Speci. C solid. intended to replace certain prescriptive requirements at the dis- Hydraulic cements are manufactured products that find their cretion of the user and reflecting the general trend towards per- principal uses in concrete and related construction materials. and durability—of hydraulic cements used in making concrete. strength. Thus. The two principal types of cement used in concrete are port. significance and use. When cement and water are mixed. formed by blending portland PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS cement with other reactive materials such as pozzolan or slag. Urbana. Ta. consistency. capable of bearing substantial compressive loads. setting properties.37 Hydraulic Cements—Physical Properties Leslie Struble1 Preface ment is a hydraulic cement. In preparation of the current chapter. Portland cement is based on many of which were used in preparing this chapter. 1 Professor. although it includes several performance requirements as listed in Table 2 of this Introduction chapter. they undergo various and the limits on chemical composition of the various types of chemical reactions that gradually change the mixture from a portland cements are discussed in the chapter of this book on plastic (or fluid). set. Particu- crystalline calcium silicate phases whose hydration leads to larly useful were two textbooks on concrete [2. Others are needed for determination of some fication for Hydraulic Cements (C 1157). which can be molded or cast. ment specification. Department of Civil and Environmental Engineering. limits in their use. Because portland extensively drawn upon. 595. to performance specifications. but hydraulic cement may not be a portland cement. the contents of sition is required. in 1992. . crete mix proportions.m r Density . s Autoclave expansion s s s Strength Minimum s s s Maximum o . s . Blended cements may solute volume method [8]. . s .. is used to calculate fineness in C 204 and C 115. method make it unlikely that routine measurement of density cial disposal...P I(SM)(MS) C 1157 GU MH HE LH MS HS Option R Density and pycnometers are now available that provide rapid and reproducible density measurements and entail no special The density of hydraulic cement.15 Mg/m3.. m .05 Mg/m3 to as high as 3.. to be 3. The standard test allows use of alternate methods.. it in fact ranges rather widely. from as low and is used in calculating concrete mix proportions by the ab. s Durability Air Content s s r Alkali reactivity ..436 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Summary of Cement Classifications (Adopted with Permission from Ref 2) Moderate Moderate Resistance General heat of High early Low heat of sulfate High sulfate to alkali-silica Specification purpose hydration strength hydration resistance resistance reactivity C 150 I II III IV II V Low alkali option C 595 I IS(MH) P(LH) IS(MS) Low reactivity option IP IP(MH) IP(MS) I(PM) I(PM)(MH) P(MS) I(SM) I(SM)(MH) I(PM)(MS) S. .... It would be better to measure density of The standard test method using the Le Chatelier flask is ac.. Expansion c . would be specified. as 3. disposal. ularly important property and not included in the cement Though the density of portland cement is usually assumed specifications. portland cement more frequently and to report the measured curate and inexpensive.. However. though not in itself a partic... o Heat of hydration o s s Volume change Drying shrinkage .. Density is measured using the ASTM vary even more substantially in density.25 Mg/m3. Activity index .. o specified optionally.m o Sulfate expansion o s s KEY: s specified for one or more types. Water requirement .. r report required but no limit specified. m specified for constituent materials. value. This variation is Test Method for Density of Hydraulic Cement (C 188). c specified under certain conditions. Unfortunately.... which requires spe. Set Time of set s s s False set o . the difficulties with the present standard ing and uses a large quantity of kerosene.... . o. it tends to be time-consum. TABLE 2—Summary of Physical Properties Specified for Hydraulic Cements Portland Blended Hydraulic Hydraulic Cement Physical Property Cement (C 150) Cement (C 595) (C 1157) Fineness s r.. which enough to affect the cement volume used in calculating con- utilizes a Le Chatelier flask filled with kerosene.. but C 1157 does not. whereas C 989. but the activity index controls the grade of slag. whereas C 989 uses a slag re- Autoclave expansion C 151 placement of 50 % (by mass). C 1012 (for blended cement) whereas C 989 and C 311 use replacement levels by mass. and C 109 store cubes in saturated lime solution. C 595 specifies an activity index for for Use as a Mineral Admixture in Portland-Cement Concrete pozzolan used in blended cement. Re- placement by volume may be sensible in certain applications. Activity (C 311) and in ASTM Specification for Ground Granulated index is a physical property but a prescriptive specification Blast-Furnace Slag for Use in Concrete or Mortars (C 989). Thus the requirement for fly ash in con- Several versions of the activity test exist. but the alkali levels in C 311 Heat of hydration C 186 and C 989 should be brought into conformance. then they are equally that the specifications in C 595 were no longer appropriate. and C 595 uses Expansion C 1038 a slag replacement of about 70 %. the blended cement will not Time of set C 266 (Gillmore). and C 109 and C 989 Physical Property ASTM Test Method use a flow of 105–115. C 109. As a performance speci- three tests compare the compressive strength of mortar con. The activity index is a useful property of pozzolan or slag when The specification for blended cement (C 595) requires that used in a blended cement or in concrete. with no obvious rationale for the difference. The ac. C 311. The test in C Volume Change 595 uses a pozzolan replacement of about 35 %. C 311 for pozzolan Sieving C 430 (No. The activity index is simply the compressive crete (C 989). and the higher stor- but a few years ago the procedure in C 311 was changed such age temperature are important in C 595. minimum activity index of slag as a mineral component in con- and Ground Slag). fication. A careful examination of all test . The test in C 595 allows the use of any portland ce- Fineness Air permeability C 204 ment in the activity test (but encourages using the same brand Turbidimeter C 115 that will be used in the blended cement). whereas C 989. STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 437 the older C 311 procedure was added to C 595. Activity Index and C 109 all use a storage temperature of 23°C. so it is recommended that the tests four test procedures (C 595. it is described in ASTM in blended cement. alkali level. C 311.8 %. These tests are related to ASTM Test Method for Some of the differences noted above may be important. again with no obvious rational for Air content C 185 this minor difference.9 %. whereas C 109 and C 989 Durability use sand contents of 73 %. If the cement tivity index test in C 595 originally used the procedure in C 311. strength of mortar using a blend relative to the compressive The specification for fly ash and natural pozzolan in concrete strength of mortar using plain portland cement. There is no specified and slag in concrete (Supplemental Cementitious Materials. so important in C 989 and C 311. so the mass depends on the specific gravities. All when applied to the pozzolan or slag. either for use in a blended cement or for use directly in Recommendations concrete. The tests in C 595 and C Optimum SO3 C 563 311 both use sand contents of 75 %. same objective. so it is discussed here the activity index of slag or pozzolan for use in blended cement and also in the two chapters of this book dealing with pozzolan be a minimum of 75 % at 28 days. wet) specifies that the portland cement have total alkalies in the Density C 188 range 0. be brought into conformance wherever possible. The C 595 uses a storage temperature of 38°C. and C 989). (C 618) also requires that the activity index at 7 and 28 days be Standards a minimum of 75 %. the test is described in an annex to C 595. C 311. For time and lower temperature) than the requirement for fly ash mineral components in concrete. The test in C 595 uses a flow of 100–115. the sealed storage conditions. This situation TABLE 3—Summary of Test Methods for is an example of how a lack of communication between C01 Physical Properties of Hydraulic Cements and C09 can lead to illogical differences between standards. C 1157 sets limits on strength of the hydraulic cement taining the mineral component with the strength of mortar not but no prescriptive limits (physical or chemical) on the containing the mineral component. The test in C 595 stores cubes in a close-fitting sealed container. whereas C 311 Drying shrinkage C 157 uses a pozzolan replacement of 20 % (by mass). but is not necessary in an acceptance test. to test the acceptance of mineral admixtures.6 to 0. For slag and pozzolan crete is somewhat more demanding (measured at a shorter used in cement. probably the most important difference. These replacement levels could Strength C 109 surely be brought into conformance. The test in C 595 uses a replacement Alkali reactivity C 227 (using Pyrex glass) Sulfate expansion C 452 (for portland cement) level by volume. and all three tests have the materials used in the cement.5 to 0. as the reaction rate of mineral ad- Significance mixtures may be particularly sensitive to temperature. but Compressive Strength of Hydraulic Cement Mortars (C 109). Method for Sampling and Testing Fly Ash or Natural Pozzolans As shown in Table 2. 325. given that all three tests have There are several important differences between these the same general objective. The Consistency effect of cement alkali on reaction of pozzolan or slag is well Water requirement included in C 109 documented and use of a high-alkali portland cement is sensi- Flow C 1437 ble in a general acceptance test for pozzolan or slag (if the port- Normal consistency C 187 land cement used in a particular blend does not contain suffi- Set cient alkali to initiate reaction. C 191 (Vicat) False set C 451 meet the strength specification). and C 989 for slag specifies that the port- Activity index C 595 Annex land cement have total alkalies in the range 0. most are probably unnecessary. [9]. if a higher water content is used. Type III portland cement is typically finer fied for all types of portland cement except III and IIIA: either than Type I. The Blaine surface area is easy to 2 An example of the benefits when the particle size distribution is optimized to achieve very dense packing is Ductal™. be retained on a 45-m sieve. ASTM Test Method for Fineness of probably the most important and widely used is fineness. the surface area does not fully describe fineness. The particle size distribution trolling particle size distribution during cement production. and 75-m (No. 200) Sieves (C 184). speeding up the strength gain. The first. mortar. In the third. which are prone to flocculate. Two cements may have the same Blaine but quite different Unless prevented through the use of dispersing admixtures particle size distributions. no more than 20. rate of strength gain and heat of hydration. cause cement is a ground material. 200) Sieves by Wet Methods (C 786). ior. may cover a somewhat different size range. which is gradually becoming available. . the Blaine Fineness also affects consistency of fresh cementitious mix. flocculation substantially increases the water demand of the cement. and (2) ASTM Test Method for Fineness of Hydraulic Cement by the 150-m (No. It is anticipated that this technology will find increasing application in the future. fineness (both the distribution. a high-performance cementitious product that has high flowability. The median particle diameter sisted by a water spray. Finer cements Using particle size distribution rather than specific surface adsorb chemical admixtures more rapidly. often requiring area would improve the specifications. fineness must be reported but no limits are specified. Increasing the fineness substantially increases the rate of hydration. Be. literature relating Blaine surface area and such properties as formance properties were discussed by Bentz et al. and there is a large body of temperatures during hydration. surface area has been a very reliable parameter for use in con- tures (paste. and high ductility. enced by fineness. can substantially improve both performance and energy efficiency during grinding. and sieving. There are three standard tests to measure cement fineness—air permeability. gain specified for a Type III portland cement. strength. 1). allows measurement of the specific surface for use in concrete is warranted. thereby shortening the setting Recommendations time. Effects of fineness on per. and Types IV and V portland cements are often 280 m2/kg by the air permeability test or 160 m2/kg by the tur- coarser. so setting time. the strength. and permeability are all influ. 50). 100). 325) Sieve (C 430). reducing strength. it has an inherently broad powder is allowed to pass through a standard-sized sieve as- particle size distribution (Fig. In addition. heat of hydration.3 of Type I or II portland cement is typically about 10 to 20 m. Increasing would be sensible to replace it with the Blaine test (C 204) in fineness is a common strategy for meeting the faster strength all specifications. Hy. 100) and 75-m (No. The influence of fineness higher admixture dosages. In C 150. but Significance no fineness limits are specified. Recent grinding technology utilizing high-efficiency classifiers allows better control of the distribution [10]. area. Finer cements also generate higher on hydration rate is well established. and it meability reduction that accompanies hydration. Likewise. in C 1157 for hydraulic shrinkage. a minimum specific surface value is speci- to 50 m or more.2 full particle size distribution curve should be considered when With increased fineness generally comes a higher proportion assessing the effects of fineness on cement and concrete behav- of submicron-sized particles. Standards Fig. and speeding up the per. there have been few parameters in the grinding process that could be used to control the particle size distribution. The second test. The Wagner test (C 115) appears to be seldom used. indirectly. and concrete). therefore However. 1—Particle size distribution of a typical portland cement (reprinted with permission from Ref 7). 3 Two other tests are available using coarser sieves: (1) ASTM Test Method for Fineness of Hydraulic Cement by the 300-m (No. mentation.0 % of the pozzolan may dration rate is a function of fineness. in blended cements Fineness is a very important physical property for cement. particularly by limiting the coarse particles (20 m) and the fine particles (2 m). The influencing the fluidity (viscosity) and. either reducing slump or. ASTM Test Method for Fineness of Portland Cement by Air Permeability parameters concerning the acceptability of pozzolan and slag Apparatus (C 204). Until recently. turbidimeter. 150-m (No. Hydraulic Cement by the 45-m (No.438 TESTS AND PROPERTIES OF CONCRETE (water-reducers or superplasticizers). containing pozzolan. Blended cements are also broad in their particle size bidimeter test. and amount retained on the 45-m sieve and the specific surface by are often bimodal. cements. This particle size control requires specialized mechanical particle separation equipment. In C 595 for blended cements. Fineness is included in most specifications for hydraulic but particles range in size from a few tenths of a micrometre cements. Helmuth and colleagues [11–13] have shown that controlling the particle size distribution of cement. uses the Wagner apparatus to measure the particle size distribution by sedi- Of the various physical properties that relate to cement quality. high strength. Similarly. controls the density with which cement particles pack. called the Blaine surface area after the inventor of the apparatus. the air permeability method) is listed as a physical requirement and must be included if the purchaser requests certification. ASTM Test Method for Fineness of Fineness Portland Cement by the Turbidimeter (C 115). The Blaine surface area is convenient to use because fied consistency rather than a specified water-to-cement ratio. changes in cement that in some way alter its con- fineness values as well as minimum values. but highly vis. Mortar with this crete except perhaps in research studies. might be described as a dough (stiff enough to knead or roll). cluding the same mineral and chemical admixtures.5 aggregation of particles). sometimes with modifications in the flow level: ASTM Test Method for Early Volume Change of Cementitious Mixtures (C 827). whereas Consistency is specified for blended cement. [17]. Cement paste. setting time. is expected to correlate with viscosity. The normal the standard tests provide no information about viscosity. and that it is par.e. with a very fluid consistency. One avoid errors due to incomplete consolidation in samples with solution is to use the Rosin Ramler distribution [4. flow of mortar. Recommendations tion in yield stress and viscosity. which thereby cause reduc. one might wonder why the minimum fineness paste consistency at the same water-to-cement ratio and in- is not specified in C 1157 as it is in C 150 and C 595. yield stress and in C 109. Funda. Efforts have been underway for a while within (for some cements). to establish the amount of water required to obtain a plastic viscosity) exist but are not used for cement and con. it must be measured settling of aggregate due to gravity. the tests and specifications concerning consis- 4 As defined in the Webster’s New International Dictionary. Flocculation (i. A similar approach is used for various other tests. pose. Tattersall and Banfill flow is quite fluid and might be described as a batter (fluid [15] argued that fundamental measures of consistency have enough to pour or drop from a spoon). a point 10 1 mm below the original surface. Given the major influence of fineness on cement and con. involves measuring the viscosity.4 mortar. 3rd Edition. vibration. ing a standard flow table. Standard measures of test. but new instruments for measuring particle size dis. which de.10]. cement ratio and on various aspects of the cement: fineness. is substantially reduced by use of water-reducing chemical admixtures. is expected to correlate and adjusted to a standard value when testing any hydraulic with yield stress. and premature stiffening flocculation. this correlation has eluded researchers. consistency of paste using penetration resistance. cement for compressive strength (other than portland and air- The consistency of cement paste depends on the water-to. 5 The same approach is used for mortar-bar expansion tests: ASTM Test Method for Effectiveness of Mineral Admixtures or Ground Blast-Furnace Slag in Preventing Excessive Expansion of Concrete Due to the Alkali-Silica Reaction (C 441) uses a flow of 100 to 115. and ASTM Test Method for Potential Alkali Reactivity of Cement- Aggregate Combinations (Mortar-bar Method) (C 227) uses a flow of 105 to 120 and a slightly modified procedure. strength. ASTM Test Method for Air Content of Hydraulic Cement Mortar (C 185). The prescriptive specifications should include maximum Nonetheless. it is a single parameter. setting time. as mental rheological measures (for example. such as portland or hydraulic cements. ASTM Test Method for Normal Con- ticularly important to be able to measure both yield stress and sistency of Hydraulic Cement (C 187). and ASTM Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Con- crete (C 157). The corresponding performance specifications (at least in part) to the highly empirical nature of both the ce- are properties such as setting time. (C 1437). It are two procedures: flow and penetration resistance.4 clear advantages over empirical measures. cement con- the average particle size and the breadth of the distribution. High fineness increases ity of concrete made using that cement. concrete flow behavior was reported by Ferraris et al. grading. behavior during (discussed later) and. . whereas the full particle size distribution A standard consistency is presumably used in these tests to is difficult to apply in correlations with other parameters. The flow falls under rheology. The an. However. autoclave expansion. which are tested at fixed water contents). Significance tribution based on sedimentation or light scattering [14] are also The significance of cement consistency is twofold. sistency is generally assumed to affect concrete workability. and other properties are measured at a speci- methods. The penetration test. Therefore. stiffness and speeds up setting and strength development. This test is most commonly used. STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 439 measure. Standards Consistency Consistency tests are normally used to measure the amount of water required to produce some standard consistency. slump of concrete. such as consolidation using measure premature stiffening (also discussed later). ASTM Test Method for Flow of Hydraulic Cement Mortar consistency (for example. (discussed later). This test is used when preparing pastes to measure setting time cous or even solid at low stress. There Consistency refers to the flow behavior of a fresh mixture. and rate of hydration reactions. at a slightly different consistency. ment and concrete consistency test methods. Strength easy to use. to processes that involve high stress. heat of hydration. Concrete workability (slump) is assumed to correlate with crete behavior. but this modifi. specified flow (105–115 in the case of C 109). a very stiff consistency and errors due to bleeding in samples scribes the particle size distribution in terms of two parameters. Low fineness slows sistency are assumed to have a similar affect on the workabil- down setting and strength development. On the other and water requirement (discussed below). with a plunger and is achieved when the plunger penetrates to crete slump to provide a measure of viscosity. autoclave expansion. However. and shape. Unabridged. prema- ASTM Committee C01 to develop a standard test using such ture stiffening. provides for measuring the consistency of mortar us- and penetration resistance of paste) are all empirical. and concrete are fluid at high stress. The consistency of mortar and The consistency tests allow selection of water-to-cement ratio concrete depends on the consistency of the cement paste plus for use in various other tests and are satisfactory for this pur- various aspects of the aggregate: quantity. ASTM Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution (C 1012). but not for behavior during processes that involve low stress. and these are hand. entraining portland. This consistency cation has not been adopted as a standard. encouraging preliminary work on models of mortar and included in C 1157. More importantly. ASTM Test Method for Drying Shrinkage of Mortar Containing Portland Cement (C 596). whereas slump and flow relate largely to yield stress. De consistency is measured using the Vicat apparatus equipped Larrard and Ferraris [16] proposed a modification in the con. Unfortu- swer is that fineness is a physical property but a prescriptive nately. probably due specification. the study of flow.. 2. are used to ensure that the cement does not produce abnormal sistency is an important contributor to concrete workability. and final set occurs when there is no visible penetration. It is particularly important to prevent premature stiffen- amount of water to provide some standard (and arbitrary) con. Limits in setting time of cements and for the paste system in concrete. Normal set is generally attrib. Similarly. modified by admixtures. Ref 2) that set generally corre- of hydraulic cement. of 50 % of the initial penetration (C 451). ment of improved standards in this area. temperature. in which final penetration must be a minimum hydration of tricalcium aluminate (C3A). fluidity cannot be S fication. because cement con. although it is recognized that scribed previously). It is very important to predict and control setting time during gle standard flow value. mineral crete may be measured using cement paste or mortar. although there is no obvious reason for this Significance variability. False set may result (C 359) utilizes the Vicat test to differentiate between false set from hydration of calcium sulfate hemihydrate (CS SH1/2) to and flash set of mortar. chemical admixtures. The test is run at a normal consistency (C 187. There is also an optional false when the level of calcium sulfate is not sufficient to retard set specification. sponds to the end of the induction period measured using ment for standard consistency or requiring that the water isothermal calorimetry. non. concrete processing so concrete remains workable for a suffi- between cement consistency and concrete workability would be cient time that it can be placed and consolidated. which It is particularly important to show that the cement is not utilizes the Vicat needle. ing of the concrete due to false set or flash set. occurs min using the Vicat test (C 191). plastic viscosity). form gypsum (CS H2). Finally. In the previous edition of this chapter. rather than measuring the layed. regained on remixing.g. However. In the ASTM Test Method for and progressive change controlled by hydration of the cement Time of Setting of Hydraulic Cement Paste by Gillmore Needles and is closely linked to consistency. Ce. time). calorimetry is a measure of the extent of chemical reactions in Test methods are needed that provide fundamental meas. it was recom. allowing the forma. Because water requirement is such an important property It has been noted (e. or C3A3CSH12). there are major technical difficulties in measuring rheological properties of mortar and Standards concrete. ing phased out and the Vicat test being retained as the standard. As noted in Wang et al. in that they do not correspond exactly to any specific There is also a test for premature stiffening (false set or change in properties or to any specific levels of hydration flash set) of cement paste. the ASTM or flash set. rendering the mixture highly thixotropic in initial set must be not less than 45 min and not more than 375 its rheological behavior. yield stress and The hydration reactions are necessary for set but not sufficient. normal consistency paste is used Set to measure resistance to penetration by a 1-mm needle at specified time intervals. set is the time elapsed from mixing until the paste sup- setting times of concrete would correlate with setting times of ports either the initial or the final needle without appreciable cement paste or mortar prepared using the same cement and indentation. but not for more clear if tests were structured to measure consistency at such a long time that finishing or form removal is excessively de- some standard water-to-cement ratio. assuming one exists.. Flash set. Stiffening is measured shortly after prone to premature stiffening. It is logical to expect that (C 266). [18]. or cement particles. or mm. perhaps consistency tests to study the influence of other factors on con. In the case of flash set. It is also thought that false set can result S Setting time is specified for all hydraulic cements in both from the formation of excess ettringite (C3A3CS H32) soon S prescriptive and performance specifications. the cement stiffens rapidly soon after Standard Test Method for Early Stiffening of Portland Cement mixing but regains its fluidity if remixed. For blended cement tion of hexagonal calcium aluminate hydrates (C4AH13 (C 595). Unfortunately. Consistency should be described the microstructure only in a narrow range of initial conditions. In the ASTM Test Method for Time of Setting of Hydraulic Ce- ment by Vicat Needle (C 191). while set is a microstructural phenome- ures of consistency based on rheology. C 1157. using more than one parameter (for example. ASTM Test Method for Early reaction. Finally. mixing (5 min for paste and 11 min for mortar) to test for early uted to the formation of calcium silicate hydrate (C-S-H). made. There is considerable variability in flow values among the various standards. concrete from a fluid material to a rigid solid. trary. In false set. There is no obvious reason to prefer one or such correlation is not generally observed. For portland ce- after mixing. and these difficulties will continue to limit develop. but it appears that the Gillmore test is be- are recognized. paste and mortar also help assure overall concrete performance. Two setting times the other of these tests. The tests components. the hydrating cement. the period when hydration begins to requirement be reported would improve the specification for occur at a rapid rate. on the other hand. Because concrete sistency. setting times or to test the response of a particular combination consistency specifications should be developed for all hydraulic of cement and chemical admixture. as de- the same water-to-cement ratio. and this change was subsequently measurements of setting behavior. not part of not assume a particular hydration reaction based solely on C 109 as was then the case. mortar. initial set and final set. adding a specification on water require. and a further improvement would be to adopt a sin. initial set must be not less than 60 min and final demonstrated.440 TESTS AND PROPERTIES OF CONCRETE tency are particularly confusing and would benefit from clari. It is reasonable to expect the chemistry to correspond to way to develop such methods. These times are arbi. it is important to recognize that hydraulic cement. initial set must be not less than 45 min and not more . Stiffening of Portland Cement (Paste Method) (C 451). stiffening and may be measured after remixing to help differ- ments occasionally show premature stiffening. Such an approach would facilitate the use of cement set is controlled by reactions of the cement and water. The relationship. either false set entiate between false set and flash set. it is expected that setting times of concrete workability (for example. but this phenomenon has not been satisfactorily ment (C 150). There are two laboratory tests for setting time of cement paste. and efforts are under. Set is a gradual This apparatus is shown in Fig. one should mended that the flow test be a separate standard. Initial set occurs when the penetration is 25 Set refers to the transformation of cement paste. false set may result from flocculation of set not more than 600 min using the Gillmore test (C 266). The blended cement specification (C 595) admixture addition. and IV at 28 days). Improvements could also be made in the specifications concerning set. Even better would be to use the test for concrete (C 403). STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 441 191. initial set must produces a substantial increase in temperature. the limitations are even more arbitrary. the ASTM Test ture greater than about 70°C may deteriorate later due to de- Method for Time of Setting of Concrete Mixtures by Penetration layed ettringite formation. and if this heat is not dissipated. During its first few days of hydration. draulic Cement (C 186) measures the difference in heat of solution of dry cement and cement that has been hydrated for Recommendations either 7 or 28 days. Finally. it can only be verified this test for Type II or Type IV portland cement (290 kJ/kg for under standard laboratory conditions. and C 403) approximately correspond with one another. type of mixing. it set specification. Premature stiffening can also be drastically affected by cement and water contents. In the future. In 1971 there was again a limit on final Vicat set. and environmental conditions in the concrete. and 290 kJ/kg for Type time depends not only on cement content. . As noted. This test is applied to mortar obtained from direct result of the cement hydration reactions. Thus. rheological parameters might provide a way to define set that is not so arbitrary and allow separating the effects of hydration reactions from the effects of flocculation. Similar changes were made to C 595. For hydraulic cement (C 1157). since there are no guidelines to judge how and when an occurrence of premature stiffening in a cement may be manifested in concrete. Penetration resistance is then computed as applied force moderate or low heat of hydration for structures from which divided by the needle bearing area. efforts are underway to phase out the Gillmore test (C 266) in favor of the Vicat test (C 191). Concrete that be not less than 45 min and not more than 420 min using the is subject to large temperature changes will crack. Fig. uses a more typical consistency. which is more robust. and there is no false substantial amount of heat. Concrete that reaches a tempera- There is a separate test for set of concrete. it is important to use cement with a mm. water content. admixture presence. but this limit was removed by 1958. C 266. where it seems equally important. because concrete setting Type II. although there are specifications of a Type II or IV portland cement. the range of times in all three specifications for the Vicat test is wide and should probably be narrowed. more research could lead to more specific and more meaningful definitions of initial and final set based on reactions occurring during early hydration (especially in the presence of admixtures. but this limit was removed in 1983. 2—Vicat apparatus (reprinted with permission from Heat of Hydration Ref 7).6 Furthermore. false set is specified in C 150 and C 1157 but not in C 595. The heat generated in concrete is a Resistance (C 403). Interestingly. There are several improvements that could be made regarding set. C 595. While it appears that cement meeting the arbitrary limits in C 191 and C 266 produce satisfactory concrete. which can substantially affect the reaction kinetics). which are concrete by sieving coarse aggregate and uses a set of needles exothermic and occur most rapidly during the first hours and with varying diameters to measure the force to penetrate 25 days after mixing. this time less than 8 h. C 1157) for the Vicat test. includes optional limits for maximum heat of hydration using mental conditions. The portland cement specification (C 150) Although there is presumed to be a correlation between paste includes optional limits for maximum heat of hydration using (or mortar) and concrete setting time. cients of thermal expansion. For premature stiffening. but also on shear history and environ. It is not logical that initial and final set should be specified in C 150 for the Gillmore test. and produces more reasonable results [19]. concrete may produce a than 630 min using the Vicat test (C 191). in the ASTM Specification for Chemical Admixtures for The ASTM Test Method for Heat of Hydration of Hy- Concrete (C 494). and the same values of setting time should be used in the three specifications. but only initial set should be specified in all three specifications (C 150. It is hoped that the different setting tests (C this test for most types of cement if the moderate heat or low 6 In 1917 the final Vicat set in C 150 was limited to less than 10 h. and pre- specification for setting time in the ASTM Specification for venting excessive temperature rise is the basis for specification Ready-Mixed Concrete (C 94). and there is an optional false set specification the paste and aggregate have substantially different coeffi- that is the same as that just described for portland cement. there is no heat is not rapidly dissipated or during hot weather. especially if Vicat test (C 191). 250 kJ/kg for Type IV at 7 days. To ensure that such a reaction does not cause . and must be taken into account during the design of land cement may also occur due to excessive formation of concrete structures. tion (C 1157) includes limits for maximum heat of hydration the specification for blended cement (C 595) sets a maximum using this test for moderate and low heat cements (290 kJ/kg of 0. cement (C 150) sets a maximum autoclave expansion of 0.020 % at 14 days when tested some other source of calcium and sulfate. blended cements (C 595). 3—Isothermal calorimetry curve of a typical portland Expansion tends to be slow. One also be obtained concerning other aspects of hydration (for reason is that blends of portland cement and fly ash may pro- example.442 TESTS AND PROPERTIES OF CONCRETE Standards Drying shrinkage is measured using ASTM Test Method for Length Change of Hardened Hydraulic Cement Mortar and Concrete (C 157). or why the expansion is lower for blended Such a curve could be used to estimate heat of hydration at any cement than it is for mineral admixtures in concrete. portland cement. these re. 4. It is known that composition and fineness of the cement can influence drying shrinkage.15 %. specific age as an alternate method to the heat of solution Although the autoclave expansion test is used in several measurement (C 186) if a suitable test method were developed. this specification is not obvious. for some portland ce- form magnesium hydroxide (Mg(OH)2). concrete performance in cases of unsoundness due to MgO and C3A hydration [21]. in due to reaction between alkalies from the cement and silica in concrete. Yet drying shrinkage is specified only for certain blended cements (P and PA in C 595). maximum autoclave expansion of 0. the higher through reaction of calcium aluminate (C3A) or of calcium level of SO3 may be used as long as the cement does not de- monosulfoaluminate (C3A3CS H12) with gypsum (CS S H2) or S velop expansion greater than 0. and the specification for hydraulic cement (C 1157) at 7 days for MH and 250 kJ/kg at 7 days and 290 kJ/kg at 28 sets a maximum of 0. Excessive expansion ments the SO3 required to optimize strength or drying shrink- may also occur due to the formation of ettringite (C3A3CS SH32) age is greater than allowed by this limit. hydration because the hydration products occupy less volume sult from the porous nature of the cement hydration products. in blended cements containing slag. the pozzolan. drying and wet. They are to some extent restrained in concrete by the aggre. which may occur in concrete and is discussed in this chap- The significance of the tests for volume change is to prevent ter in the section on durability. the ASTM Specification days for LH). than the reactants). shrinkage due to aggregate.80 %. As previously noted. is possible in blended cements deleterious volume changes. Expansion similar to that produced by alkali-silica reac- Significance tion.80 %. The hydraulic cement specifica. The same requirement These fall under the category of durability problems and are is included in the specification for hydraulic cements (C 1157). A calorimetry curve of the type shown in Fig. the laboratory by testing at an elevated pressure and temperature. Volume Change The blended cement specification (C 595) also sets a maximum limit for autoclave contraction. expansive reactions that may occur in the cement. The specification for portland kJ/kg at 28 days for Type P). Although the test measures expansion or contraction due to any cause other than applied force or temperature change. expansion using the ASTM Test Method for Expansion of Portland Ce- may occur due to reactions between cement and aggregate. The contraction may have and expansive reactions that may occur between cement and merely been autogenous shrinkage (that is. the time at which the induction period ends. The limit was apparently im- pansion) for a number of reasons: load (creep). ment Mortar Stored in Water (C 1038). posed to prevent excessive contraction that had been reported ting cycles. duce excessive autoclave expansion due to alkali-silica reaction which correlates approximately with initial set. for which it is limited to a maximum of 0.8 %. It is not obvious why batic calorimetry. The apparatus and 28 days for Types IS and IP and 250 kJ/kg at 7 days and 290 specimens are shown in Fig. so it must be accelerated in cement (reprinted with permission from Ref 2). As noted above. but the significance of Concrete can undergo changes in volume (shrinkage or ex. though the effects may not be large. discussed later in this chapter as well as in other chapters of but there is no expansion requirement in the specification for this book. specifications for blended cements and mineral admixtures. The advantage of using a calorimeter is that information would the test is explicitly applicable only to portland cement. Creep and drying shrinkage are expected. for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a In addition. Similarly. The limit on SO3 level in C 150 (and occur due to the hydration of free lime (CaO) to form calcium discussed in the chapter on chemical composition) is intended hydroxide (Ca(OH)2) or the hydration of periclase (MgO) to to prevent such expansion. it is used in this case to measure drying shrinkage. Fig.50 %. the heat of hydration makes it convenient to Mineral Admixture in Portland Cement Concrete (C 618) sets a monitor degree of hydration using either isothermal or adia. However. Autoclave expansion test results do not correlate well with between calcium sulfate and C3A). Finally. In that case. both expansion and shrinkage. The tendency to expand due to hydration of CaO or MgO is measured using the ASTM Test Method for Autoclave heat option is specified (290 kJ/kg at 7 days and 330 kJ/kg at Expansion of Portland Cement (C 151). Excessive expansion (unsoundness) may ettringite (C3A3CS SH32). all hydraulic cements are prone to drying shrinkage. expansion during hydration of port- gate. the allowed expansion is lower for blended cement than for 3 is often used in research studies to test hydration kinetics. and the balance [20]. 4—Autoclave expansion apparatus and specimens (reprinted with permission from Ref 7). . STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 443 Fig. Therefore. and many aspects of on cement-pozzolan expansion in C 595.485 for portland cement or 0. sive reactions between pozzolan and cement. inconsistency. fineness of the cement. There should be a limit on ex. Although concrete strength may be either a specified water-to-cement ratio or a specified flow. The cracks may develop because this in- provement. expansion would be easier to utilize if it were described more permeability of hydrated cement is a function of water-to- fully in a separate method.444 TESTS AND PROPERTIES OF CONCRETE deleterious expansion in concrete. now discontinued. and 15 % in order to detect excessive expansion due to an Gaynor [24] similarly showed a good correlation between mor- adverse proportion of pozzolan in combination with portland tar and concrete strength. Cubes are It is widely recognized that concrete strength depends on the moist-cured 20–72 h in their molds. and ASTM Test Method for Flexural Strength of Hydraulic Cement Mortars (C 348). and. Many of the potential pansion due to ettringite in C 595.5 % Neville [23] reported a reasonably good linear correlation. although there is a limit meability decreases as strength increases. However. For C 595. a mortar expansion test for strength is increased by reducing the water-to-cement ratio and pozzolan used in blended cement is included as part of C 595 by increasing the degree of hydration. will provide a fuller un- is currently exploring tests for cements containing pozzolan to derstanding of strength and fracture. test is run with various proportions of pozzolan between 2. with unsoundness in concrete. small cracks develop at the interface between cement Several of the standards relating to volume change need im. measure expansion due to CaO and MgO hydration associated The significance of mortar strength is broader. either 0. there is no similar durability are improved by increasing strength. For C 1157. Finally. For ordinary concrete. aggregate moisture. the strengths of Minimal compressive strength requirements are specified paste and the paste-aggregate bond control concrete strength. [22] showed no such correlation. tensile. Porosity is reduced (and strength levels measured using C 109 are specified. The nature of the fracture process has important implications to mortar and concrete strength. The latter parameter is and C 1157. terface is weaker than the bulk paste or the aggregate. Most types strength is increased) by initially packing particles very densely of portland cement (C 150) have compressive strength and by filling remaining voids with hydration products.7 This laboratory test allows engineers. This test is usually used to detect the Based on these considerations. In C 150 and C 595. that conforms to the ASTM Specification for Standard Sand (C 778). rather than included as part of the cement ratio and degree of hydration just as is strength. but in this correlation between concrete strength and strength of mortar case it is used with a nonreactive aggregate to measure expan. measured in tension. Furthermore. The development and growth of these age requirement for hydraulic cements. however. or concrete. C 151. or compression.460 for air-entraining portland cement. . although the specification describes the test. ratio is used for portland cement. Drying shrinkage is an important issue in concrete. Thus. than its relationship to concrete strength. These strength levels are easily met It is only for high-strength concrete or unusually low-strength by cements with a wide variety of chemical composition and aggregate that aggregate characteristics become important. at the same water-to-cement ratio and degree of hydration. fineness levels. When concrete is Recommendations loaded. and the subcommittee responsible for this test development and growth of cracks. tent. then stripped and strength of cement paste. 618) nor for hydraulic cements that contain fly ash. paste and aggregate. so per- blended cement specification. Bar Method) (C 227). The lack of correlation in some pozzolan used in the cement and 5 % more and less than that studies may reflect variability in parameters such as air con- proportion. A specified Significance flow of 105 to 115 is used for all other cements. and the maximum expansion for all mixtures is 0. 5. age or thermal stresses. ASTM Test Method for Tensile Strength of Hydraulic Cement Mortars (C 190). A specified water-to-cement strength is generally most important and most often specified. or they it initiates in the hydrated cement and is affected by properties may exist in concrete before it is loaded due to drying shrink- of the hydraulic cement. on the paste-aggregate bond.05 % may be predicted from mortar strength. one would expect a good alkali-silica reaction between cement and aggregate. so it seems important to have a shrink. and both parameters are influenced by Alkali Reactivity of Cement-Aggregate Combinations (Mortar. and curing conditions. The current restriction cracks reduce concrete strength. compressive Specimens are shown in Fig. at 91 days. and on immersed in lime-saturated water until they are tested. it does not list a maximum expansion level. though the specifications utilize Strength is the property that is probably most important to only C 109 (compressive strength). The strengths of both paste and the paste-aggregate bond de. a puzzling mortar. concluding that concrete strength cement. and flexural strength). shear. strength limit for fly ash used as a mineral component in concrete (C provides an indication of the overall quality of hydrated cement. minimum average compressive pend largely on paste porosity. the test is run with the proportion of and air content of the concrete. This method tests combinations of pozzolan and influenced considerably by the composition and microstruc- cement or clinker using the ASTM Test Method for Potential ture of the cement. the aggregate strength. Standards Strength There are several tests for mortar strength (compressive. both as a general indicator of concrete quality and measurement of compressive strength of mortar prepared to assure that the concrete will perform as intended during using a graded standard sand8 and water adjusted to provide design of the structure. IL. water-to-cement ratio. for all hydraulic cements. 8 A natural silica sand from Ottawa. So requirements at three and seven days. it is expected that of the autoclave expansion test. The test for cement-pozzolan problems in cement hydration affect its strength. though some cement 7 Other mortar strength tests include ASTM Test Method for Compressive Strength of Hydraulic Cement Mortars (Using Portions of Prisms Broken in Flexure) (C 349). the area of research concerned with major problem. to portland cement is a fracture mechanics. the Weaver et al. and they are so low as to be of limited should provide a better understanding of the processes of crack- use. The values are slightly lower for Type II cement. this assumption is not without risk. performance of cement and concrete. variability. but no specification. similar to the level specified for Type I portland cement. much lower for Type LH cement. Likewise. the 7-day specified strength is uniform performance as well as a specified minimum strength 19. It would be an improvement if the strength specifications ing in concrete. with a tensile strength only about one MPa. In fact. There is a method for uniformity. the water-to- In C 1157. though some have 1. failure due to cracking. While it is probably not necessary to have additional test methods and specifications for tensile strength Recommendations of cement. For ment and growth of cracks) typically occurs in tension.0 crete is a brittle material. from air drying during aging (which reduces ten- cement. ten- while specified levels are slightly lower for Type MS cement. are generally influenced by the same parameters and much lower for Types P and S cement. compressive strength may be specified as a range (both is assumed that specifications and tests for compressive a minimum and a maximum strength value). Although there is currently were raised. strength is not constant. sistent with standard practice. 7. The Even more important is the issue of strength uniformity. types have 1. somewhat lower than the mini. the existing strength specifications are between tensile and compressive strength. ier to measure. Source (C 917). cement users would get a prod. strengths are Although we use strength in compression to describe the specified at 3. Most types of hy. the cement user would be guaranteed a ments are optional). Values are lower for each cor. but rather is affected by a number of mum for Type I portland cement and Types IS and IP blended parameters. However. For Type I. the 7-day strength level is 20. mortar. it is certainly important to appreciate the differences As noted previously. Other types of strength. that control compressive strength—in particular. Evaluation of Cement Strength Uniformity from a Single and higher for Type III cement. For Type GU hydraulic cement. cement ratio and the degree of cement hydration. much lower for Type IV cement. Therefore it ment.and 28-day requirements (some 28-day require. In this way. failure (that is.0 MPa. fracture mechanics is concerned with these strength specifications do not represent acceptable min. Con- Types IS and IP blended cement. By raising the specifications to levels more con. sile and shear. ASTM Test Method for even lower for Type V cement. trainment (which reduces compressive strength more than it and higher for Type HE cement. This is a sim- draulic cement have compressive strength requirements at plifying assumption. It ments. and paste. responding air-entraining cement. and 28 days for most blended cements (C 595). the 7-day specified is known that the ratio of tensile strength to compressive strength range is 17–30 MPa. for use as standard test methods for these materials [25]. well below strength levels obtained in current practice. no ASTM test for fracture mechanics parameters of concrete. STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 445 Fig. strength are applicable to other types of strength.and 28-day require. concluded that fracture mechanics now (after intense research hanced if they were modified to include some restriction on during the last decade) appears ripe for applications in design . level. develop- though some types do not have three-day specifications. As discussed earlier. does tensile strength). fracture mechanics tests have been developed that are suitable uct that provides acceptable minimum strength levels. ACI Committee on Fracture Mechanics of Concrete has Strength specifications for all hydraulic cements would be en. sile strength more than it does compressive strength) to air en- lower for Type MH cement. 5—Casting and crushing mortar cubes for strength (reprinted with permission from Ref 7). tenth of its compressive strength. the performance specification for hydraulic ce. in that compressive strength is much eas- three and seven days. The specified range is the same for Type MS cement. This is an active area of research and imum strength levels. Correlations were good (standard errors may be used only if it is shown that the soluble sulfate in mor. and it is not yet clear whether Recommendations fracture mechanics parameters of concrete may be estimated There is a caution in C 563 that the sulfate content shown to from parameters measured on its constituents. the higher amount may be used air content and necessitates a larger dosage of air-entraining ad- only if it is shown that the cement does not produce expan.8 %). so that tests and specifications can more clearly be tied to the critical concrete properties Significance (strength. and set). level [28]. mixture.5 %. in part to properties of the cement—freeze-thaw deterioration. but also on exceeds the amount allowed for the particular cement. Details It should be noted that even a non-air-entraining cement may in- vary according to the specification.0 % or 4. As The standard test for this determination is the ASTM Test noted in Table 1. Further research is needed to understand cussed in this chapter because it is generally determined using how sulfate affects flow and set in complex mixtures of ce- physical tests. a sur- early aluminate hydration reactions. Most importantly. Durability cussed previously. bles throughout the paste portion of the concrete. Standard Test Method for Water-Extractable Sulfate in Hy. factant that lowers the surface tension of water and thereby sta- fied by subsequent silicate hydration. fly ash in a blended cement may re- sion exceeding 0. It would be more rational if C 150 and C 595 had the same Without sufficient sulfate available in solution. There are several concrete deterioration processes that relate gite slows down subsequent C3A reaction and prevents false set. however. the amount of calcium sulfate in hydraulic cement is instead determined based on early strength. yet flow is not even measured when setting the sul- erty (and therefore not included in Table 2). the maximum sulfate allowed is 3. The mechanism of this phe. Without entrained air. No additional re. Finely ground cements en- sulfate allowed is 2. Air is proportion of sulfate affects the degree of porosity during obtained in concrete using an air-entraining admixture. alkali-silica expansion.3 % to 0. method only evaluates optimum sulfate for one-day strength The volume of entrained air in concrete depends not only and does not address drying shrinkage. Because they relate in part to cement properties.446 TESTS AND PROPERTIES OF CONCRETE practice [26]. the higher amount must be shown to cause no harm. Some tect against freeze-thaw damage depends not only on the cements. rapid C3A additional requirements when using excessive sulfate. use of various other parameters of the concrete and how it is mixed. but it seems likely that the crete will deteriorate after only a few freeze-thaw cycles. it is dis. 595. ments and admixtures. But he noted that air contents in mortar are higher than air drated Hydraulic Cement Mortar (C 265). ASTM recognizes several air-entraining ce- Method for Optimum SO3 in Portland Cement (C 563). Use of finely the level of C3A. considerable work remains to be done does not have a prescriptive sulfate level and already has a before concrete strength (or strength-related performance of limit on expansion using C 1038. produce optimum one-day strength may not provide maximum strength at later ages or at other temperatures and may Optimum Sulfate Content not provide minimum drying shrinkage. In C duce the air content due to adsorption of air-entraining agent. hydration producing C2AH8 and C4AH13 (so-called hexagonal hydrates) causes premature stiffening known as flash set. However. tion process are discussed here. though porosity is modi. es- tar does not exceed 0. Flow behavior with water-reducing admixtures is sometimes affected by the sulfate The amount of calcium sulfate in cement is not a physical prop. tion processes are discussed in greater detail in other chapters mation of ettringite after set. an observation that is difficult to explain.3 % to 4. shrinkage. In C 150. and if the amount determined according to C 563 Gaynor [24] addressed the correlation of air content in exceeds 0.020 % at 14 days according to C 1038. show a change in their sulfate requirements volume of air. one would expect to select the amount of calcium sulfate that tests to predict the influence of the cement on each deteriora- produces normal setting without excessive expansion. depend. Optimum strength pre. when Lerch Air Content showed that strength is maximized and shrinkage is minimized The air content of concrete controls its ability to withstand cy- as a function of sulfate content. the maximum fluence the air content in concrete. The ef. fate level in cement. of estimated air content in concrete were 0.50 g/L when tested according to ASTM pecially considering the inherent variability of air content tests. This ments (designated A) in both portland and blended cements. most con- nomenon is not well understood. Whether the added air is sufficient to pro- sumably corresponds to minimum porosity at any age. cles of freezing and thawing. Significance fect of sulfate content of cement on both strength and drying shrinkage was established as early as 1946 [27]. on the other hand. depending on type and on train less air than do coarsely ground cements. the higher amount mortar and concrete. as dis. However. Interestingly. bilizes air bubbles. concrete structures) can be predicted from measurements of fracture mechanics parameters. and sulfate reaction. calcium sulfate reacts with C3A and water to produce ettringite.0 %. in particular by carbon impurities in fly ash. These deteriora- ment may produce excessive expansion at later ages due to for. With sufficient sulfate. and the initial ettrin. ing on type.5 % less than this maximum. Thus of this book. but also on the size and distribution of the bub- at later ages. on the dosage of air-entraining agent (whether added directly to If the amount of sulfate shown to be optimum by this test the concrete or as part of an air-entraining cement). and if the amount determined according to ground slag or pozzolan in blended cements also reduces the C 563 exceeds this maximum. also discussed previously. contents in concrete and that many non-air-entraining cements quirement is needed in C 1157 because that specification produce mortar air contents greater than 10 %. An air-entraining admixture may be added to the concrete Standards or as part of the cement (called an air-entraining cement). the ce. . Calcium sulfate is added to cement to control hydration of C3A. flow. If too much calcium sulfate is used. To prevent this de. is reactive when combined with reactive aggregate are based pansion is generally reduced by using a blended cement (poz. The primary reaction is between C3AC SH12 fication for blended cement (C 595) and the specification for and calcium sulfate to produce C3A3C SH32. in which certain forms of silica (amorphous or for non-air-entraining cement is 12 %. These tests are only reliable. ments. In this test. Excess sulfate is added to the portland cement in the form of gypsum. STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 447 Concrete air content is also important because air cements (portland and blended). They are also dif- hydroxide reacts to form gypsum (CS SH2). This was found to be a satisfactory test for predicting the performance of portland Air Content cement in concrete exposed to sulfate ions. this reaction leads to major loss of slag in C 989. The sulfate ions. Sulfate Reaction generally by reducing its water-to-cement ratio. such as in soils in the western part of the United States. the cement. there being no substantive difference between the two procedures.060 % expansion at eight weeks. Corning. re. an optional The tests to determine whether a specific pozzolan or ground specification for portland cement. and there is concern within the sulfate concentration surrounding the concrete is high. and when calcium ferent from the levels specified in related standards for min- hydroxide is depleted the calcium silicate hydrate is progres. usually by reducing the amount of C3A in expansion at 14 days and 0. 1012). the minimum air content is 16 % and the maximum air act with the highly alkaline pore fluid in concrete to produce content is 22 %. . The maximum air content silica reaction. and C 441. C 227 with every blended cement is effective in reducing expansion. The minimum air content assures that the air-en- thumb is that every 1 % increase in air content reduces training cement provides entrained air in concrete for resist- strength of concrete by about 5 % [3]. strength as well as expansion. Both the speci- and deterioration. causing entrained option. so crushed Pyrex10 glass as the reactive aggregate. NY. the test method produces deterio- Both minimum and maximum air contents are specified ration due to precipitation of gypsum as well as precipitation for each air-entraining hydraulic cement. then further reaction may occur in which calcium at three months and 0. The rule of is specified. For air-entraining ce- reactive crystalline forms). C 227. In this test. Portland cement (C 150) relies on the optional prescriptive tack involves reactions between cement hydration products and low-alkali requirement to prevent alkali-silica reaction. as in a Type II or V portland cement or a blended These expansion levels are different than those in the ASTM cement. Two tests are used. If the environmental sulfate salt contains a cation other Specification for Concrete Aggregates (C 33). which are 100 % of the value us- sively decalcified to produce additional gypsum. specific pozzolans and slags must be tested. salt is sodium.05 % than calcium. sures that no unacceptable loss of strength will occur due to entrained air. 10 Pyrex Glass No. but not aggregate is reactive. however. The at. Alkali-Silica Reaction The specified air content is the same for portland cement Another common cause of concrete deterioration is the alkali. Ex. Hydraulic cement is tested slag used in a blended cement or a specific hydraulic cement for its expansion when combined with a reactive aggregate. insofar as the al- Sulfate Reaction kali-silica expansion of mortar bars corresponds to the occur- Attack of concrete by sulfate ions is a particular problem where rence of deterioration in concrete. and an expansion of 0. Hydraulic Cements—Chemical Properties. on one of the mortar tests used to determine whether a specific zolan and slag reduce the alkalinity of the pore fluid). concrete when exposed to sulfate ions. so there is no specified air content. Therefore an alternative test was developed for ASTM Test Method for Air Content of Hydraulic Cement Mor. ASTM Committee C09 about the validity of mortar-bar tests. (C 150) and blended cement (C 595). The alkalies (sodium and potassium)9 in concrete are typically derived from the cement. To prevent this deterioration it is also important to reduce the diffusivity of the cement paste. Alkali-Silica Reaction ally prevented through use of a low-alkali cement.10 % at six months. and length changes of mortar bars prepared from this Standards cement-gypsum mixture are measured. bars are immersed in a sodium sulfate solu- the calculated volume depending on the proportion and tion and their length changes measured.020 % the hydrated cement. there is a requirement that it be measured and reported. Because the sulfate density of each mortar constituent. the air content of mortar is measured Hydraulic-Cement Mortars Exposed to a Sulfate Solution (C by the difference between measured and calculated volume. Because the ing a low alkali cement control for fly ash and natural calcium silicate hydrate is the principal strength-producing pozzolans in C 618. there is no air- an alkali-silica gel. The maximum air content as- no more air than necessary be entrained. which are 0.020 % at 14 days for phase in hydrated cement. though expansion or cracking of the concrete. not calcium. For hydraulic cements (C 1157). The resistance of portland cement to external sulfate attack is The resistance of a particular cement to sulfate attack measured using the ASTM Test Method for Potential Expan- is important because it relates directly to the performance of sion of Portland Cement Mortars Exposed to Sulfate (C 452). generally part of the aggregate. Deleterious expansion is usu. blended cements. For non air-entraining of ettringite. making C 1012 appear more aggressive than 9 These chemical constituents and their determination are discussed in a separate chapter of this book. it is necessary to limit the amount of C3ACSH12 in for mortar expansion due to alkali-silica reaction: 0. only a maximum air content (whether entrained or entrapped) reduces strength. Thus. This gel may sorb water and swell. the ASTM Test Method for Length Change of tar (C 185). 7740 from Corning Glass Works. eral components in concrete. it is important that ance to freeze-thaw deterioration. but not for blended The potential of cement to entrain air is determined using the cement [31]. reactions that are expansive and cause cracking other specifications rely on performance limits. hydraulic cement (C 1157) include optional maximum limits terioration. or blended cement (Type MS) using C 1012 is 0. but many tests (for example.448 TESTS AND PROPERTIES OF CONCRETE C 452. and C09 subcommittee chairmen who discussed issues in this Many tests developed for portland cement have been chapter: S. and strength. and mineral admixtures). Like shrinkage. but. modification. so-called delayed ettringite formation cases. both as co-author of the chapter in the previous be testing the paste system. which was the topic of a recent RILEM report [32]. Lane on alkali expansion. is permeability. crete. which may be one cause of DEF. measurements. increasing the degree of hydration. In some cases. C 1157. Kinney on sulfate. perhaps because the excess sulfate is and expansive cements. It More knowledge is needed about the fundamental mecha. The event that the optimum sulfate exceeds a prescriptive level. and the mois- Discussion ture content. One aspect of concrete performance that we do not cur- Sulfate expansion as an alternative to the prescriptive limit rently measure. and which depends largely on properties of the on C3A is an optional requirement for Type V portland cement. these limits are only invoked in C 150 and C 595 in the There is no need to develop a standard coarse aggregate. the subcommittee responsible for the Creep is another important property of hydrated cement alkali-silica tests in concrete has been exploring alternatives for that is not currently measured. it is important to to this chapter. (DEF). In hardened paste. veloped in the near future. chemical I gratefully acknowledge the many contributions of P. so perhaps a standard test method will be de- its be relaxed [29]. occurs in the hydrated paste and is The specifications for moderate sulfate-resisting cements restrained by aggregate. Clearly. Schlorholtz and P. on the perme- Recommendations ability of the paste portion of the concrete. Studies have research and for the development of new standard test meth- shown that Pyrex is not suitable as a standard aggregate [30]. the water-to-cement ratio. and C 595 to prevent the than concrete. Finally. Hawkins on sulfate optimization. I thank two graduate cements. C 1038 appears to not be a suitable performance formance may be studied using paste or mortar. Chung and I. Creep depends on the level and dura- should be brought into conformance. and these creep deformations must be measured or predicted and incorporated into design of concrete structures. . For many years now. although the expansion level is higher and produced modify existing tests or develop new tests for blended cement more rapidly in C 452. Similarly. the permeability of concrete depends. C 1038 There are many benefits of testing paste or mortar rather and C 265 are used in C 150. C 595 limits expansion at tion of load. Sulfate Reaction like drying shrinkage. Finally. for aggregate (C 33) and for pozzolan in concrete. or the related parameter the maximum expansion at 14 days using C 452 is 0. Creep. F. concrete. apply the same test method to the same deterioration Several laboratories are carrying out concrete permeability process. limit of sulfate expansion for moderate sulfate-resisting moves through the material. creep three months and C 1157 limits expansion at six months. and may be hydraulic cement is more stringent than the level specified increased by microcracking in the paste or at the interface. additional research is needed. fineness and sulfate students at UIUC. empirical and need a better fundamental basis. C. resisting hydraulic cement using C 1012 is 0. mortar.05 % at six months and 0. Alkali-Silica Reaction Concrete permeability depends also on permeability of the The level of expansion specified for blended cement and for aggregate and of the paste-aggregate interface.10 % at six months permeability is in many respects the inverse of strength. Furthermore. As discussed in the section on Optimum Sulfate. the limit on sulfate expansion for moderate sulfate. it is an important area for further Pyrex glass as a standard reactive aggregate. or ionic species. But the results test for DEF [33]. Some tests are satisfactory for all hydraulic and S. D. and further research is needed to make such correlations. would seem useful to measure creep of cement paste or mor- nisms responsible for the various properties of cement paste. in that they method by which to measure paste or concrete permeability.040 %. Much recent research is concerned with early-age creep. Finally. either capillary pores or the much smaller gel pores. ods for both cement paste and concrete. ever. Permeability of paste depends on the volume and interconnectedness of pores. part of the cement. the degree of hydration. refers to the rate at which fluid. How- ferred because they are simpler than tests using concrete.10 % at 12 months. there is as yet no standard or specification con- the fundamental knowledge is available but just needs to be cerning deterioration in concrete due to excessive formation of applied in standards (as in the case of consistency). Many of the tests described here are on creep in concrete. Efforts are generally underway to comments on sulfate optimization. Permeability. permeability. Thus. a better strategy is needed to protect from paste or mortar do not necessarily correlate with con. there is currently no standard test reasonable that these levels should be the same. the standard reactive aggregate. cement. it is important that tests of paste or mortar Acknowledgments are able to evaluate the mixtures and proportions of materials used in concrete (typical water-to-cement levels. P. such movement takes place through the small pores. The of diffusivity.10 % at 180 days. Hawkins admixtures. Tests using paste or mortar are generally pre. Park. It seems Despite its importance. in that and for highly sulfate-resisting hydraulic cement using the it is reduced either by lowering the water-to-cement ratio or by same test it is 0. for their critical deterioration) are not. effects of mineral and chemical admixtures on concrete per. and concrete. I also thank certain C01 and water. use of excess sulfate. and it has been recommended that the cement lim. As with strength. against this deterioration process. Furthermore. Concrete deforms under load. not just combinations of cement edition and in subsequent discussions. at least broadly. Because permeability is so impor- A more basic concern regarding these tests is their use of tant to concrete durability. Norris on applied to blended cement and expansive cement without set. in most ettringite after set. Tennis on activity. also depends on the pore structure of the hydrated paste. tar in order to determine the influence of the specific cement mortar. Young. Concrete and Aggre- [8] “Standard Practice for Selecting Proportions for Normal. and Roberts. J. 23. pp. Ed. Hall. 24. pp. Properties of Concrete. Westerville. Concrete...” Proceedings.” Cement. 1999. J. 260–303. 194–219. “Fracture Mechanics of Concrete: Concepts. 15. [30] Struble. 46. S.. 1946. Concrete. Design and London. and Williamson. C. Control of Concrete Mixtures. 457–460. 42–44. 2004. Organizing Committee.. R. Kyoto.” Cement Standards— [16] de Larrard. West Conshohocken. 135–144. MI. American Ceramic Properties of Portland Cement Pastes. 27–72. Vol. W. 2003. H. Vol.” Cement.. “Energy Conservation Potential of Portland pp. B. [17] Ferraris. P. Kim.” Cement. Aggregates. 1990. K. [20] Wang. C... Vol. R. West Conshohocken. tions Related to Aluminate Control. Nishibayashi. Bagneux. M. Concrete Institute. Cements for Resistance to Sulfate Attack. pp.” Phase III. 1998.. DE 86-001926. “Evaluation of the Effect of Distribution Control. M. 1999. Concrete. S. and Cement Particle Size Distribution Control. 433–437.. 169–175. T. 1993. American Concrete Institute. 1989.. 1998. 67–70. 1991. H. pp. “The Influence of Gypsum on the Hydration and Materials Science of Concrete I. M. Cement and Concrete Correlation. W. A. and Martys. Ed. MA. 68–72. and Aggregates. F. H.” in Materials Science of [33] Day. and Aggregates. [2] Mindess. Heavy. Rheological Parameters of Fresh Concrete. J. Vol. France.. R. P. 1998.. R. Hewlett. P. Vol. Concrete. and Jensen. Pitman Advanced Publishing Program. P. Concrete. and Gartner. M.. tives on ASTM C 1157. 88–93. J. S. Westerville. Skokie.” Proceedings. NJ. Detroit. [21] Helmuth. F. pp. ASTM International. B. Eds. Concrete. W. Models Properties of Portland Cement-Based Materials. Vol. S. pp. Cement... G.. E. Whiting.. L. Prentice-Hall. MI. 2001. H. and Aggregates. E. [25] “Determination of Fracture Parameters (KSlc and CTODc) of Plain Committee 211. 2002. and Aggregates.. D. 2001. ASTM Society. 23. International. West Conshohocken. 24. [19] Struble. [31] Mather. pp..” [27] Lerch. Japan. gates. D. and Ozyildirim. 22. R. 4th ed. 8th ICAAR Local 115–120. 29.. O. NJ.. M. Portland Cement [24] Gaynor. [5] Lea’s Chemistry of Cement and Concrete.. ACerS. Concrete.. 1997. STRUBLE ON PHYSICAL PROPERTIES OF HYDRAULIC CEMENTS 449 [18] Wang. “Energy Conservation Potential of Portland Silica Fume on Alkali-Silica Reactivity. [10] Johansen. London. and Banfill. “Standard Aggregate Materials [14] Malghan. Okada.. P. [15] Tattersall.. Vol. Attack on Cementitious Systems. Haecker. 2001. pp. and Ferraris. NTIS No. ASTM International. 1978. P.” Materials and Struc- [9] Bentz. H. Concrete. Englewood Cliffs. pp. C. Detroit. IL. “Cement Strength and Concrete Strength—An Association. weight. H. Vol. C. PA. Expansion Test. G.. and Zhang. W. F. W. and Aggregates. C. L. American 2. pp. K. J. 50–57. D. Prentice. and Lum. A. 14th ed.” Cement.. de Larrard. Ground Slag. [32] RILEM 181-EAS. pp. Eds. P. 241–247. Proper.” ties. pp. H. “Guide to the Selection and Use of Evaluation. and Brockman. M.. Hydraulic Cements. 2003.. 1978.” submitted to Journal of [12] Helmuth. and Monteiro. Cement Particle Size Distribution Control.” Cement. 2nd ed. pp. 1973. PA. . 13. tures. 23. Concrete Using Three-Point Bend Tests. J. Cement-Fly Ash Blends by Introducing Alkali-Quartz Reaction. and Mass Concrete.. N. “Energy ASTM International (2005). G. “An Analysis of Factors for Alkali-Silica Reaction Studies... L.. 1663–1671. J. 95–98.. 20. Vol. Inc. PA. P. “Tests and Evaluation of Portland and Blended crete. 1991. Y.” Journal of Testing and [6] ACI Committee 225. K. and [13] Tresouthick. 1985–1986.. Cement Chemistry.. Mindess and J. and Melander. Vol. Arnold. D. 2002. OH... C. J. DE 91-007537-38.. Skalny.. “A Study of Ed. R... 2003.” tional Conference on Alkali-Aggregate Reaction. Kawamura.” Phase II. NTIS No. 2nd ed. Aggregates. Thomas Telford. S. Boston. and Aggregates. [22] Weaver. pp.. 12. Mehta. Englewood Cliffs.” Concrete Concrete Research.. and M. D. A. Dunstan. “User and Producer Perspec. and West. Vol. L. F. L. and Panarese. Ed. “Effects of Cement Particle Size Distribution on Performance [26] ACI 446. S. [23] Neville.. NTIS No. Concrete. “Fresh Concrete Bentur. Garboczi. 215–241. Early Age Cracking in Cementitious Systems.. P. [7] Kosmatka. H.” Cement. “Reappraisal of the Autoclave [4] Taylor. Fly Ash. Vol.. Isabelle.” Manual of Concrete Practice. Kerkhoff. RILEM. and Chen. Vol. 2000.” Phase I.” Manual of Concrete Practice. 1989. Concrete Structure. 358 pp. D. 126–141. S. E. “Modified Slump test to Measure Evolution and Trends. S. pp. Inc. 1990. 1993. [11] Helmuth. Rheology: Recent Developments. 1984. Skalny.. 1983. F. 1R-XX.. “Cement-Admixture Interac- C00-4269-1. A... Cement.” Cement.. “The Autoclave Soundness Test Mischaracterizes [3] Mehta. Concrete. and OH. A. [1] Tennis. [28] Sandberg. Pitman Publishing.. Portland Cement Alkali Content. and Materials. 20. Conservation Potential of Portland Cement Particle Size [29] Lane. H. F. Apparition or a Dichotomy?” Cement. The Rheology of Fresh Con. 21.-S. and Darwin. “Development of Performance Tests for Sulfate Concrete VI. V. London. H. pp. and Aggregates. 8th Interna- Affecting Particle-Size Distribution of Hydraulic Cements.. “Setting of Cement and Vol. L.. pp. Concrete. Vol. K..” Cement and and Determination of Material Properties. 1252–1292. 1974. “False Set and Flash Set— References Can ASTM C 359 Be Used to Diagnose the Causes?. International. pp. “Cement Production and Cement Quality. This discussion will focus cement chemistry. with attention to the require- that provide more complete coverage of the subject [1–3]. An under. Fe2O3. FL 33406-1501. More importantly. large kiln. The compounds cements—although emphasis will be given to portland cement (or phases) responsible for hydraulic activity are expressed because there are more constraints on chemical composition as combinations of oxides. and remains. silica. Portland Cement vides an overview and introduction to the chemistry of hydraulic cements. students. Masonry. Al2O3. and usually containing calcium sulfate. by blending a carefully-proportioned mixture of calcium. ish grinding determines the particle size distribution (effects of crete. These ments. hydraulic cements was included in ASTM STP 169C and this chapter is largely similar to that in the previous edition. a phase consisting of a combina- 1 President. the effects of chemical properties on chemical compounds. One of the major components in in ASTM specifications for these cements. there are a number of textbooks and articles on the chemical composition. ods covering the composition and analysis of hydraulic ce. which oratory personnel.” Portland- cement properties and performance in concrete.38 Hydraulic Cement-Chemical Properties Sharon M. For the reader desiring more detailed information on which are discussed in Chapter 39). other form of calcium sulfate. “a hydraulic cement produced by pulverizing portland-cement Many aspects of hydraulic cement chemistry directly influence clinker. cement is tricalcium silicate. and ferrites are formed during the clinkering reactions. The final step in the manufacturing process requires procedures. or an- cement to make ready-mixed concrete and other types of con. although many of the principles related to chemical A CHAPTER ON THE CHEMICAL PROPERTIES OF composition also apply to special cements. 2 Consultant. The information may also be of interest to lab. to temperatures of about 1500°C. and CaO are the four hydraulic cements—portland cements and blended hydraulic main oxides found in clinker and cement. West Palm Beach. and iron-bearing materials to achieve the correct Introduction chemical composition for the kiln product—nodules of portland- cement clinker. and an un. DeHayes1 and Paul D. a fascinating According to the definition in ASTM C 219. moisture and carbon This chapter describes the ASTM specifications and test meth. Tennis 2 Preface and other portland-cement-based materials will not be discussed. and fin- evaluating and predicting the performance of cement in con. A raw mix is made cation provisions and test methods. ing step to reduce the rate of the aluminate reactions. portland cement is and challenging topic for researchers. crushing and grinding the clinker nodules to make the powder The audience is assumed to be those who use or specify that is sold commercially as portland cement. The performance of portland cement documentation provided by cement manufacturers. Hydraulic cement is defined in ASTM Terminology Relat- ing to Hydraulic Cement (C 219) as “a cement that sets and Chemical Composition of Portland Cement hardens by chemical interaction with water and that is capable The chemical elements found in portland cement are generally of doing so under water. SiO2. is added during this final grind- crete products. Gypsum. engineers and specifiers.” This chapter will cover two classes of expressed as oxides. cement chemistry and concrete technology. It pro. alumina. which has been. the heat- standing of the chemical properties of cement will also aid in ing and cooling conditions can affect clinker reactivity. ments in the ASTM Specification for Portland Cement (C 150). aluminates. As the raw mix is heated. referred to as phases. will also be influenced by the manufacturing process. dioxide are driven off. Florida Materials Division. expansive. cement clinker is made by heating a finely-ground raw mix in a derstanding of the chemistry can provide insight into specifi. and researchers new to the field of would otherwise make the cement difficult to use. 450 . SC 29708-9355. and compounds of silicates. Rinker Materials Corporation. are responsible for concrete performance are described because this area is of the setting and strength development characteristics of portland more concern to the user than a detailed discussion of testing cement. The objective of The properties of portland cement can be varied to some this chapter is to provide sufficient information about the extent by using raw materials of different proportions or chemical properties of hydraulic cements to enable the user to chemical composition and thereby changing the composition interpret ASTM specifications and understand the technical of the resulting clinker. Fort Mill. The single-letter abbreviations will only be used in the name of the phases. CaO.181CO2 . MgO 2.188CO2 C2S 2. individual oxides are abbreviated as the SiO2 is distributed between the two major calcium silicate a single letter. the term “phase composition” is often used (1) to indicate the composition of clinker and cement. be- Fe2O3 3.867SiO2 0. and the phrase “phase composition” will be used when discussing the compounds (phases) found in clinker and cement. In addition.5].5 formed instead of C3A and C4AF. and C4AF.600SiO24. C2S. but it is quite possible to cement will be from calcium sulfate added during the grind- comprehend and discuss the chemical properties of cement ing process. Expressed as Potential Phases Oxides Abbreviations Phase Percentage SiO2 S Al2O3 A C3S 54 Fe2O3 F C2S 22 CaO C C3A 6 MgO M C4AF 9 SO3 S¯¯ Na2O N K2O K CO2 C¯¯ H2O H paper. In C3S 4.0 % free other primary phases are C2S (2CaOSiO2). it is important to note that the phase com- on a number of assumptions [4]. the cement contains 64. but a cement chemist often expresses 114. a phase is a chemically impure compound.2 SO3 2.1 cause a solid solution—expressed as ss(C4AF C2F)—will be CaO 64. it is necessary to know how much of each phase is present. the phase composition is given (Table 2b). In addition to the oxide results (Table 2a).65 C3S4. C3S and C2S. DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 451 TABLE 1—Cement Chemist’s Shorthand for TABLE 2b—An Example of a Typical Portland- Oxides Cement Composition. 3CaOSiO2 becomes C3S.64. the Bogue cal- Phase Composition culation has been used to calculate the “potential” phase com- Although the chemical composition of a cement is expressed in position.650Al2O3 1.100Al2O3 1. about 2 % of the CaO in the be threatening to the nonchemist.859Fe2O32. Similarly. Equations 3 and 4 are Al2O3 4. and C4AF. the formula for tricalcium methods of chemical analysis.071CaO7. and also that the four major SiO2 22.702Fe2O3 (5) Na2O equivalent 0. C3A.3 modified if the ratio of Al2O3 to Fe2O3 is more than 0.479Al2O3 (6) 2. To fur- The oxide analysis in Table 2 shows 22. this procedure is based terms of its oxides. C3A. that is CaO that was not combined during the and C4AF (4CaOAl2O3Fe2O3). referenced in ASTM standards using only the abbreviations. There are many variations of position of a cement is not adequately described by a list of ox- the Bogue calculations [for example 1. and silicon dioxide (SiO2). The oxides are listed in reports in the ap- tion of calcium oxide (CaO).852SO35. C2S. Developed by Bogue in 1929. The C3S. These “impurities” are part of the materials that make up composition is more difficult.5 % minor oxides in portland-cement clinker are listed Table 1. Standard Test Methods for Chemical Analysis of Hy- it as 3CaOSiO2.043Fe2O3 (4) Cement Composition. Note the use of the term phase is used instead of com- Bogue Calculations pound. The abbreviations used to describe the major and phases. In this 1. but ther simplify the notation. lime (f-CaO).0 % total SiO2. the phrase “chemical composition” refers to the oxide analysis.600SiO2 6. but it is distributed among each of the major phases. three units calcium oxide and one unit silicon dioxide. These chemical formulas can clinkering process.6 ss (C4AF C2F) 2.852SO3 5. Using these abbreviations. In order to correlate chemical the raw feed and actually help make the cement more reactive. Using proximate order in which they are determined by classical standard chemical nomenclature.0 phases are pure C3S. Historically.430Fe2O3 2. C3A (3CaOAl2O3). as recommended in ASTM C silicate is written Ca3SiO5. but the determination of the actual phase ments. Expressed as Oxides Oxide Percentage The use of these equations assumes that the clinker reactions go essentially to completion. composition and cement performance. and cement Determination of the oxide composition of a cement is fairly phases like C3S contain several percent by mass of other ele- straightforward. There may also be about 1. indicating that the compound is composed of draulic Cement. Table 2 shows the chemical analysis equations are used in ASTM C 150: results for an ASTM Type I/II cement.692Fe2O3 (3) TABLE 2a—An Example of a Typical Portland- C4AF = 3.718Al2O3 cement chemistry. but the following ide weight percentages.071CaO 7.7544C3S (2) C3A 2. However. These do not usu- C 150 included TiO2 and P2O5 in the weight percentage of ally have a significant impact on performance. the Bogue calcula. but x. As mentioned The calcium silicates react with water to form C-S-H. composition of C-S-H may vary. Alite is the mineral name given z 3. These hy- TABLE 3—Nomenclature for Major Clinker dration reactions and compounds are not specifically part of Phases ASTM cement standards. sive strength) and early strength gains. impure phases are more reactive than the pure C3S (y z ) H2O → Cx SHy z CH (7) compounds. . The version of the Bogue calculations used in ASTM C amounts of silicon and magnesium. introduction. The (aluminate gypsum water → ettringite) alkalies. but Jeknavorian Al2O3. the results can be effectively used to compare generally secondary and too complex to be covered in this cement properties. The principal type of aluminate in nor phases and the incorporation of impurities into the major clinker is referred to as cubic. stabilizing the orthorhombic form (also 100 %. and potassium. and the reader is referred to a num- Incorporation of Substituent Elements in ber of references for more detailed information [1. with and without sulfate. and that it is necessary to differ. Histori. an previously. The value used for Al2O3 now does not include these and Hayden [7] have reported one example where excessive trace elements. and the -polymorph of belite is the predominant form in commercial C3S 3CS H2 26H → C6AS H32 (8) clinker.8–10]. paste. P2O5. and z are not necessarily integers [3]. The mineral names of the clinker phases are shown in The C3A participates in the reactions affecting setting Table 3. and hyphens are used between Impurities in the C3S crystals. ment produced at a single plant where the raw materials and kiln conditions do not change radically over time. The C2S also hydrates to form C-S-H and CH. calcium hy- forms of C3S (polymorphs have essentially the same chemical droxide. because the Bogue calculation does not account for mi. and they will have some affect on cement performance. the reaction of siliceous Tricalcium aluminate aluminate C3A phases present in supplementary cementitious materials (such Tetracalcium aluminoferrite ferrite C4AF as fly ash. and that the results are not when cement is mixed with water. SrO. of the quantity from C3S hydration. In commercial clinker. the following reaction occurs: lite exists in a number of polymorphic forms. Studies on impurities in clinker phases tions have the advantage of being easy to calculate.452 TESTS AND PROPERTIES OF CONCRETE The sum of the four major compounds will be less than crystal structure. and will also (alite water → C-S-H calcium hydroxide) incorporate Al2O3 and Fe2O3. Ferrite contains significant phases. A byproduct of the hydration reaction is CH. silica fume. is an approximation of the reactions of these materials in cementitious systems. however differences could arise due to these amounts of zinc caused severe retardation of setting and hard- elements when comparing past data. there are a number of ways of expressing to better understand the effects of composition on cement the composition of a cement. be. ground granulated blast furnace slag. C3A in clinker can contain iron and silicon. erature. For example. Sulfur. The composition. that is. but a different crystal structure). sum. Like alite. and their effects on cement performance are appropriately. sodium and potassium. fluorine. and other elements. and trace metals can also affect Although based on many assumptions. iron. the Bogue equations do not take into account the amorphous calcium silicate hydrate gel that is primarily re- incorporation small quantities of other elements in the major sponsible for the strength development of hydraulic cement phases. C3S undergoes the following reaction rities. and Tricalcium silicate alite C3S durability. y. entiate between oxide and phase compositions. hydration and characterization of hydration products are active fields of research. sodium. the mineral form of C2S found in clinker. Clinker Phases There are a few reactions that should be reviewed in order As has been shown. which includes C3S in all commercial clinker. another source of error arose in the past because ASTM and various sulfur compounds are examples. ening. and calcined clays) with calcium hydroxide. lead to a variety of polymorphic nite. When used are numerous. and many other elements have been identified within the C3S where the composition of C-S-H is expressed as Cx SHy and x phase in portland cement [6]. Monoclinic and quantity of CH produced by C2S hydration is about one third triclinic are two of the polymorphs of C3S discussed in the lit. called alkali-aluminate). Dicalcium silicate belite C2S The pozzolanic reaction. strength. but their chemistry underlies many Name of Pure Compound Mineral Name Shorthand test methods designed to predict the performance of cement: performance with respect to flow properties. (early stiffening with no substantial development of compres- Belite. the oxide abbreviations to show that the composition is indefi- ing conditions in the kiln. In general. 150 also does not correct for the amount of f-CaO present in Clinker contains other impurities that originate from the the cement and so may overestimate the value for C3S. All of the hydration reactions involving the clinker phases are exothermic. Mn2O3. The actual to impure C3S. it Hydration Reactions should be borne in mind that the Bogue calculations give only Hydration refers to the chemical reactions that take place the potential phase composition. cement performance. Mathematical modeling of always close to the true phase composition. also influence the aluminate The C3A can also participate in many other reactions. the phases contain these impu. as well as the heating and cool. C3S may contain up to 2 % of MgO. and the amount of heat generated is an important property of the cement. performance. can in. raw materials or from the kiln fuel—TiO2. cally. Chlorine. This is especially true when evaluating ce. In the presence of gyp- corporate aluminum. . hydration tives. and 90 % completion at one year. IV.5 ..5 2. .S.. function similarly to C3A.0 Insol. calcium sul- generates less heat than C3S. for most meability of the mortar or concrete. II...5 3. . 40 . max. 4. C3A contents are lower because these phases are liquid at kiln mately 70 % of the C3S in portland cement will have reacted by temperatures and control of the amount of liquid phase is im- 28 days.0 6. or other forms of calcium sulfate.. . C4AF contents tend to be higher when early setting characteristics. ASTM C 150 also includes Types I-A. ASTM C 150 permits the addition of water.. Thus. % . max. the A indicates that an air-entraining C2S admixture has been interground during the manufacturing Belite hydrates more slowly than alite. C3A hydration products are the main participants in the additional C-S-H is produced (if the hydration reactions con. C2S contents of U. ASTM Types I. by mass..3 2. Because the properties of the major phases are generally similar in different portland cements..75 0..0 SO3. is CH S → C-S-H (9) needed to control the otherwise very rapid hydration of C3A (calcium hydroxide silica → calcium silicate hydrate) and to avoid flash setting. A report by Chiesi. 25 (C4AF C2F). DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 453 other compounds are present in these materials. C3A contents of U... % . reactions leading to sulfate attack [11]..0 3..75 C3S. The chemical requirements for portland cement are summa- tents typically range from about 45 % to 65 %.. fate. ACI Committee Report 225 [11] includes a discussion on heat of hydration.. % 6. Taylor [1] reports 30 % complete hydration at and air-entrained cements. For Type V cements they range Contributions of the Major Cement Phases to from trace amounts of C3A to about 5 %. % .3 when C3A 8 % 3.0 . which can increase the strength and decrease the per. 6. % when C3A 8 % 3. In the USA.. limestone. and Gartner suggests that the strength- C3S producing capabilities of C4AF can be enhanced with the use of Alite hydrates rapidly and is responsible for early strength and chemical additives [14].0 3..0 6. .. 35 .. MgO. by mass.. tion for Processing Additions for Use in the Manufacture of TABLE 4—Standard Chemical Requirements for Portland Cements (From ASTM C 150... Cement color is influenced by the ing is a summary of the properties of the four major phases. % 3..0 3.. with an rized in Table 4. C3S con.0 3. about 9 %..0 2. and also produces less calcium hy... Follow. and processing additions (usually grinding droxide... Gypsum.. and virtually 100 % by one year.. min.. portland cements are controlled by the cement type.75 0.. and the heat of hydration of a cement Chemical Requirements IN ASTM C 150 is related to its C3S content.. Res. For Type II cements they range from about 4 % to 8 %. The idealized C3A reaction is: The aluminate phase influences setting and early strength development. 8 15 7 5 [C4AF 2(C3A)] or . The chemical requirements are the same for regular later age strength. II-A. max.. C2S. portland cements range from about aids and pack-set inhibitors) conforming to ASTM Specifica- 8 to 28 %. max. % 0. 6. through about seven days. but it may provide a basis for control of performance of cement. and average about 6 %. III.0 . Taylor [1] reports that approxi.75 0. C4AF con- with higher C3S contents will generally show higher strengths tents range from 3 % to 13 %. Fe2O3. C3A. C2S.0 6.. The hydration reactions involving aluminate contribute significantly to heat of hydration of a ce- A benefit of using supplementary cementitious materials is that ment. Myers. tinue). . . % .. and contributes mostly to process.. .. with an average of Cement Performance about 4 % [12]. .S. and III-A... C3S hydration also generates more heat than C2S hydration.. Table 1) Cement Type I II III IV V Al2O3.5 . Portland cements portant to clinker burning and kiln operation. the approximate effect of C 4 AF changing the cement composition can be predicted and can The contributions of C4AF are not well-understood. averaging about 8 % to 10 % [12]..0 6. both of which can improve Type I cements they range between 5 % and 13 % and average concrete durability.5 . with an average value of about 19 % [12]. max... 6. LOI. % . max.75 0. max. This table shows the compositional limits for average of about 55 % [12].. . and V. % .. max. composition and amount of the iron-containing phase. In addition to air-entraining addi- 28 days for C2S. max. The primary source of LOI in cement to exceed the maximum in the table if it can be shown modern cements is from water combined in calcium sulfate de.3 properties limited for all types of cement will be discussed first. TABLE 5—Relationship Between C3A and entraining and processing additions used in processing. Type II 8 3. % as the potential phase composition. An additional strength at 24-h. or possibly from contamination during clinker re. ways be necessary to add some form of sulfate in order to meet centage lost when portland cement is heated at 950°C. was fixed at 1. Insoluble residue was presses the amount of sulfate in the cement. a general purpose cement. partic- and the most common source is silicate impurities in the cal. which defines the “optimum SO3” based on compressive bined water from gypsum is contributing to LOI. 563). The present method for determining optimum SO3 stone (CaCO3). SO3 levels.75 % in 1941 present in the one of the forms of calcium sulfate (gypsum. maximum of 3.454 TESTS AND PROPERTIES OF CONCRETE Hydraulic Cements (C 465). The amount required is portland cements contain a small amount of insoluble residue. f-CaO hydrates to All ASTM types show a limit on MgO of 6 % by mass. that the compressive strength will be improved at the higher hydrate or gypsum (CaSO42H2O) and carbon dioxide in lime. IV. II. If requested. than 0.0 whereas Types II. [15]. Insoluble residue may result from fates will be included in the measured SO3 content. It is usually a silicate or alumino-silicate material. The SO3 limits are all maxima. a portland cement containing 5 % is ASTM Test Method for Optimum SO3 in Portland Cement (C of gypsum has a theoretical LOI of about 1. free lime (f-CaO) not combined during burning is mizing other properties such as setting time and shrinkage.75 % limit on insoluble residue must be considered when low C3A level in Type V cements. During storage. the manufacturer must supply in writing all relevant information about the air. % SO3. it will re- raw materials that did not combine completely in the burning duce the amount of SO3 that needs to be added. as well Cement C3A. and All ASTM types of cement are subject to a maximum limit on in. The MgO form Ca(OH)2 and it may absorb CO2 from the atmosphere to is limited because of concern about disruptive expansion of form CaCO3. but was raised to 5 % in 1926 and to 6 % in 1976 [15]. show that the added SO3 does not cause expansion greater sum is lost through dehydration during the mill-grinding step.020 % as demonstrated by ASTM Test Method for Ex- Additional moisture may be picked up from the atmosphere pansion of Portland Cement Mortar Stored in Water (C 1038). V.85 % in 1916 and was lowered to 0. The SO3 may be first limited to 0. The SO3 limit. These reactions can be quite com- ASTM cement specification proposed in 1902. SO3 contents may also vary when opti- For example. III. if only the com. SO3 (From ASTM C 150. because of the The 0.5 of the cement affects the resulting properties of concrete.0% today (2. although the limits differ for Types II.5 I. LOI was added to the specification in 1917 to preclude the presence in Optimum SO 3 the cement of deleterious amounts of carbonate minerals such Careful examination of Table 1 in ASTM C 150 shows a note as limestone and dolomite [15]. This same rationale holds for determining the level of acceptable purity of calcium sulfate the SO3 limits on Types I. These reactions contribute to a higher LOI. has the fewest restrictions. some of the combined water from gyp. partic. The SO3 content ex- solved in strong acid or alkaline solutions. Sulfate is process. In practice. The phrase “optimum SO3” may be misleading. Note D allows the SO3 content of the main contributors to LOI. anhydrite). As a precaution against oversulfating. Table 1) The limitations in Table 4 are based on the oxides. The maximum plex and may affect the cement performance [16]. loss on ignition is the weight per. SO 3 All types of portland cement have a limit on the percentage of Insoluble Residue allowable SO3. ments have the lowest allowable SO3 content.75 % in 1904 [15].5%. there are no restric- Loss on Ignition tions on the minimum SO3 contents. However. highest limit because it usually has a high C3A content and high fineness. and from water sprays used to cool grinding mills. hygroscopic and readily absorbs water. it will almost al- Commonly abbreviated LOI. Type V portland ce- cium sulfate and limestone added during the finish grinding. the portion of the cement that cannot be dis. MgO content clinker components. strength at later ages. Set at a the physical requirements in ASTM C 150. The purpose of this limit is to preclude deleterious hemihydrate. related to the fineness and composition of the cement. particularly C3A and C3S are subject to was one of two chemical properties limited in the original prehydration during storage. as different Another source of LOI is moisture picked up from the SO3 contents may maximize early strength than maximize clinker components during storage as well as during grinding. but it may also be present in other amounts of siliceous and argillaceous components from being forms. with Type III having the and limestone sources for portland-cement manufacture. percentage was first set at 4 %. one of the original two chemical require- soluble residue. Furthermore. Type V 5 2. cements 1. ularly the C3A content as shown in Table 5. 5% for Type IV cement). All that take place during hydration.3 Limitations Common to All ASTM Types of Portland Cement MgO ularly if stored outside and exposed to rain. III.3 % LOI would result from 3 % addition of limestone that exceed ASTM C 150 Table 1 limits must also be tested to (CaCO3). Type Type I 8 3. and III. The different types of cement have different oxide limitations because the composition Type III 8 4. the optimum SO3 content of a cement may be . SO3 may be present in clinker in the form of alkali sul- present in portland cements. and V have more limits. Water and carbon dioxide are concerning the SO3 limits. The chemical Type IV 7 2. added to regulate the initial setting and hardening reactions claiming. ments. Other concrete that may occur if free MgO hydrates. For example. % 10 6 9 4 4 for Type III are 8 % for moderate sulfate resistance and 5 % C4AF. The results reported in the test certificate (also called Type III portland cement. A Type I cement could have required to control the C3A reactions in a finer-ground cement. DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 455 influenced by the use in concrete of chemical admixtures. Chemical composition will also be affected by market demands. in the future. Reference to Table 4 shows that there are and are often referred to as Type I//II cements. such as. For Type II. The use of pozzolans and granulated blast-furnace ide. the SO3 % C3S by mass. it is also acceptable to have a very low C3A content because there is no minimum specified in Type I Portland Cement ASTM C 150. and the C3A ample. the conditions are met. LOI. States. blended cements. Type III Portland Cement tion. Cement composition is influ. the sum of C3S and C3A may be limited to 58 % to help ensure moderate heat of hydration. sup. It is possible that. but research has shown that limiting C3A may not always provide sufficient protection against sulfate attack [17]. the major contribution of limestone to the clinker. along with the calculated phase composi. . and SO3. signed for general use when moderate sulfate resistance or moderate heat of hydration is desired. Accord. cement compositions tend to interest in low-heat cements for applications such as roller- be more alike throughout the country than might be ex. This is be- erties specified for any other type are not required. % 54 55 55 42 52 The optional chemical requirements in Table 2 of ASTM C 150 C2S. most common cement. The hydration products of C3A changes to other properties may also occur. Type IV is not readily available in the United ical to make a high C3S cement (C3S uses more calcium ox. Opti. % 8 11 8 15 13 for high sulfate resistance. ment. Type III is allowed higher SO3 contents than Type I portland cement is to be used when the special prop. Table 1. Cement Type Optional Chemical Requirements I II III IV V C 3 A and C 3 S C3S. but typically it will be 55 to 60 Also. cause Type III cements generally have greater surface areas (to ing to ASTM C 150. or heat treatment. The upper limit of 8% on C3A also has the purpose of reducing susceptibility to Changing the chemical composition causes a change in the sulfate attack. As the construction industry strives for higher early Type V Portland Cement strengths. compacted concrete. a plant with readily available high-purity limestone content can be no more than 7 %. can react with sulfate to lead to deleterious expansion. % 18 19 17 32 22 apply only when specifically requested. in addition to there is a change in manufacturing conditions or chemical limits on insoluble residue. as mentioned in the discussion of optimum SO3. Contents of Al2O3. Many cements meet both Type I and Type II requirements given in Table 6. there may be greater demand for cements with Type V portland cement. For ex. chemical composition cannot be so extreme as to preclude meeting physical requirements such as strength and setting Type IV Portland Cement time. Even though the of the country. When composition is changed is desired. Economies of raw material sourcing must be bal. properties of a cement. facturer’s certification will normally show the complete chemical analysis. can be exceeded if certain other there are theoretical and practical limitations. has reduced the demand for Type IV ce- anced with manufacturing costs—it takes more energy to pro. Type II Portland Cement plementary cementitious materials. Type II cement is decomposition of the clinker. Type II portland cement has several restrictions on composi- mum SO3 testing for a particular cement should be repeated if tion. tent close to the maximum. for Types I through V are I. Designed for low heat of and a very expensive silica source may find it more econom. even if they have the same C3A level. As long as the physical requirements are met. strength. Even though ASTM C 150 does not limit C3S. In addition. a minimum of 40 % C2S. Optional limits on C3A C3A. Therefore. Types I and II. and Fe2O3 are limited. a manu. has a maximum limit of 5 % C3A and 25 % for to maximize one property. Examples of the phase composition. The upper limits on ASTM C 150 Chemical Requirements for Al2O3 and Fe2O3 restrict the amounts of C3A and C4AF that can Different Types of Cements be made. hydration. has no additional restrictions other than a 15 % C3A correlating cement properties with concrete performance maximum. The C3A limit for Type V in ASTM C 150 does not apply when the TABLE 6—Average Phase Composition for sulfate expansion limit. In many areas only a few limitations on phase content. Type II cements have replaced Type I as the chemical requirements are not listed for each oxide. While some Type III cements may have a C3A con- characteristics. a C3S content of 20 or 70 %. an optional physical requirement. Type II cements also meet the chemical requirements for Type calculated by the Bogue method. to less than 35 % C3S. than slags. discussed in Chapter 39. either as mineral admixtures or as components of does C2S). Type I has no restrictions on the major meet the higher strength requirements). for use when high early strength is mill report or mill certificate) are a good starting point for desired. there may be renewed duce C3S than C2S. The compositions of Type IV portland cements are restricted enced by the composition of available raw materials. limits in ASTM C 150. is ASTM C 150 Portland Cements [after 12] specified. pected. for use when high sulfate resistance higher C3S and C3A contents. leading to lower heat of hydration. and more SO3 may be oxides or the phase composition. for example. the quantity [C4AF 2(C3A)]. It was generally agreed • slag cement (Type S). The MgO specify the performance required? However. components in aggregate form a gel that leads to concrete ex. The five main types ments. and natural pozzolans are examples of pozzolanic materials.0 . However. It provides for portland or blended cements that meet performance requirements. draulic Cements (C 595). Table 7 summarizes the chemical requirements. performance requirements for cement can be easily measured zolan-modified portland cements.0 . It should be noted that an alkali content of below 0. max. calculated as (Na2O 0. with water and a source of CaO or Ca(OH)2. SO3. Blast-furnace Performance-Based Specification for slag may have latent hydraulic activity as well as pozzolanic Hydraulic Cements properties.0 4. The SO3 limits for all types of suming. The most common non-portland cement (or port. reactions (Ca(OH)2 is produced when portland cement hy. a parallel effort was underway in are: ASTM Committee C01 to develop a performance specification • portland blast-furnace slag cement (Type IS). ASTM C 1157. rather than pre- There are five major classifications of blended cements.0 2.456 TESTS AND PROPERTIES OF CONCRETE Low Alkali Limit The optional requirement for low-alkali cement limits the equiv.0 % for slag cements.60 % Hydraulic Cements (From ASTM C 595. These are summarized in a subsequent section. those for blended cements in C 1157..0 %. is a relatively new specification for cements Hydraulic Cements for general construction.658K2O). limit for blended cements. but grinding the constituents with portland cement clinker and examination and tracking of chemical properties can provide calcium sulfate.. 5. TABLE 7—Chemical Requirements for Blended alent alkali content. For these reasons. IS. Standard Performance Specification for Hy- ASTM C 595 Specification for Blended draulic Cements. % 1. % 3.. [18]. to 0.0 to 5. from 3. Pozzolans are high in SiO2 and may also contain eral Admixtures in Concrete. Table 1) maximum. Natural pozzolans and silica fume (also called mi.” significant amounts of Al2O3. and the rationales for most of these requirements are tion of specifications: why indirectly specify a property of a ma- similar to those requirements for portland cements in ASTM C terial through prescriptive requirements when you can directly 150. ASTM C 150 and that the optimum SO3 content is higher than the limit. PA. but there is no limit on MgO by a test. ble residue is limited to 1. based on the per. Loss on ignition varies • general-purpose hydraulic cement (Type GU).0 4. The development of a There are only a few chemical requirements for blended performance-based specification is a logical step in the evolu- cements. crosilica) are examples of other materials that may be used in The chemical composition of a pozzolanic material cannot blended cements. Fly ash.0 Sulfide sulfur.. in 1998. and because of the relatively con- blended cements may be exceeded if it can be demonstrated servative nature of the construction industry. Blended Hydraulic Cements Loss on ignition. and performance testing is usually more time-con- content for slag cements. but it acts as a hydraulic cement when mixed vidual types of finely-divided mineral admixtures (C 618. portland cement is the source of CaO for the pozzolanic these materials. modified to include portland cements.. contribute to the strength-gaining properties of same as for portland cements. ash may contain unburned carbon that is measured in the LOI land-cement clinker) materials used in blended cements are determination (the carbon can affect the efficiency of air- the supplementary cementitious materials blast-furnace slag entraining admixtures). max. Blended cements may be made by inter. % 3. that the redundancy in having two. covered only blended ce- centage of portland cement in the mixture. almost identical perform- • pozzolan-modified portland cement [Type I (PM)]. dele.. IP. at present not all content is limited to 5. for portland cements with the requirements being similar to • portland-pozzolan cement (Type IP and Type P). Briefly. max. approved in 1992. or by blending the constituents with portland a means to check product uniformity. max. ASTM C 1157. microsilica. A review of the history of the alkali limit is given by Cement Type Frohnsdorff et al. C 1240) provide useful guidelines about the composition of ments.. C 595 continue to be used much more extensively than C 1157. . the alkali limit is intended to eliminate deleterious expansive action arising from alkali silica I(PM) reaction (ASR).0 4. IS-A S.0 Blended hydraulic cements consist of two or more inorganic constituents (one of which is normally portland cement or finely-ground portland-cement clinker) that.60 % is not always sufficient to prevent deleterious MgO.0 5. “Chemical Composition of Pozzolanic Materials Used as Min- drates). at the time. SA IP-A pansion and cracking. although pozzolans such as fly the cement.0 expansion of concrete containing reactive aggregates. In blended ce. I(SM) I(PM)-A terious ASR occurs when cement alkalies and reactive silica I(SM)-A P. separately or in combination. % 2. Discussed in more detail in other chapters. the standards dealing with the indi- tivity of its own.0 1. The first edition of some of these classes are further subdivided.0 % for all portland-pozzolan and poz. C 1157 was • slag-modified portland cement [Type I(SM)]. always be directly related to the performance of concrete. % . but there is no Six basic cement types are considered in ASTM C 1157: limit for pozzolan-containing cements. C 989. and scriptive (usually chemical) requirements. max. The source of LOI for blended cements is the • high-early strength cement (Type HE). and ance specifications was unwarranted and. chemical requirements in ASTM Specification for Blended Hy- A pozzolan is a material that has little or no hydraulic ac. . In addition to the cement.. Insoluble residue. Insolu. There is no total or equivalent alkali and fly ash. Small amounts of other oxides may For Types LH and MH. SiO2. and there are also limits on SO3.and low-heat of hydration cements (Type MH 989) uses the slag-activity index based on actual compressive and Type LH). For Class C fly ash. and determined by a modified version of C 227 Hydraulic Cements [Test Method for Potential Alkali Reactivity of Cement-Aggregate ASTM Test Methods for Chemical Analysis of Hydraulic Ce- Combinations (Mortar Bar Method)]. a maximum and a mini. heat of hydration is measured by also be present. Al2O3. ments. Generally. Class N. Air-cooled slag has lit. have a very high specific surface area [21]. and specifying a strength range (that is. has a lower glass content. typically produced from burning lignite or sub-bituminous coals. have not been fully successful. Average of Maximum Difference Duplicates from SRM Ground Granulated Blast-Furnace Slag Component Between Duplicates Values (/) Blast-furnace slag is the nonmetallic product formed during SiO2 0. Silica fume is a by-product from the reduc- Default minimum compressive strength requirements are tion of quartz (or quartz and iron) with coal to produce silicon listed in Table 1 of C 1157. A few re.10 0. tuffs and volcanic ashes or pumicites. for Types MS and HS. Table 1) properties in addition to being pozzolanic. include siliceous. An Option R. Al2O3. The modification consists ment (C 114) describes specific chemical analysis procedures of using crushed borosilicate glass as a model aggregate. pelletized blast-furnace slag. and some cal.10 constitute 95 % or more of the total oxides [20]. for Compressive Strength of Hydraulic Cement Mortars) is and ferrosilicon alloy production produces silica fume with used to measure the compressive strength. Attempts Na2O 0. fineness and air content are not in. C 109/C109M (Test Method icon alloy production usually contains more than 90 % SiO2. moisture. well-integrated basic scheme of analysis for hydraulic ce- ral pozzolans for use in concrete. is covered by chemical composition. reported for informational purposes. consisting mostly of silicates and aluminosili- Al2O3 0. The sum of SiO2 and Al2O3 must equal ASTM C 114 requires that individual analysts demonstrate at least 70 %. ing the reference test methods. K2O 0. opaline cherts and expensive analytical instrumentation. as long as it can be Used as Mineral Admixtures in Concrete demonstrated that the method achieves the required levels of precision and bias. amorphous. Fe2O3 0. which is cooled SO3 0. and Iron Blast-Furnace Slag for Use in Concrete and Mortars (C • moderate. satisfactory shales. ASTM C 1240. sonably-equipped chemical laboratory and do not require materials such as diatomaceous earths. and Grout. The major oxides. or siliceous and aluminous. but may be used as aggregate. typically produced from the burning of an.10 0. because C 186 (Test Method for Heat of Hydration of Hydraulic Ce. the sum of these same three oxides must equal 50 % or more. blast-furnace slag can have a glass content of MgO 0.03 0. Silica Fume quirements will be discussed here. low reactivity with alkali-reactive aggregates. Silica fume is a very reactive pozzolan. CaO 0. must also meet a 70 % minimum sum of SiO2. The physical requirements for these cements are largely similar to their counterparts in C 150 and C 595. CaO. such as the ratio (CaO MgO Al2O3)/SiO2. thracite or bituminous coal. Class F fly ash. Mortar.2 iron production. for both portland cements and blended hydraulic cements. Reference test methods are “long ac- Pozzolan for Use as a Mineral Admixture in Portland Cement cepted chemical test methods which provide a reasonably Concrete (C 618) gives the requirements for fly ash and natu.” Reference test methods can be performed in any rea- ural pozzolans. Silica fume from sil- mum strength) at a particular age.3 quenched. but these constraints are in- . the very fine SiO2 particles quickly react with Ca(OH)2 and ment) while. results can only be obtained by experienced analysts. also called microsilica. and MgO. these characteristics are required to be determined and for Use as a Mineral Admixture in Hydraulic-Cement Concrete. The scope of ASTM C 114 states that any method may be Chemical Composition of Pozzolanic Materials used for analysis of hydraulic cement.16 0. If water.20 0.16 0.and high-sulfate resistance cements (Type MS cluded in some specifications. and their ability to achieve acceptable precision and bias when us- LOI. varying amounts of Fe2O3.2 cates of calcium. strength test results to characterize slags. mined by C 1012 (Test Method for Length Change of Hydraulic Cement Mortars Exposed to a Sulfate Solution).2 greater than 95 %. Although requirements for Condensed silica fume. water to form C-S-H.05 to relate the reactivity of granulated blast-furnace slag to chem.03 0. Methods for the Chemical Analysis of is also included.1 more slowly. LOI 0. ASTM C 114 procedures for analyzing Fly Ash and Natural Pozzolans cement are separated into Reference Test Methods and Alter- ASTM Specification for Fly Ash and Raw or Calcined Natural native Test Methods. sulfate resistance is deter. DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 457 • moderate.10 tle hydraulic activity. ASTM Specification for Ground and Type HS).10 0. and cined shales and clays. Class TABLE 8—Maximum Permissible Variations C fly ashes normally contain CaO and have some cementitious in Results (From ASTM C 114. raw or calcined nat.05 ical composition. Standard Specification for Use of Silica Fume cluded. and the particles are spherical.20 0. Silica fume condenses from the for specifying a different (higher) minimum strength and for gaseous phase. however other options are available and ferro-silicon alloys. and Fe2O3. Helmuth has summarized the chemical composition and properties of a variety Max Difference of the of fly ashes [19]. The values in Table 8 apply only to titled Performance Requirements for Rapid Test Methods. tion of Table 8 shows that a difference of 0. the average of the duplicates must not exceed the limits in Column 3. when the chemical analyses were not performed in the same cision and bias can be demonstrated. analyses of SRM cements. as do proce- methods). A scheme for qualifying these test methods was de. the extraction. or a variation using salicylic acid. can also be An SRM cement is prepared and certified by the National In. acceptability of optional test methods (also called rapid Methods for free CaO fall into this classification. and CaO can cause differences of quarry and imported raw materials. and portland ce. Al2O3. If Laboratory A shows a consistent ern instrumental methods to cement analysis. can be used to re- qualification procedure involves analysis of at least seven move the calcium silicates [26–30].10 % is allowed for ence Laboratory (CCRL) Proficiency Sample program [22]. duplicate analyses of the same sample. Three methods are used for sample preparation: pressed analytical procedures. and Laboratory B turer can use any qualified method. and calcium sulfate phases. refer to the American Ceramic Society’s acceptable reference material as defined in ASTM C 114. it is possible to get an approximation of the variation that can occur between two Instrumental Methods for Cement Analysis laboratories. However. limit should be rejected. which provides information on (ICP) spectrometry can also be used for complete analysis. SRMs are used as cali. Test methods must be requalified at least every two Table 8 provides a means for the user to evaluate the signifi- years. and a is unlikely that laboratories will show a consistent bias at the spectrophotometric scheme. . Selective dissolution covers a variety of procedures that at- Table 8 also provides a convenient means assessing the tempt to separate a component or phase from the composite.70 % and that for Cement B is 2. Also. Selective Dissolution bration standards for instrumental methods. but between-laboratory variation recent analysis of CCRL data [23] may provide the basis for can be inferred because all laboratories are comparing their updating the precision and bias statements in Table 1 of results to reference standards. Spe- oxides in addition to the ones included in Table 8 of this report. For example. 0. techniques are sometimes used as precursors to other methods tained for any single component shall not exceed the limits in of analysis such as quantitative X-ray diffraction. a differ- test methods used successfully to analyze hydraulic cements ence of 0. ASTM ing the composition of two or more cements. they may differ by as used is noted on the manufacturer’s certification.60 % alkali limit. Ce. Such evidence may come from a comparison of Cement A is 2. clinker. and varying degrees of automation are now in test cement. as long as the procedure shows a consistent bias of 0.05 %. This then concentrates the SRM samples. Inductively-coupled plasma from Table 1 in ASTM C 114. and a manufac. examina- results with the average in the Cement and Concrete Refer. more than 5 % in the calculated C3S content. dures such as maleic acid/methanol (M/M) extraction. A within-laboratory variation. Table 8 method is not performing in accordance with Table 1 in can be used as a guideline. Atomic absorption involves dissolution of the cement prior to paring the analyst’s duplicate results for an SRM (Standard elemental analysis. but testing been used successfully to analyze portland cements. atomic absorption spectrophotometry. M/M veloped and became part of ASTM C 114 in 1977. Six of the seven differences between duplicates ob. ASTM C 114. errors or bias of a few tenths of a percent in plant because it can be used to obtain chemical analysis of measuring SiO2. maximum allowable range.03 % can be important for plants operating near the limit for the minor oxides. For more information on analysis stitute of Standards Technology (NIST. variations for the major oxides can also influence the poten- length is the more popular technique in cement plant quality tial phase composition calculated by the Bogue equations. most recently printed in ment SRMs cover a range of compositions.10 %. are provided. subject to error for the major elements because of the number ation in results shown in Table 8. bias of 0. especially C 114 allows the use of any method.10 % in Na2O content is not trivial.75 %.05 % in the analysis of Na2O. formerly NBS) or other of anhydrous cement. cialized techniques. Table 8 has been adapted of dilution steps that are required. cement is near the optional 0. When comparing two cements. Unlike the previous SO3 example. if the SO3 content for ASTM C 114. to establish a quality assurance program for use. or when there is substantial evidence that the test cance of test results. Examples of much as 0. Fortunately. Used successfully in many laboratories.02 or ods will be discussed further. series. laboratory. In addition to being used to demonstrate competency of analysts and test methods. and others who “wet” methods. especially if the are discussed in ASTM STP 985 [24]. Methods included are X. Column 2 of Table 8. again for six of the seven Significance of Test Results SRMs. X-Ray Fluorescence (XRF) The preceding examples show that bias in test results can Both wavelength and energy-dispersive X-ray methods have have a significant impact on the minor oxides.458 TESTS AND PROPERTIES OF CONCRETE Demonstration of Precision and Bias Other Rapid Methods The competency of an individual analyst is determined by com. such as ion chromatography. XRF is well-suited to analysis in a cement For example. Additional details and restrictions on the qualifi. both of which have demonstrated acceptable Table 1 in ASTM C 114 has facilitated the application of mod. control laboratories. it ray fluorescence. The most common of these meth. This type of examination may be helpful procedures. Looking at another example. This example il- ment. One should use caution when compar- powder. ferrite. even a bias of 0. used for selected elements. and certified values 1997 [25]. These required. Briefly. two rounds of tests on nonconsecutive days are aluminate. periclase. fused pellets. when determining if a cement that is close to a specification cation procedure are given in ASTM C 114 in the section en. This provides a good in- Many companies also conduct their own interlaboratory dication that the SO3 contents of Cements A and B are not sig- sample exchange programs to monitor chemical analysis test nificantly different. but wave. and fusion followed by grinding. Analysis time is greatly reduced compared to classical lustrates the need for cement manufacturers. Cements Research Progress. it is Reference Material) cement to the maximum permissible vari. as long as acceptable pre. DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 459 Quantitative Phase Analysis with analysis of clinker and cement. ASTM C 1365, Determina- tion of the Proportion of Phases in Portland Cement and Port- Currently, there are several task groups working within ASTM land Cement Clinker Using X-ray Diffraction Analysis, was orig- Subcommittee C01.23 on Compositional Analysis of Hydraulic inally approved in 1998 and covers the determination of C3A, Cements to develop standard test methods for measuring the C4AF, and MgO contents. Work on other phases is progressing. phase compositions of cements. The impetus for this effort Even though standard ASTM test methods for QXRD have comes from the growing shift away from prescription to per- not yet been finalized for all cement and clinker phases, the fu- formance-based specifications. In addition, there is a desire to ture is promising. Advances in X-ray diffraction automation correlate cement properties with performance in concrete, re- and computer software have made it possible to collect and an- quiring a more definitive characterization of cement in terms alyze large amounts of data, and these improvements will help of the phases present and their distribution among the parti- to overcome some of the challenges inherent in the technique. cles of different shapes and sizes. Experienced diffractionists have successfully applied QXRD analysis to cement and clinker, reporting accuracy levels of bet- Microscopical Techniques ter than 5 % for C3S and 2 % for C3A [1]. Some laboratories Light microscopy has long been used to quantitatively deter- may find that good results can be obtained by combining mine the mineralogical composition of geological samples, microscopic and XRD techniques. It is very difficult to differ- and the technique can be applied to the measurement of entiate aluminate from ferrite in some clinkers, and current clinker phase content. ASTM C 1356, Test Method for Quanti- procedures for QXRD may already be capable of achieving tative Determination of Phases in Portland Cement Clinker by greater accuracy than light microscopy. Conversely, the cal- Microscopical Point Count Procedure, was approved in 1996. cium silicates are usually easily identified by microscopy and Methods for quantitative clinker microscopy with the light mi- an experienced microscopist may be able to achieve improved croscope have been reviewed by Campbell and Galehouse [31]. accuracy levels compared to present QXRD methods. Com- Determination of phase content by light microscopy is consid- bined techniques of XRD and microscopy have also been used ered a direct method since phases are identified and counted to successfully characterize periclase (free MgO). to determine the volume percentage. The disadvantages of light microscopy include (1) it is difficult to obtain a represen- Other Compositional Considerations tative sample, (2) it is time-consuming to count at least 2000 to 3000 points to get a statistical sampling, (3) the method is sub- Carbonate (Limestone) ject to errors of misidentification of phases, (4) the precision of Limestone added to portland cements during finish grinding the method can vary with the clinker microstructure (that is, has been a common practice in other countries for many years, size of crystals), and (5) the method may not be easily applied but it is relatively new in the United States. A recent PCA report to ground cement. discusses the effects of limestone in small amounts, up to 5 %, The use of light microscopy to evaluate clinker reactivity on the properties of cement and concrete [34]. An appendix to and predict strength performance of portland cement has been ASTM C 114 lists six methods for determining carbonate con- the subject of numerous papers reported in the proceedings of tent of hydraulic cements. Included are split loss on ignition, the International Cement Microscopy Association (ICMA). One thermogravimetric analysis (TGA), decomposition with HCl procedure is the Ono Method [32], named after Dr. Yoshio Ono (refers to ASTM C 25, Chemical Analysis of Limestone, Quick- from Japan, where a small amount of ground clinker or ce- lime, and Hydrated Lime), X-ray fluorescence spectroscopy ment powder is evaluated to determine kiln burning and cool- (XRF), combustion by induction furnace, and combustion gravi- ing conditions. The crystal observations can then be correlated metric method (refers to ASTM E 350, Chemical Analysis of Car- to potential strength gain. This type of compositional analysis bon Steel, Low-Alloy Steel, Silicon Electrical Steel, Ingot Iron, is not presently covered by ASTM standards, but it is an exam- and Wrought Iron). A brief synopsis of each method is given, ple of a method that might be investigated in the future. along with cautions and limitations for the methods. (The meth- Scanning electron microscopy (SEM) and other electronic ods generally determine the CO2 content of cement, and back imaging techniques have been successfully applied to charac- calculate to determine the carbonate content of the cement. terizing portland-cement clinker, portland cements, and Since the CO2 contents of different carbonate (limestone) blended cements [33]. The SEM, if equipped with an X-ray an- sources used in cements vary, when carbonate is used as a com- alyzer, can be used to perform chemical analyses of individual ponent of portland cement, ASTM C 150 requires the CO2 con- crystals. X-ray mapping produces an image of the elemental tent of the limestone to be reported on mill test reports.) composition, and also shows the distribution of the elements throughout the crystal structure. Calcium Sulfate The SO3 content was discussed in the section on ASTM C 150, Quantitative X-Ray Diffraction (QXRD) but it is also important to determine the form of the sulfate. For Analysis example, when natural gypsum is added to clinker and ground in the finish mill, enough heat may be generated to dehydrate X-ray diffraction has been used for many years to characterize the gypsum to some degree. Natural gypsum may also contain cements and is useful for identifying phases in cement. It can some anhydrite, and there is an increasing use of calcium sul- also be used for quantitative phase analysis, but the difficulties fate byproducts as sources of SO3 in cement manufacture. The are numerous. The status of QXRD analysis applied to cement form and amount of the sulfate phases can affect the hydration and clinker is discussed by Struble [34] in a report prepared reactions. As previously mentioned, gypsum and other sulfates for a 1991 ASTM symposium on the characterization of hy- can also react during storage, sometimes leading to cement draulic cements. Struble describes the problems associated flowability problems. There is interest in sulfate form and with QXRD, in general, and the specific difficulties associated amount because reports during the last several years have 460 TESTS AND PROPERTIES OF CONCRETE shown that these parameters can affect a cement’s interaction alternative materials on cement quality, so users should main- with chemical admixtures, particularly water reducers [36]. tain close communication with their suppliers. Consideration Calcium sulfates can be identified by X-ray diffraction, should also be given, when developing ASTM standards, to en- light and electron microscopy, and by differential thermal sure that specifications address all relevant properties of ce- analysis/thermogravimetric analysis (DTA/TGA) methods. ment, both chemical and physical. There is a need for reexamination of these techniques and the development of more accurate procedures for the quantitative Performance Standards Versus measurement of the calcium sulfate phases. Prescriptive Standards Alkali Sulfates Improved methods are needed to predict the performance of In addition to forms of calcium sulfate, cements may contain hydraulic cement in concrete, and many subcommittee and task alkali sulfates. The most commonly occurring alkali sulfates group activities in ASTM are working on this issue. Ideally, there are arcanite, apthitalite, and calcium langbeinite. During the would be no need to specify limits on chemical composition be- course of normal cement hydration reactions with water, these cause there would be rapid tests to correctly predict perform- alkali sulfates can contribute to set control. However, hydra- ance. However, all of the properties that contribute to the per- tion of alkali sulfates during cement storage can lead to lump- formance of hydraulic cement have yet to be identified, and ing and flowability problems. Alkali sulfates can affect the adequate performance tests have not been developed for the strength characteristics of cement, reportedly improving early properties we know to be significant. Further, even accelerated strengths but giving lowered 28-day and later strengths. tests take up to two weeks or more to produce results, especially Changes in cement alkali levels have also been reported to af- with respect to durability. It is likely that the standards process fect the effectiveness of certain air-entraining admixtures [36]. will continue to evolve, and prescriptive limits on chemical composition will be modified or eliminated as better performance Trace Elements test methods are developed. Is it conceivable that the matter will A review of the literature on cement composition shows hun- go full circle, and tomorrow’s performance tests will be re- dreds of references dealing with trace elements (primarily placed with better prescriptions? If a hydraulic cement could be trace metals, but chlorine, fluorine, and rare earth metals are adequately characterized, chemically and physically, would it also included). Covered are effects on burnability of cement be necessary to run compressive strength or setting time tests? raw materials, effects on kiln refractory materials, effects on Or, as another example, if we fully understood the mechanisms clinker reactivity and cement performance, and methods for of sulfate attack, would it be necessary to subject mortar bars to measuring trace elements. Interest in recent years has in- accelerated curing regimes? This is the approach being ex- creased because of the environmental concerns. A survey on ef- plored by a NIST-led research consortium, the Virtual Cement fects of trace elements in portland cements and cement kiln and Concrete Technical Laboratory (VCCTL), which hopes to dust has been published by the Portland Cement Association use careful and complete characterization of cements to predict [37]. This reference also provides information about the performance of concretes using computer modeling [40]. sources and effects of trace elements. Of particular interest is The composition of hydraulic cements may become more the increased attention being given to trace elements as a re- complex as environmental issues such as the concern for sult of the growing practice of using waste materials as both global warming dictate increased use of materials other than raw materials and fuels in the clinker manufacturing process. portland cement and the pozzolanic materials we are familiar Barger [38] presented a thorough discussion on the utilization with today. A necessary part of the evolution toward improved of waste solvent fuels, including a description of trace metal, ASTM standards is the development of better methods to char- hydrocarbon, and chloride balances. Analysis of cements pro- acterize the properties of hydraulic cements, leading to more duced with waste solvent fuels, using XRD and light mi- useful predictive models. croscopy techniques, showed no detrimental effects. Testing for trace elements has brought a number of techniques to the cement quality control laboratory. Discussion of References these methods is beyond the scope of this chapter, but they in- [1] Taylor, H. F. W., Cement Chemistry, 2nd ed., Thomas Telford clude atomic absorption (AA), inductively-coupled plasma Publishing, London, 1997. (ICP), gas chromatography (GC), mass spectroscopy, and many [2] Hewlett, P. C., Ed., Lea’s Chemistry of Cement and Concrete, 4th other instrumental techniques for analysis of metals, halides, Edition, Arnold Publishers, London, 1998. hydrocarbons, and other organics. Improved procedures for [3] Bye, G. C., Portland Cement. Composition, Production, and rapid determination of heating values for fuels are also being Properties, Pergammon Press Inc., Elmsford, NY, 1983. developed. [4] Bogue, R. H., The Chemistry of Portland Cement, 2nd ed., Rein- hold, New York, 1955. Concerns of the User [5] Saini, A. and Giuliani, N., “Crystal Size and Content of the Alu- Cement manufacturers may be interested in pursuing alterna- minate Phase in Portland Cement Clinker,” Proceedings of the 10th International Congress on the Chemistry of Cement, tive raw materials and fuels for economic reasons, but main- Gothenburg, Sweden, June 2–6, 1997, Vol. 1, Paper li051 (8 p.). taining product uniformity and quality should be the prime [6] Hofmanner, F., Microstructure of Portland Cement Clinker, concern of the knowledgeable user. Significant changes in raw Holderbank Management and Consulting, Ltd., Holderbank, materials or fuels may affect properties like alkali levels, sul- Switzerland, 1973. fate form, and even reactivity of the major phases [39]. Also, [7] Jeknavorian, A. A. and Hayden, T. D., “Troubleshooting Retarded physical properties such as setting time, bleeding rate, strength Concrete: Understanding the Role of Cement and Admixtures gain, and cement-admixture interactions may be affected. Data Through an Interdisciplinary Approach,” Cement, Concrete, and is just now beginning to be published about the effects of Aggregates, Vol. 13, No. 2, Winter 1991, pp. 103–108. DEHAYES AND TENNIS ON HYDRAULIC CEMENT-CHEMICAL PROPERTIES 461 [8] Mindess, S., Young, J. F. and Darwin, D., Concrete, 2nd ed., Pren- ments Published During 1997, American Ceramic Society, Inc. tice-Hall, Inc., Upper Saddle River, NJ, 2002, pp. 57–91. Westerville, OH, 1999. [9] Gartner, E. F. and Gaidis, J. M., “Hydration Mechanisms, I,” Ma- [26] Javellana, M. P. and Jawed, I., “Extraction of Free Lime in Port- terials Science of Concrete I, J. Skalny, Ed., American Ceramic land Cement and Clinker by Ethylene Glycol,” Cement and Con- Society, Inc., Westerville, OH, 1989, pp. 95–126. crete Research, Vol. 12, 1982, pp. 399–403. [10] Jawed, I., Skalny, J., and Young, J. F., “Hydration of Portland [27] Tabikh, A. A. and Weht, R. J. “An X-ray Diffraction Analysis of Cement,” Structure and Performance of Cements, P. Barnes, Portland Cement,” Cement and Concrete Research, Vol. 1, 1971, Ed., Elsevier Science Publishing Co., Inc., New York, 1983, pp. pp. 317–328. 