Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. SIGNIFICANCpER OF TESTS AND OPERTIES OF CONCRETE AND CONCRETE-MAKING MATERIALS Sponsored by ASTM Committee C-9 on Concrete and Concrete Aggregates AMERICAN SOCIETY FOR TESTING AND MATERIALS ASTM SPECIAL TECHNICAL PUBLICATION 169B 04-169020-07 ~~I~ AMERICAN SOCIETY FOR TESTING AND MATERIALS 1619 Race Street, Philadelphia, Pa. 19103 Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Copyright 9 by American Society for Testing and Materials 1978 Library of Congress Catalog Card Number: 78-51628 NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication. Printed in Baltimore, Md. Dec. 1978 Second Printing, Ann Arbor, MI December 1984 Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Foreword This publication is a revision and expansion of the report on Significance of Tests and Properties of Concrete and Concrete-Making Materials published in 1966. That publication in turn replaced editions of Report on Significance of Tests of Concrete and Concrete Aggregates published in 1935, 1943, and 1956. The present report covers several types of materials not referred to in the earlier reports but whose importance has increased greatly since preparation of the 1966 report. As was true for the previous publications in this series, the separate chapters have been prepared by individuals selected because of their knowledge of the respective subjects and because of their participation in development ofpertinent methods of testing and specifications. While independent expression by the authors has been encouraged, individual chapters have been reviewed and the entire report has been coordinated by a special committee appointed for that purpose by ASTM Committee C-9 on Concrete and Concrete Aggregates. The special committee in charge consisted of: C. H. Best, Kansas State University, Manhattan, Kansas, chairman; B. Mather, U. S. Army Engineers, Waterways Experiment Station, Vicksburg, Miss.; J. F. McLaughlin, Purdue University, West Lafayette, Ind.; R. C. Mielenz, The Master Builders Co., Division of Martin Marietta, Cleveland, Ohio; J. T. Molnar, The Standard Slag Co., Youngstown, Ohio; M. Polivka, University of California, Berkeley, Calif.; and R. D. Walker, Virginia Polytechnic Institute and State University, Blacksburg, Va. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Related ASTM Publications Concrete Pipe and the Soil Structure System, STP 630 (1977), 04-630000-07 Living with Marginal Aggregates, STP 597 (1976), 04-597000-07 Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Contents Chapter 1--Introduction--R. E. PHILLEO PART I GENERAL Chapter 2--Techniques, Procedures, and Practiees of Sampling of Concrete and Concrete-Making Materials--E. A. ABDUN-NUR Chapter 3--Statistical Considerations in Sampling and T e s t i n g - - n . T. ARNI Chapter 4--Quality in Concrete Testing--J. R. DISE Chapter 5--Needed Researeh--R. D. WALKER 5 24 44 49 PART II TESTS AND PROPERTIES OF CONCRETE Chapter 6 - - T h e Nature of Concrete--T. c. POWERS Freshly Mixed Concrete Chapter 7 - - U n i f o r m i ~ and Workability--o. T. SMITH Chapter 8 - - M a k i n g and Curing Concrete Specimens--R. F. ADAMS Chapter 9--Setting T i m e - - J . n. SPROUSE AND R. B. PEPPLER Chapter 10--Air Content and Unit Weight--F. F. BARTEL Hardened Concrete Chapter 11--Petrographlc Examination--KATHERINE MATHER Chapter 1 2 - - S t r e n g t h - - g . N. DERUCHER Chapter 13--Aceelerated Strength Tests--M. a. WILLS Chapter 14--Elastic Properties and Creep--R. E. PHILLEO Chapter 15--Nondestructive Tests--E. A. WmTEHURST AND V. M. MALHOTRA Chapter 16--Volume Change--J. L. SAWYER Chapter 1 7 - - T h e r m a l Properfies--j. A. RHODES Chapter 18--Pore Structure--GEORGE VERBECK Chapter 19--Corrosion of Reinforcing Steel--P. D. CADY Chapter 20--Corrosion of Embedded Materials Other than Reinforcing Steel--BERNARD ERLIN AND HUBERT WOODS Chapter 21--Bond with Reinforcing Steel--L. A. LUTZ Chapter 22--Abrasion Resistanee--R. o. LANE Chapter 23--Resistance to Weathering--HOWARD NEWLON, JR. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 59 74 102 105 122 132 146 162 180 200 226 242 262 275 300 320 332 351 Chapter 24--Resistance to Chemical Attack--L. H. TUTHILL Chapter 25--Resistance to High Temperatures--PETER SMITH Chapter 26--Radiation Effects and Shielding--MILOS POLIVKAAND H. S. DAVIS Chapter 27--Air Content and Unit Weight--s. a. HELMS Chapter 28--Cement Content--w. G. HIME Special Categories Chapter 29--Ready-Mixed Concrete--R. D. GAYNOR Chapter 30--Lightweight Concrete and Aggregates--v. w. LEWIS Chapter 31--Packaged, Dry, Combined Materials for Mortar and Concrete--A. C. CARTER Chapter 32--Preplaced Aggregate Concrete--a. g. LAMBERTON 369 388 420 435 462 471 503 525 528 PART I l l TESTS AND PROPERTIES OF CONCRETE AGGREGATES Chapter 33--Petrographic Examination--R. c. MIELENZ Chapter 34--Grading--w. Ia. PRICE Chapter 3S--Shape, Surface Texture, Surface Area, and Coatings-M. A. OZOL Chapter 36--Weight, Density, Absorption, and Surface Moisture-W. G. MULLEN Chapter 37--Porosity--w. L. DOLCH Chapter 38--Abrasion Resistance, Strength, Toughness, and Related Properties--R. c. MEININGER Chapter 39--Thermal Properties--8. K. COOK Chapter 40--Chemical Reactions Other than Carbonate Reactions-- 539 573 584 629 646 657 695 708 SIDNEY DIAMOND Chapter 41--Chemical Reactions of Carbonate Aggregates in Cement Paste--H. N. WALKER Chapter 42--Soundness and Deleterious Substances--L. DOLAR- 722 744 MANTUANI PARTIV TESTS AND PROPERTIES OF OTHER MATERIALS Chapter Chapter Chapter Chapter Chapter 43--Mixing and Curing Water for Concrete--w. J. MCCOY 44--Curing Materials--R. E. CARRIER 45--Air-Entraining Admixtures--PAUL KLIEGER 46--Mineral Admixtures--L. H. TUTHILL 47--Chemical AdmixtureS--BRYANT MATHER Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 765 774 787 804 823 Chapter 48--Cellular Concrete--L M. LEGATSKI Chapter 49--Organic Materials for Bonding, Patching, and Sealing of Concrete--R. j. SCHUTZ Chapter 50--Pumpability Aids for Conerete---a. c. VALORE, JR. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:48:22 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 836 852 860 STP169B-EB/Dec. 1978 R. E. Philleo ~ Chapter I--Introduction When an ASTM Committee undertakes the preparation of a statement on the significance of tests and properties of materials under its jurisdiction, it embarks on a job that will never be finished. New varieties of materials are developed, new uses for old materials surface, and testing techniques are refined. Also, for materials such as concrete with time-dependent properties, the age at which users demand test results diminishes. ASTM Committee C-9 on Concrete and Concrete Aggregates articulated its first statement in 1935 with Report on Significance of Tests of Concrete and Concrete Aggregates, ASTM STP 22. Since then, this volume has been updated every ten years. This volume presents the point of view of the 1970s. If we are curious to discover how the outlook of the 1970s differs from that of the 1960s, we need only compare the contents of the current volume with the contents of its predecessor, Significance of Tests and Properties of Concrete and Concrete-Making Materials, ASTM STP 169-A, published in 1966. In Part II on Tests and Properties of Concrete, there are new chapters on accelerated strength testing and nondestructive testing of hardened concrete. Both reflect the growing impatience of users with the 28-day strength cylinder, which, although providing an excellent evaluation of the material leaving a concrete mixer, yields data which are neither timely nor directly applicable to the structure under consideration. There is also a new chapter on preplaced aggregate concrete, an old technique which only recently has been standardized by ASTM because of its applicability to structures for radiation shielding. In Part III on Tests and Properties of Concrete Aggregates, there is now an entire chapter devoted to alkali-carbonate reactions in recognition of the increasing number and complexity of such reactions which recently have been identified. The ability of technologists to tailor concrete to highly specific and unusual applications is highlighted in Part IV on Tests and Properties of Other Materials, where the number of chapters on concrete admixtures has been nearly doubled by the introduction of new chapters on admixtures for IChief, Structures Branch, Engineering Division, Civil Works, Office of Chief Engineers, Department of the Army, Washington, D.C. 20314 Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:37 EDT 2014 1 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978tobyLicense ASTM International www.astm.org 2 SIGNIFICANCE OF THE PROPERTIES OF CONCRETE production of cellular concrete and pumping aids for concrete. The latter bears witness to a minor revolution in the placing of ready-mixed concrete made possible by the development of portable concrete pumps. The volume is the handiwork of a special subcommittee of ASTM Committee C-9, who organized the subject matter, selected the authors, and reviewed the papers. Most of the papers were authored by present or recent chairmen of the technical subcommittees having jurisdiction over the subjects of the papers. T h e subcommittee was chaired by Professor C. H. Best, and the members included Bryant Mather, J. F. McLaughlin, R. C. Mielenz, J. T. Molnar, Milos Polivka, and R. D. Walker. ASTM Committee C-9, as well as all those who produce and use concrete, are indebted to them for their timely statement. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:37 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. STP169B-EB/Dec. 1978 E. A . A b d u n - N u r 1 Chapter 2nTechniques, Procedures, and Practices of Sampling of Concrete and Concrete-Making Materials Introduction Millions upon millions of dollars change hands daily in various segments of the concrete industry, based on evidence obtained from samples. Yet, in most instances, the sample is obtained in an indifferent manner by someone who is ignorant of the basic principles of sampling (frequently a laborer or warehouseman), the use to which the sample is to be put, the tests to be performed on the sample and the final decisions to be based on or derived from the test results--all very important factors that should be considered in the sampling process. There appears to be no adequate appreciation of the importance of sampling by those who should be concerned with the problems resulting from poor sampling--those who have to make important decisions and set policy based on test results from samples--despite the cost of the large volume of samples and testing in the concrete field and the larger economic significance of conclusions which are derived from these. On the other hand, other industries confronted with similar problems have gone to great lengths to develop reliable and efficient methods and procedures. The coal, fertilizer, ore, and abrasives industries [1-3] 2 that have sampling problems similar to those found in aggregates, for example, have developed criteria and methods that increase the probabilities of proper sampling. Basic principles and approaches that can be helpful in providing sampling details for the various segments of the concrete industry have been developed by the American Society for Testing and Materials (ASTM) Committee E-11 on Statistical Methods and others [4-15]. Other sampling 1Consulting engineer, Denver, Colo. 80222. 2The italic numbers in brackets refer to the list of references appended to this chapter. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 5 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978 tobyLicense ASTM International www.astm.org 6 GENERAL procedures for concrete and concrete ingredients, that range from indifferent to very good, may be found in various ASTM standards (see Appendix) and other handbooks and manuals [16-18]. What Is Sampling The Sample A sample is a small portion of a larger volume of group of materials (such as a lot, shipment, stockpile, batch, carload, or truckload) about which information is desired. The characteristics of the sample are presented as evidence of the properties of the larger unit from which it is taken. A series of such samples provides a pattern of the variations in properties of the total universe. Universe, in this instance, means the aggregate of lots, stockpiles, carloads, and so on, which comprise any specific material used in a project or produced under regular production for the izrescribed time interval under consideration. The measurements on many samples from the universe constitute a statistical population. Sampling Sampling is the process of obtaining samples from the larger universe. When the universe is perfectly homogeneous, sampling becomes the simple physical act of taking a sample from the unit about which information is desired. In this case, any sample can truly represent the larger homogeneous whole. Unfortunately, nature, in general, and the concrete field, in particular, rarely if ever, present us with a perfectly homogeneous universe of any material or process. If the rare occasion of perfect homogeneity should occur, one would not know it ahead of time and would have to treat it as a variable. Each lot, truckload, batch, or stockpile, not only varies in some measure from similar units intended to be identically the same, but frequently varies within each such unit. The more heterogeneous the universe, the more work it takes to develop a reliable estimate of its characteristics. Therefore, it pays to save sampling and testing funds where little variability occurs and expend them where more heterogeneity is prevalent. Sampling is thus much more than the physical act of taking a sample of the larger unit as evidence of the properties of the latter. First of all, a sampling plan must be formulated to reflect the variability characteristics of the universe. After that, individual samples taken in accordance with such a plan must be obtained in such a manner that each sample is truly representative of the unit from which it comes. This broadened concept of sampling is in effect an acceptance of the fact that sampling is a complex business and the needed skill lies as much or more in the one exercising overall control of the work as in the one Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. ABDUN-NUR ON SAMPLING OF CONCRETE 7 actually taking the sample. A major reorientation of ideas on the subject is needed. Sampling Plan The development of a sampling plan requires the mastery of the sophisticated fundamentals of probability sampling, an intimate knowledge of the product being sampled, and a high degree of skill, experience, background, and creativeness. In some cases, the help of a statistician will prove advantageous in developing the theoretical aspects and procedures for the practical man to follow. Models for probability sampling, significance, and interpretation have been developed by ASTM Committee E-11: Recommended Practice for Probability Sampling of Materials (E 105), Recommended Practice for Choice of Sample Size to Estimate the Average Quality of a Lot or Process (E 122), and Recommended Practice for Acceptance of Evidence Based on the Results of Probability Sampling (E 141). ASTM Committee D-4 on Road and Paving Materials recently proposed a standard on sampling: Recommended Practice for Random Sampling of Paving Materials (D 3665). Setting up sampling plans without the use of probability techniques will in most instances introduce subconscious bias. From the standpoint of economics, sampling plans either provide a cheaper method of achieving a given reliability or result in a better reliability for a given cost. The degree of reliability should be set to fit the economic need or justification. The end result for which samples are taken affects to a large extent the details of the sampling plan. Once a sampling plan is developed for any given situation or set of conditions, it can be followed easily by the average field man under proper supervision. Details of the many approaches that can be applied to the development of sampling plans for concrete and its various ingredients are beyond the scope of this short discussion. The references in this chapter will provide the reader with an operational starting point. Taking of Sample The actual physical manipulation needed to provide a sample representing a larger unit is simpler than formulating the sampling plan, and the Annual Book of ASTM Standards provides guidelines under the various designations as shown in the Appendix to this chapter. The procedures can be mastered easily, and if the instructions are followed carefully, one can expect a reasonably reliable sample to result. Other guidelines are found in various handbooks and manuals [16-18]. In general these procedures were developed many years ago, and they are becoming outmoded with the new concepts of sampling. They can and are being improved materially in the continuing process of reexamination by the issuing body. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 8 GENERAL The relationship of a sampling plan to the actual taking of a sample may best be illustrated by an example in which the universe is the total concrete of any given class on a project. The concrete reaches the project or is made at the site in a series of batches. Although all batches are intended to be exact duplicates, this is not so in practice. Therefore, for proper evidence of the variations of the concrete properties in the universe, a plan is needed that designates which of the batches to sample in order to develop the same pattern of variation found in the universe; this is known as random or probability sampling. The second step is to sample each batch that has been tagged for sampling, in conformance with the sampling plan, in such a manner as to reflect the variation pattern in the concrete as it comes out of the mixer. This is best done by taking several subsamples at different stages of discharge from each batch and compositing them for a total sample. In case, on the other hand, it is desired to study the efficiency of mixing of the mixer, then the subsamples are tested separately to develop a variation pattern of the mixing operation to determine if such a pattern falls within the tolerances applicable to the situation. This example shows strikingly that sampling in the concrete field is not a simple matter and must not be delegated to the untrained or careless, or relegated to a laborer for convenience. Significance of Various Facets of Sampling Economic Significance Adequate sampling plans and procedures have more far reaching effects than appear on the surface. In the first place, sampling involves the costs of sampling, packaging, and shipping, which represents an investment. But samples are usually taken for the preparation of specimens for testing, which normally costs far more than the sampling and involves time, sophisticated equipment, and skilled personnel, all of which add to the sample cost. However, the greatest economic significance based on the test results from the samples is manifested in the decisions and conclusions which run into millions of dollars daily in the concrete industry alone. In many cases, such decisions are not only economic factors, but also involve safety and life. Thus it is seen that sampling is the most important link in the whole chain of construction events leading to decisions, exchange of funds between parties, contractual relations, and even safety. Under such circumstances, can one sufficiently stress the importance of sampling plans, methods, and procedures? Random or probability sampling permits one to attach measures of confidence to the estimates of population parameters. Biased or subjective sampling precludes the use of such confidence limits. This affects the reliability of decisions based on test results. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. ABDUN-NUR ON SAMPLING OF CONCRETE 9 Adams (Chapter 8) shows the importance of sampling and of the making of specimens in strict accordance with the required standards. Disc (Chapter 4) stresses the importance of the quality of testing. The question may well be raised whether the quality of testing or the proper making of specimens has any significance if the latter were prepared from samples that have been improperly selected, taken, and handled prior to testing. These are some of the factors that seem to have been frequently neglected if one were to judge by observations of actual sampling in the field. Too often, written or verbal instructions require a "representative" sample from a "typical" batch or unit. A sample, for certain purposes as previously described, must be representative of the batch or unit; but as far as the universe is concerned, there is no such thing as a single representative or typical batch or unit. A sample really represents only itself as a point under the probability curve of the universe. Therefore, such instructions are misleading, and result in improper samples. Yet, results of tests made on samples taken with such unrealistic instructions are used to make most important decisions even when the data appear most improbable. Why, then, has sampling been apparently neglected in the concrete field? Many factors have caused this situation to develop. 1. In the concrete field, samples are heavy, bulky, and dirty, and therefore, in many cases, the engineer passes the buck by sending someone at the lower echelon to take care of sampling, feeling that he would be wasting his expensive time to do so himself. 2. In the past, when testing was not used to reach conclusions by statistical or probability means, probability sampling was not nearly as important as it is now, when statistics has come into the picture. Yet, sampling procedures have not been revised substantially. 3. Automation, which makes "quality control" possible and places a premium on homogeniety has only recently come into being in the concrete field. "Perfect" homogeneity was not a practical aim or achievement as long as most operations were conducted by hand, and the influence of the personal differences between individuals was a paramount factor. 4. Decisions have been made to a large extent by whether the engineer felt the job to be satisfactory or not and not so much by test results. The latter were something to stick in the file for legal protection, and when an occasional test turned out to be low, everyone got into a huff and blamed the sample or the contractor and made the latter the goat. Since the engineer in those days was very close to the job and observed everything that was taking place, his judgment was very effective. No one ever dreamed that occasional low test results are part of everyday patterns of variation and are to be expected. If they fall within the proper variation pattern, they should not be a source of concern. Fortunately, these low test results showed up only occasionally since the natural tendency for bias in sampling is towards the better side rather than the poorer side. This problem has been discussed in detail by Abdun-Nur [19]. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 10 GENERAL Sampling and Inspection In most instances, sampling (the actual taking of the sample), which becomes one of the duties of the inspector, is frequently and unfortunately passed on to a laborer furnished by the contractor. In many instances, it has been observed that the inspector handles sampling as a matter of convenience, neglecting the fact that sampling is a most important duty to be performed in exact accord with specified techniques. As an example, on one project, written instructions, the specifications, and the formal inspector indoctrination meetings all stressed the obtaining of three sets of cylinders from three distinct batches of concrete to represent the variations in a given volume. Field observations indicated that several inspectors were making the three sets of cylinders, all at one time, from one single batch. This of course yielded erroneous records, inasmuch as the test results were being analyzed as though the tests had come from three distinct batches rather than from one batch. The record thus indicated a higher degree of homogeneity than actually existed on the project. Inasmuch as variability was tied to strength requirements, this permitted the contractor to get by with lower strenghts than desired and required for the integrity of the design by the engineer. When an inspector was asked why he was not following instructions, the answer was that "It saves making three messes, and gets the job done all in one mess." In general, when the effect of such disregard of instructions is explained, inspectors are more careful. Thus, it is not only important that the inspector be adequately trained and qualified to do his job properly and to pay special attention to his sampling plan and procedures, but it is also just as important to have surveillance to assure that such procedures are being carried out properly. Better trained and higher caliber personnel are badly needed as sampling carries a burden of responsibility that has usually been ignored. Inspection can, of course, be either internal--by the producer or contractor, to control his product--or external--by the owner, his engineer, or his representative to ascertain compliance with specifications. At the present time, there is need for both internal and external inspections to assure proper construction. A detailed discussion of this subject is outside the scope of this paper and has been treated by Abdun-Nur [20]. Protection of Samples Sampling plans, methods, and procedures are not enough to assure proper samples reaching the laboratory for the preparation of specimens for testing. The proper protection, packaging, and handling of the samples is just as important since carelessness in these factors can invalidate the usefulness of the best sample. Wills [21] has shown the undesirable effects Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. ABDUN-NUR ON SAMPLING OF CONCRETE 11 on concrete properties due to the use of bags contaminated with sugar or flour, or bags treated with chemical preservatives. Every engineer has seen concrete cylinder specimens unprotected, permitted to dry out in the hot sun or to freeze on the job. Occasionally, carelessness has resulted in heavy equipment running over specimens which were damaged beyond usefulness; yet, they were sent to the laboratory for testing with the expectation that usable results would be obtained. Proper protection, packaging, and care of samples in the field and in shipping are essential if test results obtained from specimens prepared from these samples are to mean much and if reliable conclusions are to be drawn from such results. These are serious hazards; yet data obtained in such a manner are being used every day as a guide for the uninitiated to follow. Compositing Samples The validity of composited samples depends on the purpose and end use of the test results from the specimens prepared therefrom. If a representative sample of the properties of a unit of concrete or aggregate is to be obtained, then subsamples taken from various portions of the unit and composited are in order. But if the sampling is for the study of the variations within a unit, then the subsamples should be kept separate and individual specimens should be made and tested separately. This question of cornpositing should be decided upon in the development of the sampling plan and passed down to the sampler in the form of instructions to be followed explicitly; otherwise, the analyzed results may be unknowingly very misleading. Sampling and Quality Control The control of any product is only possible through proper sampling. This is true whether the product be aggregates, various packaged ingredients that enter into the concrete as constituents at various times, or the concrete itself in the plastic stage. Sampling permits the determination of whether the process is producing what is needed and when adjustments and their extent may be required to bring the process within tolerances and up to the desired quality. To attempt to control a product by occassional sampling of the finished material is unrealistic, ineffective, and too late--by then it has already been produced and in most cases cannot be modified. Yet in the concrete field, occasional sampling of this latter type is almost standard routine. It is naive to think that this is quality control. To obtain adequate quality control of concrete, every step of the process or procedure must be controlled as well as every ingredient that enters into it. Such control has to be developed by the producer or Contractor (who is a producer in the broad sense of the word) and be built into his proCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. control. The purpose of sampling will determine to a large extent the desirable sampling plan and procedures. to determine the homogeneity for a quality control operation. the reader can also find references to other items in case he desires to go deeper into the subject. In these references. handbooks. Sampling Aggregates (D 75). . Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.s and slumps-even reject a batch that is outside of tolerances [22]. and correct weigh~. Modern automated computer-controlled batch and mixing plants are now available that will record. No further reproductions authorized. the plan can be reduced to less frequent sampling.12 GENERAL cesses or operations. and procedures in various fields. Arni (Chapter 3) treats the statistical facets of sampling concrete and its ingredients. which can be adapted to the needs of the concrete field. Sampfing Concrete and Its Constituents General The Appendix gives a list of the various ASTM standards under the jurisdiction of ASTM Committee C-9. but originating in other committees. Aggregates The workhorse of sampling methods used in aggregate work has been issued by ASTM Committee D-4 under the title. The list of references at the end of this chapter gives papers. methods. or to determine whether a material meets specifications requirements? In general. It treats various procedures for sampling aggregates at various Copyright by ASTM Int'l (all rights reserved). Is the purpose of sampling to investigate the quality of a deposit or a product. a basic full sampling plan and inspection requirement is first developed. The most the owner or purchaser can do is to sample and test to satisfy himself that the product complies with the specification requirements. When results indicate control and acceptable homogeneity for a long period of time. or useful in their work. manuals. In such a plan. but the basic plan is reinstated immediately upon the appearance of any signs that control has been relaxed. and bibliographies that treat approaches to sampling plans. where an operation is functioning under proper and effective quality control procedures. It cannot be imposed by the purchaser or owner from outside. a variable sampling plan can be most effective and economical [23]. Incentives built into the specifications by the owner or purchaser are of tremendous help in getting the producer to develop proper quality control in his operations. Whether this calculated risk is worth taking is up to the responsible en- Copyright by ASTM Int'l (all rights reserved). but if some problem develops in the concrete. even though not standardized specifically for the aggregate field. In practice. pits. warehousing. This works fine as long as everything turns out smoothly. but obviously are different from those for aggregates. and so on) or are delivered in some instances in bulk solution form. All of such materials have had some factory processing. Bonding. E 122. can be found elsewhere [16-18]. bulk sampling. and Sealing Materials These materials reach the job or the concrete products plant in packaged form (cans. it becomes impossible to determine with any certainty what the significant factors might be. Others like fly ash (ASTM Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete (C 311)) involve the same problems that are found in cement sampling. whether natural deposits. in many ways. but it is always possible that some human error somewhere along the line of processing. and stockpiles. and can delay the work. but not about the tools. and D 3665 cited previously provide guidelines for developing such sampling plans. 23-25] provide additional information that is applicable. takes time. It is quite definite in its instructions and cautions about homogeneity or variability of the material in the locations being sampled. bins. Admixtures. ASTM Recommended Practices E 105. railroad cars. Curing. and delivery may have been made and gone undetected. and invariably the processor claims very close quality control. most large users test the source for approval and after that rely on the processor's certification that the material is the same as that submitted for original approval. bags. The references on coal sampling. The acceptance of such a procedure is based on the false assumption that because it is a processed material there are no significant variations in the final product. Patching.ABDUN-NUR ON SAMPLING OF CONCRETE 13 locations such as quarries. E 141. This is. finished aggregates. No further reproductions authorized. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Various methods for sampling. barrels. It requires the taking of a sufficient number of samples to reflect the variability of the material being sampled but does not indicate how to develop a sampling plan for such a series of samples or under what conditions tompositing is valid. buckets. or concrete itself. . This assumption is made for convenience rather than because it represents a true picture--it eliminates the need for continuous testing that is costly. There are not only the normal variations in the materials that are not on record. and sampling in general [1-15. other concrete-making materials. a similar procedure to that used for cement for practically all ordinary jobs except the large government contracts. the procedures and plans are much simpler than in the ease of bulk aggregates. Many plans have been worked out and proven satisfactory and usually can be adapted to the concrete field [1-16. while the second step requires manipulative care to ensure that the sample is representative of the container. there is always the possibility that there is stratification. and can be avoided if the storage container from which the material is dispensed is kept continuously stirred to maintain the homogeneity of its contents (ASTM Specification for Liquid Membrane-Forming Compounds for Curing Concrete (C 309)). and the sample has to be taken in such a manner that it is a composite of the various strata. a tank car.14 GENERAL gineer to determine in each case.4. The second step is to take individual samples from each package that has been set aside for sampling. But if proper original or continuous sampling is desired. The first step is the random sampling of a lot or shipment which results in the selection of a number of the packages out of the whole to be used as evidence of the variation pattern of the lot. single use cylinder molds. or tank truck. curing mats. Detailed guidelines for sampling these classes of materials. When the package is relatively small and the product is in the form of a liquid of some type. If this is not the case. 23-25]. Usually this adaptation consists of a two-step procedure. then the sampling has to be related to the handling and dispensing procedures in order to develop the variation patterns. No further reproductions authorized. . which have proved satisfactory in general industrial applications and which in many cases can be adapted to the concrete field. The first step is based on probabilities and statistical principles.25]. This is likely to get rather complicated.23. The proper sampling for these materials becomes a problem similar to that of sampling any manufactured packaged article or item.10. and handling the various strata will be intermixed. ASTM Specification for Molds for Forming Concrete Test Cylinders Vertically (C 470) is the only standard available in this area. But when one gets into the larger packages. transferring. a composite sample from various portions of each of the shipping containers set aside from the lot or shipment for sampling should be taken for the second step of sampling (ASTM Sampling and Testing Calcium Chloride for Roads and Structural Applications (D 345) and Specification for Chemical Admixtures for Concrete (C 494)). For products such as form insulating mats. In the case of a powdered material that is to be dissolved prior to use. procedures have to be adapted for each material. and so on. To date. as proper shaking or stirring will permit the obtaining of a representative sample without much trouble. may be found in the industrial product control literature [1. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. such as a 50-gal drum. to this writer's knowledge. Copyright by ASTM Int'l (all rights reserved). the second step is easy. Compositing assumes that in the unloading. Needed Improvements and Their Benefits A S T M Standards In many cases. and sampling plans should depend on the purpose for which the sampling is being done. details of manipulations. In general. protection. No further reproductions authorized. A recent example of such problems is a case where a large number of cores were taken and tested by several laboratories. cornpositing. Standardization of this item is more difficult because it involves a lot of judgment which cannot be standardized. and economic decisions involving large sums are frequently made on the basis of testing of specimens from hardened concrete. and repair of concrete. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. where three cores indicated consistently a 50 percent higher strength than those tested by other laboratories--a most improbable situation if sampling had been properly conducted. Hardened Concrete ASTM Obtaining and Testing Drilled Cores and Sawed Beams of Concrete (C 42) governs the taking of cores or the sawing of beams from hardened concrete.ABDUN-NUR ON SAMPLING OF CONCRETE 15 Fresh Concrete ASTM Sampling Fresh Concrete (C 172) outlines in detail the manipulations in taking a sample from a batch but does not describe sampling plans that permit the selection of the batches to be sampled. it is fortunate that the most difficult problem of sampling aggregates from a stockpile does not exist for concrete. Some suggestions are given by Abdun-Nur [26]. . the existing ASTM standards contain the manipulative instructions for taking samples of the various concrete ingredients and other materials used in the curing. the same problems that are encountered in bulk aggregate sampling from truckloads are found also in sampling batches of concrete. ASTM Recommended Practice D 3665 provides guidance for developing such sampling plans. The American Concrete Institute (ACI) Committee 214 on Evaluation of Results of Tests Used to Determine the Strength of Concrete is trying to develop a recommended practice which it is hoped will cover this detail. Sampling procedures. and Copyright by ASTM Int'l (all rights reserved). These are important as safety decisions involving potential life hazard. but no mention is made of how to decide at what point or points such specimens should be secured. What is as important is that the recommended practice will cover the significance of the tests made on such cores or beams. These tests indicated a certain level of strength and a variation pattern--all with the exception of one laboratory. Added to this is the fact that the cost of testing specimens prepared from unreliable samples will be eliminated. and the total saving becomes very appreciable. Recognition of Variability Essentially. the main advantage is that the resulting data are more reliable. Inasmuch as the probability approach to sampling provides the required degree of reliability from the smallest number of samples of any other approach." a sampling plan that reflects the variations in any given situation or universe is needed. modifications or revisions and broadening of scope of these procedures are desirable. Just as the continued stirring of a liquid or solution keeps it so homogeneous that one can take a sample at any time and at any place in the container. such as the coal and ore industries. and industries other than the concrete industry with similar problems. This enables him to make the proper allowances in the production of his concrete to meet a given specification requirement. The importance of proper sampling and its effect on testing and making the final most important decisions needs to be stressed repeatedly. have already done a lot of development work adaptable to the concrete field. Since it must become commonly accepted that there is no such thing as "representative batch" or "typical batch. This may be true for determining compliance with specifications in the few cases where the latter are based on final performance only. To bring it about requires training of many people. . probability sampling achieves the equivalent of homogenization mathematically and permits a calculation of its reliability. particularly in the aggregate area [1-15 and 23-25]. the big problem in sampling in the field of concrete technology is the dissemination of the ideas regarding variability. It has been said that the probability testing of aggregates is of no importance since the testing of the plastic concrete is the final criterion. In most cases. But. Such a plan would provide the proper information for control of concrete and its ingredients as a basis for determining specification conformance and permit making realistic decisions when problems arise. for the concrete producer who is trying to control his product. from the engineer down to the inspector-sampler. in most cases the reduced quantity of sampling will result in an overall decrease of the total sampling cost.16 GENERAL also for the sampling of hardened concrete. The basic fundamentals for probability sampling are available. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. it is essential that he use the best probability sampling techniques to determine the pattern of variation of the aggregates or any other ingredients that go into his concrete. Of course. This perCopyright by ASTM Int'l (all rights reserved). Probability Sampling Probability sampling is our greatest need at the present time. and therefore the decisions based on such information become more realistic. ABDUN-NUR ON SAMPLING OF CONCRETE 17 mits designing to closer tolerances or lower factors of safety. Summary Sampling is probably the most important step in the testing sequence. all the owner or purchaser can do is determine whether the material as produced does or does not meet specifications. . Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and fundamental to the problem of controlling any of the products going into concrete and of the concrete itself. On this information. The one thing needed above all else is the realization that variations in composition and properties of concrete and concrete making materials are basic and can only be reduced but never completely eliminated. the actual sampling becomes a question of following instructions and being sure that there is adequate supervision by the more sophisticatedly trained personnel of the lower grade personnel who actually take samples. Control must be made an integral part of every step in production. it must be stressed that because of the widespread availability of computers and because engineers and statisticians are so comfortable with large amounts of data. Thus. it is the most neglected activity in this area of engineering. It is necessary to sample not only at all steps of production to guide production procedures. Notwithstanding all that has been stressed about the need and usefulness of probability or random sampling. one must keep in mind that a balance must be kept between the practical and theoretical. Trained Personnel Such an approach requires sophisticated and properly trained persons at various levels. millions of dollars change hands daily--yet. but this will be compensated for by the lower cost of the less skilled samplers. No further reproductions authorized. The degree of homogeneity that can be attained in practice depends on the cost of reducing variability as compared with the benefits derived therefrom [19]. Handling of the materials after they have been sampled Copyright by ASTM Int'l (all rights reserved). Incentives built into the specifications can motivate the producer to develop proper control [27-30]. but once plans and procedures have been set. but sampling should also be done on the finished product as close as possible to the point of use to ascertain compliance with specifications. Control cannot be imposed from outside by the job owner or the purchaser of over-the-counter products. and frequently judgment must be used in lieu of complicated theoretical considerations. the cost of supervision and higher grade personnel might increase. Probability sampling and sampling plans are essential to the determination of the true pattern of the existing variations. and in the long run would result in safer and more economical engineering structures. .. 1975. [15] "Acceptance Sampling. Standards. "Somg Problems in the Sampling of Bulk Materials. 1975. Bulk Sampling. pp. D. pp. A. 1951. Edwards. Washington. 59.. More detailed instructions and standards can provide better guidance. [10] Symposium on Some New Techniques in Sampling and Quality Control. Mexico City. 5. This would improve the present sampling situation immensely. C. "How Good is Good Enough. A. pp." International Symposium on Accelerated Strength Testing of Concrete. Vol. 6th ed. 1969. H. 51-56.. [12] Duncan. under proper supervision. MIL-STD-414. D.. Vicksburg. 1954. 1.. A. American Concrete Institute. Vol. are a necessity to achieve maximum reliability with minimum sampling as a basis for final important economic and safety decisions. [16] Handbook for Concrete and Cement. American Society for Testing and Materials. Copyright by ASTM Int'l (all rights reserved). U. 62.. 8th ed..S. 477-485. ." Technical Association of the Pulp and Paper Industry. July 1964. 1973. C. "Probability Sampling Methods for Wool. A S T M STP 162." Proceedings. Washington. Sept. Louis and Deming. 1949. 1963. presented at 67th Annual Meeting.. A S T M STP 242. 48. 172-175. New York. American Society for Testing and Materials. 857-895. 1962. Early. [25] Sampling Procedures and Tables for Inspection by Attributes. May 1964. Nov. 29 April 1963. March 1964. W.. [6] Slonim. No.. [8] Cochran. D. M. New York.. American Sociaty for Testing and Materials. U. and Homogeneity. 49. Jr. A. [22] Abdun-Nur. 1975. 47. E. Superintendent of Documents. March 1961. Army. 1948. 95-116. the samples will not reflect the materials as they are incorporated into the structure. pp. "Contributions of ASTM to the Statistical Aspects of the Sampling of Bulk Materials. [20] Abdun-Nur. Bureau of Reclamation." Proceedings. M. [9] Bicking. Sampling Techniques. March 1967. 2nd ed. G. MIL-STD-IOSD. E. "Inspection and Quality Control. "Bibliography on Sampling of Raw Materials and Products in Bulk.." A S T M Materials Research and Standards. 30 April 1959. and 66. Corps of Engineers. Nov. No. Miss. 11 June 1957. 24-29 Oct. Handbook H-I07. [24] Singlg-Level Continuous Sampling Procedures and Tables for Inspection by Attributes. 64. [7] Tanner. Wiley. American Society for Testing and Materials. and Immediate Evaluation of Concrete Quality.. "A General Sampling Theory. Simon and Schuster. [17] ACI Manual of Concrete Inspection. Mexico. pp.18 GENERAL needs much attention. [11] Bicking. C.. pp. Sampling in a Nutshell. Superintendent of Documents. No further reproductions authorized.. A S T M STP 114.. [23] Sampling Procedures and Tables for Inspection by Variables for Percent Defective. [21] Wills. Jan. A S T M STP 540. J. E. Vol. [13] Visman. 1960. Waterways Experiment Station. References [1] [2] [3] [4] Bulk Sampling. "Accelerated. Vot. American Society for Testing and Materials. Superintendent of Documents. [18] Concrete Manual. 1967." National Sand and Gravel Association.S. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. [19] Abdun-Nur. "Usefulness and Limitations of Samples." 6th Annual Concrete Conference." A S T M Materials Reseach and Standards. A." A S T M Standardization News. Utah. Logan.. A. American Society for Testing and Materials. American Society for Testing and Materials. [5] Tanner. C. 31-46 and 1219-1244. 1958. 1181-1188. Utah State University. 8-13. American Concrete Institute Convention. June 1964 (unpublished). [14] Sampling. Louis. Washington. Coal Sampling." A S T M Materials Research and Standards.C. "Contamination of Aggregate Samples. pp. J." A S T M Materials Research and Standards. Better qualified and trained personnel. J." Proceedings. American Concrete Institute. otherwise. "The Sampling of Bulk Materials. 1949 and subsequent revisions. 1976. "Designing Specifications--A Challenge.. E.. [27] Abdun-Nur. Journal of the Construction Division. When more than one reference is shown. 55th Annual Meeting. 19-23 Jan. E. "Adapting Statistical Methods to Concrete Production. C.." Proceedings. 13-17. APPENDIX ASTM DESIGNATIONS UNDER JURISDICTION OR RELATED TO WORK OF ASTM COMMITTEE C-9 ASTM Designation Title Sample Origin or Requirement" SAMPLING AND TEST METHODS C 29 C 30 C 31 C 39 C 40 C 42 C 70 c 78 C 85 C 87 C 88 Unit Weight of Aggregate Voids in Aggregate for Concrete Making and Curing Concrete Test Specimens in the Field Compressive Strength of Cylindrical Concrete Specimens Organic Impurities in Sands for Concrete Obtaining and Testing Drilled Cores and Sawed Beams of Concrete Surface Moisture in Fine Aggregate Flexural Strength of Concrete (Using Simple Beam With Third-Point Loading) Cement Content of Hardened Portland Cement Concrete Effect of Organic Impurities in Fine Aggregate on Strength of Mortar Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate D 75 D 75 C 172 C 31. 1. Sept.." Proceedings. 4315. 1966. E. C 192 D 75 yes D 75 C 31. [30] Adbun-Nur. National Conference on Statistical Quality Control Methodology in Highway and Airfield Construction. "yes" indicates that the standard includes sampling instructions. D. 4. 1976. 3. pp. 2.ABDUN-NUR ON SAMPLING OF CONCRETE 19 [26] Abdun-Nur. No further reproductions authorized.. 4900. . E. A.. C 192 yes D 75 D 75 "This column indicates the best source or method of sampling for the particular designation available in existing ASTM standards." Proceedings." Highway Research Board Special Report 106. American Society of Civil Engineers. "Sampling of Concrete in Service. A. Separate No. "no" indicates that no ASTM standard for sampling the material in question is available. [29] Abdun-Nur. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. each reference reflects one of the ingredients needed for the standard. [28] Abdun-Nur. A. "ina" indicates that specific sampling procedures are inapplicable. Copyright by ASTM Int'l (all rights reserved). May 1965. 1970. Washington. Journal of the Construction Division. E. American Society of Civil Engineers. Separate No. Nov. A. A. "What is the Quality Assurance System?" Transportation Research Board. "Product Control and Incentives. 1966. Longitudinal. and Torsional Frequencies of Concrete Specimens Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) Air Content of Freshly Mixed Concrete by the Pressure Method Bleeding of Concrete Air Entraining Admixtures for Concrete Comparing Concretes on the Basis of Bond Developed With Reinforcing Steel Scratch Hardness of Coarse Aggregate Particles Potential Reactivity of Aggregates (Chemical Method) Flexural Strength of Concrete (Using Simple Beam With Center-Point Loading) Sampling and Testing Fly Ash for Use as an Admixture in Portland Cement Concrete Length Change of Drilled or Sawed Specimens of Cement Mortar and Concrete Potential Volume Change of Cement-Aggregate Combinations Ball Penetraton in Fresh Portland Cement Concrete Time of Setting of Concrete Mixtures by Penetration Resistance Abrasion Resistance of Concrete by Sandblasting Copyright by ASTM Int'l (all rights reserved). C 293 D D D D 75 75 75 75 D 75 D 75 C 172 D 75 C 172 no yes yes C 172 C 42 D 75 D 75.20 GENERAL ASTM Designation C 116 C 117 C C C C 123 127 128 131 C 136 C 138 C C C C 142 143 156 157 C 172 C 173 C 174 C 183 C 192 C 215 C 227 C 231 C 232 C 233 C 234 C 235 C 289 C 293 C 311 C 341 C342 C 360 C 403 C 418 Title Sample Origin or Requirement a Compressive Strength of Concrete Using Portions of Beams Broken in Flexure Materials Finer Than No. C 192 no . no D 75 D 75 C 31. Yield. C 192 D 75. C 192 C 192. 200 (75-~m) Sieve by Mineral Aggregates by Washing Lightweight Pieces in Aggregate Specific Gravity and Absorption of Coarse Aggregate Specific Gravity and Absorption of Fine Aggregate Resistance to Abrasion of Small Size Coarse Aggregate by Use of the Los Angeles Machine Sieve or Screen Analysis of Fine and Coarse Aggregates Unit Weight. C 78. and Air Content (Gravimetric) of Concrete Clay Lumps and Friable Particles in Aggregates Slump of Portland Cement Concrete Water Retention by Concrete Curing Materials Length Change of Hardened Cement Mortar and Concrete Sampling Fresh Concrete Air Content of Freshly Mixed Concrete by the Voiumetric Method Measuring Length of Drilled Concrete Cores Sampling Hydraulic Cement Making and Curing Concrete Test Specimens in the Laboratory Fundmental Transverse. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. yes C 192 D 75. No further reproductions authorized. yes C 172 C 172. C t92 yes C 42 D 75 C 172 C 172. yes yes yes no no . C 192 C 172 C 31. Preparing. C 192 yes yes D 75 D 75 C 192 D 75. and Testing Specimens from Hardened Lightweight Insulating Concrete for Compressive Strength Resistance to Abrasion of Large Size Coarse Aggregate by Use of the Los Angeles Machine Total Moisture Content of Aggregate by Drying Test for Unit Weight of Structural Lightweight Concrete Potential Alkali Reactivity of Carbonate Rocks for Concrete Aggregates (Rock Cylinder Method) Pulse Velocity Through Concrete Capping Cylindrical Concrete Specimens Staining Materials in Lightweight Concrete Aggregates Specific Gravity. 21 yes C 31. No further reproductions authorized. and Voids in Hardened Concrete Resistance of Concrete to Rapid Freezing and Thawing Critical Dilation of Concrete Specimens Subjected to Freezing Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals Compressive and Flexural Strength of Concrete Under Field Conditions Making.ABDUN-NUR ON SAMPLING OF CONCRETE ASTM Designation C 441 C 469 C495 C 496 C 512 C 513 C 535 C 566 C 567 C 586 C 597 C 617 C 641 C 642 C 666 C 671 C 672 C 683 C 684 C 702 C 779 C 796 C 803 C 805 C 827 D 75 D 345 D 545 D 1191 Title Sample Origin or Requirement a Effectiveness of Mineral Admixtures in Preventing Excessive Expansion of Concrete Due to the Alkali-Aggregate Reaction Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression Compressive Strength of Lightweight Insulating Concrete Splitting Tensile Strength of Cylindrical Concrete Specimens Creep of Concrete in Compression Securing. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. yes yes yes C 172 C 172 D 75 no C 192 no yes C 192. no no C 192. and Testing of Concrete Compression Test Specimens Reducing Field Samples of Aggregate to Testing Size Abrasion Resistance of Horizontal Concrete Surfaces Foaming Agents for Use in Producing Cellular Concrete Using Preformed Foam Penetration Resistance of Hardened Concrete Rebound Number of Hardened Concrete Early Volume Change of Cementitious Mixtures Sampling Aggregates Sampling and Testing Calcium Chloride for Roads and Structural Applications Preformed Expansion Joint Fillers for Concrete (Nonextruding and Resilient Types) Concrete Joint Sealers Copyright by ASTM Int'l (all rights reserved). yes no no D 75. Accelerated Curing. Absorption. C 183 D 75 C 172 C 183 yes yes yes D 75 D 75 D 75 C 192. Hot-Poured for Concrete and Asphalt Pavements Joint Sealants. No further reproductions authorized. Hot-Poured. Hot-Poured Elastic Type Insoluble Residue in Carbonate Aggregates Joint Sealants. yes yes yes C 183 yes D 75. Cold-Application Type Jet-Fuel-Resistant Concrete Joint Sealer.22 GENERAL ASTM Designation D 1851 D 1855 D 3042 D 3407 D 3408 Title Sample Origin or Requirement ~ Concrete Joint Sealers. Dry. C 172. Cold-Application Type Copyright by ASTM Int'l (all rights reserved). Combined Materials for Mortar and Concrete Molds for Forming Concrete Test Cylinders Vertically Chemical Admixtures for Concrete Blended Hydraulic Cements Fly Ash and Raw or Calcined Natural Pozzolan for Use in Portland Cement Concrete Aggregates for Radiation-Shielding Concrete Concrete Made by Volumetric Batching and Continuous Mixing Calcium Chloride Standard Sizes of Coarse Aggregate for Highway Construction Sodium Chloride Preformed Expansion Joint Filler for Concrete (Bituminous Type) Concrete Joint Sealer. yes D 75. Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. for Portland Cement Concrete Pavements yes no yes yes yes SPECIFICATIONS C 10 C 33 C 94 C 150 C 171 C 260 C 309 C 330 C 331 C 332 C 387 C 470 C 494 C 595 C 618 C 637 C 685 D 98 D 448 D632 D 994 D l190 D1751 D1752 D 1850 Natural Cement Concrete Aggregates Ready-Mixed Concrete Portland Cement Sheet Materials for Curing Concrete Air-Entraining Admixtures for Concrete Liquid Membrane-Forming Compounds for Curing Concrete Lightweight Aggregates for Structural Concrete Lightweight Aggregates for Concrete Masonry Units Lightweight Aggregates for Insulating Concrete Packaged. Hot-Poured Elastic Type Preformed Expansion Joint Fillers for Concrete Paving and Structural Construction (Nonextruding and Resilient Bituminous Types) Preformed Sponge Rubber and Cork Expansion Joint Fillers for Concrete Paving and Structural Construction Concrete Joint Sealer. Elastomeric-Type. C 192 D 345 D 75 yes yes yes yes yes D 140 . Hot-Poured.ABDUN-NUR ON SAMPLING OF CONCRETE ASTM Designation D 1854 D 2628 D 3405 D 3406 Title Sample Origin or Requirement" Jet-Fuel-Resistant Concrete Joint Sealer. Hot-Poured. Elastomeric-Type. Hot-Poured Elastic Type Preformed Polychloroprene Elastomeric Joint Seals for Concrete Pavements Joint Sealants. 23 D 75. for Portland Cement Concrete Pavements D 140 yes yes yes RECOMMENDED PRACTICES C 295 C 457 C 682 C 801 C 802 C 823 D 3665 E 105 E 122 E 141 Petrographic Examinations of Aggregates for Concrete Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete Evaluation of Frost Resistance of Coarse Aggregates in Air-Entrained Concrete by Critical Dilation Procedures Determining Mechanical Properties of Hardened Concrete Under Triaxial Loads Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials Examination and Sampling of Hardened Concrete in Constructions Random Sampling of Paving Materials Probability Sampling of Materials Choice of Sample Size to Estimate the Average Quality of a Lot or Process Acceptance of Evidence Based on the Results of Probability Sampling Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. yes yes C 192. yes C 192 yes yes ina ina ina ina . Sun Apr 6 21:38:50 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. for Concrete and Asphalt Pavements Joint Sealants. No further reproductions authorized.astm. some of which are listed in the references. information about how to use these techniques in the given situations." Significance of Tests and Properties of Concrete and Concrete-Making Materials. Many sources. are already available that provide such information in great detail. Federal Highway Administration. Rather.STP169B-EB/Dec.4. by references to other sources as much as possible. A S T M STP 169-. 21. to suggest techniques that are appropriate to use in these situations. 1960.. 1978 H. Sampling 2 The first consideration in any process of evaluation of characteristics of a material is. to provide. Test results l Retired. A. Copyright9 1978 tobyLicense ASTM International www. Washington. 2Adapted from Cordon. p. formerly materials research engineer. How shall the material be sampled so that the results of whatever measurement process is to be applied will provide the needed information and the evaluation can be made with the desired degree of confidence? Variations in samples of concrete and concrete-making materials make it difficult to obtain samples with the assurance that they are completely representative of the source or production of these materials. the purpose is to identify situations that are peculiar to the testing and evaluation of cement and concrete in which statistical techniques can be of value. 20590. T. Department of Transportation. to point up some of the pitfalls and misconceptions that often cause problems in the application of statistical techniques. and. Sun Apr 6 21:38:51 EDT 2014 24 Downloaded/printed by Universidade do Gois pursuant Agreement.org . last but not least. Copyright by ASTM Int'l (all rights reserved). W. A r n i t Chapter 3--Statistical Considerations in Sampling and Testing Introduction It is not the purpose of this chapter to provide a short text on general statistical methods and procedures. Americal Society for Testing and Materials.C. D. "Size and Number of Samples and Statistical Considerations in Sampling. therefore. or quantity of finished production. It is necessary. expansion of concrete prisms due to alkali reactivity. Examples are freezing and thawing of concrete prisms. Examples are grading of aggregate. This is possible since the general characteristics of aggregate quality can be estimated from a relaCopyright by ASTM Int'l (all rights reserved). but they also measure the uniformity of concrete produced. strength of concrete. soundness of aggregate. He could at least make conservative assumptions rather than rely on fallacious information. Tests for concrete and concrete materials may conveniently be separated into the following general categories. An engineer or architect who must rely on samples or tests that do not accurately represent materials or structures could probably make more objective decisions if there were no samples or tests available. . drying shrinkage. These tests demonstrate how a given material will perform in concrete under field or simulated field conditions. These tests not only provide a check on the performance of materials and may be used for acceptance or rejection of the work. No further reproductions authorized. Performance tests may also be used as acceptance tests. to establish the accuracy desired in each case commensurate with funds and facilities available and with how much information it is deemed necessary to obtain. aggregate quality evaluation may be based on test results of a composite sample. influence of admixtures on the properties of concrete. Research Procedures--Tests which are conducted in the laboratory or field to establish relationships among the variables that influence the properties of concrete. source. Concrete Aggregates Acceptance tests for concrete aggregates establish the suitability of a deposit. Acceptance Tests--Tests which demonstrate that the materials in question will meet specific requirements of the work as specified. as well as the influence of testing and construction practices. are reflected in the strengths of the cylinders. but additional samples or samples of greater size increase the cost of testing. and rate of hardening. During preliminary reconnaisance of available deposits. since most properties of concrete and concrete materials. Examples include relationship between strength and water-cement ratio. 1. and air content of concrete.ARNI ON STATISTICAL CONSIDERATIONS 25 are more reliable as the number and size of samples increase. slump. 2. Construction Control Tests--Construction control tests are made at intervals throughout construction of a project. It may be better to make no tests than to make tests with poor samples which do not portray the actual properties of the materials. 3. (or 150 by 300 mm) cylinders is universally accepted as a standard of control in the United States. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and rate of hardening at various temperatures. The strength of 6 by 12-in. 3 TABLE 1--Size of sample requiredfor petrographic examination.4 mm. for example. 30 to 50 No. No further reproductions authorized. 8 to 16 No. No. Variations in the size of samples required for petrographic examination are shown in Table 1 [1]. 3The italic numbers in brackets refer to the list of references appended to this chapter. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Other Materials Materials used in making concrete (other than portland cement and aggregates) include water and admixtures.1 g 0. however.. the properties of and variations in the most promising source can be established with samples from locations t h r o u g h o u t the area and depth o f the deposit. 3/8 to 3/[6 in. U n d e r this procedure it is assumed that the chemical composition of a water source will not vary during the construction of the project. = 25.6 g. 50 to 100 57 lb (26 kg) 19.26 GENERAL tively small n u m b e r of tests. After preliminary analysis. are also discussed. Water may contain harmful salts. As a general rule.75 lb (340 g) 15 g 2. The n u m b e r of samples will vary with the size of the deposit. W a t e r .I t is generally taken for granted that available water will be suitable for making concrete.1 lb (8. 16 to 30 No.2 kg) 0. and 1 lb = 453.7 kg) 2. Size Fraction Weight of 300 Particles 3 to 11/2in.033 g 0. a chemical analysis of a water sample is made to establish its suitability.6 lb (1. 4 to 8 No. aggregate samples need only be large enough to include a representative portion of all materials present in the source and provide ample material for all tests contemplated as specified by standard test procedures. and the size of samples will vary with the m a x i m u m size of aggregate occurring in the deposit. Other materials. .28 g 0. For gradation analysis. and where there is a question. 11/2 to 3/4 in.0066 g Conversionfactors-1 in. samples should be large enough to assure occurrence of particles of the largest dimension in sufficient n u m b e r so that the inclusion or exclusion of one of these large particles will not affect the grading significantly. Copyright by ASTM Int'l (all rights reserved). used to treat hardened concrete surfaces. 3/4 to 3/a in. ARNI ON STATISTICAL CONSIDERATIONS 27 Mineral Admixtures--Pozzolans and other mineral admixtures may be proprietary materials or may come from natural deposits. No further reproductions authorized. This test establishes the acceptance of the material and is assumed to be representative of the production or lot under consideration. particularly epoxy resins. The performance of these materials is the responsibility of the manufacturer. The ASTM Specification for Liquid Membrane Forming Compounds for Curing Concrete (C 309) specifies that samples be taken for each lot. in addition. ASTM Sampling and Testing Fly Ash or Natural Pozzolans for Use as an Admixture in Portland Cement Concrete (C 311) requires an 3. These materials are composed of various combinations of chemicals and are sold under various trade names. It is necessary to rely on the manufacturer's recommendations when using these materials. . Bonding and Patching Materials--The use of bonding and patching materials. The ASTM Test for Water Retention by Concrete Curing Materials (C 156) determines the performance of curing materials in preventing evaporation. combinations of 50 percent linseed oil and 50 percent thinner are recommended in the literature. or shipment under test and uniformity from sample to sample. Chemical. batch. Proprietary materials for this purpose are on the market and.' A natural deposit will require sufficient samples to establish the extent and depth of the deposit. has increased in importance in the last several years. The ASTM Specification for Air-Entraining Admixtures for Concrete (C 260) and Specification for Chemical Admixtures for Concrete (C 494) give specific instructions for size and number of samples to be taken. Sealing Materials--The application of sealing materials to hardened concrete reduces the absorption of moisture and is a promising method of reducing freezing and thawing deterioration. and performance tests for compressive strength and drying shrinkage are required. With minor exceptions. lot. Curing Materials--Membrane curing compounds are used to retain the mixing water in concrete until curing has taken place. Statistical considerations in testing mineral admixtures require establishing a reliable average for the deposit. the suitability of chemical admixtures is established by their performance when used in concrete. The ASTM Test for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (C 672) is used to measure the effectiveness of sealing materials in reducing absorption. Copyright by ASTM Int'l (all rights reserved). physical.6-kg (8-1b) sample for each 91 Mg (100 tons) of material. The composition of these materials is complex and is varied to produce specific desired results. Statistical considerations are concerned with the sample being representative of the lot or production to be used on the specific work. or other unit of production. Chemical Admixtures--Nearly all chemical admixtures are proprietary materials sold under a particular brand name. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and entrained air content is also required for concrete that is to be exposed to freezing and thawing. in the form of 6 by 12-in. or rejected on the basis of individual tests. Evaluation of strength tests is discussed further in the next section. corrected. This does not preclude analysis of the uniformity and control of these properties. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. largely at the instigation of Walker. Flexural strength of beams is also used extensively for pavements. indirectly. Tests of fresh concrete provide a means of checking the proportions and properties of the concrete mixture. The required number of tests of fresh concrete will depend upon the uniformity of production. more extensively. . As in the case of aggregate acceptance tests. The measurement of the air content (ASTM Recommended Practice for Microscopical Determinations of Air-Void Content and Parameters of the AirVoid System in Hardened Concrete (C 457)) and distribution and size of air voids enables the engineer to control properly the use of air-entraining agents. (or 150 by 300-mm) cylinders broken in compression after 28 days of moist curing is generally accepted as one measure of concrete quality. It is assumed that samples taken each day represent the concrete placed during that day. usually. the strength of concrete measured by the strength of 6 by 12-in. tests of fresh concrete may have limited statistical considerations since individual tests serve as a basis for action. The density or unit weight of the concrete is used to measure the volume of a given batch of concrete and the proportions of ingredients of fresh concrete based on the volume of concrete produced [2]. in the United States. cylinders. In the final analysis. for the analysis of strengths of concrete specimens. the American Concrete Institute (ACI) began work on statistical evaluation of compression tests that eventually resulted in the publication of ACI Standard Recommended Practice for Evaluation Copyright by ASTM Int'l (all rights reserved).28 GENERAL Concrete Acceptance and Performance Tests--Acceptance and performance of concrete is established by tests of fresh and hardened concrete. The chief pioneer in this effort was Walker who published his study in 1944 [3]. The slump test and other measures of consistency indicate the water content and. No further reproductions authorized. and like other performance tests the acceptance of concrete is based on these tests. This provides an accurate means of determining the cement content per unit volume of concrete. The concrete mix will generally be accepted. Evaluation of Strength Tests One of the earliest and most widely used applications of statistics in the concrete field has been in the area of evaluation of strength tests both of mortar cubes for the testing of cement strength and. water-cement ratio of a given mixture and may be used to reject concretes having excessive water. In 1946. No further reproductions authorized. a reprint of ACI 214-65.ARNI ON STATISTICAL CONSIDERATIONS 29 of Strength Test Results of Concrete (ACI 214-77). Mean and average are synonymous terms. measured by the standard deviation or the coefficient of variation. A word is appropriate. The meaning of these terms and directions for calculating them are given in ACI 214 as well as in other statistical references [5-8]. this document has undergone a number of revisions. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and reprints of two earlier papers dealing with evaluation of concrete strengths [4]. 5. Evaluating Standard Cylinders The methods used for evaluating strength measurements in ACI 214 involve several important statistical concepts that are useful in other situations. Results obtained in the testing of carefully made concrete specimens from a concrete production that is as uniform as is possible to make it exhibit a wide scatter. . however. It is a practical impossibility to design concrete so that no standard test will ever fall below any realistic so-called minimum design strength. Coefficient of Variation versus Standard Deviation It is a common misconception that the standard deviation and the coefficient of variation are merely alternative ways of expressing the spread Copyright by ASTM Int'l (all rights reserved). but standard deviation and coefficient of variation are not. 2. The frequency with which routine tests will fall below a so-called specified minimum is determined by the average strength of the production and the spread of the distribution. 1. the most recent of which was adopted in 1977. about the difference in use between standard deviation and coefficient of variation. 3. These terms are not merely alternative ways of measuring the same thing and are not equally applicable in all situations. and the coverage will not be duplicated here. These concepts include the following. The aggregate of such results exhibits a distribution pattern of a characteristic form that has a characteristic central tendency. This point is discussed further. First published as a standard in 1957. 4. Most of these topics are adequately covered in ACI 214 and in other statistical references. In 1971 a symposium was conducted at the ACI Fall Convention on the subject "Realism in the Application of ACI Standard 214-65. and a characteristic spread on either side of the high point of the curve that describes the distribution. whether the latter is measured by the standard deviation or the coefficient of variation." This symposium presented valuable information on the meaning and use of ACI 214 and resulted in a symposium volume that included seven papers presented at the symposium. measured by the mean or arithmetic average. (See the references listed in ACI 214 and for a more detailed technical discussion of the differences between standard deviation and coefficient of variation. (a) The test measurements do not adequately represent the strength of the concrete in place. and that which one should be used in a given situation is merely a matter of convenience or preference. at the very least. but the method of analysis is similar. and its use is based on the same underlying assumptions about the data. (b) Even to the extent that the specimens represent the strength of concrete in the structure.) Accelerated and In-Place Tests for Evaluating Concrete The traditional method of evaluating strength or quality of concrete in general in the United States has been by the use of compressive strength tests of concrete cylinders. although the average strength level of a group or population of measurements from a given production may change. either explicitly or implicitly. More recent research has indicated that neither standard deviation nor coefficient of variation is appropriate over the whole range of concrete strengths encountered in practice. The ACI Building Code Requirements for Reinforced Concrete (ACI 318-71) adopted the standard deviation. Thus. which is often used as a simpler statistic is actually most often used. . This method of evaluation has always been subject to two main criticisms. specifically when the standard deviation is proportional to the average. In the 1957 and 1965 versions of ACI 214 it was assumed that the coefficient of variation was the appropriate statistic for concrete strength measurements. The standard deviation is the most generally accepted and widely used measure of variability. the most recent revision of ACI 214 recognizes both measures and recommends that the standard deviation be used for strengths greater than 211 k g f / c m 2 (3000 psi). although previous editions of this standard merely referred to ACI 214-65.30 GENERAL of measurements. and over the years the problem of which measure of variability is appropriate to use in evaluation of concrete strengths has been the subject of much discussion and controversy. The use of the coefficient of variation is appropriate whenever the standard deviation varies with the level of strength. The range. the standard deviation remains the same. (or 150 by 300 mm) cylinders tested at 28 days. So far as compressive strength is concerned. as a means of estimating the standard deviation. since. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. they represent past history because of the fact that results are usually not obtained until 28 days after the concrete is placed. Other countries have used cubes. No further reproductions authorized. This is not true. they are not subject to the same curing conditions as concrete in the structure and are tested in a very different environment from that in which the concrete in the structure exists. see Ref 9. the assumption is that. This too makes it difficult to do anyCopyright by ASTM Int'l (all rights reserved). usually 6 by 12-in. pulse velocity measurements. More recently it has been recognized that the specified strength as used was really not a minimum and it was cornCopyright by ASTM Int'l (all rights reserved). a number of other methods of measurement have been developed. Relationships between Accelerated or In-Place Tests and Standard Cylinders Testing of concrete specimens for compressive strength occupies a unique position in the field of testing of construction materials because of the fact that concrete structures have traditionally been designed on the theory that the concrete in the members of the structure achieved. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It is not the purpose of this chapter to discuss the relative merits of the methods for the purpose of such evaluation. such as 24 to 48 h. especially since they rely on various special curing conditions that cause an acceleration of strength development. The second category includes a number of systems that measure different aspects of concrete quality. but rather to examine the statistical methods involved in analyzing the results obtained by use of the methods. in particular. and. All of these methods in both categories have their advantages and disadvantages for the purpose of assessing concrete quality.ARNI ON STATISTICAL CONSIDERATIONS 31 thing about remedying the situation if serious difficulties are found. Three of these methods have been standardized in ASTM Standard Method of Making. in a reasonable length of time after placement of the concrete. to discuss what is involved in the investigation of interrelationships between the methods. Accelerated Curing. . penetration tests. and (b) various so-called inplace methods that attempt to determine the strength of concrete in place in the structure without relying on separately cast and cured specimens. and any one or any combination of them could be used for the purpose of evaluation of concrete quality. especially with the more rapid construction techniques that now prevail. and pullout tests. this specified strength has often been treated as a minimum strength that the concrete should have. In the past. a certain specified degree of strength. These involve two main categories of measurement systems: (a) accelerated methods that attempt to assess the strength of standard specimens at earlier ages. No further reproductions authorized. The first three of these are now standardized ASTM tests (ASTM Test for Rebound Number of Hardened Concrete (C 805). designated in design formulas as f c ' . and ASTM Test for Penetration Resistance of Hardened Concrete (C 803)) and a standard for the fourth is now being developed. These methods include Swiss hammer or rebound tests. and Testing of Concrete Compression Test Specimens (C 684). In an attempt to remedy or minimize the effects of one or both of these difficulties. The first category of methods is still subject to the limitation that the strength measurements are still not actually representative of strengths existing in the structure. ASTM Test for Pulse Velocity Through Concrete (C 597). correlation coefficients calculated from paired data obtained by the two methods are calculated and reported. In these reports. In published reports on these attempts. see Refs 10 and 11. In the case of strength evaluation. as in the case of a negative correlation. In either case there is often a lack of understanding of what is really meant by a good correlation or a "significant correlation coefficient. the correlation coefficient has very limited use in the field of analyzing engineering data. and many attempts have been made to develop methods for using accelerated or in-place tests to "predict" what the 28-day cylinder strengths would be. For further discussion of this point. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.32 GENERAL pletely impractical for it to be so. More specifically. Regression Lines The standard method of using paired data as a source of developing means for predicting one variable from another is by calculating a linear Copyright by ASTM Int'l (all rights reserved). Reference 11 contains quotations from a number of statistical authorities on the use of the correlation coefficient. however. There will always be a good correlation between the results of any test that exhibits such behavior and the results of standard strength tests. in other words that the relationship is completely random. In other cases. all of the in-place tests mentioned tend to show increases in the measurements as concrete strength increases due to continued hydration of the cement or to whatever cause." W h a t is meant by a good correlation is that as one of the variables being correlated increases. the other tends to increase also. The problems connected with how closely in time and character the results of strength tests approximate those in the structure remain. In fact. or alternatively. No further reproductions authorized. Thus later specifications and other documents have tended more and more to define f c ' as a strength level below which no more that a certain percentage of strength tests would be allowed to fall (ACI 214 and 318). what is meant by a good correlation is often not specified. . Thus a good correlation or a high correlation coefficient dees not in itself constitute evidence that the relationship is sufficiently close to permit the use of one type of test as a means of prediction of what will happen in another type. a statement often occurs to the effect that a "good correlation" was found between the results obtained by the use of two alternative test methods when applied to supposedly identical concretes. All that is indicated by a good correlation is that the trend exhibited by the data when one variable is plotted against the other is sufficiently well defined to permit rejection of the hypothesis that there is no relationship between the two variables whatever. the second variable tends to decrease as the first increases. this applies to the relationship between standard 28-day strength tests and those obtained by one of the alternative methods. 1. It is curious. This method is described elsewhere and will not be detailed here [5. However. The fact that this is so is usually taken account of by the recognition that a large quantity of data are needed to calculate a reliable line. and. that recognition of the scatter of the data often does not extend beyond calculation of the regression line to its use. This use is discussed by Hockersmith and Ku [15]. the better. An example is the calibration of proving rings that are used for calibrating testing machines.8. the more data. some problems with and misconceptions about such so-called prediction lines need to be discussed. even when the existence of this uncertainty is recognized. usually the easier of the two measurements to make. This point is illustrated in the case of prediction of compressive strength measurements from penetration and rebound tests in Refs 1 6 and 17. each of these parameters has an estimated variance and corresponding standard error (the square root of the variance): S b l 2 for the slope and Sbo 2 for the Copyright by ASTM Int'l (all rights reserved). there is lack of recognition of how wide this uncertainty is and of its effect on the calculated data. The user of the line often acts as though the fact that he has calculated the line from a lot of data that exhibited a certain scatter ensures that future data will now realize that this is the true line and conform to it exactly. . b~. although both sets of measurements are affected by changes in the property of interest. and reads off the corresponding value of the dependent variable without making any recognition of the fact that. No further reproductions authorized. If regression lines showing the relationship between data from two measurement systems are to be calculated and used for any purpose other than to illustrate what kind of relationship existed in the data. if the regression line really represents the behavior of the current data in the same way that it represented that of the data from which it was calculated. and the Y intercept of the line. The calculation of a linear regression line involves the calculation of two parameters: the slope of the line. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.12-14]. then the future data are subject to the same scatter as the original data. 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. in fact. b 0. This is due to the fact that. and the calculated Y value has a wide uncertainty associated with it. they are actually measuring two different quantities and are thus affected by different sets of influences that are extraneous to the property of interest. refers to the line.ARNI ON STATISTICAL CONSIDERATIONS 33 regression line using the method of least squares. several things have to be considered. Very often. however. In the situation where two measurement situations bear a statistical relationship to each other and one of the test methods is used to obtain measurements that are used to predict measurements of the other type. He makes a measurement of his independent variable. there is almost always a large amount of scatter in the data. Due to the departures of the data points from the line. 27 = 26 . there is insufficient evidence to conclude that the true slope is other than zero. calculated from the sum of the squares of the deviations of the measured Ys above and below the fitted line. . Sy 2. In general. . Copyright by ASTM Int'l (all rights reserved).. . 1--Regression curve and confidence limits f o r compressive strength versus rebound numbers... Sy. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. . ~if the slope is not at least twice as large as its standard error. a confidence interval for the fitted line should be shown on the graph of the line (Fig. . . In addition to the quantities mentioned in 1. . 2. however.- I 22 - i! i I 2 1 .34 GENERAL intercept. there is an estimated variance. These quantities. The three measures of variation (variances or their corresponding square roots) should always be given whenever a regression line is reported. give an indication of how significant the relationship is. and that the relationship is other than a purely random one. No further reproductions authorized. .- i i :1 i 2 0 I 2000 3000 4000 si sl ~S u 5000 ~'u 6000 COMPRESSIVE STRENGTH" PSI FIG. . ~. . : Ru / i z ~ 1. In addition. The standard errors of the slope and intercept are frequently omitted... f o ~ 24 R I__ 2 3 . 1). How to COMPRESSIVE 15 I 30 2jO r. the number of pairs of data from which the regression was calculated and the range of spread of both X and Y values should be reported along with the other parameters. 29 t STRENGTH. 25 / . ! 9 --~t . MPa 25 ~ 30 i 35 4p ! / 28 . In addition. and corresponding standard deviation. This is not correct and gives a too optimistic picture of the uncertainty of estimated Y values.2 MPa (4530 psi). the 95 percent confidence interval for the average rebound measurement is from 24 to 26. Often a confidence interval is plotted by multiplying the Sr by the t value for the number of points used and drawing parallel straight lines above and below the regression line. even when all the parameters and the estimates of their uncertainty and the proper confidence limits are correctly calculated and reported. It should be noted that the upper and 'lower confidence limits are represented by two branches of a hyperbola which are closest together at the point where X = ~(. this figure indicates a calculated average compression strength of 31. There are three kinds of confidence intervals that can be calculated for a fitted regression line: the line as a whole. however. It is important to remember that the first case. The meaning of the confidence interval given with a predicted Y value involves an understanding of confidence intervals in general. Thus uncertainty of the calculated Y increases as the X value departs from )( in either direction. 3. is the only one that is appropriate to use if the calculated line is to be used repeatedly as a line for predicting future values of Y from future observed values of X. a point on the line. 4. It does not infrequently happen that.50 for averages of 20 rebound numbers. Reference 5 describes how to calculate all three of these confidence intervals. Figure 1 taken from Ref 16 illustrates the point. Since the rebound numbers themselves have a distribution with a gharacteristic scatter. a confidence interval for the location of the line as a whole. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.ARNI ON STATISTICAL CONSIDERATIONS 35 calculate the quantities needed to plot the confidence interval is described elsewhere [5]. illustrated in this case by a standard deviation of 0. is that if the experiment is repeated a large Copyright by ASTM Int'l (all rights reserved).5 MPa (4350 to 4710 psi). The regression line shown is based on 16 plotted points relating strengths of 28-day standard cylinders to averages of 20 Swiss hammer rebound numbers obtained on slabs made from the same batches of concrete as the cylinders.0 to 40. with the 95 percent confidence interval extending from 30. or a future value of Y corresponding to a given value of X. thetrue meaning ofthe various quantities is not understood. The figure also shows the hyperbolic curves representing the upper and lower 95 percent confidence limits for location of the line referred to above. What it actually means.1 MPa (4010 to 5070 psi). .6 to 35. A 95 percent confidence limit is often interpreted as meaning that 95 percent of future results will be within the limits given. No further reproductions authorized. the average of all the X values used in calculating the relationship. Unfortunately. These figures combined with the confidence interval for the line give an approximately 90 percent confidence interval for the predicted compressive strength of 27. For a hypothetical rebound number of 25. this is not the limit of the final uncertainty of the predicted result. and then the principles of ACI 214. There have been proposals that regression lines relating 28-day cylinder strengths to results of accelerated tests be used. then 95 percent of the intervals so calculated will include the true average. This process in no way augments or enhances whatever information about quality resided in the original measurements. Frequently situations are reported in which a previously calculated regression line is used to make predictions as though the calculated line exactly represented all future relationships. the circumstance that the calculated line coincides exactly with the true line is highly unlikely. No further reproductions authorized. rather than using a conversion that introduces a large and unnecessary degree of uncertainty into the overall process. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. would be applied. it must have such validity within itself. but recently more detailed work has been done on its application to evaluation of concrete strengths [18-21]. in which concrete is fabricated on the assumption that a certain percentage of tests will be permitted to fall belowfc '. This does not mean that any particular one of the intervals will actually contain the true average in its exact center. For any given determination of the line and its confidence interval. The Maturity Concept A method of using accelerated tests to get numbers appropriate for use in design formulas that call for standard 28-day tests that appears to be somewhat more reliable than the straight linear equations just discussed is one that involves application of what is known as the maturity concept. if accelerated or inplace measurements are to be used to evaluate concrete. due to the uncertainties involved in transferring from accelerated to standard strengths. The fact that the data exhibit scatter is obvious when they are plotted and is recognized by the circumstance that as large a block of data as possible is used in order to make the calculated line as reliable as possible. Thus. Actually. The line is then used as though all future data conformed to it exactly. whereas all future data are subject to the same degree of scatter that characterized the original data. In general. the target numbers appropriate to those measurements should be developed and used as criteria of quality. and each time the 95 percent confidence interval is calculated. if any system of measurements is a valid system for evaluating quality of concrete. then.36 GENERAL number of times. there is no way that such a process will provide complete assurance that any selected percentage of below-strength tests will be achieved. . The use of a regression equation to convert measurements obtained to measurements that might have been obtained by some other system involves multiplying the measurements obtained by a constant and addition of another constant. Copyright by ASTM Int'l (all rights reserved). each with the same materials and conditions and with the same number of determinations. This concept goes back a long way. " Significance of Tests and Properties of Concrete and Concrete-Making Materials. the variation in size of the product will increase. The control chart became a well-established technique in production quality control during the World War II era. and when the tolerance level is 4Adapted from McLaughlin. No further reproductions authorized. it will not be described in detail here. 36. The most recent reference of this work produced by Hudson et al in 1976 shows a number of calculated log-log relationships for which linear confidence intervals have been plotted.ARNI ON STATISTICAL CONSIDERATIONS 37 Since this method has not been published as an ASTM method. 1966. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.02. F. this method shows some promise of being more useful than the methods already described. then the values of the measured characteristic could fall outside the predicted range. However. If some assignable cause (such as an increased water-cement ratio) results in a change in the distribution. Also a method of fitting a parabolic curve of the form Y = a x b is given that involves only four pairs of points. Control charts are particularly useful in controlling the quality of a product manufactured with tools or dies that wear with time. American Society for Testing and Materials. Briefly. J. p. Copyright by ASTM Int'l (all rights reserved). The best tool for doing this is by means of control charts. In general. Subcommittee C09. but they should be hyperbolic like any other confidence intervals for a plotted line. A process that is operating with only chance variation should result in some distribution of the measured characteristic. A S T M STP 169-A. The control chart is a combination of both graphical and analytical procedures. How these confidence intervals were derived is not given. and one should be able to predict a range within which a certain percentage of the data should fall. and some comments on statistical features related to the method are in order. and Hanna. J. Monitoring Production 4 One of the most effective means of maintaining the quality of a manufactured product is by continuously monitoring the quality by means of regularly performed tests throughout the process of production. The basis of the theory arises from the fact that the variation of a process may be divided into two general categories. As these tools or dies wear. S. "Evaluation of Data. Such a curve would be of doubtful value for use in future predictions. One portion of the variation can be described as random or chance variation of the process and the other as the variation due to assignable causes. the method involves establishing a relationship between the logarithm of strength and the logarithm of a quantity called maturity of the concrete that is defined as the product of temperature at which the curing is taking place and the time in days. A control chart will graphically show the trend.. .09 of ASTM Committee C-9 on Concrete and Concrete Aggregates is working on a draft of a test method. ASTM Recommended Practice C 670 gives directions and a recommended form for writing precision statements when the necessary estimates (usually standard deviations) of precision are in hand. and the person conducting the test does not care how closely his results should be expected to agree among themselves or with someone else's. There may be situations in which this is all that is required. and especially in cases where the acceptance or rejection of materials depends on the results.38 GENERAL reached. As a result of concern about problems connected with precision statements and how to develop and use them. it is only necessary to plot the data on the control chart and be ready to take corrective action when the data exceed the control limits. is information about the degree of precision that should be expected to characterize measurements obtained by the use of that tool or test method. C-9. in most cases in which people go to the trouble of obtaining measurements by means of a test method. the machine may be retooled. and control charts for ranges. Often in the past it has been assumed that writers of a test method have done their job when they have written down the procedures to be followed in conducting a test. One of the most important items of information that should accompany the tool. Three types of control charts that are frequently used are control charts for averages. D-4 on Road and Paving Materials. control charts for other measures. Also. Detailed treatment of this subject and tables of control chart constants for determining upper and lower control limits are presented in tests on statistical quality control [22-24]. No further reproductions authorized. a joint task group of ASTM Committees C-1 on Cement. standard deviations. such as percent defective. and ranges. control charts for standard deviations. may be useful. Once the limits f o r a process have been established. However. information about precision is a vital part of the test method. is that a test method is a measuring tool that has a characteristic precision. but one that unfortunately has often been ignored in the past. Both of these recommended Copyright by ASTM Int'l (all rights reserved). The second (ASTM Recommended Practice C 802) describes a recommended method for conducting an interlaboratory study and analyzing the results in order to obtain the necessary estimates. therefore. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Table 27 in Ref 7 contains the control chart constants for averages. . Precision Statements and Interlaboratory Tests One of the most important concepts associated with test methods. and D-18 on Soil and Rock for Engineering Purposes developed two recommended practices: Recommended Practice for Preparing Precision Statements for Test Methods for Construction Materials (C 670) and Recommended Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials (C 802). s In the case of single-operator or within-laboratory precision. PhiUeo has written on this topic elsewhere [25]. It is beyond the scope of this chapter to discuss the writing of specifications in detail. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The first is derived from the standard deviation of test results and the second. whether in the form of a precision statement in the test method or of some other body of information. but certain aspects of precision statements and their derivation that are not explicit in the standards are given. 6Anything said about the (D2S) limit also applied to the (D2S%) limit. is useless as an instrument for making decisions on acceptance or rejection of materials. The criterion selected for use as an index of precision in ASTM Recommended Practices C 670 and C 802 is the (D2S) limit or the (D2S%) limit. The (D2S) limit is the one deemed most appropriate and recommended for use by ASTM CommitteesC-1. 14. from the coefficient of variation. a number of interpretations are possible. Material given in the standards will not be duplicated here. One of the problems that regularly bothers people in connection with a precision statement is what interpretation should be placed on a particular failure to meet the criterion of precision given in a test method. and 15 of the 1976 Annual Book of A S T M Standards and should be studied and followed closely by any task group of ASTM Committee C-9 that is charged with writing precision a statement. One of the most important uses of precision information given in test methods is in connection with specification writing. and in the case of multilaboratory precision it is the criterion to be met by two results obtained in two different laboratories. D-4. I f two results differ by more than the (D2S) 6 limit. and in most cases a degree of judgment is involved. No further reproductions authorized. unless otherwise stated. Copyright by ASTM Int'l (all rights reserved). However.ARNI ON STATISTICAL CONSIDERATIONS 39 practices appear in Parts 13. In the normal and proper operation of the test method in a laboratory of average competence. . it is important to understand that any numerical limits placed on properties in a specification must be developed in the light of knowledge about the precision of the test method that is used to produce the results on which the decision to pass or fail the material are to be based. it is the criterion to be met by two results obtained by the same operator in the same laboratory. and D-18. Thus any test method for which there is no information on precision. In each case the limit is derived by multiplying the appropriate standard deviation or coefficient of variation by the factor 2x/2. this is the difference between two results obtained on the same material that is expected to be exceeded 5 percent of the time. C-9. Which interpretation is most appropriate depends on various circumstances connected with the situation. In the first place the reason for supplying any limit in a precision statesOther criteria with different numbers of tests or different percentages by which they will be exceeded are possible and allowed by the documents of ASTM Committee E-11 on Statistical Methods. usually the tests should be repeated. The latter is sometimes used to check the results and procedures of a single operator in a laboratory. Usually failure to meet a multilaboratory precision limit entails more serious consequences than those connected with failure to meet a singleoperator criterion. and failure to meet the criterion leads to reexamination of the materials and procedures. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and use the single-operator difference as a check on proper application of the test method within the laboratories.40 GENERAL ment is to provide a criterion for judging when something is wrong with the results. a single isolated failure to meet the criterion is not cause for alarm. The probabilities involved in the process have changed. Thus the failure of a pair of results to meet the (D2S) criterion causes suspicion that the conditions surrounding the two tests are not really the same as those surrounding the original tests from which the precision statement was derived or that the samples used in the two tests did not really represent the same materials. I f it is feasible to do so. These must be used if more than two results are to be evaluated. Another feature of many test methods that is related to the question of how many results to use is the practice of stating that " a t least" a certain number or a certain number "or more" tests should be made. . No further reproductions authorized. and the group responsible for the method has the responsibility of deciding how many tests should be made for their particular purposes and of requiring that number. One aspect of comparisons of results with an index of precision that is often overlooked is that a (D2S) limit applies only to the difference between a randomly selected pair of results. but an indication that the process under consideration should be watched to see if the failure persists. and almost always the procedures of the laboratory or laboratories involved should be examined to make sure that the test method is being applied in the manner envisioned by the written instructions and used when the precision statement was developed. For instance. Precision limits of whatever form must be tied to a definite number of results. the singleoperator (D2S) limit should be used to check whether or not the results obtained are a valid test for the purpose. Multilaboratory tests are most often used in situations where there is a dispute about acceptance of materials. ASTM Recommended Practice C 670 gives methods for deriving indexes of precision appropriate for the total range of any number of test results up to ten. In most cases. both laboratories should obtain two results by the same operator who is to be used in the between laboratory tests. What action is appropriate to take depends on how serious the consequences of failure are. Another frequently overlooked aspect of precision statements is that the Copyright by ASTM Int'l (all rights reserved). I f the test is being used to determine compliance with a specification. one cannot obtain three results and apply the (D2S) limit to the three differences thus available. In these cases. Sometimes a statement of the conditions and materials that obtained when the precision statement was developed is given. In many cases. . standard deviations. From these. One either uses the criterion in a given situation or one does not. Results obtained in a reference sample program such as that conducted by the Cement and Concrete Reference Laboratory can often be helpful in this regard [26]. materials. No further reproductions authorized. Another practice that sometimes introduces vagueness into a test method and into any assessment of its precision is that of introducing indecision as the conditions under which estimates of precision apply.ARNI ON STATISTICAL CONSIDERATIONS 41 indexes of precision given in a test method are not immutable. Whenever a test method is revised other than editorially. and in the absence of hard evidence that the limit is applicable to other situations. and then the statement is made that applications to other conditions and materials should be made or interpreted "with caution. then there would seem to be no reason for making the revision. how one applies the results with caution is impossible to determine and means nothing in practice. A definite statement about conditions and materials under which an index of precision was obtained must be given. etc. and other so-called parametric statistics are applicable. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Of course. Over the years conditions. Nonparametric Tests There are some test methods that do not provide numbers for which the customary processes of calculating means. its precision should be reexamined to see if a change in the precision statement is needed. apparatus. If this is true. operators. the excuse being that the revision has not changed the precision. an appropriate revision of the precision statement often can be made. (D2S) limits. Test methods of the latter type sometimes cause problems because of the fact that numbers are assigned to the different levels of Copyright by ASTM Int'l (all rights reserved). Very often the purpose of a revision is to provide more precise results but the precision statement is not revised. Test methods are constantly being revised. These tests include those involving measurement of what is called a nominal or classificatory scale and those involving measurement on an ordinal or ranking scale [271. its use should be limited to the known conditions. aometimes a large number of failures to meet precision criteria within or between laboratories is an indication that the indexes of precision in the test method are no longer valid and need to be revised. change. it is not necessary to conduct another large interlaboratory study to revise the precision statement if the subcommittee responsible for the test method is aware of this situation and institutes a systematic program of accumulating new data from laboratories that are routinely using the method. An example is ASTM Test for Inorganic Impurities in Sands for Concrete (C 40). Such calculations are inappropriate. and adding them up and dividing by the number of measurements has little significance. 3-5. however. 1956. The increment of one between scaling ratings of one and two. In one procedure a solution from the test sample is compared to a reference solution and judged to be lighter. 7th ed. 1973. which is the type of measurement scale appropriate to most of our test methods. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . is not necessarily the same increment as that between three and four.42 GENERAL quality of performance in the method. or the same. because the magnitudes of the numbers indicate only order or rank and are not measurements of quantities. Because of the numbers there is a temptation to average results of several specimens and even to calculate standard deviations to indicate scatter. the surfaces of specimens are observed at various times during treatment and are rated on a scale of 0 to 5. 13. pp." in Signi~cance of Tests and Properties of Concrete and Concrete-Making Materials. [2] Concrete Manual. Part 1. darker. No further reproductions authorized. In this test. A test that provides measurement on a nominal or classificatory scale is one in which results merely fall into different categories without any judgment being made that one category is higher or lower than another. [4] "Realism in the Application of ACI Standard 214-65. American Concrete Institute. May 1944. This may be treated as an ordinal scale if one end of the scale is judged to be better than the other end and the stages in between represent progression from one level to another. respectively. References [1] Mielenz.S. C. American Society for Testing and Materials. 1963. The same difference applies to two objects that measure 9 and 10 cm. the difference between an object that measures 5 cm and one that measures 6 cm is a length of 1 cm. This type of test is not very important in the concrete field. "Petrographic Examination. Stanton." Concrete." AC! Publication SP-37. R. In another procedure. Central tendency and scatter can be indicated by giving the median and the highest and lowest ranking. Vol. Copyright by ASTM Int'l (all rights reserved). for instance. 5. Reference 9 gives procedures that are appropriate to measurement on a nominal scale. ASTM STP 169. [3] Walker. 0 representing no scaling and 5 representing severe scaling. and then the numbers are treated as though they represented measurement on an interval scale. 52. Ranking numbers of this type are not amenable to the ordinary processes of arithmetic. No. See Ref 9 for other statistical procedures applicable to this type of data. "Application of Theory of Probability to Design of Concrete for Strength. five color standards may be used. When lengths are measured.. An example of measurement on an ordinal scale is provided by ASTM Test for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (C 672). 253. Bureau of Reclamation. U. pp. Revised Edition. The Statistical Analysis of Experimental Data. J. [21] Hudson.. Introduction to Statistical Analysis. 370. S. Final Report. L. T.. A S T M STP 169-A. "Prediction of Strength of Concrete from Maturity. H.. 1972. T. 1. Y. 1957. A. [17] Arni. June 1976." presented at ASTM Symposium on Preparation. Federal Highway Administration. Richard D. A." in Significance of Tests and Properties of Concrete and Concrete-Making Materials.. pp. National Bureau of Standards Special Technical Publication 300. National Bureau of Standards Handbook 91. [26] Arni. T. S. pp.Y. H. 1964. Chicago. J.. 1953. B. Highway Research Board. N. S.. pp. "Impact and Penetration Tests of Portland Cement Concrete. H. [8] Dixon. pp.. [20] Lew." West Virginia Department of Highways Research Project 47.) [16] Arni. B. [19] Hudson. "Research Study to Refine Methods and Procedures for Implementing the Method of Early Prediction of Potential Strength of Portland Cement Concrete. [24] Bennett. T. and N. N. Franklin." Materials Research and Standards. T. 1956. Homewood. [6] MeLaughlin.. [15] Hockersmith. and Interpretation of Precision Statements. No further reproductions authorized. W. G. 378. Wood. Copyright by ASTM Int'l (all rights reserved).. "Precision Statements Without an Interlaboratory Test Program. G. "The Significance of the Correlation Coefficient for Analyzing Engineering Data. W.. 1959.. [7] A S T M Manual on Presentation of Data and Control Chart Analysis. American Society for Testing and Materials. "Uncertainties Associated with Proving Ring Calibration. and Higgins. Inc. and Reichard. American Society for Testing and Materials.. Rockville. "Impact and Penetration Tests of Portland Cement Concrete. . 16-19. W. E. C. W. 1959. Highway Research Board. (Reprinted in Precision Measurement and Calibration. Jr. Preprint Number 12.. June 1976. No. S.Y. F. "Prediction of Potential Strength of Concrete from the Results of Early Tests. [10] Arni. T. "Establishing Specification Limits for Materials. Wiley. Experimental Statistics. [27] Siegel. Wiley. N. FHWA-RD-73-5.. 1956..3-2-64.ARNI ON STATISTICAL CONSIDERATIONS 43 [5] Natrella. 558. McGraw-Hill." Highway Research Record No. 1954. and Interpretation of Precision Statements. 167-174. F. [12] Daniel. [9] Siegel.. and F. June 1971. and Massey. T. 1975. and S. Transportation Research Board. T. [25] Philleo. Quality Control and Industrial Statist&s. H. McGraw-Hill. 36.." Highway Research Record No. W. I. Vol. Feb. "Evaluation of Data. 1966. and Steele. 8. Hanna. N. pp. May 1971. Vol. F. [13] Acton. B." Instrument Society of America. H. Fitting Equations to Data. Sun Apr 6 21:38:51 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1969. 1964. [18] Hudson. G... I11. H. J. H. Chicago. Use. S." Public Roads. to be published. Use. J. N. No.. Bowery. [11] Arni.. Vol. F. Wiley.. to be published." Report No. Wiley. [14] Mandell. 1976. 11." presented at ASTM Symposium on Preparation. S. 26-30. Frank. Md. 5.Y. R. H. Irwin. J. C. and Steele. 55-67... N. 21-28... 25-28. The Analysis of Straigth Line Data. Statistical Analysis in Chemistry and the Chemical Industry. J. Sidney in Nonparametric Statistics for the BehavioralSciences. A S T M STP 15D. 1-12. "The Correlation Coefficient in Analysis of Engineering Data--Its Significance of Limitations. and Ku. Sidney in Nonparametric Statistics for the Behavioral Sciences." Transportation Research Record. No. 1976. [22] Burr. E. Woodward-Clyde Consultants. N. 1971.Y. McGrawHill. Engineering Statistics and Quality Control. [23] Duncan. "Developments in the Prediction of Potential Strength of Concrete from Results of Early Tests.. 1972." to be published in ACI Symposium Volume on Accelerated Strength Testing. 1971.. pp.Y. 1963. McGraw-Hill. D.org . Washington. The properties of concrete enumerated in construction contracts are often based on the results of tests developed by the American Society for Testing and Materials (ASTM). and on quality control. Procurement of specimens is often regarded as the most important step in the testing process. it is imperative that every effort be made to avoid the use 1Manager. and reporting. it is noted that the Standard Building Code of the American Concrete Institute (ACI 318) requires that all tests of material and concrete be made in accordance with the ASTM standards. Copyright by ASTM Int'l (all rights reserved). and supervisors at all levels must be well acquainted with sampling plans and procedures. Quality of testing has a direct bearing on the reliability of such determinations. Adequate instruction of sampling personnel is essential. and fully prepared to ensure that the plans and procedures are faithfully followed. Copyright9 1978 tobyLicense ASTM International www. Sun Apr 6 21:39:01 EDT 2014 44 Downloaded/printed by Universidade do Gois pursuant Agreement. Concerns in Testing Testing of concrete and its component materials may be said to consist of sampling. No laboratory can produce satisfactory information if the samples it receives are carelessly taken or are altered by mistreatment in shipment and do not represent the material under consideration. Cement and Concrete Reference Laboratory.STP169B-EB/Dec.astm. C. 1978 J. and is therefore a key element in the construction process. R . performing specified tests. National Bureau of Standards. But no matter who the originator of the chosen standards may be. 20234. and the literature repeatedly advises that poor specimens and faulty sampling techniques will defeat the purposes for which tests are made. No further reproductions authorized. D i s e 1 Chapter 4--Quality in Concrete Testing Introduction The purpose of inspection and testing of concrete and concrete-making materials is to determine whether their characteristics and qualities as used in construction comply with contract documents. For example. The principal areas to be covered in an evaluation are (a) qualifications of personnel. and testing variance. No further reproductions authorized. and is potentially dangerous because it can lead to completely erroneous conclusions about the characteristics of the concrete in a structure. and (c) reliability of measurements. and similar pertinent data [2]. Pertinent data is generally considered to include comments about the appearance or behavior of specimens that might in any way have affected the results obtained. In studying quality assurance for highway construction materials. and in some instances. falls into the category of substantial compliance and can be used with reservations. (b) adequacy of the plant and equipment. Their academic training is relevant as well as the length and stature of their professional and technical experience. the values obtained. . the parts of the structure involved. When a final report is available. On completion of a piece of test work. or modified testing techniques.DISE ON QUALITY IN CONCRETE TESTING 45 of obsolete. concern immediately develops as to whether the testing was done in a satisfactory manner. Sun Apr 6 21:39:01 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 50 percent or more of the overall variance can be attributed to the sampiing and testing phases [1]. it can be determined if either a material complies with specification requirements and can be used. the tests performed. or fails to comply with requirements and cannot be used [2]. 2 These observations indicate that these two processes must be constantly monitored if optimum results are to be obtained. If there is any significant uncertainty about the reliability of one or more features of the report. sampling variance. A supervising laboratory technician should have several years of experience in the 2The italic numbers in brackets refer to the list of referencesappended to this paper. Qualifications of the Testing Laboratory An evaluation of the capabilities of a laboratory to do good work helps to alleviate concern about the quality of testing and the reliability of the test results. rejected. citing the methods used in obtaining specimens. resulting in a failure of testing to conform to the desired standard of excellence. the specified values for the measured characteristics. a laboratory customarily submits a written report to its client. Reports should be complete and factual. it has been found that variance in quality can be divided into material or process variance. The managers of the laboratory should be professional men of good standing in their field. Overall proficiency is necessary since adequacy in one area can be offset by inadequacies in another. Employment of an unsatisfactory procedure is a waste of time and effort. Copyright by ASTM Int'l (all rights reserved). this description should include a plan of its plant and an inventory of its equipment and reference literature. The principal elements of this phase of quality assurance have been identified as: (a) inventory of equipment requiring calibration or standardization. was established in 1929 to promote uniformity in the testing of cement and concrete. In such a review. the principal technician and the workers he supervises need not be graduates of engineering or scientific institutions. No further reproductions authorized. such as the standard chemical samples of portland cement and glass spheres for sieve calibration. (b) documentation of required frequency of calibration or standardization. the evaluation should include a check to ensure that all deviations from specification requirements reported by the CCRL have been corrected. (g) record keeping. Sun Apr 6 21:39:01 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. combined with a visit to observe the condition of the equipment and the working environment. will provide general assurance that the capability to perform the specified tests does indeed exist. particular attention should be given to equipment maintenance and calibration practices. (c) inventory of standards. it should consider doing so on the premise that it would be difficult to find a more convenient and effective way in which to obtain comprehensive and impartial evaluations of its methods and equipment at regular intervals. In this connection. If the laboratory has been inspected previously. . a joint project of NBS and ASTM Committees C-1 on Cement and C-9 on Concrete and Concrete Aggregates. A detailed review of the laboratory's approach to quality assurance is necessary in order to assess the reliability of its measurements. Advanced academic training is most beneficial. As part of its quality control program. the laboratory should enroll in the comparative testing programs conducted by the CCRL. and (h) labeling to show calibration status [3]. (f) periodic checks for prevention of errors and inaccuracies. Review of this information. Copyright by ASTM Int'l (all rights reserved). As a minimum.46 GENERAL testing of construction materials and should be able to demonstrate his ability to perform the conventional tests for concrete and its component materials in the manner stipulated under the governing procedures. In addition. The CCRL. (e) documentation of procedures and environmental conditions. (d) external sources for needed calibration or standardization services. and make use of any appropriate NBS Standard Reference Materials which might be available. however. each laboratory should participate periodically in available standardization and interlaboratory test programs. It is in order to expect that the laboratory management will have provided training in laboratory techniques and related topics in all instances where such instruction is needed. Every laboratory should be able to furnish a description of its physical resources on request. it is noted that several hundred concrete laboratories are now taking advantage of the consulting services of the Cement and Concrete Reference Laboratory (CCRL) at the NationalBureau of Standards (NBS). If the laboratory is not participating in the program. these two documents provide important guidance for improving the quality of testing in the concrete field. when a difference larger than that indicated as being acceptable occurs. . and the working condition of instruments should be evaluated. contains specific information for use in evaluating concrete testing laboratories. Steel. provides much needed general criteria for the evaluation of testing laboratories. It is now the practice to provide a precision statement for each ASTM method of test. and ASTM Committee C-9 is strongly supporting this endeavor on behalf of the concrete field. The recently developed ASTM Recommended Practice for Generic Criteria for Use in the Evaluation of Testing a n d / o r Inspection Agencies (E 548). Another important recent event was the publication of the National Voluntary Laboratory Accreditation Program promulgated by the Department of Commerce [5]. The goal of this program is to provide a national voluntary system to examine the technical competence of private and public testing laboratories that serve regulatory and nonregulatory product evaluation and certification needs. Accordingly. these statements provide estimates of the difference that may be expected between duplicate measurements made on the same material in the same laboratory by the same operator using the same apparatus within a time span of a few days. and the National Ready Mixed Concrete Association and the implementation of certification programs and requirements for technicians have made great contributions. calculations should be checked. and Bituminous Materials as Used in Construction (E 329). These statements also provide estimates of the difference that may be expected between measurements made on the same material in two different laboratories. The program will also require those laboratories that are accredited to maintain an acceptable level of competence and thus assure national interests that such capability is available. Jointly. impressive progress has been made in upgrading the quality of concrete testing. and to accredit those laboratories that meet the qualifications pursuant to these procedures. the requirements of the method should be reviewed.DISE ON QUALITY IN CONCRETE TESTING 47 Advancements in the Quality of Testing Over the years. Copyright by ASTM Int'l (all rights reserved). The more familiar ASTM Recommend Practice for Inspection and Testing Agencies for Concrete. No further reproductions authorized. Education and training efforts by such organizations as the American Concrete Institute. This information is probabilistic in nature. The requirements of the Nuclear Regulatory Commission concerning quality assurance programs for laboratories testing concrete and other materials for use in nuclear power plants are having a strong impact. the Portland Cement Association. Sun Apr 6 21:39:01 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A new manual for establishment and maintenance of a qualtiy control system prepared by the American Council of Independent Laboratories provides basic information about the qualification of laboratory services [4]. Customarily. p. T. 35. p. "Quality Assurance In The Laboratory. 32. D." in Significance of Tests and Properties of Concrete and Concrete-Making Materials. Copyright by ASTM Int'l (all rights reserved). Subtitle A." Federal Register. 4. 1976. J. March 1976. American Society for Testing and Materials. May 1975. [4] Quality Control System Requirements for a Testing and Inspection Laboratory. Vol. 6. American Council of Independent Laboratories. J. [3] Wening. 1929. W. . R.. 1976.. 1969. "Quality of Testing. and Halstead.." Public Roads. [2] Waddell. Continuing recognition of this fact. p. F. Part I--Introduction and Concepts. Title 1S. Conclusions High quality in testing is needed to support technological advancements in the utilization of concrete. Washington. Part 7. 3. No further reproductions authorized. 25 Feb. J. Sun Apr 6 21:39:01 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Quality Assurance in Highway Construction.. A S T M STP 169-A. No. Feb. Vol. 13. No.48 GENERAL When properly developed and used. with due regard for the influencing factors." Standardization News. [5] "Procedures for a National Voluntary Laboratory Accreditation Program.C. precision statements will do much to advance the quality of testing. References [1] McMahon. J. helps to ensure that specification requirements faithfully reflect the properties of this important building material. Need for Continuing Research In a period of limited economic and natural resources. continues to be one of the most widely used construction materials throughout the world. improve the engineering properties (such as tensile strength. because of its versatility and relatively low cost. it is desirable to use less energy. etc.). it seems appropriate to emphasize in this chapter concrete and its largest constituent. How are we to do this? Substituting waste pozzolanic materials for cement might help. These demands are magnified by increasing shortages. As developments occur in the use of concrete as a construction and architectural material. and other concretemaking materials also will be covered. 1978 R. volume change stability. steel. accomplish quicker and more permanent methods of repairing existing concrete. and increase our knowledge of measuring effects of the environment. No further reproductions authorized. improve resistance to attack by aggressive media (such as the sulfates).astm. which necessarily constitute a broad subject. 49 Copyright by ASTM Int'l (all rights reserved). and zoning regulations.STP169B-EB/Dec. Improved service life can be anticipated if efforts are made to discover ways to: reduce the permeability of concrete to water and dissolved salts. aggregate. 24061. and specifications is necessary to obtain optiI Head. Virginia Polytechnic Institute and State University. or perhaps more heat-efficient cement manufacturing procedures are possible. research which contributes to improved service life of concrete is important. Additional research in the areas of concrete mixture design. Inasmuch as the title of this book refers directly to concrete and concrete-making materials.org . Blacksburg. environmental requirements. new demands are placed on the quality and quantity of the materials used in concrete. Copyright9 1978 tobyLicense ASTM International www. D. Cement. Va. Walker' Chapter 5--Needed Research Introduction Portland cement concrete. Department of Civil Engineering. admixtures. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant Agreement. test methods for concrete and materials. In all aspects of producing concrete and concrete-making materials. better test methods and specifications are needed. Clearly. Response in service S.50 GENERAL mum utilization of our available materials. if solved. alkali-carbonate. Copyright by ASTM Int'l (all rights reserved). the American Society for Testing and Materials (ASTM) and. Condition of enclosure 4. alkali-silica. particularly regarding effects of aggregates on concrete. will result in economic savings. No further reproductions authorized. its Committee C-9 on Concrete and Concrete Aggregates must seek to develop specifications and tests that are more responsive to evaluating the suitability of new aggregate sources and the performance of concrete. Problems concerning portland cement concrete require intensified research. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The latest revision of ASTM Specification for Concrete Aggregates (C 33) represents an attempt to establish modular requirements for coarse aggregates based upon the use and exposure to weathering of the concrete in which the aggregate is to be incorporated. Aggregate description 3. and other cement-aggregate reactions must not be forgotten. Exposure control 7. Such problems as pavement D-line cracking. This method will be useful in evaluating the extent of damage caused by salt corrosion. which. A standard developed by ASTM Committee C-9 in 1977 is used to detect the damaging effects of the corrosion of reinforcing steel in bridge decks (Standard Test Method for Determining Half Cell Potential of Reinforcing Steel in Concrete (C 876)). Environmental conditions 2. . Special attention should be given to specification limits as a function of economic considerations and failure probability. New research is needed to provide a more reliable basis for the requirements included in this revised specification. Failure criteria 6. Learning how to upgrade marginal aggregates as well as to develop synthetic aggregates is essential. Many continuing problems exist. The Role of ASTM Specifications and Tests As economic and environmental factors increase in importance. The ultimate objective of future research as it affects the development of ASTM standards concerning concrete and the materials used in concrete is to provide a framework for evaluating the materials in relation to different elements such as: 1. in particular. Aggregate beneficiation These elements must be understood completely before this objective can be achieved. Detailed descriptions of specific problems are given in other portions of this chapter. More research in the application of petrographic methods to the aggregate evaluation process is needed. Adequate description is a cornerstone to intelligent testing and specification writing. Continued research in the general area of concrete durability with respect to weathering is essential. . will provide better means of interpreting the significance of environmental conditions for a given situation. absorption. No further reproductions authorized. Both descriptions are important and both contain areas of limited understanding. the location of the existing water table and subgrade conditions can have a strong effect. With regard to the assemblage of particles. and severe weathering. the practice has been to ascribe a greater degree of homogeneity to aggregate than actually exists. moisture environment. bridge decks. data on specific gravity. Environmental Conditions Environmental factors. some discussion of the elements listed in previous paragraphs is justified. much is yet to be learned concerning how to draw geographic lines of demarcation related to particular uses of concrete. The regions so designated come from a map developed many years ago for the building brick industry and are used because of the lack of better data. Thus.WALKER ON NEEDED RESEARCH 51 Elements Affecting Evaluation of Concrete Given the current state of knowledge. This is a difficult question at best. In addition to the need for research in predicting long-range weather trends (beyond the scope of this publication).. and amount of rainfall. For example. even slightly. frost susceptibility. Research that might improve the usefulness of the map. Essentially all sources of gravels and many ledge rock quarries produce heterogeneous aggregates. there is a printed map of the contiguous 48 states of the United States where lines are drawn delineating areas of negligible. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ASTM has Copyright by ASTM Int'l (all rights reserved). and marine structures. are less important where the concrete is incorporated into structures that are protected from the weather as compared to the relatively severe weathering exposure received by concrete in pavement. because many environmental factors enter into the problem such as maximum and minimum temperatures. In ASTM Specification C 33 (the specification for concrete aggregates). of course. Persons responsible for producing quality concrete should be more aware of the science of petrography. Aggregate Description Aggregates may be described on the basis of the assemblage of particles or on the basis of individual particles. etc. freezing index. especially on highway or airfield pavement. of the assemblage may not relate to performance in a meaningful way. moderate. The relationship of these factors or characteristics to aggregate performance has not been well documented. Copyright by ASTM Int'l (all rights reserved). . deflection. abrasion. disintegration. with large quantities of concrete and concrete aggregates going into highway or similar construction. why. For example. bridge decks. failure criteria must be established. Response in Service How does concrete respond as it exists in the working elements of highway pavement. and the type of discontinuities that exist are reasonably well documented. it is not known how. etc. its structure. Further. we cannot adequately predict how long either concrete will perform under field conditions. or vice-versa. excessive in highway pavement?" become most difficult to answer. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." perhaps a beginning step is to determine what constitutes failure. If a concrete floor slab in a building falls. The physical and chemical nature of paste. it may not be too difficult to determine that failure has occurred. and Recommended Practice for Petrographic Examination of Hardened Concrete (C 856). the questions.52 GENERAL two standards concerning the application of these methods: Recommended Practice for Examination and Sampling of Hardened Concrete in Constructions (C 823). "What constitutes pavement failure?" and "When is cracking. Whether or not the concrete is enclosed in such a way as to encourage the increase or retention of moisture has an effect on its performance. Such criteria might consider factors such as micro. It is possible that for each service environment and each level of service. or when water moves preferentially from the aggregate to the paste phase.. or other service conditions? We should have the ability to predict how long a concrete pavement will remain structurally sound without significant D-line cracking and without detrimental aggregate polishing. Condition of Enclosure Both the conditions of enclosure of the concrete and the conditions of enclosure of the'aggregates in the concrete need to be considered. How does one relate the response in service to such durability tests as ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666)? Although we may expect a concrete having a 100-cycle durability factor (DF) of 85 to perform longer in a given freezethaw environment than a concrete having a DF of 40. the performance of aggregates is affected by the nature and condition of the paste enclosure. No further reproductions authorized.and macrocracking. However. deflection. Failure Criteria When looking at the problem of "needed research. Quantitative information is needed to answer the latter question. that bridge decks are exposed more severely than are bridge piers.6 to 80 percent. American Societyfor Testing and Materials. perhaps both attempts help illustrate another area that needs research." in Living with MarginalAggregates. through its committees. R. pp. Walker. The American Association of State Highway Officials (AASHO) road test in the late fifties and early sixties attempted to establish a failure criteria based upon rider response as it affected comfort. W. H. removing the weak fractions does not leave enough strong aggregate. Typical are those found in Transportation Research 2Lin. then in other situations alternate design approaches or a different construction method might serve to modify the exposure the concrete must withstand. Modification is performed so that no significant portion of the aggregate is likely to be stressed beyond its capability. for example. Further efforts such as this are required to make the use of ASTM test methods and specifications more significant.. It is obvious. C. . 1976. "Is it conceptually feasible to exercise exposure control?".. A procedure suggested by Lin et alZ would have the water in the aggregate replaced by 100 percent ethylene glycol. and the use of ethylene glycol is obviously expensive. etc. has been publishing lists of Research Problem Statements of immediate urgency. This was later correlated to "slope variance"--a form of roughness measurement. If this seems reasonable.WALKER ON NEEDED RESEARCH 53 volume change. Copyright by ASTM Int'l (all rights reserved). the Transportation Research Board.. Exposure Control Is it possible to control concrete field response through exposure control? A better question may be. ASTM STP 597. Aggregate Beneficiation Another approach involved modifying the concrete aggregate on the assumption that the exposure is known and unalterable. "Chert-Aggregate Concrete Durability After AntifreezeTreatment. The weak fractions are simply removed. and aesthetic qualities. and Payne. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. D. since if it is. Some Specific Examples For a number of years. W. In many cases. no scale is available to measure these differences. the answer to the first question is probably yes. 76-83. In the laboratory a unifor~nly poor aggregate in concrete exposed to freezing and thawing had the 100 cycle DF of the concrete changed from 3. Attempts are made to lessen the severity of the deck exposure by surface treatments with linseed oil. No further reproductions authorized. However. However. including those mechanisms that cause low quartz to become reactive Concrete Strength Alternatives to testing of concrete cylinders and cores are needed for acceptance purposes. D.. HighwayResearch Board. 4 The following paragraphs abstract a few of the statements from these publications for illustrative purposes. D. Alkali-Aggregate Reactivity A need exists for exact determination of rocks containing alkalireactive silica or silicate. Larson.54 GENERAL Circular Number 179. and others such as the pullout. . D. The specific objectives suggested are to: 1. Several instances have been noted of alkali-silica reaction leading to distress in concrete structures in which the reactive aggregates have been rocks of types not expected to be reactive with alkalies in cement using current criteria. 1970. radioactive and electrical procedures. 1976.. probe. the onset and progression of corrosion. P. The objectives of proposed research are to develop information on the time relationship among chloride concentration at the level of reinforcing steel. 3 Other statements were developed under a National Cooperative Highway Research Program (NCHRP) project and published in NCHRP Report 100.." National Cooperative Highway Research Program Report 100. Advance means other than the specification of low alkali cement that will effectively control slowly developing alkali-silica reaction 3. 4Walker. Establish more perfectly the mechanisms of the reaction. Copyright by ASTM Int'l (all rights reserved). Controversy still exists as to what inplace strength is and whether it is determinable. Develop criteria that will permit demonstration of reactivity in slowly reactive rocks within reasonable laboratory testing times 2. R. and Cady. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or penetration tests. T. One of the more specific objectives recommended for needed research is to compare the currently 3"Research Problem Statements. and the development of spalling at the deck surface or delamination at the level of the reinforcement. Transportation Research Board. It indicates that corrosion of steel reinforcement has become the nation's most troublesome bridge maintenance problem. Bridge Decks One such statement describes the problem of the performance of bridge decks with deep reinforcement. No further reproductions authorized. There are currently procedures such as ultrasonic resonance. "Research Needs Relating to Performance of Aggregates in Highway Construction." Transportation Research Circular Number 179. prepolymers. The addition of fibers to concrete with the purpose of improving the tensile strength and cracking resistance needs additional research. if so. The committees of the Copyright by ASTM Int'l (all rights reserved). Determination of how D-line cracking develops in pavement 2. or other suitable chemicals. and limited resistance against chemical aggression. but that would defeat the purpose of this chapter and unnecessarily duplicate information already available. Improving Concrete with Chemicals or Other Means Weaknesses of portland cement concrete include low tensile strength and the resulting tendency for cracking. sulfur. Role of Aggregates in D-Line Cracking At least three theories have been advanced to explain the cause of D-line cracking. polymerizable monomer systems. especially when dealing with fresh concrete. other specific problems need to be answered: 1. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Research has provided a reasonable understanding of why pop-outs occur. Objectives of the research would include: 1. How many pop-outs can be tolerated from the several performance viewpoints? How does this vary with different structural applications of concrete? Continuing Responsibility Page after page of publications (such as those in footnote 3) could be abstracted. Perhaps these properties can be improved by modifying the concrete by combining it with polymers. No further reproductions authorized.WALKER ON NEEDED RESEARCH 55 used methods and recommend appropriate methods and develop standard procedures for these methods. and the technology is very complex. None of these theories indicate how aggregate quality relates to this deterioration. Relationship of aggregate quality to D-line cracking 3. Selection or development of tests that would discriminate aggregates causing this type of failure Performance of Concrete When Pop-Outs Occur Pop-outs are essentially superficial failures of concrete caused by near surface pressure development. Can pop-out occurrence be quantitatively related to aesthetic value? 3. However. Little research has been done. by whom? 2. What is the aesthetic value of highway concrete? Can it be quantified and. . American Societyfor Testing and Materials. R. transport. D. but we as a people are only beginning to become conscious of the nation's energy needs. No further reproductions authorized. sPhilleo. are also the chief generators of solid waste. 1976. beneficiate. Research is needed to study the energy consumption trade-offs when choosing an aggregate source or making a decision to manufacture a synthetic aggregate. Such research in some cases may be narrow. Can gradation specifications be modified to permit less energy use in their production? Cities. D. . in preparing NCHRP Report 100 (see footnote 4) is freely drawn upon in writing this chapter. Sun Apr 6 21:39:02 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It makes little sense to haul solid waste out of town while hauling aggregates into town if there is a possibility of processing some of the waste into usable aggregates.. Conclusions It should now be obvious that the directions of needed research in the area of concrete and concrete-making materials are multitudinous. Cady. E. Larson and P. modify. The research must include such things as a continued search for basic mechanisms. in addition to being generators of construction. both Larson and Cady contributed their thoughts and ideas which were of great help to the author. Introduction to Living with MarginalAggregates. Copyright by ASTM Int'l (all rights reserved). Energy and Energy Reducing Alternatives Energy is required to produce. Acknowledgments It should be noted that the work of the author. Such research must persist in time and expenditure. 1.S Can research overcome the barriers in this area? This section deserves more attention. along with T. and manufacture aggregates. p. of the Pennsylvania State University. Further.56 GENERAL Transportation Research Board are charged with the continuing responsibility of bringing to light needed research. ASTM STP 597. but to a large degree must be sufficiently broad and applied to include a concern for reaching a better understanding of the relationship between service and environment. 1978 C Powe~ ~ Chapter 6--The Nature of Concrete Introduction The term cancrete can be construed to include a considerable variety of products made from portland cement or other cementing media. The strength of concrete depends largely on the strength of the mortar. 2 In 1907. A writer's concept of the nature of concrete can hardly be revealed in a few words. etc. Copyright9 1978 tobyLicense ASTM International www. cement mortar mixed with gravel or broken stone. but his treatment of certain topics and his definitions are indicative. water. Here are some examples: in 1878 Trautwine. Zielenski. No further reproductions authorized. L. especially vibration) of portland cement. "Concrete is simply a class of masonry in which the stones are small and of irregular shape. he considered the conglomerate to be composed of 1Retired. this dependence will be much closer than in the case of other classes of masonry. in the l l t h edition of his Pocket Book for Civil Engineers. i s . .astm. formerly research counselor.. once head of the Hungarian Association for Testing Materials. the less will the strength of the masonry depend on the strength of the mortar. said "Cement concrete. Skokie." He described mortar as sand containing a volume of cement equal to the volume of voids in the sand. but in this publication the term concrete usually refers to a material which was at first a plastic mixture (or mixture that became plastic as a result of manipulation. or with all together. oyster shells. Sabin in a book on concrete said. in 1910 called concrete a conglomerate body. this discussion of the nature of concrete will have the scope indicated by that description. Sun Apr 6 21:39:08 EDT 2014 59 Downloaded/printed by Universidade do Gois pursuant Agreement. . C. 2 He said also. in fact.STP169B-EB/Dec. brick." Feret in 1896 considered water and air to be definite components of mortar (and presumably also of concrete)." Copyright by ASTM Int'l (all rights reserved). but it is not clear that he thought of cement paste as an entity. Therefore. "Nearly all the scientific principles which constitute the foundation of civil engineering are susceptible of complete and satisfactory explanation to any person who really possesses only so much elementary knowledge of arithmetic and natural philosophy as is supposed to be taught to boys of 12 to 14 in our public schools. the larger and more perfectly cut are the stone. air. or beton. since it may be stated as a general rule. Portland Cement Association.org . Ill. Research Department. and mineral aggregate. perhaps. broken brick. and the mortar to be coLnposed of paste and sand. authors of perhaps the best of early books on concrete. Even the latest definitions provide but a superficial idea of the nature of concrete. such as a combination of sand or broken stone screenings. A. or other coarse material. go far beyond a superficial definition or description to attain today's underCopyright by ASTM Int'l (all rights reserved). is a combination of portland cement and water. inert. We must. Lewis Inst. gap gradings are not common. even though fine and coarse aggregates are proportioned separately. should be considered as one. in the first bulletin from the Structural Materials Research Laboratory. (1918). and in any case the correctness of Abrams' conclusion can hardly be questioned. They give no hint as to how and why the originally plastic mass becomes hard and strong and. fine and coarse combined. F. . despite Abrams' contention that the total aggregate functions as a unit. concrete is a mass of aggregates held together by a hardened paste of portland cement and w a t e r . . Chicago. because it has simplicity and plausibility and partly because it is not altogether unrealistic. Abrams. they give no adequate basis for understanding such aspects of concrete as volume change characteristics and stress-strain-time phenomena. Ill. with gravel. broken stone. "Expressed in the simplest terms. say nothing as to how and why the mixture had plasticity in the first place. No further reproductions authorized. "Concrete is a composite material which consists essentially of a binding medium within which are embedded particles or fragments of a relatively inert mineral filler. Basic Principles of Concrete Making (1929)." Although it is possible to discern an evolution of concepts in the above definition and descriptions." D. R. The idea lingers with us. materials of varying size. McMillan in his book. In portland-cement concrete the binder or matrix. cinders. said. "Concrete is an artificial stone made by mixing cement. . Taylor and Thompson. therefore. emphasized the significance of the ratio of water to cement in concrete.. Moreover. especially when there is a gap between the largest size in the sand and the smallest size in the coarse aggregate." In their textbook on concrete. in the 1912 edition said. or some similar material which after mixing with water will set or harden so as to adhere to inert material. 1963 edition." This definition was adopted by the American Concrete Institute (ACI) Committee 116 on Nomenclature in 1964.60 TESTS AND PROPERTIES OF CONCRETE mortar and coarse aggregate. and an aggregate composed of hard. The Encyclopedia Britannica. "Concrete is a building material consisting of a mixture in which a paste of portland cement and water binds inert aggregates into a rock-like mass as the paste hardens through chemical reaction of cement with water. and he abandoned the notion that concrete is a mixture of mortar and coarse aggregate. pointing out that the whole aggregate. However. the paste is the active element. says. the early concept of concrete as a mixture of mortar and coarse aggregate tends to persist. either in the plastic or in the hardened state. indeed. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Troxell and Davis (1956) wrote. with or without air voids. Copyright by ASTM Int'l (all rights reserved). the amount being a function of certain variable factors. it shows that the individual rock 3 particles in concrete need not be in contact with each other. the greater the mean clear distance between aggregate particles. The main factors are the consistency of the paste and the gradation of the aggregate. in any case. . and the higher the air content. 4 the paste is composed of portland cement and water. the volume of concrete seldom if ever exceeds the compacted volume of the aggregate by more than 10 percent. The predominant component of concrete is an aggregation of mineral particles. inspection of broken sections of hardened concrete show that not only are the rock particles in a dispersed state while the mixture is fresh. regardless of the size or shape of the particles. not in contact with each other: freshly mixed concrete could not be plastic if the solid particles were not dispersed to some degree. The difference is significant. in fact.POWERS ON NATURE OF CONCRETE 61 standing of the nature of concrete. Gross Structure of Concrete When we inquire into the nature of concrete we find it necessary to regard concrete not as an entity--a s u b s t a n c e J b u t as a structure having component parts. and this aggregation requires a certain minimum of space per unit weight of material. The degree of dispersion actually depends upon the consistency of the paste and the volume of air. this means that the degree of dispersion of rock particles is greater the lower the water-cement ratio of the paste. the stiffer the consistency and the higher the air content. air content depends mainly on those features of aggregate grading that control 3Throughout this discussion. concrete placed by a standardized procedure contains a characteristic amount of air in the form of bubbles. To do the subject full justice would be a book-length project. called the aggregate. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as has already been indicated. and with a standardized mixing procedure. There is clear evidence that the rock particles in concrete are. In practical terms. Without an air-entraining agent. I cannot do more than touch on a few fundamental topics. only the voids that are normal componentsof the mixture. owing to settlement under the force of gravity before setting occurs. At a given paste consistency. the term rock refers to the particulate mineral matter that makes up the aggregate. but also they remain dispersed. although generally not exactly to the same degree that prevails immediately after mixing. 4Voids due to incomplete filling of mold or form are not considered here. Rock particles in plastic concrete are dispersed in a matrix composed of paste and air bubbles. No further reproductions authorized. The volume of space occupied by a properly compacted fresh concrete mixture is slightly greater than would be the compacted volume of the aggregate it contains. and usually it does not exceed it by more than 3 percent when no air-entraining agent is used. The matrix. aggregate characteristics have little effect. At an air content higher than that normally present in a given mixture. When a suitable air-entraining agent is used. as compared with the mean size when the amount of air normally present is smaller. particularly with respect to the ability of concrete to withstand the effects of freezing. it is clearly due to the mechanical stability of the matrix and to the mechanical stability of individual particles of rock.62 TESTS AND PROPERTIES OF CONCRETE the mean size of the voids in the aggregate. . by the same factors that control the normal air voids. and the original mean size also smaller. No further reproductions authorized. it is clear that the stability of the matrix is due to that of hardened cement paste. This means that with a given air-entraining agent used in different mixtures a wide range in average void size may be observed. raising the air content by means of a given approved air-entraining agent will result in a system of voids having a relatively large mean size. the mean size of air bubbles is controlled by the characteristics of the air-entraining agent used and. These characteristics also are subject to systematic variation as will be discussed later. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the gross structure of concrete appears to be that of an aggregation of rock particles slightly dispersed in a matrix of paste and air bubbles. In richer mixtures.5 by weight. The foregoing statement as to the effect of aggregate grading on air content is applicable principally to the leaner types of mixtures. if the normal air content of a given mixture is relatively high and the mean size of the voids relatively large (the two usually go together). air content and void characteristics are strongly influenced by water-cement ratio. voids being here defined as the space occupied by paste and air. the air content can be raised to almost any desired level. water-cement ratio less than about 0. itself. the air content and average air void size increasing with an increase of water-cement ratio under given conditions. any deformation would necessarily be dilatant rather than plastic. The mean size and the size range of the air bubbles in concrete are also significant structural features. Throughout the range of the most frequently used mixtures. is plastic because the cement particles and air bubbles are dispersed in water and especially Copyright by ASTM Int'l (all rights reserved). the proportion and size characteristics of air bubbles being subject to systematic variation just as is the proportion of aggregate. Interparticle Forces in Freshly Mixed Concrete We have already seen that plasticity of freshly mixed concrete is possible because the rock particles of the aggregate are slightly separated from one another by matrix material. A conclusion arising directly from consideration of the gross structure of concrete is that the firmness or mechanical stability of concrete cannot be attributed to mechanical stability of the aggregation of rock particles. in the leaner range of mixtures. In short. Also. otherwise. Specifically. Copyright by ASTM Int'l (all rights reserved). indeed. a structure having a low degree of firmness or shearing strength. Several years ago Deryagin. and this is an essential condition for the plastic state. we see that interparticle forces give freshly mixed paste in the quiescent state. changing paste from a plastic to a fluid material. Such a state is due to the coexistence of forces of attraction and repulsion between cement particles. in this case. in this case negative ions. to indicate the force developed by adsorbed films of water in spaces too narrow to accommodate the normal thickness of the films. introduced the term disjoining pressure and another. and this can be done by using an appropriate surface-active material able to increase interparticle repulsion. hence. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In some concrete mix5In previous publications I have used terms such as film pressure. When shearing stress exceeding shearing strength is applied and maintained. Thus. Attraction is due to relatively long range intermolecular forces known as van tier Waals forces. when thinking of the tendency of water to disperse a coherent system of particles. due to electrostatic repulsion and to a "disjoining pressure" (Deryagin) s maintained by adsorbed water molecules covering the surfaces of the grains. more or less. No further reproductions authorized." and any mechanical displacement of particles with respect to each other requires a certain amount of work to "lift" the particles out of their potential troughs. a pair of cement grains has a minimum of potential energy with respect to those forces when the particles are separated from each other by a certain small distance. which is the case for pastes used in concrete. a surface physicist of the Soviet Union. Consistency of freshly mixed paste can be made softer by diminishing the depth of the potential troughs. cement particles tend to assume positions with respect to each other corresponding to minimum potential energy with respect to balance of internal forces.POWERS ON NATURE OF CONCRETE 63 because the interparticle forces tend to hold particles together while at the same time preventing actual point to point contact. The forces of repulsion are. The shearing strength (yield value) and the resistance to continuous shearing stress (the mobility or structural viscosity) is often used as a measure of paste consistency. a paste is caused to flow continuously if its solid content is considerably smaller than that at normal consistency. the negative ions being held near each cement particle by positive ions selectively adsorbed from the surrounding aqueous solution. swelling pressure. about which more later. but such a measure pertains only to paste in the fluid state maintained by a sufficiently high shearing stress. disjoining action. they are said to be in "potential troughs. . Deryagin's term seems most apt. Owing to the existence of opposing interparticle forces. Electrostatic repulsion is due to what is called a Gouy diffuse layer of ions. repulsion can be raised to such a degree as to destroy plasticity. or spreading pressure. the distance amounting to perhaps ten water molecule diameters. When particles are in positions of minimum potential energy with respect to the forces acting between them. whenever a continuous supply of strong acid is encountered. Normally. and the permeability of concrete to water is so low that the action of weak acids is only superficial. and it is usually considerably higher because of the presence of alkali hydroxides. actually such reaction may increase chemical stability. expansion can be destructive. The paste in a properly constituted freshly mixed concrete has an optimum consistency.64 TESTS AND PROPERTIES OF CONCRETE tures. But. but the effect is not destructive. . In cities where rain falls through industry-polluted air and becomes distinctly acid. the water content of the paste is so high that the paste has very little plasticity to begin with. under no circumstances should it be completely fluid. That concrete is not generally destroyed this way is explainable mostly in terms of physical factors: under ordinary conditions of exposure the quantity of acid in contact with concrete during a given time is small relative to the quantities of basic material available. Any of the compounds can be decomposed by carbonic acid and. Copyright by ASTM Int'l (all rights reserved). neither too soft nor too firm (stiff). but when an ufilimited supply of sulfate ion is present in the environment. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. most of them are impure in the sense that they contain elements not ordinarily given in their formulas. All the components of hydrated cement are basic. For our present purpose it will suffice to mention a few outstanding characteristics. and when the sulfate ion concentration is too high. No further reproductions authorized. and they do not have exactly the same composition when formed under different conditions. concrete must be protected or it will be destroyed. concrete may be destroyed by it. There is one exception: the formation of calcium sulfo-aluminate by reactions involving gypsum and tricalcium aluminate tends to cause volume expansion. Hydrated cement is able to react also with carbon dioxide gas in the presence of water vapor. especially with respect to temperature and original cement concentration. the hydroxyl-ion concentration is always at least as high as that of a saturated solution of calcium hydroxide. the amount of gypsum needed to control the setting of cement gives only tolerable expansion. The reactions between the anhydrous components of portland cement and water are remarkable in that they involve a doubling of the volume of space required by solid material while the apparent volume of the system remains constant. by ordinary rain water. therefore. Practically. the particle concentration is so low that interparticle forces are relatively ineffective. Even contact with softwater streams usually causes decomposition at a negligible rate. acid action is evidenced by surface etching. such destruction is avoidable by using a cement of low tricalcium aluminate content. even though the interparticle forces discussed above exist. Chemical Nature of Hydrated Cement The chemical compounds found in hydrated cement are complex. one kind involves siliceous rocks. but when used as concrete aggregate it is less vulnerable than the hydrated cement paste which envelopes it. Limestone is. its void content usually being upwards of Copyright by ASTM Int'l (all rights reserved). Rocks used for concrete aggregates are generally materials that have survived geologic ages and are thus those that have demonstrated some degree of chemical and physical stability. Some are chemically basic. may be decomposed by the caustic solutions found in concrete. the reaction involves decomposition of the dolomite and the formation of magnesium hydroxide (brucite). Under some conditions this reaction is accompanied by destructive expansion. A principal factor determining the physical effect of such reactions is the special and selective hindrance to the diffusion of various ions through the structure of cement paste. basic and vulnerable to acid attack. opal being an outstanding example.POWERS ON NATURE OF CONCRETE 65 Chemical Aspects of Mineral Aggregates The petrographers and mineralogists contributing to this publication have much to say on this subject. as may be ascertained by referring to the literature on the alkali-silica reactions in concrete. of course. the other. some are acidic. Moreover. another is the quantity and specific surface area of the reactive form of silica. Although hardened cement paste looks the way we might expect an amorphous continuum to look. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. These reaction products are collectively that which we have already called hydrated cement. some dolomites react with the caustic aqueous solution in concrete and expand destructively. and under other conditions. The conditions mentioned involve chemicophysical factors too complex to be described here. we know that cement paste contains submicroscopic voids. This structure is the starting pattern of the structure that subsequently develops from the materials produced by reactions between the components of cement and water. Also. There are at least two other kinds of undesirable chemical attack on certain minerals that seem to be the result of conditions peculiar to the interior of concrete. I shall mention only some chemical characteristics that are of special interest because of the structural and chemical characteristics of the paste component of concrete. we know that it actually comprises a hierarchy of aggregations of matter. certain dolomites. . no expansion. Structure of Hardened Cement Paste We have already seen that freshly mixed cement paste is a dispersion of cement particles in water and that is has a certain structure owing to the forces of attraction and repulsion among the cement particles. No further reproductions authorized. Some kinds of siliceous rocks. this reaction is called dedolomitization. now we shall stress the physical aspects of hydrated cement. being greater than the limit usually stipulated for the colloidal state. even though atoms and molecules are the primary and secondary aggregations of matter in general. we have learned to think of matter as intrinsically granular. although a lower void content is possible. these particles are usually only three or four molecules thick. such as is possible only in the submicroscopic range. The amount of calcium hydroxide is different for cements having different chemical compositions.66 TESTS AND PROPERTIES OF CONCRETE 40 percent. . An outstanding characteristic of the colloidal matter in hydrated cement paste is that its specific surface area is virtually the same in all pastes made of the same cement regardless of differences in paste density. in this particular case colloidal bodies can be defined as molecular or ionic aggregations having a very high specific surface area. lack of normal crystallinity being due to the extremely small size and imperfect atomic or molecular organization of the solid material. This observation is one of the cornerstones of our concept of paste structure. These particles. Calcium hydroxide crystals are usually surrounded by and intergrown with colloidal material. The most abundant colloidal constituent of hydrated cement is an impure calcium silicate hydrate of somewhat indefinite stoichiometry. Since. we have seen particles and have been impressed by their smallness and irregularity of shape. and thus they constitute an integral part of the solid structure. but it appears that they are colloidal but with a lower order of specific surface area than those of tobermorite gel. The high specific surface area is due mostly to the thinness of the particles. one of the three dimensions. but it is usually between 20 and 30 percent of the weight of the dry hydrated cement. The colloids observed in cement paste are mostly quasicrystalline. and perhaps two. not all of the same kind chemically. we are inclined to regard the pore space as having the character of interstices in a granular aggregation. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The term gel particle refers to particles having dimensions in the submicroscopic range of sizes called colloidal. the physical states of these materials are not known exactly.) There are also amounts of calcium aluminate hydrate and calcium alumino ferrite hydrate. and among pastes made with different portland cements it is not much influenced by differences in chemical composition. The colloidal matter together with calcium hydroxide appear as a continuous solid structure apparently occupying the whole volume of any specCopyright by ASTM Int'l (all rights reserved). Along with the colloidal material in hardened cement paste is crystalline calcium hydroxide having relatively low specific surface area. (The term gel designates a rigid aggregation of colloidal material. may be regarded as the primary particles of paste structure. By dispersing the structure and examining the fragments by electron microscopy. in general. No further reproductions authorized. It has characteristics resembling those of a natural mineral called tobermorite and has thus come to be called tobermorite gel. or 0. produces about 1. expressed as a volume per unit quantity of cement. and the material would become a voidless soild. In any paste containing less than this amount 6The microscopic changes that may occur later as the result of drying and wetting are properly ignored here. . which means if complete curing has been deliberately or inadvertently omitted.6/0. and it usually has a porosity between 40 and 55 percent. this amounts to saying that if the watercement ratio is 0.72 = 2. and this means that the water-cement ratio by weight must be at least 0. The densest possible hydrated cement paste contains a continuous system of pores. as evidenced by its permeability to water. But experimentally it was found that void space cannot be eliminated. The apparent volume of a specimen of paste. the increase of solid volume takes place without appreciable change of overall volume. This experimental observation is another cornerstone on which our concept of paste structure rests. One cubic centimeter of cement. The net volume of mixing water is that which remains within the specimen at the end of the period of settlement (bleeding) which is normally from 1 to 2 h'after mixing. a specimen of hydrated cement paste may have a porosity of not less than about 28 percent. it follows that instead of 1. normally the solid matter occupies 45 to 60 percent of the apparent volume. Copyright by ASTM Int'l (all rights reserved).19 cm 3 of space per gram of cement. is determined by the net volume of mixing water per unit volume of cement.6 cm3/cm 3 of cement. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and the highest possible solid content (exclusive of unhydrated cement if any) has been found to be about 72 percent or perhaps a little more of the total volume occupied by hydrated material. No further reproductions authorized. Because of the intrinsic porosity of the structure. solid volume.2 c m a / c m 3 of cement to provide enough space for all the hydration products that can be derived from 1 cm 3 of cement. As already mentioned. As just indicated. there will be ample room within the specimen for all hydration products that can be derived from 1 g of cement. it was found that under no circumstance can completely mature paste be made entirely solid.19 by weight. which limits the solid content to 72 percent of the apparent volume. The solid content of any freshly mixed paste is a little over 62 percent of what the solid content will be after chemical reactions have converted all the cement to the hydration products described above. In other words.38. As already indicated the structure is porous. On this basis we might expect that the hydration products will require 0.6 cm 3 of space in addition to the space originally occupied by 1 cm 3 of cement. and the rest of the unit volume remains full of water or is void if all the water in such space is caused to evaporate. the volume of paste must be at least 1.POWERS ON NATURE OF CONCRETE 67 imen of hardened cement paste.6 regardless of how high the cement content may be or how little water per unit of cement.6 cm a of hydrated cement. the porosity will have a higher range if the paste is not fully mature. the highest possible solid content is about 72 percent. some of the cement remains anhydrous regardless the duration of curing. When there is more space available than the minimum required by the hydration products. and a residue of the original cement remains a permanent feature of the structure of the paste. even though some of the cells cannot become filled to this extent.68 TESTS AND PROPERTIES OF CONCRETE of water-filled space. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it is reasoned that if the hydrated material in a specimen of paste can reach an average density of 72 percent but no higher. the residue appearing in cross sections as scattered remnants of the largest grains. This being true. even when excess space is available.38 by weight. it seems almost certain that the 72 percent limit of the content of solid hydrated material will be achieved in many cells after all the cement has become hydrated. some would contain many small grains. already discussed. some higher and some lower than the average. the extra space is a feature of the structure of paste. we would not find the same volumes of cement and water in each cell. considering the size of many of the cement grains. If any of the imagined cells contain excess cement. that hold the particles practically (but not exactly) in point to point contact. . and some might contain few if any grains. No further reproductions authorized. Since some of the cells must be nearly full of solid material to start with. and since interparticle attractior tends to hold particles close together. at any sufficiently low water-cement ratio. that same degree of density can be and is produced locally at various places throughout any paste. which presumably is the case wherever the local water-cement ratio is lower than about 0. such cells can get rid of their excess material by diffusion of material into Copyright by ASTM Int'l (all rights reserved). Various observations lead to the concept that in every paste the hydration products tend to become locally concentrated to the m a x i m u m degree possible. Of course. One line of evidence supporting this view develops from consideration of the structure of freshly mixed paste. it seems that if we could subdivide a freshly mixed specimen of paste having a certain water-cement ratio into a large number of cubical cells each having an edge length of say 100 #m (about the same as the mean diameter of the largest cement particles but about 100 times as large as the spherical equivalent of a "particle" of tobermorite gel). In other words. but at the same time they form a continuous structure having an overall volume equal to the apparent volume of the paste. Although cement particles in freshly mixed paste are individually dispersed throughout the volume of mixing water.2 cm3/cm 3 of cement. we would find that the overall water-cement ratio is an average of many different local watercement ratios. they cannot be uniformly spaced because of the interparticle forces. however high the water-cement ratio. there is more than enough space to accommodate the hydration products and thus less than 72 percent of the space can become filled with solid matter. In other words. as it usually is. when the volume of cement paste is greater than 2. we would find some cells almost filled with a single grain. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. W h e n the porosity exceeds 28 percent. which is to say when the paste c o n t a i n s spaces other t h a n gel pores. for example.~ or 0. as has been verified by microscopic observations. d e p e n d ing u p o n the s h a p e of the interstitial spaces. or capillary cavities. which r e q u i r e s us to visualize an uneven d i s t r i b u t i o n o f c e m e n t gel. a b o u t 1. The t e r m c e m e n t gel is convenient for d e s i g n a t i n g the p r e d o m i n a n t l y colloidal m a t e r i a l f o u n d in h y d r a t e d c e m e n t paste. b u t it m u s t be k e p t in m i n d t h a t the t e r m includes noncolloidal c a l c i u m h y d r o x i d e a n d other noncolloidal m a t e r i a l . 8 T h e c o r r e s p o n d i n g average d i s t a n c e f r o m solid surface to solid surface is between two a n d four times the h y d r a u l i c r a d i u s . after the density of hydrated material had reached 72 percent. if any. capillaries. so t h a t eventually all the c e m e n t can b e c o m e h y d r a t e d if the average w a t e r . Any space not filled with c e m e n t gel or g r a i n r e m n a n t s is reg a r d e d as interstitial spaces a m o n g masses of c e m e n t gel a n d is called capillary space. The o r d e r o f m e a n pore size is i n d i c a t e d by the q u o t i e n t o f the volume of pore space by the b o u n d ary a r e a of t h a t space. if any. p r o p e r l y defined as a solid c o m p o s e d of colloidal m a t e r i a l . which is a b o u t the.1 nm apart on a piece of superrubber about 25 mm (1-in. 7 I have used the t e r m cement gel to designate h y d r a t e d c e m e n t paste in its densest form. but this conclusion would be hard to prove because the process would probably require geological ages for completion. No further reproductions authorized. diffuse into the excess space in the other. of course. try the following: if one could place two marks 1 .POWERS ON NATURE OF CONCRETE 69 a d j a c e n t cells l a c k i n g cement.5 A . the m e a n pore size is. However. of fresh paste containing excess cement is joined to one with a deficiency of cement. the excess cement in one cube could. g r e a t e r t h a n the m e a n size of gel pores. the two marks would have become a little over about 150 mm (6-in. a n d therefore it does not c o n f o r m exactly to the t e r m gel. and then if one could stretch the rubber until it could encompass the earth. W e can now describe h a r d e n e d paste as a solid c o m p o s e d o f cement gel.specific surface a r e a of c e m e n t gel.c e m e n t ratio is high enough. T h e c o n c e p t of p a s t e s t r u c t u r e d e s c r i b e d above. and if after hardening both are kept saturated with water. diffusion for a distance of a few micrometres can occur in a normal curing period.) long. . Copyright by ASTM Int'l (all rights reserved). t o b e r m o r i t e gel. the original inter7Theoretically. in the p r e s e n t case where m a n y of the spaces are believed to be slit-like. T h e l a t t e r t e r m is a p p l i e d in pastes so dense t h a t the capillaries are discontinuous. a n d space not filled with cement gel.2 • 106 c m 2 / c m 3 of solid m a t t e r . the q u o t i e n t is 7. for e x a m p l e . if 50~mm or (2-in. It should be noted t h a t by this definition c e m e n t gel is not synonymous with gel as used above.8 n m (18 /~) seem to be a r e a s o n a b l e estimate. if any.) apart. entails a c o r r e s p o n d i n g uneven d i s t r i b u t i o n of t h e sizes of interstitial spaces.5 • 10 -a c m or 7. r e m n a n t s o f c e m e n t grains.) cube. b u t which in any case is not known exactly. F o r a porosity of 28 p e r c e n t a n d for solid m a t t e r having a specific surface a r e a of 5. surface to surface distances range f r o m zero at chemically b o n d e d points to a m a x i m u m distance t h a t is p r o b a b l y g r e a t e r the g r e a t e r the capillary porosity of the paste. which q u o t i e n t in h y d r a u l i c e n g i n e e r i n g is called the h y d r a u l i c radius. 8To acquire an idea of the magnitude of an angstrom unit. and which is found in gel pores. Of principal interest. and by those for some minerals found in concrete aggregate. as a rule. The discussion shall be confined for the most part to chemically free water found in cement paste since it influences the properties of concrete to a very important degree. particularly the smallest. Rock Structure The structure of concrete is characterized not only by the structure of cement paste but also by the structure of individual pieces of rock making up the aggregate. we know that the pores in rocks are usually larger than those in hydrated cement paste. The pores in permeable rock are usually larger than those in cement paste. however. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. States of Water in Concrete The solid matter in mature concrete may contain water molecules or ions derived from water. also rocks are less porous than paste. as indicated by the formulas for the compounds in hydrated cement. A few kinds of rock do have fine texture. may have a coefficient of permeability to water equal to that of a specimen of hardened paste having a porosity of 50 percent. thus. or in capillary spaces in paste or rock. certain argillaceous limestones are examples of unsuitable fine textured rocks. but in most concrete aggregates most of the particles have granular structure and are porous. Among these are vesicular rocks and artificially expanded shales in which isolated voids were formed by expansion of trapped gas. and unless they are also practically nonporous they do not make satisfactory concrete aggregate. if the cement paste was originally saturated. The pores within cement gel are called gel pores. may consist of practically voidless crystals or fragments of crystals. and most are permeable to fluids. It is commonly known that water in a vessel open to the atmosphere will eventually evaporate unless the atmosphere is saturated with water vapor. in other words. some of Copyright by ASTM Int'l (all rights reserved). . certain cherts also. No further reproductions authorized. A rock having a porosity of say 1 percent. Some rocks contain pores that reduce their apparent specific gravity but do not affect their permeability. Cement paste can be regarded as a vessel open to the atmosphere so far as contained water is concerned. Some pieces. is the water that remains chemically free. rocks have a relatively coarse texture. but not all of the water it is capable of holding can evaporate unless the surrounding atmosphere is practically empty of water vapor. Such rocks are useful when concrete of low unit weight is desired.70 TESTS AND PROPERTIES OF CONCRETE stitial space among the cement grains having become segmented into isolated cavities by the growth of cement gel. Of the total capacity of mature cement paste for evaporable water. opposite surfaces are necessarily quite close together. In rocks having porosities upwards of 1 percent the relatively large pores can retain very little water at that humidity. Copyright by ASTM Int'l (all rights reserved). Because of cement paste the internal surface area is very extensive. The failure of water in concrete to evaporate as it normally does shows that it is altered to some degree by the material with which it is in contact. there is a somewhat greater weakening effect due to swelling. the pore space may be almost completely full. No further reproductions authorized. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Of course. In other words. that is. the fine textured rocks usually retain a comparatively large amount of water at an intermediate humidity. different rocks differ considerably in this respect. As has already been pointed out. However.POWERS ON NATURE OF CONCRETE 71 the water can evaporate. At low ambient humidities. van der Waals attraction between water molecules and between solid material and water molecules seems to contribute to the total cohesive force. from about one third to two thirds of it will be full when the ambient humidity is only 50 percent. Such strains correspond to the reversible part of volume changes due to drying and wetting of concrete. Some of the alteration may be due to dissolved material. which attraction holds a condensed film of water molecules. but a definite fraction of it will be retained. adsorption being aided by hydrostatic tension maintained by curved meniscuses of the water in capillary spaces. but removal of solutes only modifies the situation. Naturally.8 nm (18 . At higher ambient humidities. a considerable fraction of the total capacity of rock for evaporable water may be retained. There is good evidence that some of the evaporable water normally held in concrete contributes to its strength. the higher the humidity. The principal forces acting on water and preventing it from evaporating into an unsaturated atmosphere have already been identified as van der Waals forces of attraction and capillary-induced tension. a large fraction of the total evaporable water can exist as a thin film spread over solid surface.~) wide (see above) adsorption of two molecular layers on each surface is sufficient to fill most of such space. such forces are balanced by counterforces. A state of mechanical tensile stress between water molecules in the condensed state restrains evaporation in about the same way that van der Waals attraction restrains evaporation from a thin layer on a solid surface. but at humidities upwards of 90 percent. In spaces up to about 1. the restrained molecules are held by van der Waals forces. . that is. the amount retained being a larger fraction of the total evaporable water the higher the degree of saturation of the ambient atmosphere. water molecules are restrained from evaporating by the van der Waals forces of attraction between them and the surfaces of the gel particles. particularly the alkalies. the counterforces corresponding to elastic strains of one kind or another in the solid structure within which the water is held. and such will be the condition when the ambient humidity is about S0 percent. two absolutely identical specimens would not be likely to fail at exactly the same stress. The strength of a given kind of concrete is not a single valued property of the material. it was the fact underlying the cement-space ratio law for strength given by Feret (1897). When a concrete cylinder is subjected to a steadily increasing axial stress. under a sustained high stress less than the mean "instantaneous" strength. a variation of test results about the mean value from a large number of identical specimens would still be found. the function being such that strength appears higher the higher the rate of loading. is maintained without increase. that limit usually being established by the means at hand for compacting the mixture. however. in particular. and earlier by Zielinski (1908). . There is no tensile stress associated with the lateral strain just mentioned. the upper limit tends to be established by the strengths of the aggregate particles. as in the ordinary compression test. is a function of the rate at which stress is applied. It would be expected that with a given aggregate the more cement gel per unit volume of paste and the more paste per unit volume of matrix. as is evident when one considers air bubbles as aggregate. This does not mean. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the specimen will eventually fail. it seems that even with a perfect testing machine and with specimens exactly alike. In other words. the greater the strength of the concrete. But there are other aspects of the strength of concrete depending on the nature of its structure. For aggregates composed of strong particles. they are not likely to fail at the same elapsed time after loading. which means the lower the air content of the matrix. with aggregates composed of relatively weak particles. but after the compressive stress becomes about two thirds of the stress at failure. If a stress less than the strength indicated by an ordinary test procedure. This extra strain does denote the developCopyright by ASTM Int'l (all rights reserved). On the other hand. the upper limit of concrete strength tends to be established by the upper limit of the density of the matrix. Thus. No further reproductions authorized. and yet greater than about two thirds of that stress.72 TESTS AND PROPERTIES OF CONCRETE Strength In the above discussion dealing with cohesion and adhesion we necessarily spoke of strength. or. that concrete cannot be stronger than the strength of individual aggregate particles. There are good reasons to believe that failure is essentially a random (stochastic) process. and therefore the stress existing at time of failure is intrinsically a variable number. Strength tests of many kinds of concrete show that such is indeed the case. and the less general water-cement ratio law given by Abrams (1918). and some of these will be discussed in the following paragraphs. the observed increase in diameter at low stress is a certain constant fraction (Poisson's ratio) of the longitudinal shortening (compressive strain). further increase in compressive stress causes lateral dilation to increase more than can be accounted for by Poisson's ratio. Compressive strength. In concrete made with strong pastes. fracture surfaces usually pass through rock particles. or both kinds of fractures appear. or when subjected to shear stress. just as compact. When such stress begins to exceed tensile strength. the principal strains preceding failure would involve only the sliding of one smooth surface over another. structureless except for flaws. various properties were discussed. Therefore. Conclusion While discussing the structure of concrete and the internal forces that give it stability. the nominal shearing surfaces are likely to follow the contours of rock particles. uncemented. It would be possible to elaborate these brief discussions and to add other topics. other papers in this publication are concerned with such reviews. hence. the observed extra dilation with simultaneous internal cracking shows that tensile stress develops across the incipient fracture surfaces and causes separations at such surfaces. simply because of the granular nature of the material. or fractures appear as cracks parallel to the axis. and thus tensile stress would develop even in a continuum. Sun Apr 6 21:39:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and thus no increase in volume other than that accounted for by Poisson's ratio would be necessary. Current theory of fracture indicates that during a compression test tensile stress necessarily develops around holes. No further reproductions authorized. and no doubt interpretations in terms of structure will be found in them. or flaws in the material. These considerations amount to classifying cement paste or concrete as an intrinsically dilatant system. and again it is not difficult to account for the development of tensile stress as one rough surface is forced to move away from the other as it tends to slide. is essentially failure in tension. in which case the cause of tensile stress is obvious. . Specimens of neat cement show evidence of tension failure in a compression test. fractures appear as uneven surfaces having an inclination to the axis somewhat less than 45 deg. If failure under compressive stress were limited only by strength in pure shear. but even so the fracture surface is not smooth. however. Copyright by ASTM Int'l (all rights reserved). it is impossible for the surface of a fracture in paste to be smooth. granular systems are intrinsically dilatant. Without questioning this deduction one can at the same time suggest that tensile stress would arise anyway. this paper is concluded without further development of the subject. Since the individual particles of which paste or rock are composed are much stronger than the structure. cracks. At failure. they have a strong tendency to split. In concrete made of strong aggregate material and weak paste. vibrations due to internal splitting can be detected wifh suitable instruments.POWERS ON NATURE OF CONCRETE 73 ment of tensile stress. Such experimental evidence indicates that the failure of concrete under compression. There are two distinct classes of nonuniformity in freshly mixed concrete. and these variations are reflected in the workability. Concrete initially discharged may vary in many important respects from the last concrete in the mixer. No further reproductions authorized. may be attributed to blade wear on the mixer. Uniformity of Concrete Concrete is a heterogenous mixture of natural or artificial aggregates. which are classed as within-batch variations. that is. consistency. Tenn. S m i t h 1 Chapter 7--Uniformity and Workability Introduction Concrete is a manufactured product.STP169B-EB/Dec. pozzolans. Marquette Cement Manufacturing Company. Copyright9 1978 tobyLicense ASTM International www. inadequate mixing. Any successful manufacturing operation requires that the products produced from day to day are uniform and similar in appearance and quality. and quite often entrained air. appearance.org .astm. 74 Copyright by ASTM Int'l (all rights reserved). but increase the problems of quality control and uniformity. and other admixtures. Technical Services. within-batch variations and batch-to-batch variations. Concrete manufacturing differs from other types of manufacturing in many important respects which enhance the versatility of concrete for building construction. Concrete produced by equipment employing volumetric batching and continuous mixing by an auger is sampled and tested. 1978 D. and quality of the concrete. water. uniformity. and has to meet the same uniformity requirements (ASTM Specification for Concrete made I Manager. or overloading of the mixer. or variations may occur throughout the batch. cement. The materials used in the manufacture of concrete have wide ranges in physical and chemical composition. Nashville. improper loading sequence. Nonuniformity may be evident in freshly mixed or hardened concrete. T. 37238. These differences. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant Agreement. The materials supplied batch after batch to the mixer must have uniform properties.SMITH ON UNIFORMITY AND WORKABILITY 75 by Volumetric Batching and Continuous Mixing (C 685)) as concrete produced in central and truck mixers (ASTM Specification for Ready-Mixed Concrete (C 94)). and admixtures. and water to escape. mixing. Type and brand of cement 8. Experience has shown that variations affecting the properties of plastic concrete will also affect the properties of hardened concrete. Control must be maintained at the batching and Copyright by ASTM Int'l (all rights reserved). These variations may occur as the result of changes in one or more of the following: 1. workability. conveying. Concrete temperature 10. transporting. Air temperature 11. in certain areas. with a resulting accumulation of coarse aggregate. Type. and curing. . Differences in appearance. depositing. No further reproductions authorized. and quality of concrete placed on different days or from different mixers on the same day are designated batch-to-batch variations. every operation involved in the transportation. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. cement. finishing. The properties of the concrete in the finished structure are of primary importance. and consolidation of concrete in the forms can contribute to segregation and nonuniformity. consolidation. and quality of the finished product. Quantities of deleterious materials 6. surface texture. and shape of aggregate 5. Testing procedures After mixing. Type and condition of mixing equipment 14. Inadequate preparation of grades and forms may also influence nonuniformity by permitting sand. Different lots of cement from the same source 9. Wind velocity 13. Moisture content and absorption of the aggregates 3. placing. Humidity 12. including batching errors 2. Specific gravities of materials 7. Control of Concrete Production Production of uniform concrete can be obtained only through systematic control of all operations from selection and production of materials through batching. Aggregate grading 4. Concrete from this style of equipment may have variations throughout the batch due to batching and mixing equipment as well as possible segregation of aggregates in the storage hoppers. Properties and tests of the individual components and of the fresh concrete are valuable aids in predicting and controlling the uniformity. homogeneity. cement. Mixture proportions of aggregate. water. water. unit weight. and others to study the effects of different rates of rotation of truck mixers. 2 Additional information on practices that lead to better uniformity are found in the ACI Standard Recommended Practice for Measuring.S. . The uniformity of fresh concrete is evaluated by comparing variations in quantity of coarse aggregate and unit weight of air-free mortar of two samples. Bureau data for one series of mixing time tests on 3. air content.50 kg (1.36 kg (3. Transporting. but increased mixing beyond 2 min had little additional influence on this variable. Concrete uniformity generally has been measured in terms of compressive strength. Tests by a Number of investigators have been considered in the preparation of ASTM Specification C 94. specific gravities. and Placing Concrete (ACI 304). Concrete cylinders should be fabricated for compressive strength tests. Routine instructions for measuring.0 kg/m 3 (1. Mixed concrete should be tested for consistency.76 TESTS AND PROPERTIES OF CONCRETE mixing plants.1 lb) when the mixing time was increased from 1 to 2 min. and effect of mixing time on uniformity of concrete. and coarse aggregate in fresh concrete by a series of wash separations and weighing in air and water. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and efficient batching procedures. and placing concrete are given by the American Concrete Institute (ACI) [I]. Large variations in this test may indicate that batching procedure is inefficient.S. mixing speed. Hollister [4]. This method has been used by Slater [3]. Additional mixing time may be required if the unit weight varies more than 24. Cook [5]. or mixer blades are worn. mixer capacity. Aggregates should be tested for gradation. Some variation must be accepted. one taken from the first and last portions of the batch. slump.06 m 3 (4 yd 3) mixers showed that variation in air-free unit weight was reduced from 1. mixing. U. Bureau of Reclamation Test of Mixer Performance--The U. The Dunagan test has limited usefulness because of sampling errors and difficulties in distinguishing between cement and very fine sand. temperature. Bureau of Reclamation's mixer performance tests [6] are used to evaluate the ability of a mixer to mix concrete that will be within prescribed limits of uniformity. and mixture adjustments must be made to correct for changes in these properties. Mixing. Variation in water-cement ratio was 2The italic numbers in brackets refer to the list of references appended to this chapter. and moisture content. sand. and content of coarse aggregate or cement. effect of time of haul. but consistent concrete of satisfactory quality can be obtained if proper control is maintained. and unit weight. Uniformity tests have been used to establish required mixing time. Methods of Measuring Uniformity Dunagan Test--Dunagan [2] proposed a method for measuring the proportions of cement. air content. No further reproductions authorized.0 lb) to approximately 0.5 lb/ft 3). is described in detail elsewhere [8]. air content. . also known as the Willis-Hime method. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Data cited from previous tests indicated that the test was highly reproducible provided extreme care was used and corrections were made for sampling errors in coarse aggregate content of the small test portions. Variability of 7 percent or more in the cement content of two samples from the mixer is evidence of incomplete mixing. and coarse aggregate content.0 kg (2 lb/ft 3) should be considered evidence of unsatisfactory uniformity.SMITH ON UNIFORMITY AND WORKABILITY 77 reduced from 29 to S percent when mixing time was increased from 1 to 2 min in this same series of tests. Variations in slump. water content by oven drying. A variability index for each test can be calculated by dividing the smallest value by the largest value of three tests and divide by 100. It provides a basis for within-batch comparisons of cement content of concrete and employs a liquid with a density greater than sand but less than cement. Army Corp of Engineers Method of Test for Concrete Mixer Performance (CRD-C55-73)--This method of evaluation tests 3 samples of concrete for water content. This test is one of several mixer performance tests specified in ASTM Specification C 94. No further reproductions authorized. U. They suggested that a variation of more than 16. Centrifuge Test--This test.1 lb/ft. and differences of more than 32. air-free unit weight of mortar. ASTM Specification C 94. Copyright by ASTM Int'l (all rights reserved). Air-Free Unit Weight Test--A study designed to establish test methods and limits for variations in truck mixed concrete was reported by Bloem et al [7]. Tests are usually performed on samples of concrete from the first and last 10 percent of the load. According to their data. 3) correspond to a change in water of about 9. This liquid is used to separate the components of a carefully prepared mortar sample extracted from the concrete. and in most cases the information gained is not commensurate with the time and labor required. percent of coarse aggregate.S. They concluded that the test is quite involved.0 k g / m 3 (1 lb/ft 3) in this test indicates real differences in the proportions of the mortar ingredients. a difference in air-free unit weight of mortar of 17. and s/6 of discharge from a truck mixer were determined. The tests are performed also to determine the feasibility of altering the mixing time. unit weight of air-free mortar. 1/2. They concluded that the air-free unit weight test was an improvement over the unit weight test because the number of variables was reduced and excessive changes in this property reflected changes in water or in proportions of cement and sand.6 k g / m 3 (1. Table XI. and compressive strength of concrete obtained after approximately 1/6. contains tolerances of test results which are requirements of uniformity of a single batch of concrete.90 litres/m 3 (2 gal/yd 3) when the proportions of sand to cement were maintained constant and the water alone was varied. but not the very first and very last portions of the batch to be discharged. The centrifuge test was used in the study by Bloem et al [7]. cement content. or length of mixing. proportions of sand to cement. When the slump is maintained constant by reduction in water content. pozzolan. If the weight of aggregate per cubic metre of lightweight concrete changes. it is important that the concrete contain a uniform quantity of air. Resistance of concrete to freezing and thawing is increased several hundred percent by incorporating the correct amount of air in the concrete.5 sacks of cement per cubic metre when 5 percent entrained air was added to the concrete. each 1 percent of additional air being approximately equivalent to 2.78 TESTS AND PROPERTIES OF CONCRETE Unit Weight--Unit weight of the concrete is influenced by the specific gravity and amount of coarse aggregate. The strength of concrete decreases uniformly with increase in air content of the fresh concrete provided the water-cement ratio is held constant. or density of the aggregate.) in slump. brand or type of cement. Additional tests. For this reason. When air-entraining cement is used. a change in unit weight indicates a change in weight of aggregate. temperature of the mix. and gradation of the aggregate are required in order to determine the cause of the change. gradation. variations in unit weight are difficult to evaluate as to cause or significance. Air Content--Air content has an important influence on workability. Consequently. Air content is generally maintained at the correct level by increasing or decreasing the dosage of air-entraining agent because it may not be practical or desirable to remove the cause of the variation. No further reproductions authorized.5 to 6. Consequently. compressive strength. Sudden loss of workability may indicate a reduction in air content. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. slump. or admixture.5 cm (1 in. control of air content is more difficult because any change in the dosage of air-entraining agent must be accompanied by a corresponding change in cement content. . Within-batch variations should not exceed 1 percent. including unit weight. The unit weight test is recommended as a job control measure for lightweight aggregate concrete in conjunction with air determinations and slump. Air content of normal weight concrete may be computed by comparing the actual unit weight of concrete with the theoretical weight based on Copyright by ASTM Int'l (all rights reserved). and durability of concrete. sand grading. it may be the result of change in moisture content. Too little air will not provide workability and durability. Air entrainment also increases slump. Variation in air content obtained from a given dosage of air-entraining agent may result from changes in concentration of the agent. The test is more definitive when the weight and solid volume of coarse aggregate and volume of air are eliminated as in the air-free unit weight of mortar test. air content. Strength reductions of 16 to 20 percent at 28 days have been reported for concretes containing 5. If the slump and air content are maintained constant. many engineers prefer to use regular cement and add the airentraining agent at the mixer. moisture content. strength reduction due to air entrainment is not so great and the strength of lean mixes may be slightly increased. and water content. but it may be applied to other types of concrete as well. This method is used more than any other and is considered satisfactory for all types of concrete and mortar except those made with highly porous lightweight aggregate. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This apparatus must be calibrated periodically to guard against changes caused by rough usage. Several meters have been developed to determine directly the air content of fresh concrete.) in diameter by 1. Furthermore. and Air Content (Gravimetric) of Concrete (C 138). . A small sample of carefully selected mortar is obtained from the concrete and placed in a brass cup measuring 1. The air indicator is a miniature device that uses the volumetric principle. and. as outlined in ASTM Test for Unit Weight. An aggregate correction factor should be determined with the materials used and subtracted from the apparent reading to determine the actual air content. and the indicator is rolled several times until all mortar has been removed from the cup. the finger is carefully removed from the stem. the lid is securely fastened. With the indicator in a vertical position. Yield. Results obtained by this method are influenced by variations in mix proportions. The volumetric method (ASTM Test for Air Content of Freshly Mixed Concrete by the Volumetric Method (C 173)) consists of removing air from a concrete sample by mixing it with water in a special container. and changes in moisture content of aggregates.) high and compacted with a wire or knife blade. The apparatus is so calibrated that the percentage of air is read directly when the pressure is released. ASTM has standardized two methods for determining air content by means of meters.SMITH ON UNIFORMITY AND WORKABILITY 79 the specific gravity of the materials used. and pressure is applied by a hand pump to a predetermined amount. The pressure meter (ASTM Test for Air Content of Freshly Mixed Concrete by the Pressure Method (C 231)) consists of a special pressure-tight container and accessories designed to hold an accurate volume of concrete.9 cm (3/4 in.3 cm (1/2 in. specific gravity of ingredients. The aggregate correction factor varies only slightly for the same type of aggregate and need only be checked when there is a definite change in materials. the brass tube is inserted in the tube. Determination of air content by this method is generally preferred to the gravimetric or unit weight method. if the elevation of the place at which the apparatus is used changes by more than 183 m (600 ft). and the liquid level is adjusted to the top line. and the number of graduations from Copyright by ASTM Int'l (all rights reserved). The volume of air is determined from the difference in volume of the sample containing entrained air and the volume of the sample after it has been agitated to permit the air to escape. it should be recalibrated. any change in batch weight requires a new computation. This method is recommended particularly for lightweight concrete. The glass tube that comes with the device is filled to the top line with isopropyl alcohol. The container is filled with concrete. No further reproductions authorized. The finger is placed over the stem to prevent alcohol from escaping. Cement Content of Fresh Concrete--Constant neutralization by 3 N hydrochloric acid (HCI) for a fixed period of time (1 h in this procedure) has been employed by the California Department of Transportation [9]. must be applied to convert to percent air in concrete. No further reproductions authorized. For the latter purpose they found the titration method to be more effective than the "wash-out-method" and the "heavy media method" that were also tried in this program. In reasonably uniform concrete. agitation of the sample. The procedure requires the development and use of calibration curves when determining the relative variation of cement content within a batch. The report states that "adjustments to aggregate a n d / o r cement feed can be made as needed to improve mixing uniformity. a new calibration curve must be established" according to the procedure outlined in the report. cement. Slump--The slump test (ASTM Test for Slump of Portland Cement Concrete (C 143)) is essentially an indication of the wetness of the concrete. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.80 TESTS AND PROPERTIES OF CONCRETE the top to the new liquid level gives an indication of the air content in the mortar sample. and this is a phenomemon that would have a profound effect on the end results of the test. or working solution of acid. the most applicable use of the procedure is testing mixer efficiency.5 cm (1 in. The proposed method is essentially the same as that originally proposed by Kelly and Vail with the exception that this system [10] Copyright by ASTM Int'l (all rights reserved). The test can only provide an indication of relative air content and cannot be considered as reliable as the pressure meter or the volumetric method. Accuracy of this procedure was reported to be "within about ~h sack per cubic yard. there was no discussion of the reaction of HC1 on the aggregates. The authors of the report state in their conclusions that the test was not proven to be of sufficient accuracy for routine control of cement content during normal concrete production. Batch-to-batch variations may result from hatching errors. uncorrected changes in moisture content or grading of the aggregate. based upon the design mix. ." Field tests indicate the procedure is most useful for evaluating the performance of a concrete mixer. slump should not vary more than about 2. Rapid Analysis Method--This method of test is for the determination of cement and water content in fresh concrete. or variations in temperature. method of inserting the stopper. Relative cement contents of various portions of a batch can be determined in about 1 h.) within a batch. A correction factor. Within-batch variations in slump indicate incomplete mixing and nonuniform distribution of water or other ingredients throughout the batch." This test procedure was apparently used on concrete that did not contain calcareous aggregates. and at present. at least. Meticulous care must be used in selection of the mortar sample. "In the event of any change in source of aggregate. and removal of the finger from the tube. It can be used in the laboratory or in the field. This limitation can be removed by modifying the procedures and using larger samples by applying the restriction that the largest aggregate must weigh less than 10 percent of the specimen weight. Other factors such as durability. eriochrome black T indicator.2. and calcium titration for cement content. tap water. 0. placeability. The method relies on chloride ion titration for determining water content in the fresh concrete. Also.5 N sodium chloride (NaC1) solution.05 N potassium thiocyanate (KSCN) solution. The reagents required for water content determination are: 0. and corn- Copyright by ASTM Int'l (all rights reserved). the test can be completed in the field in 15 min. . and air content (A) of the concrete. EDTA should be stored in polythene bottles. dimensional stability. the operational accuracies of the CERL/K-V water and cement content tests as determined by extensive laboratory and field tests indicate an average error of 4 to 6 percent for water contents and 6 to 8 percent for cement contents. abrasion resistance.SMITH ON UNIFORMITY AND WORKABILITY 81 uses a titration method rather than flame photometer for calcium determination.8 cm (11/2 in. in 15 min by using w/c versus strength curves. thermal properties. by extensive field testing. and ammonia-ammonium chloride NH3/NH2 CI buffer solution. and a 50 percent nitric acid (HNOa) solution. Statistical analysis of the Kelly-Vail test data shows the development of a predictive relationship between 28-day strength (S). The reagents needed for the calcium titration (cement content determination) are: a 5 percent HNO3 solution. The cement test has a second limitation caused by the technique measuring all calcium passing through the smallest sieve rather than cement only. The equipment and method are described in the report [10]. and they indicate that only the fine aggregates cause a significant interference. to be accurate enough to estimate the strength potential of fresh concrete. that is. the Kelly-Vail water/cement (w/c) ratio (KVC). a 0. At the present time. The limitation of the method is that the 1-kg ( .01 M solution of disodium ethylenediaminetetra-acetate (EDTA) in distilled water. Compressive Strengths--Measured concrete strength is used widely as a criterion of concrete quality. This method seems to be a very useful tool for measuring and controlling the uniformity of the w/c ratio of fresh concrete in the field--much better than the other methods in use for measuring uniformity as it is related to cement and water contents. The system has been proven.). also presented is an evaluation of the repeatability of KVC measurements and 28-day strengths within and among concrete batches. Tests have been made on both fine and coarse calcareous aggregates.S-Ib) sample being used limits the maximum size coarse aggregate in the concrete to 3. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. saturated ferric alum solution. It also appears to have excellent potential for concrete strength values at a very early age. nitrobenzene (C6H~NO2). Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Both of these definitions are expressed in terms related to the physical characteristics of the concrete alone. workability is related directly to the type of construction and methods of placing. Compressive strength is a control test used to determine the degree of uniformity of concrete.82 TESTS AND PROPERTIES OF CONCRETE pactability may be more critical. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. Glanville [11] defined workability as: "that property of the concrete which determines the amount of useful internal work necessary to produce full compaction. Workability of concrete is defined in ASTM Definition of Terms Relating to Concrete and Concrete Aggregates (C 125) as: "that property determining the effort required to manipulate a freshly mixed quantity of concrete with minimum loss of homogeneity. mixing." Powers [12] defined it as: "that property of the plastic concrete mixture which determines the ease with which it can be placed and the degree to which it resists segregation.5 percent. based on the average strength of all comparative specimens is 7. . Concrete having suitable workability for a pavement might be unsuitable for use in a thin. Workability Workability is a term that is used every day in concrete construction. but strength tests are easily made and variations in strength are assumed to be indicative of variations in other properties." In actual practice. Various methods have been developed for its measurement. Concrete that can be placed readily without segregation in a mass dam would be entirely unworkable in a thin structural member. This evaluation is statistical in nature and is a method for control of strength based on the coefficient of variation. and it is a factor easily appreciated in practice. None of these tests evaluate all characteristics that are involved in this property.. Table XI of ASTM Specification C 94 lists requirements for uniformity of concrete. The permissible difference for the average compressive strength at 7 days for each sample (not less than 3 cylinders). In a well controlled laboratory. Workability means different things to different people and for different placing conditions. Workable concrete compacted by means of high-frequency vibrators would be unworkable if vibrators could not be used and hand tamping and spading were required. and these are expressed as maximum permissible difference in results of samples taken from two locations in a concrete batch. Variations in excess of this amount must be attributed to variations within the batch of concrete. ACI Committee 214 has developed a Standard Recommended Practice for Evaluation of Compressive Test Results of Field Concrete (ACI 214-65). being independent of the methods of placing and compacting. compressive strength of cylinders fabricated from the same concrete sample may vary 3 to 5 percent. heavily reinforced section. and working. type and size aggregate. If a mix is too dry. percentage of air entrained. Rich mixes are more workable than lean mixes. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. consistency or fluidity. characteristics of cement. If a mix is too wet. segregation may occur with resulting honeycomb or sand streaking on the exposed surface. and bleeding. The degree of workability required for proper placement and consolidation of concrete is governed by the type of mixing equipment. and amount and characteristics of admixture used. No further reproductions authorized. The consistency necessary for full compaction varies with the type of structure. Consistency generally denotes the wetness of the concrete which is commonly measured by the slump test. An increase in the fineness of cement increases the cohesiveness of the concrete mix as well as the rate at which cement hydrates and the early strength development. Consistency--Consistency and plasticity are terms often used to indicate workability. Differences in bleeding tendency. it may be difficult to place and compact. Cement--Very lean mixes tend to produce harsh concrete having poor workability. and type of compaction equipment available. and type of placing equipment. Workability is dependent upon the physical and chemical properties of the individual components and the proportions of each in the concrete. It is agreed generally that concrete should have the driest consistency that is practicable for placement with proper vibration. size. grading of fine aggregate. grading and shape of coarse aggregate. but concrete containing a very high proportion of cement may be sticky and difficult to finish. Neither very fine or very coarse sand is desirable. method of compaction. Factors Affecting Workability Some of the factors that affect the workability [11] of concrete are quantity of cement. proportion of fine to coarse aggregate. measurement of workability is determined to a large extent by judgement.SMITH ON UNIFORMITY AND WORKABILITY 83 Properties involved in workability include finishing characteristics. formed when it is deposited. and segregation may occur because of the tendency for larger particles to roll towards the outer edge of the heap. consistency. as measured by the slump test. None of the test methods proposed or in use today simultaneously measure all of these properties. It must not be assumed that the wetter the mix the more workable the concrete. than an equivalent amount of coarse sand. accumulation of laitance. segregation. finishing properties will be impaired because of the accumulation of laitance on the surface. type and quantity of pozzolan. quantity of water. shape of sand grains. Consequently. mobility. Sand--Concrete containing fine sand requires more water for the same consistency. and type of concrete. Rounded river Copyright by ASTM Int'l (all rights reserved). . and other properties of concrete made with cements having the same fineness and chemical analysis have been observed. pumpability. Very coarse sand can have an undesirable effect on finishing quality. based on experience. 70 to 5.6 kg (10 to 15 lb) more water per 0. More sand. method of placing. . The water content may be increased 8. crushed aggregates generally requires more sand than similar concrete made with rounded aggregates. and water are required when the coarse aggregate contains flat and elongated particles.3 cm (8 in. Bureau of Reclamation [13] experience in pumping concrete indicates that concrete containing 6. Flat or elongated particles which are defined as particles having a ratio of width to thickness or length to width respectively. segregation. aggregate should not be larger than three fourths of the maximum clear spacing between reinforcing bars nor larger than one fifth of the wall thickness or narrowest dimension between sides of forms. but aggregate larger than 6. such as ASTM Specification for Concrete Aggregates (C 33). greater than 3:1. Concrete containing aggregate graded to 2. No further reproductions authorized.765 m (1 yd 3) when crushed sand is used. ACI Committee 304 has suggested rescreening at the batch plant as the method most likely to eliminate undesirable undersize and promote uniformity. cement. The maximum size of aggregate that can be used to produce workable concrete is limited by practical considerations including type and size of structure.) maximum size aggregate can readily be pumped through an 20. angular. After the grading is established.) maximum size can be placed by pneumatic equipment.) pipe. Coarse Aggregate--The particle size distribution of coarse aggregate influences water requirements and workability of concrete. Natural sand may give satisfactory results with a coarser grading than would be permitted with crushed sand. Introduction into the mixer of a large quantity of undersize material which may have accumulated will result in a sudden change in workability resulting in a demand for additional water. Generally.8 kg/m 3 (15 to 25 lb/yd 3).84 TESTS AND PROPERTIES OF CONCRETE sand gives greater workability than crushed sand composed of sharply angular pieces with rough surfaces. should be used. ACI Recommended Practice for Selecting Proportions for Concrete (ACI 211.5 cm (1 in. Coarse aggregates meeting standard grading requirements. concrete must contain 2 to 3 percent more sand by absolute volume of total aggregate and 3.4 cm (21/2 in. and contamination of aggregate can occur during handling and stockpiling.9 to 14. are detrimental to concrete workability. In addition. it should be maintained within rather close tolerances to avoid sudden changes in workability and other concrete properties. and availability of materials.S.) may cause difficulty. If the w/c ratio is held constant.4 cm (21/2 in. Segregation is reduced and uniformity improved by separating the aggregate into several size fractions and recombining these fractions when concrete is manufactured. more cement is required. Angular sand particles have an interlocking effect and less freedom of movement in the freshly mixed concrete than smooth rounded particles. U. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Production of workable concrete with sharp.1) provides recommendations on the maximum sizes of aggregate for various types of construction. Breakage. amount and spacing or reinforcing bars. including sand. ACI Recommended Practice for Selecting Proportions for Concrete provides a basis for estimating the proportions of coarse aggregate to be used in trial mixes. Mixture Proportions--Workability can be controlled by proper proportioning of the constituent materials. In addition. it is used conveniently as a control test and gives an Copyright by ASTM Int'l (all rights reserved). including inert or cementitious materials or pozzolans. Improvement in workability resulting from air entrainment is more pronounced in lean mixes that are harsh and unworkable because of poor aggregate grading or type of aggregate used. produce an increase in slump. Finely Divided Materials--Addition of finely divided material. These materials have been used to improve the grading of sands deficient in fines. but excess workability is inefficient. instead of substituted for part of the cement. It has been reported that there is a decrease in the frequency of plugged pump lines when water-reducing retarders are used in the concrete. generally improves the workability of the concrete. The quantity of mortar required to produce the desired workability with a given coarse aggregate can be determined more effectively by laboratory tests. Improvement is more noticeable in lean mixes than in rich mixes. 1) is the most commonly used method of measuring consistency or wetness of concrete. permit a reduction in mixing water with no loss in slump. Workability will be improved if these materials are added as replacement for part of the sand. and air. and improves the workability of concrete. if the water content is held constant. An excess of mortar increases workability. However. It should not be more than is required for consolidation by modern equipment. As the proportion of mortar. It is not suitable for very wet or very dry concrete. . cement. Set retarding admixtures reduce the early rate of hardening and permit concrete to be handled and vibrated a longer period of time.SMITH ON UNIFORMITY AND WORKABILITY 85 Air Entrainment--Entrained air increases the paste volume. is increased. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. There should be sufficient mortar to fill the voids in the coarse aggregate plus a sufficient amount to permit the concrete to be placed readily in forms and vibrated around reinforcement. nor is it always representative of the placeability of the concrete. It does not measure all factors contributing to workability. Cementitious and pozzolanic materials are usually substituted for 10 to 25 percent of the cement. Chemical Admixtures--Water-reducing admixtures. acts as a lubricant. Methods of Measuring Workability Slump Test--The slump test (see Fig. or. It reduces bleeeding and segregation during handling and placing of concrete and increases cohesiveness or "fattiness" of the concrete. when added to concrete. less power may be required to pump the concrete. No further reproductions authorized. water. the grading and angularity of the coarse aggregate become less important. . the slump decreases. The first concrete may have sufficient workability for placement in pavements or mass concrete. cement.7 cm (5 in.) to approximately 4. Slump tests may be made at the mixing plant in order to check the uniformity of batching operations. as measured by the slump test and the water content of concrete.6 cm (3 in. brought to the same slump.0 percent when the initial slump is 12. and admixtures are uniform and aggregate grading is within acceptable limits.) may vary from 2. will have the same water content and w/c ratio provided weights of aggregate. Two concretes with the same slump may behave differently. and the other may be very cohesive with surplus workability.86 TESTS AND PROPERTIES OF CONCRETE FIG.) slump when placed at 32~ (90~ or the same concrete may have a slump of 14 cm (5. Tests are usually made at the point of placement and should be made whenever cylinders are molded for compressive strength testing. Copyright by ASTM Int'l (all rights reserved). the percentage change in water content required to increase the slump 2. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Popovics [14] has presented data indicating that the relationship between consistency values.) when placed 10~ (50~ Air entrainment and water-reducing admixtures will increase slump of concrete if all other conditions remain the same. Each 1 percent increase or decrease in air content will produce approximately the same influence as a change in water content of 3 percent. is parabolic. No further reproductions authorized. As the temperature of the concrete increases.). that is.5 cm (1 in. 1--Slump test. The slump test should be performed ~n strict accordance with the requirements of ASTM Test C 143. the concrete is tapped on the side with the tamping rod.2 cm (4 in. indication of the uniformity of concrete from batch to batch. Repeated batches of the same mix. Additional information on workability of the concrete can be obtained if. that is. one may fall apart after tapping and be harsh with a minimum of fines.) at 21~ (70~ may only have a 7.5 percent when the initial slump is 5.5 in. An average change in water content of 3 percent generally is considered necessary for a 2.5 cm (1 in.) change in slump. Concrete placed at a slump of 10.1 cm (2 in. but the other concrete may be required for more difficult placement conditions. after removing the slump cone. 1.01 in.6-cm (1/4-in.84 in.SMITH ON UNIFORMITY AND WORKABILITY 87 The slump generally is reported to the nearest 0. but if consolidation of the concrete is practical.31 in.10 in. A hollow plastic rod 1. This rod can move freely inside the tube and can be used to measure the height of mortar that flows into the tube and remains.63 and 0. . the upper part serves as a handle and the lower one is for testing.).) in diameter and 0. Placeability--An article by Angles [16] described a placeability apparatus Copyright by ASTM Int'l (all rights reserved).6 cm (0.) long which contains a graduated scale in centimetres. this reading in centimetres represents the workability of the mix.1 cm (2.) long. Slump reported by different operators on the same batch of concrete may vary by as much as 1. the slump test is not a valid control test for this type of concrete. a falling away or shearing off of a portion of the concrete from the mass. The apparatus is comprised of the following four principal parts. The length of this part is 15. Statistical determinations and equations are reported else where [15]. Studies have been made and reported on 420 concrete batches by five laboratories. Two types of openings are provided in this part: 4 rectangular slots 5. 2) is reported to measure slump directly in 1 min after the tester is inserted in the concrete [15].) in diameter and 2. The most unsatisfactory form of slump is the shear slump.) wide. and its lower part is used to make the test.18 in.) ir. and 22 round openings are distributed uniformly in the lower part. It is impossible to lay down rules on the correct point to measure the slump. The disk also serves to prevent the tester from sinking into the concrete beyond the preselected level. 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. In the upper part of the tube there is also a small pin which is used to support the measuring rod at the beginning of the test. This reading in centimetres is referred to as the K-slump.84 in. The rod is plugged at each end with a plastic cap to prevent concrete or any other material from entering.). An aluminum cap 3 cm (1.25 cm (0.9 and 1. K-Slump Tester--The K-slump tester (see Fig.51 in. 4. 2.36 in. A chrome-plated steel tube with external and internal diameters of 1. 3. thickness which divides the tube into two parts. If this condition exists.8 cm (0. No further reproductions authorized.) long and 0.3 cm (0. that is. A disk floater 6 cm (2.09 in. The first reading is taken after the tester has been in place (the disk resting on the concrete surface) for 60 s.24 cm (0.75 in). The tube is 25 cm (9. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.89 in.3 cm (1/2 in. The K-slump tester is reported to measure an index which is related to workability after the device is removed from the concrete. It may be difficult to consolidate in the forms.) in diamter and 25 cm (9.) long which has a little hole and a screw that can be used to set and adjust the reference zero of the apparatus.5 cm (6.) which includes the solid cone that facilitates inserting the tube into the concrete. the concrete probably lacks the necessary plasticity for the slump test. .smA.= 22S GMS (71111 OZ.7.591 (.O .Jol _ ~ r ~ 28. COLLAR AND P O I N T .~__~ (2.SS( "6 HOLE O(A..59J (2551 m D li! Jill TUBEPATTERN MAT. 18 GAUGE STEEL TOTAL WEIGHT OF PARTS NO 4.o61 THROUGH HOLE FOR 1. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized.5 DIA. 2--2-K slump tester.501 2 -0 " 2 5 COLLAR FLOATER MAT.591 .- I -"" ~z--5 [3351 ~T (. AND SLOT WIDTH 6 . RIVET PROTRUDING 2..) ASSEMBLED PARTIAL AND TESTER SIDE VIEW SECTION NOTE : . .T O T A L WEIGHT 3 8 2 GRAMS. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.A L L DIMENSIONS IN M t L L I M E T R E S .I I2.5.88 TESTS A N D P R O P E R T I E S OF C O N C R E T E 63. --I m . ( 1 3 4 8 4 OUNCES) FIG.IS GAUGE STEEL sO. = O_~_).( .CHROME PLATE TUBE. S m m (255) ~o (. (. (INCHES)..5 INSIDE TUBE (..0 . . t . (50) 15.D.5 GMS ( 6e40Z I FIG. (6. CLEAR ACRYLIC TUBE MAT.D ~ 2 ...(?.O.50. WT : 21.5 OIA.. 19. 11rl AS SUPPLIED WT : I0 BMS (0:55OZ) I MODIFIED WT : 07 GMS { 024 OZ) PLASTIC CAPS 6 .I'D' .5 I. STEEL WT.el} 17. .9 Z (''~' 0 l93 :~..545~ ' t.491 14. (. ~ (. No further reproductions authorized.) ~0~ (.D.D.L 7 TUBE POINT 2 MEASURING ROD MAT.9 1.0.8 GMS. 89 . 20.. (.• 20.50..SMITH ON U N I F O R M I T Y A N D W O R K A B I L I T Y ~16. ALUMINUM b-~-I . ~ IE SO.t oz) 3 SCALE DATUM MAC.. 2--Continued.~. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. DRILL AND TAP FOR NO IO-Z4 UNC 4ram LONG (16) SOCKET SET SCREW -~T-Ii i ~ol . Copyright by ASTM Int'l (all rights reserved).81) 1 z~176 T-= -.D.50.. and location of the vibrator. heavy gage container of suitable size with two vertical channels at the midpoints on the inside of the longer sides 2. on which the test apparatus rests. No further reproductions authorized. made of round horizontal bars with openings between them of a size appropriate to the maximum size of aggregate in the mix under test 3. The author also suggests that internal vibration could be used by fixing diameter. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. are bleeding. is switched on. and bulk density. amplitude. for example 25 kg (55 lb) of concrete into Compartment B with a standardized scoop. A screen. 3--Remolding apparatus. The equipment is comprised of three units: 1. The shutter is removed and the vibrating table. . Remolding Test--The remolding test apparatus (see Fig. according to Angles. The test is performed by placing a known weight." The FIG. The time required for the concrete to pass through the screen and attain the same level in both compartments is measured with a stop watch.90 TESTS AND PROPERTIES OF CONCRETE that would simulate the operation of placing concrete under typical conditions. Placeability is the time expressed in seconds required from turning on the switch to leveling of the sample along the full length of the box. segregation. 3) was developed by Powers [12] to measure "the relative effort required to change a mass of concrete from one definite shape to another by means of jigging. A rectangular. Copyright by ASTM Int'l (all rights reserved). frequency. secured by removable clamps. Other data and observations that could be obtained. A plate to act temporarily as a shutter during the placing of the concrete in Compartment B of the container. and it is claimed that tests can be performed faster and precision is greater than with the slump test. The depth of concrete must be at least 20. The remolding test and slump test were used by Cordon [17] in an extensive series of tests on air-entrained concrete. required to mold the concrete to a cylindrical form. The apparatus weighs 13.).6 kg (30 lb) and consists of a 15. The number of 0. One disadvantage of this test is that it requires a large sample of concrete. 4) [18] was developed principally as a convenient method of measuring and controlling consistency in the field. It is filled with concrete. and the minimum distance from the center of the ball to the nearest edge of the concrete is 22.). Ball Penetration Test--The Kelly ball test (see Fig. When percent sand was reduced as the air content was increased and slump was constant at 10. avoiding excess working.2 cm (4 in. It might be concluded that the remolding test is more sensitive to changes in air content than the slump test. is a measure of the workability of the concrete. This method has not found widespread use and no ASTM standard has been written about it.3 cm (8 in. and slump and percent sand were maintained constant.9 cm (9 in.). the remolding effort was also constant at approximately 42 jigs.) diameter ball and stem which can slide through the center of a stirrup.2-cm (6-in. and the plate is placed on top of the concrete.6-cm (l/4-in.SMITH ON UNIFORMITY AND WORKABILITY 91 equipment consists of a metal cylinder mounted inside a larger cylinder and a suspended plate which fits inside the smaller cylinder. A slump cone is placed inside the smaller cylinder so that the bottom rests on the base. 4--Ball penetration apparatus.) drops. as measured by the remolding test. He found that workability. the legs of which rest on the concrete to be tested. the slump cone is removed. No further reproductions authorized. The flow table on which the apparatus is mounted is then operated. The surface of the concrete is struck off level. Copyright by ASTM Int'l (all rights reserved). . FIG. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The ball test can be performed on concrete in the forms. was increased when air content was increased. the container is fastened to the drop table.32 with a standard deviation of 0. The ball penetration test was compared with the slump test by Howard and Leavitt [19]. The Thaulow concrete tester (see Fig.) four times for each revolution. and the number of revolutions of the crank handle necessary to bring the concrete to the 5-1itre mark is a measure of the consistency. If the concrete is very dry. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ACI has prepared a Recommended Practice for Selecting Proportions for I FIG. equipped with a slump cone.). The ball penetration averaged 1. The ratio of slump to the penetration of the ball is between 1. released.394 in. The cone is removed. and the ball penetration only required 10 s when used on paving concrete. Copyright by ASTM Int'l (all rights reserved). and the depth of penetration read immediately on the stem to the nearest 0. They concluded that the slump test required approximately 10 min.92 TESTS AND PROPERTIES OF CONCRETE The ball is lowered gradually onto the surface of the concrete. and further compacted by 15 drops of the table.5 with a standard deviation of 0. The slump cone is fastened.. and lifted off. . filled with concrete in the usual manner. Twenty tests were made using each method. The handle is allowed to fall freely from the vertical position alternately on each side of the container until the concrete is remolded and the entire periphery is at the 5-1itre mark. and fitted with a stainless steel handle. The method has been adopted as the ASTM Test for Ball Penetration in Fresh Portland Cement Concrete (C 360).45 and the slump average 2. No further reproductions authorized.T h a u l o w c o n c r e t e tester.81. and a drop table actuated by a crank which drops the table through 1 cm (0. The slump cone is fastened in the container. The number of blows required is an indication of the workability. 5 . 5) [20] consists of a 10-1itre container with a gradation mark at 5 litres. filled in the usual manner.5 and 2 and is fairly constant for a given mix but varies according to the mix.6 cm (l/4-in. and 10 to 52 s may be required for concrete with less than 0-cm (0-in.6 to 10.).2 cm (3 to 4 in. . a sheet metal pan. Concrete with a slump of 2. Differences in consistency of very dry mixes cannot be measured with the slump cone.4-cm (6 by 12-in.1 FIG. This method is very suitable for very dry concrete.2 cm (3 to 4 in. and concrete with a slump of 7.).6 to 10.1 cm (1 to 2 in.) requires less than 7 drops. For example.Vebe apparatus. Compacting Factor--The compacting factor test (see Fig. Vebe Apparatus--The Vebe consistometer (see Fig. but the Thaulow equipment is considered to have merit for this application. 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. free-moving rod which serves as a reference end point.). 7) has been developed in Great Britain [11]. The ratio of the weight of concrete in the cylinder mold to the weight of concrete I' /-1 '.1 cm (2 in. and the vibrating table is set in motion. The door at the bottom of the hopper is opened.) requires 14 to 28 drops. The door of the second hopper is opened.) cylinder.) slump. 6) [21] consists of a vibrating table. and the concrete is allowed to fall into the cylinder which is struck off and weighed. and removed. slump cone. The concrete has a slump less than 0 cm (0 in. 6-. 0 to 3 s is required for concrete with a slump of 7. The cone is placed in the pan. and plastic plate attached to a graduated. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The apparatus consists of two conical hoppers fitted with strong doors at their base and a 15. No further reproductions authorized. The plastic disk is brought into position on top of the concrete.SMITH ON UNIFORMITY AND WORKABILITY 93 No-Slump Concrete (ACI 211). filled with concrete. and the concrete drops by gravity into the somewhat smaller hopper below. The top hopper is filled with the concrete to be tested and struck off without compacting it.5 to 5.2 by 30. but the variation is too vigorous for concrete with a slump greater than about 5. 94 TESTS AND PROPERTIES OF CONCRETE FIG. then the lid and the ball are placed in position with the ball resting on the surface of the concrete. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Wigmore Consistometer--The Wigmore consistometer (see Fig. 7--Compacting factor apparatus. The sensitivity of this test is considered good for medium consistency concrete.75 corresponds to a slump to 0 to 2. A 5. but less than some other tests for very dry concrete.1-cm (2-in.2-cm (3 to 4-in. An average compacting factor of 0. The apparatus is placed on the table and the concrete is compacted by turning Copyright by ASTM Int'l (all rights reserved). The container is filled with concrete which is compacted on the table by 8 drops. and 0.) diameter ball which is fastened to a sliding stem is mounted in the lid of the container. . No further reproductions authorized.) slump.5 cm (0 to 1 in. from the same batch fully compacted in the mold is the compacting factor.90 is approximately 7.6 to 10. This apparatus consists of a galvanized container and handoperated compaction table. 8) is described by Orchard [22].). The container is again filled with concrete and leveled off. The number of drops-required may vary from 20 for very wet concrete 15. The U.6 cm (%2 in. water. Grouts must be very fluid to penetrate small cavities. finely divided filler. 8 . Flow Cone--Contraction joints in dams.Wigmore consistometer. voids in preplaced aggregate. The slump test and other described methods of measuring concrete consistency are unsuitable. It is claimed that the Wigmore consistometer is an improvement over the slump test because work is actually done on the concrete in a way which resembles field conditions. Grouts consist of cement and water or combinations of sand.S.2-cm (6-in.) four times per revolution of the cam and the number of drops required to lower the ball and stem 19. and admixtures. Variations in results may be expected if the ball comes in contact with large aggregate.SMITH ON UNIFORMITY AND WORKABILITY 95 T FIG. Corps of Engineers has prepared a standard test procedure for measuring the flow of grout mixtures of means of the flow cone (Method of Test for Flow of Grout Mixtures (CRD-C79-58)) (see Fig. .) slump to 200 to very stiff concrete. and openings around post-tensioned cables may be filled with grout pumped under pressure. cavities behind tunnel linings. 9). cleavage planes in rock fbundations. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized.) into the concrete is considered a measure of the consistence of the concrete. the handle attached to the cam at the rate of about 1 rps.7 cm (73/4 in.. The table drops 0. cement. This method Copyright by ASTM Int'l (all rights reserved). It consists of a brass tube. the tube is filled to a prescribed level with grout. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The immersion body has protuding cams on the sides so that grout can pass between them when the immersion body is placed in the tube containing the grout. The angle of twist or consistency factor is read by an index pointer attached to a cross strut. The immersion body is then placed in the tube and released.) long and 6. The flow cone is mounted firmly with the top surface level. When comparing grouts. 9 . the speed of mixing and the mixing time have an influence on efflux time and should be maintained constant. Otto Graf Viscosimeter--The Otto G r a f viscosimeter (see Fig. The sample of grout is placed in a metal pan mounted on a platform that can be rotated at a constant speed of 60 rpm. Suspended from a music wire is a 7. In practice. The number of seconds reCopyright by ASTM Int'l (all rights reserved). No further reproductions authorized. Grout Consistency Meter--A meter for measuring consistency of grout has been developed at the University of California and is described elsewhere [23]. .) inside diameter mounted on a base in an upright position.3-kg (16-1b) paddle assembly to which a torque is applied as the sample of grout is rotated. The grout consistency meter (see Fig. and 1725 ml of mixed grout poured into the cone.2 c m (27/16 in.2 cm (113/32 in. and an immersion body weighing 5 kg (11.96 TESTS AND PROPERTIES OF CONCRETE FIG. The finger is removed. 10) is essentially a torque meter.2 c m (351/2 in.) long. and the number of seconds until the first break in the continuous flow of grout is the efflux time. outlines the procedure to be used in the laboratory and in the field for determining the consistency of grout mixtures by measuring the time of efflux of a specified volume of grout from a standardized flow cone or funnel. 11) has been used in Europe to measure fluidity of grouts. approximately 90. the discharge tube is closed by placing the finger over the end.1 lb) that is 28.F l o w cone.. lO--Grout consistency meter. The ratio of viscosimeter reading to flow cone reading was approximately 1:5. No further reproductions authorized. The tests indicate that the flow cone provided the same information as the viscosimeter and was as effective for control purposes.SMITH ON UNIFORMITY AND WORKABILITY t 97 1"3 ~7 r--" I I i S FIG. . control. This equipment was specified as a control measure for grouting operations on a post-tensioned bridge. Tests were made immediately after mixing and again 30 min after mixing. Consistency was also measured with the flow cone. New products are being developed in all phases of industry at a rapid rate. Conclusions Concrete knowledge and technology have increased during the years. delivery. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and improvements in concrete production. and placing techniques must also be developed. more widespread use of available knowlCopyright by ASTM Int'l (all rights reserved). but additional knowledge will be required if concrete is to maintain the position it has established as the universal building material. quired for the body to assume its final position is a measure of the fluidity of the grout. At the same time. 2-cm (3 to 4-in. New methods of mixing.) slump concrete is placed today. consolidating.) slump concrete in walls. edge for controlling uniformity. and workability will improve the competitive position of concrete.6 to 10.1-cm (0 to 2-in. as readily as 7. placing. 11--Otto Graf viscosimeter. The slump test and other tests Copyright by ASTM Int'l (all rights reserved).98 TESTS AND PROPERTIES OF CONCRETE FIG. The slump test is an old friend and has served its purpose well. floors. We do not like to see old friends pass away. No further reproductions authorized. quality. . Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and so on. New tests and methods for quality control and measurement of workability must be developed concurrently with methods of mixing and placing concrete. but change is inevitable. and finishing concrete may permit the use of much less water and improve concrete quality. Eventually it may be possible to place and consolidate 0 to 5. When used with 7.) aggregate. In this paper the author suggests the following summary of proposed terminology as an effort toward standardization. Polatty [25] reported that such a device. concretes that can be shown to be dissimilar. as identical. 22 Dam. I. where sand bins were filled 17 to 20 times each day with sand of widely varying moisture content. The equipment was used at Allatoona Dam with mixes containing 15. Two-Point Workability Test Tattersall [26] discusses the principles of measurement of the workability of fresh concrete and a proposed simple two-point test. called the "plastograph. Compactability 3. The slump test and other tests used to indicate consistency can be made only after the concrete is discharged. Workability 1. In this paper the author points up that an understanding of workability of fresh concrete is important: (a) to make possible the design of mixes for particular purposes. Qualitative A. More general use of devices of this type will improve quality control of concrete throughout the industry. Each of the test methods is capable of classifying. . and (c) to contribute to the efficient use of manufacturing processes such as vibration. (b) to provide a method of control in the manufacture of the mix. Meters have been developed to measure moisture content of sand and coarse aggregate in the bins at concrete plants and promote better control of mixing water." gave a better indication of workability than the slump test and indicated a moisture change in time to make a correction in the same batch.6 or 3.) maximum aggregate and three bags of cement per cubic metre. pumping extrusion. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Van Alstine [24] attributed the uniformity obtained at Denver Reservoir No. and corrections can be applied only to subsequent batches. to the use of an electrical resistance moisture meter. the equipment was less efficient. No further reproductions authorized. there is no test that is fully satisfactory and the property of workability cannot even be defined except in the most general terms. and the like.SMITH ON UNIFORMITY AND WORKABILITY 99 used to measure uniformity may be replaced by more efficient test methods in the future. Flowability 2.2-cm (6-in.8-cm (3 or llA-in. Tattersal contends that in spite of all the efforts (papers that have been written and the many proposed tests) over the past 30 years. Methods of measuring consistency of concrete while it is being mixed in the mixer drum should be developed so that corrections can be made immediately. Stability Copyright by ASTM Int'l (all rights reserved). 100 TESTS AND PROPERTIES OF CONCRETE 4. Values for yield value and plastic viscosity are obtained by plotting (P--PE)/w against w.9-1itre (20-qt. P is power under load. The balance of this paper [26] discusses test procedures. and PE is power when the bowl is empty. Yield Value C. where w is speed. Slump B. Tattersall states that such a procedure is valid only for a simple Newtonian liquid whose flow properties are completely defined by the constant ratio of stress to shear rate. and further modifications to allow application of vibration. and that ordinary observation shows that fresh concrete is not a Newtonian liquid and it consequently follows that any test based explicitly or implicitly on the assumption that it is. The development of improved testing procedures for freshly mixed concrete is still a requirement of the concrete industry. The author states there is evidence to indicate that in practice it may be sufficient to treat the material as conforming with the Bingham model and that it approximately obeys the following relationship: the stress at a rate of shear--the yield value is equal to the product of the plastic viscosity and the rate of shear. Compacting Factor C. Extrudability II. No further reproductions authorized. and the two-point test. Finishability 5. and conclusions. The two-point test appears to yield more information concerning the performance of a concrete mixture than any of the present test procedures being used to determine workability. Copyright by ASTM Int'l (all rights reserved). compacting factor. The rapid analysis method of determining water and cement contents of freshly mixed concrete appears to have good potential for determining and consequently controlling concrete uniformity. will be inadequate. The test procedure constitutes the measurement of power required at three separate speeds to operate a 18. Vebe time. . results. Pumpability 6. then repeat the power measurement at all 3 speeds when the bowl contains 21 kg (46.28] further explains the rationale of a two-point workability test and the relationships between slump.) food mixer when empty. V-B Time III. Mobility The objection to the several workability tests are that they were almost without exception single-point tests. The yield value and plastic viscosity are constants. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Tattersall [27. Quantitative Fundamental A. Quantitative Empirical A. and it follows that measurements at two shear rates are required to determine them. whereby only one measurement was made at one specific rate of shear or set of shearing conditions.5 lb) of concrete. Viscosity B. R. "Field Testing of Concrete. London. and Wilson. [16] Angles. [27] Tattersall. American Concrete Institute. Journal. May." Report No. Bureau of Reclamation. W. T. W. "Principles of Measurement of the Workability of Fresh Concrete and a Proposed Simple Two-Point Test.. D. S. W.. and Neelands. p. Army Construction Engineering Research Laboratory. Wiley New York. No.. 1976. "A Method of Determining the Constituents of Fresh Concrete. Vol. pp. L.. "Effect of Time of Haul on Strength and Consistency of Ready-Mixed Concrete. L. 1931. [24] Van Alstine." Journal. R. Copyright by ASTM Int'l (all rights reserved). 1959. E. Jansen. R. Sept... American Society for Testing and Materials. Part II. 1952. July. pp. [15] Nasser. "The Grading of Aggregate and Workability of Concrete. "Tests of Concrete Conveyed From a Central Mixing Plant. 1932. No. 1974. 5th ed. Report No. American Concrete Institute. 405-417. I. Sandor.. [8] "Proposed Tentative Method of Test for Cement Content of Freshly Mixed Concrete. "Kelly Ball versus Slump Cone. E. G. Vol.SMITH ON UNIFORMITY AND WORKABILITY 101 References [1] AC1 Committee 311. Proceedings. 129-136." Proceedings. 96. 1946.. U..." Journal. Rilem Seminar Proceedings. July 1962. Proceedings. 1962." Journal. Bureau of Reclamation. Vol. W. Vol. Vol. 1963." Fresh Concrete." Road Research Technical Paper No. p. A. Collins. 1955." Journal. U. W. D. C. Proceedings. [3] Slater. [19] Howard. 48. "Restoration of Barker Dam. 1947. [25] Polatty. ACI Manual of Concrete Inspection. Joint Research Group on Vibration of Concrete. and Leavitt. [11] Glanville. F. [12] Powers.. [5] Cook.. G. American Concrete Institute. CA-DOT-TL-5149-1-76-65." Magazine of Concrete Research. [21] Bahrner. 1977. April 1948. [20] Thaulow. Vol. "Entrained Air--A Factor in the Design of Concrete Mixes. [26] Tattersall. M.. 881. "Water Control by Use of a Moisture Meter. Vol. 84. [4] Hollister. Dec. American Concrete Institute. 1961. U. Gaynor. H. Polivka. 5. D. 1952. American Society for Testing and Materials. American Concrete Institute. 61. and Milos. American Concrete Institute. G. W.. Sept. 25. "Tests of Concrete From a Transit Mixer. H." Magazine of Concrete Research. pp. [23] Davis.. and Mathews. 1976. A. Concrete Technology. 1976. 419 [13] Concrete Manual. Proceedings. "Report on Consistency Tests on Concrete Made by Means of the Vebe Consistometer. [2] Dunagan. Oct. Stationary Office." Journal. p. J." Journal. Vol. 44. W. Proceedings. . Nov. 1952. S. 341-347. 26. 42. March 1940. R. London. Vol. 28.. [22] Orchard. "Relations Between the Change of Water Content and the Consistence of Fresh Concrete. 28. S." Journal. D. "Ball Test for Field Control of Concrete Consistency.. 7th ed. 28.. A.. American Society for Testing and Materials. "Testing Uniformity of Large Batches of Concrete. [14] Popovics. B." Journal. "New Type of Consistency Meter Tested at Allatoona Dam. pp." Proceedings.. G.. 39." Horak Cementforening. 51. 1952. Vol. C. 31. J. G. No. [10] CERL Technical Report M-212. Vol." Proceedings. Proceedings. V.. S. American Concrete Institute. pp. T. 239." Bulletin. 1970. E. Vol. American Concrete Institute. C. Sun Apr 6 21:39:10 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement... "The Rationale of a Two-Point Workability Test. May 1955. 353-354. H. H. Proceedings. M. C. [9] California Department of Transportation." Concrete Manual. 1. "The Relationships Between the British Standard Tests for Workability and the Two-Point Test.. Oct. [7] Bloem.. "Studies of Workability of Concrete. 2. 7th ed. John. [6] "Variability of Constituents in Concrete (A Test of Mixer Performance). Oslo. 413-428. Sven. 48. R. D. No further reproductions authorized. M.. 1949. Vol. American Concrete Institute. American Concrete Institute. K. [17] Cordon. [28] Tattersall. C." Magazine of Concrete Research. [18] Kelly. Sept. 1. Svenska Cemenfforeningen. Concrete. Vol. 1973. American Concrete Institute." Journal. American Concrete Institute. 1930. Feb. (Test 26). 1973. and finishing the specimens of any kind for either field or laboratory-mixed concrete. the word "making" means paying attention to all the details of mixing the concrete (in the case of laboratory-mixed concrete). "Curing" pertains to temperature. Vol. These are reference procedures and other ASTM standards refer to C 31 and C 192 either for a portion or all of the procedures for making and curing the required specimens.STP169B-EB/Dec. Sacramento. ASTM Making and Curing Concrete Test Specimens in the Laboratory (C 192) provides detailed procedures for making and curing concrete specimens in the laboratory. No. 95822. 102 Copyright by ASTM Int'l (all rights reserved). ASTM Making and Curing Concrete Test Specimens in the Field (C 31) provides detailed procedures for making and curing concrete specimens in the field. Sun Apr 6 21:39:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant Agreement. which are the factors of the curing process of concrete governing the rate of strength gain and many other properties of concrete for which tests are made. 629. In this discussion. Other test procedures may supply additional details or make exceptions to ASTM Methods C 31 and C 192 to accommodate them to the specific specimens or tests to be made. consolidation. It is most important that the tests and specimens be made by trained personnel and that the details of the various methods be followed precisely. No further reproductions authorized.astm. F. specimen molds. Materials Research and Standards. 1963. moisture. 1978 R . The significant differences resulting from having strength tests made by trained and untrained personnel (contractor's personnel in this case) has been pointed up by Wagner.2 Wagner's study showed that strength tests of the same concrete made by trained 1Consulting concrete engineer. A d a m s ~ Chapter 8--Making and Curing Concrete Specimens Introduction This chapter covers in general the importance of properly making and curing concrete specimens. 2Wagner. Only in this way can meaningful and reproducible test results which are not open to question be obtained. By far the number of specimens are made for strength tests. 8. Aug. p. placing. Copyright9 1978 tobyLicense ASTM lntcrnational www. However. K.. specimens are made for many other purposes. that is. 3. and time. on construction jobs. W.org . Calif. Also supervisors should periodically review the work of those making the tests to determine whether it is being done satisfactorily. One or both of these options for curing must be selected. particularly if litigation results. ASTM Method 31 provides strength specimens for determining: (a) the adequacy of designated mix proportions for producing the required job strength. Also.ADAMS ON MAKING AND CURING CONCRETE SPECIMENS 103 personnel were higher and more uniform than those made by untrained personnel. When job strength tests fail to meet specification requirements and the rejection of concrete is considered. (b) evaluation of different mixtures or materials. and (d) the attainment of sufficient strength of the concrete in the structure so that forms or shoring may be removed or the structure may be put in service. (c) quality control purposes.7~ (73. Deviations are noted so that a defense is available in case of controversy. Copyright by ASTM Int'l (all rights reserved). particularly if it can be shown that the person making the test had not complied with the test procedures. . ASTM Method C 192 provides detailed procedures for mixing concrete and making specimens for a wide variety of purposes such as: (a) job trial mixtures. they should be supplied with the required tools and equipment. No further reproductions authorized. or (c) providing specimens for a variety of research purposes. This method provides for two curing procedures: (a) job curing where the specimens are stored at the job under temperature and moisture conditions as near like those of the structure as possible or (b) standard conditions where the specimens are taken to the laboratory and moist cured at 21 + 1. (b) the basis for acceptance of job concrete. depending upon the purpose for making the tests. Sun Apr 6 21:39:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Likewise. The competency of the testing and personnel becomes the subject of controversy. Personnel should periodically review the test procedures in order to refresh their memory of the details. and a conscientious effort must be made to achieve this condition when the curing option has been selected. Engineers and technicians responsible for supervising and making these tests must be thoroughly familiar with the test procedures and should be trained in making the tests strictly in accordance with the detailed procedures. the importance of storing cylinders to be job cured so they will be as near like the structure with respect to temperature and moisture conditions must be appreciated. Two recent additions to ASTM standards should be mentioned and discussed briefly.4 + 3~ after the first day in the field. the tests are almost always questioned. Training has been provided to job personnel not responsible for making tests so that they can observe the tests to determine whether proper procedures are being followed. The importance of making the proper choice between field and standard curing can be appreciated when the considerable strength differences which result from curing cylinders under standard conditions or on the job when the ambient temperature is near freezing are recognized. B. V. No further reproductions authorized. not in columns or walls. However. American Concrete Institute. . These are more commonly referred to as cast on place pushout cylinders (CIPPOC).. It is much easier to correct conditions causing low strength concrete when this is known at an early age. 1963. 1969. (C 873) provides for making and testing concrete cylinders which are molded in place in the concrete member in special plastic molds which can be easily removed when the desired age for strength tests is reached. 3Malhotra. American Societyfor Testing and Materials. and Chojnacki. 68. Vol. All three procedures utilize curing at elevated temperatures. The value of having meaningful strength results at one or two days is obvious.. Proceedings. 4Malhoti:a. V. provided correlation of the two procedures have been made using the same materials and mixtures. M. These strength results are not the same as 28-day strength results. Vol. p. M. Vol. and Berwanger. 3-5 Therefore these accelerated tests can be reliably used to judge the quality of the concrete or to predict the 28-day strength. Sun Apr 6 21:39:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. p. SSmith. C. 1079. 894. These cylinders are surrounded by the concrete in the structure until they are removed for testing and are subjected to nearly the same temperature and moisture environment as the structural member. G. they do produce results which are reproducible and correlate well with the 28-day strength. 963. Copyright by ASTM Int'l (all rights reserved). N. P. Accelerated Curing. ASTM Method of Making. Such specimens are more readily used in slab placements. and Testing of Concrete Compression Test Specimens (C 684) provides for accelerated curing of strength specimens by three different procedures so that strength test results are obtained at either one or two days age. Proceedings. Proceedings.104 TESTS AND PROPERTIES OF CONCRETE ASTM Method of Test for Compressive Strength of Concrete Cylinders Cast in Place in Cylindrical Molds. 1971. p. and Zoldners.. 66. 63. American Concrete Institute. B.Master Builders. TechnicalDevelopment. Copyright9 1978tobyLicense ASTM International www. Ohio 44118.respectively. Many criteria for defining setting time of concrete had been suggested.3] consisted of measuring the change in electrical resistance of concrete mixtures with time. He concluded that one or more points between these two extremes represent the setting time of concrete and. summarized the problems involved and the progress made. Originallywritten for STP 169A by T. M. H. impairment of bond of freshly placed concrete to concrete in place. and early strength gain. ability to strip forms. Electrical Measurements The electrical measurement method [2. Cleveland. including loss of workability before placing.org . and their merits were discussed as summarized below. Engineering.STP169B-EB/Dec. For a cont Director. like the setting time of cement. Subsequent investigations of the rate of hardening of concrete have tended to substantiate these conclusions. 2The italic numbers in brackets refer to the list of references appended to this paper. No further reproductions authorized. He pointed out that the setting time of cement does not adequately define the setting time of concrete and warned that very misleading conclusions may result from assuming such to be the case. 1978 J. Copyright by ASTM Int'l (all rights reserved). and director. and conversely. as long as concrete maintains any significant degree of workability. stating that as soon as concrete has any appreciable strength it has certainly set. in developing methods for measuring the setting time of concrete. will necessarily have to be defined by a particular test method and apparatus. Methods of Test The various methods of test for determining the setting time of concrete which had been proposed or investigated prior to 1955 were described by Scripture. Peppler ~ Chapter 9--Setting Time Introduction Scripture's paper on Setting Time [1] 2 published in 1955. as of that time.astm. Sun Apr 6 21:39:18 EDT 2014 105 Downloaded/printed by Universidade do Gois pursuant Agreement. it is not set. Scripture was of the opinion that none of these criteria represents the setting time of concrete. Sprouse and R. Kelly. time of finishing for floors. A similar concrete mixture containing calcium chloride. Bleeding Characteristics This method had been suggested but no data were available on its application to the determination of setting times. penetration rods. in general. the electrical resistance was found to increase fairly steadily until it reached a point at which the curve leveled off. modified Gillmore and Vicat needles. Penetration tests. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It was considered questionable whether this method measures the setting time of concrete for those interested in anything except floor finishing. though somewhat subject to personal factors.106 TESTS AND PROPERTIES OF CONCRETE crete mixture without any additive. No further reproductions authorized. Consistency Measurements Apparatus suggested for use in relating change in consistencywith setting time were the Vebe apparatus. had an almost constant and very low electrical resistance throughout the period of test. were considered to be unsatisfactory because of interference of large pieces of aggregate. and the Kelly ball. but doubt was expressed that the results really represented the time of setting of concrete as a whole in view of the discrepancy between the setting times of neat cement and mortar pats. gave more reproducible results than those obtained on neat cement paste. based on measurement of wave velocity. however. . was considered to have application as a research tool but was cited as being too high in cost and requiring too delicate a technique for consideration as a standard test method. Troweling Method A method based on determining the point at which it is just possible to finish the surface of the concrete by steel troweling was described as giving reasonably reproducible results. Because of a wide variation Copyright by ASTM Int'l (all rights reserved).a metal tube were considered sufficiently promising to merit further investigation. it appeared that such a test method would be very limited in its application and would be of little use where it is desired to show the effects of chemical admixtures on the setting time of concrete. Velocity and Frequency Measurements The soniscope method [4]. 8 sieve. Results obtained using conventional sonic apparatus to measure fundamental frequencies and employing a mix confined in . if applied to mortar sieved through a No. The penetration methods. Therefore. Changes in Volume Determination of the setting time of concrete from measurement of changes in volume of the setting concrete in a dilatometer was considered to be open to the same objections as those stated in connection with heat of hydration determinations. of course. Strength Determinations One method based on strength determinations consisted of casting specimens in flexible containers and determining deflection. the proposed method was not considered promising. be applicable only to air-entrained concrete. since setting time of concrete means something different to each individual. Scripture tentatively concluded that probably more than one definition of setting time would be needed. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. since a fairly sharp break in the curve appeared to occur at a definite time. Such a method would.SPROUSE AND PEPPLER ON SETTING TIME 107 in bleeding characteristics of different concrete mixtures. Heat of Hydration Though curves obtained by this method showed sharp changes where the setting time of cement would be expected. From limited results obtained by a tension test method it appeared that this method showed some promise. Some work had also been done on both compressive and flexural strength determinations. . Curves in which percentage of air was plotted against time after mixing showed very definite points of inflection when the concrete became sufficiently rigid to resist deformation by the air pressure commonly used in this type of meter. depending on the specific application and that setting time would probably be defined in terms of a maximum Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. its applicability in determining the setting time of concrete was doubted on the basis that the method measures a chemical property of cement and that the shape of the curve could be completely changed by modifying the gypsum content of the cement without actually changing the setting time of the cement or concrete. Deformability Changes The pressure-type air meter had been employed to determine changes in deformability of air-entrained concrete. but sufficient reliable data were not available to demonstrate the suitability of any of these methods for measuring setting time. In conjunction with penetration resistance tests.54 cm (1 in. The first reading was taken with a needle having a 6.108 TESTS AND PROPERTIES OF CONCRETE change in some physical rather than chemical property of the concrete. the container being large enough to permit a minimum of ten undisturbed readings of penetration resistance. The authors stated that these tests were made to provide further information on the early hardening characteristics and to give confidence that the retarded concrete would proceed to develop proper strength. Their work and application of their method by others indicates that correlation can be established between the hardening of concrete and of the mortar sieved from it.2 cm (6 in. a 14 dm 3 (Ih-ft3) container was filled with concrete for observation of its hardening progress and its response to vibration during the period of penetration tests of its mortar. determined by a particular test method. though not equal to those of corresponding concrete. A second concrete cylinder was made for test at 48 h. The authors state. rapid. After the mortar had been vibrated in the container. Therefore." In their test procedure the mortar was sieved from the concrete and placed in a container at least 15. Penetration resistance readings were taken at such intervals as necessary to define the hardening characteristics by means of penetration needles of appropriate end areas.45-cm 2 (1-in. . are of similar character and reliably indicative of what may be expected of the concrete. Tuthill and Cordon [5] developed a method based on the use of Proctor penetration needles to determine the hardening characteristics of concrete mortar sieved from concrete.) deep. the size being dictated by the penetration resistance of the mortar and the maximum capacity of the spring. Penetration Resistance Method Substantial progress has been made in measuring the rate of hardening of concrete subsequent to publication of the 1955 paper on Setting Time.). "Results of tests indicate that this equipment provides an accurate. Tuthill and Cordon defined the vibration limit of concrete as that point Copyright by ASTM Int'l (all rights reserved).6 MPa (4000 psi). it was covered and placed in a room maintained at the desired temperature of test. any definition would necessarily await the establishment of a suitable test method. Bleeding water was poured off before making a penetration test. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 2) bearing area. No further reproductions authorized. and economical method of determining hardening characteristics of concrete mortar which. Smaller needles were used in subsequent readings. In making penetration resistance readings the pressure on the needle was applied steadily and gradually until the needle had penetrated the mortar to a depth of 2. and a concrete test cylinder was made from the same concrete for determination of compressive strength of the concrete when the penetration resistance of its mortar reached 27. and subsequent readings were taken with this needle until penetration resistance reached or approached the maximum capacity of the spring. In scope this specification provides a procedure for determining the time of setting of concrete with a slump greater than zero by testing mortar sieved from the concrete mixture. They indicated that a mortar was considered completely hardened when its penetration resistance reached 27. No further reproductions authorized. since the hardening of concrete is a gradual process. after initial contact of cement and water. subsequently proposed a test method based on the procedure developed by Tuthill and Cordon.6 MPa (4000 psi). after initial contact of cement and water. required for the mortar sieved from the concrete to reach a penetration resistance of 3.6 MPa (4000 psi).5-cm (6 by 12-in. They stated that a running vibrator will not sink of its own weight into concrete that has passed the vibration limit and that. The definitions of times of setting are admittedly arbitrary. at which time the same concrete from which the penetration resistance mortar specimen had been made had developed a compressive strength.14 on Methods of Testing of Setting Time of Concrete. Such agreement. Users of the test method are not in complete agreement that 3.4 MPa (500 psi) is.6 MPa (4000 psi) penetration resistance. it has been demonstrated that the vibration limit will be reached at a resistance of approximately 3. Subcommittee C09. It is apparent that the above definitions of times of setting are based on Tuthill's and Cordon's vibration limit and the penetration resistance at which they considered the mortar to be hardened. is not essential. This specification defines setting times as follows: (a) time of initial setting--the elapsed time.2 by 30. it is a point beyond which a delayed second layer of concrete will not become monolithic with its preceding layer. required for a mortar sieved from the concrete to reach a penetration resistance of 27.) cylinder of approximately 0. These arbitrarily defined points serve as convenient reference points for determining the relative rates of hardening of mortars from different concretes during both the early and later stages of hardening and Copyright by ASTM Int'l (all rights reserved).4 MPa (500 psi) and (b) time of final setting--the elapsed time. in fact. however. The times of setting are determined from rate of hardening curves obtained from a linear pioL of rate of hardening data. ASTM Committee C-9 on Concrete and Concrete Aggregates. Under this method times of initial and final setting of concrete are determined on the basis of a rate of hardening test made by means of penetration resistance needles on mortars sieved from the concrete mixture. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. determined on a 15. . as measured by resistance of the concrete mortar to the penetration test.7 MPa (100 psi). This method has undergone many revisions since it was first adopted and is presently entitled. That is. the vibration limit or that mortar should be considered to be completely hardened at 27.03. with elapsed time as the abscissa and penetration resistance as the ordinate.4 MPa (500 psi).SPROUSE AND PEPPLER ON SETTING TIME 109 during hardening of concrete when it no longer can again be made plastic by revibration. ASTM Test for Time of Setting of Concrete Mixtures by Penetration Resistance (C 403). 7 Q.8 ! Cs A f / C: . . respectively.o 6. 1 . Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. by the lower storage temperature. rather than an average of three or more. = (~ -. Retardation of initial set probably would have been greater if the mortar specimens for low-temperature storage had been at 10~ (50~ at the start of the test.E f f e c t o f low t e m p e r a t u r e on setting time. ~ Copyright by ASTM Int'l (all rights reserved). 1 to 4. however. rl ---1--. that the entire body of data from a rate of hardening test provides much information of value which may not be apparent if only the initial and final setting times are reported. and admixtures upon the time of setting and hardening characteristics of the mortar. n- 13. slump. The concrete mixtures were both batched and mixed at approximately 23~ (73~ and were similar in all respects.5 0 n :E 27. these arbitrarily defined points also make it simpler to specify time of setting requirements. type and brand of cement.0 m 4. Where the test method is being used as a part of performance specifications.110 TESTS AND PROPERTIES OF CONCRETE for determining the effects of variables such as temperature. Typical rate of hardening curves obtained by the penetration method are shown in Figs. It should be kept in mind. h FIG. 23 and 32~ (73 and 90~ Temperature of all of the mixtures after mixing was ap- 34. Changes in the rate of hardening during the hardening period can be of considerable interest and value in scheduling concrete placing and finishing operations.- . Initial and final setting times of the mortar were retarded approximately 4 and 7 h. Figure 2 demonstrates the effects of a retarding admixture at two storage temperatures.F-...V. except that after mixing and sieving to provide mortar for penetration tests. The rate of hardening tests were made in accordance with ASTM Test C 403 except that each curve represents a single rate of hardening test. mortar specimens from the two mixtures were stored at 23 and 13~ (73 and 55~ respectively. Figure 1 demonstrates the effect of a low-storage temperature on rate of hardening of mortars sieved from two concrete mixtures. 1 M P a = 145 psi.- / 0 0 2 4 6 8 I0 12 14 16 Time. namely. additions.9 eQ. cement factor. mixture proportions. 8 .3 2 ) / 1 .6 dr I/ C i~ 20. . and mortar temperatures at 24~ (75~ at the start of test.266 weight percent of cement.. 27.5 | I Y /32oc/ 3 . /l 34.6 9~ Cement A t3.. 3 the rate of hardening of a mortar sieved from a concrete mixture is compared with the rate of hardening of a separately mixed cement:sand mortar. B " E tie" ~ ~ 23 ~ I ] / // /' ~ 3.8 = 6. ~ 2--Effect of temperature and retarder on rate of hardening.e FINAL SET.8 g ~ 6. companion mortar specimens from the two types of mixtures were stored at 23 and 32~ (73 and 90~ respectively.. which was added at the rate of 0..5 A FINAL SET. o ~ 0 z 4 6 8 10 12 t4 le Time. - z 4 e J~k~A_ _SgZ~ f e Time.7 -(/) 13. Copyright by ASTM Int'l (all rights reserved). o---wlthretarder 1o ~z I ~4 ~6 h FIG.5 .. With this particular cement and admixture.SPROUSE AND P E P P L E R ON S E T T I N G TIME 111 proximately 24~ (75~ The concrete mixtures were similar in all respects except that concretes containing the admixture. 3--Rate of hardening of screened versus mixed mortar. .= t //. No further reproductions authorized. the retarding effect of the admixture was greater at the higher storage temperature.. h F I G . After sieving mortar from the concrete mixtures.9 ~.~I 27. Cement of the same brand and o 34.6 ~ u ~ Cement / 20. o 145 psi. 1 MPa : = ( ~ --32)/1. In Fig.8. were reproportioned to maintain a constant cement factor. 1 MPa = 145 psi. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Individual pins were subsequently pulled out of the concrete at increasing time intervals by means of a spring scale and the load at bond failure measured.7 cm (5 in. Tests on the two mortars were conducted simultaneously.w f~ Q n. Rate of hardening curves were obtained by plotting bond stress against time on a linear scale. 1 k g / m a = 1. Figure 4 illustrates differences in the rate of hardening of concretes made with two different brands of Type I portland cement. Though the concrete made with Cement B had a higher cement factor than that made with Cement A.13.Type C.8 0 .~ 34. 0 tl. Type ! C.7 . The pins were held firmly in a vertical position by a special jig during specimen fabrication.5 m m (3/8 in. ~ 6.) by vibrating the concrete around them in a beam mold immediately after the concrete was mixed.E f f e c t o f b r a n d o f c e m e n t on rate o f hardening.F.e-. . were embedded vertically in concrete to a depth of 12. and ambient temperatures were the same during the mixing and testing period.5 A.= 280 Kg/m a Cement w 20.= 307 Kg/m3 Tests at 23"C i 6 FIN!L SlIT ! 8 10 Time. Bond Pullout Pin M e t h o d In 1957 a paper by Kelly and Byrant [6] was published describing a bond pullout pin method for measuring the rate of hardening of concrete. and sand from the same lot were used in both the concrete and the mortar mixtures. and the method was based on measurement of the rate of development of concrete bond strength. it reached final set approximately 1 h later.5 ~ l 2r.) in diameter. In this test procedure the whole concrete was utilized. The concretes contained sand and coarse aggregates from the same sources.8. i I |Z 14 16 4 . h FIG. respectively.6 U c 0 0 2 i 4 ~_ I !t / i i Cement B.F.9 a 3.. rather than the mortar portion. and the water cement (w/c) ratio and cement:sand ratio were the same for both mixtures." t. No further reproductions authorized. 1 M P a -~ 145 psi. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. = (~ -- . ~ 32)/1. Stainless steel pins. 3 Copyright by ASTM Int'l (all rights reserved). for the separately mixed mortar. 9.686 l b / y d . Initial and final setting times were approximately 1/2 and 1 h greater.112 TESTS AND PROPERTIES OF CONCRETE type. No further reproductions authorized.03. On the basis of the observed relationship between time and the degree of hardening of concrete.) to permit the use of a conventional 15. the rate of hardening specimens were stored for the duration of the tests at the temperatures indicated on the charts. For example. All of the concrete mixtures for which rate of hardening curves are shown were similar in all respects. however.2 cm (6 in. expect for differences in brand of cement used or the addition of a chemical admixture. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. On the other hand. the results can be interpreted without concern as to the possible effects of removal of coarse aggregate or of manipulation and exposure of the sample during the process of sieving the concrete to obtain mortar for the penetration tests. Figure 7 shows the rate of hardening at various storage temperatures of a reference mixture and of a mixture containing a water reducing admixture. The temperature of the mixing room was maintained at approximately 23~ (73~ and all concrete mixtures were at approximately the same temperature upon completion of mixing.) beam mold. A favorable feature of the bond pullout pin test method is the fact that the rate of hardening determinations are made on the whole concrete. modification and refinement of the method are desirable.2 cm (6 in. Instead. They believed. Figure 6 illustrates the differences in rate of hardening that can result from a change in the brand of Type I cement being used in a given concrete mixture. Preliminary studies indicate that higher bond stresses may be reached by reducing pin diameter or reducing depth of embedment or both. a proposed tentative test method was drafted for consideration by ASTM Subcommittee C09. Typical rate of hardening curves obtained by the bond pullout pin method are shown in Figs.03.SPROUSE AND PEPPLER ON SETTING TIME 113 The authors stated that in the hardening process no sharp breaking point occurs which can be interpreted as time of setting.t4 as an alternative method for determining time of setting of concrete.14 in which the test procedure was essentially the same as that described in the above paper. Subsequently. concrete hardens at a gradually increasing rate until it reaches a definitely hard or set condition. 5 to 7. rather than on the mortar sieved therefrom. except that the depth of pin embedment was increased to 15. they were of the opinion that a test method to measure setting time p e r s e is not feasible. The mixtures differed only in that the cement factors of the Copyright by ASTM Int'l (all rights reserved). the relation between the embedded surface area of a pin and combined weight of beam and specimen are such that the maxim u m load is limited unless the specimen is physically restrained from being lifted during the later stages of hardening. that the rate of hardening of concrete under any given set of conditions can be determined and that setting times can be arbitrarily defined on the basis of such rate of hardening determinations. Therefore. Figure 5 illustrates the effect of different storage temperatures on rate of hardening. . This method is under consideration by ASTM Subcommittee C09. Immediately after their fabrication. 6 psi.E f f e c t o f temperature on rate o f hardening. ~ -. No further reproductions authorized.8 1.0 E 5. 1 k g f / m m 2 = 67. Copyright by ASTM Int'l (all rights reserved).Type i / / v" jr 4.8. S . reaching a maximum of about 1. respectively..E f f e c t o f b r a n d o f c e m e n t on rate o f hardening.5 h when tests were discontinued. = (~ -- 6 . The acceleration started at about 10 h and appeared to increase at a uniform rate.4 2 4 6 8 Time.6 132~23"C CementC.114 TESTS AND PROPERTIES OF CONCRETE 7. (~ 10 12 14 16 reference and admixture-containing concretes were 307 and 262 k g / m 3 per yard.~. L. Rates of hardening of the two types of concrete were very similar at 21 and 32~ (70 and 90~ and during the early stages of hardening at 10~ (50~ In the later stages of hardening at this temperature the water-reducing admixture accelerated the hardening rate. .32)/1.6 /4-~ementE / TiDeI Cements Temperature 25~ Z. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ~ 32 )/1..6 psi.h 10 12 14 16 FIG.2 c O*C 2. 1 k g f / m m 2 = 67. c o m 5. = 7.4 0 0 2 4 6 8 Time.h FIG.8.0 E i 4.2 CementC~ CementD Sr~y/ .8 qo o rn 1. = (~ Effect of Variables The results of setting time tests are influenced by several variables. . Setting times of concrete vary with type and brand of cement.E f f e c t o f water reducer on rate o f hardening. However. Type 1 21"C t '/ IO*C . 1 and 5. h FIG. set-retarding admixtures. 7 . additions and admixtures all influence setting time to some degree.32)/1.SPROUSE AND PEPPLER ON SETTING TIME 7. 1 0 ] . Tuthill et al [7] concluded that the time to the vibration limit and the time rate of setting may be influenced more by the brand and possibly the type of cement than by differences in the variety of water-reducing retarders investigated. differences in setting times resulting from a change in brand of Type I cement can be as great as those resulting from a substantial variation in ambient temperature. the effect varies with the nature of the cement and the admixture.4 J # ~ 0 0 2 ~ 4 I 6 8 O---NO ADMIXTURE O'--W1THIADMIXTUREI 10 12 14 16 Time. slump and.2 I Cement F. In regard to admixtures. cement factor. Vollick [8]. 1 k g f / m m 2 = 6 Z 6 psi. Variations in temperature have appreciable effects on setting times as illustrated in Figs. the retardation usually increasing with delay in introduction of the admixture [ 9 . His work indicates that Type III and Type II cements accelerate and retard. In general. as compared with Type I cement. of course. setting times are accelerated by an increase in cement factor and retarded by an increase in slump. ' / - ~ tD "o n'l I 115 / 1. Copyright by ASTM Int'l (all rights reserved).0 ~ NE 32"C ~ iv' I // 4. In general. As shown in Figs. ~ -. illustrates substantial differences in times of setting of concretes that are similar in all respects except for type of cement. in Fig. the change in setting time per degree change in temperature increases with decreasing temperature. recent studies have indicated that time of addition of set-retarding admixtures may have an effect on time of setting of the concrete. No further reproductions authorized. Mixture proportions. respectively. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.8. 4 and 6.. 7 of his paper on water-reducing. the range of results obtained 3These numbers represent. However. Figure 8 is a semilogarithmic plot of the penetration data plotted linearly in Fig. data points so plotted generally do not deviate appreciably from a straight line. in 1973. Figure 9 is a semilogarithmie plot of the bond pullout data plotted linearly in Fig. Data from both test methods yield approximately straight lines when the penetration resistance and bond stress are plotted on the logarithmic scale. and unless an adequate number of determinations are made at this stage of hardening the estimation of initial setting time may be inaccurate. Copyright by ASTM Int'l (all rights reserved). 5. respectively. .14 on Setting Time of Concrete is presently considering the desirability of specifying in ASTM Test C 403 that rate of hardening test data be plotted on a semilogarithmic scale. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Some. They also feel that.03. 3 Therefore. No further reproductions authorized. the position of the line is a matter of judgment on the part of the operator. The ASTM Subcommittee C09.1 percent. whereas a linear plot yields a curved line. ASTM Subcommittee C09.116 TESTS AND PROPERTIES OF CONCRETE Reporting Results In a previous publication Polivka and Klein [11] and Loughborough [12] plotted rate of hardening test data on a semilogarithmic scale. the (1S percent) limit as described in ASTM Recommended Practice for Preparing Precision Statements for Test Methods for Construction Materials (C 670). Repeatability The repeatability of rate of hardening determinations made an accordance with ASTM Test C 403 has not been positively established. The single-operator coefficient of variation for time of initial set has been found to be 7. feel that it provides a more meaningful picture of the manner in which the concrete is hardening.03. In well-controlled tests. 1.14 voted to approve a proposed revision to the precision statement of ASTM Test C 403. who prefer the semilogarithmic scale to the linear scale. while with a linear plot a smooth curve can usually be fitted fairly closely to all data points. The following statement is based on data received from five laboratories which had participated in a round-robin test program: 1. it appears that the setting times determined by either method of plotting are essentially the same. maintain that an average straight line can be drawn more accurately than an average curve through the plotted points derived from the required three separate rate of hardening tests. and the value for the range of a set of three values which should be exeeeded not more than 5 percent of the time. From data available. since the data points on a semilogarithmic plot seldom form a perfectly straight line. who prefer the linear plot. They also point out that the slope of the curve obtained by a linear plot is undergoing the most rapid rate of change in the critical area of initial set. Others. demonstrating that the resulting curves are approximately straight lines. No further reproductions authorized.p.9 o - co r r- ro r 11> ~ ~. Penetration Resistance. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.m --t m \ # 0 z o) F m m m -o . Kgf/mm 2 \ . .-Q > z m C O C~ "(3 3O ~1 . MPa r~ \ \ -'t o e: "I :r co Bond Strength. o~ L~ -I =7' co o~ . r~ o o oo (I Copyright by ASTM Int'l (all rights reserved).~ e. 7~ (73 + 3~ A retarding admixture must 4These numbers represent. just prior to mixing. results of two different laboratories on similar materials should not differ by more than 15 percent of their average (see footnote 4). The multilaboratory coefficient of variation for time of initial set. The tolerances were established on the basis that the temperature of each of the ingredients of the concrete mixtures. This specification set tolerance limits for effect on setting time of five types of chemical admixtures as determined by the penetration resistance method. the (1S percent) and (D2S percent) limits as described in ASTM RecommendedPractice C 670. in which case it may be desirable to specify the sizes of the needles to be used over various ranges of penetration resistance.118 TESTS AND PROPERTIES OF CONCRETE on three separate batches by the same operator with the same apparatus. when results are based on the average of three tests. on three different days should not exceed 16 percent of their average (see footnote 3). results of two different laboratories on similar materials should not differ by more than 13 percent of their average (see footnote 4). has been found to be 5. 2. when results are based on the average of three tests. It is anticipated that the repeatability of ASTM Test C 403 will be improved by further refinement of testing procedures as additional experience is gained in use of the method. on three different days should not exceed 23 percent of their average (see footnote 3). Therefore. has been found to be 4. and the temperature at which the time of setting specimens are stored during the test period shall be 23 + 1. 4. the range of results obtained on three separate batches by the same operator with the same apparatus. 3. 4 Therefore. there are indications that penetration resistance values may differ substantially depending upon the size of needle being used.5 percent (see footnote 4). Therefore. Copyright by ASTM Int'l (all rights reserved).2 percent. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . using similar materials. The single-operator coefficient of variation for time of final set has been found to be 4. No further reproductions authorized. using similar materials. For example. respectively. The influence of temperature variation from center to edge of specimen and the effect of boundary restraint also need further elucidation.7 percent (see footnote 3). Application of Setting Time Tests In Acceptance Specifications A suitable method for measuring the rate of hardening and determining the setting time of concrete was essential to the development of ASTM Specification for Chemical Admixtures for Concrete (C 494). The multilaboratory coefficient of variation for time of final set. Precise correlations between time of setting test results and slab finishing operations have not been reported in any published work. private communication. . however. time of setting tests are invaluable in planning concreting operations and determining whether special measures will be required for set control. In Field Concreting Job conditions frequently require a greater degree of and closer control of retardation or acceleration than is required under ASTM Specification C 494. Copyright by ASTM Int'l (all rights reserved). However. the type and dosage of admixture can be tentatively selected. utilizing the concreting materials to be used in the work." In this instance the method was being used in the field on three large highway 5Peter Smith. avoidance of cold joints in mass concrete. The purpose of ASTM Specification C 494 is to provide methods and criteria for evaluating chemical admixtures under highly standardized testing conditions in the laboratory that are not intended to simulate actual job conditions. structural considerations. Ontario Department of Highways. If control is required. The more stringent requirements may result from unusual temperature or exposure conditions at time of concrete placement.. such as slip form construction. Because it is a tentative standard test method and utilizes less cumbersome apparatus. No further reproductions authorized. By prior studies in the laboratory under simulated job conditions.SPROUSE AND PEPPLER ON SETTING TIME 119 reach initial set at least 1 h later but not more than 3 h later than the reference concrete and must reach final set not more than 3 h later than the reference concrete. Sr. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. materials engineer. or special types of concreting operations. the former method has been used more extensively. An accelerating admixture must reach initial set at least 1 h sooner but not more than 3 h sooner than the reference concrete and must reach final set at least 1 h sooner than the reference concrete. Both the penetration resistance method and the bond pullout pin method have been used advantageously in the field. subject to verification and adjustment based on time of setting tests made on the job during actual construction. An admixture that is required neither to accelerate nor retard must reach both initial and final set not more than 1 h sooner or 1 h later than the reference concrete. an engineer for one construction agency s utilizes the latter method stating: "Although the pin pullout apparatus is quite bulky and awkward for general field use. it is advantageous in that the rate of hardening test is made on actual job concrete. It seems reasonable to believe. such as avoiding cracking of the concrete deck when steel bridge girders deflect during placement of the deck. that setting time tests made on slab concrete at the jobsite would provide guidance in scheduling finishing operations. effect of the subgrade. The influence of predictable temperature cycles for various job conditions on the rate of hardening of mass concrete could be estimated from the data thus obtained. It has been noted by one construction engineer (see footnote 5) that concrete in the structure sets up at a slightly faster rate than concrete in beam specimens used for the bond pin pullout test. Determinations of setting times made on small specimens may not be alrectly applicable to the same concrete in a structure. 75. however.120 TESTS AND PROPERTIES OF CONCRETE projects to determine the influence of different retarders on rate of hardening of pavement concrete under field conditions. Wallace and Ore [13] reported that tests performed on samples of concrete at the batch plant do not reflect the influence of the increasing temperature occurring within massive blocks in the dam. Summary The development of test methods for measuring the rate of hardening of concrete. Difference in conditions of exposure between the time of setting specimens and the concrete in a structure can lead to misapplication of time of setting test results. sieved from the mass concrete at a temperature of about 11 ~ (52 ~ were immediately taken into each of three rooms wherein the air temperature was maintained at 10. one should give due consideration to disparities between the mortar or concrete in the test specimens and the concrete in the structure. such as relative surface to volume ratios. and 100~ while rate of hardening tests were performed. exposure to wind and sun. In interpreting results of setting time tests for application to an actual concreting operation. or exchange of heat with the subgrade. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Factors that affect the setting time of concrete can now be evaluated with reasonable accuracy and concreting operations planned or adjusted accordingly. This is particularly true in the case of flat slab work where the time of setting of the slab may be strongly influenced by wind velocity. They conducted tests in which mortar samples for penetration resistance tests. . 24. By means of time of setting tests the need for set-controlling admixtures can be established with certainty and type and dosage can be determined on a quantitative basis. probably due to the differences in the concrete volume and resultant temperature rise. No further reproductions authorized. has been an important contribution to concrete technology. Copyright by ASTM Int'l (all rights reserved). on the basis of which setting times can be defined and determined. and the radiant heat of the sun as pointed out by Schutz [14]. and 38~ (50. 1963. M. Nov. 1166. and Dodson. p. [13] Wallace. L. American Concrete Institute. Vol. American Concrete Institute.SPROUSE AND PEPPLER ON SETTING TIME 121 References [1] Scripture. D. 1960. M. T. p. 199. L. 52. Adams. "Measuring the Rate of Hardening of Concrete by Bond Pullout Pins. [7] Tuthill. Vol. p. [14] Schutz. "Observations in Testing and Use of Water-Reducing Retarders. "Early-Setting Behavior of Concrete--A Brief Discussion.. 1955. p. J." Ontario Hydro Research Quarterly." Journal. Vol. "Effect of Current Frequency on Measurement of Electrical Resistance of Cement Pastes.. J." Journal. Vol." Journal. G. American Concrete Institute. 64. and Heroine. Alexander. Vol. "Use of the Soniscope for Measuring Setting Time of Concrete. 1959. [10] Farkas. E. R. 1960. Proceedings. p. M. p. E. H.. discussion. 816. Vol. 1960. American Society for Testing and Materials. [3] Calleja. and Bryant.. 1951. Part 2. Dec. "Setting Time of Concrete Controlled by the Use of Admixtures. American Society for Testing and Materials." Proceedings. M. Vol. Set-Retarding Agents. 1963. A S T M STP 266. American Society for Testing ~nd Materials. A. 32. Vol.ol. . [8] Vollick. -~2. 1960. 1176. 1187. 51. American Society for Testing and Materials. Journal. 67." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. [5] Tuthill. G. W. C. and Cordon. H.. p. E. 15. "Setting Time. L.. 1964. American Society for Testing ~nd Materials. and Ore. Jan." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. American Society for Testing and Materials.. W. American Society for Testing and Materials. E. Vol. p. T." Effect of Water-Reducing and Set-Retarding Admixture on Properties of Concrete.. Jr. H. A S T M STP 266. A." Effect of Water-Reducing and Set-Retarding ~ldmixtures on Properties of Concrete. 55. 1952.. A S T M STP 266. [9] Bruere.. "New Techniques in the Study of Setting and Hardening of Hydraulic Materials. [2] Calleja. "Effect of Water-Reducing Admixtures and Set-Retarding Admixtu~res on the Properties of Plastic Concrete. B. 53. "Effect of Water-Reducing Admixtures ~nd Set Retarding Admixtures as Influenced by Portland Cement Composition. "Structural and Lean Mass Concrete as Affected by Water-Reducing.. American Concrete Institute. 273. R." Nature. 329. A.. E. [11] Polivka. March 1952. Proceedings.. "Importance of Mixing Sequence When Using Set-Retarding AgQnts with Portland Cements. American Society for Testing and Materials. p. J." Proceedings. 49. V. Proceedings.. A S T M STP 266. 1956. Jr.." Journal. Sun Apr 6 21:39:18 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Significance of Tests and Properties of Coner#te and Concrete Aggregates. [12] Loughborough." Proceedings. No. Proceedings. "Delayed Addition of Set-Retarding Admixtures to Portland Cement Concrete. p.. aS. F. "Properties and Uses of Initially Retarded Concrete. discussion. V. Milos and Klein.. No further reproductions authorized. A S T M STP 169. J. 1955. [4] Whitehurst. 525. Proceedings. 4. Dec. [6] Kelly. American Concrete Institute. 769. Copyright by ASTM Int'l (all rights reserved). l President. together with an appreciation for carefully following details of the procedures. 53210. Sun Apr 6 21:39:19 EDT 2014 122 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. an understanding of the limitations of the various methods. Tests for air content and unit weight are made of fresh concrete to provide a control on these properties in the hardened concrete and also to determine volume of concrete being produced from a given batch and its unit cement content.. an increase in volume of air results in a lower unit weight. For all concrete. 435. unit weight determinations are used to establish the volume of batch produced and to establish actual cement contents. Further. Tests for unit weight are made to control weight p e r s e of both lightweight and high-density concretes. Therefore. Tews Lime and Cement Co. a m i n i m u m of training is required before proficiency in the testing technique is acquired. Copyright9 1978tobyLicense ASTM International www.org . 2See p. Nevertheless. Procedures are outlined in various ASTM standards which are straightforward and well within the capabilities for performance and understanding of the average concrete technician. F. 1978 F. Wis. The interrelation between air content and unit weight should be obvious. The significance of air content and unit weight in hardened concrete is discussed in detail in this publication by Helms. B a r t e l 1 Chapter 10--Air Content and Unit Weight Introduction Tests for air content and unit weight of freshly mixed concrete are made frequently both in the field and in the laboratory. whereas a reduction in air content increases unit weight.STP169B-EB/Dec. 2 Air content most commonly is determined to ensure the presence of small amounts of air prescribed in concrete in order to obtain its beneficial effects on resistance to freezing and thawing and effects of deicing agents applied to concrete for snow and ice removal.astm. testing procedures for these properties are combined in ASTM methods and should be performed in sequence in the field. Milwaukee. Copyright by ASTM Int'l (all rights reserved). is essential to obtaining and interpreting results. using gravimetric. and it is expected that the method most appropriate for the conditions and materials will be used. No further reproductions authorized. Concrete containing aggregate graded up to 50 mm (2 in." From the known volume of the measure and the weight of its contents. (c) relative yield. in which a constant amount of water is added at the mixer. pressure. an error of 0.) may be tested in a 14 dm 3 (0. In the field where. . (b) volume of concrete produced per batch. The strikeoff of the top surface must be done " . and moisture contents of aggregates is essential. the 28 dm 3 (1. an error of 2 percent in the moisture content of sand in an average concrete mix.02 in the specific gravity of the aggregates will result in an error of about one-half Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. average moisture contents of aggregates are assumed and consistency is controlled by varying the amount of water added at the mixer to maintain slump.BARTEL ON AIR CONTENT AND UNIT WEIGHT 123 Test Methods Three tests for air content of fresh concrete. and Air Content (Gravimetric) of Concrete (C 138). in many cases. Larger containers should be used for concrete containing still larger aggregate as specified in ASTM Test C 138. or volumetric methods. or ratio of actual volume produced to the designed volume of the batch.5 ft 3) container.) in size is used. One disadvantage is that an accurate knowledge of batch proportions. Each of the procedures has its advantages and disadvantages. Also. Gravimetric Method In the gravimetric procedure the unit weight of concrete is determined in accordance with ASTM Test for Unit Weight. where aggregate u p to 75 mm (3 in. Yield. The theoretical unit weight is calculated from the weight and bulk specific gravity of each ingredient in the concrete mixture following the calculations outlined in ASTM Test C 138. with a flat cover plate using great care to leave the measure just level full. the unit weight of concrete as determined is compared with the theoretical unit weight of air-free concrete.0 ft 3) measure should be employed. When the gravimetric procedure for determining air content of fresh concrete is used. the weight per cubic metre (foot) of concrete can be computed. specific gravities. The test is made of a sample of concrete in a measure of specified volumetric capacity. The measure is filled in three layers. currently are standards of ASTM. For example. The gravimetric method for determining air content has serious limitations as a field test. In ASTM Test C 138 details of the calculations are outlined to determine: (a) weight per cubic metre (foot). (d) actual cement content as kg/m 3 (lb/yd 3) of concrete. and (e) air content of concrete. the gravimetric method should not be relied upon for accurate results. Tests for unit weight are part of the gravimetric method. and each layer of concrete is consolidated by rodding and tapping the sides of the measure a specified number of times. will result in an error of one percentile in computed air content. . . 006 m 3 (0. Also. be 3The italic numbers in brackets refer to the list of referencesappended to this paper. In the laboratory. Klein and Walker [1] 3 applied Boyle's law. where lightweight aggregates are used. the concrete used in the test need not be discarded. Copyright by ASTM Int'l (all rights reserved). Possible inaccuracies when porous or nonsaturated aggregates are used have been referred to previously. to the determination of air content of fresh concrete. Thus. involving the relationship of pressure and volume of gases. Samples of concrete tested in this apparatus must. reliable results can be obtained for concrete containing normal weight aggregates. in most concrete mixes. The major advantage of the pressure method is that no knowledge of specific gravities. however. however.). whose specific gravity is exceedingly difficult to determine.20 ft 3) for testing concrete containing coarse aggregate particles up to 50 mm (2 in. this aggregate correction factor may be quite large and difficult to determine accurately. The ASTM test requires the measuring bowl to have a capacity of at least 0. or batch quantities of the concrete mixture need be available to determine its air content. Furthermore. where specific gravities and moisture contents are accurately known. the only compressible ingredient is the air entrained or entrapped in the mixture. No further reproductions authorized. moisture contents. it can be used for other tests or in the preparation of specimens. the drop in water level in the neck of the calibrated apparatus indicates the air content of the concrete directly. and a higher than true air content of concrete may thus be indicated. For concrete containing larger aggregate. . In the case of slag vesicular volcanic aggregates or lightweight aggregates. Two types of air meters are described in ASTM Test for Air Content of Freshly Mixed Concrete by the Pressure Method (C 231). The instrument must be calibrated for use at various localities if differences in altitude are considerable. Menzel [2] refined the apparatus and proposed a standard test procedure.).5 mm (11/2 in. A complicating feature of the test is that the pressure may compress air within the interstices of nonsaturated. wet sieving is specified to remove particles larger than 37. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the results vary with changes of barometric pressure. When the proper pressure is applied. as in other procedures. porous aggregates. a predetermined pressure is applied to a column of water above a sample of concrete in a container of known volume. Pressure Method The pressure method for determining air content of fresh concrete is based on the fact that.124 TESTS AND PROPERTIES OF CONCRETE percentile in air content computed under this method. This complication may be compensated for by determining a correction factor for the air within the aggregate as outlined in ASTM Test C 231. In Meter Type A. it is not recommended that the gravimetric procedure be used. of course. and the "Ohio Method" [6] using a hook gage. test larger samples of concrete. the drop in pressure provides a measure of the amount of air within the concrete. such as the rolling method developed by Menzel [2]. For concrete containing larger aggregate. No further reproductions authorized. no knowledge of specific gravities or moisture contents of ingredients need be known. The apparatus has the advantage of not having test results influenced by changes in barometric pressure. In the test. the air content is computed from the unit weight of airfree concrete determined by displacement in the test. The drop in water level from its original mark provides a direct measure of the air content of the concrete. and the unit weight measured prior to removal of the air." air is removed from a known weight of concrete by stirring in water. mixing of water and concrete is repeated until no further drop in water level indicates the removal of all air from the mixture.BARTEL ON AIR CONTENT AND UNIT WEIGHT 125 discarded and cannot be used in specimens or for further testing because of the contact of concrete with water during the test.). however. as with the pressure method. wet sieving is specified to remove particles larger than 25 mm (1 in. In the "Indiana Method. In Meter Type B in ASTM Test C 231 a known volume of air at an established pressure is released to contact concrete in a sealed container. Volumetric M e t h o d Inaccuracies in determining air content of fresh concrete containing porous aggregates by the gravimetric and pressure methods have been described. Other volumetric procedures.) are used. then concrete and water are intermingled and agitated until the air in the concrete is displaced by washing action. The apparatus is sealed. With the apparatus described in ASTM Test for Air Content of Freshly Mixed Concrete by the Volumetric Method (C 173). . The chief disadvantage of the volumetric method is in the physical effort required to agitate water and concrete sufficiently to remove the air. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5 mm (11/2 in. Compressibility of air within the aggregate must be taken into account in test results as it must be with results from the Klein-Walker apparatus. can be used with such materials to obtain accurate measurements of air content. Further. The method requires the use of a container for concrete of not less than 0. With Menzel's volumetric apparatus the quantity of water added to compensate for air removed from a known volume of concrete by mixing with water (on a rolling apparatus) provides a measure of the air content. The volumetric procedure. Miesenhelder [5] reported the disadvantages of the latter method to be the difficulty in mainCopyright by ASTM Int'l (all rights reserved).075 ft 3) when aggregrates up to 37. the hook-gage or "Indiana Method" described by Miesenhelder [5]. water is filled to mark over a sample of concrete in a container of known volume.002 m 3 (0. and volumetric procedures gave comparable results. A device known as the Chace Air Indicator has been used extensively to measure air content of fresh concrete. the appropriate ASTM test method for air content should be used for acceptance or rejection of the concrete. the tube is inverted from horizontal to vertical several times until all mortar has been displaced out of the cup into the alcohol. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. aside from the limitations mentioned above. Its principal use would appear to be as a speedy screening device to indicate when air contents apparently are approaching or do not conform with specification limits. calculations dependent on the volume of mortar in the concrete yield an indicated air content of concrete. the air is washed from the mortar. Additional studies of the air indicator were reported by Grieb [8] and Newlon [9].126 TESTS AND PROPERTIES OF CONCRETE taining the necessary accuracy of scales under field conditions and the possibility of incomplete removal of air because of the physical exertion required in the stirring process. No further reproductions authorized. Significance of Test Results Tests for air content of fresh concrete are most commonly made in the Copyright by ASTM Int'l (all rights reserved). After adjustment of the alcohol level to mark. Results of gravimetric tests agreed with other procedures as long as specific gravities and moisture contents of ingredients were known. pressure method test results were in accord with other data when concrete was made with dense aggregates. . consolidated in the brass cup. and the brass cup inserted into it. and volumetric procedures gave substantially the same air contents as did the other methods as long as all of the air was removed from the sample tested.5 mm (1/2 in. for tests carefully conducted. and struck off to make the cup level full. Comparison of Test Results The existence of three ASTM procedures for determining air content of fresh concrete logically raises the question as to which is most accurate. Tests by Britton [11] using ASTM gravimetric.) in diameter by 12. The drop in level of the alcohol from its original mark is a measure of the air content of the mortar. A sample of mortar is secured from the concrete.) high attached to a rubber stopper. It involves a volumetric procedure utilizing a pocket-sized graduated glass tube into which is fitted a brass cup 25 mm (1 in. In the ASTM Symposium on Measurement of" Entrained Air in Concrete [10] the results presented by the various authors are in substantial agreement. Many studies have been made on this subject. pressure. When this is indicated. Tests reported by Willetts and Kennedy [7] under laboratory conditions showed the Chace Indicator to be accurate within plus or minus 0. In the course of this intermingling of mortar and alcohol. The graduated glass tube is filled with isopropyl alcohol.6 percentile two thirds of the time for air-entrained concrete. 5 mm (11A in. Wuerpel [16] has pointed out that the optimum air content for the mortar phase of concrete Copyright by ASTM Int'l (all rights reserved). the problem in the case of air-entrained concrete is to control the air content to ensure the beneficial effects without unduly reducing its strength. In mass concrete. but they would be too high for the concrete as a whole. each percentile of entrained air reduces compressive strength about 5 percent. and salts used for removal of snow and ice from pavements. The Bureau of Reclamation generally requires removal of larger sizes of coarse aggregate by handpicking before a test for air content is made. tests by the Portland Cement Association [13] and the National Sand and Gravel Association [14] indicate that.) sieve before testing for air content. There are exceptions. In the case of rich mixtures. can be counteracted by reproportioning the mix by reducing water and sand contents to maintain the slump and volume of mortar in the concrete.4 mm (3/8 in.an air-entraining admixture to concrete or by using an air-entrained admixture to supplement the air entrainment achieved by use of an air-entrainment cement. Thus.) or 75 mm (3 in.) to 152 mm (6 in. On the other hand. the 4 to 7 percent limits on air content should probably be raised. Along with these beneficial effects. This reduction in strength.) or more in diameter are used.). by reproportioning of the mix. there is usually a decrease in the strength of concrete. Air entrainment is obtained by using an air-entraining cement or by adding . It is from this background of information. and others show the need for a minimum of about 3 percent entrained air in concrete mixtures containing 50 mm (2 in. however. . for example. As a matter of fact.BARTEL ON AIR CONTENT AND UNIT WEIGHT 127 field on concrete that is assumed to contain entrained air. where the 4 to 7 percent limits on air content should not be applied. for a given water-cement ratio. air-entrained concrete mixtures (containing up to about 275 kg/m a or 470 lb/yd 3) actually may be greater than that of normal concrete. the reduction in strength may be only 10 to 15 percent instead of the 20 to 25 percent which could be expected were the mix not reproportioned.) through a 37. it is possible that the strength of lean. unfortunately. Numerous tests have demonstrated that purposefully entrained air increases the resistance of concrete to destructive agencies such as freezing and thawing. that most specifications require 4 to 7 percent air in freshly mixed air-entrained concrete. in which cobbles of aggregate 152 mm (6 in. Gonnerman [13]. the Corps of Engineers [15] wet screens its concrete containing a nominal maximum size aggregate of 75 mm (3 in. seawater. especially in relatively rich mixes. In concrete mixtures used in Kansas pavements in which the maximum size of aggregate is about 9. Thus. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) sieve.) or 75 mm (3 in. these limits may be applicable to that portion of the concrete which would pass a 50 mm (2 in. however. Studies by Wuerpel [12]. No further reproductions authorized.) maximum size aggregate to secure the full benefits of increased resistance to freezing and thawing. The above discussion of exceptions to the usual specification limitations on air content indicates that the air content of the mortar or cement paste portion of the concrete should be of principal concern. together with field experience. coupled with intelligently prepared specification limits. The temperature of the concrete is important in that more air is entrained by the same dosage of air-entraining admixture at 20~ (70~ than at 38~ (100~ and more at 4~ (40~ than at 20~ (70~ [19. or as an addition interground with the cement. This is particularly necessary for mixtures for heavyduty floors or for very high-strength concrete which might be used in preCopyright by ASTM Int'l (all rights reserved). Concrete of high slump will ordinarily entrain more air than that of low slump. There are indications that pumping of concrete may remove some air from certain mixtures. 30 to 50 size increased. or the durability of the concrete. Repeated handling and agitation of concrete prior to placing might cause loss of air content. I t should not be overlooked that the air in the lower portion of a deep section will be compressed by the weight of concrete above it. However. So far discussion has been confined to air content of concrete as mixed. particularly that of the sand. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. numerous small air bubbles closely spaced throughout the mass are more effective in securing the beneficial effects of air entrainment than are a smaller number of relatively large voids. number of air voids. No further reproductions authorized. The air content of concrete containing a fixed amount of air-entraining admixture added at the mixer. for example. this will affect the volume of air but probably not the spacing. . in transit-mixed ready-mixed concrete.t h a t it does not contain more than about 1 to 1. tests of fresh concrete for air content by the ASTM standards described here constitute the best means for controlling the end results in the field.5 percent. it is the air voids in the hardened concrete that secure the beneficial effects attributed to air-entrained concrete. Vibration in consolidating concrete in the forms may also remove air from the mass [22]. The quantity of air will increase with mixing up to a point and then will gradually decrease. varies with many factors. Air content determinations are sometimes made to ensure that nonairentrained concrete is " n o r m a l " .20]. Nevertheless. It is important that the effects of these factors be understood so that test results obtained may be evaluated and adjustments made to secure compliance with specifications. tests have shown air content to increase during about the first 12 min of mixing and then slowly to decrease [21]. Powers [17] and Klieger [18] have shown that the air content of fresh concrete should be governed by the spacing and size of voids in the cement paste. should ensure the desirable properties of air-entrained concrete. The grading of the aggregate. In concrete of a given air content. even with all these complications. handling and placing of concrete on the job can affect the air content of concrete in place. Walker and Bloem [19] found that the air content of concrete increased as the proportion of sand in the Nos. also has its effect on air content. And. of course.5 percent of air.128 TESTS AND PROPERTIES OF CONCRETE should be 8. These test methods..5 to 9. Less air will be entrained in rich mixtures than in lean ones under given conditions. recommend that their products not be used with air-entrained concrete. On the basis of the estimate. the density of individual particles varies with size. In the case of lightweight aggregates. are used to control weight p e r se of both lightweight and high-density concretes and to establish the size of batch (or yield) being produced. or from weights per cubic metre (foot) of dry loose aggregate. as gradation of the lightweight aggregate changes even a relatively small amount. Recently the need for radiation shielding in various nuclear devices has increased the use of high-density concrete.BARTEL ON AIR CONTENT AND UNIT WEIGHT 129 stressed designs or heavy-load-carrying columns. This difficulty in accurately determining specific gravity and absorption of lightweight aggregates makes conventional concrete mix design procedures inaccurate. For a given aggregate. The subject of radiation effects and shielding is discussed in detail in this publication by Polivka and Davis. the greater the ability to shield against radiation. however. Details of the procedure are outlined in the Recommended Practice for Selecting Proportions for Structural Lightweight Concrete of the American Concrete Institute [23]. especially when particle shape is rough and irregular. to ensure that even a moderate amount of air is not being entrained. The unit weight of high-density concrete has been of interest for many years where it was used in such things as counterweights. Concrete. . The weight of all materials to be used to produce a cubic metre (foot) of concrete is estimated on the basis of experience. The unit weight procedure for proportioning and controlling concrete mixtures made with lightweight aggregates. it is the weight of hardened (not 4See p. dam gates. Unit weight tests of fresh concrete. circumvents these difficulties. with its relatively high-weight to low-cost ratio. particularly in hot summer temperatures. the greater the density of a material. with the larger particles being less dense because they have been expanded more. the specific gravity will change significantly. Copyright by ASTM Int'l (all rights reserved). 420. at the time high-strength concrete is placed. If the actual unit weight ef the fresh concrete differs from the estimate appreciably. and so on. special highdensity aggregates have been used to increase unit weight of concrete. Further. has been used extensively for this purpose. it is extremely difficult to determine accurately specific gravity and absorption. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 4 Obviously. Where space limitations prevail. No further reproductions authorized. It is difficult to produce high compressive strengths with air-entrained concrete. for example. it is impractical to bring these aggregates to an exact condition of saturated-surface dry. In general. it will be necessary to increase or decrease quantities of materials until the yield approaches a full cubic metre (yard). Many manufacturers of metallic aggregates for heavy-duty floors. a trial mix of concrete is mixed and tested. Thus. from data supplied by the aggregate manufacturer. This makes apparent the desirability of making an air content test. as previously stated. U. Relative yield is defined as the ratio of actual volume of concrete obtained to the volume as designed for the batch. S. [4] Pearson. and volume of concrete being produced. A. 47. . 1947. C. W. B. B. 1947. American Society for Testing and Materials. can ensure the beneficial effects of entrained air in hardened concrete. H. The use of ASTM Test C 138 to determine yield of concrete has been referred to previously. Proceedings. 47. 1958.. F. American Concrete Institute." Journal. Vol. 1948. p. 1947. and Kennedy." Proceedings. Corps of Engineers.S. [2] Menzel. J... 832. P.130 TESTS AND PROPERTIES OF CONCRETE fresh) concrete which is of concern for radiation shielding. C. Vol. 865. Unit weight tests are reliable for controlling yield of concrete. p.. 1961. S.. W. Copyright by ASTM Int'l (all rights reserved). "Washington Method of Determining Air in Fresh Concrete. T. June 1946. however." Bulletin 176." Proceedings. Highway Research Board." Proceedings. J. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vol. 1947. It indicates whether a full cubic metre (yard) is being delivered or whether the batch is short of its design volume. [6] Barbee.. "Indiana Method for Measuring Entrained Air in Fresh Concrete. Vol. p. W. p. References [lJ Klein. Proceedings. American Society for Testing and Materials. Highway Research Board. [10] Symposium on Measurement of Entrained Air in Concrete. will yield an accurate measurement of the amount of air. [9] Newlon. [8] Grieb. 833. [7] Willetts. 28. E. "The Ohio Method of Determining the Amount of Air Entrained in Portland Cement Concrete. 914. 901. and Gooding. "The Effect of Sampling Errors on Unit Weight and Air Determinations in Concrete." Proceedings. Waterways Experiment Station. Nov.. Vol. 210. Tests for air content. p. coupled with intelligently selected specification limits. L. American Society for Testing and Materials. and for evaluating unit weight when stated in specifications. Highway Research Board. No further reproductions authorized.." Miscellaneous Paper No. "The AE-55 Indicator for Air in Concrete. Vol. American Society for Testing and Materials. 47. Yield as such is defined as the volume of concrete produced per batch. Army. H." Bulletin 305. 1947. the control must be exercised through unit weight determinations of freshly mixed concrete. 47. D.. Vol. Relative yield is of special importance to the commercial transactions between a readymixed concrete producer and his customer. American Society for Testing and Materials. "A Limited Investigation of the Chace Air Meter." Proceedings. 1956. H. C. Jr. 47. and Walker. carefully made in accordance with the appropriate ASTM test method. B. "A Method for Direct Measurement of Entrained Air in Concrete. "Procedures for Determining the Air Content of Freshly-Mixed Concrete by the Rolling and Pressure Methods. "A Field Investigation of the AE-S5 Air Indicator. p. p. 42. and Helms. 657. 6-189. [5] Miesenhelder. weight. Summary Tests for air content and unit weight of fresh concrete. [3] Tremper. H.. F. Nov. [15] "Investigation of Field Method for Determining Air Content of Mass Concrete. "Effect of Vibration on Air Content of Mass Concrete. "Purposeful Entrainment of Air in Concrete.. 1953. 40.th So-Called 'Sand Gravel' Aggregates. D. 1958. T. 45. Sun Apr 6 21:39:19 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Proceedings." Journal American Concrete Institute. [23] "Recommended Practice for Selecting Proportions for Structural Lightweight Concrete. "Tests of Concrete Containing Air-Entraining Portland Cements or Air-Entraining Materials Added to Batch at Mixer.BARTEL ON AIR CONTENT AND UNIT WEIGHT 131 [1l] Britton. Vol. May 1954. S. W. E. "Studies of Concrete Containing Entrained Air. L. [19] Walker. Proceedings. R. Proceedings. p.. "Void Spacing as a Basis for Producing Air-Entrained Concrete. Sept. Waterways Experiment Station. E. 1946." Pennsylvania Slag Association. Vol. Sept. 909. 46. 477. [13] Gonnerman. Vol. p. 629. Proceedings. Vol. P. 1946. 49. National Ready Mixed Concrete Association. L. 6-352. C. S. 42. 50. D. [17] Powers. p. American Concrete Institute. [22] Crawley. 28. E." Journal. Proceedings. American Concrete Institute.. p. Army. 149. Copyright by ASTM Int'l (all rights reserved)." Journal American Concrete Institute. and Bloem. C. C. O. . Vol. [21] Mumford." National Ready Mixed Concrete Association. 741. [16] Wuerpel. Proceedings. Vol. American Concrete Institute.. American Concrete Institute." Technichal Memorandum No." Technical Information Letter No. 1948. [18] Klieger. Oct. 1946." Journal American Concrete Institute. p. [20] Symposium on Entrained Air in Concrete. Vol. Proceedings.. April 11. "Control of Quantity of Entrained Air in Concrete. 1953. H. pp. 305.. "Report of Investigation of Different Methods for Determining the Amount of Air Entrained in Fresh Concrete. "Laboratory Studies of Concrete Containing Air-Entraining Admixtures. U.." Marquette Cement Manufacturing Co. June 1944. [14] Walker. 1950. June.. Corps of Engineers." Journal. R.. 1949. Vol. P. June 1946. "Effect of Entrained Air on Concretes Made w~..S." Journal. 305. Proceedings. "Effect of Time of Mixing." Journal. [12] Wuerpel. 42. 55.. Feb. p. No further reproductions authorized. p. American Concrete Institute. 601-699. 1952. and Bloem. This paper is intended to show that petrographic examination provides information useful in evaluating hardened concrete. to outline what it involves.U. and to show how this information can be applied. Copyright9 1978tobyLicense ASTM lntcrnational www.Chief. except after-the-fact. they use standardized procedures not directly related to the specific environment or that do not determine the particular properties relevant to performance in the specific instance. ArmyEngineer Waterways ExperimentStation. EngineeringSciencesDivision.STP169B-EB/Dec.S. to note the problems inherent in its use. (b) " W h y did this material behave in use in the way it did?".StructuresLaboratory.org . 39180. and (c) What can be anticipated as to the future service of this material?" The first question is never answered unequivocally. The most useful method for developing practical information upon which to make decisions that depend on prediction of probable behavior of materials is the study of why materials behaved in use as they did. by determining how the material did behave in use. to describe the kinds of information that it can produce. 1978 Katharine Mather 1 Chapter 11 Petrographic Examination Petrography is the scientific description of the composition and texture of rock. No further reproductions authorized. Sun Apr 6 21:41:38 EDT 2014 132 Downloaded/printed by Universidade do Gois pursuant Agreement. Thus. Petrographic examination of hardened concrete--a man-made rock--is the examination of concrete by the techniques used in petrography to determine the formation. Petrographic examination of hardened concrete is included among the l Geologist. Miss. Generally. Copyright by ASTM Int'l (all rights reserved). The questions that materials testing and evaluating tries to answer are: (a) "How will this material behave in use?". and internal structure of the concrete and to classify it as to its type. Vicksburg. composition. and serviceability. testing construction materials amounts to obtaining certain kinds of information about certain samples in specified conditions and extrapolating to the conditions of intended use insofar as they can be predicted.astm. Testers of materials are unable to compress time or to anticipate ann reproduce the environment that the material will experience. condition. including the systematic classification of rocks. it is.K. MATHER ON PETROGRAPHIC EXAMINATION 133 subjects in this volume because it helps to improve the extrapolation from test results to performance in use. namely ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295). In nearly all cases. they cannot expect a clear. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The petrographer should not expect petrographic results to be taken on faith. It offers direct observational information on what is being tested and what is in the structure. No one should hesitate to examine concrete with all available means. the rationality of the techniques producing them should be demonstrable. No further reproductions authorized. physicists--anyone concerned with the production or use of concrete. giving another way of appraising the relation between samples being tested and materials in use and judging how similar the two are. the more he directs the petrographer toward the important aspects. The engineer may not be familiar with the techniques that the petrographer may use or with his approach. and may not realize which petrographic findings are useful and relevant. the more clearly he defines the features prompting his interest. mutually understood statement of the problem. may not find out all the engineer could tell him about the concrete. Methods--Standardized and Described There is a recommended practice for petrographic examination of concrete aggregates. ASTM Recommended Practice for Examination and Sampling of Hardened Concrete in Constructions (C 823). should question the indicated conclusions and verify them in as many ways as possible. from novice to expert. the engineer who asks for an examination of a particular concrete suspects that the concrete is unusual. [2] gives guidance for the examination of concrete in constructions for many purposes in addition to petrographic examination of the samples taken. as well as Copyright by ASTM Int'l (all rights reserved). Communication Problems A petrographic examination of concrete ordinarily begins and ends with a problem of communication between the person who requests the examination (usually an engineer) and the person who makes it (usually a petrographer). On this basis. the desirability of assembling reports and legal documents concerning the construction is pointed out. . Steps to be taken before examination and preliminary investigations are outlined. all. Both should remember that the essentials of petrographic examination of concrete are practiced anytime anyone looks intelligently at concrete either in a structure or as a specimen and tries to relate what he can see to the past or future performance of the concrete. engineers. Unless the two succeed in producing a clear. useful answer to be obtained economically. chemists. clear that many of the most useful petrographic examinations are made by inspectors. which was adopted in 1975. the petrographer may not realize the engineer's responsibility for decision and action. a Type I.134 TESTS AND PROPERTIES OF CONCRETE the usefulness of interviews with contractors and others connected with the construction and with the owners. from specimens in field exposure. simulated service. Sampling hardened concrete is discussed. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. with the preparation of appropriate sampling plans and selection of the number and size of samples. or infrared absorption spectroscopy. The features may also make more comprehensible similar or related features of concrete from constructions. It is the hope of the subcommittee by which the recommended practice was prepared that it will be useful not only to petrographers but also to engineers and others who have reason to examine constructions. . It turned out to be a more complicated document than was expected. The illustrations appear in ASTM Adjunct C 856. a number of pure phases were synthesized and examined by the methods listed above. Other publications of interest are found in the volumes of the Fifth International Symposium on the Chemistry of Cement [3] and those of the Sixth International Symposium on the Chemistry of Cement [4]. and laboratory curing may be features interesting and revealing in themselves in laboratory experiments. it appears bimonthly and covers a wide field of cement and concrete topics and has the advantage of being truly international since the editorial board and the contributing 2The italic numbers in brackets refer to the list of referencesappended to this paper. Copyright by ASTM Int'l (all rights reserved). Information needed to accompany samples is described. Procedures for detailed investigations of the concrete in place in constructions are described. Evaluation of Methods of Identifying Phases of Cement Paste [1] 2 was published. In 1976. were examined at ages to one year. No further reproductions authorized. examine hydrated cement by X-ray diffraction. laboratory tests. Pastes of three cements. from specimens in simulated service. What may be recognized as features produced in field exposure. One of the most stimulating serial publications came into being in 1971. a white cement. The subcommittee hopes that this recommended practice will serve the engineers who buy a petrographic examination and then want more understanding of what they are getting and why. differential thermal analysis. ASTM Recommended Practice for the Petrographic Examination of Hardened Concrete (C 856) was adopted in 1977. because the purposes differ for examining concrete from constructions. and from specimens after laboratory curing. and that it will remind concrete petrographers of things that they may have forgotten or neglected. It will be helpful to those who wish to determine alite and belite residues in paste. Another publication relevant to the petrographic examination of hardened concrete is Guide to Compounds of Interest in Cement and Concrete Research [2]. that it will also serve petrographers approaching the examination of concrete for the first time. Cement and Concrete Research. from specimens in laboratory tests. and a cement containing no tricalcium aluminate (C3A). and users of the constructions. an International Journal [5]. occupants. looking at the samples from it with the eye and the stereomicroscope. concretes change through time more rapidlythan most aggregates. and so a sensible sampling plan is carried from the macro. All of these circumstances combine to make each petrographic examination of concrete unique and thus to make the methods harder to generalize and standardize.to the microscale. Copyright by ASTM Int'l (all rights reserved). More people are using sophisticated equipment and techniques in the study of cement hydrates and even of concrete. but the determining steps are looking at the constructions. . Concretes are more complexthan most rocksused as aggregates. to single crystals a few micrometres cubed that are examined by microprobe and to the nanometre-sized material examined by the transmission electron microscope. This real and exciting probability brings with it dangers of losing touch with the importance of the very great range in scale. and usually then forming one or more working hypotheses that indicate to the petrographer how to make the transition from the macroscale to the microscale most economically in knowledge gained for each unit of effort. Proper caution is needed so that proper sampling is done at all levels of scale. and preferably using more than one method so as to obtain an independent verification. paste concentrates are made from several cores. to X-ray diffraction samples which may be milligrams of material hand-picked under the stereomicroscope or a few grams of paste concentrated by hand-picking the aggregate from carefully broken concrete. petrographic techniques for the examination of hardened concrete had been described and discussed but not standardized. to core samples with dimensions in hundreds of millimetres that can be examined with great advantage at low magnification by a stereomicroscope on a large stand. their constituents are lesswell known. For example. Before the production of ASTM R e c o m m e n d e d Practice C 856. to thin sections with scales ordinarily about 800 mm 2 by 15 to 30/zm thick. In 1966 1 wrote: At present I know of no laboratory where petrographic examinations of concrete are made that is equipped to use all the methods that have yielded useful information and no one person who has digested the available approaches and developedthe ability to choose the particular combination of techniques best suited to each problem encountered. No further reproductions authorized. MATHER ON PETROGRAPHIC EXAMINATION 135 authors do come from most of the centers in various parts of the world where cement and concrete research is carried out. from constructions with dimensions in hundreds of metres (kilometres in the case of pavements).K. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Each examination presents some new facet for the petrographer who is willing to learn. and may bring about a breakthrough by orders of magnitude in our ability to interpret the behavior of concrete in constructions. Few cases will be found in which all the steps in scale listed above will be used. and that is good and highly desirable. samples should be taken from deposits in several cracks and voids in several cores. to scanning electron microscope specimens that may be 200 mm a or much smaller and thinner. In 1977 there is more sophisticated equipment in more laboratories but the number of laboratories may have diminished. 136 TESTS AND PROPERTIES OF CONCRETE One should also bear in mind the straw that broke the camel's back theory of concrete deterioration. because it will be possible to characterize the hydration and reaction products more clearly and consequently the chemical reactions of normal hydration or abnormal deterioration. it is highly probable that evidence of more than one deteriorative mechanism (or what appears to be such eyidence) will be present in any sample of deteriorated concrete. those that need to be answered to solve the problem that caused the examination to be requested. the articulation or packing in space of the component elements making up any sort of external form [6] or heterogeneous solid body. and contractor's personnel who have been present during construction and those who have later inspected or occupied the construction. Both questions may be answered on any useful scale by choice of technique or techniques of appropriate resolving power. The goal of relating better established and more familiar techniques in petrographic examination of hardened concrete to the more intimate and detailed insights made possible by the newer techniques remain to be achieved completely and while progress since 1966 is considerable. inspectors. . with much more certainty than is possible without identification of the reaction products. The history of the construction and its behavior is of great importance. Approach Step one. which says that unless the concrete was hit by a truck or a large object from outer space. in the concrete. These right questions should be answered insofar as they can be in the context. Purpose and Approach Purpose A petrographic examination attempts to answer two general objective questions: "What is the composition?" and "How is it put together?" The first question refers to the recognizable individual constituents present on the scale at which they are considered. limited as it will be by money. that is. and to evaluate. is to define the problem in order to find and ask the right questions. the relative roles of chemical attack and physical attack in producing deterioration. the task is not yet complete. Copyright by ASTM Int'l (all rights reserved). The second question refers to structural fabric. The newer techniques offer an opportunity to understand in much more detail than previously the chemical reactions that have gone on in a concrete. The resolving power needed differs depending on the specific questions to be answered. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and for this kind of information the petrographer should consult engineers. No further reproductions authorized. or both. in any case. Sorting out the major cause or causes from the minor causes or secondary effects of deterioration requires the exercise of the petrographer's best judgment. . Fabric and composition together define. The approach to the ideal varies depending on the problem. No further reproductions authorized. Fabric includes all of the structural elements. on the scale of the coarse aggregate. or." on the scale of the residual unhydrated cement or the calcium hydroxide crystals. ranging in scale from gross to atomic. the skill with which the questions are asked. The fabric appears on the scale of the lift or course or batch or the structural crack. characterize. The closest naturally occurring analogue to hardened cement paste is silty clay. MATHER ON PETROGRAPHIC EXAMINATION 137 time.K. on the scale of the sand grains or the air voids in the mortar or the "microcracks. One important decision in a petrographic examination is the decision whether the request for the petrographic examination was made because of problems created by the physical structure of the concrete or because of problems created by its chemical composition. and reactions between cement paste and solutions from external sources. with a demonstration clear to all concerned that the right questions were answered with all necessary and no superfluous detail. The best petrographic examination is the one that finds the right questions and answers them with maximum economy in minimum time. instrumentation. because it has been shown to be unsolvable under the circumstances. reactions between cement and aggregate. or on the scale of the atomic structure of any crystal forming a part of any of the structural components. and comprises both structure and texture as those terms are used in rock description. Fabric and Composition Fabric--the packing of component elements in space--is the heterogeneity obvious as one looks at a weathered concrete structure or at a broken or sawed surface of concrete. Composition and fabric are so closely interrelated in concrete that they cannot be separated clearly. The closest naturally occurring analogue among rocks to the fabric of concrete is graywacke conglomerate with abundant matrix. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Problems arising from the chemical composition include those resulting from errors in batching. and the state of the art. either because the problem is adequately solved. is knowing when to stop. One measure of the petrographer's skill. in some cases. reactions between a contaminant and cement paste. Problems arising from the physical structure or fabric include inadequacies in mixing or consolidation and inadequacy of the air-void system to provide frost resistance. Were the construction practices employed suitable for producing concrete capable of giving satisfactory service in the particular environment and exposure? Were the materials that were chosen susceptible to participation in chemical reactions that have deleterious conseCopyright by ASTM Int'l (all rights reserved). and the skill of the petrographer. on the scale of the hydrous calcium aluminates and the scale of the almost amorphous crystalline hydrous calcium silicates in the hydrated cement paste. and form the basis for descriptive classification of solid multicomponent substances. or wetting and drying cycles. and exposure. Investigating composition and fabric provides a specific. Specimens exposed to simulated weathering tests. The standard tests do not always supply information that permits discrimination between one piece of concrete and another. but direct observation on the relevant scale does. but the No. and its top is different from its bottom as cast. Paste. Each comparison leaves out of account some characteristics of the things compared. history. they are essential. and concretes can be grouped rationally and compared usefully within classes and between classes. 2 cylinder in the set of three broken on Day A in Laboratory B is unique and different. or concrete of known proportions. laboratory specimens made to be examined or salvaged just after having been tested for strength provide a good source of such comparative material. 1 and 3 and from all the members of the other possible sets. if the basis for the grouping is objective. There are n possible concretes all having S0-mm (2-in. or prolonged drying are not to be considered as representative of normally cured or of naturally weathered concretes. fabric. but one is probably the originator. this individual combination of fabric and composition reflects the history and forecasts future performance of the concrete. perceptibly and logically.138 TESTS AND PROPERTIES OF CONCRETE quences? Was there a failure to modify the environment. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. by improving the drainage so as to increase the ability of the concrete to survive the chemical or physical character of the environment? Usually several causes have interacted. the appropriate techniques are pointed out more clearly. so that it is necessary to bear in mind that the accidentally or deliberately omitted factors may prove to be important. from Nos. as well as from climate to climate. Each structure and each part of a structure is unique in terms of composition. of each specimen and each thin section. No further reproductions authorized. Natural weathering differs from part to part of a structure.) slump. unique definition of what is being examined. Copyright by ASTM Int'l (all rights reserved). elevation to elevation. for instance. . with 31-MPa (4500-psi) compressive strength at 28 days. Comparisons To say that each structure and specimen is unique does not mean that comparisons are useless or impossible. and curing history offers the logical basis for comparison and extrapolation. because specimens that are cracked or that have slender cross sections sometimes carbonate very rapidly. with air content of 5 percent. mortar. Specimens exposed to laboratory air outside the moist room or curing tank for more than a few hours are much less suitable. What is investigated at any time is particular concrete. age. and subgrade to subgrade. if it can be identified. The salient lesson from the study of composition and fabric of concrete is the individuality and uniqueness of each structure or part of a structure. materials. not concrete in general. Unless it can be demonstrated that the constituents. there is no logical basis for assuming any connection between constituents. and service behavior. age. Class of Concrete The restriction to concrete of one class is necessary because changes in cement content. depart from those found in serviceable concrete of the age and class in the region. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.1 by weight in w/c ratio. . or it is possible to sort mass concretes fairly homogeneous in age in order of increasing cement content. only by comparison with the range of constituents and fabrics in normal satisfactory concrete can that which differs from the normal be recognized and its differences specifically defined. "fairly homogeneous" in cement content and w/c ratio means a m a x i m u m difference in cement content between concretes of about 30 k g / m 3 (50 lb/yd3). It is possible by microscopic methods to sort mass concretes that are fairly homogeneous in cement content and w / c ratio in order of increasing age. No further reproductions authorized. all mass concrete appears very inferior. and 0. If. particularly in w/c ratio. Copyright by ASTM Int'l (all rights reserved). In terms of the ability to sort mass concrete microscopically. Class of concrete is important in the definition as it implies relative homogeneity in mixture proportions. MATHER ON PETROGRAPHIC EXAMINATION 139 Interpretation of Observations Normal Concrete For this discussion. cement content. or the fabric. the criteria for paving concrete are applied to mass concrete. or the proportions of constituents. water/cement (w/c) ratio.K. " n o r m a l " constituents and fabrics are defined as those present in serviceable concrete of the class and age in the region. and provenance. "Serviceable" is used instead of "undeteriorated" because it is possible to tell whether concrete in a structure is serving as it was intended to but the criteria that distinguish inevitable chemical and physical changes from deterioration in concrete 20 or 50 years old have not been well established. which it is not for the purpose it is intended to serve. and m a x i m u m size of aggregate. Even when it can be shown that a concrete has a peculiar service record and some unique feature or features not shared by a dozen others of comparable class. for example. or proportions. The most valuable information that can be obtained by petrographic examination of concrete comes from the examination of normal concrete. or whether both are related to some third or nth factor that is the effective cause of the abnormal behavior. and m a x i m u m size of aggregate large enough to change the class entail such large changes in properties that no close comparison will be significant. it remains to be seen whether the known unique feature and the peculiar service record are connected causally. or fabric. For example. but it is not abundant and is confined to voids near outer surfaces. if it is 15 years old. manufactured coarse aggregates. temperature varies considerably with altitude. The aggregates economically available in an area are determined by the regional geology and consequently show some homogeneity of composition resulting from similarity of origin and history. Provenance of Concrete Restriction of an investigation to one region assists in rational comparison from several points of view.140 TESTS AND PROPERTIES OF CONCRETE Age of Concrete Some restriction on the ages of concretes compared is necessary unless age is the variable being studied. and synthetic aggregates. essentially comparable range and distribution of temperature and precipitation. in one case calcium sulfoaluminate was found in many voids as far as 130 mm (5 in. and synthetic aggregate sources are not common. In a particular region. and precipitation with orientation to prevailing winds. it differs conspicuously from others of comparable age and class in the region and the difference probably justifies some concern about its future. but in a region of high relief and broken slopes. calcium sulfoaluminate is commonly present in concrete over 5 years old made with Type I or Type III cement. it may be impossible to judge the significance of observations. The extent of a region of comparable concrete may vary from a few square miles to many thousands. In other field concrete from the region. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or the Atlantic or Gulf Coastal Plain. but the peculiarity is probably of less practical importance. If the concrete of unknown age is in fact 5 or 7 years old. making important differences in exposure over short distances. Metropolitan marketing areas served by water transportation usually have available a selection of natural coarse and fine aggregates. depending on variation in: (a) regional geology-as it determines quantity and uniformity of aggregate supply.) from the outer surfaces of a concrete pavement of high flexural and compressive strength and of unknown age. No further reproductions authorized. All variations Copyright by ASTM Int'l (all rights reserved). cements and aggregates economically available are used in making concrete which is exposed to the climate characteristic of the region--the prevailing temperature range and temperature frequency distribution and the characteristic amount and sequence of precipitation. has widespread. no manufactured aggregate is produced. . Unless the age is known or unless one has younger and older concretes of otherwise comparable characteristics so that the age of the unknown may be estimated in relation to the knowns. (b) topography--a region of low relief and generally uniform slope such as the Great Plains. it is peculiar. only one type of natural sand and gravel is available. and (c) patterns of distribution of aggregates and cement from competitive sources--in some areas. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The existance of satisfactory structures built in many different ways underlines the need to define "normal" concrete in objective and restricted terms. on what is desirable in mixture proportions or methods of placing or consolidation. . Normal and Unusual Concrete Although the most important kind of petrographic examination of concrete is the examination of normal concrete. effects of both cement-aggregate interactions and of environmental influences would be easier to recognize and could be interpreted more usefully. in an organization placing concrete in a large area. Cement plants per state range from none in New Hampshire and Vermont to 19 in Pennsylvania [7]. Composition If the changes in composition of cement paste with time in laboratory conditions were known for a representative number of cement compositions and w/c ratios. Would such traces be unique and specific evidence of what is supposed to have happened? Reconstruction of History of Field Concrete To pass from consideration of simple petrographic examination to the petrographic examination of concrete that has aged and perhaps deteriorated in service introduces two important new unknowns--time and the precise environment of the structure. No further reproductions authorized. Before and during the early stages of the examination. What observable traces could the process or processes leave in the concrete? 3. but anomalies remain in the results. The effects of the passage of relatively short periods of time on the constituents present in several cement pastes of known w/c ratio stored under laboratory conditions have been investigated. Ports and coastal areas may be served by overseas and domestic cement sources. What process or processes could produce the described results? 2. MATHER ON PETROGRAPHIC EXAMINATION 141 between the two extremes just mentioned can be found in availability of aggregates.K. usually the concrete that a petrographer is asked to examine has behaved in an unexpected way. the information on the history and behavior should be considered and the following questions asked: 1. although both the composition of the pastes and the nature of the environments were known and controlled far more thoroughly than the composition and environment of any field concrete. An additional influence that may appear is a prevailing engineering opinion. Copyright by ASTM Int'l (all rights reserved). and the characteristics that undeteriorated comparable concrete would have. In practice. The difference probably is that the chert gravel in the Memphis walls is more likely to be critically saturated when it freezes. or the engineer. a decrease in available information. such simple cases usually can be and are explained on the spot to the satisfaction of those concerned.? The winters are colder in St. and in Memphis a larger proportion of the higher mean annual rainfall occurs in winter. There is thus a build-in bias in the sampling process. Concrete produced where there was little intent for control to be exercised. Furthermore. the physicist.142 TESTS AND PROPERTIES OF CONCRETE Environment Why do exposed vertical walls of chert-gravel concrete in the vicinity of St. The field concrete that is examined by a petrographer is concrete that has worried some responsible person enough to make the effort and expense of sampling and testing appear justified. neither can the chemist. the worst concrete. The Weather Bureau's climatological data for the location are a valuable source of information that can assist in many petrographic examinations of hardened concrete. . The discovery in Mississippi of several highway pavements and associated structures affected by sulfate attack and by combined sulfate and acid attack [8] emphasizes the need to make use of available information on the composition of foundations and subgrades. Louis. Copyright by ASTM Int'l (all rights reserved). but the mean annual rainfall is lower. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Several reasons make reconstruction of the history of deteriorated field concrete difficult. Thus. generally have fewer popouts than apparently similar walls in the vicinity of Memphis. Normally the concrete that a petrographer sees as part of his assigned duties is controversial concrete sent in by organizations with alert conscientious concrete technologists or concrete that has become the subject of controversy under other situations. Deteriorated field concrete that is submitted to a laboratory or to a petrographer is almost never concrete that has performed abnormally for one single obvious cause. rarely is sampled and sent to a petrographer. the examination of samples of field concrete after extended service involves an increase in complexity. good concrete is rarely controversial. Mo. Tenn. in any particular instance it may be important and yet impossible in the present state of our knowledge to decide what weight belongs to each. sometimes the petrographer can recover evidence not accessible by other approaches. conditions of placing. Louis. as compared to examinations of laboratory test specimens of hardened concrete.. and a decrease in the confidence that may be placed in the answer. the older the concrete the less information is likely to be available about materials. proportions. It does not belittle the petrographer to admit that he cannot make bricks without straw. that is. this generally means that he sees only the poor concrete produced under conditions where a degree of control was intended. No further reproductions authorized. especially on samples from seawater exposures or from other wet environments. Frequently the most conspicuous process is carbonation of other surfaces and along the borders of old cracks. The use of X-ray diffraction to examine cement-paste concentrates from field concrete has revealed that vaterite. The sequence from poorly crystallized vaterite. No further reproductions authorized. Accelerated freezing and thawing in water according to ASTM Method C 666. however. Vaterite is known to persist for several months in laboratory specimens stored in room conditions. Procedure A. Aggregate sources. a laboratory procedure often results in symptoms different from symptoms encountered in a field example of the process the test is intended to simulate. The most advanced process may conceal the evidence of others that was more important in effect. when examined using light microscopy. and the general quality of the workmanship. and sometimes in the interior. MATHER ON PETROGRAPHIC EXAMINATION 143 Although one can deduce from the concrete that w/c ratio was high or low. Samples of field concrete. calcite. can be located from their composition--the constituents present and their size distribution are diagnostic of the region and sometimes of the particular source. deteriorated field concrete usually shows superimposed traces of several processes. rarely aragonite. produces a characteristic loss of surface skin and loss of mortar. frequently are found to contain secondary calcium carbonate near their outer surfaces. was found by optical methods to be common on mortar bars that had been tested according to ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (C 227) and had been found on concrete specimens tested for resistance to freezing and thawing according to ASTM Test for Resistance of Concrete Specimens to Rapid Freezing and Thawing in Water (C 666). and almost never vaterite. Maine [12]. is generally found to be calcite. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vaterite. Finally.K. particularly of natural sand and gravel. Laboratory test exposures are simplified compared to natural exposures by the exclusion of some factors and the regulation of those retained and often are "accelerated" by altering some factor so as to remove it from the range possible in nature. one cannot reconstruct the alkali content of the cement. Consequently. when examined by optical methods. is frequently a major constituent of the secondary calcium carbonate [9]. not recognized by optical methods. the form-birefringent spherulitic calcite with interstitial water. along old cracks. with at least one in an advanced stage. and usually that cement content was high or low or medium. and aragonite to well-crystallized calcite in the carbonation of pastes and mortars has been clarified by Cole and Kroone [10]. . Field concrete that is not air-entrained and is deteriorated by natural freezing and thawing develops sets of subparallel cracks normal to the placing direction of the concrete or deteriorated regions Copyright by ASTM Int'l (all rights reserved). which is not like the condition of specimens exposed on the meantide rack at Eastport. and vaterite is now known as a natural mineral [11]. Such calcium carbonate. an International Journal. Highway Research Board. K.. 1971. 113. Sixth International Symposium on the Chemistry of Cement. Fifth International Symposium on the Chemistry of Cement. C. Inc. Tokyo. Gefiigekunde der Gesteine. [7] "Portland Cement Plants." Transportation Research Circular No. with the electron probe and infrared spectroscopy. Moscow Stroyizdat 1976. [3] Proceedings. "Sulfate Attack on Concrete Pavements in Mississippi. and Mielenz. still offers the chance of sorting out the qualitative and quantitative differences in hydration products and in submicroscopic fabric that are related to serviceable and deteriorated concrete. F.S. W.C. No further reproductions authorized. in part available in English preprints which were distributed before the meeting to registrants.C. in four volumes. Alkali-carbonate and alkali-silica reactions exist together in varying degrees of development in some concretes. Chicago. Washington. Geological Society of America. Canada and Mexico." Pit and Quarry Publications. 12. 176. 1968. 1969. differential thermal analysis. Ill. and thermogravimetry. 1960. [6] Structural Petrology. Copyright by ASTM Int'l (all rights reserved). and inconspicuous degrees of reaction may be the only recognizable peculiarities in cases of unsatisfactory service with possibly expensive consequences. as is alkali-silica reaction... Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. Vols. I-IV.c o n c r e t e and m o r t a r . . Field concrete that has deteriorated primarily because of the alkali-silica reaction usually has much more advanced and conspicuous internal symptoms of this reaction than are f o u n d in m o r t a r bars o f expansive combinations examined after test according to A S T M M e t h o d C 227. O n the other hand. Highway Research Board. 1974. Closure " T h i n g s which are s e e n " . 127. 205-216. 88-102.. [4] Proceedings. translation of B. [8] Lossing. U. D... Highway Research Board. National Academy of Sciences. some field concrete regarded as undeteriorated has shown a range of evidence of alkali-silica reaction.144 TESTS AND PROPERTIES OF CONCRETE parallel to the nearest free surface. June 1976. pp. Roy. D. National Research Council.. National Research Council." Special Report No. Memoir 6.. L. p." w e r e not made of things which do a p p e a r " [13] to the eye and to the light microscope. Cement and Concrete Research. References [1] "Evaluation of Methods of Identifying Phases of Cement Paste. The use of X-ray diffraction. Highway Research Record No." Proceedings. These p h e n o m e n a are not reproduced in accelerated freezing and thawing in water. bimonthly. 1973. Transportation Research Board. 1966.. in conjunction with the observing eye and the light microscopy. pp. Sander. [5] Della M. Ed. 1972. [2] "Guide to Compounds of Interest in Cement and Concrete Research. Pergamon Press. Ed. electron microscopy. R." Symposium on Effects of Aggressive Fluids on Concrete. "Cooperative Examination of Cores from the McPherson Test Road. Dolch. The several alkali-carbonate reactions are described in other papers in this volume. [9] Mather.. 1938. Washington. pp. [13] St.." Chapter 11. "Correlation Between Laboratory Accelerated Freezing and Thawing and Weathering at Treat Island. American Bible Society. "Carbonate Minerals in Hydrated Portland Cement.. 1953. 250. Sun Apr 6 21:41:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vol. B.K." Proceedings. New York. C. and Kroone. Paul. 1960. Copyright by ASTM Int'l (all rights reserved). B. Maine. D. "Vaterite from Ballycraigy. T. Northern Ireland. [11] McConnell. Verse 3. King James Version. New Testament. 184. The Holy Bible. 32. "Epistle to the Hebrews. . 50. MATHER ON PETROGRAPHIC EXAMINATION 145 [10] Cole. Vol. pp. p. American Concrete Institute.57. B. F. Vol. 1959. No further reproductions authorized. Larne." Nature. Sept.. K. originally published 1611. 141-172.A. W. and Mather. [12] Kennedy." Mineralogical Magazine. 535-544. J. No. tension. pavements. College Park. (b) of all the properties of hardened concrete. Department of Civil Engineering. and (c) by means of correlations with other more complicated tests.astm. concrete must have strength. or a combination of these. or any other of its numerous areas of service.org . Therefore. Hence. however. the ability to resist force. or. 1978 K . The results of tests on hardened concrete. in compression. The forces to be resisted may result from applied loads. 2The italic numbers in brackets refer to the list of references appended to this paper. These tests. even if they are known late. more commonly. tests to determine strength are the most common type made to evaluate the properties of hardened concrete. from a combination of these. D e r u c h e r 1 Chapter 12 Strength Introduction Whether used in buildings. 1professor. those concerning strength usually can be determined most easily. the strength of concrete is taken as an important index of its general quality. because (a) the strength of concrete. Sun Apr 6 21:41:42 EDT 2014 146 Downloaded/printed by Universidade do Gois pursuant Agreement. from the weight of the concrete itself. have a policing effect on those responsible for construction and provide essential information in cases where the concrete forms a vital structural element of any building. the results of strength tests can be used as a qualitiative indication of other important properties of hardened concrete [1]. University of Maryland. bridges. Copyright9 1978tobyLicense ASTM International www. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved).STP169B-EB/Dec. Md. has in most cases a direct influence on the load-carrying capacity of both plain and reinforced structures. help to disclose any trends in concrete quality and enable adjustments to be made in the production of future concrete [2]. shear. 2 The results of tests on hardened concrete usually are not known until it would be very difficult to replace any concrete which is found to be faulty. N. 20742. the concrete-making properties of the various ingredients of the mix are usually measured in terms of the compressive strength. (c) cores of hardened concrete cut from structures. is about 1S to 20 percent of the compressive strength. better able to withstand severe exposure. (2) as control tests in conjunction with (a) tests on plain or reinforced concrete members or structures. or testing on the strength and other properties of concrete. Specimens Specimens to determine the compressive strength of concrete are obtained generally from four different sources: (a) cylinders made in the laboratory. or (b) tests to determine other properties of hardened concrete. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. strong concrete will be more impermeable. and capping of the specimens. as measured by the modulus of rupture. The tensile strength of concrete is roughly 10 to 12 percent of the compressive strength. to determine the effect of variations in materials or conditions of manufacture storage. for the following reasons: (1) in research. (b) cylinders made in the field. No further reproductions authorized. strong concrete may have greater shrinkage and susceptibility to cracking than a weaker material. The compressive strength of concrete. and molding. Concrete also exhibits tensile and shear strength.DERUCHER ON STRENGTH 147 Compressive Strength Significance of CompressiveStrength Concrete is used in many ways and is subject to a variety of different loading conditions. in which compressive strength is frequently used as a measure of these properties. . and the flexural strength of plain concrete. In general. ASTM Making and Curing Concrete Test Specimens in the Laboratory (C 192) describes in detail methods for preparation and examination of the constituent material. and (d) portions of beams broken in flexure. proportioning and mixing or concrete. one of its most important and useful properties and one of the most easily determined. Finally. Cylinders made in the laboratory constitute a large portion of the compression specimens. In the making of such specimens large variations can be introduced into the Copyright by ASTM Int'l (all rights reserved). Very often the dominant stress is compressive in nature. strength is also indicative of other elements of quality concrete in a direct or indirect manner. and so different types of stress develop. In addition to being a significant indicator of load-carrying ability. On the other hand. and (3) to evaluate mix designs for laboratory or field use. Each type of specimen has a specific purpose or purposes. determining the consistency of the mix. curing. since this material has long been known to exhibit its best strength characteristics when subjected to compressive loading. is indicated by the unit stress required to cause failure of a specimen. and more resistant to wear. character and grading of the aggregate. The ASTM Obtaining and Testing Drilled Cores and Sawed Beams of Concrete (C 42) covers the procedure for securing and testing the cylindrical cores which are used most commonly for determining compressive strength. of which one would like an approximate value of the compressive strength. or to measure and control the quality of the concrete. When cylinders are prepared in the field. and moisture content at the time of testing. ASTM Test for Compressive Strength of Concrete Using Portions of Beams Broken in Flexure (C 116) describes the procedure and apparatus necessary to determine compressive strength of concrete from broken portions of beams tested in flexure. character and grading of the aggregate. In addition. These variations may be attributed to the character of the cement. size and shape of the specimen. Compressive test results of cored hardened concrete usually result in lower compressive strength than anticipated. All Copyright by ASTM Int'l (all rights reserved). However. and moisture content at time of testing also have a bearing on the compressive strength [4]. a correction factor must be applied [3]. The method is not meant to be used as a comparison with laboratory cylinder tests. Cores are drilled only when results of the standard cylinder tests are questionable or when investigations are made of old structures. temperature. The purpose of cylinders made in the field may be to check the adequacy of the laboratory mix design. should be used. ASTM Making and Curing Concrete Test Specimens in the Field (C 31) describes the detailed method of making standard cylinders in the field. other factors. size of the aggregate. The accuracy by which the test is made is much less than a laboratory test ___3 percent but is considered appropriate. Making Specimens The compressive strength of concrete depends primarily on the water/ cement (w/c) ratio. size of the aggregate. conditions of mixing. curing and aging. to determine when a structure may be put in service. they should be made from the same concrete used on the job. This test is extremely useful where beam specimens are made to determine the modulus of rupture. curing and aging. such as character of the cement. the same curing process. temperature. No further reproductions authorized.148 TESTS AND PROPERTIES OF CONCRETE results of the compression test if great care is not taken in the manufacture of the specimen. or as closely as possible. The characterization of the cement for a given w/c ratio plays an important role in the early compressive strength development of concrete. conditions of mixing. ASTM Test for Compressive and Flexural Strength of Concrete Under Field Conditions (C 683) describes the methods by which concrete may be tested if made in the field. When the method is used and a correlation attempt is made. Finally. size and shape of the specimen. . Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as in highway construction. . The presence or absence of adherent dirt or clay. higher compressive strengths usually are obtained at a given w/c ratio with smaller maximum sizes of aggregates. Data from compression tests of concrete containing very large aggregates. Some cements gain their strength more rapidly at first. The time of mixing is governed by the ASTM Specification for Ready-Mixed Concrete (C 94). Tests have shown that the strength for a given w/c ratio show the greatest difference among cements at the early ages. The earliest studies in concrete showed increases in strengths with continued mixing. 6]. In the high strength range. and the type of mixer are all involved in fixing the period in which gain in strength with time of mixing is significant. but to some extent to different cements within a single group. as the maximum size of the aggregate is increased. the type and consistency of the concrete. the size and shape of the particles. Surface conditions. Also. therefore. whereas others show greater increase at later periods. are conflicting because of limitations in the size of specimens [9]. For 90 days and later the differences are much less [5. The size of the batch. In general. The importance of thorough mixing for the development of strength and for uniformity throughout the batch has long been recognized.). No further reproductions authorized. over 31 MPa (4500 psi). The ends of Copyright by ASTM Int'l (all rights reserved). greater strengths are obtained for a given cement content. These characteristics have a greater effect on flexural strength than on compressive strength [7] The shape of the particles influence the strength of the concrete by affecting the quality and the amount of paste that is required for workability with a given mixture. although the gain in strength with age is not always the same. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the bond with the cement paste may be weakened where relatively large surface areas of the flat pieces of aggregate occur. 10. and the gradation are the characteristics of the aggregate which are of principal concern to the strength of concrete. The principal effect of changing the aggregate grading is to change the amount of cement and water needed to make the mixture workable with the desired w/c ratio. . The surface conditions of the aggregate affect the adhesion of the cement paste to the aggregate particles. lower w/c ratios can be used for suitable workability and. considerable changes in grading will affect the strength of the concrete only to a small degree [8]. will not intersect the end bearings. This applies not only to the five types covered by ASTM specifications. Compression tests of concrete are conducted ordinarily on cylindrical specimens with height equal to twice the diameter so that surface rupture.DERUCHER ON STRENGTH 149 portland cements behave more or less similarly. the roughness. When the w/c ratio is the same and mixtures are plastic and workable. but the increase became slight after a first rapid rise. especially when they happen to be or combined in planes of shear and tension.16 cm (4 in. produced upon fracture. and the texture affect the adhesion. If the slump is between 2.24 by 30.62 cm (1 and 3 in. the strength of a cylinder 91.44 cm (36 in. The use of cardCopyright by ASTM Int'l (all rights reserved).54 and 7. to specify procedures for compacting.) in diameter have been used for concrete containing very large aggregates. a cylinder of poorly compacted concrete will have a lower strength than one that is compacted properly. .). Care must be exercised to vibrate only long enough to obtain proper consolidation. A reduction in the size of the specimen below that of the standard 15.12].) in diameter.08 cm (2 in.62 cm (3 in. the concrete may be either vibrated or rodded.48 cm (6 by 12 in. 50 if 20. However. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.88 cm (72 in. the specimens must be consolidated by vibration. Although the cardboard is paraffinned heavily. then the choice is determined by the slump.54 cm (1 in. A uniformly stressed cylinder which has been molded properly will break in the shape of a double cone with vertex in the center of the cylinder [I0]. Overvibration tends to cause segregation.24 by 30.) should be rodded. If the specifications under which the work is being performed do not state the method of consolidation.44 cm (36 in. in most cases it absorbs part of the water in the concrete mixture. cardboard molds are used quite often in the field.). The size of the cylinder itself affects the observed compressive strength. or vibrating the concrete in the mold.32 cm (8 in.) in diameter by 182.) cyclinder will yield a somewhat greater indicated compressive strength [13]. The ASTM Specification for Molds for Forming Concrete Test Cylinders Vertically (C 470) defines adequate paper molds as well as lightweight sheet steel molds. a larger mold may be used. Generally.) high may be only about 82 percent of that of a standard 15. Cylinder molds should be of nonabsorbent material and are generally of steel. in some cases molds as large as 91.24 by 30. Thus. No further reproductions authorized. rodding. If a mold having a diameter less than three times the maximum size of the aggregate is used.24 cm (3 to 6 in.40 cm (10 in.). Unless the specimens are molded carefully. Concrete with a slump greater than 7. it should be placed in the cylinder in three layers and rodded 25 strokes per layer if the cylinder is 7. and 75 if 25. the indicated compressive strength will be lowered. C 31 and C 192.). When the slump is less than 2.) cylinder.) cylinder is the standard for aggregate smaller than 5. the mold is filled and vibrated in two layers [14]. When the concrete is to be rodded. such as those used in dam construction. These methods are specified in order to permit reproducibility of results by different technicians [15].62 to 15. erratic and irregular results will be obtained.). When vibrating. It is accepted generally that the diameter of the specimen should be at least three times the nominal size of the coarse aggregate. it is necessary for the standards for making specimens.150 TESTS AND PROPERTIES OF CONCRETE the cylinders should be formed carefully to give parallel. the oversize aggregate may be removed by wet screening [1I . for example. smooth surfaces so as to obtain uniform distribution of stress. A 15. however.48 cm (6 by 12 in.48 cm (6 by 12 in. If the aggregate is too large for the size of mold available. and sulfur compounds [16-18]. and testing specimens of concrete stored under conditions intended to accelerate the development of strength are covered. The standard curing conditions require that the specimen be held at a temperature of 23 + 1. Concrete can gain in strength only as long as moisture is available and used for hydration. Slight irregularities can be made good by scraping if the capping material has not set too hard [19]. No further reproductions authorized. Capping procedures are standardized under ASTM Capping Cylindrical Concrete Specimens (C 617).4 + 3~ and in the "moist conditions" until the time of the test (ASTM Method C 192).002 in.) should be capped. according to ASTM Method C 617 the surface of the capping must not depart by more than 0. and Testing of Concrete Compression Test Specimens (C 684). All surfaces that depart from a plane by more than 0. According to ASTM Method C 617. The cap should be as thin as possible and the plane surface of the cap at either end of the specimen should be truly at right angles to the axis of the cylindrical specimen. and all caps should be checked for this by means of a feeler gage and steel straightedge. The choice of which procedure to use should be made by the user on the basis of his experience and local conCopyright by ASTM Int'l (all rights reserved). If neat portland cement is used for capping.) cube. gypsum plaster can be used for capping provided it has a strength of over 31 MPa (S000 psi) when tested as a 5. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. but care is necessary to avoid overheating the melted mixture to prevent loss of rigidity. curing. and reduction as great as 9 percent have been noted. it should be mixed about 3 h before use to minimize any harmful effect due to shrinkage.7~ (73.005 cm (0. Further.DERUCHER ON STRENGTH 151 board molds may lower the observed compressive strength on the average about 3 percent. A method of accelerated curing concrete is given by ASTM Making. The most common capping materials are neat portland cement paste. The term "curing" is used in reference to the maintenance of a favorable environment for the continuation of the chemical reactions which take place. . high-strength gypsum plaster. Suitable mixtures of sulfur (melted) and granular materials applied about 2 h prior to testing are recommended also. In this method.5 deg from perpendicularity with the axis of the cylinder or a cant of I in 96. mixes that are rich in cement generate considerable heat of hydration which may expel moisture from the concrete in the period immediately after setting. The capping procedure should be carried out at least 3 days before testing [20]. While simply retaining moisture within the concrete may be sufficient for low to moderate cement contents. It is through the early curing process that the internal structure of the concrete is built up to provide strength and water tightness.08 cm (2 in. Any variation from this procedure may produce a specimen having a different strength from that which would be produced under standard conditions. three procedures for making. Any material which is sufficiently strong and can be molded can be used for capping. Accelerated Curing. the more rapid the rate. The rate of loading has a definite effect on compressive strength. give higher strengths at 1 to 3 months [23]. The three procedures are: warm water. S. 1 min) and for hydraulic machines 138 to 345 kPa/s (20 to 50 psi/s). No further reproductions authorized.05 in. . For this reason. (b) one which minimizes loss of water by interposing an impermeable medium or by other means. boiJmg water. Test Procedure Once the specimen is made. and autogenous curing. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ASTM Test for Compressive Strength of Cylindrical Concrete Specimens (C 39).2~ (70~ lower temperatures at the time of casting and for a few hours thereafter. Two methods of field curing presently are used: (a) one which interposes a source of water. in the form of ponding. although the effect is usually fairly small over the ranges of speed used in ordinary testing. The rapid stiffening in the first few hours under the higher temperatures apparently is detrimental to the later development in strength. The chemical reactions proceed more rapidly at higher temperatures [22]. the method by which it is tested may further affect the strength obtained. Two of the more important influences are the rate of loading and the eccentricity of loading. Temperature also plays an important role in the curing process of concrete.1~ (40 to llS~ The U.152 TESTS AND PROPERTIES OF CONCRETE ditions. The effect of eccentric loading is obvious and the alignment of all machines should be checked.4 to 26. A t h i r d method of curing which is used in the manufacture of concrete products is the artificial application of heat while the concrete is maintained in a moist condition [21]. which applies also to testing of cores. Any eccentricity will tend to decrease the strength Copyright by ASTM Int'l (all rights reserved). concrete gains in strength with age. Cylinders to be used for quality control should be cured according to the standard conditions. the higher the indicated strength [24.11 c m / m i n (0. specified that the rate of loading for screw-powered machines shall be 0. or a wet material to prevent or counteract evaporation a n d . an increase in age provides for further chemical combinations if the conditions are favorable for continued reaction. The results of tests on concrete indicate that the relationship between strength and rate of loading is approximately logarithmic. Curing and aging cannot be separated. however. specimens cured at 21. A rapid rate of loading may indicate as much as a 20 percent increase in the apparent compressive strength. Tests of specimens sealed against loss of moisture show higher early strength but lower strengths at later ages as the temperature is increased in the range of 4. Bureau of Reclamation has found that for job control. cylinders made in the field and tested to measure the strength of the concrete in the structure should be cured in the same manner as the structure. Provided favorable conditions are met.25]. Compressive strength is a measure of the indirect effect of admixtures which may be beneficial for one purpose. The case of simple uniaxial tension rarely is encountered in strutCopyright by ASTM Int'l (all rights reserved). Significance of Results The results of a compression test are essentially only comparative as the value of the compressive strength obtained cannot be regarded as equal to the strength of the concrete deposited in the work. The reason for this is due to the factors affecting the mix which have already been discussed. it is important that the center of the spherical surface of this block be in the flat face that bears on the specimen. temperature changes. giving the specimen as even a distribution of initial load as possible. to ensure that a concentric and uniformly distributed load is applied to the specimen. modulus of elasticity. Owing to increased frictional resistance as the load builds up. shrinkage. a spherically seated bearing block is required on one end. The value will give only an indication of the quality of concrete. tensile strength. . This lack of knowledge regarding the relationship between the strengths of concrete in a cylinder and in a structure requires the use of a larger factor of safety than would otherwise be necessary. this approximation is very useful to the engineer. the amount of decrease being greater for low-strength than for high-strength concrete [26]. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.DERUCHER ON STRENGTH 153 of the specimen. and the specimen should be centered carefully on this bearing block. the spherically seated bearing cannot be relied upon to adjust itself to bending action that may occur during the test [27]. but detrimental to another property [29]. Only an approximation can be made of these properties. fire resistance. In order that the resultant of the forces applied to the end of the specimen should not be eccentric with the axis of the specimen. Compressive strength may be used as a qualitative measure of other properties of hardened concrete. The object of the block is to overcome the effect of a small lack of parallelism between the head of the machine and the end face of the specimen. or permeability [28]. Compressive tests further aid in the selection of ingredients that may be used in making concrete. It is desirable that the spherically seated bearing block be at the upper end of the specimen. No further reproductions authorized. No exact relationship exists between compressive strength and flexural strength. Tensile and Flexural Strength Significance of Tensile and Flexural Strength Flexural tension is developed most commonly in beams and slabs as the result of loads. Nevertheless. wear resistance. and in some cases moisture changes. and that the specimen itself be centered carefully with respect to the center of this spherical surface. Therefore. a relatively large specimen must be used if a measurable load is to be applied and a large number of specimens are required to ensure a reliable average. However. the plane on which fracture occurs is Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. As concrete which has to withstand tensile stresses normally is reinforced. Another procedure for obtaining an indication of tensile strength is given in ASTM Test for Splitting Tensile Strength of Cylindrical Concrete Specimens (C 496). = one-half the depth of the beam. It is difficult to apply the load truly axially and to grip the ends of the specimen without imposing high local stresses. While high compressive stresses occur at the lines where load is applied. The second method is intended for use with small specimens and not as an alternative to the test with third-point loading. The beam test for flexural tension and split cylinder test are the simplest procedures for determining the tensile strength and are the tests usually performed. The tensile strength develops more quickly than the compressive strength and is usually about one-tenth the compressive strength at ages up to about 14 days. The results of the flexural tests are expressed by the formula R -= M c / I where in consistent units R M c I = modulus of rupture. and ---. significant principal tension stresses may be associated with multiaxial states of stress in walls. Cracking of concrete is usually a tensile failure and this alone makes the tensile strength of concrete quite important. or deep beams. Specimens It is not easy to perform an axial tension test on concrete. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In this test a standard cylinder is loaded in compression on its side. although it is of great importance in determining the ability of concrete to resist cracking due to shrinkage on drying and thermal movements. Flexural tension tests may be made in several ways. falling to about 5 percent at later ages.154 TESTS AND PROPERTIES OF CONCRETE tures or members and can be obtained in laboratory tests only with care. the most common being ASTM Test for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) (C 78). shells. ASTM Test for Flexural Strength of Concrete (Using Simple Beam with Center-Point Loading) (C 293) also is used to a limited extent. Fracture occurs along the plane which includes both lines through which the load is applied. .moment of inertia of the cross section. its tensile strength has not received much attention. = maximum bending moment. No further reproductions authorized.). settlement of the supports.) longer than three times its depth and that its width should be not more than one and one-half times its depth. 31]. A typical speciman used would be 15.). maximum applied load. (5) the arrangement of parts should be stable under load. (3) there should be provision for longitudinal adjustment of the position of the supports so that longitudinal restraint will not be developed as loading progresses. ASTM Method C 31 stipulates that the length of the beam should be at least 5. The splitting strength is calculated as follows T = 2P/Trld where in consistent units T P l d = = = = splitting tensile strength.08 cm (2 in. . length. Many of the parameters which affect the compressive strength of concrete also apply to the flexural strength as well. and deformation of the supportCopyright by ASTM Int'l (all rights reserved).24 by 15. Making Specimens ASTM Methods C 192 and C 31 describe the procedures for making flexural specimens and also cylinders for the splitting tensile strength test in the laboratory and in the field. The minimum depth or width should be at least three times the maximum size of aggregate.72 cm (18 in.24 by 53. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Apparatus for measuring deflection should be so designed that crushing at the supports. (4) there should be provision for some lateral rotational adjustment to accommodate beams having a slight twist from end to end. The principal requirements of the supporting and loading blocks of the apparatus for the flexural strength of concrete are as follows: (1) they should be of such shape that they permit use of a definite and known length of span. Test Procedure Flexural strength measurements are extremely sensitive to all aspects of specimen preparation and testing procedure [32].34 cm (6 by 6 by 21 in. As the depth of the beam is increased. and is tested under third-point loading on a span of 45.DERUCHER ON STRENGTH 155 subjected largely to a uniform tensile stress. there is a decrease in the modulus of rupture [30. so that torsional stresses will not be induced. (2) the areas of contact with the material under test should be such that unduly high stress concentrations (which may cause localized crushing around bearing areas) do not occur. and diameter. since the concrete is not homogeneous. As the temperature increases. The supporting and loading blocks should be located with a reasonable degree of accuracy (0.156 TESTS AND PROPERTIES OF CONCRETE ing and loading blocks or of parts of the machine do not introduce serious errors into the results. A beam that has been allowed to dry before testing will yield lower flexural strength than those tested in a saturated condition. in tests to determine or control the quality of concrete. When such beams are used primarily as a control of concrete quality. The dimensions of the concrete specimen should be measured to the nearest 0. One method of avoiding these sources of errors is to measure deflections with reference to points on the neutral axis above the supports.025 cm (0. the strength decreases [37]. the variation being as much as 15 percent for the range of rates that may be obtained in the average laboratory [34]. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . Tests indicate the following order of decreasing magnitude of the strength obtained: (1) center loading. after which loads should be applied at a rate such that the extreme fibers are stressed at 0. The rate of load application. No further reproductions authorized.). uniformity of results will be assured only if the beams are cured in a standard manner and tested while wet. with moment computed at center. this is determined from the load at rupture and the dimensions of the specimen. Consequently. this loading method seeks the weakest section. ASTM Test C 78 is also prescribed for tests of beams sawed from hardened concrete. Deflectometers and strainometers should be located carefully and checked to see that they operate satisfactorily and are set to operate over the range required [33].93 MPa (150 psi) or less per minute. Ordinarily only the modulus of rupture is required. may cause considerable variation in the results of flexure tests. The conduct of routine flexure tests is usually simple. (2) center loading. Third-point loading probably gives lower strengths because the maximum moment is distributed over a greater length of the beam. they should be turned on their sides before testing and will Copyright by ASTM Int'l (all rights reserved).01 in. The temperature of a beam at the time of testing will also affect the resuits. Concrete beams may be loaded rapidly at any desired rate up to 50 percent of the breaking load. Third-point loading invariably gives lower strengths than center-point loading. and (3) thirdpoint loading [35]. The assembly of supports and specimens should be placed centrally in the testing machine and should be checked to see that they are in proper alignment and can function as intended. unless standardized. with moment computed at point of fracture. a series of load-deflection observations are made. Beams may be tested under either center-point or third-point loading.2 percent of the span length). When the modulus of elasticity is required. Curing effects the tensile strength in much the same manner as it affects the compressive strength [36]. The splitting tension test has been used to evaluate bond splitting resistance of concrete. The design procedure would be exactly the same except that the tables would have to be prepared on a basis of fiexural strength instead of compressive strength. The results of the test on these specimens given an indication when the concrete has gained sufficient strength that load may be applied or the forms removed. under certain conditions. The splitting tensile strength is the easiest to perform l~nd gives the more uniform results.DERUCHER ON STRENGTH 157 usually require capping because of the irregularity of the sawed surface (sides are not plane and parallel). Shearing and Torsional Strength Significance of Shearing Strength The shearing strength of concrete is a most important property of the material since it is the real determining factor in the compressive strength of short columns. The strength of concrete beams depends also.32 cm (1/8 in. The load should be applied such that the stress increases between 689 and 1379 kPa/min (100 and 200 psi/min. Many agencies which are involved in pavements only make flexural specimens. However. The tensile strength from the splitting tests is about one and one-half times greater than obtained in a direct tension test and about two thirds of the modulus of rupture [39]. . The effectiveness with which the material in the bearing strips is able to conform to the irregularities of the specimen surface and distribute the load affects the results.8 of the compressive strength for lean mixtures [40].5 of the compressive strength for rich mixtures to about 0.) thick plywood shall be used for bearing strips. Copyright by ASTM Int'l (all rights reserved). Care must be taken to apply the load through a diametrical plane.) Significance of Results In the case of pavement construction it appears that the flexural strength of concrete is equally important (or more so) as the compressive strength. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. With increased emphasis on control of cracking in reinforced concrete an appreciation of the tensile strength has become more important. The average strength of concrete in direct shear varies from about 0. It has been suggested that pavements be designed on the basis of flexural strength [38]. No further reproductions authorized. For uniformity ASTM Test C 496 specifies that 0. The test for splitting tensile strength described in ASTM Test C 496 is simple to make. upon the shearing strength of the material. the three general methods of estimating tensile strength give slightly different results. 158 TESTS AND PROPERTIES OF CONCRETE Torsion The application of torsion alone to a concrete specimen produces pure shearing stresses on certain planes. shear. Results of Tests There is no universally accepted criteria of failure of concrete.. and axial load. unconfined compressive strength. ASTM Recommended Practice for Determining Mechanical Properties of Hardened Concrete Under Triaxial Loads (C 801) is useful in determining the strength and deformation characteristics of concrete such as shear strength at various lateral pressures.f ~ ' = K ( f 3 ) o where in consistent units jq = = f~ = K. ASTM Recommended Practice C 801 allows four ways in which the data may be presented: (1) graphical plots of the following equations fl =fi' +K(f3)" or. tensile. Just as nearly all structural members are acted upon by various combinations of moments. Combined Stresses Significance of Combined Stresses Concrete in structures is almost never subjected to a single type of stress. Prior to the application of this relatively new standard extensive research was conducted on cylinders with combinations of axial tension and lateral compression. angle of shearing resistance. and torsion and axial compression [41. Therefore. for the strength increase beyond the uniaxial strength f~ . . the case of pure shear acting on a plane is seldom if ever encountered in actual structures. Further. a = largest principal stress. deformation modulus. and shearing stresses. the concrete in them is usually subjected to some combination of compressive. the strength of concrete subjected to torsion is related to its tensile strength rather than to its shearing strength. there is no single correct way of discussing the behavior of concrete under combined stresses and many ways in presenting the results. and creep behavior. hence. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Copyright by ASTM Int'l (all rights reserved). and empirical coefficients. However.42]. No further reproductions authorized. smallest principal stress. failure under these conditions will occur in tension rather than shear. strength in pure shear. The fatigue strength in axial compression is about 55 percent of the static compressive strength. No additional gain is obtained for longer rest periods [48]. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. His minimum stress was 5 percent of the ultimate and the maximum or critical stress ranged from 47 to 60 percent of the ultimate. The value of the minimum principal stress should be indicated on the curve. Failure under repeated loads is especially important in pavement design.4 MPa (2000 psi). Tests to determine the fatigue strength of concrete should be made on specimens as large as possible in order to decrease the influence of lack of homogeneity. (4) Mohr stress circles constructed on an arithmetic plot with shear stresses as ordinates and normal stresses as abscissas. Thus. the specimens generally are aged and air dried before being tested in order to prevent gain of strength during the test. Fatigue Strength Concrete will.DERUCHER ON STRENGTH 159 (2) A graphical plot of the stress difference versus axial strain. No data are available to establish the fatigue strength in axial tension. Copyright by ASTM Int'l (all rights reserved). Because of the time involved. The fatigue strength increases as the rest periods are increased in duration to 5 min. His results nevertheless agree with more recent work conducted on concretes of much higher strength [45-47]. (3) A graphical plot of axial stress versus axial strain for different confining pressures. . Stress difference is defined as the maximum principal axial stress minus the minimum principal stress. At least three triaxial compression tests. Frequent rest periods during a fatigue test may raise the fatigue strength as much as 9 percent higher than if there had been no rest periods. each at a different confining pressure. when subjected to repeated load. and even larger dimensions might be desirable in some cases. it takes a minimum of two weeks to several months to apply as many as ten million cycles of load. Concrete does not have a fatigue or endurance limit at least at less than ten million cycles of load as most bodycentered cubic metal does. No further reproductions authorized. in shear. Because of the large size of specimens used. Early work on fatigue was conducted on low strength concrete [43]. should be made on the same material to define the envelope to the Mohr stress circle. fail at a load smaller than its static ultimate strength. The cross section of the specimen should be at least three times the maximum nominal size of the aggregate. Further tests have shown the fatigue strength at ten million cycles is about 55 percent of the static flexural strength. the large testing machines required are usually capable of applying load at a rate ranging from only a few cycles a day to 500 cpm. He discovered that there was a critical stress below which concrete subjected to repeated loading increased in strength and elasticity. or under combined stresses. Thus in the early classic work of Probst [44] the strength of the concrete tested was only just over 12. [6] Keil. 1966. Hayward. Vol. Wiley. Mariemont. [12] "Effect of Wet-Screening to Remove Large Size Aggregate Particles on the Strength of the Concrete. [22] Klieger. Vol. "Investigations of Internal Vibration of Concrete." Proceedings. American Concrete Institute. New York. Feb. American Society for Testing and Materials. [23] "Curing Concrete Specimens.. [18] Werner. H.. C. American Society for Testing and Materials. H. D. Vol. 1941.. 54. American Society for Testing and Materials.. 1966. Vol. Civil Engineering and Building Construction Series No.. F. [5] Lea.. "Strength of Hardened Concrete. 41. 1973. [8] Neville. "Effect of End Condition of Cylinder in Compression Tests of Concrete. [10] Kesler. p. Vol. Paul." Corps of Engineers. [11] McMillan." Proceedings. 1216. p. Concrete Technology. 729. 1958. S. p. 30. 30. "The Effect of Type of Capping Material on the Compressive Strength of Concrete Cylinders. H. 1954. F." Proceedings. Ohio. Sept. 1959.." Journal of the Institute of Civil Engineers. [24] Watstein. Copyright by ASTM Int'l (all rights reserved)." Acta Polytechnia Scandinavia. 3. 1930. No. New York. T. 1946. 1166." Proceedings. p. E. 1965. M. [15] Tuthill. ASTM STP 169A. American Society for Testing and Materials.. "Modern Developments in Cement in Relation to Concrete Practice. Wiley. Vol. Vol. Ohio River Division Laboratories. American Society for Testing and Materials. Vol. Vol.. 59.. New York. p. Special Report 16. 1952. 41. 1958. Vol." U. Bureau of Reclamation.. 1945. B. G. 802.. "Effect of Type of Test Specimen on Apparent Compressive Strength of Concrete. Vol. H. [20] "Methods of End Conditions Before Capping Upon the Compressive Strength of Concrete Test Cylinders. F. 1943.S. Jan. 58. Stockholm. [14] Forssblad. W. P. Materials of Construction." Proceedings. D. R. "Curing Temperature. July. American Society for Testing and Materials. C. E. [3] Mather." Proceedings. "Effect of Mixing and Curing Temperature on Concrete Strength." Proceedings. L. June 1958.. 1924. 1036. 1953. Part I. M. 29." Significance of Tests and Properties of Concrete and Concrete Making Materials. "Cements. Wiley. p. Age and Strength of Concrete. A. No further reproductions authorized." Third International Symposium on the Chemistry of Cement. A. p. [13] Kesler." Report of the Bureau of Public Roads presented to the SixtyFirst Annual Meeting of the American Society for Testing and Materials. L. New York. 117. 521. [7] Krebs." Construction Review. and Rader. R." Proceedings. 521. "Effect of Length to Diameter Ratio on Compressive Strength--An ASTM Co-operative Investigation. 1963.. E. 20.. "Over-Vibration and Re-Vibration of Concrete. Vol." Proceedings. "The Effect of Type of Capping Material on the Compressive Strength of Concrete Cylinders. American Society for Testing and Materials. American Society for Testing and Materials. 1216. [9] McMillan. "Suggested Procedure for Testing Concrete in Which the Aggregate is More Than One-Fourth the Diameter of the Cylinders. American Society for Testing and Materials. 27. "Effect of Straining Rate on the Compressive Strength and Elastic Properties of Concrete. . F. F. D. 45.. [4] Mills. F. London. American Concrete Institute. F. 1953. [21] Bergstrom. 1944. George. 49. "Suggested Procedure for Testing Concrete in Which the Aggregate is More Than One-Fourth the Diameter of the Cylinders. Highway Materials. 1954." Proceedings. Vol. C. R. "Effect of Length to Diameter Ratio on Compressive Strength--An ASTM Cooperative Investigation. George." lndian Concrete Journal. R. Part II. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1959. Part I." Proceedings.. [16] Kennedy.160 TESTS AND PROPERTIES OF CONCRETE References [1] Kesler. p. p. [19] Gonnerman. p. Bryant.. 1038. 59. 1063. [17] Werner. E. American Concrete Institute. D. Properties of Concrete. [2] Orchard.. McGraw Hill. 24. 1930. "A Limited Investigation of Capping Materials for Concrete Test Specimens. p. and Davis. and Walker. L. 1955. "Research of Fatigue Strength. [34] Talbot. F. 1931. "A Study of the Failure of Concrete Under Combined Compressive Stresses. 1964. [45} Nordly. [32] Walker. American Society for Testing and Materials. [37] Waters. "Comments on an Indirect Tensile Test on Concrete Cylinders.. p. p. 9. W. May 1954. L. 45.. [31] Nielson. 11.. . L. 63. E. 1906. New York. "Effect of Size of Specimen. Jan. Vol. F. "Part 3: Effects of Variations in Testing Procedures. p. II.. Jan. "Effect of Speed in Mechanical Testing of Concrete. [27] Shank. 105. "A Critical Review of Research on Fatigue of Plain Concrete. [46] Murdock." Proceedings." The Structural Engineer. "The Strength of Concrete. McGraw-Hill. [26] Davis. "The Effect of Allowing Concrete to Dry Before It Has Fully Cured. Copyright by ASTM Int'l (all rights reserved).. J. "Fatigue of Concrete--A Review of Research. No. No. 185. Oct. 30. Vol. American Society for Testing and Materials." Proceedings. E. University of Illinois." Public Roads. 54. and Brown. Engineering Experiment Station. H.. XIII." Magazine of Concrete Research. 1930. 1917. Part 1. Engineering Experiment Station. 8. [29] Nash. "The Effect of the Method of Test on the Flexural Strength of Concrete. 1957. [41] Richart. R. Vol. 221. 7. Shear. 1954. F. "Tests of Concrete: I.. [28] Kesler. p. Seattle." Magazine of Concrete Research. 57. "Factors Influencing Concrete Strength. V.. J. July 1955.. The Testing and Inspection of Engineering Materials. Vol.. American Concrete Institute. C. T. Urbana." Part 2: "Effects of Curing and Moisture Distribution. D. Vol. Ill. Ill. F. and Method of Loading Upon the Uniformity of Flexural Strength Tests. J. "Apparatus for Flexural Tests of Concrete Beams. E... 177. p. and Richart. Ill. p. "Statistical Relation Between Cylinder Modified Cube. "The Influence of Rapidly Alternating Loading on Concrete and Reinforced Concrete." Report of ASTM Committee C-9 on Concrete and Concrete Aggregates. and Garwood. G.. and Wiskocil.. 1941. E. E. 31. March 1954. Part If. 106. B. No. Troxell. American Society for Testing and Materials. 1. London. Sun Apr 6 21:41:42 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vol. p. [48] LeCamus. "Studies of Flexural Strength of Concrete. 12. A. 1959.. 1923. 10. J. 36. W. and Kesler. Vol. E. 1955. p. T. 17. F. J. "Effect of Various Factors on the Flexural Strength of Concrete Test Beams." Proceedings. Urbana." Bulletin No. 55. and Beam Strength of Plain Concrete. [38] Wright. [40] Talbot. Vol. E." Proceedings. 15. F. J. American Society for Testing and Materials. [42] Smith.. W. 47. "Effect of Range of Stress on Fatigue Strength of Plain Concrete Beams." Bulletin No. Proceedings." Speed of Testing of Nonmetallic Materials. "Plastic Flow of Concrete at High Overload. 1965.. Brandizaeg. Wash. Vol. No.. "Tests of Concrete Road Aggregates. R. Vol. Vol. G. American Society for Testing and Materials. 1931 and No. Stanton and Bloem. University of Illinois. J: F. 191. P." Magazine of Concrete Research. Highway Research Board. 137. March 1942. 1966. C. Urbana. C. University of Illinois. 591. 975. [47] Murdock. 1955. Q.. "The Shearing Strength of Cement Mortar.. 15." Proceedings.. Ill. American Concrete Institute.. 1122. University of Illinois. American Concrete Institute.. T. Vol. Appendix VIII. 493. A.. H. 55.. J. W. Engineering Experiment Station. 1928. E. p. University of Washington. No. p. 1959. 1178. Engineering Experiment Station. 417.DERUCHER ON STRENGTH 161 [25] Shideler. 334." Journal. No further reproductions authorized. Cement and Concrete Association. A. 1957. C." Proceedings." Bulletin No. and McHenry.." Proceedings. E. Vol. [33] Goldbeck. N. ASTM STP 185. No. 1933. 105. M.. Size of Aggregate.. Engineering Experiment Station.. Urbana. K. [30] Wright.. [43] Probst. [39] Wright.. P. [36] Price. No. C. 87. Bond. 1951. 20. P." Bulletin No. "Further Investigations of Alternating Loads on Concrete. D. American Concrete Institute. 1949. p. Dec. [44] Probst." Bulletin No. p. 20." Proceeding of a Symposium on Mix Design and Qualtiy Control of Concrete. R." Proceedings." Cement and Concrete Research. p." Magazine of Concrete Research. [35] Kellerman. American Concrete Institute. A. N. "The Design of Concrete Mixes on the Basis of Flexural Strength. 394. P. Vol. March 1954. and Brown. F. 09 on Accelerated Strength Testing in 1964 to canvass the needs of the concrete industry and to study the suitability of several procedures being developed by King [I.) cylinders of concrete as delivered to the job site in order to determine quality. This situation is considered by many to be too precarious for construction to proceed on a sound technical basis and with adequate assurance of safety. Further delay is certain if concrete must be reinforced or replaced. A positive response to this canvass led to a cooperative test program among nine laboratories to evaluate three procedures involving the use of either hot 1Supervisor.2] 2 and Akroyd [3] in Great Britain and Smith and Chojnacki [4l and Malhotra and Zoldners [5] in Canada for possible standardization.Md.02. No further reproductions authorized. Cement Technical Center. During the 28-day period. Concrete and Aggregate Department. 21227.astm. Martin Marietta Cement. Currently. 1978 M . thus setting the stage for a catastrophic collision between advancing construction technology and the price owners are willing to pay for their capital facilities. Committee C-9 on Concrete and Concrete Aggregates of the American Society for Testing and Materials (ASTM) formed Subcommittee C09. the later age is still specified for compression tests of 152 by 304-mm (6 by 12-in. Surely. extensive and costly delays are encountered when 28-day test results are low. Baltimore. Copyright by ASTM Int'l (all rights reserved). 2Theitalic numbers in brackets refer to the list of referencesappendedto this paper. economics dictate that work continue without knowing quality.org . H. it is not unusual for a multistory building to rise several floors before the strength tests are conducted. Sun Apr 6 21:41:43 EDT 2014 162 Downloaded/printed by Universidade do Gois pursuant Agreement. since a field investigation may be necessary to verify the load-carrying capacity of the structure. Wills ~ Chapter 13--Accelerated Strength Tests Introduction Rapid construction practices throughout the concrete industry have brought increasing pressure on specifying agencies to assess the quality of concrete at an earlier age than 7 or 28 days after placement. Furthermore. Conversely. an earlier assessment of concrete quality is absolutely essential. Copyright9 1978tobyLicense ASTM lntcrnational www.STP169B-EB/Dec. molded cylinders immersed 15 h.5 h. Procedure B--Modified Boiling At 23-h age. 57 size (1 in. Cement contents were 265. Experimental Program Each of the procedures was conducted with two types of cement: Type I. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 35~ (95~ Cylinders immediately put in 35 ~ water for 24 h. and tested according to standard methods of ASTM. it was necessary to curtail some Copyright by ASTM Int'l (all rights reserved). Procedure C--Fixed Set Followed by Boiling At final Proctor set. and 385 k g / m 3 (450. general purpose (or Type II meeting Type I specifications) and Type III.0 to 6. Despite the plans of the subcommittee. Procedure G--Fixed Set Followed by Hot Water. molded cylinders boiled 15 h. They were used in combination with sufficient air-entraining admixture and mixing water to produce an air content from 5. molded cylinders immersed 15 h. Four additional procedures were considered. 550. place in insulated container for 46 h. high early strength. 90~ (195~ At initial Proctor set.0 in. molded cylinders boiled 3.0 to 3. 4). or 25.).WILLS ON ACCELERATED STRENGTH TESTING 163 or boiling water to accelerate the strength development of concrete. Additionally. All materials conformed to appropriate ASTM specifications. Concretes were mixed without a retarder and with a normal dosage of a water-reducing retarder. Procedure E--Fixed Set Followed by Hot Water. No further reproductions authorized. 55~ (130~ At initial Proctor set. One of these employed autogenous curing in an insulated container wherein the heat of hydration of the cement caused the acceleration. Fine and coarse aggregates were graded to a No. 325. molded cylinders immersed 15 h.0 percent and slump from 51 to 76 mm (2. In all cases. also. and 650 lb/yd3). they had the option of conducting one or more of the following procedures: Procedure D--Autogenous Curing At 1-h age. Test Procedures The nine participating laboratories were to conduct each of the following procedures: Procedure A--Hot Water. .4 mm to No. 75 ~ (I 75 ~ At initial Proctor set. compressive strength was measured at 1 or 2 days of age and was compared to strengths developed under standard curing conditions at ages of 28 days and 364 days. cured. All specimens were prepared. Each laboratory used materials available in their locality without interchange between laboratories. Procedure F--Fixed Set Followed by Hot Water. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the container was not opened. involving the measurement of final Proctor set followed by boiling. in turn. Copyright by ASTM Int'l (all rights reserved). Foremost. Procedure A--Hot Water. Once curing was initiated.CYLINDERSNN ' 5] 51 :: ] 5 ~ m m 5~L ]02ram mm mm 311El METAL PLATE lO00 WATT HEATING ELEMENT THERMOSTAT FIG. The tops of the cylinders were covered by about 102 mm (4 in. Procedure C. Details of the autogenous curing container are shown in Fig. 1. F. Polyurethane foam was used to retain the heat of hydration of the cement which. 1--Hot or boiling water accelerated curing tank. No further reproductions authorized. Specimens were not placed in a tank already containing those being cured. 2. required too many overtime man-hours to conduct and was abandoned. Finally.) of water. only four of the nine participating laboratories conducted Procedure D. 35 ~ (95 ~ Immediately after casting. Consequently. Accelerated Curing Apparatus The six accelerated procedures involving the use of either hot or boiling water were conducted in a thermostatically controlled tank. which was optional. all laboratories conducted the remaining aspects of the program for Procedure A (Hot Water) and Procedure B (Modified Boiling). the tightly closed cylinder molds were immersed INSULATED rATER TANK l _ WAT_EE LE_V_EL__ WATER LEVEL f. . However. Procedures E. Water volume and heater capacity were sized to prevent an appreciable reduction in the water temperature desired.164 TESTS AND PROPERTIES OF CONCRETE aspects of the experimental program. and G were not conducted since they also required measurement of setting time and overtime. as shown in Fig. accelerated the strength development of the concrete. J \ FT') THERMOMETER~ ~ OUTERCONTAINER ]~ / PLASTICGARBAGE IL/ "~/ ~ / i/ / 1 / STEEL COVERPLATE ~E k.O..~.2--Autogenous curing container. _ ~ =B ISALMOSTNOAIRSPACE / BETWEENCYLINDERAND . 3 and 4 for concretes made with Type I cement. but it appeared that each laboratory was obtaining significantly different results. . Procedure A can be used with a high degree of confidence in assessing concrete quality when the tests are made by the same laboratory. accelerated strength did seem to relate to 28 and 364-day strength equally and with good correlation within a given laboratory. ~BT H E R V" ~ . Sulfur mortar caps were applied to the cylinders and aged at least I h prior to measuring compressive strength at an age of 26 h + 15 min. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Obviously. however. .12) SECTION A-A LID FILLEDWITH POLYURETHANE RECESSIN LID ~ 381turn FOR MAX. in 33 to 37~ (92 to 98~ water.WILLS ON ACCELERATED STRENGTH TESTING C O N C R E T E ~ CYLINDER 165 INNERCONTAINER-SHEETMETAL 162mm iNSIDE die. Therefore.~ POLYURETHANEINSULATION FOAMEDIN PLACE ( k _. The relationships were at a higher strength level. Since the test procedures were carefully controlled. Although not shown. where they remained for a period of 24 h _ 15 rain.O.1 to 1. 28-day. and 364-day data are shown in Figs. The hot water procedure accelerated concrete strengths from 1.-MIN. they emphasized the impact of materials on the results. the same general trends were observed with concretes made with Type III cement. particularly the type of cement. No further reproductions authorized. Graphical comparisons between accelerated. B E L~( _ _ . Copyright by ASTM Int'l (all rights reserved).6 times those achieved after a day of standard moist curing. as accelerated strength increased both 28 and 364-day values also increased./ E ___ E E r >/WLK O. Indeed.~LE 318rnm =[ SECTION B-B FIG.NSULAT. 5 4. At 23 h _ 15 min from the time of casting. ] ] i (2) ACCELERATED 40 50 20 LAB. Reduction in water temperature was limited to 3 ~ (5 ~ and was required to recover to the boiling point in no more than 15 min. No further reproductions authorized. Trends discussed previously are reemphaCopyright by ASTM Int'l (all rights reserved).15 min. ] _> Go Go nn 0 (J >(:3 ~o (6) (41 / 50 40 30 20 LAB. the sealed molds were placed in a standard moist room. (2) (4. After 3. NO. 6 (61 LAB. NO.5 h _ 5 min. NO. 3--Relation of accelerated to 28-day strength acceleration by immersion in 35~ (95~ water.-c~ Z b.I n. at which time.1 times that measured after a day of standard moist curing. including molds and covers. 8 / 50 / (41 LAB. NO. the cylinders. cylinders were removed from the molds and allowed to cool for about 45 min. their age was between 28. 9 LAB. 4 // LAB. Results for concrete cured by modified boiling are shown graphically in Figs. . 5 / / "1- t. NO. ]2 i (0) STRENGTH. were immersed in boiling water. ]0 (19) (0) LAB. Modified boiling accelerated concrete strength between 1. NO. NO.1 to 2. NO. NO. 5 and 6 for Type III cement.I-u~ LAB.166 TESTS AND PROPERTIES OF CONCRETE ) (8000} PROCEDURE A I0 20 0 HOT WATE'R / / / (6) (4) 10 TYPE'I CEMENT 50 40 30 20 LAB.000) MPo (psi) FIG. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. They were capped with sulfur mortar at least 1 h before strength was measured. Procedure B--Modified Boiling After casting the cylinders. accelerated comCopyright by ASTM Int'l (all rights reserved). Procedure C--Fixed Set Followed by Boiling Although the fixed set-boiling procedure was abandoned by the subcommittee during the course of the cooperative test program. 4 LAB. MPo (psi) (40001 FIG. Most important was that the laboratories still obtained what seemed to be significantly different results. The procedure's main disadvantage was overtime man-hours. 5O 3O 20 LAB./. NO. 9 5O 3O (4: PROCEDURE A HOT WATER LAB. On the plus side. (4) lO 20 ! i STRENGTH 0 / / ]o ] TESTING 167 20 i ~ 50 40 3O 20 s (z) I. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 5 / -/ / / // LAB. (8000: i (6) 20 0 I ~.-CD z (6) (. good correlations of accelerated strength to 28 and 364-day values were obtained. NO. 12 I (2) (0) (2) ACCELERATED STRENGTH.=I o 4.D (67 to LAB. particularly with the retarded concrete. I LAB. NO. within a given laboratory. Procedure B was also seen to have equal merit in assessing concrete quality. 6 LAB.. No further reproductions authorized. l l (0) TYPE TCEMENT z o LAB. . ~E oL ) (2) >- . sized. NO. However. Therefore.'3 ~ (4) (E 0.WILLS ON ACCELERATED I0 /. 4--Relation of accelerated to 36d-day strength acceleration by immersion in 35~ (95~ water... NO. lO (2{'0) I (2) LAB. Again. NO. NO.'. NO. NO. 8 / ' . this is attributed to each using locally available aggregate and cement. six laboratories did conduct it. 168 TESTS A N D PROPERTIES 20 .o :30 (4) PROCEDURE B (2) {2) FIG. 6 (2 a ~b ('4 (6) -/ LAB. NO. ] l i 20 LAB. NO.1 times the concrete strength measured after a day of standard moist curing. (8000) 30 . / oo 30 ~.6 to 2. 5 50 . 12 I (4) (2) (4) (2) (4) ACCELERATED STRENGTH. Procedure D--Autogenous Curing One hour after mixing. MPo (psi) (6000) S--Relation of accelerated to 28-day strength acceleration by boiling for 3. NO. and C--and ranged from 1. 1 (2'.5 h. It still appeared that differences between laboratories were significant but that within a given laboratory. B. . NO. 4 / LAB. No further reproductions authorized. pressive strengths obtained were the highest among the three procedures-A. This served to build confidence in the basic premise that the accelerated strength test could be used on a par with the standard. IO i MODIFIED BOILINC TYPETn"CEMENT LAB. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. NO. They remained Copyright by ASTM Int'l (all rights reserved). 28-day strength assessment of concrete quality. molded cylinders were sealed in plastic bags and placed inside the autogenous (insulated curing) chamber. NO. (4) no 2O 2~ :ff LAB. 8 / L A B NO. 9 50 . correlation with later age strength was quite good. LAB. I-z o~ (61 >_ m o') W 141 / LAB. 40 OF C O N C R E T E I/o I 20 50 / (6) 40 20 i 30 40 50 f. NO.o 3O 20 0 LAB.. NO. MPo (psi) (6000) FIG. 0(. ]2 I i (2) (4) (2) (4) (4) ACCELERATED STRENGTH..G) u. NO. Only four laboratories performed this procedure but their data were sufficient to justify including autogenous curing in the ASTM standard as were Procedures A and B. 40 / (61 169 LAB. Sulfur mortar caps were applied and aged at least 1 h before strength was measured at an age of 49 h _+ 15 rain. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.9 Z uJ n. which is beneficial to early hydration reactions. 6--Relation of accelerated to 364-day strength acceleration by boiling for 3.. after which they were removed from the molds and allowed to cool for 45 min. Considering that high concrete temperatures are detrimental to the early hydration reactions of cement. NO. NO. 1 :I:" (21 (. 8 LAB.5 times those obtained after an equal length of standard moist curing--the highest level of acceleration measured.. No further reproductions authorized. Accelerated 2-day strengths ranged from 1.J > o9 o3 uJ (6) / I / 40 30 20 LAB. Concrete quality can be assessed with a high degree of confidence using this procedure Copyright by ASTM Int'l (all rights reserved). ] l LAB. 20 LAB. there for 46 h. 9 50 t .. NO. NO.4 to 2. (4) g_ LAB.WILLS ON ACCELERATED STRENGTH TESTING 2o (8000 30 40 20 30 40 20 30 ! ! I i I ~... 6 ' (2) LAB.5 h.. With this procedure.< t-. lO i 40 $0 MODIFIED BOILING TYPE ]IT CEMENT. NO. NO. . 5 0 50 40 30 (4) 20 13.) >. Procedure D should be most conducive to producing the highest accelerated strengths.o ro (6) - / / (4) PROCEDURE B (2) (2) LAB. the heat of hydration of the cement causes the acceleration but at a low rate of temperature increase. NO. I.. 54 15.96 2.320 0.76 (285) (400) 5 I III 15.905 0.725 2.31 9.770 0.90 2.910 0.93 2.59 (125) (280) (420) (335) (535) (230) 10 I III 19.905 0. MPa B0.090 0. Cement Type B0.28 (235) (185) 11 I III 14.13 24. test procedures. and D. the regression equation for Laboratory 10 using Procedure B and Type I cement was Y -----19.955 0.27 17.440 0.48 (2055) (2075) (1320) (2240) (2365) (3405) 1.31 23.62 (410) (525) 12 I III 17.925 1.10 15.960 0. compared to 1 day with the other procedures.07 (270) (155) 6 I III I III I III 14.935 0. MPa SE. Least squares fits. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.515 1.20 (2775) (3510) 1.985 0. The statistical model involved the assumption of separate regression equations for each cement type in the form of Y = B0 + B~X) where B0 was the intercept coefficient and B1 was the slope coefficient.870 0.65 (1965) (2270) 1.96 2.86 1.120 0.65 15.170 TESTS AND PROPERTIES OF CONCRETE since 28-day strength levels will be approached closely at 2-days age. and standard errors are summarized in Tables 1 through 4 for Procedures A.195X1) (6895 • 10 -6) psi TABLE 1--Linear regression analysis for Procedure A. Simple Linear Regression a Lab No.10 0. Significance of Test Procedures Being convinced that laboratories.960 0.86 (305) (125) 4 I III 19.65 (2560) (2270) 1.17 14.86 1.095 0. Based on their analysis. (psi) 1 I III 13. the terms of which are defined in the text.375 0.290 1.83 3.975 2. the subcommittee analyzed the data from that viewpoint [6-8].980 1.96 (2770) (2750) 1.765 0.34 13.69 1.62 1.31 3.580 0.475 1. C.195X1MPa = (19. .540 0.48 + 1. No further reproductions authorized.525 1.86 (2215) (2590) 1.76 (2080) (1995) 1.10 18.915 0. and cement types had significantly different effects on the data.44 16.07 (285) (300) 8 9 aAccording to the model Y = Bo + BIX. correlation coefficients.940 0. respectively.48 + 1.825 1.905 0.915 0.815 1.985 1. B. Copyright by ASTM Int'l (all rights reserved).285 1. (psi) BI r SE.440 0. 950 0.24 1. Copyright by ASTM Int'l (all rights reserved).280 1.950 0.965 0.955 0.860 0.960 0. 3 t h r o u g h 6 for each laboratory.79 9.840 1.095 1.48 2.86 3. the 28-day s t a n d a r d test was j u s t as variable.985 0.96 9. No further reproductions authorized. C o r r e l a t i o n coefficients were quite high in most cases. A f t e r studying the s t a n d a r d errors.810 0. F u r t h e r .58 1.82 16.000 is perfect.950. it was concluded t h a t all three p r o c e d u r e s were e q u a l in c o r r e l a t i n g a c c e l e r a t e d a n d later-age strengths.t o .060 0. 0. Simple Linear Regressiona Lab No.86 14.965 0. Subsequently.79 13.430 0.970 0.86 16. a situation presently ignored in assessing concrete quality within a certain l a b o r a t o r y .96 11.970 0. the variances in m a k i n g TABLE 2--Linear regression analysis for Procedure B.90 1.62 14.000 1. the terms of which are defined in the text.b a t c h a n d b a t c h . a n d s t a n d a r d error c o r r e s p o n d i n g l y low at 1.225 0.03 2.015 0. it was f o u n d t h a t a c c e l e r a t e d compressive strength c o r r e l a t e d with 364-day strength as well as 28-day strength. (psi) 1 I III I III I III I III I III I III I III I III I III 12.21 1.910 1. whereas 1.58 13. Therefore. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.52 13.07 4.03 1.050 1.b a t c h s t a n d a r d deviations a n d coefficients of variation were o b t a i n e d which e n a b l e d the p r e p a r a t i o n of precision s t a t e m e n t s . MPa B0.24 0.17 1. the s u b c o m m i t t e e e m b a r k e d u p o n the p r e p a r a t i o n of a tentative test m e t h o d t h a t i n c l u d e d P r o c e d u r e s A.020 0. W h i l e a c c e l e r a t e d strengths m e a s u r e d by the nine l a b o r a t o r i e s were significantly different.41 18. Precision Statements F r o m the c o m p u t e r analysis.975 0.27 (1860) (2400) (2580) (2025) (1430) (2170) (1680) (1905) (2265) (2155) (2450) (2835) (2825) (2580) (1380) (1945) (2630) (2650) 1.07 (195) ( 95) (225) (315) (175) (185) (115) (155) (585) (295) (230) (180) (180) (130) (270) (505) (360) (445) 4 5 6 8 9 10 11 12 aAccording to the model Y : B0 + B1X. a n d D. MPa SE.79 1. L a b o r a t o r y 8 h a d a m u c h h i g h e r s t a n d a r d error.28 0.280 1.66 1.13 15.145 1.195 1. .975 0.13 18. Cement Type B0.780 1.55 19.89 19. w i t h i n .290 1. In fact.865 0.48 3.48 17.34 0.55 17.930 0.530 1.171 WILLS ON ACCELERATED STRENGTH TESTING Note t h a t the correlation coefficient was extremely high.975 0.515 1.800 0. (psi) B1 r SE.220 1. B.24 M P a (180 psi). its d a t a d i d not fit the a s s u m e d m o d e l well. as w o u l d be expected by t h e close fit of the d a t a to the linear r e l a t i o n s h i p s shown in Figs.55 2. 800 0.86 9.Bo + BjX.705 0. Simple Linear Regressiona Lab No.560 0. B e c a u s e of the s m a l l d i f f e r e n c e s b e t w e e n t h e m . Cement Type B0.975 0.96 16.970 0. the terms of which are defined in the text.230 1.850 0.79 12. MPa Bo.06 7.780 0.172 TESTS AND PROPERTIES OF CONCRETE TABLE 3--Linear regression analysis f o r Procedure C.930 0. MPa SE.72 10.900 0. (psi) 4 I III I III I III I III I III I III 16.000 1.970 0. Simple Linear Regressiona Lab No.03 1.93 2. Cement Type Bo. MPa B0.970 0. and Testing of Concrete Compression Test Specimens (C684) was p u b l i s h e d .72 1.79 22.910 0.07 3.850 1.58 2.89 20.41 1.45 3.875 1. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.07 1.930 0. (psi) 4 I III I III I III I III 11.125 0.415 1.80 (2375) (2680) (1565) (1845) (1480) (2450) (2980) (4360) (1085) (3080) (2330) (2145) 0.955 0. t h e y w e r e c o m b i n e d i n t o a single p r e c i s i o n s t a t e m e n t w h e n A S T M M a k i n g Accelerated Curing. (psi) Bl r SE.190 0.810 0.870 1.925 0.96 0.55 2.000 0.17 9. these strength measurements seemed compatible and were therefore pooled across l a b o r a t o r i e s a n d c e m e n t types. No further reproductions authorized.82 (1660) ( 550) (3195) (3285) (1040) (1445) (2445) (1425) 1. w h i c h w e r e p r e p a r e d a c c o r d i n g to A S T M R e c o m m e n d e d P r a c tice for P r e p a r i n g P r e c i s i o n S t a t e m e n t s for T e s t M e t h o d s for C o n s t r u c t i o n M a t e r i a l s (C 670). (psi) Bl r SE.845 1.900 0. .48 1.950 0.960 0.20 16.31 0 62 1.03 22.48 10.120 0.300 0.34 1. T h i s r e s u l t e d in t h e f o l l o w i n g p r e c i s i o n s t a t e m e n t s .315 0.48 21.24 16. the terms of which are defined in the text.830 0.41 4. TABLE 4--Linear regression analysis f o r Procedure D.105 0.400 1. Copyright by ASTM Int'l (all rights reserved).38 18.45 (140) ( 60) (590) (215) (250) (280) (305) (210) 5 8 12 ~According to the model Y = Bo + BIX.52 1.965 0.775 0.54 30.980 0.06 14.990 1.990 1.10 1. MPa SE.90 (220) (225) (335) ( 90) (275) (205) (195) (155) (520) (355) (295) (275) 6 8 10 11 12 aAccording to the model Y =.45 2.90 1.65 7. Therefore. 2. 2.2 percent of their average (D2S percent).6 percent for a pair of cylinders cast from the same batch. multiday coefficient of variation (1S percent) has been determined as 8. multiday coefficient of variation (1S percent) has been determined as 8. The single-laboratory coefficient of variation (1S percent) has been determined as 3.5 percent for the average of pairs of cylinders cast from single batches mixed on 2 days. results of two properly conducted strength tests by the same laboratory on the same materials should not differ by more than 24. Therefore. Therefore. The single-laboratory coefficient of variation (1S percent) has been determined as 3. 35 ~ (95 ~ 1. Therefore.7 percent for the average of pairs of cylinders cast from single batches mixed on 2 days. The single-laboratory. results of two properly conducted strength tests by the same laboratory on the same materials should not differ by more than 20. results of two properly conducted strength tests by the same laboratory on the same materials should not differ more than 8.0 percent for a pair of cylinders cast from the same batch.2 percent of their average (D2S percent). Procedure B--Modified Boiling 1. multiday coefficient of variation (1S percent) has been determined as 7.2 percent for the average of pairs of cylinders east from single batches mixed on 2 days. No further reproductions authorized. results of two properly conducted strength tests by the same laboratory on the same materials should not differ more than 8. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 2. results of two properly conducted strength tests by the same laboratory on the same materials should not differ more than 10. results of two properly conducted strength tests by the same laboratory on the same materials should not differ by more than 24.6 percent of their average (D2S percent).4 percent of their average (D2S percent).WILLS ON ACCELERATED STRENGTH TESTING 173 Procedure A--Hot Water. . Therefore. The single-laboratory coefficient of variation (1S percent) has been determined as 2. Procedure D--Autogenous Curing 1. The single-laboratory.9 percent for a pair of cylinders cast from the same batch. Prediction of Later-Age Strength Prediction of later-age strength involves the use of statistics to estimate the size of confidence intervals about both the accelerated compressive strength and the regression lines determined from the statistical analysis of Copyright by ASTM Int'l (all rights reserved). Therefore. The single-laboratory.1 percent of their average (D2S percent).5 percent of their average (D2S percent). 195Xl MPa = (19. depending upon a certain laboratory's control of the strength measurement as indicated by its standard deviation. predictions can be made. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. From the regression equation this yields an estimated average 28-day strength of 39. There are twelve pairs of data points. 7. standard error of estimate.48 + 1.195X0 (6895 • 10 -6) psi with a standard error of estimate of 1.8 MPa (5760 psi). However. variance. average value of accelerated strength.. The 95 percent confidence interval is 39.25 MPa (180 psi).5 percent. For an average accelerated Copyright by ASTM Int'l (all rights reserved). Confidence intervals can be calculated from the statistical analysis according to the procedure shown in NBS Handbook 91 [9] and then. number of data points. . selected value of accelerated strength. The plot of the equation with its 95 percent confidence interval is shown in Fig.~ = SE F ratio for 2 and 10 deg of freedom.174 TESTS AND PROPERTIES OF CONCRETE the data. or standard error. The singlelaboratory coefficient of variation for cylinders cast from the same batch is 3. The regression equation is Y = 19.0 percent and the D2S limit is 8. and S = E X12 .0 to 40.7 MPa (5650 to 5900 psi) when the accelerated strength is without error. each the average of two cylinders from the same batch of concrete. These confidence intervals are necessary to predict 28 or 364-day compressive strength realistically.( E Xl)2/n Assume the average strength of two cylinders tested at 1 day of age by Procedure B in Laboratory 10 on the same materials was 17 MPa (2460 psi). The confidence interval was constructed by calculating Y for several selected values of X1 and plotting Y ___ W1 where WI =(SE)(2F)~/2( 1 + (X1S - - ~)2)1/2 and F = = n = XI = . the accelerated strength has a sampling distribution whose variance is described in the precision statement for Procedure B.48 + 1. An example of this is shown for Laboratory 10 using Procedure B to accelerate concrete made with Type I cement at three concentrations with and without a normal dose of retarder [10]. No further reproductions authorized. 38 I - 36 I _ I 0 co p.~ 44 i 0 Q.2 vi 46 ~. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. in 95 tests out of 100. 42 40 I--" (5650) CO I (5) -4 I (1.5) (3) ACCELERATED STRENGTH. No further reproductions authorized. each laboratory must conduct enough tests with a given set of materials and a certain procedure to establish the regression line and measure the standard error before predictions of later-age strengths are possible. strength of 17 MPa (2460 psi) the D2S limit is 1.WILLS ON ACCELERATED STRENGTH TESTING (7000) 12 14 16 I I I 18 i ! I I I I i & v 2. Copyright by ASTM Int'l (all rights reserved). the 28-day strength wilt lie within this interval when the accelerated strength is 17 MPa (2460 psi). Therefore. Projecting the limits of this interval to the confidence interval for the regression line results in 37.5) FIG. MPa (psi) 7--Prediction of 28-day strength for Laboratory 10 using Procedure B with Type I cement. . -r I-(.l = ----4 0. 54 I f 32 I I I i I (2) (2. . Furthermore. Each different measurement of accelerated strength produces a new confidence interval for 28-day strength.44 MPa (210 psi)..0 MPa (4-145 psi) for the 95 percent confidence interval.9 Z hl 20 175 (6) (6090) i -- ~900) I .. a new regression line is obtained when different materials or accelerated test methods are employed.0 MPa (5480 to 6090 psi) for the approximate 95 percent confidence interval for 28-day strength.8 to 42. Hence. . Dividing by (2) ~/2 to obtain the limit for the average of two cylinders yields _ 1. . 8 and are represented by the equation Y = 10.. In view of the individual correlations. For two independent variables.l 02 03 0.4 o 0. The sodium alkali (Na20) content exhibited a high coefficient of correlation with a low standard error relative to the 1-day accelerated strengths. No further reproductions authorized. governing the 1-day compressive strength of concrete cured in 35~ (95~ water--Procedure A. for 1-clay accelerated strengths and two cylinders were moist-cured at 23 ~ (73 ~ in 100 percent relative humidity for 28-day strengths..176 TESTS AND PROPERTIES OF CONCRETE Effect of Cement Chemistry In order to explain the differences between laboratories.34 (1 + Na20) MPa = 10. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or both. only combinations involving Na20 produced a useful correlation with 1-day accelerated strength.. Four 152 by 304-mm (6 by 12-in.) test cylinders were molded from each batch. % FIG. An attempt was made to hold the slump constant at 76 to 102 mm (3 to 4 in. Procedure A.. moreCopyright by ASTM Int'l (all rights reserved). . the physical and chemical properties of each cement along with the compressive strength relative to that cement were compiled and computer analyzed initially for individual correlations.34 (1 + Na20)(6895 X 10 -6) psi (50OO) 50 no {4ooo) ff (3000) 20 Z oo (2000) . After all cylinders were tested.).-.E f f e c t o f alkali content on accelerated strength. Two cylinders were cured according to ASTM Method C 684. Similar concrete batches were mixed utilizing eight Type I cements mixed with the same source of sand and gravel. a program was conducted to determine the chemical or physical properties.5 No20. several multiple correlations were attempted. The data are shown in Fig. 8 .w-- ]0 Y = ~034 ( I + N o 2 0 ) C~ oooo) u =(1500) (1+ Ne20) Ld (0 0 I I I I O. 4. Significantly different results were obtained in the nine laboratories due to the use of local materials including cements. most of the data were obtained on Procedure A. with equal variance in the data. this caused the principal variation between laboratories since each used a different Type I cement. Consequently. Summary and Conclusions ASTM Subcommittee C09. 35~ (95~ Procedure B. Autogenous Curing. 2.28 LOI MPa = (10. the variation between the different Type I cements was mainly attributable to variations in alkali content. and one the heat of hydration of the cement to cause the acceleration. The amount of acceleration produced by these procedures ranged from 1. only loss on ignition (LOI) coupled with the Na20 produced a better multiple correlation than Na20 alone and is represented by the equation Y = 10. standard strength ranged from good to excellent within each laboratory.45 Na20 + 0. An analysis of variance of these data substantiated the following conclusions. The omission or addition of a normal amount of chemical retarder in the concrete produced the same results. since each of these involved the measurement of Proctor time of set before heat was applied to the concrete.WILLS ON ACCELERATED STRENGTH TESTING 177 over. Copyright by ASTM Int'l (all rights reserved). Hot Water. 3. Modified Boiling. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 5.1 to 2. . With the autogenous procedure. Undoubtedly. No further reproductions authorized. accelerated compressive strength related to 364-day strength as well as 28-day strength. 1. 6. Correlation of accelerated strength with 28 and 364-day. When cement types were separated. Batches of concrete mixed on different days did not affect the results significantly.09 conducted a cooperative test program between nine laboratories to study the merits of seven test procedures for accelerating compressive strength development of concrete with heat. During the course of the program it was determined that one of the boiling water procedures and three of the hot water procedures were not practical because of large overtime expenditures necessary to conduct them.28 LOI)(6895 X 10 -6) psi Therefore. 2-day strengths as much as 86 percent of the 28-day strength were developed.5 times the compressive strength developed after 1 or 2 days of standard moist curing.34 + 9.34 + 9. Significantly different results were obtained between laboratories because of variations in alkali content of the cements.45 Na20 + 0.02. Procedure D. two boiling water. Four of these procedures involved the use of hot water. [7] Hopper. 1963.. M... 376-381." Proceedings. W. private communication. T. May 1961..H o t Water. W. S. 1971. July 1976." Report MRP/MSL 76-188. S.. 6441. Institution of Civil Engineers. Malhotra. Ottawa. G. N. and Chamberlin. and Steele. J..Y. Downsview. Washington." DHO Report RB 35. Dixon. H. J. F. 50th AnniversaryConference of the Institution of Structural Engineers. 370. McGraw-Hill. S. Mineral SciencesLaboratories.." Report No. in Introduction to Statistical Analysis. . 1968. New York State Department of Transportation. W h e n the m e t h o d is limited to a single laboratory-procedure-materials set of conditions. E. References [1] King. W. Aug. W. W. pp. 1941. V. 1970. Oct. M. "The Accelerated Curing of Concrete Test Cubes. R. Va. Nov. Experimental Statistics. London. 1969. it results in a n assessment of concrete quality at 1 or 2 days of age as reliable as that o b t a i n e d after 28 days of s t a n d a r d moist curing. June 1960. "A New Method for the Accelerated Testing of the Strength Development of Portland Cements. [3] Akroyd. "Prediction Equations for Accelerated Strength Testing of Concrete.. Mines and Resources. Bibliography Brandenberger. pp. "Accelerated Testing of Concrete. P. 3rd ed. Vol. 1974. Department of the Interior.C. B.. [10] Arni. G. 256-262. It includes Procedure A . P. Albany." Internal Report MPI 68-42.. V.. Ont. No. No. 170. H.178 TESTS AND PROPERTIES OF CONCRETE Therefore. May 1963. [9] Natrella. M. G. 386-387." unpublished report. H. Bureau of Reclamation.Ont. J. Ontario Department of Highways. Highway Research Board. 209-220. B. M. and Chojnacki. the results of this p r o g r a m have justified the p r e p a r a t i o n of a standardized m e t h o d for accelerated strength tests which can be used with as much confidence as the 28-day test in assessing concrete quality. and Hendrix. 1958.. and Zoldners.. W. D. National Bureau of Standards." Journal of Applied Chemistry.. No further reproductions authorized. [2] King.S. "Accelerated Testing of Concrete.A u t o g e n o u s Curing. Minerals Processing Division Department of Energy.. C. p. Zurich. T." Highway Research Record. Charleston. private communication. 25-36.. 1-22. J. J. Copyright by ASTM Int'l (all rights reserved). "Prediction of Potential Strength of Concrete from the Results of Early Tests. Department of Energy. Aug. "'Some Field Experience in the Use of an Accelerated Method of Estimating 28-day Strength of Concrete. 1957. G. Engineering Research and Development Bureau. D. and Massey. pp." unpublished report. 10. Ont. N.. [5] Malhotra. "Accelerated Test for 7 and 28-day Compressive Strengths of Concrete. Concrete Manual.. 30 Dec. U." Journal.. 20 Nov. A method was adopted by A S T M a n d recently advanced to a s t a n d a r d designated A S T M Method C 684.. Hudson.. [6] Natrella. W. 1968. W. Vol.M o d i f i e d Boiling. Federal (Swiss) Materials Testing Laboratory. 1951. 19.. 188. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Mines and Resources. [8] Miller. pp. "Accelerated Strength Testing of Concrete Cylinders. Bodenschatz. Research and Development. N. "An Accelerated Method of Estimating the 28-Day Splitting-Tensile and Flexural Strengths of Concrete. Ottawa.. J. New York. pp... [4] Smith. a n d Procedure D . Union Carbide Corp. NBS Handbook 91.. Procedure B . J. Vol. Downview. V. Aug. "Rapid Estimation of Concrete Strength Potential for Hydro-Quebec Dams with Special Reference to Modified Boiling Method. P. No." Journal of Testing and Evaluation." VHRC 70-R8. Department of Energy.. M.. M. Ont.. Canada. and Lapinas. Copyright by ASTM Int'l (all rights reserved). P. 51-54." Canadian Pit and Quarry. V. . March 1969. F.. No further reproductions authorized. Orchard. "Accelerated 28-Day Test for Concrete.. McGhee. 2. Minerals Processing Division. Ont. 1976.. Mines and Resources. Virginia Highway Research Council. R. pp. K. Canada. 1970. Jones. "Water Bath_Accelerated Curing of Concrete. Ont.. Malhotra. and AL-Rawi. N.. Smith. 1967. R. March 1974. and Biekley. Ontario Department of Highways. 2.. G. March 1966.. and Bauset. H.. Ottawa.. Zoldners. Sept. D. Smith. H. pp. K. Downsview. Sun Apr 6 21:41:43 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "The Effect of Cement Properties and the Thermal Compatability of Aggregates on the Strength of Accelerated Cured Concrete.WILLS ON ACCELERATED STRENGTH TESTING 179 Malhotra. "Earlier Determination of Concrete Strength Potential. Jan. 95-101." Ministry of Transportation and Communications." DHO Report RR 124. and Tiede. A. R." Report MPI(A) 69-16. "Accelerated Testing of Concrete--The Sky's The Limit. R. Charlottesville.. Robert Hooke in 1678 discovered that for many materials this ratio is constant over a fairly wide range of stress. much of it is not applicable to concrete. D. 20314.STP169B-EB/Dec. Civil Works. the body is deformed.astm. concrete behaves quite differently under applied load than does a crystalline material. to proportion sections and to determine the quantity of steel required in reinforced concrete members. This ratio is termed the modulus of elasticity. Engineering Division. Structures Branch. when working stress design procedures are employed. Copyright9 1978tobyLicense ASTM International www. it is common to consider them separately as elastic properties (instantaneous) and creep (time-dependent). and it has become one of the most commonly 1Chief. Office of Chief Engineers. Different materials vary widely in their response to load. to compute loss of prestress in prestressed structures. the rate at which it is applied. to compute stresses from observed strains.C.org . E. Philleo Chapter 14--Elastic Properties and Creep Introduction When a load is applied to a body. Sun Apr 6 21:41:44 EDT 2014 180 Downloaded/printed by Universidade do Gois pursuant Agreement. Department of the Army. This response is known as rheological behavior. Because of the peculiar "gel" structure of cement paste. and the elapsed time after the load application that the observation is made. Elastic Properties A body which returns to its original dimensions after enduring stress is elastic. 1978 R. A knowledge of the rheological properties of concrete is necessary to compute deflections of structures. No further reproductions authorized. Washington. For a particular body loaded in a particular environment the amount of the deformation depends upon the magnitude of the load. Copyright by ASTM Int'l (all rights reserved). and. A quantitative measure of elasticity is the ratio of stress to corresponding strain. Although a vast amount of work has been done on the rheology of materials. While instantaneous effects and time-dependent effects are not entirely separable. T h e slope of the chord drawn between any two specified points on the stress-strain curve. 1-..PHILLEO ON ELASTIC PROPERTIES AND CREEP 181 used parameters to describe material properties even though many materials do not exhibit a linear stress-strain relationship. the manner in which its modulus of elasticity is defined is somewhat arbitrary. . Chord M o d u l u s ." Concrete has neither a definite proportional limit nor elastic limit. They are defined in ASTM Definitions E 6 as follows. Secant M o d u l u s .T h e slope of the stress-strain curve at any specified stress or strain. Copyright by ASTM Int'l (all rights reserved). Unit Strain FIG.." The elastic limit is "the greatest stress which a material is capable of sustaining without any permanent strain remaining upon complete release of the stress.. Two additional terms are used to describe limits of elastic behavior: (1) proportional limit and (2) elastic limit. The proportional limit is defined in ASTM Definitions of Terms Relating to Methods of Mechanical Testing (E 6) as "the greatest stress which a material is capable of sustaining without any deviation from proportionality of stress to strain (Hooke's law).Variousforms of static modulus of elasticity. Tangent M o d u l u s . Initial Tangent M o d u l u s . No further reproductions authorized. Various forms of the modulus which have been used are illustrated on the stress-strain curve in Fig..T h e slope of the secant drawn from the origin to any specified point on the stress-strain curve. Therefore. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.T h e slope of the stress-strain curve at the origin. 1. The modulus in tension is usually equal to the modulus in compression and is frequently referred to as Young's modulus of elasticity. It can be shown that the following relationship exists among Young's modulus of elasticity." The transverse strains are opposite in direction to the axial strains. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as well as in the direction of the stress. The magnitudes of the lateral strains are different for different materials." and shear strain is defined as "the tangent of the angular change between two lines originally perpendicular to each other. Poisson's ratio is defined in ASTM Definitions E 6 as "the absolute value of the ratio of transverse strain to the corresponding axial strain resulting from uniformly distributed axial stress below the proportional limit of the material. . depending on the mode of vibration. E = Young's modulus of elasticity. and G = modulus of elasticity in shear. also called the modulus of rigidity or torsional modulus. For a material obeying Hooke's law. Shear stress is defined in ASTM Definitions E 6 as "the stress or component of stress acting tangential to a plane. Copyright by ASTM Int'l (all rights reserved). or shear. and Poisson's ratio -- E 2G 1 where /~ = Poisson's ratio. is the ratio of shear stress to shear stain. The parameters may take many forms.182 TESTS AND PROPERTIES OF CONCRETE Modulus of elasticity may be measured in tension. Likewise. Poisson's ratio is constant below the proportional limit. No further reproductions authorized. only the measurements of modulus of elasticity by "static" test methods will be described here. but the two most commonly used are Young's modulus of elasticity and Poisson's ratio. Thus. modulus of elasticity in shear. compression. there are changes in dimension in directions perpendicular to the direction of the applied stress. two parameters are required to describe the elastic behavior of a material. if any two of these quantities are determined. Since these phenomena and their application to concrete are discussed elsewhere in this volume. the velocity with which a compressional shock wave travels through an elastic body is proportional to the square root of Young's modulus." When stress is applied in a given direction. the third can be calculated. The shear modulus. It can be shown that the natural frequency of vibration of an elastic body is proportional to the square root of either Young's modulus or the shear modulus. Thus. Modulus of Elasticity in Compression Since structural concrete is designed principally for compressive stresses. instead of being observed on a dial gage. Copyright by ASTM Int'l (all rights reserved). It stipulates a chord modulus between two points on the stress strain curve defined as follows: the lower point corresponds to a strain of 50 millionths and the upper point corresponds to a stress equal to 40 percent of the strength of concrete at the time of loading. There are also available compressometers in which the strain. The selection of the gage length is important. Thus. Because of restraint where the specimen is in contact with the steel platens of the testing machine. and it must be large enough to span an adequate sample of t h e material. ASTM Test for Static Young's Modulus of Elasticity and Poisson's Ratio in Compression of Cylindrical Concrete Specimens (C 469). The upper point is taken near the upper end of the working stress range assumed in design. No further reproductions authorized. These include both gages embedded along the axis of the specimens and those bonded to the surface. 2. 2The italic numbers in brackets refer to the list of references appended to this paper. whereas the upper yoke is free to rotate as the specimen shortens. .) cylinder is the specimen size most commonly used for the determination of the modulus of elasticity in compression.2 and it is cited in ASTM Method C 469 as an acceptable device. encroach on the ends of the specimen. however. It must not. the determined modulus is approximately the average modulus of elasticity in compression throughout the working stress range. The pivot rod and dial gage are arranged so that twice the average shortening of the specimen is read on the di~l. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The only ASTM standard test method for static modulus of elasticity of concrete.PHILLEO ON ELASTIC PROPERTIES AND CREEP 183 by far the greatest amount of work on the elastic properties of concrete has been done on concrete in compression. It must be large in comparison with the maximum aggregate size so that local strain discontinuities do not unduly influence the results. The lower point is near the origin but far enough removed from the origin to be free of possible irregularities in strain readings caused by seating of the testing machine platens and strain measuring devices. The lower yoke is rigidly attached to the specimen. Electrical strain gages have also been used successfully. ASTM Method 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. is a compressive test method. strains near the ends may differ somewhat from strains elsewhere in the specimen. A convenient device for measuring the strains is a compressometer. The 150 by 300-ram (6 by 12-in. This type of device was used in the first comprehensive investigation of modulus of elasticity by Walker [1]. strains should be measured along the axis of the specimen or along two or more gage lines uniformly spaced around the periphery of the cylinder. Half the specimen height is said to be the preferred gage length. such as the one pictured in Fig. is indicated and recorded by an electrical device such as a linear differential transformer. In order to compensate for the effect of eccentric loading or nonuniform response by the specimen. A large numer of results have been reported in the literature [2-4]. Because the test is intended to measure only time-dependent strains. has practical value. it is important that the specimen be loaded expeditiously and without interruption. would be useful. It has been demonstrated [6-10. which is discussed later. The range of results has been from 7 000 to 20 000 MPa (1 000 000 to 3 000 000 psi) for structural lightweight concrete and from 14 000 to 35 000 MPa (2 000 000 to 5 000 000 psi) for normal weight concrete. A simple relationship between modulus of elasticity and other easily measured properties of concrete. 15] that such failures are related to the properties of the testing machine rather than the properties of the concrete. except those with very low strength. No further reproductions authorized. concrete cylinders. In most testing machines. . the shape of the stress-strain curve at high stresses is of significance in determining the ultimate load-carrying capacity of a concrete member. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. For this purpose an automatic stress-strain recorder is helpful but not essential. Although the standard method of test is not concerned with the behavior of concrete at stresses above 40 percent of the strength. fail suddenly shortly after the maximum load has been attained. an approximate equation adopted by the American Concrete Institute (ACI) Building Code [5]. 2--Compressometer. temperature and moisture conditions should be controlled during the test.184 TESTS AND PROPERTIES OF CONCRETE FIG. Since it is desired that only those length changes due to load be measured. such as strength and unit weight. While no theoretical relationship exists. By using a suitably stiff testing machine or by artificaUy stiffening a testing machine Copyright by ASTM Int'l (all rights reserved). . Modulus of Elasticity in Flexure Since a principal use of reinforced concrete is in flexural members. Since Young's modulus in tension does not appear to differ from Young's modulus in compression at low stresses and since there is no strain range beyond maximum tensile stress to be investigated. The test is complicated by the limited stress range of concrete in tension and the problems associated with gripping the tension test specimens. 3--Complete stress-strain curves (taken from R e f 15).006 CONCRETE STRAIN I 0. Figure 3 illustrates such stressstrain curves. Unfortunately. there is relatively little stimulus for the development of data on the tensile modulus. it is possible to obtain stress-strain curves covering a strain range several times as great as that required to attain m a x i m u m stress.002 I I 0. certain other corrections must be made to take care of discontinuities in the shear deflection curves at load points.. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.010 FIG.004 0. 3 -20~ w r 15 ~ z 10 w 1 9 DAYS ~ . Copyright by ASTM Int'l (all rights reserved). In applying shear corrections. several investigators have determined Young's modulus on specimens loaded as beams.008 g 0. The corrections most com- I I I I i 25 . No further reproductions authorized. An obvious approach is to measure deflections caused by known loads and to calculate the modulus of elasticity from well-known beam deflection formulas. _ ~ ~ ~: c~ 5 0 0 I 0. Recent work has been concerned with the development of specimen shapes which will ensure uniform stress distribution throughout the section in which measurements are made. Modulus of Elasticity in Tension A limited amount of work has been done on the determination of Young's modulus in tension of concrete [11-13]. the depth-to-span ratios of concrete beams normally used for such tests are so large that shear deflection comprises a significant part of the total deflection. _z g.PHILLEO ON ELASTIC PROPERTIES AND CREEP 185 by surrounding the concrete specimen with steel springs. . and depth of the beam. The load may be converted to fiber stress by standard beam formulas. strain gages have been placed on the tensile and compressive faces to determine strain as a function of applied load. moment of inertia of the section with respect to the centroidal section. applied central load. distance between supports. The eccentric load is continuously adjusted so that the HYDRAULIC T I .48----~. The portion of the expression outside the brackets is the simple beam formula.0. 4--Test specimens for stress distribution in a beam (taken from Ref 15). In some tests.E .1 + (2. Such tests have the advantage of indicating the position of the neutral axis. In a comprehensive investigation of the compression side of a concrete beam Hognestad et al [15] utilized specimens of the types shown in Fig. modulus of elasticity. therefore. . Ill "SR-4 GAGES FIG. P1 " NEUTRAL SURFACE al Ii lbll . Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . Copyright by ASTM Int'l (all rights reserved).4 + 1. For center-point loading he gives the following deflection formula -. 4. No further reproductions authorized.= ~__~ a2 cT t ' ' F///~!-k2~c . the computed modulus of elasticity are in error. Poisson's ratio.5/~) -. but if the stress-strain curve is nonlinear the computed stresses and. . I~ '~.186 TESTS AND PROPERTIES OF CONCRETE monly used are those of Seewald [14]. V I . . For such tests the beam is usually loaded at two symmetrical points so that there is a constant stress condition between the two load points. I : : ~.~ ~. . The central prismatic portion of the specimen is loaded both concentrically and eccentrically.84 where: 6 P l E I /~ h = = = = = = = m a x i m u m deflection. the section simulates that portion of a beam between the neutral axis and the extreme compressive fiber. and = polar moment of inertia of the cross section. In these tests the stress-strain curves in flexure agreed very well with stress-strain curves obtained on companion cylinders con centrically loaded in compression both below and above the maximum stress. The second depends on the speed of testing. The complete stress-strain curve in flexure can be determined from the observed loads and strains if the following two assumptions are made: 1. When a given torque is applied to a body the angle of twist in a given length is inversely proportional to the shear modulus as indicated by the following equation L G~----- where G L 4~ I ---. = torque. The distribution of strain across the section is linear. = angle of twist per unit length. as well as a magnified axial strain or by mounting strain gages on the surface of a specimen perpendicular to the direction of loading.modulus of elasticity in shear. Thus. is most often determined dynamically or by calculation from Young's modulus and Poisson's ratio. When a direct static determination is desired. A method for testing concrete cylinders has been described by Andersen [16]. Modulus of Elasticity in Shear The shear modulus. The first has been amply verified in these and other tests. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Poisson's Ratio Static determinations of Poisson's ratio are made by adding a third yoke and second dial gage to a compressometer so that a magnified transverse strain may be measured. 2. time-dependent effects are held to a minimum. No further reproductions authorized. If the specimen is loaded expeditiously. He used a level bar with micrometer adjustment for measuring differences in angular change of two radial arms placed a fixed distance apart on a horizontally positioned specimen. The same considerations apply to gage length for lateral strain measurement as for longitudinal strain measurement except Copyright by ASTM Int'l (all rights reserved). All fibers follow the same stress-strain curve. or modulus of rigidity. a torsion test is the common procedure. .PHILLEO ON ELASTIC PROPERTIES AND CREEP 187 strain on one surface remains zero. 25. This behavior is not associated with crystalline slip. concrete creep is considered to be an isolated rheological phenomenon associated with the gel structure of cement paste. creep of concrete is approximately a linear function of stress up to 35 to 40 percent of its strength. . Furthermore. When the value is below 0. gel water movement is Copyright by ASTM Int'l (all rights reserved). In metals and other crystalline materials creep has been attributed to slip in crystals.188 TESTS AND PROPERTIES OF CONCRETE that for lateral strains there is no upper limit since end restraint is not a factor. The particular aspect of the gel structure of concrete which causes its unusual behavior is the accessibility of its large internal surface to water.20. No further reproductions authorized. A principal view among investigators [21-25] is that creep is closely related to shrinkage. While slip of this nature undoubtedly occurs in aggregate particles and within crystalline particles that are part of hydrated paste. Thus. A review of current knowledge of creep is to be found in the 1964 ACI Sym- posium on Creep of Concrete [19]. Probst [17] has shown a systematic increase in the value of Poisson's ratio with stress repetition and Brandtzaeg [18] has shown a marked increase at very high stresses. Poisson's ratio is also commonly computed from results of Young's modulus and shear modulus determined dynamically. At high stresses or under conditions of rapidly alternating loads a different picture emerges. there is ample evidence that these are only secondary factors in the creep of concrete. The dynamic values are usually in the vicinity o f 0. Procedures for determination of Poisson's ratio are included in ASTM Method C 469. Finally.50 there is a decrease in volume of the body as a compressive load is applied. Creep of concrete is observed at all stresses. In creep. the order of magnitude of concrete creep is much greater than that of crystalline materials except for metals in the final stage of yielding prior to failure. Brandtzaeg's work indicates that above about 80 percent of the strength there is an increase in volume as additional compressive loads are applied.15 and 0. The movement of water into and out of the gel in response to changes in ambient humidity produces the well known shrinking and swelling behavior of concrete." All materials undergo creep under some conditions of loading. The static value at stresses below 40 percent of the ultimate strength is essentially constant. Crystalline slip is normally detectable only above some threshold level of stress. This unique aspect of the problem has the advantage that creep may be measured without extremely sensitive equipment but the disadvantage that little of the research which has been done on other materials is applicable to concrete. for most concretes the values fall between 0. Mullen and Dolch [20] found no creep at all in oven-dried pastes. Creep Creep is defined in ASTM Definitions E 6 as "the time-dependent increase in strain in a solid resulting from force. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In fact. compaction. Unless the work is restricted to very mature concrete. The stress is restricted to the range throughout which creep has been found to be proCopyright by ASTM Int'l (all rights reserved).f Concrete in Compression (C 512). A test procedure has been standardized in ASTM Test for Creep o. and degree of hydration.PHILLEO ON ELASTIC PROPERTIES AND CREEP 189 caused by changes in applied pressure instead of differential hygrometric conditions between the concrete and its environment. In at least one investigation [32] Poisson's ratio was found to be zero. This concept is supported by the similar manner in which creep and shrinkage curves are affected by such factors as water-cement ratio.27] is delayed elasticity. The fact that creep is associated primarily with the cement paste phase of concrete produces a serious difficulty in the interpretation and application of creep data. mix proportions. curing conditions. although provision is made for other storage conditions or other ages of loading. If a load is suddenly imposed on a body consisting of a solid elastic skeleton with its voids filled with a viscous fluid. This concept is supported by the concept that creep strain is proportional to the applied stress over a wide range of stress. Measurement of Creep The use to be made of creep measurements usually determines the age at which creep tests are begun and the stress level to which specimens are loaded. This is the behavior exhibited by the theological model known as a Kelvin body. Creep of concrete has been attributed by some [28-31] to viscous flow of the cement paste. No further reproductions authorized. Frequently information is desired'at early ages when the cement is hydrating relatively rapidly. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The reduction in strain rate with time has been attributed by these investigators both to the increasing viscosity of the paste and to the gradual transfer of load from the cement paste to the aggregate. . Creep measurements must necessarily be made over a considerable period of time and during that time the cement paste continues to hydrate. In fact Poisson's ratio for creep has usually been found to be less than for elastic stress. the load will be carried initially by the fluid and will gradually be transferred to the skeleton as the fluid flows under load. properties of aggregate. The concept of delayed elasticity has been chiefly responsible for the widespread attempts to reproduce the theological behavior of concrete by means of theological models. A convincing argument against it is the fact that the volume of concrete does not remain constant while it creeps. Another explanation of the effect of gel water [26. The method stipulates loading moistcured specimens at an age of 28 days to a stress not exceeding 40 percent of the strength of the concrete at the time of loading. Another argument against the concept is the partial recovery of creep when the load is removed. the specimens do not maintain constant physical properties throughout the test. which consists of a spring and dashpot in parallel. most creep testing has been concerned with specimens subjected to compression. This has led to the development of numerous logarithmic equations for creep. and shrinkage. the total shortening at any time may be considered the sum of elastic strain. Limitations on gage lengths similar to those in the test for modulus of elasticity apply. most modern theories deny the independence of shrinkage and creep and thus indicate that the two effects are not additive as assumed in the test. 40]. While this correction is qualitatively correct and yields usable results. Many sets of data show an approximately straight line over a considerable period of time. This correction is intended to eliminate the effects of shrinkage and other autogenous volume change. provided in the latter case the load is measured and adjusted frequently. common to plot creep test results on a semilogarithmic graph in which the linear axis represents creep strain and the logarithmic axis represents time. Creep Equations Creep under constant stress always proceeds in the same direction at a rate which is a decreasing function of time. No further reproductions authorized. It is also required that there be companion unloaded specimens. It is. In that test method the results are reported by listing the strains at specified ages up to a year. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.190 TESTS AND PROPERTIES OF CONCRETE portional to stress. As with testing for modulus of elasticity.37.34-36] have studied creep in flexure because of the obvious application to beam deflections. The load may be applied by a controlled hydraulic system or by springs. 39. It is now common to label creep which occurs in the absence of drying "basic creep" and to label the additional deformation not accounted for by shrinkage "drying creep" [33]. Such an equation is cited in ASTM Method C 512. . drying creep. basic creep. therefore. The age of loading for a standard test is necessarily arbitrary. The method is intended to compare the creep potential of various concretes. A limited amount of work has been done in tension [32. In addition it is suggested that the report contain the parameters of the following equation 1 = ---ff + F ( K ) lOge (t + 1) Copyright by ASTM Int'l (all rights reserved). Thus. Length changes of these specimens are measured and subtracted from the length changes of the loaded specimens to determine creep due to load.38] and in torsion [16. It is required in the test method that the stress remain constant throughout the one-year duration of the test within close tolerances. Testing at a single age of loading is satisfactory got this purpose. Several investigators [11. While it is not intended that a theoretical logarithmic law should be inferred from the equation.n ) + 13e-Pk(1 -. the age at time of loading. F ( K ) = creep rate. calculated as the slope of a straight line representing the creep curve on the semilog plot.e . . E = instantaneous elastic modulus." t ) where ec k t a. 101 [42]. McHenry [41] added coefficients to take into account the effects of hydration during the loading period with the following triple exponential equation ec : c~(1 -. A summary of creep equations is given in Concrete Society Technical Paper No. o. and m = = = = specific creep. They are usually grouped together in pairs. No further reproductions authorized. m = ultimate creep strain per unit of stress.PHILLEO ON ELASTIC PROPERTIES AND CREEP 191 where = total strain per unit stress. in which force is proportional to strain. the slope of the least squares line is a convenient parameter for comparing the creep characteristics of different concretes. /3. in days.e . while a Copyright by ASTM Int'l (all rights reserved). in which force is proportional to the rate of strain. r. The elements normally used are the ideal spring. for a sustained stress. Typical of these is the Lorman [24] equation C m mt m n+t (7 where c = creep strain after time. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A spring and dashpot in parallel form a Kelvin unit. time after loading. Most of the other equations which have been used to describe creep have been based on the assumption that there is a limiting value of creep. and empirical constants. and n = the time at which half the ultimate creep is attained. and the ideal dashpot. p. Rheological Models Many investigators have used mechanical models as' an aid in setting up mathematical equations. t. and t : time after loading. By selecting an appropriate group of elements it is possible to produce a system empirically which can reproduce any given set of creep data. While many of the investigations have included complete unloading as a portion of the study. Two are a m (a) ak ~k(b) a2~r ~~(d) FIG. Figure 6 shows how the theory applied to creep recovery. it should not be considered as representing the structure of the real material. which is pictured in Fig. No further reproductions authorized. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The effect of each increment of load lasts forever. 5. there has been only a limited study of other forms of variable loading. Typical of models which have been proposed is that of Freudenthal and Roll [43]. Three sets of specimens are required to produce such a figure. While the model is an aid in visualizing creep behavior and in writing equations for that behavior. Principle of Superposition Of considerable practical value is a knowledge of the response of concrete to changing loads.192 TESTS AND PROPERTIES OF CONCRETE spring and dashpot in series form a Maxwell unit. McHenry [41] proposed a theory of superposition whereby the effect of each change in load is assumed to be added algebraically to the effects of all previous loads. S--Typical rheological model for representing creep (taken from Ref 43). The material is assumed to have a perfect memory. The models are frequently simplified somewhat if some of the spring or dashpot constants are made time-dependent or stress-dependent. . Copyright by ASTM Int'l (all rights reserved). Fabrication and testing of concrete specimens containing such large aggregate is expensive. This finding has made it possible to develop significant data for mass concrete from small specimens.Qgo . and age at loading. 80 120 AGE AFTER CASTiNg. a_ 0. it is used regularly in computing stresses in mass concrete from measured strains.) aggregate.3 I I ~MEASURED CREEl" RECOVERY 2 Q28 t~. Most of the creep studies which have been conducted have been for the purpose of determining the effect of one or more of these variables on creep. Work at the Waterways Experiment Station of the Corps of Engineers [45] and at the University of California [46] has demonstrated that for paste contents normally used in concrete the creep of sealed specimens. No further reproductions authorized. The principle is consistent with the preponderance of observations that only partial recovery occurs when a specimen is unloaded. is proportional to the paste content.PHILLEO ON ELASTIC PROPERTIES AND CREEP 193 loaded at an age of 28 days. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . having identical water-cement ratios and air contents in the mortar phase but different amounts and sizes of a given coarse aggregate. Effect of Specimen Size It has been demonstrated [45. Copyright by ASTM Int'l (all rights reserved). Mass concrete commonly contains 150 mm (6-in.~ o. A third set is loaded at 90 days to the same stress level as the original sets. The principle of superposition is valid if the strain in the last set equals the difference in strains of the first two sets.0 0 40 FIG. One of these is unloaded at 90 days. conditions of storage. While there is not unanimous agreement [44] on the principle of superposition. type of aggregate. DAYS 6--Principle of superposition (taken from Ref 41). Effect of Paste Content Creep is influenced by mixture proportions.1 LU t) 0. A general treatment of the effect of aggregate properties and paste contents covering the entire range of paste contents from 0 to 1 has been given by Neville [47]. One aspect of the effect of mixture proportions is of continual interest in the field of mass concrete.2 Z o COMPUTED CREEP RECOVERY-uzb . That is the relationship between creep and paste content.48] that creep of sealed specimens is in0. Hansen and Mattock [50]. consistency of concrete. and relaxation of the steel. age at loading. . This observation plus the observation concerning mass concrete in the preceding paragraph indicate that the techniques and specimens of ASTM Method C 512 are applicable to all types of concrete sealed to prevent loss of moisture. Creep and Shrinkage in Concrete. in an investigation of both size and shape of specimens. Ross [49] investigated the effect of specimen size on shrinkage and found at each age an excellent correlation between shrinkage and the ratio of exposed surface to volume of specimen independent of the shape of the specimen. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. air content.194 TESTS AND PROPERTIES OF CONCRETE dependent of specimen size. Information of this sort may make it possible to apply correction factors to the'data obtained from ASTM Method C 512 to determine the creep in any size and shape of structure. Since the initial pretress is limited by the strength of the steel and the load-carrying capacity of the Copyright by ASTM Int'l (all rights reserved). Loss of Prestress In contrast to the lack of precision needed for deflection measurements. shrinkage of the concrete. After the prestress is applied. The equations take into account the effects of type and quantity of cement. While a precise prediction of these deflections is possible only if the elastic and creep properties are known. an accurate knowledge of the early-age rheological properties of concrete is valuable to the prestressed concrete industry. there is a loss of prestress resulting from creep of the concrete. Creep Prediction Equations A series of creep prediction equations has been published by Committee 209. It is not uncommon for a reinforced concrete flexural member eventually to reach a deflection three times as great as its initial deflection. For unsealed specimens exposed to a drying atmosphere it is evident that there must be a size effect associated with the moisture gradients within the specimen. found that shrinkage and creep were dependent only on the ratio of surface to volume. of the American Concrete Institute [51]. Significance of Properties Deflection of Flexural Members Concrete flexural members undergo deflection upon application of load and continue to deflect with the passage of time. No further reproductions authorized. Relatively little creep testing is directed to predicting deflections of specific structures. The creep of a structure may be only a fraction of that in a test specimen. the required precision is usually not great. and size of member. relative humidity. the load carried by the steel is a function of the ratio of the modulus of elasticity of steel to that of concrete. The procedure requires the installation of a large number of strain meters within the structure during construction. The time is divided into small intervals. tanks. Stress Calculations A prerequisite for the calculation of stresses from measured strains is a complete knowledge of a material's rheological behavior. stress calculations must be made continually from the time the concrete hardens to the end of the period for which results are desired. a knowledge of the complete stress-strain curve for concrete has assisted in the refinement of strength design theory. These structures are unreinforced and contain complicated stress distributions because of temperature conditions resulting from the heat of hydration of cement. the thermal coefficient of expansion and shrinkage data must also be available. Perhaps the most extensive use of creep data has been in the stress analysis of mass concrete structures [52]. 7. tunnels. To convert strain data to stress. Design is impossible unless these quantities are known or assumed. the change in strain must be accounted for by adding or subtracting an amount of stress sufficient to produce the desired strain increment at the appropriate age of loading. a knowledge of Poisson's ratio as well as modulus of elasticity is needed.PHILLEO ON ELASTIC PROPERTIES AND CREEP 195 member is limited by the residual prestress. A discussion of the accuracy of the method has been given by Pirtz and Carlson [53]. It is necessary to run creep tests on sealed specimens in the laboratory at enough ages of loading so that by interpolation and extrapolation a complete knowledge of rheological behavior is available. By this technique it has been possible to obtain an accurate assessment of the safety of dams and to evaluate the effectiveness of various methods of temperature control. At the location of each strain meter. When stresses result from nonuniform temperature or humidity as well as from applied load. For many types of structures such as arches. Structural Design When reinforced concrete is designed by working stress theory. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. If during any interval the change in strain is different from that which would be expected from the creep produced by the sum of all the stresses present at the point at the start of the interval. a knowledge of the factors governing loss of prestress has important economic implications. Therefore. Such data can be represented pictorially by a creep surface such as that shown in Fig. it is assumed that creep is a linear function of stress and that the principle of superposition applies. As discussed previously. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and flat slabs. . perfect bond between the concrete and steel is assumed under design load conditions. .o iiiii----..Or .. 7--Typical creep surface.. \ \ ~0\\~\\ \ o\\\\\\ .. No further reproductions authorized.~ ~ ..196 TESTS AND PROPERTIES OF CONCRETE ~. In some structures in which designers wished to minimize deflections.~ ". Specifications for structural concrete are primarily concerned with strength.. The technique takes into account the effects of mixture proportions and aggregate properties.. contractors have been restricted to those aggregates among the economically available materials which have been demonstrated to produce concrete having the lowest creep.. -.... \". and where building codes impose limits on deflections a knowledge of creep behavior is also necessary... . It has not been considered feasible to complicate the specifications by additional rheological requirements. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement... \ ~'.....\I 75 ~ a 100 Time After Loading..... o.\ \ 50'OJ5102030 \ 50 . and it has been used to establish construction controls required to reduce cracking in mass concrete structures [55]. Days FIG. It has been pointed out that a knowledge of modulus of elasticity is required for some aspects of structural design.. ~o. \'.. Specifications Limits on rheological properties are almost never included in specifications... The problem has been ap- Copyright by ASTM Int'l (all rights reserved). o 6 . A method developed by Houk et al [54] measures the strain capacity in slow loading directly by laboratory flexural testing of relatively small beams. l...\ "...... American Concrete Institute. p. p. Vol. R." Proceedings. 320-322. Madison. Jan. R. Vol. D. However. 1936. E." Journal. American Society for Testing and Materials. [10] Blanks." Civil Engineering. "A Comparison of Physical Properties of Concrete Made of Three Varieties of Coarse Aggregate. Wis.. R. pp." Proceedings. and Brown. Stanton. and Maldari. 584-2 to 584-6. Supplement. in Pa. 317-320 and 339-346. A. Oct.S. 1919. E. R. in Pa. Jensen. March 1947.PHILLEO ON ELASTIC PROPERTIES AND CREEP 197 proached in the ACI Building Code [5] by a s s u m i n g that the m o d u l u s of elasticity is related to strength a n d u n i t weight as follows E = W l's 4 3 f c ' where E = m o d u l u s of elasticity. both are p r o b a b l y a d e q u a t e for the i n t e n d e d purpose." Proceedings. 461-469. H. [2] Teller. Poisson's Ratio.. Vol. Bureau of Reclamation. [3] "Bibliographies on Modulus of Elasticity. p. when there is no compression reinforcement. Oct. in kilograms per cubic metre. "Plastic Flow and Volume Changes in Concrete. W = u n i t weight. 37.. F. The ratio of long-time deflection to i m m e d i a t e deflection is assumed to vary from 1." Laboratory Report No. G. and McHenry. American Society for Testing and Materials. 30. 39. pp.. to 3. Copyright by ASTM Int'l (all rights reserved). [5] Building Code Requirements for Reinforced Concrete (ACI 318-77. 35. American Concrete Institute. Denver. 19." B.0. University of Wisconsin. thesis. 21. 1938." Beton und Eisen. 377. the interest in rheological properties is increasing.. S. 1977. 1937. 19 and 20. when the a m o u n t of compression r e i n f o r c e m e n t equals the tension r e q u i r e m e n t . Part 1. No." Journal. Vol. L. References [1] Walker. [9] Ramaley. Proceedings. "Modulus of Elasticity of Concrete. Neither of these estimates can claim a high degree of precision. 1928. 28. discussion of a paper by V. [6] Whitney.. [11] Davis. pp. E. Davis. Vol. [8] Kiendl. Part 1. Colo. 1930. Part 2. 510. P. W. American Concrete Institute. "Digest of Tests in the United States for the Determination of the Modulus of Elasticity of Portland Cement Mortar and Concrete. Vol. Nov.. D. E.). May 1949. Vol. American Society for Testing and Materials. O.8. . a n d f c ' = specified compressive strength. p. 5.. and Volume Changes of Concrete. "Bruchzustand und Sicherheit im Eisenbetonbalken. 317. T.. 51.. Vol. [4] Philleo. No further reproductions authorized. Part 2. 635. [7] Saliger. American Society for Testing and Materials. and McHenry. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as structural design increases in sophistication a n d as applications of prestressed concrete increase. U.. C. "The Plasticity Ratio of Concrete and Its Effect on the Ultimate Strength of Beams. Berlin. pp. S. 1955. "Plastic Flow of Concrete Relieves High-Load Stress Concentrations. D. "Stress-Strain Curves for Concrete Strained Beyond the Ultimate Load." Proceedings. No. 1943. Proceedings. This interest is evident in the steadily increasing a m o u n t of creep testing b e i n g performed. SP-12.. H. "Comparison of Results of Three Methods for Determining ~oung's Modulus of Elasticity of Concrete. p. Reiner. "Abhandlungen. Proceedings. R. 16. G. G." Symposium on Shrinkage and Cracking of Cementive Materials. K. L. 64." T.. "Shrinkage and Time Effects in Reinforced Concrete. W. G. 3. University of Illinois. F. F." The Structural Engineer.. 90. April 1929. T. [26] Freyssinet. M. Department of Scientific and Industrial Research." Bulletin No.. The Society of Chemical Industry. 603. 12. pp. Lewis and Co. p. W. G. Minneapolis. 1935." StructuralEngineering. 69. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Chapter 8. 1947. [28] Freudenthal. Vol.. E. S.. Stockholm. 52. 1082-1102. N. l. [17] Probst. 1955." Proceedings. [31] Glanville. and Lee. & A.. 1146-1171. pp. Vol. [36] Chang. Strain and Flow. [37] McMillan. pp. "Set Concrete and Reinforced Concrete.. C. D. 522. Vol. VoL 198. "Experiments on the Creep of Concrete Under Two-Dimensional Stressing. North-Holland Publishing Co. p. Wiley. Copyright by ASTM Int'l (all rights reserved). E. 49-56.. "Creep Behavior of Concrete in Tension. Amsterdam." Bulletin No. [23] Seed. 1940. Ames. 4... W. [30] Thomas. 1950.. A. P." Building Research Technical Paper 21." Magazine of Concrete Research. p." Aerodynamischen Inst. M. 7.. "Creep of Concrete.. Ltd. London. W." Bulletin No. N. Ill. 207. 56. Royal Institute of Technology. 290-360. American Society for Testing and Materials. Vol. [25] Hansen. [13] Johnson. Report No. Oxford University Press. Iowa. 1958.. F. No. [35] Vaishnav. [21] Lynam. R. University of Illinois." Magazine of Concrete Research. 1973. [24] Lorman. N. 48. 6. B.. The Inelastic Behavior of Engineering Materials and Structures. Hanson. "Creep of Portland-Cement Paste. [19] Symposium on Creep of Concrete (ACI SP-9). [16] Andersen. 1960. American Concrete Institute. University of Illinois Engineering Experiment Station. T. 1915. "Concrete Stress Distribution in Ultimate Strength Design. [38] Wajda. [27] Torroja.. 1956. pp. "Shrinkage and Creep in Concrete. and Dolch. Wiley. Vol... and Paez. and Kesler. 1939. 2nd Ed. H. No. M. "Experiments with Concrete in Torsion.. Growth and Movement in Portland Cement Concrete. 1964." Journal. Building Materials. A. [14] Seewald. Vol. "Creep and Shrinkage in Reinforced Concrete Structures." Public Roads. Jan. 1928. Vol." Swedish Cement and Concrete Research Institute. "Prediction of the Rheological Behavior of Concrete from Its Sonic Properties.. F. 14. 1257-1272. pp.. "Relationship Between Strength and Elasticity of Concrete in Tension and in Compression. 7.. . 253-267. H.. and MeHenry... Sept. London. Ill. "Further Investigations on the Creep or Flow of Concrete Under Load. A. Vol. 455-479. 1964. A. [18] Brandtzaeg. Engineering Experiment Station. Ill. [22] Lea. 1955. 8. 1934. pp. "The Deformation of Concrete. Urbana. S. 587. Minn. Urhana. 3. Aug. Vol. and Thomas. C." Proceedings. Urbana. Their Elasticity and Plasticity. Dec. Dec. 100. 1961.. 3. M. London. pp. 17-22. "Correlation of Sonic Properties of Concrete with Creep and Relaxation. [32] Ross. E.. "The Failure of Plain and Spirally Reinforced Concrete in Compression. American Society for Testing and Materials." Transactions. 8. L.198 TESTS AND PROPERTIES OF CONCRETE [12] Johnson. an der Technischen Hochschule. London. [33] Neville. "Conception of Creep of Unreinforced Concrete and an Estimation of the Limiting Values. "Tests of Concrete in Tension. Dec. F. American Society of Civil Engineers. R. No. 1951. pp. T. J. 41. London. 3-10. 5130. editor." Engineering.. R. [29] Reiner. [15] Hognestad. and Kesler. 1927. June 1926. American Concrete Institute. 1964. W. Vol. June 1954. Aachen. No. C. pp. H. No further reproductions authorized. C. Vol. and Holloway. (British). R.D.. Report No. pp.. W. thesis. Deformation. No." Ph. M. L. London. New York.. E. pp." Proceedings. Properties of Concrete. E. 1931. No. "The Influence of Rapidly Alternating Loading on Concrete and Reinforced Concrete. I20] Mullen. M." The Reinforced Concrete Review. "Correlation of Creep of Concrete with its Dynamic Properties. 11. "Theory of Concrete Creep. 949. C. London. New York. A. 40. 190.. [34] Chang.. E. University of Minnesota. pp. D. Theoretical and Applied Mechanics. 1954. A.. 1948. 9.. Vol. 1933. " Journal. 1957. Proceedings. 253-261. E. David and Carlson. Aug. ACI Special Publication SP-6. A. Size. American Concrete Institute. 1944. Feb.. Akad. "Shape. 63. . Proceedings. M. R. 75-99." Report of a Working Party of Materials Technology Divisional Committee. Jan. [55] Houghton. "The Development of Stresses in Shasta Dam. and Adams. Jan. "The Influence of Size and Shape of Member on the Shrinkage and Creep of Concrete. C. American Concrete Institute. D. Vol. 888-896. A. [49] Ross.. K. 267-290. March 1970.. 59. 6-132 Report 3. pp. 27. 1973. Vol. 257-283. 1972. American Concrete Institute. [47] Neville. R." Reported by ACI Committee 209. D. [40] Glucklich. 161-172. M." Magazine of Concrete Research. pp. Proceedings. Frederic. pp. Vol. Milos. David. [52] Raphael. 1956. [50] Hansen. Ivan E. J. [54] Houk. Nauk Armianskoi SSR. Sun Apr 6 21:41:44 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1. and Mattock. American Society for Testing and Materials. 46. Vol. [41] McHenry. and Temperature Effects in Concrete Structures. Proceedings of the Engineering Foundation Conference. 16." Journal. I. Tekhiniceskie Nauki. and Shrinkage. Pirtz. March 1964.. 54. "Studies of Creep in Mass Concrete. "Creep Mechanism in Cement Mortar. American Concrete Institute. 1963. A. [45] "Creep of Mass Concrete. 21-30. 1. "Influence of Size upon Creep and Shrinkage of Concrete Test Specimens". [44] Davies.... 287-299. [53] Pirtz. U." Miscellaneous Paper No. 8." Concrete and Constructional Engineering. Jr. 923-946. 39." Economical Construction of Concrete Dams. H. 118. [46] Polivka.. July 1962. W." American Concrete Institute. Copyright by ASTM Int'l (all rights reserved). 9. Concrete Society Technical Paper No. 9. American Concrete Institute. Armenian Academy of Sciences (Yerevan).. pp." Journal. "Prediction of Thermal Stress and Strain Capacity of Concrete by Tests on Small Beams. No. Their Economic Implications. Army Engineer Waterways Experiment Station. [51] "Prediction of Creep. "Some Experiments on Applicability of the Principle of Superposition to the Strain of Concrete Subjected to Changes of Stress with Particular Reference to Prestressed Concrete. "Creep of Concrete as a Function of its Cement Paste Content. Fiziko--Mathematicheskie (Estestvennye). pp.. and Ishai. American Society of Civil Engineers. S.966. H. No. C. 1069-1084. and Davis. Vol. June 1958. Vol. pp. [48] Karapetrin. 87-100 (in Russian). and Roll. D.. Shrinkage. pp. 289-321. Vol. A.S. L. pp. Vol. A.PHILLEO ON ELASTIC PROPERTIES AND CREEP 199 [39] Duke. pp. "Concrete Strain Capacity Tests. Special Publication 27. D. pp. D. 1958. 1971. R. Proceedings. and Houghton. O. J. 1963... "Tests of Strain Meters and Stress Meters under Simulated Field Conditions. "Creep and Creep Recovery of Concrete Under High Stress. 101. "A New Aspect of Creep in Concrete and Its Application to Design." Symposium on Mass Concrete." Transactions. No further reproductions authorized. M. pp." Proceedings." Magazine of Concrete Research. p. J. T. 1953. American Society for Testing and Materials. Paxton. VoI. No. M. 22. Vol. [43] Freudenthal. pp. [42] "The Creep of Structural Concrete. American Concrete Institute.." Symposium on Mass Concrete: ACI Special Publication SP-6. "Some Properties of Concrete Under Sustained Combined Stresses. American Society of Civil Engineers. Vol. pp." Proceedings. 1944. 1111-1142. No. 43.. 44. F. L. 67.. M a l h o t r a 2 Chapter 15 Nondestructive Tests Introduction For many years one of the goals of those engaged in the control of concrete quality and in the service behavior of concrete has been the development of suitable nondestructive tests to supply the information desired. During recent years. tests which are identified generally as nondestructive may be subdivided into three groups: (a) those identified as sonic tests. Transplex/OSU.org . Not all such tests meet the requirements of the aforementioned definition. the results of such tests have led to the computation of values of Young's modulus of elasticity that are somewhat higher than those determined from slower applications of load in which both elastic and plastic deformations may occur. generally involving measurement of the velocity of a compressional pulse travelling through the IProfessor of Civil Engineering and director. suchtests should be applicable to concrete in the structure. For example. To be of greatest usefulness. Construction Materials Section. CANMET. M. 1978 E. (b) those identified as pulse velocity tests. W h i t e h u r s t ~ a n d V. Ottawa. 43210. In general. 2Head. The Ohio State University. the damage in these cases is generally agreed to be more cosmetic than structural and repairs normally are made for aesthetic reasons. For purposes of this discussion.astm. No further reproductions authorized. and Resources. Mineral Sciences Laboratories. Copyright9 1978 tobyLicense ASTM International www. Canada.STP169B-EB/Dec. However. A. it has been defined as dynamic testing in which the load is applied and removed in a manner such that the effects of creep during testing are negligible. there has been a growing tendency to assign to the family of nondestructive tests a number of tests which measure in situ some parameter which may be related theoretically or empirically to compressive strength. Sun Apr 6 21:31:12 EDT 2014 200 Downloaded/printed by Universidade do Gois pursuant Agreement. however. since some produce sufficient damage to the concrete tested in the structure to require repair of the surface. Department of Energy. The term "nondestructive tests" has been assigned various meanings throughout the years. generally involving determination of the resonant frequency of a specimen. Mines. and which does not result in destruction or damage to the concrete. Copyright by ASTM Int'l (all rights reserved). Columbus. Ohio. The pickup is usually a piezoelectric crystal. The driver was placed in the center of the specimen and the pickup at one end. The oscillator was tuned until a maximum indication was observed on the metering device. and maturity concept techniques. and (c) those involving measurement in situ of a parameter to be related to compressive strength and generally consisting of surface hardness. Equipment used to perform tests of this nature varies from the hammer and home-made sonometer reported by Powers [1] 3 to electronic signal generators for driving the specimen and highly complex electronic counters for measuring the actual number of vibrations per unit of time. rebound. in some cases. . The frequency of the oscillator was then varied. often a phonograph pickup cartridge. These are available individually from a number of sources and are also available in a combined form suitable for direct use in testing of this nature. By far the majority of such tests involves the determination of the fundamental resonant frequency of a specimen. the specimen was supported on knife-edges located at the nodal points for flexural vibration (a distance of 0. penetration. The large bulk of the apparatus falls between these extremes. and a metering device. primarily because of the difficulty encountered by many operators in matching the tone emitted by the concrete specimen to the tone of the sonometer and because. pull-out. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. a driving unit. Sufficient power was applied to the driver to cause mild vibration of the specimen. a pickup unit. The hammersonometer method has been largely superseded by other methods. The use of the complex counter is generally restricted to research laboratories. Copyright by ASTM Int'l (all rights reserved). another amplifier. Sonic Tests The expression "sonic testing" is generally considered to include all testing of concrete which involves the generation of a sustained vibration in the concrete.224 of the specimen length from each end).WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 201 concrete. When the frequency approached that of resonance for the specimen. No further reproductions authorized. an amplifier. The frequency at which this occurred was recorded as the fundamental transverse frequency of the specimen. The driving unit is frequently a permanent-magnet speaker with a rod attached to the speaker coil. The components required for performing a test of this nature are an audio signal generator. the amplitude of specimen vibration increased considerably. the striking of the specimen resulted in a change in its characteristics [2]. Subsequent investigations indicated that if the specimen was allowed to rest uniformly on a sheet of soft sponge rubber the restraint on the specimen would be sufficiently low to remove the necessity for mounting it at its nodal 3The italic numbers in brackets refer to the list of referencesappended to this paper. In earlier tests. 4] have shown that a somewhat different characteristic of concrete. the node occurring at the center of the beam. The specimen is thus vibrated with a twisting motion. and provides a schematic diagram illustrating use of the components enumerated above. . and B are factors depending for their values upon the shape of the specimen tested and Poisson's ratio. may be determined from studying the behavior of a specimen vibrating at or near resonance.2 G -- 1 (4) Several investigators [3. Detailed instructions for their calculation may be found in ASTM Test C 215. The constants C. Poisson's ratio may be calculated from the relationship -. Longitudinal..202 TESTS AND PROPERTIES OF CONCRETE points. and n t~ fundamental torsional frequency. In this technique. n r fundamental longitudinal frequency. Copyright by ASTM Int'l (all rights reserved). Further investigations have included the use of longitudinal vibrations in which the driving unit is placed against one end of the specimen and the pickup unit against the other. In this case. psi. generally applied to prisms. This has now become a generally accepted practice. the damping constant and the logarithmic decrement of a free vibration. Where E and G are determined as outlined above. cPs. also. the driving unit is placed against one corner of the specimen and the pickup against a diagonally opposite corner. lb. W = weight of specimen. n = fundamental transverse frequency. psi. D. No further reproductions authorized. its damping capacity. Two measures of this characteristic are suggested. The relationships between the several fundamental frequencies and other properties of the concrete are given as follows Dynamic E = C W n 2 (1) Dynamic E = D W ( n ' ) 2 (2) Dynamic G = B W ( n " ) 2 (3) where Dynamic E = dynamic Young's modulus of elasticity. longitudinal. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and torsional frequencies. cPs. ASTM Test for Fundamental Transverse.~ /~ . Considerable attention has also been directed to the use of torsional vibration for testing concrete specimens. and Torsional Frequencies of Concrete Specimens (C 215) makes provisions for testing concrete specimens for fundamental transverse. Dynamic G = dynamic modulus of rigidity. the nodal point occurs at the center of the specimen. cPs. After resonance has been located. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In an effort to minimize these effects.f2 (s) where f0 = resonant frequency of vibration. f2 = frequencies on either side of resonance at which the amplitude is 1 / ~ times the amplitude at resonance. A frequency counter has been found to be satisfactory for this type of work. the driving oscillator is turned off and the decay of the specimen vibration recorded on a moving film strip. For some reas o n . cPs.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 203 The damping constant is given by f0 0 - - - f i -. provided that a sufficiently precise method of determining vibration frequency is available.A2 (6) where b = logarithmic decrement.p e r h a p s this difficulty in obtaining supports that exercise sufficiently low restraint on a specimenmthese test methods have not been used Copyright by ASTM Int'l (all rights reserved). Obert and Duvall [3] supported their specimens on piano wires accurately located at the nodal points. a cathode-ray oscillograph may be used as the indicator. This becomes extremely important since the frequency range betweenf~ and f2 is very small indeed. . These values may be determined if a meter is used as the indicating device for determining resonance. A z ----. To determine A1 and A 2. and A1. The damping constant and logarithmic decrement are related by Q- 7~ 6 (7) Both of the aforementioned methods have a disadvantage in that the damping effects of the specimen supports must be extremely low. and f l . No further reproductions authorized.amplitudes of two successive vibrations after the driving force has been removed from the specimen. the amplitudes of successive cycles may be measured accurately. The logarithmic decrement is given by Zl 6 = I n . When the film has been developed. and B. although Pickett [8] has suggested that tests of a similar nature might be useful in testing concrete pavements. This and similar techniques have not been widely used. are subject to two major limitations. specimens must be either cylinders or prisms. Further. long-time creep in compression. was used in predicting the compressive strength of concrete. with the possible exception of the last. have reported tests in which the logarithmic decrement. logarithmic decrement.204 TESTS AND PROPERTIES OF CONCRETE widely. Chang and Kesler [5. creep in flexure under uniform loads. They report an accuracy of prediction generally within five percent for the limited tests made. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It has been suggested that they may be used to study the setting characteristics of concrete. C. most efforts to relate the elastic properties of concrete to its strength have been largely unsuccessful. Copyright by ASTM Int'l (all rights reserved). and creep in flexure under concentrated loads in which reasonably good correlations were obtained between these measured creep values and values predicted on the basis of dynamic modulus of elasticity. and in weathering studies it is fairly common to equate a 30 percent decrease in dynamic modulus to a 50 percent decrease in flexural strength. They have also been used to study the effect of moisture content and to compare different mixes [3]. The methods are basically applicable to specimens of relatively small size and are of little value in studying the behavior of concrete in place. In more recent reports. With the exception of the work of Kesler and Higuchi [4]. Kesler and Higuchi [4].6] have reported studies of short-time creep in compression. . A pickup was then moved about on the surface of the wall to determine points of maximum vibration. It is perhaps due largely to these restrictions that recent attention has been directed toward the development of devices for determining pulse velocity in concrete. in combination with the dynamic modulus of elasticity determined from the transverse resonant frequency of a specimen. but such usage has generally proved unsuccessful. Unfortunately all of the techniques discussed above. and for other purposes [9]. Somewhat better results have been obtained in efforts to correlate changes in dynamic modulus of elasticity to changes in strength. No further reproductions authorized. because of the complexity of the calculations involved in computing the constants D. The quantity measured was the velocity of the standing wave. to investigate the efficiency of various curing compounds [7]. Mention should also be made of the possibility of using sustained vibrations for testing concrete in place. The greatest use of sonic techniques has been made in evaluating the performance of concrete specimens subjected to natural or artificial weathering. of uniform cross section (square or rectangular). however. and compressive strength of the concrete studied. since the frequency of vibration was known and the wave length of the vibration within the concrete could be determined. relaxation in compression. Long and Kurtz [7] have reported such tests in which a large auditorium-type loudspeaker was attached rigidly to a concrete wall and driven at a fairly high power level. and a camera with a moving film strip. thus eliminating the necessity for computations involving the magnitude of the current flowing through the galvanometer. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Long and Kurtz [7. p. Subsequent investigations in this country and abroad have resulted in the Copyright by ASTM Int'l (all rights reserved). The geophones were placed in the backs of the holes and the holes filled with cotton waste. When the energy impulse reached the second pickup. They stated that only very limited experiments of this nature had been conducted but that the method appeared to hold great promise providing the apparatus could be adapted to the measurement of much shorter time intervals than those of which the seismograph was capable. . approximately 6. Tests were made on concrete replacement pillars in mines and involved the use of two geophones. In a discussion of this paper.09 m (20 ft) apart vertically. the voltage from its amplifier ionized the second thyratron and cut off the flow of current. 1067] reported performing somewhat similar experiments with a Shepard seismograph in which the longitudinal velocity of the pulsation created by a single impact was measured between arbitrarily placed geophones. This device consists of a capacitor which begins to charge when the first thyratron is ionized and stops charging when the second is ionized and a vacuum-tube voltmeter which measures the charge. The meter may be calibrated directly in units of time. were drilled into the pillars. the substitution of an electronic interval timer for the ballistic galvanometer was suggested. The deflection of the galvanometer was directly proportional to the time required for the wave to travel the distance between the two pickups. The energy impulse thus generated actuated the first pickup. approximately in line with the two pickups. and at the same time the camera lens was opened and the moving film strip exposed. No further reproductions authorized. A hammer blow was struck at the base of the pillar. Long et al [11] undertook further investigations along these lines and in 1945 reported on the instrument and technique that resulted from their work. This device was found to be more reliable than the ballistic galvanometer for field use. The apparatus consisted of two vibration pickups (in the form of phonograph cartridges). After the film was developed. two high-gain amplifiers. the transit time of the impulse in traveling from one geophone to the other was determined by measuring the distance between the two signals on the film. Two holes. two thyratron tube circuits.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 205 Pulse Transmission Tests The application of pulse transmission techniques to the testing of concrete is believed to have had its origin with Obert [10]. The impact of a hammer blow was impressed upon the concrete in a horizontal direction. the speed of motion of the film having been controlled carefully. two amplifiers. and a ballistic galvanometer circuit. The velocity could then be calculated. the voltage from which energized the first thyratron and started a flow of current through the galvanometer. The physical and electrical features of the Soniscope have passed through several stages of improvement since 1947. The receiver may be any one of a number of types of pickup. In these instruments the impulse is generated by a mechanical blow.S. . The maximum range of the Ultrasonic Concrete Tester is believed to be about 2 m (7 ft). work of a similar nature was being conducted in England. These include the Micro-timer developed by the U. and a number of these instruments have been built by various laboratories in the United States and Canada. In 1946 the Hydro-Electric Power Commission of Ontario. provide visual presentation of transmitted and received signals on a cathode-ray tube. a similar pulse receiver. Canada. South African Council for Scientific and Industrial Research. Research.206 TESTS AND PROPERTIES OF CONCRETE development of a number of other devices quite similar in most respects. These changes improve the accuracy of measurement on very small specimens but limit the usefulness of the instrument for field testing. Bureau of Reclamation. and devices developed at the National Physical Laboratory. and accurately measure the time interval between the two. in an effort to develop a technique for examining cracks in monolithic concrete structures. and electronic circuits which actuate the pulse generator. This instrument and the uses to which it has been put have been described at length by Jones [15. Transmitted and received signals are displayed on a long persistance cathode-ray oscilloscope containing a calibrated time base for determining Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Several devices have been reported which incorporate some of the features of the Soniscope and some of the Electronic Interval Timer. A more complete report was published by Leslie and Cheesman [12] in 1949. since the high frequencies suffer much greater attenuation in passing through concrete than do the lower ones. No further reproductions authorized. France. began a series of studies which resulted in the construction of an instrument known as the Soniscope. the Condenser Chronograph developed by the Danish National Institute of Building Research. These investigations resulted in the development of an instrument known as the Ultrasonic Concrete Tester. whereas that of the Soniscope in testing reasonably good concrete is 15 m (50 ft) or more. The device consists basically of a pulse generator using piezoelectric crystals. Development of this instrument was first reported to Committee 115. and the Laboratoires du Batiment et des Travaux Publics. During approximately the same time that the Soniscope was being developed in Canada and the United States. Considerable use of the instrument has been reported in Canada [13] and the United States [14]. frequently that of a spring-loaded hammer operated by a motor-driven cam at the rate of about five blows per second.16]. The Ultrasonic Concrete Tester differs from the Soniscope primarily in the much higher frequency used within the transmitted pulse and in the repetition rate which is about three times as great as that of the Soniscope. of the American Concrete Institute in 1948. All make use of either hammer blows or small explosive charges to generate the impulse. and results appear to be unaffected by the size and shape of the concrete tested. Because of the fundamental theoretical relationship between pulse techniques and resonant frequency techniques. The quantity actually measured by all of these instruments is the transmission time of an impulse passing through the concrete under test. . If the path length between generator and receiver is known or can be determined. such values of modulus should be the same as those determined by resonant frequency tests upon the same specimens. in many respects. pulse transmission techniques have been applied to concrete for many purposes and.Poisson's ratio. This. however. of course. = mass density.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 207 the transit time between signals. in most areas of investigation. only limited agreement has been reached concerning the significance of test results. Because of these presently unexplainable differences. and ---. If the modulus of elasticity is to be computed from the pulse velocity. the relationship generally recommended is (1 + ~)(1 -.2v) E = V2p (8) (1 . the velocity of the pulse may easily be computed. most of those experienced in the use of pulse velocity techniques are inclined to leave their results in the form of velocity without attempting to calculate moduli therefrom. Copyright by ASTM Int'l (all rights reserved). = longitudinal pulse velocity. The experience of several investigators [19. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.20].. within the limits of transmission of the instrument employed. has shown that on some occasions this is true and on others it is not. Theoretically. No further reproductions authorized. It is in the interpretation of the meaning of this velocity and in its use for determining various properties of concete that agreement is incomplete. Whereas the use of the sonic tests has been restricted primarily to the evaluation of specimens undergoing natural or artificial weathering and the techniques for such use have been largely standardized. is a highly desirable attribute and. The devices mentioned above and the uses to which they have been put have been described in detail by Whitehurst [17] and in several publications of the Rdunion des Laboratoires d'Essais et de Recherches sur les Materiaux et les Constructions [18]. there is a strong inclination for users of the pulse technique to endeavor to compute the dynamic modulus of elasticity from the results of the tests. The technique is as applicable to concrete in place as to laboratory-type specimens. makes the pulse transmission techniques more useful than those involved in sonic testing. provided care is taken when testing very small specimens. Development of one such device has been reported in the United States and another in France.# ) where E V p /z = dynamic modulus of elasticity. 24. notably Great Britain and Russia. it is possible to measure the transverse pulse velocity and the Rayleigh pulse velocity as well.848 represents the correction for Poisson's ratio. although it has been suggested that if the cracks are fully water-filled their locations may be more difficult to ascertain. Fundamentally all of the pulse velocity techniques and equipment developed for use on concrete result in the measurement of the compressional. If this is done.208 TESTS AND PROPERTIES OF CONCRETE This equation relates modulus to pulse velocity and density in an infinite medium and presumably should apply only to mass concrete. independent investigators have reported widely different degrees of success through the use of these techniques [I 7]. the value of Poisson's ratio is assumed to be 0.24. The factor 0. In rare cases. to merit no more than mention at this time. of cracks in concrete. 1958. There appears to be little question of the suitability of such techniques to determine the presence. . and the presence or absence of cracks within the concrete. its uniformity. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. pulse velocity. No further reproductions authorized. The occurrence is sufficiently rare with present equipment. In some instances investigators in these countries have appeared to have greater confidence in the use of such techniques for acceptance testing than has been the case in the United States. 206. its modulus of elasticity. Highway Research Board. Jones [16] has reported values of minimum velocity considered acceptable Copyright by ASTM Int'l (all rights reserved). taken in this case to be 0. Experiences in the use of pulse velocity measurements for evaluating concrete quality have been reported in many other countries. when the test is being made across a corner of a structure and the path length involved is fairly long (in the order of 4 to 6 m (15 to 20 ft)).000216 V2d(0. its setting characteristics. Under these circumstances it is theoretically possible to calculate Poisson's ratio directly from any two of the measured velocities. However. or longitudinal. Eq 8 is reduced to E = 0. for concretes having unit weights in excess of approximately 2240 k g / m a (140 lb/fta). with the Soniscope-type instrument. k g / m a (lb/fta). and to some extent the magnitude. The most complete report of the experiences of users of pulse velocity techniques in the United States and Canada may be found in "Effects of Concrete Characteristics on the Pulse Velocity--A Symposium. however.848) (9) where d = weight of concrete. Leslie and Cheesman [12] have suggested that best results are obtained if. The use of pulse velocity techniques for testing concrete has been suggested for evaluating the strength of concrete. In all of the other fields of investigation. 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." Bulletin No. The main disadvantages of this approach are: the delay in obtaining test results. and curing conditions. Filina [22] has reported in some 80 various items of equipment for testing concrete which are in use in the USSR. the lack of reproducibility in test results. however. Zashchuk and Nefedova [23] have described the design and operation of ultrasonic testing equipment used in connection With the construction of the Moscow Ring Road. there have been a large number of attempts over the past 40 years to develop quick.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 209 for concrete for certain specific structural purposes in Great Britain as follows: prestressed concrete--T sections prestressed concrete--anchor units reinforced concrete frame building suspended floor slab 15 000 ft/s 14 300 ft/s 13 500 ft/s 15 500 ft/s In a later publication [21]. the accepted methods of evaluating the quality of concrete in structures consist of testing simultaneously cast companion specimens in compression and flexure. and reproducible methods for testing concrete in structures. however. and the high cost of testing. These. In-Situ Testing for Strength Properties In current concrete practice. compacting. the specimens may not be truly representative of concrete in a structure because of different placing. it appears that the investigator must have a rather intimate knowledge of the concrete involved before attempting to interpret velocities as measures of strength or other properties of the concrete. Beyond these areas of agreement. They state that toward the completion of the road ultrasonic methods replaced all other techniques. size and type of coarse aggregate remains uniform. he stated that "pulse-velocity has rarely been used as an acceptance criterion for structural concrete because it is usually too difficult in site-work to ensure that the control of mix proportions. It is further agreed that periodic. Because the direct determination of strength implies that concrete specimens must be loaded to failure. inexpensive. . As a result." Several reports are available of the use of pulse velocity techniques in Russia. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. combined with the fact that structural units are considerably larger and more massive. systematic changes in velocity are indicative of similar changes in the quality of the concrete. it becomes abundantly clear that Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. casts further doubts as to the validity of such measurements of the strength ofin-situ concrete. This is particularly true if the aggregate involved is a lightweight aggregate. the necessity of testing the specimens to failure. It is generally agreed that very high velocities are indicative of very good concrete and that very low velocities are indicative of poor concrete. including those making use of ultrasonics and vibrations. therefore. penetration. However. Therefore. . and pull-out techniques. about 20 impact readings are taken at short distances from one another. The tip of a hammer can be fitted with different diameters of balls. Williams Testing Pistol--In 1936. Although these tests are relatively simple to perform.) for concrete with compressive strengths as low as 7 MPa (1000 psi). Also included is a brief description of the maturity concept. and its rebound number. attempt to measure some other property of concrete from which an estimate of its strength is obtained. No further reproductions authorized. engineers are cautioned that interpretation of the test data must always be carried out by specialists in this field rather than by technicians performing the tests. On the basis of several hundred tests. its resistance to penetration by projectiles. Z is the curved surface area of indentation.06 in. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5 mm (0. Surface Hardness Methods The known surface hardness methods are of the identation type. using a given mass activated by a given energy. Frank Spring HammerwThe Frank spring hammer consists of a springcontrolled mechanism housed in a tubular frame. Williams [26] reported the development of a testing pistol weighing about 0. within limits. the analysis and interpretation of the test data are not so easy because concrete is a complex material. empirical correlations have been established between strength properties and the data obtained from surface hardness tests. The basic principles of various indentation devices to measure the hardness of concrete have been outlined by Gaede [24] and Vassitch [25].210 TESTS AND PROPERTIES OF CONCRETE nondestructive methods of testing concrete cannot be expected to yield absolute values of strength. These methods. and measuring the size of indentation. The depth of indentation is only about 1. and (c) Einbeck pendulum hammer. (b) Frank spring hammer. and the mean of the results is considered as one Copyright by ASTM Int'l (all rights reserved). The three known methods employing the identation principle are: (a) Williams testing pistol.9 kgf (2 lb) that uses a ball as an indentor. Some such properties of concrete are its hardness. Williams established the following relationship: fc is proportional to 1/Z' wherefc is compressive strength. and impact is achieved by placing the hammer against the surface under test and manipulating the spring mechanism. rebound. Because of the difficulty of precisely measuring the curved surface area. The following sections describe in some detail the surface hardness. this method was not accepted widely. and these consist essentially of impacting the surface of concrete in a standard manner. There is little apparent theoretical relationship between the strength of concrete and its hardness as so measured. The diameter of the impression made by the ball is measured by a magnifying scale or other means. Generally. Kolek [33] also has attempted to establish a correlation between the hammer rebound number and the hardness as measured by the Brinnel method. when completely retracted. the strength of concrete under investigation can be predicted with an accuracy of 20 to 30 percent by the use of test hammers. developed a test hammer for measuring the hardness of concrete by the rebound principle. There appears to be little apparent theoretical relationship between the strength of concrete and the rebound number of the hammer. is correlated with the compressive strength of concrete. This hammer can be used on vertical surfaces only and is. A typical relationship between compressive strength and 4Reunion Internationaledes Laboratoiresd'Essais et de Recherchessur les Materiaux et les Constructions. .29]. the sliding index is read to the nearest whole number. it is desirable to know the mix proportions. When the plunger is pressed against the surface of the concrete. Ernst Schmidt [32].WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 211 test value. According to Jones [27]. the spring is released automatically. taking a rider with it along the guide scale. Einbeck Pendulum H a m m e r w T h i s hammer consists of a horizontal leg. Rebound Method In 1948. a Swiss engineer. The hammer impacts against the concrete and the spring-controlled mass rebounds. at the end of which is pivoted an arm with a pendulum head weighing about 2. According to Weil [30] and a RILEM 4 working group [31]. in turn. The surface hardness tests are simple to use and provide a large number of readings in a short time. and these are then correlated with the compressive strength of concrete. and moisture condition of the concrete under test. type of coarse aggregate used. The Schmidt hammer consists of a spring-controlled hammer mass that slides on a plunger within a tubular housing. To interpret the data correctly. The indentation is made by holding the horizontal leg against the concrete surface under test and allowing the pendulum head to strike the concrete. therefore. This reading is designated as the hammer rebound number. The detailed procedure for calibrating the hammer has been described elsewhere [34. Williams has claimed somewhat better accuracy with the testing pistol. the impact hammers have been standardized in a German standard [28. By pushing a button. The diameter or depth of identation (or both) is measured and this. While the hammer is still in its testing position. However. within limits empirical correlations have been established between strength properties and the rebound number. The diameter and depth of indentation are measured. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. age. No further reproductions authorized.3 kgf (5 lb). it retracts against the force of the spring. Copyright by ASTM Int'l (all rights reserved). the rider can be held in position to allow readings to be taken.35]. less versatile then the Frank spring hammer. Hammer type : N-2 / I Hammer number : 3 0 8 0 W .-..~ / +o ~5 . =: -.-/." " / t0j / / ~ / 200C 0 ~'~ ill. " 9 40O0 ' ~ . ASTM issued a tentative Test for Rebound Number of Hardened Concrete. From Ref 35. 5000 rp Z i 04 p " Totolnumberofcy. For example. . However. and tested under laboratory conditions by a properly calibrated hammer lies between _+ 15 and -+-20 percent.' ! # . .. (c) age of the specimen. . " 9. (C 805). . .-:/~./ 50<) if) / X 550C ~ 8 Nu ZO(? r 5000 UJ ~. cured./// . "./ ~ r a b o u n d ~.'o\o . ( f ) type of cement. (d) sm'face and internal moisture condition of the concrete. . ( h a m m e r I 50 150 0 >- l 35 40 le5 ~ C~ in horizontal p o s i t i o n ) FIG.J 9 .1 250C . 1. " I // "/ . is shown in Fig. These limitations are discussed in detail elsewhere [35.C}.. there is a wide degree of disagreement among various research workers concerning the accuracy of the estimation of strength from the rebound readings.'. Although the rebound hammer provides a quick. According to Kolek [33] and Malhotra [35].~e. All cylinders were tested in SSD condition 1 25 REBOUND N U M B E R . .. >t) " I . the accuracy of estimation of compressive strength of specimens cast.. (e) type of coarse aggregate.. d ~J Q r/ "" ~'" "" f'~" 9 ~87 / " o\o t / Coarse agqregate . crus. + I / " -. shape and rigidity of the specimen. By consensus. .." *" .:. . the probable accuracy of prediction of concrete strength in a structure is +_ 25 Copyright by ASTM Int'l (all rights reserved). . 1--Relationship between compressive strength and rebound number for limestone aggregate concrete obtained with Type N-2 hammer.. (g) type of mold.::.'v ~ ' 20 . .212 TESTS AND PROPERTIES OF CONCRETE rebound number for limestone aggregate concrete. . "-.." .. In 1975.'" [~// " " "'/ ]' " 't 9 . 55OO .37-39]. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. there is a general correlation between compressive strength of concrete and the hammer rebound number.". it has many serious limitations and these must be recognized.. and (h) carbonation of concrete surface. number is overage of iO hammer reoclings On each one of the test cylinders ..mestone Free aggregate : natural eand 4500 + / .inflereteeted =460 t . inexpensive means of checking uniformity of concrete." " ". However. 350 _z .~/~. the results of the Schmidt rebound hammer are affected by the following: (a) smoothness of surface under test.. obtained by Zoldners [36]. . No further reproductions authorized. (b) size. It cannot be overemphasized that the rebound hammer must not be regarded as a substitute for standard compression tests but as a method for determining the uniformity of concrete in the structure and comparing one concrete against another.5 in. and Law and Butt [45] are shown in Fig. and other related equipment. the only equipment which is known to be available and meets the requirements of ASTM Test C 803 is the Windsor probe. 3. The exposed length of the probe is measured by a calibrated depth gage. The rear of the probe is threaded and screws into a probe driving head which is 12. a number of organizations in both the United States and Canada have carried out studies with this technique. .). Arni [42] has reported results of a detailed investigation on the evaluation of the Windsor probe.) cylinders and 610 by 610 by 200-mm (24 by 24 by 8-in. The relationships established by Arni [42]. The method of testing is relatively simple.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 213 percent.125 in. loaded cartridges. Penetration Techniques The evaluation of hardness by probing techniques was first reported by Voellmy [40] in 1954.5 mm (3. Apart from the data reported by Voellmy. In the other technique. a depth gage ibr measuring penetration of probes. and a frustoconical point on the front. and the depth of the penetration of the pins was correlated with the compressive strength of concrete. and the depth of borehole was correlated to the compressive strength of cubes. a length of 79. a new technique known as the Windsor probe was introduced in the United States for in-situ testing of concrete [41].3 mm (0. In one case.6 mm (0. 44] has reported results of his investigations on both 152 by 305-mm (6 by 12-in. No further reproductions authorized. the probing of concrete was achieved by blasting with spit pins. At the present time. hardened alloy probes. Since its introduction.) in diameter and fits snugly into the bore of the driver. ASTM issued Test Penetration Resistance of Hardened Concrete (C 803). A relationship between the exposed probe length and 28-day compressive strength of 152 by 305-mm (6 by 12-in. The use of two techniques was reported. and they appear to have received little acceptance in Europe or elsewhere. The Windsor probe is basically a hardness tester and provides an excellent Copyright by ASTM Int'l (all rights reserved). Malhotra [44]. In 1975. Briefly. a hammer known as Simbi was used to perforate concrete.) cylinders is shown in Fig. using a single probe templet.).25 in. The exposed length of the probe is taken as a measure of the compressive strength of concrete. the powder-activated driver is used to fire a probe into the concrete.) concrete slabs. and Malhotra [43. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. there is little published work available on these tests. 2. The Windsor probe equipment consists of a powder-activated 1gun or driver. The probes have a diameter of 6. In 1966. .. ] . ./~950/.2 1. 21 ~ >- ..(25mm) Size of slabs probed 2 4 X 2 4 X ~ in... I .. .. FIG...5 3 3 3 + 5385 X psi ..... 2-6~ Exposed Probe Length... . .... c~ oo cv ~ I ~0 '" Aggregate type = limestone Maximum size = I in.. t .. z. ...4 ]. No further reproductions authorized.} 5oo ... 2--Relationship between exposed probe length and 26-day compressive strength of concrete. 3--Relationship between exposed probe length and 28-day compressive strength of concrete as published by different investigators. .IS.. 40 . . . In. . 41 Confidence Umits ..0 2..~ L . From Ref 35.E= 327 psi / 3000 ~ o . .. .214 TESTS A N D PROPERTIES OF CONCRETE mm 30 40 ~2 60 50 .. 2 - LO 12 28 14 16 18 - 20 :~ 14 22 Exposed Probe Length.. .. ? -Jr'. . .X FIG.. . 50 60 .2 2. .... (/I .. AI:~. From Ref 35. . . mm 30 ff 600(: .. ._. f X 4.4 01. . . ...Molhotro I .... Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement... in.oi Y/'J . Copyright by ASTM Int'l (all rights reserved).. . (610 X 6 1 0 X 2 0 0 mm) 1..000 ~ ~ I ..6 '~ 2. Y= .. . . in Greece. the softestof all minerals. The Windsor probe equipment is simple. the hardest of all known substances. The pull-out techniques. wearing of safety glasses is strongly recommended.3. Because of its shape. Because of the very nature of the test equipment. In 1968. s Named after mineralogist Mohs who deviseda scale of hardness in ~r talc. The within-batch standard deviation and coefficient of variation. Ten minutes after driving. However. and Rutenbeck [53] have reported data on the pull-out tests proposed by Richards. Tremper [48] in the United States reported results of laboratory studies dealing with pull-out tests covering strengths up to 35. though in use in the Union of Soviet Socialist Republics [47] since 1935. in the United States. with change in source of aggregates. is No.) in diameter. The pull-out force is then related to compressive strength. 5 Therefore. Richards [50]. is driven into a concrete surface using a gun. The penetration of the probe into the concrete is affected by the hardness of the aggregate as measured on Mohs' scale of hardness. Malhotra [44].1 and 0. and Gaynor [46] indicate that the variation in the probe test results is large compared with the variation in compressive strength on companion specimens. and needs little maintenance except for occasional cleaning of the barrel of the gun. 10. as reported by various investigators. Pull-Out Tests Utilizing a special dynamometer.37 in. 4).) long and 4 mm (0. the necessary pull-out force being measured on a manometer. has advocated these tests on structural concrete members. . it cannot and should not be expected to yield absolute values of strength. No further reproductions authorized. it is desirable for each user of the Windsor probe to prepare his own calibration charts for the type of concrete under investigation. a pull-out test measures the force required to pull out from concrete a specially shaped steel rod whose enlarged end has been cast into the concrete (Fig. new calibration charts become mandatory. the nail is extracted. without extensive calibration with specific concretes. Copyright by ASTM Int'l (all rights reserved).2 MPa (5000 psi). 34 mm (1. In recent years.16 in.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 215 means of determining the relative strength of concrete in the same structure or relative strengths in different structures. the ratio of the pull-out to compressive strength being between 0. 1 and diamond. Gaynor [51]. In 1944. 5). reported the development of a test in which a standard nail. is given No. are relatively new elsewhere. the generating lines of the cone running at approximately 45 deg to the direction of pull (Fig. The concrete is simultaneously in tension and in shear. The system has a number of built-in safety features that prevent accidental discharge or escape of the projectile from the gun. Tassios [49]. are shown in Table 1. the steel rod is pulled out with a cone of the concrete. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Malhotra [52]. The published data by Arni [42]. rugged. a From Ref 35. 7.7 3.8 5. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1 1 semilightweight (Expanded shale as coarse aggregate) 25 25 19 3/4 quartz 19 19 3/4 3/4 19 25 1 3/4 50 mm 2 in.30 4. cylinders (152 by 305-mm) 24 by 24 by 8-in. days 0. and 28 3. 7.105 0.5 7. prisms (150 by 150 by 1690-mm) 24 by 24 by 8-in. slabs (610 by 610 by 200-ram) 6 by 23 by 48-in. slabs (610 by 610 by 200-ram) 6 by 6 by 66-in. No further reproductions authorized.57 2.I 384e 48a 28 c 48a 20r 189b 136b Total Number of Probes 3 and 91 3 and 91 7 and 28 35 7 and 29 7 and 28 3. Gaynor limestone Malhotra gravel gravel.143 in.Copyright by ASTM Int'l (all rights reserved). trap rock Type of Aggregate Used Arni Investigation Reported by Maximum Aggregate Size TABLE 1--Within-batch standard deviation and coefficient of variation of probe measurements.124 0. a m --4 m 0 z 0 "1"1 0 --4 "o m O "o z m r . 6.054 0. (152 by 305-mm) cylinders ranged from 2000 to 6000 psi (13.3 MPa).05 Coefficient of Variation. f9 probes per test. el6 probes per test.37 1.8 to 41. and 28 Age of Test.4 5.21 4. walls (150 by 580 by 1210-mm) 6 by 23 by 48-in.14 1. 16 by 20 by 8-in. limestone.16 0. slab (410 by 510 by 200-mm) 16 by 20 by 8-in. a3 probes per test.4 3.5 mm 3.17 0. slab (410 by 510 by 200-mm) 6 by 12-in.062 0.66 3. walls (150 by 580 by 1210-mm) Type of Specimens Tested 256. b4 probes per test.62 2. c2 probes per test.087 0. % Standard Deviation NoTE--Compressive strength of 6 by 12-in. o.00in. Shaft . (12ZOrnrn) // d2=2..I I I~ [~ // ~Steel II/ Nuts .1rnrn) h =2.3 x 9. No further reproductions authorized. E E ' r : F. . 5 . . From R e f 52. (127. 7. x 0. I T- I I ~1"-. a ..8mm) d2 -dl 0r =67 degrees FIG. ' .Srnm) i /Threaded I I"~1 : l I -- ..08in (52.) cylinders is shown in Fig.217 WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS I / Bearing Ring \\ Threaded Shaft Embedded Head --------A \ // // \\ d I =5. .. From R e f 54. 5.Smrnl ~ L ..O-in. 6. / FIG. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. *a. A relationship between the pull-out strength and 28-day compressive strength of 152 by 305-mm (6 by 12-in.. 4--Sketch showing the relative posttion and dimensions o f the ring-bearing plate and the embedded head.A line drawing of the pull-out assembly. together with the cone of concrete./ " . immediately after the test.57.. Though these data cannot be compared directly because of the use of difCopyright by ASTM Int'l (all rights reserved).375-in.25 in..0 turn) t_ . ~ h '1 e"~' 2. 2o.. L _ _ . and Malhotra and Carette [54] have been compared with those reported by Rutenbeck [53] and are shown in Fig. o...7o.. The results obtained by Malhotra [52]../ 1 (. {51xg. W a e h e r .j ' 9 ' :. (57.25-in.. _ .. 9 i 7.24X-791 p s i . The technique is simple. Another disadvantage is that the pull-out tests being used in North America have to be planned in advance and. indicating that the strength value obtained in the pullout test is probably a measure of the direct shear strength.1 34.4 4.- - - - - 138 Compresl~ve strength volues ore the overoge of three test results.8 5. if a pull-out force of a given minimum strength is applied without failure.5 j x x 276 . and inexpensive.5 62 6.NocmalPortlond ASTM TypeI 9 :5/4-in.1 4. 8 0 0 o 2' IM O Z 2.. ferent materials and pull-out assemblies.3 >t. it may be assumed that a minimum strength has been reached for in-situ concrete and the structural unit need not be stressed to failure. The testing can be done in the field in a matter of minutes and the test results are reproducible.6 8.9/ . 6--Relationship between pull-out and 28-day compressive strength of 152 by 305-ram cylinders. Pull-out slrenglh vOluesom oneltwo tilt results. . Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. size crush~J grovel =Noturol$ond T 5000 Z ~ 2000 .~ 4 0 O 0 9 tO ---~ / / f nt Coorle ogg Fine ogg J f 41.8 3.) 6000 x x x N 5ooo z Y = 6. The main advantages of the pull-out tests are that they do measure the insitu strength of concrete.(19-mm)n-~t.SE.0 552 2B-DAY TEST RESULTS -~ 700(] J48.218 TESTS A N D PROPERTIES OF CONCRETE MPo I . effective.3 9. cannot be performed at random after the concrete has hardened.X F I G . Copyright by ASTM Int'l (all rights reserved). The major disadvantage of the pull-out test is that damage to the concrete surface must be repaired. The pull-out strength is of the same order of magnitude as the direct shear strength of concrete. However. the correlations appear to be much alike. uJ I 0 0 0 0 300 400 500 600 700 800 900 I000 I100 1200 1:300 28-DAY PULL-OUT STRENGTH. unlike the other in-situ tests. From Ref 54.= 684 psi Z Correlation coefficient = 0. No further reproductions authorized.P S I . . Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized.PSI 69 0 1600 1400 FIG. . Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement./ K ~o j ~4f~IC ROtiO=0-41 [ Corm ~rl~lte = ~ ~4 LCal~otte /~r Entroin~gand WoterReducing . 8--Relationships between maturity of concrete and its compressive strength. . From R e f 54.5 6.9 8.1 5. .5 400o 276 -r (1972) 2017 ~2ooo i I000 13.8 / o /~-~ 2OO RUTENBECK (1973) 400 600 800 I000 1200 28-13AY PULL-OUT STRENGTH.7 11'~52 / 7O00 =.entigrede Degree Houri ) FIG.== ! | 8 300O 2500 E i K 2000 1500 .8 ON NONDESTRUCTIVE TESTS 219 MPo 0 ~176176 4.ed 6 7 1000 500 400 600 800 I 0 0 0 1200 t400 1600 1800 2000 $ Moludfy Meter Reodlng-(C.HOTRA and CARETTE (1975) - ~oo x 41. .4 2. . 7--Comparison of relationships obtained in this investigation with those obtained by others.3 IK~. I0 Admlxturu Wenl Lh.3 9.WHITEHURST AND MALHOTRA 1. 48.1 / _z 5000 34. . strength of concrete in structures can be monitored successfully. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.0. The combined effect of time and temperature has been the subject of study by several investigators since 1904 but no hypothesis was formulated in early years. this concept has serious limitations and these must be recognized. Saul [57]. It is generally agreed that the maturity concept is applicable only if: (a) testing of concrete is confined within the range of Copyright by ASTM Int'l (all rights reserved). m. and others [58. Nurse [56]. As a result of his investigations. He defined the datum temperature for maturity as the temperature at which the strength of concrete remains constant. the maturity concept has been used to estimate the in-situ strength of concrete during construction stages in a number of buildings in the Toronto area. Malhotra [65] and others [66] have attempted to relate compressive strengths obtained using accelerated-strength tests with the maturities for these tests. Hudson and Steele [64] have used the maturity approach to predict potential strength of concrete on highway projects in West Virginia using the equation logS28 = 2. the most important being the temperature of curing. However.75 logSe -. the CN Tower being one of them [62. Swenson [61] has used the maturity concept to estimate the strength gain of concrete in structures.9844 + 0. However. and attempted to establish a rational basis for datum temperature for use in maturity calculations.59]. One such relationship is shown in Fig. Then in the 1950s. The advantages of the use of the maturity concept are obvious.12.2 ~ (10 ~ The maturity of in-situ concrete can be monitored by thermocouples or by instruments called maturity meters. The strength of in-situ concrete is then estimated using prior relationships established between maturity and compressive strength of test cylinders. In recent years. Maturity was defined as the product of time and temperature with a datum temperature of --10~ (14~ In 1956. the concept of maturity was advanced by Mclntosh [55]. with proper use of in-place thermocouples. No further reproductions authorized. and strengthmaturity relationships were published.220 TESTS AND PROPERTIES OF CONCRETE Maturity Concept It is well known that the compressive strength of well cured concrete increases with time.51 logm (10) where S2s = predicted 28-day compressive strength. the increase in strength is governed by many factors other than curing time. he concluded that the datum temperature was -. 8. psi Se = compressive strength (psi) of specimens tested at an early age and having a maturity. and m = degree hours of maturity at the time of test (~ h). 63]. Plowman [60] examined relationships between concrete strength and its maturity. to follow progressive changes in the quality of concrete in either specimens or structures. In general. and to determine the presence or absence of cracking in monolithic concrete. It appears that the sustained frequency tests have their main application in tracing the course of deterioration in specimens subject to weathering or exposure tests. particularly in the case of those devices which do not provide for visual examination of transmitted and received signals. throughout a structure. The most exhaustive investigation of these factors reported to date is that of Jones [16]. Usually the most pronounced influence on results is the type of aggregate used in the concrete because of the wide ranges possible in elasticity and density. including pavements. it is both desirable and proper to compute the dynamic modulus of elasticity or rigidity from the appropriate resonant frequency. The level of effective pulse transmission is the limiting condition that will govern the operating range. temperature. or lack thereof. Summary It has been the experience of users of dynamic testing that many factors influence the results in varying degrees. application of these techniques to structures.6 and 26. and admixtures. aggregate-cement and water-cement ratios. Recognizing these influences and making proper allowances for them are basic requirements in evaluating such test data.8~ (60 and 80~ (this is a rather limited range) and (c) no loss of moisture by drying occurs during the curing period. depending on the characteristics of instrumentation and on the inherent property of concrete to attenuate the impulse. Frequently the maximum size of coarse aggregate must be considered in comparing different series of tests. type of cement. . No further reproductions authorized. reinforcement. and difficulties in the interpretation of measurements on any but the most elementary forms. This maximum range may vary from perhaps a few centimetres (inches) in unset concrete to 15 to 18 m (50 to 60 ft) in sound concrete of high quality. Velocity tests on concrete are not hampered significantly by size and shape effects. The major applications of pulse velocity tests on concrete are to establish the degree of uniformity. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 221 maturity represented by about 3 to 28 days at normal temperatures. With respect to the prediction of values for other properties of concrete on the basis of the results of dynamic tests. Other factors influencing results include moisture content. is hampered by boundary effects. density. The attenuation of the impulse may lead to important errors. Such computation is necessary if results of tests on specimens of different sizes and shapes are to be compared. Since both the resonant frequency and the weight of the specimen can be measured directly and Poisson's ratio does not enter heavily into the computations (if Copyright by ASTM Int'l (all rights reserved). (b) the initial temperature of concrete is between 15. power requirements. 1113. C. Since results of these tests are not dependent upon size and shapes of the concrete tested. [6] Chang. No evidence has yet been presented to suggest that any better relationship exists between pulse velocities and other properties of the concrete than between resonant frequencies and these properties.. L. 41." Proceedings. 460. 1053. p. American Society for Testing and Materials.. p. 35." Proceedings. 1956. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. American Society for Testing and Materials. 1257. Highway Research Board. 1044. p. C. Vol. and Kesler. [5] Chang. T. Copyright by ASTM Int'l (all rights reserved). With respect to pulse velocity techniques. E. Vol.222 TESTS AND PROPERTIES OF CONCRETE longitudinal resonance is measured). W. W. Vol. it is believed that there is little danger of the introduction of significant error in making these computations. [3] Obert. S. direct comparisons may be made between tests made on different concretes or different sections of the same concrete. 1938. p.." Proceedings. E. . References [1} Powers. there seems to be very little reason for computing anything other than pulse velocity from the results of such tests. p.. No further reproductions authorized. and Higuchi. The computation of dynamic modulus of elasticity from pulse velocity requires a knowledge of both the unit weight of the concrete and Poisson's ratio. both of which values at least in the case of tests on structures. p. 1941. Batchelder and Lewis [20] have shown that the velocity itself correlates better with the results of resonant frequency tests on laboratory specimens than does the modulus of elasticity computed from velocity tests.. Y. C.. [4] Kesler. must be estimated." Proceedings. 38. [2] Thomson. Vol. "Correlation of Sonic Properties of Concrete with Creep and Relaxation.. "Prediction of Creep Behavior in Concrete from Sonic Properties. 1956. 1940. 6] indicates that two dynamic parameters may define the strength of concrete and its creep characteristics. "Measuring Changes in Physical Properties of Concrete by the Dynamic Method. The use of resonant frequency techniques for predicting other properties of concrete does not appear to be well supported by data presently available. "Discussion of Dynamic Methods of Testing Concrete with Suggestions for Standardization. However. and Duvall. It is emphasized that all the in-situ tests and concepts discussed in the paper cannot and do not yield absolute values of compressive strength of concrete in a structure and must not be considered as a substitute for standard compression tests. 436. Vol. E. although the work of Kesler [4] and Chang and Kesler [5. 1953. American Society for Testing and Materials. "Determination of Compressive Strength of Concrete by Using Its Sonic Properties. I. Part II." Proceedings. T." Proceedings. the techniques discussed are satisfactory for determining relative strengths of concrete in different parts of the same structure or relative strengths in different structures. American Society for Testing and Materials. 53. The pull-out test does measure strength but this is probably the shear strength of concrete from which an estimate of compressive strength may be made. S. and Kesler. T. 40. Vol. T. "Measuring Young's Modulus of Elasticity by Means of Sonic Vibration. C. 56. [12] Leslie. p. A. Vol. The StructuralEngineer. International Symposium on Nondestructive Testing on Materials and Structures. E. No further reproductions authorized. 53. J. [32] Sehmidt. Highway Research Board. Paris. Bulletins Nos. 41. 131..S. J. 301-306.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 223 [7] Long.. 1051. E.. D. RILEM. "Comparison of Dynamic Methods of Testing Concrete Subjected to Freezing and Thawing. June 1965. Highway Research Board. R. A. American Concrete Institute. T." Proceedings. R. 320-321. 1043." Journal. A. "Soniscope Tests Concrete Structures. [25] Vassitch. and Nefedova. and Lewis. American Society for Testing and Materials. No. G. 2. J. "Effect of Curing Methods Upon the Durability of Concrete as Measured by Changes in the Dynamic Modulus of Elasticity. . Ernst. 43. "The Testing of Concrete by an Ultrasonic Pulse Technique. and Kurtz. Vol.. [30] Well. R. RILEM. RILEM.. Pavle. 311-319. 176. and Cheesman. 1945. 53. 1043.. p. V.. G. Jan. 1940." Proceedings. 19S3. Cambridge University Press. Paris. Copyright by ASTM Int'l (all rights reserved). p. J. pp. E. 32. 7. 1949. [23] Zashchuk.. 1-7. p. J. 1953." Proceedings. 1954. p. [15] Jones. 47. 33. 2." Proceedings. [9] Stanton. 26. Vol. American Concrete Institute. 1954. Vol. 1963. pp. W.. 107. American Concrete Institute. 1944. Proceedings. Vol." Draft Code of Practice (June 1955). 14. 29. Kurt. 1949. [19] Cheesman. [22] Filina. No. July 1936. W. 1951." Standard Code DIN 4240. [24] Gaede. "Pulse Velocity Testing of Concrete. T. p. and Sandenaw. German Committee for Reinforced Concrete. 1949. Symposium on Nondestructive Testing of Concrete and Timber. pp. 15-30. Vol. "Measurement of Pressures on Rock Pillars in Underground Mines. "An Ultrasonic Method of Studying Deterioration and Cracking in Concrete Structures. [26] Williams. "The Non-Destructive Testing of Concrete. (in Russian). J. [10] Obert. Proceedings. U. pp. Vol. Vol. W. R. 321-326. pp. 1955. International Symposium on Nondestructive Testing of Materials and Structures.. "A Review of Pulse Velocity Techniques and Equipment for Testing Concrete." Beton i Zhelezobeton. G. Gustav. F." R. pp.. Vol. American Society for Testing and Materials. E. Feb. Vol. International Symposium on Nondestructive Testing of Materials and Structures. 1962. p. Proceedings. American Concrete Institute.. t953. London. Proceedings. American Society for Testing and Materials." RILEMBulletin. 1943. Kurtz. 11. Berlin. [29] "Ball Test for Cellular Concrete (Kugelschlagprtlfung von Gasund Schaumbeton). 224-225. H. 1053. p. "The Control of Concrete Quality in Road Pavements Without Destructive Tests. 17. A. [21] Jones. "Dynamic Testing of Concrete with the Soniseope Apparatus. G.. Proceedings. 1954. Deutscher Ausschuss for Stahlheton. 41. B. 53. [27] Jones. Vol. 1953. "Pribory dlya Kontrolya Kachestva betonnykh i zhelezobetonnykh konstruktsii. Proceedings. 6. B. [16] Jones. 226.. Vol. London. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. American Society for Testing and Materials. [17] Whitehurst. Beton und Stahlbetonbau (Berlin). [18] Reunion des Laboratoires d'Essais et de Recherches sur les Materiaux et les Constructions (Union of Testing and Research Laboratories for Materials and Structures). June. [31] "Report of the RILEM Working Group on the Nondestructive Testing of Concrete. "Tests Comparing the Modulus of Elasticity of Portland Cement Concrete as Determined by the Dynamic (Sonic) and Compression (Secant at 1000 psi) Methods. 310-319. pp. L 3521. 433. 1966. 19S4. T. Bureau of Mines. H." Bulletin No. March 19S3-June 1954. "An Instrument and a Technique for Field Determination of the Modulus of Elasticity of Concrete (Pavements).." Magazine of Concrete Research. [8] Pickett.. 258. 121-125. 8. Paris. Vol. Aug. [28] "Ball Impact Test for Normal Concrete (Kugelschlagpriifung yon Beton mit dichtem Gef0ge). March 1961. No. R. 20. [14] Whitehurst. p." Journal. June 1969. [11] Long. Vol. "Ball Impact Testing for Concrete (Die Kugelschlagpriifung yon Beton)." Avtom.. p. [20] Batchelder. F.. pp. L. 3. No. M. 2. Paris... I. 13-18. Sept. No." Journal. 1952.." Journal." Bulletin No. Proceedings. 2. pp. Dorogi. 50. Highway Research Board. 27. Vol. p. Institution of Civil Engineers. "Dynamic Testing of Pavements. New Series No. April 194S. Vol. Non-Destructive Testing of Concrete. E." Proceedings. W. [13] Parker." Proceedings. Proceedings. Dec. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. pp. [44] Malhotra. Public Roads. "Pull-Out Strength Tests of Concrete. 37. No. Vol. [43] Malhotra. T. Highway Research Board. M. pp. 1957. Maine. [49] Tassios. J. Discussion. Proceedings. C.. No. B. 305. Vol. RILEM Jan. 1972. Internal Laboratory Reports issued by National Ready-Mixed Concrete Association. pp. D. American Concrete Institute. Bailey. pp.-Feb. Louisiana HPR (7). No further reproductions authorized." Proceedings. 21. T. 169-183. 27-36. pp. Vol.-Feb. Vol. June 1958. Magazine of Concrete Research. Magazine of Concrete Research. Mines and Resources. 1975. Todd. Jan. 1968. Journal. Journal. pp. Detroit. pp. 10. Paris. Vol. 161-165. pp. 249-256. W. Department of Energy. 1968. Dec. SP 22. International Symposium on Nondestructive Testing of Materials and Structures. Washington. 1974. pp.. Vol. 14. 21-28. Jan. V. M. 1969. pp. No... 44. V. "Preliminary Evaluation of Windsor Probe Equipment for Estimating the Compressive Strength of Concrete. Highway Research Record. 1969. 50. G. Vol. Texas. March 1958. Discussion. 17. Proceedings. [36] Zoldners. Department of Energy. A. Proceedings. RILEM. 1969)." presented at 39th Annual Convention of the National Ready Mixed Concrete Association (New York.. V. Vol. pp. E. 2.. Vol. 28. 1954. 28." Mines Branch Monograph No. J. 1961. 1976. 1. Vol. 27-32. G." Paper presented at the Research Session.. "In-Place Strength of Concrete--A Comparison of Two Test Systems. 61-66." Mines Branch Investigation Report IR 71-1. R.. 3-15. [56] Nurse. 1975. 158] Bergstrom. [39] Grieb. W." Publication No. Department of Energy. 323-336. [59] Rastrup. "Testing Hardened Concrete: Nondestructive Methods. Ottawa. 3." CANMET Report 76-8. National Technical University. 14-27. 55-67. Aug. 1954.. No. 51. [55] Mclntosh. R. 304-305. pp. M. [45] Law. 1949. [41] Kopf. Dec. No.. A. and Carette. Owen. Materials and Structures. American Concrete Institute. Annual Meeting of American Concrete Institute. Journal. No. pp. Pulse Velocity. J. M. pp. W. Mines and Resources. 1976. No. G. D. J. Vol. 54. pp. [46] Gaynor... No. [60] Plowman. III. 7. L.. Vol. V. N. Vol. 875.. V. [37] Greene. [34] Malhotra. [48] Tremper. 79-92. M. American Society for Testing and Materials. Magazine of Concrete Research. 8. 45-50. 1938. "New Developments in In-Place Testing of Shotcrete. No. 43. 24. 2. 2. A. 880-887. Dallas. Transportation Research Record 558. Research Project No. G. 4 Nov. Louisiana Department of Highways. [53] Rutenbeck. Materials and Structures.. 45-49. Ottawa. 1969. "Comparison of Pull-Out Strength of Concrete With Compressive Strength of Cylinders and Cores. Magazine of Concrete Research. D.. pp.. Berwick Academy." Research Report No. [38] Mitchell. No. H. 22. No. V. 272. Highway Research Board. Bulletin No." Paper presented at the 1973 Engineering Foundation Conference on Use of Shotcrete for Underground Structural Support. Athens. 55-68. No. M. Magazine of Concrete Research. [40] VoeUmy. 13-22. "The Measurement of Concrete Strength by Embedded Pull-Out Bars. [51] Gaynor. 14. T.. 2. G. G. 9. 1. 1972. "Concrete Strength Study. Engineering Journal (Canada). Magazine of Concrete Research. Erik. Vol.. Nov. S. [47] Skramtajew (sic) (also Skramtaev). London. Transportation Research Board. No. Vol. Published with NRMCA Technical Information Letter No. pp. [54] Malhotra. 256-1 to 256-20. Ottawa. Mines and Resources." ACI Monograph No. No.. 44. Canada. Proceedings. 127-140. 30.. 68-2C(B). "Nondestructive Methods for Testing Concrete. 79-88. 378. R. P. No. 9. C.. .-Feb.. 8. "A New Nondestructive Method of Concrete Strength Determination. 19-31. 1949. [61] Swenson. G. 1.. and Rebound Number. 3. [50] Richards. Copyright by ASTM Int'l (all rights reserved). Discussion pp. RILEM. 2. pp. Jan. W. American Concrete Institute. 285-303. [52] Malhotra. pp. and Burt.. A. 1944. Vol. Vol. South Berwick. [62] Bickley. Detroit. 6. G.. D. S. pp. [42] Arni. J. 8. E..224 TESTS AND PROPERTIES OF CONCRETE [33] Kolek. J. No. R. M. M. pp. 61. [35] Malhotra.. and Hoagland. 1970. [57] Saul. American Concrete Institute. pp. Magazine of Concrete Research. 34. Canada. and Steele. 1975. pp. . B. No further reproductions authorized. W. V. G. Sun Apr 6 21:31:12 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. pp. Transportation Research Record 558.WHITEHURST AND MALHOTRA ON NONDESTRUCTIVE TESTS 225 163] Mukherjee. 1-12. [65] ~Malhotra. Mines and Resources. and Dietz. P.. 29-44." Circular IC 277. Mines Branch Information. pp. Transportation Research Board.. 1975. Copyright by ASTM Int'l (all rights reserved). Transportation Research Record 558. K.. [66] Ramakrishnan. "Maturity Concept and the Estimation of Concrete Strength--A Review. Canada. Transportation Research Record 558.. Ottawa. [64] Hudson. Transportation Research Board. M. 87-92. J. S. Department of Energy. 1971. V. 1975. Transportation Research Board. Tex. This dimensional instability is of considerable importance to the construction industry. Many factors affect the magnitude of these volume changes. but volume changes due to unsound materials or chemical and mechanical action are not reversible and are cumulative as long as the action continues. subgrades. reinforcement. No further reproductions authorized. Reliable information is available on the major factors affecting the magnitude of volume changes. S a w y e r 1 Chapter 16 Volume Change Introduction Concrete is subject to changes in volume during and after the hardening period. L. Volume changes due to variations of temperature. These volume changes. 77001. Sun Apr 6 21:41:45 EDT 2014 226 Downloaded/printed by Universidade do Gois pursuant Agreement. or connecting members. However. Normal volume changes would be of little concern if the concrete were free to deform. Due to concrete being weaker in tension than in compression. and loads are partly or entirely reversible. with satisfactory dimensional stability. The magnitude of volume changes generally is stated in linear rather than volumetric units.astm. can be prevented or minimized by controlling the variables that affect volume changes. and due to applied loads. concrete usually is restrained by foundations. This is for convenience. restained shrinkage causing tensile stresses is usually more important than expansion that causes compressive stresses. as these linear changes can be measured easily and are of primary interest. and the understanding of the nature of these changes is important for those using concrete as a construction material. The volume changes that or1Chief. Normal volume changes in hardened concrete can result from changes in temperature and moisture content. if excessive. When proper attention is given to these factors. Copyright by ASTM Int'l (all rights reserved). can result in high stresses and cracking. Excessive volume change. humidity.STP169B-EB/Dec. Research and Development. and stresses can be produced in the concrete which may cause distress and even failure. concrete can be produced that is relatively free of cracks. It is an important consideration whether the volume changes occur in hardened concrete or prior to hardening. with resulting high stresses and cracking. with resulting poor performance of the concrete.org . Houston. 1978 J. Lone Star Industries. Copyright9 1978 tobyLicense ASTM International www. This begins shortly after the concrete is placed and continues until maximum compaction of the solids. therefore. volume changes can occur due to cement hydration." For example. During this period. and wind velocity can have a pronounced effect on rate of evaporation and. Bleeding is the term used to describe the accumulation of water at the surface of fresh concrete due to sedimentation of solids." This change in volume or length due to creep is largely unrecoverable in newly placed concrete. They may be practically eliminated by taking appropriate measures during construction to reduce the rate and total amount of water evaporation from the surface of the plastic concrete.60 in. However. absorption. However. ranging from negligible up to 0. Reactions between the water and the cement. it is largely recoverable when it occurs in old or dry concrete. and bleeding.SAWYER ON VOLUME CHANGE 227 dinarily occur are small. or 0. Also. thermal change. and evaporation of bleed water tend to decrease the volume of the concrete. Although this creep continues for years. concretes of equal strength but of different ages will have different creep Copyright by ASTM Int'l (all rights reserved). Continuously Applied Stress When a sustained load is applied to concrete. temperature. surface cracking of the plastic concrete can occur. per 100 ft). particle interference. This latter deformation is called "creep. Volume Changes in Fresh Concrete Freshly mixed concrete remains plastic for a relatively short time. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Volume Changes in Hardened Concrete Hardened concrete undergoes small changes in volume due to sustained stress and changes in temperature and moisture content. the rate decreases with time. or loss of plasticity of the concrete due to setting stops further sedimentation. Also. a change in length of 500 millionths of a metre per metre may also be expressed as 0. These length changes are often expressed in "millionths. cracking can occur one day but not the next. absorption of water by the aggregates. Creep is proportional to stress within normal stress ranges. deformation caused by this load can occur immediately. This "plastic cracking" can occur soon after the concrete has been placed. . When the surface of the fresh concrete is subjected to rapid drying. a time-dependent deformation which begins immediately but continues for years can result from this sustained load.05 percent. These cracks appear mostly on horizontal surfaces and may have considerable depth.05 m in 100 m (0.1 percent change in length. Small changes in relative humidity. concrete may be subjected to potentially destructive forces due to chemical and mechanical attack. However.5 • 10-6/~ when the effect of moisture change is taken into account [4].5 to 6. consequently.31. The method of curing prior to loading has an influence on the amount of creep of the concrete. for 100 ft for 100~ The coefficient of expansion is essentially constant over the normal temperature range and is usually between 6. these volume changes are on the same order of magnitude as observed for steel and. Temperature Changes As the temperature of concrete rises and falls. Copyright by ASTM Int'l (all rights reserved). Consideration of these changes. Fortunately. and the duration of the sustained stress. creep is dependent upon the magnitude of the stress.5 • 10-6/~ or 0. and curing conditions. The coefficient of thermal expansion of a given concrete can vary with the degree of water saturation of the concrete [5]. 2 The thermal coefficient of concrete can be calculated by using the weighted average of the coefficients of its ingredients [2. The mineral composition and structure of aggregates are the major factors determining the coefficient of thermal expansion of concrete [6]. water-cement (w/c) ratio and concrete age. reinforced concrete structures perform satisfactorily over a wide range of temperature variations. No further reproductions authorized. type of cement. amount of cement paste. due 2The italic numbers in brackets refer to the list of referencesappended to this paper. This is a physical phenomenon common to all materials. Other factors affecting creep are: type. These changes are largely dependent on the volume changes of the concrete's two principal components.10 m for 100 m of concrete subjected to a rise or fall of 100~ (0. amount of steel reinforcement. amount. Normal moist-cured concrete has the most creep. Concrete loaded at a late age will creep less than a concrete of equal strength loaded at an early age. Concrete that has been cured with high-pressure steam (autoclaving) has less creep than atmospheric steam-cured concrete. help to avoid damage to structures from internal stresses caused by the thermal volume changes of the concrete. size and shape of the concrete mass.228 TESTS AND PROPERTIES OF CONCRETE characteristics. This varies with factors such as aggregate type. for concrete it is complicated by differential expansion of its components which produces high internal stresses.66 in. mix proportions. The average value that is frequently used for this length change is around 10 • 10-6/~ (5. and maximum size of the aggregate. Thermal expansion of concrete is influenced by the type of aggregate. These changes in volume and the internal stresses produced by these changes have a strong influence on all types of concrete structures. and the application of a proper thermal coefficient of expansion for concrete in structural design. concrete expands and contracts. the age and strength of the concrete.3 and 11. the cement paste and the aggregate [1]. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.7 • 10-~176 (3. . Therefore. Concrete that is exposed to the atmosphere loses some of its moisture content and. However.. therefore. Rocks with little or no quartz. ambient temperature. The coefficient for various rocks that are used for concrete aggregates varies from 3. The amount of cement is of greater importance than the type of cement. These thermal changes in mass concrete usually are minimized by one or more of the following techniques: using low-heat portland cements (Types II and IV). with the possibility of cracking under traffic loads [8].0 to 7.6 X 10-6/~ (2. therefore. amount of mixing water. chilling the aggregates. . therefore. and the method of curing. Factors affecting the maximum concrete temperatures are: heat of hydration of the cement. The differences in shrinkage Copyright by ASTM Int'l (all rights reserved). if kept continuously moist. No further reproductions authorized. Moisture Changes Concrete expands due to a gain in moisture. concrete normally exists in a somewhat contracted state. and even for aggregates of a given type but from different sources. replacing part of the cement with a pozzolan. rhyolite. cooling the in-place concrete. Rocks. such as quartzite and sandstone. basalt. concrete is mainly influenced by the proportion of quartz present. chilling the mix water. etc. have intermediate coefficients [7]. Drying shrinkage can cause larger volume changes than normally are observed due to expansion of moist concrete. such as limestone. Thermal changes in pavements can be important as temperature gradients can cause curling of the slab.SAWYER ON VOLUME CHANGE 229 primarily to the large differences m the thermal coefficient of expansion of the various types of aggregate. The rate of expansion decreases with time and is very small after several years. rate of construction. Thermal changes in mass concrete are important.0 X 10-6/~ Data indicate that the thermal expansion of rock and. have a high quartz content and. and the specific heat and thermal conductivity of the concrete. and cracking can occur as the concrete cools from this maximum temperature. such as granite. Igneous rocks with medium quartz content. it will orpand slowly for years. Concrete that is allowed to dry will contract or shrink.6 to 12. The amount of shrinkage observed as concrete dries is dependent upon several factors. such as: amount and type of aggregate. the total expansion is normally small enough to be unimportant.25 percent. ambient temperature and relative humidity. the highest coefficient. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Expansion of the moist concrete begins after the initial setting shrinkage has taken place and. have the lowest coefficient. as the heat liberated due to cement hydration can result in high maximum concrete temperatures. initial concrete temperature. although cements with more than the optimum sulfur trioxide (SOa) content can cause more than normal expansion in moist concrete. and contracts with a loss in moisture. This total expansion is usually less than 0. properties and amounts of admixtures. However. Shrinkage of plain concrete in the range of 0. Much of the reported data have not differentiated between the two and combined shrinkage is reported as drying shrinkage. the swelling that occurs during continuous wet storage over a period of several years is only about one-third of the shrinkage observed in concrete air-dried for the same period. due to the reaction between carbon dioxide and cement constituents.04 to 0. it seems inconsistent to rely on the behavior of either neat pastes or rich mortars to predict the ultimate shrinkage of concretes. relative humidity.08 percent has been observed when the concrete was exposed to air at 50 percent relative humidity. Alternate cycles of wetting and drying cause cycles of swelling and shrinking. This is about the same as the thermal contraction caused by a decrease in temperature of 56~ (100~ For concrete exposed to weather. However. It cannot be said that a cement. No further reproductions authorized. Oven-dry concrete or saturated concrete is not very susceptible to carbonate shrinkage. will have therefore more or less shrinkage than a cement meeting the requirements for another type [IO]. ASTM Measuring the Drying Shrinkage of Mortar Containing Portland Cement (C 596) can be used to determine the effect of portland cement on the drying shrinkage of a graded Ottawa sand mortar subjected to stated conditions of temperature. appear to be of little practical significance [9]. . a cement that is deficient in gypsum can result in more shrinkage than would be the case if the cement contained the optimum amount of gypsum [11]. Normally aggregates act as a restraint on concrete volume changes due to Copyright by ASTM Int'l (all rights reserved). However.72 in. However. for 100 ft).06 m/100 m (0. Shrinking and swelling of concrete due to wetting and drying is almost exclusively a property of the cement paste [131. Concrete that has been subjected to carbonation shrinkage will still shrink and swell with changes in moisture content. because it conforms with the chemical and physical requirements of any one type of cement. at intermediate humidities. Carbonation shrinkage. however. This means that concrete when dried from a saturated condition to a state of equilibrium with air at 50 percent relative humidity can shrink about 0. takes place concurrently with drying shrinkage. The drying shrinkage of mortar as determined by this method has been shown to have a linear relation to the drying shrinkage of concrete made with the same cement and exposed to the same drying conditions. carbon dioxide produces a gradual irreversible shrinkage. The amount of shrinkage varies with the humidity and reaches a maximum at around 55 percent relative humidity.230 TESTS AND PROPERTIES OF CONCRETE due to cement type and period of moist curing. prior to drying. and rate of evaporation of the environment. especially if the tests are concluded at early ages [12]. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the volume changes due to temperature and moisture variations frequently tend to offset each other. the amplitude of these changes is likely to be smaller than before carbonation. The reported data are sometimes conflicting but. quartz. Aggregates with a high modulus of elasticity and those with rough surfaces offer more restraint to shrinkage. Also. the use of the largest practical size minimizes shrinkage. feldspar. keeping the total aggregate content of the concrete as high as possible will help to minimize shrinkage.04 percent when dried and subsequently wetted [14]. Even though the relationship between change of water content and change of volume is not the same for all pastes [15]. as the effect on shrinkage is a function only of the total quantity of the aggregates per unit volume of the concrete [16]. therefore. or any practice that increases the water requirements can increase shrinkage. in general. are more resistant to shrinkage of cement paste. slate. As concrete with large size aggregates tends to have a greater total aggregate content. Shrinkage of structural lightweight concrete varies from equal to about double that of normal weight concrete [19]. Some aggregates are hard and difficult to compress and. dolomite. The use of high slump concrete. Concrete made with sandstone. The use of dirty sands or unwashed coarse aggregate containing clay can cause excessive shrinkage. shrinkage can be minimized by keeping the water content of the paste as low as possible. it has been reported that in practical concrete mixes the size and gradation of the aggregates have little affect. The total amount and properties of the aggregates have an influence on shrinkage. Aggregates embedded in the cement paste restrain the shrinkage of the cement paste. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and limestone [18]. Water reducing admixtures generally have a tendency to reduce drying shrinkage due to reduced water requirements [20]. This can contribute to excessive volume changes and disintegration of concrete. Some water-reducing admixtures increase shrinkage although they reduce water content. all admixtures that reduce the unit water content do not reduce drying shrinkage. . as inferior aggregates are generally rejected on the basis of tests other than dimensional change characteristics. The amount of water per unit volume of concrete is the most important controllable factor affecting shrinkage.SAWYER ON VOLUME CHANGE 231 wetting and drying. This is particularly true for those that contain an Copyright by ASTM Int'l (all rights reserved). Accelerators such as calcium chloride and triethanolamine tend to increase shrinkage. high fresh concrete temperatures. However. and pyroxene may shrink up to two times as much as concretes made with granite. Admixtures have a varying effect on the drying shrinkage of concrete. an increase in the amount of aggregate tends to decrease shrinkage. however. it has been found that some aggregates can have dimensional changes greater than 0. therefore. hornblende. Fortunately this is rare. an admixture that increases the unit water content may be expected to increase drying shrinkage. Higher values for dynamic Young's modulus of elasticity of concrete have been found to be associated with lower shrinkage and expansion values [17]. However. No further reproductions authorized. ASTM Specification for Chemical Admixtures for Concrete (C 494) limits the increase in drying shrinkage due to the admixture to 135 percent of the control concrete when the length change of the control is 0.02 to 0. It has been observed that shrinkage should be considered a rate process rather than in absolute terms when its effect on cracking of the concrete is considered [24].010 percent when the length change of the control concrete is less than 0. in other uses cracks are little more than interesting phenomena [23]. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. particularly when the concrete is restrained. Some data indicate a surface volume to shrinkage relationship that can be expressed as a volume to surface ratio. The susceptibility of concrete to cracking is influenced by several factors. . However. Volume changes in hardened concrete. it can be argued that although cracks are serious defects for some uses. entrained air has little effect on drying shrinkage.030 percent or greater or an increase in shrinkage of not over 0.232 TESTS AND PROPERTIES OF CONCRETE accelerator to counteract the retarding effect of the admixture. Pozzolanic materials. Factors such as degree of restraint. and tensile strength of the concrete effect the ability of concrete to resist cracking.03 percent drying shrinkage.03 percent at 28 days with the tests being made on mortar bars. Cracks in a concrete member are potentially weak spots with respect to applied load. Within normal limits. shrinkage continues over a longer period for the larger unit. The steel reinforcement tends to restrain but does not prevent drying shrinkage. thermal). However. No further reproductions authorized. amount of shrinkage (drying. produce tensile stresses and can result in cracking of the concrete. carbonation. The rate and total amount of shrinkage is affected by the size and shape of the concrete unit. Some care must be taken in relating shrinkage observed on small laboratory specimens to shrinkage expected in large concrete members. Also. The rate and total shrinkage is less for a large mass of concrete than for a small size concrete unit. such as pumicite or raw diatomaceous earth.030 percent. when used as a replacement for cement. with the difference depending on the amount of reinforcement. however. ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolans for Use in Portland Cement Concrete (C 618) limits the increase in drying shrinkage due to these materials to 0. it is reported that the use of up to 30 percent fly ash--used as a replacement for cement--did not increase shrinkage [22]. Reinforced concrete shrinks less than plain concrete. they offer avenues of egress and lower the resistance of the concrete to attack by aggressive solutions. Copyright by ASTM Int'l (all rights reserved). A combination of the least amount of shrinkage and the highest tensile strength should give good resistance to cracking. Structures with reinforced concrete having normal amounts of reinforcement usually have 0. tend to increase shrinkage. Some of the stress produced in the concrete by these factors can be relieved by creep of the concrete. Some chemical admixtures can increase shrinkage by altering the SO3 content required for minimum shrinkage from that determined when the cement was manufactured [21]. this expansion can increase until disintegration occurs. Where available. Excessive concrete expansion due to the hydration of uncombined or free calcium oxide (CaO) and hardburned. For these chemical tests. 4. if the action continues. A combination of wrong choices could result in seven times as much shrinkage as would result from the best choices [25]. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 5. as this tends to reduce water requirements. (It should be noted that the term unsoundness as used here is not the same as unsoundness when used for aggregate. and the amount of expanCopyright by ASTM Int'l (all rights reserved). rather than the sum. ASTM Chemical Analysis of Hydraulic Cement (C 114) can be used. Use the minimum water content required for proper placement. Signs of attack are generally first evident as expansion. as clay functions like gel instead of restraining shrinkage [27]. crystalline magnesium oxide (MgO) (periclase) is referred to as unsoundness. When materials are such that the concrete has inherently high drying shrinkage. . The above plus the other constituents of the cement are determined by this method. The following methods help to minimize volume changes [26]. 3. Tests made during the manufacture of portland cements and for acceptance testing of cement include tests for free CaO and MgO as well as for SO3 and alkalies.SAWYER ON VOLUME CHANGE 233 Control of Volume Changes Many factors influence volume changes.) The presence and amount of these materials in cements depends on several factors such as burning and cooling conditions during production of the cement. This potential unsoundness is normally detected by the ASTM Test for Autoclave Expansion of Portland Cement (C 151). Avoid aggregates that contain excessive amounts of clay. of the individual effects. No further reproductions authorized. use fine and coarse aggregate that exhibit low shrinkage characteristics when used in concrete. I. The undesirable effects of unsound cement have been recognized and reflected in specifications over the years. This attack can be due to internal causes. Use the largest total amount of aggregate. Chemical Attack and Unsoundness Volume changes can occur in concrete due to the concrete being subjected to chemical attack. The net volume change can be the product. and it appears that several factors can act at the same time to increase drying shrinkage. and. The hydration of these materials is slow and their potential expansion is delayed [28]. Avoid high slumps and high concrete temperatures which tend to increase the water demand of the concrete. 2. such as unsound cement or chemical reactions between cement and aggregates. the effects of additional adverse factors can be critical. as these can affect the volume stability of concrete under certain conditions. This plus the 6. If the C3A is above 8 pereent. does not exeeed 0. and under moist conditions this reaction can cause excessive expansion and cracking of concrete. expressed as SO3. There is some question as to whether the autoclave test provides adequate protection against unsoundness with blended cements I291. For Type II and IIA. and for these cements ASTM Specification C 150 permits additional SO3 in amounts up to 0. a maximum of 3. For Types IV and V.25 h. ASTM Specification C 150 limits the amount of SO3 based on the type of cement and the tricaleium aluminate (C3A) content of the eement. For Type III and IIIA cements having 8 percent or less C3A.5 percent SOa is allowed. this is not a problem with commercial cements since specifications restrict the SO3 contents to safe levels. ASTM Specification for Portland Cement (C 150) limits the maximum autoclave expansion to 0. loss of strength. However.5 percent above the specified limits. then 4. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.0 percent limit placed on MgO content by ASTM Specification C 150 generally is considered to provide protection against unsoundness. ASTM Test for Potential Expansion of Portland Cement Mortars Exposed to Sulfate (C 452) sometimes is utilized when it seems advisable to determine the potential sulfate resistanee of portland cements. and disintegration can occur due to reactions between the alkalies in cement and constituents of aggregates. ASTM Specification C 150 has this limit of 0. it is reeognized that this is more restrictive than necessary for some cements. the maximum is 3. For Type I and IA cements having a C3A content of 8 percent or less. No further reproductions authorized. but if the C3A is over 8 percent. However. These alkali-aggregate reactions can be controlled or reduced by using nonreactive aggregates or by using cements with alkali contents less than 0.3 percent SO3 is permitted.234 TESTS AND PROPERTIES OF CONCRETE sion is limited in cement specifications.60 percent for all types of cement as an optional chemical requirement that may be specified Copyright by ASTM Int'l (all rights reserved). the maximum allowed is 3.50 g/litre. the ealeium sulfate in the hydrated mortar at 24 _+ 0. when the cement is tested with the additional SO3 by the ASTM Test for Caleium Sulfate in Hydrated Portland Cement Mortar (C 265).5 percent SO3 is allowed. this higher SO3 limit is only permitted when it has been demonstrated by the ASTM Test for Optimum SO3 in Portland Cement (C 563) that this higher SO3 is required to provide the optimum SO3 level for this particular cement.80 percent for all types of cement. then up to 3.5 percent SO3. . a maximum of 2. Calcium sulfate when present in excessive amounts can eause expansion due to the continued formation of calcium sulfo-aluminate. Excessive expansion.0 percent SO3. This method is primarily for use in research and not for use as a basis for acceptance testing. This type of expansion is not detected by the autoclave test [30].0 percent SO3 is permitted. However.60 percent expressed as sodium oxide (Na20) equivalent. These siliceous constituents or argillaceous dolomitic limestones can react with alkalies. An additional safeguard is provided in that this higher level ean only be used if. No further reproductions authorized. Determination of the presence and quantities of these materials is helpful in evaluating the potential reactivity. magnesite or siderite. such as calcite. Data obtained by the following test methods will assist in making this evaluation. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Certain materials are known to be reactive with the alkalies in cements.SAWYER ON VOLUME CHANGE 235 when the cement is to be used in concrete with aggregates that may be deleteriously reactive.6 percent alkalies calculated as sodium oxide or with the addition of a material that has been shown to prevent harmful expansion due to alkali-aggregate reaction. or contact with moist ground shall not contain any materials that are deleteriously reactive with the alkalies in the cement in an amount sufficient to cause excessive expansion of mortar or concrete. Some materials render an aggregate deleteriously reactive when present in quantities of 1. . or silicates of magnesium such as antigarite (serpentine) [31. or ferrous iron. Appendix XI of ASTM Specification C 33 gives various methods for evaluating the potential reactivity of an aggregate.0 percent or even less. ASTM Test for Potential Reactivity of Aggregates (Chemical Method) (C 289) covers the chemical determination of the potential reactivity of an aggregate with alkalies in portland cement concrete. Results obtained by this test may not be correct for aggregates containing carbonates of calcium. However. Therefore. however. under some circumstances they may be derived from other Copyright by ASTM Int'l (all rights reserved). while not completely reliable in all cases. The error introduced by calcium carbonate is not significant unless the test values indicate that the potential reactivity is marginal. ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295) outlines procedures for petrographic examination by means of optical microscopes of materials proposed for use as aggregates in concrete. This appendix lists a number of methods that have been proposed for detecting this potential reactivity. Alkalies participating in the expansive reactions usually are derived from the cement. However. interpretation of data. provides helpful information. ASTM Specification for Concrete Aggregates (C 33) states that fine and coarse aggregate for use in concrete that will be subject to wetting. and examination of concrete structures containing a combination of fine and coarse aggregates and cements for use in new work. if such materials are present in injurious amounts. the aggregate may be used with a cement containing less than 0. This test can be made quickly and.32]. extended exposure to humid atmosphere. ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227) covers the determination of the susceptibility of cement-aggregate combinations to expansive reactions involving the alkalies by measuring the increase (or decrease) in length of mortar bars. dolomite. magnesium. evaluation of potential reactivity of an aggregate should be based upon judgement. these methods do not provide quantitative information on the degree of reactivity to be expected or tolerated in service. ASTM Test for Potential Alkali Reactivity of Carbonate Rocks For Concrete Aggregates (Rock Cylinder Method) (C 586) covers the determination of the expansive characteristics of carbonate rocks when immersed in a solution of sodium hydroxide (NaOH) at room temperature. This method is intended to supplement data from field service records. and the use of lithium and barium salts has been reported as a means of reducing expansion due to the alkali-siliceous aggregate reaction [33]. ASTM Test for Effectiveness of Mineral Admixtures in Preventing Excessive Expansion of Concrete Due to the Alkali-Aggregate Reaction (C 441) covers the determination of the effectiveness of mineral admixtures in preventing excessive expansion caused by the reaction between aggregates and alkalies in portland cement mixtures. petrographic examinations. The incorporation of fine ground pozzolanic materials in the concrete can provide some protection. then it is preferred to use the quantities of cement and admixture proposed for use on the job and the maximum mortar expansion at 14 days be limited Copyright by ASTM Int'l (all rights reserved). when made with a high-alkali cement. These length changes indicate the general level of reactivity of rocks and whether tests should be made to determine the effect of aggregate prepared from the rocks upon the volume change in concrete. A minimum value of 75 percent for reduction of mortar expansion is an optional requirement in ASTM Spec!fication C 618 when the pozzolan is proposed for use in combination with a high-alkali cement and an aggregate known to be potentially deleteriously alkali reactive. If the cement to be used on the job is available. Expansions produced in the mortar-bar test by the alkali-carbonate reaction are generally much less than those produced by the alkali-silica reaction for combinations having equally harmful effect on concrete in service. this method is not recommended as a means to detect alkali-carbonate reactions involving dolomite in certain calcitic dolomities and dolomitic limestones. This evaluation is based on the expansion developed by cement-admixture combinations in mortar bars made with reactive aggregates (borosilicate glass). This method is particularly applicable to certain cementaggregate combinations common in the central part of the United States.236 TESTS AND PROPERTIES OF CONCRETE constituents of the concrete or from external sources. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . No further reproductions authorized.200 percent or more at an age of 1 year may be considered unsatisfactory for use in concrete exposed to wide variations in temperature and degree of saturation with water. Cement-aggregate combinations that expand 0. and tests of aggregate in concrete. However. This test is useful as a research or preliminary screening method rather than for specification enforcement. This test. ASTM Test for Potential Volume Change of Cement-Aggregate Combinations (C 342) covers the determination of the potential expansion of cementaggregate combinations by measuring the linear expansion developed in mortar bars subjected to variations of temperature and water saturation during storage. furnishes information on the likelihood of harmful reactions occurring. These limits provide moderate (Type II) or high (Type V) sulfate resistance when the concrete is subjected to water containing sulfate. Various researchers have shown that the use of some pozzolans can increase the resistance of concrete to sulfate attack. if soils contain less than 0.20 percent sulfate ion. No further reproductions authorized. expansion can occur due to the formation of calcium sulfoaluminate (ettringite). It should be noted that a mineral admixture that is effective in preventing excessive expansion caused by the alkali-aggregate reaction is not necessarily suitable for use as an admixture in concrete.Al203. For soils containing between 0. In general.10 and 0. some researchers have shown improvement in sulfate resistance when calcite filler was used [36]. [34]. or water con-.0 percent.Al2Oa. Type II cement should prevent damaging sulfate reactions. Type V cement limits the CaA to a m a x i m u m of 5 percent and the tetracalcium aluminoferrite plus twice the tricalcium aluminate [4 CaO.SAWYER ON VOLUME CHANGE 237 to 0. no damaging sulfate reaction would be expected.Fe203 + 2(3 CaO. This can cause cracking of the concrete by developing tensile stresses that are high enough to overcome the tensile strength of the concrete. and Type V or cements with little or no C3A can be used when high sulfate resistance is desired. However.AI203)] or solid solution (4 CaO. The test for mortar expansion should be performed with each cement to be used on the job. or water containing more than 2000 p p m sulfate ion.20 percent sulfate ion. Others have shown that for long-time resistance the concrete should be made with high quality pozzolans and a sulfate resisting cement [35].Fe203 + 2 CaO.50 percent sulfate ion. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the magnitude of the expansion is reduced by restraint and a self-stress is developed. it must meet the requirements of the specifications covering the class of mineral admixture to which it belongs. For soils containing more than 0. If hardened concrete is subjected to water or soils containing soluble sulfates. Expansive and Nonshrink Concrete Several types of expansive cements have been formulated.10 percent sulfate ion. or water containing between 150 p p m and 1000 p p m sulfate ion. For soils containing more than 0. or water containing more than 1000 p p m sulfate ion.020 percent. ASTM Test C 150 limits the amount of CaA in Type II and IIA cement to a m a x i m u m of 8 percent. ASTM Type II cement can be used for moderate sulfate resistance. tains less than 150 p p m sulfate ion. .38]. usually based on the formation of hydrated calcium sulfoaluminates to give controlled expansion. There is some controversy regarding the effect of calcareous filler on sulfate resistance. In addition. Type V cement should be used. The level of Copyright by ASTM Int'l (all rights reserved).Fe2Oa) to a m a x i m u m of 20. In concrete made with these expansive cements. severe damage can be expected unless Type V cement or other means are taken to prevent or reduce damaging sulfate reactions [37. mix designs. Since the potential for expansion under conditions of controlled restraint of concrete made using shrinkage-compensating cement cannot always be predicted satisfactorily from tests of mortars made in accordance with ASTM Test C 806. and other physical and chemical effects. Test Methods Used for Determining Volume Changes Of a more general nature than methods previously mentioned and for testing hardened concrete for volume change. ASTM Test for Length Change of Hardened Cement Mortar and Concrete (C 157) can be used to determine the length changes of cement mortar and concrete due to causes other than Copyright by ASTM Int'l (all rights reserved). ASTM Specification for Expansive Hydraulic Cement (C 845) has been developed to cover hydraulic cements that expand during the early hardening period after setting. This method is of particular value in the determination of volume changes that occur during the plastic state. patching. schedules. evaporation. ASTM Test for Early Volume Change of Cementitious Mixtures (C 827) covers the determination of early volume change in cementitious mixtures. The specimens used in this method are not completely unrestrained so that the measurements are primarily useful for comparative purposes rather than as absolute values. drying shrinkage is about one-half the magnitude of that occurring in conventional concrete [40]. Three kinds of expansive cements are identified. hydration. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ASTM Test for Restrained Expansion of Expansive Cement Mortar (C 806) can be used to determine the length changes of expansive cement mortar while under restraint due to the development of internal forces resulting from hydration of the cement. including shrinkage or expansion due to subsidence. including cement paste. and it is noted that expansive cements also may be prepared in other ways. This method also can be used to study expansion involving degrees of restraint or variables in cements and cement contents. or environmental treatments. For testing these expansive cements. No further reproductions authorized. Preplaced aggregate concrete differs from conventional concrete in that it contains a higher percentage of coarse aggregate. Expansive or nonshrink materials are available commercially for use in grouting. Preplaced aggregate concrete (intrusion or grouted concrete) can be used where concrete of low volume change is required. and due to the point to point contact of the coarse aggregate. and other applications where it is desirable that the concrete fill a given volume after hardening. and concrete. mortar. grout.238 TESTS AND PROPERTIES OF CONCRETE this stress can be varied to give either shrinkage-compensating concrete or--with higher stress levels--chemically prestressed concrete [39]. this test using concrete specimens is of value. . These tests may be continued beyond the time of hardening. ASTM Test for Restrained Expansion of Shrinkage-Compensating Concrete (C 878) provides a method for determining the expansion of concrete made with shrinkage-compensating cement. American Concrete Institute. p. 1971. D." Proceedings. 9. Jan. visible cracks. p." Interrelations Between Cement and Concrete Properties. 1976. p." Temperature and Concrete. 29. Detroit. 1959. "Causes and Control of Volume Change. [7] Zoldners. 797-808. Arni. "Slab Warping Affects Pavement Joint Performance. No.. [5] Powers. Bloem. American Concrete Institute." Journal.. or o t h e r s t r u c t u r a l defects.. and Mullen. 1951.. [11] Lerch. [8] Hveem.SAWYER ON VOLUME CHANGE 239 externally a p p l i e d forces a n d t e m p e r a t u r e changes. H.. pp. Detroit. National Bureau of Standards. G. N." Masters thesis.. M o r t a r . 4. Detroit. American Concrete Institute. March 1969. William. April 1952. [6] Zoldners. p. SP-2S. Aug. 661-680. University of Maryland. American Concrete Institute. p. tests such as A S T M Test for D r y i n g S h r i n k a g e o f Concrete Block (C 426) can be used as a r o u t i n e s t a n d a r d i z e d p r o c e d u r e for d e t e r m i n i n g the drying shrinkage of concrete b l o c k . 1971. N. G. American Concrete Institute. brick. G. 5. N." Temperature and Concrete." TSA-87. Vol. Part 4. Stanton. "The Influence of Gypsum on the Hydration and Properties of Portland Cement Paste. 46. pp. p. N. or o t h e r concrete p r o d u c t s u n d e r specified accelerated drying conditions. SP-2S. 47. 33. G. [3] Mullen. L. American Concrete Institute. 3." Proceedings." Temperature and Concrete.. "A Study of Thermal Properties of Concrete and Concrete Aggregates.. "Shrinkage of Hardened Portland Cement Pastes. Portland Cement Association. "Thermal Properties of Concrete Under Sustained Elevated Temperatures. N. To d e t e r m i n e the volume changes in concrete p r o d u c t s . L.. "Thermal Properties of Concrete Under Sustained Elevated Temperatures. American Society for Testing and Materials. "Thermal Properties of Concrete Under Sustained Elevated Temperatures. "Thermal Properties of Concrete Under Sustained Elevated Temperatures. References [1] Zoldners. G. This test is sufficiently restrictive to be used as a basis for a c c e p t a n c e testing a n d can be a d a p t e d for studies o f volume c h a n g e involving different schedules or e n v i r o n m e n t a l treatment. A S T M Test for Length Change of Drilled or Sawed Specimens o f C e m e n t M o r t a r a n d Concrete (C 341) can be used to d e t e r m i n e the length changes of drilled or sawed specimens due to causes other t h a n externally a p p l i e d forces a n d t e m p e r a t u r e changes. W. 48. [10] Blaine. SP-2S. T. "Effects of Temperature Changes on Concrete as Influenced by Aggregates. June 1951. 1252-1292. No further reproductions authorized.. W. Ill." Temperature and Concrete. C. Vol. Vol. The a p p a r a t u s r e q u i r e d for testing by these m e t h o d s is given in A S T M Specification for A p p a r a t u s for Use in M e a s u r e m e n t of Length Change of H a r d e n e d C e m e n t Paste. D. and Evans. Copyright by ASTM Int'l (all rights reserved). . Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 8. Proceedings. These specimens can be t a k e n from existing concrete structures b u t m u s t be free f r o m reinforcing steel. Skokie. pp. [9] "Effect of Initial Moist Curing on Drying Shrinkage of Concretes Made With Different Types of Cement. T. 7. F. 1971.. N. Section 9." Journal. p. [4] Zoldners.. 1971. [2] Walker. 1946. Detroit. R. G.. SP-25. a n d Concrete (C 490). Portland Cement Association Research and Development Laboratories. " Proceedings. T. [20] MacPherson. R. L. [23] Fling." Proceedings of The Fifth International Symposium on the Chemistry of Cement. p. W. C. E. H. Sept. p. 1959. Highway Research Board. M. 99. p. 1968. 177. Tokyo. "The Effect of Water-Reducing Admixtures and Set-Retarding Admixtures on the Properties of Hardened Concrete. Louis. H. p. F. Tokyo. C. American Concrete Institute. E." The VI International Congress on the Chemistry of Cement. Portland Cement Association. 1.. Copyright by ASTM Int'l (all rights reserved). [34] Mehta.. H. May 1951. "Evaluation of The Quick Chemical Test for Alkali Reactivity of Concrete Aggregate. pp. Part II. T. p." Journal. Research and Development Laboratories. American Society for Testing and Materials. 1. "Fly Ash in Concrete. A. and Helmuth.. p. "Causes and Control of Volume Change. 1960. June 1953. [14] Roper. No. 3." Journal. [33] McCoy. C... C. No. R. p." Effect of WaterReducing Admixtures and Set-Retarding Admixtures on Properties of Concrete. "Expansion of Cements and Methods To Determine It. March 1976. Jan. Sept.. Section 10... Mo. "Correlation Between Chemical and Mortar Bar Tests for Potential Alkali Reactivity of Concrete Aggregates." Bulletin 171. "Causes and Control of Volume Change. H. March 1969. Highway Research Board. Portland Cement Association." Journal. 88. 419-437... No. 38. June 1976. R. p. 47. Chapter 12. R. p. W. and Whiteside. Porter." Journal. Portland Cement Association.. G.. "Causes and Control of Volume Change.. St.. and Frohnsdorff. 9. Harold.. American Concrete Institute. 33. p. W. Benton. Jan.. R." Journal. Itzhak and Stern. H. A.." Ash Utilization Symposium. Berger. [28] Calleja. Aug. "Crack Control in Perspective. . Naua. [13] Powers." Proceedings of the Fifth International Symposium on the Chemistry of Cement. [36] Soroka. "Mechanism of Expansion Associated with Ettringite Formation. "Effect of Aggregate on Shrinkage and a Hypothesis Concerning Shrinkage. 1973. Portland Cement Association Research and Development Laboratories. [26] "Volume Changes of Concrete. p. [17] Blaine. J. C. Vol. 693-708. Proceedings. "New Approach to Inhibiting Alkali-Aggregate Expansion." Design and Control of Concrete Mixtures. 39. N3. and Arni. National Bureau of Standards. Vol. L." Cement and Concrete Research." Interrelations Between Cement and Concrete Properties." Journal. Sept. Vol. 1968. J. No. [18] Carlson." Materials Research and Standards. [32] Chaiken. 1967. 215. No further reproductions authorized. 9. 19.. T.. [19] "Guide for Structural Lightweight Aggregate Concrete. 2. l l t h ed. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Concrete For Long-Time Service in Sulfate Environment. Moscow. p. 3. Part 4. Vol.. "Structures and Physical Properties of Cement Paste.. 1972. 5. Jan. I11. [15] Powers. C. [25] Powers. and Fischer. American Concrete Institute. W. Vol. L. 1958. W. [16] Pickett. 1968. Vol. "Causes and Control of Volume Change. p. Jan. 29." Bulletin 284. 581-590. Skokie. J.. A. [31] Mielenz.. Vol.. 457 (Report of ACI Committee 213). "Limitations To Fly Ash Use In Blended Cements. J. 1956. 1959. G. pp. [29] Brown. 1960." Bulletin 45. 6. 1938. 1. and Caldwell.. 594-595. 1959. J. [30] Gonnerman. J. 6. p. "Shrinkage and Expansion of Concrete. S. 33. E. 1976.. 38. 1974.. and Benton. R. T. Skokie. Lerch. 55. [24] Roper. p. 1. 3. Gerald.. 2. [22] Abdun-Nur. 703. "Volume Changes in Concrete. 1961. Vol.. "Cement Paste Shrinkage-Relationship to Hydration. J. "Drying Shrinkage of Concrete as Affected by Many Factors. [35] Kalousek. pp. R. P." Proceedings. American Concrete Institute." Cement and Concrete Research. I11. Research and Development Laboratories. "Investigation of the Hydration Expansion Characteristics of Portland Cements. 1961. pp. T. "Effect of Calcareous Fillers on Sulfate Resistance of Portland Cement. Vol. 3." Ceramic Bulletin. 52. A S T M STP 266. p. p. No. K. p. Jan. p. 30. [21] Verbeck. 13.240 TESTS AND PROPERTIES OF CONCRETE [12] Swayze." Journal." Journal. G. "Volume Change of Concrete Affected by Aggregate Type. 1959. Bernard and Halstead. R. D. Portland Cement Association Research and Development Laboratories. Aug. p. 1959. C.. P. Clifton." Public Roads. Jan. Young's Modulus and Concrete Shrinkage. Vol. American Society for Testing and Materials. 86. [27] Powers. T. pp.. G. K. "Expansive Cements. [39] Mehta. W." Journal American Concrete Institute. Aug. Sept. 6th ed. Moscow. pp. Milos." Journal American Concrete Institute. p. Denver. P." The VI International Congress on the Chemistry of Cement. 4. 443-444. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. Oct. 1976. [40] "Preplaced Aggregate Concrete for Structural and Mass Concrete. 785-797 (Report of ACI Committee 304).SAWYER ON VOLUME CHANGE 241 [37] Concrete Manual U. .S. No further reproductions authorized. 1974. 10-12. Bureau of Reclamation. 1969. 1956. [38] Byers. and Polivka. pp. "Fields Procedure for Evaluating Potential Sulfate Damage to Concrete. D. and that dissipation of this heat under ordinary circumstances would extend over as much as a century or more. l Civil engineer. The investigations were stimulated by the realization that in massive structures the heat generated by hydration of the cement could be responsible for volumetric changes influencing the integrity of the structure.C. This last property is included because of its significant influence on the thermal and physical behavior of concrete in most of its uses. Results are given in the Boulder Canyon Reports [1]. and heat of hydration of cementitious materials.astm. Bureau of Reclamation in conjunction with the design and construction of Boulder (Hoover) Dam between 1930 and 1935. One of the earliest and most comprehensive studies of the fundamental thermal properties of concrete was carried out by the U. Only at very high and very low temperatures do the expansion characteristics vary from those under normal conditions. bridges. This has been long recognized for such structures as highways. Sun Apr 6 21:41:45 EDT 2014 242 Downloaded/printed by Universidade do Gois pursuant Agreement. A . 2The italic numbers in brackets refer to the list of referencesappended to this paper. thermal diffusivity.S. No further reproductions authorized. The favorable thermal insulation characteristic of normal weight concrete. and buildings. 2 As with most construction materials. have been used effectively in building construction and for other applications where resistance to steady-state heat flow is needed. Copyright by ASTM Int'l (all rights reserved). In recent years the unique ability of concrete to damp out annual and daily ambient temperature variations (unsteady state) and to store or release heat over significant time periods is being utilized by designers.STP169B-EB/Dec. thermal expansion (or contraction). Copyright9 1978tobyLicense ASTM International www.org . R h o d e s ~ Chapter 17--Thermal Properties Introduction The thermal characteristics of concrete covered in this chapter are: thermal conductivity. and the even more favorable properties of light-weight concretes. specific heat. Officeof Chiefof Engineers. Washington. 1978 J. there is a direct relationship between a change in temperature of concrete and its change in length or volume. Department of the Army. walls. its thermal conductivity as shown in Table 1 is many times that of air which it replaces in concrete [3]. thus keeping the unit of time at 1 s. ranging from 0. In U. entrained air. water/cement (w/c) ratio. and age. customary and British units. and users of conductivity values are cautioned to assure that compatability and consistency exists. square metre. The amount of free water in concrete. regardless of density.2 W / m . s q u a r e foot. the approved SI (Syst~me International) units are obtained. exhibit a fairly constant thermal conductivity value of 1.1441314. Kelvin. Other factors of slight or negligible importance in their effect on conductivity are cement type and content.6 w/c and ages from 3 days to 1 year [3]. conductivity is frequently expressed in Btu per h o u r .0 B t u . Thermal conductivity of concrete varies directly with moisture content [4. and temperature) significantly influence the thermal conductivity of a specific concrete. Values of conductivity in these units may be converted to the SI units by multiplying by 0. density. engineering disciplines frequently express temperature gradients.RHODES ON THERMAL PROPERTIES 243 Thermal Conductivity Definition and Units Thermal conductivity is a measure of the ability of the material to conduet heat and may be defined as the ratio of the rate of heat flow to the temperature gradient. While water is a relatively poor conductor of heat compared with rock. Neat cement pastes. areas.S. f t 2. Copyright by ASTM Int'l (all rights reserved). The effect of moisture on thermal conductivity values from oven-dry to a moist condition (not necessarily saturated) are given in Table 2. while with lightweight concretes the amount of air voids and moisture content mask the effect of aggregate type. Parameters and Values Three principal conditions (water content. degree Fahrenheit per inch. Thermal conductivity measured under reduced moisture conditions has little meaning because the specimens suffer extensive cracking due to drying. In normal metric use it can be considered to be the number of kilocalories passing between opposite faces of a 1-metre cube per unit of time when the temperature difference is 1 ~ An alternate set of dimensions is joules per second. and time in units most useful to them. i n . is a major factor influencing thermal conductivity. K (8. No further reproductions authorized. Largely by custom. The mineralogical character of the aggregates largely determines the thermal conductivity for normal weight concrete. degree Celsius per metre. . By dimensional manipulation and substitution. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.3 to 0. 5]. ~ at normal air temperatures and in a moist condition. both within and between systems of units [2]. / h . watts per metre. . mortars./h 9ft2 9~ Moisture Condition W/m 9K Moist 50% relative humidity Dry 2. For moist n o r m a l weight concrete the conductivity at .0 Moist 50% relative humidity Dry 2.79 5.5 0..in. normal-weight.0 Moist 50% relative humidity Dry Expanded Shale Concrete 0.2 1.2 5 0 ~ has b e e n f o u n d to be a b o u t 50 percent greater t h a n at n o r m a l t e m p e r a t u r e s [3]. may be aerated (foamed) or c o n t a i n a very lightweight porous aggregate.157 W/m.. This has been a t t r i b u t e d Copyright by ASTM Int'l (all rights reserved).0 11.0 10.85 5.9 16. At elevated temperatures.2 0 75 -150 -250 - 4. ~ 0.0 2. a n d structural light-weight concretes the mineralogical characteristics of the aggregate m a r k e d l y affect the conductivity of the concrete. Btu . densities less t h a n 960 k g / m 3 (60 l b / f t 3). 7] given in T a b l e 5 are for air-dry or low moisture contents.9 2.1 3. Over a t e m p e r a t u r e range from room t e m p e r a t u r e s to .56 2.0 23.62 4.4 15.3 23.244 TESTS AND PROPERTIES OF CONCRETE TABLE 1--Thermal conductivity of water.3 Limestone Concrete For heavy-weight. as shown in T a b l e s 3 a n d 4.8].3 16.3 2.4 Sandstone Concrete 20.2 5 0 ~ the t h e r m a l conductivity of oven-dry n o r m a l weight a n d lightweight concrete is essentially c o n s t a n t [3.2 1.7 1.1 5 7 ~ ( .0 TABLE 2--Typical variations in thermal conductivity with moisture at normal temperatures.6 3. K 68 32 Conductivity. up to about 7 5 0 ~ (1380~ conductivities of c e m e n t pastes./h-ft 2.0 18.59 0. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.0 2. Btu 9in.1 5 7 ~ ( .0 15... ~ 20 0 - 18 -- 59 -101 -.0 36. T h e r m a l conductivities [6.0 Moist 50% relative humidity Dry Quartz Gravel Concrete 3.7 19. No further reproductions authorized. Conductivity.0 10. I n s u l a t i n g light-weight concrete.3 5. ~ Water Temperature. a n d concrete decrease in a consistently u n i f o r m m a n n e r .9 0. 2 3. / h 9ft 2 9 ~ W/m.62 0. / h 9f12. Btu 9 i n .85 resulting values at about 400~ a r e a s f o l l o w s [5]: cement paste 1:3 mortar sandstone concrete ilmenite concrete W / m 9K Btu 9 i n .9 0.7 1. Btu 9 i n .22 TABLE 4--Effect of aggregate type of conductivity of moist concrete at normal temperatures.9 8.2 1.4 1.0 2.2 0.2 1. No further reproductions authorized.3 3.0 2.9 in the aggregate [9].6 1. lb/ft 3 kg/m 3 Aggregate type Hematite Marble Sandstone Limestone Dolerite Barite Expanded shale Expanded slag Expanded slag 179 143 t 20 126 136 180 89 103 60 2870 2290 1920 2020 2180 2880 1430 1650 960 Conductivity.245 RHODES ON THERMAL PROPERTIES TABLE 3--Effect of aggregate type on conductivity of dry concrete at normal temperature.3 3.9 2.3 3. / h 9ft 2 9 ~ 0.1 4.6 2. ~ W / m 9K 28 28 24 23 23 22 21 20 20 t8 18 15 15 14 14 14 14 13 5.1 2. from (750~ .0 1.56 0. Dry density.1 3.9 5.2 Copyright by ASTM Int'l (all rights reserved).75 1.4 1. Moist density.5 3.2 2. Ib/ft 3 kg/m 3 Aggregate type Hematite Quartzite Quartzite Dolomite Quartzite Limestone Quartzite Sandstone Sandstone Granite Limestone Marble Limestone Basalt Rhyolite Barite Dolerite Basalt Expanded shale to disruption 190 150 152 156 3040 2400 2440 2500 153 147 133 150 151 151 152 152 157 146 190 147 158 99 2450 2350 2130 2400 2420 2420 2440 2440 2520 2340 3040 2350 2350 1590 of the intercrystalline excessive thermal expansion bonds Conductivity.2 10.6 1.2 2.2 3. C o n d u c t i v i t y 4.5 4.6 2.5 2. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. K 18 12 10 10 8.0 2.6 8.46 0.9 2. / h 9 ft 2 9 ~ Aerated 0. The ASTM Test for Steady-State Thermal Transmission Properties by Means of the Guarded Hot Plate (C 177) requires oven-dry specimens and limits their thickness to 100 mm (4 in.20 0. No further reproductions authorized.72 52 Expanded Clay 0.11 0.17 Vermiculite 1.4 1. and to saturated or nearsaturated concrete. The method will accommodate flat disks or slabs only. Test Methods The test method for thermal conductivity developed for the Boulder Canyon Reports [1] used 200 mm (8 in. but will accept solid disks or slabs under rather rigorous flatness tolerances.07 0. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.246 TESTS AND PROPERTIES OF CONCRETE T A B L E S--Thermal conductivity of insulating concrete. resulting in further decreases in conductivity [9]. Density.) diameter cylinders subjected to steady heat flow conditions. kg/m 3 lb/ft 3 320 480 640 800 960 20 30 40 50 60 400 825 Thermal Conductivity.5 0.). The ASTM Test for Steady-State Thermal Transmission Properties by Means of Heat Flow Meter (C 518) determines conductivity by comparison with the conductance of oven-dry materials previously measured by ASTM Test C 177.0 1. W / m 9K B t u 9 i n . Use of water as the heating and cooling mediums limited the results to a specific portion of the temperature range between the freezing and boiling points of water. The Corps of Engineers [10] Test for Thermal Conductivity of Lightweight Insulating Concrete (CRD-C 45) measures conductivity directly under steady-state conditions in a manner similar to that of ASTM Test C 177.2 Above temperatures of 400~ gradual disintegration of the fully hydrated cement paste occurs. Test for Thermal Diffusivity of Concrete (CRD-C 36) and Test for Thermal Diffusivity of Mass Concrete (CRD-C 37).8 25 0. with conductivities not higher than those of the best insulating concrete.14 0. and temperature differential through the oven-dry specimen is from 32 to 60~ (90 to 140~ Two indirect methods for determining thermal conductivity. Nominal specimen thickness is 25 mm (1 in.26 0.75 1. . The procedure can accommodate loose insulation materials.). have been developed and used for Copyright by ASTM Int'l (all rights reserved).10 0. according to the Boulder Canyon studies [1].22 and 0.1868 • 103. tended to increase the specific heat of the concrete. The actual values found were 0. ~ at 7 percent mixing water by weight and higher.0 (either Btu/lb 9 ~ or cal/g. The specimen. . at a selected moisture content. was coated with mercury on all surfaces to retain moisture.22 cal/g. which is obtained from either the foot-pound or CGS values by multiplying by 4. developed a nonsteady-state hot-wire method for determining thermal conductivity of concrete or rock. K. with the Portland Cement Association [8]. There are no moisture or density restrictions.24 cal/g. and measurements are completed within a few minutes time. ~ at 4 percent of mixing water by weight of concrete and 0. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Specific heat varies directly with concrete temperatures. Parameters and Values The mineralogical differences among such aggregates as generally used have little effect on specific heat of the concrete. soaking.~ the specific heat (and heat capacity) values are the same.24 cal/g. with values at normal temperatures ranging between 0. These values represent mass concrete mixes and several aggregate types [11]. Campbell-Allen and Thorne [5] developed. Specific heats of most rock types tend to increase up to at least 400~ (750~ and hydrated cement pastes up to 1000~ (1830~ Investigations by Harmathy and Allen [12] indicate the specific heat of expanded aggregate light-weight concrete differs little from that of normalCopyright by ASTM Int'l (all rights reserved). In those systems of units where the heat capacity of water is 1. and conductivity calculated therefrom. In SI units. and electrically heated internally and cooled externally.RHODES ON THERMAL PROPERTIES 247 several years by the Corps of Engineers laboratories [10]. Lentz and Monfore. Its acceptability or modifications are not known. or boiling in water. With these methods the thermal diffusivity property is measured. ~ Increased water content.~ (Btu/lb. Test temperature range is 10 to 65~ (50 to 150~ and the specimens have been conditioned by exposure to spray. No further reproductions authorized. Specific Heat Definition and Units The rigorous definition of specific heat is the ratio of the amount of heat required to raise a unit weight of the material 1 deg to the amount of heat required to raise the same weight of water 1 deg. for experimental work up to 200~ (400~ a hollow-cylinder steady-state system for measuring conductivity. specific heat is expressed in joules/kilogram. A thermocouple cast along the axis of a prism (or in the center of a split and lapped specimen) measures temperature response to a measured alternating current input. as indicated in Table 6. 232 0. and Other Materials (CRD-C 242) and ASTM Test for Specific Heat of Liquids and Solids (D 2766). Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. p . although even with this volume a typical or representative sample is not always assured. cement.219 0.k / c . Normally the test is run at about room temperature to minimize heat loss corrections.) in size. Among the most suitable of the procedures is the Corps of Engineers [10] Method Test for Specific Heat of Aggregates. When calculating diffusivity from its parts. J/kg. Thermal diffusivity is defined numerically as thermal conductivity divided by the product of specific heat and density. and cement pastes. K cal/g. as cement or cement pastes for example are the Corps of Engineers [10] Test for Mean Specific Heat of Hydraulic Cements. care is required to assure Copyright by ASTM Int'l (all rights reserved).248 TESTS AND PROPERTIES OF CONCRETE TABLE 6--Typical specific heats of concrete. for materials which can be broken into particles not larger than 25 mm (1 in.C 124). Cement Pastes. No further reproductions authorized. Thus the diffusivity results from the consolidation of three other properties which appear in differential equations defining heat flow and heat storage under unsteady state conditions.248 weight concrete at ordinary temperatures and also increases up to at least 600~ ( l l l 0 ~ Testing Methods Some type calorimeter apparatus is employed in all procedures to measure the specific heat (heat capacity) of hardened concrete. Temperature. ~ 10 38 66 SpecificHeat. Thermal Diffusivity Definition and Units The diffusivity property is described as a measure of the facility with which temperature changes take place within a mass of material. More precise methods applicable to materials with which water may or would react. aggregates. These require smaller samples (up to 100 g weight) and provide for cooling media whose physical or chemical properties differ from those of water. . Concrete. or ot 1. and Other Materials (CRD. A test weight total of about 1 kg (2 lb) can be accommodated. 9deg C 917 971 1038 0. is to calculate thermal Copyright by ASTM Int'l (all rights reserved). Typical diffusivity values in Table 7.12. No further reproductions authorized. Both thermal conductivity and density are sensitive to moisture content of the concrete.29030 X 10 -2 = m2/h Parameters and Values Those variables and conditions which influence thermal conductivity.0016 m2/h (0.58064 X 10 -s = mVs or ft2/h • 9.017 W/h) at and somewhat above normal room temperatures. where W = J/s Note that in approved SI base units.RHODES ON THERMAL PROPERTIES 249 that the dimensional units of the three constituents are compatible. show the general range to be expected for normal-weight and structural light-weight concrete. To convert from British to more convenient SI units ft2/h X 2. . Test Methods One practice. and density also affect thermal diffusivity. higher diffusivity values are associated with concrete which heats or cools most easily. and derived thermal diffusivity values should be based on conductivities and densities which correspond to the condition of the concrete in service. diffusivity values are usually small. For example: British S y s t e m U n i t s conductivity specific h e a t density thus a SI U n i t s conductivity specific h e a t density thus a B t u / h 9 ft 2 9 ~ p e r ft Btu/lb 9 ~ lb/ft 3 ft2/h W / m 9K J / k g 9K kg/m 3 m2/s. diffusivity values for a specific concrete will decrease as the concrete temperature increases. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. specific heat.13]. taken from [1. Since specific heat varies directly with temperature.0012 to 0. not necessarily always preferable.013 to 0. Within the same system of units. Thermal diffusivity of concrete is determined largely by the mineralogical characteristics of the coarse aggregate. The Bureau of Reclamation [1] reported diffusivities for neat cement pastes ranging from 0. 0055 0.5 millionths/~ has been widely used. Two Corps of Engineers [10] test methods. CRD-C 36 and CRD-C 37. which can be defined as the change in linear dimension per unit length divided by the temperature change.38 m2/day 0. The first is a normal expansion typical of anhydrous solids.027 0. Thus a moisture gradient is created from the surface of the specimen inward.0015 0.0025 0. and diffusivity values will be applicable to dry environments only. Type of aggregate in concrete m2/h Thermal diffusivity.085 0. Second.42 0. The 0. moisture. Copyright by ASTM Int'l (all rights reserved). change in length is a complex process reflecting principally materials.132 0.23 m 3 (8 ft a) cube specimen is heated to about 65~ and the surfaces then cooled by a water spray. and temperature individually and together. While a general value of 10 millionths/~ (5. ft2/h ft2/daya Quartz Quartzite Limestone Basalt Expanded shale 0.65 0. and the concrete mass must be termed "moist" rather than either "dry" or "saturated.0061 0.56 1. specific heat. The actual thermal expansion is the net result of two actions occurring simultaneously." Tables and charts for converting the temperature change time history at the center of the specimen to the thermal diffusivity which was responsible for this change over the observed time duration.060 0.059 0. there is a hygrothermal expansion or contraction associated with the movement of internal moisture from capillaries to or from gel pores. they are quite reliable. .190 0.065 0. While the results are applicable only to moderate temperature ranges.016 2. Test methods for conductivity are essentially limited to an oven-dry condition. and density as determined from laboratory tests.250 TESTS AND PROPERTIES OF CONCRETE TABLE 7--Typical thermal diffusivity values.036 Convenient when computing heat flow in large structures. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. concrete has a positive coefficient of thermal expansion. Thermal Expansion Definition and Units As with most construction materials.146 0.0079 0. No further reproductions authorized. The cylinder specimen is heated in boiling water and then cooled in a running bath of cold water. diffusivity from conductivity.04 1. determine diffusivity directly from a partially saturated concrete cylinder or large moist concrete cube specimens. where the expansion coefficients for oven-dry and saturated conditions were half the maximum expansion coefficient of 11 • 10-6/~ which occurred at 75 percent relative humidity. For concretes used in Ilha Solteira Dam in Brazil. so the coefficient of thermal expansion is a constant figure. In addition. Powers [14] showed one aspect of the significance of the moisture content of paste specimens. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Berwanger and Sarker [15] found the coefficient decreased from 7. Quartzites and other siliceous aggregates exhibit high thermal expansion properties. and values with other natural rock types usually are between these two. which makes the paste sensitive to water movements caused by temperature changes.1 millionths/~ for temperatures above and below 0~ respectively.RHODES ON THERMAL PROPERTIES 251 Parameters and Values Since aggregate comprises from 80 to 85 percent of concrete. Generally the coefficient of expansion increases with decrease in the w/c ratio. Below the freezing point of water. widely among aggregates because of differences in mineralogical content. which occurred at about 60 percent relative humidity. its thermal properties greatly influence the behavior of the concrete. A similar relationship was found for concrete. Copyright by ASTM Int'l (all rights reserved). and concrete containing such aggregate frequently show values up to 13 • 10-6/~ at normal temperatures. and Monfore and Lentz [16] showed a similar typical decrease from 9. Thermal expansion can vary. See Table 8. but its expansion coefficient ranges from 9 to 22 • 10-6/~ which may be several times that of the aggregate itself. most of the capillary water and essentially all of the adsorbed water is contained within the gel pore system.4 to 6.7 to 5. Cement paste occupies only about 15 to 20 percent of the concrete volume. For a given concrete mix. 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.8 millionths/~ There is some evidence that the coefficient continues to decrease with further decreases in temperatures. The slowing rate of contraction at low temperatures is continued contraction of the concrete (and of the ice already formed) and an opposite expansion resulting from the formation of additional ice. the magnitude of thermal expansion or contraction at temperatures from freezing to about 65~ is the same for each unit temperature change. Some limestone aggregate concrete exhibit expansion values of 5. so the thermal expansion coefficient decreases. . the length changes are smaller per unit of temperature. except that the dry and saturated condition values were from 65 to 80 percent of the maximum value. No further reproductions authorized.6 X 10-6/~ for comparable conditions. but a general decreasing trend thereafter. Some sources report a slight increase in coefficient of thermal expansion with age up to 3 months. 5 13. but conditioning of the specimen and control of the conditions while under test may be difficult.2 10. Over a number of years the Bureau of Reclamation and Corps of Engineers have conducted thermal expansion coefficient tests of specimens composed of concrete mixes having moderate to low cement factors and large-size aggregates.2 10.64) (5. For calcareous aggregate concrete.E f f e c t o f age on t h e r m a l expansion.0 (6. .51) (7.2 12. and the expansion coefficients do not lend themselves to unique groupings by rock type. and at higher temperatures starts to shrink [I 7].0 millionths/~ (2. from the actual job sources.62) Basalt Concrete c Units are millionths/K (~ 10.75) (8.89) Quartzite Mortar d 12.5 millionths/~ (12. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. dQuartzite natural sand.5 millionths/~ above 425~ (800~ For expanded shale aggregate concrete the values were 5.14) (7.98) (5.18) (7.42) (7.67) (5. As stated previously.12) (7.8 10.9 13.8 14.96) (5.8 millionths/~ (4.6 (5.4 13.0 15. Philleo [17] reported thermal expansion coefficient of 8. Days 4 9 17 30 48 62 Quartzite Concrete/' 12. The aggregates.33) (8. Some typical results are listed in Table 9..90) ~Results are from University of California (Berkeley) tests with llha Solteira (Brazil) materials.34) (7. Physical measurement of specimen length change with the necessary accuracy is not a major obstacle. bAll natural quartzite aggregate. Up to about 100~ the paste has achieved its natural expansion.7 10. and the wide variety of environmental conditions to which concrete is exposed has precluded development of a standard test method for general use.65) (5. ~ Approximate Age.7 (7.75) (7.9 millionths/~ for similar temperature levels.2 10. continuing to do so up to about 500 or 600~ At this level only the original dry ingredients remain.9 12.7 millionths/~ below 260~ (500~ and 22. the expansion of concrete exposed to increasing temperature is the net result of the inherent thermal expansion property of the aggregate and a complex hygrothermal volume change of the cement paste. The values therein are applicable for an average temperature of about 38~ Test Methods The significant effect that moisture and temperature have on behavior of concrete.2 13. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized.252 TESTS AND PROPERTIES OF CONCRETE TABLE 8 .69) (8.5 millionths/~ (4. CBasalt coarse aggregate and quartzite sand.0 15.8 millionths/~ and 8.6 16. are frequently complex in terms of type and mineralogical content. or concrete are known~ the resulting temperature rise can be calculated.6 12. Parameters and Values The hydration reactions of portland cement have been studied and reported by many authors for many years.5 6.3 6. All the compounds present in cement are anhydrous. There is general agreement that the tricalcium aluminate (Ca A) is the largest single compound contributor to the evolved heat.2 4. and when in contact with water are all attacked at various rates and at varying times. some quite sophisticated. When the amount of this heat and the heat capacity of the paste.0 13.4 4.2 7. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. followed by tricalcium silicate (C3S) and tetracalcium Copyright by ASTM Int'l (all rights reserved). in which a length comparator similar to that described in ASTM Specification for Apparatus for Use in Measurement of Length Change of Hardened Cement Paste. The heat liberated up to a specific time or age is measured in calories per unit weight of cement (cal/g) or kilojoules per kilogram (kJ/kg).17]. is used to measure length changes of a specimen alternately immersed in 60 and 40~ water baths.7 5.RHODES ON THERMAL PROPERTIES 253 TABLE 9--Thermal expansion coefficientsfor mass concrete.5 Many test procedures.9 11. and Concrete (C 490). Dam Name Aggregate Type Hoover Hungry Horse Grand Coulee Table Rock Greers Ferry Dworshak Libby Jupia (Brazil) limestone and granite sandstone basalt limestone and chert quartz granite-gneiss quartzite and argillite quartzite Coefficient of Thermal Expansion.2 6.9 7. millionths/K millionths/~ 9. have been developed in conjunction with research studies [8.1 9. .5 11. No further reproductions authorized. Heat of Hydration Definhion and Units When water is added to cement the reaction is exothermic and a considerable amount of heat is generated over an extended period of time. Test for Coefficient of Linear Thermal Expansion for Concrete (CRD-C 39).1 7. The operator is free to change the temperature limits and substitute oven drying if this better serves the data user.6 5. Mortar. assuming no heat loss to the surroundings. The Corps of Engineers follow a standard. mortar. and finally dicalcium silicate (C2S). has a significant influence on the amount of heat generated at ages of 3 days and greater.15~ hydration ceases. and between 10 and -. variable. and sometimes inconsistent or controversial. Heat Evolved in cal/g Compound C3S C 2S C3A C4AF 3 day 1 year 13 year 58 12 212 69 117 54 279 90 122 59 324 102 in the total heats generated by each compound. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As with most chemical reactions. When water is first brought into contact with portland cement there is a very rapid and very brief heat evolution. Verbeck [19] suggests this is the result of a dense hydration product created by high temperatures at early ages surrounding the cement grains.40 w/c cement pastes cured at 21~ are given in Table 10. According to Verbeck [19]. the rate of cement hydration increases with temperature. Although the data apparently indicates progressive increases TABLE l O--Typical compound contribution to heat of hydration[18]. There then occurs a 1 or 2 h delay. followed by a gradually increasing hydration rate to about 6 or 8 h. Possible causes and significance of the regression characteristics are discussed in Ref 18.4 to 0. which thereby substantially retards subsequent hydration. At and below 0~ (32~ a sharp drop in rate of hydration occurs. and a slow decline in rate thereafter. the reader is referred to Lea [6] or other comparable texts for a comprehensive presentation on the chemistry of cements.254 TESTS AND PROPERTIES OF CONCRETE aluminoferrite (C4AF) with about equal contributions. reaching possibly a rate of I cal/g/min. other minor compounds. . This degradation in hydration is generally true for temperatures above about 24~ (75~ and becomes significant at 52~ (125~ and above.8 w/c ratios are greatest at intermediate ages. No further reproductions authorized. but continue to be evident at up to 6 years. The nature and interrelationships of the chemical reactions are complex. The differences over the range 0. and subsequently the hydration process slows to a rate less than that corresponding to normal placement and curing temperatures. The w/c ratio. values at intermediate ages for both CaA and C4AF deviate from this pattern. and gypsum content cause variations in both early and later age hydration rates. Approximate contributions of the four principal calculated compounds in 0. The accelerating effect of high curing temperatures is limited to early ages. in pastes. alkalies. Relative proportions of the four major compounds. the hydration product steadily increases in volume filling the capillary void space in the - - Copyright by ASTM Int'l (all rights reserved). 4 to 0. Raw or calcined natural pozzolans (sometimes used to replace a portion of cement in mass concrete) vary widely in their composition. a minimum fineness limit considerably above the portland cement value is imposed.4 to 0. Chemical admixtures. all cements are so finely ground that the moderate variation in fineness of different cements is no longer an important factor in cement hydration.8 had only a slight effect on heat liberation for Type IV (low-heat) cements. In a study of portland blast-furnace slag cements. Thus a high w/c ratio will tend to result in more complete hydration and in more heat developed. When used in concrete. No further reproductions authorized. but produced an increase of 10. Prior to about 1935. Klieger and Isberner [21] found there to be no consistent difference in heat of hydration up to 3 days of age between Type I and Type IS cements. but will reduce the total heat evolved by a value up to onehalf of the replacement percentage figure [20].9 cal/g for Type III at 1-year of age. Data reported by Verbeck [18] show that an increase in w/c ratio from 0. However. The increases in heat of hydration resulting from an increase in w/c from 0. may range in fineness before processing from below to well. as the term is used here. in finely divided form and in the presence of moisture. Fly ash. and adiabatic curing of concrete containing a fly ash replacement will serve to increase substantially the chemical activity of the fly ash component. resulting in more rapid and complete hydration. The finer cements presented much more surface area to be wetted. The reaction between the glass in the fly ash and the lime in the cement is particularly sensitive to heat. In recent years. If the capillary void space is small (low w/c ratio) the available space will become filled completely with hydration products and hydration of the remaining cement will cease. retarders.8 cal/g. and Copyright by ASTM Int'l (all rights reserved). also classified as a pozzolan.4 cal/g for Type II (moderate-heat) cement to 15. . refer to materials added in relatively small amounts to mortar or concrete during mixing to modify some characteristic of the product. or 14 percent. Pozzolans are defined in ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete (C 618) as siliceous or siliceous and aluminous materials which in themselves possess little or no cementitious value but.RHODES ON THERMAL PROPERTIES 255 paste. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. for Type III (highearly) at 3 days of age. especially after World War II. will react chemically with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. and at later ages up to 1 year the Type IS cements exhibited slightly to moderately lower heat generation characteristics. Generally accelerators.8 ranged from 11. the fineness of a cement was a major factor in the rate and amount of heat developed during hydration. high-early strength cements are finer enough than other types that their extra fineness works with their more active chemical compounds to produce earlier strength and more rapid release of heat. above that of portland cement. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. water reducers will effect the rate of hydration of the cement.256 TESTS AND PROPERTIES OF CONCRETE to some extent. Monfore and Ost [22] developed a refined calorimeter for measuring early rates of heat liberation which ideally is suited for laboratory research. maintained in a temperature environCopyright by ASTM Int'l (all rights reserved). The procedure is not recommended for pozzolan blends and for slag cements where a portion of the test sample usually remains im soluble at the end of the test procedure. The method is sensitive to the initial starting temperature.22-m 3) insulated and sealed cube. but this will result in understating the heat generated where higher w/c ratios are encountered in construction. Most significant to the user.5~ thus producing nearly isothermal conditions at any temperature level. In this calorimeter the temperature rise of a sample of hydrating cement weighing up to 8 g can be held to less than 0. developed prior to 1940. the difference being the heat of hydration up to that age. The method is well-suited to determining the effects of additions and admixtures to the cements. is that the storage temperature is standardized at 23~ (73~ which is almost never representative of the environment experienced in a concrete construction. There is little if any evidence that air-entraining admixtures influence either the rate or the total amount of heat generated for a specific cement or cement blend. as well as properties of specific cement compounds or other similar materials. A technique for measuring directly the temperature rise of a concrete specimen and then calculating the accummulated heat responsible for the temperature change is described in the Corps of Engineers Test for Temperature Rise in Concrete (CRD-C 38) [10]. No further reproductions authorized. determined the heat developed by a 0. The Carlson-Forbrich vane conduction calorimeter. The test usually is limited to 3-day duration. Test Methods The most widely used method for determining the heat of hydration of a hydraulic cement over long periods of time is by heat of solution. The procedure requires several corrections and Lea [6] discusses a number of possible errors. The specimen is an 8-ft 3 (0. but the processes are not well delineated and will differ significantly with different cements and proprietary products. .40 w/c ratio cement paste by measuring the rate of heat flow from the paste receptacle through cooling vanes into a water bath. Because of difficulties in controlling extraneous heat transfer. ASTM Test for Heat of Hydration of Hydraulic Cement (C 186). other than laboratory techniques. This procedure requires determination of the heat of solution of unhydrated cement and of a cement sample hydrated for a specific period of time. but the results include the immediate heat of hydration (0 to 1 h).40 is required. A standard paste w/c ratio of 0. and is neither adiabatic nor isothermal. the test period usually was limited to 3 days. When positive control over temperature rise is desired. mortar.RHODES ON THERMAL PROPERTIES 257 ment corresponding to its own temperature history for a period of 28 days. . with values in calories per gram. Specification limits for these types and typical ranges for others not subject to restriction are indicated as follows. (b) the aggregates proposed for use in the prototype structure may be incorporated in the test. replacing up to 35 percent of the cement in a mix by natural or processed pozzolans or one of the several types of fly ashes will reduce significantly both the hydration rate and the total amount of heat generated. IP and P). these structures should be monolithic and in intimate contact with the foundation and abutments in order to achieve the design stress distribution and stability. The importance of heat generation and disposal of that heat has long been recognized by designers of large dams. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or concrete mixture are known. A minor difficulty is maintaining an adequate insulation condition at the later stages when cement hydration rate is very low. While the range of values for specific heat of concrete is relatively narrow. Cracks which disrupt the stress pattern and decrease stability Copyright by ASTM Int'l (all rights reserved). Advantages are (a) cement-pozzolan blends may be used. and (c) the temperature rise approximates the nearly adiabatic conditions existing in the interior of a massive structure. Significance of Thermal Properties Heat Generation and Temperature Rise The heat resulting from the exothermic water-cement reaction over a given time interval is expressed easily in terms of temperature rise when the specific heat value for the paste. No further reproductions authorized. Type Type Type Type Type Type Type I (C 150) II (C 150) III (C 150) IV (C 150) IS (C 595) IP (C 595) P (C 595) 7 days 28 days 63 to 88 70 84 to 95 60 70 70 60 83 to 109 80 101 to 107 70 80 80 70 In lieu of established specification products. the heat generation characteristics of the cementitious materials available for use in concrete are quite broad. upper limits on the heat of hydration of the cement may be imposed through ASTM Specification for Portland Cement (C 150) (Types II and IV) and ASTM Specification for Blended Hydraulic Cements (C 595) (Types IS. Upon final completion. 258 TESTS AND PROPERTIES OF CONCRETE are caused principally by thermal tensile stress created by concrete volume changes associated with a temperature decline as heat is dissipated. the shallower lifts to facilitate the loss of heat at locations where restraint is high. Concrete in massive structures is usually placed in horizontal lifts from 0. and capacity of the refrigeration-pumping plant are determined primarily from the thermal Copyright by ASTM Int'l (all rights reserved). the temperature rise at Glen Canyon and Dworshak Dams was limited to 14~ (25~ Biological shielding structures of concrete are widely used with nuclear reactors. Control of thermal stresses by restricting lift thickness and placement frequency is especially effective for concrete which must be cast at a high initial temperature. In exceptionally large concrete structures. Waugh and Rhodes [23] have listed experiences at several large mass concrete dams constructed by the Bureau of Reclamation. Heat Flow The rate at which heat flows into. through. . Such shields are up to 2 m (6 ft) in thickness. While several design and construction practices are available to deal with temperature changes which tend to occur. rate of water circulation. The favorable trend toward lower peak concrete temperatures has allowed the use of larger monolith lengths without serious consequences. as a result of heat loss or gain.75 to 2. restricting the amount of heat that causes the temperature rise is a fundamental and certain scheme for mitigating the thermal stress problem.3 m (2.5 ft) in thickness.5 to 7. initial temperature of the water. Pier footings and heavily reinforced raft foundation slabs up to 2 m thick and totaling 2000 m a of concrete with cement contents of 400 kg/m a (675 lb/yd a) have been successfully placed with no cracking detected [5]. Recently. Peak temperatures in the concrete of as much as 36~ (65~ above the initial placing temperature may be expected. Peak interior concrete temperatures about 50~ (90~ above initial concrete placing temperature required exterior insulation to control gradients and cooling rates for prevention of thermal cracking. duration of the cooling operation. the Corps of Engineers. The ease or difficulty with which the concrete undergoes temperature change. principally arch and gravity dams. and is measured by the thermal diffusivity of the concrete. a n d the Tennessee Valley Authority. and the heavy aggregates generally required are responsible for cement contents up to 350 k g / m a (590 lb/yd3). embedded pipe cooling is used frequently to remove much of the heat generated during hydration of the cement. Spacing of the cooling pipes. or out of a concrete structure is governed by the thermal conductivity of the concrete. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. depends also on the heat capacity. No further reproductions authorized. Water is circulated through pipe coils placed at the bottom of each new lift of concrete. In consideration of heat and energy costs. When these changes are not allowed to occur. strain will develop. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. expressed by thermal diffusivity.04 to 0. designers now utilize the damping effect. No further reproductions authorized. when unrestrained. of leveling out the cyclic air temperature variation. temperature decreases are most important in that tensile strains will likely result.) will occur. Besides being important in the dissipation of internal heat. either by internal or external forces. thermal properties of concrete contribute to damping ambient cyclic variations. The practice of precooling concrete materials so as to depress the initial temperature of the concrete at the time of placing is resorted to frequently in massive concrete construction. Few buildings. A minimum opening of this magnitude is needed to permit successful and complete grouting.08 in. A low thermal expansion coefficient is beneficial. this period of time is short compared with the time the concrete is warmer than the surroundings. Normal weight concrete ideally combines strength and durability with a favorable thermal diffusivity property which is most effective in reducing the heating and cooling requirements of the building interior. The design of prestressed concrete reactor vessels should include Copyright by ASTM Int'l (all rights reserved). magnitude of this strain is determined primarily by the coefficient of thermal expansion and the amount of temperature change. This practice reduces the peak temperature which subsequently will be attained. For arch dams and similar massive structures containing joints which subsequently must be closed by grouting. Volume and Length Changes Linear and volumetic changes. A maximum placing temperature of 10~ (S0~ is specified frequently for large concrete dams which is usually well below the ambient air temperature during the normal construction season. in addition to their lower dead weight structural advantage. since this will tend to reduce the total length or volume decrease and lessen the magnitude of the potential thermal strain. cause neither strain nor stress. . the product of temperature drop and thermal expansion (or contraction) coefficient should be such that joint openings of at least 1 to 2 mm (0. but during the period the concrete is at a temperature below air temperature heat will be gained from the surrounding air.RHODES ON THERMAL PROPERTIES 259 properties of the concrete. including heat generation characteristics of the cement. are designed without consideration for thermal insulation. The light-weight aggregate concrete and foamed or cellular concretes will provide a measurable degree of insulation for the interior. However. residential or industrial. This low placing temperature will reduce the rate of cement hydration initially. In mass concrete structures. [3] Lentz. in general. Research and DevelopmentLaboratories. Thermal conductivity at higher temperature levels and the resulting thermal expansion or contraction can be determined analytically for introduction into the stress and strain patterns. tensile strain. may create thermal incompatabilities and possible failures where the repairs are subjected to extremes of temperature. G. 1. and possible development of cracks. A. and Monfore. 9. [2] Jakob. E. Vol. warrant consideration of thermal expansion coefficients as they may effect either joints or stresses. 1966. Portland Cement Association. Part VII." Journal. Surface insulation is also utilized to avoid development of steep thermal gradients which would result in large differential length changes. The principal thermal property to be considered in rigid pavement design is coefficient of thermal expansion under the cyclic variations in ambient temperature. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Thermal Condnctivities of Portland Cement Paste. Thermal expansion may be significant where epoxy mortars are used for concrete repair. 1950. Bulletin 207. 1940. H. New York. References [1] "Thermal Properties of Concrete. A. Bulletin No. ." Boulder Canyon Project Final Reports. No. G. principally rigid frame or continuous structures. Portland Cement Association. American Concrete Institute Recommended Practice for Cold Weather Concreting (ACI 306) [24] set forth guidance for concrete placement at low temperatures. Bureau of Reclamation. No further reproductions authorized.." Research Dept. E. [4] Brewer.. Spacing and width of expansion joints are determined mainly by the amount of thermal expansion resulting from the amplitude of the ambient temperature cylce and solar heating of the pavement slab. and accelerating the hydration process by the addition of calcium chloride or similar admixture will reduce the duration of protection required. 1967. Aggregate and Concrete Down to Very Low Temperatures. Wiley.260 TESTS AND PROPERTIES OF CONCRETE consideration of stresses or strains originating from temperature gradients during operation as well as during shut-downs. have thermal coefficients greater than 36 millionths/~ (20 millionths/~ and filled epoxy systems about 23 millionths/~ (13 millionths/~ These values. Jan. Elements of Heat Transfer and Insulation. Max and Hawkins. Copyright by ASTM Int'l (all rights reserved). 1. W. Winter Concreting and Insulation Newly-placed concrete must be maintained at temperature levels which will facilitate hydration and development of minimum strength requirements.. Protection is required to prevent freezing of the uncombined free water in saturated new concrete. Epoxy resins. Conventional building construction. "General Relation of Heat Flow Factors to the Unit Weight of Concrete. from two to four times those for normal portland cement concrete. The Chemistry of Cement and Concrete. Portland Cement Association. 67. Sun Apr 6 21:41:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1958. ." Research Department Bulletin 97. Portland Cement Association. No. Vicksburg. A. Detroit. Vol. "Laboratory Studies of Blended Cements-Portland Blast-Furnace Slag Cements. April 1955. No. Sept. Portland Cement Association... 2nd ed. [17] Philleo. with quarterly supplements. "Mass Concrete for Dams and Other Massive Structures. A. Feb.RHODES ON THERMAL PROPERTIES 261 [5] Campbell-Allen. Wexham Springs.." ACI Comm 207. "Physical Properties of Concrete at Very Low Temperatures. George. Detroit. A. 1. E. Publication SP-39.S. W. and Lentz. 1949. [12] Harmathy. "The Physical Structure and Engineering Properties of Concrete. M. [9] Temperature and Concrete. Waterways Experiment Station. T. 2. [20] "Investigation of Cement-Replacement Materials. R." Proceedings.. G. G. Vol. W. [24] ACI Committee 306. April 1970. July 1958. May 1966. Research and Development Laboratories." Journal. 1971. 132-142. "Some Physical Properties of Concrete at High Temperatures. 9. and subsequent discussions. No. Miss.. pp. Miss. Research and Development Laboratories. No further reproductions authorized. G. Oct. Vol. 3rd ed. T.. Fourth Internatiorml Symposium on the Chemistry of Cement. Cement and Concrete Association. Oct. "Energetics of the Hydration of Portland Cement. E." Journal. 1966.. 1959." Journal. Portland Cement Association. E. G. 4. and Allen." Journal... Publication SP-25." Journal. Vol. New York. No. 8. [13] "Mass Concrete for Dams and Other Massive Structures. No. American Concrete Institute. [14] Powers. W. Portland Cement Association. U. No. A. [10] Handbook for Concrete and Cement. 4. American Concrete Institute. 1967. Z. P. Properties of Concrete. May 1965. 1. 70. Army Engineer Waterways Experiment Station. Washington. "Recommended Practice for Cold Weather Concreting (ACI 30666). [19] Verbeck. B. 6-123. R. April 1970. C. 2. 7. [7] Neville. [22] Monfore..." Journal of the Power Division. "Control of Cracking in Concrete Gravity Dams. Research and Development Laboratories. Journal. [11] ACI Committee 207." Magazine of Concrete Research.. "An 'Isothermal' Conduction Calorimeter for Study of the Early Hydration Reactions of Portland Cements..." Journal. Slough. 1970. American Concrete Institute. Vol. W. [8] Lentz. M. 3. C. Proceedings. No. 1965. 1962. 1973.C. 2.. Aug. PO 5. 7. Paul and Isberner.." Research Department Bulletin 145. and Ost.. "Thermal Conductivity of Concrete at Very Low Temperatures. [18] Verbeck. March 1963. D. L. [23] Waugh. Vol. "Thermal Properties of Selected Masonry Unit Concrete. 43. [6] Lea. Portland Cement Association." Research Department Bulletin 90. Vol. Copyright by ASTM Int'l (all rights reserved). MP No. and Rhodes. Sept. J. New York." Corps of Engineers. 15. E. Portland Cement Association. [16] Monfore. National Bureau of Standards. Wiley. Vol. E. 1973. Chemical Publishing Co. [21] Klieger. Research and Development Laboratories. "Cement Hydration Reactions at Early Ages. Monograph 43. 1973. and Thorne. Vicksburg. Detroit." American Concrete Institute. 3. Report No. A. D. and Monfore. Vol. No. American Society of Civil Engineers. 1960. "The Thermal Conductivity of Concrete. [15] Behavior of Concrete Under Temperature Extremes. F.. American Concrete Institute. American Concrete Institute. 67. or voids. and permeability are directly influenced or controlled by the relative amounts of the different types and sizes of pores. Copyright9 1978tobyLicense ASTM lntcrnational www. are also important but are not treated in detail here. Feldman and G. G. size. I11. and bleeding channels and pockets. The pores can exert their influence on the properties of the concrete in various ways. L. 47907. Sun Apr 6 21:31:16 EDT 2014 262 Downloaded/printed by Universidade do Gois pursuant Agreement.org . The engineering properties. it is primarily the total volume of the pores that is important. Chicago. The porosity of the aggregate is treated extensively elsewhere in this volume. creep. The revision of this chapter was completed by W.STP169B-EB/Dec. Copyright by ASTM Int'l (all rights reserved). Formerly director of research. is largely a function of changes in surface energy at the solid-to-pore interface and. The assistance of R. entrained or entrapped air voids. American Admixtures Company. Litvan is gratefully acknowledged. Dolch. Irreversible drying shrinkage may involve capillary phenomena. in concrete consist of pores in the hardened cement paste. depends upon the nature of the solid surface and the total surface are of the pore system. Other void spaces such as honeycombing. Most of the important properties of hardened concrete are related to the quantity and the characteristics of the various types of pores in the concrete. shrinkage. at least that part of drying shrinkage that is reversible. F. therefore. durability. it is not surprising that there has been considerable interest in developing ways of measuring and characterizing the different types of pores in concrete and in elucidating I Deeeased. The permeability is influenced by the volume. Therefore. and voids in the pieces of aggregate. because they are the result of poor practice and are not inherent to properly prepared concrete. such as strength. and continuity of the pores. No further reproductions authorized. Shrinkage. which is the result of gross failure properly to consolidate the concrete. The resistance of concrete to freezing and thawing and deicer scaling is controlled by the volume and the characteristics of entrained air voids. As regards the strength and elasticity of the concrete. Lafayette. Purdue University. which result from excess water content or poor mix proportioning. 1978 George Verbeck i Chapter 18 Pore Structure Introduction The pores. Ind. not their size or continuity.astm. the volume of this space. aggregate. which initially was determined by the water/cement (w/c) ratio of the paste. If these air voids are the result of the use of an added air-entraining agent. At any time. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and generally speaking that part with the largest pore sizes. the bulk volume of the gel eventually will be sufficient to fill this space and produce a paste free from capillary space. At higher w/c ratios. which has a bulk volume larger than that of the original unhydrated cement. No further reproductions authorized. and pastes having a relatively large volume of capillaries will be produced. These submicroscopic capillary spaces include a wide variety of "sizes" and "shapes. In this technique mercury is forced under pressure into the dried and evacuated pores. and relatively small air voids. If the original capillary space is small (w/c ratio about 0. ." Various experimental methods have been used to investigate this portion of the pore system. this part is interconnected. Hydration reduces the size and volume of this capillary space. depending upon the history of the concrete. and placed consists of hardened cement paste. Hardened concrete that is properly proportioned. is continually reduced by the formation of the hydrated gel. they are termed entrapped air. After the concrete has hardened. The volume that enters is the volume of the pores and the pressure required to cause entrance is related to the size of the pores. the water-filled pores may tend to dry. mixed. If they are the result of the inevitable inability to effect complete consolidation of the plastic concrete. or the air-filled pores may tend to become water saturated.or gas-filled. even after complete cement hydration. At least at early ages. the most useful of which has been mercury intrusion porosimetry. they are termed entrained air.35 by weight). or Copyright by ASTM Int'l (all rights reserved). that part of the original water-filled space not occupied by hydration products constitutes part of the pore system of the paste. Pores in Hardened Cement Paste The water-filled space in a freshly mixed cement paste represents space that is available for the formation of cement hydration products. the external moisture conditions. and the dimensions of the concrete member. the gel volume is not sufficient to fill the original water space in the paste. Porosity of Concrete The pores formed in the original plastic concrete are either water. This capillary space can be visualized as a submicroscopic system of voids randomly distributed throughout the hydrated cement paste matrix.VERBECK ON PORE STRUCTURE 263 the various mechanisms by which they influence the properties of the concrete. As hydration proceeds. water that can be removed by heating to about l l 0 ~ or by vacuum pumping through a trap kept at the dry-ice point (--78~ or by exposure to strong desiccants. if the original w/c ratio was small enough. that most of the capillary spaces become isolated cavities separated from each other by the gel that is the hydration product. there are small gel pores and large capillary pores with a size region between the two that is more or less missing. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In a freshly-mixed or very young paste the capillary channels are.) diameter is imposed by the m a x i m u m pressure available to the equipment. In this way a pore size distribution can be determined. . his work has been interpreted to mean that gel pores of a characteristic volume and size are produced as part of the gel. These pores that are part and parcel of the hydration product were called gel pores by Powers. in such a paste. As the spaces become filled with hydration product on continued curing. essential elements of what has become known as the Powers model for hardened cement paste are a gel containing about a quarter of its volume of gel pores and a residual capillary pore space. This socalled evaporable water will have. The pores in the gel are generally smaller than the capillary pores. No further reproductions authorized. to the size of the entranceway of the pores. when saturated. Copyright by ASTM Int'l (all rights reserved). and that the capillary pores are the rest of the original water-filled space that has not become filled with gel. In this technique the amount of a vapor adsorbed on or in the pores is determined as a function of the ambient vapor pressure. This gel is itself a porous solid. a volume of about onefourth that of the bulk volume of the gel. interconnected. The mercury porosimeter has been used to investigate the small-size portions of the pore structure of cement paste. but a lower limit of about 3 nm (30 . The most notable of these are the Brunauer-Emmett-Teller theory using the relatively low vapor pressure portion of the data to obtain the specific surface area and the capillarycondensation theory using the higher vapor pressure portion for the pore size distribution. the method most used to investigate the size of the very small pores has been that of vapor adsorption. varying from about 1 #m for young pastes in which the cement hydration has progressed only a little. a time may come. Studies on hardened cement paste have shown that the size of its largest pores depends principally on the degree of hydration.264 TESTS AND PROPERTIES OF CONCRETE more exactly.1 #m in mature pastes that are more completely hydrated. and this volume equals that of the pores from which the water came.~. Certain theories are then used to relate these data to the surface area of the solids in the material and to the pore size distribution of its pores. Thus. Therefore. ipso facto. and it has been inferred that the pore space according to this model is bimodal. If a paste has such a low w/c ratio that not all the cement can ever become hydrated. to about 0. and if he did not precisely say so. that is. the gel will fill completely all the space not occupied by unhydrated cement and will have a characteristic porosity containing. The product of cement hydration that constitutes the solid fraction of the hydrated cement material is composed of very fine particles. over the range where they both apply. Comparisons between pore size distributions obtained by sorption and by mercury porosimetry. A calcium silicate hydrate ( " C . which is a few hundred angstrom units. this space is termed "interlayer space. a pore system is formed in the paste that is approximately continuous from the