237–318. [28] Gutteridge, W., “On the Dissolution of Interstitial Phases in [11] “Guide to the Selection and Use of Hydraulic Cements,” Man- Portland Cement,” Cement and Concrete Research, Vol. 9, No. ual of Concrete Practice, ACI Committee 225, American Con- 3, 1979, pp. 3 19–324. crete Institute, Detroit, MI, 1999. [29] Takashima, S., “Systematic Dissolution of Calcium Silicate in [12] Gebhardt, R. F., “Survey of North American Portland Cements: Commercial Portland Cement by Organic Acid Solution,” Re- 1994,” Cement, Concrete, and Aggregates, Vol. 17, No. 2, 1995, view of the Twelfth General Meeting, Cement Association of pp. 145–189. Japan, Tokyo, 1958, pp. 12–13. [13] Mather, K., “Factors Affecting Sulfate Resistance of Mortars,” [30] Struble, L. J., “The Effect of Water on Maleic Acid and Salicylic Proceedings, 7th International Congress on the Chemistry of Acid Extraction,” Cement and Concrete Research, Vol. 15, 1985, Cement, V., Paris, 1980, pp. 580–585. pp. 631–636. [14] Chiesi, C. W., Myers, D. F., and Gartner, E. M., “Relationship Be- [31] Campbell, D. H. and Galehouse, J. S., “Quantitative Clinker Mi- tween Clinker Properties and Strength Development in the croscopy with the Light Microscope,” Cement, Concrete, and Presence of Additives,” Proceedings, Fourteenth International Aggregates, Vol. 13, No. 2, Winter 1991, pp. 94–96. Conference on Cement Microscopy, Costa Mesa, CA, Interna- [32] Ono, Y., “Microscopical Observation of Clinker for the Estima- tional Cement Microscopy Association, Duncanville, TX, 1992, tion of Burning Condition, Grindability, and Hydraulic Activity,” pp. 388–401. Proceedings, Third International Conference on Cement Mi- [15] Weaver, W. S., “Committee C-1 on Cement—Seventy-Five Years croscopy, International Cement Microscopy Association, Hous- of Achievement,” Cement Standards—Evolution and Trends, ton, TX, 1981, pp. 198–210. ASTM STP 663, P. K. Mehta, Ed., ASTM International, West [33] Stutzman, P. E., “Cement Clinker Characterization by Scanning Conshohocken, PA, 1978, pp. 3–15. Electron Microscopy,” Cement, Concrete, and Aggregates, Vol. [16] Johansen, V., “Cement Production and Cement Quality,” Mate- 13, No. 2, Winter 1991, pp. 109–114. rials Science of Concrete I, J. Skalny, Ed., American Ceramic So- [34] Struble, L. J., “Quantitative Phase Analysis of Clinker Using X- ciety, Inc., Westerville, OH, 1989, pp. 32–34. Ray Diffraction,” Cement, Concrete, and Aggregates, Vol. 13, [17] Stark, D., Durability of Concrete in Sulfate-Rich Soils, Portland No. 2, Winter 1991, pp. 97–102. Cement Association, Skokie, IL, 1989. [35] Hawkins, P., Tennis, P. D., and Detwiler, R., The Use of Lime- [18] Frohnsdorff, G., Clifton, J. R., and Brown, P. W., “History and stone in Portland Cement: A State-of-the-Art Review, EB227, Status of Standards Relating to Alkalies in Hydraulic Cements,” Portland Cement Association, Skokie, IL, 2003, 44 pages. Cement Standards—Evolution and Trends, ASTM STP 663, P. K. [36] Dodson, V., Concrete Admixtures, Van Nostrand Reinhold, New Mehta, Ed., ASTM International, West Conshohocken, PA, 1978, York, 1990. pp. 16–34. [37] An Analysis of Selected Trace Metals in Cement and Kiln Dust, [19] Helmuth, R. A., Fly Ash in Cement and Concrete, SP040T, Port- SP109T, Portland Cement Association, Skokie, IL, 1992. land Cement Association, Skokie, IL, 1978. [38] Barger, G. S., “Utilization of Waste Solvent Fuels in Cement [20] “Ground Granulated Blast-Furnace Slag as a Cementitious Con- Manufacturing,” Cement Manufacturing and Use: Proceedings stituent in Concrete,” Manual of Concrete Practice, Committee of the 1991 Engineering Foundation Meeting, Potosi, Missouri, C226, American Concrete Institute, Detroit, MI, 1991. July 28 to August 2, 1991, Paul Brown, Ed., American Society of [21] Roberts, L. R., “Microsilica in Concrete, I,” Materials Science of Civil Engineers, New York, 1994, pp 41–55. Concrete I, J. Skalny, Ed., American Ceramic Society, Inc., West- [39] Hills, L. M. and Tang, F. J., “The Effect of Alternate Raw Materi- erville, OH, 1989, pp. 197–222. als on Clinker Microstructure and Cement Performance: Two [22] Cement and Concrete Reference Laboratory, http://www. Case Studies,” Proceedings, Fourteenth International Confer- ccrl.us, June 6, 2005. ence on Cement Microscopy, Costa Mesa, CA, International Ce- [23] Moore, D., Chemical Analysis of Hydraulic Cement to ASTM C ment Microscopy Association, Duncanville, TX, 1992, pp. 114: Precision, Bias, and Qualification Criteria, unpublished re- 412–426. port, April 2003, 54 pages. [40] Bentz, D. P., Haecker, C. J., Feng, X. P. and Stutzman, P. E., “Pre- [24] Rapid Methods for Chemical Analysis of Hydraulic Cement, diction of Cement Physical Properties by Virtual Testing,” ASTM STP 985, R. F. Gebhardt, Ed., ASTM International, West Process Technology of Cement Manufacturing, Proceedings of Conshohocken, PA, 1988. the 5th International VDZ Congress, September 23–27, 2002, [25] Struble, L. J., and Burlingame, E. C., Eds., Cements Research Düsseldorf, Germany, pp. 53–63 (2003). See also: http://vcctl. Progress, 1997 : A Survey of the Literature on the Science of Ce- cbt.nist.gov. 39 Mixing and Curing Water for Concrete James S. Pierce1 Preface Mixing Water WALTER J. MCCOY, THEN DIRECTOR OF RESEARCH A popular criterion as to the suitability of water for mixing confor Lehigh Portland Cement Company, wrote the first version crete is the classical expression, “If water is fit to drink it is all of this chapter for ASTM STP 169. For ASTM STP 169A, Mr. right for making concrete.” This does not appear to be the best McCoy revised his chapter and added information on typical basis for evaluation, since some waters containing small municipal water analyses, tolerable concentrations of impu- amounts of sugars or citrate flavoring would be suitable for rities, the effects of sugar in mixing water, and the effects of drinking but not mixing concrete [1], and, conversely, water suit- water hardness on concrete air content. He also added several able for making concrete may not necessarily be fit for drinking new references. For ASTM STP 169B, Mr. McCoy, then [2]. In an attempt to be more realistic, some concrete specifica- Director of Cement Technology for Master Builders, made tions writers attempt to ensure that water used in making con- only minor changes to the ASTM STP 169A version of the crete is suitable by requiring that it be clean and free from dele- chapter. This current version is essentially Mr. McCoy’s (now terious materials. Some specifications require that if the water deceased) chapter with limited updating. There has been very is not obtained from a source proven to be satisfactory, the little new technology published regarding mixing and curing strength of concrete or mortar made with the questionable wa- water for concrete. The ASTM STP 169D edition as prepared ter should be compared with similar concrete or mortar made does, however, reflect recent standards developments with water known to be suitable. The U.S. Army Corps of Engi- promulgated by ASTM Subcommittee C09.40 and Committee neers, in addition to a general description of acceptable water re- C09. quirements [3], also states that if the pH of water is between 6.0 and 8.0 and the water is free from organic matter, it may be re- Introduction garded as safe for use in mixing concrete. (An exception to this is the case where potassium or sodium salts or other natural This chapter is concerned primarily with the significance of salts are present in excessive amounts.) This standard also states quality tests of various types of waters for mixing and curing that if water is of questionable quality before the water is judged concrete and makes no attempt to include the effect of the to be acceptable, it should be tested in mortar cubes for which quantity of mixing water. The quality of water is important the average 7- and 28-day compressive strengths must equal at because poor-quality water may adversely affect the time of least 90 % of those of companion test specimens made with dis- setting, the strength development, or cause staining. Almost tilled water [4]. Other than comparative tests of this type, no spe- all natural waters, fresh waters, and waters treated for cial test has been developed to determine the quality of mixing municipal use are satisfactory as mixing water for concrete water, and hence it is difficult to judge the fitness of water for if they have no pronounced odor or taste. Because of this, use in concrete. However, due to environmental concerns, Speci- very little attention is usually given to the water used in fication C 1602/C 1602M was developed and is available for mix- concrete, a practice that is in contrast to the frequent checking water. This specification provides compositional and pering of the admixture, cement, and aggregate components of formance requirements for mixing water and may be used for the concrete mixture. In fact, most of the references appear nonpotable sources and for water from concrete production to be outdated, but they still represent the bases for modern operations. concrete technology with regard to water for mixing and Guidance on mixing water quality is available using curing. American Association of State Highway and Transportation Recent environmental regulations place restrictions on Officials Designation T26. In ASTM C 94, Specification C discharging wash water from mixer drums and provided the 1602/C 1602M is cited for water requirements. When water impetus to develop ASTM C 1602/C 1602M, Specification for quality is questionable, service records of concrete made with Mixing Water Used in the Production of Hydraulic Cement the questionable water should be examined. If service records Concrete, and this standard is referenced in discussions on are not available or not conclusive, then the water quality mixing water. should be clarified by comparing compressive strengths and 1 Chief, Water Resources Services Division, U.S. Bureau of Reclamation, Denver, CO 80225-0007. 462 PIERCE ON MIXING AND CURING WATER 463 times of setting of specimens made with the water in ques- in appearance gave good results. Distilled waters gave con- tion and with distilled or 100 % potable water. ASTM C crete strengths essentially the same as other fresh waters. 1602/C 1602M requires compressive strengths to be a mini- 6. Based on a minimum strength-ratio of 85 % as compared mum of 90 % of the strength of specimens made with dis- to that observed with pure water, the following samples tilled or 100 % potable water, and the time of setting in the were found to be unsuitable for mixing concrete: acid wa- test mortar should not be more than 1 h quicker nor more ter, lime soak water from tannery waste, carbonated min- than 1 1/2 h slower than the time of setting when distilled or eral water discharged from galvanizing plants, water con- 100 % potable water is used. taining over 3 % of sodium chloride or 3.5 % of sulfates, This specification also permits the use of wash water from and water containing sugar or similar compounds. The mixer washout operations for mixing water, as long as it meets concentration of total dissolved solids in these waters was the compressive strength and time of setting requirements. over 6000 ppm except for the highly carbonated water, Specification C 1602/C 1602M also cites optional chemical lim- which contained 2140 ppm total solids. These data its that may be used when appropriate for the construction. support one of the principal reasons for the general These limits are being re-evaluated in light of the need to use suitability of drinking water, for few municipal waters more wash water. contain as much as 2000 ppm of dissolved solids and most Caution must be exercised when groundwater supplies are contain far less than 1000 ppm. Very few natural waters tapped for mixing water supplies. The rule of thumb about be- other than seawater contain more than 5000 ppm of dis- ing potable is still only a guide, and before critical concrete op- solved solids [6]. erations are undertaken, comparative tests for strength and 7. Based on the minimum strength-ratio of 85 %, the follow- time of setting should be completed to ensure specification ing waters were found to be suitable for mixing concrete: compliance. Specification C 1602/C 1602M prescribes testing bog and marsh water, waters with a maximum concentra- frequency. The density of the water is used as an indicator and tion of 1 % SO4, seawater (but not for reinforced concrete), is determined using C 1603, Test Method for Measurement of alkali water with a maximum of 0.15 % Na2SO4 or NaCl, Solids in Water. water from coal and gypsum mines, and wastewater from The two principal questions regarding mixing water qual- slaughterhouses, breweries, gas plants, and paint and soap ity appear to be: “How do impurities in the water affect the con- factories. crete?” and “What degree of impurity is permissible?” The fol- Many of the specifications for water for mixing concrete, lowing discussion is a summary of available information on especially those requiring that it be potable, would have ex- these two items. cluded nearly all of the aforementioned waters, but contrary to this rather general opinion, the test data show that the use of Effects of Impurities in Mixing Water many of the polluted types of water did not result in any ap- The most extensive series of tests on this subject was conducted preciable detrimental effect to the concrete. The important by Abrams [5]. Approximately 6000 mortar and concrete speci- question is not whether impurities are present, but do impuri- mens representing 68 different water samples were tested in ties occur in injurious quantities? It should be noted that the this investigation. Among the waters tested were sea and alkali conclusions on suitable waters cited earlier were based entirely waters, bog waters, mine and mineral waters, and waters con- on tests of specific samples from the indicated sources, and it taining sewage and solutions of salt. Tests with fresh waters should not be assumed that all waters of the type described and distilled water were included for comparative purposes. would be innocuous when used as mixing water. Time of setting tests and cement and concrete strength tests Typical analyses of municipal water supplies as reported from 3 days to 2.33 years were conducted for each of the vari- by the U.S. Geological Survey are given in Table 1. Although ous water samples. Some of the more significant conclusions dated, there is no reason to believe that typical analyses have based on these data are as follows: changed much from those in Table 1. Collins [7] reported that 1. The times of setting of portland cement mixtures contain- these analyses represent public water supplies used by about ing impure mixing waters were about the same as those 45 % of the cities of the United States that have a population of observed with the use of clean fresh waters with only a few more than 20 000. These analyses indicate they would be ac- exceptions. In most instances, the waters giving low rela- ceptable sources for mixing water. However, when investigat- tive compressive strength of concrete caused slow setting, ing a municipal source, analyses for several periodic tests but, generally speaking, the tests showed that time of set- should be examined to determine if comparisons with distilled ting is not a satisfactory test for suitability of a water for water are needed. Such an examination will also provide a per- mixing concrete. spective on the variability of inorganic and organic compounds 2. None of the waters caused unsoundness of the neat port- present. The presence of certain compounds may not create a land cement pat when tested over boiling water. serious deleterious effect, but the variability may cause varying 3. In spite of the wide variation in the origin and type of wa- effects on the efficiency of air-entraining admixtures, the time ters used, most of the samples gave good results in con- of setting, and the strength development. crete due to the fact that the quantities of injurious impu- A concrete manual [8] published in Denmark in 1944 rities present were quite small. points out that humic acid and other organic acids should be 4. The quality of mixing water is best measured by the ratio avoided because their presence means a danger to the stability of the 28-day concrete or mortar strength to that of simi- of concrete. Most organic compounds will have an effect on lar mixtures made with pure water. Waters giving strength time of setting and comparative tests should be conducted to ratios that are below 85 %, in general, should be consid- evaluate the effect. ered unsatisfactory. An article appearing in a 1947 British publication [9] dis- 5. Neither odor nor color is an indication of quality of water cusses the harmful effects of using acid waters in concrete and for mixing concrete. Waters that were most unpromising claims that the harmful effects of organic acid are not evident 464 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Typical Analyses of City Water Supplies (PPM)a Analysis Number 1 3 5 6 7 Silica (SiO2) 2.4 12.0 10.0 9.4 22.0 Iron (Fe) 0.14 0.02 0.09 0.2 0.08 Calcium (Ca) 5.8 36.0 92.0 96.0 3.0 Magnesium (Mg) 1.4 8.1 34.0 27.0 2.4 Sodium (Na) 1.7 6.5 8.2 183.0 215.0 Potassium (K) 0.7 1.2 1.4 18.0 9.8 Bicarbonate (HCO3) 14.0 119.0 339.0 334.0 549.0 Sulfate (SO4) 9.7 22.0 84.0 121.0 11.0 Chloride (Cl) 2.0 13.0 9.6 280.0 22.0 Nitrate (NO3) 0.54 0.1 13.0 0.2 0.52 Total dissolved solids 31.0 165.0 434.0 983.0 564.0 a Taken from Collins [7]. as soon as those of mineral acids, while deleterious salts have different effects varies with the other factors involved, such a greater effect on early-age strengths than at later ages. as the composition of the cement, cement content, and am- Kleinlogel [10] stated that mixing water should not con- bient conditions. tain humus, peat fiber, coal particles, sulfur, or industrial wastes containing fat or acid. Use of Seawater in Mixing Concrete An article in Ref 11 contains a tabulation of maximum In addition to the supporting reference previously mentioned limits for impurities in mixing water that is summarized in in Abrams’s paper [5], the English article [9] also states that Table 2. seawater with a maximum concentration of salts on the order The limit for suspended particles in Table 2 agrees with of 3.5 % does not appreciably reduce the strength of concrete, the requirements of the U.S. Bureau of Reclamation [12], although it may lead to corrosion of reinforcement. which has a turbidity limit of 2000 ppm for mixing water. A paper by Liebs [14] contains the results of comparative Sugar is probably the organic contaminant that causes 7-, 28-, and 90-day compressive strength tests of concrete mixed the most concern. Steinour [13] explained that, although with fresh water and with seawater. The data show that the sea- sugar as a contaminant in the field has gained a bad reputa- water concrete had about 6 to 8 % lower strengths than the tion as a retarder and strength reducer, these judgments need fresh water concrete. No efflorescence was observed. The arti- qualification. Laboratory tests have shown that, although cle in Ref 11 pointed out that concrete made with seawater smaller amounts retard the setting, they increase the strength may have higher early strength than normal concrete, but development. With larger amounts, the setting is further re- strengths at later ages (after 28 days) may be lower. Steinour tarded and early strengths such as those for two and three [13] stated that the use of seawater may cause a moderate re- days (or even seven days) are severely reduced. The later duction in ultimate strength, an effect that can be avoided by strengths, however, are increased or at least not affected ad- the use of a higher cement content. He also noted that concrete versely, provided proper curing is maintained as required. in which seawater is used as mixing water is sound but its use With still larger amounts, the cement becomes quick-setting may cause efflorescence or dampness, and in reinforced con- and strengths are reduced markedly for 28 days and proba- crete the risk of corrosion of the steel is increased. Seawater bly permanently. The amount of sugar that can cause these definitely should not be used for making prestressed concrete. TABLE 2—Tolerable Concentrations of Impurities in Concrete Mixing Water Impurity Maximum Tolerable Concentration 1. Sodium and potassium carbonates and bicarbonates 1000 ppm 2. Sodium chloride 20 000 ppm 3. Sodium sulfate 10 000 ppm 4. Calcium and magnesium bicarbonates 400 ppm of bicarbonate ion 5. Calcium chloride 2 % by mass, of cement in plain concrete 6. Iron salts 40 000 ppm 7. Sodium iodate, phosphate, arsenate, and borate 500 ppm 8. Sodium sulfide 100 ppm warrants testing 9. Hydrochloric and sulfuric acids 10 000 ppm 10. Sodium hydroxide 0.5 %, by mass, of cement if set not affected 11. Salt and suspended particles 2000 ppm PIERCE ON MIXING AND CURING WATER 465 Hadley [15] points out that seawater was used in the con- other is that it might contain aggressive impurities that would crete for the foundation of the lighthouse at the extremity of be capable of attacking or causing deterioration of the con- the Los Angeles breakwater, which was built by the U.S. Army crete. The latter possibility is unlikely, especially if water satis- Corps of Engineers in 1910, and that 25 years later it was ex- factory for use in mixing concrete is employed. In some in- amined and found to be in good condition with sharp-edged stances the staining or discoloration of the surface of concrete corners and no disintegration. There are several references in from curing water would not be objectionable. The most com- the literature that indicate that salt water has been used in mix- mon cause of staining is usually a relatively high concentration ing plain concrete without incurring trouble at later periods. of iron or organic matter in the water; however, relatively low Much of the concrete for the Florida East Coast Railway was concentrations of these impurities may cause staining, espe- mixed with seawater with no detrimental effect due to its use cially if the concrete is subjected to prolonged wetting by [16]. Most engineers are of the opinion that seawater should runoff of curing water from other portions of the structure [3]. not be used for mixing reinforced concrete; however, Dempsey Test data from the Corps of Engineers [20] show that there [17] describes construction of military bases in Bermuda using is not a consistent relationship between dissolved iron content coral aggregate and concludes that seawater seems to be satis- and degree of staining. In some cases, 0.08 ppm of iron re- factory for making reinforced concrete and causes no problem sulted in only a slight discoloration, and, in other cases, waters beyond an acceleration in stiffening of the mixture. No harm- with 0.06 ppm of iron gave a moderate rust-colored stain, while ful effect on the durability of reinforced concrete had occurred 0.04 ppm produced considerable brownish-black stain. Gener- at the end of four years. Nonetheless, extreme caution is urged ally speaking, the conditions of these tests were such as to when mixing water for reinforced concrete is selected. If the accentuate the staining properties of the water, since consider- water contains salts, the residual salts in the concrete when ably more water was evaporated over a unit area than would combined with air and moisture will result in some corrosion. be the case in most instances in the field. With respect to organic impurities in water, it is virtually Effects of Algae in Mixing Water on Air Content impossible to determine from a chemical analysis if the wa- and Strength of Concrete ter would cause objectionable staining when used for curing A rather extensive series of laboratory tests reported by Doell concrete. It is advisable to use a performance-type test proce- [18] showed that the use of water containing algae had the un- dure, such as Designation CRD-C 401 of the Corps of Engi- usual effect of entraining considerable quantities of air in con- neers [21]. This method outlines three procedures for evalu- crete mixtures with an accompanying decrease in strength. The ating the staining properties of water proposed for use in data in Table 3 were extracted from Doell’s paper and are curing concrete. The Preliminary Method is intended for use based on tests with 19.0-mm (3/4-in.) maximum-size aggregate in selecting sources that are worthy of more complete inves- concrete having a water/cement ratio of 0.5 and a slump of 40 tigation and consists of evaporating 3000 mL of the test wa- to 75 mm (1.5 to 3 in.), with a constant ratio of coarse to fine ter in the concave area formed by the impression of a 100- aggregate. mm (4-in.) watch glass in the surface of a neat white cement In addition to the detrimental effect on strength, one of or plaster of Paris specimen. The Complete Method can be the important aspects of these data is that considerable quan- used to evaluate those sources that the Preliminary Method tities of air can be entrained in concrete by the use of mixing indicate to be promising. In the Complete Method, 11 dm3 (3 water containing algae. gal) of test water drips on a mortar specimen exposed to heat lamps and forced air circulation. The Field Method is in- Effect of Hardness of Mixing Water on tended as a means of evaluating the water finally selected for Air Content of Concrete use and involves the curing of a 1.9-m2 (20-ft2) slab of con- Wuerpel [19] reported a series of air determination tests with crete with the test water for at least 28 days with maximum waters of various degrees of hardness that shows that the air exposure to the sun with the test slab placed at a slight angle content was not affected by the hardness of the water. sufficient to keep it in a wet condition with minimum runoff. The test results by each of these three methods are evaluated Curing Water by visual observation. The Corps of Engineers’ Standard Practice for Concrete There are two primary considerations with regard to the suita- [22] clearly states that there must be no permanent staining of bility of water for curing concrete. One is the possibility that it surfaces where appearance is important. For these surfaces, might contain impurities that would cause staining, and the the contractor has the option of using nonstaining water or of TABLE 3—Effect of Algae in Mixing Water on Air Content and Strength of Concrete Mixture Compressive Strength, Number Algae in Mixing Water, % Air in Concrete, % 28 days, MPa (psi) 10 none control 2.2 33.3 (4830) 8 0.03 2.6 33.4 (4840) 7 0.09 6.0 27.9 (4040) 5 0.15 7.9 22.8 (3320) 9 0.23 10.6 17.8 (2470) 466 TESTS AND PROPERTIES OF CONCRETE cleaning the surface after completion of moist curing. No for Concrete and Cement, U.S. Army Corps of Engineers, Vicks- cleaning is required for surfaces that will subsequently be burg, MS, 1979. stained when the structure is in service. [5] Abrams, D. A., “Tests of Impure Waters for Mixing Concrete,” Proceedings, American Concrete Institute, Vol. 20, 1924, pp. Summary 442–486. [6] Proudley, C. E., “Effect of Alkalies on Strength of Mortar,” Pub- Mixing Water lic Roads, Vol. 5, 1924, pp. 25–27. The significance of the foregoing information presented is that [7] Collins, W. D., “Typical Water Analyses for Classification with Reference to Industrial Use,” Proceedings, ASTM International, any naturally occurring or municipal water supply suitable for West Conshohocken, PA, Vol. 44, 1944, pp. 1057–1061. drinking purposes can be used as mixing water for concrete [8] Plum, N. H., Christiani, and Nielsen, “Concrete Manual,” Bul- and that most naturally occurring waters ordinarily used for in- letin No. 39, Copenhagen, Denmark, 1944. dustrial purposes are satisfactory. Many waters that upon ca- [9] “Water for Making Concrete,” Title No. 44–197, “Job Problems sual examination would be judged to be unsuitable because of and Practice,” Proceedings, American Concrete Institute, Vol. color, odor, or contamination with impurities, as in the case of 44, 1948, pp. 414–416; reprinted from “Water for Making Con- marsh water, alkaline sulfate waters, and water containing in- crete,” Concrete and Constructional Engineering, London, Vol. dustrial wastes, could be found to be satisfactory when tested 42, No. 10, 1947, p. 295. in mortar or concrete since, in many instances, the strength [10] Kleinlogel, A., Influences on Concrete, Frederick Ungar Publish- would be greater than 90 % of the strength of comparative ing Co., New York, 1950, p. 158. specimens made with pure waters. In the case of seawater, a [11] “Requirements of Mixing Water for Concrete,” Indian Concrete strength reduction ranging from 8 to 15 % can be expected de- Journal, March 1963, pp. 95, 98, and 113. pending on job conditions; however, seawater ordinarily is not [12] Concrete Manual, 8th ed., U.S. Department of the Interior, Bu- recommended for use as mixing water in reinforced concrete. reau of Reclamation, Washington, DC, 1981, p. 70. The hardness of water usually does not affect air content of [13] Steinour, H. H., “Concrete Mix Water—How Impure Can It Be?” concrete; however, with certain anionic and nonionic admix- Journal, Portland Cement Association, Research and Develop- ment Laboratories, Skokie, IL, Vol. 2, No. 3, 1960, pp. 32–50. tures, additional dosage may be required to obtain the desired [14] Liebs, W., “The Change of Strength of Concrete by Using Sea air content. Algae in mixing water, however, can entrain air Water for Mixing and Making Additions to Concrete,” Bautech- and significantly reduce strength. nik, 1949, pp. 315–316. [15] Hadley, H., “Letter to Editor,” Engineering News-Record, May Curing Water 1935, pp. 716–717. It is improbable that a water used for curing would attack con- [16] “Job Problems and Practice,” Proceedings, American Concrete crete if it were of the type suitable for use as mixing water. Or- Institute, Vol. 36, 1940, pp. 313–314. ganic matter or iron in the curing water can cause staining or [17] Dempsey, J. G., “Coral and Salt Water as Concrete Materials,” discoloration of concrete, but this is rather uncommon espe- Proceedings, American Concrete Institute, Vol. 48, 1951, p. 165. cially where a relatively small volume of water is used; how- [18] Doell, B. C., “The Effect of Algae Infested Water on the ever, the suggested performance tests [21] will determine if a Strength of Concrete,” Proceedings, American Concrete Insti- water possesses any potential staining qualities. tute, Vol. 51, 1954, pp. 333–342. [19] Wuerpel, C. E., “Influence of Mixing Water Hardness on Air En- trainment,” Proceedings, American Concrete Institute, Vol. 42, References 1946, p. 401. [1] Clair, M. N., “Effect of Sugar on Concrete in Large Scale Trial,” [20] Mather, B. and Tye, R. V., “Requirements for Water for Use in Engineering News-Record, March 1929, p. 473. Mixing or Curing Concrete,” Waterways Experiment Station [2] Neville, A. M. and Brooks, J. J., Concrete Technology, Longman Technical Report No. 6-440, U.S. Army Corps of Engineers, Group UK Limited, Essex, UK, 1987, pp. 74–75. Vicksburg, MS, Nov. 1956, p. 36. [3] “Requirements for Water for Use in Mixing or Curing Con- [21] “Method of Test for the Staining Properties of Water,” CRD-C crete,” CRD-C 400, Handbook for Concrete and Cement, U.S. 401, Handbook for Concrete and Cement, U.S. Army Corps of Army Corps of Engineers, Vicksburg, MS, 1963. Engineers, Vicksburg, MS, 1975. [4] “Test Method for Compressive Strength of Mortar for Use in [22] Engineer Manual, Standard Practice for Concrete, EM 1110-2- Evaluating Water for Mixing Concrete,” CRD-C 406, Handbook 2000, U.S. Army Corps of Engineers, Washington, DC, 1985. 40 Curing and Materials Applied to New Concrete Surfaces Ben E. Edwards1 Preface thorough, up-to-date discussion of the current understanding of cement hydration with extensive references, as well as extended TO PREPARE THIS CHAPTER, THE CONTENTS OF ALL coverage of methods and materials, types of construction, and of the previous editions were drawn on. The author acknowl- techniques of monitoring curing. The document is revised on a edges the previous authors, Ephraim Senbetta [1], Rodger Car- five-year cycle. Interest in high performance concrete has stimu- rier [2], C. E. Proudley [3], and John Swanberg [4]. The title of the lated much research and discussion, and “Curing of High Per- chapter was changed from “Curing and Curing Materials” to re- formance Concrete: Report of State of the Art” published by the flect the change in scope of ASTM Subcommittee C09.22, which National Institute of Standards and Technology (NIST) [7] also has initiated efforts to provide standards for materials that do not contains a thorough discussion of the physical and chemical fulfill the curing function but are not addressed elsewhere, such changes involved in cement hydration and a historical review as evaporation reducers, silicate treatments, bond breakers, and of ACI curing requirements. It closes with suggestions on dry shake hardeners. The current edition will review and update research needs to improve the assessment of curing and an the topics addressed by the previous authors, introduce new extensive list of references to recent work. A more general technology and perspectives, and include up-to-date references. discussion of curing theory and practice, also including extensive references, titled “Curing Portland-Cement Concrete Introduction Pavements,” [8] has been prepared by Toy Poole of the U.S. Army Corps of Engineers (USACE) and is to be published by the Understanding of the processes that lead to the hardening of Federal Highway Administration (FHWA). concrete continues to expand as more sophisticated tech- Long established techniques and materials continue to be niques are used to observe and characterize the chemistry in- used effectively, and some refinements based on better under- volved. However, the conversion of fresh concrete to a solid standing of the process are being adopted. The concept of mass when cementitious materials hydrate is still the central initial curing is defined and discussed in ACI 308R as a means fact, and the dependence of the ultimate properties of the to minimize occurrence of shrinkage cracking from very early material on the degree of hydration of the cement motivates surface drying before traditional curing procedures may be interest in curing. ASTM Standard Terminology Relating to applied. Fogging and evaporation reducers are effective for Concrete and Concrete Aggregates (C 125) and ACI Cement initial curing. Internal curing has been developed as a means and Concrete Terminology (116R) [5], define curing as “action of providing additional water to very low water/cement ratio taken to maintain moisture and temperature conditions in a (w/c) concretes where self-desiccation can create problems. freshly placed cementitious mixture to allow hydraulic cement This chapter will attempt to touch on these and other develop- hydration and (if applicable) pozzolanic reactions to occur so ments not addressed in previous versions. that the potential properties of the mixture may develop.” In Test methods to assess the effectiveness of curing continue addition, other properties, particularly of the surface region of to be a vexed issue. Whether it is preferable to measure some a concrete mass, may be affected by materials applied and/or property of the final product concrete rather than the behavior actions taken soon after placement. of the materials or processes used in curing is still under debate. No effort will be made in this chapter to review the history Some researchers persist in measuring concrete strengths as a of the understanding of curing and related tests and specifica- function of curing procedures although curing procedures af- tions. The reader is referred to previous editions of this chap- fect only the outermost few millimetres of any concrete. ASTM ter, and to other documents referenced below. Test Method for Water Retention by Concrete Curing Materials A Task Group of The American Concrete Institute (ACI) (C 156) has been used since 1940 to measure loss of water from Committee 308 on Curing, chaired by Ken Hover, has created a “cured” specimen, despite widespread discontent with the re- an excellent Guide to Curing (ACI 308R) [6], which provides a producibility of the test. Recent changes to the procedure seem 1 Chief Chemist, BEE Laboratory, Blowing Rock, NC 28605. 467 468 TESTS AND PROPERTIES OF CONCRETE to have improved its precision. Attention has also turned to en- After concrete is placed and all other subsequent opera- vironmental measurements, which assay the worksite conditions such as finishing and texturing are completed, curing tions to determine whether the concrete has received adequate procedures may involve either keeping the concrete moist by curing action. The maturity method [9] of estimating concrete ponding or covering with wet material and/or sealing the sur- strength development using the measured temperature his- face with sheet material or liquid membrane-forming curing tory of the concrete during curing is proving useful to better compound to prevent evaporation. For formed concrete place- characterize overall results in testing programs. More exotic ments, forms will provide adequate protection against mois- nondestructive test methods using X-rays, microwaves electrical ture loss as long as they remain in place. After removal, other resistance, and magnetic resonance are providing more curing procedures may be needed depending on the age of the detailed information on the progress of hydration in new concrete at the time of form removal. concrete. Some of this technology will be addressed below. In contrast to the situation reported by Senbetta [1] in Standard Test Methods 1994, the study and practice of curing concrete seems currently to be an increasingly active field. Indicators include Although a wide range of test procedures have been used to the increasing number of presentations at the Transportation evaluate whether a particular concrete specimen has been ade- Research Board Annual Meetings and ACI sessions devoted to quately cured, ASTM publishes only one test method to evalu- curing, as well as more publications in various journals. ate the water retaining properties of a curing material. Because the method has exhibited poor interlaboratory reproducibility, Curing Methods and Materials for a multitude of variants have been developed by state agencies, Water Retention and internationally, with the hope of improving local reproducibility, or better measuring particular characteristics of liq- The methods and materials employed in the curing of concrete uid membrane-forming curing compounds. vary depending on the type of concrete, the type of structure ASTM Test Method for Water Retention by Concrete Curing including the orientation of the structural members, and the Materials (C 156) was first published in 1940. In a delayed re- ambient conditions during the curing period. Control of loss of sponse to the report of Leitch and Laycraft [11] and comments mix water may be accomplished with a barrier material, either from many others, C 156 has been modified with a requirement a solid sheet, such as polyethylene film, or a liquid-applied film, that the test cabinet environment be characterized by a meas- which dries to form a membrane, or by maintaining a wet en- ured evaporation rate in addition to controlled temperature and vironment with fog, by ponding or with water soaked blankets. relative humidity. Control of air velocity is necessary to achieve Flat work such as pavements and floors require much closer at- the desired evaporation rate, but air velocity is more difficult to tention to control of water loss than formed mass concrete. On control than evaporation rate over an extended time. A proce- the other hand, care should be exercised to avoid large thermal dure for measuring the evaporation rate is specified in an Annex gradients in mass concrete where heat of hydration may be- to the method. A further change to the method relaxes the spec- come a problem or in slabs exposed to direct sunlight. ification for the mold used to cast mortar specimens for the test. Particularly for large flat surfaces (pavements or floors), In recognition of a trend established many years ago by state De- initial curing may be required as soon as concrete is placed partment of Transportation (DOT) laboratories, and suggested and consolidated and prior to the finishing operation. If, at by the work of Leitch and Laycraft [11] and of the Corps of En- this stage, conditions are such that rapid evaporation of wa- gineers [12], the 150 300 50 mm (6 in. 12 in. 2 in.) mold ter from the concrete is expected, and if the concrete is a specification is replaced by a requirement of minimum surface type that has minimal bleeding, such as silica fume concrete, area of 12000 mm2 (18.6 in.2) and minimum depth of 19 mm actions should be taken to either alter the ambient conditions (3/4 in.). In the author’s experience, smaller molds can be used near the surface of the concrete by fogging, or evaporation of by a single operator to run triplicate determinations with less water can be prevented or reduced by spraying an evapora- time and effort than required for handling a single 150 300 tion reducer on the fresh concrete surface. Fogging literally mm (6 in. 12 in.) mold, also consuming far less cement and calls for the formation of a cloud of water droplets immedi- sand. A recently completed round robin involving six laborato- ately above the concrete surface without appreciably adding ries and four different curing compounds, organized by the Cal- to the water on the surface. Specialized fogging nozzles are ifornia DOT, is the basis of a new precision statement being bal- commercially available for this purpose. Spray-applied evapo- loted for addition to the method. It shows the single operator ration reducers do not interfere with finishing the concrete standard deviation among test results to be 0.038 kg/m2 and the nor do they have a lasting curing effect. They are different interlaboratory standard deviation among test results to be from liquid membrane-forming curing compounds. Although 0.070 kg/m2. There appears to be no loss of precision with there are many evaporation reducers being marketed, the smaller molds used by some of the participants. Hopefully the user is dependent on the manufacturer for details on use and state DOTs that have developed variants of the ASTM method performance expectations. No standardized performance will find the advantage of a uniform testing method across the tests are available. Under windy conditions, some kind of country to be good reason to adopt the ASTM procedure. windscreen protection may be helpful or even required to It has long been recognized that the results of the C 156 test complement other measures taken. On the basis of experi- are sensitive to the timing of the application of curing com- ence with minimizing plastic shrinkage cracking of bridge pound. The procedure specifies that the mortar surface shall be decks, the Kansas DOT has issued guidelines [10] providing free of surface water but not dry below the surface. Application specific sequences of procedures to be applied as dictated by of curing compounds to surfaces that are still bleeding or have weather conditions. Certain types of concrete, such as latex- standing water results in disruption of the film-forming char- modified concrete, may not require any action to prevent dry- acteristics of the curing material. In the field, if careful attention ing beyond the first 24 h. is not paid to time of application, a product that meets the lab- EDWARDS ON NEW CONCRETE SURFACES 469 oratory test requirement may not provide the expected protec- ASTM Specification for Polyethylene Sheeting for Construction, tion. Covarrubias [13] reported that three of eight compounds Industrial and Agricultural Applications (D 4397) covers all the tested according to C 156 (and passing) also performed satis- necessary properties of polyethylene sheeting used for concrete factorily when applied 30 min after molding the specimens, i.e., curing and therefore no additional tests are required for material while the mortar was bleeding. These products can presumably meeting this specification. Other sheet material is to be tested by be applied to pavements immediately after finishing. No infor- ASTM Test Methods for Water Vapor Transmission of Materials mation is provided about the nature of these products. (E 96) rather than C 156. This change recognizes that while the ASTM Test Method for Evaluating the Effectiveness of water loss from liquid membrane-forming curing compounds is Materials for Curing Concrete (C 1151) was published as a a combination of loss during film formation and loss through the proposal in 1987 and as a standard in 1990 as a possible alter- dried film, for sheet materials the loss rate should be constant. In native to C 156, but withdrawn in 1998 due to lack of interest. practice, test results using Method C 156 for sheet material are The method measures a property of the affected specimen more likely to depend on the quality of the seal of sheet to speci- rather than the behavior of the applied material. By measuring men than on the inherent water transmission rate of the product the absorptivity of a near surface layer and comparing it to that under test. The new test limit of 10 g/m2 loss in 24 h is set in terms of an internal layer, the relative degree of hydration, and of Method E 96, Procedure E (37.8°C, (100°F)), and represents a therefore the efficacy of the applied curing procedure, is more stringent loss rate requirement than previously required in determined. The method has been applied to analyzing con- recognition of the known characteristics of polyethylene sheet (D crete of all ages in the field, but was not accepted as a routine 4397 lists 5.5g/m2 loss in 24 h as the requirement for 4 mL poly- test for liquid membrane-forming curing compounds because ethylene). The new test limit corresponds to 0.03 kg/m2 in 72 h, of the complexity of the procedure. The technique is still used which is below the level practically measurable by the C 156 pro- with many variations in research situations. cedure. The equivalent AASHTO specification for sheet material Other tests that have been used in studies involving curing, is M 171, which does not yet reflect these changes. but are not under the jurisdiction of ASTM C09 Concrete Subcommittee C09.22, include measurements of absorptivity, Liquid Membrane-forming Curing Compounds hardness, gas permeability, chloride intrusion, freeze-thaw Liquid membrane-forming curing compounds are paint-like stability, and strength. Most properties of new concrete are products that can be applied to freshly placed concrete by changing rapidly in the first few days of its life and the age and spray, brush, or roller, and dry to form a membrane or film temperature history of the specimens must be carefully that retards the evaporation of water. They offer the advan- specified if results are to be compared. tages of ease of application, low material and labor costs, and ready availability. However, there are wide variations in the Standard Specifications quality of available products and they are sensitive to the time of application and the thoroughness of the applicators. Despite ASTM C09 Concrete Subcommittee C09.22 has jurisdiction over years of effort by many researchers, the performance of any three material standards related to curing, one for sheet material given batch of curing compound as measured by C 156 is still and two for liquid membrane-forming curing compounds. The not accurately predictable by any other measurable property. American Association of State Highway and Transportation Offi- ASTM Specification for Liquid Membrane-forming Curing cials (AASHTO) publishes related specifications as do the USACE Compounds (C 309) covers the workhorses of curing technol- and many state departments of transportation in the United ogy. They have evolved under pressures of environmental States. Worldwide, specifications are written in many countries concerns so that the products used in highest volumes are but most seem to resemble the ASTM requirements, so that prod- water-borne emulsions with little or no VOC content, capable ucts manufactured for the U.S. market are widely acceptable. of providing protection to large areas of concrete at low cost in both labor and materials. AASHTO M 148 is a corresponding Sheet Materials specification, but revisions lag several years behind C 309. In addition to traditional burlap, polyethylene sheeting, poly- The problems of assuring the quality of the products and the bonded burlap, and various types of water-soaked fabric, a num- workmanship of the applicators remain. ber of new products have appeared on the market providing The specification includes requirements for water reten- various reputed advantages. Several versions of polyethylene tion, reflectance of white-pigmented compounds, and drying bonded to woven or nonwoven synthetic fabrics are available time. The water retention requirement calls for mass loss of no having superior strength, and are therefore more suitable for more than 0.55 kg/m2 of surface in 72 h when applied at 5.0 multiple uses. Some of these also act as a water reservoir if the m2/L (200 ft2/gal) when the testing is done according to ASTM sheet or the concrete is wetted before being covered, and pos- C156. This is, by far, the most important requirement, even sibly reduce or eliminate the blotchy surface marking often en- though measurement is difficult and the validity of the qualify- countered with polyethylene alone. Another product employing ing value is still under debate. The requirement for a minimum an aluminized film bonded to the top surface offers exceptional reflectance of 60 % is related to the prevention of heat buildup protection from solar heating of flat surfaces by reflecting in concrete exposed to solar radiation. The pigment also helps almost all-incident radiation. “Bubble-wrap” type materials are to visually assess completeness of coverage. The maximum dry- available to provide insulating properties in cold weather or to ing time requirement is to guard against the concrete having a shield against heat gain from the environment in hot weather. tacky or slippery surface and to make sure the curing com- None of these newer characteristics have been measured by pound does not track off when walked on. The major classes of standardized tests for curing applications. film formers used for concrete paving are based on petroleum ASTM Specification for Sheet Materials for Curing Concrete waxes or hydrocarbon resins. For commercial floors styrene- (C 171) covers burlap, polyethylene sheeting, and poly-bonded acrylic resins are widely used because they can also serve as burlap, and was revised in 2003 to simplify the required testing. sealers for in place concrete. Chlorinated rubbers were once 470 TESTS AND PROPERTIES OF CONCRETE widely used for their excellent water retention properties, but The initial w/c of the concrete sets a limit on the ultimate have fallen from favor because of their low UV resistance (they results since at w/c ~0.4 the excess water limits the initial darken in sunlight) and more recently problems of resin sup- density on placement, and at w/c ~0.4 incomplete hydration ply related to environmental and economic issues. Styrene- resulting from internal desiccation may lead to high capillary butadiene resins also have excellent water retention but low UV porosity. The necessity for special curing attention for high per- stability. Acrylic resins as solutions or latexes show excellent UV formance concrete arises from this relationship. These effects stability but inferior water retention properties. have been extensively discussed and analyzed elsewhere [6,7]. Corps of Engineers Specification CRD-C300 is similar to A frequently reported failure is plastic shrinkage cracking, C309, but calls for water retention of 0.31 kg/m2 in seven days which results from rapid surface drying before the concrete when tested by CRD C 302 (which is similar to the ASTM has hardened sufficiently to resist shrinkage stress. This crack- method). However, the spec is not being actively maintained by ing radically reduces the durability and increases the perme- the Corps and good quality cures manufactured to meet C 309 ability of the surface. It is especially likely to occur in mixes are generally acceptable for Corps applications. with low w/c, and low bleed rates, for instance those with silica Many state DOTs have generated variants or extensions of fume or other pozzolans. Wojakowsi of the Kansas DOT [10] these specifications in response to their perceived needs. Like- has demonstrated that careful attention to maintenance of wise most European countries and members of the British curing conditions by use of fogging, evaporation reducers, and Commonwealth have established specifications and test meth- sheet products, each applied at the appropriate time, allows ods for curing compounds. A review of these is beyond the production of crack-free bridge decks from high performance scope of this chapter. concrete mixes. Failure to attend to any of the details results in Liquid Membrane-Forming Compounds with Special shrinkage cracking of the surface. Similar results have been Properties for Curing and Sealing Concrete (C 1315), a new reported from the Virginia and Iowa DOTs. specification, was adopted in 1995 in response to a perceived A more subtle effect of poor curing has been proposed by need to replace General Services Administration Federal Spec- Shotwell [16] to explain scaling of driveways and sidewalks ification Curing Compound, Concrete, For New and Existing during the first season of exposure to freezing and thawing. Surfaces, TT-C-800, which was withdrawn in 1978. Compared Petrographic examination of poorly cured mortar with a to C 309, the new specification calls for more stringent water porous surface layer showed that a relatively dense band of retention performance (0.40 kg/m2 in 72 h when applied at 7.4 carbonated matrix is formed just beneath the surface and m2/L (300 ft2/gal)) and minimum solids content (25 %) and inhibits penetration of water into the underlying concrete. The includes requirements for resistance to UV degradation (non- result is concentration of water in the porous top layer leading yellowing), chemical resistance, and compatibility with adhe- to freeze-thaw scaling. Typically, in otherwise good concrete, sives used to bond tile or carpet to concrete. These properties the deterioration decreases after the initial scaling. are important in a range of applications including commercial Studies of curing focus primarily on whether desired floors, bridge decks, and high performance concrete (HPC) in properties such as low permeability or other measurable quali- general. The Environmental Protection Agency (EPA) has ties of concrete products are attained. An alternate approach is adopted a regulation [14] allowing products classified as cur- to determine if the materials or processes used perform so as ing and sealing agents and defined by compliance to C 1315 to to maintain the conditions required for optimum hydration. have a Volatile Organic Compound content of 700 g/L, This requires careful monitoring of temperature, ambient whereas curing compounds meeting C 309 are allowed only and/or internal humidity, and air flow as well as evaluating the 350 g/L. Practically speaking, this regulation allows solution- ability of liquid membrane-forming curing compounds and based products to be sold for curing and sealing whereas only sheet material to impede or prevent the evaporation of water. emulsion based products can realistically meet the VOC limit set for curing compounds. Effects of Ambient Conditions on Curing A few state DOTs have adopted material specifications calling for the use of -methyl styrene polymer in liquid mem- The need to take deliberate steps to ensure proper curing of con- brane-forming curing compound formulations, especially for crete is dependent on the ambient atmospheric conditions. In bridge decks. The specifications call for lower water loss than certain environments where the relative humidity and tempera- in C 309, typically around 0.3 kg/m2 in 72 h. There is little ture are favorable, no deliberate action may be needed to cure evidence that the specified resin yields products that are really the concrete. But, usually conditions require action for some por- superior to equivalent formulations with similar resins. tion of the curing-sensitive period. Control of ambient conditions may involve application of energy rather than materials, but nev- Effects of Curing on Concrete Properties ertheless it seems appropriate for discussion in this chapter. Although there are no standard definitions, ambient condi- For any concrete mix, proper curing allows for maximum tions may be put into three temperature categories; hot, 32°C hydration of cementitious materials resulting in the greatest (90°F); cold, 10°C (50°F); and normal, (10–32°C) (50–90°F). possible reduction in capillary porosity of the initial mixture by ACI Committee 306, Cold Weather Concreting, continues to the formation of products of hydration. This process, in turn, struggle with defining cold weather in a way that is useful to con- results in minimum permeability and maximum strength and struction professionals [17]. The severity of the environment as durability. Consequential effects include reduced shrinkage it concerns curing is affected by relative humidity and wind and maximum protection from rusting of reinforcing steel. For speed. Therefore, by determining the ambient temperature, rel- detailed discussion of these factors see for instance ACI 308R ative humidity, wind speed, and concrete temperature, the rate [6]. A recent article by Erlin, Nasvik, and Powers [15] summa- of evaporation of water from the exposed surface of fresh con- rizes the current understanding of curing with particular crete can be estimated. A nomograph [18] has been commonly reference to low w/c mixes. used for this purpose. With the advent of readily accessible com- EDWARDS ON NEW CONCRETE SURFACES 471 puter power, the equations upon which the nomograph is based mittee C09.22 is attempting to produce a specification covering have been reduced to programs that output the evaporation rate performance requirements for silicate products, but to date all given the ambient conditions, or allow calculations of the effects available information is manufacturer specific and formula- of actions such as reducing the initial concrete temperature [19]. tions are proprietary. Nasvik [22] has reported the use of sili- As has been pointed out in the ACI Guide to Curing Concrete [6], cates prior to diamond polishing of floors to enhance surface at low ambient temperatures evaporation rates from fresh con- hardness, and various manufacturers recommend their use in crete surfaces may be even greater than at any other conditions conjunction with less aggressive polishing techniques. because the concrete is warmer than the air, providing an added driving force for evaporation. Thus, early measures to protect Bond Breakers concrete surfaces may be even more important in cold than in Bond breakers for tilt-up construction are another target for hot weather. Because the original nomograph was based on specification writing. Some products are presented as acting models for evaporation from bodies of water and wind speeds both as curing compounds and bond breakers, while others measured at a height of six feet above the surface, Jeong and perform only the bond breaking function. In this area too, no Zollinger [20] have taken the additional step of modifying the test methods exist to characterize the performance of bond evaporation model on which the nomograph is based to more breakers and therefore users must depend on manufacturers’ accurately reflect real-world values in concrete. Their model and claims. A range of products are established in the market, but experimental data indicate high sensitivity of evaporation rates formal comparisons are not possible without an agreed on test to wind speed at the concrete surface and suggest that the ACI method. A task group within C09.22 is drafting a specification nomograph overestimates evaporation from concrete surfaces and exploring test procedures. after bleeding has stopped. High temperature curing, commonly referred to as accel- Dry Shake Hardeners erated curing, but better described as heat curing, has received Granular materials, including natural silicate minerals, considerable attention in the wake of failures of cast products ferrosilicates, and iron may be broadcast on freshly placed attributed to excessive temperatures during the curing cycle. In concrete and trowelled into the surface to produce exception- the precast industry, heating concrete forms, usually with ally wear resistant surfaces. Here again a multitude of products steam, increases the turn over rate for reuse of the forms by are available but no specification literature exists beyond rapidly producing sufficient strength to allow form removal. that supplied by the manufacturers. A draft specification is Increased temperature generally increases the rate of all currently being circulated in C09.22. chemical reactions, but a number of precautions apply. At high temperatures some equilibrium reactions may actually be New Developments reversed, and all of the complex hydration reactions involved in hardening of concrete are not affected equally by tempera- Internal Curing ture. Perhaps even more importantly, thermal expansion Increasing use of high performance concretes has brought stresses introduced in the plastic concrete must be relieved in with it several new concerns and response to new problems. the hardened products to prevent cracking. The probable Aside from the need for special attention to early curing cause of some failures is the formation of deleterious hydra- conditions [7] the possibility of internal desiccation leading to tion products at higher temperatures. Agreement on maximum autogenous shrinkage arises in low w/c mixes. Mather and allowable temperatures, and heating and cooling cycle rates is Hime [23] calculate that for concrete made with w/c below 0.4, being sought in ACI 308 T.G. on accelerated curing. not all of the original mixing water-filled space can be filled Heat curing of high-performance concrete has been stud- with hydration product. They observe that the critical feature ied by Freyne, Russell, and Bush [21]. Based on experiments of the chemical reaction between the constituents of the ce- involving 31 different HPC mixtures and six different heating ment and the mixing water is the ratio of their volumes, and schemes, and the measurement of 1 day and 28 and 56 day that for w/c of less than 0.4 some of the cement will remain un- strengths they concluded that heat curing was damaging to hydrated. In practice, externally supplied water is ineffective in ultimate strength potential and sometimes even failed to penetrating into mass concrete because of the rapid develop- accelerate early strength development. Intense heat (60–71°C ment of low permeability of the mass. A process described as (140–160°F)) was found to be more damaging to ultimate internal curing has been developed to help reduce cracking in strength than moderate heat (30–42°C (86–108°F)). They HPC slabs, and provides a solution to the w/c dilemma. concluded that heat curing might be useful in a business model Internal curing differs from traditional curing in that it emphasizing speed of construction, but not always pragmatic involves an addition to the concrete mix before it is placed in a model emphasizing life-cycle cost. rather than action taken after placement. Internal reservoirs of water are created by adding high moisture content struc- Other Materials Applied to New Concrete tural lightweight aggregate (see chapter in this volume on Lightweight Concrete and Aggregates) or water absorbing Silicates polymers to the mix. This water is more strongly held than Application of alkali silicate solutions to new concrete has been the free mix water, but available to become water of hydra- practiced for many years. In 1998 a note was added to C 309 tion or gel water throughout the mass as needed. Strictly specifically excluding silicates from the specification since they speaking this is curing by means of an admixture rather than are not membrane formers. No known silicate formula reduces action taken to retain water. Both AC I and RILEM (Interna- water loss in the C 156 test to the level specified by C 309. How- tional Union of Laboratories and Experts in Construction ever, when properly applied, silicates do harden and/or densify Materials, Systems and Structures) [24] are actively develop- concrete surfaces. Under certain conditions, they are used to ing specifications around these products. Bentz and Snyder produce highly polished, nearly impermeable floors. Subcom- [25] have developed equations for calculating the level of Voltage is applied to the primary of the transformer. a plot of resistivity vs. concrete strength. Wei. ASTM Standard Practice for resistivity begins to rises as dissolution and precipitation com- Estimating Concrete Strength by the Maturity Method C 1074. Unless one understands the be useful in designing curing systems for concrete. Since rapid construction An X-ray environmental chamber at the Technical Univer. and new test procedures for evaluating ing. hydration process in internally cured HPC as a change in the ously shows a readable value of the local integrated water loss in average bulk property of cement paste or mortar [30]. For a discussion voltage and current in the toroidal mold are measured to provide of these methods see the chapter in this volume titled Predic. its curing (hydration) history. These An array of instrumental data on hydration is appearing. it does difficult because with direct current. (308S) offer extensive guidance. Their data for mixtures ranging from tion of Potential Concrete Strength at Later Ages. providing a profile practicable curing procedures have been applied. electrodes introduce errors. Needs for Future Work Research on Hydration Some of the work called for in the previous version of this Instrumental analytical methods for study of the early stages of chapter has been accomplished. X-ray absorption is proportional Reliable curing monitoring methods that can be used by to the density of the material through which the X-rays are pass. schedules are frequently important. and (IV) hardening period wherein resistivity of the maturity testing method for determining in-place increases as hydration continues to immobilize water in the mix. which employs a transformer principal. and its ment saturate the mix water. The method generally assumes that best All of these effects are seen in less than 24 h. efforts to find methods to sity of Denmark has been used to measure drying/hydration of establish how long curing measures must be applied in specific cement pastes at various depths within the specimens under situations or to specific structures will undoubtedly continue. and strength have been around for over 60 years. and Li [35] have devised useful for measuring the curing environment in test chambers. (II) competition period wherein rate of strength development [27]. humidity and air velocity. pete. ous cements and admixtures. carefully controlled conditions. Maturity test. kg/m2. Following changes in the resistivity of fresh concrete is tinually varying atmospheric conditions. The unit. current is used to avoid polarization. and there has been an the hydration process include X-ray absorption.472 TESTS AND PROPERTIES OF CONCRETE saturated lightweight fine aggregate required for complete state should be distinctive allowing continuous measurement curing of HPC. polarization effects at the not appear to be appropriate for measuring the effects of mate. unlike nonreactive information in a multidimensional understanding of the porous materials in which a drying-front can be observed to pro. avoiding separate measurements of temperature. 0. to free and bound water allowing the monitoring of hydration terest. With Senbetta [1]. (III) setting period wherein resistivity slowly increases as hy- has been developed for regulating and ensuring the proper use drates are formed. In practice of the cement hydration process. these specimens initially appear Another essential component of future developments to to dry uniformly throughout as water is consumed in hydration improve the curing of concrete is the developments of effective [29]. complex chemistry of cement hydration. The device is effective even with con. development by Tikalsky and Tepke [28] at Penn State. the same specimen in its initial saturated condition. which becomes the secondary of a trans- Maturity testing methods as a means of predicting concrete former. nuclear increase in effort and attention to curing in general. the device should be useful for laboratory studies of vari- be terminated and/or when forms or bracing may be removed.3–0. relative progress as the microstructure of the product develops. and a dried specimen will absorb less than determine the effectiveness of the curing are much desired. in the . need for curing and its profound impact on the properties of Proton Magnetic Resonance would seem to offer a way to concrete. microwave resonance and resistivity programs at NIST and within the USACE are aimed at better measurements. time. of the proportion of water in the sample of each type. However. inspectors at job sites. Active magnetic resonance. Li. a noncontacting method of measuring concrete resistivity. the only work found in this field is the use of nuclear Curing Meter relaxation NMR experiments (T2 relaxometry) to follow the The Curing Meter devised by Hansen and Jensen [26] continu. It might be evolution of gases are still issues. and if high frequency alternating rials applied to the concrete surface since calibration of the de. Although impractical for field- the index may be used to decide when curing procedures may work. Unfortunately. as well as the effects of curing pro- Commercial systems are available and a system is under cedures on hydration.5 w/c allowed them to identify four periods in the early mating methods are based on calculation of a maturity index uration of cementitious mixtures: (I) dissolving period (initial hy- associated with the relationships between a concrete mixture’s dration) wherein resistivity falls as soluble components of the ce- temperature changes. This work contributes to understanding of the mechanisms educational programs to enable people to develop a real ap- of water movement in the drying/hydration of cement and may preciation for the value of curing. composed of an evaporation cell and a capillary Time-Domain-Reflectometry microwave spectrometry [31] tube mounted on a thin aluminum plate is shown to register the has been applied to cement samples to show signals assigned total loss from a fresh concrete surface over a time period of in. uniformity of contact and vice assumes evaporation from a free-water surface. The ACI Guide (308R) and Specification cementitious mixtures. Mortar or concrete is cast in a Maturity Testing ring shaped mold. All of these have been applied to give a more understanding and better practical control of all the factors detailed understanding of the early stages of hydration of involved in curing. so a high w/c ratio specimen will absorb less X-rays than a the properties of concrete at the end of the curing period to lower w/c specimen. the steps prescribed to cure the concrete merely be- follow the kinetics of transfer of water from the free to gel and come requirements that one must satisfy without concern for combined states since the chemical shift of the proton in each the end result. this author feels that. ceed from the surface inward. experimental data have been used in combination with the NIST There is an opportunity for someone to integrate all of this CEMHYD3 computer model to verify that. 6. EDWARDS ON NEW CONCRETE SURFACES 473 construction of concrete structures. Aalborg University. “Drying/Hydration in Cement Pastes During Curing.. 45–47. Federal Register: September 11.” Journal of Materials. Paper No. 1971. 2003.” Kansas DOT. curing of the concrete con. “Polishing Concrete with Diamonds. Session 709. “Maturity Testing Is the Future. American Concrete Institute. No. 3.. 1998. tional. 176. Dehn. pp. T. MI. No. D. Krumbach.. Kärger. Dec. Destructive Testing. Properties of Concrete and Concrete Aggregates. Madsen..msi-sensing. the primary means ments. Waterways Experiment Station. N. that is how soon after the [15] Erlin. and Carino. Gaithersburg. Vol. 1998. [13] Covarrubias. The effectiveness Rule. or a membrane-forming curing compound. Evaporation. Cement Hydration Process Using Resistivity Measurements. R.. Dakkouri. Meggers. Extension to Internal Curing Using Saturated Lightweight Fine pp.S. May/June. Dec.” Materials [8] Poole. University of Leipzig. struction. and Griesel. “Amount of Water Required for Properties of Concrete and Concrete-Making Materials. J. P. N.. Vallee. F. 361–365.” Significance of Materials Journal. 2003. E. 606–616. C.” NISTIR 6295. www.. A. 1978. P. ASTM International. Institute of Standards and Technology. Vol. Inc. M. Water Balance and Water [10] Distlehorst. pp.. 774–786. Vol. Report.. Russell. 2003. 2003 “How Poor Curing Leads to Scaling. J. N. Materials. June. KS. Tests and Properties of Concrete and Concrete-Making pp. 1966. water absorption.” Significance of Tests and 1863–1867. PA. West Conshohocken. Vol.. 557–565. . URL: http://www.engr. and Jensen. pp. “What Is Cold Weather?” Concrete International. 9. Lamond. “Curing and Curing Materials. and Zollinger. November 2003. “NMR Studies on Hardening Kinetics. “Curing Materials. 2004. URL: http//ciks. FL. “Guide to Curing Concrete. American [27] Arneson. K.. V.. Klieger and J. 1999.” Engineering Institute. C. West Conshohocken. B. W. Vol.” Significance of Tests and [23] Mather. Nov. 1997... M. E. 1994. M.” Concrete Con- West Conshohocken. 2003 “Curing Portland-Cement Concrete Pavements. Zimmermann. mentary. Z. Friedemann. 100. 58–59.. 3. 522–529. origins of batch-to-batch variability and develop products with [20] Jeong. Vol. 2003 [9] Carino. O. gov/bentz/drying/ Oct. “Use of Curing Membrane in Concrete Pave- From the curing materials point of view. Sept. W. Chapt. Aggregate” Cement and Concrete Research. B. 2000 tional. URL: http:// Mexico. 2003.. D. pp. pp. plas- Architectural Coatings. T. 1991. G. O. Concrete: Report of State of the Art. Eds. [12] “Tests of Membrane-forming Compounds for Curing Concrete. G. Penn State. durability problems arise as a result of poor concrete sur. [3] Proudley. H.. D. F. 56–58.. pp. [17] Basham. Transport in Cement Matrices for High-Performance Concrete.” Significance of Tests and 2002. C. K. Dec. ASTM STP [26] Hansen. URL: www.php Nov.. Army Corps of Engineers. ing evaluated. compounds used in volume are low-cost. Detroit. [22] Nasvik. [2] Carrier. “Concrete Curing: Plastic Shrinkage Cracking. is preventing the drying of concrete [14] National Volatile Organic Compound Emission Standards for by covering the surface of the concrete with cloth. ASTM Complete Hydration of Portland Cement.org/tc_icc. J.” scale are applied to study manufacturing techniques and the Kansas Department of Transportation. K. logy and Model for Evaluation of Curing Effectiveness in Concrete Pavement Construction. PA.. low-margin items. [21] Freyne. D. ASTM International. No. 11. H. X.nist. pp.htm. [6] ACI 308R-01. 2001.rilem. 25.” 76th Annual Meeting of the Transportation Research Board. ASTM International. Germany. “Water Retention Efficiency of [32] Li.” Proceedings of the ence. Nasvik. 40–49.. P. Vol. 478–483. pp.. J.. 1954. cbt. “Heat Curing of References High-Performance Concrete Containing Type III Cement” ACI [1] Senbetta. B. 100. F. the [18] ACI 308. K. and re. Depart- 169. MD. Detroit.. [30] Nestle.. created Sept. Freude.-H. Geier. pp.. F. Hobson. Environmental Protection Agency. crete. and König. T.” and Structures. J. Technical Memorandum No. W. Vol. J. January.. crete Construction. 5.. of curing. Jan. University of New Mexico (in press). Curing Meter. CRC Press. and Anderson. 58–59. 1999. PA. E. and Li. paper. Detroit. E. 1955. 40 CFR Part 59. J-P. 449–454.htm. and Snyder. [16] Shotwell B.. draft document to be published by FHWA. S. If available technologies for studies at near molecular [19] Wojakowski... pp. J. J.1–98 “Standard Specification for Curing Concrete. Sept. 24. 48848–48887. E. “Protected Paste Volume in Concrete. “Curing Materials. R. Materials Journal. 6. “The Maturity Method.. ASTM [25] Bentz. of these materials depends on the quality of the materials. pp.. PA. and Hime. the 63. Eds. No.” ACI No.” (03-2183) Transportation Research Board..” technology of their formulation and manufacture remains rudi. 88–90.” Concrete Interna- Concrete Institute. STP 169A. as stated earlier. No. Malhotra and N. “Curing of High Performance html/ curing. Final tic. November/December. and Temperature.. 2001. 2003. N. “Preliminary Interpretation of Portland Membrane Curing Compounds. K. and how well they are applied and kept intact Enough?” Concrete Construction. Jr. “Curing Concrete. MI. and Powers.. October 2001.13.” Handbook of Non.. 2004. August 2002. flectivity need to be characterized and their contribution to cur.. Hansen. “Curing Materials.. ASTM International. The special prop. E. 6-385 U. For a great deal of con. Finally.com/tdr_concrete.edu/News/Eps/2001_summer/ [7] Meeks. pp. and in place for the specified length of time. “Development of Test Methodo- predictable reliability and special properties. J. “Evaporation Rate Program. F..” Con- erties of sheet materials for insulation. 253–257. Wei.” tinues to be an under appreciated step. National [29] Bentz.. and Tepke. 34. [5] ACI 116R-00 Cement and Concrete Terminology. C. Carino. and Bush. pp. time of application of the materials. “How Much Curing is concrete is placed. 29. L. Proceedings of the 15th European Experimental NMR Confer- Bleeding. pp. Properties of Concrete and Concrete-Making Materials. 41st Annual Paving and Transportation Conference of New [31] Material Sensing and Instrumentation.” Concrete Interna- STP 169B. June 2002. W. No. Boca Raton.. it may be possible to understand the Research. J.. 970882. Bureau of Materials and film formation process.. and Laycraft. 6. [4] Swanberg. January 2003. 12–17 June 2000. 101–146. D. 25. Topeka.” American Concrete [28] Tikalsky.psu.. face properties because of the lack of adequate curing. D. West Conshohocken. J.. ment of Building Technology and Structural Engineering. 2003 [11] Leitch.. and Wojakowski. [24] RILEM TC 196-ICC: Internal curing of concretes. D. 2003. 6 Jan. pp. H. MI. 2003. because liquid membrane-forming curing Vol. Such voids are larger than those ronments. Such voids are generally spherical from Gonnerman’s report is of particular significance: in shape and considerably smaller than the natural air-voids. Entrained Air—The air. W. and C (1983) by Paul Klieger.S. THE CONTENTS OF THE ing workability. Grace & Co.) A material conforming to the requirements in ASTM cement. and ASTM STP tion procedures. and yield of cementitious mixtures. 4. synthetic detergents (petroleum fractions). Army Corps of Engineers. The following definitions can be useful in discussing air- entrainment in mortars and concretes: Introduction 1. These were the forerunners of materials called air- entraining additions. (2) is concerned with this class of materials. as well as alter the workability entrainment. The current edition will some of the topics that will be addressed in this chapter. This chapter classifications: (1) salts of wood resins (pine wood stumps). ment that inadvertently contained “crusher oil” reduced surface (See ASTM Terminology Relating to Concrete and Con- scaling as did many of the blends of portland and natural ce. enhancing durability. Materials similar to presently used additions are called entraining admixtures. the crusher oil and tallow was due entirely to the additional air 6. The author acknowledges the adequate performance. and construction parameters 169A (1966). U. ground with hydraulic cement. crete Aggregates (C 125) for the definition of an admix- ment that contained tallow added during grinding of the natural ture. The following paragraph tentional air-entrainment. tious mixtures at the time materials are batched for mix- tion of the cement. and effect- TO PREPARE THIS CHAPTER. what are the effects of concrete mate- authors of the prior three editions: ASTM STP 169 (1956) by rial properties including other chemical admixtures. times referred to as natural air-voids.—Conn. B (1978). Laboratory tests disclosed that the beneficial effect of C 260 can be regarded as an air-entraining admixture. Entrained Air-voids—Air-voids resulting from the use of in- ment is presented by Gonnerman [1]. A thorough survey of the early development of air-entrain. now used to produce air-entraining ce. the use of which results in intentional air-entrainment. 474 .. There are many materials capable of functioning as air- ments. the air-entrainment was not intentional an addition.3] came to similar conclusions. In an extensive evaluation program. Air-entrainment should be 3. (3) salts of 1 Research Fellow. field conditions. is a well-established means for greatly enhancing the ability of 2. the air-entraining admixtures when added with the other concrete Bureau of Public Roads [4] separated 27 commercial air- ingredients at the time of mixing. Cambridge. Entrapped Air-voids—Air-voids not resulting from inten- mandatory when concrete is to be exposed to such harsh envi. ing. how can they be specified and tested to ensure 4th edition were drawn on.41 Air-Entraining Admixtures Ara A. tional air-entrainment. both as to the process of entraining air. review and update the topics addressed by the previous authors.) but resulted from the presence of the crusher oil or the use of the tallow as a grinding aid during the production of the Materials Used as Air-Entraining Admixtures cement. Consul. Definitions sponding up-to-date references. concrete to resist the potentially destructive effect of repeated that becomes part of a mixture during the process of air- cycles of freezing and thawing. Wuerpel. R. and introduce new relevant technology with corre. Air-entrainment—The introduction of air in the form of discrete air-voids or bubbles dispersed throughout the Air-entrainment in concrete has been universally accepted and mixture as a result of the use of air-entraining materials. Air-Entraining Addition—Air-entraining material inter- entrapped in the concrete by these air-entraining agents. how do they function. (See ASTM Terminology Other investigators [2. Jeknavorian1 Preface What are these materials. Air-Entraining Admixture—A material added to cementi- showed no relationship between surface scaling and composi. made up of discrete air-voids. particularly when chemical deicers are being used. These projects (test roads constructed in 1935–1937) 5. resulting from intentional air-entrainment and are at as on pavements and bridge decks. produc- Carl E. the more widely used entraining admixtures submitted for test into the following method for obtaining intentionally entrained air. MA 21240. but they did show clearly that portland ce. on air content and hardened air-void parameters? These are tant—Concrete and Concrete Materials. In Relating to Hydraulic Cement (C 219) for the definition of these early instances. and Later work by Powers and Helmuth [20] indicated that.6 0. plasticity and workability are nearest air-void. particularly when chemical deicers are used. the air content of the mortar fraction is essentially TABLE 1—Air-Void Parameters at Optimum Air Contents of Concretes (Adapted From Tables 17 and 18 of Ref 14) Maximum Size Cement Content.75) 9. pressure below the tensile or rupture strength of the paste.20) a Optimum air contents determined from the relationship between expansion during 300 cycles of freezing and thawing and air contents of concretes. 4 (4. umetric air-content requirements for concretes made with dif- To achieve the improvement in frost resistance.5) 6.) There less. enabling a reduction in water content. As Dodson [6] sive forces. capillary cavities contributing to the growth of ice bodies in sulfonates. (mm) 21⁄2 (63) 4. shows this effect of maximum size of aggregate on the op- spacing factor.20) No.18) 11⁄2 (37.152–0. Powers’ [17–19] total air contents of the mixtures shown in Table 1 vary through contributions to the understanding of how entrained air func. and is the most important air-void parameter for increased.0 10. Paillere [8]. in which the air-entraining agent is used as factor for frost resistance should be about 0.5) 4. maximum distance from any point in the cement paste to the ally entrained air. agents by the different degree of hydrophobicity they impart to the surface of the entrained air-void. timum air content along with void spacing factors.3 0. general performance characteristics for each group. A study another important factor may be the diffusion of gel water to [12] on the various fractions for one class of materials.012 (0. (The to characterize an air-void system and laboratory freezing and discussion to follow will also be applicable to the use of air.008 in. _ Cement Content. A modified and expanded version of Helmuth’s has previously noted. alkyl. which promotes ice Hardened Concrete growth within the void causing water to be withdrawn from the surrounding paste by suction. and (7) or. Ramachandran sible for distress to cementitious mixtures.24] provided further substantiation of the void spacing factor mitigated with air-entrainment.203 mm) is required for ex- concrete plays a significant role on sound absorption. have to travel. to reach a protective thus reducing segregation. (6) fatty and resinous acids and Powers developed the concept that internal hydraulic pres- their salts (paper pulp and animal hide processing).009 (0. Pow- vide an excellent description of the chemistry of air-entraining ers showed that the air-voids must be well-distributed through- admixtures and discuss their function in freshly mixed and out the cement paste and sufficient in number so that each void hardened concretes.4 0. This is an indication of the distance water would placement and consolidation can be achieved more readily.5 0.007 (0.3 L Optimum Air Mortar Air Optimum Air Mortar Air in.23) 5. (0.0 9. to provide concrete with a high degree of resistance to freezing Powers [18] developed the concept of air-void spacing factor and thawing. Although the vide efficient protection to the cement paste. (0.0 0. modern air-entraining agents continue model of ice penetration in concrete has been proposed by Chat- to consist of anionic materials based on their track record of terji [21]. (4) salts of petroleum tions in providing increased frost resistance have been out- acids (petroleum refining).18) 4. ferent maximum sizes of coarse aggregate.2 0. thawing data available at the time to show that the void spacing entraining cements. (processing of animal hides).2 0. Table 1.01 in.007 (0. Kodama [9]. the inten. % Content. Water movement under suction is The major reason for the use of intentionally entrained air is therefore unable to produce expansive pressure. and Bauverlag GmbH [10]) pro. during the freezing process. and the pro- air-entraining agents into five broad categories and provide tected volumes overlap to leave no unprotected paste.5 8.25 mm) or an addition during the grinding of the cement clinker. water volume produced during the freezing process is respon- Several reports (Rixom [5]. similar performance to neutralized Vinsol Resin®. To keep this internal [7]. to the use of intention. [22] indicates that an upper limit study [13] found that the internal surface area of air-entrained of about 0. these cavities resulting in the development of additional expan- ance are obtained from the C8 to C10 fraction.30) 10. who attributes the specific efficiency of air-entraining providing cost-effective and predictable air-entrainment.008 (0.7 0. Another air-void.007 (0.28) 7. % in. These tests called attention to the need for different vol- are discussed in detail by Lerch [15] and Bruere [16]. and bleeding is reduced. (5) salts of proteinaceous materials standing. a wide range. (mm) Content. Whiting and Nagi [11] classify current provides protection to the adjacent cement paste.008 (0. The void spacing factor is defined by Powers as the average are numerous other advantages.18) 3 ⁄8 (9.006–0. in includes gum and wood rosins. These and other advantages concept.0 8.0 9. JEKNAVORIAN ON AIR-ENTRAINING ADMIXTURES 475 sulfonated lignin (paper pulp industry). and size and distribution of the air-voids to pro.0 0.5 8.20) 4.20) 3 ⁄4 (19) 5. Wang treme exposures. The hydrophobic surface is Function of Entrained Air in Freshly Mixed and reported to minimize the ice-paste bond.5 9.5 9. which are reported to provide addition to the generation of hydraulic pressure during freezing. Dodson [6]. (mm) Content.5 9. adapted from tionally entrained air must have the proper total volume of air. .1 0. _ of Aggregate 51⁄2 bags/yd3 L 7 bags/yd. Work by Mielenz et al. sure created by the resistance to flow or movement of excess ganic salts of sulfonated hydrocarbons (petroleum refining).008 (0. Uniformity of frost resistance.011 (0. Extensive freezing and thawing tests by Klieger and Gillot [14] report that alkali-silica reaction can be partially [23. %a Content. Ref 22.5 8. indicates optimal air-void and freeze-thaw perform. % in. For example.008 (0. also. 23) 577 0.3 Concrete. Pleau et al. Additional refinements of the technique enabled the de. sorbed at air-water interfaces and that the surface tension of ance of the concretes when frozen and thawed while immersed the water is decreased about 25 %.27] probed the conse- trained air by the use of an air-entraining admixture will pro. However. well-distrib- increases and workability and cement content held constant. (mm) of air millions Expansion None 1. More recently.79) 302 0.8 1. thors as the distance that freezable water must travel through In concretes without intentional air-entrainment. specific [11] have prepared a comprehensive summary of the various surface. For some air-entraining admixtures. mortar is required in the mixture. evolution.0 0. the cement paste to reach the perimeter of the nearest air-void. Mielenz and his co-workers dealt and Parameters of the Air-Void System in Hardened Concrete extensively with the origin. and number of voids per lineal inch of traverse were factors—concrete materials and mix design.2 3.8 0. system in concrete.3 0. Voids/in. They showed that in the concentrations termination of the total number of air-voids per unit volume of normally used in concrete.013 (0. voids in concrete. The degree of in-filling is reported to be associated and containing a sufficient number of air-voids to meet the void with the duration of moist curing coupled with wet/dry cycling.010 (0. the air con.009 (0. air-entraining admixtures are ad- concrete. (38 mm) maximum size. therefore. trasted with total volume of voids alone. as con.22 39 D 5.2 3. [25] found that the flow concretes dealt with paving-type concrete in which the coarse length concept.2/in.0 4.33) 416 0. handling opera- determined on the hardened concretes as described in ASTM tions. fluences the air-retention properties of discrete air-voids training some volume of air but also that the air-void system formed during mixing.25) 480 0. Air-entrained concretes were pre.5 5.013 (0. whereby the flow length is defined by the au- aggregate was generally about 11/2 in.6 0. rendering the concrete less durable than otherwise indicated The importance of size and distribution of air-voids. In addition to the determination of air content of contributions to the understanding of the mechanism by which the freshly mixed concrete as described in ASTM Test Method air-entraining admixtures function and the influence of a num- for Air Content of Freshly Mixed Concrete by the Pressure ber of different variables. tent may range up to as high as 1 or 2 % by volume. Entrained Air In Freshly Mixed Concrete pared using an acceptable proprietary air-entraining admixture and four nonproprietary materials that exhibited a potential for General entraining air. by the spacing factor. a reduction in total Recently.1 4. The authors found that the size distribution of circles inter- this air is composed of entrapped air-voids that are too large to cepted by a plane and chords intercepted by a line of traverse be effective with respect to improving frost resistance or work.33) 387 0.78 100 Fa 5. and effects of the air-void (C 457). construction practices. a number of refinements to the interpretation of concrete air content with an increase in maximum size of coarse various microscopic analysis have been proposed to allow bet- aggregate is to be expected. As the maximum size of coarse aggregate must be characterized by a large number of small. in.79 550 a A commercial air-entraining admixture meeting the requirements of ASTM C 260. The results of these measurements and the perform. even in the presence of deicing chemicals. spacing factor requirements for adequate resistance to freezing and may increase the effective spacing factor. .28–30] have made significant in these tests. thus possibly and thawing. 0. % % C 457 Voids/in.8 3. less uted air-voids to provide a high degree of frost resistance. and field conditions—that can Practice for Microscopical Determination of Air-Void Content affect air content and quality. ter correlation of air-void systems in hardened concrete to Most of the early field and laboratory work on air-entrained freeze-thaw durability. the air content.11 29 B 6. void spacing factor.006 (0. Freezing and Air Content Specific Number of Thawing % Pressure Air Surface.3 Cycles for Air-entraining Meter Content. can be seen in the results of a study made some years ago in the laboratories of the Factors Influencing Amount and Character of Portland Cement Association.1 0.10% Admixture (C 231). The two studies [26.9 0. quence of in-filling of air-voids by the deposition of ettringite vide an air-void system well-distributed throughout the matrix crystals.476 TESTS AND PROPERTIES OF CONCRETE constant at about 9 %.0 3. The provision of an additional 3 % of intentionally en.15) 990 3.1 4. provide an indication of the actual spatial distribution of air- ability.9 9. Number of in. the TABLE 2—Influence of Air-Void Characteristics on Resistance of Concrete to Freezing and Thawing Air-Void Characteristics (ASTM C 457) Void Spacing Factor (L).1 0. [22] and Bruere [16. It is apparent from these data that interfaces produces a “film” of air-entraining admixture that in- an air-entraining admixture must not only be capable of en. Whiting and Nagi Method (C 231). This adsorption at air-water in water are shown in Table 2.08 19 A 6.26 82 E 5.031 (0. A non-air-entrained concrete was also included Mielenz et al.0 4. Not dodecylbenzenesulfonate) compatible with naphthalene sulfonate- based HRWR. evolution of the air-void system can occur. Synthetic Alkyl-aryl sulfonates and Rapid air generation. Oxygenated petroleum residues Proteinaceous materials Animal tallow Saponin . Mielinz that as long as concrete in the plastic state and in some nous film enclosing each air-void. Moreover. Synthetic Alkyl-aryl ethoxylates Primarily used in masonry mortars. although such interchange is of signifi. Bruere [30]. the overall experience with air-entrained only slightly soluble in water. slower air oil acids alkanolamine salts generation. is influenced by numerous factors. and (4) water content of the mixture. At the same volumetric air content. which associates general performance charac- air. Minor air loss detergents sulfates (e. state of motion. both air gain and air loss of coconut fatty acids possible with continuous mixing. Vegetable Alkali and Relative to wood rosins. Tall Oil Fatty acid—major Slower air generation. workability aids Miscellaneous Alkali/alkanoloamine Older technologies not currently used acid salts of lignosulfonate as concrete air-entraining agents. Compatible with all admixtures. sodium with mixing. especially in acid salts of a mixture of tricyclic low slump mixes. number of air-voids per unit volume. In such instances. and (3) transmission of air across the air-water interface. Smallest air-voids acids—minor among common agents. some of which are: (1) concentration and type of the air-entraining admixture and its in. (3) amount of mix. water-cement ratio. Compatible with all admixtures. thus The amount and character of the air-entrained in concrete possibly accounting for both air gain and air loss. (2) the fineness and composition of cement gredient in the air-entraining admixture influences the amount and supplementary cementitious materials. has shown that such changes do not teristics with the various types of agents. (5) temperature. different air-entraining ter cessation of mixing. take place to any significant degree in air-entrained pastes af. and (6) gradation of the fine and adhesion of the air-voids to particles of cement or aggregate. however. and character of entrained air-voids by its effect on: (1) surface ing energy (time and shear rate). All of these factors will be operative during the mixing opera- cluded that both the total volume of air and the size distribu. JEKNAVORIAN ON AIR-ENTRAINING ADMIXTURES 477 calcium salt of the active constituent in the admixture may be thereafter. Some air loss possible. and air loss possible with continuous mixing. (2) use of other admixtures in the Mielenz and his co-workers theorize that the type of organic in- concrete mixture. Air may increase component.. tricyclic with prolonged mixing. (4) flow and slump of mortar tension. [21] have theoretically con. the author prepared Table 3 due to interchange of air between air-voids and dissolution of (cited in [11]). tion. Based on extensive field experience with the common tion of the air-voids can change in the unhardened concrete classes of air-entraining agents. or concrete mixture.g. admixtures will produce air-void systems having different spe- cance during the mixing process and may be for a few minutes cific surfaces. Mielenz et al. Small to mid-sized air-voids. (2) the elasticity of the film at the air-water interface. and compatible with all admixtures. Applicable for cellular concretes. and void TABLE 3—Classification and Performance Characteristics of Common Air-entraining Agents Classification Chemical Description Notes and Performance Characteristics Wood derived Alkali or alkanolamine salt Rapid air generation. phenolic. Type and Amount of Air-Entraining Admixture fluence on surface tension. coarse aggregates. Coarser bubbles. Minor air gain some Vinsol Resin® acids. terpenes Mid-sized air bubbles. the film at the cementitious mixtures is consistent with the observations by air-water interface may include a precipitated solid or gelati. the active components may partially precipitate. and accelerators may increase air content creases and the void spacing factor increases [21]. Sand gradation is of more importance in leaner versus richer mixes. set accelerators and retarders. with and increase in air content in concrete mixtures [11. placing. and variable air contents. increase in initial slump up to been reported by Berke et al. pumping aids. where the influence of gradation on entrained air is not as marked. retarders. may increase. At without superplasticizers. excellent freeze-thaw treated with surface-active coatings. the specific surface of the air-voids generally de- reducers. higher air contents will be obtained with higher alkali cements. may possibly result in an altered void size distribution of the entrained air. An appreciable increase (3 %) in the quantity of sand particles passing the No 200 sieve (75 m) will decrease the amount of entrained air. whereas oxidized decayed vegetable matter can have the opposite effect. Work by Klieger viscosity modifying agents in air-entrained concrete has no significant effect on freeze-thaw durability. hardness. The ASTM C 185 mor- in air-entrained concrete. and tar test can be useful to detect possible changes in air content high-range water reducers. re. if more than one cement is being used and Chemical Admixtures soluble alkali contents differ significantly. and an increase in the fine- the air-void system to be influenced by interaction between the ness of cement will result in a decrease of the air-entrained in class of air-entraining admixture and the various mixing. air contents will most often increase ment differently. [32].45]. Nevertheless. durability has been obtained both in laboratory and field concretes with these admixtures.15. Other aggregate properties that can affect the performance of air-entraining admixtures include surface texture and shape and organic contaminants [11. and consolidating operations. the rate at which air-voids are Cement entrained in various concrete mixtures can be affected by As the cement content increases. Several studies [33–36] approximately 6–7 in. Although the volume of air-entrained and Stark [31] note that chemical admixtures such as water.42.44]. able detergents present in water can result in excessively high quiring adjustments in dosages of air-entraining admixtures. Sand in the middle fractions. and shrinkage control agents (SRAs). On the one hand. the viscosity of the mix becomes in- both increase and decrease air contents with the spacing fac. and consequently require higher doses of air-entraining agent to achieve specified air contents [11]. Workability and Flowability ceptable air-void systems in concrete admixed with SRAs has Within the normally used range. mid-. to recycled wash water or potable water with relatively high ducing admixtures and polycarboxylate-based superplasticiz. Nonpolar contaminants such as oils can decrease air content. cor. Therefore. the mortar [42–44]. At fixed dosage lev- factor. recommended dosages. pigments. found that superplasticizers can higher slumps (Fig. admixtures is that an increase in the dosage rate will increase Soluble alkalis in cements will influence the required amount the volume of air-entrained and decrease the void spacing of air-entraining admixture dosage [11. and these require less An almost universal guide for the use of air-entraining air-entraining admixture to develop a given mortar air content. tor either remaining unchanged or increasing slightly. Some regular (non-air-entraining) cements dling. more. Guidance on how to assure ac. but decrease when air-entraining admixtures adsorb on rough and cracked surfaces. When air-entraining agents are added This would especially apply to lignosulfonate-based water re. Fig. Moreover. naturally entrain more air than others. Nondegrad- somewhat when used in normal. 1). one can expect an admixture will tend to diminish. (150–175 mm) is accompanied by an involving high-performance concrete mixtures. No 30–100 (600–150 m) is most effective stabilizing entrained air. Several reports [37. care must be exer- A large variety of other chemical admixtures may be used cised to adjust dosages when necessary.38] found that the use of with a far lesser probability of some air loss. . ability to the target slump. the various superplasticizers tested affected air-entrain. when retempering water is used to restore work- over. sufficient to retain the air-voids and prevent coalescence [11]. els. Whiting crease in air content.41]. manifested by higher void spacing factors than Fibers those normally considered acceptable for adequate resistance Synthetic and steel fibers may possibly increase air content if to freezing and thawing. air stability can be enhanced with angular sand particles.478 TESTS AND PROPERTIES OF CONCRETE spacing factors. suggesting minimal impact on air-void quality. han. The maximum and median size of the individual air- voids may decrease [40]. The authors state further that high-range water reducers requiring an increased dosage to achieve target air content. the air-entraining potential of the class of air-entraining admixture. thus ers. Furthermore. 1—Effect of slump on entrained air content (Ref 11). associated with cement properties. Furthermore. rosion and ASR inhibitors. Little information has been Water published that discusses the interaction of these admixtures An increase in water-cement ratio is likely to result in an in- on air content and the air-void system in concrete. Fine Aggregate Changes in grading of sand may alter the volume and nature of air in the mortar [39]. These include normal. order of material addition to a truck mixer. With no slump concrete (as Mixing in the case of paving and extruded concrete applications). The air content will increase with thaw durability to similar corresponding mixtures with lower increased time of mixing up to about 2 min in central station- workability. after which the air content may remain ap- risk of segregation and the coalescence of air bubbles. Khayat et al.50] have cautioned that entrained ary [15] or paving mixers (and up to about 15 min in some air can lower the viscosity of SCC mixtures thus increasing the transit mixers). which has be. such as pozzolans (fly sorption of the chemical on rapidly hydrating aluminate ash. air content remains unchanged by adjusting the air-entraining tors feel that fly ash uniformity and changes in air content agent dosage. several screening tests have been pro. removal of the effec- admixtures. everything else entraining agent. As indicated in Table 3. field experience has found the the drum and on the blades. as long as the including cement in the fly ash slurry [58]. Alternately. If vibration is applied as required. values are also not uncommon. being equal. Metakaolin. less air will such loss-on-ignition. air Gebler [56] called attention to the effect of certain fly ashes contents may possibly increase with prolonged mixing. calls for using a reagent-grade surfactant and not generally affect the hardened air-void system.61]. generally require increased amounts of air-entraining specific surface and spacing factor. Different air-entraining ad- [53–55]. from an increase in the ratio of air-escape to foam-generation in the latter portion of the mixing period. The impact of slump on air generation can be line prior to the water reducers and the addition of cement and most significant at the far ends of the workability range for supplementary cementitious materials. Some ASTM C 618 class C ashes may actually lower mixtures may require significantly different mixing periods to the dosage of air-entraining admixture dosage. tive portion of the entrained air will not occur.) and ground granulated blast-furnace phases of the cement. Klieger and reach maximum and constant air content. [49. that the critically important spacing of small en- air contents have been reported when the air-entraining ad. The air-void system. The reduction in air may result from an increase in store the required viscosity to minimize these potential con. as characterized by slags. etc. and mixing time [11. use of up to ten times the normal dose of air-entraining agent condition of blades. is not uncommon to achieve target air contents. Although higher however.15. mixture is added after the cement has been batched [11]. Other investiga. trained-air-voids in the matrix is not significantly disturbed. The concrete entraining agent to the sand either contained in the weigh slump will influence the extent to which vibration can alter hopper or on the conveyor belt. A common mode of batching is adding the air. air-entrainment varies inversely with temperature come a common practice by many concrete producers. is re. Preferably. In one study The amount of air-entrained by any given mixer will decrease [46]. The “Foam Index Test” [6]. is a [15. unlike silica fume. With regard decrease will result from overloading the mixer. silica fume. espe- in reducing the stability of the entrained air-void system as a cially when the concrete is re-tempered with water or normal function of time after mixing. An increase in entrained air will Vinsol Resin®. There is increasing evidence. namely. The use proximately constant for a considerable period before de- of viscosifying admixtures or fillers such as limestone can re. are possible by measuring the surface area of the carbon content in fly ashes [59]. in a given concrete mixture. from adsorption of Supplementary Cementing Materials the chemical by unburned carbon in fly ashes.43]. no slump and self- consolidating concrete mixtures. creasing. an approximate 30 % relatively simple procedure involving adding increments of increase in air-entraining agent dosage would correspond be an air-entraining agent to an aqueous slurry of fly ash until a required for a roughly a 30°F (15°C) change in concrete tem- stable foam is produced. modern day concrete operations. and wood rosin-based air-entraining occur if the mixer is loaded to less than rated capacity. agents should be dispensed separately from the other chemical and if the mixture is designed properly. Furthermore. a paving mixer. which claims improved predictability to concrete and with higher slump [11]. be entrained at 40°F (4. Changes in concrete temperature do less variability. the The amount of air-entrained can vary with the type of mixer. For concrete slumps above 5 in. very fine particles in the mixture with prolonged mixing action. is impaired if hardened mortar is allowed to accumulate in erations. and a agents to be more effective for these applications. be entrained at 100°F (38°C) than at 70°F (21°C) and more will posed to predict relative changes in the dosage of air. Moder- Batching: Sequence of Material Addition ately small air-voids may tend to work upward if the vibration The air content of concrete mixtures can be affected by the is intense and prolonged. air-entraining with just enough intensity and duration to effect consolidation. In some cases. (125 mm). the rate of air content loss increases test. will cause air-voids to rise to the surface and be expelled. a number of investigators [47–52] have confirmed develop significant differences in the volume of air-entrained that these highly workable mixtures exhibit comparable freeze. phenomenon and techniques for control are described in an ACI Committee Report [57].0 %. gum rosin. entrapped voids can be appreciably as the blades become worn. . A central to self-consolidating (SCC) and self-leveling (SLC) concrete drum stationary mixer. or as the mixing action included in the entrained air-void system from compaction op. The larger natural voids are most readily expelled [21. and a transit mixer may mixtures. One general rule of thumb. cerns. In order to minimize unexpected Temperature changes in air content due to changes in fly ash properties For a constant amount of air-entraining admixture. Further details concerning this and high range water reducing agents at the jobsite. the air-entraining air content [11].60]. A reported improved version of the perature.4°C). lower even by intense vibration. or from ad- Supplementary cementing materials. JEKNAVORIAN ON AIR-ENTRAINING ADMIXTURES 479 [23] indicates that the optimum mortar air content remains at admixture can be introduced near the discharge of the water about 9. considerable irregularly-shaped. Vibration ported to have no significant effect on air-entraining agent Intensive internal vibration applied to freshly mixed concrete dosages to achieve a target air content [11]. does not usually appear to admixtures to attain the proper volume of entrained air be harmed by prolonged agitation. In other words. mixing speed. externally applied vigorous vibration may differentiating between the air in the aggregate particles and cause an increase in air content. the the entrained air in the paste. Migration rate of the air-voids is a function were then chosen at random and the distance to the nearest of bubble size. Although such measurements are time researchers in the early 1990s. freeze-thaw data because the predicted air-void distribution ment.9 m/min). a vibration frequency Mixed Concrete eliminates the possibility of significant errors of 8000 vpm is recommended for paver speeds greater in differentiating between air in the aggregate particles and air than 3 ft/min (0. desired air-void system. specifically a sin- this technique holds some promise as a means of applying ad. originally developed by European variety of structures. nondurable—can be predicted. representing air- tains bubble size. in this case. As a scribed in the C 173 Test Method for Air Content of Freshly general guide for slip-form operations. and injecting into a water must travel to the nearest air-void. Following the traditional grinding . The viscous fluid re. ASTM C 457 is a procedure for de- Freshly Mixed Concrete termining the total air volume. Points in the paste buoyancy recorder. concrete pro- work. in a cubic cell of cement paste [64]. was used to place nonoverlapping spheres. and thus the AVA. tions in air contents may possibly result from variation in the rather than on the size and distribution of the air-voids in the amount. as Progress has been made with various automated tech- currently designed. cement-paste matrix.63]. is a function in turn of the mixed concrete in the field. Mielenz and his co-workers [21] show the results of meas- With the introduction of the AVA (the so-called “air-void ana. as with many of the other variations in concrete liably indicate air-void parameters directly on the freshly materials and production practices. Since air-entraining admixtures are generally incompati. quirements of the ASTM C 260 Specification for Air-Entraining tor) within the paste fraction or increase the ratio of air Admixtures for Concrete. which can be related to bubble size distribution. General Comments Specifications and control tests will continue to be prima- One of the most frequent and pronounced causes for varia. As an improved means of better ascer- crete is still in the plastic state. bration and temperature fluctuations. care must be exercised to pre. which consists this procedure is generally adequate for use with all ordinary of comprises a computerized control unit (PC) with a 19 in. and allows the bubbles to rise and contact a voids. The method calls for sieving the taining the accuracy of spacing factor to predict the distance mortar fraction from a concrete mixture. is not expected to be operated under field niques for measuring the air-void parameters in hardened con- conditions. extensive correlation of results with the established does not adequately represent the actual random distribution ASTM C 457 method needs to be performed before the AVA of air-void. produced by air-entraining admixtures conforming to the re- prove the distribution of the air-voids (number. whereby three zones of durability—probable. type. The change in buoyancy is recorded as a function of tial distribution. traverse equipment enable the measurement of chord-size dis- and Air Content (Gravimetric) of Concrete (C 138). inaccurately low air content readings due to insufficient time to expel the air. as shown in method (ASTM C 173). Until such a test has become ac- alertness and adequacy of the control and inspection given the cepted by standards organization such as ASTM. and a microscope objective dense aggregate.480 TESTS AND PROPERTIES OF CONCRETE significant air loss (up to 4 %) can occur after 30 s of vibration. the RapidAir 457 Automated-Air-Void-Analyzer. the delicate buoyancy measurements are intolerant of vi. they can provide reassuring evidence of the ef- indication of the quality of the air-void distribution (specific fectiveness of the air-entraining admixture in providing the surface and spacing factor) can be estimated while the con. factor of air-voids by either a linear traverse method or a modi- mined in freshly mixed concrete either by the gravimetric fied point-count method. or the volumetric per unit volume of concrete can be calculated. Yield. a computer program viscous fluid contained within a column. A mean spacing model for air-voids is proposed method can be recommended for acceptance testing. intermediate. urements of air-void characteristics of cores taken from a wide lyzer”) instrument [62. a video camera. and spacing Up until recently. tents in the range of the optimum air contents shown in Table vent them coming in direct contact while being dispensed into 1. specific surface. rily based on the volume of air-entrained in the concrete. or spacing fac. do not correlate well with ASTM C 666 ditional quality checks on air-entrained concrete prior to place. where the larger bubbles rise faster than smaller air-void surface tabulated for each point. which is most useful for determining Table 2. tribution of air-voids from which the total number of air-voids sure method described in ASTM C 231. the air contents of concretes made with lightweight aggregates. only the total air content could be deter. ducers and specifiers will continue to rely on the total air con- ble with other admixture types. both total air content and some consuming. Additional refinements of the linear method described in ASTM Test Method for Unit Weight. and will be assured that the size and distribution of air-voids the concrete during mixing. Large errors may be introduced where highly mounted on a moving stage. this method is time consuming and yield paver speeds. and more. crete [66–69]. The volumetric method de- added air is in the form of relatively large natural voids. until techniques such as the AVA can re- This last cause. However. Attiogbe [65] feels that the air-void parameters time. the pres. or condition of the air-entraining admixture. thus providing a spa- ones. will provide adequate resistance to freezing and thawing when Any influence that would maintain or even actually im. While as measured and calculated by ASTM C 457. However. vesicular or porous aggregates are used due to the inability of In some instances. One of the more promising methods is based on Regarding the ASTM C 231 Pressure Air Meter method. with lower frequencies at lower in the paste. Further. Hardened Concrete The important characteristics of the entrained-air-voids can Methods for Determining Air-Void most readily be determined in hardened concrete by micro- Characteristics scopic examination of sawed and ground surfaces of a sample of the hardened concrete. gle spacing factor. types of mortar or concrete mixtures containing reasonably color monitor. boundary surface to air volume (specific surface) would be desirable. ” 9th Inter- The testing required by ASTM C 260 reduces simply to a national Conference on Alkali-Aggregate React.1. M. B. American Concrete Institute. respect to the effectiveness of the entrained air in enhancing [4] Halstead W. The methods by which these effects may be 1. need to evaluate the influence of these air-entraining materials [5] Rixom. 1954. 19 June 1941. also.. era. lar admixture under test will produce relatively stable air-voids [15] Lerch. After scanning. Since there was no ready and reliable means for de. 1. Collins. K. 1992. No. Application of Concrete Admixtures.. M.” expect that the quantity of the air-entraining admixture repre. American Concrete Institute. T. J. L. 46–52. all in comparison with a similar concrete mixture [9] Kodama. Vol. The accuracy of the RapidAir system was verified recently by an extensive round robin test program conducted References by 13 European laboratories [69]. 1998. tested are given in ASTM Methods of Testing Air-Entraining Ad.” Engineering News-Record. 33. M. Vol. R. Noyes Publications. 291–297. cation. Aug. Rilem and thawing. McHenry. 1. a contrast enhancing tech. Vol. The plane section is crete shows a void spacing factor not exceeding 0. Vinsol Resin®.” Research that will become widely dispersed throughout the matrix of Laboratories. 272–1 to 272–20. “Manufacturing Air-entrained Concrete. 58. March rious effect on other properties of such mixtures. C. Park air-entraining admixture under test may exert on the bleeding. New York.” Journal. and Numanno. Supple- sion of chemical requirements. and T. “Void Spacing as a Basis for Producing Air- ence admixture. [18] Powers. A. Skokie.” Consulting Engineer. Vol. 23–26... the size and distribution of the air-voids ings. IL. pp. “Air-Entrained Concrete. A further consideration that is receiving attention is the Research Department. [1] Gonnerman.” Journal. and the length change on drying of a concrete mix- Report 10.. JEKNAVORIAN ON AIR-ENTRAINING ADMIXTURES 481 and polishing steps of ASTM C 457. This specifi. test and a comparison with the system produced by the refer.. American Concrete Institute. 41. pp. Konkurit. C. M. F. which are prob. which have been found from statistical Ronbunshu. H. ment. Raado. 68. and Methods of Concrete Construction (Canada). 1950. ing Agent and Silica Fume on Alkali-Silica Reaction. No. Portland teristics of the air-void system produced by the admixture under Cement Association. “Effect of properties of the laboratory concrete. Capman & Hall.. on other concrete properties. 1961. and Technology. analysis of numerous C 260 certification reports to have no ad- [14] Wang. Proceedings of the Estonian Academy of Sciences. IL.. No. possibility that the freezing and thawing tests. 1995. “A Working Hypothesis for Further Studies of Frost for evaluating air-entraining admixtures on a performance ba. 12. Ridge. Vol. Engineering. Nov. Discussion by R. Australian Journal of Applied Science. Oct. 126. pp. Feb. a performance-type specification Wiley. D. J. 1996. No. NJ. London. 1945.” PCA.. and Chemical Factors on Bubble Characteristics in Cement Paste.. T. 268–278. 40. “History of Air-Entraining Cements. Pow- as satisfactory air-entraining admixtures precludes the inclu- ers. Vol. “Combined Effect of an Air-Entrain- ditional significance versus the 28-day results. 243–245. Concrete Admixtures. Bulletin No. it will be reasonable to Alkylsulfonates on Freezing Resistance of Cement Mortars. N. and Chaiken. pp. M. and Gillot. 52–61. A.. H. 2. No. [6] Dodson. 41. It remains es. Skokie. mm) and no single test greater than 0.” Public Roads. cedure. American Concrete Institute. V. pp. pp. IL.26 mm). Lippmaa. Vol. Skokie. air-void system if the average of all tests of the hardened con- and the rest of the surface is black. 2002. sentially the same as it appeared initially. “Air-entraining Agents and Air-entraining Water containing a reference air-entraining admixture. G.” Proceedings. ford assurance that if. “Chemical Analysis and Sources durability. New York. A Look at the Record. in concrete mixtures was recognized to be a major factor with Concrete Briefs. 1999. 184–211.. “More Durable Concrete with Treated Status of Current Specifications and Test Cement. Science.” (2) that the admixture contains nothing that will have a delete. A. very indirect method of determining whether: (1) the particu. pp. 5A.. [10] Anonymous. C. and Nagi. H.. werk & Fertigteil-Technik. the air-void parameters are immediately calculated. E. “Chemical Admixtures for Concrete. Concrete Admixtures Handbook: Proper- ties. 1990... 2002. crete. “The Air Requirement of Frost Resistant Con- ably the most costly and time-consuming part of the testing pro. 2nd ed. compressive and flexural strength. Vol. 12. ASTM C 260 currently evaluates the effects that any given [7] Ramachandran. (ASTM C 260) was developed in 1950 by ASTM. 29.. [19] Powers. C. T. the particular sample of tent in Concrete. termining these air-void characteristics and since there was a 27. pp... W. Terzaghi.” Konkurito Kogaku. D. the admixture under test exerts satisfactory influence on certain [12] Piroja. 1954.” Beton- mixtures for Concrete (C 233).009 in. field mortar or concrete so as to produce an air-void system [16] Bruere. Resistance of Concrete. Vol. The wide variety chemically of materials that can function Feb. “Basic Principles of Air-Entrained Concrete.. sented by the sample will develop satisfactory air-entrainment Vol. pp. W. H. 2. 2002. H. pp.M. Research Department. Vol. (0.” Proceed- During the early 1940s. pp. pp.23 mounted onto the moving stage placed under the video cam. neutralized Reducing Agents for Concrete. Portland Cement Association. Proceedings. 245–272. Concrete Materials Entrained Concrete. Vol. 1949. (0. Douzono. A recent modification to ASTM C 233 and [13] Fujiwara.. M. 1100–1106. E. Results for Air-Entraining Admixtures pp. 1995.. The criteria of ASTM C 260 af. Journal. [11] Whiting.. 61–71. sis. Portland Cement Association. [2] Swayze. Van Nostrand Reinhold.. [3] Hansen. Highway Research Board. pressive strength tests. 1945. Maruoka. The CSA Standard A23. can be supplemented by an examination of the charac. “Manual on Control of Air Con- tures and conditions in ASTM C 233.. S. Proceedings. A. under the conditions of the specified mix. “Study on Relation Between Void Structure and Sound Absorp- tion Characteristic of Porous Concrete. H. 78–86. 56. D. . Brewer. A. C 260 eliminates the need for later age (6 and 12 month) com. resistance to freezing [8] Paillere... and Nikitina. ture.010 in. “Relative Importance of Various Physical and having the proper characteristics for enhancing durability. of Air-Entraining Admixtures for Concrete. in field concrete. 1. has adopted nique (described in EN 480-11) is used to obtain a surface of this alternative and considers the concrete to have a satisfactory the concrete plane section where air-voids are bright white.” 3rd ed. 1961. W. A. T. V. 946–949. 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Between Foam Index.” ACS Division of Fuel “Distances Between Air-Voids in Concrete by Automatic Chemistry Symposia. Methods. No. R.. J.. pp. 2001. E. 2002.” Concrete Constituent in Concrete. SP-79. “Effect of Fly Ash on the Air-Void Sta. Analysis System for Analyzing the Air-Void System in Hardened [61] R&T Update Concrete Pavement and Research Technology. P.. C. May 2003.. K. B. Vol. No. J. R. Chermant. H. LaCount. 46 No. pp. E. pp. American Concrete Institute.. Proceedings of the 24th International Conference on Cement [60] Higginson.. 155–158. and Suuberg. “Relationships pp. and VanDam. Concrete. Coster. [57] Kulaots. Vol. 42 Chemical Admixtures Bruce J. Christensen1 and Hamid Farzam2 Preface Introduction THE FIRST EDITION OF THE CHAPTER ON “CHEMICAL Most chemical admixtures react chemically with the cement in Admixtures” was issued in 1966 and was prepared by Dr. Bruce concrete. The reports of unfavorable behavior of some admix- Foster [1]. The chapter in ASTM STP 169B [2], published in tures with certain cements and under certain conditions of 1978, was an updating of Dr. Foster’s paper prepared by Bryant use are counterbalanced by a record of successful use under Mather. In 1994, the chapter was again updated by Bryant controlled conditions in many concreting operations. How- Mather and appeared in ASTM STP 169C [3]. In the preparation ever, when experience with specific admixture-cement combi- of this chapter, the contents of the previous editions were drawn nations under similar job conditions is not available, tests upon and some duplication of information from the previous with specific materials should precede a decision for use in edition exists. We acknowledge the authors of the previous edi- construction. tions and their contributions to the literature on this topic. The The use of chemical admixtures has become an integral current edition will update the topics addressed previously, pro- part of everyday concrete production. Newer levels of concrete vide up to date references, and focus primarily on new tech- performance are now possible that previously were not [9–12]. nologies that have been developed. The review period has been Economic benefits are available for the concrete producer by limited to contributions made during the last decade. Attempts the use of chemical admixtures, creating a win-win situation have been made to uncover all relevant research, but undoubt- for manufacturer and user [13]. edly, important research may not be covered or may be un- Many of the admixtures currently have a valid ASTM speci- knowingly omitted in this review. fication (refer to the 2003 edition of the Annual Book of ASTM This discussion is limited to certain features of chemical Standards [14–22]) by which to demonstrate conformance admixtures regarded as most appropriate to the scope of this against. Many of the newer admixtures, though, do not and volume. For a more comprehensive review of knowledge in various levels of activity in committee are underway to develop this field, reference should be made to the following additional them. It seems prudent that this document should discuss both works: categories of chemical admixtures, as both are currently used a. In 1991, the American Concrete Institute (ACI) published in the field. its most recent report of its Committee 212 on Admixtures for Concrete, entitled “Chemical Admixtures for Concrete” Types of Materials and Their Action (ACI 212.3R-91) [4]. in Concrete b. In 1993, Committee 212 published its most recent report on Superplasticizers for Concrete, entitled “Guide for the Admixtures Currently With an ASTM Use of High-Range Water-Reducing Admixtures (Super- Specification plasticizers) in Concrete” (ACI 212.4R-93) [5]. c. In 1995, V. S. Ramachandran published the second edition Water-Reducing and Set-Retarding of the Concrete Admixtures Handbook: Properties, Sci- Admixtures ence, and Technology [6]. Water-reducing admixtures may be used in at least three d. In 2002, the Portland Cement Association published the different ways: (1) to produce concrete with a lower water to fourteenth edition of Design and Control of Concrete cementitious materials ratio (w/cm); with no change in cement Mixtures, where Chapter 6 discusses Chemical Admix- content or slump; (2) to produce a higher slump, with no tures [7]. change in cement content or w/cm; or (3) to produce concrete e. In 2003, ACI published the most recent report of its Com- with reduced cement content, with no change in w/cm or mittee E-701 on Materials for Concrete Construction, enti- slump. In the first case, the usual benefits accruing from the tled Chemical Admixtures for Concrete (ACI E4-03) [8]. use of a lower w/cm normally will be obtained, and, in many 1 Group Manager, Admixture Product Development, Degussa Construction Chemicals, Master Builders Inc., Beachwood, OH 44122. 2 Vice President, Product Development and Quality, Cemex USA, Houston, TX 77024. 484 CHRISTENSEN AND FARZAM ON CHEMICAL ADMIXTURES 485 cases an increase in strength greater than that normally retarders with some cements may actually produce an early stiff- produced by the reduction in w/cm alone may result. In ening. The outcome may be highly dependent on the chemistry the second application, easier placing of concrete may be of both the cement and the set-retarding admixture used [23]. obtained. In the third application, a reduced cost should result. The effects of molecular weight fractionation on the Set-retarding admixtures may be used in at least two retardation and dispersing efficiency of lignosulfonates have different ways: (1) to delay the time of setting, and (2) improve been reported [24–26]. Reknes and Gustaffsson [24] found that compressive strength development. In the first case, the benefits the high molecular weight fractions of a softwood sodium are typically realized when concrete temperatures are greater lignosulfonate obtained from the sulfite process gave better than room temperature. In the second case, the benefits are dispersing efficiency and slump retention, as well as less retar- from changes in the chemical hydration and not necessarily dation, than the low molecular weight fraction. Maximum from additional water reduction. achievable water reductions were increased from 10–20 %. Materials used as conventional set-retarding and/or water- Zhor and coworkers [25,26] reported investigations on a reducing admixtures are some of the following: (1) lignosulfonic methylsulponated organosolv lignin that was also fractionated. acids and their salts; (2) modifications and derivatives of ligno- They found that the minimum level of retardation occurred at sulfonic acids and their salts; (3) hydroxylated carboxylic acids the maximum molecular weight, but an optimum in dispersing and their salts; and (4) modifications and derivatives of hydroxy- performance was observed in the middle of the molecular lated carboxylic acids and their salts. In each of these, the weight range. primary component has both water-reducing and set-retarding properties. In the formulation of products of Classes 2 and 4, Accelerating Admixtures these admixtures may be modified by the addition of other com- Accelerators have their primary application in cold weather ponents to give various degrees of retardation, no significant concreting. They may be used to permit earlier starting of change in setting time, or acceleration, while at the same time finishing operations. They reduce the time required for curing preserving the water-reducing properties. They also may be and permit earlier removal of forms because of more rapid modified by the addition of an air-entraining admixture. The early-strength development. water reduction resulting from the use of conventional water- The accelerating admixture that is most widely used is reducing admixtures is typically from 5–12 % [8]. A part of the calcium chloride [27]. The addition of recommended amounts water reduction found with lignosulfonate water-reducers may of calcium chloride, which are typically 1–2 % by cement be the result of the additional air entrained by these materials. weight, has been found to reduce the water requirement by a In addition to varying with the particular cement employed, the small amount over that required to produce the same slump amount of water reduction by a given admixture is also with no calcium chloride added. The magnitude of the effect influenced by dosage, cement content, type of aggregate, and the of calcium chloride on time of setting depends on the dosage, presence of other admixtures, such as air-entraining agents or the particular cement used, the temperature, and other factors. pozzolans. Water-reducing admixtures are effective with all The recommended maximum dosage has a substantial effect types of portland cement, portland blast-furnace slag cement, on time of setting at normal temperatures and can produce a portland-pozzolan cement, and high-alumina cement. very rapid set at high temperatures, as is also the case with a The extent of retardation in time of setting caused by very large dosage at normal temperatures. retarders depends on the cement characteristics, the tempera- Calcium chloride does not entrain air but its use enhances ture, the admixture dosage, and other factors. Overdosage the effectiveness of air-entraining admixtures so less air- may produce times of setting in excess of 24 h or more, but entraining admixture is required for a given air content. in such cases, if the concrete finally sets and has been pro- Calcium chloride may result in early stiffening and in many tected from drying, ultimate strengths developed may be cases, therefore, is not added until after mixing has com- satisfactory if forms are left in place for a sufficient length of menced. Calcium chloride used at maximum dosages can time. Severe overdosage of lignosulfonate admixtures may affect the color of the hardened concrete. produce excessive air contents and consequently reduced The addition of calcium chloride to reinforced concrete strength. Lignosulfonate water-reducing retarders usually has the potential to promote corrosion. As such, other non- entrain 2–3 % of air when used in normal dosages. The hy- chloride accelerators are used in applications where corrosion droxylated carboxylic admixtures do not entrain air. How- of embedded steel is a concern. Common materials are inor- ever, both classes of material enhance the effectiveness of air- ganic sodium or calcium salts of nitrites, nitrates, thiocyanates entraining admixtures from the standpoint of volume of air and thiosulfates [6], of which thiocyanates are the only class produced, so that less air-entraining admixture may be re- with a potential for promoting corrosion. At the dosages used quired when added to concrete containing one of these other in commercial accelerators, though, they have been shown not admixtures. It is important to note that while the air-void to promote corrosion [28]. Alkali metal salts are very rapid spacing obtained with water-reducing retarders is slightly accelerators and often used in shotcreting applications [29,30]. greater than that for an equivalent amount of entrained air Lithium-based salts are commonly used to accelerate calcium produced by typical air-entraining admixtures, the perform- aluminate cements [31]. Other materials are organic accelera- ance of concrete containing water-reducing retarders, as tors, such as triethanolamine or calcium formate. measured by freezing and thawing tests, often has been found Nonchloride accelerators, such as nitrites, nitrates, and to be better than concrete of the same air content, but with- thiocyanates are most effective at temperatures below 21°C, out the water-reducing retarders. This increase might be the performing much better at 5–10°C [6,32,33]. ASTM C 494 result of the reduction in w/cm. specification for Type C admixtures requires testing at nomi- Contrary to expectations, water-reducing retarders usually nally 21°C, which does not fully elucidate the effectiveness of have not been found effective in reducing slump loss resulting these materials. Consideration should be given to testing these from substantial delays in placing mixed concrete. The use of admixtures under more appropriate conditions [34]. 486 TESTS AND PROPERTIES OF CONCRETE High-Range Water-Reducing Admixtures The primary disadvantage of the PCEs is a propensity to (HRWR) entrain some amount of air in the absence of an air-entraining High-range water-reducing (HRWR) admixtures were added to agent. The amount of air entrained increases with increasing ASTM C 494 in 1980 and their use to produce flowing concrete dosage, similar to a lignosulfonate. This is the result of the is covered by ASTM C 1017, adopted in 1985. They have been surfactant-like structure of the polymer, namely a hydrophopic used to produce high-strength concrete by taking advantage of backbone with hydrophilic side chains. To offset this defi- their ability to substantially lower the w/cm. Alternatively, they ciency, many commercial products are formulated with can be used to produce “flowing” concrete (200 mm slump) defoamers or other components to minimize air entrainment. or self-consolidating concrete (550–750 mm slump flow) discussed in Chapter 58. Early generation HRWRs based on Admixtures Currently Without an ASTM melamine or some versions of naphthalene generally had poor Specification workability retention, often requiring addition of the HRWR at the job site. New generation HRWRs often maintain adequate Mid-Range Water-Reducing Admixtures workability retention over time, thereby they may be added at (MRWR) the batch plant. Mid-range water-reducing (MRWR) admixtures were first The addition of HRWRs to air-entrained concrete may in- introduced to the market in the mid-1980s [59,60]. The first crease the spacing factor and decrease the specific surface area generation products contained lignosulfonate as the primary of the air-void system [5]. However, a reduction in the resist- dispersing component. The retardation, which typically ance of such concretes to freezing and thawing has not been increased as the dosage of water reducer increased, was offset observed, provided the spacing factor is generally not more by the additions of the appropriate amount and type of accel- than double the maximum recommended limit [35]. Some erating additives. Newer generation admixture formulations reduction in resistance to salt scaling has been observed with may contain polycarboxylate ethers as the primary dispersants. concrete exhibiting increased spacing factors [7], but on other It is possible to achieve water reduction levels of 5–12 % or occasions concrete with poor air void systems has performed more with these admixtures or slump levels of 125–200 mm. adequately [36]. Nevertheless, it would be prudent to evaluate MRWRs are also noted for the improvements they provide to the effect of a specific high-range water reducer on the frost the workability of the concrete. Pumping pressures have been resistance of a concrete mixture if this is a significant factor for shown to decrease by the addition of these admixtures [59]. the application of the concrete. The finishing characteristics of the concrete containing Seven CANMET/ACI Symposia have been held on the topic MRWRs are improved, making these admixtures highly of Superplasticizers and Other Chemical Admixtures to date desirable for flat work applications [61]. [37]. This document focuses exclusively on the developments At this time, there is no ASTM specification for MRWRs. that have been discussed during the last four meetings, which Most are certified to meet the requirements of a Type A, covers the period from 1994 to 2003. whereas some are able to meet the requirements of a Type F. The most significant new development in HRWRs in the last There was considerable effort put forth in ASTM Committee decade has been the introduction of a class of materials known C09.23.3 in the late 1990s and into the early 2000s to develop as polycarboxylate ethers (PCE) [38–50]. These polymers consist a specification for these types of admixtures. First efforts were of an ionic backbone grafted with pendant nonionic side chains. to develop a modified version of ASTM C 1017, where the These polymers provide dispersion by means of both electro- target slump was adjusted down from 215 mm (25 mm) to a static and steric repulsion, the latter of the two believed to be the value of 150 mm (12 mm). The time of setting and compres- dominant mechanism [51,52]. As a result, these polymers are sive strength of the MRWRs were compared against that of a highly efficient dispersants, typically 2 to 3 times more effective Type A water reducer. It was found that it was not possible to on a mass basis than naphthalene or melamine-based HRWRs, adequately differentiate the MRWRs from a Type A based on and exhibit excellent workability retention. Water reduction is these characteristics. The next efforts were again to use an ap- essentially linear with increasing dosage of polymer and can proach based on ASTM C 1017, where the starting slump was exceed 40 %. Another advantage of this dose efficiency is the decreased from 100 mm to 50 mm and increasing dosages of lack of retardation with these polymers, since less of the surface the admixtures were used to increase the slump while moni- of the cement grain is covered with adsorbed polymer. toring the time of setting. This was continued until differences Another key aspect to the performance benefits of the in the time of setting as a function of slump increase were ob- PCEs is the ability to tailor the polymer to the needs of specific served. No differences in setting time at a fixed slump increase applications. Modifications to conventional HRWRs are lim- were observed until the retardation levels were on the order of ited primarily to changes in overall molecular weight or 2.5 h beyond a control, which were well beyond the 1.5-h limit substitutions of other monomers [53,54]. Variations to the in the standard. The final efforts focused on using the differ- structures of PCEs, on the other hand, are considerable and of- ences in finishing characteristics as a means of distinguishing ten result in a performance difference when used in concrete the MRWRs from Type A water reducers. Data collected using [55–57]. Variations in length and graft density of the side a finishing machine [61] were inconclusive and the pursuit of chains, charge density in the backbone, and molecular weight a specification was abandoned. of the overall polymer are all examples of molecular modifications that can affect such performance characteristics as Corrosion-Inhibiting Admixtures (CIA) early strength development, time of setting, workability reten- Steel reinforcing bars embedded in concrete form a passive tion and viscosity of the cementitious system. Additional func- oxide film, due to the high pH created by hydroxyl ions. This tional chemistries, such as shrinkage-reducing admixtures, can oxide film can be destroyed by a sufficiently high concentra- be grafted to the polymer to provide further enhanced per- tion of chloride ions or because of a decrease in pH from car- formance [58]. bonation, resulting in corrosion. The products of the corrosion CHRISTENSEN AND FARZAM ON CHEMICAL ADMIXTURES 487 reactions create a volume expansion, causing cracking and tive siliceous aggregate, and (2) a sufficient concentration of hy- spalling of the concrete structure. Reduction in chlorides or droxyl ions, i.e., high pH. Since sodium and potassium oxides water ingress can be achieved by a number of approaches. are the main species affecting the pH of the pore solution, the Addition of mineral admixtures decreases the permeability of latter requirement is met by the presence of soluble alkalis. the concrete internally, while surface sealers or membranes Sources of the alkali can be internal—cement, aggregate or poz- will limit penetration at the surface. Neither of these ap- zolan, or external—seawater, deicing salts or the like. The alkali- proaches may be sufficient, though, if a crack forms from the silica reaction itself is not destructive. The product of the reac- surface, providing a low resistance pathway for the chloride tion, though, is a gel that is susceptible to swelling in the ions to the steel. presence of water. Due to the low tensile strength of concrete, Chemical admixtures are another means for delaying or the expansion forces generated by this swelling can result in eliminating the onset of corrosion in concrete structures. cracking and spalling [73]. HRWRs can reduce the w/cm, thereby decreasing the perme- Various strategies have been employed to mitigate or sup- ability of the structure. In addition, the use of corrosion- press ASR [72]. The first is to eliminate reactive aggregates inhibiting admixtures (CIA) has been shown to be effective from the cementitious mixture. Good quality aggregate is not [62–65]. One classification method is to define the CIAs by available in many regions and it is often economically or physi- their chemical nature, namely whether they are inorganic, or- cally impractical to ship in appropriate aggregates. Another ganic, or vapor-phase. The more common method is to classify approach is the use of mineral admixtures, namely low-alkali them by the electrochemical reaction that they predominantly pozzolanic materials like metakaolin, class F fly ash or silica affect, which are the anodic or cathodic reaction, or both fume, as well as hydraulic materials like ground granulated (mixed). Some CIAs can be applied topically [65,66], though blast furnace slag. All have been shown to provide reduction in the majority of the literature discusses the use of integral CIAs. expansion [72]. Class F fly ash has been stated to be the most Calcium nitrite is one of the most widely used CIAs and is cost effective approach, but may not completely mitigate ASR believed to act as an anodic inhibitor [70]. Typical dosages range in some instances [72]. from 5–30 L/m3 of concrete for a 30 % solution. It also acceler- Two primary classes of chemical admixtures are discussed ates hydration and must be used in combination with a retard- in the literature to mitigate ASR. The first is the use of air- ing admixture to achieve acceptable times of setting under entraining admixtures (AEAs). This approach is somewhat summer conditions. It has been reported to meet the require- effective but has created concerns that the air voids cannot ments for an ASTM C 494 Type C – Accelerating Admixture [67]. provide sufficient space for both the expansive gel and an Alkanolamines are also used in formulating CIAs [65]. Spe- advancing ice front when used in freeze-thaw environments cific details are not readily available in the literature, as these [72,74]. The second is the use of lithium salts, i.e., LiOH, LiCl, compounds are components in many proprietary CIA formu- Li2CO3, LiNO3. There have been numerous reports on the abil- lations. Brown et al. reported on the performance of these ity of these materials to virtually eliminate expansion due to materials [68,69] and compared them to calcium nitrite and ASR over long periods of time [75–83]. The preferred salt form other organic CIAs. in most instances is LiNO3. This is primarily because it does not Nmai et al. [70] discussed an organic-based CIA, consisting exhibit a concentration that must be exceeded to prevent of a mixture of amines and esters in a water medium. The ad- expansion, referred to as the pessimum limit. Compounds such mixture was characterized as a mixed inhibitor and has a rec- as LiOH2 will increase the pH of the pore solution and can ommended dosage of 5 L/m3 of concrete. It imparts corrosion actually cause expansion if an insufficient amount is used [84]. protection by a dual mechanism: (1) inhibition by amine tech- LiNO3 has also been shown to have insignificant effects on the nology already used in the petrochemical industry, and (2) pro- plastic and hardened properties of either air or non air- tection by film formation on steel reinforcing bar from fatty es- entrained concrete when used at the dosages typically required ters. Tests with precracked concrete beams subjected to for ASR suppression [85]. chloride ponding showed significantly longer times to corro- The recommended dosage of lithium is based on the alkali sion for samples treated with this organic inhibitor than those content of the cement and a molar ratio of [Li]/[NaK]0.7 to treated with calcium nitrite. 0.8 should be exceeded [77]. This translates to dosages in the Tourney and Berke [71] discussed the need for an ASTM range of 3–5 L/m3 of a 30 % solution of LiNO3. Combinations of specification for a corrosion-inhibiting admixture. Their con- class F fly ash and LiNO3 have been shown to be particularly ef- tention was that specifications like ASTM C 494 are designed fective, both from an economic and technical perspective [72]. primarily to demonstrate harmlessness and do not evaluate the Yet another approach to minimize ASR is to limit the performance of the CIA for what it is claimed to do—delay or ingress of water into the structure. This is typically a strategy prevent corrosion. In 2003, the final form of a specification used for existing structures that do not contain concrete was approved at the main committee of C09 and is due for designed to address the potential for ASR. Application of publication in 2004. A key aspect of the specification is the lithium salt solutions to the exteriors of structures has only requirement that the amount of chloride required to initiate been marginally successful. Another approach is to dry the corrosion must be higher in the presence of the CIA than in surface of the structure and apply a sealer to prevent addi- its absence. Therefore, materials that only slow the rate of tional ingress of moisture. chloride ingress will not meet the specification. No ASTM specification exists at this time for these admixtures, though a task group has been formed to develop one. Admixtures for Suppressing Alkali-Silica The primary focus of the group is to develop an acceptable test Reactions method from which to develop specifications for expansion. The deleterious effects of alkali-silica reaction (ASR) are well The current ASTM C 1260 method requires some modification, known [72–89] and expounded on in Chapter 34 of this volume. especially to prevent leaching of lithium salt from the mortar In short, the reaction requires two main components: (1) reac- bar during testing. This is potentially being addressed by 488 TESTS AND PROPERTIES OF CONCRETE addition of lithium salt to the sodium hydroxide bath during At this time, there is no ASTM specification for VMAs. The testing [86]. Modifications to the molds are also potentially need for a specification has been discussed at recent meetings, required to address issues discussed by Ong and Diamond [87]. but no activity has occurred to date. Many of the materials An AASHTO method that is similar to ASTM C 1260 is of mentioned above have been tested in a manner consistent with relevance, as well [88]. ASTM C 494, with no water reduction taken into account, and found to be harmless to the concrete properties. Viscosity-Modifying and Anti-washout Admixtures Shrinkage-Reducing Admixtures (SRA) Many applications for concrete (underwater concreting, for One of the mechanisms of cracking in concrete is volume example) require that the mixture remain highly cohesive dur- change due to drying shrinkage. One means of minimizing this ing transport, pumping, placing and prior to setting. Sufficient type of shrinkage, and subsequently the tendency of structures cohesion may not always be achieved by mixture proportion- to crack, is by the use of a shrinkage-reducing admixture (SRA). ing alone. Concrete contains cementitious materials, which are These materials first appeared in Japan in the early 1980s and fine powders and can therefore easily be washed out of the the US patent literature in the mid-1980s [109]. The admixtures concrete mixture during placement in water or in the presence consist primarily of low molecular weight polyoxyalkylene of moving water. In this application, the viscosity-modifying aklyl ethers. They are liquids at room temperature and soluble admixture (VMA) acts as an anti-washout admixture (AWA). in aqueous systems and some hydrocarbon solvents. Typically Another application is in the production of self-consolidating they are treated as water in the cementitious mixture, so the concrete (SCC) discussed in more detail in Chapter 58. These amount of added mix water is reduced by the amount of SRA mixtures are highly fluid, yet must remain stable—i.e., resist used. Dosages of 0.75–2 % by cement weight are used resulting segregation in both a dynamic and static state, until hardened. in typical reductions in unrestrained drying shrinkage of as Early approaches to maintaining stability and minimizing much as 80 %. bleeding were to increase the proportion of fine materials The primary mechanism of action of these materials is the (cement, sand, filler, etc.) in the mixture. These mixtures are reduction of capillary tension inside the pores that develops more susceptible to creep and shrinkage [90]. In contrast, ad- during drying [110]. This tension pulls on the interior walls of dition of a VMA makes it possible to use a more conventional the pores, resulting in shrinkage of the bulk specimen. The mixture design, while still maintaining the desired stability. reduction in capillary tension is achieved by decreasing the Organic versions of these admixtures are based on a surface tension of the water in the pores, which results by number of different chemistries [91–98]. One class is the natu- addition of the SRA to the mixtures. Pore sizes in the range of ral polymers. These include such materials as polysaccharide a few to tens of nanometers are believed to be the main sizes gums (welan, xanthan, etc.), starches (potato, corn, etc.), and contributing to shrinkage [110]. proteins. A second class is semi-synthetic polymers like cellu- Additions of SRAs have been shown to decrease the com- lose ether-based materials (hydroxy methyl, hydroxyl propyl, pressive strength of concrete at 28 days by up to 15 % [111]. This carboxymethyl, etc.). A third class is the synthetic polymers like can be offset best by using a water reducer to decrease the w/cm polyethylene glycols, polyvinyl alcohols, or polyacrylamides. and still maintaining workability. Depending on the specific Inorganic versions can include swelling clays (bentonite), as chemistry of the SRA, a slight increase in air content of 0.5–1 % well as high surface area materials like silica fume or colloidal can be observed on occasion [109], as well as some retardation silica [99]. of time of setting [112]. It has also been reported that because Some of the materials impart cohesiveness by binding these materials affect the surface tension of the pore water, they water, thereby increasing the viscosity of the water phase. Oth- can potentially impede the ability of an air-entraining admix- ers, like gums, are believed to affect the interaction between ce- ture (AEA) to develop an adequate air-void system [113]. As ment grains through polymer entanglement and hydrogen such, the resistance of concrete containing a SRA to freezing bonding, thereby increasing the viscosity of the mixture [91]. and thawing cycles can be negatively impacted. This is espe- Yet others, such as silica fume, significantly increase the sur- cially true when the SRA is used in combination with a rosin- face area of the mixture and the physical binding of the water. based AEA and a naphthalene-based HRWR [114]. Kamimoto et Bury et al. [100] discussed a modified cellulosic polymer al. [113] showed that the resistance of concrete to freezing and in the form of a fluidized suspension that binds the free water, thawing cycles could be improved by delaying the addition of minimizing bleeding and imparting viscosity modification. Use the SRA versus adding it initially to the mixing water. of the polymer as an AWA decreased the mass loss to roughly Despite the lack of an ASTM specification [111] and some one-tenth of the amount lost in the absence of the AWA. Unlike of the disadvantages discussed above, SRAs are now finding some other cellulose ethers [101], this particular polymer widespread usage in concrete applications in Japan and North exhibited little change in time of setting from the control America [115–117]. Shah et al. [118–120] have published a num- mixture. ber of works on the benefits of this class of admixtures. See et Khayat and coworkers have published extensively on the al. [121] have demonstrated the benefits of an SRA using ring effects of VMAs on the plastic and hardened properties of tests, where both the shrinkage rate and shrinkage potential concrete [102–108]. In one study, it was found that the use of were decreased in mixtures containing the admixture. Tests by welan gum or HPMC lowered the flexural strength by 10–30 % the Hawaii Department of Transportation reported positive and gave similar or slightly better compressive strength benefits in the field when used in a bridge application [122]. relative to reference concrete. In another study, it was found that the resistance to freezing and thawing cycles of concrete Cold Weather Admixtures containing VMA was acceptable. The best air void system was Accelerating admixtures have been discussed and are used to obtained when the AEA was added after the VMA and a HRWR increase the rate of hydration, particularly as the concrete tem- were added. perature approaches the freezing point of water. While these CHRISTENSEN AND FARZAM ON CHEMICAL ADMIXTURES 489 materials accelerate time of setting and early strength devel- HCAs are retarding admixtures that act on all the cement opment, they do not necessarily prevent the concrete from phases to delay hydration, in contrast to conventional sugar- freezing. When temperatures below the freezing point of water based retarders, which act primarily on the silicate phases are experienced, additional precautions may be necessary to [135]. Hydration can be arrested for weeks at a time with an ensure that the concrete does not freeze and cease to gain HCA, if desired, and then when the effect of the HCA wears off, strength. Examples of traditional approaches to minimizing setting and strength development proceed as normal. Hydra- the potential for freezing are: (1) heating the concrete before tion that is still arrested by an HCA can be re-activated by the leaving the batch plant, (2) using higher cement contents addition of an accelerating admixture meeting the require- and/or Type III cements, and (3) heating and insulating the ments of ASTM C 494 Type C. This attribute is particularly use- area of placement. Option 1 can increase the potential for plas- ful for long hauls, overnight or weekend stabilization of plastic tic shrinkage cracking [123], while in-place costs using Option concrete. High dosages of conventional retarding admixtures, 3 can be twice that of summer concreting [124]. on the other hand, can permanently arrest hydration and make Another approach is the use of cold weather admixtures the concrete unusable. They can also cause rapid stiffening, (CWA), sometimes referred to as antifreeze or freezing- exhibiting similar signs to flash or false setting. protection admixtures. CWAs have a dual mechanism of Dosage rates of HCA, and the corresponding amounts of action: they depress the freezing point of the pore solution and accelerator to reactivate, are highly variable and depend on a accelerate hydration of the cement. Most of the chemicals that number of factors [136]. These include the age of the concrete, are used are inorganic salts that exhibit eutectic (easily length of stabilization time required, temperature of the con- dissolved) temperatures significantly below 0°C [6]. Organic crete, and time of setting required after reactivation, etc. HCAs materials such as propylene glycol are also mentioned [125]. are formulated using carboxylic acids and/or phosphorus- Senbetta and Scanlon [28] discussed test results of con- containing organic acids and/or their respective salt forms crete containing a CWA that would prevent the concrete from [6,140]. freezing at temperatures as low as 20°F (7°C). The CWA was Senbetta and Scanlon [28] reported that concrete in which found to meet the requirements of ASTM C 494 for Types C an HCA was used and reactivated after 18 h of storage, when and E. Because the admixture contains sodium thiocyanate, it tested for resistance to freezing and thawing, gave equally good was evaluated for its effect on corrosion of steel and was found results as concrete not so treated. The same HCA was studied not to promote corrosion at a dosage of 8L/100 kg of cement. by Senbetta and Dolch [138] for effects on paste as revealed by Korhonen and Brook [126] documented a more comprehen- X-ray diffraction, thermogravimetric analysis, differential ther- sive study on this commercial CWA. Similar work on another mal analysis, scanning electron microscopy, and determination commercial admixture and a developmental product was of nonevaporable water content, surface area, and pore size published the following year [127]. distribution. No significant differences between treated and Farrington and Christensen [128] have recently published untreated pastes were noted. Additional studies by Ragan and results on a further improvement to the original CWA devel- Gay [139], as well as many others [140–143], have showed the oped by Brook et al. [129]. Concrete was batched at 11–13°C utility of these admixtures and the general lack of degradation and cured at temperatures as low as 11°C. Acceptable times in properties of the stabilized concrete once activated. of setting and early compressive strength development were No specific ASTM category exists for HCAs. Most commer- possible with combinations of the CWA and a HRWR. Korho- cial products meet the requirements for ASTM C 494 Type B or nen and coworkers [124–127,130–132] have published exten- Type D. No recent discussion has occurred in the ASTM C09.23 sively on the performance of CWAs and the benefits of using subcommittee around the need for a separate specification. them for cold weather concreting. Additional studies have been conducted in Japan [133], as well as field data reported Other Chemical Admixtures by Nmai [134]. Most CWAs will meet the requirements for ASTM C 494 Other types of admixtures not discussed in this document Type C and/or E. As such, the harmlessness of the material include gas-forming admixtures, grouting admixtures, expan- with regard to the parameters of the standard is demon- sion-producing admixtures, bonding admixtures, flocculating strated. At this time, though, there is not a specification for a admixtures, fungicidal, germicidal, and insecticidal admix- CWA that demonstrates its ability to provide freezing point tures, damp-proofing admixtures, permeability-reducing depression. Therefore, a new section, ASTM C09.23.5, has re- admixtures, and color-conditioning admixtures. Air-entraining cently been created to oversee the development of an appro- admixtures are discussed in a previous chapter of this book, priate test method and specification for this class of chemical hence are not discussed here, as well. admixtures. Acknowledgment Hydration Controlling Admixtures (HCA) The production of ready-mixed concrete results in waste from We appreciate the efforts of Laura Holland, Librarian, and wash water and returned plastic concrete. Disposal of these Peggy Enderle, Administrative Assistant, in securing the refer- materials is an economic burden for the producer, as well as an ences for this document and assisting with the bibliography. environmental concern for the surrounding community. Reuse of the material into freshly batched concrete generally results in accelerated hydration and slump loss, making its use impracti- References cal in many instances. 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A., “Off-the-Shelf Antifreeze 5th CANMET/ACI International Conference on Superplasticiz- Admixture for Concrete: Initial Laboratory Investigation,” ers and Other Chemical Admixtures in Concrete, SP–173, ERDC/CRREL Technical Report TR–01–2, U.S. Army Corps of American Concrete Institute, Farmington Hills, MI, 1997, Engineers, Engineer Research and Development Center, Jan. pp. 249–266. 2001, 17 pp. 494 TESTS AND PROPERTIES OF CONCRETE [132] Korhonen, C., “New Developments in Cold-Weather Concret- [138] Senbetta, E. and Dolch, W. L., “The Effects on Cement Paste ing,” Cold Regions Engineering: Cold Regions Impacts on of Treatment with an Extended Set Control Admixture,” Transportation and Infrastructure, Proceedings of the 11th Cement and Concrete Research, Vol. 21, No. 5, Sept. 1991, International Conference, Anchorage, AK, American Society pp. 750–756. of Civil Engineers, Reston, VA, pp. 531–537. [139] Ragan, S. A. and Gay, F. 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W., “Use of Recy- on the Properties of Fresh and Hardened Concrete,” Materials cled Wash Water and Returned Plastic Concrete in the Pro- for the New Millennium: Proceedings of the 4th Materials duction of Fresh Concrete,” Advanced Cement Based Materi- Engineering Conference, Vol. 2, American Society of Civil als, Vol. 1, No. 6, 1994, pp. 267–274. Engineers, New York, NY, 1996, pp. 1617–1626. [137] Ramachandran, V. S. and Lowery, M. S., “Effect of a Phospho- [142] Nakamura, S. and Roberts, L. R., “Recycling Returned nate-Based Compound on the Hydration of Cement and Concrete,” Concrete Engineering International, Vol. 3, No. 3, Cement Components,” 4th CANMET/ACI International Confer- April 1999, pp. 56–61. ence on Superplasticizers and Other Chemical Admixtures in [143] Muszynski, L., Chini, A., and Bergin, M., “Re-using Wash Wa- Concrete, SP–148, American Concrete Institute, Farmington ter in Ready-Mixed Concrete Operations,” Concrete (London), Hills, MI, 1994, pp. 131–152. Vol. 36, No. 2, Feb. 2002, pp. 16–18. 43 Supplementary Cementitious Materials Scott Schlorholtz1 Preface admixture, n — a material other than water, aggregates, hydraulic cementitious material, and fiber reinforcement that is THIS WRITER IS INDEBTED TO PRIOR AUTHORS OF used as an ingredient of a cementitious mixture to modify its this chapter [1–4] because their work provides the background freshly mixed, setting, or hardening properties and that is for this version. I have borrowed from their ideas and specific added to the batch before or during its mixing. words. However, following the format provided by Cain [4], The definition continues to list the various types of ad- this chapter will present less discussion of the use of these ma- mixtures that are commonly available. The verbiage given for terials in concrete and more on the characteristics of the var- the term mineral admixture is as follows: ious materials and the significance and use of their accept- mineral admixture, n deprecated term. ance tests. For discussion of the use of these materials in DISCUSSION – This term has been used to refer to different concrete, the reader is referred to three reports from the types of water insoluble, finely divided materials such as poz- American Concrete Institute (ACI): ACI 232.1R “Use of Natural zolanic materials, cementitious materials, and aggregate. These Pozzolans in Concrete” [5]; ACI 232.2R-96 “Use of Fly Ash in materials are not similar, and it is not useful to group them un- Concrete” [6]; and ACI 234R-96 “Use of Silica Fume in der a single term. The name of the specific material should be Concrete” [7]. Updated reports on these materials are used; for example, use “pozzolan,” “ground granulated blast- currently being prepared by the appropriate ACI Committees. furnace slag,” or “finely divided aggregate,” as is appropriate. Hence, the use of “mineral admixture” has been discour- Introduction aged. However, what will now be used to denote a generic reference to this broad class of apparently dissimilar materials This chapter will touch on the history of the use and interest in that were all used for similar reasons? The discussion given fly ash, natural pozzolans, and silica fume. It will chronicle the above indicates that the specific term (i.e., “pozzolan”) should paths that the various specifications for these materials have be used; however, that is lengthy and awkward when referring taken through ASTM task groups, subcommittees, and com- to several materials at the same time. For example, who will mittees. A discussion of tests and specification limits will follow pay attention when a speaker indicates that the talk will be at that point in the chapter. about Class C fly ash, Class F fly ash, calcined natural pozzolans, and ground granulated blast-furnace slag rather than Supplementary Cementitious Materials simply mineral admixtures? This has led to the use of another generic term for these materials. That term is supplementary Readers of this chapter will note that a change in terminology has cementitious material (SCM). The term is not currently defined taken place. Prior versions of this chapter all used the term “min- in ASTM C 125. The American Heritage dictionary [8] gives the eral admixture” throughout the title and text of the document to following definition for the word “supplement”: describe the wide variety of materials that are commonly added supplement, n – something added to complete a thing, to concrete to increase the paste content of the mixture. These make up for a deficiency, or extend or strengthen the whole. same materials will now be referred to as “supplementary ce- The new terminology is not perfect but it does give a bet- mentitious materials (SCMs)” throughout this chapter. This ter indication of why the various materials are added to con- change was needed because the ASTM Subcommittee on Termi- crete mixtures. It also gets rid of the word “admixture” which nology (C09.90) could not reach a consensus on an adequate def- is of questionable merit when high replacements (dosages) of inition of the term “mineral admixture.” Hence, part of this sec- the supplementary cementitious material are used. The over- tion will be devoted to explaining the reasons for the change. all thrust of the change in terminology appears to be a positive step forward. It gives a clearer indication that the mate- Definitions rials are being added to supplement (i.e., strengthen) both The term admixture is defined in ASTM Standard Terminology physical and chemical properties of the mixture; and hence, Relating to Concrete and Concrete Aggregates (C 125-03) as the materials are not simply being used to replace portland follows: cement. The new verbiage also pertains when the SCM is sim- 1 Scientist, Materials Analysis and Research Laboratory at Iowa State University, Room 68 Town, Ames, Iowa 50011; also, chair of ASTM Subcommittee CO9.24 on Supplementary Cementitious Materials. 495 496 TESTS AND PROPERTIES OF CONCRETE ply being used to reduce the cost of the concrete mixture (i.e., trated in Fig. 2, where the crystalline compounds and the glass extend). scattering halos have been labeled on the various X-ray diffractograms. This is not a new observation; rather it is an old Fundamental Properties observation that is often forgotten [20–27]. According to Mielenz [9], “mineral admixtures include finely di- The composition of the glass varies considerably between vided materials that fall into four types: those that are (a) ce- the materials as do the crystalline minerals that are commonly mentitious, (b) pozzolanic, (c) both cementitious and pozzolanic, observed (refer to Fig. 2). For example, the “reactivity” of fly ash and (d ) those that are nominally inert chemically.” They include has been linked to the amount of amorphous material, the ther- natural materials, processed natural materials, and artificial ma- mal history, the presence of specific crystalline components, the terials. They are finely divided and therefore form pastes to sup- chemical composition of the glass phase(s), and the particle size plement portland cement paste. This is in contrast to soluble ad- (fineness) of the bulk material [27–29]. All of these complicat- mixtures that act as chemical accelerants or retardants during ing factors have made it difficult to devise a single (simple) cate- the hydration of portland cement or otherwise modify the prop- gorization scheme that works for all SCMs. Hence, the current erties of the mixture. The chemical compositions of the four thrust in Subcommittee C09.24, the subcommittee that has ju- types of finely divided materials vary widely, both within and be- risdiction over the specifications pertinent to their use, has been tween the various groups, and this has made categorization dif- to push towards the use of a series of performance tests that iso- ficult. This is illustrated in Fig. 1. The data for the figure were ex- late the key properties that the SCM is being used to enhance. tracted from a variety of historical papers and reports on fly ash [10–16]. The deprecation of the term “mineral admixture” was Cementitious Materials Not Discussed related to the fact that it was difficult to define. Figure 1 suggests Cementitious materials such as natural cements, hydraulic that this may be partially due to the fact that the materials tra- limes, portland-pozzolan cements, ground granulated blast- verse such a wide range of chemical composition. furnace slag, and slag cements were discussed in the previous For instance, silica fume is currently specified to contain versions of this chapter. They will not be dealt with here be- at least 85 % SiO2. This restricts its overall (bulk) composition cause specifications for those materials are no longer under to the apex of the triangle shown in Fig. 1. Natural pozzolans the jurisdiction of ASTM Subcommittee C09.24. exhibit a very wide range of chemical composition. However, Low-Reactivity Materials Not Discussed they typically contain only small amounts of calcium and mag- Such materials as ordinary clay, ground quartz, ground lime- nesium [17–19], and this means that they will plot very near the stone, bentonite, hydrated lime, and talc were once used to im- SiO2 (Al2O3 Fe2O3) axis of the triangle. Fly ashes, shown prove workability and reduce bleeding in concrete. However, as data points in the figure, appear to break into different they are admixtures with low reactivity. Now, more suitable groups; however, there is considerable overlap between the and available materials such as fly ash and slag have largely groups. Class F fly ashes roughly plot parallel to the SiO2 taken their place for these purposes. Therefore, such materials (Al2O3 Fe2O3) axis. In contrast, Class C fly ash plots roughly will not be dealt with further in this chapter. Interested readers perpendicular to the SiO2 (Al2O3 Fe2O3) axis. These gen- should refer to prior chapters in this series [1–3] for additional eral trends in bulk chemical composition fail to indicate the information on these types of materials. similarities between the various materials. However, the materials from the SCM types denoted above as a, b, and c do have Fly Ash and Natural Pozzolans a property that makes them all similar. The common property is the lack of crystalline structure—all of these finely divided History and Use materials are primarily composed of glass. This fact is illus- Although slag cements and natural pozzolans had been used in concrete in local areas for many years, it was the use and acceptance of fly ash in concrete in the national market in the late 1940s and early 1950s that created the need for national specifications governing the use of these materials. It was recognized that the use of fly ash in concrete would have the following benefits: (a) improved workability, (b) lower heat of hydration, (c) lower cost concrete, (d) improved resistance to sulfate attack, (e) improved resistance to alkali-silica reactions (ASR), (f) higher long-term strength, (g) opportunity for higher strength concrete, (h) equal freeze-thaw durability, (i) lower shrinkage characteristics, and (j) lower porosity and decreased permeability. Good results were being obtained with fly ash [10–13,30,31] and natural pozzolans [20,32], and therefore there was a need for an ASTM specification for their use. A very simplistic time- line of events pertinent to the development of the various specifications is given in Fig. 3. For completeness, the figure also in- Fig. 1—Ternary diagram illustrating the bulk composition cludes events related to the development of the specification for of fly ash, natural pozzolans, and silica fume. silica fume. the Subcommittee proposed two standards on fly the use of increased quantities of fine material may be indicated ash. The tial replacement or substitute for portland cement. In point of fact. and effect on autoclave expansion. (2d) Class C fly ash. CCRL 27. One of these dealt with the methods of testing and was to promote workability and plasticity. 2—X-ray diffractograms for common supplementary cementitious materials: (2a) Silica fume.08. (2b) Class N pozzolan. . It was published as ASTM C-9 on Concrete and Concrete Aggregates. chemical Portland Cement Concrete (C 350-54T) and covered only the use and mineral. The preparation of a specification for fly ash for use in port.” The fly ash was to be published as ASTM Tentative methods of Test for Fly Ash as an treated only as a portion of the fine aggregate and not as a par- Admixture for Portland Cement Concrete (C 311-53T). (2e) GGBFS (slag cement). CCRL 32. Ex- industry and was not approved by Committee C-9 until several perience has shown them to be of less concern than expected. SRM 2696. This work was done Tentative Specifications for Fly Ash for use as an Admixture in by Subcommittee III-h dealing with all admixtures. later designated as Subcommittee C09. (2c) Class F fly ash. fly ash into one class where a class distinction would have allowed land-cement concrete was begun in 1948 by ASTM Committee the better fly ashes better recognition. magnesium oxide. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 497 Fig. Notes of other proposed standard dealt with specifications for fly ash caution on the use of fly ash in concrete were inserted in the with various chemical and physical limits. changes were made. In of what is now designated as Class F fly ash in concrete “where early 1953. This latter proposal early versions of the specification and dealt with the amount of met with serious opposition from some members of the cement sulfur.03. these changes lumped all but many of the reflected limits are still in the specification. CCRL 11. different requirements on drying shrinkage. with Robert E. ASTM C 350 was revised repeatedly based on new experi. Class N was the natural pozzolan from finely divided mineral materials other than cement and pig- .03. so the between natural pozzolans and fly ash were recognized by designation was dropped from ASTM C 618 in 1980.498 TESTS AND PROPERTIES OF CONCRETE Fig. ASTM C 402. At that time differences use of Class S pozzolan in the construction industry. fly ash. and ASTM C 350 was combined with ASTM C 402 resulting in ASTM Supplementary Cementitious Materials. There was no apparent Concrete (C 402-57T) was published. but could contribute edging the prospect that the use of fly ash in the mixture might desirable qualities to the concrete mixture. In 1960. ASTM Tentative Specifications for Raw or Calcined ognize it as a material with cementitious characteristics com- Natural Pozzolans for Use as Admixtures in Portland-Cement pared to those of the original Class F. and reactivity with cement alkalies. Slag. 3—Time line of important events for natural pozzolans.24 in 1992. ASTM Committee C-9 formed a new subcommit- fineness. requirements for natural pozzolans. Philleo Specification for Fly Ash and Raw or Calcined Natural Pozzolan as chairman. In 1977. Three classes was changed to C09. loss on ignition.10 on Fly Ash. the scope of ASTM C 350 was Class F allowed for other materials that could not meet the extended to cover fly ash as a pozzolan in concrete acknowl. tee.24 was of material were dealt with in three columns. Class F was the fly “to develop and maintain test methods and specifications for ash from ASTM C 350. Class C fly ash was added to ASTM C 618 to rec- In 1957. A new Class S having the same requirements as ence and research. Mineral Admixtures. and silica fume. In 1980. ASTM C09. Then in 1968. The scope of ASTM C09. The number designation of the subcommittee for Use in Portland Cement Concrete (C 618-68T). result in a reduced amount of portland cement. Class C fly ash generally exhibits greater hy. and Fe2O3 (plus many addi- Comments about natural pozzolans will be interjected when the tional elements of interest) is not a concern.24 tionale that it served only to define the material as a pozzolan to review the status of test methods and specification limits for [46]. as noted by several The moisture content is limited to 3 % maximum because authors [38–44]. However. cations for a material with a high insoluble residue.0 %. namely. ifested by test specimens containing these different classes of ma. mineralogy. The new scope for C09. tion.” This cre. and instead had new interest in slag and eventually silica fume. Subsequent research showed that a fly ash with up to 17 % SO3 ated a dilemma that we are still dealing with today—fly ash is did not give significant delayed volume changes or setting generically (classically) attributed with enhancing the properties problems. Recently. especially when associated with soluble alkali. low-sulfur coal from the western United States.0 % (maximum). and Classification loss on ignition.24 are fly ash (Classes F and C). can contribute terials? After all. Class F fly ash around which the earlier version (C 350) of the CaO) content than Class F with the corollary result of lowering specification had been written [33. and geological origin. silicon dioxide (SiO2) pozzolans. 2000. fly ashes that display cementitious properties when gauged with The first editions of this specification limited the SO3 to 3 %. when Class C fly ash was added to ASTM C 618. Actually. mination of the total SiO2. zolanic contribution had to come from its makeup of SiO2. the deter- loted. listed at 4. water do not conform to the definition of pozzolans. with four consecutive meetings failed to produce any items to be bal.27) for slag cement. the expense and delay in running these tests natural pozzolans. and Fe2O3. It ference recognized between Classes F and C in the specifica- contains higher amounts of elemental calcium (commonly ex. ASTM C 618 states that Class F fly ash The limit on loss on ignition (LOI).” Hence. CaO) and is less of a pozzolan pass as Class C. on bulk chemistry. used in substantial proportions in concrete. testing for discol- draulicity and makes a greater contribution to early strength than oration can be considered. There is a limit on the sum of three jurisdiction of C09. many of the fly coal” and Class C fly ash is “normally produced from lignite or ashes available in the eastern United States could not pass limits . when ASTM Specification for Natural Pozzolans Al2O3. refers to ASTM Test Methods for and fly ash into subgroups that reflect how a specific source of Chemical Analysis of Hydraulic Cement (C 114) with modifi- material will perform when mixed with hydrated lime or ce. The test is easy and inex- enhancing sulfate resistance. However. These classification schemes have been based Coal and Coke Ash By X-ray Fluorescence (D 4326). [30. Currently the only differentiation pensive to run and the values determined are needed in other made between the two classes of fly ash in ASTM C 618 is coal parts of the test methods. plus aluminum oxide (Al2O3) plus iron oxide (Fe2O3).24 is “to develop and maintain standards for supplemen. that obtained from the Class F fly ash. How do we deal with the divergence of properties man. There are also limits on the sulfur trioxide (SO3). Therefore. Class F has was recognition of the fact that this was a new material made always required a minimum of 70 % and this limit served well available because utilities had begun to burn larger quantities of for many years. None of The earliest versions of ASTM C 618 assumed that the poz- the classification schemes has been adopted for practical use. The subcommittee now had no concern for chemical admixtures subcommittee has not been able to make a better one. The task group was disbanded in 2002 after was significant and not altogether worthwhile. At that time. The SO3 content for natural pozzolans is currently chapter. so when they are present. At one point in the development of the specification. there and C is the total of SiO2 plus Al2O3 plus Fe2O3. Chemical Requirements tary cementitious materials other than ground granulated blast Table 1 of ASTM C 618 gives the chemical requirements for fly furnace slag. subcommittee (C09. the name of the subcommittee was changed to three groups based on analytical calcium content [45]. expressed as oxides.0 %. ASTM C 311. the Canadian Standards Association (CSA) has split fly ash into In 2001. source and bulk chemistry. Rapid and ment. specifying the methods to be There have been many attempts to classify natural pozzolans used in the determinations. there have been ations in the total of those three constituents for any material no changes to the requirements for natural pozzolans that were have not been observed to correlate directly with results in con- not brought on because of experiences with fly ash. the main materials currently under the ash and natural pozzolans. moisture content. this is not a helpful distinction. Class C requires a minimum of 50 %. Hence. The scope of the have been made to ballot similar fly ash classification schemes in subcommittee was changed to reflect the formation of a new ASTM C 618.” This new subbituminous coal. Also. Since 1968.34]. The only specified difference between fly ash Classes F In 1977.36]. was originally set at 12. Class C fly ash often ex. Mielenz [37] was among the first to note that “Class C Sulfur in fly ash and natural pozzolans is reported as SO3. in crete. Performance in most instances is normally interpreted instrumental methods may be employed similar to those in C as the ability of the material to enhance the ultimate strength 114 or in ASTM Test Method for Major and Minor Elements in of the mixture. Any material passing the Class F requirement will also pressed as calcium oxide. however.35. specification limits differ from those for fly ash. there is considerable evidence that Class F fly the material would become sticky and hard to handle if too ashes perform better than Class C ashes for controlling ASR or much moisture were encountered. vari- ASTM C 350. three constituents is based on that assumption. This new fly ash this is the subcommittee’s way of recognizing that Class C may exhibited both chemical and mineralogical differences from the have 20 % more analytical calcium (expressed as an oxide. This is the only chemical dif- hibits self-cementitious characteristics when mixed with water. Hence. the SO3 limits for fly ash were raised to 5 % of concrete summarized in the History and Use section of this (maximum). Al2O3. and silica fume. quicker instrumental chemical testing procedures. to efflorescence. now set at a maximum of is “normally produced from burning anthracite or bituminous 6. there was enough interest in the use of natural pozzolans there was a suggestion to remove the requirement with the ra- that users requested the formation of a new task group in C09. much of this section will deal primarily with fly ash. Now. Attempts Supplementary Cementitious Materials.” This distinction has been controversial. to date all attempts have failed. At that time. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 499 ments. The minimum requirement placed on these in Concrete (C 402) was combined with the fly ash specification. Higher amounts of sulfur trioxide. to form the current ASTM C 618. natural elements. the sum of the other three oxides. the determination of LOI was chosen because it was an requirement even if the SCM met the mandatory physical re- available test method from ASTM C 114 and was preferable to quirement by passing the autoclave test.1 CCRL 24 1998 C 25 1. In that instance.35 47.7 CCRL 10 1991 C 28 6. The supplementary Agencies frequently lower this maximum when they are sure optional chemical requirements were removed in 1983 (bulk there are competitive materials available in their marketplace.13 43. Class C fly ash is usually below 1 % LOI.52 0.3 CCRL 4 1988 F 20 0.36 0.32 25.24 18. The maximum LOI was already at 6.10 23.0 % for Class C fly with coal.10 19.45 0.3 CCRL 29 2001 F 20 0.57 25. This was initially a compose during heating at 750°C (e.56 0.97 0.13 24. The removal of LOI for natural pozzolans is set at a maximum of 10.11 0. Everyone concedes. Originally.3 CCRL 33 2003 C 20 1.. Currently.4 much lower.19 39.59 42.5 CCRL 3 1988 F 20 0. quirements for fly ash or natural pozzolans.15 10. This is these optional requirements was associated with the replacement the same value given in the initial version of C 402.7 CCRL 11 1992 F 27 0. that the lower the Supplementary Optional Chemical Requirements loss on ignition.0 %.47 0.1 CCRL 32 2002 N 23 0.25 20. the temperature given in ASTM C 114.19 16.1 CCRL 19 1996 F 28 1.0 CCRL 8 1990 F 29 0. it was found that many agencies were dropping the limit to and are quicker and more desirable [47].38 0.15 0.21 37.46 0.4 CCRL 30 2001 F 20 0.40 0.65 26.70 43.10 25. was added providing typically fails to burn off all of the carbon present in the fly ash. issued in 1957. for a 12. LOI is run at 750°C rather With the advent of better (more complete) combustion in electric than 950°C.6 CCRL 13 1993 C 23 1.8 CCRL 16 1994 F 27 0.4 CCRL 27 2000 C 25 1. This meant carbon content (see Fig.6 CCRL 7 1990 F 29 0.52 0. Subcommittee C09.43 0.03.21 0.19 24. It is important to note that the LOI of natural pozzolans is not nor.79 0. 4).70 0. The note under ASTM C 618.50 0.1 CCRL 5 1989 F 27 2.15 21. this limit .28 29.0 CCRL 2 1987 C 12 1.54 0.7 CCRL 23 1998 C 25 1.24 0.8 CCRL 21 1997 C 23 2. The bulk magnesium oxide content (analytical Mg. however.50 18.7 CCRL 22 1997 C 23 2.6 CCRL 12 1992 F 27 0. Table 1.8 CCRL 9 1991 C 28 3.13 36.1 CCRL 17 1995 C 29 1.18 33.37 0.44 38. the determination of free carbon.69 0.60 39. instrumental tests for carbon are frequently run instead of LOI ket.81 36.0 %.9 CCRL 31 2002 N 23 0.40 32.9 CCRL 28 2000 C 25 1. This is especially true 6.8 CCRL 6 1989 F 27 2.15 10.30 0.38 34.8 CCRL 20 1996 F 28 1. the LOI test method given in C 311 ash. % CCRL 1 1987 C 12 0. clays or carbonates). loss on ignition in fly ash is directly related to tional chemical requirement (1977 through 1983).1 CCRL 25 1999 F 20 0.48 0.43 0.74 0.500 TESTS AND PROPERTIES OF CONCRETE TABLE 1—CCRL Test Results for the Available Alkali Test Number Available Alkali Standard Coefficient of Sample Year Class of Labs (as %Na2Oe) Deviation Variation.40 0.18 2. of prescriptive chemical requirements with performance tests.25 18.33 0.22 15. ex- mally associated with the presence of free carbon.21 0. ically been limited to 5 % (maximum).14 30.0 % maximum LOI if acceptable performance records were provided. mandatory requirement (1968 through 1976) and then an op- Historically.80 47.23 0. power plants and with the coming of Class C fly ash to the mar.8 CCRL 14 1993 C 23 1.24 0.77 1.14 0.g. magnesium oxide) and 2001 (available alkali).5 CCRL 34 2003 C 20 1. When the specification was first that specifiers could limit usage based on an optional chemical written.3 CCRL 15 1994 F 27 0. Rather it is pressed as an oxide) of fly ash and natural pozzolan has histor- more commonly attributed to the presence of minerals that de.08 was divided in the action to lower when additional fuels such as petroleum coke are burned along the limit.4 CCRL 18 1995 C 29 1. the easier will be the control of air entrainment Currently there are no supplementary optional chemical re- content in the concrete.33 0. and they were giving satisfactory results in concrete.12 29.0 CCRL 26 1999 F 20 0. Brink and Halstead [13] termination of sodium and potassium was not trivial—it was la. 2c and 2d). after the subcommittee became tion. is very common in Class C fly ash (compare another method had to be devised to put the alkali into solu- Fig. (b) specimen grinding and The available alkali test method dates back to about 1950 washing during the alkali extraction phase are poorly defined. fly ash and pozzolans are only partially soluble in acid so natural pozzolans.5 % is about 0. while only sporadically identified in Class F fly ash and ever.5 % the historical signifi. and EPRI [15]. pact on the test results. came the method of choice for measuring alkali content. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 501 Fig. 2b.9 %. Brink and Halstead [13]. Hence. it rapidly be- would indicate the presence of periclase (MgO) in the SCM. approach the 1. showed that the release of alkali from Class F fly ash often con- borious and required highly trained technical staff. page 126). Since no member of the subcommittee could remember sion has been linked to a variety of different experimental vari- why the limit was originally set at 1. if the precision val- silica reaction (ASR). At that period in time the test method was most probably and (c) carbonation of the calcium hydroxide has a major im- considered highly innovative because it employed new tech. This is especially true when the test results alkali test and its relevance to the ongoing battle against alkali. was considerably more complex than had been anticipated [16]. Historical data extracted from Davis [10. this was assumed to give an estimate of quired by the purchaser for mineral admixtures to be used in how much alkali the fly ash could contribute to alkali-silica re- concrete containing reactive aggregate and cement to meet a action. such as: (a) calibration standards do not adequately rep- cance and rationale behind the limit remains a mystery. not identical) to one described by Moran and Gilliland [50] (see Later work indicated that the relationship between bulk mag. the test method typically exhibits poor inter- limitation on content of alkalies. The specimens are cured for 28 days at a temperature pozzolans. Similar observations were reported for Class C fly ash . which was used by the U. Appendix B. the available alkali (or available “alkalies” in amount of alkali (sodium and potassium. Prior to the use of the flame photometer the de. absolute. How- iclase. The more comfortable with the conservative results produced by the method summarized in ASTM C 311-53T is very similar (but autoclave test. However. alkali solubility data for a small nology (flame photometry) that was greatly enhancing the abil. The test is long and applied to fly ash but later the limit was also applied to natural tedious. ables. A note to this supplemental chemical requirement of 38°C and then the alkalis are washed from the pulverized stated that the limit was “Applicable only when specifically re. In concept. ues for CCRL samples 9 and 10 are ignored. normally expressed as older versions) content was limited to 1.5 % specification limit (note.S. Concerns were voiced about both the re.” Since about 1989 there had laboratory precision (see Table 1) and this limits the applicabil- been much discussion in the subcommittee about the available ity of the test results. that the D2S limit liability of the test method and the significance of the 1. of materials. number of natural pozzolans and Class F fly ashes indicated that ity of analysts to determine the alkali content of a wide variety the release of alkali could continue out to 90 days of curing [50].11]. the redundant specification limit was removed. Minnick [12]. 4—Relationship between carbon content and loss on ignition for fly ash. was based on the concern that the presence of magnesium soluble and total alkali in portland cements [49]. Using a larger suite of fly ash samples. Bureau of nesium oxide content and the presence of periclase in fly ash Reclamation during the 1940s. The poor preci- limit. specimens. [48]. That method became the “available alkalies” test. Per. Also. for this test method). ASTM [14]. The purpose of the available alkali test is to estimate the Up until 2001. resent the unknown samples. Hence.5 % (maximum) in the equivalent sodium oxide) that a fly ash or pozzolan can release chemical or optional chemical requirements. This initially only when it is reacted with calcium hydroxide. tinued past the 28-day curing period specified in the available when the method proved fruitful in the determination of water alkali test. Since the subcommittee could not remember the available alkali test. the 1. a performance test was adopted that Their test results indicated that the amount of alkali extracted would differentiate between SCMs based on their ability to re- increased when the fly ash-calcium hydroxide ratio was duce the expansion caused by ASR. and Walker [52] indi. In addition. Finally. rationale for setting the limit at 1. was provided so that the alkali content of the SCM could be tion in mortar bar expansion (see Fig. tent is fast and allows one to perform testing on a routine basis sion (see Fig. Secondly.5 % in 1957. Work by Buttler. in 1986 [51]. measured and the total alkali burden of the cementitious mate- ably better relationship between the sum of the oxides rial could be calculated.5 % specification limit for Fig. The determination of total alkali con- (SiO2Al2O3Fe2O3) and the reduction in mortar bar expan. . 5—Relationship between available alkali content and the reduction of mortar bar expansion for data from the Cement and Concrete Reference Laboratory (CCRL) Pozzolan Proficiency sample program. 6). These facts made the 1. The test method that was decreased. used in the test method also plays a critical role in the amount The strategy for removal of the specification limit was com- of alkali that was liberated during the 28-day curing period. posed of three steps.5 % limit very difficult with a much better turnaround time than was possible with the to support. they reached a cated that the selection of the fly ash to calcium hydroxide ratio consensus to remove the limit. test results from the CCRL Pozzolan adopted will be described later in this chapter. 6—Relationship between the oxide sum (SiAlFe) and the reduction of mortar bar expansion for data from the Cement and Concrete Reference Laboratory (CCRL) Pozzolan Proficiency sample program. 5). There is a consider. Morgan.502 TESTS AND PROPERTIES OF CONCRETE Fig. a test Proficiency testing program show little indication of a strong method for measuring the total sodium and potassium content relationship between available alkali content and the reduc. First. soundness.4 211. No maximum limit was placed on given in C 430. Strength testing is normally conducted on mortar specimens con- cation used specific surface as a measure of fineness.3 222. tests on a nationwide basis and not as a guide to mixture designs ment by the 45-m (No. are mentioned to indicate the difficulty experienced measuring The strength activity index test with lime was controversial fineness in a way that correlates with results in concrete.4 188. Table 2). Hence. etc. The zolan.54].5 18.1 CCRL 12 1992 F 26 947. they indicated that the performance test results procedure appeared to effectively remove the bias in the test should guide the selection and replacement level appropriate results reported for CCRL Pozzolan Proficiency samples 7 and for any given mixture of SCM and cement.53. SRM fly ash results. The percent-re.0 CCRL 8 1990 F 25 595.5 18. amount of water needed to produce a concrete mixture of ad. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 503 available alkali was removed. in the test methods and associated specification limits has been face in 1968.9 405. both dependent on fineness. The consensus went back to specific sur. which indicated that the selection of a calibration Physical Requirements standard was less critical when the additive correction factor The mandatory physical requirements.7 937.0 24. this appeared to fix the fineness sity. when the pro.0 35. 325) Sieve (C 430) began to call for the for specific projects. The history of early changes substituted in 1965. test is simple. strength activity index. the test was felt to be as much a test of the contributing to the concrete reaction.7 193. mean particle diameter was activity index with portland cement).53].5 25. Strength tests have always played a fundamental role in the equate workability and the apparent reactivity of the SCM are acceptance of fly ash and natural pozzolans for use in concrete. quick. water tion standard (SRM 114n) “gave results comparable to the best requirement. strength material being analyzed). a new fineness requirement was discussed by Mielenz [37. the fineness determinations. and inexpensive and can be run at a high Class C fly ash makes its own contribution of lime to the mix- frequency for quality control purposes. single SRM (cement standard 114) for both cement and fly ash crete mixture.5 23. pozzolanic activity index with portland cement. Their test results indicated that the cement calibra- ASTM C 618.9 CCRL 11 1992 F 26 1068. 325) sieve.48. a note stating this disclaimer has use of the new electroformed sieves [4. The exact reason for the poor precision is difficult to tained test does not measure the fine material that is actually pinpoint. higher carbon contents can give readings indicating Part of the reason for the controversy was probably related to higher surface area. but it generally acts as an lime (fineness. This section will deal with them in that order. and uniformity of fineness and den.0 32. specification limits have always been subject to criticism because termined by wet washing through a 45 m (No. Instead. At that time.3 267. C 206 test. The mortar tests and associated added for Class N pozzolans that consisted of fineness as de. This is in good agreement with the work by Butler and Kanare [56].7 CCRL 6 1989 F 21 960. it TABLE 2—CCRL Summary of Test Results from the Lime Pozzolanic Strength Index Number Standard Sample Year Class of Labs Mean (psi) deviation (psi) COV (%) CCRL 5 1989 F 21 1042.” Hence. Fly ash in concrete. which would assume a finer product when the very poor interlaboratory precision of the test method (see actually the material is coarser or less fine [55]. Then.2 CCRL 7 1990 F 25 782. the reader must bear in mind that the pur- added the new fineness test and a new specification limit in pose of standardized testing is to ensure that the product (fly ash 1971. These changes been used since the early versions of the specifications.7 200. The new calibration limit.9 CCRL 10 1991 C 23 2851. The tests are meant to be used as product acceptance cedure in ASTM Test Method for Fineness of Hydraulic Ce. The limit was initially set at 20 % (maximum. The first versions of this specifi. 8 [57]. This was done in response to concerns voiced the total alkali content of the SCM because the subcommittee about both the calibration procedure and the calibration could not reach a consensus on an appropriate value for the standards used in the test method [56]. Part of the reason the tion factor rather than the multiplicative correction factor method had stayed around so long was because it was quick. for Class F and Class N pozzolans in 1992. In the for some time prior to being removed from the specification. A they do not directly correlate with the performance of the SCM maximum of 12 % retained was the original limit.1 21. However.4 CCRL 9 1991 C 23 2144. The requirement was dropped for Class C fly ash in 1985. consist of fineness. Although there is not a direct correlation. purity. calibration problem and still allowed laboratories to use only a Fineness of a SCM is important in its contribution to a con.) as it was of the fly ash or natural poz- accurate indicator of the amount of fine material present. however. The sieve calibration ture. % retained) or natural pozzolan) meets minimum requirements listed in the but was later raised to 34 % (maximum) in 1973. so this test was irrelevant.1 . standards. The requirement was dropped procedure was changed in 1994 to utilize an additive correc. set forth in Table 2 of was used. Specific taining specific proportions of lime and SCM (pozzolanic activity surface was measured by ASTM Test Method for Fineness of index with lime) or on mortar cubes containing specific amounts Hydraulic Cement by Air-Permeability Apparatus (C 206) (this of portland cement and SCM (compressive strength of mortar is the Blaine test adjusted to compensate for the density of the cubes. The method was subjected to several round robin stud. ten prior test results. low alkali cements tended to decrease the early strength terious quantities. The curing temperature was reduced from 38°C (sealed con. Also. product. and. though the amount of SCM used in the test mixture was sig- and the alkali content of the lab cement that would be used in nificantly reduced. cement test. now only reduce the water demand about method) to reflect field usage. This greatly simplified the curing requirements of However. the water re- was published in 1990. is prepared for the strength activity index with portland ing a test result. carbon (or LOI). the pozzolanic activity index ter-cement ratio of 0. normal water-to-cementitious-materials ratios. The flow of the test mortar (containing 20 % SCM) is scrutiny. to periclase and free lime. and depends pri- of the SCM. Hence. if those materials are present in deletion. The new test method was rial. The changes in the method pertained to quirement limits were held constant. The subcommittee has discussed this issue The mandatory physical requirements for uniformity in- several times and is currently waiting to see how frequently test. Hence. Of more concern are tests con- need to conduct density tests prior to proportioning the mortar. as equivalent Na2O). for standardization purposes clave test provides a conservative approach to identifying the alkali content of the lab cement needed to be constrained potential soundness problems related to periclase and/or free so that test results could be compared across the country.485 and the flow for the mixture is deter- test with portland cement was subjected to considerable mined. Some Class F activity index test allowed the subcommittee to delete the 7-day fly ash has failed this test due to the lime. for example. This was done even SCM replacement level. This also helped to eliminate the 5 % for the current test method. The changes to the flow properties of the mortar will the water requirement limits because it has reduced the range be described later with the discussion on the water requirement of test results that are obtained. in block or shotcrete mixes. To date. 0. lime water). the water to fly ash or natural pozzolan and cement ratios are this approximation apparently failed to cover an adequate low. Users still need land cement test has been that it fails to consistently reject finely to pass the autoclave test when using higher SCM replacements. applications because chemical admixtures (water reducers) perature was that the alkali content of the portland cement have become so commonly used in the construction industry. The drier consistency of the paste used in new test method was a 7-day alternate with the previous 28-day the autoclave test constrains the hydration of periclase and lime requirement. Helmuth and West [61] have reported did not mean that job cement of any arbitrary composition concerns about the validity of the autoclave test when evaluat- could not be used in the evaluations. For fly ash. Extensive testing has indicated that the auto- gain of the test specimens.60]. The uniformity of the fineness is specified ported instances where materials have passed the specification since it is an easily determined indicator of a change in the limit but exhibited little potential as a pozzolanic material. this limit will de- was changed to reflect the subcommittee’s opinion that any test pend on fineness. However. as measured by the autoclave expansion test. which often re- limit. Such a change is important because it might affect Hence. One side effect of the reduction in curing tem. The control mortar is proportioned at a fixed wa- During the mid to late 1980s. the name relative to the control cement. ground materials that exhibit marginal to negligible pozzolanic Note D of Table 2 states that “If the fly ash or natural pozzolan properties (for example. clude limits for fineness ( 5 percentage points) and density ing labs report this anomalous behavior. however.59. by trial and error. The availability of a 7-day result from the strength when they are present in a “hard burned” state. the limit is set at a maximum water demand of 105 %. this dictates from the studies (ASTM report RR: C09-1001). The other uniformity requirement The water requirement limit gives some measure of the in Table 2 of ASTM C 618 is on density. Hence. needed to be constrained within a specific range (0. For natural poz- only 28 days. This lime in fly ash [16. The most important addition to the unsound pozzolans. however. curing temperature. this has impacted the usefulness of the testing. name to avoid confusion with the old method. two labs have re. such behavior may no longer be relevant to field the test method. flow properties. Rather.50 % to Soundness. In addi. This can be partly will constitute more then 20 % by weight of the cementitious attributed to the low dosage of SCM (20 % replacement) that is material in the project mix design. The changes the amount of water that will be used for the test mortar. pulverized quartz). water demand in concrete. was too short to ascertain the “pozzolanic” nature zolans this limit is set at a maximum of 115 %. For were substantial so the revised test method was given a new fly ash. a change of contribution to workability that the SCM will impart to a 5 % in the uniformity of density is not thought to be significant . High alkali cements tended to will indicate any possible delayed expansion problems related increase the early strength gain of the test specimens. to a lesser extent. Reducing the quantity of SCM that is added to the test mortar tainers) to standard laboratory conditions (23°C. after using the ( 5 %). submerged in makes the method less sensitive to problematic behavior [58]. would have been adequately hydrated when used in concrete at One complaint about the strength activity index with port.80 %. it was retained for that reason alone. not variation in the test method. these concerns were attributed the subcommittee was striving to reduce the interlaboratory to the influence of unsound cements containing pozzolans. the method would simply indicate how a marily on the fineness and surface characteristics of the mate- SCM behaved with any given cement. on conducted at room temperature.” range of behavior. Ex- a coarse Class F fly ash was used to simulate a material that cessive autoclave expansion is highly significant in cases where would consistently fail to meet the specification limit. this is still an active issue in the subcommittee. even though the lime lime pozzolanic activity test. the replacement of portland cement duced the water demand about 8 % to 10 % in the pozzolanic is done by mass (20 %) rather than volume (35 % in the old activity index test. constrained to be 5 % of the flow value that was obtained for ies and extensive changes in procedure and evaluation resulted the control mortar. the test specimens for auto- used in the mixture. Both requirements are compared to the average of the new test method for a little over a decade. In the new method. with a maximum duration of the glassy spherical particles in the fly ash. Good fly ashes. During the development of the test method clave expansion shall contain that anticipated percentage. The test is performed using the mortar that The other tests all required 28 days of curing prior to produc. concrete mixture. When the pozzolanic activity index test was replaced with named the strength activity index with portland cement and it the strength activity index test in the late 1980s. Ultimately.504 TESTS AND PROPERTIES OF CONCRETE was the only strength test that produced a result in seven days. ducted on fly ash or pozzolans that have high water demands. Rather it simply meant that ing blended cements. the trend is also evident in CCRL test results illustrated in Fig. Hence. Ground Blast-Furnace Slag in Preventing Excessive Expansion Increase of drying shrinkage is a requirement because of Concrete Due to the Alkali-Silica Reaction. These inconsistencies forced the subcommittee to improve strength parameters in mortar and concrete [58].60 % equivalent Na2O to modern practice in which the SCM is treated as part of the (Control 1 in Fig. 8. factor helps to avoid the situation where increasing fineness The new test procedure is called the Effectiveness of Fly Ash values and carbon content (LOI) lead to an increase in water or Natural Pozzolan in Controlling Alkali Silica Reactions and it demand. ASTM C 441. uniformity fly ash replacement level is a major factor in controlling ex- requirement for air-entraining solution demand. The test procedure for the uniformity of air-entraining agent demand has recently been challenged as not being sensitive enough [65]. Dunstan [41] has hypothesized that The multiple factor is defined as the sieve fineness multi. This is especially true in controlling alkali-silica reactivity.67. effectiveness pansion caused by ASR [32.68]. the Standard Test Method for the Effectiveness of Pozzolans or turing processes. Therefore. 8. This is typically related to the increased wa. maximum) is too low for many otherwise ac. Early work by Hanna [32]. Mielenz et al. The required “reduction of mortar expansion” does not apply to fly ash and the required mortar bar expansion at 14 Fig. For Class F fly ash to reduce the expansion caused by ASR (see Fig. Hence. 1950s. the test method is currently being re-evaluated and may be revised in the future. this optional test will deal with the concern that some fly ash causes problems with control of entrained air in the concrete mixture. lists the supplementary optional physical Extensive work by many researchers has clearly indicated that requirements as multiple factor. ASTM C 618. [69] have indicated that natural pozzolans typically perform better than fly ash in controlling expansion related to ASR (also.020 % limit was set assuming the cement in the mixture. Hence.60 %.64]. originated from a time when the SCM was commonly The control cement for the test is typically chosen with an used to replace a portion of the aggregate. This relationship does not apply to Class C fly ash be. The 0. 5). cementitious material. recent other raw materials [62].44. In the meantime. Briefly. and hence. equivalent basis and a control cement is used to set the level of ter demand of the mixture. too low a commentary describing how the procedure should be used to act as a multiplier. Stan- ton [67]. which dates back to the pared against. 7. This is in contrast alkali content between 0. the relationship does not and interpreted (see Appendix X1 of C 311). and effectiveness in when the replacement level is near the pessimum level for the contributing to sulfate resistance. Also. the test pro- apply to natural pozzolans because the LOI is not related to cedure is based on the mortar bar expansion test described in carbon content and the fineness can be adjusted by manufac. However. Table 3. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 505 either as an indicator of product change or in effect on con. fly ash class designation should impact the ability of a fly ash plied by the LOI (or free carbon content). The test method. Lerch [66]. 7—Theoretical relationship between fly ash replace- days (0. refer to Fig. and Pepper and Mather [68] set a firm foundation upon which nearly countless other authors have built. drying shrinkage. expressed as the SCM tends to be obscured by the variability present in the equivalent Na2O) could meet that limit [69]. This some natural pozzolans will cause an unacceptable increase in method was modified to substitute SCM for cement on a mass drying shrinkage. The new test procedure is accompanied by cause the LOI is generally below 1 % and is. expansion (performance) that the test specimens will be coming shrinkage [63.52 % as Na2O). this tends to put the test specimen containing SCM at a disadvantage. this has served to cause the rejection of crete mixture design. cementitious system.020 %. Class F fly ash and natural pozzolans have been used to reduce the expansion caused by alkali-silica reaction for over 50 years. to 25 %).42. the 5 % uniformity limit on that low-alkali portland cements (less than 0. However. alkali content 0.50 % and 0. ment level and expansion due to alkali-silica reaction ceptable fly ashes (especially when the replacement is limited (adapted from Dunstan [41]). Since total cementitious material content and water content both have a significant influence on shrinkage. In addition. was adopted in 1993. This is probably because most agencies materials that might have been helpful in correcting alkali-sil- currently limit SCM replacements to about 15 % to 25 % of ica reaction in concrete. therefore. ative water requirement. Fly ash will generally reduce dry. This concept is illustrated in Fig. note that the multiple factor has exhibited good correlation with the rel. The problem with the test method is related to the high air content (18 3 %) used in the evaluation. Davis [20]. has been linked to 6).71]. changes in the storage containers for the test procedure have increased the sensitivity of the test and this limit can now only Supplementary Optional Physical Requirements be reached by cements with very low alkali contents [70. the paste content of the mortar containing the SCM is greater than in the control mortar. The multiple the test method and specification limit for the test. . The subcommittee will consider a lower air content that would make the test more sensitive. However. the reactivity with cement alkalies test has not been a satisfactory method for selecting fly ash that can help to reduce expansion caused by alkali-silica reaction. That is why they were not generally applicable or definitive enough to a joint C09. control cements with considerably lower alkali contents may based on the Standard Test Method for Length Change of Hy- also be used to decrease the expansion of the control speci. entrainment. or equal to.72. In both instances the test takes at least six months to were used with the job cement at replacement levels of 15 %. tween Classes F and C fly ash is not properly drawn in ASTM C A new test method was adopted for the effectiveness in 618.506 TESTS AND PROPERTIES OF CONCRETE Fig. 8. The new techniques and associated specification limits will be This chapter has already suggested that the distinction be- adopted when they become available.” Fly ash B was effective containing fly ash or natural pozzolan is compared to the at the 22 % replacement level. 8) to be considered “effective. This test method.75 % lection of combinations of materials that could provide the per- as Na2O). 8) dures. In addition. alkali content 0.24-C09. The specification limits can be applied via two different proce- tem. It also provides a more robust solution to the problem Test Requirements Not in the Specification of materials selection and optimization than was ever provided Various other tests have been proposed and used in research. A test mixture must exhibit an The first method (Procedure A) is very similar to that expansion less than. draulic-Cement Mortars Exposed to Sulfate Solution. In this particular instance. These dealt with. Again. heat of hydration. In this instance two different fly ashes (A and B in Fig. The ab- at the 35 % replacement level. The method was not designed to These have been considered for use in these specifications. include. but provide a mitigative solution to the ASR problem. ability to reduce expansion. 35 %. 1012. The expansion of the mortar bar specimens 1 in Fig. Hence. the control specimen (Control given in C 1012. among other things. and 22 %. ASTM C mens (Control 2 in Fig. method is relatively quick because test results are available in 14 days. neither fly ash could sulfate resistance needed for a particular job. In this instance. The cement used to fabricate the test spec. The new test to evaluate how dosage influences mortar bar expansion in the procedure is accompanied by a commentary describing how it test specimens. was needed because of the concerns voiced in the method applicable to regions that only have access to very the literature about how different sources of fly ash influence low alkali cements. and the associated specification limits This tends to make the test more conservative and it also makes given in C 618. the performance of concrete exposed to soluble sulfates imens should have an alkali content equaling or exceeding that [38–40. this is tive at reducing expansion) from the many different sources of the reason for the 100 % (maximum) expansion limit given in material that are commonly available for any given job. near the pessimum level for that particular cementitious sys. respectively. The test method is dex in hopes of being able to forecast the possible contribution . 8.26 Task Group entitled “ASR and Perfor. discernment mance Limits” is still actively pursuing more robust methods between Classes F and C. complete. and effect on air of eliminating or minimizing the impact of ASR on concrete. by the available alkali test. The Table 3 of C 618. it is apparent that the 14-day only portland cement to designate the level of expansion that criterion tends to provide a conservative estimate of the SCM’s would be acceptable for any particular job. The subcommittee has worked with a test for hydraulic in- contributing to sulfate resistance in 1996.73]. 8—Illustration of how the new test for the Effectiveness of Fly Ash or Natural Pozzolan in Controlling Alkali-Silica Reactions can be used to select fly ash and replacement levels.39 % as Na2O). at the solute expansion limits are selected based on the level of replacement levels used in the study. the test was adopted to simplify the se- of the job cement (Job Cement in Fig. The second reduce the expansion below the level of the very low alkali method (Procedure B) uses control specimens containing cement (Control 2). performance equivalent to the control cement. while fly ash A was just effective absolute expansion limits given in Table 3 of C 618. This helps to avoid using SCM dosages that are should be used and interpreted (see Appendix X2 of C 311). The test is run at several levels of SCM replacement formance needed for specific job requirements. test specimens containing various proportions of job cement The new ASR test method was created to provide a better and SCM are simply checked to make sure that they provide method of selecting good material combinations (those effec. alkali content 0. If such a mixture Silica fume is almost as fine as tobacco smoke. eign materials” such as carbon and wood chips. to a concrete mixture made by a pozzolan with various cements. Hydraulic-Cement Concrete and Mortar (C 1240) that was The foam-index test is a quick test to show possible published in 1993. They consist of mandatory requirements for silicon surance program. That limitation was resolved by a round robin conducted in 2003. which was at 2. Since it deals with one cement visions. as well as ASTM of success. Since then. Temperature to add silica fume as a new class or column in the existing rise tests were also tried without conclusive results. Cementitious Mixtures. Some agencies. alloys. was over 2 % [79]. Silica fume (sometimes referred to as condensed silica fume or moisture content and LOI. the results apply only the ASTM Standard Specification for Silica Fume Used in to that single combination. The determination of the bulk chemistry of silica fume had long been hampered because of the lack of high-silica content Silica Fume standards. Along with gave a measurable strength. Such a program inating task group from ASTM decided to report elements from might use some tests not discussed in this chapter that a pro. Test procedures from ASTM C 311 were to be the subcommittee have just been slow to accept new testing pro. Army Corps of Engineers. According to Richter [79].78]. and in various (d) high strength. 2a) and is Class C. if not.27 %. has proven totally acceptable because the complex contribution (b) retarded alkali-aggregate reaction. ered “prescriptive” and a performance test was available for . No such test procedure (a) reduced heat of hydration. The some fumes none or very little of that oxide is present. In 2003. since the pro. be used effectively for quality assurance.” Some of the first field experimentation The early versions of C 1240 had an optional chemical re- with silica fume in concrete in the United States was done in quirement for the available alkali content of silica fume. moisture content. the Canadian specification and ASTM are limiting qualifying sources of pozzolan based on prior testing history silicon (expressed as SiO2) to 85 % and higher” [45. “most research has been done on silica the U. This Kentucky in 1982.79]. C09. Class F. Still. The ASTM task group at first thought or even of mixtures without aggregate were tried. has guided the preparation of the initial version of the strength and heat of hydration. used where possible and modified when needed. Quality Assurance Some of the tests discussed earlier could be used as part of a Chemical Requirements quality assurance program. the title of the specification was changed to and only the source of fly ash under test.03. the chemical analysis as conventional oxides even though in ducer has found to indicate possible changes in product. According to Malhotra et al. both the base document and the changes in the amount of air-entraining agent required when title of the specification have been subjected to a number of reusing fly ash in the concrete. but are present since then Norway has made significant advances on various from the process that produces silica fume.S. they gave desirable information. C 1240. SiC). once used sealed storage fume produced from the production of silicon or ferrosilicon and complete testing before shipment. Manz [74] suggested a performance test meas. Such a test would desirable properties: help discern between Classes F and C. that organiza. types of concrete mixtures has not allowed any correlations that (e) increased sulfate resistance. The limit was set at will therefore know the tests that really apply to his situation.10 organized a task group to develop a specification for the requirement was removed in 2000 because it was consid- the use of silica fume in concrete. These foreign tions on condensed silica fume began in the late 1940s and materials do not come from contamination. such as According to Richter. Prescription grams such as those proposed by McKerrall and Ledbetter [75] and performance specifications were both to be used when for Class C fly ash. with 16 different Fly ash is a by-product of coal combustion in an electric steam fumes with a minimum of 85 % SiO2. when the deprecated term “mineral admixture” was removed from the document. reported as silicon dioxide (SiO2). [77]. (c) reduced freeze-thaw effects and water erosion. is usually con- ducer will know more about the factors that affect change and sidered the active constituent in silica fume. in measuring both contribution to C 311. used for information on heat of hydration with varying degrees much of the thinking from that specification.6] discuss some of those tests that Fig. done by a producer of fly ash than by a user. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 507 of a pozzolan to the strength of a concrete mixture. However. at various temperatures. In 1984. The orig- and producer product certification [76]. In January 1985. However. uring strength with no cement in the mixture. 2a that small amounts of reduced mineral species may oc- cannot be used in a specification such as ASTM C 618 but can casionally be found in silica fume (moissanite is silicon carbide. the fly ash would be assumed to be this fineness. Most of the 6 % LOI is due to “for- [77. This seemed silica fume can be used to make concrete with the following at least to be one factor that could be isolated. A quality assurance program can better be dioxide. “The first investiga. Moisture content is limited to 3 % maximum to metal or ferrosilicon metal in submerged-arc electric furnaces avoid problems in handling. inasmuch as ASTM C 618 and Chemical requirements for silica fume are listed in Table 1 of ASTM C 311 cannot be expected to be a complete quality as. it is mostly amorphous (refer to Fig. Since very little is known about the other types at the tion began an effort to avoid the consequent cost and delay by present time. aspects of silica fume. Various other strength tests of mortars spherical in shape [80]. Silicon. and are acceptable. no other oxide except power plant and acceptability is therefore more a matter of potassium oxide (K2O). appear to have been directly adopted microsilica) is a by-product from the production of silicon from C 618. it was decided These same temperature rise tests on mortars have been not to try to incorporate silica fume into ASTM C 618. ASTM Subcommittee requirement was adopted directly from ASTM C 618. Note in ACI Committee reports [5. in various proportions. Members of ASTM C 618. which yielded a standard reference material History and Use (SRM 2696) for silica fume. The remaining two requirements. quality assurance than quality control. By late 1986. it is more advisable to test a ASTM Standard Specification for Silica Fume for Use in complete concrete mixture rather than a laboratory mortar. (f) reduced permeability. and loss on ignition. a minimum of 85 % when it was found that. . which was to enhance specific prop- also felt a need to measure particle size or specific surface area erties of the concrete mixture. The specification limit is set at sealed curing at 38°C) but with higher temperatures in mind. change greatly increased the compressive strength of cubes from the test mixture and the specification limit was increased Closing Statements to 105 % (minimum) of the control. They had been conducting this type of testing on a rou. This 0. However. 10 % by mass of cement. Finally. all of the silica fume will from C 311. was set the control mix tends to contain much less water than the test with the old C 311 test procedure (pozzolanic activity index. a mortar mixture. employed. to reflect this increase in strength. tine basis for as long as they had been testing silica fume. cation limit at seven days. the task group is currently working on procedural changes to the test uses mix proportions that consider the silica fume an ag- test method that will provide results that are more concise. and specific surface. the notion that finely divided materials containing free car- ever. there is an oversize provi. However. similar to the ASTM Test Method for Specific Surface Area of mining the available alkali content as specified in C 311. test. able alkali limit was being balloted for removal. This is a measure of the reac. These demands evaluated and rejected because of the variation of results require the use of supplementary cementitious materials. the reactivity with cement alkalies. 325) sieve. the accelerated being re-evaluated by the silica fume task group because they pozzolanic strength activity index. it has also changed the way that the materials are crete containing the silica fume. water demand of the mixture containing 9 % silica fume With respect to the accelerated pozzolanic activity index tends to be high. the user simply wants to be assured that it will not cause as to the source of both the silica fume and the cement. Again. a new expansion category (very high resistance. The phys. Rather Alumina or Quartz by Nitrogen Adsorption. The specifi. since the water required to pro- formed before ASTM C 311 was changed in 1989. als. can significantly delay the certification of the material. in very recent times because this often appeared to be a property relevant to the use the push has been to produce high performance concrete on a of the material. which has been used for natu- rect some discrepancies in the test method. the ture required to entrain a stable air-void system. C 1069. The optional physical requirements consist Physical Requirements of the determination of the uniformity of air content measure- Physical requirements are given in Table 2 of C 1240. taining a water-to-cementitious-material ratio of 0. The method is with both users and producers indicated that few were deter. This is in contrast to the original rea- The task group developing the silica fume specification son for using the material. The silica fume replacement is fixed at round-robin work conducted for this specification was per. The test measures the amount of admixture that easily pass through a 45-m (No. the appears to have been directly adopted from C 618. This caused the test specimens to always and natural pozzolans (Procedure A. It is uncertain why this value is different from the pozzolanic strength activity index in 2002. 85 % (minimum) of control. The gregate addition (rather than a cement replacement). Since uniformity requirement for the percentage oversize test the use of a high-range water reducer is not allowed. Normally. an 80 % reduction in expansion as compared to the control The initial version of the test was replaced with the accelerated specimen. normal value (75 % reduction). Hence. however. The specification limits are the technician to vary the water reducer dosage to make the also similar to those given for fly ash and natural pozzolans. The major discrep. C 1240. Optional Physical Requirements port the total alkali content of silica fume. this is The reactivity with cement alkalies test was directly different from any prior methods published in ASTM C 311. The adapted from C 441. Note A of Table 2 warns that agglomerations of extremely bon can have a significant impact on the amount of admix- fine material can also fail to pass through the sieve.485). duce a plastic mortar mixture is determined using the flow test. the current specification allows one to monitor and re. Discussion and Teller (BET) nitrogen adsorption method. been set at a replacement of 10 % and the test does not allow The new version of the test method allows the use a high-range for the use of a high-range water reducer to correct for the water reducer in the mixture containing silica fume. the silica fume content of the mortar mixtures has than the control mixture (formulated at a fixed w/c 0. Material retained is required to produce a specific amount of air (18 3 %) in on the 45-m (No. 325) sieve. sion that 10 % (maximum) of the material may be retained on The uniformity of air content test was directly adapted the 45-m (No. A mini- most had been determining the total alkali content of the silica mum specific surface area of 15 m2/g is specified in Table 2 of fume. flow of the test mortar similar to the control mortar. between operators and laboratories.05 % expansion at one year) has been added to Table 3. Hence. All of the optional physical requirements are currently uniformity of the oversize measurements. Optional physical requirements for silica fume are given in Table 3 of C 1240. This allows water demand of the silica fume. 325) sieve is an indication of foreign mate.508 TESTS AND PROPERTIES OF CONCRETE determining the ASR resistance of cement-silica fume combi. In many instances today. However. especially in the case of fly tivity of a given silica fume with a given cement and may vary ash.485. are rather inflexible and. The air permeability (Blaine fineness) test was routine basis for many different applications. Again. and sulfate resist- ical requirements consist of the determination of oversize. ancy in the method was related to the fact that the test speci. test. it was decided to nations. An interesting fact became apparent when the avail. absolute expansion lim- have a significantly higher water-to-cementitious-material ratio its). mixture containing silica fume. The note at the bottom of Table 2 in the specification Enhanced awareness of environmental concerns has led to a points out that “Accelerated pozzolanic activity index is not to resurgence in the use of supplementary cementitious materi- be considered a measure of the compressive strength of con. This was done to cor. the ance. ral pozzolans for more than 50 years. while main. in the instance of the sulfate resistance Under physical requirements. it should be noted that specimens are cured at 65°C. ments. The test is meaningful because it reinforces rials such as carbon and wood chips in the bulk product. measure the specific surface area by the Brunauer. How.” any problems in concrete. The sulfate resistance test method for silica fume is basi- mens (containing 10 % silica fume) were proportioned on a cally the same as that which was described earlier for fly ash constant flow basis. Emmett. . old and sometimes they appear to be firmly rooted in the past PA. ASTM International. Committee 226. S. tions to their limit. that subcommittee C09. What specification..” Proceedings. 59. West Conshohocken.74. Mixtures of this type will probably generate great appeal of Fly Ash for Use in Concrete. Vol. J. (or rejection) of the material. PA.” Manual of Concrete Practice. 2002. duction of high-reactivity metakaolins. ASTM International. All efforts must be directed at [9] Mielenz. pp. E. pp. Detroit. Project 2422-10. J. 1959. low NOx burners. they have the potential to alter the quality of Lea’s Chemistry of Cement and Concrete.” ASTM STP 99. Vol. Third Edition. N. all stretch the specifica.24 needs to take to improve these doc. There is little doubt of what we need to produce—we need to en- [8] American Heritage Dictionary. nificant benefits to concrete mixtures. pp. D. PA. Admixtures for Concrete. or should they even be applied to [12] Minnick.” Proceedings. would [11] Davis..81–85]. SCHLORHOLTZ ON SUPPLEMENTARY CEMENTITIOUS MATERIALS 509 What needs to be done to make the specifications for these [3] Tuthill.. “Mineral Admixtures. because they have the potential of imparting the benefits from 56. 471–631. 1955. Soft- sure that the materials are used to produce concrete that meets Key International Incorporated. General Properties of Concrete.54. “Weathering Resis- apply to the composite material? Would either existing specifi. ASTM International. MD. and Davis.” keeping the new or refined requirements as performance. Vol. Conshohocken. Materials Research Society Symposium. PA. G. 1954. The direction tures for Concrete.” Appendix C in “Summary of Methods for Determining ASTM International. J. ever. ASTM International. 1941. the needs specified by the user. West Con- the whole group of generic materials covered under the speci- shohocken. pp. “Studies Relating to the Testing tures. 281–293. 1994. these specifications cannot be static. that Materials. ASTM International. 127–130. “Pozzolanic Materials and Their Use in Concrete. ACI 232. the supplementary cementitious materials [15] Electric Power Research Institute. MI. zolans. 37. 375–387. American Concrete Institute.. Solem. pp. silica fume and fly ash) that they now wish to 577–612. These benefits have been verified by decades of use of a Database of Chemical. F. market. Current issues. 1998. “The Interpretation of X-ray Patterns of Poz- Properties of Concrete and Concrete Aggregates. and pro. This suggests a rethinking of Properties of Concrete. materials (say. Vol. West document is currently moving forward at a good pace.. pp. ACI 234R-96. MI. pp. H. ACI. Version 3. The many tests used in the ASTM specifications dis. ties of North American Fly Ash to Study the Nature of Fly Ash and Its Utilization as a Mineral Admixture in Concrete. Kelly. Part 1—Materials and precipitator additives. relates directly to the fact that the majority of the materials are [18] Cook. 804–822. 33.. E. “Fundamental Characteristics of Pulverized ASTM STP 169A. and Kelly. West Conshohocken. L.. “Chapter 46—Mineral Admixtures. however. burning of spot market coal. ASTM International. cation provide robust enough requirements for the acceptance American Concrete Institute. ACI. “Natural Pozzolans. [20] Davis.” Proceedings of the ASTM. fications then it would greatly simplify dealing with such mix- [13] Brink.. H. J..” Manual of Concrete Practice. Vol. 1986. Vol. Manual of Concrete Practice. Coal Fly Ashes. 1–39. the silica fume or the fly ash.. Vol. Properties of Concrete. 54. Detroit. J. Performance and Specifications for Admixtures. J. national. J.” cussed in this chapter are significant in controlling and defin- Proceedings. The benefits range from Final Report.” Significance of Tests and Properties of Concrete and Concrete-Making Materi- are another matter. there is no reason to limit [14] ASTM. 3–33. West Conshohocken. “Prop- it is difficult to predict where changes will occur. W. R. “Chapter 46 .. This Edward Arnold Ltd. ASTM STP 169C. 2002. hence. R. E. Use in Cement and Concrete. M. Concrete. and Halstead. R. pp. West Conshohocken. pp.. “Investigations Relating to the Use of Fly Ash as the new material? If reliable performance limits could be set for a Pozzolanic Material and as an Admixture in Portland-Cement Concrete. p.History and Background. C..” Proceed- some agencies have already developed mixtures of two or more ings. ing the aforementioned properties and their use in the concrete 1990. 1956.. 1970. PA. August 1983. West [2] Higginson.Mineral Admixtures. This will be necessary because at present [10] Davis. Surrey University Press.” Chapter 10.. W. PA. In conclusion. ASTM Inter- needs to be the goal. Committee 226. [22] Minnick. “Mineral Admixtures. 1129–1158. oriented as possible. England. erties of Cements and Concrete Containing Fly Ash.” Significance of Tests Conshohocken. the specifications for fly ash and natural pozzolans (C 618) [4] Cain. PA. Many authors have reviewed C 618 and C [6] American Concrete Institute. 314. Davis. 1994. J. 4th Edition. pp. Committee 226. F. W. Part 1—Materials and General alytical strategies or techniques. 3rd ed. pp.. These specifications are now about 50 years als.” 311 and many have been critical of them [29. PA. PA 1950. rather than looking ahead to future concerns. C. They [17] Lea. 3–15. R. For example.. E. must be in a continuous state of revision and refinement. Part 1—Materials and General Many of the criticisms have been addressed by the subcommit.” Cement Replacement Materi- by-products from major industries. to meet new environmental regulations or the rapidly changing [19] Massazza. 1155–1177. “Use of Natural Pozzolans in such as co-combustion of biomass with coal. D. [1] Meissner. ACI 232. tance of Concrete Containing Fly Ash Cements. enhanced performance to production of mixtures that are more [16] McCarthy. Detroit.” Significance materials better? The silica fume specification is only about one of Tests and Properties of Concrete and Concrete-Making decade old and is still in a constant state of revision. C. E. 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Montebello... “Sulfate Resistance of Concretes American Concrete Institute. 31–37. . F. American Concrete Institute. and Faber. “Variability of Concrete-Making Materials.. Concrete and Aggregates.” Proceedings Methods of Testing Fly Ash for Use with Portland Cement. [66] Lerch. ASTM International. K. 1987. Making Materials. D. J. Slag or Silica pp. Slag & Other pp. Durability. Fly Ash in Portland Cement Concrete. 214–224.” Cement. Scheetz. Fume. 1952. ASTM International. Vicksburg.” Proceedings. 52. Final Report. C. E. E. Boca [65] Lane. 1983.. Concrete. Symposium N. L. R. H. 5.. J. Silica Fume. Aitcin. Silica Fume. J. PA. ASTM STP 169C. Feldman. Vol.” Final Report for NCHRP Project 18-5. Condensed Silica Fume in Concrete..S. 13. P. 659–680. DOE/METC-85/6018. Detroit. Water Resources Technical Proceedings. and Ledbetter. and Aggregates. “Fly Ash or Use in Concrete – A the Corps of Engineers ‘Pozzolan Quality Management Critical Review. Cement. C. E. and Lewis. 1981.” Proceedings. V. and Rossenberger. MI. Mineral By-Products in Concrete. J. U. 1975. 1998. E.. P.. 1986. T. for Use of Fly Ash in Portland Cement Concrete.” Cement. P. “Properties of Fly Ash and Exposition. Concrete. and the ef. Iron blast furnace slag is used as a supplementary cementitious Ground blast furnace slag with cementitious properties material in concrete when it is granulated or pelletized. TX 77478. and United States in 1896. This ASTM C 125 further defines ground granulated blast furnace current edition will review and update the topic as addressed slag as “the glassy granular material formed when molten by the previous authors. and include up-to-date references. Paris underground metro system beginning in 1889. Since the late 19th century. respectively. 14090 Southwest Freeway. Table 1 shows typical replace. the contents of the 4th edition were drawn lating to Concrete and Concrete Aggregates (C 125) as “the non- upon. and can do so under water. The authors were C. then can also be produced using a pelletization process described in ground to a fine powder. ment and requirements of the ASTM standards. Portland blast-furnace slag cement was • decreased porosity and chloride penetration. L. or can be in the form of a portland-blast spread use of slag cement in the United States began in 1982. with the opening of the granulation and grinding facility at Beth- ment rates for various applications [2].” and E. . Cain. C. History Some of the reasons for using slag as a supplementary cementing material in concrete are [1]: The first recorded instance of slag being used as a cementitious • higher ultimate strengths with a tendency toward lower material was in 1774. ground granulated blast-furnace slag is a hydraulic ce- Introduction ment since it sets and hardens by chemical reaction with water. furnace slag blended cement. . of each previous edition. Slag Cement Association. MD steel plant. when it was combined with hydrated lime early strengths. mixer—was first developed in South Africa. cement use has been common in many areas of the world. and ground pelletized forms of the product. and used as a mortar by Loriot. For • lowered expansion from alkali-silica reaction. lehem Steel’s Sparrows Point. Wide- ing concrete batching. In the As a supplementary cementing material. The material when used with an appropriate activator to produce mortars or grouts will not be covered in this chapter. portland blast-furnace slag cements were first produced in the • equivalent durability in freezing and thawing. consisting essentially of silicates and alumi- editions. 512 . slag replaces a 1950s slag cement as a separate material—added at the concrete portion of portland cement in concrete at rates generally be. instance. Iron blast furnace slag is described by ASTM Terminology Re- mentitious material. Suite 300. slag-lime cements were used in the construction of the • lower temperature rise due to lower heat of hydration. The author acknowledges the authors of the previous metallic product. Prusinski1 Preface Definition IN PREPARING THIS CHAPTER ON SLAG AS A CE. utilized in the Empire State Building’s masonry mortar. H. introduce new technology that has [iron] blast-furnace slag is rapidly chilled as by immersion in been developed. This chapter will cover the develop. molten condition simultaneously with iron in a blast furnace. Canada. Popularity of the 1 Executive Director. ing process was introduced in Canada in the late 1970s. and ground to cement fineness.44 Slag as a Cementitious Material Jan R. Ground granulated (or pelletized) blast furnace slag is also its use as a blending material with portland cement. Tuthill. that is developed in the Mineral Admixtures. slag • improved resistance to sulfates and seawater. then gained popu- tween 20 % and 80 % by mass of cementitious material. where this subject was included in the chapter on nosilicates of calcium and other bases. Sugar Land. a brief history. Blended • better finish and lighter color. larity in many other countries. J. the “Production” section of this chapter. Separate cementitious slag produced with the pelletiz- placement can occur by adding slag as a separate material dur. commonly referred to as “slag cement” and this term will be fects of slag on the freshly mixed and hardened properties of used within this chapter to describe both the ground granulated concrete. Higginson. This re. water .” Like portland cement. including the United States and depending on application and desired properties. slag cement use 1996–2004 [4]. Cementitious Materials for Use Marine exposure 25–70 % Mass concrete (heat mitigation) 50–80 % in Concrete. Variations in material sources and environmental ASTM Committee E38. ASTM Alkali-silica reaction mitigation 25–70 % Standard Specification for Blended Hydraulic Cements (C 595) Sulfate resistance is specified (or the equivalent AASHTO M240). The American Association of State Highway and Concrete pavers 20–50 % Transportation Officials equivalent specification of the same High strength concrete 25–50 % name is AASHTO M302.5 million tons in 2004 w/cm 0. The task group based its either expressed or implied. These replacement rates are recommended for individual applications and are based on Committee E38 on Resource Recovery in 1982. Once it was developed. Interior flatwork 25–50 % Basement floors 25–50 % Specifications Footings 30–65 % Walls and columns 25–50 % Slag cement is available as a separate cementitious material Tilt-up panels 25–50 % Prestressed concrete 20–50 % and as a component of blended cements. If a blended cement is desired.S. from North America. as well as Lower permeability 25–65 % blended cement—is CSA A3001. Specification Development ASTM C 989 was originally developed under the jurisdiction of * Percentages indicate replacement for portland cement by mass. Type II Equivalence 25–50 % In Canada. including temperature and mixture components. jurisdiction for this Fig. Nothing had a minimum of long drawn out testing and at the same time contained herein shall be considered or construed as a warranty or guarantee. Use of slag cement expanded rapidly in the following Concrete Paving 25–50 % decades with the expansion of granulation and grinding plants Exterior flatwork not exposed to deicer salts 25–50 % in other U. Slag cement use has more than tripled in Exterior flatwork exposed to deicer salts with 25–50 % the United States since 1996 to about 3. You should consult your slag cement professional for assistance. including any warranty of fitness for a particular findings on (a) extensive tests of a wide range of ground slags purpose. included all reasonably effective slags. among other things. When used as a sep- Precast concrete 20–50 % arate product in concrete. Japan. trial batches should tions and instead develop performance-based criteria. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 513 product in the Mid-Atlantic area of the United States grew TABLE 1—Suggested Slag Cement Replace. quickly. Results may vary due to a variety of task group succeeded in getting realistic test requirements that circumstances. regions. coinciding with publication of ASTM Standard Specifi- ment Levels [2] cation for Ground Granulated Blast-Furnace Slag for Use in Con- Concrete Application Slag Cement* crete and Mortars (C 989) in 1982 and ACI 233-R in 2003 [3]. . England. the task group working on the specifi- conditions may require alternate substitution rates. 1) [4]. the applicable standard for all cementitious Type V Equivalence 50–65 % materials—including portland and slag cement. ASTM C 989 is the specification nor- Concrete blocks 20–50 % mally cited. By starting in historical performance.S. Consult your slag cement cation was able to avoid unnecessary prescription specifica- supplier for additional assistance. 1—U. That be performed to verify concrete properties. and (b) all available literature. and South Africa (the last two with extensive use records as admixtures).45 (Fig. As with all concrete mixtures. Because the test though it has never happened). but also can be less of Slag To Concrete Strength. as the “aggregate” to determine the effectiveness of pozzolans or slag cement in preventing alkali-silica reaction. The reference cement used be ground to its optimum fineness. Some feared that sul- Laboratory strength test procedures can be misleading in fides would produce sulphuric acid and corrode rebars (al- evaluating a slag’s performance in the field. and others felt that SO3 might involves curing at room temperatures and the average field affect the cement and provide the effect of an over-sulfated ce- temperature of concrete placed in the United States is higher ment. Most of the slag cement available in the Sulfide sulfur is limited to 2. Slag is harder to grind dance with ASTM Test Method for Compressive Strength of than portland cement. It was found that performance portland cement should be about 3800 cm2/g [7]. ASTM Committee C09 gave approval to ASTM Test Grade 80 75 % 70 % Method for Hydraulic Activity of Ground Slag by Reaction with Grade 100 95 % 90 % Alkali (C 1073). It should be noted that the current version of ASTM C 989. This accelerated method utilizes job materials (aggre- Index consecutive Any individual gates. recommends ASTM Test Method for Effective- In concrete. This nonmandatory proper credit for its contribution to better workability in a information is helpful in interpreting the specification and in concrete mixture. This method originally was designated ASTM E Grade 120 115 % 110 % 1085 because its preparation had been started when the originating task group was under Committee E38. placeability.6 and 0. Slag is more sensitive to temperature differ. Effectiveness of Slag in Preventing Excessive Expansion of Con- It should also be noted that slag is not usually given crete Due to Alkali-Aggregate Reaction. and X3. the slump test do not measure the contribution to workabil. because slag hydration is ac. but that number was quickly changed by ASTM to a C number so it could be . slag is penalized by the lower labora. of slag might vary significantly with other portland cements and that the standard cement provided the best differentiation be. Proportioning of mixtures (Table 2). Specific surface by air per- ASTM C 989 specifies three “grades” of slag cement: Grade 80.9 %. which is the opposite of what replacement. 28-Day Index Quality Control Test In 1985. An interground blend will result in the Hydraulic Cement Mortars (C 109)) that have 50 % slag cement cement being finer than the slag. They are X1. be approved without some limits on sulfur. to the strength of companion cubes made with the is desired. but also a fineness requirement of a maximum of 20 % re- Slag Activity Index and Grade tained on a 45 m (No. Slag grades are defined by the “slag set for that parameter. re- North America is either a grade 120 or 100 and can be used in ported as SO3. ity. each can reference 100 % portland cement. although there is no apparent evidence project cement. but has no limits placed. 325) sieve. or ease of consolidation that slag will make. but no limits are Grade 100. Contribution be greater than shown in laboratory tests. ASTM C 989 (Table 2) sets forth not only the slag activity index. meability is to be determined and reported. The smooth. Idorn concludes that the must have a minimum 28-day strength of 5000 psi and an alkali fineness of the slag should be about 5000 to 5500 cm2/g and content between 0. Also. that this would affect the slag reactions. if field temperatures are low. is the opportunity to grind the slag finer. This test method utilizes highly reactive pyrex glass this benefit [5. the strength of mortar cubes (tested at 7 and 28 days in accor. is limited to 4 % maximum in ASTM C 989 virtually all concrete applications.514 TESTS AND PROPERTIES OF CONCRETE standard was changed to ASTM Committee C09 on Concrete Fineness and Concrete Aggregates in November of 1982. ASTM approved a new test method. Sulfate Resistance. The SAI is the ratio of arately. this contribution results in less water required ness of Pozzolans or Ground Blast-Furnace Slag in Preventing and in better concrete overall. Although the ASTM C 109 procedure does evaluating the slag when any of the preceding factors are im- adjust for water requirement by equalizing flow. Appendix X3. ASTM C 989 tory temperature.5 % maximum and sulfate ion. as compared to intergrinding with cement at the mill. ASTM Test Method for Po- TABLE 2—Slag Activity Index (ASTM C 989) tential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar-Bar Method) (C Slag Activity Average of last five 1567). provides for the determination of chloride content of the slag ences than is portland cement. In 2004. Use of Appendicies in ASTM C 989 Slag’s strength contribution to concrete in the field will often ASTM C 989 has three appendices. The task group did not feel that the specification would than room temperature. Chemical Requirements tween grades of slag. One of the benefits of grinding slag sep- activity index” (SAI) as shown in Table 2. that test and portant to a user of concrete. This is to avoid any excess amounts of these prod- for field use should be based on applicable concrete tests with ucts in the concrete. X2. dense surface tex. and Grade 120. By grinding the two materials separately.6]. Excessive Expansion of Concrete Due to the Alkali-Silica Reac- ture and the particle shape of the ground slag account for tion (C 441). slag and portland cements) and is helpful in determining Minimum % samples sample specific dosages of slag cement required if the job materials are known. ASTM C 1567 may result in lower dosages of slag ce- 7-Day Index ment required to control expansion of a specific reactive aggregate than ASTM C 441 (which would only test a specific Grade 80 — — Grade 100 75 % 70 % slag/portland cement combination to control reactivity of a Grade 120 95 % 90 % pyrex glass aggregate). celerated to a greater extent by increases in curing temperature and it is retarded more at lower temperatures. . 3).” lowed to cool slowly in ambient air. tain slag: This material has a low glass content. and according to the American Concrete Institute ground into slag cement. glassy “granule” that can be finely practice.” which contains at least 70 % ground into slag cement. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 515 found in the construction volumes of the test methods. two of which can The test is helpful in guiding fineness level required and “in result in the material that becomes slag cement: evaluating the hydraulic activity of slags from different • Air-cooled slag is produced when the molten slag is al- sources. This iron is then subsequently clinker. (Note that Type S “slag cement” is quenched in a “granulator” with large quantities of water to rarely used and that the term “slag cement” in current produce a sand-like. Stockpiled granules are transported to a grinding period—to the bottom of the blast furnace. Standard Specification for Concrete Aggregates (C 33). The quate correlation with tests stipulated in Specification C 989. which con. These materials descend—over a 6 to 8 h ground. 5) are the similar to portland cement iron oxides into molten iron. “slag cement. Once the slag has passed through the granulator it is slur- ried to dewatering bins where most of the granulation water is Production removed (and recycled in plant operations) and the granules are transported to storage piles. which contains and cannot be used as a slag cement (Fig. The resulting powder is slag cement (Fig. at this point is principally a glass (noncrystalline). slag-modified portland cement. or as a concrete aggregate conforming to ASTM ASTM C 595 defines three types of blended cement that con. the fur. sified as hydraulic cements. 2—Iron blast furnace. This product is along with portland cement used as a lightweight aggregate or it can be finely ground • Type S. where preheated mill (such as a ball mill or a vertical mill) and ground to a fine air is blown in from the bottom. ASTM periodically from the bottom of the blast furnace. “This test method can be used as a quality-con. 6). if the glass content is high enough. molen material into a rotary drum which tosses the mate- tains less than 25 % ground granulated blast-furnace slag rial into the air resulting in rapid cooling. Most of the slag cement available [3]. iron and molten slag. the material to have cementitious properties. Fig. An iron blast furnace (Fig. 4). between 25 and 70 % ground granulated blast-furnace slag • Pelletized/expanded slag is cooled quickly through the use along with portland cement of water or steam. trol test for slag production from a single source after ade. • Type IS. and limestone. which allows nace is batch fed with three materials from the top: iron ore. once finely coke. The final products. as they both require grinding before they can be clas- used as a material in steel manufacturing. portland blast-furnace slag cement. are molten C 1073 states. The molten iron is sent to the steel production facility. The morphology of a slag granule When iron is manufactured in a blast furnace. is not cementitious. slag” as specified by ASTM C 989). 2) chemically reduces and converts Slag granules (Fig. granulated blast-furnace slag along with portland cement • Granulated slag is made when the molten material is rapidly and/or hydrated lime. generally refers to “ground granulated blast furnace in the United States is produced using a granulator (Fig.” molten slag can be processed in three ways. Pelletization of slag involves feeding the • Type I(SM). tapped powder. It can be processed by screening and crushing for use as a construction aggre- Blended Cement gate. Cooling in ambient air will produce air-cooled. Fig. Composition and Quality Typical chemical and physical properties of slag cements available in North America are shown in Table 3 [3]. 4—Molten slag entering a granulator. Fig. and is highly consistent in composition and properties because of the quality control and assurance procedures of the blast-furnace and granulation/grinding Fig.516 TESTS AND PROPERTIES OF CONCRETE Fig. the slag granules become slag cement. These properties are determined by the raw feeds into the blast-furnace. and the grinding operations. noncementitious slag. 6—After grinding. Although slag cement is a by-product of iron production. slag with a high glass content (generally greater than 90 %) will have cementitious properties. it is a manufactured material. 3—Molten slag being drained into a pit (inset). . which will rapidly quench the slag and solidify it in a glassy state. 5—Slag granules in a stockpile (background) waiting to be finely ground into slag cement. After screening and crushing this slag can be used as a construction aggregate. When finely ground. the granulation (or pelletization) process. the amount of water to silicate hydrate (C-S-H). ties will each have their own quality procedures. in blended cements). including the alkali concentration. The result of a portland/slag pays careful attention to the slag chemistry (both composition cement system is generally a concrete with significantly de- and variability) as slag behavior is a major consideration in creased permeability. ensuring the quality of hot metal (molten iron). Workability. slag ce. The granulation tors. ent. The principal hydration product from the slag. for a specific concrete mixture [10]. With a slag/portland system. Slag can also be activated by • Color alkali hydroxides alone (alkali-activated concrete) or with hy- • Loss on ignition drated lime (as in some Type S blended cements). since they often dictate the pace and manpower require- process in the slag processing procedure is fundamental. Concrete containing slag ce- formation of a crystalline structure.1–1. fineness slag chemistry. increased slump) under water. slag cement is a hydraulic cement. and decreased Fineness (Blaine) 4000–6500 cm2/kg Specific Gravity 2.94 concrete durability. will depend significantly on glass content. and slag cement glass content and chemical composition. but are important parameters for concrete contrac- to a concrete mixture or its hydraulicity. but the hydration will amount of water is increased). Calcium hydroxide is a S 0. Workability and finishability are difficult to quantitatively lated slag is a primary factor in determining its contribution measure. and Consolidation The use of slag cement has several effects on the plastic prop- Effect on Hydraulic Activity erties of concrete.85–2. 7. by mass. One method for determining TABLE 3—Typical Composition of U. The reactivity of slag slag and portland cements. As previously mentioned. both the portland and Al2O3 7–16 % slag components produce C-S-H when combined with water. Therefore. calcium. stronger paste-aggregate interface.9]. Both the higher strength. Finishability. slag cement manufacturing facili. but some of The hydration of slag cement is significantly activated by the variables that may be monitored include: alkali hydroxides. decreased aggregate/paste bond. the relative amount of C-S-H is increased and calcium hydroxide is decreased. • Basisity when cured at higher temperature situations (such as heat Ultimately.2 % highly soluble mineral. slump retention. portland/slag cementitious systems meet the performance requirements of ASTM C 989 (if a sepa. Heat in- • Chloride content creases the solubility of alkali hydroxides. reduction with slag cement can vary from 0 to 5 %. Generally. or the applicable sections of ASTM C 595 (for use land-only systems [8. since it chemically hardens by reaction with water and does so Reduced water demand (or alternatively. ments to perform a finishing task. It is generally recognized that glass content of the granu.7–2. improve consolidation. ground granulated blast furnace slag must curing in a precast plant). the amount of water continue for a longer period of time. This is attributed by several researchers . hydrated portland cement also produces about 15 to MgO 5–15 % 25 % calcium hydroxide. curing temperature. investigators have not developed clear-cut Chemical Oxides (except sulphur) Typical Range (% by wt) relationships between glass content and the strength contribution of slag. and greater durability.S. Consequently this quick ment is often cited as having superior workability and finisha- cooling is necessary so that the slag will be composed largely bility properties. This is due to both a dilution of lime-containing portland cement compounds and the reaction of the calcium hydroxide portland cement product with the glass phase of the operations. CaO 32–45 % However. Slag glass content is by microscopic count. As a result of these statistically based specifications and the well-controlled production process. During blast furnace operations. As important as glass Cements [3] content is in slag. is shown in Fig. slag cement proportions and To ensure product quality. the to grinding) are closely monitored to ensure high levels of reactivity of portland/slag cement binders can be very differ- consistency and performance. the addition of even relatively • Glass content small amounts of portland cement can substantially acceler- • Chemical composition ate the reaction of slag cement. tems in concrete (or mortar) depends on the interaction of the lationship among numerous variables. and can increase pumpability.0 % florescence.5 % strength and its presence contributes to increased porosity. percentage of slag cement is increased. it does not contribute to concrete Fe2O3 0. By itself. particle size. slag granules (before grinding) and slag cement (subsequent While the reactivity of slag cement alone is very slow. Effect on Properties of Freshly Mixed Concrete ment is found to be one of the most consistent materials used in concrete. ef- MnO 0. It can reduce water demand. can achieve similar—or even superior—early strengths as port- rate material).2–1. however. The reactivity of portland/slag cement cementitious sys- Slag reactivity and performance depends on the inter-re. Therefore. many other factors are also involved. calcium hydroxides (among other activa- • Particle size and/or Blaine fineness tors). and also impact the quality Rapid chilling or quenching of the molten slag inhibits the of the finished concrete surface. the plant operator slag cement (to form more C-S-H). SiO2 32–42 % In a portland/slag cement system. increase workability/finishability. as well as promotes • Titanium content increased reactivity of the portland/slag binder. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 517 of glass or amorphous material. As the water reaction is the same as with portland cement. and heat. of the portland and slag cements. slag cement will hydrate at achieve a given slump is reduced (or the slump for a given a slower pace than portland cement. and produce finishes with fewer “bugholes” in formed surfaces. and whether or not the unit volume of water is the same. Time of Set Slag cement at levels above 25 % of cementitious material by mass will generally increase the time of set of concrete at 70°F. In higher temperatures. particularly with regard to finishing. as concrete finished too soon or too late (with respect to bleed water formation) may result in poor surface durability and plastic shrinkage cracking. reduce vibration requirements. chloride or non-chloride accelerating ad- characteristics.518 TESTS AND PROPERTIES OF CONCRETE These improvements may reduce the time of placement of concrete. Bleeding may be reduced when slag fineness is higher or unit water content is lower. allow increased speeds for slip-form pavers. particularly in congested reinforced members. including: mixtures. improve surface finish of flatwork. Figure 8 cement concrete and the same concrete with 50 % slag illustrates. and the quantity of portland cement in a mixture • Low water absorption after mixing significantly affect time of set. Fig. improve consolidation of concrete. and use of heated materials are effective in reduc- • Increased paste cohesiveness and volume ing time of set. time of set will increase significantly. dense surface of slag cement particles properties.11] to improved rheological properties and particle lower temperatures. however. range of slag cement percentages and temperatures [12]. a reduction in slag percentage • Better particle dispersion or an increase in portland cement content will also be a po- • Higher fluidity of paste tential strategy for maintaining appropriate times of set at • Reduced vibration to achieve consolidation low temperatures. at [5. for a specific concrete mixture. . in cooler Fig.6. This difference will reduce substantially and may become insignificant as the temperature increases to above 85°F. 7—Slump versus water content for a plain portland temperatures. Also. The main difference will be whether the slag is more coarsely or finely ground when compared with the portland cement it is replacing. the times of set for a cement replacement [10].10. 8—Time of set characteristics for a typical concrete at various temperatures and slag cement replacement percentages [12]. a longer time of set may be an advantage as it will provide more working time. Bleeding capacity and rate are important. because the portland cement setting • Smooth. Bleeding Bleeding capacity and bleeding rate of concrete with and without slag cement are similar. and combating alkali-silica reaction. As noted As with all concrete.13]. and curing pects of concrete durability. igating sulfate attack. as duced and the interconnectivity of pores becomes more tortu- well as an improved paste-aggregate bond. Curing is necessary to cast concrete production operations. such the point that adequate release strength can be achieved in less as fogging. through 70 % mixture. The initially slower ous. rate of evaporation. Strength Permeability is decreased principally by the higher volume Slag cement will generally have a positive effect on the ulti. Duration of curing is dictated by many factors including tem. or greater. from one day to one year [9]. Figure 9 illustrates the compressive strength of mortar perature. mit- duration is not extended. and curing com. the w/cm ratio and the curing conditions. as practiced in some pre- to achieve desired concrete properties. the application of heat. ponding. Concrete made with slag cement typi. 9—(a) Mortar cube strength at various slag cement replacement levels. will result in significant reductions in permeability [14–17]. of calcium-silicate hydrate generated in a slag/portland cement mate strength (both compressive and flexural) of concrete. such as corrosion resistance. permeability reductions are positively strength than an equivalent plain portland cement concrete correlated with the percent of slag replacement. wet burlap. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 519 Curing Requirements cement. ment levels and ages. However. fected by the presence of slag cement in the concrete. the characteristics of the portland measured by ASTM Standard Test Method for Electrical Indi- Fig. ages may gain sufficient strength and maturity in the time that Reducing permeability is a key factor in improving many as- plain portland cement concrete is normally cured. Figure 10 shows an example of the reduction in elec- Early strengths can be significantly affected by several factors trical conductivity due to increased slag cement contents—as including the temperature. between 7 and 14 days when cured at 70° or higher. proper curing practices must be followed previously. Overall pore size is rehydrate that is generated in a portland/slag cement system. system. . Typical curing practices. where slag cement percentage may be up to 80 %) It is well documented that the use of slag cement in concrete may necessitate longer curing times. than 24 h without an increase in total cementitious materials pound are compatible with concrete containing slag cement. (b) concrete compressive strength at various slag cement replacement levels. will tend to significantly ensure that the concrete will have sufficient moisture available increase the rate of strength gain of slag cement concrete to to develop required properties. water/cementitious ratio. normally cause lower initial strength gain compared to a plain The reduction in permeability beyond 28 days is much more sig- portland cement system. Higher percentages of slag cement (particularly in mass concrete Permeability placements. lower percent. from 3 to 28 days [9]. content [8. polyethylene. As permeability is reduced the transport of deleterious sub- Effect on Properties of Hardened Concrete stances within the concrete and propagation of deterioration mechanisms are commensurately reduced. The microstructure is changed as pores are partly filled This is due principally to the higher volume of calcium-silicate with C-S-H in lieu of calcium hydroxide. and cubes and concrete mixtures at various slag cement replace- rate of strength gain. Duration of curing may or may not be af. Permeability reductions begin generally within the first 28 hydration characteristics of a portland/slag cement system will days of placement. and continue as long as hydration continues. nificant in slag cement concrete than in plain portland cement cally available in North America will generally produce higher concrete. Additionally. 19. by limiting the transport of chlo. while with the Sudsbury greywacke. portland cement alkali content.16–21].23.22–24]. 1293) can be used. 10—Permeability of concrete based on the rapid chloride permeability test (ASTM C 1202) [adapted from Ref 14]. is required. Reduced permeability plays eral factors will influence the rate and severity of ASR. Additionally. Another study con. making them unavailable land cement and with calcium hydroxide to form expansive for reaction. combination with a high-alkali portland cement. Slag cement and higher resistivity of the concrete.520 TESTS AND PROPERTIES OF CONCRETE Fig. 25 % sion potential of a reactive aggregate. The researcher Figure 11 is one example of how slag cement can reduce suggested that the lower corrosion is due to both continued ASR. whether specific combinations of portland and slag cements centration of chloride ions do reach the reinforcing steel and and aggregates will exhibit expansive reactions. it is important to on the corrosion resistance of reinforced concrete. but this test takes one year to run. cluding aggregate reactivity. the rate of corrosion is slowed in concrete 1567 is inconclusive or if greater assurance of nonreactivity containing slag cement [20].45 [14]. and aggre- the steel. The use of forcement passivity. often 40 % to as much as 70 % slag cement binding capacity of slag cement concrete. Sev- by many researchers [5. Cementitious materials content is 635 lb/cu yd. The research showed that increas. ASTM Standard Test Method for Determination ing slag contents (between 25 and 50 %) resulted in increased of Length Change of Concrete Due to Alkali-Silica Reaction (C concrete electrical resistivity and lower chloride diffusion rates. as little as 25 % slag cement is also reduced [21]. cation of Concrete’s Ability to Resist Chloride Ion Penetration • It reduces permeability. would be required. may be needed to reduce potential expansion to the desired cluded that the corrosion rate in cracked concrete containing level [3. To mitigate ASR in the Spratt Mitigation of Alkali-Silica Reaction limestone. hydration products of the tri-calcium aluminate phase of port- • It consumes alkalis in hydration. therefore slowing the mobility of (C 1202)—at a range of w/cm from 0. merous researchers [9. as documented by nu. rides to the reinforcing steel thus maintaining the passivity of presence of water in the concrete. • It reduces the hydroxyl concentration of pore liquid that Corrosion Resistance reacts with an aggregate.25]. appropriate expansion reduction can be achieved. Therefore testing is recommended to ensure that land/slag system has been shown to not affect steel rein. the alkali. The use of slag cement in concrete has a positive influence When using slag cement to reduce ASR. ettringite—can be controlled with appropriate amounts of slag . wet/dry cycles. Al- The reduced diffusion rates are attributed to both reduced per. “Low” permeability is generally defined as less than 2000 coulombs. would be required [23]. The concrete was made with two reactive aggregates in long-term hydration inducing autogenous healing of cracks. as noted use an appropriate level of slag cement in the mixture. the slight reduction of pH in a port. Slag cement mitigates ASR in several ways: Mitigation of Sulfate Attack • It reduces the total alkalis in the system thus reducing the External sulfate attack—where waterborne sulfates react with alkali-silica ratio. levels varied from 0 to 50 % and were measured using the concrete prism test ASTM C 1293.9. If ASTM C corrosion is initiated.35–0. gate size. ASTM C 1567 can serve to quickly determine (within 16 days) Some research has indicated that even when a critical con. though ASR reduction can be accomplished with as little as meability from pore structure refinement and greater chloride 25 % slag cement. a slag cement level of 35 % of cementitious material Slag cement can significantly reduce or eliminate the expan. in- the largest role in this effect. Slag cement helps reduce Figure 12 shows the effect of slag cement replacement on heat by: sulfate resistance for a slag cement combined with Type I port. six months to achieve moderate and high levels of sulfate Typically. tested for two years at various levels of slag cement substitution. levels of portland with slag cement to achieve an appropriate reduced portland cement content). using ASTM Standard The hydration characteristics of slag cement.5 % slag cement substitution was effective in eliminating through dilution. ance was achieved at 35 % replacement [26]. of 0. tween the internal concrete and external surface. and up to 65 % for high sulfate resistance.. 11—Mortar bars. when the minimum thickness of a concrete element resistance. posed that at least 35 % slag cement should be used to miti- Very high levels of resistance can be achieved with a combina. measures to ment combination if the alumina content of the slag cement reduce heat are required. Slag cement can reduce sulfate attack curing temperatures.40 % as a guide (ASTM C 1293 Appendix X1). discussed previously in . required to achieve required strength. Reduction of Heat in Mass Concrete ASTM C 989 proposes expansion limits. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 521 Fig. been found to be highly effective.05 % at heat and mitigation of cracking in mass concrete placements. thus reducing trans. while the Sudbury aggregate is mitigated at 25 %. as • Reducing the rate of early heat generation due to slag much as 50 % slag cement may be needed for moderate sulfate cement hydration characteristics. mation (DEF. the use of slag cement has level of sulfate resistance. higher temperatures. For this concrete. resistance. ment hydration will result in a high maximum temperature in ity to mitigate sulfate attack. research has found that the use of slag • Reduction in calcium hydroxide. In many cases. a “high” level of sulfate resist. cement in concrete. is large enough to cause concern that the heat generated by ce- The alumina content of slag cement can influence its abil. occurs when concrete is subject to high (160°F) tential for delayed ettringite formation. This is one reason that curing tempera- through three mechanisms: tures are limited in precast operations and controlled in mass • Reduction in concrete permeability. • Reducing the amount of total cementitious material A different type of sulfate attack. which is a contributor in cement may be effective in controlling DEF expansion at the reaction. Another researcher pro- cement to provide moderate or high levels of sulfate resistance. pletely understood. slag used. respectively. it is particularly impor. with two different reactive aggregates [adapted from Ref 23]. concrete. expansion of the Spratt aggregate is mitigated using 35 % slag cement. used in concrete to determine the appropriate amount of slag cement needed to achieve the required level of protection. cooling pipes. as well as its in- Test Method for Length Change of Hydraulic-Cement Mortars creased strength potential. • Reducing portland cement content by the percentage of land cement. This situation may require higher replacement taken to control heat (e. portland cements or 150°F for portland cements with rapid It is important to test the specific materials that will be early strength development) [28]. Among other measures that can be exceeds 11 %. delayed ettringite for.g. enable it to facilitate the control of Exposed to a Sulfate Solution (C 1012). concrete pours. Using 1-year expansion limits of 0. gate DEF in higher-temperature curing (160°F for most tion of Type V and slag cements. with no strength Slag cement can be used in conjunction with a Type I or II penalty even in early strength [27]. therefore.10 and 0. One researcher found that as little as • Reduction in the total amount of tri-calcium aluminate 17. or sometimes referred to as “internal sulfate Another benefit of using slag cement is the reduced po- attack”). tested in accordance with ASTM C 1293. as well as a significant differential temperature be- tant to evaluate the sulfate resistance of the portland/slag ce. Although the mechanism of DEF is not com- port of sulfates into the concrete. insulation blankets. DEF expansion in temperatures up to 195°F. 522 TESTS AND PROPERTIES OF CONCRETE Fig. One of the reasons for limiting tems. 13—Specific heat of hydration of plain portland cement and substitution with slag cement up to 75 % [29]. using 75 % under the curve. ASTM C 989 proposes that mortar bars that expand less than 0. In adiabatic testing. the increase in tem. Figure tion from 0 to 75 % substitution when tested in a semi-adiabatic 14 shows. mentitious material (by mass) is usually recommended. is reduced by slag cement and 564 lb/cy (334 kg/cm) total cementitious mate- an even greater amount. and 0. concrete elements. Peak temperature was limited to 130°F and differential did perature accelerates the hydration of portland/slag cement sys.05 % at 6 months achieve equivalence to a Type V high sulfate resistant cement. but the area center and surface of a 10-ft thick concrete footing. . the section on sulfate attack. not exceed 28°F.10 % at 6 months achieve equivalence to a Type II moderate sulfate resistant cement. These levels are achieved by 15 and 35 % slag cement. 12—Testing in accordance with ASTM C 1012 shows the sulfate expansion of a mortar bar made with Type I (non-sulfate resistant) cement and various levels of slag cement substitution. a slag cement content from 65 to 80 % of ce- Figure 13 shows the effect of slag cement on heat of hydra. therefore. Fig. representing total heat generated. hontas Parkway Bridge in Virginia. respectively [26]. rials. well within specification limits [30]. to achieve appropriate heat reduction in mass peak temperature in mass concrete is DEF potential. the temperature rise in the duced by nearly 50 % at the 75 % substitution level. for the 10-ft thick massive footings on the I-895 Poca- condition. Not only is the peak specific heat of hydration re. 14—Temperature of concrete at the center a surface of 10-ft thick footing for I-895 Pocahontas Parkway Bridge in Virginia [30]. 15). The average increase in shrinkage was dividual studies have found shrinkage to be less. Shrinkage restrained conditions. or the 2. the mixture. when varied from 20 to 80 %. the amount of slag cement in from 62 comparable concrete mixtures.9 %. 15—Relative shrinkage (see note above) of slag cement concrete at various slag substitution levels [31]. had no discernable Fig. the drying shrinkage of concrete con- Shrinkage in slag cement concrete is generally not significantly taining slag cement was only marginally higher than concrete different than shrinkage in plain portland cement concrete. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 523 Fig. Over 62 mixtures. In. A compre.5 % (Fig. which examined 32 references and analyzed data reduced to 1. the increase of shrinkage of slag versus non-slag concrete was very small (2.9 %). Also. . and when corrected for paste volume (due to slag ce- same when comparing slag and non-slag concretes. concluded that in un. respectively). without slag cement [31]. and no correlation was found between shrinkage and slag substitution level. A 75 % slag cement concrete mixture with 564 lb/cy of cementitious material was able to not exceed maximum specification requirements for peak and differential temperatures (specification values of 165°F and 35°F. ment’s lower specific gravity than portland). the difference was hensive study. more. [5. and repeated cycles of freez- ide—a principal contributor to efflorescence staining as it ing and thawing.524 TESTS AND PROPERTIES OF CONCRETE effect on the level of shrinkage. cement substitution levels increase. such as environ. especially at higher replacement levels [39–41]. Slag cement may help lessen the propensity of concrete or Additionally. field concrete made with slag (or fly ash) [42–44]. Any concrete exposed to deicing salts in freezing and thawing environments is potentially susceptible to scaling.9. adequate strength must be developed in any con- mortar to effloresce. increased percentages of slag cement will increase the sistent particle size. Other laboratory and field studies have shown similar or even improved scaling resistance with slag cement concrete. materials. white portland Durability in Freezing and Thawing cement. The light color of slag cement generally will lar study of restrained shrinkage cracking of slag cement con.37. assuming that w/cm is 0. . if concrete containing the material to temporarily turn a dark early freezing is expected. or the Rock ‘n Roll Hall of Fame in Cleveland. as noted above. These re- ume) is critical in limiting shrinkage. silica fume. Slag cement concrete.S. as well as lowered permea- are more sensitive to temperature—and because these gains gen- bility—helps achieve this reduction. formance of concretes made with supplementary cementing • Where applicable. aggregate vol. curing practices. and material have not experienced problems with scaling. Fly ash produces lighter colored concrete as slag set and differences in bleed water rates and amounts. variable than with concrete containing only portland cement. Some researchers feel that ASTM C 672 is a particularly cant effects on shrinkage. One particu. Most studies of concrete produced with slag cement under freez- The Delaware Department of Transportation eliminated the re- ing and thawing conditions show that the concrete is durable quirement for painting Jersey median barriers when slag ce- and compares similarly to ordinary portland cement concrete ment was used. some cases (such as the Canadian Embassy in Washington. aggregate. many laboratory studies using ASTM Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (C 672) (or similar tests) have indicated that concrete made with slag cement is less resistant to deicer salt scaling. fume (Fig. Fig. and porting practices must take into account potentially longer times of land cement. and concrete compressive strength is at least 4500 psi. Fig.33]. darker colors may require more pigment. in resulted in smaller crack widths [33]. clockwise: slag cement. The decreased level of calcium hydrox- crete prior to the first frost cycle. several Northern U. Other factors. so entrainment of air is generally no more lightness of the concrete. because of their increased visibility. w/cm of paste) had the most signifi. surface-to-volume Transportation (that specify and utilize slag cement in concrete) ratio of the concrete member. has not been undertaken. freezing and thawing resistance In colored concrete. When good concreting design and placement practices are used. In highways and parking facilities. In exposed architectural crete indicated that cracking was delayed to later ages. Building Code Requirements for Structural Concrete. Color A comprehensive study of creep in slag cement mixtures Slag cement is a light-colored material when finely ground. paste content. 16). nor has the the On- factors other than slag cement (volume and elastic modulus of tario Ministry of Transportation [39]. 16—Cementitious materials from top. or in conjunction with. may require longer cur. humidity). mixtures containing slag searchers suggest that a different testing standard. 17. fly ash. DC. the light color im- Environments proves night visibility and may reduce lighting requirements. Class C fly ash.45 or less. BNQ NQ cement can reduce shrinkage by: 2621-900—the laboratory scaling resistance test procedure • Adjusting paste volume of the mixture to take into account adopted by the Quebec Ministry of Transportation—may provide the lower specific gravity (and higher relative volume) of significantly improved correlation between lab and field per- the slag versus portland cement. and concrete this is generally considered a positive attribute and. going ing times. In any spacing. State Departments of mental conditions (temperature. especially if placement temperatures are low. Fig. or silica indicated that long-term creep may be less [32. ACI 318. In a re. conversely.38]. As with all concrete. Proper finishing and appropriate curing techniques are particularly important for concrete of any type that will be exposed to deicer salts and freezing/thawing conditions. give concrete a lighter appearance. the use of slag may reduce the is closely related to development of an appropriate air void amount of pigment or coloring agent required for certain col- system with adequate air content and proper bubble size and ors. 18). However. harsh test that does not correlate well with the performance of As minimizing paste content (or. to protect the concrete appropriately). Because slag cement concrete strength gains leaches out of concrete or mortar. thus reducing total paste volume. compared to non-slag concrete [9. slag cement concrete—with up to 50 % replacement for portland cement—has provided good scaling durability in the field. ment may allow a decrease in total cementitious material.34. however. Finish.34–38]. the higher ultimate strength of slag ce. cent survey [41]. allows up to 50 % slag cement replacement when concrete is exposed to deicing chemicals. but several individual studies have generally much lighter than portland cement. erally develop more slowly at early ages—it is important to en- Another aspect of slag cement is the tendency of hardened sure that adequate strength is achieved prior to freezing (or. Slag cement contains no carbon and has relatively con- case. has been used in lieu of. may exhibit greening for longer periods of nomenon is due to a reaction of sulfide sulfur in slag cement time. 18—Rock ‘n Roll Hall of Fame in Cleveland used slag cement concrete in the exposed concrete pier foundation (inset) in lieu of white portland cement to closely match the white color of the tile exterior. Often. and will after several weeks and developed the typical light color of slag normally disappear with a few days’ exposure to air and light cement concrete (Fig. and porosity of the con. the amount of after form removal. The propensity to. Typically called “greening. Additionally. but disappeared crete surface. curing conditions. DC shortly ward greening depends on the rate of oxidation.” this phe. eral months. or has undergone high levels and long periods slag and is being demolished may show internal evidence of Fig. green or green-blue color. of moist curing. Concrete where formwork remained for ex. DC used slag cement in architectural concrete to achieve a very light color. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 525 Fig. 17) [45]. 17—Canadian embassy in Washington. concrete test cylinders (this propagates an oxidation reaction that eliminates the that appear very light on the outside will exhibit greening on greening effect). Figure 19 illustrates greening in exposed architectural with various portland cement compounds. old concrete that contains tended periods. Visible greening is a harmless condition. . concrete at the Canadian Embassy in Washington. Because form stripping was delayed sev- slag in the concrete. the inside once broken. greening was initially extensive. as slag is a con. An early compatibility of portland cement with aggregates. durability. ful in improving mixture workability and reducing stickiness due to the fine particle size of the silica fume. or both. and 9 % silica fume and which achieved 15 000 psi field interface thus producing a stronger bond and a less permeable strength in 56 days. 19—Greening is evident after forms were removed from the Canadian Embassy in Washington. Greening disappeared after several weeks resulting in the desired light concrete appearance of slag cement concrete (see Fig. greening. and is gaining increasing acceptance by performance concrete. which utilized 1050 lb/yd3 of reduces the potential for expansion. as previously discussed. slag Other Supplementary Cementitious Materials cement can replace an additional percentage of the portland Slag cement is compatible with all supplementary cementi. performance concrete with 30 % slag cement and 20 % fly ash crete to achieve high levels of strength or low permeability. 65 % portland cement. The specifiers. once the concrete is cracked and opened. The only both. and. permeability reduction. Fly ash substitu- ment it replaces. including pavements with 35 cementitious materials in a concrete mixture is referred to as % slag and 10 % fly ash. that when both early and long-term strength or permeability reductions. and/or to reduce embodied energy and heat of hy- land cement. Additionally. In and improve finishability. if the slag cement is finer than the portland ce. The use of slag cement in combination with silica fume time greening might be a concern is in those situations where has the benefits of improving the workability of the port- appearance is important and when concrete is not allowed to land/silica fume system to decrease stickiness of the mixture be exposed to air and/or light (such as a swimming pool). if higher levels of supplementary sistent material that contains no carbon. In locations where slag cement replaces a portion of the portland cement. slag cement tends to improve the paste-aggregate ment. and known limitations. research has shown these cases. Using three mixtures in most of its concrete. the use . and is compatible in the same way as port. The Iowa Department of Transportation uses ternary tious materials. once the rate has been established. when dration associated with concrete mixtures. cement. and admixture use. Chemical Admixtures Both Class C and Class F fly ashes have been used suc- When used with chemical admixtures.526 TESTS AND PROPERTIES OF CONCRETE Fig. 20 % slag and 15 % fly ash. DC. air entraining admixture addition may in. small fly ash is typically used in much of the concrete produced. As with any change to a concrete mixture. the use of slag cement is not recommended. or to achieve high-strength (13 000 psi) [48]. ash is unusual and can necessitate special testing requirements highly consistent air contents are achievable. economy. cementitious material. When high-strength concrete application for high-rise construction aggregates are susceptible to alkali-silica reaction. 17). cement can be included to increase the total level of supple- For instance. and beyond 14 days and throughout the life of the Slag cement compatibility with aggregates is no less than the structure (principally through the slag cement) [46]. mentary cementitious materials in a mixture. 27 % slag ce- Additionally. are important. slag cement was the Key Tower in Cleveland. a portland/slag/silica fume Compatibility with Other Materials system can achieve superior results by enhancing strength and permeability reductions at early ages (principally through the Aggregates silica fume). Additionally. such as fly ash and silica fume [47]. The use of slag cement was especially help- interface [46]. slag adjustments may need to be made to admixture addition rates. in high- a ternary mixture. or lower embodied energy and emissions. tion beyond 20 % for a Class F fly ash or 30 % for a Class C fly crease slightly. slag cement has no cessfully with slag cement to improve strength. However. However. 35 % slag and 15 % fly ash [41]. construction of Houston’s Reliant Stadium utilized a high- Silica fume is sometimes used in high-performance con. materials are desired to achieve enhanced strength. achieved field strengths of 17 000 psi at 28 days (Fig. Material.5% 33.9 % 28. • Use of a recycled material The high level of portland cement replacement that is • Reduced landfill requirements commonly achievable with slag cement enables dramatic re- • Reduced virgin material use ductions in embodied energy.2% 44. and carbon dioxide values include all operations and transportation required to produce the concrete raw materials. emissions. Additionally.2 % 23.8% 9. as well as concrete plant operations. and Virgin Material Use in Concrete Using Slag Cement [49] 3000 psi Ready Mixed 5000 psi Ready Mixed 7500 psi Precast Concrete Concrete Concrete Concrete Block Item 35 % Slag 50 % Slag 35 % Slag 50 % Slag 35 % Slag 50 % Slag 35 % Slag 50 % Slag Virgin Material 4.3 % 6. Table 4 shows the percent reductions achiev- • Reduced greenhouse gas emissions able when 35 and 50 % slag cement are used as a substitute in TABLE 4—Reductions in Embodied Energy.5 % 19.1 % 29. energy. The 900 lb/cy mixture typically in energy required to produce slag cement [49]. In concrete this is highly significant because.7 % 36.1 % 30.0 % * Reduction percentages are based on substituting 35 or 50 % slag cement with portland cement in a typical concrete mixture for the specified concrete type.8 % 6.2 % 42.9 % 31. and virgin material • Reduced energy use in concrete.6 % Carbon Dioxide Emissions 30. PRUSINSKI ON SLAG AS A CEMENTITIOUS MATERIAL 527 Fig. is a to 25 % of the ingredients by weight in concrete. home of the NFL Texans. 20).8 % 10. Using slag emissions contributed from all the ingredients. Carbon Dioxide Emissions.3 % Energy 21. .7 % 25. 20—Reliant Stadium in Houston. Values for all materials are based on average values calculated in the referenced studies. even though portland cement comprises only about 10 Slag cement. The concrete met the requirements of high strength (13 000 psi). when compared to portland cement. utilized a high-performance ternary mixture of portland and slag cements and Class C fly ash in the four massive “super columns” that support the retractable roof (inset). low heat (massive placement). being a by-product of an iron blast furnace. and virtually self-consolidating consistency.1 % 42. as well as trans- cement in concrete has several environmental benefits: portation and concrete plant operations. of slag cement provided low-heat of hydration and virtually A study comparing the energy to produce a ton of portland self-consolidating concrete for the four “super columns” that cement versus a ton of slag cement showed an 86 % reduction support the retractable roof.3 % 14.7 % 32.6 % 4.8 % 6. the production of slag cement provides a 93 % reduction in virgin materials used (including water) and a 98 % reduction in Environmental Benefits carbon dioxide emissions. it is responsi- recovered industrial material that has low embodied energy ble for about 90 % of the embodied energy and carbon dioxide and emissions.3 % 46. but contractors may experience some differences. Conclusions [5] Fulton. changed. TX. 167. States began in the early 1980s. 64–65. lowering block). and smoothness provide benefits in the workability of freshly mixed concrete. compared with ordinary portland cement concrete. the particle shape. May 1982. but may require some adjustments to finishing and curing practices. pp. to 37 %. SCIC No. 1974. These benefits result primarily from the increased C-S-H and decreased calcium hydroxide in slag cement concrete. Discussion of “Admixtures for Concrete” (ACI the advent of green building certification systems such as the 212. U. Silver Spring. American State tax incentive for sustainable construction practices [50]. Vol. University of Alabama. Birming- 19th century). Sugar Land. April 1983. [4] 2004 U. S. Also. “Twenty Years of Experience with Slag Cement. lena (Fig. “The Properties of Portland Cement Containing Milled Granulated Blast-Furnace Slag. Concrete International: Design & Construction. and concrete tainability of concrete by reducing raw material use. W. energy by up emissions. References ied energy and emissions is becoming more mainstream with [1] Lewis. Slag Cement Association. is resistant to deicer salt scaling (up to a level of 50 % replacement). and materials with lower embod. K. 21) in Manhattan utilized slag cement at a 45 % level [2] Concrete Proportioning.. November 2005.. 4–46.S. Concrete Institute. Green Building Council’s LEED™ rating system. [7] Idorn. slag cement contributes to the environmental sus- mixed concrete. and decreasing energy. The He. pp. Slag Cement Statistics. TX. should remain relatively consistent) • Differences in bleed water capacity and rate These differences are normally minor.1R-81).” Monograph. structure to help gain LEED certification. F. as well as a New York [3] Slag Cement in Concrete and Mortar (ACI 233-R). MD. 7500 psi precast concrete.528 TESTS AND PROPERTIES OF CONCRETE Slag cement substitutes for 20 to 80 % of the portland cement in concrete and provides a wide range of benefits. surface density. Johannesburg. especially at lower placement tem- Fig. or even mixture design. tion. G. [6] Wood. Publication No.” Worldwide. Farmington Hills. Some of the benefits are: • Freshley mixed concrete— • Reduced water demand • Improved workability and consolidation • Longer working times in warm weather • Hardened concrete— • Higher ultimate strength • Lower permeability • Greater protection for steel reinforcing against corrosion • Mitigation of alkali-silica reaction • Mitigation of sulfate attack and delayed ettringite formation • Reduction of heat in mass concrete • Lighter color • Compatibility with other concrete-making materials Besides these benefits. to help • Lower strength before about 7–10 days (unless curing gain green building certification and a New York State tax temperatures are elevated) incentive for green building construction. in the structural concrete in this 45-story high-rise residential Sugar Land. Placing. 5. 27. Virgin material is reduced by up to 15 %. and curing slag cement concrete is similar to plain portland cement concrete. and exhibits approximately equivalent shrinkage characteristics to ordinary portland cement concrete. . material in most parts of the United States and Canada. 2002.. even though much of the construction occurred during the winter. Slag Cement Association. 1981. and carbon dioxide emissions by up to 46 %. MI. including: • Increased time of set. Portland Slag cement is a widely available supplementary cementing Cement Institute. org. D. Using recycled materials. The Effect of Slag Cement in Concrete. M. Wide-scale use of slag cement in the United ham. NRMCA ing of granulation and grinding facilities at the Sparrows Point. it should be noted that slag cement concrete is durable in freezing and thawing conditions. Two-day forming • Slight changes in admixture requirements (but once cycle was not affected by the use of slag cement. 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Sept. Vol. J. TX. 1997. No. 2003.” pansion of Mortars and Concrete Cured at Elevated Tempera- Concrete International. pp. No. J. and Ip. C. G. 8. MI. SCIC No. ing and Thawing With or Without De-icing Chemicals. Presented to Lafarge. Vol. Silica Fume. MI. Vol. K. mance Concrete due to Restrained Shrinkage. 1996. D. “Corrosion of Steel in Concrete tional Conference.” Building Research Es. 2. 6.. tute. SP-79. Ground. Silica Fume. and Innis. W. SP-79. 1. D. Ontario. 1998. M.. “The Efficacy of [41] Sippel. 1957. Farmington Hills. Committee Supplementary Papers. SCIC No. C. “Durability of Concrete in Marine Environment— “Scaling Resistance of Ground Granulated Blast Furnace (GGBF) A Review. “Effects of Ground Granulated Blast Ternary Cementitious Systems for Controlling Expansion Due to Furnace Slag in Portland Cement Concrete... 1989. Cement Association. Z. M. 2.. [43] Bouzoubaa. Quebec. Farmington Hills. 1–20. J. Sugar Land. M. N. 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Inventory of Slag Cement Concrete. M. D.slagcement.” Slag Cement Association News. TX..” Version 1. Sugar TX. 10. “Canadian Use of Ground Granulated Blast. Slag and Nat- Engineering. . Slag Cement Association. PART VI Specialized Concretes . dustry in the United States until the late 1920s when the first The changing demographics of companies operating in the revolving drum truck mixers were developed [3]. ASTM C 94/C industry also fosters greater technical sophistication and greater 94M was first published in 1933. The 1994 edition of this chapter on ready-mixed concrete mittee C09. there specification at the time of this printing. as measured by the amount of portunities for technology transfer through the American Con- cement used within the United States. larger companies that operated across several states. 2 Retired from National Ready-Mixed Concrete Assocation since 1995. the industry’s use grew crete Institute. There also exist a significant number of large privately held companies that produce in the range of 2 ASTM International has two specifications covering ready. National Ready-Mixed Concrete Association.8 million cubic meters). The his- Volumetric Batching and Continuous Mixing (C 685/C 685M). was concrete producer is the concrete technology expert. quantified by the number of companies that still operate smaller local family- Introduction owned businesses.5 to 3. a freshly mixed and unhardened state. the estimated U. This discussion industry statistics are better quantified with reporting by pub- pertains to ASTM C 94/C 94M-04a. aggregates.45 Ready-Mixed Concrete Colin L. MD. 1955. concrete and other ready-mixed concrete industry and how it operates. This tion C 94/C 94M on Ready-Mixed Concrete and provides the trend has continued with larger multinational corporations authors’ perspective of the intent of the specification require. the current version of the lic companies and information on the Internet. the ready-mixed concrete industry relied on as an expert on concrete material technology and in- consumed about 5 % of the portland cement produced in the novative products by highway departments and other specifiers. In the early days. the competition was with site. ASTM International. ready- THIS CHAPTER ON READY-MIXED CONCRETE HAS mixed concrete production was 405 million cubic yards (310 been a part of ASTM STP 169 since it was first published in million cubic meters) [5]. ASTM C 685/C 685M. MD 20910. and now 6 or 7 % of companies probe on ASTM C 94/C 94M because of its much greater use. Silver Spring. range of 60 000 cubic yards (46 000 cubic meters) annually in the United States [8]. and the building products. Increasingly. but it was not a recognizable in. At that time. He is now published in 1971. 533 . Gaynor2 Preface 1975. and other technical organizations have helped greatly. The volumetric batching with use of performance specifications. still exists a large segment of the industry. but the emphasis will the concrete has changed.2]. Lobo1 and Richard D. These average numbers are quite skewed History of the Industry due to a wide distribution of company size and structure. In 1933. However. establishing vertically integrated company structures that in- ments. However. dustry whereby acquisitions and consolidation had resulted in This chapter follows the organization of ASTM Specifica.S. research. His involvement in standards development. and now a consultant from Silver Spring. to 5 million cubic yards (1. duce less than 10 % of the concrete. and operates about 12 plants and 125 mixer trucks. The “average” ready-mixed concrete ASTM C 94/C 94M and C 685/C 685M are specifications company produces about 700 000 cubic yards (535 000 cubic for concrete. In 2003 the industry used approximately 75 % of the total cement consumption [4]. small companies operating less than 15 trucks The first concrete mixed off-site and delivered to the job may account for more than half the number of companies and pro- have been furnished in 1913. torical pattern where 10 % of the companies produced 50 % of This paper will cover both specifications. The mixed concrete: ASTM Specification for Ready-Mixed Concrete estimated number of companies has changed from about 5000 (C 94/C 94M) and ASTM Specification for Concrete Made by in 1978 to 3700 in 1994 to about 2400 in 2003 [7. as manufactured and delivered to a purchaser in meters). Trends in potential impact on these specifications. the ready-mixed continuous mixing specification. developments in technology that are changing the clude cementitious materials. United States.8]. 1 Vice President of Engineering. At the present time. and op- mixed concrete. Transportation Research from about one-third to two-thirds in the period from 1950 to Board. They form the basis for The average quantity of concrete produced per plant is in the a contract between a manufacturer and a purchaser [1. and asphalt paving operations.40 on Ready-Mixed Concrete and Richard Gaynor [6] indicated a change in trend of the ready-mixed concrete in- has been a member of the subcommittee since the early 1960s. Colin Lobo is the current secretary of ASTM Subcom. duce 50 % of the concrete. they are incor. permits tests in 0. Although the density method. the purchaser’s responsibility to invoke should be within 1 or 2 % of that determined by the standard the pertinent code requirements in the construction specifica. settlement in forms. clean. cally ensures that 2 to 3 % more will be ordered than is needed. (25 mm) too thick [11. contractor. concrete seldom seen on the job site.12]. The ASTM C 94/C 94M and C 685/C 685M specifications are used in a number of rather different situations. that has been found useful over the years and has been re.6 m3) capacity truck mixer. the Associated is 3/8 in. it is realized that when concrete is batched into a and make decisions during the course of the job [10]. A third and important use is the protection of the public When yield is confirmed by the density test. fier) and a contractor. over-excavation. the effect on concrete pro- crete is defined as the total weight of the batch divided by the portions can be dramatic. and testing agency. the volume of hardened concrete is about 2 % less supplier who agrees in his contract with the job contractor to than its volume in the plastic state. In 1965. because in real practice separate and joint responsibilities of the various parties in a the larger density measures are cumbersome to handle and are typical job—the owner. 10 yd3 (7. versions of C 94/C 94M and C 685/C 685M. As such. in small jobs. it will take 1 to 2 % of a capacity batch to coat the drum and blades. the specifications address the C 138 based on coarse aggregate size. the concrete discharged from the truck tractor. or some loss of air. This material is principally mortar with a negligible amount of coarse aggregate. ble source of error is in the weights of materials batched.534 TESTS AND PROPERTIES OF CONCRETE Specifications 94M requires tests in standard 1/2 ft3 (14 L) unit weight buckets for improved accuracy. Therefore. and appropriate adjustments made in batch proportions if de- terial for incidental construction. ficiencies are found. More recently a partnership between the of that concrete by ASTM C 138. The volume of concrete dis- American Society for Concrete Contractors and the National charged is then the weight of concrete discharged per revolu- Ready-Mixed Concrete Association have produced checklists tion times the number of revolutions divided by the density. ment that if there are differences. another possi- interest by incorporation by reference in public building codes. crete actually used on a job will be greater than that calculated At the other end of the scale. both specifications include the state. It is. circumstances often dictate that job specifica. A 6-in. Seldom do the contractors’ initial estimates agree that C 685/C 685M. there is a need for close cooperation between the used concrete or ordering short loads. Scale In this instance. Compared to the batched propor- concrete density (unit weight) as determined by ASTM Test tions.76 m3) batch is mixed in a clean calculation of the volume of fresh concrete. Since the ready-mixed concrete producer functions as a Estimates should be revised towards the end of every pour and supplier of materials and often has no binding contract with communicated to the concrete producer to avoid returning un- the owner. The volume of con. Due to different tolerances on weighing materials. Here. are then passed down to the contractor and finally to certified calibrations should be conducted at least annually. contract is between an owner and his representative (the speci. washed-out truck mixer. the purchaser’s specifica.to six-month intervals and owner. can Association adopted a “Joint Statement of Responsibilities” produce slabs that average 1 in. perhaps to a homeowner. The statement addresses the separate and joint weighing the concrete discharged in a given number of revo- responsibilities of each party and is helpful in defining the tra. yield test. yield tests must be made early in the job specifications form the basis for an agreement to furnish ma. and Air Content weight of a capacity batch. spillage. Because the quantity of con- comply with ASTM C 94/C 94M or C 685/C 685M. Yield. for concrete preconstruction conferences and ordering concrete that provide guidelines to establish responsibilities and Truck Mixer Hold Back identify responsible individuals to address specific situations Generally. This might be a revision in future producer. these ASTM from plan dimensions. metrically using mobile mixers. these checks are made. ASTM C decrease from 36 to 26 %. four or five batches each day. and General Contractors and the National Ready-Mixed Concrete deflection of bar joist construction. a Inevitably. if the amount of mortar retained is equal to 2 % of the Method for Density (Unit Weight). The unit weight used is the discharged will drop from 600 to 470 lb/yd3 (356 to 280 average of the results of three tests made on separate samples kg/m3). and other factors that affect the yield determination. Yield or Volume In-Place In major public and private construction. Under ASTM C 685/C 685M. A note explains that the volume of concrete delivered may be porated by reference in the job specifications. closely with the amount delivered by the concrete producer. (150-mm) slab that contractor and the concrete producer. the cement content of the concrete (Gravimetric) of Concrete (C 138). which are binding on the accuracy should be checked at three. however. when a 1 yd3 (0. The batch will be harsh to handle 138. (9 mm) too thick will require 6 % more concrete. There has been some consideration ASTM C 94/C 94M and C 685/C 685M are specifications for of deferring to the smaller density measure sizes permitted in ready-mixed concrete. sis of purchases and then describes the method of testing and However. ASTM C 94/C and will have low cement content and low strength. for concrete batched volu- viewed by both associations periodically and republished with. The practice of ordering full loads by many contractors practi- tions shall govern. lutions of the cement feeder and then determining the density ditional roles of each. . the basic less than expected due to waste. this does not significantly An early section in both ASTM C 94/C 94M and C 685/C 685M affect the volume of concrete delivered if the truck delivers defines the cubic yard (or cubic meter) of concrete as the ba. which is not shored. the requirements.2 ft3 (6 L) air meter bases. specifying agency. content. air tion and the purchase order for concrete. a check on the yield is made by out change [9]. and the sand as a percentage of the total aggregate will from different loads. If the concrete producer through a purchase order from the con. spreading of forms. The concrete producer is a material Further. Basis of Purchase Since mixers are washed out and wash water and solids discharged only at the end of the day. tolerance on the yield from the quantity ordered is difficult to tion requirements differ from those in ASTM C 94/C 94M and establish. This issue is one that has resistance to freezing and thawing. the production and place- with properties quite different from the “standard mixes” in ment schedule will be disrupted. Control of such pliance. slump. it is possible to produce back perhaps 50 % greater. Sometimes this is an on the job site. has started work on standardizing a similar procedure. perhaps because of past bad experi. self-consolidating concrete. if the w/cm ratio is to be weight of structural lightweight concrete. Another difficulty is that readily available in standard mixes. ASTM subcommittee on Fresh Concrete Tests. and water scaling. re. and C options do not include a requirement for a rameter. required strength. low-permeability corrosion-resistant concrete. gregates will vary from batch to batch making accurate meas- ences or in an effort to provide characteristics that were not urement and/or adjustments difficult. the moisture content of the ag- attempt to ensure quality. of ingredients. sand.40! fies minimum cement content. not reasonably consistent with the strength obtained at the de- especially when a variety of concrete types are batched during sired w/cm ratio. . On well-controlled jobs. those required in the “Building Code Requirements for Struc- the effect on proportions is much more dramatic since the tural Concrete” (ACI 318) [14] or “Specifications for Structural gross volume of the drum is about 25 % larger than a truck Concrete” (ACI 301) [15]. 4 yd3 (1. and the hold many high-performance concretes. strating compliance with the specified maximum w/cm ratio and high-performance concrete. However. From the user’s tio. then compliance with a specified tions: A. for determining the water content of concrete by rapidly At least at this point. the surface to be coated is much greater. or C. formance-based method that addresses other characteristics to C09. the purchaser and delivery time. more accurately measured performance though Option B does include both cement and water content.30 or lower and values as low as 0. controlled low-strength materials. sulfate exposure. The situations can vary but in many not been widely used in their specifications. which would apply. lated w/cm ratios greater than 0. The options are as follows: maximum w/cm ratio for field acceptance is inappropriate Option A is the performance format in which the pur. the strength level specified for The principal reason that it is not included is the difficulty of the concrete should be consistent with the specified w/cm ra- actually measuring the w/cm ratio in practice. maximum water content. LOBO AND GAYNOR ON READY-MIXED CONCRETE 535 The solution is to increase cement. specifiers use a number of systems of enforc- are flowing concrete. or intrusion of chlorides in rein- weights up to about 40 % in such small truck-mixed batches. provide better assurance of “durability” than other maximum water-cementitious materials (w/cm) ratio even much more reliable. Water-Cementitious Materials Ratio in The writers’ opinions on w/cm ratio specifications is that Specifications they should not be used and do not.35 are being specified in parking structures for re- Ordering Information sistance to intrusion of chlorides. large agencies are requiring 2 to a particular period. deicer salts and associated been under considerable discussion for several years [18. The Port Authority cases the producer may have more expertise or knowledge of New York and New Jersey have used it in specifications that than the purchaser on acceptable local practice [13]. unit For all of the above reasons.60. pervious concrete. con. AASHTO tures. strictly enforced in the field. which depends on delays related to traffic or often includes additional requirements. if required. without an understood statistical tolerance. w/cm ratio ranges from 0. The concrete producer has difficulty conforming to a max- Both ASTM specifications include the fundamental elements of imum w/cm ratio since the amount of water necessary to pro- prescription and performance specifications and list the basic duce a given slump will vary with local ingredient materials information needed by both parties. The producer should ensure that used with the recorded quantity of cementitious material the basic information required for the mixture is provided with batched to calculate a w/cm ratio. to require submission of laboratory trial batch or previous crete with reduced shrinkage characteristics. as a single mixture pa- The A. fiber-reinforced field mixture proportions with accompanying test data demon- concrete. include payment adjustments in airport construction and feel that it has helped greatly to improve construction quality [17]. B. B. forced concrete. include durability is most likely covered in job contract docu. common use a few years ago. The growing number of the procedures used by specifiers to determine compliance types of chemical admixtures and supplementary cementitious with maximum w/cm ratio specifications are rarely defined. which range from 0. delivered is of the desired quality. concretes with w/cm ratios as low as 0. For some time AASHTO has had a test procedure. Concrete with three or even and then relying on routine strength tests to determine com- five admixtures is becoming more common. air content. The maximum w/cm ratios usually cited are ferred to as short loads.19].40. One of the simplest is concrete. Additionally. that is. If a clean tilting central mixer is used. the method and although they have thought it was useful it has chaser’s responsibility.50 to 0. In mixer.5 to 3 m3) trial batches instead of laboratory trial The Ordering Information section requires the purchaser batches to improve the accuracy of the mix approval process. although C 94/C 94M indicates that it is the pur. The idea is that the measured water content in the test can be ments. A broader per. A concrete producer chaser specifies cement content. materials permits the concrete producer to produce concrete and if every batch is to be checked. and would have to furnish concrete with an average w/cm ratio of admixtures. characteristics.02 to 0. not unlike that chaser specifies strength and the producer selects proportions used in ACI 318 or in ASTM C 94/C 94M for strength. to specify the size of coarse aggregate. the standard deviation of the Option B is the prescription format in which the pur. so that the purchaser is at least assured that concrete being perspective.03. T 318. as low as 0. concrete in C 94/C 94M is based on strength.35 or even lower to avoid batches that have calcu- Option C is a mixed format in which the purchaser speci. At a minimum. anti-wash-out ing maximum w/cm ratio specifications. the performance format of ordering drying a small sample of concrete in a microwave oven [16]. Currently. a w/cm ratio is needed to ensure durability. and admix. Some of the newer applications In practice. This system breaks down if the specified strength is mixtures can be a significant challenge for concrete producers. Increasingly. Several State DOTs have tried the order. and one of three op. and testing of consistent and uniform concrete batches. and water from concrete production operations. if a producer conducts qualification tests for a com- event. those compositions of lesser impact on con- proves” the submittal. wash-out operations as mixing water in concrete if the water livery. fication requirements and associated testing frequencies are Once mixture proportions are identified in a submittal. tests. most mixtures have specified design strengths. many cases prohibit. non- or cement content mixes—not strength or for other perform. delivering. the mixing. The specification provides for a testing frequency for these a beginning for performance specifications. and total solids in the wa- furnish if he did not have a strength test record. This recognizes that more Code ACI 318. Another aspect of adhering to submitted mixture propor. admixtures. cation criteria apply to the total mixing water with the intent mittal of mixture proportions in the case of a strength-based that when a concrete producer qualifies a certain critical com- specification. It should be noted that the amount of air-entraining ad- This section includes references to the commonly used ASTM mixture required to produce the required air content may in- specifications for cement. alkalies. potable. and to make adjustments in proportions to conform to a lower Optional limits can be invoked by the purchaser on the required average strength level compared to what he would amount of chlorides. C 94/C 94M does not address mixture ognizes that one or more of these sources may be combined to submittals. and returned concrete. aggregates.536 TESTS AND PROPERTIES OF CONCRETE Approval of Mixtures because there is no ASTM specification or because there is a Under all three of the options of ordering concrete in ASTM C feeling that the use of the material requires different batching. 1940 when virtually all concrete was furnished as prescription ASTM C 1602/C 1602M defines water sources as potable. if the purchaser requests it. As a result producers are increasingly tions is that adjustments to concrete mixtures are necessary on reusing wash water as mixing water and are considering in- a real time basis to accommodate variations in ingredient ma. For strength test results during the course of the job govern in any instance. Ideally. the disposal of wash water. The qualifi- There has been some question as to the usefulness of a sub. with a statistical allowance for testing variability. mixing water with lower concentrations of solids cating compliance with specification requirements. for a performance-based specification. This process started prior to about for water in C 94/C 94M make reference to this specification. de. yard runoff. ing water. This is at least ter. These are addressed in ACI 318 for mixtures and in make up the total mixing water used in concrete. either air-entraining admixtures should be added either with the sand . monitoring and control is needed when wash water with a late the required over-design when he has accumulated 15 tests higher solids content is used. sulfates. the in. strength and setting time based on the density of the total wa- There is. Potable wa- ACI 301 for mixtures and construction means and methods. it is dif. and other ingredients are not included. The 90 % limit for furnished with higher cement content and much higher strength is intended to allow equivalence to acceptable water strength than is actually needed. and in ance with the job specification and the pertinent submittal. 94/C 94M and C 685/C 685M. position of the concrete mixture that describes the details of the Considerable pressure from evolving environmental regu- ingredients and proportions are really irrelevant. and the strength acceptance criteria of crete properties can be used without qualification testing. pH wash water before the water is batched into the mixer. made with potable water. meets the qualification tests for strength and set time men- Adoption of performance-based requirements and elimination tioned above. If the producer was free to vary proportions to produce the required performance. can delay construction schedules. crete proportions is firmly embedded in specifications and ASTM C 1602/C 1602M. position of water. The qualification of wa- ficult to reduce cement content without generating opposition ter sources requires testing for effects of the water source on or suspicion from specifiers or contractors. The sion inhibitors. bination of wash water and potable water at a solids content of mittal should furnish mixture pre-qualification test data indi. These regulations control. A crease. or testing procedures than those for “nor- manufacturer is required to furnish proportions of ingredients mal” concretes. Quali- Today. expansive cement. This information is related to that required to be furnished on the delivery ticket. The qualification requirements indi- plement a quality control program that is designed to control cate that the strength should not be less than 90 % of the con- strength with a high degree of uniformity at the target level trol and setting time should not be retarded by more than 90 that complies with the specified strength. Water Quality The system of requiring submittal and “approval” of con. Typi- Materials cally. that will be used. and even double. It rec- ance-based requirements. are thereby qualified for use. 50 000 ppm. established for other sources of water. ASTM C 1602/C 1602M has an optional limit of 50 000 ppm of solids in total mixing water. Oftentimes a required resubmittal ment from returned concrete in freshly mixed concrete. The com. more of its process water. Mixer Wash Water centive would exist for him to invest in sophisticated quality ASTM C 1602/C 1602M permits the use of water from mixer control processes that facilitate the production. The specification requires the density of wash water crete suppliers will have the incentive to adopt more formal to be measured daily and establishes testing frequency for and advanced quality control systems. in the American Concrete Institute (ACI) Building ter that the producer intends to use. The design professional or specifier rarely “ap. if these admixtures are added to high number of materials such as fibers. a provision that permits a producer to recalcu. As currently written. and water. Selected job lations is forcing the ready-mixed concrete industry to reuse site acceptance tests can then be used to demonstrate compli. was approved and the requirements codes in the United States. this permits up to about 15 lb/yd3 (9 kg/m3) of dry solids. The qualification criteria apply to the total mix- of prescriptive mixture proportions are necessary before con. and the concrete is min or accelerated by more than 60 min. In 2004 a specification for mixing water for use in concrete. corporation of returned concrete or the partially hydrated ce- terials and seasonal factors. ter is permitted to be used without qualification testing. batching. the sub. corro. The net result is strength and setting time when compared to control concrete that there is little incentive for the concrete producer to im. C 94/C 94M allows the addition of air entraining uring the density and solids content of wash water slurries admixture followed by 30 revolutions of mixing. ASTM C 1603/C 1603M also provides guidance on dicating that some fly ashes containing carbon adsorb air- blending two sources of water to stay within a predetermined entraining agent. Meininger [35] and Helmuth [36] described tests in- uations. Although it does age of the returned concrete used. a more practical cement. and temper- not appear that similar problems are experienced when other ature history. duration of the slurry [25]. the anon top of it at the plant.30]. cement factor. Such methods are in the process of being standardized. such as slump flow and other empiri- slurry. and and a target value. These issues pered with water at the job-site and fresh materials are batched are the subject of other chapters in this book. It establishes methods of There have been a number of problems that have surfaced estimating the solids content of water from the measured recently in the control and measurement of air content. the admixture for the required air content and a reduction of concrete air content during delivery. With in- fective admixture dosages can be established by determining creased use of self-consolidating concrete. Ozyildirim [37] and Hover Returned Concrete [38] have made studies to determine if the pressure meter ac- ASTM C 94/C 94M is silent on the reuse of returned concrete curately measures the air content of plastic concrete and but there are efforts currently to address it in the specification. LOBO AND GAYNOR ON READY-MIXED CONCRETE 537 or with an increment of clean mixing water. have been used very effectively to overcome some of procedure is to specify the slump of the concrete before addi- the negative effects of using recycled water at higher solids tion of the high-range water reducer and to accept the fact that content. The of water. While several concrete producers have installed production facilities. alternative measures the loss on ignition (LOI) of the dried solids from the water of concrete consistency.5 % of the specified air content. and ducers to be added at the plant. retarders. Requiring a slump level prior computerized systems that automate the process [25. These studies the same day or even the next day. a preliminary sample is taken prior to discharge and has a low ASTM C 1603/C 1603M establishes procedures for meas- air content. This allows problems associated with slump loss with time and improved the producer to maintain a production mass balance whereby the linear relationship of dosage to concrete slump level. which suspend the hydration of and testing. Slump the generated wash water is reused. a property that is easier to measure in production sit- years ago. A low LOI value represents a low degree of hydration of cal measures to quantify the rheology of concrete will be nec- cement indicating that the HSA is functioning for the storage essary. a higher degree of hydration [29. The job-site addition crease in the mixing water requirement for target slump and of high-range water reducers (HRWR) to produce flowing con- can result in lower strength. the amount to be expected in hardened concrete. Generally. However. the resulting concrete will be of lower commonly used accelerators. This caused a higher dosage requirement of or specified target solids content or density. Factors that affect the 231) does provide the desired measurement and that the air properties of the resulting concrete include the quantity and content of hardened concrete is often either lower or higher for . This operational process eliminates steps of removal of in two different formats: a “maximum” or “not to exceed” value. treated with HSA without adversely affecting concrete proper- Increasingly the industry is moving towards zero-discharge ties [31–33]. Laboratory studies have represent the use of wash water that has been clarified through demonstrated that returned concrete can be successfully a settling pond system. or water reducers are strength due to a higher water content and will set faster. A simpler qualitative quality control The section on air content contains a table of recom- tool is to monitor the rate of settlement of solids in a column mended air contents taken from ACI Committee 211 [34]. Water slurries used at higher solids content. Unhydrated cement will settle at a faster rate indicat- delivery tolerance is 1. Sufficient caution and control should swer generally appears to be that ASTM Test Method for Air be exercised to ensure that the resulting concrete mixture Content of Freshly Mixed Concrete by the Pressure Method (C meets the purchaser’s requirements. New admixture larger quantity of wash water slurries with higher solids con- chemistries for high-range water reducers have reduced the tent without adverse affects on concrete properties. Ef- to adding the admixture at the plant is not practical. reclaimed from returned concrete. When ing the effectiveness of the admixture dosage used [28]. separate tanks that HRWR admixtures. It is more common for high-range water re- feed admixture-treated water at constant solids content. which is related to the solids con- The section on slump in ASTM C 94/C 94M contains tolerances tent. fines from process or storm water settling basins. drying. This slurry is then used as a part or whole of the mixing Slump and Air Content water in concrete. Hydration slump of the flowing concrete is subject to strict slump control stabilizing admixtures (HSA). The cement and tracking a variety of factors have limited its widespread use. It also disposal.28]. These batched into or at the same time as wash water. The use of these admixtures facilitates the use of a the slump of the flowing concrete will vary. Some density. The tolerance varies by level of slump. Returned concrete and mixer wash water systems that allow for the controlled and quantified use of is processed through concrete recycling or reclaiming units HSA-treated returned concrete. The percentage used will depend on the density of the wash water slurry. whether the pressure method provides a reasonable estimate of In this scenario the concrete remaining in a truck mixer is tem. Hydrated cement also causes ac- crete has created a number of field control problems when the celeration of the setting time of concrete [24–27]. Returned concrete is stabilized for reuse on quality are not significant or important [20–23]. the operational challenges of that wash out and separate the aggregates. com- establishes a 30-min period after arrival on the job during which posed primarily of partially hydrated cement. sand fines are maintained in a slurry suspension in agitation tanks. this possibility effects are exacerbated when a larger quantity of returned should not be ignored with the increasingly sophisticated concrete is used and when the returned concrete has reached admixture systems that are being developed and used. Complete recycling sys- retention has also improved with these newer generation tems include accurate water density gages. If job-site adjustment is preferred. cause an in- the producer is responsible for the slump. Hydration stabilizing ad- Research and industry experience with the use of wash water mixtures (HSA) were originally developed to treat and reuse re- at relatively low solids content has been that effects on product turned concrete. ica fume in preweighed bags. Naturally if the plant uses a separate indi- screeds that are mechanically troweled. (125-mm) lines. There crete at the point of placement in the job. The authors believe that port the batch weights. tion of the zero reading or tare. It has been reported that ASTM C 94/C 94M requirements for measuring materials rec- the air void systems generated from these air entraining ad. Likewise even those with the Another problem is the development of surface delamina. the batcher discharge that tests be made on discharge from the truck. the volume of air lost is in the larger requirement tends to ensure the correct cement weight and. the air will not be lost and the strength in-place a separate material and batch it with an accuracy of 0. With the increasing use of computerized batch- have been typically measured in hardened concrete specimens ing equipment. Another alternative tance away where the boom will be in a horizontal position. loop in the flexible hose or laying a length of hose on the deck The weighing tolerance is 1 % of the required cumulative [42]. closely together to determine if loss of air is likely to be a prob. Cumulative weigh- vide resistance to cycles of freezing and thawing [43]. The air bubbles then expand and fail to reform when the concrete drops out the end of the pump line or im. the batcher tends to “rathole” when it discharges into the mixer portation unit. might be to weigh the silica fume to 100.5 %. This can be as simple as inserting a mulatively on a single scale provided cement is weighed first.538 TESTS AND PROPERTIES OF CONCRETE a multitude of reasons. of the desired amount. however.3 % of the capacity of the scale. it Batching silica fume is not addressed in the current ver- should be recognized that strength tests will be reduced 15 to sion of C 94/C 94M. Under normal conditions. When for air content and strength. slag. and the cementitious materials blend as they are loaded. indicated by the specific surface. the pump line. More recently. Hover has The primary reason for weighing cement first is related to the demonstrated that even though air content is reduced through flow characteristics of fly ash that could cause it to be over- a variety of placement methods that cause concrete to fall weighed and result in a lower batched quantity of cement. Naturally these are is. if the test samples are obtained after the last ingredient it is possible to meet current batching toler- pumping with the pump located near the truck with the boom ances by batching 60 % of the desired amount if 5 % by weight near vertical. silica fume is used. vidual materials in a cumulative batcher.or 10-year-old automation are likely to use sil- sues that must be resolved in a pre-job conference or earlier. The concrete producer prefers separate batchers are used. specifier. an excess of mineral admixtures. anything. . This would speed up batching and pro- trained air in industrial floors or. fume by weight of cementitious materials. batches less than about half the batching capacity of the This occurs in industrial floors with mechanical and vibrating cumulative system. ognize both individual scales and hoppers for weighing a sin- mixtures are of smaller size and could possibly function for gle material and cumulative scales and an associated hopper freezing and thawing resistance at lower total air contents. For small batches where the cumulative weight is less should not exceed 1 or 1. The solution has been to insert Cement. separate from most of the cement.3 % of the amount de- The contractor. the tolerance is from 0 to 4 %. This system. Air can also be lost when concrete than 30 % of scale capacity. Although a number of vidual silica fume weigh batcher the tolerance would be 2 % factors are involved. Batching and Measuring Materials by gies for air-entraining admixtures create more stable air void ASTM C 94/C 94M systems but need additional mixing energy to develop the required air void system and air content. provide 8 % air because 3 % will be lost during placing. Another aspect is that newer technolo. pumper. ing of cement and supplementary cementitious materials (also C 94/C 94M establishes that the point of sampling for referred to as mineral admixtures) also has the advantage that acceptance testing is at the discharge point from the trans. The problem is exacerbated if the scale capacity. the air content will be reduced. it has now become possible to have the using ASTM C 457. Producers still using lem and what procedures will be used. the loss of air in pumping weight. This means that the tolerance of any this occurs when a section of the boom is essentially vertical and individual weighing is based on a tolerance percentage of the concrete slides down from its weight and develops a vacuum in intended cumulative weight. to keep the air con. and producer need to work sired with a tolerance of 0. This through a certain distance. If he agrees to must blend the two materials. newer systems should not attempt to weigh silica fume for tions and blisters when air-entrained concrete is steel troweled. particularly with the newer long to cumulative batchers irrespective of the format used to re- boom pumps with 5-in. Normally this would be within 10 % for 5 % of pump location is such that placement occurs both close to the silica fume and correspondingly less for 10 or 15 % of silica pump with a critical boom configuration and also a long dis. Some specifications require testing the con.3 % of may be significantly lower. including a recognition of the size of air voids in plastic concrete [39. A note is needed in ASTM C Another issue is the observation that much of the initial air 94/C 94M to explain the fact that cumulative tolerances apply can be lost during pumping. However. there have been attempts to computer do the subtraction and print the weights of the indi- standardize the Air Void Analyzer that measures the distribu. With the load cells and au- concrete is placed at a higher level with a less critical boom tomation now available it is possible to treat the silica fume as configuration. if size bubbles and the remaining air content is adequate to pro. and other pozzolans may be weighed cu- some resistance in the line. Likewise. fly ash. This will slow down the batching process. The for weighing more than one material. this is currently being considered 20 % if cylinders are made from samples obtained at the truck since it is a small amount and if it is weighed cumulatively as discharge.40]. Cementitious Materials pacts an elbow in the boom [41]. and the pumping contrac. which makes the have been a few instances when individual separate batchers concrete producer. and the ter- primary intent with entrained air is to obtain a proper air void minology that is used. the solution is to avoid the use of en. which is rare. developed from the use of dial scales system in concrete characterized by a proper spacing factor and where the material weights were accumulated as materials bubble size. were used for cement and fly ash and the fly ash wound up in tor responsible for the final results for acceptance of the tests one part of the batch. vide some flexibility in controlling the batching process when tent below 3 or 4 %. is dropped or discharged from a belt conveyor. at least. the contractor. dial scales and 5. if this of cementitious materials is desired. These parameters were weighed. 5 kg) or 1 gal (3. different sized connections. Mixing Water Batching Plant ASTM C 94/C 94M defines mixing water as any water added to the batch plus surface moisture on aggregates. [45] for new equipment are 0. When water is weighed. quantity in the mixer truck prior to batching is possibly ques- ored fill pipes. Admixtures are required to be free-draining with access provided for inspection. through a system of levers to a load cell. then the minimum batch size those of the Concrete Plant Manufacturer’s Bureau (CPMB) that can be batched is about 3 yd3 (2. and fins. whichever accuracy will be 5 %. The accuracy of the placed in the wrong silo. whichever is greater. or shrinkage used. truck water tank to wash down the truck chute. Often the automatically when the required weight has been reached. LOBO AND GAYNOR ON READY-MIXED CONCRETE 539 Although it is not addressed in ASTM C 94/C 94M. tionable as this is generally verbally communicated by the tively colored bills of lading to distinguish between materials. driver to the batch man. Some producers use keys and locks on fly ash pipes and Chemical Admixtures control access to the keys. or an ad. and some mini. if the dosage rate is 1/2 oz/100 lb (0. when started. but by a revision to C 94/C 94M in 1992. The tolerance on batching added water is 1 % of are relatively basic and straightforward. Earlier load cells were not widely accepted since the dial reducing admixtures.5 % on added water and curacy and calibration requirements are similar to NIST Hand- is considered more realistic. or concrete strength. variations of this size would is less. Because fly ash tends to flow freely Chemical admixtures are rarely batched by weight.78 L). Other sources of mixing water include scale provides a mechanical backup in case of a failure of the that which is in the mixer during a job site wash out.5-m3) load.3 mL/kg) and the than 30 % of scale capacity. In some cases. Use of load cells to support the from certain water-based admixtures that are used in batchers has the potential to simplify a scale by eliminating significant quantities. Producers generally use different col. A semiautomatic control is one that. This will require about 40 gal of water from the (b) prevent charging if the discharge gate is open. not a percentage of that being batched. the overall batching pacity or 3 % of the required cumulative weight. corrosion inhibitors. to the plant. fill pipes can be at different locations in the plant. NRMCA Check List [46] are the same as in C 94/C 94M. Aggregates can be weighed either in cumulative or individual It should be noted that on small batches of lean concrete weigh batchers. the tolerance is 0. many site to discharge this water. either discharged or used with the next batch with the appro- als. Even in a 10-yd3 (7. The scale ac- list [46] establishes a tolerance of 1. The truck driver is normally advised by the visions to prevent discharge of the device until the material is company to record the amount of job-site-added water on the within tolerances. or liquid The requirements of ASTM C 94/C 94M for the batching plant admixtures. . Scales in concrete plants generally consist of a container The total mixing water consists of that measured in the supported at the four corners and transmit reduced loads plant plus that from free moisture on aggregates. is generally quantifiable through the measuring device on the ASTM C 94/C 94M does not define or require different truck water tank (site gage or water meter). signs.6-m3) capacity amount in individual batchers. such as high dosages of high range much of the lever system and dial scale that has typically been water reducing admixtures. and that now beginning to disappear. ice. In a 2-yd3 (1. justment for that absorbed by less than SSD aggregate.3 m3). and the drum. However.2 % of the capacity of the scale when tested The tolerance on the total water is 3 % of the total water con. that Calibrated beam or springless dial-indicating devices are from wash water measured through the batch plant. and tent is 280 lb/yd3 (166 kg/m3). ric dispenser systems are quite sophisticated and are inte- los. when they are added in prepackaged fixed amounts. rack before the vehicle departs the plant. The space between these double-walled bins needs to be grated into plant automation. interior of (c) prevent discharging if the charging gate is open. The NRMCA Check. and distinc. The scale accuracy requirements of the 10 lb (4. includes interlocks to: Mixers need to be cleaned at the job site before returning (a) prevent charging until the scale returns to zero. the effects will be significant. C 94/C 94M requires testing the scale at tent. some specifications [44. 3 % tolerance will govern. For cumulative weights less batch. setting time. Volumet- mon walls between multi-compartment cement and fly ash si. batched to within 3 % of the desired amount or plus or minus the amount or dosage required per 100 lb (50 kg) of ce- Aggregates ment. the ultimate importance to concrete quality is questionable. and the nominal total water con. This means that at less than 10 % of scale capacity. The CPMB Standards [45] provide mal quantities that could enter the mixer at the wash-down a consistent terminology for plant control systems.1 % of capacity. and there is always the possibility that material can be priate corrections to the plant batch water. with standard weights. it is carried back to the plant and concrete plants contain several silos for cementitious materi. the not change the air content. Additionally. When facilities are not provided at the job (d) prevent discharge until the material is within tolerances.3 % of scale ca. dispenser is accurate to 1 oz (30 mL). which electronic load cell system in the middle of a placement. This does mean that if a water meter is accurate to about its quarter points. The basic batching tolerance in cumulative the admixture batching accuracy may be as large as 25 % batches is 1 % of the cumulative weight and 2 % of the required of the amount batched. water A manual control is one that is operated manually and is may be added from the truck water tank on arrival at the job dependent on the operator’s visual observation of the scale or site that is within the limit permitted by the specification or meter. Scales are required to the total water content. A delivery ticket will indicate the maximum additional water semiautomatic interlocked control is similar but contains pro- permissible. be accurate to 0. except through cracks. delivery ticket and obtain the signature of the person An automated control starts and stops automatically and requesting this addition.45] do not permit com. stops that which controls the strength of the concrete. the pres. book 44 [47] with some minor differences that were clarified ent ASTM C 94/C 94M tolerances are more easily achieved. types of batching controls. recorders. Standard sizes range from 2 to 15 yd3 (1. semiautomatic batcher. and provide a record for the producer to determine what Central Mixing the scale did for every batch shipped. The differences between the types are lization. control panels has made great strides. One of the most popular is a horizontal The CPMB Standards define both digital and graphical shaft planetary mixer that is used in precast concrete plants. Manual—a combination of manual batchers except that an agitator. Generally. There are three types of mixing operations defined in ASTM C A batching system consists of the required combination of 94/C 94M: individual batchers. Digital recorders must reproduce the scale reading sion will depend on a number of other factors. Interlocks are optional. market volume. been introduced recently although the general concept is The development of computerized batching systems and not new. reduced wear. operation. and less noise. their low overall height and rapid mixing. simulated weights. truck. This is the type used in most ready-mixed concrete (a) that must start with a single starting mechanism. Mixing Concrete signed but overrides are in place to allow for manual control of batching. The CPMB Standards de. Central mixing where concrete is mixed in a central plant types: mixer and delivered to the job in a revolving drum truck. and the cost of such In addition to the recognized PMMD types. Horizontal shaft mixer—these have a horizontal cylindrical charged into a mixer. and space for the driver and purchaser to sign. 1. Truck mixing where ingredients are loaded into a revolv- 3. Several innovations in batching efficiency and plant zontal axis non-tilting mixers. and ing compartment with rotating blades or paddles. market area. and whether ready-mixed concrete is produced in central mixing plants. lower plant heights. Tilting mixers—revolving drum mixers that discharge by devices: tilting. c. However. are optional. fine four principal types of concrete plant mixers: 4. ex. 2. identify the by central mixing is in the range of 20 to 25 % of total plants. More a truck mixer. The rated capacity ranges from 30 to 50 % of gross and may have separate starting devices. There are mixer in operation.5 to 11. locked or automatic batchers and volumetric devices in The Standards of Plant Mixer Manufacturers Division which the interlocks. Semiautomatic batching—a system of semiautomatic inter.50] shows that the deci- identified. presumably shear rates that result in more efficient dispersion of cement and produce significant Recorders cement savings [48]. other than those required for indi.5 cept water or admixture not batched at the same time. m3). blade life in trucks. the than actual batch weights are recorded. These have greatly simplified been considerable interest in several other high-energy mixing the process of recording batch weights and printing delivery designs that are reported to provide more efficient mixing at tickets. Automatic batching—requires a combination of automatic 1. livery tickets. They print de. (PMMD) of the Concrete Plant Manufacturers Bureau [45] de- vidual batchers. number of factors. digital recorders have become the norm. drum volume.” and “Digital Concrete Certification Recorders. they record and print basic information such as plant. Partially automatic—includes at least one automatic or volving drum truck mixer.540 TESTS AND PROPERTIES OF CONCRETE These definitions refer to the capability of a control as de. sand moisture content. plants.” “Digital Batch Documenta. lower electrical costs. The CPMB Standards define the following a. they must be clearly CPMB study of economic factors [49.” They were popular several years ago because of tolerance. This sequence allows a higher number mixing compartment with blades or paddles rotating of trucks to be moved through the plant and increases the about the horizontal axis.1 % of scale capacity or within one increment on volu. and truck uti- metric batching devices. or other requires a less-skilled truck mixer operator. central plant mixer with the mixing completed in a re- 2. provide information for billing and inventory control. The principal advantages of truck mixing are lower capital destination. time required for batching and moving truck mixers through 3.” is that it provides centralized control of the mixing process and All require that if target weights. material batched. investment. The percentage of the ready-mixed concrete produced the degree to which they record and print tickets. including the within 0. there has systems continues to decline. Vertical shaft mixers—these mixers have an annular mix- ance and reset to start. The technical advantage of central mixing tion Recorders. ing drum truck mixer for mixing and delivery. Graphical recorders were once popular for large jobs Another type is a slurry mixer that mixes the cementitious where one mix design was produced for extended periods. A number of new designs have production rating of the plant. There has been some renewed interest batching systems that do not exactly follow the definition of in these mixers recently with demonstrated shorter mixing automatic systems above by which the batching of the next cycles. This materials and water prior to charging this mixed slurry into made it easy to identify mistakes and malfunctions. batch is started before the previous batch is completely 4. Non-tilting drum mixers—these are revolving drum hori- the plant. higher energy levels. but because of The concrete producer is constantly trying to reduce the rapid wear are little used today. (b) where each batcher must return to zero within toler. The mix- (c) where discharge of any ingredient may not start until ing compartment or pan may rotate or not. and . Shrink mixing where concrete materials are blended in a automatic. The choice between central or truck mixing depends on a large fine three types: “Digital Recorders. water or admixture batchers may be semiautomatic or b. It is generally an addition to a truck mixing recently. give an indication of whether all materials are This contrasts with Europe and Japan where close to 100 % of within batching tolerances. These are similar to a truck configurations have been developed to facilitate this. or nonagitating unit. they individual batchers have returned to zero and discharge through a door or hatch in the bottom of the all weighed ingredients have been batched within “pan. control chute movement. fine and coarse aggregate starting after the sand starts. ASTM Uniformity of mixing in truck mixers depends greatly on C 94/C 94M still requires a minimum of 1 min mixing for the the batching sequence used to load cement aggregates and wa- first cubic yard and an additional 15 s for each additional cu. mixers and that the mixer be capable of mixing concrete in 70 Although most State Departments of Transportation to 100 revolutions. Then the coarse aggregate a truck mixer. Cement-last loadings are typically used for special cements be more easily positioned on the truck chassis to comply with or when charging cement from a remote bin. are that the volume of mixed concrete not exceed 63 % of the one where water is batched into the truck mixer first fol- gross drum volume for truck-mixed or shrink-mixed concrete lowed by the cementitious materials which are then mixed or 80 % when used as an agitator for central mixed concrete. portance of the loading sequences is likely much less if. but in mixer drums without large drum was greater and mixers would hold 80 % of the gross buildup of hardened concrete and worn blades it pro- drum capacity. the angle of inclination of the to produce cement dust. may need some adjustments. The other 75 % of the Two general types of inclined axis truck mixers are in use to. As will be noted TMMB Rating Plate conform to C 94/C 94M required maximum later. ex- riod of 30 to 60 s of mixing in the central mixer and complete tending through the charging procedure but ending before the process by additional mixing at mixing speed in the truck the coarse aggregate to reduce dust. of the water is important. The idea was to partially mix and shrink the vol. With the larger units used duces uniformly mixed batches of concrete. loss of slump and use of retem. and discharge quantity of water added at the tail end and this quantity from within the truck cab. drum. The final water batched washes all unit. Starting the charging sequence with coarse ducers are able to ship a mixer loaded to 80 % of gross drum aggregate helps avoid sand packing in the head of the volume. The large discharge discharged into the truck mixer as the aggregates are be- openings used on truck mixers designed to discharge low ing loaded. as in The same minimum limits apply to front discharge units but the most ready-mixed concrete operations. and sand should be ribbon loaded together with about 10 % ume of concrete before it was placed in a truck mixer for final coarse aggregate loaded last to clean off the blades in the mixing. The charging Shrink Mixing of solids into a mixer should be started with the coarse Early in the development of the ready-mixed concrete industry. and the front discharge ribboned with the solids.5 m3) mixers. All truck mixers that have a transported in a revolving drum truck mixer. The requirements of ASTM C 94/C 94M for truck mixers 3. (DOTs) permit 60 or 90 s mixing time in central mixers. The cementitious materials should be ribboned with ing to optimize production cycle times by using a shorter pe. . day’s 9 to 11 yd3 (7 to 8. This also reduces wear in the truck mixers. ter into the drum for mixing. With a rear discharge unit. Ribbon Loading. they demonstrated that 45 to dards of the Truck Mixer Manufacturers Bureau (TMMB) [54] 90 s mixing times were feasible if care was taken to blend or establishes minimum and maximum gross volume require- ribbon-load all ingredients as they entered the mixer. The Stan- drum central mixers. bic yard. if any. This loading the truck weight laws of the various states. Attempting to ribbon all materials simul- criteria are met after shorter periods. for a minute or so and then the aggregates are added. loading sequences to ensure uniform mixing in truck of 63 % of gross drum volume for concrete mixing [54]. Front discharge units tend to have much larger gross drum crete is mixed at the job site. The result is that the manufacturer’s rated mixing ca- (FHWA) [52. plants designed to keep cement essentially dry until the con. Because of weight laws only a small percentage of pro. volumes than rear discharge units to allow for the cylindrical pering water can be avoided [51. The specific loading and mixing procedures slump concrete for slip formed and paving applications are vary with the particular slurry mixer used. mixers must not attempt to achieve uniform ribbon loading or ASTM C 94/C 94M requires revolution counters on truck blending of ingredients. the Federal Highway Administration concrete. With special loading sequences in truck mixing deliver concrete at a slump higher than about 4 in.53] conducted mixing efficiency tests of tilting pacity may be less than half the gross drum volume. About 25 % of the added water is batched as the last ingredient either from the plant or the Truck Mixing rear nozzle from the truck water tank. the concrete will be maximum limits are not applicable. even in hilly areas. rear discharge unit. Slurry Mixing. A large number of central mix plants use shrink mix. added water is incorporated prior to the solids and portions day: the traditional rear discharge unit. The charging sequence mixer. This minimum can be reduced if mixing uniformity 1. The other today the angle of inclination of the drum to the horizontal is type of slurry mixing is a process where a slurry is mixed less and few. discharge end. follows procedures similar to ribbon loadings for aggre- Many contractors prefer front discharge units because the gate except adding a higher percentage of coarse aggre- truck driver can drive into the job with little direction from gate up front. The im. ments for standard rated sizes of rear discharge truck mixers. it tends to be a somewhat more expensive unit than a strength after adequate mixing. slurry. but with several modifications it is preferred and most often used. can carry 80 % of the gross drum volume in a separate high energy mixer in the plant with the slurry without spilling. LOBO AND GAYNOR ON READY-MIXED CONCRETE 541 somewhat greater flexibility when long deliveries are required especially sensitive to spilling concrete when they are used to in rural areas. the mixer can 2. The charging procedure is sensitive to the contractor personnel.52]. section to clear over and past the truck cab and to avoid spilling In the mid-1960s. Generally. aggregate to ensure that about 10 % of the required weight shrink mixing was designed to permit hauling a larger batch in enters into the head of the drum. this procedure will always eliminate cement balls. Because the front discharge unit requires a special truck the solids into the mixer and ensures uniform slump and chassis. especially in hilly areas. taneously should not be done. (100 mm).5 m3) capacity. Today there are two types of slurry mixing. Al- The extra carrying capacity of central mixed concrete is though there is often insufficient water to make a true much less of a consideration with present weight laws and to. When units were only 5 This procedure slows down the loading process and tends or 6 yd3 (4 to 4. 4. within the limits set by the max. Two distinct samples are taken after discharging concrete temperature is less than about 70°F (21°C) [59]. The specification requires 30 revolutions at mixing speed Cement balls consist of cement. ers are not equipped to mix at speeds higher than about 20 rpm. only when water is not added [51. At least 30 revolutions are required at mixing the job.542 TESTS AND PROPERTIES OF CONCRETE “Cement balls” and “sand streaks” are sometimes a prob. The ASTM specifications recognize that many of the re- justment. tent on a preliminary sample before a significant quantity is imum w/cm ratio. These adjustments can add up towards the limits of time and ally shipped from the plant at a slump less than the specified total number of revolutions. concrete is gener. streaks of sand during discharge and could be related to the in. Concretes with slumps over 6 in.55]. However. slump loss is less of a problem and the admixture is added at mance for the production facility [46]. With the carboxylate-based HRWR admixtures. re- ASTM C 94/C 94M recognizes that concrete loses slump with sulting in an increase of the mixing water requirement. the higher temperatures. ing procedure can be found to avoid them without going to The specifications further require that discharge be com- slurry mixing. speed to incorporate these additions into the concrete mixture. the required range at the job site. the plant to a higher slump such that the desired slump is in Generally. The literature on this issue is exten.55–58]. particu. However. Because of the difficulty of measuring aggregate mois. could be used as long as the slump was acceptable for place- 2. the effect will be to decrease slump. engines and had only one basic drum speed. ment and no water was added. properties of the cementitious materials. maximum with some water held back to allow for a job site ad. water can be added only once on arrival at discharged. not get mixed until some of the concrete has been discharged. ture and inevitable traffic or job site delays. including con. and coarse aggregate. to ensure incorporation of the water. The rate at which slump many years ago when mixers were powered by separate mixer is lost depends on a great number of factors. At approximately 15 and 85 % of the load. sand. Both can be waived by the purchaser if the concrete can be ternal condition of the mixer. routinely necessary. placed without the addition of water. Many modern day mix- ment factors are more prone to cement balls but usually a load. and strate that concrete strengths tend to improve with time. about 6 rpm. The 300 revolution limit can be a problem with longer Slump tests of samples taken after the discharge of 15 and haul distances and job site adjustments that require subse- 85 % of the load can be made as a quick test of the probable quent mixing. if mixing is at 22 to 25 rpm as few as 5 the desired level. In the past. or 10 revolutions will be sufficient [58]. initial tempering to obtain the desired slump is pre-job conference [10]. keeping within the 300 revolution degree of mixing uniformity. air-free unit weight of concrete. and if slump loss enough to affect mixing uniformity. The “one” addition of water permitted in lem in truck mixers with the traditional ribbon and cement-last ASTM C 94/C 94M should not be taken too strictly and the loadings. by the ASTM Subcommittee. C 94/C 94M also requires mixers limit was a problem with addition of high range water reduc- to be examined or weighed routinely to detect accumulations ing admixture at the job site. This was done because the older of hardened concrete. whichever comes first. the 90-min time limit is too conservative when the the six tests. It is important to note and recognize that the accuracy of larly with moderately low slump concrete. Repeated tempering or retempering. Acceptable performance requires compliance with five of Clearly. Generally what happens is that the sand charging is driver should be permitted to adjust the amount added over a started too early. slump. With soft aggregates that are subject to grinding. 7-day compressive strength. Both field and laboratory data demon- 5. Sand is the passage of time and that either water will have to be added more subject to grinding than coarse aggregate because of its to restore slump or the slump on initial mixing will have to be large surface area. it should have been. should not be permitted. ments for water and air by determining slump and/or air con- Under ASTM C 94/C 94M. that is a requirement for obtaining a Certification of Confor. Tests by NRMCA confirm They can usually be ground up by mixing concrete with a that the 30 revolutions are necessary if mixing is at less than slump of 3 in. air content. For central mixers. coarse aggregate content. discharge performance is a problem a small water addition at the job site will be suffi- will also have deteriorated enough to be noticeable. specifier. with high ce. pleted within 90 min after the cement is wetted or before the Another sign of improper mixing is the observation of drum has completed 300 revolutions. but 6. and the admixtures used. cient. The 300 revolution limit was developed higher than that required at the job. Concrete producers also pre- cumulations of hardened concrete have become significant fer to incorporate the admixture at the plant. packs into the head end of the drum and does period of perhaps 3 to 5 min on arrival at the job site. air-free unit weight of mortar. it has been found that when blade wear or ac. Some time ago an attempt was made to allow 90 min The limits set for mixing uniformity include tests for: to the start of discharge with the provision that the concrete 1. The proposal was not accepted 3. The 90-min time limit has been one of the more controversial requirements in the speci- Mixing Uniformity Testing fication. This is the type of issue that should be discussed at a However. cannot or will not be enforced. generation of HRWR admixtures resulted in a high rate of gram has a process in place for an annual inspection of trucks slump loss. especially after quirements such as the 90-min time limit can be waived by the discharge of a significant quantity. C 94/C 94M provides for means to make job-site adjust- sive [51. in the authors’ opinion. rear portions of the load. the time limit can only be justified by a samples can be taken during discharge or directly from the concern that the prohibition against water addition. after the ad- mixer at points approximately equidistant from the front and justment on arrival at the job site. Except for a very few soft aggregates. The NRMCA Plant Certification pro. the 300 revolution Control of the Addition of Water limit is of no practical consequence. (75 mm) or less and then adjusting the slump to about 15 rpm. . The crete temperature. the slump test deteriorates at these high slump levels. limit on revolutions tended to control delivery time. an and the sample is taken as a single increment near the start of organization of equipment manufacturers. mitted if the samples are obtained after at least 1/4 yd3 (1/4 m3) mum bin capacities for rated capacity of concrete that can be has been discharged. can be added. There are about 900 accredited laboratories un- tional to cement content. Slump The program is required by the Florida Building Code and is is readily adjustable and the unit can be started and stopped as supported by the concrete industry. The procedure in ASTM C 685/C 685M produced. and for specialty applications. which will allow the measurement with the base of a certified through one of the ACI Laboratory Technician pressure air meter. concrete samples. 3. this means the sample should be taken at two or proved. Additionally. be qualified and knowledgeable in the proper conduct of the test procedures required. District of Volumetric Batching and Continuous Mixing Columbia. Local specifications and practices tories that conduct testing of construction materials include: typically address temperature criteria for concrete. NVLAP—National Voluntary Laboratory Accreditation mounted and consists of individual bins for sand.or trailer. AASHTO—American Association of State and Highway Transportation Officials in Washington. uniformity testing. In cold weather a minimum concrete tempera. has established discharge. 2004 about 110 laboratories in Florida were certified and The unit is versatile and has been used in a variety of work. Certification requirements for laboratory technicians problems with test results.06 m3) of concrete and mixing time is 15 or 20 s. The equipment is truck. ASTM C 685/C 685M. Preliminary tests of air content and slump are per- standards for volumetric concrete mixers that establish mini. The density test is considered useful for yield ratory technicians who are involved in concrete acceptance calculations and additional information in the case of testing. Program. this is seldom done The Volumetric Mixer Manufacturers Bureau (VMMB). the first portion of concrete Testing Laboratories discharged is of a more fluid consistency than the bulk of the Both ASTM C 94/C 94M and C 685/C 685M contain require. ASTM C 685/C 685M requires calibration laboratories. both where the amount of concrete is relatively limited. load and samples from this portion are more likely to have ments that the individual who samples and tests the concrete lower measured strengths. Water and admixtures are controlled with quirement for acceptance testing on transportation construc- valves and flow meters. Florida. Certification in Engineering Technologies (NICET) personnel ture requirement is imposed based on the section size and this certification programs are becoming increasingly popular. in Gaithersburg. The aggregates are delivered The AASHTO Accreditation program is probably the most through calibrated gates that control the amount of material recognized by state highway agencies and is generally a re- being delivered. tion projects. and the Florida Department of Transportation. In somewhat larger work where re. middle portion of the batch. hold the AASHTO accreditation. Maryland. LOBO AND GAYNOR ON READY-MIXED CONCRETE 543 C 94/C 94M covers concrete furnished in both cold and Certification programs. accredited by CMEC to comply with ASTM C 1077. C or slump is low. 1. when cement is the last ingredient loaded in the mixer and the concrete is not well mixed. A2LA—American Association of Laboratory Accreditation. In at six-month intervals. engineering testing concrete is needed. cement. Another popular regional vates the concrete for discharge. is repeated from ACI 306R [60]. Grade I certification. Sampling quirements are less than about 40 yd3 (30 m3) per hour. As of 2004 there were specifications. concrete. Some of the in a note that problems may be encountered as concrete tem. a retest of a new sample is required before the about 57 000 technicians currently certified under the ACI concrete is considered to have failed. C 94/C 94M does not specify a Requirements for accreditation of laboratory facilities that maximum concrete temperature in hot weather but indicates conduct acceptance testing are also increasing. The materials are fed into an inclined der the AASHTO program and all 50 state central laboratories chute that contains a mixing auger. organizations that sponsor accreditation programs for labora- peratures approach 90°F. Production rate is inversely propor. Maryland. and density tests when process. and are used to produce concrete in accordance with in Gaithersburg. Volumetric concrete mixers have been available since the 2. Mix. coarse ag. mixing uniformity evaluation on units of a similar design. except those for been used as a job-site mixing plant. . The mixing auger holds about 2 Materials Engineering Council (CMEC). The concept of requiring demonstrated knowledge of strength specimens are made. The risk is that for VMMB rating plates [61]. Sampling at a single point during discharge should be ers that meet the requirements of these standards are eligible permitted in ASTM C 94/C 94M and C 172. This requires an ACI Concrete Field Compressive Strength Testing Testing Technician. are required to be taken in accordance with The advantage of the unit is that it produces freshly mixed ASTM Practice for Sampling Freshly Mixed Concrete (C 172). If either falls outside the the test procedures has grown rapidly. The standard reflects many of the requirements of permits sampling any time after at least 2 ft3 (0. if the air Grade I Field Testing Technician program. More recently. additional air-entraining admixture or water 94/C 94M has included requirements for certification of labo. and water. The ACI and the National Institute for hot weather. slump. In 2004 there were about 3000 laboratory technicians 138M. Therefore. This section of C 94/C 94M allows are also a requirement for laboratories that conform to ASTM density tests to be conducted in accordance with C 138/C C 1077. gregate. it has Under ASTM C 94/C 94M. The auger mixes and ele. The units are available in sizes laboratory accreditation program is that of the Concrete from 4 to 12 yd3 (3 to 9 m3).” In practice. or an equivalent ASTM C 94/C 94M requires air. The units may encounter problems with false setting more regularly spaced intervals “during discharge of the cements because of the very short mixing time. More often. ft3 (0.06 m3) has C 685/C 685M and requires the manufacturers to conduct a been discharged. 1960s. strengths and other properties are im. in Orlando. the first concrete discharged can Sampling and Testing have high strength and will not be representative of the majority of the batch. Generally. 0 % in the structure and for developing information on the as- Good 2. If they do not agree. (3. expected. MPa] or less than 0. f’c.9 %. calculate the ranges strength specimens be made in accordance with ASTM Test and convert the average range to the estimated coefficient of Methods of Making and Curing Concrete Test Specimens in variation. required by the project specifications.0 % [64]. tween 15 and 30 tests. of Variation [62] NRMCA Publication 133 [66] outlines an orderly and de- Excellent Below 1. that is. The prac- Fair 3. Testing with a within-test coef. but allows 4 by 8 in. or Failure to Meet Strength Requirements A section in both specifications requires that. depending on the standard deviation ficient of variation of 4 % will have one range in three ex. discard the 2.5 % liberate process for determining the strength of the concrete Very good 1. cured under standard moist curing proce- FR dures and tested by ASTM Test Method for Compressive Cv Strength of Cylindrical Concrete Specimens (C 39). panel of three engineers. the manufacturer and purchaser confer to see if they can agree on what adjustments. other than low strength. However. handling. %.0 to 3. the writers’ opinion. for strength levels less than should be possible to obtain a within-test coefficient of varia- about 8000 psi (55 MPa). psi (MPa). this is the result of problems of capping. jobs (laboratories) can do better.544 TESTS AND PROPERTIES OF CONCRETE Both ASTM C 94/C 94M and C 685/C 685M require that 60 pairs of cylinders have been tested. or testing. 4 by 8 in. (2. The average of any three consecutive strength tests should 1. (150 by 300 mm) cylinder tests. . with correction factors for in- Table 1 can be used to evaluate cylinder testing data. is in the range of 5 % [63]. if not most. then a decision is to be made by a TABLE 1—Standards for Evaluating Perform.5 %! Improve testing. but stances where the standard deviation is calculated from be- recognize that whether a single low test is sufficiently un. This ders. What this means is that when 15. And whether or not the lower or higher test is disregarded. usual to discard the result depends on “normal” quality of the testing on that job. Here is some general guidance that is the opin.9 %. meet these requirements. Data than 3/32 in. ASTM C 31 indicates that 6 by 12 in. the Field (C 31). vised to conform to the two acceptance criteria used in the ACI sidered suspect.4 MPa) below the specified strengths up to 5000 psi [35 average the two and accept the result.0 % signment of responsibility for deficiencies. large ranges can be larger than indicated in Table 1. developed from several labs testing specimens (70 MPa). an unsuccessful attempt was made to that if you have less than 60 pairs of results. The average within-test coefficient of variation of 6 by 12 curing. If neither cylinder is unusually high or low.8865 for two cylinders. or even a little better [62].9 % or less.5907 for three cylin- specified strengths greater than about 8000 psi (55 MPa). many. size. Within. (150 by 300 mm) is the standard Cv coefficient of variation. of improper sampling. (100 by 200 mm) bonded caps. (100 by 300 mm) If the coefficient of variation is much over 2. the test should be con. Note also Several years ago. as indicated in the pre. A test is X defined as the average of results from two cylinders made where from the same sample and tested at the same age. and is because few compression testing machines are available X average strength. and the 7-day result is normal.0 to 4. An arbitration process is preferred ance of Testing Using Within Test Coefficient and recommended as the first course of action.0 % tice suggests that if the cause of the low strength was im- Poor Above 4 % proper testing. curing. if the concrete was properly tested. with load capacities greater than 300 000 lb (1335 kN). the party responsible should bear the cost of the investigation. C 1231. If the range between two cylinders exceeds 8 or 9 % of In 2005 ASTM C 94/C 94M and C 685/C 685M will be re- their average more than 1 time in 20. should be made. and testing these concretes. Increasingly. realize that cylinder. of this concrete. is now permitted for concrete strengths cylinders is in the range of 3. Neat cement caps are an option and often ground made from the same batch. if any. up to 12 000 psi (80 MPa). it in. or greater that value. F factor used to estimate standard deviation from average (100 by 200 mm) cylinders are being used for concretes with range: 0. Use of un- test coefficient of variation of 4 by 8 in. consider the possibility that the sampling and testing may A table provides advice on the “over-design” needed to be poor (see Table 1 [62]).” A proposal was made to set a limit There is some concern that the within-test coefficient of on the range of pairs of cylinders that are averaged for a test variation may be larger for very high strength concretes. No individual strength test should be more than 500 psi lower result. (100 by 200 mm) specimens when R average range. the ranges in Table 1 would be about 10 % larger inite evidence. the frequency of modify the section of ASTM C 94/C 94M that required dis. tions given in ACI 318–02 [14]. 318 building code: ion of the authors: 1. 30. With only carding the result of a test of a single cylinder if it “shows def. With careful attention.5 to 2.4 mm) thick and probably should not be per- has shown that the multilab coefficient of variation of strength mitted on concrete with strength greater than about 10 000 psi test results. 0. 10 600 psi (73 MPa) on a 6 by 12 in. sulfur mortar caps must be less cision statement of ASTM C39. tion of 2. if any. ends are not sufficiently flat to give optimum results. [65]. ten results. If the higher of the two values is more like the other tests be equal to or greater than the specified strength.90 fc for specified strengths equal to 2. The values given have been calculated from the equa- ceeding 5. but in and permit discarding the low value. is about 2. Silver Spring. The ready-mixed industry has made great strides to- ASTM STP 169C.census. May 1975. 16 June 1975. Farmington Hills. Maryland.” Cement and Concrete Research. data). No. MI. control personnel. and middle and upper management. P. Many of crete. July 1977.. 29 Oct. p. 18 pp. F. [10] “Checklist for Concrete Pre-Construction Conference” and There are new challenges on the regulatory front that “Checklist for Ordering and Scheduling Ready-Mixed Con- changes the way the concrete industry can function.” Significance of Tests Highway Quality and the FHWA “Highways for LIFE” Pro- and Properties of Concrete and Concrete-Making Materials.org. and Slimak.. “Spending ity for certain aspects of projects. There is a strong desire of the more technically competent 22. quality America..” Paul Klieger Symposium on sis on performance while eliminating prescriptive limits. 5. 318-02) and Commentary (ACI 318R-02). 249. M. both small and large. B. Silver Spring. 74. http://www. PA. 2004.. DC. [19] Barton. things will change greatly. p. 75–77. 7. “Re-use of Wash Water as Mixing Water.usgs. sales force. p.” ACI Concrete International. wards the goal of higher level of quality and this commitment 1994. C. p. 1980. To the extent that [12] “Standard Specifications for Tolerances for Concrete Construc- innovations have been developed.” Journal. Construction defect litigation has [16] AASHTO T 318 “Test Method for Water Content of Freshly Mixed Concrete Using Microwave Oven Drying. www. 30 March 1973. MD. reuse of returned concrete and wash water. D. Silver Spring. p. the specifications have not tion and Materials (ACI 117-90). A significant aspect in the future is the focus on Farmington Hills.” Minerals Yearbook—Cement. National Ready Mixed Concrete American Concrete Institute. sustainable and “green” construction. Sustainability not only includes recycling but also conservation [14] “Building Code Requirements for Reinforced Concrete (ACI of energy and resources and prolonged service life.. Washington. pp. that the producer is confident that the prod. West more detailed discussion of ASTM C 94/C 94M that analyzes Conshohocken. This has also Sampling and Testing. Vol. MD. plant operators. Quality of Mixing Water. R.gov/minerals. pp. pp. tion. 1999. MD.” recognition that an effective means of promoting the increased Concrete Products. National Ready Mixed Concrete quality focus has been emphasized from the federal and state Association. This refer- can Concrete Institute.” CIP 8 Concrete In Practice.” North American Industry [24] Meininger. pp.” Back [1] Cement and Concrete Terminology. naics. R. Silver Spring. Peterson. 72-1. concrete producers and contractors. S. June 1991. Silver Spring. Concrete Dollars Effectively.09 Methods of Testing and Specifications In 2005. Farmington Hills. Ready Mix Firms. References [23] Ullman. p. The future of concrete con. 511–521.. “How to Make Concrete that Will Be Immune to the evolve construction specifications to achieve a higher empha. resulted in a reluctance by some entities to accept responsibil- [17] Bognacki. B.” unpublished memorandum to ASTM struction will only get better with these initiatives in place.. ACI especially when they create conflicts in specifications or cause Convention.. Marsano. MI 1991. 281–287.. 1–24. Bureau of Ready-Mixed Concrete.” Standard developed a high level of caution and conservatism within the Specifications for Transportation Materials and Methods of construction industry and this stifles innovation..03. Vol. Towards that end the industry has increased [9] “Joint Statement of Responsibilities. MI. Spring.nrmca. Silver Spring. p. “Ready Mixed Concrete. 2004. Subcommittee C09. Geologi- cal Survey. N. Association. LOBO AND GAYNOR ON READY-MIXED CONCRETE 545 Closure [3] Pictorial History of the Ready-Mixed Concrete Industry.. 23rd Edition. Effects of Freezing and Thawing. 30 March 1973. 1989.er. J. September 2000. 9. ASTM International and NRMCA published a for Ready Mixed Concrete. “C 94/C 94M and C 685/C 685M Requirements for acceptance of responsibilities. The [5] NRMCA Industry Fact Sheet. J. “Waste Treatment and Disposal Costs for the Ready-Mixed Concrete Industry. Department of Commerce. 27–29. 50–56. National environmental management that facilitates the processing and Ready-Mixed Concrete Association.” American Concrete Institute. MD. [22] Pistilli. MD. not just the [4] “Cement in 2004. ence will be of interest to readers of this chapter. . M. National Ready-Mixed Concrete Association. 7. Maryland. “Properties and Possible Recycling of Solid Waste from Ready-Mixed Concrete. 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Volumetric Mixer Manufac.” of Strength Test Results of Concrete. 1999. Spring.” American Publication 133-99. 1991. Cylinders from ASTM International. cation C 94/C 94M on Ready-Mixed Concrete. MD. [64] “Report of Within Test Precision of 4 8 in. 2004. ADA058262. NTIS Document Acquisition No. U. Silver International RR: C09-1027.. MD. Standards..vmmb. L. Vol. Air Force. MD. Silver Spring. p. 214. 2004. 1970. These concretes use of foaming-type agents. or sanded insulating lightweight aggre- Structural gate mixtures. where lighter weight is developed pri. most light- structural properties of lightweight aggregates. clude pumice and scoria types. Compressive strengths from made from pyroprocessed shales. ASTM the sintering process wherein a bed of raw materials including 169A and ASTM 169B were authored by D. Lewis. Ries1 Preface (2500 psi). sity as determined by ASTM Test Method for Determining Den. Bulk density. Specified density concrete. and placement characteristics of densities between 1760 to 1840 kg/m3 (110 and 115 lb/ft3). finite resources of quality natural sands. sistance ranging between insulating and structural concrete. Davis and J. In ASTM STP 169 cylinder lined with refractory materials similar to cement kilns).4 MPa (100 to 500 psi). thermal resistance is high. slates. Naturally occurring als brought about by internal curing when using water. Structural/Insulating weight aggregates. durability. lite.4 to 17 MPa (500 to 2500 psi) are common with thermal re- expanded fly ash. as well as weight aggregate concrete used in structures have equilibrium strength making. ASTM fuel is carried by a traveling grate under ignition hoods. slates. Salt Lake City. 3. W. lightweight aggregates are mined from volcanic deposits that in- entraining lightweight aggregates. and gravels. 1 Director of Engineering and President. soft shales and clays that structural/insulating. with additional information on 1450 to 1920 kg/m3 (90 to 120 lb/ft3) are often used. Pyroprocessing methods include concrete with densities between traditional lightweight and the rotary kiln process (a long.2 MPa strength range from about 0. seldom exceeding 800 kg/m3 (50 lb/ft3). This is a definition. E. 548 . lightweight concrete to reflect the current state of the art. No single description of raw material processing is all- Classification of Lightweight Aggregates inclusive and the reader is urged to consult the lightweight and Lightweight Aggregate Concretes aggregate manufacturer for physical and mechanical properties of the aggregates and the concretes made with them. stones. or blast furnace slags. slowly rotating. respectively. em- gates (C 330) and the Standard Building Code for Reinforced ployed primarily for high thermal resistance. clays. expanded slags. With low densities. have limited structural applications in their natural state. for example. or they may incorporate both structural and in- Structural lightweight concretes generally contain aggregates sulating lightweight aggregates. from raw materials such as. fly ashes. W. Insulating concretes are very light nonstructural concretes. this chapter was authored by R. and the 169C was authored by T. Holm. and compressive strength ranges normally associated an environmentally sound practice as it minimizes demands on with each class of concrete are summarized in Table 1.46 Lightweight Concrete and Aggregates Thomas A. The 318 code definition is structural low-density low-strength aggregates such as vermiculite and per- concrete made with lightweight aggregate. clays. is also discussed. and insulating. UT 84117. A. Kelly. dynamics and the enhanced hydration of cementitious materi. This is ductivity. Lightweight aggregate concretes are broadly divided into three Structural lightweight aggregates can be manufactured groups based upon their use and physical properties: structural. thermal con. Expanded Shale Clay and Slate Institute. Al- THE GENERAL PRESENTATION OF THIS EDITION IS though structural concrete with equilibrium densities from similar to previous editions. quire compressive strengths and densities in the intermediate marily by inclusion of large amounts of air or gas through the between structural and insulating concretes. may be produced with high air contents and include structural lightweight aggregate. that incorporate Concrete (ACI 318) [1]. rapid agitation of molten slag with controlled amounts of air or water. canic sources. Cellular concrete is covered in a separate Industrial applications that call for “fill” concretes often re- chapter in this volume.69 to 3. nearly horizontal normal-weight concretes. This chapter primarily addresses structural concretes where weight reduction is achieved through the use of light. the equilibrium den. These concretes are not intended to sity of Structural Lightweight Concrete (C 567) not exceeding be exposed to weather and generally have a compressive 115 lb/ft3 and the compressive strength is more than 17. Holm1 and John P. and those mined from natural porous vol. not a specification and project requirements may permit higher equilibrium densities. This Virtually all manufactured structural lightweight aggre- edition also includes new discussions relative to the moisture gates are produced from raw materials including suitable shales. Structural lightweight concrete is normally classified by a minimum compressive strength that was jointly Insulating established by the ASTM Specification for Lightweight Aggre. The cellular structure within the particles listed in ASTM (C 330) and ASTM Specification for Lightweight is normally developed by heating certain raw materials to in. Aggregates for Concrete Masonry Units (C 331). as well as strength 24 MPa (3500 psi). W.43) (3. ASTM Stan- cipient fusion. the particles. and moisture content. cement content requirements. lightweight aggregates exhibit considerable differences in particle shape and texture. or irregular.22) or insulating C 332 at equilibrium (1. relatively smooth skins to highly irregular surfaces with large exposed pores.22) (1. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 549 TABLE 1—Lightweight Aggregate Concrete Classified According to Use and Physical Propertiesa Type of Lightweight Typical Range of Typical Range of Class of Lightweight Aggregate Used in Lightweight Concrete Typical Range of Thermal Aggregate Concrete Concrete Density Compressive Strength Conductivities Structural Structural-grade C 330 1440 to 1840 (90 to 115) 17 ( 2500) not specified in C 330 at equilibrium Structural/Insulating Either structural C 330 800 to 1440 (50 to 90) 3.00) or a combination of oven dry C 330 and C 332 Insulating Insulating-grade C 332 240 to 800 (15 to 50) 0.50) oven dry a Densities are in kg/m3 (lb/ft3). Annapolis.000040 in. size. as well as other physical properties. The relative density of the pore-free vitreous material may be determined by pulverizing the lightweight aggregate in a jar mill and then following procedures used for determination of the relative density of cement.4 (100 to 500) C 332 from (0. high-strength vitreous matrix (Fig. as well as the pores from 30-year-old bridge deck. rodded).50) to (0. Shapes may be cubical. Particle shape and surface texture directly influence workability. P.065) oven dry (0. vibrated. density 1680 kg/m3 (105 lb/ft3). and varies not only for different materials. Particle Shape and Surface Texture Depending on the source and the method of production. Bulk density is a function of particle over the Chesapeake Bay. weak particles formly distributed system of pores that have a size range of ap. The relationship between proximately 5 to 300 m (0. Fig. rounded. density. durable./h ft2 °F). and water demand in concrete mixtures. perlite and vermiculite to limit over-expanded. Strong. lightweight aggregates contain a uni. . Properties of Lightweight Aggregate the method of packing the material (loose. coarse-to-fine aggregate ratio. 2 for a hypothetical lightweight aggregate. and thermal conductivity in W/m °K (Btu in. compressive strengths in MPa (psi). This volume includes the pores within the particles but does not include the voids between the particles. illustrated in Fig.7 to 3. at which temperature gases are evolved within dard Specification for Lightweight Aggregates for Insulating the pyroplastic mass causing expansion that is retained upon Concrete (C 332) provides minimum density requirements for cooling. Lane Memorial Bridge within.) and which are developed the particle relative density and the bulk density of a sample is in a relatively crack-free. 1).45) to (0. Relative Density The relative density of an aggregate is the ratio between the mass of the material and the volume occupied by the individual particles contained in that sample. gradings. but for different Internal Structure of Lightweight Aggregates sizes and gradations of a particular material. Bulk Density Aggregate bulk density is defined as the ratio of the mass of a given quantity of material and the total volume occupied by it. that would break down in mixing. Textures may range from fine pore. Maryland: compression shape. Table 2 summa- Lightweight aggregates have a low particle density because of rizes the maximum bulk density for lightweight aggregates the cellular structure.4 to 17 (500 to 2500) C 332 from (0. and generally increases when particle size decreases. angular. 1—Contact zone—structural lightweight concrete This volume includes the voids between. Relative density of individual particles depends both on the relative density of the poreless vitreous material and the pore volume within the particles. ... standards are established by weights passing each sieve size.5) Vermiculite 160 (10) 88 (5. coarse aggregate 880 (55) .. coarse aggregate 880 (55) .. weight aggregate particle size distribution permits a higher ideal formulations are developed through volumetric weight through smaller sieves. This modification recognizes considerations...550 TESTS AND PROPERTIES OF CONCRETE TABLE 2—Requirements of ASTM C 330.. Fig. interparticle voids. combined fine and coarse 1040 (65) .5) Group 2 fine aggregate 1120 (70) . aggregate ASTM C 332 Group 1 Perlite 196 (12) 120 (7... and internal particle pores. C 331.. combined fine and coarse 1040 (65) . and that while for normal-weight aggregate with the exception that light. aggregate Grading the increase in relative density typical for the smaller Grading requirements are generally similar to those provided particles of most lightweight aggregates.. 2—Schematic representation of lightweight aggregate bulk volume. . and C 332 for Dry Loose Bulk Density of Lightweight Aggregates Maximum Dry Loose Minimum Dry Loose Bulk Density Bulk Density Aggregate Size and Group kg/m3 (lb/ft3) kg/m3 (lb/ft3) ASTM C 330 and C 331 fine aggregate 1120 (70) . particularly those close to 35 % of the theoretical total saturation of all pores for Fig. aggregate will be so low that the partially saturated particle mal-weight aggregates generally absorb less than 2 %. absorbtion can be divided into several regions. In- mediate. 3—Absorption vs. mixing water. Relative Density and Absorption of Fine Ag. and fill within the first few hours of exposure to moisture. the rate of weight aggregates it is primarily adsorbed. proper aggregate combinations to meet fresh concrete density Internally absorbed water within the particle is not imme- specifications and equilibrium density for dead load design diately available for chemical interaction with cement and considerations. Pores close to the surface are readily permeable materials in several standard sizes that include coarse. Recognition of this essential difference is important in mixture Following the prescribed procedures. the rate of moisture absorption into the lightweight more than 25 % by weight of dry aggregate. By combining size fractions or by terior pores. 3. fill slowly. and field control. however. and fine gradings. surface moisture. rated” particle density in a pycnometer and then determining Based upon a 24-h absorption test. Due to their porous structure. As can be seen in Fig. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 551 Structural lightweight aggregate producers normally stock to the surface. By contrast. Rate of absorption tion. clay. connection. A fraction of the interior pores are essen- sand. After the tents is that with lightweight aggregates the moisture is largely moisture content is known. . be directly computed. The tially non-interconnected and remain unfilled after years of aggregate producer is the best source of information for the immersion. the fractional part of the pore volume occupied by of lightweight aggregates is dependent on the characteristics of water. a wide range of concrete densities may be obtained. or slate (ESCS). lightweight aggregates will absorb from 5 to water. the degree of satura- proportioning. that is. nor. and distribution. batching. with many months of sub- replacing some or all of the fine fraction with a normal-weight mersion necessary. sary to take weight measurements in the pycnometer. conducted in accordance the absorbed moisture content on the sample that had been im- with the procedures of ASTM Test Method Specific Gravity and mersed in water for 24 h. the over-dry particle density may absorbed into the interior of the particles whereas in normal. inter. With lightweight aggregate it is more Absorption of Coarse Aggregate (C 127) and ASTM Test accurate to report partially saturated after a 24-h soak because Method Density. time for typical structural grade expanded shale. The im. will generally be in the range of approximately 25 pore size. After a 24-h immersion in gregate (C 128). density will be essentially unchanged during the time neces- portant difference in measurements of stockpile moisture con. but is extremely beneficial in maintaining longer periods of curing essential to improvements in the hydration Absorption Characteristics of cement and the aggregate/matrix contact zone. the particle is not fully saturated yet. lightweight aggregates absorb ASTM C 127 procedures prescribe measuring the “satu- more water than their normal-weight aggregate counterparts. water-to-cementitious materials ratio. Proportioning Lightweight Concrete Due to pre-wetting. is then determined by the difference between the as-received ration necessary for adequate pumping is determined by prac. The degree of satu. and. To accurately determine the amount of absorbed water From a practical perspective and considering the fact that and the amount of surface water it is necessary to run the most lightweight concrete is placed by pumping. and the absorbed moisture contents. inappropriate. practice is to batch the lightweight aggregate at a moisture con. 4) tical field experience for each aggregate and may be obtained from the lightweight aggregate supplier. the usual usual moisture test as follows. ready-to-batch surface moist sample. After towel drying. the internal pores. therefore. Conduct the drying procedures (24-h immersion). (Fig. 4—Schematic representation of volumes occupied by the ceramic matrix. and the degree of saturation of absorbed water (see Fig. meas- dition greater than the “Absorption Value” defined by ASTM ure the weight of the surface dry sample. 2). there will invariably be a film of surface water on the lightweight aggregate. . for an accurate determination of the “net” mixing water to sion “saturated surface dry” for lightweight aggregates is achieve the desired workability and to determine the effective theoretically inaccurate. The surface water (adsorbed) on the lightweight aggregate defined ASTM 24-hour “absorption” value. As with normal-weight Proportioning procedures used for ordinary concrete mixes concrete it is essential to evaluate this quantity of surface water apply to lightweight concrete with added attention given to Fig. In this condition the absorbed test to calculate the moisture content absorbed within the sam- (internal) moisture content will be in excess of the arbitrarily ple.552 TESTS AND PROPERTIES OF CONCRETE structural lightweight aggregates. Measure the weight of the wet. The use of the ASTM expres. analytically misleading. the rate of further absorption will be very to unfavorable ambient conditions and poor curing practices. this practice serves to drive the heavier mortar fraction down Proportioning by this method requires the determination of from the surface where it is required for finishing. gregate suppliers should be consulted for mixture proportion Air content of lightweight aggregate concretes is deter. It is essential to consult the aggregate supplier on methods and duration of prewetting. un- intended consequence of high strength concrete is early-age Admixtures cracking. it is essential to properly prewet the lightweight used for calculating the water-to-cementitious materials ratio at aggregates prior to pumping. stockpile with sprinkler systems. Prewetting is often done at the the time of setting. High cementitious concretes are vul- to the influence of aggregate porosity. With 4 to Prewetting will result in an increased relative aggregate density 6 % air contents. moisture available from the slowly released reservoir of ab- weight concretes. in turn. Because of the elastic compatibility of out of the concrete. The basic principles required to secure available for internal curing has been known for more than a well-placed concrete also apply to lightweight concrete: four decades. or experience has shown that high strength concrete is not nec- for lowering density of semi-structural “fill” concrete. . The mixing water requirements are lowered while maintaining higher water content due to prewetting will eventually diffuse optimum workability. aggregate production plant and continued at the concrete for internal curing and the continued cement hydration after plant or can be done entirely at the concrete plant by wetting external curing has ended. Lightweight When lightweight aggregates have been preconditioned to concretes batched with pre-wet aggregates carry their own in- levels of absorbed moisture greater than that developed after a ternal water supply for curing and as a result are more forgiving one-day immersion. nerable to self-desiccation and early-age cracking. lightweight concrete can meet Prewetting water-to-cementitious materials specification requirements Lightweight aggregates may absorb part of the mixing water with the same facility as normal-weight concrete. however. when exposed to increased pumping pressures. minimizing water transfer from the concrete significantly improves durability and resistance to mortar fraction that. workable mixes that use a minimum strength gains made possible by the use of saturated normal- amount of mixing water. This process is often density of lightweight concrete. concrete need not necessarily be high strength. Time-dependent improvement in the quality of concrete Mixing. and improves workability. retarders. as volumes of cement. Standard Practice for Selecting (c) proper consolidation in the forms. high volumes of supplementary cementitious materials that superplasticizers. weight concrete should begin as soon as possible. the lightweight aggregate. Field tions are frequently developed for high thermal resistance. and benefit Air contents higher than required for durability considera. causes slump loss during pumping. while effective. This absorbed water is available. The reason is Properly proportioned structural lightweight concrete can be better hydration of the cementitious materials provided by mixed. Standard Test water may be substituted for normal-weight aggregates to pro- Method for Air Content of Freshly Mixed Concrete by the vide “internal curing” in concrete containing a high volume of Pressure Method (ASTM C 231). Excessive vibration should be avoided. delivered. referred to as water entrainment. recommendations necessary for consistent pumpability. and entrained air. Volumetric measurements assure Lightweight aggregate batched at a high degree of absorbed reliable results while the pressure method. The any type of concrete is to avoid segregation of coarse aggregate fact that absorbed moisture in the lightweight aggregate is from the mortar fraction. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 553 concrete density and the water absorption characteristics of (b) equipment capable of expeditiously moving the concrete. curing operations similar to normal- relative density factor. strength reduc. bleeding and segregation are reduced and factor that. Air Content Prewetting will significantly reduce the lightweight aggre- As with normal-weight concrete. will provide erratic data due cementitious materials. The most important consideration in handling sorbed water within the pores of the lightweight aggregate. however. and Curing containing prewet lightweight aggregate is greater than that of concrete containing normal-weight aggregate. On comple- absorbed and surface moisture contents and the aggregate’s tion of final finishing. Placing. Blending lightweight aggregate containing absorbed Use of water reducers. net water. ACI 211. aggregates. and Proportions for Structural Lightweight Concrete. significantly from the slowly released internal moisture. in turn. developing a longer period of internal cur- the lightweight aggregate and mortar matrix. density than that associated with normal-weight concretes. low and the water-to-cementitious materials ratios can be established with precision. and superplasticizers will water is significantly helpful for concretes made with a low ra- result in improved lightweight concrete characteristics in a tio of water-to-cementitious material or concretes containing manner similar to that of normal-weight concretes. will slightly increase the are sensitive to curing procedures.2. mined in accordance with the procedures of ASTM Test Method for Air Content of Freshly Mixed Concrete by the Internal Curing Volumetric Method (C 173). A frequent. To avoid loss sorbed within the lightweight aggregate prior to mixing is not of workability. Structural lightweight concretes are generally proportioned Well-proportioned structural lightweight concretes can be by absolute volume methods in which the fresh concrete placed and screeded with less physical effort than that required produced is considered equal to the sum of the absolute for ordinary concrete. (d) quality workmanship in finishing. develops higher fresh concrete density. Thus. Ag- tural lightweight concrete than for normal-weight concretes. Water ab. scaling. The first documentation of improved long term (a) well-proportioned. reduces density. weight aggregates was reported in 1957 by Paul Klieger [2]. with essarily high performance concrete and that high performance reduced compressive strength as a natural consequence. air-entrained lightweight gates’ rate of absorption. and placed with the same equipment as normal. ing as well as a larger differential between fresh and equilibrium tion penalties due to high air contents will be lower for struc. Specified Density Concrete ASTM C 138. tion of permeability that develops from a significant extension usual commercial practice in North America is to design light- in the time of curing. lightweight concretes were the same as commonly used for tion and pozzolanic activity at the interface. should be based upon the calculated equilibrium density that. calcined shales. is a function of ambient con- when supplementary cementitious materials (silica fume. from 32 to 96 kg/m3 (2 to 6 lb/ft3). Holm reported on lightweight aggregate for concrete masonry units. the dead loads used for design hydrates is contingent upon the availability of moisture. equilibrium density of structural lightweight concrete. Carlson long-term service performance of lightweight concrete.554 TESTS AND PROPERTIES OF CONCRETE who. Bloem [3] states. is typical [9]. the lightweight aggregate and the matrix. air content should not vary more than 1. curing and autogenous shrinkage have been published. Structural Lightweight Concrete.1 lb/ft3) above oven- Changes in lightweight aggregate moisture content. exposed to unfavorable drying conditions [10]. When sociation. Their Comprehensive information detailing the properties of light- tests confirmed that availability of absorbed moisture in light. The Although there are numerous structural applications for all principal contribution of internal curing results in the reduc. The fresh density of lightweight aggregate concretes is a dressing the role of water entrainment’s influence on internal function of mixture proportions. Sampling should be conducted in accordance with water in lightweight aggregates for extended internal curing. This would tend to support the suggestion properties. “Concrete Strength Measurement— ASTM Test Method for Density of Structural Lightweight Con- Cores vs. as well as usual job site variation in entrained the constituents of the batch of concrete are known. To avoid adverse effects on durability. concrete will increase equi- adequate volume of prewet lightweight aggregate has also librium density. metokaolin. The improved qual. clays and slates. which from some com. commented in detail on the role of absorbed fication. weight aggregate. The benefits of internal curing go far beyond any improvements in long-term strength gain. When weights and moisture contents of all relative density. 5). ASTM C 143.” presented to the National Sand and crete (C 567) describes methods for calculating the in-service. The first two deal with structural-grade concretes. “Measured strength for lightweight variations in fresh density exceed 4 lb/ft3. and entrained-air content. Since 1995 a large number of papers ad. 10 lb/ft3). an adjustment in concrete cylinders was not reduced by simulated field curing batch weights may be required to restore specified concrete methods employed. Density binations of materials may be minimal or nonexistent. Holm [12]. and that the high absorption of lightweight aggregate may have the workability.5 % from beneficial effect of supplying curing water internally. Reduced sen. ASTM C 173 are used The use of specified density concrete is based on engineers’ de- to verify conformance of field concretes with the project speci. In his 1965 report. Normal-weight sand replacement will typically in- concrete possible with the addition of lightweight aggregate crease unit weight from about 80 to more than 160 kg/m3 (5 to containing high volumes of absorbed moisture. Using increasing amounts of cement to obtain high sitivity to poor curing conditions in concretes containing an strengths above 35 MPa (5000 psi). Extensive tests reported in ACI 213. ASTM C 567. and reduction in normal-weight concretes. and Valore less sensitive to poor field curing conditions. been reported [8]. In limited cases. ASTM Practice Sampling Freshly Mixed Concrete (C 172). or dry density (Fig. Properties of Lightweight Concrete cured exposed slabs with test results obtained from laboratory specimens cured strictly in accordance with ASTM C 31. Addi.” This was target values. ash. fly ditions and surface area/volume ratio of the concrete element. cisions to improve structural efficiency by optimizing concrete . It for lightweight concrete. In most instances. suggest frequent checks of the fresh concrete to facilitate proximate calculated equilibrium density may be determined. as well as the Design professionals should specify a maximum fresh density fines of lightweight aggregate) are included in the mixture. plemental natural sand volumes) have provided long-term dura- It appears that in 1991. alumina-silicates with calcium hydroxide liberated as cement Unless otherwise specified. demonstrated that despite wide Sampling and Field Adjustments initial variations of aggregate moisture content. acteristics were developed. strength. Powers [6] showed that extending the weight concretes where part or all of the fine aggregate used is time of curing increased the volume of cementitious products natural sand. different proce- stress concentrations resulting from elastic compatibility of the dures particularly suited to measure lightweight concrete char- concrete constituents. Philleo [7] was the first to recog. in addition. conducted during North American durability studies. tionally. as limits for acceptability should be is well known that the pozzolanic reaction of finely divided controlled at time of placement. grading. bility and structural efficiency by increasing the density/strength nize the potential benefits to high performance normal-weight ratios [15]. confirmed by Campbell and Tobin [4] in their comprehensive program which compared strengths of cores taken from field. in turn. an ap- air. test procedures for measuring properties of ity was attributed to internal curing. Long-span bridges using concretes with three-way formed which caused the capillaries to become segmented and blends (coarse and fine lightweight aggregates and small sup- discontinuous. internal curing provided by absorbed water minimizes for most conditions and structural members. lightweight concretes (coarse and fine lightweight aggregate). weight concretes and lightweight aggregates has been pub- weight aggregate produced a more forgiving concrete that was lished by Shideler [11]. fresh density. and better cement hydra. air contents. Standardized field tests for slump. of and the relative density and moisture content of the light- which Bentz et al. may be assumed the “plastic” (early) shrinkage due to rapid drying of concretes to be reached after 90 days. water demand. Carlson [13]. [5] cited the improved integrity of the contact zone between and Valore covered both structural and insulating concretes. adjustments necessary for consistent concrete characteristics. Gravel Association and the National Ready Mixed Concrete As. Cylinders. Addressing the [14]. equilibrium density was found to be about 50 kg/m3 (3. Decrease in density of exposed concrete is The benefits of internal curing are increasingly important due to moisture loss that. 42) 23 (3.81 0.5 %.08 1. marine structures.60) 41 (5. Specified density 48 to 69 MPa (7000 to 10 000 psi) [17]. and consumer products in North America.5S 5L .73 Physical Properties @ 29 Days Compressive Strength MPA (ksi) 39 (5. Specified density concrete has the added benefit of enhanced cement hydration. concrete is achieved by replacing part of the ordinary normal. This resulted in 5.50) 26 (3. Slump 100 mm (4 in. 1050 kg/m3 (1770 pcy) Natural Sand. Fig.50) E (Test) / E (Calc.0 (580) 4.06 0.5 %.75S. 5—Concrete density versus time of drying for struc.60).17) 17 (2.27) 28 (4. and 100 % of the normal-weight limestone coarse aggregate was replaced by an equal absolute volume of lightweight aggregate [10]. Air 5. Air 3. Slump 140 mm (5.05 1.5 (504) Note: 1.09 0. precasters are able to maximize the number of concrete elements on a truck without exceeding highway load limits.25L .4 (498) 3. 2.81 0. See section on “Internal Curing” for more detail.14 Tensile Split Strength @ 29 Days MPa (psi) 4. Shown in Table 3 are the physical properties of concrete in which 25.61 0.5 0. ACI 318) GPA(ksi 103) 31 (4.38) Elastic Modulus (Calc.2 (615) 3. 708 kg/m3 (1190 pcy) Natural Sand. 50.12) 42 (6.85) Elastic Modulus (Test) GPa (ksi 103) 30 (4. This reduces the number of truck loads which lowers transportation and project cost. 35 MPa (5000 psi).89) 41 (5. For more than 20 years precast concrete manufacturers have evaluated trade-offs between the concrete density and transportation costs. 1840 kg/m3 (115 lb/ft3).4 (492) 3. All concrete mixtures contain 446 kg/m3 (752 pcy) cement.49) 28 (4.) 3.25) 22 (3. wallboard. By adjusting the density of the concrete. All concrete mixtures.17) 20 (2. 11.80) 34 (4.89) 17 (2. 15.70) 24 (3. 12 in. Mortar Mixture “M” contains 716 kg/m3 (1208 pcy) Cement.81) 24 (3. strengths are presently being specified for precast bridge mem- TABLE 3—Physical Properties of Concrete Mixtures Limestone Coarse Aggregate replaced by varying percentages of structural Lightweight Aggregate. tural lightweight concrete.00 1. The concept of specified density concrete is not new. and several other parts of the world [16]. ACI 318) 1.75) 29 (4. ACI 318) GPA(ksi 103) 26 (3. While compressive strengths of 21 to 35 MPa (3000 to 5000 weight aggregate (Relative Density 2. Specified density concrete is defined as concrete with While most structural lightweight aggregates are capable of a range of density less than what is generally associated with producing concretes with compressive strengths in excess of normal-weight concrete.9 1.10) 29 (4.09) 26 (3.12) 47 (6. precast steps. and 21 % reductions in density. 2320–2480 kg/m3 (145–155 lb/ft3).88) Elastic Modulus (Test) GPa (ksi 103) 24 (3.75L LWA NONE Target Equilibrium Density 2300 (143) 2160 (135) 2050 (128) 1920 (112) 1800 (112) 2000 (125) kg/m3 (lb/ft3) Physical Properties @ 18–24 h Compressive Strength MPA (ksi) 24 (3. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 555 Specified density concrete has been used on bridges.30) 23 (3.5 in. Europe.28) 28 (4.60) with either coarse or psi) are common for cast-in-place lightweight concretes.92) 20 (2.42) 15 (2.91) 42 (6.25) 27 (3. higher fine lightweight aggregate (Relative Density generally 1.67) 23 (3.49) 20 (2.48) E (Test) / E (Calc.10) 26 (3..7 (531) 3. as well as reducing the environmental consequences of trucking products. ACI 318) 1. precast elements.. a limited number of lightweight aggregates and greater than the code-defined maximum density for light. especially into central cities. All strength and modulus tests conducted on 152 304 mm (6 in. respectively. 75.25S.) 4. Opportunities for increased trucking efficiency also apply when transporting smaller concrete products (hollow core plank.) cylinders.89 0.97) 18 (2.27) 20 (2. Mixture Number 1 2 3 4 5 M Coarse Aggregate Limestone . and other consumer products). Compressive Strength density.96) Elastic Modulus (Calc. . Concrete manufactured and tested at Prestressed Plant to optimize structural efficiency and reduce transportation costs. can be used in concretes that develop cylinder strengths from weight concrete.92) 31 (4. 04 w 3 c fc [18] on normal-weight concretes report similarly wide . but Shrinkage this is known to be only a first approximation that does not As with ordinary concretes. a reduction in stress concentra- Modulus of Elasticity tion. splitting tensile strength. The (a) shrinkage characteristics of the cement paste fraction. as the modulus is significantly affected weight aggregate may be increased by reduction of the top size (25 %) by binder characteristics. normally cured concretes. Tensile splitting strength test data aggregate concretes. in the project according to the procedures of ASTM Test Method turn. shrinkage of structural lightweight reflect aggregate particle strength. concretes is principally determined by nor the concrete’s moisture content and distribution. as determined by ASTM Standard (b) internal restraint provided by the aggregate fraction. The strength ceiling of a particular light. in a particular grading formulation. it is essential for design engineers The modulus of elasticity of concrete is a function of the modu. and more reliable indicator of tensile-related properties than (d) humidity and temperature environments. conducting splitting tests. laboratory Shear. and other variables.4°F) and 50 % relative humidity prior to Test Method for Creep of Concrete in Compression (C 512). Creep ance the compressive stresses in the still-moist interior zones. These values are prin- ranges may be assumed to follow the ACI 318 formula cipally based upon the results of the comprehensive testing program of Shideler [12]. to have an accurate assessment of these time-related charac- lus of each constituent (mortar. wide envelopes of one-year specific creep values for all light- lus of normal-weight concretes is higher because the moduli of weight. (paste volume fraction). For practical design conditions. gressing slowly into the interior of concrete members will result in the development of outer envelope tensile stresses that bal. and normal-weight teristics as a necessary design input. As tensile splitting results vary for necessary to meet specified strength levels. aggregate characteristics. weight concrete due to the lower aggregate stiffness. practical design criterion that is known to be a restraining skeletal structure (aggregate fraction).) cylinder. first approximation. and changes in camber. lightweight- behavior of concrete in actual structures. surface characteristics. and tests should be conducted on specific concretes proposed for crack resistance are related to tensile strength. Time-related increases in concrete strain due to sustained ASTM C 496 requires a 7-day moist and 21-day laboratory air stress can be measured according to the procedures of ASTM drying at 23°C (73. The modu. type of curing. ACI 213 [10] demonstrates aggregates) and their relative mixture proportion. tensile strength has been defined as a function of compressive strength. Creep and shrinkage characteristics of any concrete type are ting-tensile strengths vary from approximately 75 to 100 % of principally influenced by water and cementitious materials normal-weight concretes of equal compressive strength. lightweight aggregate concretes are proportioned with cemen- sult with the aggregate suppliers for laboratory-developed titious material quantities similar to that required for normal splitting strength data. (c) the relative absolute volume fractions occupied by the crete Specimens (C 496). and the time required to reach a plateau crete specimens that are allowed to dry correlate better with the of equilibrium is longer when the as-batched. Moisture loss pro. cementitious materials will not significantly raise the maximum wc the density in kg/m3 (lb/ft3). age at time ing lightweight fine aggregate with normal-weight fine aggregate of loading. tensile splitting strength of 2. Splitting tests are conducted by applying Aggregate characteristics influence the quantity of cemen- diametrically opposite compressive line loads to a concrete titious materials (the shrinking fraction) necessary to produce cylinder laid horizontally in a testing machine. Particle strength. Structural lightweight concrete split. rate of shrinkage strain development in structural lightweight Tensile splitting strength tests on structural lightweight con. Lightweight aggregate concrete where will demonstrate a strength “ceiling” where further additions of E the secant modulus in MPa (psi). moisture. loss of prestress. slightly greater than that of normal- where development of early-age tensile-related forces occur. As will normally increase tensile strength. strength. When design Tensile Strength conditions require accurate elastic modulus data. Replac.0 MPa (290 psi) is a requirement shape. termine the fractional volume and quality of the cement paste quirements of ASTM C 330. A minimum a required strength at a given water content. creep and shrinkage strains will cause an increase in long-time deflections. which is. development length. the and normal-weight aggregates have a range of values that nar- modulus of elasticity of concretes with densities between 1400 rows significantly and closely envelopes the performance of to 2500 kg/m3 (90 to 155 lb/ft3) and within normal strength the normal-weight “reference” concrete. but not always. and attainable strength. as well as the strength characteristics of the vitreous material This or any other formula should be considered as only a surrounding the pores. When structural different combinations of materials. the specifier should con. concrete is slower. Test Method for Splitting Tensile Strength of Cylindrical Con. and applied stress/strength ratio. aggregate type. the shrinkage of lightweight concrete is should be developed prior to the start of special projects generally.5 fc E 0. lightweight. The formula generally overestimates the modulus for high-strength lightweight concretes. Long-term investigations by Troxell E 33wc1. Test results for higher- the natural aggregate particles are greater than those of light. Traditionally. aggregate absorbed moisture is high [10].556 TESTS AND PROPERTIES OF CONCRETE bers and offshore applications. and grading influence water demand and directly defor structural lightweight aggregates conforming to the re. is used throughout North America shrinkage medium (cement paste fraction) and the as a simple. Strength ceilings differ for each lightweight fc the compressive strength in MPa (psi) of a 150 by 300 aggregate source and are the result of pore size and distribution mm (6 by 12 in. phases are securely bonded. beam flexural tests. steam-cured concretes with a blend of lightweight weight aggregate particles. torsion. bond strengths. dependent upon tensile strength of the coarse aggregate for Static Modulus of Elasticity and Poisson’s Ratio of Concrete particle and the mortar and the degree to which the two in Compression (C 469). The time as in handling precast or tilt-up members. This proven record of high resistance to The expression “contact zone” includes two distinctively dif- weathering and corrosion is due to physical and chemical ferent phenomena: (1) the mechanical adhesion of the cemen- mechanisms that include: (a) a higher resistance to macro. (b) superior aggregate/matrix adhesion. Deterio- mains an inadequate correlation between the results of this ac. aggregate moisture ergy and Technology (CANMET) on various types of concretes content. and (2) the cracking. Near-surface pores provided by the lightweight fine that cause separation. Kondratova listed several web- to severe environments support the findings of laboratory in. Maine. specimen drying times. A high incidence of interfacial cracking or ag- Resistance of Concrete to Rapid Freezing and Thawing (C 666) gregate debonding will have a serious effect on durability if provides a useful comparative testing procedure. ration will result. The various mechanisms that act to maintain continuity. adequate attention. sure at low tide. of the mortar remaining firmly attached to the top side of the weight concrete is tested. Durability Field Tests Numerous accelerated freezing and thawing testing programs For more than 25 years. [23].24]. over 100 cycles of freezing and thawing. and further improve exposure conditions. An equally serious consequence of microcracking for Lightweight Aggregates for Structural Concrete” requires is the easy path provided for the ingress for aggressive agents modification of the procedures of ASTM C 666 to provide 14 into the mass of the concrete. specimens placed on a mid-tide wharf experience alternating tion in the presence of deicing salts on mature bridges indicate conditions of seawater immersion followed by cold air expo- similar performance between structural lightweight and nor. This profound improvement proportioned for thermal resistance by using high volumes of in the quality. the specimens experience mal-weight concretes [19]. and microstructure stems from a . Treat Island Severe Weather Exposure Station maintained by cretes proportioned with proper air-void systems provide good the U. sites that could be used to examine the performance of these vestigations and demonstrate that properly proportioned and specimens. When light.S. protective layer of concrete over the reinforcing steel. with pieces of apparently sound mortar sep- celerated laboratory test and the observed behavior of mature arating from the bottom of the aggregate. so entrained air and low cement contents will be significantly comparisons with “reference” concretes should be based upon reduced. and be maintained between the aggregate and the enveloping It is widely recognized that while ASTM Test Method for mortar matrix. In typical winters. Several comprehensive investiga. Very low density. as a the pyroprocessed silica/alumina-rich lightweight aggregate result. crete conglomerate may come from the failure of either the ag- cretes have a high strength/modulus ratio. titious matrix to the surface of the aggregate. It is imperative that permeability and withstood severe exposure were examined and reported by strain capacity characteristics of the concrete be sufficient to Bremner et al. En- fluence of air-void system. has the air void system necessary to protect the matrix. gate particle. been conducted by the Canadian Department of Minerals. normal-weight concretes that do not contain supplementary The matrix protective quality of insulating type concretes cementitious meterial [19. tions into the long-term weathering performance of bridge five sets of specimens incorporating lightweight aggregate decks [20] and marine structures [21] exposed for many years have been placed at this site. or from a breakdown in the disruptive dilation of concrete starts is higher for light. provide adequate resistance to the intrusion of chlorides and carbonation. have not received the same attention as aggregates have been shown to accommodate etringite [15]. Observations of the resistance to deteriora. After more normal-weight concretes. ASTM C 330 “Standard Specification aggregate. non-structural concretes will not data specific to the concretes considered. ment hydration. In order that concrete performs satisfactorily in severe minimize leaching of soluble compounds. Micro-cracking is miti. field exposure testing programs have conducted on structural lightweight concrete studying the in. bridges have demonstrated concretes with a high integrity contact zone between aggregate/matrix with low levels of Contact Zone microcracking [5]. is significantly influenced by the resistance to macro transition layer in a number of mature structures that have and micro-cracking. Starting in 1980. This will reduce overall concrete permeability. protect reinforcing steel from corrosion. or crete. The Durability of any concrete. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 557 envelopes of results for differing natural aggregate types. Army Corps of Engineers at Eastport. both normal-weight and light. the contact zone causing a separation of the still-intact phases. which is clearly the The contact zone of lightweight aggregate concrete has dominant form of structural deterioration observed in current been demonstrated to be significantly superior to that of construction. Concrete durability results. Collapse of the structural integrity of the con- gated by the high ultimate strain capacity provided when con. Aggre- Long-term pozzolanic action developed at the surface of gates are frequently dismissed as being inert fillers and. integrity. these cracks fill with water and subsequently freeze. than 25 years of exposure to a severe marine environment. cement content. there re. rendering ineffective the days of drying in laboratory air after 14 days of moist curing. [21]. etc. morphology and distribution of chemical elements at the weight. they and the associated contact zone have not received will combine with the calcium hydroxide liberated during ce. and (c) the variation of physical and chemical characteristics of the reduction of internal stresses due to elastic matching of coarse transition layer of the cementitious matrix close to the aggre- aggregate and the cementitious matrix. weight concrete than for equal strength normal-weight con. and testing environment have exposed to the extremely harsh marine environment at the arrived at similar conclusions: air-entrained lightweight con. Core samples taken from hulls of 70-year-old lightweight properly proportioned concretes of both types were providing concrete ships as well as 40-year-old lightweight concrete durable performance [22]. usually with some concretes exposed to natural freezing and thawing. it is essential that a good bond develop the integrity of the contact zone. and reported that the deterioration rate was similar placed lightweight concretes perform equal to or better than for the lightweight and normal-weight concretes. The ratio at which gregate or cementitious matrix. research has identified ettringite. rapid temperature and toughness characteristics of the cement matrix and the ag- changes. the aggregate surface linking up with micro-cracking in the Though laboratory studies and field experience have indi- transition layer. long-term disruptive expansion. These lenses weight aggregate [26]. alkali-silica gel. cementitious matrix [25]. sharing characteristics in compression. Hoff [29] reported that specially developed testing quantify durable concrete characteristics. cated no deleterious expansion resulting from the reaction be- The phenomenon of bleed water collecting and being en. These factors cause a predominantly tensile-related Most lightweight aggregates suitable for structural concretes failure. hardness. splitting cylinders. ACI 201 “Guide to Durable Concrete” reports no documented in- gate. librium density in the range of 110 lb/ft3 (1760 kg/m3) and tion should not be surprising because. because of localized yielding and the closure of temperature and volume-change Fire Resistance cracks. a full comprehension has not been developed includes: regarding the accommodation mechanism by which the pores • The pozzolanic alumina/silicate surface of the fired closest to the aggregate/matrix interface provide an accessible ceramic aggregate combines with CaOH2 liberated by space for products that cause deleterious expansion. In either case. the high-quality mi. the significance of in. with structural light. Structural lightweight fact that inadequate concrete performance is seldom related to concrete bridge decks that have been subjected to more than this parameter.558 TESTS AND PROPERTIES OF CONCRETE number of characteristics unique to lightweight concrete that Additionally. while with normal-weight concrete gregates should be considered a potential source to develop there is an abrupt transition at the dense aggregate/porous ce. While hydration of the portland cement. The permeability active normal-weight coarse aggregate in which some of the non- of concrete is greater than the permeability of its constituents. Pre- creasing permeability is even greater. Implication of Contact Zone on Failure Mechanisms Abrasion Resistance Exposed concrete must endure the superposition of dynamic Abrasion resistance of concrete depends on strength. however. procedures that measured ice abrasion of concrete exposed to In general. trapped under coarse particles of lightweight aggregate is miti. Weakest link mechanisms. aggregate was observed in concrete made with a well-known re- erate corrosion of embedded reinforcement. it is still the elastic similarity of the aggregate and the surrounding not fully understood how these products impact service life. including truck traffic. the uniaxial compressive strength is traditionally are composed of solidified vitreous ceramic comparable to considered the preeminent single index of quality. ance for lightweight and normal-weight concretes. above are produced using either natural sand or a naturally weight concrete. and dilation due to chemical gregates. However. and . gate for reactive material to precipitate in a benign manner. structural lightweight aggregate concrete slabs. forces including variable live loads. reactive fine aggregates were replaced with lightweight fine ag- This increase in permeability results from interfacial flaws at gregates [28]. • Hygral equilibrium between two porous materials (light. the aggregate/matrix interface is a boundary occurring coarse aggregate. alkali-aggregate reaction until they have been demonstrated mentitious matrix interface. This observa. • Reduced micro-cracking in the contact zone because of and corrosion products in these near-surface pores. No evidence of alkali-lightweight aggre- have water-to-cementitious materials ratios significantly gate distress was observed in tests conducted on samples from a higher than in the rest of the matrix. despite the quartz on the Mohs Scale of Hardness. When tested according to the procedures of ASTM Method for tions. Yet. tween the alkalis in the cement and the lightweight aggregates. weakest link mechanisms are undetected in arctic conditions demonstrated essentially similar perform- uniaxial compression tests due to concrete’s forgiving load. when sup. bridge decks that were more than 30 years old [27]. performance is the integrity of contact zone. Many lightweight concrete mixtures designed for an equi- blasted vertical surfaces of building structures. as well as by visual examination of sand. factor that enables lightweight aggregate to reduce disruptive ex- While the reduction in compressive and tensile strength pansion is the availability of space within the expanded aggre- due to poor contact zone is important. another ness is profoundly improved. Increasing permeability cipitation of alkali-rich material in the pores of an expanded inevitably leads to penetration of aggressive agents that accel. the natural aggregate portion of a sand-lightweight concrete gated if not eliminated. these natural ag- between two porous media. Resistance to Alkali-Aggregate Deleterious weight aggregate and porous cementitious matrix) as Expansion opposed to the usual condition with normal-weight aggre. show has diverted our focus from life-cycle performance and the wearing performance similar to that of normal-weight con- development of appropriate measurement techniques that cretes. In most concretes the limiting factor in the long-term Fire Tests of Building Construction and Materials (E 119). by an appropriate ASTM test procedure or by having an established service history to be of negligible effect. faces such that they act as a source of silica to react with the al- plementary cementitious materials are used in concretes kalis from the cement at an early age to counteract any potential containing normal-weight aggregate. The pyro- crostructure of the contact zone around lightweight processing of the aggregates tends to activate the particles’ sur- aggregate is moderately enhanced. this zone of weak. are decisive in tensile failures in both dynamic and durability exposure condi. This has been verified in practice by the mixture should be evaluated in accordance with applicable examination of the contact zone of lightweight concrete tensile ASTM standards. moisture gradients. walls. The simplicity and ease of compression testing 100 million vehicle crossings. changes. marine salts. where bleed-water lenses form around essentially stance of in-service distress caused by alkali reactions with light- nonabsorbent coarse natural aggregates. As maintained earlier. When supplementary 70-year-old marine structure and several lightweight concrete cementitious materials are added. as well as on the bond between these two phases. New York. May 1967. Nov. July 1957. C 567). T. and Mann. Continuity or Discontinuity in Cement Pastes. C.. “State-of-the-Art Report on High-Strength. PA. “Carbonation of Marine Structural Lightweight Concrete. P. 1957.. August 1988. A. ERDA. T.. E. J. April 1980. Interna- require minimum values for compressive and tensile splitting tional Symposium. T. strength. [17] Holm.” Second International Conference on Performance of Concrete In A Marine Environ- ment.” Concrete International. R. E.. D.. A. “Lightweight Aggregate Concrete Subject to Severe Weathering.. Strength High-Durability. [12] Holm. Vicksburg.. [18] Troxell. R. Society. Acknowledgments 54. VA... “Early High Strength Concrete for Prestressing. Norway.. Sixth International Conference on Durability of Concrete.. of Concrete.” Cement and Concrete Research (1999). R. Superior performance is due to a combina.” J.. K.. Structural Low Density Concrete [14] Valore. 1956.” ACI Journal. I. Specifications [5] Holm. C 496.S..” Performance of Concrete in a Marine Specifications for structural lightweight concrete usually Environment. Army Corps of Engineers. specified range [6] Powers. J. “Concrete Strength Measurement—Cores and ready exposed to temperatures greater than 1093°C (2000°F) Cylinders. ASTM International.L. “Lightweight Aggregates for Masonry Units. lower coefficient of thermal expansion [2] Klieger. P.. 2002. 6—Fire endurance (heat transmission) of concrete Warming. A. Detroit. Proceedings. 2000. T. and the inherent Proceedings. 1958. and [7] Philleo. “Capillarity of air content. T. and Bremner. R. Kristiansand. E. during pyroprocessing. Eds. B. T. “Core and Cylinder Strengths of Natural and Lightweight Concrete. Journal American Concrete Institute. MI.. Andrews By-The-Sea. Nov.” 213) [14]... “Lightweight Aggregate Concrete for Structural Use. Jr. and Tobin. 2003. 509–532.. McGraw-Hill.. 58. [4] Campbell. April 1967. air contents. R. water. Mindess. [8] Holm. Detroit.. April 1967. P.. Vol. I. A. pp. World Conference on Prestressed Concrete. June 2000. and Newman. [19] Holm. C. pp. “Structural Lightweight Concrete. designed.” U. Vol. T. 6). Greece 2003. Oct. ACI SP 109. Journal for Applications in Severe Marine Environments” [15]. and constructed Fine Aggregate. D. St. West Conshohocken. M. American Concrete Institute. the relative density factor of the lightweight aggregates. A. “Physical Properties of High Strength Lightweight Aggregate Concretes.” Proceedings. “Performance of Structural Lightweight Concrete in a Marine Environment.. J. St. 1980. and proportions of coarse-to. Thessaloniki. CA.” ASTM Proceedings. [9] Bentz. “Protected Paste Volume on Con- Structural lightweight concrete is a unique construction crete-Extension to Internal Curing Using Saturated Lightweight material that should be specified. H.” Bremner Symposium on High-Performance Light- Conclusion weight Concrete. A. “Insulating Concretes.L.. T. American Concrete Institute. [15] Holm. MI. American Concrete Institute. E. “Specified Density Concrete—A Tran- sition. maximum limitations on slump. [1] “Standard Building Code for Reinforced Concrete. 53. J. W. 53. the Guide for Structural Lightweight Aggregate Concrete (ACI [13] Carlson. Structural Low Density Concrete for Applications in Severe Marine Environments.. W. J. P. Copeland. T.. 65. T. forced Concrete [1].. thermal stability developed by aggregates that have been al- [3] Bloem. Vol. Vol. and Ries. in a manner that recognizes and takes advantage of its [10] Guide for Structural Lightweight Aggregate Concrete.” Proceedings. May 1959. ACI SP-65. ACI 318 Building Code Requirements for Rein. G. Raphael. American Concrete Institute. A. fine aggregate.” Proceedings. pp. High-Durability. C. Canada. London. A. [21] Holm.. San Francisco. M. Vol. J.. J. R. and Vaysburd. Journal American Concrete Institute.” Material Science of it is also influenced to a lesser degree by cementitious Concrete II. H. A. [20] Walsh. [16] Holm. Canada. Skalny and S. Westerville. OH.. 298–328. 2003. and Davis. T. C. Second International Congress of Lightweight Concrete. “Restoring Salt Damaged Bridges. and the “State-of-the-Art Report on High.” Second International Conference on Structural Light- weight Aggregate Concrete. W. Sixth International Conference on Durability [10]. HOLM AND RIES ON LIGHTWEIGHT CONCRETE AND AGGREGATES 559 beams have demonstrated greater fire endurance periods than References equivalent-thickness members made with normal-weight aggregates (Fig.” Handbook of The principal sources of information for this chapter include Structural Concrete. “How Information Technol- ogy Can Help Sustainability and Aid in Combating Global Fig.” Civil Engineer- ing. “Concrete Science and Reality. Thessaloniki. and Goldfarb. ACI unique physical and mechanical properties (ASTM C 330. “Long Time Creep and Shrinkage Tests of Plain and Reinforced Concrete. Bremner.” ACI tion of lower thermal conductivity (lower temperature rise on Committee 318. Aug. Committee 213.” (lower forces developed under restraint). American Ceramic materials. unexposed surfaces). L. 1956. and a limitation on maximum fresh density. PCA Research The density of lightweight concrete depends primarily on and Development Lab. “Moisture Dynamics in Lightweight Aggregate and Concrete. Andrews-By-The-Sea. and Snyder. Bremner. T.. 1991. 1983. Chapter 7. 383–402.” Bremner Symposium on High-Performance Light- slabs as a function of thickness for naturally dried specimens weight Concrete. June 1984. .” Proceed- ings. Greece. [11] Shideler. A. ACI Journal. [22] Kondratova.. T. T. [28] Boyd. MI. June 2000. Canada. American Concrete Institute. A. W. A. T. W. “The Durability of Lightweight Concrete Structural weight Aggregate Reduces Expansion in Concrete Containing Members. 1984. . American Concrete Institute.560 TESTS AND PROPERTIES OF CONCRETE [23] Bremner.. A.” unpublished private communica- International Symposium Concrete Structures in Arctic Regions.” Proceedings.” Kuibyshev.. T. Russia.” Eleventh ICAAR [25] Bremner. “Aggregate [27] Bremner. “Alkali-Aggregate Tests on Structural Light- Interaction In Concrete Subject To Severe Exposure. American Performance of Structural Lightweight Concrete. 1991.. “High Strength Lightweight Aggregate Concrete March/April 1986.. Quebec. for Arctic Applications. Symposium on the [26] “Guide to Durable Concrete” ACI Committee 201. Calgary. “Addition of Light- [24] Khokrin... [29] Hoff. Bremner. C. W. Concrete Institute. Nov. and Holm. Detroit. T.. T. Highly Reactive Normal-weight Aggregate. W. G. “Elastic Compatibility and the International Conference. 1973 (In Russian). Nov. Detroit MI 2001. S. and DeSouza.2R... T. H. Behavior of Concrete. and Holm. 1991.” Journal. Canada.” FIP-CPCI weight Aggregate Concrete. tion. Holm. 1 Professor and Chair. Two of spans. dress cellular concretes of various densities and provide in The purpose of this chapter is to provide an overview of depth information on the properties. a stable preformed foam is chapter.9]. some of the fun. Hence. coated with cement paste. These reports ad- slabs and roadways. the foam concentrate. The achieved by adding a calculated amount of air as a preformed bubbles maintain their shape through the setting stage and be- foam to a cementitious slurry with or without the addition of come discrete air cells in the cementitious matrix.10 to 1 mm (0.). Additional information on cellular concrete has also of cellular concrete. pumped or otherwise transported to the point of placement. ing foam (or a foaming agent) in the mix or by generating a gas terial. the In general. Background which is factory-produced using a chemical reaction process for Cellular concrete is a lightweight concrete. 561 . cations for cellular concrete are usually concrete applications The American Concrete Institute (ACI) published three that are required to resist modest loads over relatively small reports of its Committee 523 on Cellular Concrete [5–7]. the mixing time. proved strength and dimensional stability. Birmingham. Normally. This method of producing air cells is best thermal conductivity. The cast-in-place construction. batch density prepared foam or by the generation of gas within the fresh control of this process is difficult at best.” respectively. cementitious mixture. Legatski [1]. In the foaming process. Density control is cal reaction. the volume of Introduction air cells produced depends on the amount and properties of Cellular concrete is a low-density material having a homoge. Legatski [2] who up. physical properties. It is also possible to form air cells in the slurry by vig- of cellular concrete. mix design. which react with the solu- Reducing the mixture density by the addition of preformed ble alkalis in the cement slurry liberating hydrogen gas and foam is accompanied by a reduction in strength properties and forming bubbles. which is the process most commonly used for cement slurry or a cement grout (containing aggregate). consisting of a sys. High-pressure increased insulating value. This chapter does not address AAC.47 Cellular Concrete Fouad H. In the interest of consistency. the terms earlier contributions as their work provides the background “foamed” and “gas concrete. and the third include: floor fills. which generates gas in the slurry (mortar). Department of Civil and Environmental Engineering.4]. and includes up-to-date references. Detailed technical information on cell size varies approximately from 0. University of Alabama at Birmingham. and the temperature of neous void or cell structure formed by the addition of a the water and other materials. AL 35294. the air cells (bubbles) into the plastic mixture: through blend- dated various sections and stressed new applications of the ma. typical appli. which are some- for this edition. Fouad1 Preface in.004–0. steam curing is employed in this case. The author acknowledges both father and son for their in the fresh mix by a chemical reaction [3. minum paste are added to the mix. Examples of nonstructural cellular concrete applications the reports address cast-in-place cellular concrete. The current edition updates the topics. introduces added to the cementitious slurry during mixing in an ordinary new information on the material properties and applications mixer. and common applications material. and reducing lateral loads on wall structures. air cell generation.04 AAC is available in the published literature [10–15]. It deals only with air cells produced using tem of macroscopic air cells uniformly distributed in either a preformed foam. which provides im- As a result of the reduced strength properties. there are two basic methods for introducing chapter was authored by his son Leo A. sloping roof screeds. orous mixing of the slurry with a foaming additive in a high- speed mixer. sand or other materials. times used in referring to the process used to generate the void damental aspects of the earlier publications are retained in this system. Consequently. been presented in special publications by ACI and the Portland Cement Association [8. In ASTM STP 169C in 1994. and the concrete is presented in ASTM STP 169B in 1978 and was authored by Pro. filling voids to support report is devoted to precast cellular concrete. fessor Leo M. The air cells must be tough and sufficiently stable in order to withstand the rigors of mixing and placing as the air cells are THE CHAPTER ON CELLULAR CONCRETE WAS FIRST separated. and use of the the production. it is possible to select a reduced suited for factory production in the manufacture of autoclaved concrete density to satisfy strength requirements and provide aerated concrete (AAC) structural elements. It is usually cast in densities ranging The other method for forming air cells is through a chemi- from 320 to 1920 kg/m3 (20–120 lb/ft3). In the high-speed mixing method. Typically. The air cells created by the preformed small amounts of finely divided aluminum powder or alu- foam may account for up to 80 % of the total volume. It covers a broad spectrum of concretes ranging in land pozzolan cement conforming to the requirements of density from 320 to 1920 kg/m3 (20–120 lb/ft3). or tuff. Substitution of pozzolanic duce concrete with lower unit weight and thermal conductivity materials for a portion of the cement lowers the actual cement [17].7 and 7 MPa (100 and 1000 psi). Higher rates of early underground thermal conduit linings. strength. These concretes are usually produced in cast densities of Water for mixing and curing cellular concrete should be 800–1920 kg/m3 (50–120 lb/ft3). A brief description of the basic sity. or port- concrete. the water-cement salts. or ASTM Standard Performance Specification for excellent insulation properties and is used primarily in Hydraulic Cement (C 1157) are used in cellular concrete. alkalis. pumping. Foam concentrates inclusion of such material is recommended if it is locally are typically based on hydrolyzed protein or synthetic deter- available as its procurement from afar often results in a higher gents. Group II aggregates. and compressive strength. or sintering various natural or artificial materials mixtures. The classification into two groups is based ter. resulting in preformed foam with density approximately grade in order to increase the strength-density ratio [16]. sonry Units (C 331) may be used in cellular concrete. acids. and the 28-day strength portland cement (Type III). are more (50 lb/ft3).0–3. Blended cements may result in slower rates of strength roof decks. The mixture properties are potable and free of deleterious amounts of oils. fill for slab-on-grade subbases. Fine Aggregate In densities ranging from 800 to 900 kg/m3 (50–120 Natural or manufactured sand meeting the requirements of 3 lb/ft ). provided tests or service records have densities to cast-in-place walls. The lightweight aggregates may be of structural times. ASTM Standard Specification for Lightweight Aggregate Neat-Cement Cellular Concrete for Insulating Concrete (C 332) specifies two groups of light- Neat-cement cellular concrete consists of portland cement. ASTM Standard Specification for Lightweight Ag- to improve strength or impart special desired properties to the gregates for Structural Concrete (C 330). and compressed air in predetermined proportions in a gregate (such as perlite or vermiculite) replacing all or part of foam generator. densities. and the specific characteristics of the sand.5 lb/ft3). Sanded cellular concrete is cellular concrete that contains fine aggregate (sand) in addition to cement. shale. water absorption. time. floors. or ASTM Standard mix. nonstructural applications for thermal and sound insulation. water. Lightweight Aggregate Cellular Concrete Preformed Foam Lightweight aggregate cellular concrete is similar in density to Preformed foam is produced by blending a foam concentrate. Based on density range and the components of the Lightweight Coarse Aggregate mixture. It is typically made of strength development may be achieved by using high-early- neat cement mixtures with preformed foam.4 to 17 MPa (500–2500 psi). Performance ingredients as well as other materials that may be used in specifications for evaluating foam concentrates in cellular con- cellular concrete is given herein. content and permits lower densities of the neat-cement calcining. wa. which are prepared by heat processing to range with an upper limit on cast density of about 800 kg/m3 expand products such as perlite and vermiculite. sanded cellular concrete but with low-density lightweight ag. and preformed foam. and placing) and until the Materials concrete hardens. pumice. Sand of tions of the material range widely from nonstructural fill for other gradation not conforming to these standards have also thermal and sound insulation of floors and roofs at the lower been used in some cases. tion capable of producing stable air cells that remain intact during handling (mixing. Typically.562 TESTS AND PROPERTIES OF CONCRETE Classification of Cellular Concretes Cement Cellular concrete weighs substantially less than normal weight Portland cement. sand or lightweight aggregates are added tar (C 144). are relatively heavier in weight and may be used in higher density cellular Sanded Cellular Concrete concrete where improved strength is desired. while reducing the heat of hydration. which are prepared by expanding. has (C 595). It contains no aggregates. or performance of the concrete. on the expected concrete unit weight and thermal conductivity. compressive strength is generally between 0. and organic materials that would adversely affect the set ratio. cement cellular concrete is usually limited to the low-density Group I aggregates. range. weight aggregates. cellular concrete. exceeding 800 kg/m3 (50 lb/ft3). For this group. commonly used in insulating cellular concrete as they will pro- density or insulating concrete. crete mixtures are given by ASTM Standard Specification for . and applications vary according to density and ASTM Standard Specification for Aggregate for Masonry Mor- strength. ASTM Standard Method for Testing Foam- ing Agents for Use in Producing Cellular Concrete Using Pre- In its basic form. clay. portland blast furnace slag cement. and preformed Water foam. firewalls. cellular concrete is made by blending formed Foam (C 796) provides test procedures for evaluating preformed foam into a cement slurry. The liquid expands in volume up to about 30 the sand. In densities not ASTM Standard Specification for Portland Cement (C 150). cellular concrete is considered in a semistructural ASTM Standard Specification for Concrete Aggregates (C 33). Applica. primarily dependent on the cement content. The foam concentrate must have a chemical composi- cost of the final product. such as slag. cellular concrete may be classified as follows: For cellular concrete incorporating lightweight coarse aggregates. often re. and development during the first 3 to 5 days. and roofs at the higher shown that it produced cellular concrete of the desired quality. This class of cellular concrete is referred to as low. The in the range of 32–56 kg/m3 (2. the 28-day compressive strength ranges Specification for Lightweight Aggregates for Concrete Ma- approximately from 3. and it may or may not foam concentrates in a standard cellular concrete mix for den- contain aggregate materials. water. ASTM Standard Specification for Blended Hydraulic Cements ferred to as insulating concrete or low-density concrete. scoria. Neat. required workability. increase the Mixture Proportioning compressive strength of the concrete. The choice of these parameters is usually based on volume chapter on Chemical Admixtures. reduce water permeability. The fiber reinforcement may also improve the energy ab. The first tion for Chemical Admixtures for Concrete (C 494) and should step in mix proportioning is the selection of the wet density of be used in accordance with manufacturer recommendations.) has been found to be very significant portion of the material volume (25–80 %) is air. These factors.19]. the cement will seek Fiber reinforcement may be used in cellular concrete to help water from the preformed foam resulting in a loss of volume control shrinkage cracking. quired. the fiber’s efficiency. Chemical Admixtures latex can set up an additional matrix within the normal cement For cellular concrete with cast density of 1440 kg/m3 (90 lb/ft3) structure and impart specialized properties to the material. water reducing admixtures may be used to reduce the water to cement ratio in the mix and. for a portion of the cement usually has reasonable cost savings and the foam volume output per unit of time. The proposed fiber length ranges from about 13 to 38 mm (0. Depending on its chemical structure. The fiber quantity is a compromise based on the re. from the unit volume gives the volume of air required per unit tion for Fly Ash and Raw or Calcined Natural Pozzolan for Use volume of concrete [1. and cost. Slurry or chemical admixtures with the foaming agent or other ingredi. hence. Grout mixtures are slurry mixtures with aggregates. Slurry mixtures are low-density mixtures without aggregates. the foam density (32–56 kg/m3 (2. as a Mineral Admixture in Portland Cement Concrete (C 618) Three foam gun calibration factors are necessary for mix may be used in cellular concrete to the advantage. proportioning. tension. and weight of the foam volume (which is considered as water). compression. and the water-ce- Guidance for use of chemical admixtures is provided in this ment ratio. Guidance on the use of Concrete (C 869). For these mixtures. are the foam/air volume ratio (usually about tial replacement for the portland cement. that density and the specific application. FOUAD ON CELLULAR CONCRETE 563 Foaming Agents Used in Making Preformed Foam for Cellular or reduce permeability and absorptivity. its 523. Too high a water-cement ra- glass. Compatibility of the the strength and thermal conductivity requirements. The ample of the proportioning of grout mixtures is given in ACI upper limit depends upon the projected use of the concrete. nylon.75 in. or above. cement ratio for a specific density. and aggregate (if used) for a unit Supplementary Cementitious Materials volume of concrete (cubic meter or cubic yard) subtracted Fly ash or natural pozzolans conforming to ASTM Specifica. efficient for cellular concrete. the cement content.0–3. water. grout mixtures are proportioned using the absolute (solid) vol- ents in the mix should be established by trial batches. The water-cement ratio can be within a reasonable range for a selected density. cement content. . If different properties such as higher strength are re- elasto-plastic over a wide range of deformation and crack width. or other special tio results in excessive water bleeding and a lower compressive composites.). the cement and sand (or other aggregate) are usually Polymers weighed into the batch.07). the sum of absolute volumes of cement. which can be then selecting a water-cement ratio that is compatible for both established by trial test batches. The selection of these two demonstrated a ductile elasto-plastic load-deflection behavior variables will result in a cellular concrete of a given strength when tested to failure in bending. strength concrete mixture. A lower fiber Batching.5 in. The upper length limit depends on the increasing Accurate batching of ingredients is more critical with cellular difficulty of dispersing fibers in the mixture as the length is in. Mixing. strength and thermal conductivity of the material. The mixture water is metered while the Polymers such as latexes and acrylics may be used as additives preformed foam is time injected into the mixture through a in cellular concrete to improve certain strength characteristics calibrated nozzle.3R [6]. which can be obtained from a mentary cementitious material may be added as a filler or par. A length of 19 mm (0. polypropylene. An ex- ume of cement is often the starting point for trial mixtures. Accelerating admixtures Density is a critical parameter in the mix proportioning of cel- may be used if early strength development is required. and Application Techniques length limit is based on the fiber’s ability to bond with the cement paste. ume method. calibration test.50–1.05 to 1. concrete mixtures than with regular concrete. ment content and water-cement ratio should be reduced by the crease compressive strength. and its cost. lular concrete as it is a direct function of the compressive cal admixtures should conform to ASTM Standard Specifica. Fiber Reinforcement If the water-cement ratio is too low. According to this approach. mentitious materials must be compatible with the foam Proportioning a slurry mixture involves selecting a density and concentrate and other ingredients in the mix.6. It should be without adversely affecting significant properties of the cellu. Guidance for use of supplementary cementitious materials is provided in this volume chapter on Slurry Mixtures Supplementary Cementitious Materials. with densities 560–624 kg/m3 (35–39 lb/ft3). the density. the cellular concrete. loading and unloading also remained gregate). and water-cement ratio A volume of fiber equal to about 0. the other materials must be batched accurately. reduce the heat of hydration.5 lb/ft3)). Chemi. polyester. Grout Mixtures sorption and spall resistance properties of the cellular concrete.5 % of the absolute vol. polymers is provided in this volume chapter on Polymer-Modi- fied Concrete and Mortar. Because a creased. quired workability of the concrete. The supple. Its pozzolonic properties improve flowability. In this study. in. Substituting fly ash 1. may be varied according to the designer’s experience. Their pro- Research using monofilament polypropylene fibers in cellular portioning involves selecting a cement content and a water- concrete mixtures. Various fibers used include steel. and based on the characteristics of the ingredients (cement and ag- shear [18]. Supplementary ce. (yield) and an increase in density. pointed out that the weight of water calculated from the ce- lar concrete. termination of the thermal conductivity by the guarded hot tures. This wet density to oven-dry density for the different cellular concrete maintains the quality and freshness of the material. its ingredients. but Oven-dry density is commonly used to relate the physical other methods can be used. the oven-dry density may be concrete application. The rotary mixtures varies due to the different water content requirements. slurry is produced in these mixers. Detailed studies were conducted to contribution of cellular concrete. For the latter purpose. As a result. drum action of a ready-mix truck is acceptable for sanded The wet density of the cellular concrete is an important job-site mixtures with densities greater than 800 kg/m3 (50 lb/ft3). and air dried under job conditions justments can then be made to account for pumping distances in low-humidity environments may have density losses ap- and other special application conditions. Since roof deck assuming that the water required for hydration of the cement applications are cast slope-to-drain. Finishing operations. should be kept to a minimum. is meaningless in the case of cellu- cellular concrete may be varied over a wide range. evaluate the thermal properties of cellular concretes of various . continuous. and the specific applications depending on the quality requirements of oven-dry density. Mixing should efficiently mix the ce. The lower density cellular concrete has The thermal conductivity (k) of a material is the time rate of lower thermal conductivity (higher insulation). the concrete should be consolidated by tapping (floor-fill applications). the air-dry density of cellular concrete tive displacement pump. the thermal conductivity increases. It should be pointed erties of cellular concrete cast at different densities and with or out that the slump test.564 TESTS AND PROPERTIES OF CONCRETE The mixing technique should be compatible with the type Density of mixture. due to air drying is a function of temperature. The ratio of the the preformed foam is added just prior to placement. and rotary drum mixers may all be acceptable for air-dry density (at a stated age and curing condition). Although piston pumps are efficient for grout mixtures plate method in accordance with ASTM Standard Test Method at densities greater than 1440 kg/m3 (90 lb/ft3). Instead. duration of the dle type or shear mixers are common methods for both batch drying period. the ability to control the density of the material its oven-dry density and is measured by means of the Guarded over a wide range suitable for various applications is the major Hot Plate (ASTM C 177). the job requirements./h ft2 °F).2 C A ] kg/m3 or [(1. may be avoided by stating the moisture condition of the mate- ment and water and properly blend them with the other in. it is considered as an additional variable that significantly impacts the physical properties and the mix Thermal Conductivity design of the material. Pumping is the most common method of placement. and the When referring to the density of cellular concrete. and the surface-area ratio of the element. rial at that specific density. pad. The thinner floor-fill mixtures utilize a calculated with sufficient accuracy from the mixture data by rolling screed to provide a constant thickness.3 ft) C weight of cement. humidity. kg/m3 (20–120 lb/ft3). high shear.0 m (3. As the density a unit area for a unit difference of temperature. The ther- compensated for by improvements in strength properties. these fills are several meters (feet) thick so that they are cast in lifts of up to 1. density is is usually about 80 kg/m3 (5 lb/ft3) less than its wet density. across by lighter weight and reduced strength. Paddle. The as-cast or wet density is usually determined at the point Cellular concrete mixtures are typically job-site produced of placement in accordance with ASTM C 796. Significant moisture conditions ingredients including the preformed foam. For low-density applications (roof deck and engineered The air-dry density of cellular concrete usually represents fill) with neat-cement slurries at densities less than 800 kg/m3 the condition of the in-place material.18–21]. quality assurance tool to control uniformity of the mixtures. through a unit thickness. place without the need for consolidation. and thick based on the available area to be cast. If ready-mix trucks are used for sanded mixtures the wet density. Screed rails may also be used. The change in density (50 lb/ft3). Generally. they do not ef. but this is are watts/meter-Kelvin or W/mK (BTU in. cured. Geotechnical fill applications have the greatest variation where in casting techniques. Mix ad. in general. proaching 160 kg/m3 (10 lb/ft3). kg/m3 (lb/yd3) of concrete. confusion method of placement. lifts are cast on a daily basis until the final fill profile is reached. In determining and placed. 320–1920 lar concrete since the material is placed in fluid consistency. The oven-dry density (D) is for casting and darby finishing the material by experienced calculated as follows: tradesmen. smoothing with D [1. Because the density of in normal weight concrete. Workability Cellular concrete in the low-density range (less than 800 kg/m3 Physical Properties (50 lb/ft3)) is a flowable material with excellent workability. After the cement/water water-cement ratio. the grout is delivered to the job site and the sides of the container and not by rodding. the final product. the preformed foam is Although the relationship between air-dry density and wet den- added and blended prior to or during placement with a posi. Cel- measured at the point of placement for quality control. and for the de- as Moyno or peristaltic pumps are used for low-density mix. kg/m3 (lb/yd3) of concrete. clude as-cast density (wet density or plastic concrete density). lular concrete cast. Positive displacement pumps such properties of various types of cellular concretes. rotary drum mixing action is not ideal. accompanied transfer of heat by conduction. which is used to measure the consistency without aggregates in the mix [1. The succeeding A weight of aggregate. mal conductivity of cellular concrete is primarily a function of Nevertheless. As the mixture is pumped. sity seems complicated. The units of k increases. it is handled as a liquid and poured or pumped into Several studies investigated the physical and mechanical prop. the wet density of the concrete.2 C A )/27] lb/ft3 a darby or bullfloat is usually sufficient [20]. mission Properties by Means of the Guarded-Hot-Plate Appara- Casting techniques are different for each type of cellular tus (C 177). for Steady-State Heat Flux Measurements and Thermal Trans- ficiently pump low-density mixtures. string lines provide guides is 20 % of the weight of the cement. the and continuous mixing procedures. . low densities [22]. 2—Approximate relationships between density and oven-dry density for cellular concretes over the entire den. compressive strength for different types ofcellular concretes sity range [9. Since low-density cellular concretes have very cellular concrete include cast density. conductivity to oven-dry density for cellular concretes over the Using a vibrating table to vibrate the molds lightly may also be entire density range [9. low tensile strengths. aggregate type and amount. Similar curves can be developed for different cement factors. The compressive strength of neat- cement cellular concrete was predicted by Hoff [25]. and Fig. The compressive strength can increase when the water-cement ratio increases. with Fig. 3 shows the relationship Tensile Strength of Cylindrical Concrete Specimens (C 496). Figure 1 shows the relationship of thermal tapped with a rubber hammer while the mold is being filled. with approximately 5 % increase in thermal conductivity for each percent Tensile Strength increase in density due to free moisture. 1—Relationship between thermal conductivity and Fig. with increase in moisture content and density. FOUAD ON CELLULAR CONCRETE 565 Fig. as long as there is a more significant reduction in the air- cement ratio [19. special admixtures. The splitting tensile strength is determined in ships between density and compressive strength for different accordance with ASTM Standard Test Method for Splitting types of cellular concretes. cement content.24].17]. strength is beneficial and usually cost-effective for specific and curing conditions. adding fiber to increase the tensile cement ratio. [9]. water-cement ratios. The tensile strength of cellular concrete bears a similar relationship to the compressive strength as with normal weight Compressive Strength concrete. applications. and various ingredients or admixtures. The thermal conductivity increases used in preparing the test specimens [6]. water. it is recommended to determine the compressive strength in accordance with ASTM Standard Specification for Lightweight Aggregates for Structural Concrete (C 330). 3—Compressive strength versus density for sanded the exception that the sides of the cylindrical mold shall be cellular concrete mixtures at different water-cement ratios [9]. For oven-dry densities greater than 800 kg/m3 (50 lb/ft3). It should be pointed out that the compressive strength of cellular concrete depends on both the water- cement ratio and the air-cement ratio. Other studies also attempted to develop relationships between the strength and mix proportions of cellular concrete [26. Tensile strength is typically 10–15 % of the compres- The principal factors affecting the compressive strength of sive strength. for sanded cellular concrete mixtures at different water- cement ratios.23. The compressive strength for cellular concrete having an oven-dry density not exceeding 800 kg/m3 (50 lb/ft3) should be determined in accordance with ASTM Standard Test Method for Compressive Strength of Lightweight Insulating Concrete (C 495). Figure 2 shows approximate relation.17].27]. Fire tests conducted on concrete slabs made of different types of concretes demonstrated a su- Ec W1. the cement. The specifically. The increase in density is the Very limited data are available on the shear strength of cellu. occurs. It The modulus of elasticity (Ec) of cellular concrete is a function should be considered. low as the larger pores will not fill by suction.6) f c (lb/in2) ducted in a manner very similar to ASTM Standard Methods of Fire Tests of Builiding Construction and Materials (E 119). This may be related to the chemistry of the ingredients.” It ways: 24-h immersion. MPa (lb/in. Cellular concretes have considerably higher water absorption values than normal weight concretes.19] that the ACI 318 Code equation for relatively high-cement content. Tests of cellular concrete beams with cast density ume or a percentage of the initial weight or density. cellular concrete has good freeze-thaw resistance because of its high air content and its It was also reported [6.1 to 0. where W (wet density 80) kg/m3 or (cast density 5) Freeze-Thaw Resistance Cellular concrete is usually covered by roofing material such lb/ft3.2). supplementary cementitious materials absorbed energy is greater at lower densities that can withstand (if used). Some concentrates more deformation before “bridging and locking” of the material do not produce a discrete cell structure within the cement ma. their method of generating foam. the sample is reweighed and increased density. In the case of direct exposure to severe freezing and thawing environments. Water Absorption cellular concrete surfaces must be treated for protection. Fire Resistance lar concretes whose wet density varied from 1280 to 1872 Cellular concrete is incombustible and has excellent fire re- kg/m3 (80–117 lb/ft3).32] studied the impact and energy trix. primarily due to the lower density of cellular concrete. In each case.5 (37. shear tests of cellular concrete reinforced with polypropylene fiber were also reported [18]. long-term immersion (120 days). however. because the cellular concrete has a lower compressive strength.566 TESTS AND PROPERTIES OF CONCRETE Shear Strength compared to the initial condition. sistance properties because of their cellular structure and their terial but also with the quality of the mixture ingredients— ability to absorb loads and crush in a controlled manner. Their work showed that high energy rapid rates of loading expansion pressure. the bullets were captured within the panel after penetrating to trates require more mixture water that evaporates during approximately two-thirds of the depth. The consequence of water Energy Absorption absorption is a higher density. Fire tests were con- Ec (W1. mixing. The amount of water absorbed Low-density cellular concretes possess excellent deformation re- by cellular concrete varies not only with the density of the ma. panels subjected to high energy cell structures of the mixture will interconnect resulting in impact using small caliber hand guns at close range showed that channels for high water absorption. Walkability improves with ing. Also. depending on the composition of the mix- crete of the same density. It is reasonable that drying shrinkage of moist-cured cellular concrete may vary cellular concrete has a lower modulus of elasticity than con. Express- ranging from 800 to 1440 kg/m3 (90–120 lb/ft3) have indicated ing water absorption as a percentage by volume more accu- that the shear strength of such mixes may be estimated using rately reflects the effect of sample size. water absorption and may be expressed as a percentage by vol- lar concrete. If heavy construction traffic (such as wheel- . and as the density increased. density. from 0. Highest fire endurance ratings were achieved at the lower den- or sities. The of its density and compressive strength. Zollo and Hays [18. and as hot mopped asphalt or pitch. ture and whether or not aggregates are used. and by can be judged by examining the surface distress such as foot- tide cycle. hardening and leaves more pore spaces. a decrease in the fire endurance resulted for each type of concrete. Drying Shrinkage The drying shrinkage of cellular concrete is not usually critical Modulus of Elasticity when it is used in roof deck insulation and fill applications. the following equation was selected to sistance properties as compared to normal weight or light- represent best the test results weight aggregate concrete. Lower quality concen. Although its water absorption is the modulus of elasticity was applicable for cellular concretes high. the rate of water penetration through cellular concrete is ranging in density from 368 to 1872 kg/m3 (23–117 lb/ft3). prints caused by normal foot traffic.04) f c (N/m2) perior performance for low-density cellular concrete [28–30].5) (28. and placing (usually by pumping). Nevertheless. and therefore not exposed di- fc 28-day compressive strength. the cellular concrete matrix. rectly to the elements. produced only localized damage. Direct area to volume relationship. or their els. and preformed foam concentrate. in structural applications.6 %.31. which was attributed in part to If a preformed foam is not able to withstand the rigors the fibers and in part due to the low-density void structure of the of batching. the specimen is weighed prior to test. absorption capabilities of fiber-reinforced cellular concrete pan- their dilution rate. but made with lightweight aggregate. At each interval of testing. to sustain normal construction foot traffic without damage is Water absorption may be measured in three different an important factor and often referred to as “walkability. In a laboratory study [1] of modulus of elasticity of cellu. and the surface the ACI Code requirement for lightweight concrete [1]. Supplementary cementitious materials may decrease the amount of water Walkability absorbed because their smaller particles fill available spaces The ability of a low-density cellular concrete roof deck or floor between cement particles. 36].) thick. the insulation system for future reroofing. autoclaving (which is steam curing under part of the structure. Depart. the dimension of a standard wood bottom plate. In many cases. fills over structures. cast-in-place walls. In general. Standard roofing membranes are used over cellular con- nology using low-density cellular concrete [37]. The face of the concrete should be protected by wooden boards or finished deck is then covered with a waterproofing membrane. granular fills are major advantages in these applications. pressure and high temperature) is employed to provide the mation are typically cast over galvanized steel decking (corrugated terial with improved structural properties and dimensional or fluted) to provide improved fire ratings. those portions must be replaced or repaired prior such as protective structures for advanced military weapons. concrete (AAC) is more suitable for manufacturing precast low- sulating roof deck fills. FOUAD ON CELLULAR CONCRETE 567 barrow. to casting the cellular concrete. Fire ratings exist for many of these constructions. lighter materials can occupy much of the vol. Common applications include roadway rehabilitation. Floor fills are occasionally cast over corru.) thick above the top of the fact that it does not require the compaction required by the flutes. for Floor fill mixtures may also be cast on top of precast con. material storage. even if they degrade. In most applications place over wood-frame construction that is typically wood load balancing or weight credit techniques are combined joists and a plywood subfloor. sistance. This grout is pumped into bridging over poor soils to name a few. cially designed mixtures.) is expected. they are not commonly used due to the low strength and high drying shrinkage of Roof Deck Fills moist cured low-density cellular concrete. Typical applications in. Thus.5 within the engineered fill solution. drainage for “ponded roof decks” and protects and preserves ings were discussed in detail by Hoff [35. The load over poor soils. place it with 480 kg/m3 (30 lb/ft3) cellular concrete. and various pipeline and culvert applica- ume and then be topped with the cellular concrete floor fill. Roof deck applications for new construc. floors of these structures while minimizing added dead load. Precast Elements wood sleepers and cinder fill. Preformed foam is ing. It is not the purpose of this chapter to Only a few of the most commonly used applications are dis. These include built-up systems as well as sin- entails filling the voids of nuclear vessels with a fluid low-den. and as a low-density engineered fill for use in a va. fills behind retaining walls. the existing clude: fills for thermal and sound insulation of floors. every unit of soil removed. wood. vide a flatter floor.S. to reduce the in. structure must be checked for its ability to support additional and roofs. engineered fills can eco- grout at 1600–1760 kg/m3 (100–110 lb/ft3) having a cement nomically replace common geotechnical solutions such as pil- content of 256–298 kg/m3 (564–658 lb/yd3). and tunnel lin. This involves filling the steel deck flutes or lower the density.33]. gle-ply membranes such as ethylene propylene diene monomer sity cellular concrete. blast attenuating walls. precast wall and load. other means. It foam added to a cement/water slurry resulting in a density of can be worked like wood. surcharging. terrazzo. 480–640 kg/m3 (30–40 lb/ft3). sandwiched within the fill. it is advantageous to remove part of the purpose of floor fill is to provide fire resistance and sound at. Autoclaved aerated The largest single use of low-density cellular concrete is for in. four units of cellular concrete can crete units for leveling the camber of these members to pro. Specialized applications or damaged. and roofs. If the existing roofing is not removed. which would support the walls of the ves. etc. etc. cussed in this chapter.34]. raise the elevation without additional load. cellular concrete floor fills are cast over a variety of floor substrates such as concrete. floor rehabilitation. Substrates such as concrete (precast or cast-in-place) and wood decking are also common for this application. bridge approaches. Although this chapter does not address AAC. The U. It levels the merits. walls. (EPDM). however. In AAC. polyisobutylene (PIB).5–2 in. The floor fill is cast 3. If the existing roofing system is wet riety of geotechnical applications. The technology crete roof decks. and a slope-to-drain roof deck. This solution provides positive fragmentation shields. additional seismic re. Expanded polystyrene insulation taching roofing to the cellular concrete deck. The sloping roof deck usually incorporates EPS board floor panels. stability. Engineered Fills Floor Fills Cellular concretes provide alternate solutions to standard geo- Floor fill mixtures are job-site produced from a sand/cement technical procedures. For example. board in the slurry so that it is “cemented” or bonded to the structural deck. polyvinyl chloride (PVC). The excellent flow characteristics of cellular concrete and gated steel decks 38–51 mm (1. the sur. tile. [8. load-reducing For thick fills. and added to the sand/cement grout. it is . typically weighing 1920 kg/m3 (120 lb/ft3). Each application must Precast cellular concrete elements may be produced from spe- be analyzed on its individual requirements. existing soil. The roof deck system over which the in. The vast number of applications is due to the ability Cellular concrete is an excellent material for reroofing ap- to control the density of the material. ment of Energy reported on a new innovative void-filling tech.8 cm (1. modified bitumens. discuss these roofing membrane systems further. removal and replacement of poor soils. and it holds nails. Nailing is important in the case of at. It is then topped with the final cellular con- Applications crete roof deck fill resulting in a slope-to-drain surface ready Cellular concrete can be used in a wide variety of applications for the membrane roofing. Nailing within board (EPS) is often included in a sandwich construction over seven days of concrete placement is desirable. the the structural deck. and re- tenuation characteristics to floor/ceiling systems.23. the better the nailability and sawability of the otherwise casting the slurry on to the deck and laying the EPS material [5. Nailability and Sawability The typical mixture utilizes a predetermined quantity of Low-density cellular concrete can be sawn. plications. In tions [37]. scaffolds. Each Cellular concrete floor fills are very effective in floor re. density blocks and steel-reinforced panels that have structural sulating cellular concrete is cast generally becomes a permanent properties. floors. thermal insulation. and sels and prevent them from collapsing. application is unique and must be considered on its individual habilitation for the renovation of older buildings. and the quality of other ingredients such as Properties. [1] Legatski. R. 91–100. L. S...” (ACI 213R-87) (Reapproved 1999). [2] Legatski. Vol. M.” ACI Commit- Concrete” and C 15. 138... de Groot. essary to bring the wet density within the specified range. signed for the application. C.” ACI Materials Journal. No. well as continuing research into new areas such as specialized pp. F. pp. ACI 523. Properties such as permeability.. cific density and mixture of cellular concrete could be de. pp. and currently two Prentice Hall. If [11] Autoclaved Aerated Concrete. “Rational Proportioning of Preformed Foam and cost-effective material is desired. C. T. R. Lim.” ACI 523. Vol. [12] Bave. Vol. 2002.. John Wiley and for Preformed-Foam Cellular Concrete. “On Production and Application of AAC materials. pp. F. 1971. J. T. 133–146. Svanholm.. “Porosity-Strength Considerations for Cellular 169C.. PA..” ACI SP-29.. 2003.10 “Autoclaved Aerated Concrete Masonry” tee 523. June 1954. Folker H. Ed. Properties of Concrete. 402–409. C.. 10. Concretes Above 50 pcf with Compressive Strengths Less Than 2500 psi. American Concrete Institute. 1992. [21] Reichard. 2.. Alexandria. Skokie.. T.3R-93. and No. Aroni. February 1967.. Economics. the Robinson. F. American Concrete though it has been used in construction for over 50 years. mixing. M. “Cellular Concretes. C. G. 12–18.” ASTM STP [24] Tam. Vol. Wittman.” ACI Materials Journal. R. D. ACI Committee 213. A. “Development of De- formable Protective System for Underground Infrastructure Us- ing Cellular Grouts. Khan.. July 1991. Winter 1998. nificant opportunities for expanding existing applications. Cement Association. There are sig. May 1954.. . New York. Quality Control and Testing Co. “Mechanical Properties of Insulating able option for a broader range of applications. and the use of supplementary cementitious [13] Dubral. G. Vol. G.03. Field quality control procedures for cellular concrete involve [9] Special Types of Concrete. D. “Chapter 49 — Cellular Concrete. 1. 12. materials and innovative mixture proportions will make it a vi. Al. 2nd ed.S..” ACI Commit- claved Aerated Concrete Elements (C 1452)..” ASTM STP [25] Hoff. are active in producing standards for AAC. sand gradation. J. Djebbar. December 2003. and Hays. [26] Nehdi. No. “Chapter 48 — Cellular Concrete. Vol. Concrete. 490–498. 64. 39. 533–539. Moisture and water-cement ratio. 1993. Lightweight Concrete... ACI 523.” Cement and Concrete Research. Vol.” Concrete the point of placement.” of the mixture.. Wittman. MI. Building Product In The U. ASTM subcommittees C 27.. 99. E and FN Spon.. M. Fifth Alexandria International Conference of Structural and sistance. and Darwin.. “Autoclaved Aerated for subsequent curing and compressive strength testing. Eds. W. 1983.” ACI Journal. and for Aggregate standards are ASTM Standard Specification for Precast Auto. Manufactured Concrete Magazine. Proceedings. Currently published [6] “Guide for Cellular Concretes Above 50 pcf. tee 523. 5. F. NY. The ability to introduce a large volume of macroscopic. [20] Benjamin. new Institute. M. pp. September–October 2001. Jenny and Albert Litvin. batching. M.. L. 631–635. tinctive properties. Upper Saddle River. Conshohocken. material performance properties. pp. “Engineering Material Properties of discrete air cells uniformly distributed throughout the matrix a Fiber Reinforced Cellular Concrete. and Dembowski. “Autoclaved Cellular Concrete— cylindrical test specimens from the measured wet density at the Building Material of the 21st Century. Conshohocken. 1971.. Ed. G. and Hurd. 1978. Decks. 3rd ed.” ACI Materials Journal. Concrete-Making Materials. “Regional Climatic Conditions. September–October 1998.” Advances in Autoclaved Aerated Concrete. 1978. 253–316. 2. and Lee. The Netherlands: Elsevier Scientific Publishing Company. A. Jr..” Conference Proceedings of the ture quality. 1386) and ASTM Standard Specification for Reinforced Auto- [7] “Guide for Cast-in-Place Low-Density Concrete. I. and Lo.. Y. H. 1999. London. Vol. ACI Committee 523. 1993. No.” Magazine of Concrete Research. 95. G. W. Com. West Concrete. parameters—strength and density. pp. American claved Aerated Concrete (PAAC) Wall Construction Units (C Concrete Institute. 50.. IL.” ACI SP-29. insulative. M. D.60 “Precast Autoclaved Aerated [5] “Guide for Cast-in-Place Low-Density Concrete. makes it suitable for a large number of specialized applica- The Aberdeen Group. NJ. Detroit. L.” ACI Journal. P. 817–836. freeze-thaw re. and Khan.. 1971. Significance of Tests and Properties of Concrete and Concrete. pp.” Autoclaved Aerated Concrete. American Concrete Institute. 1992. March 1987. 2. Y. K.. J. American Concrete Institute. “Lightweight Insulating Cellular concrete has a variety of unique properties that Concrete for Floors and Roof Decks. 836–851. tions.” Publication #C780411. A. J. The actual quality control procedure involves securing [14] Portland Cement Association. in developing standards for this material. [16] “Guide for Structural Lightweight Aggregate Concrete. ACI SP-29. pp. Detroit. A. “Neural Network Model [3] Neville. MI. moved from protection at the casting location to the laboratory [15] Fouad. “Relationship Between 169B. [19] McCormick. PA. 1992. Significance of Tests and Properties of Concrete and Strength and Volumetric Composition of Moist Cured Cellular Concrete-Making Materials. F.. pp. F. pp. material should have only minor deviations in density. Concrete: An Experimental Program For Establishing A New pressive strength and density are the primary indicators of mix. “PAAC — A New Precast Product in the U. Slight adjustments in the mixture may be nec. Young. W. Pearson Education. Portland measuring the wet density of the material at the point of place. pp. No.. The physical properties of the mixture are repro- Worldwide. 98. and Wittman. Egypt. Summary [17] Steiger. American Concrete Institute. The Netherlands: RILEM. [18] Zollo. as [22] Valore. H. Lightweight Concrete. No. 104–110. S. A. After a few days. Sons. inert. K. Eds. S.. Cellular Concrete. C. Septem- References ber–October 2002. Building Physics and lated to the mixture design parameters such as cement content. is the key factor that provides cellular concrete with its dis. No. and water absorption correspond to these measured Geotechnical Engineering. it is possible that a spe. 9.. Whenever a lightweight. 1994. and placing procedures are consistent. [8] Lightweight Concrete..1R-92. 773–796. West January 1972. Y.S. 1994. ASTM International. ASTM International.. H. ment and comparing this density with the design wet density [10] Fouad. Report Number IS183. The physical properties of cellular concrete are closely re.. Concrete. “Cast-in-place Low Density Concrete in Roof Cellular concrete has many potential new applications. H. these samples are Technology Today..568 TESTS AND PROPERTIES OF CONCRETE worth noting that ASTM has been active since the early 1990s [4] Mindess.A. Folker ducible within acceptable limits.1R-92. [23] Nehdi. “Fire [34] LaVallee.” Signifi- Committee on Fire.” ACI Materials Concrete. 503–524. pp.” 29. Lightweight Concrete. of Lightweight Insulating Concretes. . pp. 19. Vol. 1999... F. C. 1971. G. “Prediction Relations for [32] Zollo. 1970. A... “Habitat for Fiber Reinforced Compressive Strength of Altered Concrete.” Lightweight Concrete.” ACI Innovative Technology Summary Report. 1978. 97. G.. No. “Testing Applied to the Evaluation Detroit. 217–232. The Aberdeen Group. [35] Hoff. 5. Science and Technology. MI. Gustaferro. No. D. FOUAD ON CELLULAR CONCRETE 569 [27] Narayanan. H. “Lightweight Concrete and Aggregates. 221–251. C. Abrams. [28] “Fire Resistance of Architectural Precast Concrete. [31] Hays. A. American Concrete Institute. C. SP.. Portland Cement Associa. Lightweight Concrete. and Zollo. M. ASTM International. K. D. West September–October 1974. MI. 181–220. Skokie. MI. American Concrete Institute. D. and Hays. R. pp. Testing of Fiber Reinforced Concrete.. pp. S.. 6. ASTM STP 169B. 161–180. pp.” ACI tion.. PA. Detroit. Office of Concrete Institute. 1995.. S. Abrams. Department of SP-155. Materials.. Development Bulletin No. A. “Low Density Concrete Backfills for Lined Tunnels. cance of Tests and Properties of Concrete and Concrete-Making Journal of the Prestressed Concrete Institute. SP-29. 1971. N.” Publication Resistance of Lightweight Insulating Concretes. F. A. 1971. and Litvin.” Concrete International. IL. M. S. June 1994. C. and Ramamurthy. pp. Conshohocken. R. May–June 2000. Journal. W.” DOE/EM-0458. ACI SP 29. “Cellular Concrete to the Rescue. Vol. [36] Hoff. Missile Impact to Building Envelopes During Storm Events.S. Prepared by Armand H. 367–373. U. “Fire Resistance Detroit. American Concrete Institute. “New Applications for Low-Density Concretes. of Damage to FRC and Other Material Systems Caused by Large [37] “Low-Density Cellular Concrete Void Filling. H. 23–26. [30] Gustaferro. pp. Vol. [29] Gustaferro. RD004B.” Research and #C99A039. 16. Office of Environmental Management. and Litvin. American Energy.” PCI [33] Lewis.. August 1999.. gle grain of sand in his palm. Concrete can even be enhanced as a shielding material of pertinent radiation shielding materials used in concrete. neutrons. concrete SUBCOMMITTEE C09. First is the enormous volume of • Practice for Making Test Cylinders and Prisms for Deter. chemical composition. knowledge of radiation concepts is essential for design- study by this subcommittee led to the development of ASTM ers. If the grain of sand is thought to 1 Technical Staff Member. are balanced by an 638. As an example. called protons. This properties. Building from this foundation of understand- crete (C 637) ing. All elements consist of unique configurations of atoms. The neu- • Test Method for Expansion and Bleeding of Freshly Mixed trons and protons are bound into a tight mass at the center of Grouts for Preplaced-Aggregate Concrete in the Labora. NM 87545. Sub. • Specification for Aggregates for Radiation-Shielding Con. Volkman1 Introduction Radiation Shielding Primer History and Responsibilities Beginning with the early days of the nuclear industry. University of California. an atom has some num- • Specification for Grout Fluidifier for Preplaced-Aggregate ber of neutrally charged particles. are developed. The with the use of special additives and aggregates to provide spe- predecessor subcommittee. the atom. a certain number of concrete standards in addition to ASTM C 637 and ASTM C positively charged particles. atoms are uniquely configured with the same Preplaced-Aggregate Concrete (C 938) number of protons for each element. Basic concepts. think of children playing on the beach. but they may contain a • Test Method for Flow of Grout for Preplaced-Aggregate variable number of neutrons. Electrons contribute virtu- (C 941) ally no mass to the atom of an element.41 is responsible for the preplaced-aggregate maintain the electrical stability of atoms. Electrons • Test Method for Water Retentivity of Grout Mixtures are also bound to the atom. 570 .41 IS RESPONSIBLE FOR ASTM has been used as a radiation shield because its mechanical standards dealing with concrete for radiation shielding. was estab. MS-K718. for Radiation-Shielding Concrete (C 638) [1] Preplaced-aggregate concrete is a method used to make Pertinent Atomic Structure and Physics very dense and uniformly consistent radiation barriers. Los Alamos National Laboratory. designated C09. cific attenuation characteristics.08. consisting of selective nuclear physics to- standards as noted: gether with applicable material properties and interactions. Now visualize the grain of sand Aggregate Concrete in the Laboratory (C 953) centered inside the beach ball. called electrons. the entire mass of an tory (C 940) element is concentrated in the nucleus of its atom. Los Alamos. In order to establish a firm ba- lished as a result of a joint symposium conducted by ASTM and sis for using the materials mentioned in ASTM C 637 and the American Nuclear Society in 1965. Like elements with differing neu- Concrete (C 939) tron counts are called the isotopes of the element. make it compatible for withstanding imposed service de- tablishing and maintaining the standards needed for regulation mands. empty space that is contained within the atom.02. mining Strength and Density of Preplaced-Aggregate Con. called the nucleus. One is holding a large crete in the Laboratory (C 943) plastic beach ball with both arms. associated with a Concrete (C 937) particular element. and ease of construction concrete systems subcommittee is assigned the charter of es. follows: In addition to protons and electrons. The designation and titles for these standards are as equal number of negatively charged particles. the significance of the tests and specifications needed to • Descriptive Nomenclature of Constituents of Aggregates make concrete for radiation shielding is evident. Essentially.48 Concrete for Radiation Shielding Douglas E. To committee C09. Results of three years of C 638. while the other cradles a sin- • Test Method for Time of Setting of Grouts for Preplaced. but they orbit the nucleus in a set for Preplaced-Aggregate Concrete in the Laboratory pattern of separate levels or shells. Fundamental to the structure of any par- • Practice for Proportioning of Grout Mixtures for ticular element. • Test Method for Compressive Strength of Grouts for There are two important concepts to keep in mind with the Preplaced-Aggregate Concrete in the Laboratory (C 942) preceding model of the atom. These particles are important in maintaining the tromagnetic waves.57022E22 Al 125.07852E22 3. X-rays because the source of X-rays is external to the nucleus. rather than just wave-like phenomena. consider a sampling of the non-ionizing fission process by striking other potentially unstable atoms and electromagnetic spectrum: creating a chain of fission activity. so called because their atoms are com. This is because heavy elements are composed of an gamma rays. • Microwaves have frequencies of 2 540 000 000 Hz and tic covering of the beach ball can be thought to represent the wavelengths of 12 cm (5 in. ton. During radioactive decay. without orbital electrons. trons that are emitted from the nucleus of an atom.47809E22 3.61986E22 5.0955 3. particle component of electromagnetic waves is called a pho- which contain large numbers of protons. achieve a more stable configuration. Table 1 provides a listing of elements and the and a wavelength of 100 nm [3].16 0. This type of ra- matter or energy. ionizing electromagnetic waves. have a frequency starting at around 1 000 000 000 000 000 Hz tained in matter. For a comparison of light and heavy elements. VOLKMAN ON CONCRETE FOR RADIATION SHIELDING 571 TABLE 1—Number of Atoms in 4000 psi (27 580 kPa) Concrete Element Unit Weight Proportions Grams per cm3 Atoms per gram Average Atoms per cm3 Si 1234. In contrast.0353 1. This spontaneous stabilization process transforms X-rays and gamma rays.12403E22 be of comparable size to the nucleus of an atom.65 0.84 0. increasingly larger numbers of neutrons. compared to the Nuclear particles.014 2. cle characteristics. zero charge he- contains one proton and no neutrons. of heavy elements is so configured to afford sufficient volu.0272 1.61724E21 O 1846. Gamma rays are similar to X-rays but the element into sulfur-32 [2]. Gamma rays are different from number of atoms per cubic centimeter for normal weight con. and neutron.14452E22 1. hydrogen protons and neutrons (He) occur. while uranium-235 con.66081E21 Fe 59.80718E20 Ca 311. and this term is essentially interchangeable with x-rays and stable.95 0.) electron orbits of the atom. this high ratio of stitute ionizing radiation too.1851 1. are usually thought to have higher energy levels (more cycles Neutron particles are released during spontaneous or in- per second). heavy elements. Only ionizing radiation needs shielding. but neutrons to protons creates the potential for instability as the three listed particles are representative of the usual type of contrasted by the light elements.0032 1. this is called (positron). instigating fission activity are beryllium and its alloys. and two or- tains 92 protons and 143 neutrons [2].94455E22 1. the more stable state of uranium-235 [2]. such as alpha.25828E22 4. metric separation of the individual protons to accommodate During the decay of certain atoms.46 0. duced fission. necessitates particle nucleus. particularly large ones.0208 2.23227E22 1.84 0.02649E19 P 1. while gamma rays are generated from the nucleus.09 0. beta.46933E20 S 7.78172E21 Mg 23. have very stable nu.97579E23 5.55564E19 H 15.54048E22 4. This process of altering Beta particles consist primarily of negatively charged elec- atoms to achieve stability is called radioactivity. matter. consider the decay of and the two major categories are as follows: phosphorous-32. These length of 5000 km (3100 miles) materials are excellent participants to initiate chain reactions • AM radio waves have frequencies of 1 000 000 Hz and because the low neutron binding energy of beryllium provides wavelengths of 300 m (1000 ft) a ready source of neutrons to encourage this process [5].87837E22 7.09 0. To understand the significance of ionizing elec. the helium atomic cleus of an atom. A neutron in the atom decays into a proton • Electromagnetic waves and an electron.36 0.7322 2. ing regarding atoms is the enormous number of them con. emission of pairs of cles. The second important understand. Sometimes dioactive particles or energy have the ability to interact and a beta particle is released as a short-lived positive electron alter the structure of atoms of biological tissue. Other nuclear particles exist.0744 2. or both. lium atom consists of two protons. A stable. such as X-rays. If the ra. Subsequently. ergy levels.76452E22 4. and the proton count of the atom increases by Ionizing electromagnetic waves consist essentially of one to 16. Alpha particles consist of positively charged helium atoms.30 0.50282E22 2. then the plas. The structure of the nucleus ionizing radiation requiring shielding [4]. two neutrons. As an example of beta radiation.0008 1.88916E19 Na 35. crete used at Los Alamos National Laboratory.1901E20 Ti 5.0094 5. electromagnetic waves predominately display parti- posed of the fewest number of protons. is released. Instability in the nu. In . such as plutonium-239 into the forces perpetuated by the positive charges of those parti.4493E20 K 45. At the opposite end of the spectrum. which quickly annihilates in the electric field of ionizing radiation. bital electrons. Notable neutron sources for • Electricity has a frequency of 60 cycles/s (Hz) and a wave.0042 1.36 0. are somewhat un. con- proton count in the nucleus. A forced release of the electron from the nu- • Nuclear particles [1] cleus occurs. At high en- Light elements. The clei. to be released from the atom to dioactive emission defines alpha particles.50 1. neutral radiation particles and energies will simply Pair production attenuates photons through the proximity pass through most atoms but eventually will make an impact. Light elements. However. may be in an unstable configuration. the chance the electrical charges of the atoms comprising matter. The physical size. quently. radiation. ondary radiation. though. Because of ness can be reduced. Dense elements consist of large atoms that have numerous Radiation shields are designed and constructed to capture all shells of orbital electrons. Conse. the trating radiation is only a biological threat if the particles are in. which will health. materials is the key for optimum photon attenuation. cancer. Recall a previous statement that atoms have photons will attenuate quicker with heavy elements. the nuclei of heavy or light atoms. but photons are released from the interaction. making it an isotope of the element. the electri. and absorb the particles. eV. the mechanics of a shield can be viewed. shield thick- decay of naturally occurring radioactive materials. such as contained in mag- Shield Mechanics netite or steel. pacting the nucleus of an atom. An depending on the amount and length of time of the exposure. type of collision. beta. Energy loss occurs as a result of numerous interactions as the Instead. if houses. penetrations Photon attenuation is attained from different processes from through the floor. nonpene.5 electron volts (eV). coma. while penetrating radiation constitutes a particle impacts the receptive nucleus with sufficient energy to biological threat from sources external to the being. and binding energy is released as secondary gamma not penetrate human skin. neutron. scattering. Alpha and probability that the neutron will collide rapidly and multiple beta particles are deflected and absorbed by interacting with times in its path through the shield. causing it to quickly de- ous newspaper accounts describe radon contamination of cay into two different. through a shield. and environment issues. These deposits develop as by-products from the that increase the probability of quick absorption. safety. Radiation cause the release of another neutron from that nucleus. Alpha particles can. are most important for shielding purposes. tenuation mechanisms are important in stopping photons. very heavy (dense) elements. of the nucleus and the electrical (Coulomb) fields of the atom . In con. Increasing the mass of a shielding material pacts and bounces off the nucleus in a process called inelastic is the most effective method of increasing the probable inter. of cells composing the various organs [4]. the target atom has an increased neu- Although beta particles can penetrate and damage human skin. contain large nuclei from iron. thermal neutrons are absorbed by im- Radon gas is an example of naturally occurring non. and influence of the electrostatic field between the of shielding focuses on the radiation requirements for neu. nucleus. respectively. the neutron slows enough for the physics of Shielding is required to protect people and the all. such as boron. those described for neutron particles. there are three types of neutron particles of in. Simply stated. Three at- vast amounts of empty space within their confines. Neutron Attenuation A radiation source emits a fast neutron into its concrete shield. Fast neutrons have kinetic energy levels exceeding 500 000 eV [6]. Physical and Biological Perspective Heavy materials. However. genetic mutations. This occurs because plumes of radon gas exist in-situ a radiation shield contains certain elements. tron count. cally charged particles of atoms do not affect neutrons. Slow neu. abundance of hydrogen in a radiation shield increases the Penetrating radiation consists of gamma rays and neutrons. deflect. unless ingested. scientific accelerators produce beams of Therefore. these particles collide inelastically or elastically with deflected travel path slows the neutron. Intermediate en- encompassing environment from the effects of radiation. in the ground. gamma rays are absorbed by the interaction with orbital hitting a small atom of a light element. Design electrons. such as for utilities. without leakage of sec- Generally. which are big targets for emitted neutrons.572 TESTS AND PROPERTIES OF CONCRETE addition to fission. The fol- energy levels less than 0. will allow the gas to mi. of hitting the big atom of a heavy element is much greater than trast. They are grouped according to the the hypothetical path of a high energy neutron and photon level of kinetic energy associated with the particle. newly emitted neutron has significantly lower energy. more stable elements. Consequently. as the probabilistic occurrence that a neutron or pho- Radiation from these processes must be shielded to address ton will interact with a sufficient number of atoms. Attenuation is best explained by following terest in radiation shielding. at retention of neutrons in this energy range. The neutron particle remains an entity from this action with orbital electrons. its gaseous form. not just one. low energy. As with gamma rays. another attenuation mechanism to prevail. Now. Both ergy neutrons have a propensity for retention in the nucleus of nonpenetrating and penetrating radiation can ionize or break atoms. number of orbital primary and secondary radiation emitted by a source. Interaction with dense grate into occupied space. The neutron is retained in the penetrating alpha and beta radiation [7]. The exposure effects on humans consist of radiation sickness. Such Any material of sufficient thickness can be used as shielding materials are often used in concrete shields to increase the against alpha. such as magnetite or steel. Intermediate or lowing descriptions highlight the shielding evolution for neu- epithermal neutrons have kinetic energy in the vicinity of 5000 trons and photons. sterility. but they are harmful if ingested. Attenua- cataracts. In concrete. funda- neutron particles for a variety of experimentation purposes. This probability that elastic scattering will occur quickly after neu- type of radiation can penetrate the body and damage the atoms trons attain intermediate energy levels. Eventually. mentally. such as hydrogen. are particularly adept the bonds of atoms in human body cells. slow. Numer. neutron retention is not an absorption process because the troduced internally. Slow. and gamma radiation. although an actual shield will attenuate enor- trons are referred to as thermal neutrons and have associated mous numbers of radioactive particles. The fast neutron im- electrons of atoms. charged particles significantly increase the probability that trons and photons. The isotope betas cannot penetrate body organs. and death— tion by this type of interaction is called elastic scattering. this type of radiation is easily inhaled into the lungs where it will damage tissue. Although the floor of a house Photon Attenuation is capable of shielding against radon radiation. iron. and second. Proper mixing and placement of the concrete is essential to teracting with an atom of an element. 99. purposes. In this process. natural minerals used in concrete for radiation shield- • Hydrogen. tion mechanisms inherent in and characteristic of a particular ence of the atom and disintegrates into two electrons of oppo.0 barns [9] matrix. natural materials used in concrete for radiation important for inelastic scattering of neutrons.0 barns for high-energy photons with an atom [8]. The result of this interaction causes the photon to absorption cross section and releases low energy gamma rays deflect and to lose energy. shielding consist of serpentine (3MgO 2SiO2 2H2O). the impact between the pho. breaking ores (such as magnetite. is anti-matter.5 to 4. As with Compton scattering. special shielding minerals. Absorption Cross Section The absorption cross section is the material property represent.2 [10]). 8.3 barns of pair production is the predominant process of attenuation • Oxygen. high-energy neutrons. 755. a known carcinogen. water. The absorption cross sections of some typical elements site charge. Their use in con- aggregates in concrete for this purpose. and • Silicon. Terms for Shield Design Calculations Concrete Materials Of the numerous material properties and constants associated with shield design. iron or . valued as a shielding material. as well as scattering and absorbing ing cross section. absorption occurs through the interaction Absorption of low energy photons occurs through photo. are an expression of the sum of the scattering attenuation mechanisms inherent in and characteristic of a particular ele. For all practical absorb lower energy neutrons. with an orbital electron of a target atom. The scattering cross sections of some typical elements Shielding Attributes commonly found in concrete shields are listed as follows: Heavy. such as iron. This conglomeration of materials Scattering Cross Section results in a concrete mix consisting of both light and heavy ele- The scattering cross section is a function representing the ments as is required to achieve an effective radiation barrier. For concrete mixes. 1.5 reduce the energy. limonite (Fe2O3 XH2O. These aggregates are substituted • Iron. the photon enters the electrostatic influ. dense aggregates consisting of (Fe2O3 H2O).2 barns [9] ton and the orbital electron dislodges the electron from its shell An elemental isotope. In this process.2 barns with a specific gravity ranging from 4. 0. which has a large scatter. two fundamental terms are selected for dis- Normal-weight concrete consists of cement. Scattering cross sections make the barrier as homogenous as possible. heavy elements. Such a radiation barrier is effective at scattering An element. Hydrous homogeneous nature of the concrete is more important than aggregates moderate neutrons through elastic scatter and also the particular set of heavy aggregates used.6 to 5. can alter dustry with clients or designers in the nuclear industry. also referred to as im- heavy elements are the best concrete materials to scatter and pure goethite. such as boron-10.0 barns for usual concrete aggregate to obtain a high-density concrete • Barium. Knowledge of these terms is important to enhance coarse aggregate. and hematite) are used as dense materials are known as hydrous aggregates. serpentine contains asbestos. ilmenite. ilmenite. steel. Typically. rather than any particular heavy aggregate used. VOLKMAN ON CONCRETE FOR RADIATION SHIELDING 573 [2]. are Light. Absorption cross Manufactured products used for gamma shielding typically sections are an expression of the sum of the absorption attenua. steel. The final density and crete enhances the hydrogen content of the shield. is most beneficial when used as an elastic photons. the gamma-ray energy. and iron ores (such as [10]). which can be gen. sity. the composition of normal-weight concrete into an efficient radiation shielding material.2 barns action with an orbital electron of an atom. Dense materials con- electric effect. barites. 1. in the form of sand and coarse aggregate.0 barns (FeO TiO2). The final mix den- all remaining energy to the expelled electron [2]. hematite (Fe2O3) [11]. For photons. This effect is called • Iron. the photon inter. such as hydrogen. For instance. The addition of natural or manufactured communication exchanges between people in the concrete in- minerals. and iron energy of the photon is completely dissipated by first. sisting of heavy elements are the best materials to control acts with an orbital electron of an atom. scattering material. 4. forming low energy photons. • Silicon. These magnetite. • Boron. iron. as well as colemanite (2CaO 3B2O3 5H2O [11]). This is the most significant attenuation as secondary radiation. Natural Minerals to Enhance ment. goethite For gamma radiation. Large. 4. ilmenite • Boron. • Barium. Manufactured Aggregates to Enhance ing the probability that a neutron or photon will be absorbed Shielding Attributes by interaction with an atom of an element. thickness of concrete shields is proportional to the Caution must be exercised in working with some of these density of the mix [1]. 0. is the most important aspect of gamma radiation shield design. In this process. 11. The physics • Hydrogen. barytes. by imparting used to increase mix density for shielding.5 barns Compton scattering.0 barns ing consist of magnetite (elemental composition Fe2O3 FeO • Oxygen. The properties of boron-10 are highly mechanism of medium energy gamma rays. and hematite) are the electron free of its atomic shell. or positron. probability that a neutron or a photon will be scattered by in. and cussion. It commonly found in concrete shields are listed as follows: annihilates quickly. element. The positive electron. 2. consist of ferrophosphorous (FeP or Fe2P or Fe3P). sand.0 barns A scattering attenuation mechanism involves photon inter. barite (BaSO4). has a very large in the atom. erated as secondary radiation from thermal neutron capture [8].7 barns witherite (BaCO3) [10]. 0. with a specific gravity ranging from 3. Manufactured iron and Boron carbide (B4C) and calcium boride (CaB6. caution is advised in using this material [10].8) limonite [8–12 %] c Heavy ore Boron additives barite (4. Densities product from the production of phosphorous.6) iron or steel shot (7. Table 2 lists these aggregates along with the density of each material. able using heavy aggregate in the mix.574 TESTS AND PROPERTIES OF CONCRETE TABLE 2—Aggregates Used in Shielding Concrete [1] Natural Mineral Manufactured Local sand/gravel Crushed aggregate calcareous (2. Compressive and rupture strengths both Commonly Specified for Given Heavy Aggre. and steel punchings [11]. Type of Aggregate Density. The average compressive strength of the 20-year-old heavyweight concrete in the reactor shield increased in the same . Concrete Ilmenite 3500 to 3850 220 to 240 core samples from the shielding of this plant were obtained and Ferrophosphorus 4550 to 4800 285 to 300 tested for physical and thermal properties. Because of its Standard heavyweight concrete.7) a heavy slags (~5.8) borated diatomaceous hematite (4. decrease with time due to radiation exposure and high tem- gates [1] perature. Ferrophosphorous is a by. lb/ft3 Density.6) calcium boride 2.2–4. which Magnetite 3500 to 3750 220 to 235 had been operating for over 20 years. magnetite. Barite. as well as laboratory test specimens. A nuclear power plant.3) basaltic (2. The results from this Barite and boron additive 3200 to 3450 200 to 215 testing were compared with the test results of samples from the Magnetite and boron 3350 to 3600 210 to 225 original construction.6) magnetite c ferroboron (5. kg/m3 Ontario Hydro Research Division researched the effects of Barite 3450 to 3600 215 to 225 radiation exposure on concrete.1) ferrosilicon (6.4–2. as well as ferro boron.0) ilmenite (4. can achieve densities up to 3850 kg/m3 (240 lb/ft3) [1].4–3.7–3.4) gerstley (2.6–5.5–7.0) borate a Specific gravity is shown in (). such as degradation.8–6. although the effect is tolerable under normal reactor conditions [12]. using natural iron ore aggre- poor attributes as a concrete aggregate. Irradiation Effects There are damaging effects to concrete used as radiation barriers from the scattering and absorption processes.8) [15–25 %] b steel punching serpentine (2. Irradiation of concrete causes dissociation of water into its hydrogen and TABLE 3—Densities of Shielding Concretes oxygen components. additive A summary of some of the findings of this research follows: 1. Table 3 lists concrete densities attain- with borax (Na2B4O7 10H2O) [11].6) [10–13 %] goethite (3.5–7.3) sheared bars (7.0–4.5–2.5 Boron additives calcium borates borocalcite colemanite (2.0) Hydrous ore Metallic iron products bauxite (1. gate. c Refer to chapter section on Concrete Materials steel shot.2) earth (1.4) boron frit (2. neutron absorption. was studied.0) siliceous ferrophosphorous (5.8–2.0) witherite (4.7–7. b Water of hydration is indicated in [].3–2.5) are manufactured products that are efficient for than 4000 kg/m3 (250 lb/ft3) [1].3) boron carbide (2. with a specific steel aggregates are used to achieve concrete densities greater gravity of 2.5 to 2.4–2. and ilmenite are the traditional materials Boron frit consists of the fritted product of silica (SiO2) used for this endeavor. thermal concrete standards. For concrete shields functioning at temper. enced ASTM Standards. specifically used in concrete for radiation shielding. uniformity on specific gravity and fixed water content. it is common to in. 3. Of course. . concrete 2. natural mineral. higher w/c ratios ASTM C 637 must be monitored so satisfactory performance for strength is This standard is a specification of fine and coarse aggregates not sacrificed. common components of concrete. The following are The samples. so further testing with the test ra- high temperature applications. Cast-in-place concrete for radiation shielding or precast con- atures less than 105°C (220°F). specific gravity. deleterious Placement and Verification Considerations substances.0 times the played variations (approximately 10 %) between samples cost of normal concrete on the farthest face compared with samples closest to the • High hydrogen content. were roughly 30 % less for the bility may affect cost. 4. and boron frit glasses. gates are covered by this specification. these special materials also increase the cost of shields through both higher material costs and the expense ASTM C 638 associated with construction.0 to 9. competitiveness of the thermal conductivity. However. As a worst-case scenario. 20-year-old heavyweight concrete shield samples as com. The be written specifically for each shielding job.) from the exposed face of concrete subjected Radiation Shielding to a radiation flux. In this way temperatures would be important. concrete should be made with diation source can follow. which is a measure of heat trans. Composi- tion. which helps explain the rate at These values must be considered “Ball Park” values be- which a material undergoes temperature change. below the minimum specified. procedures. The verification process starts with a visual inspection up to 50 % of its compressive strength when it is exposed to of the shield. because total original water content to be lost over the useful life of the it provides specific descriptions of special aggregates used in concrete shielding [14]. Limonite dehydrates above shielding deficiencies can be corrected during facility con- 200°C (400°F). concrete [15] 3. The following paragraphs occurring as a result of high temperatures. A key provision of the specification is the requirement for tor or accelerator may require concrete masses that are pro. Facility designs may impose space constraints a 3 % limitation on the variation of bulk specific gravity of the on the design of the shield. There is hibitive in size. However. contractors varies. covered are iron minerals and ores. the mixing and Descriptions of the various fine and coarse aggregates specifi- placing operations are more difficult because the very heavy cally used in concrete for radiation shielding are presented. If shielding requires ag. All shield penetrations and other deficiencies temperatures of 430°C (800°F) for a long period of time. as well as requirement exceptions for the various refer- Normal-weight concrete. nuclear and mechanical properties are affected ASTM Standards by both temperature gradients and changes in temperatures. facility. and cause material and labor costs fluctuate. The specification nomenclature defers to ASTM C 294. up to 370°C (700°F) [1]. subjecting the concrete to lower recorded. fixed water content. One such process. showed comparative costs for general categories of concrete shields: compressive strengths 10 to 20 % less than the samples ex.3 times the cost of normal radiation source. ness. while hydrous aggregate must not fall more than 5 % tate the use of special shielding materials to increase effective. with no special aggregates or addi. boron minerals. Radiation flux through the shield is then measured. These types of constraints necessi. 1. and compared with calculated values. VOLKMAN ON CONCRETE FOR RADIATION SHIELDING 575 progression from the radiation source through the shield. Standard Descriptive writer should have knowledge of cost of the various materials Nomenclature for Constituents of Concrete Aggregates for the available for shielding and the difficulties involved in con. briefly summarize the two standards. as amended by ASTM C 637 for aggregates. grading. structing the shield with these materials. It incorporates the use of a test radiation Concrete used in a nuclear reactor to shield the core may lose source. Shield verification practice for nuclear facilities should pared with the laboratory-tested heavyweight concrete follow good engineering practice and include documented specimen [13]. crease the water-cement ratio (w/c) of the concrete in the initial construction of the shield. high-energy gamma rays and neutrons from a reac. aggregates or the special fine aggregates make uniformity This standard is useful to obtain an understanding the specific harder to achieve when compared with the construction prac. and other factors such as material availa- fer through a material. effects from radiation have caused as much as two-thirds of the ASTM C 638 is useful as a supplement to ASTM C 637. To prevent excessive water loss from concrete for radiation shielding. specifications for the ma. • High density. gregates high in fixed water. In general. manufactured aggregate.0 times the cost of normal tracted on the farthest face from the radiation source. • High density. Natural and synthetic mineral aggre- tives. For instance. Therefore. used at the Idaho National Engineering Laboratory. The test radiation source should be heat-resistant aggregates to prevent excessive compressive sufficiently large to emulate actual operating conditions of the strength loss and to avoid dehydration. For need to be recorded in a log. barium minerals. was established to verify the integrity Temperature Effects of a concrete shield. aggregate components used in concrete shielding. Specifically tice for normal concrete. free water will be present in the crete shield blocks should comply with normal-weight ASTM concrete for 10 to 20 years. Research indicates the maximum temperature occurs in the Cast-in-Place or Precast Concrete for first 30 cm (12 in. The modulus of elasticity of the concrete shield also dis. fer- terial components and the construction of the concrete should rophosphorus. The thermal diffusivity. taken closest to the radiation source. is satisfactory to shield any nuclear radioactive source. sample. and abrasion resistance test requirements are listed. while serpentine can withstand temperatures struction without impacting construction schedules [16]. dense concrete shield.576 TESTS AND PROPERTIES OF CONCRETE Preplaced-Aggregate Concrete for lows the process used in the field to construct preplaced- Radiation Shielding aggregate concrete. tion of thermal neutrons. 1989. Neutrons and photons are emitted radiation for which grout to maintain fluid characteristics while reducing water. as lb/ft3) is required for shielding radiation. Appara- are utilized in which reinforcing steel and mix aggregates are tus. and Davis. shields are typically designed. Materials. steel. and test methods for the Normal-weight concrete provides good radiation shielding fluidifier. pressive strength. Milos pansion and bleeding characteristics of preplaced-aggregate Polivka. This test also measures the effect of the fluidifier on the compressive strength of the grout for preplaced-aggregate References concrete. ASTM C 937 Ionizing radiation is a biological hazard requiring shield- This is a specification for fluidifier used in grout to enable the ing. are gratefully acknowledged. grout for preplaced-aggregate concrete. Katherine Mather. Special forms consistency for use in preplaced-aggregate concrete. Alfonso concrete improve shielding effectiveness. The amount of fixed water in con- ASTM C 939 crete can be supplemented by the use of hydrous aggregates.” Significance of Tests and Properties of Concrete and Concrete-Making Materials. technical resources provided by This test method measures the property of freshly mixed Thomas Brown and Alice Slemmons. ASTM C 942 the Laboratory as an institution does not endorse the viewpoint This test method provides a measure of the compressive of a publication or guarantee its technical correctness. formed in the laboratory or the field. Harold Davis. and procedures are covered. minimization of ex- Pioneers in the field of concrete for radiation shielding. Also. gate additive can be mixed in the concrete to enhance absorp- ity of the grout for preplaced-aggregate concrete. The precise location of these Conclusions components and the stringent inspection requirements guarantee a shield of uniform matrix. greater than 4000 kg/m3 (250 This test is essential to determine the setting time of grout. Essex. qualify fluidifiers or to determine the effects of admixtures in Louella Kissane. sampling. John King. while the density is calculated from prism yond concrete for radiation shielding. and procedure standards are covered. sampling. Furthermore. or iron ASTM C 938 ore for aggregates produces a heavyweight concrete that is This practice describes the method of testing required to select most suitable to shield electromagnetic radiation or to scatter correct mix proportions for grout used in preplaced-aggregate fast neutrons. M. Temperature. The use of iron. and administrative staff. Shielding. and its predecessor C09. The presence of hydrogen in a shield is impor- concrete.08 have been given the task to perform this service. therefore. initially placed. enabling the development of this ASTM C 941 chapter. West Conshohocken. This test method establishes the time of efflux for grout which contains high amounts of fixed water. and procedures are presented. preplaced-aggregate concrete is used ASTM C 953 when very heavy-weight concrete. This standard covers physical re. The Los Alamos National Laboratory strongly supports academic freedom and a researcher’s right to publish. the amount of bleed water. S. quirements. or when an especially well as the acceptability of components of grout mixed to fluid high level of uniformity of the mix is needed. characteristics. pp.. in-place concrete techniques or by using preplaced-aggregate construction methods. It fol. 1978. 8–28. sampling. covered in a separate chapter within this publication. Concrete Radiation Shielding. Subcommittee C09. Therefore.02. sampling. .. Hydrogen is abundant in concrete because of mixing water. freshly mixed hydraulic-cement grout over a period of time. “Radiation Effects and specimen. this topic is measurements. or the free water that rises to Acknowledgments and Disclaimer the top of grout. The cylinders are used to determine com- Preplaced-aggregate concrete has commercial applications be. Wilson. It may be per. In general. composition. bility but hardens in conditions that tend to restrain expansion. PA. made immense contributions to the technical subject matter. ASTM STP 169B. rial to capture both. F. This strength of hydraulic-cement grout. Calibration of apparatus Concrete shields are constructed using standard cast- and procedures are presented. Longman Sci- cylinders and prisms for preplaced-aggregate concrete. which has expansive capa- chapter is designated LA-UR-05-3520. M. humidity. 1978. A boron aggre- through a standard flow cone in order to determine the fluid. then pressure grout fills the voids to make a homogeneous.41 deal specifically with making preplaced concrete. but altering the constituents of the mix can optimize the shielding properties. H. is determined. entific & Technical. 420–434. as well as the support hydraulic-cement grout to retain mixing water. ASTM Interna- ASTM C 943 tional. Although neutron and photon Fluidifier is used in preplaced-aggregate concrete where a very radiation attenuate differently. pp. The preplaced-aggregate concrete is ASTM C 940 normally used to ensure density and uniformity requirements This test determines the amount of expansion exhibited by of a shield. tant to moderate neutrons. preparation of [1] Polivka. [17]. For radiation shielding usage. concrete is an excellent mate- dense concrete is required. David Padilla. This is used to provided by my boss. unmatched by normal-weight ASTM has been active in preparing and maintaining standards concrete placement techniques. England. This practice covers procedures for making standard test [2] Kaplan. and Dean Keller. The following ASTM standards for concrete used in radiation shielding. Springer-Verlag. Vol. American Concrete Institute.. II—Shielding Materials. Shielding. nal of Testing and Evaluation. 136–167. [16] Oswald..” 1962. II—Shielding Materials. Springer-Verlag. Engineering Compendium on Radiation [7] Glen.116 Shielding. Vol. Berlin/Heidelburg.. 31–33. 1. 1992. 1975. R. pp. Engineering Compendium on Radiation [17] Jaeger. Shielding. F. A.. 276. G. p. URL: http://www. and Bussolini. Berlin/Heidelburg. the Idaho Chemical Processing Plant-Fuel Processing Facility. Ed. Vol. “What is Nuclear Shielding?. pp. G. J. No. VOLKMAN ON CONCRETE FOR RADIATION SHIELDING 577 [3] Moulder.. P. Engineering Compendium on Radiation Alamos. p. Engineering Compendium on Radiation Shielding.” Concrete for Ra. Engineering Compendium on Radiation College of Wisconsin. Springer-Verlag. Journal of Testing and Evaluation. R. Jan. Berlin/ [13] Mukherjee. 1975.. P. J. No. [9] Jaeger. Aug. Detroit.. No. E. Engineering Compendium on Radiation Colemanite and Boron Frit in Concrete for Time-Strength Rela. Ed. Vol. II—Shielding Materials. 27 Feb. Ed.. Vol. England. NM.. Vol. R. ican Society of Civil Engineers. Springer-Verlag.. M. p. 1975. Vol.” Civil Engineering.edu/gcrc/cop/powerlines-cancer-FAQ/toc. Berlin/Heidelburg. 1975. New York. [15] Jaeger.. G..169. Essex.. Amer... Medical [11] Jaeger. II—Shielding Materials.” [10] Kaplan. Vol. II—Shielding Materials. Vol. 1951. [8] Callan. H.. R. “Properties of High-Density Concrete. G. 87. Ed. J. 247–249. Springer-Verlag. Jan. G. 1989. R. II—Shielding Materials. D. Shielding. 1975. 12–13. “Comparison of Fine Particle [14] Jaeger. Los Alamos National Laboratory. Jan. 20. p.. Vol. Scientific & Technical. M.. E. and Shaffer. 80–110.. Aug. Ed. “Shield Verification Testing at diation Shielding. pp. Springer-Verlag. Springer-Verlag. . G. 237. 20. Longman Electromagnetic Fields and Human Health. 1. Radiation Worker Training. 1. 1975. R. Shielding.. Berlin/Heidelburg. J.” Journal of Testing and Evaluation. mcw.” Jour- Heidelburg. [6] Volkman. K. 20.html. 1992. 94 1992. “Concrete for Radiation Shielding. Concrete Radiation Shielding. Ed. L. F. tionship. pp. 1991. 1975. [4] HS Division of Los Alamos National Laboratory. G. Engineering Compendium on Radiation Berlin/Heidelburg. [5] Jaeger. p. 2003 “Power Lines and Cancer FAQ 2). Los [12] Jaeger. pp. R. II—Shielding Materials. Ed.. E. Shielding. Basic Berlin/Heidelburg. polypropylene. so workability tests that employ vibration to produce dynamic Introduction conditions are often more appropriate than the standard slump test because placement in practice normally employs Fiber-reinforced concrete (FRC) in the context of this chapter is vibration. The fiber content should be as small as Subcommittee C12.40 on Glass Fiber Reinforced Concrete Made by the Spray. shotcrete. common in conventionally mixed FRC or in fiber-reinforced Whether the fibers are steel. They are under the jurisdiction of ASTM Committee Aspect ratio and fiber content also figure prominently in C27 on Precast Concrete Products and ASTM Subcommittee determining property improvements in hardened FRC. cussed. The author acknowledges shape. or other materials yet to be evaluated.25 % by volume. 3800 Bays Ferry Trail.06 on Surface Bonding. and microsynthetic fibers in slabs- long slender needlelike particles in freshly mixed FRC. FRC mixtures with low slump flow quite easily when vibrated. 1 % fibers by volume of concrete. helped to address this problem. respectively). in the crosynthetic multifilament or fibrillated fiber types such as 1 Principal. Nature of FRC What is possible in terms of miscibility. and abrasion by and macrosynthetic fibers are generally 40 to 80. that influences the effect of fibers in concrete. C27. nylon. many oped. the aspect ratio should be as small as possible to minimize loss Up Process. but fundamentally it is the volume of the standards of ASTM Committee C9 on Concrete and Ag. and property improvements. but may subsequently become partially aligned by vi. Aspect ratios for steel mixing. is therefore a compromise that varies A brief explanation of the nature of FRC insofar as it differs widely with the nature of the proposed application. fibers to concrete appear very severe when judged under the vious author. they act like very as little as 0. The standards for Fiber-Reinforced Concrete (A 820/A 820M). tend to impart considerable cohesion to FRC mixtures. and usually the action of conventional mixers. Ideally. Johnston. Steel fibers are quite widely used in slabs-on-grade at carbon. However. Also excluded are glass fiber-reinforced mortars of workability and as large as possible to maximize the resist- for surface-bonded masonry that are under the jurisdiction of ance of fibers to pullout from the matrix and thus their rein- ASTM Committee C12 on Mortars for Unit Masonry and ASTM forcing effectiveness.1 kg/m3 tionale governing development of tests and the significance of of polypropylene (132 lb/yd3. the author of the 4th edition. formwork. More than from concrete without fibers is necessary to understand the ra. or inter. possible to minimize loss of workability and as large as possible to maximize reinforcing effectiveness. and include up-to-date references. introduce new technology that has been devel. although the advent of high-range water reducers has pared by the spray-up or other special processes are not dis. or equivalent diameter for fibers of bratory consolidation. static conditions of the standard slump test. impact. This makes the reduction in workability associated with adding tion will review and update the topics as addressed by the pre. Both fiber con- Thin-section. less than 100. Performance Concrete Technologies. The current edi. they are subject to bending. THE CONTENTS either monofilaments or multifilaments. but many meter (lb/yd3) of concrete. conventionally mixed concrete containing discontinuous fibers The workability-reducing effect of fibers depends largely that initially are randomly oriented in three dimensions in the on fiber content and fiber aspect ratio. and is defined for fiber monofila- geometrical constraints at mold surfaces. Aspect ratio is not easily determinable for mi- age caused by breakage that produces shortening and. or subgrade. Fiber content is applicable specifically to it are under the jurisdiction of ASTM defined most conveniently in practice in kilograms per cubic Subcommittee C09.49 Fiber-Reinforced Concrete Peter C. rock. IN PREPARATION OF THIS CHAPTER. cementitious mixtures tent and aspect ratio are often limited by workability consider- that generally do not contain coarse aggregate and are pre. 78 kg/m3 of steel. During on-grade at as little as 0. 9. Tatnall1 Preface case of multifilament strands. ments like steel in the ASTM Specification for Steel Fibers faces with existing concrete. Aspect ratio is the ratio mixture. Colin D. ations. placeability. and the needlelike of the 4th edition were drawn upon.3 lb/yd3. fraction of fibers regardless of the density of the fiber material gregates may apply to FRC with or without modification. of fiber length to diameter. 578 . surface finishing. glass fiber-reinforced. The high specific surface of fibers. and must resist both dam. 15. GA 30062. glass. separation that causes greatly increased specific surface. is un- the properties determined in the tests. or shotcreting and by noncircular cross section.1 % by volume.42 on Fiber-Reinforced Concrete. Marietta. stability. 4000 to 100 000/kg (1800 to 45 000/lb) [1]. air content or density tests. For Freshly Mixed FRC some mixtures rendered extremely cohesive by a high fiber content. external vibration is preferable for FRC when in fiber length or aspect ratio. and unit weight bucket) to develop a possibly the lower the probability of zones of weakness due to test more appropriate for FRC than the slump test because fiber deficiency arising from nonuniform distribution. ever. surface deformation (similar to deformed rebar). ened states are surface texturing. the true influence of fiber size and number per unit concrete mixtures with the same time of flow (Fig. and in the ASTM Specification low-slump and no-slump concretes without fibers. and choice between rodding and vibration. thus nullifying the validity of the test result. or combinations of macro and microfibers of is a measure primarily of stability under static conditions. under the dynamic conditions produced by the internal or Fiber size determines the number of fibers per kilogram external vibrators normally used for placement in practice. or pound of their batch weight and their number per cubic me. Another test that assesses workability under vibration is the ASTM Test Method for Flexural Toughness and First-Crack the British Standard Test for the Vebe Time of Freshly Mixed Strength of Fiber-Reinforced Concrete (Using Beam with Concrete. In smooth monofilaments of uniform cross section are now quite contrast.) flow times in the range of 8–30 s the nominal maximum aggregate size. 1) [6]. BS 1881. vibration should be fibers (Fig. and compactability [5]. fiber blends (hybrids) consisting of ei. tive of placement in practice. content and aspect ratio on the workability of FRC with steel For consolidation of test specimens. and bundling of parameters that determine workability. 1). have taken place over the years. crimping to a Workability wavy rather than a straight profile. Accordingly. fiber size is that the fiber length should be at least as large as 2) [7]. fibers with a water-reactive glue or paper prior to separation in mobility. since . so internal optimize fiber performance in both the freshly mixed and hard. they are satisfactory from the view point of mo- tre or cubic yard of concrete. disturbing the fiber distribution is much less impor- rare. Examples of innovative techniques adopted specifically to tant in. The volume on the performance of hardened FRC is uncertain. Consolidation is accomplished quite easily under vibra- cially available types of steel fibers. hooked or enlarged ends. Part 2. namely. vibration is acceptable. For fibrillated or One test that assesses the workability of FRC under vi- monofilament polypropylene or nylon fibers. Other sampling requirements specific to FRC are iden. It is just as effective for FRC as for Third-Point Loading) (C 1018). as well as macrosyn. demonstrating Perhaps the only point of fairly universal agreement regarding the effects of fiber content and aspect ratio quite clearly (Fig. cult to determine because it depends on how completely the It determines the time required for a sample of FRC to exit bundles separate during mixing and what is their average the narrow end of an inverted slump cone after an internal cross-sectional size. How. Times more than 30 s mean that the FRC will be very dif- FRC and the range of FRCs possible with different amounts ficult to place and consolidate fully. the slump of FRC mixtures is lower than that of conventional ever. should consult appropriate references [2–4].C. uniform fiber distribution is important in to pullout from the matrix. For example. 2). together with their proven and potential (greater than 50 mm) flexible fibers like polypropylene may applications. for conventional concrete do not provide for vibration or re- Innovations in fiber development that combine reductions quire rodding. Fibers impart considerable the mixer. When ASTM standards rarely more than 65 mm. Otherwise. straight tion or rodding that may disrupt the fiber distribution. thus minimizing the workability. For example. but slight consolidation may occur during important is the requirement that prohibits wet-sieving to re. the number varied from tion. FRC mixtures flow readily thetic fibers which mimic the size and shape of steel fibers. vibrator is inserted (Fig. Reinforced Concrete Through Inverted Slump Cone (C 995). thus maximizing reinforcing effec. so external vibration is required rather than internal vibra- Compared with fibers produced in the early 1970s. which polypropylene. the lesser the average spacing between them and cone. test works well with steel or other rigid fibers. internal vibrator. More recently. but are estimated in the tens of millions. tend to wrap around the specified 25-mm-diameter internal vibrator. Inverted cone (I. the internal vibrator may simply create a central Sampling and Consolidating Test Specimens hole in the sample with the outer portions retained indefi- Sampling FRC mixtures for testing should be in accordance nitely in the cone. are appropriate for placement and consolidation by vibration Readers interested in more details regarding the nature of [7]. How- the same material have been introduced. stability or cohesion to FRC mixtures that may cause them to ther combinations of different materials such as steel and appear unworkable when judged only in terms of slump. tiveness in the hardened state. the real number bration is the ASTM Test Method for Time of Flow of Fiber- dispersed as monofilaments in freshly mixed concrete is diffi. It is move large aggregate because of possible adverse effects on as effective as ASTM C 995 in demonstrating the effects of fiber fiber content and uniformity of distribution. disturbing the natural fiber distribution may affect the test re- reducing effect. the greater the number of fibers per unit volume of basis of using readily available equipment (that is. the test is a good indicator of the mobility of (C 172). Some types of long and types of fibers. with improvements in the resistance of the fiber sult. Reinforced Concrete Through Inverted Slump Cone (C 995). when properly proportioned. TATNALL ON FIBER-REINFORCED CONCRETE 579 polypropylene. Most primarily mobility. Nominal length is generally 15–50 mm. the test implying secondary assessment of compactability. It measures for Fiber-Reinforced Concrete and Shotcrete (C 1116). a slump concrete. beams prepared according to ASTM C 1018 or ASTM C 1399. It was first recommended on the Obviously. again nullifying the validity of the test re- with the ASTM Practice for Sampling Freshly Mixed Concrete sult. partial splitting (fibrillation) Adding fibers to freshly mixed concrete significantly alters its to produce multifilament strands with cross links that separate behavior in terms of the three widely recognized rheological into branched monofilaments during mixing. for example. It is probably better for FRC mixtures with chosen for FRC mixtures when ASTM standards permit a long synthetic fibers or mixtures that are very cohesive. FRC mixtures under internal vibratory conditions representa- tified in the ASTM Test Method for Time of Flow of Fiber. bility. indicating satisfactory compactability. in five commer. 1—Inverted slump cone test with relationships between inverted cone time and slump for FRC and plain concrete [6]. the mobility or the vibration time may be abnormally large. Both the inverted cone and Vebe tests are inappropriate for late closely. 3. and the essentially linear relationship passing higher workability FRC mixtures because the test times become through the origin suggests that both are measuring primarily too short (less than 3 s) to be determinable with reasonable pre- Fig. 2—Effects of fiber content and aspect ratio on slump. In contrast. Both the inverted slump cone and Vebe test results corre.580 TESTS AND PROPERTIES OF CONCRETE Fig. . and inverted cone time [7]. 3. right). namely. the re- range of 3–10 s represent adequate workability for placement lationship between inverted cone time and slump is quite non- by vibration [7]. left ) [7]. Vebe times in the flow of FRC under vibration (Fig. linear (Fig. V-B time. the test end-point can nearly always be reached even though the same rheological characteristic. ) if rodding becomes difficult method of determining fiber content and its variation within a or produces visibly unsatisfactory consolidation. and Unit Density contents of synthetic fibers primarily to control plastic shrink- Air content is just as important for the durability of FRC as for age cracking in slabs-on-grade that is now quite common in conventional concrete.1 % by volume. of a 100 by 200 mm (4 by 8 in. For the inverted cone. 3—Relationships between inverted cone time and slump or V-B time for FRC with steel fibers [7].6 lb/yd3 of polypropylene or nylon). has made this issue more important. For freshly mixed FRC. C 173/C 173M. However. subject. cision. The potential load or placement unit of FRC. tion and Sampling of Hardened Concrete in Constructions For routine quality control. Proper sam. and therefore potentially the most accurate when slump exceeds 75 mm (3 in. TATNALL ON FIBER-REINFORCED CONCRETE 581 Fig. such ing relatively low fiber contents of steel fibers (0. induction coil that surrounds the mold. and unit weight in ASTM Test Method for Unit collected after washout using a magnet. Yield. Other types of fiber may in principle be isolated by pling in accordance with ASTM C 172 and C 1116 is essential. (about 1 kg/m3 or the modification to require consolidation by vibration when 1. ASTM Test Method for Air Content of Freshly native procedure that indirectly determines the fiber content Mixed Concrete by the Volumetric Method (C 173/C 173M). Method of Test for Fiber Content of Steel Fiber Concrete. is a concern in quality control. and only complete JSCE-SF7. Consequently. An alter- 138/C 138M).25–0. which employs a washout procedure using a con- consolidation will ensure accurate assessment of entrained air tainer not less than 6 L (0.) cylindrical sample in a non- and ASTM Test Method for Air Content of Freshly Mixed Con. ventory and concrete production are carefully monitored tests In North America. times less than about 8 s may not volume.2 ft3) in volume [8]. when uniformity of distribution is performance-based specifications. the practice of us. after placement. Engineers standards for testing steel FRC include a Standard tion is greater for FRC mixtures than for conventional con. there is remarkably little information on this using the principles given in the ASTM Practice for Examina. North America also highlights the issue. washout and collected by appropriate means. However. a statistically based sampling plan may be appropriate float. such as floata- When the in-place uniformity of fiber content is to be deter. yield. fibers are used and the resulting number of fibers per unit volume of concrete is small. The practice of using very small fiber Air Content. as shown in Fig. the concern rather than just the average fiber content. most direct. particularly when large native for such mixtures that produce flowing concrete. Yield. cretes. The standard pressure meter.38 % by tests become necessary.) as provided in C 231. particularly when and volumetric techniques. 20–30 kg/m3 or 33–50 lb/yd3) in industrial floors that provide valid results because the FRC may flow freely through originated in Europe and is now common in North America the cone. This procedure is obviously variation from uniformity throughout a truck load or mixer inapplicable for stainless or other alloyed steel fibers that are batch prior to placement. it is arguable that if fiber in- (C 823). and Air Content (Gravimetric) of Concrete (C to determine the weight per unit volume of concrete. are applicable with fiber contents are as low as 0. Fiber content is proportional to the induced current. . slump may be the most practical alter. slump is less than about 75 mm (3 in. The fibers are content. tion in water in the case of polypropylene or other fibers that mined. washout appears to be the sim- Vibration may also be desirable for high fiber content mixtures plest. C 231. The Japan Society of Civil for excessive entrapment of air due to incomplete consolida. and the standard requires cali- Fiber Content bration of the apparatus with data obtained using the washout Verification of the fiber content in freshly mixed FRC and its procedure. 4 [9]. the development of standard tests to for determining fiber content are no more necessary than tests reliably establish fiber content and its uniformity has not been for determining the water and cement contents of conven- considered a high priority because of the trend toward tional concrete. especially at high fiber contents. They are then weighed Weight. or throughout the end product not magnetic. However. magnetic (paper or plastic) mold employs an electromagnetic crete by the Pressure Method (C 231). the maximum acoustic event rate corresponds closely to these characteristic levels of load and deformation [14]. but the use of fibers only in zones of compressive stress is usually of less Fiber Content and Orientation interest than in flexure. The measurement was based on detection of zirconia present in a known amount in the parent glass. or shear. just as the methods for determining the water content and cement contents of conventional hardened concrete have value for investigative purposes but not for routine quality control. 4—Steel fiber contents of freshly mixed FRC by macrocracks. strain-softening (Fig. either molded mation. 5—Load-deflection schematics for matrix and typical reliable enough to be employed on a routine basis for quality FRCs in flexure. matrix strength contributes substantially to composite specimens or cores. visibility. strength increases this technique is applicable in principle to any composite are also modest.5 % steel fiber content where the fiber and matrix densities are significantly different. tension. It can be useful in relating crack development under load to local deficiencies in fiber content or to fiber orientation predominantly parallel to the crack [12]. The condition is termed “first crack” and is clearly identifiable for direct tension and flexure by a sharp reduction in stiffness (Fig. the results are reported to de- crack strength is a more important and meaningful parameter pend somewhat on fiber orientation [8. in practice. where the behavior of both matrix and FRC is of- Hardened FRC ten quite curvilinear. microcracking does occur as the FRC is loaded. For compression. Verification of fiber content and its uniformity in hardened FRC is possible for some fibers. . Precast strength based upon it can correspond to widely different concrete products are monitored in this way in Sweden. total length. the maximum load and any tional covermeter placed on a specimen surface [10]. Prior to the start of visible and continuous cracking.9] and on proximity of than the ultimate strength based on maximum load because it the surrounding coil to the ends of the specimen [9]. However. which is only as between bone and flesh in the human body. Nevertheless. ever. 5). or both.582 TESTS AND PROPERTIES OF CONCRETE control. The electromagnetic technique standardized in JSCE-SF7 [8] is applicable to 100 by 200-mm Strengthening Below first crack and the associated values of load and defor- (4 by 8-in. first- types of steel fiber. there are no techniques for determining the fiber content of hardened FRC that are conveniently practical and Fig. even when the fiber aspect ratio is as high as 100. but there were calibration problems attributed to the matrix and varying water contents in the samples. At this stage. fibers at the concentrations that are normal in FRC (less than 1 % by volume of concrete) have little effect on mechanical behavior. for direct tension. The techniques developed to date are too complex or unreliable. Clearly.) cylindrical samples of hardened FRC. account must be taken of the thickness of the section and depending on whether the FRC exhibits strain-hardening or the orientation of the fibers [10].12]. 5). how- serviceability conditions in terms of deflection and cracking. the on- tromagnetic technique can also be employed using a conven- set of macrocracking. For example. but may when appropriately verified have value for investigative purposes. it appears that fibers containing known amounts of elements having distinct radiation intensity bands not characteristic of anything in the matrix may in principle be detected and quantified in concentration using this technique. that is. the microcracks have become Fig. Fiber orientation and uniformity of distribution have been Increases in first-crack strength attributable to fibers are examined using X-ray radiography to produce visual images of quite small for both flexure and direct tension. and there are characteristic levels of load and deformation at which the FRC eventually starts to exhibit cracks that are significant in continuity. X-ray fluorescence spectrometry widely used for elemental analysis of materials has been applied to determining the fiber content of zirconia-based glass fibers in glass fiber-reinforced cement [13].9]. Interferences from other trace elements such as strontium in the cement are also possible. only about 25 % for 1. The elec- corresponds to a specific serviceability condition. even at high the arrangement of steel fibers in a planar cross section of FRC fiber contents well above the 1 % maximum normally possible [11. Nev- ertheless. and acoustic emission measurements confirm that electromagnetic and washout techniques [8. Although apparently only employed with steel fibers. and width. In contrast. Mechanical Properties (Static Loading) The role of fibers in hardened FRC is primarily to promote crack distribution and reduce crack widths. but is of course limited to the magnetic FRC strength and stiffness. For FRC in tension and flexure. first crack is not easily identifiable. As the load-carrying capability of the matrix becomes progres. 8) [18]. They affect only the strain-softening phase of which have long been accepted as the basis for selecting al- FRC behavior after the maximum load has been reached lowable concrete stresses in design and material acceptance in (Fig. 5 and 8). serviceability in terms of deformation or cracking may be pect ratio. ability level may be a more useful and acceptable design criterion than toughness. such as anticipated earthquake exposure where preservation of struc- Toughening tural integrity even with severe damage is the primary concern. flexural or compressive strength. plain concrete. . is the characteristic of FRC that most For compression. retained strength at this service- of strain-hardening or strain-softening that follows first crack. strength of FRC in tension or flexure is governed primarily by Toughness. 6—Strengthening effect of steel fibers in mortar for direct tension [15. Clearly. In such cases. for example. it can vary over a wide range in terms of the degree more relevant. 8). performance up to a specified permissible level of carried by the fibers. Generally.) is the primary factor governing FRC compressive (Fig. TATNALL ON FIBER-REINFORCED CONCRETE 583 Fig. 9—Toughness of FRC in flexure compared with concretes with silica fume and 0. Its im- fiber content is not statistically significant (Fig. Depending on fiber type. 9). the presence of silica the flexural failure patterns of beams with and without fibers fume. Again. for example. pressive strength. possible using a mortar matrix (Fig. Fig. practice than. crack (Figs. 7—First-crack flexural strengths of FRC and matrix for Fig.5 % steel fibers [17]. the relationship between strength and clearly distinguishes it from concrete without fibers. amount. In many other applications where the serviceability conditions sively reduced by macro-cracking. the behavior of the FRC are less severe and catastrophic structural damage is not composite after first crack becomes largely attributable to load anticipated.16]. Accordingly. matrix strength as determined by matrix quality control. the first-crack of deformation (Figs. 7) [17]. which is determined largely from the area matrix parameters rather than fiber parameters at the fiber under the stress-strain or load-deformation curve after first contents possible in concrete in practice. and in terms of the strength retained over any selected interval the addition of silica fume (Fig. 6) [15. and as. etc.16]. 5 and 8). most of the standard tests evaluate the toughening effects of fibers up to specified defor- Fig. capability is relevant in some engineering applications. This manifestation of toughness or energy absorption strength. increasing the fiber content or aspect ratio are not nearly as effective as measures to improve matrix strength. 8—Typical stress-strain curves for FRC with steel fibers in compression [18]. confirming portance is more difficult to relate to engineering design and the widely held view that fibers have minimal effect on com. It is qualitatively demonstrable by comparing parameters (like water-cement ratio. Method of Test for Compressive Strength and Compressive Toughness of Steel Fiber Reinforced Concrete. converting it to a stress using a formula that In general. both Tb and are specimen-specific parameters that tween the two extremes of “very small deformation/deflection and very fine cracks permissible” (for example.75 % importance). or at the maximum load. 10). unlike. tc. 100 or 150 mm (4 and 6 in. The specimen size. the test end-point may be tionalize how the overall average load can be of direct use in specified to reflect one or more specific aspects of serviceability. 10—Toughness in flexure. as in thin specimens load-deformation or stress-strain curve or as a toughness factor representative of shotcrete or bridge deck overlays. the rationale for determining strength after first crack in inverse proportion to it. They are the Fig.). or thick or toughness index derived from portions of the area under specimens sampled from thick FRC placements like pavements. [8]. and the Method of Test for Shear Strength of Steel Fiber Rein- forced Concrete. Consequently. fiber length) restrict the span-to-depth ratio to 3. the multiple changes of them. it follows that the test end-point deflection repre- With regard to evaluation of strength. and pa- is questionable because load is converted to stress assuming rameters derived from it do not have the same meaning in the material behavior is linear elastic. as in ASTM C 1018. provides for double mula for determining first-crack deflection shows that it is pro. these curves. the test end-point deflection. and span limits (only two retained at or near the test end-point can be useful in design. If L /D changes. or as an aver. of JSCE-SF4) using an appropriate specified apparatus (Fig. the standards differ in that the minimum standard thickness of 100 mm (4 in. and the area. shear of a prismatic specimen (essentially the same as the beams portional to L2/D where L and D are the beam span and depth. the stan- (Fig. Therefore. shape. ASTM C 1399. The problem with tests that determine only the The main parameter derived from Tb. 300 or 450 mm (12 or 18 in.) cylinder.0 are not possible for practical reasons.0. 5) and material behavior is no longer linear elastic. However. square cross-sectional sizes. these may be stated qualitatively as somewhere be.) (Tb/tb) for the whole deflection interval. Clearly.584 TESTS AND PROPERTIES OF CONCRETE mation or load limits rather than to complete failure of the test specimen. Naturally. and loading TbL configuration. the equivalent flexural area under these curves is that the result is specimen-specific. ASTM C 1550. 11). shape. respectively. 10). dard is not adaptable in principle to circumstances where the With regard to toughness. . permitted. there is the option to quantify them by (Fig. JSCE-SF4 [8]. corresponding to a strain of 0. The standard for shear. comprising the seg- cube or a 150 by 300-mm (6 by 12-in. is clearly invalid after first crack is analytically questionable. the test result fails to characterize b material behavior in a manner conceptually independent of tbbD 2 specimen and testing variables. flexural strength of the matrix) so long as the span-to-depth ra- age over a prescribed strain or deformation interval. c d 2tc In the Japanese standard for flexural testing. the choice using the linear elastic formula for flexural stress. 12).0 [19]. is subject to the same limitations. is specified arbitrarily is derived as the average load divided by the cylinder cross- as 1⁄150 of the span. and the Japan Society of Civil Engineers Method of Test for Flexural Strength and Flexural Toughness of Steel Fiber Reinforced Concrete. and span.) or an L/D of test result may be expressed either simply as the area under the 3. it is difficult to the test end-point to reflect anticipated serviceability condi. In some tio. ments both before and after first crack. strength that is highly dependent on specimen size. shape.). While the of test end-point in terms of deformation or deflection is quite load retained at or near a test end-point selected on the basis arbitrary and therefore unrelatable to anticipated serviceability of serviceability may be useful for design. Standardized Tests for Strength and Toughness of FRC Flexural performance receives the most attention because of its relevance to many FRC applications. rationalize how the overall average rather than the strength tions. sented by L /150 is a fixed multiple of the first-crack deflection fer considerably in that the test result may be expressed as the (approximately 50 depending on the modulus of elasticity and strength at first crack. JSCE-SF5 ing of a structure or in shotcretes for tunnel or rock slope ap. for example. Performance in compression and shear receives less attention. The corresponding standard for compression. in bridge decks cannot reflect FRC material behavior independent of specimen with deicer exposure) or “very large deformation/deflection and size. Tb (Fig. Since the for. JSCE-SF4 [8]. JSCE-SF4 [8]. in principle. Again. JSCE-SF6. there is no possibility of selecting sectional area to convert it to a stress. design. notably in flexure when terms of end-point serviceability from one specimen shape to the maximum load is not reached until well after first crack another and from one span to another. it is difficult to ra- conditions. JSCE-SF5. compressive strength that has the same significance (but not necessar. converted to a stress In most existing standards for toughness testing. very wide cracks permissible” (for example. An equivalent compressive strength specifying numerical limits on deflection or crack width. or 4Tc both. and but the conversion of load to strength is simpler and more spans. anywhere within these qualitative extremes. It represents an average load ily the same value) whether determined on a 100-mm (4 in. Consequently. is much the same in principle with Tc measured to a limit- plications where short-term structural integrity is of paramount ing deformation. but Japanese standards exist for FRC with steel fibers [8]. Moreover. tb (Fig. these standards dif. is fixed at 3. JSCE-SF6 [8]. depending on justifiable than for flexure. L /D. in earthquake load. Performance differences attributable to able meaning and significance relative to an established refer. which is analogous to the yield point for first-crack strength and are derived so that elastic-plastic or steel. 13). 14. derived. R10. It represents the maximum stress that can be sustained yield-like material performance corresponds to residual without serious macrocracking and is largely dependent on the strength factors of 100 and fully brittle material performance matrix. etc. I10. for example. Shear strength is determined simply as load divided by cross-sectional area. in Fig. No measure of toughness is established in this test. 11—Toughness in compression. readily achievable in FRCs with amounts and types of fibers The third important set of parameters are residual that produce superior reinforcing effectiveness. I5. . etc. ample. shape. This is a level of performance to elastic-plastic behavior (I5 4. ness indices. TATNALL ON FIBER-REINFORCED CONCRETE 585 Fig.4) and the MS fibers which practicing engineers can easily relate. ASTM C 1018 [21]. JSCE-SF5 [8]. derived as the area under the using the first-crack strength and its corresponding specimen- curve up to the specified end-point deflection divided by the area up to first crack. strength factors. 13). material performance is characterized in terms of three parameters or sets of parameters defined to ensure in principle their independence of specimen size. (Fig. for ex- ence level of material performance.8. 14—Influence of steel fiber type on ASTM C 1018 Fig.or thick-section FRC construction. R5.20. and one that is with marked strain-softening (I5 3. 13). a specified deflection interval expressed as a percentage of the ural strength (Fig. typi. and loading configuration [19–21]. and the index value are related in such a way that index subscripts and actual values correspond for the elastic-plastic reference level of material performance.9. fiber type (Fig.. 14) or amount [1] are clearly identifiable. 12—Shear strength test. JSCE-SF6 [8].10. the corresponding end-point deflection. Index values more or less than the subscript provides for selection of the test end-point deflection to reflect value indicate the average slope of the curve and degree of a wide range of anticipated serviceability conditions (Fig. but are readily converted to a retained load capability dices.1). 14). 14 between the HE 60 fibers with approximately fied by mild steel in tension. 13). They are therefore equally adaptable to test specimens representing thin. I20 8. 13). They represent the average strength retained over The first parameter of importance is the first-crack flex. Fig. toughness indices for 750 by 150 by 100-mm beams [1]. I20 20. Fig. 7). They are non-dimensional as The second important set of parameters are toughness in. span-depth ratio. that is. The index subscript. as previously discussed (Fig. first crack (Fig. derived directly from tough- 80 kg/m3 (135 lb/yd3) of HE 60 fibers in Fig. 13—Flexural toughness indices. The rationale for defining these parameters In n (Fig. I20. elastic-plastic (Fig. strain-hardening or strain-softening behavior observed after It also ensures that each parameter has a readily understand. In the ASTM C 1018 standard for flexural testing of FRC. after first crack to a factor of 0. R10. they have the potential for use in design stipulated in JSCE-SF4. Yet. and clearly distinguishable. ASTM C toughness indices. right). 15. in principle and in experimental reality (Fig. formance characteristics that are clearly distinguished by all nificance is probably more easily understood by practicing en. Because ASTM C 1018 is a fairly expensive setup. where succes. the design of FRC with steel fibers is recommended on the basis of minima for conventional flexural strength and the equivalent flexural strength. 1399 was developed to provide a simpler method to determine ASTM C 1018 requires reporting of first-crack strength.30. and are probably only useful for design commercial laboratories able to conduct the method. ASTM C 1018 toughness parameters. R5. . 16—Equal toughness based on JSCE-SF4 [8] but not in FRCs with the same Tb and b at the end-point deflection terms of ASTM C 1018 parameters [21]. and residual strength factor. I5 and I10. remain approximately constant servo-controlled testing machines. task groups dealing with industrial floor design and shotcrete tunnel linings have prepared recommendations giving values of residual strength calculated as the product of first-crack strength and residual strength factors determined as in ASTM C 1018 but on different specimen sizes. 16).20 is optional. the design of FRC slabs based on residual strength factors is also being discussed [22]. 5). Testing to larger deflections as appropriate to anticipated serviceability conditions is also recommended. For FRCs characterized by gradual strain-softening published. They are probably most useful shown in Fig. except perhaps I5. in Fig. (Fig. In 1997 ASTM C 1018 was updated to require closed-loop.586 TESTS AND PROPERTIES OF CONCRETE Fig.10 as a minimum. testing non- and performance differences by fiber type or amount are fibrous concrete can result in significant values of I5. sive factors. In Belgium. 15—Influence of steel fiber type and amount on ASTM C 1018 residual strength factors [1]. 5).. specific load. as gineers than toughness indices. In Sweden. followed by essentially plastic behavior (Fig. In Canada. with few flection (Fig. the post-cracking load carrying capability of FRC. the ASTM C 1018 toughness indices have been used in design in many FRC shotcrete projects [23]. where the end-point deflection is 1⁄300 of the for characterizing FRCs that exhibit sudden strain-softening span instead of 1⁄150 of the span as specified in JSCE-SF4. When comparing the ASTM C 1018 and JSCE-SF4 standards. it is possible to have two different Fig. for example. and an appendix provides the rationale for establishing appropriate toughness indices and residual strength factors. 15 (left) between perhaps I10.10. Thus. it is important to recognize that. and their sig. etc. they can have quite different per- where serviceability limits have been established. R5. and reporting of I20 and R10. and users are cautioned to use the 30 kg/m3 and 80 kg/m3 (50 lb/yd3 and 135 lb/yd3) of the same I5 and I10 values with this fact in mind until the update is fiber. ASTM C when deflection serviceability limits are known. residual strength factors decrease with increase in de. b [8]. 16. In this setup. For this reason the test method is being modified equal amounts of HE 60 and HE 30 fibers and between to mediate this abnormality. In Japan. 25–27]. to high-frequency traffic loading may justify flexural fatigue testing. complexity and expense of the instrumentation needed to eliminate the influence of extraneous energy losses mitigates Resistance to Cracking against widespread acceptance and routine use of such tests in Cracking can develop in FRC either directly due to application quality control of FRC. High-Rate Loading Flexural fatigue tests in FRC have shown some benefits attrib- Uses of FRC that involve resistance to explosives or earthquake utable to fibers in terms of stress or strength that are to some loading. Test Method for Length Change of Hardened Hydraulic Ce- ment Mortar and Concrete (C 157/C 157M) are also possible. reflecting the core around which the FRC is cast and against which it subse- widely different strain rates actually imposed by a diversity of quently undergoes drying shrinkage [32–34]. Again. (Fig. The method conditions the specimen by pre-cracking the beam specimen in a controlled manner. In all cases. Multiple-Cycle High-Rate Loading Typical results show that fibers have much more effect on A form of empirical impact drop-weight test is described in ACI crack development in the ring test than on free shrinkage (Fig. This test was proposed as a standard by the ASTM bility criteria. Since the detection and meas- Determination of the energy actually absorbed by the speci.” the method provides for scaling of results whenever specimens do not comply Fig. Then a load-deformation curve is generated by testing the conditioned specimen. Weighted pendulum rigs variables such as reversing/non-reversing stress. Strain-rate sensitivity of data may also be affected by the to the outer one by applying sealant to the others.4 % lower than Test Method C 1018 test results [24]. comparison of areas un.24]. the development of refinements . TATNALL ON FIBER-REINFORCED CONCRETE 587 1399 utilizes testing equipment normally found in most commercial laboratories. the experimental ized for FRC in the near future. or as a result of loss of moisture and associated differ- der the load-deflection curves for impact and slow flexure ential shrinkage of the exterior of the FRC against restraint shows that the slow (static) flexure test provides a conservative provided by the relatively more moist interior. Impact Cracking Under Restrained Shrinkage values can exceed static test values by as little as 20–70 % [25] Most investigations have employed a steel ring or cylindrical up to as much as several hundred percent [27]. estimate of toughness determined in the more complex and expensive instrumented impact test (Fig. but is applicable to all fiber reinforced concretes. which assesses the toughness of a thin panel in terms of energy absorption. Com- parison of results using this test method with residual strengths at the same net deflections from Test Method C 1018 have been reported to be an average of 6. factors makes it unlikely that fatigue testing will be standard- ural impact performance [25–27]. but adds mation-measuring equipment coupled to appropriate data-ac. Since this test method utilizes a “structure. or impacts on pavements and bridges due to vehicles extent equipment-specific because of differences in testing or aircraft. and thus the results are specimen-specific. Free (unrestrained) shrinkage factors make it unlikely that a fully instrumented impact test measurements on companion prisms tested according ASTM will be standardized for FRC in the near future. each with its own equipment-specific strain place through all three exposed surfaces or may be restricted rate. cepted for several reasons.19.2R [6]. the complexity and expense of the equipment Mechanical Properties (Dynamic Loading) and the time needed to conduct such tests mitigate against widespread acceptance and routine use in quality control. based on modified Charpy impact testers and instrumented cycling rate. However. possible. and spacing of cracks are moni- polymers like polypropylene than for metals like steel.28–30]. Drying may take impact testing rigs. location. urement of very fine cracks depends on the means of detection men exclusive of extraneous losses to the support system is not and magnification available. and to compare its reportedly very poor precision. Single-Cycle. 19) [32. width. and aspect ratio (Fig. further to its complexity. etc. but was not ac- used to specify FRC requirements and to monitor FRC com. may justify impact testing. Both effects increase with increase in fiber content of blows sustained by the specimen to first crack or failure. stress range. These tored as drying progresses. An average residual strength is determined from this curve. Results of testing with this method have been Subcommittee on Fiber-Reinforced Concrete. The method was developed initially to monitor performance of thin fiber reinforced shotcrete linings in underground support applications such as deep hard rock mine support. 17—Energy absorption or toughness compared for impact and slow flexure [19. various fiber-reinforced concretes during the mixture propor. Incorporating toughness drop-weight arrangements with fast-response load and defor. with the end-point deformation fixed. including its empirical nature and pliance with construction specifications.35]. A more recent development is ASTM Test Method C 1550. in which impact is recorded simply as the number 19) [32]. which probably is greater for the number. Toughness in this test method is defined at various central deflections providing post- cracking flexural behavior assessment for differing servicea. rate sensitivity of the fibers. Uses of FRC in airport and highway pavements subjected tioning process or in research and development work. The combined influence of all these quisition systems have been used in research to evaluate flex. 17) [3. with the target thickness and diameter within given limits. 544. measurements into the test has been attempted [31]. 18) [6. Furthermore. of load. 20). 0. and 2-in.75. but was not entirely elim- plastic shrinkage and associated cracking that sometimes oc. for fiber-reinforced and also allows serviceability in terms of crack development to be unreinforced concrete slabs. 0. this method using fibrillated polypropylene fibers of 13-.) fibers.38]. In Crack widths and spacings between cracks can be measured addition to the ring test.05. humidity.5-. It involves fan-forced air flow related to the end-point deflection selected in toughness tests.and 2-in. and frictional bond and 51-mm (0. are effective in preventing this problem are questionable.2 % of 19- evaporation. and temperature 35°C of temperature. small volumes of polypropylene or nylon fibers. the ring test can also be used to monitor the ing can be reduced from 20 to 90 %.48. .75-. and wind speed causing high surface (95°F)) [39]. Recent results obtained with to quantify the influence of fiber parameters and fiber proper. This has helped induce plastic shrinkage cracking. It product of crack length times width.2 % by volume indicate that plastic shrinkage crack- In principle. for example. Monitoring crack develop- plastic shrinkage potential of restrained FRC slabs is being de. Fig. the third benefit im- Concrete. It compares the area of cracking. determined as the parted by them in addition to strengthening and toughening.) lengths in amounts of 0. ties such as modulus of elasticity. ment in this way makes it possible to quantify the ability of veloped by the ASTM Subcommittee for Fiber-Reinforced fibers to control cracking in concrete.1. and there is a need Cracking Under Load for some form of standard test to confirm such claims [36]. 18—Flexural fatigue performance of FRC with steel fibers relative to first-crack strength and in terms of actual stress [29]. and 0. A standard to assess the specimen loaded in slow flexure. 19—Free shrinkage and crack development under restrained shrinkage in ring test for matrix and FRC with steel fibers [31]. inated under the conditions of the test (water-cement ratio cur within a few hours of placement under adverse conditions 0. alternatives that require further study quite easily with appropriate visual magnification of the are slabs restrained at the edges or fitted with a centrally cracked surface. The best results were achieved using 0. Claims by manufacturers that fibers. E. on cracking (Fig. f .588 TESTS AND PROPERTIES OF CONCRETE Fig. 19-. particularly and 51-mm (0. strength. incorporating laser holography for detection and high-power over the surface of newly molded slabs under controlled con- microscopes for crack width measurement have facilitated ditions of temperature and humidity sufficiently severe to more comprehensive and reliable testing [34]. relative humidity 40 %. on the tension face of a test placed cylindrical insert [37. 2R). A. and Shah. 1984. steel fibers may rust if exposed to moisture and ASTM C 1018 Shows Importance of Fibre Parameters. 1999. maximize short-term property improvements. In the absence of an established satisfactory performance record. [5] Behavior of Fresh Concrete During Vibration (ACI 309. 111–134. 1992. may be suspect are being considered by the responsible ASTM subcommittee. Vol. but. ASTM standards for conventional concrete subjected to freez. pp. [4] Balaguru. 21 [21]. of the future must be engineered to minimize mixing and place- The durability of the matrix is assured if it meets the relevant ment difficulties. 2. Gordon and Breach Science Publishers. However. Japan Society of Civil Engineers. pp. “Measurement of Fiber Content of Steel Fiber Reinforced Concrete by Electro-Magnetic Fig. V. D. Concrete. The fibers No durability tests have been standardized specifically for FRC. 6. 148. T. and Aggregates. Farmington Hills. al. Farmington Hills. problem. C. ASTM C 1116 requires credible evidence that unfamiliar fiber types will not react adversely with the cementitious matrix or any chemical or mineral admixtures it contains. [8] “Recommendation for Design and Construction of Steel Fiber Reinforced Concrete.1R). and Kobayashi.” Concrete Library International. confidence placed in reinforcing bars and tendons [41]. Fiber Reinforced Cement Compos- ites. No. C. 2001. References The fibers commonly used in FRC. in Evaluation of Steel Fibre-Reinforced Concretes According to cracked FRC.. 1996. 41–69. “Comparative Performance polypropylene.40]. pp. 21—Crack development in the ASTM C 1018 flexure Method. carbon-steel and [1] Johnston. salt scaling. and acrylic fibers [2. Ed. P. P. and stabilizing additives may inhibit any ultraviolet American Concrete Institute. McGraw-Hill. attack for polypropylene. Detroit. and fiber compatibility tests for fibers that for FRC to meet all of these objectives. ficient ultraviolet radiation. [7] Johnston. MI. 20—Crack development compared for 19-mm poly. monitoring also obscures the significance of the data. Inconsistent and confusing performance tests in existence di- propylene and 25-mm steel fibers in ring test [33]. pose no problem in uncracked FRC. American Concrete Institute. 233–246. 191–200. Much remains to be done in developing standard test reactivity tests. such as those that are now well known for glass fibers and many natural cellulose-based fibers and those that remain to be fully investigated for aramid. American Concrete Institute. “Fibre-Reinforced Cements and Concretes.1R-96. minishes the confidence that potential users of FRC have in this material. M. May 1992. No. though it seems reasonable to expect such effects from the ex. K. The ASTM Subcommittee on Fiber-Reinforced Concrete is developing a specification for polymer fibers for use in concrete that will address most of these concerns. test for two types of steel fiber [21]. and aggregate term. ACI 544. No.3. “Measures of the Workability of Steel Fiber Reinforced Concrete and Their Precision.3. be proposed for use in FRC hindsight suggests that compatibility of fibers with the moist alkaline environment of cement Durability paste and tests to confirm it should be a high priority.. 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C.. of Fibre Cement Composites. Sept. Proceedings. pp. July–Aug. Vol. 297–305. “Microcracking in Fiber Aspect Ratio. Concrete Society (UK). “An Experimental Study of [24] Banthia. American Concrete Institute. Whistler. National Research Council. 1978. A. 19–42... S. nation of Fibre Content. 275–288. Construction Press Ltd. RILEM Committee 49-TFR. C.. D. 87.” Concrete Construc- Concrete. P.. 6. pp.1. 1978. No. March 1979. Paper 5. Vol. 29–47. SP-44. B.. 173–179. Backer. Nov. U.K. 2. 1986.” Proceedings. RILEM Sympo. P. 1978.” Symposium Proceedings. Part I: Assessment and Calibration. No. pp. P. 673–677.. pp. 1972. [41] Bernard. I.. S.” Steel [36] Schupack.. Construction Press Ltd.. G. pp. Concrete International.. E. pp. P. 1987. C. pp. 1986. 651–656. pp. Vol.–Dec. S. 4.” Journal. No. Reinforced Concrete.” Cement. Feb. D. Shrinkage of Steel Fiber Reinforced Concrete.” 96. 117–126. Malmberg.” Materials and Structures. D. 1987. Reinforced Concrete. Reinforced Cement and Concrete. tion. 1991. “The Effect of Low Addition International. “Definition and Measurement of Flexural [37] Kraai. “Steel Fiber Reinforced Shotcrete for Support of Mechanical Properties. “Designing Fiber Reinforced pp.. Vol. Proceedings. pp. ICON-1. and Dubey. P. 211. Ramakrishman.” Proceedings. Nov. “Complete Stress-Strain Curves for Steel Fibre Reinforced Concrete. et al. 53–60. Concrete Based on Toughness Characteristics. “Properties of Steel Fiber Rein- [15] Johnston. and Young. Composites by X-ray Fluorescence Analysis. [29] Nagabhushanam. Proceedings.. and Vondran. M. E. pp. Vol. RILEM. Fibre Concrete by X-ray Technique. No. “Toughness of Steel Fiber Concrete. and Coleman. 665–676.” [16] Johnston. B. 1999. R. Institute. Symposium on Developments in Fibre can Concrete Institute. 36–47. Construction Press Ltd. 2001. Journal. RILEM Symposium on Testing and Test Methods of [35] Chern. Symposium on Testing and Test Methods of Fibre Cement [30] Johnston. and Skarendahl. pp. B. “Challenges for Fibre Reinforced Concrete. 1990. 20. 293–302. D.. “Flexural Fatigue Strength of Steel Fibre Re- Symposium on Testing and Test Methods of Fibre Cement inforced Concrete Beams. S. Concrete Fiber Composites.. [19] Johnston. p. 56–64. 38–43. J.. [22] Moens. Proceedings. “Seven Case Studies of Fiber Concrete... R.. RILEM pp. 443–460. M. and Stanley. 289–295. June 21–22. sium on Testing and Test Methods of Fibre Cement Composites. 11. C. and Nemegeer. 20. No.” ACI Materials Journal. Pittsburgh.. 2.. J. B. No. . 177–193. Fly ash is also less effective than gregate fraction can be preplaced either very rapidly with bulk cement in chemically fixing water and so is undesirable in handling equipment or slowly and carefully by hand labor.5]. mortar. Several manu- technique has been used since 1937 and is generally credited to facturers of fluid grouts that meet the ASTM C1107 Specifica- Lee Turzillo and Louis Wertz [1]. The coarse ag. tion for Packaged Dry. The original chapter was written by B. followed by grout injection at a attenuated by hydrogen atoms. Research and Development. and water and placing the mixture applicable to PA concrete. such as of repairing concrete and masonry structures. NC. shielding subject to high neutron flux which is more effectively depending on the application. partial the total concrete volume. Davis. reduced permeability. in a timed sequence independent of replacement of cement with fly ash causes a slight reduction in mixing and placing cementitious constituents. 591 . While there have been some improvements in the chemical composition and performance of the grout fluidi. sand.” Actually a highly fluid structural Raymond E.50 Preplaced Aggregate Concrete Edward P. Since the specific gravity of placement of coarse aggregate. in ASTM 169C. 1 Chemist. it was first used as a method parted by any pozzolan to portland cement concrete. Materials Lamberton. unit weight of the concrete. claim that their product can be used as the slurry. of the ASTM C618 Specification for Fly Ash and Raw or Calcined While the two-step placement procedure would increase Natural Pozzolan for Use as a Mineral Admixture in Concrete. in a form. Fly ash should meet the Class F requirements structures. In 1943 Wertz was granted a U. Jr. and for high density biological shielding [6–8]. The same PA concrete is an alternative to blending the fine and working stresses used in conventional concrete design are coarse aggregate. The that mixed and placed by conventional methods. the basic method and testing of PA concrete has not admixtures. generally high water/cement (w/c) ratio grouts that are pressure injected Introduction into soil or rock formations to increase strength or reduce permeability. fly ash is particularly beneficial in now widely accepted for other specialized applications such as the PA concrete process in that it improves pumpability and placement of mass concrete under water. it bears no resemblance to the low-strength. it produces concrete of making concrete that involves placing coarse aggregate in a comparable in strength and other physical characteristics to confined space and later injecting a fluid grout into the voids. The drying shrinkage of PA concrete is about 50 % the PA concrete method. In the case of PA concrete the coarse gap-graded aggregate is preplaced in the form and a structural grout is Cementing Materials injected into the coarse aggregate mass in such a way as to fill Cementing materials suitable for use in conventionally placed void spaces where it hardens to form dense homogeneous concrete may be used with equal confidence for placement by concrete. representing roughly 60 % of this material is appreciably less than that of cement. costs over that of conventional methods in a great majority of Fly ash is often omitted when concrete is to be used for routine concrete work. Hydraulic-Cement Grout (Nonshrink) Patent for the method of filling cavities using (PA) concrete [2]. and improved railroad bridge piers and tunnel linings [4. The slurry containing a mixture of portland cement. fiers. in heavily reinforced retards initial set. In addition to the beneficial properties normally im- this low shrinkage characteristic. and water that is injected into the coarse aggregate significantly changed since this chapter was last updated by mass is referred to as “grout.S. It is customary practice to substitute less than that of conventionally placed concrete with similar pozzolanic quality fly ash for part of the portland cement. stitution in the range of 15 to 35 % by weight of portland cement to-point contact of coarse aggregate particles. Sub- material proportions [3]. EPH Solutions. Grout used in PA concrete work is a structural The term “preplaced aggregate” (PA) concrete refers to a method material. Because of is common. A. particularly lower heat generation. The method is particularly applicable to placement of concrete in THIS CHAPTER ON PREPLACED AGGREGATE (PA) structures containing a profusion of inserted fixtures [9]. Injected into coarse aggregate. This is due apparently to the point. The method is resistance to chemical attack. Holub1 Preface time convenient to the overall construction schedule. cement. Charlotte. concrete is basically the information from the previous editions of ASTM 169. it has the advantage of permitting high density biological shielding. where freeze-thaw conditions are severe and a specific min- grading. If the expansion time is more rapid. propor- exercised during placement to avoid degrading friable aggregate. fly ash. to High-density aggregates typically used in PA concrete con- cause expansion of the grout prior to initial set in an amount struction are described in the ASTM C638 Descriptive Nomen- sufficient to more than offset setting shrinkage of the grout clature of Constituents of Aggregates for Radiation-Shielding that would otherwise take place beneath coarse aggregate Concrete and typical specifications for these aggregates are particles. placement temperature. and limonite. it is common For mass concrete applications. For routine structural repair construction of high-density biological shielding. and (c) of such a grading that grout will flow readily by gravity alone Grout Mix Proportions through the void system. The advan. the grading is equally standard grout fluidifier formulation is used with low alkali ce- suitable for use with normal-density aggregates. most importantly. it may be depressed when the aggregate for biological shielding. bleeding aggregate may cause excessive bleeding. reinforcing or restricted form configuration. Either natural ments. The particles should be of such tough. The only absolute requirements are that it be (a) free of imum air content is required. grout surface monitoring procedures. performance-type specifications tage of the method for this type of work is two-fold. As formulated by the manufacturer if necessary when use of cement indicated in Table 2. and within the tight confines of complex formwork requirements but aggregate composition and grading. it is approximately 50 % complete in 1 h and strength and increase drying shrinkage. Further decrease in this screen. A trommel-type screen is generally more effective ratio is usually precluded by pumpability limitations. Extra caution must be Aggregate Concrete. of concrete or masonry. Grading 1 of ASTM C637 Specification mixing and pumping time are shortened unnecessarily. Fer- aluminum powder. Grout fluidifier is customarily used as a commer. This gas-forming reaction should be so timed that. which is particularly well-suited for depending on job complexity. The heavy normally are employed. both fine and coarse as described in ASTM C 637. respectively. ilar to that of an air-entraining agent with respect to freeze-thaw durability.47. grout tion appears in Table 2. from the grout and so cause premature thickening. geothite. It contains a water-reducing agent. (b) sufficiently saturated that it will not absorb water entraining agent incorporated in the grout mix if required. Grout mix proportions may be selected in accordance with ASTM ness and hardness that they do not fracture or degrade during C938 Practice for Proportioning Grout Mixtures for Preplaced- transport and placement into the forms. tions are normally in the range of 2:1:3 to 4:1:5 by weight in which Normal aggregate grading limits for most structural the ratio represents. How- Coarse aggregate grading is far less critical than is fine aggregate ever. High-Density Aggregates mote fluidity of the grout mixture and. the weights of cement. A typical grada.592 TESTS AND PROPERTIES OF CONCRETE Fine Aggregate timed reaction of the aluminum powder with the alkalies of Fine aggregate. properly graded. and a chemical buffer to assure properly rophosphorous varies widely in hardness and some of it may . Although Since the expansive characteristic of the grout is dependent described in this specification in connection with high-density on the alkali content of the cement. an air content determination surface dust that would prevent bond of grout to the aggregate should be made using grout fluidifier and job cement and an air- particles. 638 are suitable for placement by the PA concrete method. Excess fines 5 to 8 %. for Aggregates for Radiation-Shielding Concrete.40 is anticipated. somewhat finer with an alkali content less than 0. although particular care should be exercised with the softer crete. presented in ASTM C 637. In the absence of very closely spaced an amount equal to 1 % by weight of the cementing materials. An air-entraining agent or air-entrained cement Coarse Aggregate should not be used routinely in the PA concrete process. and sand.43 to 0. Gap-graded fine 95 % complete in 3 h. fication for Grout Fluidifier for Preplaced-Aggregate Con. will increase water requirement and so reduce compressive at 21°C (70°F). grout characteristic of most shielding installations. although the former is cement should be determined. Grading 1 of ASTM C 637. This reaction results in the formation of hydro- execution of the work. is essential to successful the cement. natural minerals such as barite. Oversize material will cause obstruction gen gas to expand the fluid grout. Grout fluidifier is added in in the range of 43 to 48 %. have been placed by the Specifications for PA concrete placement vary widely in detail PA concrete method. requiring only that a minimum stipu- particles of mineral ore or steel punchings or a blend of these lated compressive strength be exhibited by test cylinders and coarse aggregates are placed in the form with no possibility of that good construction practice be followed in accordance with segregation such as may occur when coarse aggregate and such accepted publications as ACI Standard 304 [10]. specifications may be entirely of the placement around multiple embedments. The release of grading is required where high-density sand is used or where hydrogen bubbles and the expansive reaction have an effect sim- coarse aggregate grading is finer than normal. prescription type. insert spacing. For grout is combined in a plastic mass and placed by conventional difficult projects such as large heavily reinforced structures or methods. Grading 2 of ASTM C 637. Second. Grout Fluidifier Grout fluidifier is required on all PA concrete work to pro. At a slow expansion rate. therefore. Specifications A wide variety of high-density aggregate. The ratio of water to cementing materials (cement plus Aggregate graded within these limits will exhibit a void content fly ash) is in the range of 0. and in-place density. and the product custom usually preferable from the standpoint of pumpability. the ratio of cementing materials practice to scalp coarse aggregate on a 20-mm (3/4-in. a suspending agent. than a deck screen in washing the aggregate particles to the required surface cleanliness. tends to increase.) wash to sand may be reduced to as low as 1:2. All aggregates described in ASTM C cially preblended material conforming to ASTM C937 Speci. Performance of grout fluidifier in combination with job or manufactured sand may be used. usually in the range of of the void channels in the coarse aggregate mass. setting forth not only compressive strength forcing. the method is well-suited to concrete biological shielding. applications are shown in Table 2. For typical structural applications. closely spaced rein. Measurements of nation of iron ore and steel punchings. Using this technique. in and the total volume of bleed water. calculations can performed less frequently. This test is analogous pletes the blending process. HOLUB ON PREPLACED AGGREGATE CONCRETE 593 be so soft and friable as to be unsuitable for placement by the mm (12 in. Short tations but also carefully describe sampling procedure with voltage pulses are transmitted on electrically calibrated detec- respect to quantity represented by each sample. Reflectometer provides a more accurate means of determining ticular care. 800 cm3 of fresh grout are placed in a 1000-cm3 graduate. The test for expansion in accordance with ASTM C 940 All high-density aggregate should be weighed before place. grout expansion. . Using careful testing and sam. all expansion has ceased.) tion causes some size degradation of the more friable of the two coarse aggregate. Slotted sounding wells may also be used. expansion and accumulated bleed water at four 15-min inter- pling procedures. Expansion. permits placement temperatures to be divided by initial volume. consideration should be given to reclaiming undersize material and incorporating it in concrete to be placed by Fluid Grout Characteristics conventional methods. penetrations. Where watertight test requires only observation of total grout expansion 3 h after steel forms are used. Using such methods. frequency of tor wires located within the aggregate mass and the pulse sampling. any placement by the PA concrete method. Grout Surface Monitoring Water retentivity of freshly mixed grouts should be Grout surface monitoring is of particular importance in determined in accordance with ASTM C 941 Test Method for ensuring complete penetration of all voids within the coarse Water Retentivity of Grout Mixtures for Preplaced-Aggregate aggregate mass and complete contact with embedments and Concrete in the Laboratory. Grout bleeding. All of these materials are obviously far of sounding wells may be specified. and the lower end of the range required for plus 12 mm (1/2 in. location of the grout Compressive Strength of Grouts for Preplaced-Aggregate surface can be determined with an accuracy of about 300 Concrete in the Laboratory. Before any mined with sufficient accuracy by simply observing grout or adjustment is made to the mix design. The Time Domain specifications for these materials should be written with par. in accordance with ASTM C939 Test Method for Flow of Grout gates may be blended continuously by streaming through me. Test Method for Expansion and Bleeding of Freshly Mixed ment and sampled frequently to determine unit density and Grouts for Preplaced-Aggregate Concrete in the Laboratory is void content. it is possible to specify in-place density of vals following mixing and at 30-min intervals thereafter until concrete placed by the PA concrete method as close as 1 %. expansion is virtually complete at 3 h. including grout and accumulated bleed water. with or water around the sensor wires alters the impedance conformance sampling and testing performed at the job site. is high. Typical few rotations in a concrete mixer followed by washing and consistencies range from 21 to 30 s with the upper end of the screening. location of grout surface can be deter. The tant consideration. often no more than once a day. location and frequency PA concrete method. Bleeding.7-mm (1/2-in. some of this friable material in the blending operation. tiveness of mixing equipment and procedures. but the total volume of grout down through the aggregate mass. If permitting an experienced operator to locate the grout surface the aggregate is relatively friable and breakage during transit with an accuracy of about 80 mm (3 in. in which a float on the end of a line is dropped Compressive strength of hardened grouts should be deter- into the sounding well and the depth to the grout surface physi. For critical applications. Fluid grout characteristics are always routinely tested during Where blended aggregates are to be used. The aggregate may be precooled in the observer should then note and report not only the total volume form by flooding it with chilled water or covering the coarse of the specimen.). This be made to determine required grout density. expressed in combination with precooling the grout ingredients and using percent. in practice either type of blending opera. be made routinely at about 2-h intervals. for Preplaced-Aggregate Concrete (Flow Cone Method) should tering gates onto a belt ahead of a washing screen that com. expressed in percent. aggregate with flaked ice and allowing the ice to melt and drip at the aforementioned intervals. reported as the volume of bleed water (total volume minus grout volume) divided by initial volume. For routine repair work and for many structural and grout consistency are all strongly influenced by the effec- concrete applications. expansion may continue as long as 4 h at lower temperatures Temperatures and with some low alkali cements. Grout Aggregates should always be tested prior to shipment. normal temperature. measuring the time in seconds for dis- be inspected separately and the final blend again inspected for charge of 1725 cm3 of grout through a 12. range suitable for use with plus 20 mm (3/4 in. and allowance must be made for a loss of tency to be controlled within a range of 2 of a stipulated value.) [10]. such as a combi.) coarse aggregate what more accurate. mined in accordance with ASTM C 942 Test Method for cally measured. reflections assembled and displayed on an oscilloscope. The utility and significance of the test procedure is mass may be determined in-place by metering water into and greatly enhanced if observations are made of both total grout out of the aggregate-filled forms. void content of the entire coarse aggregate mixing. is achieved within the range of 5 3°C (40 5°F). adequacy of the mixing moisture seepage through the forms or through insert or procedure should be evaluated carefully. Specifications usually require grout consis- aggregate fractions. as well as location and more expensive than normal density aggregate and purchase spacing of grout insert pipes and vent pipes. or they may be batch blended by a to the slump test for conventionally placed concrete. Temperatures at the time of grout injection are often of great Following the procedures of ASTM C 940. the two materials must grout viscosity or flow. Based on these determinations. is calculated as total volume minus initial volume ice in the mixing water. grout surface location in a nonflooded aggregate mass. They should not only call for specific gravity limi.) orifice particle size gradation and homogeneity of the blend. Aggre. approximately importance where minimum thermal shrinkage is an impor. particularly for deep mass concrete Compressive Strength placements. and the location where tests are to be performed. Although with normal cement and at although a tolerance of 2 % is a more common limitation. Although the latter method may appear to be some. inspection holes drilled in the side of the forms. Grand Rapids.” Journal. No. fractions of an inch away. J. 581–595. A. R.” 1992. Vol. 24.” Journal. 52. CO 1981. pp. T. Vol. H. 57. “REMR Technical Note References CS-MR-9. Oct. Because of the fact that densely packed large Concrete. Oak Ridge National Laboratory. E. 446–449. No. Y. p. E. Discrepancies in test results Journal.. American Concrete Institute. The PA concrete process is an internationally accepted method Mass. 8th ed. TN. 204–212. 155–172. “Strengths of Prepacked Concrete and Reinforced Concrete Beams.. American Concrete testing procedures such as the Schmidt hammer and the Institute. King. U. per. G. “Floating Caisson Facilitates Repair of Grand Coulee very dense aggregate and grout with a relatively high per.) prisms. Proceedings. Chapter 8. Jr. a Fully Vibration-Controlled Forging Hammer Foundation. 2nd ed. pp. D. Miracle Bridge at Mackinac. E. 1969. this method are well established. “High-Density Concrete for Shielding Atomic Energy Plants. Density 1960. Vol. 28-day strength on concrete placed by the PA method using Downs. D.313. struction problems. H. pp. Department of the Interior. 35–39.S. American Concrete Institute.. pp. Vol. mortar.” Nucleonics. 1955.. E. May 1958. pp. and Neelands. Johnson. might be expected. Proceedings. Nov. Density determinations on the standard 150 by 300. No. C. 22–1 to Closure 22–17. 421–444. for example. two notes of caution are in order. pp. 66.. ver. R. Proceedings. pp.” ACI Committee 304. S. 7. pp.. “Process for Filling Cavities.” Patent No. May accordance with good practice. American Concrete cle size. Preplaced-Aggregate [1] “Guide for the Use of Preplaced Aggregate Concrete for Struc. [8] Davis. 4. Jansen. 28. In 1739. are cut. June 1955. Oak Ridge. E. Wm. Army Corps of Engineers. on which final acceptance tests are performed. L. A. 1971. No. pp. G. American Concrete Institute. No. [4] Davis. “Mackinac Bridge Pier Con- by 6-in. American Concrete Institute. Concrete. R. R. W. B. Hardened Concrete 29. C.. U. R. Concrete.. No. mm (6 by 12-in. and Moriguchi. Proceedings.” Power Engineering... C. G. Penstock Tunnel Liner Backfilled with Prepacked Concrete. pp. pp. Windsor probe should be used and interpreted with particu- Davis. This limitation on minimum core diameter is even Institute. Jan.. Journal. Eerdmans Publishing Co. 6. 785–797. Proceedings. Vol. 49. 965–977. Vicksburg. “Kemano particle and another test. 43. 2. Vol. 2. Test methods for evaluating the properties Olds.S. S. and Density of Preplaced-Aggregate Concrete in the Labora. No. Spillway Bucket.” ACI Committee 304. coarse aggregate particles are in close proximity to the Davis.” formed on the structural mortar. E. Proceedings. Dec. 1975... “How to Choose and Place Mixes for High Density lar caution..4-Specialized Repair Technique:. March 1947. Secondly. MS. 11. “Restoration of Barker formed surface. From these test cylinders. crete. 45–48. Aug.) test cylinder will result in an erroneously low [7] Klein.. Lamberton. “Report on Design and Placement Techniques of the same methods employed with conventionally placed con- Barytes Concrete for Reactor Biological Shielding. pp.110. American Concrete Institute. 1957.S.. Density of hardened concrete is normally determined by cast- [5] Keats. pp. and Haltenhoff. strength between what is essentially a test on an aggregate Davis. Bureau of Reclamation. Proceedings. M.” Journal. J. New York. 8. Proceedings.. and Crockett. J. 100 by 100 by 150-mm (4 by 4 [6] Davis. 8th Edition. Hardened concrete placed by the PA method is evaluated by [9] Tirpak. 1956.. 2. G. of the fresh grout and coarse aggregate fractions employed in March 1970. “Placing Concrete in Deep Mines. “Special Concretes and Mortars. Vol. 1953. 633–667... Vol. MI. covered only with a thin layer of structural Dam. tionally placed concrete should be of a diameter equal to at [10] “Preplaced Aggregate Concrete for Structural and Mass least four times that of the maximum coarse aggregate parti. and Meier. pp. “Design and Construction of figure. However. April 1950.. Vol. pp. tory. E.594 TESTS AND PROPERTIES OF CONCRETE Time of Setting [2] Wertz.” Making Test Cylinders and Prisms for Determining Strength Journal. This procedure is particularly important in counter. Proceedings. B.” Handbook of Heavy Construction.” Report No. “The Maintenance and Reconstruction of Concrete ing test cylinders in accordance with ASTM C 943 Practice for Tunnel Linings with Treated Mortar and Special Concrete. struction. centage of fly ash replacement of the cement. and Wendell.. Den- Preplaced-Aggregate Concrete in the Laboratory. No. Steinman. 1997. J. 5. Jr. 64. . L. McGraw-Hill. Time of setting of grouts should be determined in accordance 9 March 1943. 1954. Concrete Manual. American Concrete Institute. V. S. U.. “Investigation and Repair of Hoist Dam. No. tionable as deficient density. April 1967. on attempting to determine 3.” of concrete placement appropriate to certain specialized con- Concrete International. Vol. 60–65. such tests may show a substantial variation in 44. more important with PA concrete by reason of the fact that there is a higher percentage of large aggregate particles with Bibliography a correspondingly greater possibility that these particles will be torn loose from the grout matrix. nondestructive Akatsuka. G.” Journal.” Civil Engineering. E. tural and Mass Concrete Applications.” Civil Engineer- ing. B. A. D.. F. 10. C. 37–39.” Journal. Journal. 1980. 1956. American Concrete Institute. April 1948. “Prepakt Method of Concrete Repair. 93–103. B.. pp. “QA Put to Work on the PCRV. cores extracted from conven. with ASTM C 953 Test Method for Time of Setting of Grouts for [3] Concrete Manual.” weight construction where excessive density may be as objec. 287–308. 813–826.. structed RCC field test sections at Jackson. and a variety of pavement applications. asphalt laydown equipment. hardened RCC are similar to The 52-m-high Willow Creek Dam confirmed the economy those of conventionally placed concrete. Saucier with the U. and spread. will support a roller while being generate savings in time and money as compared with tradi- compacted” [1]. concrete placement methods. “concrete compacted by roller compaction. dozers. grade control include increasing spillway capacity for earth fill dams. The United States continuities or restrictions on placement rate. E.. with one or more bull. low permeable liners. RCC is spread with heavy-duty The U. air-entrained concrete crete can be transported. [8]. would that. In addition to new dams. bratory roller at a Tennessee Valley Authority (TVA) project. months. completed in 1987. con. Application of has 37 RCC dams with the highest being Olivenhain Dam in San RCC is often considered when it is economically competitive Diego.51 Roller-Compacted Concrete (RCC) Wayne S. Cannon [3] presented results of tests on a lean cally mixed using high-capacity continuous mixing or batching concrete using 75-mm maximum size aggregates transported equipment. Worldwide the highest RCC dam is Miel for RCC are for mass concrete such as dams and heavy-duty I in Columbia at 188 m. Lost Creek Dam in Oregon [5] in 1972 and 1973. PA. However. port facili. Figure 1 shows construction of the pavement applications including intermodal yards. and rock-fill construction equipment or. Adaska1 Preface structures in riverbeds. At the Rapid Construction of Concrete Dams Conference preparing the current edition. 40-m high C. The most significant changes in 1970.S. contains 1. Properties of fully compacted. THE ORIGINAL CHAPTER ON ROLLER-COMPACTED concrete was authored by Kenneth L. lated from soil-cement applications the concept of placement struction. Worldwide. warehouse and other industrial parking and storage areas. Corps of Engineers (USCE) soon thereafter con- asphalt type pavers. He noted that the increase in shear strength of cement-stabilized material would result in The American Concrete Institute (ACI) in Cement and Concrete a significant reduction of the cross section when compared Terminology (ACI 116R-99) defines roller-compacted concrete with a typical embankment dam and that use of continuous (RCC) as. For paving applications. Siegrist Dam in Lebanon. grade 1 Director. CA. Dams Army Engineer Waterway Experiment Station and first ap. delivered with trucks or conveyors.12 million m3 of RCC RCC may be considered for applications where no-slump con. the dam is 97-m high and con- with other construction methods. Large vibratory rollers are used to exter. 5420 Old Orchard Rd. It is typi. placed. crete dams that could be constructed rapidly and economi- Much of the content of the original work was drawn on in cally. Bu- Introduction reau of Reclamation’s (USBR) 90-m high Upper Stillwater Dam. spread by a front-end loader. there are more than 280 RCC dams in 39 coun- ments. and compacted by a vi- the case of mass concrete such as dams. placed within horizontally slip-formed. and compaction of an embankment with cement-enriched granular bank or pit-run material using high-capacity earth- Definition moving and compaction equipment. In 1972. extremely tional concrete gravity dam construction. RCC can further be defined as a stiff. the low-water and rapid construction possible with RCC. durability. located predominantly in Japan and China. RCC has also been used exten- Other applications include overtopping protection for earth fill sively in the rehabilitation of existing dams. facing elements [7]. Forty-seven of these dams are greater than 90-m high and involve large placement areas with few interferences or dis. Mississippi [4] and nally consolidate or compact the roller-compacted concrete. Skokie. dry concrete that has the consistency of damp gravel. Portland Cement Association.S. Applications dams. The structure con- content and absence of entrained air in most RCC affects some tained 330 000 m3 of RCC and was placed in less than five physical properties such as shrinkage and freeze-thaw durability. in its unhardened state. similar to those used in earth dams. and compacted using earth. Ideal RCC projects will tries. The two major applications tains 1070 m3 of RCC. Public Works. in the case of pave. The in-place RCC cost averaged about $26 per m3 when considering all the different mixes used [6]. buttressing of existing concrete dams. The U. Completed in 2003. RCC developed as a result of efforts to design and build con- peared in the previous edition of ASTM STP 169C in 1994. 595 .S. and quality control. ties. Raphael [2] presented a paper in which he extrapo- are in the sections on mixture proportioning. IL 60077. in by truck. Corps of Engineers (USACE). as well as reduced construction times. The yard size was doubled in 1979 with a sec. When inspected in 1984. British Columbia. The difference in percentage savings usu- crushed-rock base. Mississippi in. Siegrist Dam. log handling in more than 200 dam rehabilitation projects. The project included 16 350 m2 of 0. proven to be a cost-effective pavement for many conventional pavement applications including warehouse facilities. 2. To achieve nificant RCC pavement in the United States at Fort Hood. Approximately 500 000 m2 of a 180- of conventional concrete. The Tennessee Valley Authority in 0. WA. Since then.15. and residential streets. According to the Seattle office of the U. 1—Construction of C. PA. Savings associated with RCC are primarily were in excellent condition [12]. Information on yards. mixing. E. To en. roadway inlays. [12].16]. quality product similar to what is expected of conventional . and transporting roller-compacted the auto industry.35. these pavements of concrete placed. freight depots. conventionally placed concrete. However. The first use of RCC unit cost per cubic meter of RCC is considerably less than pavement in Canada was built in 1976 at a log-sort yard at Cay. the highest measure of cost effectiveness and achieve a high- This was a large parking area for tanks and other tracked vehi. Two of the largest paving projects to date have been for ment for batching. RCC 16–19 mm. RCC is designed to have the strength was completed in 1989. most RCC pavement projects are placed typically costs between $19 and $24 per m2 [14]. due to reduced cement content. pavement range from 20–30 % less than conventionally placed m-thick RCC pavement placed in a two-lift operation on a concrete [12. forming. and other special ap- designing RCC for spillways and overtopping protection plications. and seismic reinforcement for cles surrounding a maintenance shop. The Saturn automobile plant in Tennessee concrete is similar to CTB. The 15 000 m2 area of existing concrete dams.5 MPa. RCC has been used for rehabilitate Ocoee Dam No. Approximately 830 000 m2 of 175-mm-thick pave- that it contains a well-graded coarse and fine aggregate. This 4-m by 80-m service road proved the feasibility of cost histories of RCC and conventional concrete show that the RCC for use in pavement construction [11]. ment was placed in 2003 for the Honda manufacturing facility hance surface texture. RCC has considerably more cementi. paction costs. Approximate costs of RCC cuse. According to the contractor on this project. RCC has been used heavy-duty pavements such as tank hardstands. the maximum size aggregate is limited to in Alabama.S. intermodal yards. indus- Pavement trial access roads. Construction in 1975. ment and cement-treated base (CTB) material. constructed in 1942 [10]. large commercial parking areas.25-m pavement was placed in one lift and achieved a flexural 1980 was the first to use RCC as overtopping protection to strength of 5. the first use of RCC Advantages pavement in North America was a runway at Yakima. mm-thick pavement was placed for parking areas and access tious material than CTB. In addition. The primary advantage of RCC over conventional construction stalled the first known RCC test pavement in the United States is in the speed of construction and cost savings. Although equip. in the past ten years RCC has also been applications can be found in Ref 9. and com- In 1984 the Corps of Engineers constructed the first sig. intersection The use of RCC for pavements evolved from the use of soil ce. placement. In general. and differs from most soil cement in roads [13]. control structures in rivers. Note use of conveyors to place roller- compacted concrete (photo courtesy of Gannett Fleming). with heavy-duty asphalt type pavers. ally depends on complexity of placement and on total quantities ond RCC application.596 TESTS AND PROPERTIES OF CONCRETE Fig. The USACE at Vicksburg. replacements. Texas. The use pavements.5 14 18 41 Portland Cement Concrete (C 618). therefore. as much as possible. placement.75 . to alkali-silica reactivity (ASR). which fre- The strength of RCC is primarily dependent on the quality quently use a NMSA of 25 mm. degree of compaction. The grading limits of individual coarse aggregate size fractions ment given in ASTM Specification for Portland Cement (C 150) should comply with those used in conventional concrete. Changes from the grading or quality require- benefits from rapid construction include reduced administra. They include Type II (moderate heat). the following design and construction ob. a 50-mm NMSA. construction time tional concrete have also been successfully used in RCC dam for large projects can be reduced by one to two years. Aggregate for RCC should placement rate of 224 800 m3 per month was achieved [17]. there are no dowels. pozzolan. reduced risk of flooding. 4. Type IP (portland-pozzolan cement). aggregates that readily achievable for even large structures. In addition mentitious material has a significant effect on the rate of hy. pavement surface texture.. and earlier operation of the should be supported by laboratory or field test results that show facility. Early RCC mass concrete dam projects in the United States Materials used a 75-mm nominal maximum size of aggregate (NMSA). more at- tical after mixing. multi. at Tarbela Dam in Pakistan. tain aggregates should follow procedures used for conven. and (3) as a mineral filler to provide supple- Typically. At Olivenhain Dam.0 33 44 100 its conformance with ASTM Specification for Fly Ash and Raw 12. zolans are usually preferred especially for dams. that the concrete produced from the proposed materials fulfills tages in all aspects of construction that are related to time. However. and seldom significantly reduces the cost [15]. ASR and free lime content. since they normally contribute less heat of hydration than Class C and have .. portland cements with lower heat-generation characteristics than Type I are of. In the case of mental fines for mixture workability and paste volume.. rapid placement is well as on its cost and availability at each project [18]. as possible. six days a week. and water. greater sulfate resistance. ments of ASTM Specification for Concrete Aggregates (C 33) tion costs. Cement Grading RCC can be made using any of the basic types of portland ce. desired. 50 76 100 37. In pavements. the use of larger aggregate greatly lection of materials for chemical resistance to sulfate attack.75–50 mm 4. Before specifying a low-heat Sieve Size (mm) 4. RCC construction offers economic advan.0 mm type cement. sulfate resistance. not require complex construction procedures. Maximum size aggregate for other applications include tional concrete construction.75–19. increases the probability of segregation during transporting and potential alkali reactivity. TABLE 1—Ideal Coarse Aggregate Grading [15] ten specified. the engineer should determine its availability in the project area. of pozzolan will depend on required material performance as To minimize the treatment of cold joints. to minimizing the chance for segregation during handling and dration and the rate of strength development and. The type of ce.0 44 58 The selection of a pozzolan suitable for RCC should be based on 19.5 61 81 Pozzolans 25. Although larger sizes have been successfully used in Japan and ment or a combination of hydraulic cement and pozzolan. Basically. Fine aggregate gradings Furnace Slag for Use in Concrete and Mortar (C 989). ADASKA ON ROLLER-COMPACTED CONCRETE 597 concrete structures. aggregates for RCC should be shifts per day. a smaller NMSA provides a relatively smooth significantly affects strengths at early ages. however. Cementitious Materials is less prone to segregation and is becoming more widely used. meet the same standards for quality and grading as required for High production rates make dam construction in one season conventional concrete construction. and resistance to abrasion with cer. since lifts are typically thinner and gradation of the aggregate. RCC can be made with any of the basic types of hydraulic ce. or steel reinforcement. Cumulative Percent Passing furnace slag cement). Also the strength development for these 75 100 63 88 lower-heat cements is usually slower than for Type I. (3) design should avoid. Indi- or blends of these with ground granulated blast-furnace slag as vidual size groups are normally combined to produce gradings specified in ASTM Specification for Ground Granulated Blast. a record evaluated for quality and grading. preferably crushed coarse aggregate. Other construction [19]. . (2) to reduce cost. the requirements of the project as is provided for in ASTM C 33. and the than for mass concrete placement [18].5 21 28 63 or Calcined Natural Pozzolan for Use as a Mineral Admixture in 9. With dams and other mass Aggregates placement projects. and Type IS (portland blast. For RCC pavement proportions of cement. Use of pozzolans in RCC mixtures ple mixtures and other construction or forming requirements may serve one or more of the following purposes: (1) as a par- that tend to interfere with production. . RCC needs no forms or finishing. and (4) the design should tial replacement for portland cement to reduce heat generation. Se. To minimize thermal cracking in mass applications. Type IV (low-heat) cement is not generally available in the United States. projects a NMSA of 16–19 mm is typically specified. that may mean the use of two paving machines working in tandem. For Class C pozzolans. spreading.. approaching those given in Table 1.. the contractor will typically run two 10-h As with conventional concrete. When compared to do not meet the normal standards or requirements for conven- embankment or conventional concrete dams. overtopping protection for embankment dams. tie rods. Class F and Class N poz. (2) operations should include as few laborers tention may be needed with regard to set time. They also help reduce expansion due jectives are desired: (1) RCC should be placed as quickly as prac..75–75 mm 4. It is also beneficial in maintaining lift surfaces in an unhardened state 9. crushed 48–59 150 m 6–18 19. Again. during RCC startup activities. 150 m 12–28 0–10 75 m 6–18 .0 mm 83–100 and Type of Coarse Percent of Total 12. ASTM Test Method for Air Content of Freshly aggregate volume.75 .18 mm 28–46 37.. The use of proper compaction techniques that lower the en- The larger percentage of fines is used to fill voids and con. Where close control of grading of the Minimizing frost damage in RCC has been achieved by coarse aggregate and RCC production are desired. as with conventional mass concrete. Also. increase strength. (2) tarding admixture as specified in the ASTM Specification for minimum amount of cementitious material. the required total minus Mixture Proportioning 75-m fines may be as much as 10 % of the total aggregate volume.5 mm. be greater for RCC than acceptable for conventional concrete.5 mm 66–85 4. Another im- Admixtures portant consideration for mass RCC is the minimization of heat rise due to the chemical reactions of the cementitious ingredi- Water-Reducing and Retarding Admixtures ents.36 mm 38–56 75 mm.36 mm 75–95 80–100 be more easily mixed in conventional central plant drum mix- 1..5 mm 72–93 Aggregate Aggregate Volume 9. (3) pozzolans or Chemical Admixtures for Concrete (C 494) may be considered for any RCC placement. RCC can 2. Water-reducing and retarding admixtures have proven beneficial for improving and extending the TABLE 4—Typical Combined Aggregate Grading Limits for RCC Pavement Mixture [20] TABLE 3—Approximate Ratio of Fine to Total Aggregate Volume [15] Sieve Size Cumulative Percent Passing Nominal Maximum Size Fine Aggregate Ratio.5 mm. Once concrete has dried through self-desiccation. and lower the per- tribute to compactibility. compactibility. dry concrete. factors such as The use of a water-reducing and retarding admixture or a reuse of (1) the largest nominal maximum-size of aggregate. By improving the workability. 19. strength. trapped air-void content. and.598 TESTS AND PROPERTIES OF CONCRETE workability of RCC beyond the typical 45 min to 1 h specified TABLE 2—Fine Aggregate Grading Limits on most projects. Most of the problem comes from the difficulty of entraining a good air-void system in such a low-paste. factured fines. Fineness modulus 2. crushed 29–36 2. ferentiate between entrained and entrapped air voids. Typical Mixed Concrete by the Volumetric Method (C 173) and Test gradation range for RCC pavements is shown in Table 4. Sieve Size Passing [15] Passing [ASTM C 33] longer haul distances. size separa.18 mm 55–80 5–85 ers and transit truck mixers. The extended workability is especially bene- Cumulative Percent Cumulative Percent ficial during warmer weather. and for placement of thick lifts. low. or extra pozzolan. the grading band for road trapped air content in RCC mixtures will vary depending on the base material can be quite open resulting in possible gap grad.35]. with most mixtures using approximately 3–8 % [18]. Depending on the volume of cementitious material and the NMSA. ing and segregation.10–2. Research has indicated that air-entrainment may be limited to the more are also specified as shown in Table 2. As with conventional concrete construction. frost resistance [10].0 mm. for mass RCC are given in Table 3. manu..5 mm 100 100 until the next layer or adjacent layer of RCC is placed. compactive effort applied in consolidating the material.. rounded 41–45 75 m 2–8 . material ratios (w/c) so that the permeability of the paste is mended in ACI 304R. however.75 mm 51–69 75 mm.0 mm. thereby 4. as recom. The en- tained in ASTM D 2940.75 mm 95–100 95–100 creating a better bond. crushed 39–47 600 m 18–36 37. workability. Air-Entraining Admixtures Air-entrainment of RCC has had only limited application to date. The additional fines are usually made meability of the concrete should also improve the pavement’s up of naturally occurring non-plastic silt and fine sand. expressed as a percentage of the total s [30. in the case of RCC. have used locally available road sure Method (C 231) determine total air content and do not dif- base material with grading requirements similar to that con. it is dif- The required amount of material passing the 75 m may ficult to again become critically saturated by outside moisture. However. rounded 35–45 300 m 11–27 19. the primary considerations for mixture proportioning are durability. proportioning mixtures with sufficient low-water-cementitious tions should follow normal concrete practice. Method for Air Content of Freshly Mixed Concrete by the Pres- Some designers. Approximate fine workable mixes with Vebe consistency times less than about 35 aggregate contents. Required dosages of water-reduc- 600 m 35–60 2–60 ing and retarding admixtures are normally several times as 300 m 24–40 5–30 much as recommended for conventionally placed concrete. rounded 27–34 1. 59 Entrapped air content on 37.1 1. compactibility and engi- in the mixture to enhance performance at the lift joints.56 0. using ASTM Test Method based on w/cm and strength relationship. unit weight of mortar. The final step involves the selection of the w/cm ratio and the sistencies are typically determined in accordance with ASTM Test proportions of cement and pozzolanic materials to produce a Method for Determining the Consistency and Density of Roller. The method calcu. Instead of deter- or moisture-density relationship. The next step is and high workability. sand-aggregate ratio. mortar. and the water values for estimating RCC trial mixture proportions.5R discusses four mining the water content by Vebe time or visual performance. to select an aggregate grading that contains a minimum vol- high pozzolan contents. A recommended premise behind the method is that workability and strength refine aggregate as a percentage of the total aggregate volume is quirements are treated in two independent steps. Once the volume of each ingredient is calculated. ture proportions are project-specific. High Paste Method—This method results in mixtures that The procedure includes three major steps. approach similar to that used for selecting soil-cement and ce- ture determined by solid volume. fine aggregate. under compaction. Because of the consistency test equipment A number of mixture-proportioning methods have been requirements and differences in the nature of RCD design and successfully used for RCC structures throughout the world. kg/m3 a) Vebe 30 sec 150 133–181 122 107–140 107 85–128 b) Vebe 30 sec 134 110–154 119 104–125 100 97–112 Sand content.1–4.22].41 0. Most mixture-proportioning methods are variations Maximum Density Method—This method is a geotechnical of two general approaches: (1) a w/cm approach with the mix. clean and normally graded aggregates ume of voids for a given compaction energy.2–4. . sand.1 except that it incorporates the use of a consis. and com- are evaluated on a job-specific basis. Another method for proportioning nonair-entrained RCCP proximate water demand is based on nominal maximum size mixtures is referred to as the optimal paste volume method. and (4) cooling procedures for the materials content. and entrapped air content for trial RCC mixture proportioning studies. The ap. the mixture is adjusted accordingly. pressive strength.55 0. Proportioning by this approach approach with the mixture determined by either solid volume is also covered in Appendix 4 of ACI 211. struction. Vp/Vm. termed VC value. % a Quantities for use in estimating water.5–3. neering properties are suitable for the particular project. and (2) a cemented-aggregate ment stabilized base mixtures. This Roller-Compacted Dam Method—The roller-compacted is usually confirmed in a test section using the placing meth- dam (RCD) method is used primarily in Japan.0 mm 50 mm 75 mm Contents Average Range Average Range Average Range Water contentb.41 0. as ified Effort (D 1557). paste with enough binding capacity to satisfy the strength re- Compacted Concrete (C 1170).27–0. The method based on the nominal maximum size and nature of the course is based on the assumption that an optimal RCC should have aggregate. % by volume a) crushed aggregate 70 63–73 55 43–67 45 39–50 b) rounded aggregate 55 53–57 51 47–59 43 39–48 Paste: mortar ratio.1 0. by volume 0. The first step is generally contain high proportions of cementitious materials.5 0. for Laboratory Compaction Characteristics of Soil Using Mod- lates mixture quantities from solid volume determinations. paste method is to provide excellent lift-joint bond strength and All of the methods include the preparation of trial mix- low joint permeability by providing sufficient cementitious paste tures to confirm that the workability. predominant mixture-proportioning methods: the desired water content is determined by moisture-density re- Corps of Engineers Method—This proportioning method is lationship of compacted specimens. Although mix- tency meter. The major advantage of the high quirements [21. used in proportioning most conventional concrete.1 0.3 fraction. and to adjust the paste volume to obtain the required workability. If the similar to proportioning conventional concrete in accordance laboratory-proportioned mixture proves unsuitable for con- with ACI 211. Table 5 provides typical ships between the consistency.44 0. The procedure consists of determining relation.31–0. ADASKA ON ROLLER-COMPACTED CONCRETE 599 blended cements. TABLE 5—Typical Values for Estimating RCC Trial Mixture Proportions [15] Nominal Maximum Size of Aggregatea 19. The method is ods and equipment that are planned for use on the job.33–0. coarse aggregate ratios are determined by trial batches Vebe con. construction.5-mm 1. this method is not widely used in proportioning making it difficult to generalize any one procedure as being RCC mixtures outside of Japan.2 1. standard. % of total aggregate volume a) crushed aggregate 55 49–59 43 32–49 34 29–35 b) rounded aggregate 43 38–45 41 35–45 31 27–34 Mortar content. a just enough paste to completely fill the interstices remaining comparison of the mortar content to recommended values when the granular skeleton has reached its maximum density maybe made to check the proportions.3. The aggregate and desired modified Vebe time. The optimum water. b Lower range of values should be used for natural rounded aggregates and mixtures with low cementitious material or aggregate fines content. ACI 207. Attempts mass RCC range from 0. tents and may contain nonplastic fines to fill aggregate voids. there are nu- decreased strength. The study also are due to drying shrinkage (primarily in pavements) and ther. increased voids exposed to natural weathering of Treat Island. aggregate grading. and autogenous). volume change (thermal. have will occur within the matrix of the concrete resulting in typically performed very poorly. field applications have shown an air-entraining admixture can tioning. RCC should generally be lined with high-quality concrete to gregate. It is difficult to quantify typical values in either case. The compressive strength of RCC is determined by several Freezing and Thawing factors including the water to cementitious materials ratio. the mize combinations of cementitious materials. The coarse aggregate at the surface The two significant changes in volume experienced with RCC remained firmly embedded in the RCC matrix. and degree of compaction. Re- concrete. jor influence on the physical properties of RCC. which has been used to evaluate cracking.18. Laboratory specimens of nonair- curing. compacted mass. heat rise that pavers according to ASTM Specification for Solid Interlocking causes expansion of a massive concrete structure is due almost Concrete Paving Units (C 936) and ASTM Test Method of Sam- entirely to the chemical reactions of the cementitious material. Because of its dry consistency. Resistance of Concrete to Rapid Freezing and Thawing (C 666). is a much harsher test that traction joints in the individual lifts of the freshly placed RCC. Procedure A (in water) and large blocks of mass RCC material ventional concrete. and durability. thermal coefficient of ex. and entrain air in RCC mixtures. creep. drying. The study concluded that except for some surface wear (fines were removed up to a depth 2 mm). and to opti. Maine [18]. Acceptance criteria for durability tests of concrete [23]. specific heat. creased with increasing strength and maximum aggregate size. overflow spillways of RCC dams subjected to frequent use. However. nonair-entrained concrete that in comparable conventional concrete mixtures due to the products such as concrete pavers and precast concrete pipe.31]. compressive strengths of RCC were visually inspected. com. paction (consolidation) of RCC requires more effort than con. Finally. grading. Erosion tests in quite similar and differences are primarily due to differences test flumes have indicated the excellent erosion resistance for in mixture proportions. when subjected to ASTM C 666 testing [18. laboratory and and therefore is almost totally controlled by mixture propor. Observations of various projects from heavy-duty pavements such as log sort yards to RCC spillways have also indi- Compressive Strength cated excellent resistance to abrasion/erosion. Poisson’s ratio. Degree of compaction has a significant influence on entrained RCC tested according to ASTM Test Method for compressive strength. Abrasion/Erosion Resistance pansion. relies heavily on the presence of air-entrainment for acceptability. some studies indicated that aggregates contributed Aggregate quality. The difficulty although one researcher has indicated the permeability of RCC comes in trying to incorporate the tiny air-entrained bubbles to be greater than conventional concrete [24]. change associated with drying shrinkage is normally less than Similar to other no-slump. The percentage of pozzolan has a significant influence prevent abrasion/erosion damage [18]. search has indicated that the abrasion resistance of RCC in- In general. Hard. it has not been practical to quality and grading of aggregate. grading. noted that surface wear typically occurred within the first 2–3 mal expansion and contraction in mass concrete. consideration must RCC in the field [12. even ened RCC permeability is comparable to conventional concrete. With respect to thermal considerations. degree of compaction. The significant material properties of hardened RCC include compressive strength. years. RCC [25]. As a result.15 to 15 109 cm/s [18]. the permeability tends to be lower. on the strength development of RCC especially at early ages. In Piggott’s study [29] a total of be given to the fact that most specifications accept 96–98 % of 34 RCC pavement projects in the United States and Canada maximum density.30. Because of its dry consistency. ASTM Test Method for Abrasion Resistance of Con- A wide range of RCC mixtures can be proportioned. tensile and shear strength. lower water content. placement method. more to abrasion resistance than cement content [26]. just as crete (Underwater Method) (C 1138) has been used to evaluate there is a wide range of mixtures for conventionally placed the performance of RCC for use as streambank protection. Without full compaction. Delays in compaction may also result in a merous examples of good performance of nonair-entrained decrease in compressive strength. together with porosity of the mortar matrix. Volume years of service and then stabilized. Durability lus. RCC will have lower cement. In fact. Nevertheless. and quality hardened properties of RCC and conventional concrete are primarily govern abrasion/erosion resistance. and voids content. ASTM C 666. pling and Testing Brick and Structural Clay Tile (C 67) rely on Therefore.27–29]. The projects ranged in age from 3–20 compacted at less than maximum density will be reduced. and physical properties have a ma. Typical values for uniformly throughout the no-slump RCC mixture. and water con. This lower shrinkage has resulted in less RCC derives its durability from its high strength and low per- cracking and revised design considerations for RCC pavements meability. tensile strain capacity. paste. For large dams a common practice is to install con. the freeze/thaw durability of RCC. water and ag. effectively be used to provide good freeze/thaw durability. With regard to air entrainment in RCC.600 TESTS AND PROPERTIES OF CONCRETE Properties of Hardened RCC cementitous mixtures such as those for RCC pavements. Acceptance of RCC according to C 666 criteria usually Permeability results in mixtures of very high strength not typical or eco- The permeability of RCC is largely dependent on voids in the nomically viable for most RCC paving projects. The Compressive strength and aggregate size. permeability. For higher to entrain air are most effective in RCC mixtures with a Vebe . elastic modu. the use of lesser amounts of cementitious material a combination of minimum compressive strength and mois- in mass RCC construction lowers the potential for thermal ture absorption. ACI Compressive strength tests are conducted in the design phase 207 on Roller Compacted Mass Concrete recommends that for to determine mixture proportion requirements. the performance of Volume Change the RCC was very good. and curing is accomplished as rapidly sign of wetter consistency mixes tends to reduce segregation. Dump trucks are the most common and 45 min from the time of initial mixing. Conventional pavers provide 80–90 % of modified Proc- mixed RCC between truck loadings so that the least amount of tor density. ADASKA ON ROLLER-COMPACTED CONCRETE 601 consistency time less than about 35 s using clean. paction has to be provided by the vibratory rollers. 2). humidity. placement to avoid segregation. and reclamation of aggregate from the stockpiles been established and proven by large-scale. systems are typically used on large dam projects and where Each RCC mixture will have its own characteristic behav- there is a concern that truck hauling may contaminate the ior for compaction depending on temperature. conveyors. These times can be increased for RCC mixtures with maneuver. One of the most important steps in RCC construction is difficulties in getting uniform mixing and discharging the dry compaction.3 m have been used has been based on the The batching and mixing plant requirements for a project to realization that the spreading of the RCC with heavy dozers not be constructed using RCC are essentially the same as for a only remixes and redistributes the concrete to overcome segre- project built with conventional concrete [15]. is more than 30–45 min old and the mix temperature is above In confined areas where dump trucks may be difficult to 21°C. especially in hot weather. as possible. De- spreading. Con- Construction veyor systems must be designed to minimize segregation at transfer points. equipped with vibrating screeds. The hard surface. such as adjacent to forms. but spaced so that they will not be delayed at the for conventional concrete are tilt drum mixers. continuous flow (such as a pugmill) or asphalt pavers are equipped with tamping and vibrating screeds. RCC batch quan. or finishing. or cooler required to supply RCC to the placement area. paver must be scheduled to provide a continuous supply of Tilt Drum Mixers—The most common central mixing plant concrete. tures have been hauled. but with care and proper procedures. ing plant to the placement area are dump trucks. The recent use of successfully especially as a final pass to remove surface cracks water-reducing and retarding admixtures to improve workabil. Rubber-tire rollers have also used method unsuitable except for small projects. Typically. RCC mixtures with a 75 mm NMSA have a A major benefit of RCC is the cost savings that result from op. in the case of mass concrete. These mixers paving machine and thus permit the mixed concrete to dry out are generally available locally and can be used effectively to and loss workability. and asphalt spreading RCC. they are only method to use. The production. in the case of RCC pavement. greater tendency to segregate when they are dumped unto a timizing material selection and the speed of construction. whereas heavy-duty pavers have achieved up to 95 %. times are increased. possible after it is spread. Dozers are the preferred method of placement placement. The design of dams where lift thick- Batching and Mixing ness greater than 0. placing. plant stoppages is required. or backhoes may be extended set times due to pozzolans. reinforcing steel. Transporting Compaction of RCC should be accomplished as soon as The most common methods for transporting RCC from the mix. As a result.6 m. In tight areas ity has allowed greater use of transit mixers. There are no forms. Depending on weather conditions. thickness range from a minimum of 0. ASTM graded Special care must be taken during transportation and fine aggregate. ness). RCC is usually compacted with self-propelled consistency mixture generally make this type of mixing vibratory steel drum rollers. and the . gation but also provides compaction. most cost-effective method for earthwork placement. large power tamper jumping jacks are most suitable. Typical lift quantities of concrete can be placed rapidly with minimum la. Conven- and plant availability will dictate which type of mixing tional asphalt pavers have been used. compacting. tion in strength can be expected if RCC is compacted when it protective covers should be provided to minimize moisture loss. The use of a transfer device is also rec- produce RCC. horizontal shaft mixers provide the most intense and which allows for much higher initial compaction from the paver fastest mixing action of any mixing plants. Placement and compaction of the very dry mixture is typically Placement done using equipment and techniques similar to those used for Tracked dozers are the fastest. large for dams and other nonpavement applications. as well as in full-scale produc- for conventional concrete. Mounding of the RCC during loading and unloading operations should be avoided. previously placed RCC layer. Conveyor temperatures [18].15 m (compacted thick- bor and equipment. well-controlled test are done in the same way and with the same equipment as section construction and testing. As a result. plasticity of the aggregate fines. ommended whenever practical to eliminate starting and stop- tities are typically less than the drum capacity and mixing ping (Fig. aggregates. Because of its dry consistency. admixtures. wind. Due to the speed and quantity of Continuous operation of the paver is critical to achieving material mixed. front-end loaders. to over 1 m although no general production in the United States has exceeded 0. of plant that will provide uniform mixing of the cementitious Placement of RCC pavements is typically accomplished by materials. almost all the com- Horizontal Shaft Mixers—Whether single or dual shaft. transporting. These procedures have stockpiling. RCC can be produced in any type tion of RCC for dams in Japan and at Elk Creek Dam [15]. Many pugmills are resulting in less compacted effort required from the vibratory equipped with transfer or gob hoppers to temporarily store the rollers. these mix- entire process of batching. Heavy-duty portable or permanent. Transit Mixers—While transit or truck mixers are the most Compaction widely available and are capable of producing a quality RCC. or compaction should be completed within 15 min of spreading a combination of both. and water. however. horizontal shaft mixers are the preferred mix. batch. mixing. overall grading. Often the size of the project the use of heavy-duty asphalt type paving machines. Trucks delivering RCC to the ing method especially for large projects. and tears and provide a smooth tight surface. dumped and remixed successfully. Substantial reduc- form of transportation. conveyors. a smooth surface without bumps. A modified Vebe test. The test section hoses or coarse sprays that may erode the paste and fine ag. verifying for RCC lifts in the range of 150–300 mm. compacting. to modify placing. NMSA. Because dures are typically specified. and curing sprinkling systems or complete submersion. moist cur. A white pigment. uid Membrane-Forming Compounds for Curing Concrete (C During construction a number of quality control proce- 309) has become popular for RCC pavement projects. Typically. consistency and ventional concrete. Another important element of inspection is to monitor the time within Quality Control the various stages of construction. Most specifications require that the RCC mixture be compacted within 45–60 min of mixing For most RCC projects it is essential to have a quality control and about the same time limit is used to ensure adequate bond- program that addresses the activities. and and membrane-forming curing compounds. low the contractor time to adjust the size of his batching. curing compounds are typically applied at density tests. and to change any other operation curing compound conforming to ASTM Specification for Liq. of Roller-Compacted Concrete Using a Vibrating Table (C . compaction techniques. Consistency and Compactability owner. 2—RCC being placed with heavy-duty paver. higher application rates then for conventional concrete. transportation. It may be as simple as visual observations or as elabo. ing for placement of multiple lifts or adjacent paving lanes. that is considered essential to the success of the job. and fabrication and testing of beams and cylinders. The quality control program is typically the joint responsibility of the contractor. 18. Method A of ASTM Test Methods for Consistency and Density sented in references 10. or owner’s representative. and respon. application must ensure a uniform void-free membrane exists surface cracking or consistency changes may be indicators of across the entire RCC pavement surface. calibrations. moisture tests. gradation tests. procedures. ing. Water cure may be ap. Preconstruction inspection and testing typically include bratory roller will achieve the desired density of at least 98 % sampling and testing the quality of the raw materials.602 TESTS AND PROPERTIES OF CONCRETE Fig. and 32. for evaluation of the mix design and allows the contractor to ing has been used for most projects. Use of open-ended the RCC during production operations. burlap ing. Over compaction or that the type and size of the mixing plant. four to six passes of a dual-drum 10-ton vi. mix- Other methods of curing include plastic sheeting. Intermediate transfer device used to maintain a constant flow of material to the paver. The extent of the inspection The Vebe or similar apparatus is used to measure the consis- and testing program will depend on the nature and size of the tency or workability of many RCC mass concrete mixtures. placing. and inspecting and calibrating the production and testing equipment to ensure proper operation. The Visual inspection for signs of segregation during placement. sibilities for the specific project. project. The test section provides Because of the relatively low-water content of RCC. construction deficiencies that need to be corrected. since it may reduce the placing and compaction equipment meets the project require- density of the upper portion of the lift. develop and demonstrate the proposed techniques for mix- plied by water trucks equipped with fine mist spray nozzles. spreading. Among them are regular plant of the more open textured surface with RCC compared to con. Curing Constructing a test section is also part of the preconstruction quality control program. ments. it is usually not applicable for the drier RCC pave- rate as constructing a test section and having an on-site testing ment mixtures. however. should be constructed sufficiently early in the contract to al- gregates from the surface should not be used. transporting. 15. or transporting system. jointing. engineer. A thorough discussion of quality control procedures is pre. excessive rolling should be avoided. conducted according to lab. (4) develop representative freeze-thaw durability the surcharge plate (Fig.” ACI 116R-99.. ASTM Practice for Molding Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Hammer (C 1435). ASTM D 1557. O. 1973. ASTM D 1557.” Concrete International: The primary objective of cylinder preparation is to duplicate Design and Construction. W. Manual of moisture content and dry density of a material for a specific Concrete Practice. section or in the laboratory to determine the degree of com. paction To ensure the accuracy of the nuclear gages being [5] Hall. . American Concrete Institute. used for pavement applications. New York. pp. New York. E. “Roller Compacted Concrete Studies at Lost Creek Dam. The test is used to determine the relationship between the [1] “Cement and Concrete Terminology. is a well-established test for soils that can also be applicable with References RCC. M.” U. This test [2] Raphael. ington Hills. Port- used. C-73-10. (2) establish standardized the freshly mixed RCC. The vibrating hammer (C 1435) and pneumatic tamper work for a wide range of RCC mixture consistencies. UK. Sutton. U. pp. minimum of 95–98 % of maximum wet density. OR. on Hydropower & Dams. ASTM Practice for Making Roller-Compacted Concrete in Cylinder Molds Using a Vibrating Table (C 1176). The main advantage of RCC over conventional Fig. (5) determine methods for air-entrainment... NY. D.” Economical Construction of Concrete Dams. the compaction (consolidation) effort and consequently the [8] “2003 World Atlas & Industry Guide. “Feasibility Study of No-Slump Concrete for Mass in-place density in the field is compared with the theoretical Concrete Construction. No. D. pp. a test block is made during the early stages of the project land. with a Vebe time between 10 and 60 s. construction is in the speed of construction and cost savings. L. 20–28. 1972. R. and enhance performance. (3) establish standardize mixture design quired for a ring of mortar to appear around the periphery of methods.. [7] Oliverson. several alternative methods have been developed for RCC and are being used successfully. skid resistance. 1971. monitor is compacted density. T. The test can be used for (6) improve mixing efficiency using conventional concrete overall assessment of the RCC workability. 5. R. ADASKA ON ROLLER-COMPACTED CONCRETE 603 Cylindrical test specimens for determination of compressive strength of RCC cannot be fabricated using the standard procedures used for conventional concrete. (4) pneumatic tamper method. Density measurements are 143–152. maximum density or maximum density achieved from a test Army Engineer Waterways Experiment Station. Specifications [6] Schrader. One of the most important quality control parameters to American Society of Civil Engineers. June 1974. (2) vibrating hammer method. Primary applications are for dams. May 1984. including (1) Vebe method. Vol. The Vebe test measures the time re. and Houghton. 221–247. MI. mum dry density at optimum moisture content. Army Engineer District. Part 1. 2003.” Concrete International: Design and Construction. Additional research and development is needed to: (1) improve surface texture. J. “Upper Stillwater Dam— Preparation of Test Cylinders Design and Construction Concepts.” The International Journal in-place density of the RCC after compaction in the field.. American Society of Civil Engineers. “Concrete Dam Construction Using Earth Com- In-Place Density paction Methods. The Vebe test is used for wetter mixtures generally with Vebe times of 35 s or less [34]. and pavements. W.” Miscellaneous Paper No. 5. and (7) expand the use of admixtures suitable for control of the uniformity of the mix during pro. 6. A. Each of these methods has advantages and disadvantages.S. 6. Performance of RCC has been very good even under freeze- thaw conditions. The modified Proctor compaction test. This test is suitable for RCC mixes test procedures. “The Optimum Gravity Dam. Surrey. including retarders and water reducers to extend working time duction and placement. Note ring of mortar along side of container. roller-compacted concrete has advanced significantly as a viable construction technique. and kept available for calibration purposes. 3—Determining Vebe time according to ASTM C 1170. 38–45. May 1984.. As a result. and results in the establishment of a maxi. Closure Over the past 30 years. (3) modified Proctor method. and Richardson. Both the modified Proctor (ASTM D 1557) and gyratory compaction method are used for the drier RCC mixtures. Vicksburg. and joint 1170) is used to determine consistency and compactibility of construction methods in pavements. 3). No. Oct. “Construction of Willow Creek generally require the in-place density of the RCC to achieve a Dam. spillways.S. pp. but is generally not mixing equipment. overtopping protection. 1999.” Rapid Construc- method is more applicable for the drier RCC mixtures typically tion of Concrete Dams. joint design spacing. and (5) gyratory compaction method [33]. [3] Cannon. Farm- compactive effort. The [4] Tynes. taken during placing of RCC using a nuclear density gage. E. J. J. Vol. MS. and McKinnon. MI. Roads... IL. Aug. sistance of Roller Compacted Concrete Pavements.” Engineering News-Record.. “Freeze-Thaw Durability and Deicer Salt Re- 1992. 2nd ington Hills. New Zealand. L.. Farmington Hills. 30. Compacted Concrete.S. May 1999. L.. Conference Proceedings.604 TESTS AND PROPERTIES OF CONCRETE [9] “Design Manual for RCC Spillways and Overtopping Protec. F. Cahners Publishing. [27] Ragan. 1995. ments. et al. S. D. Corps of Engineers. IL. T. Farm. Compacted Concrete Pavements. M. Skokie.12. 3rd ed. New York. Poor Quality Materials—Concepcion Dam. 1992. 2002. New York. May 1993. MS. “Roller Compacted Concrete Paves Factory Vicksburg. N.” ACI 207. P. 16. 2004. 1989.S. pp.” pacted Concrete—A Review.” EB218. 27–40.. Sept.. 287–297. “Design of Roller Compacted Concrete Pave- tion..” RD126. Concrete Construction.” Con. New York. R. [33] Amer. “No-Slump Roller Compacted Concrete (RCC) for [12] Keifer. 2003. Delatte. “Using Gyratory [21] Gagne. J. U.. 2nd ed. J. N.10R-95. U. Experiment Station. “Proportioning for Non Air-Entrained RCCP. p.” Miscellaneous Paper SL-86- [15] “Roller Compacted Concrete. CRD-C 161-92. Waterways Experiment Station. “Mixture Proportioning of Roller Com. IL. N. Washington. Compaction Concepts”. MI. 1990. Compaction to Investigate Density and Mechanical Properties crete International. R. MS. W. [22] Marchand. MI. Transportation Hills. Aug. MS. Manual of [30] Dolen. [17] Rosta. Skokie. and Schrader. S-76-16. Washington. Department of [32] “Roller-Compacted Concrete Quality Control Manual.. U. J. [31] Marchand.S. Skokie.. September Portland Cement Association. Oct. American Concrete Institute. NJ.. “Freezing and Thawing Durability of Roller- Concrete Practice. American Concrete Institute. “Evaluation of the Frost Resistance of Roller- p.” RP366. 318-ft-tal RCC Impoundment is [29] Piggott... A. et al.” Symposium [20] “Standard Practice for Selecting Proportions for Roller. “High Performance Pavement: RCC Roll-Out in Al.5R-99. [28] Waddell. Association. Concrete. Farmington Hills.. Portland Cement 4. Farmington Hills. American cellaneous Paper No. Waterways Experiment. Portland Cement Association. [34] “Roller-Compacted Concrete Density—Principles and Practices. J. NY. [35] Cannon. C. American Concrete Institute. A.. Compacted Concrete.” Journal of Materials in Civil Engineering..” Concrete 2003.. IL. Ed.” Use in Mass Concrete Construction. Study of Long Term Performance. “Air-Entrained Roller Compacted Concrete. MI. “At Olivenhain. American Concrete Compacted Concrete (RCC) Pavement Mixtures Using Soil. “Permeability of Roller Compacted [11] Burns.” Malhotra. [19] Gaekel.. V. [13] Munn. “Compaction Study of Zero-Slump Concrete.. NY. 1993. Washington. 37. D. [25] Saucier. 1986..” Mis. and Dobrowolski. Institute. Feb. CANMET/ACI International Conference. ogy. New Zealand. V. ments. New York. SP-122. DC. [18] “Roller Compacted Mass Concrete. pp. MI. 3rd CANMET/ACI International Conference. et al. 2002. Portland Cement Association. American Concrete Institute. San Diego. A.” Technical Report SL-84-17. pp. Concrete International. Skokie. on Performance of Concrete. Young. March 1988. American Concrete Institute. [14] Hampton. [24] Banthia. Manual of Concrete Practice. SP-171. 1999.” Engineering News-Record. P. C. MI.” EB215. American Society of Civil Engineers. “Special Concretes and [16] Mindess. J. Hall. pp. American Society of Civil Engineers. 2006. Part 1. Farmington Hills. Part 1. Farmington Hills. 2000. U.. S. McGraw-Hill. the Army. NY. Corps of Engineers.” Advances in Concrete Technol. “Paving with Roller Compacted Concrete. DC. SP-126. 101–114.. R. Army Corps of Engineers. Concrete III. March 1986. Vicksburg. Portland Cement Association. J. American Concrete Institute. . and Storey.” Roller Compacted Auckland. DC. NY. “RCC Mixes and Properties Using Ed... [26] “Erosion and Abrasion Resistance of Soil-Cement and Roller- New York. 2003. [10] “State-of-the-Art Report on Roller-Compacted Concrete Pave. Prentice Techniques. NY. 2002. U. Army Corps of Engineers.” Highway and Heavy Construction. [23] Rollings. 2000. CA. 457–486. 1997. D.S. Army Engineer Waterways Society of Civil Engineers. 1110-2.” Roller Compacted Concrete II. 454–466. 15 Jan.” Durability of Concrete. Department of the Army. Farmington of Roller-Compacted Concrete. pp. Auckland. 2003. Upper Saddle River.. 1997. Oct. MI.. “Roller Compacted Concrete Pavements—A Ready to Fill. K. R. NY. Concrete. M. O.” Engineer Manual No. 1992. T.. Research Board 1834. IS541.. Malhotra. New York. 1999. W.S. IL. K.. Vicksburg. S. Jr.” ACI 325.” Concrete Construction Handbook. 1978. E. July 7. abama. and Darwin. Skokie. 1984. initially with 20-mm ( 34⁄ -in. all of them deck overlays.25) due to the process.) Although there are many types and formulations of latexes Surfactants are added to the latex formulation in the manufac. Acrylic polymers have also been used widely for more The current edition reviewed and updated the topics of the pre. In 1957. acrylates (PAE). water-resistant Introduction coatings for basement masonry walls. overlayments. contributing to the improved properties that the latex adds to styrene-acrylate (SA). these latexes are composed of or- incorporate an antifoam agent in the latex prior to use in order ganic polymers that are combinations of various monomers. overlaid with latex-modified mixes. etc.) thick mortar modified with SB latex was in- Modified Mortar and Concrete (C 1439) in 1999. Membership in what polymer is dispersed. to determine if this would provide a long-lasting duced permeability. thus used are copolymers of styrene-butadiene (SB). polyvinyl acetate (PVA). These polymer stalled as an experimental coating on a bridge deck in Cheboy- modifiers mainly contribute to adhesion. These surfactants also function as water reducers. it is the nature of these ethylene (VAE). polymer.19 (C09. and vinyl acetate- the mortar and concrete. manufactured. thousands of bridges have been fiers are used in a variety of applications. styrene. a Task Group processes resulting in the production of latex by the emulsion was formed in Subcommittee C09. (A cubic centimeter of Latex Types a latex containing 50 % polymer solids of 0. June of 1992 with the papers being published in STP 1176 [1]. that is. and now with 38-mm (112⁄ -in. are available in the literature [4–6]. wearing surface. Pine Knoll Shores.03. a designation that has frequently been the process. land cement are suitable in mortar and concrete applications. However. Michigan. NC 28512-6524. Polymer modi. 605 . The latexes most commonly ment. relying on the adhesion properties of the latex to permanently mer Modified Concrete and Mortar was held in Louisville in bond the overlay to the deck concrete [2]. C09.44 issued One of the first widespread uses for latex-modified port- Latex and Powder Polymer Modifiers for Hydraulic Cement land cement was as mortar for bridge deck overlays. Since then. and bridge mortar.20 m-diameter particles would contain approximately 10 1012 particles. Latex-modified mortars are developed and included up to date references.18 (C09. gan. The polymer particles in a latex are spheres and typically between 0. This Task Group started butadiene rubber (SBR). no matter under a new subcommittee. vinyl acetate. portant. than 30 years to increase the strength properties and durabil- vious authors introduced new technology that has been ity of mortar in thin sections [3].52 Polymer-Modified Concrete and Mortar D.44). Concrete and Mortar (C 1438) and Test Methods for Polymer. In January 1987. Acrylic latexes display resistance to ultraviolet radia- the resultant mixture is called polymer-modified mortar or con. 1 Consultant. When latex is used as an additive to portland cement mixes. Typical properties of these latexes are given in surfactants to foam when agitated. Committee C09.) concrete.) pounds.50 m in diameter. crete. to control the air content of the portland cement mix. butadiene. and self- leveling flooring applications. It is therefore necessary to Table 1. The first ASTM sponsored Symposium on Poly. are also used in many applications where aesthetics are im- ter. and the product therefore became known as styrene- mer Modified Cementitious materials. ceramic tile thin sets and grouts. water resistance. This original process used a styrene-butadiene (SB) need identified for standards development in the area of Poly.7-mm ( 12⁄ -in.03. The war stimulated research into synthetic latex 169C by Kuhlmann and O’Brien. this subcommittee numbers about 50. acrylate. such as patching com. As the names indicate. stucco. this “natural” latex from South- THIS CHAPTER ON POLYMER MODIFIED CONCRETE east Asia was the raw material that established the rubber and Mortar is a revision of the original chapter in ASTM STP industry. tion of the particles from the mechanical stress of the process. tion so they resist yellowing and chalking. Gerry Walters1 Preface Latex was originally produced from the sap of the rubber tree and. 12.05–0. Descriptions of the formulations and manufacturing processes as well as premature chemical reactions with the portland ce. and increased durability. only those formulated specifically for use in port- turing process (emulsion polymerization) to prevent coagula. These latex-modified mortars Latex is a dispersion of small organic polymer particles in wa. prior to World War II. and then in June of 1989 this activity was organized used incorrectly today when referring to all latexes. re. used in a variety of functional and decorative coating applications such as ceramic tile thinsets and grouts. the product is used by mixing with water and the other by the polymer network. chemical and physical structure of the polymer. water is being consumed and removed from the latex. This film ensures an adequate supply of water to been produced that allow the use to be extended to applications allow hydration of the cement as well as the development of where moisture is present. 1). concrete (11 600). manufacturers’ recom. therefore. adhesion and impermeability properties. the particles will not become closely packed but will form intermittent voids. in which the particles are flocculated. the latex particles eventually coalesce into a film that is inter- woven throughout the hydrated cement particles. lescence of the latex. • composition of the latex. mortar applications. while this is taking place. A compact configuration of the latex particles is a necessary stage in the process of film formation. powders from other polymers have water loss. reducing at less than 80–100 % relative humidity. The success of this process is dependent on several factors: • physical properties of the latex. The mechanism of latex modification of portland cement in. and this occurs only if the particles are dispersed sufficiently to allow them to easily move past each other in the water phase. .606 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Typical Physical Properties of Latexes Latex Type Acronym % Solids Viscosity. • Latex particles coat the cement grains and aggregate form- and stucco. dry ingredients (cement and fine aggregate). [10] proposed the following hypothesis for concrete overlays on bridge decks and is the only latex that the mechanism of latex reinforcement of portland cement: has been evaluated for overlays by the Federal Highway • Latex provides equal workability at significantly lower wa- Administration [7]. Advancements in processing technology allow producers • Microcracks form to relieve shrinkage strain due to drying to now convert some latexes into a dry. coating these particles and the aggregate surfaces with a semi-continuous plastic film. the temperature below which the polymer spheres will not coalesce to form a film. °C pH Styrene-butadiene SB 47 20–50 5–15 9–11 Acrylic copolymers PAE 47 20–100 10–12 9–10 Styrene-acrylic copolymers SA 48 75–5000 10–18 6–9 Polyvinyl acetate PVA 55 1000–2500 15–30 4–5 Vinyl acetate-ethylene VAE 55 500–2500 10–15 5–6 a Minimum film forming temperature. that is. Figure 2 is a schematic Fig. that is. however. particle size and quality of dispersion. The chemistry and reaction processes of 13 mm ( 12⁄ in. and thus a poor quality (spongy) film. ture (MFFT). and concrete. In all cases. However. plus SB. and • environment. floor leveling. time and temperature of application. such as patching.9]. With continual water removal. applicable to areas where there would be no exposure to mois. as well as adhesion between the aggregate and cement hydrates. should be maintained above the MFFT so that film volves two processes: the hydration of the cement and the coa. This coalescence results in partially filled void spaces (Fig. Hz MFFTa. This is typically 24 h for thin sections. that is. are used in ter/cement ratios. concentrating the latex particles and bringing them closer together. formation can occur. Application temperature. ing a continuous polymer matrix throughout the structure. 1—Electron microphotograph of latex-modified of the proper film formation process. With a poor dispersion. This film formation mendations should be followed to assure proper application of is governed by the latexes’ minimum film formation tempera- these products. Styrene-butadiene is the most commonly used latex for Isenburg et al. The MFFT of latexes Mechanism of Latex Modification used in cement will vary with latex composition but typically ranges between 4–10°C (40–50°F). Recently. Proper film formation of the latex is required to retard ture. The other latexes.) thick. powder form. As a • Microcrack propagations are restrained and held together powder. These powders Laboratory studies have been conducted that confirm have typically been made from polyvinyl acetate and were only most of the features of Vanderhoff’s mechanism [10]. shipping cost and simplifying the mixing process [8. and three to seven days for thicker cement hydration occur the same as in conventional mortar sections. both by cement hydration and evaporation. tile grout. it is advisable that the cement be evaluated prior to the bubbles [11]. corresponding unmodified mix at equal workability. where a faster setting time is required. For this latex-modified mixes has been shown to be small. and the particular choice of aggregate. The wa- The level of latex modification is usually measured as the ter level of a latex-modified mix should be lower than a weight ratio of polymer solids to cement. Most The choice of the cement. fine aggregate. or. The requirements of the end Type III cement can be utilized. sion of an antifoam in the latex. setting times [12]. and stone used performance properties plateau between 15–20 % solids. The latex producers can make recom. . The in the appropriate mix is based on the requirements of the 10–20 % level represents the range for optimum. discrete reason. work for compatibility with the particular latex being used. ment (C 150) Type I or II portland cement is suitable with la- The amount of air generated can be controlled by the inclu. water content. cost effective application. lected is dependent on the level of performance required. performance. Calcium suloaluminate and use determine how much air is required and therefore how dicalcium silicate cements can be used to obtain the fastest much antifoam to use. aggregate/cement ratio. there are a few that will entrain excessive air. air For most applications. Some other formulation considerations that are important Materials are the type and amount of antifoam added. ASTM Specification for Expansive Cement mendations for the proper antifoam to be used with their (C 845). The kind of air that is entrained in concrete. Type K cement has been used to reduce shrinkage product. tex-modified mixes. a trial mix should also be made with all of the cement are compatible with the latexes used in mortar and recommended ingredients. And since the cement and aggregate can affect the cracking in overlays [13]. Cement When latex-modified mortar and concrete are mixed. Although most brands of portland air content. 2—Process of latex film formation. Formulating with Latexes The amount of water used in the mix should be kept to the minimum required to obtain the desired workability. WALTERS ON POLYMER-MODIFIED CONCRETE AND MORTAR 607 Fig. ASTM Specification for Portland Ce- is entrained within the mix due to the surfactants in the latex. The level of latex se. an There are two types of polymer modifiers covered in ASTM increase in cement will also increase the total amount of latex Specification for Latex and Powder Modifiers for Hydraulic in the mixture if the latex-cement ratio is constant.15 and a water/cement of 0. Fine ag. based on a specified latex solids-cement ratio. % 72.7 suitability of the fine aggregate to produce quality concrete. since fine contaminants such as dirt or clay can Materials Parts. Most latex-modified aggregate size will depend on the thickness of the application. fine aggregate.15. depending not only on the application being considered. polymer-modified concrete mixtures. Good gradation is important since there is little Silica flour 120 200 excess water available in these mixes for workability. keeping in mind that the wa- No admixtures should be used in conjunction with a latex mix. maximum size should concrete criteria for quality and used a cement factor of 300 be no greater than one-half the thickness of the application. Weight.3 and thus degrade the properties of the cured concrete.40.50 Fine aggregate 785 kg (1725 lb) Latex (48 % solids) 0. TABLE 2—Representative Mixture Propor- tions for Latex-Modified Mortar Suitable for Concrete Patching TABLE 4—Representative Mixture Propor- tions for Latex-Modified Concrete for an Overlay Parts. Polymer modi. less than 0. Water 90 gregate should conform to ASTM Specification for Concrete Formulation Constants Aggregates (C 33). the amount of additional Admixtures water required can be calculated. Table 3 gives a formulation for a metal coating. max (19 gal) water/cement 0. a ratios.37. Portland cement is used with fine aggregate at a range of turer.) From this. posed to moisture and the other for general use. maximum size should be no lar latex product before designing the mix.00 Portland cement 300 kg (658 lb) Fine aggregate 3.5 can require excessive amounts of water to achieve slump. quantity used will depend on the strength required. Defoamer 0. In self-leveling. and cement. without prior knowledge and approval of the latex manufac. where a large amount of fines Acrylic latex (48 % solids) 62.30 Coarse Aggregate Filler/cement 2 The choice of coarse aggregate for polymer-modified concrete should be based on concrete practices and comply with ASTM Specification for Concrete Aggregates (C 33). by weight Material Quantity Portland cement 1. The selection of the a maximum water-cement ratio of 0. also on the latex being used.40 is common. concrete mixture proportions have followed conventional just as in non-modified mortar. The specific high-range water-reducing admixture can be used.31 Coarse aggregate 520 kg (1150 lb) Water. Trial mixes should be done to confirm the Solids content.15. From this. Of course. ture proportion for mortar to be used to repair concrete. although deviations from this can be accommodated. Cement Concrete (C 1438). potable. with higher cement contents generally providing an increase in Polymer Modifiers strength. amount of latex required can be determined.40 NOTE—This mix provides a latex solids/cement of 0. ter in the latex is included in the total water calculation. One type is for use in areas not ex. a water-cement ratio of ride requirements of the application. but also a tendency for more shrinkage. Table 4 gives a typical concrete mixture that is used for overlays.8 (15. depending on the end use.2) Polymer solids/cement 0. The next step would be to select Water an appropriate water-cement ratio. approximately 0. Mixture Proportions Concrete Mortar Mixture proportion procedures for latex-modified concrete Mortar incorporating latex modification consists of portland are usually based on a latex solids/cement ratio of 0.608 TESTS AND PROPERTIES OF CONCRETE Fine Aggregate Most fine aggregates that are suitable for mortar or concrete are TABLE 3—Sprayable Formulation for an suitable for latex-modified mixes. kg/m3 (658 lbs/yd3). It is important to know the solids content of each particu- ness of the application. Portland cement Type I 100 ticularly true for concrete sand. the greater than one-third the thickness. but fier is tested in accordance with ASTM Test Methods for Poly. Table 2 gives a representative mix- mer-Modified Mortar and Concrete (C 1439). (Because most latex for- Water should be clean. from 1:1 to 1:4. Cleanliness is particularly Acrylic Latex Cementitious Metal Primer important. latex. Water 72 L. by weight increase the demand for water in the mix and adversely affect workability.24 Latex (48 % solids) 93 L (24. A range of mixture proportions are possible for mortar. The coarse aggregate should be clean. non-reactive. kg/L (lb/gal) 1. and sized for the thick. and water. This is par. and meet the minimum chlo- mulations function as water reducers.5 gal) Formulation constants: latex solids/cement 0. . that is. that is. where sam- fied mixes due to evaporation of water from the surface of ples experienced over 70 freeze/thaw cycles and 130 cm (50 the mix. Hardened Properties erties: bond strength. strength of a modified mortar to a properly cleaned concrete There are some differences. This evaporation causes the formation of a film. Freshly Mixed Properties since the latex polymer tends to seal the matrix and limit the The water-reducing property of the latexes is evidenced by good amount of water permeating the concrete. The setting time of latex-modified mixes is controlled pri. Air Void System and a reduction in permeability. can be considerably shorter than unmodi. WALTERS ON POLYMER-MODIFIED CONCRETE AND MORTAR 609 Properties crust. Combined. The degree of improvement Air voids in latex-modified concrete do not always conform to of any particular property varies somewhat with the particular the size criteria established for conventional concrete [11. Mortar with a flow of ever. freeze/thaw durability. For mortar and concrete repair work. these result in the following improved prop. 3—Setting time of latex-modified concrete. that is. made to evaluate the characteristics of the components of proves the final product in two ways: (1) by reducing the each particular mix to ensure that the mix fully meets the amount of water required in the freshly mixed concrete and (2) customer’s requirements. and thawing in conventional concrete is not necessary in latex- modified concrete containing 10–20 % polymer solids/cement. typical for mixes made with a water-cement ratio of 0. on the concrete or mortar surface that can tear if over- finished. depending Bond on the requirements of the end use. the bond similar to that of unmodified mixtures (see Fig. due to the influence of surface usually exceeds the tensile strength of the substrate each particular polymer type. or in. The voids are. and tend to decrease in diameter as the total 120 cm and concrete with a slump of 15–20 cm (6–8 in.17]. For some thin-layer appli. In a five-year out-door exposure study.16]. thus creating a some- the proper selection of the amount of latex and antifoam used. latex used. however.) is air content increases.) of rain per year. however. how- workability at a low water-cement ratio. The air content of the mixes can vary widely. Complete and detailed information on these latexes The same void spacing factor required for resistance to freezing can be found in Ref 14. demonstrated both in the laboratory and in the field. flexural strength. Producers usually recommend that trial mixes be The addition of latexes to portland cement mixes generally im. The available working time for concrete [18]. The adhesion property of latex-modified mixes has been cations. All of these can be achieved by concrete surface is chemical in nature. air contents above 10 % are desired to improve trowel. air contents in of SB latex-modified mortar indicated that its bond to the the range of 4–6 % are desired. 3) [15. all spherical. Bond tests of this mortar have demonstrated that ultimate marily by the reaction of portland cement with water and is failure should be in the parent concrete. shear bond values of acrylic modified Fig. what homogeneous combination of the two materials [10]. . by providing dispersed polymer in the matrix of the hardened state. Bond studies of other latexes have also been finishing. A study ability.37. reported. 6) [26]. In adhesion tests of samples cured ing and Thawing (C 666) and ASTM Test Method for Scaling normally in air. carbonation studies have shown that inclusion of since this material has been used extensively for thin-bonded latexes in concrete significantly reduces the carbonation depth overlays on concrete bridge and parking garage decks of the concrete (Fig. crete modified with SB latex have been reported frequently For instance. Resistance of Concrete Surfaces Exposed to Deicing Chemi- fied with SB. when the bonds were tested. Permeability lays [20]. and EVA latexes exceeded the bond cals (C 672) [3.610 TESTS AND PROPERTIES OF CONCRETE Fig. 4—Effect of weathering on adhesion of acrylic-modified mortar. two of which had SB latex mortar over. Wear resistance. 20 000 vehicles.76 MPa (300–400 psi) at 28 days’ property that has been measured frequently on latex-modified cure for direct tensile bond strength are typical. not considered a problem. Additionally. Adhesion per. proved resistance to freezing and thawing as measured by tex-modified samples failed cohesively. with failure concrete. All showed a decrease in strength. shown in Fig. was laboratory study compared the bond strengths of five differ. The concrete sometimes fails C 666 be- strength of the unmodified control by factors ranging from 2 cause it does not have the proper air void system [13]. Values of 2. as 30 years of field experience has ter before testing. 4) [3]. Figure 7 gives the results of a study of SB-modified Freeze-Thaw and Scaling Resistance compared to conventional concretes. documented by the Oregon Department of Transportation ent latexes [19]. major interest for bridge and parking deck applications [3. samples were also submerged in wa. Chloride permeability is another [21–24]. although not shown any freeze-thaw deterioration. This is to 3 [15]. the la. PAE. 5. The low permeability to water results in im- (Fig.07–2. primarily on SB-modified concrete. The PVA failed at the 23–45 years for a lane having an average daily traffic of over bond line at a strength of 1.27]. whereas the controls ASTM Test Method for Resistance of Concrete to Rapid Freez- failed at the bond line. Their study of the wear characteristics of latex-modified and VAE had the highest values and that all but the PVA concrete bridge deck overlays indicated a life expectancy of failed in the parent (substrate) material. indicate that SB [25]. The bond properties of con. Nihon University reported that mortars modi. since this is of occurring in the substrate if surface preparation is proper. Cores were tested for overlay adhesion and resulted The pore-sealing effect of latex in a concrete mix results in a in failure of the base concrete. In this study. formance in the field was reported in a study of 20-year old bridge deck overlays. sist Chloride Ion Penetration (C 1202) [28]. mortar more than doubled those of the unmodified control and wearability. The results.28 MPa (185 psi).7]. Another evidenced by the thousands of bridge decks in service. Figure 8 shows . major reduction of its permeability to both gases and liquids. using the ASTM Test The durability of concrete modified with SB latex has been Method for Electrical Indication of Concrete’s Ability to Re- demonstrated by superior resistance to freezing and thawing.16. as the modified mortars always exceeded the control. 5—Bond strength of latex-modified mortars. WALTERS ON POLYMER-MODIFIED CONCRETE AND MORTAR 611 Fig. . 6—Carbonation resistance of latex-modified concretes. Fig. 7—Permeability of concretes versus cure time. Fig.612 TESTS AND PROPERTIES OF CONCRETE Fig. 8—Chloride ion resistance of latex-modified concrete. . and a fine blast furnace slag to restore skid Strain Capacity resistance to pavement that had been worn smooth by traffic The ability to absorb movement (strain capacity) is an impor. This reinforcement provides the coats for exterior insulation finish systems. and for cross sections greater than 20 mm ( 34⁄ in. and sulating foam is typically attached to the substrate with an acry- • functional coatings for water-resistant basement coatings.). Because of the crete is appropriate. and flexibility. latex-modified mortar has no minimum thickness requirement. . chloride penetration from a ponding study of PAE-modified Skid-Resistant Coatings concrete [3]. late latex-modified cement mortar. WALTERS ON POLYMER-MODIFIED CONCRETE AND MORTAR 613 Fig. skid-resistant covered with a polymer-modified cementitious layer rein- coatings for pavement and ship decks. Figure 9 clearly indicates concrete surface and cured for one day under burlap and that the strain capacity of mortar that is modified with an acry. [29. bridge decks. and still provide weather resistance and Mortar long-term performance. The adhesion of the latex-modified mortars make them especially suitable for Portland cement mixes containing latex are typically used this use. foam with structural integrity as well as protection from mois- nance coatings for metal. the adhesion properties of latex. Exterior insulation finish systems (EIFS) are applications for A wide variety of applications have been developed since the usually acrylic latex-modified cement mortar. are possible as long as the appropriate fine Insulation Finish Systems aggregate is selected and an adequate amount of latex is used. the resistance to permeability per. as Adhesives and Base Coats for Exterior thin as featheredge. In all cases.) or less. adhesives and base forced with a fiberglass scrim. where the following properties are desired: adhesion. Wood. polyethylene film. ture and sunlight. and mainte. coatings can be relatively thin. late copolymer increases as latex content increases [13]. and is used. utilized a slurry of SB latex. low permeability. These include: tion. the choice Cement-based coatings have been formulated with an acrylic of whether to use mortar or concrete is based on the thickness latex for application over a variety of substrates in order to im- of the application—for thin layers. Because of its adhesion characteristics. mortar prove appearance as well as performance. an insulating material such as expanded polystyrene foam • concrete repair for parking garage floors. is attached to the outside surfaces of walls of buildings.30]. Decorative Coatings As with conventional portland cement systems. taking advantage of formance of latex-modified concrete is evident. Mortar coatings. durability. steel are some surfaces that are typically coated. approximately 3 mm ( 18⁄ in. The in- swimming pools. The slurry was broomed and screeded onto the blasted tant feature of latex-modified mixes. adhesion of the latex. In this applica- material was introduced in the 1950s. portland cement. A unique concrete pavement application. and industrial floors. weatherability. Thin coatings of acrylic and SB-modified cement mortars are applied to decks of ships in order to provide a skid-resistant Applications and protective surface to the steel substrate. 20 mm ( 34⁄ in. The insulating foam is then decorative spray coatings for exterior walls. concrete. 9—Effect of latex content on strain capacity of mortar.) con. Because latex-modified mortars and concretes bond so Latex-modified mortar in thin coatings adheres to a metal well. For exterior applications. Im. based on Federal concrete were placed by a pump. wind. • Adhesion to ferrous metal surfaces. • Capability of curing in damp enclosed areas. fied concrete. PAE. land cement. but only to a limited degree due to the rapid drying. a major concern with any equipment that is used with surface. Two-component systems are commonly used cur. that is. making the finishing operation difficult.6 for thinsets and grouts. This new modified con- Portland cement coatings have been formulated with acrylic crete was 75 mm (3 in. Most equipment and tools used for conventional mortar and • Solvent-free composition. demonstrating good adhesion and flexibility. garages in the United States have been protected with this type Since latex-modified mortars and concretes require air of overlay during this time. a 58-year-old concrete stadium in ommended.) against the vertical surface. Applied to mm (6 in. flexibility. Thousands of bridges and hundreds of parking for rapid evaporation of water. PVA latex should not be used. The existing concrete under identical conditions at the field installation and tested tread-and-risers were used as the form for pouring new rein. respec. and VAE. has been used to test the water-resist. to Cementitious metal primers modified with latex can be ap. roll. im. The construc- titious primers that provide low-cost protection of metal tion techniques were similar to those of an overlay. tions. create an environment years [20]. time is allowed for latex coalescence. and replaced with concrete containing SB latex.614 TESTS AND PROPERTIES OF CONCRETE Water-Resistant Basement Coatings forced concrete containing SB latex. buggies.) wide strip. these systems is cleaning. therefore. 30 % latex solids has demon. and airless spray. that is. The water-based cementitious mortars are low odor old surface was blast cleaned. For this application.75 mm to minimize the time that the surface of the freshly mixed ma- (20–30 mils). Typically. The restora. Whereas no drying would occur while the modified gredient (filler/cement) in one container and mixing it with the material is in the pump hose. 0. tems. A laboratory procedure. equipment be cleaned thoroughly with water immediately af- creased. 25 mm (1 in. if a buggy in the maintenance and marine industries. that is. Care should be exercised when ambient conditions. coloration from the effect of sunlight on the butadiene. these coatings provide resistance to tures of this application was that the 3000 m3 (4000 yd3) of water penetration. strated corrosion resistance as evaluated in a salt spray cabinet (Method of Salt Spray (Fog) Testing (ASTM 117–90)) as well as Limitations by several years’ exposure at an Atlantic Sea coast test facility. polymer-modified concrete has ant properties of these coatings [3]. and 150 latex to be used on concrete block basement walls. ter use and before drying occurs. concrete. Because of the adhesion properties of the modi- • Flash and early rust resistance. occurred in 1981. not suitable for underwater applications unless sufficient cure tural restoration and concrete pavement repair. this thin section is well bonded and serves as an • Protection of rusty as well as clean metal surfaces. these latex-modified systems are more sensitive lack of trained contractors.4 and A118. can be easily applied without sag as these primers terial is exposed to the atmosphere so that crusting does not oc- are high in solids. rela- The SB latex has been used for this application for over 20 tive humidity. A 50-cm (20- Latex-Modified Cement Maintenance Paint in. for instance. than conventional mortars and concrete with low water contents because of the film-forming characteristics of the latex. such as stucco that uses white port- grouts that meet the ANSI Specification for Latex Portland Ce. ered to prevent drying if the transport time were long. Thick films. A polymer-modified were used rather than a pump to transport latex-modified cementitious coating can be prepared by blending the dry in. modifier have been bridge and parking garage deck overlays. drying to achieve their optimum properties. . cally can be used for mixing the two components together. name a few.) thick on the horizontal tread. As with conventional portland cement. Those tively. This cure time can be monitored by samples cured downtown Chicago. concrete have been used successfully with latex-modified sys- • Ambient cure. expedient repair. latexes/polymers not containing butadiene. been used to repair deterioration at the centerline of 56 km (35 miles) of interstate highways in Pennsylvania [31]. and screeds. Specification TT-P-1411. One of the unique fea- the outside of the wall. • Weatherability. trowels.) deep. During conditions of head concrete repair. On concrete pavement. the substrates. the buggy might have to be cov- liquid (latex/defoamer/water) in another. that provement in properties is observed as the polymer level is in. periodically until the design properties are achieved. the SB is not the preferred choice due to a dis- ment Mortar A118. that is.50–0. was removed by a scarifier Latexes have been used to formulate two-component cemen. Latexes and powder polymers provide high adhesion. are recommended. This includes pumps. SA. proved water resistance. polyethylene. A power mixer typi. This would be of more concern. these materials Shotcrete should be used with caution during extreme weather condi- Latex-modified shotcrete has been used for vertical and over. between 4–30°C (40–85°F). the paste was scrubbed in to as- and non-flammable and afford a number of benefits: sure bond. it is important plied by brush. or where exposure to moisture is pos- Ceramic Tile Thinsets and Grouts sible. Whatever equipment is being used. Equipment Considerations • Flexibility. and it was cured for one day under wet burlap and • Corrosion and water resistance. For outdoor applications Latex-modifiers are used to formulate thin-set adhesives and where color is important. and temperature. Concrete Rapid drying causes a skin (or crust) to form on the surface if The majority of concrete applications incorporating a latex it is allowed to dry. 28 days is rection of Soldier Field [21]. and impact strength. It is important. these systems are Other applications for this modified concrete are struc. Y. West Conshohocken. Latex Modified [8] Walters. Inc. Pore Characteristics and Chlo- ride Ion Penetration in Conventional Concrete and Concrete Containing Polymers. “Performance History of Latex-Modified trict. Eds. 1971. L. D.. DC. J. 1980. Part VI.” Cement. Dec.. DC. 1992. and Aggregates.” Wiss. and Spring. 1990. American Concrete Institute. D. lottesville. D. A. 1985. E.. Spring. lottesville. 3–14. “Latex in the Construction Industry.. Ramachandran. F. “Microstructure and Strength of the Bond Between Concrete [28] Whiting. Measuring the Bond Strength of Portland Cement Based Repair [3] Lavelle. lays has been published [32].” SP-99.. “Styrene-Butadiene Latex Modi. and Latex Modified Concrete Repair Materials for Concrete Vol. C.. Jan. Kuhlmann and D.. tions. V. Concrete Overlays. 1. 1981. Concrete 80/16. can Concrete Institute. [21] Pfeifer. 1.4). L. Uniaxial Tension. dards and Technology. G. 1987. Fall Convention. Rapp. 6. 123–144. American Concrete. “Very-Early Strength Latex-Modified Concrete Concrete Pavements and Bridge Decks Using a Latex-Modified Overlay. ASTM Specification for Latex and Powder Polymer Modi. W.. “Restoring Skid Resistance to [12] Sprinkel.” Transactions. J. FHWA/RD/ JHRP- Air Content of Latex Modified Concrete. ASTM International. L. A. Ameri- Highway Commission.. 9. K. [13] Sprinkel. ACI Manual of Overlays (ACI 548. 1988. J.” Polymer-Modified Hydraulic Cement [27] Clear.. ton DC. 48–49. VA. Hardened Properties of Concrete Mixtures Containing Three [35] Polymer Concrete–Structural Applications: State-of-the-Art Re- Formulations Used in Bridge Deck Overlays. July 1984. MD. PA. 25 Jan. MI. Washington. DC.” Transportation Research Board. 1984. Janney. “Vinyl Acetate-Ethylene Copolymer Redis.–Feb. Elstner and Assoc. D. “Curing and Chloride Perme- and Styrene-Butadiene Latex-Modified Mortar. Strength of Latex Modified Concrete and Mortar. Sutton. April Type K Cement.” Highway Re. M. A. “Marquam Bridge Repair. Farm. 1980. L. ASTM STP 1176. fiers for Hydraulic Cement Concrete and Mortar (C 1438) was [19] Walters. SP-69. S. 1999. L. E. L. Vol. Kuhlmann and D. [25] Howard. T. Feb. and Foor. Cement Modifiers. pp. and Hockett.” Applications of Polymer Concrete. [34] Guide for Polymer Concrete Overlays (ACI 548. Sept.” ACI Materials Journal. G. pp.. and Aggregates.” National Institute of Stan- dustry... 1987. 1990. M. pp. A. Char- RD-78–35.” presented at search Board. ACI Manual of Concrete Practice. [24] Sprinkel. I. 1981. Manual of Concrete Practice. and Miyake. “Preliminary Minimum Strength Levels for Portland Cement [5] Walters. 12. WALTERS ON POLYMER-MODIFIED CONCRETE AND MORTAR 615 Specifications. [22] Knab. L. Manual of [16] Smutzer. 1978. J.. DC. “Utilization of Latex-Modified Concrete for West Conshohocken. “Latex-Modified Concrete Overlay Containing [31] “LMC Specified for Centerline Repairs. Jan. Walters. N. “A Test Method for Measuring the Bond has also published guides and reports [33–35]. Farmington Hills.” Report No. B.. O.” Virginia Transportation Council. [32] Standard Specification for Latex-Modified Concrete (LMC) [14] Polymer-Modified Concrete (ACI 548. [29] Scholer.” ACI Materials to Concrete. Materials Journal. B. Concrete..” fiers for Bridge Deck Overlay Concrete.. Concrete Practice. Park Ridge.3R). Farmington Hills. C. “Latex Modified Portland Ce. als Journal. W. PA.. B.” Transportation Research Board. 87. Part VI. Federal Highway Adminis- [10] Isenburg. M. ability. and Reports [17] Marusin. tration. B. R. MI. FHWA-RD-76–70. and Vanderhoff. ton. 2. and Chollar. K. Farmington Hills.” Chemistry & In. C. 5 Aug. Gaithersburg. Polymer-Modified Concrete. 337–429. I.. C. FHWA.” Roads & Bridges. Slabs. Vol.1R). G. pp.” Report No. 1976. 1978.. J. Vol.. Concrete Overlay and Joint Replacement. “A Comparison of Latex-Modified Portland Ce- published in 1999. “Accelerated Carbonation of 1990. Lane. Virginia Highway & Transportation Research Council. 4. and [6] Dennis. DC. 1993. [30] Sprinkel. [23] Knab. Concrete Admixtures Handbook. ASTM STP 1176. “Chloride Permeability versus tance of Concrete Pavement. and Milliron. “Overview of Latex Modified Concrete Overlays. A. “Polymer-Modified Mortars and Concretes. MI. American Concrete Institute. Noyes Publication.. “What Are Latexes?” Concrete International. D.” Transportation Research Board. 1984. M. Philadelphia. L. Concrete Practice. C.. J. Volume 3: Performance After 830 Daily Salting Applica- Eds. M. “Time-to-Corrosion of Reinforcing Steel in Concrete Mixtures. American Concrete Institute. G. [4] Thompson. D.. J. Indianapolis. Washington. 1989.. L. pp. 75–90. 597–605. MI. Part VI. and Lavelle.. The American Concrete Institute [18] Kuhlmann. As stated ear. D. Ed. search Record 370. Part VI.. S. ington Hills. ASTM International. Restoration of Seats in Soldier Field for Chicago Park Dis- [2] Kuhlmann.” Transportation Re- persible Powder Hydraulic Cement Admixtures. 11–16. pp. Pavement Overlays Using Direct Shear. [33] Guide for Use of Polymers In Concrete (ACI 548. 1991.. R. M. Farmington Hills. 4. Walters.” Report No. K. The S/B Latex Story.” ACI Materi- lier. TRR 1669. [20] Sprinkel. M. Federal Highway Administration. G.. [26] Ohama. July–Aug. S. 1993... April 2005. 1989. C. ment Mortars. pp. Pendell Publishing Co. M. A.” of Concrete Practice. R. ACI Manual [15] Ohama. American Concrete Institute. Washington.5R). IN.” Concrete International. 135–150. April 1987. NJ. “Acrylic Latex-Modified Portland Cement. 1988. American Concrete Institute. MI. 387–394. Portland Cement Slag Slurry. Washington. 1990. MI. “Twenty-Year Performance of Latex-Modified References Concrete Overlays... No. Chicago. J. Slant Shear Bond Test Methods.. “Microstructure. C.. Vol. M. “Solid Grade Acrylic crete Institute. Washing. De- An ACI specification for using SB latex-modified concrete over- troit. No. . Washing- [1] Polymer-Modified Hydraulic Cement Mixtures... M. “Thin Applied Surfacing for Improving Skid Resis- [11] Kuhlmann. pp. Japan Con- [9] Tsai. Char. A. MI. Detroit. Y.” Indiana State port (ACI 548. 1989. DC. Burch.. No. VA.” Cement. Federal Highway Administration. Washington. pp. ment Concrete—A Laboratory Investigation of Plastic and MI. [7] Clear. J.. E. Part VI. 11. Vol. Guides. Midland. 83..6R). “Evaluation of Test Methods for American Concrete Institute. and Kuhlmann. No. and Sprinkel. No.. July-Aug. Mortar by Pneumatic Pressure (ACI 805–51). Blastcrete. and ACI agreed to cover concrete design and con. of standards and the rate at which they were generated needed The current edition will review and update topics as addressed to adequately cover current technology and the industry’s need by the previous author. etc. summary of the various organizations currently developing Currently. Blocrete. U. tations. term “pneumatically placed mortar” to describe the dry-mix ment and application of appropriate standards. which were projected pneumatically at high velocity onto a surface. Jetcrete. Both the number this chapter. designated as Gunite. generic term that encompassed the many proprietary dry-mix Nevertheless. has in turn led to greater interest and acceptance of The term “shotcrete” was coined by the American Railway En- shotcrete and to a general recognition of its capabilities. Spraycrete. the ACI documents have been refer.S. Since 1988. subcommittees of ASTM Committee C09 have was originally published in STP 169C [1]. Professor M. structural system. rial. in Europe and elsewhere.46.S. it has for Shotcrete. and unique characteristics as a construction process. Pye1 Preface Moreover. However. the primary ASTM standards used for shotcrete construction were based on practices for concrete. AUTHORED BY I. introduce new technology and current for new standards. ACI documents. process in its Recommended Practice for the Application of In the United States. In addition. Department of Energy (DOE) Yucca Mountain Project. or component are more likely to be based on empirical and heuristic methods than on codified de. ASTM agreed to address material specifications and Canada. and include up-to-date references and a concentrate its efforts through a subcommittee on shotcrete.53 Shotcrete* John H. VA 22201. ACI has been publishing articles and reports “sprayed concrete” is more commonly used. In the preparation of published ten standards covering shotcrete. 616 .S. bibliography. ASTM Committee C09 decided to industry practice. crete. Shotcrete currently is methods. Institute (ACI) and ASTM. In a memorandum of understanding This standardized the use of the term in the United States.46 is adapting existing become universally accepted only in the last 30 years or so. is a need for continuous improvement and assurance of the Guncrete. albeit generally Shotcrete Defined subjective. the contents of the 4th edition were drawn upon. gineering Association (AREA) around 1930 to provide a single. Introduction sign or rigorous analytical or numerical design approaches. In contrast. As early as 1920. it has become apparent in recent years that there processes. the term struction practice. THIS CHAPTER. Nucrete. Confirmation of the performance of shotcrete. and all countries basing their shotcrete technology on test methods. The scope and mission of subcommittee C09. stated in January 2000: “To develop and maintain standards ment in concrete construction for more than 90 years. the design and selection of shotcrete as a mate. facilitated by the develop.” Subcommittee C09.” It is replaced by ASTM Specification for Portland Cement (C 150). Nuclear Waste Technical Review Board (NWTRB) concerning the potential application of shotcrete at the U. C09. has been shared by the American Concrete was used in the text of this first ACI recommended practice [5]. limi. Arlington. Nuclear Waste Technical Review Board. [4]. in the taining standards for concrete and its associated technologies. The * The views expressed by the author do not imply a position on the part of the U. until 1988. Its shotcrete standards or developing new ASTM standards. the term “shotcrete” including shotcrete. LEON GLASSGOLD. on shotcrete since 1911 and standards on shotcrete practice The shotcrete process is a unique construction method us- since 1951. ing compressed air to pneumatically project mortar or con- encing ASTM standards for material specifications and test crete against a surface at high velocity. O. in 1936.46 was Although shotcrete has been a viable and important ele. A recent review of U. shotcrete standards includes a tional concrete construction. ACI initially used the quality of shotcrete installations. In 1990. Fuller of Lehigh Uni. interest of clarification and consistency. 1 Senior Professional Staff. responsibility for creating and main. defined in ASTM Terminology Relating to Concrete and versity performed experimental tests on gunite (shotcrete) slabs Concrete Aggregates (C 125) as “a mortar or concrete that is using ASTM specifications C 9–17 for cement [2]. similarly defined in Guide to Shotcrete (ACI 506–95) [6]. standards and recommendations for the shotcrete industry [3].S. as versatility and its applicability to a large variety of singular uses described later in this chapter in the section on ASTM and shot- provide economical alternatives and complements to conven. Specification for Packaged. and uniformity. In 1999. recognizing and taking 1116). ACI 506 tributes can be found in Guide to Shotcrete [6] and other ACI also produced the 1966 Standard Recommended Practice for 506 committee documents.3R-82) [22]. Since that time. Shotcreting. tensile. Committee A1 on Ferrous Metals and cannot be revised or . Additional data followed from Gillmore Needles (C 1398). Fiber-Reinforced Concrete Subcommittee C09. welded wire fabric. replaced the est article on Gunite. under the auspices of concrete This group of standards comes under the jurisdiction of ASTM technology. Shortly thereafter. on the basis 2003. the Department of the Navy. In July of 1989. n-shotcrete in was reactivated to revise and update the aforementioned rec- which most of the mixing water is added at the nozzle”. ACI 506 “wet-shotcrete. can pro- crete (C 1604/C 1604M). ACI. ASTM Test Method for Time of Setting of into account the effects of shotcrete placement when sampling Shotcrete Mixtures by Penetration Resistance (C 1117) was and testing shotcrete are important. However. ing the state of the art of shotcrete in the early 1960s. and many others before 1385).and dry-mix shotcrete has improved significantly inforced Concrete (Using Centrally Loaded Round Panel) (C both the strength and the durability of shotcrete [10]. published what may have been the earli- to Shotcrete (ACI 506R-85) [6]. Still earlier. published in 1985. and prestressed wire [6]. Historically. PYE ON SHOTCRETE 617 term encompasses two distinct processes: dry-mixture and wet. Chemical Admixtures Subcommittee C 09. most from its inception in 1911. O. the range and variety of applications. bond. a special publication. ACI 506 references ASTM standards for re- As previously indicated. since 1988 [24]. published two shotcrete standards in 1989. In in the literature [10]. duce a very durable material. are mixed prior to introduction into the delivery to producing a number of reports and standards including hose. SP-14 [19]. In 1957. the auspices of ACI committee C 660 as outlined in the ACI the wet-mix process did not become a fully accepted technol- publication CP-60. In addition to ACI and Shotcrete concrete standards. In 1942. Currently nozzleman certification is under what would later be called the wet-mix process [8]. the U. permeability. which contains many papers describ- crete. Subcommittee studies at the University of Toronto.2–77) [23].42 pub- of evaluation of test results [10–18].S. and the 1984 State of the Art Re- In 1911. and Test Method for Time of Setting of Portland-Cement Pastes flexural strength in addition to bond. has sponsored many ACI symposia and seminars in addition cluding water. plastic and hardened physical properties of the in-place shot.23 crete applications. This standard was discontinued in pressive strength. The addition of silica fume lished ASTM Test Method for Flexural Toughness of Fiber Re- in both wet. in. Pre-blended. Combined Mate- Early concerns about the durability of shotcrete. a dual-tank pneumatic device. Fuller. ASTM Practice for Preparing and Testing Specimens from Shotcrete Test Panels (C 1140) and ASTM Specification for Admixtures for Shotcrete Shotcrete Properties (C 1141). ACI Committee 506 (ACI 506) processes as follows: “dry-mixture shotcrete. Bureau of Stan- C0. the 1982 Guide to the Certification of Shotcrete Early References Nozzlemen (506. Most recently. In 1984. Test Method for Obtaining and Testing Drilled Cores of Shot- composed of sound materials and properly applied.46 published ASTM Practice for Sampling for Shotcrete (C dards. ogy until the early 1950s. Shotcreting (ACI 506–66) [20]. Subcommittee C0.46 published ASTM Speci- 1939 [9]. and ommended practice for shotcreting. Guide ment Users (NACU). Subcommittee C09. In June 1989.42 published ASTM the shotcrete process and can influence its performance char- Specification of Fiber-Reinforced Concrete and Shotcrete (C acteristics and properties. ACI has been reporting on shotcrete al. although the final hard- Fiber-Reinforced Concrete (Using Beam with Third–Point ened product has in many respects performance characteris- Loading) (C1018). various types of concrete pumps were adapted to the wet-mix shot. method of Method for Flexural Toughness and First-Crack Strength of placement.42 published ASTM Test Shotcrete differs from concrete in manufacture. the one well-known and popular document. were subsequently dispelled. the emphasis published and was subsequently withdrawn in December of on shotcrete performance was placed primarily on such phys- 2002. inforcing bars. Early tests for establishing the com- Gillmore Needles (C 1102).46 published ASTM evidence consistently demonstrates that good-quality shotcrete. Current 1550). Methods and techniques of crete overlays or shotcrete linings. A subsequent series of tests were per- Laboratory Determination of the Time of Setting of Hydraulic- formed by the University of California and attributed the prop- Cement Mortars Containing Additives for Shotcrete by Use of erties to pneumatic placement. when the True Gun. the Fiber- shotcrete manufacture and placement are important factors in Reinforced Concrete Subcommittee C09. The results typically showed that shotcrete compared fication for Materials for Shotcrete (C 1436) and in 2000 ASTM favorably with concrete. An ar- out-of-date Standard Recommended Practice for Shotcreting ticle published in Cement World magazine in 1916 described (ACI 506–66) [19]. and associated at. Dry. When shotcrete is used to provide structural support it is often combined with other reinforcing elements. Therefore. In February 1998. ASTM published ASTM ical properties and characteristics as compressive. Containing Accelerating Admixtures for Shotcrete by Use of density.” A more comprehensive description of each process. ACI formed Committee 805 on Pneumati. and physical properties. ASTM C 125 defines these different practice (ACI 805–51). was introduced. then known as the National Association of Ce- port on Fiber Reinforced Shotcrete (ACI 506. Proportioning and Application of Shotcrete (ACI 506.2–77) [21]. Subcommittee C09. the 1977 Specification for Ma- terials. and density were carried out by January of 2002 and was replaced by Test Method for The Professor M. cally Placed Mortar which was retired after completion of the mixture shotcrete. ASTM and Shotcrete crete process and resulted in the acceptance of the wet-mix ASTM Committee C09 has produced ten shotcrete standards process as a viable and economical method for many shot. shrinkage. n-shotcrete in which most of the ingredients. which addressed the toughness of thin con- tics similar to those of concrete. in November 1988. reported rials for Use in Wet or Dry Shotcrete Application (C 1480). a proprietary dry-mix process [7]. 09 • The fiber losses typically incurred during the application on Monolithic Refractories describes refractory shotcrete as of the FRS are 20 % for wet-mixture and up to 40 % for “cold nozzle-mix gunning” and has produced ASTM Practice dry-mixture shotcrete. These losses need to be considered for Preparing Refractory Concrete Specimens by Cold Gun.42 has developed the committee report on fiber-reinforced shotcrete (ACI 506. • Where crack widths are limited to 1–5 mm.S. and synthetic materials. additives. An article on the application of prepackaged • Early strength and stiffness can be important in ground refractory castables indicates that these two standards are in. and compensated for. To counter its imposed on the fiber type and fiber content used these service conditions. [36–42]. In addition. vary with temperature [25]. R. the report [28] further indicated Loaded Round Panel) (C 1550). displacement. strength. • Laboratory-based tests (e. The need for additional stan- that design information related to fiber-reinforced shotcrete dards for fiber-reinforced shotcrete has been recognized. thermal a need to establish the performance of new fibers. and erosion. FRS performance criteria should be based in 1971 in experimental work performed at Battelle Memorial on load. are satisfied by thickness. type. a device that provided the mecha- The design of fiber-reinforced shotcrete is alternatively nism for projecting cement mortar and plaster onto a surface based on common usage. ing. trial and error. He even- “design” refers to the process of determining the thickness tually sold his patent rights to the Cement Gun Company. abrasion.1R. ma- crete may be exposed to service temperatures of up to 3400°F terials. rigorous calculation (numerical models). modulus of rupture. Carl E.g.08 on Basic Re.e. chemical attack. refractory shotcrete uses a wide range because of the application process of shotcrete. steel and syn- fractories has also produced ASTM Practice for Preparing thetic. case of tunnel. Research and application of fiber-reinforced shot. empirical observa. in the number. i. • FRS systems also are largely dependent on the stiffness of Standards for refractory shotcrete are produced by the matrix (cementitious materials) and fiber content. for both static and dynamic load- C09.. support applications. the 24-h strength of refractory shotcrete process or dry-process shotcrete. and slope The shotcrete process had its origins around 1911 with the stabilization [31–35].and mine. The report further states that fiber-reinforced shot. Subcommittee C08. The process Although standards for shotcrete are developed by ASTM and application of fiber-reinforced shotcrete are described in Subcommittee C09. Subcommittee C09. standards for fiber-reinforced concrete and shotcrete. ther. there is strength. The design of the refractory shotcrete • Shotcrete process imposes constraints on the fiber- lining must account for such factors as thermal cycling. and shotcrete process have a considerable effect on (1870°C).618 TESTS AND PROPERTIES OF CONCRETE rewritten for shotcrete use by a subcommittee of Committee fiber-reinforced shotcrete. Refractory shotcrete differs from conventional shotcrete in Papworth [32] makes an important observation on the several ways. such as compressive the performance of fiber-reinforced shotcrete. ing ASTM Specification for Fiber-reinforced Concrete and crete and conventional or plain shotcrete are essentially the Shotcrete (C 1116) and ASTM Test Method for Flexural same. types of expansion. Toughness of Fiber Reinforced Concrete (Using Centrally sociated properties.and mine-opening support. Because of fiber. the design of fiber- fractory shotcrete. ning (C 903). ASTM Committee C8 on Refractories. In the the effects of thermal gradients that result from firing the re. such as polypropylene fibers [29. These aspects may not be considered specifically in terms of a systematic design but may be arrived at as a result of trial and error or empirical observational methods and Refractory Shotcrete supplemental testing [35]. invention of the cement gun. History of Shotcrete Aside from conventional shotcrete applications. immediately set about improving and promoting the viability sure that flexural. fiber-reinforced shotcrete provides significant Test Specimens from Basic Refractory Gunning Products by 40–80 mm deformations. adequate and several new and coherent standards are needed • There is potentially significant uncertainty in determining for refractory shotcrete using a common set of terminology the ductility requirements due to tunnel displacements. and application methods. and finishing procedures. batching.30]. The technology has grown to include steel. these properties may vary throughout the reinforced shotcrete linings can be summarized as follows: refractory lining section. Thus.46. Around 1908. standard beams) may not always provide realistic representative data on loading de- Fiber-Reinforced Shotcrete formation. and energy considerations. Typically. • Performance of FRS is strongly influenced by specific tory shotcrete dictates the need for both special application fiber type(s) and fiber performance. Pressing (C 973). and torsional demands on the of Gunite as a construction process through considerable . wet- of materials.. shearing. and density. and compara. The aim in design is to en. Rapid setting of most refrac. Subcommittee C08. patents in February and May 1911. reinforced shotcrete (FRS) system. both subcommittees are expected to participate in their crete over the last two decades have led to a significant increase development. reinforcement. These standards should be reviewed carefully for suit. includ- 98) [28]. and material ability before being specified by a project. and materials used as fiber reinforcement. The physical properties. The primary difference is that refractory shot. current fiber- reinforced shotcrete applications include tunnel. the term issuance of U. and was limited. natural materials. Fiber-reinforced shotcrete using steel fibers was first reported • As a minimum. which and the amount of reinforcement. Lankhard [27]. ments on sprayed cement mortar which culminated in the tive experimental simulation [33–35]. the principal difference being the material used and as. is similar to the 28-day strength. and nomenclature [26]. Early Developments opening support. In 1998. Akeley [36] began his experi- tion. basis of laboratory and large-scale testing that fiber type. There are practical lim- mal shock. Typically. remediation of concrete structures. Institute under the direction of D. thermal conductivity. light. stone. the nozzle is used primarily for introducing compressed air at the nozzle to increase the ve. alternatively. and strengthening and re. or #2 is provided in the Guide to Shotcrete (ACI 506–95) [6]. the Supplementary Cementitious Materials range and variety of applications. PYE ON SHOTCRETE 619 experimentation and research. Producing high-quality shotcrete that will consistently Concrete (C 989). Refractory Concrete. or silica fume may be used in shotcrete. and steel repair. or special [6]. boat building. wood structures. but the predominant binders are calcium aluminate cements with varying purities and alumina con- Shotcrete Equipment tents. masonry. Dry-mixture shotcrete is usually proportioned Guide to Shotcrete (ACI 506–95) [6]. and. lime is typically not used. block. conform to ASTM Specification for Materials for Shotcrete (C Mixed Concrete (C 94/C 94M). the constitutive materials. Shotcrete also may be made from normal. or #2 identified in Table 1 in ASTM Specification for Materials mixture shotcrete process to introduce water and liquid ad. dams. Typical shotcrete applications that utilize Concrete Made by Volumetric Batching and Continuous Mixing these supplemental cementitious materials are described in the (C 685/C 685M). the basic materials used in the applications over wood frames. Shotcrete Applications Materials Early engineering literature between 1911 and 1918 describes a wide range of shotcrete applications that includes exterior When Gunite appeared in 1911. free from substances . while fly-ash and silica reservoirs. blended prepack. There are no ASTM specifications for calcium aluminate The term shotcrete encompasses two distinct processes. 1436). associated attributes. refractory. SP-57 [41]. or. material-handling heavyweight aggregates. Blended hydraulic cements conforming to ASTM Specifi- concrete. both wet. Also. Heavyweight aggregates Fiber-Reinforced Concrete and Shotcrete (C 1116) may be used. port- Shotcrete Systems land cement can be used. pile. cation for Blended Hydraulic Cements (C 595) or ASTM Per- inforcing of all types of structures. vented by concerns for personnel safety. and sea walls. ture shotcrete process. In contrast. and mixed in the field by using portable proportioning and mixing equipment. linings and coatings. Lightweight aggregates aged. canals.and dry-mixture shot. with the occasional addition of lime. Water used for mixing and curing shotcrete in both wet and set accelerators to the shotcrete. relining of Specifically. fume are in common use. Aggregates crete materials may be delivered to the job site by truck from a Aggregates used to produce shotcrete are typically required to ready-mix plant conforming to ASTM Specification for Ready. The primary binder used in shotcrete has been portland cement ventional shotcrete is applied in a range of thicknesses for that conforms to ASTM Specification for Portland Cement (C structural and nonstructural applications. terials for Shotcrete (C 1436). 150). refractory linings in the manufacture used in shotcrete are prescribed in ASTM Specification for Ma- of steel. ACI clas. and aqueducts. Con. rust-preventative linings for large terials currently used in shotcrete are in some respects the same steel water pipelines. rock surfacing and stabilization. and semiautomatic nozzle booms that are operated in condi- duction of new types of delivery equipment and improved tions where manual shotcrete application is difficult or is pre- methods of shotcrete application. The following is a discussion of a replacement for hand-placed mortars and cement plaster. the plastic and hardened physical properties of in-place shotcrete. Fly Shotcrete [6] and other ACI 506 documents. Binders sifies shotcrete as conventional. The post-World War II period and equipment in wide use today include remote-controlled saw a significant upsurge in the use of shotcrete and the intro. tion for Concrete Aggregates (C 33). and but they currently include some additions and refinements. and pri. Slag should conform to ASTM Specifi- readily available in both commercial and technical literature cation for Ground Granulated Blast-Furnace Slag for Use in [6]. Nor- constraints or lack of available bulk materials. should conform to ASTM Specification for Aggregates for Radiation-Shielding Concrete (C 637). specifi- cement. Nozzle manipulation systems dry processes should be potable—that is. Silica fume should conform to ASTM Speci- achieve specified design or performance requirements requires fication for Silica Fume for Use in Hydraulic Cement Concrete that batching and mixing conform to ASTM Specification for and Mortar (C 1240). because of logistical. Supplementary cementitious materials such as fly ashes. Combined Materials for Use in Wet or should conform to ASTM Specification for Lightweight Aggre- Dry Shotcrete Application (C 1480) and ASTM Specification for gates for Structural Concrete (C 330). or In some cases. repair of concrete sand. the component materials typically used to produce shotcrete. Combined grading Shotcrete Nozzles limits for shotcrete aggregates should comply with grading #1 The water ring in the body of the nozzle is used in the dry. in general. mal-weight aggregates should conform to the ASTM Specifica- aged materials conforming to ASTM Specification for Pack. depending on the application. fireproofing of steel structural process were portland cement and well-graded fine concrete members. for Shotcrete (C 1436). coating of brick. The description ashes and natural pozzolans should conform to ASTM Specifi- and operating characteristics of equipment for dry-mixture and cation for Fly Ash and Raw and Calcined Natural Pozzolans for wet-mixture shotcrete equipment are generally understood and Use in Cement (C 618). A comprehensive found in ACI 547R. Pre-Blended. tunnel linings and relinings. The majority of the Gunite applications developed in the first ten years of its existence are still in use today [36–40]. information on a variety of refractory cements can be cally dry-mixture and wet-mixture shotcrete. Guidance in the selection of grading #1 mixtures to the mix when used. formance Specification for Hydraulic Cements (C 1157) may be used. partition walls. portland cement may be blended with supplemental cementitious materials. coke ovens and furnaces. For some refractory applications. description of each process. The constitutive materials currently abrasive-resistant linings. The constituent ma- bridges. Water locity of the ejected material and for introducing liquid quick. natu- mary and ancillary equipment can be found in the Guide to ral pozzolans. coal bunkers. in the wet-mix. slag. Dry. or dry- yet been developed. project size. curing com- should meet the requirements of ASTM C 1141. be evaluated using samples of accelerated shotcrete under the Within the industry. If it does. such as latexes and acrylics. wet. with some limits. Because some of Prescriptive Versus Performance Specifications the quickset accelerators cause significant reductions in ulti. ASTM efforts needed for administration and inspection of work per- Specification for Admixtures for Shotcrete (C 1141) references formed under prescriptive requirements typically are much the ASTM Specification for Latex and Powder Polymer Modi. Fabric for Concrete Reinforcement (A 497) and may be un. testing of shotcrete. When fibers of any type location and environmental considerations. Alloy Steel Deformed Bars for Concrete Reinforcement (A however. performance-related requirements. ASTM C 1398 does not Proportioning Shotcrete Mixtures specifically define the time of set for a portland cement mortar containing and accelerating admixture. An ASTM standard for anchors used in shotcrete has not will usually determine which of the two processes. and based. can impose . Many have specialized mix shotcrete. or ASTM Specification for Zinc-Coated (Galvanized) Bars for Concrete Reinforcement (A 767). however. those that regularly perform the work. greater than those for work that is based on performance fiers for Hydraulic Cement Concrete and Mortars (C 1438). and technically correct in every respect. Performance specifications require only that a stated result ceptible to plastic-shrinkage-induced cracking. leaving the means and methods to the contractor. stringent that well-qualified contractors will be prevented from eral admixtures in wet-mixture and dry-mixture shotcrete can using their innovations and special experience. Shotcrete specifications should not be so limited or 260). including the choice of shotcrete process. over prescriptive versus performance-based specifications. These materials contractor’s operations. Because the final product depends on strict control of the tives to produce a polymer-modified shotcrete. should be noted that latex-modified shotcretes are highly sus. The tion to reducing permeability and absorption. Currently. have been used as addi. and fall-out of shotcrete. This encourages contractors to use their greatest ability to Reinforcing achieve the required benefit. in wet. they should and their engineers. be achieved. which makes administration much easier and Specification for Deformed and Plain Billet-Steel Bars for Con. Mixing water should not Specification for Epoxy-Resin-Base Bonding Systems for Con- increase the chloride ion content of the shotcrete. so that accelerators (quicksets) that induce both early initial and final effective bonding between subsequent layers of shotcrete can set in dry. All responsibility is assigned to the Reinforcing bars used in shotcrete should conform to ASTM contractor. should be well thought out and directed to the requirements of the project. ASTM Specification for Rail-Steel approach requires a clear statement of the required improve- Deformed and Plain Bars for Concrete Reinforcement (A 616). where appropriate. the contractor. performance or prescriptive. greatly reduces the required inspection and testing efforts.5. Air-entraining admixtures are not experience. An analysis of a project considering these factors 1116). They can be prescriptive or performance based. and applied or allowed to harden before shotcrete application admixtures should not exceed the values outlined in Table potentially can act as bond-breakers resulting in sagging. Polymers. they should meet the requirements of ASTM knowledge and equipment and experienced and skilled per- Specification for Air-Entraining Admixtures for Concrete (C sonnel. prescriptive specifications must be de- are reported to increase flexural and tensile strengths in addi. crete should conform to ASTM Specification for Sheet Materi- als for Curing Concrete (C 171) and ASTM Specification for Admixtures Liquid Membrane-Forming Compounds for Curing Concrete Admixtures for both wet-mixture and dry-mixture shotcrete (C 309). the crete (C 881/C 881M). for Concrete Reinforcement (A The selection and proportioning of shotcrete mixtures depends 185) or ASTM Specification for Welded Deformed Steel Wire on many factors. if epoxies portions. Those in the best position to maintain expertise are typically used in the dry-mix shotcrete process. coated or coated with zinc or epoxy. Polymers but they must clearly define the intent of the work. Quick-setting pounds are not recommended and should not be used. decreased freeze-thaw resistance. 706). it also is a specialized area of activity for most owners possible reduction in other durability properties.620 TESTS AND PROPERTIES OF CONCRETE that could be injurious to shotcrete. is most appropriate. is most feasible and what type of specification. ASTM Specification for Axle-Steel Deformed and Plain Bars for including. mixture shotcrete. Plain. This crete Reinforcement (A 615). Welded wire fabric for Selection and Proportioning of Shotcrete shotcrete should conform to ASTM Specification for Steel Materials Welded Wire. the choice of materials. many shotcreting firms have considerable provisions of ASTM C 1140. However. who may not use shotcrete extensively. Specifications be found in the Guide to Shotcrete (ACI 506–95) [6]. they should comply with ASTM sult. pro- mended in normal shotcrete applications. Prescriptive specifications are more detailed. General guidance in the application of chemical and min. type of delivery equipment. Presently. relatively thick overhead layers of material to tunnel linings and for similar applications. ASTM Specification for Low. tailed. aggregates. If shotcrete is applied in multiple layers. thorough. ments and must designate the means to be used for verification.4 of Building Code Requirements for Reinforced Concrete sloughing. Bonding compounds not properly total chloride ion content of the water. is expected to continue for some time [6]. Although the application of shotcrete is very much technology mate shotcrete strength. It specifications. cement. and methods for achieving the desired re- are used as bonding agents. 4. Curing materials for shot- (ACI 318–99) [42]. The debate Concrete Reinforcement (A 617). they should conform to the requirement of ASTM thickness and volume of shotcrete to be placed in a given Specification of Fiber-Reinforced Concrete and Shotcrete (C time frame. equipment.and wet-mix shotcrete are commonly used to apply be effectively achieved. Fabric. and are used. Perfor- Miscellaneous mance specifications usually are preferred because they allow Bonding agents usually are not required or typically recom. The mixed at project sites is produced using mobile equipment.2–98 [44]. that batched at a central ready-mix concrete plant and delivered . Proportioning of Dry-Mixture Shotcrete scribed in the ASTM Test Method for Flexural Toughness and In current practice proportioning for dry-mixture shotcrete First-Crack Strength of Fiber-Reinforced Concrete (Using usually is less complicated because most mixture designs use Beam with Third-Point Loading) (C 1018). Compressive strength (minimum at specified age) shotcrete. Alterna- cluding higher cement factors. For proper dry-mixture shotcrete application. for Concrete Aggregates (C 33) contains fine aggregate that can Typical prescriptive requirements may include but are not be adapted readily to dry-mixture shotcrete application with limited to the following: minor changes [6]. Slump (wet mixture only) the related testing costs are a small proportion of the overall 7. and may constrain the construction approach to a the maximum allowable size of the coarse aggregate depends significant extent to prevent the potential for confusing or con. Chloride ion content Higher slumps in the 100–150 mm (4–6 in. Aggregate source. type of batching. Another traditional source of shotcrete at project sites is dures of ACI 211. somewhere between 8 and 10 % may be required at 5. Use of admixtures (Initial/final setting time) used with accelerated shotcrete. lower water-cement ratios. the key 1. Density or absorption factor in wet-mix shotcrete. Mixture proportions or limitations ing is most appropriate for medium-to-large projects. in which 6. Air content (wet mixture only) project budget. terials manufactured according to the requirements in ASTM sidered because of the increased potential for shrinkage and the Specification for Packaged. PYE ON SHOTCRETE 621 restrictions. the requirements (1–3) may be usually beneficial in helping to achieve the specified properties necessary. aggregates. In most performance specifications. the inclusion of the remainder depending on the of wet-mixture shotcrete. The designer may very little coarse aggregate. The individual constituents of the shotcrete as durability. the contents of the prepackaged materials should be effectively predampened to facilitate uniform and consistent mix- Proportioning of Wet-Mixture Shotcrete ing immediately before field application. and shotcrete placing equipment. fume and fly ash. Proportioning for wet-mixture shotcrete follows the proce. Pre-blended.) and 9 mm (3/8in. Permitted admixtures and dosage confirm the mixture proportions is a suitable alternative if 4.7–45. the maximum aggregate size being also want to prescribe the shotcrete process. cement. the shotcrete process can create A considerable quantity of shotcrete that is batched and conditions that require some adjustments in approach. 8. Compressive strength (minimum) Proportioning: General Batching and Mixing The basic approach to proportioning shotcrete mixes is consistent with normal concrete practice. and a higher specific surface logistical constraints at a project site. are determined to be key performance require. Dry. This approach ef. It should be emphasized that preconstruction 8. These packages contain the materials but also the equipment and the performance capa. ASTM Specification mixing. when properties other than strength. Initial and final setting times previous similar projects. They bility of the nozzlemen. as de. type. As lb). dry admixtures. If 4 % air entrainment is required in the 4. Specification for Materials for Shotcrete (C 1436). Meeting the air-content requirements of the hard- 1. on the material hose size. The use of water-reducers is In most applications. Cement-binder type ened shotcrete can be a problem because entrained air is lost 2. lower coarse-to-fine aggregate tively. or in other previously implied.) or less nor- 7. However. between 6 mm (1/4 in. Maintaining optimal slump is an important 6. However. In many Typical performance requirements may include but are wet-mix applications. thus providing an indication of the usually are available in sealed bags of 22. Confirmation of the quality and consis- mixture design is preconstruction or field-testing as outlined in tency of shotcrete materials used in these products is Section 6.1–91 [43] and ACI 211. In addition. Preconstruction testing to 3.4 of the ACI Guide to Shotcrete [6]. Maximum water/cementitious material ratio through the pump and significant amounts of air are lost on 3. Bond strength the pump hopper.) range often are 9. and stockpiled materials are used as required in the ASTM tion usually results in changed in-place physical properties. Chloride ion content performance of the shotcrete mix has been demonstrated on 10. Water-cement ratio (wet mixture only) testing may not be necessary on small projects—especially if the 9. These factors must be con. Air content (wet-mixture only) mally being required for consistently uniform placement. Supplemental cementitious materials. type and content there is a lack of previous data. preconstruction test- 5. such large containers. used decreases as the size of the aggregate increases. and other additives. Cement type and amount design requirement is a compressive strength with a default 28- 2. under special circumstances. mixture should meet ASTM and ACI requirements for shot- ments. the toughness may be specified. in. Aggregate grading exit from the nozzle. achieved by sampling as required in the ASTM Practice for fectively captures not only the contribution of the constituent Sampling for Shotcrete (C 1385).4 kg (50–100 performance of the total shotcrete system and process. and the quantity of coarse aggregate flicting requirements. or access or ratios. The most terials for use in Wet or Dry Shotcrete Application (C 1480) practical means of confirming the potential performance of a are frequently used. especially for the wet-mix. 11. Generally. bagged preblended ma- for the aggregate remaining in place. project-specific shotcrete application. rebound of larger aggregate particles during shotcrete applica. the sand-aggregate ratio may be as high not limited to the following: as 65–75 %. Combined Ma- development of fine surface cracks in the shotcrete. the shotcrete mixture can be adjusted to include silica crete materials. in bulk bags of 454–1820 kg (1000–4000 lb). 50–75 mm (2–3 in. General ture process.). when there are limited lay-down areas. and grading day strength of 34.5 MPa (5000 psi). NDT devices and methods such as impact but if these procedures are not practical. On medium-to-large or complex projects. Ready-mixed shotcrete can be delivered to where multiple layers of shotcrete are applied. However. However. in order to ensure that bonding is effectively achieved ultrasonic and pulse velocity methods. compressive strength is considered a good general indi- plied material. shotcrete that have been previously discussed. all admixtures are added ACI Guide for the Evaluation of Shotcrete 506. quality. the capabilities of the plant. As previously indicated. ASTM has only one specification that is applicable Subcommittee C09. during mixing except for conventional accelerators and quick. strength determination.2R-96 [45]. uniform production and consistency in batching and performance parameters. thin sections ranging from 50 to 150 mm (2 to 6 in. The moisture Drilled Cores and Sawed Beams of Concrete (C 42/C 42M) for content and bulk density of the sand should therefore be con. For wet-mixture shotcrete. cated. standard or quickset accelerators can be bond. should be based on a minimum but sufficient number of representative samples. ready-mix plants use and would include such elements as preconstruction testing. workmanship. The tests used in a project quality assur- Miscellaneous ance program should provide data and information that. As previously indi. Additional information strength. tration Resistance of Hardened Concrete (C 803/C 803M). for acceptance testing and construction control and for assess- Specifications for weight batching are found in ASTM ing the condition. A project quality assurance program normally should be commensurate with the size and complexity of the shotcrete project. weight batching for cement and aggregates and volumetric prototype tests or mock-ups. which are added at the nozzle in liquid established by the specifier of tests. and certification of the nozzlemen—essentially covering all troduced by weight but occasionally by volume. Ponding oped for evaluating concrete structures [48]. ASTM Test Method for Rebound Number of Hard- that comply with ASTM C 309 or sheet materials meeting the ened Concrete (C 805). using cur. Sampling and testing of hardened application are essential in the production of high-quality shotcrete during construction or on a post-construction basis shotcrete. water is Preconstruction testing as described in the Specification for added at the nozzle by the nozzleman at a rate that depends on Shotcrete (ACI 506. density. Batching On small projects. ASTM Test Method for Pene- requirements of ASTM C 171 can be used. plan that indicates the number of samples and their locations. quality assurance will typically be minimal. In the dry-mix process. In the wet-mix process. and the envelopment of any reinforcement used in the added in nonliquid (dry) form during mixing or at the nozzle shotcrete. Core specimens are typically provided firmed when these problems are encountered. For shotcrete quality. when Curing of in-place shotcrete requires the same attention as for evaluated and assessed. probes. Pozzolans usually are in. can be used in or continuous sprinkling provide the best curing conditions. depending on aspects important to the performance of the shotcrete system. batch mixture proportions can be Specimens obtained for this purpose also can be used to verify achieved manually by using cement in 42. Time pound should not be used between the applied layers. fiber-reinforced shotcrete.6-kg (94-lb) bags and the thickness of shotcrete and aid in the visual assessment of weight-calibrated containers for aggregates and pozzolans. and uniformity of the shotcrete in ac- Specification for Ready Mix Concrete (C 94/C 94M) and for cordance with the ASTM Standard Practice for Examination and volumetric batching in ASTM C 685/C 685M.622 TESTS AND PROPERTIES OF CONCRETE by ready-mix trucks. the quality assurance Batching by weight is generally the preferred method. and uniformity also may be important Again. limits on delivery and discharge usually are imposed to prevent significant prehydration losses. age. ASTM C taining and Testing Drilled Cores and Sawed Beams of Con- 685/C 685M. As with con- ing the occurrence of sand pockets and laminations in the ap. curing compounds hammers. Mixing Testing Currently. rials. ASTM Test Method for .46 has adapted ASTM Test Method for Ob- to batching and mixing of dry-mixture shotcrete. Batching of shotcrete materials typically is by weight or volume. shotcrete-to-substrate dry-mixture shotcrete. On-site program would be expected to be much more comprehensive mixers use volumetric or manual batching.). the Guide to Shotcrete (ACI 506R-95) crete (C 42/C 42M) and developed ASTM Test Method for [6] provides excellent supplementary information on good Obtaining and Testing Drilled Cores of Shotcrete (C 1604/C mixing practice. sand bulking and variability in moisture content are els (C 1140) and ASTM Test Method for Obtaining and Testing potential sources of error in batch proportions. defects. should conform to either ASTM C 685/C 685M or ASTM C 94/C depending on the type of structure or application. Uniform and consistent mixing is essential for 1604M) to account for the differences between concrete and producing high quality dry-mixture shotcrete and for minimiz. If significant prehydration Quality Assurance and Testing losses are expected. mixing requirements cator of the quality of hardened in-place shotcrete. Nondestructive testing (NDT) methods. shrink- on mixing pumped concretes is available in ACI 304. form. For producing Sampling of Hardened Concrete in Constructions (C 823). directly relate to the performance of concrete to fully develop the strength and durability of the the shotcrete material or structure and satisfy the purpose shotcrete. Because shotcrete typically is applied in relatively of the sampling and evaluation plan. Evaluation of shotcrete properties is discussed in in liquid form. typically devel- ing procedures as specified in ACI 506.2–95) [46] uses the ASTM Standard Practice the appearance of the shotcrete. toughness in addition to bond. absorption. curing com- the project site as wet-mixture or dry-mixture shotcrete. crete.4R-94 [47]. provisions can be made to retard the shotcrete mixture using admixtures meeting the requirements of Quality Assurance ASTM Specification for Admixtures for Shotcrete (C 1141). evaluating shotcrete. flexural 94M depending on the mode of mixing.2 is important. permeability. additional information on the Extraction of core samples should be based on a sampling required batching tolerances can be found in ASTM C 1116. prequalification of shotcrete mate- batching for water and admixtures. On projects using volumetric for Preparing and Testing Specimens from Shotcrete Test Pan- batching. Acceptance criteria for shotcrete core strengths usually is setting accelerators. specifications. current technology. Ameri- resulted in efficient. pp.” Report No. O. “The Use of Compressed Air in Handling Mortars dards for shotcrete be developed to address the current state and Concrete. PYE ON SHOTCRETE 623 Pulse Velocity Through Concrete (C 597). “The History of Shotcrete. MI. will continue crete process.” Chapter 55 in Significance of Tests C 1550. and contractors. except for admixtures.” Concrete Interna- tional.46. pp.. of shotcrete. [9] Yoggi. A. Detroit. for Examination and Sampling of Hardened Concrete in Struc- rial adhering and not sagging or sloughing.” shotcrete standards for quality assurance or performance con. plastic-state properties. industry. S. SP-14A. biggest challenge in developing new or adapted standards. 1. shotcrete generally has met the expectations of project [5] Recommended Practice for the Application of Mortar by Pneu- owners. varying between 0 and 200 mm (0 and 8 in. L. Therefore. Vol. Methods accepting or rejecting both plastic and hardened shotcrete. P. and Durham. where applica. ity and performance of shotcrete... Fall 2000. improvements in reliability and consistency that have in turn [6] Guide to Shotcrete (ACI 506R-95). dressed in terms of standards development are in the plastic [13] Morgan. are used to qualify the individual materials used in the shot. Subcommittee C09. ASTM C 1140. “Shotcrete. W. No. ing on conventional statistics and appropriate geostatistical out subsidence.” Cement World. firmation must be seen as relevant and useful by both owners 1966. No. ASTM C 1398. American Concrete Institute.). Summer 2004. and Part III. I. Vol. SP-14. for which ASTM C 1141 to review Committee C09 standards and determine which of replaces ASTM Specification for Chemical Admixtures for them are applicable to current shotcrete practice. and Lorig. pp. T.” Concrete International. with the in-place mate. G. Detroit. however. The goal of shotcrete stan. can be used to determine the uni. This approach should be based on the use of ap- ble. American Concrete Institute. MI. PA. shotcrete that will in turn enable industry to confirm the qual. 10.. ASTM C 1436. Winter 2002. it is essential that a comprehensive set of stan. “Laboratory Study of Shotcrete. 86–93. M. Except for ASTM C 1116.. and hardened- state properties.. “Durability of shotcrete industry’s efforts to evaluate the performance of Dry-Mix Shotcrete. 78–85. “Durability of Shotcrete. Part I. L. 11. [3] Tatnall. H.. Spring 2001. on the recognition that as a material. Washington. I. ponent. Summary [2] Fuller. U. pp. L. pullout devices. Properly placed tures (C 823) for shotcrete structures. J. 1994. H. important tool for a wide range of applications in construction. and ASTM [1] Glassgold. Vol. Wet-mixture shot. Vol. Detroit. . As emphasized previously. effective. “Compressed Air and Live Steam for Placing Con- to the means and methods for the systematic evaluation of crete. A. and Shideler. ACI Committee 805. 1989. and. ACI Committee 506. These areas represent the International. “Field- Those who develop these standards must clearly recognize the Oriented Investigation of Conventional and Experimental shotcrete process. Shotcrete has a long and established history as an effective and PA. designers. D. inspectors. ASTM STP 169C. ASTM In- ternational. ASTM References C 1141. account for the processes and practice of shotcrete application. for the performance of shotcrete as a material. L. 11. MI. R. and contractors. 47–50. Specific areas that currently need to be ad. ture as a whole.” Concrete does not impose unnecessary economic burdens on contrac. Department of Transportation.” Shotcrete Magazine. as for placing ordinary concrete utilize procedures that place con. No. Current ASTM specifications and test methods sampling methods [49]. manufacture. and to develop new standards for shotcrete or to adapt existing recommended practices for concrete and concrete-related ma. can Concrete Institute. “U. Fernandez-Delgado. structural system.. In addition. DC. Test parameters should directly relate to key Differences between concrete and shotcrete can again arise performance or design parameters that constitute the basis for from the type of application and shotcrete process. 165–184. C09.. American Con- velopments in shotcrete technology have resulted in significant crete Institute. An approach that could be used for this purpose would be crete may have a slump at the pump hopper that varies to adapt the guidelines identified in ASTM Standard Practice between 38 and 75 mm (112⁄ and 3 in. tors or owners. sampling and Evaluation of Shotcrete ACI 506. August 1916.S. structural ele- formity of the in-place shotcrete as described in Guide for the ment. 13–20. 1981.46 will continue Most of the current ASTM test methods.S. J. 8. and economical construction. “Freeze Thaw Durability of Shotcrete. International. Lamond. Litvin. indicated in the ASTM Practice for Examination and Sampling crete in its final position at close to zero velocity with slump of Hardened Concrete in Constructions (C 823). terials include four general divisions of concrete technology: materials. E.. or component. 1995. Shotcrete Standards Update. Inc. 1968. G. Shotcreting. or com. of shotcrete technology and the testing needs of the shotcrete 504–521. G. The current shotcrete subcommittee. and Gebler. Testing require. “Shotcrete Durability: An Evaluation. in general. G. pp. R. [14] Parker..” National Association of Cement Users.” Cement Gun Co. P.. 27–33. ASTM C 1480.. [4] Lorman. 1989. testing methods must account for both spatial and temporal ments for the plastic state of shotcrete are. Such standards will make a significant contribution [8] Springer. ASTM Test Method for Pullout Strength of propriate sampling and testing methods that implicitly account Hardened Concrete (C 900). “Report Showing Results of Tests Made on Gunite Slabs. W. Klieger and J. 11. D. No.. [7] Prentiss. Detroit. de- matic Pressure (ACI 805–51). J. shotcrete.” Shotcrete The use of shotcrete continues to increase. dards development.. a result largely based Magazine.. specifically with regard to the acceptance or rejection 1989. [12] Reading. 8. W. 1911. Engineering Properties of Shotcrete. pp. J. Where Concrete (C 494/C 494M). and the broad range Shotcrete for Tunnels. MI.. C. J. L. Sampling and testing standards are needed to facilitate the [15] Seegebrecht. concrete standards for shotcrete if necessary. Allentown.. L. West Conshohocken. 3. 1926. FRA-OR&D 76–06.. Eds. August 1975. Part II.4R-94 [47]. changes are appropriate. The cost benefits associated with applying new [11] Litvin. G. F. similar variability in a way that is representative of the shotcrete struc- to those established for ordinary portland cement concrete. and types of shotcrete application. 1951.” Concrete and hardened state of shotcrete. should be achieved in a way that [10] Glassgold.). with sampling and test- dry-mixture shotcrete normally has zero in-place slump with. pp. concrete standards have been adapted in an attempt to and Properties of Concrete and Concrete–Making Materials. December 1911. Lon- [23] State of the Art on Fiber Reinforced Shotcrete (ACI 506. P. L. R..” Bul.18 (2003) 71–83.. 1994. University of Illinois. Vol. 1986. S..A. J. “Design Criteria for Shotcrete as a Support in Underground Construction. thesis. Building Research Station.” Journal. [21] Specification for Materials. N. Detroit. Urbana. and Peter Robins. 1978. American Concrete (withdrawn as an ACI standard in 1983). Allentown. R. [27] Lankard D. De- [28] Report on Fiber-Reinforced Shotcrete (ACI 506. April 11–15. W. 1989.624 TESTS AND PROPERTIES OF CONCRETE [16] Gebler. [26] Fisher. SP-43. ACI Com. Litvin.2–77). May 2000. 1977. Second Edition. [43] Standard Practice for Selecting Proportions for Normal. PA.. H.2–98). UK. MI.” Tunnelling and Underground Space Shotcrete in Ground Support. 3. 27 March 1992 (unpublished). Heavy- 289–305. Beth. and Hills. [44] Standard Practice for Selecting Proportions for Structural Light- als Journal. can Concrete Institute. Society of Engineers. XIX.. do Jordao. I.. H.” presented at American Ceramic Society Meeting. “Practical Geostatistics. D. American Con. R. 1998. Technology 18 (2003) 57–69. “Design Guidelines for Use of Fiber-Reinforced Milestones up to the 1960s. [19] Shotcreting. Refractory Concrete: State-of-the-Art at the 28th Annual Symposium on Refractories.” Shotcrete Magazine. [46] Specification for Shotcrete (ACI 506. “Field Experiences with Steel Fiber-Reinforced Shotcrete for Ground Support. crete Institute. MI.” South African Presented at the Engineering Foundation. Gunite. MI. American Ce. [49] Clark. pp. R. Canadian Tunneling Magazine. mittee 506. American Concrete Institute. 1979. Detroit. Shotcrete for Underground Support III.” Concrete International. “Research in Fiber-Reinforced Shotcrete: Bringing New York. Detroit.. Vol. Northlands. troit. EFNARC European Specification for Sprayed Concrete. 1973. “The Use of Steel Fibre Reinforced Shotcrete [37] Rodriguez.. ACI Com. J.. MI.02. “The Combined Q/NATM System – The Design System of Ductility of Mesh and Fibre Reinforced Shotcretes. don and New York. Dec.2–95). 1984.. UILU-ENGf-75–2018. Detroit. It’s Application and Uses. P. IL. Detroit. A. No. August 1975. 1977. 1991. Institute. Heere. Vol. Louis. 2004. Shotcrete. H. ACI Com- Shotcrete (ACI 506. Concrete. R. De- Regulated-Set Cement. and Labrum. . London. 1998. B. 1976. A. T. L. Vol. [29] Morgan.. May 2000. Testing of Concrete. A. 1984..” presented American Concrete Institute. Properties. Shotcrete in the United States: A Brief History. Shotcrete for Underground Support IV. K. Lehigh University. 11. MI. D. troit. No. W. American Concrete Institute. “Samuel W. PA. Proportioning and Application of [47] Guide for the Evaluation of Shotcrete (ACI 506. SP-128. P.. pp. [38] Jordan. SP-54.” Steffen Robertson & Kirsten Inc. and Morgan. S. Whittles Publishing. MI. “Carl Akeley — A Tribute to the Founder of Shot. R.” Journal. American Society Ryan.1R-84). 6. Mix Shotcrete Containing Rapid Set Accelerators. F. D. “Specification of Shotcrete Toughness. Rapp. Chicago. mittee 506.. Association. Engineering Foundation.. and Heere. I.. ACI Committee 506. A.” M. Detroit. Bulletin No. 7. pp. Institute Detroit. Sprayed Concrete. [25] Glassgold. May–June 1992. July 1990. American Compilation No. MI. weight Concrete (ACI 211. American Concrete Institute. Use of Shotcrete for Underground Structural Support. Ward.” and Specification of Primary Tunnel Support. V. 272–315. Detroit. 1981. Ameri- [20] Recommended Practice for Shotcreting (ACI 506–66). H. C. MI.. “Evolution of Fiber Reinforced New York. W. and Chan. Summer 2002.1–91). weight. Parker.. Shotcrete. A. “Durability of Dry-Mix Shotcrete Containing [41] Refractory Concrete. “Comparative Evaluation of [35] Kirsten. The Cement Gun Co. A. R. J. “Durability of Dry. West 91). IL..” Construction and Quality Assurance for the Stave Falls Tunnel.. Skokie. pp. 1973.. 1964. J. R. sponsored Tunnelling — First Quarter 1983. “Application and Use of Shotcrete. ACI Committee 506. R. A. Membrane. American Concrete Institute/American Society for Civil Engineers.4R-94). Brazil. 259–262. pp.. M. D. 1984. West Conshohocken. Handbook on Nondestructive [22] Guide to the Certification of Shotcrete Nozzlemen (ACI 506. mittee 506. Simon Austin letin 22. American Concrete Institute. Detroit. PA. L. MI. (ACI 318–99). Structural Applications of Pumped and and Mesh Reinforcement in Shotcrete Used for Tunnel-support Sprayed Concrete.. 1991. Cement and Concrete of Engineering Contractors. MI. 1978. 1971. N. 1999. C. Western quirements and the Dry-Mix Process. “Installation Properties of Gunning Mixes. UK. No. C. 2116 Gauteng. 26. 141–156. “The Equivalence of Fibre Litvin. Vandewalle. H.. “Refractory Shotcrete – Current State-of-the. Sprayed Concrete: Tunnel Support Re- [39] Weber. Detroit. 1918. J. [45] Placing Concrete by Pumping Methods (ACI 304. part II . D. Vol. American Concrete Institute.3R. “Shotcrete Design. Paper No. 1989. Detroit. ACI Committee 547. Vol. American Concrete Institute. South African Institute of Mining and Metallurgy. 56–58. W. MI.. R. Report (ACI 547–79).1R-98). Systems. Press. “The Cement Gun.” ACI Materi.” Shotcrete Magazine. “History of Sprayed Concrete Lining Method — Part I: [32] Papworth. MI. MI. Engineering Foundation. I. No.. and Mass Concrete (ACI 211. 407–434. D 72..2R-96). American Concrete Institute. W.. A. 90.” Shotcrete Magazine. “Shotcrete Practice [34] Kirsten. 1966. Mahar. [31] Ripley.” Shotcrete Magazine. ASTM International. [30] Banthia. [24] Annual Book of ASTM Standards. H. Pergamon Spring 2002. St. Detroit. Detroit. Conshohocken. Morgan. MI. ACI Committee 506.. Inc. “The Cement Gun. D. 3.. crete. Detroit. Development Department. A Handbook for Engineers. American Concrete Institute.. MI. Kovári. South Africa. Heere. D. W. H.” Art.. SP-14. 1978. “The Cement Gun. March 1914. and Morgan. [33] Kirsten. Metallurgy.. [48] Malhotra. and Shideler. 4. D. [42] Building Code Requirements for Reinforced Concrete Structures [17] Glassgold. 10.” Shotcrete Magazine. R. American Concrete Institute. 1997.. ASTM Bibliography International. Eds. and It’s Work. P. [40] Collier. M. Science to an Art. and Carino.01 and 4. D. L.. American Concrete Institute.” Elsevier Applied Science. American Concrete Institute/American Society of Civil Engineers. and Schutz. May/June lehem. MI. 89.” The Journal of The the Process of Innovation. Detroit. 1.” Journal of The South African Institute of Mining and Portland Cement Association. P. W. Conference on Shotcrete for Underground Support VIII Campos [36] Teichert. 1995. R. 1996. PA. The Cement Gun and for the Support of Mine Openings.” Shotcrete Magazine.” Report No. and Wuellner. New York.O. pp. Watford. MI. American Concrete [18] Gebler. Fall 2003. MO.. 33. Box 55291. Design and Application. Summer 2002.. American Concrete Institute. Traylor. ramic Society. Detroit. SP-57. 1996.. Apr. ASTM Specification for Latex Agents for Bonding Fresh to Hardened Concrete (C 1059) provides for the classification of latex bonding agents according to use: Type I (redispersable) for Introduction use in interior work not subject to immersion in water or high humidity.8 MPa (400 psi) when tested inclusion of the polymer in the plastic-concrete mixture in dry for Type I systems and 8. silicones. There is no frost damage to concrete if it is dry Systems Used with Concrete as Measured by Direct Tension. chlorinated rubber. The concrete fall into three general groups: (1) bonding admix. Since Type II latices are non-redispersable. masonry. such as wood. NC 28752. the latex may be allowed to dry be- dienes. linseed oil. and include up to date classified by ASTM as polymer modified mortar and concrete references. and injurious solutions including acids. cially severe where the concrete is exposed to alternate cycles There are two test methods available for determining the of wetting and drying or freezing and thawing. or both. Test Method for Bond Strength of Latex Systems Used with Con- coatings quite often are applied to concrete to prevent ingress crete by Slant Shear and ASTM C 1404 Bond Strength of Adhesive of the solution. also suitable for However. application of the fresh mortar or Organic materials in common use for bonding and patching of concrete must be accomplished before the slurry dries. because concrete is inherently porous and alkaline. and adhesives in the field or laboratory. metal. ASTM Specification Latex Agents for Bonding Fresh to Absorption and subsequent chemical or physical attack Hardened Concrete (C 1059) requires a minimum bond can also be reduced by polymer impregnation [3] or by strength as tested by C 1042 of 2. Marion. use in other areas.54 Organic Materials for Bonding. There is no ASTM adhesive specification associated with C Epoxy resins have been used to bond overlays and patches 1404. bitumens. and (3) resinous mortars. time after application of the Type I latex. ing agent [4]. introduce new technology. acrylics. to concrete. and water. bond strength of polymer modified mortar or concrete. it can be attacked both physically and chemically by certain Type I latices are generally based on polyvinyl acetate. The chapter was expanded to include a new standard test method to determine the bond and tensile strength properties Latex Adhesives of overlays. fore application of the fresh mortar or concrete. and plastics. salts. (2) adhesives. Type II latices are generally based on styrene butadiene or Attack of concrete by water or injurious solutions is espe. trated in Fig. tems are redispersable. patches. bond strength of latex systems used as adhesives: ASTM C 1042 Since such attack can only occur in a wet environment. tems after immersion. urethanes. THE CONTENTS mortar or concrete to hardened concrete are classified by the of the 4th edition were drawn upon. When applied neatly. The current edition will American Concrete Institute (ACI) as bonding admixtures. The fresh mortar or concrete can be applied at any concrete include epoxy resins. spray.6 I/1Pa (1250 psi) for Type II sys- the form of a latex or unreacted premixed epoxy resin and cur. Patching. ject to high humidity or immersion in water. and Type II (non-redispersable) for use in areas sub- Concrete is one of the most durable materials of construction. Since Type I sys- oil-based paints. polyvinyls. and are covered in detail in Chapter 52. 625 . [1]. acrylic polymers. This test method is usually used only to determine the and to bond a variety of materials. and Sealing Concrete Raymond J. importance of slurry application of Type II systems is illus- tures. styrene buta. and vinylesters. Organic materials that have been used for sealing of or roller. 1 [5]. and all chemical attack requires the presence of water [2]. the systems do not 1 Construction Materials Consultant. Type II latices are mixed with cement or cement and Bonding and Patching Materials sand and are applied as a slurry or grout. Schutz1 Preface Admixtures Admixtures that are used to improve the adhesion of plastic IN PREPARATION OF THIS CHAPTER. Type I systems are applied neatly either by brush. polyesters. review and update the topics as addressed by the previous Mortars and concrete prepared with these materials are authors. mild ments with internal tendons and for span-by-span erection acids. when temporary post tensioning is applied. and as a binder in epoxy mortars or of the bisphenol A and epichlorohydrin) are generally used. class. cretes. These curing agents are generally of the chemical 4. Suitable systems materials. meet the requirements of C 1059. Type II — For use in non-load-bearing applications for binders (for the manufacture of resinous mortar and concrete bonding freshly mixed concrete to hardened concrete. Type V — For use in load-bearing applications for bonding vinylester systems that cure by polymerization. hardened concrete to hardened concrete and other mate- The epoxy resins cure by cross-linking. tems for Crete (C 881) classifies epoxy resin systems by type. tar or concrete to existing hardened concrete) and also as 2. and as a binder in epoxy mortars or epoxy con- are available for use as adhesives (for bonding new plastic mor. patches or overlays). and oils. Type VI — For bonding and sealing segmental precast ele- that of good concrete and will be resistant to alkalies. grade. Type III — For use in bonding skid-resistant materials to liquid epoxy resins of the bisphenol A type (reaction products hardened concrete. When applied as a slurry. or polyamides. . Type I — For use in non-load-bearing applications for bond- Epoxy resins are the most widely used organic systems for ing hardened concrete to hardened concrete and other bonding. and color. 1—Example of bond strengths obtained using Type II latices applied as a slurry and neat ASTM test method C 1042. shrinkage is much less with these than with the polyester or 5. such as amines. ASTM Specification for Epoxy-Resin-Base Bonding Sys- they exceed the minimum requirements. patching. curing rials and as a binder for epoxy mortars and concretes. epoxy concretes used on traffic-bearing surfaces or sur- These resins are mixed with a curing agent immediately prior faces subject to thermal or mechanical movements. Patching. polyamines. low molecular-weight 3. solvents. Epoxy Resins as Adhesive.626 TESTS AND PROPERTIES OF CONCRETE Fig. to use. and overlaying concrete. For these purposes. The cured-resin freshly mixed concrete to hardened concrete. therefore. and Seven types are described by this specification according Overlaying Materials to their proposed use: 1. Type IV — For use in load-bearing applications for bonding groups. systems will have tensile strengths between 10 and 20 times 6. according to Concrete with a Multi-Component Epoxy Adhesive.5 and 15. since the resin systems are sticky and vis- sequential because the total tensile strength of the thin glue cous. surfacings or resinous overlays) may be economically pro- tems Used with Concrete (C 882) is a test method that de. the sand/aggregate ratio is usually the reverse of that line (1 mm or less) is less than the tensile strength of the used for portland-cement concrete. Grade 1 — low viscosity. such as those conforming to ASTM C 881. ACI 503.5 and 26.5°C (40 and 60°F). since a structural places water in the event the repair is made under water. this test method may Resistant Surface on Concrete by the Use of a Multi-Compo- be used to determine the thermal compatibility of any nent Epoxy System. the differences in linear coefficient of same guidelines as proportioning portland-cement concrete expansion between the epoxy resin and the concrete is incon. This from vertical. bond is required in most adhesive applications. suitability of epoxy resins for use with concrete: Thin resinous mortars (also referred to as skid-resistant 1. product. For applications as an adhesive. Epoxy-resin systems are used quite commonly as the sole 2. oil. since solvent may be entrapped during cure is not applied as in span-by-span erection. by ACI 503. adhesive to prevent further corrosion. Concrete and an Epoxy-Resin Overlay (C 884). Voids in excess of 12 % will result in a permeable mass rial in a thin glue line will be extremely high [6]. Steel. and overlays are generally thick. When applied in layers 40-mm (112⁄ -in. the sample is tems conforming to ASTM C 881 are able to cure under humid subjected to five cycles of temperature change between conditions and bond to damp surfaces. Standard Specification for Repairing Concrete Two ASTM test methods are available to determine the with Epoxy Mortars [3]. Type III.2. volume. Wood.5°C (40°F). the most economical method is to prepack ag- test. temperature to be defined by the manufacturer of the cover bonding techniques in detail [7]. Class B — For use between 4. 4. 503. details this method [7]. a resin with a low modulus of able temperature to be defined by the manufacturer of the elasticity. In the thin glue Proportioning epoxy-resin mortar or concrete follows the lines usually used. method eliminates the need for mortar mixers. duced by applying the resin by roller. linear coefficient of expansion of epoxy-mortar systems [7]. When . squeegee. gregates into the void and then inject the epoxy resin as a grout Epoxy-resin systems conforming to ASTM C 881 Types I. mal coefficient of expansion between the thick resin mortar 6. For example. and Concrete. E. Class C — For use above 15. These thin overlays have strength of the composite cylinder. Where unusual curing in the system. the epoxy resin should mental precast elements when temporary post tensioning contain no solvent. both for reasons of economy and thermal com- rates are desired. a layer Some epoxy-resin systems are water sensitive before cure.0 and 32. Grade 3 — non-sagging consistency. the excess aggregate 6 in.2 by 152A-rom (3 excess onto the uncured resin. Class F — For use between 24. product.5 and 18. This temperature may be considerably different from greater in thickness. Figure 2 illustrates the effect of aggregate loading on at a temperature other than that for which it is normally in.1. must be used. of epoxy-sand mortar is applied to a slab of cured and Therefore.1°C (6°F). which has a diagonally cast bonding area at a 30° angle Several applications may be applied if desired. After suitable curing of the bonding agent. and foreign material and coated with the epoxy-resin Grade 2 — medium viscosity. creep of the epoxy resin is not a The total of voids in the system should be less than 12 % by problem because the effective modulus of elasticity as a mate. troweling. or spray to properly prepared concrete surfaces. and F are defined for Types 6 and 7. Where consistency requirements: reinforcing steel is exposed. it is desirable to include coarse aggregate that of the air or the applied material.0°C (75 and 90°F). concrete. and C are defined for Types 1 through 5. Class E — For use between 15. Class A — For use below 4. the highest allow. Standard Specification for Bonding Plastic Concrete to 1.3. with resultant poor chemical and freeze/thaw resistance. resinous mortar and concrete. Standard Specification for Producing a Skid- developed for epoxy-resin systems. Crack lines between Where large cavities are to be repaired by use of an epoxy- the crete and the epoxy mortar constitute failure of the resin concrete.5°C (60°F). In thin glue lines. Sys- dried concrete. and V have relatively high elastic moduli. tended. the difference in ther- 5. Although ACI 503. the lowest allowable Hardened Concrete with a Multi-Component Epoxy Adhesive. II.0°C (40 and 65°F). ASTM Test Method for Bond Strength of Epoxy-Resin Sys. Standard Specification for Bonding Hardened Classes A. it is possible to use a class of bonding agent patibility.4. SCHUTZ ON ORGANIC MATERIALS FOR CONCRETE 627 7. Class D — For use between 4. In this test method. Since such patches 3. flow characteristics and are distinguished by the viscosity and roller. Type VII — For use as a non-stress-carrying sealer for seg. a Class A system will cure rapidly at room The use of epoxy resins as a binder for mortars is covered temperature. from the bottom of the void. and the test is performed by determining the compressive transporting of resinous mortars. The epoxy-resin systems may be applied by brush. However. binder for concrete patches and overlays. and the base concrete will result in failure of the overlay or The temperature in question is usually that of the surface patch by shearing of the concrete adjacent to the resinous mor- of the hardened concrete to which the bonding system is to be tar or concrete. they can only be used under dry conditions. B.) portland-cement mortar cylinder. ASTM Test Method for Thermal Compatibility Between 20 years and have a good service record. If high-modulus binders are used. and cause both a rubbery cure and later shrinkage of the Three grades of systems are defined according to their adhesive. After cure. each section of may be swept off and recovered. mixtures. or spray to a termines the bond strength by using the epoxy system to horizontal concrete surface and broadcasting fine aggregate in bond together two equal sections of a 76.5°C (60 and 80°F). This approach displaces air or dis- IV. 25°C (77°F) and 21. After the epoxy has cured. Brick and Other Materials to Hardened Classes D. and ACI the range of temperatures for which they are suitable. been used for sealing bridge decks and other flatwork for over 2.) or applied. the steel should be cleaned of rust. whereas the lowest vis. be performed There is considerable difference between asphalts and prior to use. Oil may be for over 25 years has now been standardized and published: absorbed into the resin. core into the surface of the substrate and leaving the core at- plied to the surface of the concrete). For gravity-flow sealing of cracks in concrete encountered. Asphaltic coatings generally for resistance to that particular chemical exposure and tem. . ASTM C 1583–04.e. Acrylic.0 in. Bituminous Coatings viscosity. cation and curing of the system. oils. It stresses the This test method is suitable for both field and laboratory necessity for preparing the concrete surface to be treated be. craze when exposed to ultraviolet light or high temperature. the forms A test method which has been in use with many variations should be coated with polyethylene rather than oil. basements. and vinylester resins have been used successfully. grease. are used to protect foundations. propriate because of their low viscosity. and a tensile load is applied to the disk. The choice may be dictated by economy. unless they are specially formulated. It is often desirable to use resins other than epoxies for mor. free of oil. tures from water. impairing the cure of the system. and it is recommended materials. tars and overlays. or other contaminants such as residues of The test specimen is formed by drilling a 50 mm (2. that a compatibility test. (2) the surface must be clean (i. Coal-tar coatings have a tendency to crack and decks. waxes.628 TESTS AND PROPERTIES OF CONCRETE Fig. or polishes that may have been ap.10]. of the test specimen. use to determine: the near-surface tensile strength of the fore application of the resin system. and (3) water vapor must tached to the concrete. when used for chemi. and similar struc- perature. 2—Effect of sand aggregate-binder ratio on the thermal coefficient of expansion of an epoxy system. The modes of failure possible are shown in Fig. These resins are avail. using forms for epoxy-resin mortar or concrete.) curing compounds. such as ASTM C 884. Epoxy resins have been used extensively for pressure Coal-tar coatings possess a high degree of water resistance grouting cracks to restore the structural integrity of a concrete and should be considered wherever continuous immersion is member [7]. tems. the vinylester and the polyester resins have bet. coal tars. the bond strength of a repair or overlay. the high molecular-weight methacrylate resins are ap. hesive used. but. This report should be Overlay Materials by Direct Tension (Pull-off Method). Three surface conditions concrete surface. 3. and gasoline. underground pipelines. terials but are attacked readily by solvents. The tensile or bond strength and mode of failure are reported. The most common use for coal-tar coatings is the protection of able with viscosities lower than 25 cps. or must be met if an application is to be successful: (1) the surface the tensile strength of a repair material or overlay or the ad- must be strong and sound. Tensile Strength of Concrete Surfaces and ACI Committee 503 has issued a guide covering the use of the Bond Strength or Tensile Strength of Concrete Repair and epoxy resin in concrete construction [7]. cure rate. A steel disk is bonded to the top surface not be expelled from the concrete (out-gassing) during appli. When formulated with epoxy-resin sys- cosity epoxy resins will be in the range of 100 to 400 cps [9. each system should be evaluated or pretested ings may be permeable to water. Asphalts are resistant to many mildly corrosive ma- In general.. The thermal coefficient of expansion of these resins is Bituminous materials include both asphaltic and coal-tar-based similar to that of the epoxy resins. asphaltic coat- cal protection. studied by those planning to use these materials. ter acid resistance than the epoxies. Further. and specific chemical resistance [8]. polyester. excellent long-term performance has been recorded [9]. when subject to forklift or other vehicular The polyurethane-based coatings exhibit extremely good traffic. permanent markings or stains from rubber tires. or 100 % solids systems. or B (moderate color change). polyurethane. Bituminous coatings may be used with reinforcing fabric as a curing compound and will perform as a sealer or may be and tape to increase their resistance to impact on back-filling applied to hardened concrete as a sealer. Tests are also included for resistance to acids and alkalies. have better resistance to rubber-burn than single-component ance but tend to yellow on outdoor exposure. Such reinforcing also increases their thickness use of these compounds as curing mediums. choice for protection of exterior concrete.” that is. Tests are in- The acrylic-amine epoxy-resin systems exhibit better resistance cluded in the specification for bond of commercial adhesives. The aliphatic coatings. however. All organic ings for concrete floors. as ceramic tile or vinyl tiles and floor coverings. They may. which can affect the adhesion of covering materials such yellow. This thickness is considered a minimum to achieve rinated-rubber. cally resistant as the epoxy-resin systems. lution. mum of 25 % vehicle solids is specified in order to provide a polyurethane. as solvent solutions and include: coumaroneindene. dry film thickness of 0. These materials are often used to prevent dusting of con- Because these epoxy-resin systems will tend to chalk and crete. also exhibit staining. scuff and abrasion resistance and form the basis for many coat. sure to UV radiation: Class A (essentially non-yellowing).025 mm (1 mil) at the specified cover- The most commonly used coatings in this group are chlo. Chapter 43 covers the and handling. epoxy-resin-based coatings have proven very successful. Latex Coatings Sealing and Curing Compounds Latex coatings are relatively insensitive to dampness and al- Compounds conforming to ASTM Specification C 1315 Liquid kalinity and have become the most widely used coatings for Membrane-Forming Compounds Having Special Properties for architectural interior and exterior concrete surfaces. two-component polyurethane or epoxy-resin-based coatings The aromatic polyurethanes exhibit good chemical resist. chlorosulfonated polyethylene. However. a mini- acrylic. They do Synthetic-Resin Coatings not harden or dust proof the concrete as such but do provide a Synthetic-resin coatings other than latex-based coatings that protective resinous coating. and Class C (no restriction on color acrylic-amine systems [11]. There are three classes low concentrations of organic acids and caustics are encoun. For protection for interior use. They may be applied as solvent so. These compounds as well as their impermeability and service life. they are not suitable as exterior architectural coatings. 3—Schematic of failure modes. They are often used in conjunction coatings may exhibit this phenomenon to some degree. and styrene-butadiene. Two Curing and Sealing Concrete can be applied to fresh concrete types of latices in common use are acrylic and polyvinyl . The with an epoxy-resin-based prime coat. age rate. may exhibit the phenomenon of “rubber-burn. chlorinated rubber. water-based. depending polyurethanes have excellent ultraviolet resistance and are the on the composition of the tires. and epoxy. Although C 1315 is a performance specification. SCHUTZ ON ORGANIC MATERIALS FOR CONCRETE 629 Fig. where aggressive The specification covers two types. to ultraviolet radiation. and epoxy resins. neoprene. they are not quite as chemi. for use where color changes are acceptable). styrene-acrylate. styrene. which will resist the abrasion and are successfully used for sealing concrete are generally applied dusting caused by foot and wheel traffic. the desired characteristics. These coatings. Type I (clear or translu- solutions such as mild concentrations of inorganic acids and cent) and Type II (white pigmented). based on their resistance to yellowing or darkening on expo- tered. are the most widely used sealers. polyamide. resin-based. Class These may be either polyamine. amine-adduct. styrene acrylate. change. They are usually based on chlorinated rubber. Title No. A. C. R. DC. M. S. 1968. 1994. and acrylics form semipermeable films. 1975.” Technology Transfer. 1981.. Brookhaven National Laboratory.” National fore. Nov. Sauer. Materials commonly termed “sealers” or “penetrating sealers” [4] Nawy. chloride ion profile after 21 days of ponding with a salt solution.” Journal.” Concrete International.” Vir- One extensive test program [12] indicated that an alklyl. pp. 37–42. 155–159.. P. ginia Department of Transportation. Influences on Concrete. Many act as effective chloride ion shields. Feb. “Polymer Cement Con- are used to reduce the water absorption and chloride ion pene- crete.. Nov. NCHRP. The alkoxysi. DC. L.1–503. New York. test method is described by Marusin [13]... 503. Since these latices [1] Woods. American Concrete Institute. 503R. termining the depth of sealer penetration and weight gain and [15] Marusin. these materials have shown good der. treated. D. G. 51.. and Rehabilitation.. J. performed well in simulated exposure tests. 1995. Frederick Ungar Publish- and the presence of vapor pressure does not result in failure. Washington. a methyl methacrylate. These tests also indicate that although there are trends [13] “Sealers for Portland Cement Concrete Highway Facilities. Detroit.S. [7] Manual of Concrete Practice. and moisture-cured polyurethane. not form films but react within the concrete pores to form a hy. pp. 1971. A. U. surface dampness is not a problem. CO. pp. - performance in laboratory tests and field applications and form Federal Highway Administration. Denver. [9] “High Molecular Weight Methyacrylate Concrete Crack Bon- drophobic layer. 15. Most of these materials do not change the [5] Author’s laboratory data. As a class..4. Such a portation Research Board. Department of Commerce. Part 5. minimal. and a linseed oil-based sealer Use. T. 1968. heavily filled or pigmented. G. MI. a [11] Roberts.” ACI Mono- are water borne. When graph 4. generic type does not ensure the effectiveness of a sealer. p. American Concrete Insti- tute. tration of concrete. A. Bureau of Reclamation.. “Evaluating Sealers. “Rapid Concrete Bridge Deck Protection. being of a particular NCHRP Synthesis 209. effective chloride shields [13]. J. Sealers [3] “Concrete-Polymer Materials. Jan. H.. 2.” in the performance of a generic type. Penetration is also Construction. .” SHRP-5–344. “Organic Coatings: Properties.” Concrete International. 9–10. ing Company. 79–81. DC. and Litvan. Richmond. National Research Council. p. ers is highly dependent on the characteristics of the concrete pp. March 1976. VA. they form permeable coatings. 1989. “Laboratory Investigation of Concrete Sealers. Demonstration Project No. Washington. There- [14] “Concrete Sealers for Protection of Bridge Structures. Washington. While both are suitable for interior concrete References coatings. DC. alkoxy silane. lanes. Repair Many materials are marketed for this application. and Sun. Detroit. The sealers based on urethanes. April 1988. 1989. Washington. 1993. Nov. it is recommended that pretesting should be carried out Cooperative Highway Research Program Report 244. [2] Kleinlogel. and the polysiloxy silanes do Washington.) being reported as a general maximum 73-14. p. oligomeric alkoxysilanes. F. 10. appearance of the concrete significantly. Selection. MI.” Journal. Dec. [12]. American Concrete Institute.” Third Topical Report.630 TESTS AND PROPERTIES OF CONCRETE acetate latices. [10] Special Provision for Gravity Fill Polymer Crack Sealing. “Durability of Concrete Construction. 56. “Epoxy Adhesive in Prestressed and Precast Bridge seal the concrete but reduce water inflow. E. The test consists of de. the acrylic gives the best results in exterior exposure due to its superior ultraviolet resistance.” Building Science Series 7. Sealers do not actually [6] Schutz. 3 mm (1/8 in. an amine-cured epoxy. 1950. [12] Aitken. G. American Concrete Institute. Other tests [10] indicate that the performance of these seal. Trans- with the candidate sealers and the concrete in question. pp. DC. epoxies. p. Silanes [8] Sprinkel. The MSDS for products containing silica sand there- duce up to 40 bags/s. Cementitious Mixtures Dennison Fiala1 Preface from the producing locations. C. updated the chapter in ASTM STP Sheet (MSDS) that must comply with Federal Regulation 169B. The The first producers of packaged. or a combination of both to proportion precautions for safe handling and use. Texas. emer- and placed them in the package. the product. Brust. and Owen Brown. in 1987. Dry. fire and explosion hazard data. GA updated 29 CFR 1910. and ex- and today represents the largest selling product. Inc. Wexford. The tentative specification of cancer. was the original author of this chapter for STP with a detailed hazardous warning covering the ingredients in 169A.. gency first aid procedures. ASTM STP 169B. Compressive strength minimums for concrete mortar (sand topping mix) Current Specifications and other concretes were slightly lower than for the same mixes today (see Table 1 from ASTM C 387-99) The Products Initially. Arlington. and continues to grow. combined materials for mortar and concrete. Washington University. Packagers provide their industrial customers Louis. Processes used weigh or vol. building supply yards. Products were available from crete. and mucous membranes. A.6 kg (94 lb) bags of portland cement. pneumoconiosis. and ASTM STP 169C. was accepted by the Administrative Committee on Standards in Warning statements are required on the MSDS and other 1956. but now must also warn of the possibility the ASTM Bulletin in April 1955. Some production lines are able to pro. Texas Indus. those required by the current ASTM C 387. but not limited to. The Occupational Health Early History and Safety Administration (OSHA) and the American Con- ference of Governmental Industrial Hygienists (ACGIH) In 1935 packaged concrete mixes first appeared on the market have both listed it as a hazardous material with specific per- and were soon an ever-growing industry covering a variety of missible exposure limits listed for workers in contact with this packaged cement based products both for the homeowner and material. in respiratory disease. combined materials MSDS for products containing portland cement must address for mortar and concrete either introduced the ingredients sep. dry. high-capacity production lines control proportions. Today. The compressive strength minimums for mortar for unit areas including package wording as well as accompanying data masonry and for normal-strength concrete were the same as sheets. ASTM STP 169A. PACKAGED. PA. Carter. a potential car- Automated process lines help keep uniformity and quality at a cinogen by The International Agency for Research on Cancer high level of control. control measures. Manager of Quality Assurance. (LARC). and the ingredients of the mix. the list of specifications covering packaged materials hardware stores. Although the packaged industry began with mortar and con- manded by the market today. the contractor. ume measurements. 631 . package sizes were generally larger than de. Consultant.55 Packaged.1200. Missouri. the chapter for ASTM STP 169C. generic caveat. The most important step in standardization 1 Consultant. posure can affect the skin. Professor A. Concrete mix was the first product produced Portland cement is classified as a nuisance dust. the ASTM addresses the hazards of a standard or method with a Department of Civil Engineering. and ASTM C 387. DRY. Portland cement is known to produce a high pH when in contact or mixed with water. disposal of spills. including silicosis. dry. and arately into the package or mixed them in small increments provide other information including. eyes. St. Savannah. W. COMBINED MATERIALS FOR MOR- tar and Concrete was covered in the three previous editions of Hazardous Considerations ASTM special technical publications. classify them by acute and chronic exposure. These locations were accus- tomed to handling 42. Silica sand was concluded to be. This is accomplished with a Material Safety Data tries. lumber yards. fore contain a hazardous statement warning not only of the The first publication of ASTM tentative specification for danger of the inhalation of dust from silica sand and its effect packaged. these issues. was for information only and was published in pulmonary fibrosis. as are a high-strength mortar and specification. Since it is essential that all ingredients be Ingredients used in producing these repair materials dry before packaging. two paragraphs on mixing mortar to comply with the property ify the performance of the packaged materials so that the values of C 270. ments used for these products are not currently addressed Each package must produce at least the minimum physical re.03. and the allowable decrease in length or shrinkage in air Specification for Mortar for Unit Masonry (C 270) that is under after 28 days is 0. Compressive Strength Water Kind of Material Retention 3 days 7 days 28 days Concrete High-Early Strength – 17. ingredient compliance. This is not the case aggregates. and prod- to produce the packaged materials. High early-strength concrete is test. Cementitious Materials for Concrete This specification was first issued in 1980. formance criteria to accept compliance rather than address the cedures require that standard ASTM methods be utilized. and amount of water of testing that are ASTM standards. Sampling and testing pro. homeowner is afforded the same protection of performance as the contractor or highway engineer who also may use prepack. These length change requirements are the jurisdiction of ASTM Committee C 12 and specifies the same based upon an initial length measurement at 3 h age. a section on aggregate preparation limits are not referenced to ASTM specifications.0 (2470) 24. ting times and early strength requirements. age. etc.0 (3480) Lightweight – 17. the specification cretes must comply with the applicable ASTM specification for has kept pace since it was issued.0 (3840) Normal Strength Normal Weight – 17. lar to those in C 387. admixtures. This specification therefore uses per- quirements required for that product. The required compressive strength of would be packaged for distribution. The identification of the The allowable length increase after 28 days in water is mortars for unit masonry are the same as those found in ASTM 0.15 %.15 %. a bond strength requirement . The rejection of products is addressed and may be made In a recent attempt to have the specification invoked by by the user for several reasons. and approved by the consensus process. jection of products are clearly defined. performance levels for the Types N. package sizes were specified. As modern products have ever-faster set- The ingredients used for producing these mortars and con. standardized ASTM tests are required to ver. The responsibility for developing this specification was incorporating both normal-weight and lightweight aggregates presented to Subcommittee C09. ASTM standard for that ingredient. and reasons for re- breakage and water absorption by the ingredients in the pack..0 (2470) Type S 75 12.0 (2470) 24. Container construction require.0 (3480) Lightweight – using normal wt.0 (2480) 24. State Highway Departments. the requirements of this specification are simi- C 270. S.0 (5075) Mortar for Unit Masonry Type M 75 17. Packaging and mark- ments are established to ensure adequate protection against ing instructions are part of the specification. the governing subcommittee decided to revise Furthermore. Dry. Recently.1 % by weight.0 (3480) High Strength Mortar – 20. three kinds of mortar for unit masonry. such as the cements. must conform with the applicable now. in ASTM documents. constituents of the product by prescription. sandA 17.0 (1740) Type N 75 5.632 TESTS AND PROPERTIES OF CONCRETE TABLE 1—C 387 Physical Requirements Min. Testing to verify Packaging and marking include requirements that specify performance and compliance to the specifications are methods the proper product identification.17 because the materials and four types of mortar. in response to State ASTM C 387 Packaged. Dry.0 (2900) 35.0 ( 725) A Lightweight concrete using normal weight sand may contain some portion of lightweight fines of these materials is the requirement that the ingredients used For many years. which have been examined recommended for mixing. Testing cubes for 3-h strength was first addressed in this included in the specification. yield.0 (2470) 24. Rapid Hardening aged products. ucts had to be produced in certain sizes. ASTM C 928 Packaged. normal strength concrete is the same regardless of whether The principle requirement is a 3-h compressive strength lightweight aggregates are used. since many of the ce- the moisture content of dried aggregates to 0. Combined Materials Highway Departments’ requests to standardize the perform- for Mortar and Concrete ance of concrete repair materials being offered in the market- The specification currently covers four types of concrete— place. and M mortars as ASTM Generally. as products can be produced in any size package. Freshly mixed grout using highest water/solids ratio (sug- rapid hardening materials for concrete repair must exhibit a gested by manufacturer) minimum bond strength of 6.0 lb/ft2 (10 kg/m2) of scaled material. 3. 0. This also applies to temperature of place. (supplied by manufacturer) quently adopted by the Corps of Engineers under CRD-C @ Maximum temperature (specified by manufacturer) 621-89a. Use of the Products Performance of the grout in the early volume change (C 827) or height change (C 1090) tests classifies the grout by By Whom grade.2 MPa (1500 psi) at seven days when tested by this method.8) (27. This was not a very convenient method for those who ment and maximum working time. Grout retained in mixer for maximum working time This specification was first issued in 1989 and was subse.6) Very rapid hardening 1000 3000 4000 b (6. This effort is still underway. all grades are required to attain smaller quantities to the do-it-yourself (DIY). consistency at 5 min after addition of the mixing liquid 3 (76) 100 Scaling resistance to deicing chemicals after 25 cycles: Concrete specimens. minimum. market.9) (20. Both rapid hardening and very 1. % Rapid hardening. as . the home- strength limits. the user is advised to consult with individuals skilled in dealing with such matters.7) (27. consistency at 15 min after addition of the mixing liquid 3 (76) 100 Very rapid hardening. Hydraulic–Cement @ Maximum temperature (specified by manufacturer) Grout (Nonshrink) 4.8 MPa (1000 psi) at one day and @ Minimum temperature (specified by manufacturer) 10.0 lb/ft2 (5. was added to the specification. (mm) mortar min. CEMENTITIOUS MIXTURES 633 TABLE 2—ASTM C 928-99 Performance Requirements Compressive Strength. % Consistency of concrete and mortar: Concrete slump min. For the more severe use and exposures that require a higher level of performance. and • Grade C combination volume-adjusting.15 based on length at 3 h. and hardened ASTM Test Method for Bond Strength of Epoxy-Resin Systems grout height change must be run on several grout preparations: Used with Concrete (C 882). after 28 days in air.5 Mortar specimens. as follows: over the years for simplifying the specification. lived in city or urban areas. early volume change (C 827). Nonshrink grouts may be placed at differing owner would have to buy a minimum of one 42. It incorporates a minimum The specification is somewhat cumbersome as compres- requirement for bond strength when tested in accordance with sive strengths. psi (MPa) 3h 1 day 7 days 28 days Rapid hardening 500 2000 4000 b (3. project. DRY. (3. b The strength at 28 days shall be not less than the strength at seven days. max 1.17 mm) for 100 % of its surface would have about 2. been approved. Freshly mixed grout using highest water/solids ratio (suggested by manufacturer) ASTM C 1107 Packaged. of cement. after 28 days in water. One of the major decisions for the original production of In addition to the requirement that the various grades of mortar and concrete in packaged units was the desire on the nonshrink grout must comply with specific minimum and part of the manufacturers to provide these materials in maximum height changes. (254-mm) square spalled to an average depth of 1⁄8 in. FIALA ON PACKAGED. but none have • Grade A pre-hardening volume-adjusting. 2. and enough bulk sand or sand and gravel for his formance criteria. 0. max visual rating 2. Ready-mixed concrete then. • Grade B post-hardening volume-adjusting. % Allowable decrease. c A 10-in. maximum Allowable increase. homeowner minimum compressive strengths at specified ages.4) (13. The minimum physical requirements include compressive Prior to the availability of packaged mixes. The specification currently covers three grades of The governing subcommittee has had several proposals nonshrink grout. Grout retained in mixer for maximum working time This is another example of the continuing review and (supplied by manufacturer) improvement of ASTM specifications by the subcommittee and @ Minimum temperature (specified by manufacturer) committee structure. Dry.0 kg/m2) of scaled materialc a It is recognized that the characteristics and qualities of hardened repair material other than those mentioned in Table 3 might need consideration when certain kinds of concrete repairs are to be made.15 based on length at 3 h.6) Length change.6-kg (94-lb) bag consistencies but are required to meet the same minimum per. Flow of in. 8 mm (2 in.)) are required. The deposit bulk materials for job-mixed concretes and mortars. where the urgency to patch and reopen high- politan areas. and carry mortar and concrete home for those DIY projects. brick and block for various DIY projects.0 0.1) 28 day 5000 (34. small building projects. and barbecue pits. materials add to the contractor’s problem and lead him toward Because many of these repair products have demon- the prepackaged concept. they are becoming increasingly popular for use in other concrete repair projects Applications with contractors.2) 7 day 3500 (24. minimum psi (MPa) 1 daya 1000 (6. High-strength mortar also serves as a mortar to lay packaging of mortar and concrete. In many cases. both small and large. strated their capabilities in highway repair. Concrete mix is also used for other columns and heavy machinery by using material that meets construction and repair needs. today. most prepackaged mortar for unit masonry is not used on ma- Various service companies. 14.634 TESTS AND PROPERTIES OF CONCRETE TABLE 3—ASTM C 1107-99 (Table I Performance Requirements) Compressive Strength.to 90. and others. highway engineer. Sand Today the DIY market is served with a variety of package mix is frequently employed for overlays of deteriorated slabs. where space limitations make it more difficult to ways quickly justifies the use of these more costly materials. other user purposes have brick.3 Minimum. % 0. State highway departments are the largest users surface. These applications require the use of a bonding media to en- lb) bags. where mortar deterioration is much-needed utilities in homes and industry. warehouses. homeowner or do-it-yourselfer.) or Although the DIY market was the primary purpose for the even less. These include floors of garages. served those who purchased a minimum of one or more High-strength mortar or sand mix (sand topping) is used cubic meters (cubic yards).0 Minimum % at final set 0.5. Contractors. where thin layers (less than 50. Contractors will set building pair of existing concrete. especially when the brick is to serve as a walkway. the overlay may be as thin as 6. are finding that packaged mortars and con. such as telephone. and the and manufacturing plants needing fast repair in areas that are list continues to grow. small contractors do use the product for water. patio been served. are also learning that Rapid hardening and very rapid hardening repair products. the packaged materials are essential to their use in both repair covered by ASTM C 928.3 0. are constructing slabs on grade for such uses as driveways. The applications for prepackaged materials are many. and 28 Days Maximum.0 NA 0. This is particularly true in the larger metro. 3. retaining walls. While be made and highways reopened in a matter of a few hours.0 NAb 4. and patios and are using the concretes covered by likely of the prepackaged products to find application by the ASTM C 387. the purchaser must so specify in the purchase contract. such as the construc- larly effective in highway repair work where small patches can tion of parting walls. jor construction sites. The sizing of packages permits the family to purchase sure that the new topping will not separate from the base slab.0 0.8-kg (10.0 a When required. potential for accidents resulting from closed highway lanes is Environmental considerations and disposal of excess or waste sufficient to make the additional cost of materials trivial. ASTM C 1107 in its many consistencies.to 40. Both DIY homeowners and contractors quickly reusable for vehicular traffic. sizes of mortar and concrete from 4. evident on existing brick and block buildings. Prepackaged mortar for unit masonry crete are convenient for their repair jobs as they install their is applicable for tuckpointing.9) 3 day 2500 (17. or driveway. Its uses are established . % NA 0. b NA not available. have their largest application with the and construction. Prepackaged concrete also finds uses in the re. natural gas. Nonshrink grout covered by ASTM C 1107 is the least sidewalks.0 Height change of moist cured hardened grout at 1. These packaged mortars and concretes are particu. of ASTM C 928 rapid and very rapid hardening concrete repair Mortar for unit masonry is used for the typical laying of materials.5) Grade Classification A B C Prehardening Post-Hardening Combination Volume Volume Volume Controlled Type Controlled Type Controlled Type Early-age height change Maximum % at final set 4.35 mm (1⁄4 in. quirements of the specification. In this section. by ASTM specifications. Therefore. the uniformity of the raw materials ages. These tables have been in- the requirements of the user. determined in accordance with ASTM Test The term quality control has many meanings. the cementitious components represent special formulations or combination of ingredients that have limited . The construction requirements of ments may be made with construction supply houses to make packages are included in the specifications. the Specifications are written because of a need to standardize the user also hopes that uniformity of performance is maintained performance of products between what the manufacturer by the producer. These products together with the repair prod. In general. aggre- able in most. hardware stores. lumberyards. All manufacturers maintain some form of quality control Each of the prepackaged mortar and concrete specifications program in order to ensure that the product they make meets has a table of physical requirements. products or sell from their manufacturing facilities. Rejection of Product land Cement (C 150) or ASTM Specification for Blended Prepackaged mortar and concrete specifications incorporate Hydraulic Cements (C 595). prepackaged mortars. the user also may reject a shipment if the meets ASTM Specification for Hydrated Lime for Masonry package weights vary from the printed weight by more than a Purposes (C 207) requirements. C 928. quently referred to as the “shelf life” of the material. package sizes were part of the ASTM specifications. that the ingredients have a reasonable useful life. . Preparation of Aggregates. In many tection for both producer and consumer. This is not Standards for Producer and Consumer the case with ASTM C 928 and C 1107. The most obvious reason for product rejection is that the sonry cements under ASTM Specification for Masonry product fails to meet some or all of the physical requirements Cement (C 91) as well as Portland-lime varieties proportioned of the specification. Other characteristics are included and vary by product. to existing ASTM documents. in accordance with ASTM C 270 where the hydrated lime In addition. The prepackaged mortar and concrete specifications contain a list of physical requirements. Methods for Water Vapor Transmission of Materials (E 96). are listed adhere. the physical retaining a uniform production. or if the average weight of a given number The cementitious components permitted in the production of packages is less than that printed on the bag.1 % by weight. This is fre- struction projects. therefore. specified amount. cluded in this chapter for reference. the producer is required to produce a within the specifications covered in this chapter by reference mortar or concrete to some higher guaranteed performance. Container construction is specified in terms of water-vapor transmission Quality Control of the package. or ASTM C 1157 Performance provisions for the user to reject the product failing to meet re- Specification for Hydraulic Cement. instances. Future Needs of Prepackaged Product potential in the area of mortars and concrete and therefore Specifications have not been considered for coverage by ASTM specifications. he uses is vital to his efficiency. visualizes and what the user demands. ucts covered by ASTM C 928 and the nonshrink grouts covered by ASTM C 1107 can be found in most construction supply Packaging houses. it is Both producer and user have the same goals that can only frequently difficult to develop a specification with a minimum be realized through adequate specifications of the materials of options. For the producer. the section. but currently they are not. ASTM specifications. if not all. There are no other limits to which the manufacturer must The cementitious components. FIALA ON PACKAGED. For this reason. Physical Requirements uct. Mortars for unit ma. Aggregates for ASTM C 887. quality control provides the assurance that Significance of Specifications the product meets the applicable specification. Aggregate quality is specified in ASTM C 387 by reference Concrete Products to ASTM Specification for Concrete Aggregates (C 33) and There are many additional prepackaged concrete products ASTM Specification for Aggregate for Masonry Mortar (C 144). The producer is interested in main. and C 1107 supporting member. In addition. CEMENTITIOUS MIXTURES 635 by the need to ensure positive and complete contact by a gate qualities. This results from the fact that these specifications are basically prescription specifications. There are no similar provisions in the other specifications. with few exceptions. The entire standardization process in ASTM ensures that the where the specifications are written to performance criteria. DRY. and gates shall have a moisture content of less than 0. Arrange. available on the market that should be applicants for coverage These specifications provide for grading and for other aggre. used to produce the end product. All broken of products to meet ASTM C 387 are required to meet existing packages also may be rejected. since this makes his process run quirements involve strength minimums to be met at various test more efficiently. are not specifically referenced but are left to the discretion of the manufacturer through the use of performance criteria. Most producers of these products do not offer the At one time. These components are essentially cements covered either by ASTM Specification for Port. in order to ensure deliveries of full truckload quantities directly to large con. retail home centers. For the user. development of specifications is unbiased and. the The proprietary components used in ASTM C 928 and standards for prepackaged mortars and concrete provide pro- C 1107 are not covered by ASTM specifications. Occasionally. usually with minimum val- Materials ues. sonry produced in accordance with ASTM C 387 utilize ma. Availability The dryness of aggregates is covered in ASTM C 387 under The concrete and mortars covered by ASTM C 387 are avail. quality control is the maintenance of the performance of a product that begins with the raw materials used to produce that prod. A. St. . will follow. depending on the Rapid Concrete Mortar need to place the finished floor in service This specification effort has been underway for some time and A specification effort is presently underway in Subcom- is currently before C9. Shot- that weekend project or for the small-contractor one-day crete is also a reinforcing technique used to repair deteriorated project. Carter.03. and the work of the subsequent authors of this quirements. ment of Civil Engineering. use too much water in placing his concrete. Depart- years. and Owen Brown. Brust. These materials generally utilize fine aggregate chapter. mixes have been offered to meet specific project re. These products need no troweling or secondary place- signed to provide specific performance characteristics for the ment operations. poured-in-place concrete structures. Texas.43.03. modified and un. tant. Many of these materials are pumped in-place user that are being considered by ASTM. Louis. markets. has been available to users for many author of this chapter in ASTM STP 169A. frequently called Gunite when the ma. this product will help the average user produce a better crack-resistant slab. This type of concrete permits rapid utilization sloughing. and self-level much as the spreading of water. It is anticipated that a prepackaged version. Arlington. Savannah. Manager of Quality Assurance. A. under the cracks. Shotcrete materials are frequently used in underground tractor user with a prepackaged concrete with fast-setting coal mines to cover and reinforce the ribs and roof to prevent characteristics.20 A fiber-reinforced concrete mix aids the homeowner in on Shotcrete is preparing a specification for this class of ma- producing a finished slab with a minimum of drying shrinkage terials.636 TESTS AND PROPERTIES OF CONCRETE Fast-setting concrete mix provides both the DIY and con. Shotcrete Acknowledgments Prepackaged shotcrete. C.. Washington University. GA. Because of the general tendency for the homeowner to jurisdiction of Subcommittee C09. Self-Leveling Flooring Materials A new class of floor resurfacing products has emerged from Mortar Products Europe for use in both the construction and reconstruction There are many prepackaged mortar products that are de. Consul- meeting the same specification. They also are employed in major tunnel projects as of the finished slab or footer and is particularly adaptable for temporary support during construction of tunnel linings. mittee C 09. These products are offered in normal or fast-setting varieties. Inc. if desired. Both fiber and non-fiber reinforced. The author wishes to acknowledge the work of the original terial is to be dry-applied. Missouri. W. modified. Subcommittee C09.17. Texas conforming to ASTM C 33 and can utilize coarse aggregate Industries. their own investigations in the mid-90s in an effort to evaluate titious ratio leading to higher strength and durability. will need and 80s. Okamura and his team presented the first publication on Definition SCC in 1989 at the Second East-Asia and Pacific Conference on Structural Engineering and Construction (EASEC-2) [4].56 Self-Consolidating Concrete (SCC) Joseph A. The early results es- dating Concrete. hard-to-reach or highly reinforced sections [3]. Then First named High Performance Concrete (HPC) in Japan in the various publications were presented in the first half of the 90s. Thailand. ACI 116R-90 “Cement and Concrete Terminology” document Large construction companies as well as Precast/Pre- states that the concrete reaches its final compactness through stressed Concrete Products companies also started to take a the operation of consolidation and not compaction.. Professor Okamura from the University of Tokyo Fast Team whose task was to draw recommendations on the use started to investigate the growing durability problems related of SCC in Precast/Prestressed operations by early 2003 [13]. Box 234. reducing the risks of surface common definition. this document presents no consolidation energy was used previously in the late 70s a condensed state-of-the-art description that. As a result. the use of Self-Consolidating scribe SCC [2]. quired less post-demolding operations than normal concrete. this terminology has been accepted worldwide. the name changed to Self-Compacting Concrete [1] to which attracted researchers from other countries. Various definitions have been used in recent years to de. According to a recent National Ready-Mix Concrete tures was the improper consolidation of the fresh concrete Association (NRMCA) survey. Degussa Admixtures Inc. points: The Precast/Prestressed industry quickly realized the benefits of • SCC is fluid enough to fill the forms without internal/ex. the industry as well as the scientific lished in Japanese. Rec- then. pled with the reduction of labor was an obvious motivation for • SCC remains homogeneous during and after placement. Therefore. The [10–12]. the acronym SCC will be tablished that SCC could be poured in a shorter time and reused indifferently of the terminology. tural segment of the industry also saw the aesthetic advantage However. the Netherlands. late 80s. The acceleration of the pouring process cou- ternal energy. with SCC. In this document. OH 44652. ommendations and guidelines for the use of SCC were devel- in the United States. and guidelines for the use of SCC were pub- a relatively new material. 8282 Middlebranch Road. By the end of the year 2000. Middlebranch.47 on SCC as well in using a concrete that easily flows even through restricted ar- as the American Concrete Institute (ACI) has yet to agree on a eas of the form without vibration. Therefore. Since the potential benefits SCC can bring to the industry [5–9]. Inc. 2 Essroc Concrete Technologies. Korea. serious look at this technology. Daczko1 and Martin Vachon2 Preface concept of a high durability concrete requiring no consolidation to achieve full compaction—SCC was born. In 1986 he proposed the cated they were either testing or occasionally producing SCC. but mainly for logistic reasons. either to increase placing rate or to allow placing in further updating. defaults and homogeneity. to concrete structures in Japan. which is concrete based on the use of low water/cemen. if needed. the concept was refined to permit the use of local discussed in this technical publication for the first time. Being raw materials.O. in 2002 a proposal was made to adapt the oped through cooperative work in Europe by the late 90s terminology to make it compatible with ACI terminology. not for its increased durability in 2002 a new ASTM terminology was adopted: Self-Consoli. 1 Product Line Manager. 22 out of 23 respondents indi- due to unskilled labor on the jobsite. Most of them share the following common Concrete (SCC) started to spread throughout the United States. In the follow- SELF-CONSOLIDATING CONCRETE (SCC) IS BEING ing years. The Precast/Prestressed Concrete Insti- tute (PCI) has been very active in 2002 with the creation of a In 1983. It should be noted that concrete requiring community is still learning. the ASTM Subcommittee C09. One of his finding was that a The Ready-Mix Concrete industry is also experimenting major cause of the poor durability performance of these struc. potential. this technology. and Canada started HPC. The Precast industry is driving the SCC technology imple- History mentation in the USA. The architec- • SCC is able to flow through dense reinforcement. 637 . However. the producers of structural concrete elements. avoid confusion with the more widely accepted definition of Sweden. P. in time. The use of SCC can have a significant impact on the working en- SCC can replace conventional plastic concrete in almost vironment [17]. 4—Architectural panels. Table 1 summarizes the various benefits. and walls to floors.638 TESTS AND PROPERTIES OF CONCRETE Fig. The concrete was mixed on-site But there are other advantages. from Surface Quality 2. from its ease of placement resulting in shorter pouring time. The applications are various and cover most of the new dimensions for shape and textures. 6. concrete ele- the estimated 2003 SCC production is still under 100 000 m3. ments or buildings will be designed considering SCC from the start with shapes. SCC was first used in 1991 for the construction of bridge tow- ers in Japan [14]. still marginal with less than 1 % of penetration in both Ready As a result.g. . when m3 of SCC was used. used where the SCC had to maintain a 30 % slope [16]. architectural precast concrete producers can Mixed Concrete (RMC) and Precast/Prestressed [15]. and architectural panels. ever. and Environmental Benefits utilities (Fig. 1—Akashi-Kaikyo Bridge. the anchorages of the bridge.5 to 2 years because of the use of SCC. It is estimated that the construction time was shortened by 20 %. It can still be anticipated that. textures. workers from 150 to 50. For architects it also opens erations. it is difficult to establish precise trends as each plant has different constraints. wet-cast industry. was for the construction of the walls of a natural gas quality (Fig. Again. SCC can be advantageous for the produc- The applications are multiple. the concrete will ened from 22 to 18 months while reducing the number of lose enough paste locally to change its surface quality (Fig. SCC’s high deformability allows for a better-molded surface in 1998. the first large-scale project using Advantages SCC has been the Akashi-Kaikyo Bridge. Therefore. application is mainly driven by the cost per unit. e. Moreover. SCC elements have very few bug holes. However. architectural elements (Fig.. tilt-up.S. completed in 1998 As previously mentioned. 1). in the future. 3—Bridge. the use of SCC in Japan is dotted line). 6). However. 2—Double T. the obvious advantage of SCC comes (Fig. How- Fig. 5). the successful use of SCC for a given Fig. However. because the raw material cost to produce SCC is higher than for normal concrete. and pumped into the forms through a pipe system. If placed adequately (see section on place- tank for the Osaka Gas Company where approximately 12 000 ment). SCC is mainly used in precast for structural (Figs. ranging from structural columns tion of beams in Plant A but not in Plant B. 2 and 3).. These are the recommended standards from any Precast/Prestressed application. and structures that would be im- Applications possible to achieve with normal concrete. It has even been reported the Netherlands. 4). Fig. SCC is mainly used in Precast/Prestressed op- fects after demolding the elements. A second application. In the U. the construction period was short- leakages occur in the forms under vibration. Over 290 000 m3 of SCC was used for the construction of This advantage alone can justify its use for many applications. significantly reduce the time allocated for patching surface de- In Europe. . specific raw material Admixtures characteristics can help achieve better performances. Unlike for conventional concrete. Supplementary cementitious materials such ture (VMA) can also be used to improve the stability of an SCC as ground granulated slag. air-void system. since it will significantly influence the stability as well of ASTM Specification for Chemical Admixtures in Concrete (C as the cost of the mix. and shrinkage cost. 5—Jail cell. as it can increase the stability of the mix and reduce the need for additional cementitious materials. Other admixtures such as beneficial to increase the stability of the mix and/or reduce its set accelerators. Fig. cation for Hydraulic Portland Cement (C150). When needed. just to name a few. Rounded or cubical shaped coarse aggregates are easier to use than angular aggregates as they facilitate flow. ious HRWR will have different effects on the mix stability and. a high proportion of engineering standpoint. or silica fume can also be mixture by increasing its viscosity. However. 6—Surface quality-normal concrete (left) and SCC (right). fly ash. To achieve the high fluidity it is rec- Cementitious Materials ommended to use a High Range Water Reducer (HRWR). However. a Viscosity Modifying Admix- ing cement type. make the SCC mix more cost efficient. as long as they are not dele- Hardened Properties section. The usual air en- cation for Hydraulic Cements (C 1157) can be used. These benefits will be reviewed in the fine particles (passing #200 sieve). However. SCC can be produced with any materials used for the production of conventional concrete. Natural as well as manufactured sand can be used for Other advantages can also be expected from SCC from an SCC. DACZKO AND VACHON ON SELF-CONSOLIDATING CONCRETE 639 materials can help reduce the paste content requirement and. and complementarities. The raw SCC can be produced with the same admixtures used for nor- material selection is an important part of the mix design process mal concrete. Engineer. Var- Hydraulic cement meeting the requirements of ASTM Specifi. Fig. the higher will be the requirements in viscosity in order to keep the mix homogeneous A safer and more comfortable working environment can as it flows through obstacles. retarders. Where the use of ground limestone is permitted. training admixtures can also be used to generate the adequate ing and durability concerns must be considered when specify. size. corrosion inhibitors. or Performance Specifi. the larger the aggregates. Chemical admixtures meeting the requirements for SCC. can be used with SCC. the addition of ground limestone may result in increased drying shrinkage values and should be considered during the mixture design and qualification process. which are two key elements in the suc. Aggregates The aggregate should be selected based on their shape. the set of materials available at the plant. it can help produce highly stable and flowable mixes with a reduced impact on cost. Specification for consequently. 494) and air-entraining admixtures meeting the requirements cessful use of SCC. therefore. The quest for a well-graded combination of cementitious reducing admixtures. of ASTM Specification for Air-Entraining Admixtures for Con- crete (C 260) may be used. terious. also attract better skilled labor and reduce employee turnover. can be beneficial. trials should be made to select the right one for Hydraulic Blended Cements (C 595). There is no limit to the maximum aggregate size. Materials Aggregates meeting ASTM C 33 requirements are appropriate for producing SCC. The paste is the phase that provides the plas. factor comes into play to influence the concrete fluidity: the erties). well-balanced combination of dry aggregate combination void The paste design involves the determination of the w/c and sup. by blocking gaps between rebars (Fig. the higher the concrete fluidity will be. It is important then to take great care when designing it. ACI is re. another should first be established (fresh and hardened concrete prop. .2 mg/m3 Industry goal is 1 mg/m3 Savings due to elimination of Energy Consumption: 10 % vibration Forms cost: 20 % Maintenance Cost: 10 % Illness time: 10 % Mix Proportioning a plastic material when all the voids between the aggregates are filled (Fig. However. volume. Consequently. on the SCC raw ing the ACI and PCI guidelines or project specifications. 8). and passing ability for the application at the lowest paction without external energy. aggregate proportioning will have a direct ef- strength and durability and should. This balance is not easy to achieve and guidance from volume. concrete fluidity is managed through a bility.01 mg/m3 Max 0. aggregates proportioning should be made ticity/flowability to the concrete. fect on the filling paste need and. plementary cementitious materials replacement ratio and should be based on structural and durability needs.75 to 4 m/s2 0 m/s2 Protective measure required if 0. Fig. the Step 2: Paste Content Optimization largest aggregates often have a tendency to restrain SCC flow The paste content selection is a critical part of the mix propor. However. duces the aggregates interaction as the concrete flows by in- sponsible for mixture proportioning and ACI 211 is develop. its Step 1: Designing the Paste ability to keep the aggregate in suspension (yield stress) de- The paste is the driving force of strength development and dura. As for any concrete. the higher will be the SCC flu- This section will briefly cover the basic elements of SCC idity. when flowing through reinforcement. fluidity paste volume. tioning process. be designed us.075 mg/m3 Dust 3–4 mg/m3 0. creasing the distance between the aggregates. and paste fluidity level. goal is always to achieve an adequate level of fluidity. the expected performances a report that includes placement guidance. supplementary cementitious materials. It is then important to optimize the aggregates documents will guide you in the right selection of cement type. as the paste fluidity is increased by the addition of superplasticizer. However. These material cost. The greater the ing guidelines. This complementary paste volume (fluidity paste) re- an experienced SCC technologist may be required. the highest packing density is usu- ratio. ally obtained with a high fraction of the largest coarse aggregate. The optimum paste volume in order to reach the right balance between packing density selection is a complex process. there are four steps to consider in the mix design paste fluidity. sta. therefore. distance between the aggregates. Then. ACI Committee Self-Consolidating Concrete is preparing mix design. The concrete starts to behave as and flowing ability through reinforcement. However. For a given paste volume. SCC requires additional paste cost. 7—Paste content optimization. proportioning towards the highest possible packing density. Consequently. indirectly. the A minimum volume of paste (filling paste) is then required. 7). creases. the higher the paste flu- methodology: idity.640 TESTS AND PROPERTIES OF CONCRETE TABLE 1—Benefits of SCC (Recommended Standards from the Netherlands) Normal Concrete SCC Recommended Limits Noise Protection 93 dB 80 dB Protective measure required if 80 dB Vibrations 0.25 m/s2 Quartzite dust Not measured 0. Various concepts exist for the design of SCC. SCC obeys Step 3: Aggregate Proportioning the same relationship as regular concrete with respect to As seen in Step 2. Because of the high level of fluidity required to achieve full com- bility. and water/cementitious For a given set of aggregates. Placement Batching and Mixing SCC can be placed by most methods used for conventional concrete. set of admixtures. therefore. it is almost impossible to antici- pate the admixture dosages without running test batches. Some equipment. except for discharge type. and admix. Table 2 be able to detect changes in moisture content of 0. With mixing trucks special attention should be paid to load size if the terrain is hilly due to the fluid nature of SCC and a tendency to spill [21]. Step 4: Admixtures Dosage Adjustments SCC can be discharged and placed much faster than con- As with any other type of concrete. The the aggregate resulting in blocked pump lines. is either continuous or discontinuous. if not designed properly. However. sume constant drop heights. is used with SCC. impart energy into the concrete.. The workability retention of the mixture being used should be evaluated to correspond with the maximum haul time possible for the project under consideration. Transporting All of the four categories. Therefore.5 % [12]. aggregate moistures is critical during batching operations. dency to segregate [22]. mined as a combination of all of the three aforementioned categories. Each sary based on the mixture proportions. The relative ratings as- tor trucks. including agita. This should be discussed and tion. This sequence should be established during gories: the mixture qualification stage [12. air content. pumping the concrete’s performance [18]. may have a ten- Fig. The energy imparted to the concrete during placement should Some guidelines require that in-line aggregate moisture probes be considered during the mixture development stage. upon the placement equipment/technique used [23]. mixture is critical to ensure that the paste is not forced past quirements as those for producing conventional concrete. etc. If transport is made with nonagitating equipment. excellent control of pressures may be higher or lower than conventional concrete.. are given a relative rating of high. In the absence of agitation the mixture. ment intermittent or continuous? timum mixing time for an SCC mixture will be influenced by • Single Discharge Volume—How much concrete will be the plastic viscosity of the mixture. therefore.19]. may require attention to reduce or eliminate affect the amount of energy delivered to the concrete. • Discharge Rate—The volume of concrete being discharged Some SCC mixtures may require longer mixing time to over a set time frame. medium. DACZKO AND VACHON ON SELF-CONSOLIDATING CONCRETE 641 any tendency for leaking. A higher viscosity mixture placed prior to the first stop in placement? will require longer mixing times than a lower viscosity mixture • Relative Energy Delivered—This is the overall rating deter- to reach a steady state in fluidity. buckets. This is particularly important if the concrete is to be delivered across an area that will cause jostling and. retarda. etc. which would also certainly such as buckets. SCC has been • Discharge Type—Is the energy being supplied during place- mixed in precast plants using only a 60-s mixing time. ventional concrete. TABLE 2—Relative Comparison of Placement Techniques and Energy Delivered [23] Single Discharge *Relative Energy Placement Technique Discharge Rate Discharge Type Volume Delivered Truck Discharge High Continuous High High Pumping Medium/High Continuous Medium High/Medium Conveyor Medium Continuous High High Buggy Medium Discontinuous Low Low Crane and Bucket High Discontinuous Low Low/Medium Auger (Tuckerbilt) Discharge Medium Continuous Medium Medium Drop Tube High Discontinuous High High . or acceleration will have to be optimized experimentally. placement technique is given a relative rating in four cate- tures being used. precise coordination between quired to obtain the desired level fluidity. special care should be taken to ensure that the SCC mixture being used is stable. the dosage in admixtures re. shows the relative energy imparted to the concrete depending A specific batching sequence of materials may be neces. Discharge type Traditional concrete transporting equipment. Depending amount of free water in a SCC mixture significantly influences upon the viscosity of the SCC mixture being used. 8—Aggregate blocking. The op. materials. Therefore. delivery and placement is critical. If the SCC is to be pumped an appropriately stable Concrete batching and mixing systems should meet the same re. a delivery/placement plan be agreed upon prior to the start of The reason is that every cement reacts differently with a given the job. produce a homogenous mixture [20]. or low. The use of SCC can permit greater design flexibility in concrete elements. values [30]. but it is influenced by many SCC follow the same general rules as conventional concrete. During placement. . If elements are Finishing and Curing intricate in design or if the formwork has multiple corners. variables including the type of SCC mixture as well as the cast. Depending upon the fluidity retention characteristics of the suggested a maximum flowing distance of 15 m or less to elimi. a mixture coating of form oil should conform to the minimum required that retains its fluidity should be developed to eliminate any or as recommended by the manufacturer. Therefore. sive creep and a decrease in the modulus of elasticity (MOE). mixture. it has With lower viscosity SCC mixtures some bleeding of the been found that in some precast operations steam curing can mixture through gaps in formwork is possible. a larger the in-place concrete [24]. the time the gaps are small enough so that they become plugged very quickly with mortar and no problems are experienced. The timing of the finishing procedures becomes criti- The Japanese Society of Civil Engineers (JSCE) has cal. the surface may not hold a broomed or roughened sur- nate the potential for separation of the paste from the aggre. Further research is of cementitious materials as well as an increased sand-to-total- underway in this area to investigate the influence of the con. Uncontrolled place. cated to any job using SCC in flatwork. It should be noted that SCC mixtures could be de- fresh concrete continuously being introduced into the bottom veloped to produce acceptable shrinkage. Some studies have shown that the pressure on formwork SCC is produced using the same materials used to produce of SCC mixtures may be less than that of vibrated concrete and conventional concrete. dency to bleed. aggregate ratio (s/a). In addition. Excessive form oil can be pushed ahead of the flowing SCC mixtures can be produced to provide good durability concrete and cause staining of the elements. Other examples have been cited in surface area of concrete will need to be finished at a single time. The method of placement has been shown to influence the Some SCC mixtures will have a significantly reduced ten- surface finish of pieces cast with SCC [21]. In addition. form. Therefore. the discharging concrete The measures required are those similar to when one is using should be flowing in the same direction as the concrete in the silica fume concrete. Improved durability (due to absence of vibration) Fig.642 TESTS AND PROPERTIES OF CONCRETE If a discontinuous placement technique is used. the hardened properties of less than full hydrostatic pressure. sure on the bottom of the form will never be reduced due to However. These adjustments to a mixture may re- crete’s rheology on form pressures. The rate of placement should be such that any entrapped With the mixture proportions used in SCC and a new gen- voids are provided the opportunity to escape. an adequate number of finishers should be dedi- free-fall dropping heights greater than 5 m [25]. The majority of be significantly reduced or eliminated [29]. Some SCC mixtures are produced using an elevated content ing technique and placement rate [26–28]. the properties. with SCC. eration of polycarboxylate high range water reducers. chance for pour lines or cold joints. a SCC mixture with a moderate viscosity and relatively higher All typical techniques for finishing concrete can be employed level of fluidity will be necessary. because the volume of SCC that can be maximum dropping height of 5 m to ensure homogeneity of placed is greater than that of conventional concrete. creep. formed surfaces. SCC Hardened Properties mixtures can be developed to overcome this issue. appropriate measures should be ment can lead to entrapped air voids that can migrate to the taken to eliminate the possibility of plastic shrinkage cracking. face immediately after placement and some time delay may be gates during placement. the JSCE has suggested a necessary. 9—Slump flow test. and MOE of the form [27]. North America where SCC has been successfully placed with Therefore. the pres. therefore. If mixtures are pumped sult in a relative increase in drying shrinkage and compres- from the bottom up (usually for aesthetic reasons). When developing a mixture. was one of the major reasons for the initial development of Monitoring the time it takes for the concrete to reach a SCC. such as the column seg. Slump Flow Test This procedure relies on the use of the Abram’s cone. as well as its SCC characteristics of fluidity. . 10). The V-Funnel is presented Concrete Rheometer in Fig. 10—U-Box and L-Box filling apparatus. such as the slump flow test. and other rheological characteristics of SCC. They provide indication on the static and Test methods have been developed worldwide to quantify the dynamic segregation resistance of a SCC (Fig. are useful for laboratory development and others. They are frequently regation resistance). These two tests simulate the casting process by forcing a SCC sample to flow through obstacles under a static pressure. are recorded. passing ability and stability (seg. 11—V-Funnel apparatus. Fig. U-Box surface values. but they all simulate more or less real scale casting environments. used in the field as an acceptance test method. The Quality Control final height H and H2/H1 for the U-Box and the L-Box. The force is then converted into stress. are useful for acceptance V-funnel and Orimet testing in the field. these two test methods give an in- from one country to the other. knowing the flow distribution of the concrete in the device. A rheometer is a device that applies a range of shear rates and monitors the force needed to maintain these shear rates in a plastic material. DACZKO AND VACHON ON SELF-CONSOLIDATING CONCRETE 643 Fig. dication of its viscosity. it should be noted that the slump flow of 500 mm can also be done as an evaluation of mixture stability will influence the air-void system. If a mixture SCC viscosity. is unstable it may allow for the coalescing of larger air bubbles resulting in increased spacing factors and decreased specific L-Box. respectively. The cone is filled in one layer without rodding and the diameter instead of the slump of the concrete sample is measured after the cone has been lifted (Fig. However. A few of these methods are briefly pre. The dimensions may vary orifice under its own weight. ability to flow through reinforcements. This test is mostly used for evaluating the SCC self-compactibility as it mainly relates to its yield stress. Some methods. allowing drawing the stress/shear rate relationship. 9). Neither one of them allows for measuring yield stress or viscosity. this type of equipment is fairly expensive and not easy to use at a job site. Therefore. A few concrete and mortar rheometers are available on the market and have been and are still used for measuring the yield stress. regation test. viscosity. By monitoring the time it takes for the SCC to flow through an sented in the following paragraphs. Both tests are used in the field and are sometimes used as acceptance tests. numerous lighter test methods have been developed for SCC. 11. They are of a tremendous help in the understanding of SCC behavior. Figure 9 shows how the relationship be. A. it has been shown that the fluid. the spread difference [1] Ouchi. It is high per- Abrams cone or the Orimet setup. Japan Sieve Stability 1998. M. M. M. thought should be given to establishing appropriate quality Berlin. One can find the point at [5] Skarendahl. Evanston. Kochi. 1. the maximum slump flow value then is set at this on Self-Compacting Concrete. to set quality control parameters.1–16. K. Maekawa.. proportioned with consistent “Development of High Performance Concrete Based on the Durability Design of Concrete Structures. 12—J-Ring. The French Civil Engineering Asso. control criteria. the Netherlands. pp. Japan 1998. structures will be designed and constructed with SCC and without the ring or the height difference between the con. This procedure is used to evaluate the resistance to static seg.5 times the maximum aggregate size. This is good news for the concrete industry. ciation has published a complete procedure (in French and [3] Collepardi. 445–450. “The Development of Self-Compacting Concrete in can be used rather than the column segregation test for qual. K.. Kochi. The concrete is flowing from formance in the plastic state. A sample of concrete is poured over a 5-mm ceedings of the First North American Conference on the Design sieve and the amount of mortar passing through the sieve in a and Use of Self-Consolidating Concrete. ity level of a given SCC mixture. Regulatory Work on SCC. Kunishima.” Proceedings of the Interna- tional Workshop on Self-Compacting Concrete. 2-min period is measured. and Okamura. “Self-Compacting Concrete in Sweden. pp. Kochi. in the years to come..1–10. in mind.. 1998. Once it becomes a more mainstream tech- ment configuration. “Self-Compacting Concrete: What is New?. It must be used in conjunction with an SCC is considered a high-performance concrete.. M. 377–380. some perplasticizers and Other Chemical Admixtures in Concrete. Germany.S.” Pro- regation of a SCC. pp. tween the column segregation test and slump flow can be used Chiang-Mai.. J-Ring Conclusion This apparatus is used to force the SCC to flow through reinforcement (Fig. The size and the spacing technology has the potential to change concrete construction between the bars can be adjusted to simulate any reinforce. For example. 2003.. on Self-Compacting Concrete.. [4] Ozawa. pp. crete inside and outside the ring are measured. 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FL.” Proceedings of the 3rd International RILEM Symposium Institute. Vol... accuracy. 187 ACI 308R. 348–349 autogenous curing method. 146 ACI 506. 535 ACI 201. 616–617 grading. AASHTO T259. 17–18 lightweight aggregates. thermal conductivity cement chemistry effect. radiation shielding. 543 Aggregates surface treatment and. 553. 167.1R-98. 595. accuracy. 513 self-consolidating concrete. 59 353–354 cross section. 263–265 AASHTO M148. aggregates. 514 tory. 324. 618 bulk density. 275 625 ASTM C 1138. 246 ACI 116R. 142–143 ACI 506.G. 227–228 experimental program. 185 ACI 304R. 246 ACI 121. 311 ACI 121. 513 procedure significance.2R. 617. 484 modified boiling method. 627 539 Accelerated curing. 146–147 ACI 805–51.4R-94. 65. 311 application of test methods. 184. 190 ACI 216. 504 AASHTO Materials Reference Labora. 599 alkali-silica reactivity. 627 batching and measuring materials. 184–185 Absolute volume method.1R. 185 AASHTO TP 164. 622 characteristics. 261–262. 63. 535 see also Air-entraining admixtures. 191 ACI 211.1. 185–186 ACI 228. 328 mortar. 114–115 apparatus. 622 examination. 184 ACI 211. 410 measurement. 186–187 ACI 301. Accelerating admixtures.. 82 lightweight aggregate concrete. 141–142 ACI 506. 573 ACI 318. 472 abrasion resistance and. 170. 143 pozzolan. 457 Abrasion. 637 626–628 AASHTO T260. 599 definitions. 262 abrasion resistance and. 319. 80. 639 curing and. 250 ACI-209R-92. 184–192 ACI 211. 52 Acceptance plans. 467. 556 drying shrinkage and. 600 ACI 306R. 244. 190–192 ACI 228. 145–146 Activity index AASHTO M240.1R-04. 62 Acceptance testing. 617 and. 311 AASHTO T199. 302 AASHTO M171. 219 shotcrete. 19–20.3-82. 513 warm water method. 353–354 ACI 363. 83.5R.2. 187 ACI 234R. 619. 471 absorption measurement. 22–23 concrete. acceptance testing. 28. 339 647 . 469 test Acoustic shielding properties. 22 Additives. 467. content analysis in hardened AASHTO R18.3R-91. 616–617. 620 finishing procedures and. 620 alkali-carbonate rock reactivity. 218 ASTM C 779. 64. 621 content analysis in hardened Abrasion resistance. 187–192 ACI 214. 366 tests. 19–20. 201 ASTM standards. 208 AASHTO Accreditation Program. 184 Chemical admixtures mixture proportioning and. 51. ASTM C 944. 351–352 ACI 503. lightweight aggregate concrete. 623 coarse high temperature and pressure ACI 544.1R.1. petrographic quality of aggregates and. 551–552 555–556. 587 degradation. 484 Admixtures AASHTO T318.4. 144–145 hydraulic cements. 558 ACI 302. 366–367 method.2R-96. 599. 210 roller-compacted concrete. 84. epoxy resins. 65. 495 ASTM C 418. 358 ACI 503. 141–149. 45–46 AASHTO T277.3R. 339.2R. 68–69. 149–152 ACI E4-04. 437–438 AASHTO M302. 82. 592 Aged concrete. 544. Absorption ACI 309. 54 results.Index A maturity method.2. 53 Acceptable quality level. 554. water. 184–185 ACI 304. 469 precision. 187–188. 143–144 ACI 506. 608 concrete types. 247 ACI 207. 346 ACI 308T. 622 bleeding and. 84. 621 concrete.4R-93. 59–60. 484 Adiabatic temperature rise. aggregates. 185–186 ACI 233R. 143–144 ACI SP 191. 202 chemical composition. 485 slag. 190–192 ACI 213. 137 polymer-modified concrete and compressive strength and. 17–18 Adhesive materials. 142–144 Acid attack. 471 ACI 506R. 407–408 AASHTO TP 64. 470. self-consolidating concrete. 292 test methods. 477–478 elastic properties. 639 sequence of material addition and. 75–76 polymer-modified concrete and quarry sampling. 347–348 supplementary cementitious materi- workability and. 134–135 shape and texture. 597–598 microscopic. 73 compatibility with slag. 365–366 pressure air measurement. 349–350 gravimetric. 561 Air-void system frost resistance. 311 surface texture. 347–348 influence on behavior and perform. 383–384 shape. 291. 77 test result interpretation. volumetric method. 343. 358 type and amount. 75 preplaced aggregate concrete. 13–14 materials used as. 481 dry rodded. 410 hydraulic cements. 365 on density. 573–574 voids. 348 unconfined. 474–481 compressive strength at high specific gravity. 429 definitions. 369 Air cells. entrained. 356–360 Air-entrained concretes. 294–296 polishing. 598 deleterious substances. preplaced aggregate of algae in mixing water. 592 Air ice formation. 609 . 288–289 296 permeability. hardened fresh fiber-reinforced concrete. 294 packing. 373 wet degradation and attrition tests. 291–292 preplaced aggregate concrete. entrained. 346 measurement. 355–356. air content measurement and. 339–340 water absorption. arbitrary deletion. 476 fire resistance and. 474–475 content analysis in hardened surface moisture. 61 cellular concrete. 293–294 pavement wear and. 537–538 proportions in hardened concrete. 289–290 mortar. 338 ance of concrete. 592–593 of hardness in mixing water. pores and pore distribution. 5 thermal expansion. 562 shrinkage. 396 definition. 76 variability and uncertainty. 371 underwater abrasion test method. 277. 372–373 mixtures. particle size distribution. modified point-conduct method. 62 coefficient of thermal expansion. 342–343 recycled concrete. 239 polymer-modified concrete and 368–370 freeze-thaw damage and. 608 411 pressure versus with potentially expansive rock. 538 concrete. 12. 293–294. 74 mortar. 299 microscopic analysis. 372–373 effect of surface preparation. 168 lightweight aggregate concrete. 12 future trends. 296–297 physical properties. 12 classification. 290 Air content. 337–340 air-entrained concretes. 581 image analysis techniques. 12–13 strength. 76 422 roller-compacted concrete. 351–352 determination. alkali reactivity. 478 volume fraction and drying Air-free unit weight test. 290 concrete. 526 specifications. 304 geometry evaluation. 476 high-strength. 337–338 function in fresh and hardened size and distribution. freeze-thaw testing. potential alkali reactivity. 475–476 measurement. 298–299 concrete. 369–370 289–290 concrete. 639 density. 619 als and. 73 attributes. 348–349 grading effect. 288–304 achieving dispersion and small bub- grading. 476–480 shape. 12. 73 ble spacing. 76–77 mortar. 73–74 polymer-modified concrete and reducing field samples to testing size. 475 frictional properties. 352–353 ready-mixed concrete. Air entrainment to enhance radiation shielding 368 freeze-thaw durability. 298 383–384 fresh concrete. 14 proportions in hardened concrete. 76–77 linear transverse method. 290 hardness. 480–481 manufactured. effect. 553 precision and bias. 340 fine void space. air content. 13 status of specifications. 371–372 effect calculation errors. 127. 608 see also Petrographic evaluation gradation. 505 coatings. 218 Air voids grading. 292–293 freeze-thaw tests. 340 wear. 384 structure. 406–407 freeze-thaw damage mechanism. 279 specific heat. 374 Air-entraining admixtures. 362–363 size. 360–362 thermal properties.648 TESTS AND PROPERTIES OF CONCRETE Aggregates (continued) reactive. 277 concrete. 294–299 innocuous. 372–373 dispersion and spacing. 370–371 hydraulic cements. 474 consistency. test. 404–406 significance and use. comparison of fresh and hardened Micro-Deval test. 425–430 self-consolidating concrete. relative density. 592 sampling. 300 426–427 soundness. 421–422 sampling. introduction into plastic spacing factor. 78 297–298 porosity. 303 transition zone. 446 constituents. 465 freeze-thaw durability. 295–296 nomenclature. 405–406 gravimetric method. 446–447 microscopic analysis. 79 origin and geometric characteristics. 77–78 290–292 properties. 65–66 air entrainment and. 13 workability and. 477 temperature. 292 fineness modulus. purposely. 465 effective. 65 shotcrete. factors influencing in large. 340–342 479 size and flexural strength. 298 high-density. 388 fresh versus microscopic. 411 ready-mixed concrete. 426–427 roller-compacted concrete. 350– 351 faulty testing. 620 607. 551 admixture. 405 fly ash and pozzolan. 544. 478 expansion. 401–403 ASTM C 123. 118. 62. 404 ASTM C 115. slag effect. test result interpretation. 61. 221. 420–421 ASTM C 67. 544 457 potential. 384 aggregates. 280 402–404 ASTM C 109. 600 ASTM C 191. 184–185. portland cement. 537. locations. 419 shape. 392. 292. 136. 457–459. 19. 436–438 ASTM C 265. 440–442 symptoms. 404–406 mixing operations. 62. 76. 562. 65. 635 ASTM C 207. ASTM C 173. 133–135. INDEX 649 ready-mixed concrete. 639 mental effects. 419–420 397. 119–120 mitigation. using coarse aggregate with poten. 542–543 480. 620 ASTM C 150. 301. 410–411 ASTM C 25. 471 compared to alkali-silica reactivity. 395. 420. 383. 339. 421 ASTM C 33. 28 ASTM C 187. 342–343 ASTM C 185. 358. 151–152. resistance to. 597. 441–442. 366. ASTM C 243. 26 mechanism of reaction and surface texture. 380. 407–408 462. 598 411 grading. 292–293 Alkali test method. 505–506 543–544 ASTM C 231. 512. 417 ASTM C 39. 539–540 ASTM C 219. ASTM C 188. 53. 578 chemical requirements of portland ASTM standards. 60–61. ANSI A118-4. 349–353. 84–85. 384. 196. 379. 441. Alkali-aggregate reactivity. 233. lightweight aggregate ASTM A 497. 495. 32. 515. specific surface. 26. 480. 279 159 tially expansive rock. 84–85. 59. 84. 355. 265 . 36. 614 ASTM C 266. 53. 395. 227. 340–342 ASTM C 183. 543. 196. 421–422 622 ASTM C 190. 420. 46. 200. 119–121 identifying potentially reactive 544 ASTM C 233. 390 ASTM C 206. 175–177 616–617 with and without air-entraining Ambient conditions. 447. 639 553–554. 407 mixing water. 44. 639 410–422 ASTM A 820. 538–539 ASTM C 227. 413–415 128–129. embedded. 421 ASTM C 42. 474. 157–158. 361. 444. 564 field service record. 457. 157. 413 cementitious materials. 439 composition. 401–402 ASTM C 91. 291 470–471 ASTM C 128. ASTM C 214. 77–78. 257. 337–340 ASTM C 177. 543 ASTM C 236. 75. 360. 448 safe reactions. 389 ASTM A 617. 77. 435. 430. 387. 374. 558 ASTM A 615. 155. 179. 581 release. 405. 608. 382 ASI 342. ASTM A 767. 581 distress manifestations. 444. 53. 81. 84. 53. 581. 107 limiting cement alkali level. 562. ASTM C 157. 289. 127–128. Alkali Accreditation. 81. 362. 480. ASTM C 232. expansive dedolomitization reaction. 460 ASTM C 125. 310 ASTM C 204. 40. 635 Alkali-silica reactivity. ASTM C 127. 620 446–448. 361 ASTM C 267. 234. 80. ASTM C 156. controlling. 61. 620. 46. 310. 359. 63. 439. 115. 359. 598 hydraulic cements. 299–300 Aluminum. 467. 500 480–481. 635 structures with. 349–353. 553. 361 mechanism of reactions and distress. ASTM C 114. 355–357. 539 ASTM C 235. 61. 465 American Association for Laboratory ASTM C 131. 53. ASTM C 186. 348. 437. 474 reactivity. 244 ASTM C 142. effects on curing. 635–636. 358. 74. 444. 619. 82. 108 ASTM A 706. 620 ASTM C 144. 554 concrete. 53. 221. 299. 46–47. 53. fly ash and natural pozzolan. 53–54 366–368 content. 337–343. 554. 372. 84. 359. 411–413 562. 437. 53. 88. 437. 621. 66–67. 84. 74. 19. 394 Alkali-aggregate reactions ASTM A 185. U. 219. 597. 539 318–319 compared to alkali-carbonate rock batching plant. 459 cement. 488 299. 538 Alkali sulfates. aggregate constituents. 292. 554. moisture availability and environ. 281. 436–438 Alkali-reactive dolomite. 418–419 ASTM C 88. 451. 453–455 chemical and mineralogical ASTM C 29. 292. S. 80–81. 63. 447. 450–456. 84. 437. 80. ASTM A 616. 437. 53. 280. 476. 441–440. Alkali-carbonate rock reactivity. 620 ASTM C 143. 442. 337. 131–132. 444 rock cylinder expansion test. 501–502 390. 620. 411 ASTM C 70. ASTM C 171. 18–19. 212. extraneous sources. 253 ASTM C 192. 311. 437. 219. 614 ASTM C 138. 127–128. 620 260. 407 Anti-washout admixtures. in mixing water. 5. 315–316. 587 concrete microbars. 457 by admixtures. 413 554 442. 520 514 ASTM C 260. 450 admixtures. 447–448 failure to meet strength requirements. 635. 63–64. 622 concrete prism expansion test. determination by chemical ASTM C 40. 438–442. 402 ASTM C 117. 444 composition. 363. 48. 380 501–502 ANSI A118-6. 358. 459. 422 ASTM C 85. limitations. 185. 59. 410. 343. 88. 53. ASTM C 78. 481 aggregate. 447–448. 406–408 chemical admixtures. 62. 581. 127–128. 622 ASTM C 215. 327. 60–61. 620 84. 361. 5. 299. 534. 419. 474. ASTM C 172. sampling. 404–405. 551 Algae. 387 control of water addition. 60. 446. 619. 53. 469 types. 614 ASTM C 136. 19. 503 Alkali silica gel. petrographic evaluation. 401–408 ASTM C 94. 415 ASTM C 31. 437. 221–222. 43. 539 437. gravel and sand. 45. 487–488 compressive strength testing. 579. 350 ASTM C 151. 437. 43. 439. 80–81. 619. 533–545. 540–542 ASTM C 234. 436–438 quarry sampling. 467–469. 131–132. 155–156. ASTM C 496. 508 ASTM C 348. 407–408. 53–54 639 ASTM C 917. 379. 171 168. 570. 158. 143. 480–481. 632–635 ASTM C 1252. 359 472 ASTM C 359. 296–297 ASTM C 876. 93–97. 444–448. 119. 405 420–422 ASTM C 943. 559. 445 ASTM C 1231. 137 ASTM C 1107. 485–489. 503 ASTM C 806. 559. 635. 633 ASTM C 1176. 639 ASTM C 973. 456. 158. 442. 64 packaged. ASTM C 1073. 39. 562. 223. 18. 325. 328. 549–550. dry. 154–155. 617. 576. 145. 167–168. 497–499 ASTM C 682. ASTM C 953. cementitious mixtures. ASTM C 851. 19. 620. 499. 633 ASTM C 1138. 369 ASTM C 451. 69. 543 ASTM C 360. 441. 84 ASTM C 332. 53 ASTM C 779. 47. 221. 39. 207–208. 411. 133. ASTM C 801. ASTM C 464. 417–418. 513. 127–128. 63. 114. 190–192. 81. 129–130 ASTM C 1012. 419–422 ASTM C 403. 155. 366 ASTM C 805. ASTM C 617. 437–438. 301. 514–515 ASTM C 349. 437. 437. 157–158 ASTM C 310. 521. 157–158. 538 310–311. 160–162. 622 456–457. 632. 366 ASTM C 291. 161–162. dry. 404–405. 617. 619 589. 19. 328–329 ASTM C 1218. 439. ASTM C 1017. 377–378. 19. 359 ASTM C 1069. 155–156. ASTM C 942. 528. 221. 456 ASTM C 989. 576. 435. 223 ASTM C 401. ASTM C 1078. 437. 210. 444–448. 622–623 ASTM C 1137. 397–398. 136. 404–406 ASTM C 512. 633–635 441 ASTM C 802. 190–192. 570. 607 600 ASTM C 457. 79. 549–550. 498–500. 19. 635. cementitious mixtures. 459 ASTM C 567. 407. 582. 456–459. 629 ASTM C 563. 187–188. 149–150. 379. 562. 439. 444 ASTM C 1090. 398. 53. 446. 576. 627–628 ASTM C 1202. 498 ASTM C 796. 610 ASTM C 1064. 447–448. 244. 505. 221–222 ASTM C 671. 625–626 ASTM C 331. 318. 160–161. 60. 600 ASTM C 1294. 469 methods. 592 ASTM C 1315. 366. 359. 84. 554. 576. 359. 28 packaged. 501. 617 ASTM C 402. 331. 309–311 632 ASTM C 778. 565. 593 ASTM C 1362. 190. 19. 221–222. 303. 26. ASTM C 294. 617 508. 404–405 ASTM C 586. 221–222. 80. 619 ASTM C 1018. 575. 232. 303 ASTM C 1040. 448. 26. 562 480. 53. 579 ASTM C 941. ASTM C 944. 456. 374. 154–161. 378. 187–192. 260. 579. 196. 437–438. ASTM C 490. 152 ASTM C 1077. 63. 263. 454 ASTM C 881. 53. 635 ASTM C 579. 576. 212. 575. 380. 368. 155 509. 581. 622 633 ASTM C 418. 576. 380–381. 469–471. 622 ASTM C 1116. 19. 88–89. 196–197. 26. 603 ASTM C 470. 149–150. 18. 145–147. 562 ASTM C 1152. ASTM C 637. 63. 67 . 330 507–508. 80. 520. 362 ASTM C 937. 160. 63. 620. 601. 594 ASTM C 290. 136. 619 ASTM C 666. 244. 437. 562 ASTM C 670. 410–411. 170. 186. 576. 199–200. 303 556–557. 618 ASTM C 293. 623. 26 ASTM C 341. 408. 437. 506. 570. 141. 234. 597. ASTM C 597. 544 ASTM C 495. 221. 152. 79. 598. 597. 425 ASTM C 618. 620. 524 ASTM C 1074. 341–343 ASTM C 511. 454 ASTM C 938. 476. 239–240. 570. 565 ASTM C 918. 411. 223 619. 129–130. 521 ASTM C 309. 136–137. 623 use of appendices. 626–627 ASTM C 1170. 366. 383–384. 592 ASTM C 1038. 543–544. 209. 592 ASTM C 1324. 215. 548–550. 198. 361. 288. 439 513–515. 631–632. 576. 602–603 ASTM C 469. 68–69. 310–311. 444 ASTM C 672. 361 ASTM C 1140. 202. 593 ASTM C 1356. 81 ASTM C 884. 294 ASTM C 873. 599. 446. 621 505–509 ASTM C 638. 439. 200. 619. 619 ASTM C 295. 135. 591. 559 ASTM C 940. 398. 562. 378. 556 632–633 ASTM C 1293. 556. 411–412 ASTM C 1151. 179. 618 ASTM C 1222. 260. 170 440–442. 212. 570. 63. 294–296 ASTM C 869. ASTM C 452. 610 ASTM C 494. 514 419. 212. 170. 470. 262. 75–76. 437. 600. 208. 447. 219. 440 ASTM C 684. ASTM C 903. 155 562. 133–135. 592. 32. 67 ASTM C 685. 81. 593 ASTM C 289. 557. 196 blended hydraulic cements. 619 565 ASTM C 928. 570. 479. 635 250. 157 441. 88–89 ASTM C 803. 27. 617–620. 533–534. 593 limitations. 36. 204–209. 152. 457. 622–623 292–300. 136 ASTM C 1157. precision. 510–521 ASTM C 518. ASTM C 823. 63 ASTM C 387. 52–54. 232 ASTM C 887. 447–448 ASTM C 845. 444 267. 359. 517. 440 ASTM C 827. ASTM C 350. 142. 454 ASTM C 330. 515. 579. 548. 564 ASTM C 1105. 141. ASTM C 642. ASTM C 1059. 160. 570. 136. 437–438. ASTM C 702. 622 ASTM C 1079. 411 ASTM C 1084. 316 ASTM C 878. 228 ASTM C 936. 221. 456–459. ASTM C 856. 366 ASTM C 1102. 517. 622–623 390. 562. 155–156.650 TESTS AND PROPERTIES OF CONCRETE ASTM C 270. 410. 634–635 619. 324. 584–586. 253 ASTM C 939. 435. 119. 311 microscopic analysis. 620. 570. 90–91. 536. 20. 311 ASTM C 566. 639 ASTM C 465. 514 361–363. 154–157 ASTM C 595. 575 ASTM C 596. 246–247. 74. 594 ASTM C 292. 223 622–623 ASTM C 441. ASTM C 1117. 26. 419 ASTM C 535. 570. 497. 404. 591. 627. dry. cementitious mixtures. 250. 83–84 packaged. ASTM C 900. 556 ASTM C 882. 570. ASTM C 311. ASTM C 1240. 86–88. 413. 437. 504–507. 239. 357 ASTM C 1067. precision and bias. 28. 617. 260–261. ASTM C 1260. ASTM C 430. 408. ASTM C 1141. 411. 53. 406. new concrete surfaces. 368–370 materials. INDEX 651 ASTM C 1365. polymer-modified concrete and ASTM D 3665. 361 Batching zones. 13 ASTM E 288. 348–349. 341 Batching plant. 52 scaling. 106 ASTM C 1436. 244 ASTM D 5882. 320 Bituminous materials. 112–116 ASTM C 1550. 617–618. 520 Attrition test. 244. 537 planes of weakness due to. 621. 114–115 623 Atmospheric diffusion. 265–266 ASTM D 4791. 133–134 self-consolidating concrete. 458 concrete. 250 Atom. 296–297 Bonding materials. 617. 112 ASTM C 1585. aggregates. 39 Bituminous coatings. 135 Bond breakers. 20. 52 postbleeding expansion. 52 water-cement ratio. 584. 514 placing and finishing. 107–108 crystals. 617. 30. 479 Blistering. 322 recycled concrete. 621. 12 test methods. 118–119 Calcium chloride in admixtures. 587. 625 ASTM E 994. 20 blisters. 118 ASTM C 1543. 628–630 BS 1881. ASTM D 6087. 586–587 ASTM E 660. organic. 243. 623 ASTM E 1187. 625–626 ASTM D 4580. reducing. 485 ASTM E 119. contamination of recycled ASTM D 4748. 397 ASTM D 4788. 119 ASTM D 1557. 116. 619. 112–113 ASTM C 1556. 570 supplementary cementing ASTM C 1567. ASTM D 4326. 99–101 ASTM C 1480. 610 Ball penetration test. 27 Bias. 459 strength and density. 518 ASTM C 1453. 99 ASTM D 672. 195–196. 167 ASTM E 2226. slag effect. 619 BS 812. 111 Calcium hydroxide ASTM E 177. model. 623 ASTM F 1869. 25 Bearing strips. air Blended cement. 608 ASTM E 1550. 244. 204. 109 hydration product. 274–275. 283. 84. 366. 184 aggregate. 116–118 ASTM C 1603. 428 paste-aggregate bond. 119–121 ASTM D 2419. 47. 118–119. contamination of Bulk density. 373 content and. 366. 337 Bleeding. 322 cement. 244. 26–27 Brines. 514. 250. 201 Blast-furnace slag. 113–114 ASTM C 1581. 603 Basic water content. 20 controlling. 459 ASTM E 289. 340–343 sulfate soundness test. ASTM C 94. 619. 168. 373 ASTM D 4971. 499 Beneficiation. 108–109 ASTM C 1398. 67 special applications. petrographic evaluation 471 ASTM D 4397. 428 mortar flaking. 109–111 ASTM C 1404. 615. ASTM G 40. 116 ASTM E 122. 628 Autogenous volume changes. 7 water content and water-cement ASTM C 1583. 239 C ASTM E 96. 221–222 Autogenous shrinkage. 621–622 Bogue calculations. 176–177 ASTM E 141. 104–106 ASTM C 1437. 608. 566 duration of. 641 Bleed water. see Slag ASTM E 11. 27. 451–452 ASTM D 3398. splitting tensile strength mortar. 617. 439 ASTM E 1301. 111. 106 ASTM C 1399. 101–102 bleeding and. 337 189–190 significance. 609–611 ASTM D 3744. 418 ASTM D 4944. 52 effects on plastic concrete. 321 statements. 111–112 ASTM C 1402. shrinkage and. slag. 101–103 ASTM E 105. 589. 617. 620 ASTM E 1323. 625 ASTM E 707. 102–103 ASTM C 1451. 36 ASTM E 1738. 250 ingredient effects. 584. 52 thixotropic mixtures. 411 Ball-bearing abrasion test machine. 243. 254 . ASTM D 6928. acceptance testing. 119. 52 plastic shrinkage. 366. 373–374 shotcrete. 200. 568 ASTM E 2159. 379 Bonded capping. 52 fresh concrete. 115 ASTM C 1558. 558 ASTM D 2940. 250 mathematical models. 216 ratio. 116 ASTM D 2936. 107 ASTM C 1385. shotcrete. cement. 437. 620. 81. 579. 469 capacity. 462–463 B placement conditions. 168. 103–104 ASTM C 1438. 515 ASTM D 3042. 19. 111 chemical analysis of hydraulic Brickwork. 369. 621 ASTM E 329. 118 ASTM D 448. 438–439 280 ASTM E 6. 52 volume change. 275 fundamentals. 356–357 Brucite. 320 ASTM E 303. 17. 106 ASTM C 1439. 463. 603 ASTM E 1085. 250 219 chemical admixtures. 617. 101–102 ASTM D 75. 373 surface appearance. 246. 106 effect on galvanic current. 128 ASTM C 1604. 101–102 ASTM D 2766. 39 Bulk modulus. 366 surface determination. 229 roller-compacted concrete. 106 ASTM C 1452. 60 Binders. 373 paste-steel bond. 129–130 ASTM D 4460. 380. high temperature and. 598 sequence of material addition. 396 549–550 ASTM D 6607. 211 durability. 39–40 rate. 250 increasing. 250 ASTM F 2170. 27 Blaine fineness. 246. 623 ASTM E 350. aggregates. 25 effects on hardened concrete. 20. 599. 469 and. 558. 369 Blaine test. 539–540 Bond. 289 ASTM D 3319. 106–107 ASTM C 1383. 622 Backscattered electron SEM. 601 Bleed-reducing admixtures. 102–106 ASTM C 1435. 368 and. 366. 121 ASTM C 1602. 9 Laboratory. Chemical contamination. mechanisms in deterioration. 254–256 fire resistance. 126 portland-cement paste. 40–41 614 expansion due to hydration. 260 bleeding and. and. 614 concrete. Cement maintenance paint. 132 paste strength and. 478 135 deposition. portland cement. 53 cold weather. 20 precast elements. 7. 263–265 classification. 310 fresh. 164–167 thermal conductivity. 164 walkability. 6. 265 workability. 11–12 scaling. preplaced aggre. and application Cement particles. 243 uniformity. 254–256 energy absorption. 526 Carbonate. 562 composition and fire resistance. 10–11 seawater and brines. 488 Carlson-Forbrich van conduction gate concrete. 129–130 Cement chemistry. 564 CEN/TC 154. 66 shielding. 256 potential alkali reactivity. 230 170–171 roof deck fills. particle shape. 256–263 freeze-thaw resistance. 486 depth of. 174 Cement gels. 266 density. 459 methods and. reinforcing steel. 216–217 Cementing materials. 233 Carbonation fresh concrete. 63 Calcium oxide classification. 489 Chemical resistance. roller-compacted concrete. 63–64 paste strength and. 564 compressive strength. radiation mixtures. 566 CEMHYD3D. 484–489 Calcium sulfate.652 TESTS AND PROPERTIES OF CONCRETE Calcium hydroxide (continued) Cement Center-point loading. volume change. 9. 411 analysis. 126 analysis in reinforcing steels. 396 Cellular concrete. 539 California Division of Highways. 46–47 Chemical shrinkage. 567 diffusivity. mixing. 567 thermal properties. 126 leaching. 216 modulus of elasticity. 169 cellular concrete. 486 reactivity. 233 Cementitious materials 487–488 Casting direction. 12. 565 276–277 carbonation. 8–9 service life. 115–116 Capillary absorption tests. 591 suppression of alkali-silica reactions. 42–46. 309. 566 fresh. 567 film thickness and aggregates. 39–40 accelerating. 10–11. alkali-carbonate rock Cement content high-range water reducing. properties. recycled 171 modified. 563 strength. 6 Chemical resistance. accelerated curing compatibility with slag. modeling degradation and Certification. batching and measuring materials. 6 see also Sulfate resistance materials. flexural strength. 567 222–223 supply of aggressive agents. 64 hydration controlling. 486–487 Carbonate rocks. 11 efflorescence. 259 shear strength. dispersion. 81 Calcium silicate hydrate. 13 sulfate resistance. structure. 167–168 tensile strength. 367 test methods. sulfate attack Cement-aggregates combinations. dry.201 improving. 265–266 floor fills. 568 thermal expansion. tests. sulfate resistance and. 253–254 Cathodic protection. 575 titious materials Chemical attack. portland cement. testing personnel. 597 water-reducing and set-retarding. 310 mid-range water reducing. 253 applications. 244 Cement and Concrete Reference cellular concrete. 485 459–460 polymer-modified concrete and acceptance testing. shrinkage-reducing. workability and. 566 water content. 563–564 Cement paste acid attack. cementitious 484–485 Cast-in-place concrete. drying shrinkage. 311 hydration and. 607 air-entraining. calorimeter. 472 seawater and. 41–46 Chert. 567 permeability. pore water. ready-mixed concrete. involved in leaching or mineral air entrainment and. analysis. rheology. workability and. 254 batching. 257–258 mortar. 566 creep. quality control. 360–361 nailability and sawability. 310–311 Central mixing. 65 Chemical reactions air cell introduction. 478 Calcium sulfoaluminates. 44–45. 565 220–221 Chloride-induced corrosion. attack by other chemicals. compressive strength. 566 hardening. 5 prestressed concrete. 561 Cement mortar. 266–267 compressive strength. 566–567 Cement paste matrix. Supplementary cemen. 254–256 drying shrinkage. 566 density. 212 Chloride penetration. 11–12 Chi-square test. 566 elasticity. 19 Calcium sulfate reaction. 266 petrographic evaluation. 564 see also Packaged. 253–267 techniques. latex-modified. properties. 563 Capillary tension. 47 Chemical admixtures. 564–565 X-ray diffraction. 219. 561–568 Cement mix. 488–489 Capping procedures. 226 effect on sulfate resistance. 245–247 . 169 water absorption. 126 488 Casting techniques. 562 Centrifuge test. 254–256 engineered fills. permeability and. 9 recycled concrete. 18–19 viscosity-modifying and anti-washout. 436 Ceramic tile thinsets. 567–568 rheology. 160 405 bleeding and. latex. 112–113 540–541 Calcium nitrite. 146 corrosion-inhibiting. cellular concrete. 255 analysis of type. 396 Carbonation shrinkage. ion effect. 10 Chloride proportioning. 218. 562–563 hardened. 221 hardened. acceptance testing. 343. polymer-modified concrete and Consistency 486–487 mortar. measurement. 520 Coefficient of thermal expansion. 283–284 Cohesion. 360–361. 362 Concrete-making materials concrete cores. CRD-C 300. INDEX 653 Clay normal consistency. 128–129 chloride-induced. 215 cement paste. 280 high temperature and. 419–420 171 petrographic evaluation of Concrete rheometer. on gravel and sand. 14. 101. 181 in alkali-carbonate rocks. lightweight aggregate CRD-C 55–92. 368 Compressive members. 557–558 CRD-C 124. 180 expanded. 470 203 379 CRD-C 302. petrographic evaluation. 395–396 Correlation coefficient. 179 CSA A23. 117–118 resistance. detection. 629 hydraulic cements. 601–602 CRD-C 37. Cold weather admixtures. 10–11. 164–167 tensile. 41–46 embedded glass. 166–167 definition. 278. 613–614 aggregates. 329 importance. 369 microbars. 170–171 artificially generated. 383 concrete. 600 Corrosion significance and use. embedded steel. 230 concrete. 555–556 Core testing. 513 . 65 Cracking. 194 lightweight aggregate concrete. alkali reactivity. 593 test. 80 recycled concrete. 27–28 cement paste. 341–342 Compressometer. 11 Control chart. Concrete embedded copper and copper alloys. 599 property specification and recycled concrete. 201–203. 543–544 Corps of Engineers method. properties. CRD-C 621–89a. 167–168 aggregates. 202–203 roller-compacted concrete. embedded lead. 362 materials repairs to deteriorated structures. 8 181–182 reinforced steel. 419–420. 229 modulus of elasticity. 128. 53 CRD-C 45. 488–489 fresh concrete. 178–179 Clay lumps. 23 estimation. assessing severity in existing Coal. 181 394 470 embedded zinc. 470 Compressive strength. mechanisms. 629–630 see also Uniformity. Hardened chloride ion effect. 196–198 Contamination CRD-C 148. synthetic-resin. 200–201 Copper and copper alloys. 179–180 aggregates. 565 91–92 Creep. 216 Coefficient of variation. 228 Compression Contact zone. 422 hardening. 362–363 materials. 169–170 naturally occurring. 202 factors affecting. 164–166 Clinker particles. petrographic evaluation. 130. 187 see also Fresh concrete. 230 Compaction.2–14A. roller-compacted Construction Materials Engineering CRD-C 38. 132–133 embedded asbestos. 177–178 CSA A3001. 327 measurement in compression. 210–211 Laboratories. 129–132 178 high temperatures and. Cored specimens. 181–182 Crusted stone. roller-compacted Construction. 103 178 CSA A23. 5 damage. 601–602 Council. 396 CRD-C 401. 54 CRD-C 39. 32–35 precautionary steps against. 355–356 perceived relative importance of new steels. abrasion resistance and. 222–223 cathodic protection. 203 test procedures. 390–392 bleeding capacities. 202–203 virtual testing.2–23A. embedded organic materials. 202 test result significance. 185–186 Continuous penetration measurement. slag effect. 164–171 Clinker phases. 452 types. 39. 246 Compactability. deflection. curing effects. 232 Composition. 481 definition. 411 426–427 workability and. 524–526 laboratory specimens. 628–630 definition. 439–440 slag effect. 170 lightweight aggregate concrete. self-consolidating wood. embedded. 421 embedded lead. 171 abrasion resistance and. 12–13 Corrosion resistance. 360–361 185–186 structures. concrete-making prestressed concrete. 289 bleeding and. petrographic evaluation. 61 creep measurement. 23 Consolidation fire-damage. air content and. 46–47 embedded aluminum. 465 abrasion resistance and. fiber-reinforced concrete. 517–518 587–589 Color. 278–279 Core and pullout test. 180–181 CSA A23. slag effect. 30–35 168–169 latex. 175 Crushing. particle shape. measurement. 643 Corrosion-inhibiting admixtures. 197 embedded concrete. 171 effect on concrete. 447–448 66–68 embedded plastics. 202 ready-mixed concrete. roller-compacted CRD-C 36. 227 examination. 633 cellular concrete. 84 Crank’s solution. versus probe penetration 556–557 preplaced aggregate concrete.1. 177–178 properties and performance. 362–363 concrete chloride samples. 202 concrete. 170 Coatings volume change. effect of specimen size. hardened cement. 379 recycled. physical properties. 170 bituminous. 233 concrete. 602–603 Crack damage. embedded in new concrete. roller-compacted concrete. 181 Creep coefficient. petrographic Construction Materials Reference CRD-C 44. 201 elastic properties and. 386 Concrete prism expansion test. 602–603 concrete. 5 embedded fibers. 289 189 glass fibers. 301–302 Elastic modulus. 215. bleeding and. reinforced steel Density. Curing water. 319–320 self-consolidating concrete. 181 bleeding. petro. 178–179 see also Alkali-silica reactivity slag effect. 175–177 Degree of consolidation. compounds. 355 cellular concrete. 289. 304 materials.654 TESTS AND PROPERTIES OF CONCRETE Curing degree of consolidation. 245. 276–277 Dolomitic carbonate rocks. during fires. 46 Deteriorated structures. 174–182 modeling. 178 Dehydration. 247–249 Embedded materials. 446–448 effects on concrete properties. 26 importance. hydraulic cements. 194–196 specimens. strength testing. 472–473 as cross-check to air content Dynamic modulus of rigidity. 164. 254–256. 469–470 lightweight aggregate concrete. 80 abrasion resistance and. 301 199–200 Cylinder strength. 126 paste content effect. slag effect. 303 bleeding and. 619–620 uniformity of materials. density. 417–418 Dilation methods. 181 321–322 Drying other metals. 470–471 hardened concrete. 244–245 Electrical methods. 260. 367 cellular concrete. 629 test. 581 fiber-reinforced concrete. 131 elastic modulus. 315–316 new concrete surfaces. 594 Efflorescence. 300–304 supplementary cementitious EN 1097-1:1996. 469 radiation shielding. 165–166 members. cement paste. 245 cement paste. ground-penetrating radar. 540 tion. 329 organic materials. aluminum. aggregates. 303–304 Dunagantest. 179 Delayed ettringite formation. 564 Dry shake hardeners. 200–201 Dedolomitization. 41 asbestos. 411 thawing. 179–180 slag. compres. fire resistance. 194–195 Curing compounds. 280–281 Poisson’s ratio. 196–198 Darcy’s law. 180 262–263 new concrete surfaces. 471 fresh fiber-reinforced concrete. 196–201 D Diameter-aggregate size ratio. 442 zinc. 83 shielding properties. glass. 367 air content effect. 254 fresh concrete. 61 EN 197. repairs. 180–181 Deicing salts. polymer-modified virtual testing. 505 EN 1097-2:1998. 134 95–96 366–367 Discontinuity. 302–303 from ultrasonic measurements. coarse aggregates. 215 Deflection. 19. 47 property specification and estima- concrete and mortar. 613 Digital recorders. 553–554 in-place. 301 Echo method. 395 measurements. 589 ambient conditions effects. 257. 301–302 Durability. 160–161 Elastic strain. 11–12 modulus of elasticity Darcian flow. 203 DIN 1048. 181 301–302 Distress. 200 Decorative coatings. 11. 367 cement paste. 10–11 test methods. 554 157 materials for water retention. 107–108 accelerated. 276 Electolytic cell. 472 typical values. 23. 9–10 plastics. 304 roller-compacted concrete. 14. 127–128 lead. 217–219 486–487 definition. 181–182 Degree of hydration. 360–362 Drying shrinkage. aggregates. roller-compacted concrete. 524 sheet materials. roller-compacted concrete. effects. 174–175 Delamination Dressing-wheel abrasion test machine. 218 Curing meter. 181 Deleterious substances time. 468–469 significance. 62–63 drying shrinkage and. 574 Elastic constants. time of setting. 316 Diatomite. 600–601 liquid membrane-forming curing 603 Durability factor. 171 Elastic properties. compressive and flexural Dilatometry tests. 314–316 needs for future work. 194 595–596 Diffusion coefficients. 11–12 in tension and flexure. Degradation. from ultrasonic Damping properties. 566 wood. 519 hydraulic cements. 436. roller-compacted concrete. 469–473 measurement. fibers. 421 general condition. 523–524 see also Corrosion. 73 E paste strength and. 198–199 D-cracking. 222 . Drilled-in pullout test. 371 sive strength and. 471 EN 1097-9:1998. 465–466. due to alkali-carbonate rock concrete. 130 voids content. 302 Elasticity. 241–242 Diffusivity in compression. 393 hydraulic cements. 174–175 corrosion-inhibiting admixtures. 411–412 copper and copper alloys. 77–78 effectiveness. 471–472. 470 106–112 improvement. 41–43 reactivity. 468 measurement Dynamic modulus of elasticity. freezing and significance and use. new concrete EN 1097-8:1999. 301 virtual testing. 472 steel. 557 internal. 524 graphic evaluation. 446–448 lightweight aggregate concrete. 467–468 significance and use. 156 high temperatures. 109–111 Drilled cores. Difference two sigma limit. 642 preplaced aggregate concrete. freezing and thawing. 187 determination. 47 Dissipative particle dynamics approach. 199–200 Dams. 203 expansive. Direct tension test. 177–178 detection. 367 composition effect. petrographic evaluation. 602 permeability. 179 air content and. 126 surfaces. 440 workability and. air entrainment and. 277–278 polymer-modified concrete and overlaying materials. 46 Fine materials sampling. 113–114 aggregates. 169 Field concrete optional chemical requirements. petrographic examination. 69 sampling. contact zone and. in concrete. 179 hydraulic cements. 587–589 chemical composition. 358–359 Expansive cements. 600–601 Ettringite. 503 Freezing and thawing Grab sample. 566 use. specimens. 157. 278 276–277 cellular concrete. 480 polymer-modified concrete and Flexural strength testing. 8. 337–340 Finishability. 600 lightweight aggregate concrete. 582–589 bleeding and. permeability and. 283–284 testing. 67 Friable particles. 161–162 Evaporation rate. 440 Flow tester. 475–476 F Flowability. 137–138 Fluid grout characteristics. 243 penetration resistance versus time. of concrete. 582 compatibility with slag. cellular concrete. 262–263 558–559 scaling resistance. 157–160 Environment. 203 concrete. 169 cellular concrete. 289 durability. 567 air content and. 186–187 slag effect. as adhesive. 289–290 aggregates. 133. 18 German impact test. 260–261 Glass Fineness Foam. 63 slag effect on properties. 526 static loading. 245 Frictional properties. 211–212 284–285 degree of saturation. 337–338 damage. fire cement paste component and. fresh concrete. 360 Fatigue strength. 558 Flow test. fresh fiber-reinforced aggregate concrete. 83 preplaced aggregate concrete. resistance to. 591 Gel-space ratio theory. 585 factors influencing entrained air. 475 dynamic loading. 582–587 controlling alkali-silica reaction. 468 as recycled concrete contaminant. 274–286 use of salt water. embedded. preplaced petrographic evaluation. 160–161 air entrainment and. 387 slag. investigation and repair. 239 resistance. mortar. modulus of elasticity. mortar. 129–130 Finishing air-void system. Flash set. cellular concrete. Grading. 73 strength and. 290 cracking resistance. 457 air content and. 134–136 determining air voids. 395 materials. Flexural strength. 257. 503–505 242–243 Field curing. 361 concrete. slag effect. 243 loss on ignition. 80. 158 rographic examination. 212 fresh concrete. 476 Energy absorption. 440 air-void system. 260. 566 Epoxy resins. 438–439 562–563 reactive. 17–18 Fineness modulus. 638–639 Fire resistance. 407 Frost resistance hardened. 563 fineness. 396 concrete. roller-compacted concrete. 159–160 Environmental benefits Fire endurance standards. cellular concrete. 476–480 self-consolidating concrete. compressive Finisher’s foot. 618 fire resistance and. roller-compacted 275–276 recycled concrete. 340 . 276 176–177 Fibers. 289 lightweight aggregate concrete. 277 which deterioration measure to Epoxy. 367 as deleterious substances. 589 chemical requirements. 496–499 Galvanized corrugated steel sheets. 66 sulfate resistance and. versus hardened 411 Flexural deflection. 210–212 physical requirements. 7–8. 7. 379 Fiber content. 178 Fick’s first law. 581–582 Fluid penetration coefficient. 275 effect of container. preformed. 353 fiber content and orientation. 105 spalling and cracking. 626–628 factors influencing behavior. 517–519 False set. and embedded steel. patching. factors influencing in bleeding and. 158 Epoxy-coated reinforcing steel. 397 supplementary cementitious Free moisture. mechanism and air content. testing. 610 Erosion resistance. cellular concrete. transport test methods. 339–340. 557 Entrained air. 587 classification. 174 volcanic. 198–199 476–480 Floor fills. 478 history and use. 265 372–373 fresh. 524 Engineered fills. bleeding and. 567 function of entrained air. 19–20 Failure. 499–500 entrained air. 597–598 517–518 dilation methods. Fire damage. 91 500–503 Gas flow. 478–479 rheology. 279 Fresh concrete Expansive dedolomitization reaction. 233 Galvanic current. 613 Flexure. shotcrete. 90 durability air entrainment. 593 tests for. 578–589 Fly ash. 579–582 avoiding alkali-silica reactivity. Gas diffusion. 274–275 see also Weathering 219–221 see also High temperature. 360–361 specification. Fiber-reinforced concrete. INDEX 655 End conditions. G Fiber reinforcement 505–506 cellular concrete. 40–41 Flow cone. 499–500 Galvanized reinforcing steel. calcium chloride and. 527–528 aggregate component and. 566 abrasion resistance and. effect on pet. 299 Exterior insulation finish systems. 160 slag. entrained air and. 497–498 Gillmore test. criticism. 514 Fogging. 159 self-consolidating concrete. 642 rapid tests. 106 petrographic examination and. specimen. aggregates. 499 Frying pan moisture test. volume change. 454 examination. 281–282 Insoluble residue. in mixing water. 446–447 Gravimetric method. 521–523 sampling. portland cement. 480–481 thermal volume change. preplaced aggregate Heat evolution. thermal conductiv- instrumental methods of analysis. 45–46 selective dissolution. 280 Image analysis techniques. 458 Grout consistency meter. 563 temperatures. preplaced aggregate Heat release. 458 concrete. 537. 457–458 Ground-granulated-blast-furnace slag. 609–613 Hydration controlling admixtures. 310 alkali-silica reactivity. 280 concrete. 384. 438–439 determining consistency. 489 specifications. 245–247 . 285 Inspection by variables. 203 ity. 299–300 tio. 444–446 packaged dry mixtures. 282 320–321 determining air voids. 593 486 x-ray fluorescence. 285–286 Ice formation. 232–233. 450–460 Gravel. activity index. 278 Industrial cinders. 472 Ionic diffusion. 66. 310 Hydrating cement pastes. 593 hydraulic cements. 459 concrete. 587 aggregate determination. 447–448 surface monitoring. 310–311 moisture content influence. cellular concrete. 599 sulfate reaction. 310. 309–312 creep. 321–322 destructive tests. Time of setting density. 435–448. portland cement paste. 257 ated curing method. 311 8–9 fineness. 298–299 ment. proportions of coarse and fine aggre. 303 spalling and cracking. fiber-reinforced Hardened concrete. 42 High temperatures H aggregate concrete. 5–6 in sulfate attack. 633 High paste method. 411 portland cement. 340 porosity. 441–442 quantitative x-ray diffraction. High-range water reducer. 234 quantitative phase analysis. 283–284 concrete. 20 blended. 47 determining thermal properties. concrete. 285 I behavior mechanisms. 517 Graphical recorders. 312 determination of additives and thermal conductivity. 221 significance. 146–147 HYMOSTRUC model. 446 mix proportions. 371–372 microscopic techniques. 18 mix proportions. 440–441 mixtures. 444 gate concrete. 592 Heavyweight aggregate concrete. chemical analysis methods. 69 ready-mixed concrete. 446–448 cement content analysis. 278–279 IBB rheometer. 77–78 sampling. slag effect. 439–440 sampling. 240–241 effect on Impact testing. 196. 456 Greening. 320 air-void system. 639 Hydraulic pressure theory. 437–438 386–387 gates. 310–311 flexural strength and. 279 Indices of precision. durability. 311–312 consistency. 441–442 459–460 latex-modified. 311 thermal cycling. volume change. 279–280 Impurities. determination. 245 life. 311 modulus of elasticity. 447–448 measurement. 170 compressive strength and. 463–464 ASTM C 1084. 337 aggregates. 475–476 see also Fire resistance Hooke’s law. isothermal International Cement microscopy microscopic analysis of aggregates. 459 surface monitoring. high set. 207 388 Hydration. water move. Hydrogen bonding. 614 reduction. 594 Hydraulic activity. calorimetry curve. 338–339 mortar. 5 Ground penetrating radar. 441–442 fluidifier. 229 maleic acid analysis. 23 function of entrained air. 280–281 system. 592 mixing water. 285 strength. 6–8 Intrinsic permeability coefficient. 26 calcium oxide analysis. 411 very high strength concrete. 6–8 test method. 452–453 definition. diffusivity. 282–284 evaluation. Bleeding. 309 refractory concrete. 282–283 Half-cell potential surveys. 285 Infrared spectroscopy. 542 see also Portland cements Gypsum self-consolidating concrete. Non. 563 Heat generation. 14 model. air content sample. definition. 524–526 water content. Insulating concrete. 215–216. 254–256 lightweight aggregates. 550–551 polymer-modified concrete and volume change. 592 6–7 456–457 mixtures. 383–384 air content. 227. 540 properties. at frozen surfaces. 383–384 products. 168–169. 310 mechanical properties and. microstructure. air-void Hardened cement paste. 436 Grout Hardening reactions.656 TESTS AND PROPERTIES OF CONCRETE Grading (continued) petrographic evaluation. 465 optimum sulfate content. 280–281 Infrared-thermographic techniques. 7 High temperature and pressure acceler. effect of slag. 394 chemical analysis. 92 Assocition. 312 194. 239 Hydration shells. gate concrete. 6 modeling degradation and service early reactions. 14. Impulse response method. Heat of hydration. 41–43 Interparticle forces. preplaced aggre. hardened density. and bulk modulus. 18–19 see also Air content. Poisson’s ra. 156 in cement hydration. petrographic evaluation. preplaced aggregate aggregates. cellular concrete. 337–338 preplaced aggregate. preplaced aggre. determination. petrographic cement type analysis. 70 Hard core/soft shell microstructural coupled with air blast. 219. 442. performance-based specifications. 69 Hardness heat of hydration. 46–47 Hydraulic cement. 47 new concrete surfaces. admixtures. compressive M Mini-volumetric air meter. 463–464 density. 643 Loss on ignition recycled concrete. 54 Lithium. 310 algae in. durability. 554 Maturity functions. hydraulic cement. 125–126 Kelly ball test. 170 concrete. 92 shrinkage. 557 Maturity. ready-mixed admixtures. 54 resistance to alkali-aggregate 150 ISO/IEC 17025. 562 Maleic acid. 330 polymer-modified concrete and field tests. hydraulic L 295–296 cement. see Corrosion. 606–607 rate. structural. INDEX 657 Ionizing electromagnetic waves. 641 548–559 portland cement. 619–620 modulus of elasticity. 599 Isothermal calorimetry curve. fly ash and natural pozzolan. importance. embedded. 221–222 Miner’s rule. 571 petrographic evaluation. in ready-mixed concrete. 119. formulating with. 282 K-slump tester. 149–152. expansion due to hydration. 536 high temperatures. 166 Mixing water. content. 151–152 specification. 285 Linear transverse method. 54 reactions. 554–557 precautions. 177 Low-alkali cement. 556–557 39–40 impurity effect. cellular concrete. recycled JSCE-SF6. 557 Maturity index. 121 mixer wash. compressive strength. analysis. high tempera- specifications. 62 strength and. 61 Light elements. 264 portland cement. 132 Mill certificate. 554–555 Mercury intrusion porosimetry. 552–553 strength-maturity relationship. 221 self-consolidating concrete. 131–132 Mixer. 239 Microstrain. air entrainment and. 18 permeability and. heat reduction. 152 Irradiation effects. hydrating sampling. 601 Lightweight aggregate concrete. 548–549 Mass concrete. 23 cement pastes. 278 J specified density. 584. 556 Mechanical properties. 573 Le Chatelier’s method. 479 459 500–501 roller-compacted concrete. 67 properties. 542 air content. 254–256 fly ash. 149 mortar. 629–630 132 Mid-range water reducing admixtures. 360–361 Micro-fillers. 258 uniformity testing. 621–622 abrasion resistance. uniformity. 515 properties. 23 Lignite. 394–395 new concrete surfaces. 408 JSCE-SF5. 472 Iron blast furnace. ISO 9002. 608 fire resistance. determination. 607–608 flexural strength. 558 Maximum density method. 135 486 modification mechanism. 521–523 539 contact zone. 369–370 Kurtosis. 39 reaction. 366–368 definitions. 464–465 insulating. 556 Metakaolin. 14 Laser diffraction method. 52. 67 sampling. 554 Micro-Deval test. 249 536–537 field adjustments. slag batching and measuring materials. 549 Microcracking. coarse. compressive strength and. ready-mixed concrete. 408. 487 Micro texture. 586 see also Cellular concrete reactivity. avoiding alkali-silica JSCE-SF4. 556 interpretation of results. 454 shotcrete. 469–470 hardening reactions. 138 Length-diameter ratio. 554 Mathematical models. 554 Mean. 581–582 classification. 562 reinforced steel. 396–397 JSCE-SF7. hardness. 571 Magnesium oxide Mixing Light microscopy. 19. 215 Laboratory technicians Liquid membrane-forming curing Microstructure certification. air content. 150–151 shotcrete. 456 ing attributes. 136. 255 soft water and. 625–626 direction. 551–552 concrete. 454 Minerals. 584 Lightweight aggregates Metallic contaminants. 64 coatings. 219. cause. Embedded K internal curing. 465 creep. water content adhesives. 396 Leaching. to enhance radiation shield- Lead. 555–556 effect. Microscopic techniques. 465 classification. suppressing alkali-silica mathematical modeling. 553 Magnetite. 644 tensile strength. 574–575 proportioning. 373 Latex Loading Microwave oven drying. 558–559 Maturity method. 499–500 Mineral deposits. 558 Magnesium sulfate reaction. 168 splitting tensile strength and. 285 330–331 seawater. 462–466 cellular concrete. 548 application. 495 L-Box. 557–558 Materials characterization. 136 Mineral admixtures types. compressive strength and. 549–552 high temperatures and. 459 Liquid displacement techniques. arithmetic. 462–463 . 605–606 Los Angeles abrasion. 8–9 competency. 548 239–240 J-ring. organic materials. embedded. 559 ture and. 548–549 Metals. 584 absorption characteristics. 553 Magnetic rebar locator. 543 compounds. bleeding. 553–554 materials internal structure. qualifications. 81 Nuclear particles. 39–40 pulse velocity method. 47 pulloff tests. 11 N epoxy resins. 635 performance. 471 P determining processing effects. 622–623 106–107 in compression. continuous evaluation. air rebound method. 471 379–380 curing. rejection of product. 339 Permeability bleeding capacities. see Time of Moisture content. 377–398. 634–635 hardened concrete. 567 Orimet. 377–378 sealers. 373 132 NT Build 443. 630 Petrographic evaluation. 210 tation Program. 362 polymer-modified concrete and Mortar bar method. 39–40. 626–628 Petrographers. cementitious mixtures.633 natural. 135 consistency. 207–213 Nailability. 410 Neat-cement cellular concrete. bleeding and. 358 bonding and patching materials. high temperature NT Build 492. bleeding and. 324–328 maintenance. petrographic evaluation. 109 bituminous coatings. 395 aggregate size requirements. 319–320 hazardous considerations. 87–88 strength testing. establishing properties and dry shake hardeners. 619 wear testing. cellular concrete. 331 Particles time of setting. dry. 246 Penetration methods. time of Molded specimens. in-place strength testing. 467–468 applications. 404–405. 68–69 strength. 566 shotcrete. 378 ground penetrating radar. 328–330 condition. 330 Periclase. 635–636 preliminary determination of echo method. 601 Moisture clog spalling. 635 selecting and interpreting other infrared-thermographic techniques. 187 degradation and service. applications. 221 Mortar O Perlite. 12 cement content analysis. 302 Percolation plots. 378–379 applied silicates. 600 625–626 Permeability coefficients. bond breakers. 280 method. 632 Operating characteristics. time of setting. 610–613 Mortar flaking. 320 quality control. 469–473 Packaged. 168 polymer-modified. Nurse-Saul maturity function. 405–406 Organic materials. expansion due to hydration. 101. 304 lightweight aggregate concrete. 320 Paste content. 472 ASTM C 387. 298 hardened cement. 380–381 combined methods. 80 specimen. 643 acceptability. epoxy resins. 631–633 alkali-reactive carbonate rocks. 28 roller-compacted concrete. 625–628 in tension and flexure. 562 626–628 contamination detection. 54 Overlaying materials. 317–319 382–383 Modified point-count method. latex-modified. ideal. 382–383 Nondestructive tests. 136–137 use of. measuring penetrating radar. using real-shape aggregates. 549 content. 247 setting behavior and. petrographic evaluation. 596. 103 Oils. 39 maturity method. chemist’s shorthand. 284 Nonplastic mixtures. 625–630 mortar. 635 purpose. 330–331 Paint Models pin penetration test. 519–520 and mortar Organic impurities. 314–331 availability. 247–250 MTO LS-614. 556 stress wave propagation methods. 137 Nonparametric tests. 632 observations included in. Paste-steel bond. 301 see also Polymer-modified concrete testing. 97 pullout test. 197 319–320 Patching materials. 107 static. 633–635 413–415 . 632–633 particle condition. 328 abrasion resistance and. 383–384 hydration research. 27–28 219. 156 age of concrete under study. 296 resonant frequency methods. aggregates. roller-compacted concrete. hardened probe penetration test. 196–198 spectral analysis of surface waves Paste-aggregate interface. 282–284 Nuclear methods. 386–387 maturity testing. 379 320–321 specifications. 322–324 shape. 127 Nuclear-shielding properties. 613 Operator subjectivity. 331 future needs. 41–42 Modulus of elasticity 314–317 Paste-aggregate bond. 628–630 relationship with porosity. 384. slag effect. oxidation and chemical attack. ground Moisture condition No-slump concrete. Osmotic pressure hypothesis. compressive strength and. 572 Oxides. strength. Nozzles. 379 Neutron attenuation. 631 quality. 43–44 Monitoring. 635 tests. 381–382 NMR.658 TESTS AND PROPERTIES OF CONCRETE Mode. 321–322 packaging. cellular concrete. size distribution. 614 cement and concrete. 322 flexural strength and. 64 Penetration resistance data. 378 effectiveness of curing. 322–328 Pavement Mohr failure envelope. air content density. 211 National Voluntary Laboratory Accredi. 451 correlation of samples with aggre- New concrete surfaces gates previous tested. 571–572 setting. shotcrete. 127 high temperature and. 198–199 surface hardness methods. 472 ASTMC 1107. 378–380 impulse response method. 12–13 thickness measurement. 11–12 packaged dry mixtures. 22 decreasing. effect on density. 97 ASTM C 928. test for. 311 266 cement paste. aggregates. bleeding and. 471 631–636 performance. 311 cementing materials. 608 formulating with. 328–330 bond. portland cement. INDEX 659 approach. 567–568. 614 Pozzolans. 459 aggregates. 496–499 394–395 . 457 Pulloff tests. cellular concrete. 608 activity index. 453 compressive strength. 609 chemical requirements. 215 standards. ASTM C 150. 185 applications. Precision. 563 Portland cement paste lightweight aggregate concrete. advantages and disadvantages. 210 247–250 sulfate soundness test. 421 Porosity. 608 bleeding and. 327 605–615 trace elements. 26–27 lightweight concrete aggregates. 610–613 classification. 609–611 505–506 standardization. 75 Plasticizers. 594 self-consolidating concrete. 607–608 Powers’ spacing factor. 499–500 standardization. 454 temperatures at time of grout injec- 116–117 loss on ignition. Polishing. corrosion. 472 properties. embedded. 620 500–503 cement content. 440 recycled concrete. 631 hardened. 356–357 purpose. 592 Pin penetration test. 459–460 Preplaced aggregate concrete. 115–116 455–456 Prestressed concrete. grout fluidifier. hardened concrete. 609 controlling alkali-silica reaction. 504 Proton attenuation. loss. 605–606 Pozzolanic reaction. 372–373 452 327–328 Polymer-modified concrete and mortar. 317–319 fresh. 608 optional chemical requirements. Proportioning. petrographic evaluation. 572–573 polymer modifiers. 210–211 aggregates. 359–360 cement content analysis. 324–328 high temperature and. 200. 379 formed during concrete production. 136. 451 Prewetting. 238–240 sulfate resistance and. 452–453 radiation shielding. limit. 60–61 abrasion resistance and. 450–451 density. 576 size and height. 390–392 Pore water. 102–106 optional chemical requirements. 591 source of concrete. 593 texture. 460 Prestressing force. 437. 598–599 modification mechanism. 606–607 Powers’s spacing factor. 186 types. 28 observations. 247 phase composition. 499 Pumice. bleeding and. 591–594 responsibilities. 212 systems. Plastics. 293–294 self-consolidating concrete. bleeding and. 174 552–553 equipment considerations. ASTM C 150 chemical require. 455 abrasion resistance. 210 Bogue calculations. 12–13 aggregates. 209 Portland cement Preformed foam. 593 Placing. 411 239 acceptance testing. test for. 210 chemical composition. 203 Poiseuille-Hagen law. 620–621 limitations. 331 air void system. 232. Pullout test. 265 workability and. 9. strain capacity. sulfur trioxide. 350–351 alkali-silica reactivity. 610 natural Pulse velocity method. 195. 328 degree of hydration. 563 cellular concrete. insoluble residue. 609–613 chemical composition. 310 specifications. 460 Production control. 280 substitute elements in clinker phases. 594 Plastic concrete. 260 environment effect. 208 carbonate. avoiding composition. 597 Probe penetration test. 408 concrete exposed to freezing and size distributions. chemical requirements. 249–250 sampling. 451–452 Premature stiffening. reconstruction of history of field alkali sulfates. 66 modifiers. 9 strength index. 613–614 volume change. 454–455 versus core testing. 318–319 permeability. 209–210 proportioning. 454 tions. 207–208 chemical properties. 211–212 aggregates. cement. 106 magnesium oxide. 594 Petrography. 575 friable particles. 503–504 dolomitic carbonate rocks. 12 Precast concrete. 114 Proton magnetic resonance. 296–297 hardened concrete. 329–330 freeze-thaw resistance. capillary tension. 613 history and use. 460 562–563 concrete. 614 heat evolution. 239–240 cement. 615 physical requirements. 503–505 clay lumps. 239 chemical analysis of hydraulic 394–395 measurement. bleeding and. aggregates. workability. 379 Pores raw or calcined natural. 221–222 cellular concrete. 597 thawing. 607 carbonation. 553 Poisson’s ratio. 454 time of setting. 640–641 types. 104–106. 608 ments. 593 Phase composition. Pressure meter. 180 performance versus presciptive 169–170 Plastic shrinkage. 641–642 hydration reactions. 18 crusted stone. 210 cement phases and performance. 208–209 relationship with permeability. blast-furnace slag. 592–593 for soundness. 392–394 shotcrete. 315–316 roller-compacted concrete. 9 shotcrete. 395–398 calcium sulfate. 42 grout surface monitoring. 475 roller-compacted concrete. 458 methods. characterizing. 6–7 polymer-modified concrete and latex Postbleeding expansion. 592 451 453–455 grout mix proportions. lightweight aggregates. 450–453 fluid grout characteristics. 103–104 mortar. bleeding and. 593 Placement dry. 249 roller-compacted concrete. cellular concrete. 283 246–247 Revibration. strength testing. cementitious mixtures. abrasion testing. 573 Relative density. 322–324 S cement. 537 Saturated flow. 10 Scanning electron microscopy. 602–603 truck mixer hold back. 70 Scattering cross section. effect on lime Quartz. 575 314–317 ready-mixed concrete. 156. 597–598 Seawater. 602 Quality assurance mixing uniformity testing. 567 aggregates. 514–515 water-cementitious materials ratio. 203–204 hardened concrete. 395–397 Quarry sampling. 643–644 volumetric concrete mixers. 540 hardened. placing. 562 Range. 595–596 shotcrete. 312 compressive strength testing. 576 damping properties. 598 self-consolidating concrete. 538 Rewetting. 187 Radon gas. Reusable molds. 349–350. Residual stress. fiber-reinforced concrete. 255 Quick set. 610 batching and measuring materials. 157.660 TESTS AND PROPERTIES OF CONCRETE Q mixer wash water. 601–602 Quality. 534–535 admixtures. Sawability. 310 R forced steel selection. 7 Regression lines. 553–554 curing. 600 rials. 265–266 hydration stabilizing admixtures. 599 slag. 573–575 Relaxation. hydraulic water quality. time of setting. bleeding and. 266–267 reactivity. 9 127–128 air void system. 23 Returned concrete. 622 ordering information. 67 fresh concrete. 537 pavement. 20 572 Resonant frequency methods. 25 Radiation shielding. 534 quality control. 544 Roller-compacted concrete. 537 air-entraining admixtures. 574 Remixing. 310 Reinforcing bars. 507 returned concrete. 161–162. calculations. 596 Quality control sampling. 396 other methods. 9 air content. 567 uniformity. 534–535 Rheologic properties. 597 mixing operations. 117–118 Saturation index. specifications. 598 mixing water. 74. properties. 573 control of water addition. 579 physical and biological perspective. high temperatures. cellular concrete. Sand temperature effects. Scaling. 19 irradiation effects. air-entraining admixtures. 40–41 ened concrete. 543 water-reducing and retarding roller-compacted concrete. 542–543 Ring test. 201–203 contamination. Rheology slag effect. 595 supplementary cementitious mate. preliminary determination. reuse. 573 limitations and usefulness. preparation. 190 Quantitative phase analysis. 22 unit. 572 standardization of methods. 543 preplaced-aggregate concrete. 533–545 Revolving-disk abrasion test machine. 18 density. 114 shielding. 620 size. test methods. micro structure effects. Rheometers. 65 Radioactivity. 61–63 535 Rotating-cutter drill press. radiation 543–544 Rice husk ash. 108–109 basis of purchase. bleeding and. 19–20 mechanics. 533 aggregates. 568 slump and air content. 201–204 resistance. 316 statistical considerations. 618 dissolution. 297 concrete materials. dry. 340–342 cement. Rock cylinder expansion test. lightweight aggregates. 598–599 packaged. 549 Sampling. petrographic evaluation. 245 Rapid chloride permeability. 17 absorption cross section. Salt attack. 537. 630 high-range water reducers. 24–25 scattering cross section. 534 Quantitative x-ray diffraction. 254–256 approval of mixtures. 118 determination of uniformity. 47. 420–421 394–395 ments. see also Specimens atomic structure and physics. 596–597 Sealing compounds. 536 96–97 bleeding and. 386–387 terms for design calculations. 545–603 Sealers. aggregates. 536–537 cementitious materials. 629 history of industry. alkali-carbonate rock Refractory concrete. tests. 574–575 Remolding test. 16–17 570–572 Relative humidities. 539 188–189 Sawed specimens. organic. 539–540 fresh cement and concrete. recorders. hardened concrete. 572–573 Representative sample. bleeding and. 588 Scoria. 25 fresh fiber-reinforced concrete. 575 314–316 petrographic evaluation. 378 mixing. 459 yield. 554 placement and verification. 543 Roller-compacted dam method. 573 dynamic modulus of elasticity. 316 Sandblasting. 543 placement. 464–465 . 277 Refractory shotcrete. 536 Roundness. and curing. 421–422 285 Salts. 602–603 635 testing laboratories. 24 Sample Reinforced steel. 316 Sanded cellular concrete. 81 Saturated steam conditions. hydraulic Rebound method. see Corrosion. Roof deck fills. fire and. 542 dams. hard- batching plant. 542 advantages. shotcrete. 459–460 Recycled concrete. 384. 540–542 construction. 255 Ready-mixed concrete. dissolved. rein. 535–536 definition. 570–576 Rejectable quality level. hardened concrete. 601 cellular concrete. 524 538–539 cement paste. recycled concrete. failure to meet strength require. 316–317 workability and. 537–538 proportioning. 538 Rheological methods. 23 Specific heat. cellular concrete. 638–639 batching. 636 history. 429 workability. definition. 19 admixtures. 617 effect on fresh concrete properties. testing for. 504 history. 514 compressive strength and. 618 fire resistance and. properties. 276 sizes. 264 chemical requirements. 394 uses. 82 refractory. cellular concrete. 643–644 surfaces. 61–62. 440–441 petrographic evaluation. 80. 82 history. 194 concrete. 614 ground granulated blast-furnace 130–131 materials. 622 specifications. 80–81 Setting. 80–85 Set-retarding admixtures. 66–67 Splitting tensile strength. 515 83–84 proportioning. 537 method. compressive strength. aggregates. 622–623 U. 619 chemical composition. 260 testing personnel. 169. 515 dimensions. 392–394 Specimens. self-consolidating Slurry mixtures. 132 definition. 514 Specific surface Service life blast-furnace air-void system. 114 absorption tests. 523–524 ready-mixed concrete. 320 Shrinkage-reducing admixtures. applied to new concrete test result interpretation. 9. splitting tensile Sheet materials. 317 advantages. 642 fire resistance and. 265. 429–430 Self-leveling flooring materials. 469 compounds in. 293–294 placement. 514 samples derived from. 7. strength petrographic evaluation. 517 splitting tensile strength and. fire-damage. 514 134 Shale. 82–83 ACI and. flexural strength and. self-consolidating Speedy moisture test. Sewer lines. 637 compatibility with slag. INDEX 661 Sedimentation. 512–528 test methods. 514–515 standard initial curing. 254 394 Specified density concrete. 621 environmental benefits. 219 sulfate soundness test. 619 fineness. curing. petrographic evaluation. 526 129–130 aggregates. 639 Skewness. 641–642 physical requirements. 637–638 permeability and. 488 Slump flow test. 300 quality control. 638 chemical composition. 563 Spring coefficient. 613 high temperatures and. 383 supplementary cementitious testing. 616–623 definition. 7 Silane. 516–517 length and diameter. Single-use mold. 639 avoiding alkali-silica reactivity. 556 rate of loss. 542 Spectral analysis of surface waves slag effect. 408 creep and. 641 Skid-resistant coatings. 12. 554–555 Set. 356–360 aggregates. 202 nozzles. 127–128 Shear strength. 617 production. concrete. sampling. in the field. moisture condition batching and mixing. test result interpretation. 114 applications. 618–619 grades. 619 517–519 in the laboratory. see Time of setting blended cement. latex-modified. 23 . 519–526 compressive strength and. acid attack. 356–358 finishing and curing. petrographic evaluation. 538 Soundness. 566 materials. 513 transporting. 81–82 Shrinkage Slump see also Sample lightweight aggregate concrete. 644 Sodium sulfate reaction. 83 Shear stress. history. 135 dry-mixture. cement use. 507–508 petrographic examination for. 135–136 Shotcrete. 9. polymer-modi. 507 rials. 619–620 avoiding alkali-silica reactivity. 484–485 bleeding and. 83 wet-mixture. 353 Shrink mixing. S. 640–641 Silicates. 292–293 modeling. 283–284 supplementary cementitious mate. 355 batching and mixing. 216 Slag. 340–341 541 Slump test. 616–617 effect on hydraulic activity. properties. hydraulic cements. 47 expanded. 134 prepackaged. 81 Specific gravity. 641 chemical requirements. 82 fiber-reinforced. 508 air voids. Shape. 637–644 Silica fume. 133–136 Sieve stability. 620–621 quality control. 457 definition. 526–527 field curing. 526 from existing structures. 512–513 standard final laboratory curing. aggregates. 621 Slate. 526 359–360 environmental benefits. 300 strategies to improve. 81–84 applications. 340–342 aggregates. 394 compatibility with end conditions. 280–281 Self-desiccation. 258 Standard deviation. 84 ASTM and. 195–196 composition. petrographic evaluation. 638–639 drying shrinkage. 630 Soft particles. 408 Soniscope. 642–643 history and use. 349 rials. 361–362 Self-consolidating concrete. 527–528 molds. 507–508 Solid-phase admixtures. 81 testing. 457 flexural strength and. 347–348 chemical admixtures. 475 proportioning. 81 equipment. 513–515 test data. 69–70 fied concrete and mortar. 621–622 ties. 229 transporting. 617–618 effect on hardened concrete proper. 618 sulfate resistance and. 169 Spacing factor. 643 Sphericity. 639 bleeding and. 471 Spalling. 83 quality assurance. ready-mixed concrete. 276 supplementary cementitious mate- hardened. 392–393 strength. 358 applications. 512 making and curing. 636 activity index. 437. 133–134 aggregates. bleeding and. Weathering tests reduction. 277–278 mens. 356–358 splitting. bleeding and. 198–199 cement paste. 25–26 internal. 429–430 reinforced concrete. 465 Sulfur trioxide. 133–134 Strength. 113–114 Testing machine. 370–371 Sulfur mortar. 280–281 test specimen preparation. 215 Swelling. 258 Temperature statistical parameters. 619 cellular concrete. 230–232 Strength index. 282 Strengthening. Surface appearance. 322–324 atures. 495–504 trends. 278 purposes. 507 427–428 testing. 446 technique. 538–539 evaluation authorities. 311 aggregates. 23 Studded tire wear. 25 117 Sweating. 171 Sulfate resistance Temperature rise. 259–261 T skewness. 284 see also Compressive strength fume Thermal cycling. 352–353 arithmetic mean. 22–23 hydraulic cements. 25 Sulfate soundness test. 262 workability and. 25–26 106–112 9. 80 Strain capacity. 63 Statistical parameters. Tensile creep. modulus of elasticity. 73–74 new. 496 Thawing. 23 Structural integrity. 281. Pozzolan. 324–328 Thermal incompatibilities. 26 Stucco. Tension. 210 141–149 drying shrinkage. fire and. definitions. concrete. 495–496 Texture. cement content analysis. 28 shotcrete. 629 regression lines. improving service Surface sealer. 257. 23 magnesium sulfate reaction. 373 Surface treatment. 22–28 Stress wave propagation methods. fire and. 479 testing. 575 Statistical uncertainty. 526–527 Testing personnel. 216 range. relationships. 262–263 Tensile strength. 322–328 aggregates. rebound test method. 259 Temperature-matched curing Steel Sulfate content. 258 standard deviation. 503–504 Surface hardness methods. Silica Thermal cracking. 23 Structure. 428 evaluation. measurement. design. 520–521 radiation shielding. 54 paste-aggregate interface. 503 Thaumasite. 53–54 hydraulic cements. 447–448 air entrainment and. 125 test requirements not in high temperatures. 80 see also Fly ash. 543 nature of. polymer-modified con. 53 hardened cement. 328 cement paste. 277–278 Sulfate corrosion. combined states. 505 Thaulow concrete tester. 32. high temper- Stress-strain curve. air content. 51–52 fatigue. Supplementary cementitious materials. 141–152 compatibility with slag. strength and. 256–259 Synthetic-resin coatings. 429–430 variables affecting. statistical considerations. 202 Stoke’s law. 24 calcium sulfate reaction. 613 tests.662 TESTS AND PROPERTIES OF CONCRETE Statistical considerations. air entrainment. 479 Testing laboratories. 23 Sub-bases. 622–623 hardened concrete. concerns. 257–258 sampling. 51–54 tests. 22 Sulfate attack. 17 delayed ettringite formation. 254 Surface texture. 309. 23. 127 embedded. abrasion resistance kurtosis. bleeding and. 298 correlation coefficient. characteristics. 126 rebound method. 259 strength estimation. 81 accelerated curing methods. Thermal diffusivity. 247 260. 347–348. 297 thaumasite form. aggregates. 342–343 evaluation of test data. 126 129–130 Testing effect of algae in mixing water. 187 number of subsamples. 229–230. 549 inspection by variables. 584–587 ASTM C 94. 63. 137–138 454–455 continuing improvements in quality flexural. 519 Supplement. 127–128 specifications. 23 319–320 Surface preparation. 426–427 Stress. see Sulfate attack Temperature measurement. slag effect. 26 life. 68–69 compressive strength. 234 Stockpiles. 504 fire resistance of steel. sampling. 52–53 hardened fiber-reinforced concrete. 132 prediction at later ages. 23 sodium sulfate reaction. hardened fiber. ready-mixed concrete. 506–507 test methods. 323–324 optional physical requirements. pozzolan. portland cement. 259 cellular concrete. 169 difference two sigma limit. 639 Thermal conductivity. 565 crete and mortar. 564–565 nondestructive in-place. 134–135 Superplasticizers. 23 external. high temperatures. 10 of. effect of chlorides. 289 505–506 Thermal coefficient of expansion. Surface moisture. 257. 444–446 batching and measuring materials. 136–137 soundness. pin penetration test. 563 pressive strength and. see Bleeding operating characteristics. 24–25 control. air content and. 136 quality assurance. 226–227. air content speci- coefficient of variation. 582–583 111–112 Thermal expansion. 80–81 self-consolidating concrete. 22–23 mitigation. 141–149 fineness. in sulfate attack. slag effect. capping technique. 261–262 lightweight aggregate concrete. 257 test procedures. 147–149 fundamental properties. com- pavement concrete. 556 Stratified random sampling. 495–496 shotcrete. definitions. 80 cellular concrete. 127 bleeding and. see Freezing and thawing. 125–127 538–539 technician competency. 281–282 . impermeable. and. 125–138 Sulfoaluminate attack. 12 137 probe penetration test. 257. 94–95 Very high strength concrete. INDEX 663 Thermal methods. 87–88 workability and. 562 test methods. 38 aggregates. 89–90 USBR 4908. 428 Volume change. 229 roller-compacted concrete. petrographic Bureau. 70 300 significance. and. 394–395 thermal conductivity. time of setting. 643 autogenous. 47–48 in concrete. 232 test methods. air content rheological methods. 230. 229. 19 portland cement mortar and basics. 463–464 chloride ingress. test of fire and. 566–567 concrete. 219–221 Voids content. 86 mixer performance. 95–96 USBR 4910. 60 restrained. 230–232 as function of punch location. 97 standard for determining. portland cement. 43–44. 394–395 frequency. 92–94 evaluation. 227–228. 601 properties of hardening cement paste Thermal properties. 543 preplaced aggregate concrete. 243–245 properties of hardened cement paste Thermal methods of analysis. 460 Laboratory. test result interpretation. 395 ultrasonic methods. 96–97 VCCTL. 255 Toughness. tests. 235 disadvantages. elastic modulus. Bureau of Reclamation. 415–417 Third-point loading. 229–230. slag effect. sulfate resistance concrete. 68 Voids heat generation. 226–236 self-consolidating concrete. 90–92 V Volumetric concrete mixers. 61–64 concrete. 263 135 190–191. 36–37 concrete. 216 thermal expansion. 232–233 Tuff. 518 USBR 4911. 97 types. 94–95 rocks. hardened fiber-reinforced Vibration. Underwater abrasion test method. 583–584 479–480 WATEQ model. 281–282 NMR. ready-mixed concrete. 411 computer modeling. 260 setting time. 594 Volumetric method. 566 Transport adiabatic temperature rise. 242–247 definition. 235 Two-point workability tests. 45–46 air entrainment and. 68–69 Volumetric Mixer Manufacturers test result significance. 88 determination.S. 643 Wagner test. delayed ettringite formation. 301 specific heat.233 thermal. 429 Volcanic cinders. fire resistance. 429 U-Box. 280 541–542 Visual survey. 242–243 heat release. 262 swelling clay minerals.221 Time-domain-reflectometry microwave evaluation. bleeding and. 63. 245 future directions. 39 92–94 water. 102–103 Thermal shielding properties. 230–232 Ultrasonic concrete tester. cellular concrete. petrographic evalua- test methods. 83 rheology of fresh cement and analytical methods. 43–44 temperatures. 76–77 temperature versus time. 260. 221–223 fresh concrete. 36–37 expansive cement mortar and spectrometry. 444 advantages. 240–242 chemical shrinkage. 30–37 CaO and MgO. 276–277 history. 478 mechanisms. 233–236 Type K expansive cement. 465–466 . 32. 234–235 Truck slump meter. 641 and concrete. 301 hydraulic cements. 43–44 426–427 Truck mixing. Viscosity-modifying admixtures. 425–430 specimens. restrained volume changes. high W virtual testing. 235–236 Tricalcium aluminate. 406 current ASTM method. 36–37 due to alkali-silica reaction. 88–89 USBR 4907. 217–219 Thixotropic mixtures. 40–41 coefficient of thermal expansion. flexural strength. 348–349 heat of hydration. 88 tion process. exfoliated. hardened Transporting and concrete. 136 Vermiculite. 93–94 Vebe appartus. 226–227. 86–90 density. 32. 216–217 Thermogravimetry tests. 61 high temperatures and. petrographic evaluation. 438 Toughening. 44–45 for cellular concrete. 66. 368 drying shrinkage. 361 electrical methods. 86–97 as function of design and construc. 472 evaluation of uniformity. 219. hardened fiber-reinforced Vicat test. 219–223 Time of setting. 38 measurement. 170 heat flow. 584–587 Virtual Cement and Concrete Testing absorption Trace elements. 46–47 concrete. length advantages. 38–48 cellular concrete. 45–46 curing. 543 thermal methods. 312 roller-compacted concrete. 5–6 gas. 441 Water concrete. density. air entrainment and. 317 bleeding. Uniformity expansion due to hydration of free 106 concrete-making materials. 470 aggregates. 488 determining. ionic diffusion. 245–247 laser diffraction method. 215 other penetration methods. 41–46 aggregate. Walkability. 302 Ultrasonic methods carbonation shrinkage. 13 Virtual testing. 86–87 measuring. 285 x-ray diffraction. 600 modifications. 221–222 data manipulation. 429–430 U tion. analysis. 234 TT-C-800. 442. 89–90 U. 38–39 city. 277. 97 V-funnel. 351–352 Transition zone. 215–223 thermal diffusivity. 199–200 concrete with reactive carbonate 276 time of setting. 30–31 alkali-carbonate rock reactivity. drying shrinkage. 94–95 properties involved in. 614 normal consistency concrete. 117 recycled concrete. 371–372 Water-resistance basement coatings. 179–180 hardened concrete. Young’s modulus. 112 Willis-Hime method. 468 no-slump concrete. 312 hardened concrete. 115 fresh concrete. 581 484–485 flow test. 598 579–581 relation with rock type. aggregates. 353 density test. 64 sulfate resistance and. 218. 261 368–370 Wigmore consistometer. 63 cement paste. 534 bleeding and. entrained air and. 478–479 air content and. 59–60 Water-cementitious materials ratio theoretical considerations. see Bleeding Vebe apparatus. cement phases. test methods. bleeding and. truck slump meter. cement paste. 372–373 quality control uniformity. slag effect. 536 historical evolution. 64 Water-immersion test method. 67 ready-mixed concrete. 117 cement paste. 73 Water-reducing admixtures. 339 time of setting. 69 polymer-modified concrete and mixer uniformity. 162 self-consolidating concrete. determination. 106. Windsor probe test system. 61 Z mortar. 60–61 embedded. 68 X bleeding and. 226–227 cellular concrete. 43 ball penetration test. 62. 290 157–160 terminology. 63–64 Y Water gain. 324 X-ray diffraction 220–221 Wind velocity. 243–245 rapid freezing and thawing tests. 178 Wear. 194–195 roller-compacted concrete. 63 quality. 64 as galvanized coating for steel. 68–69 bleeding and. 63 volume of freezable. tests. 12 Wigmore consistometer. 9–10 Weeping. 69–70 mixing. 61–63 as steel coating. embedded. 342 transport test methods. 67 458 thermal conductivity and. 10 workability and. 232 air content and. high temperatures and. 535 see also Freezing and thawing uniformity of concrete. 64–66 data. ready-mixed concrete. 66–68 Water retention. 178–179 Wave reflection factor. 517–518 stress.664 TESTS AND PROPERTIES OF CONCRETE Water (continued) Weather conditions. 59–71 Rietveld analysis. 396 free. 112 Wet degradation test. 283 Weathering remolding test. 61 Water-cement ratio. hydraulic cement. 63. water content uniformity. 39. 67 lime-saturated. 66 fresh fiber-reinforced concrete. 63. 42–43 311–312 aggregate size and. 289 244–245 factors affecting. 169 . 211 156–157 two-point tests. 255 other processes. fiber effect. 70 ready-mixed concrete. aggregates. 40. 245 basic. Workability. 10. 64 cement content uniformity. see Bleeding definition. 68 Water content Wick action. 154–155 strength testing. 155–156 surface texture and. grout consistency. bleeding and. 68 petrographic examination. 289 X-ray fluorescence. 243–244 production control. non-evaporable. 62–63 Yield Water penetration. 470 Wood. 97 heat of hydration and. curing materials. temperature and. see Mixing water tests. 564 uniformity. 212 curing and. 68–69 Zinc Water-vapor diffusion. 578 fresh fiber-reinforced concrete.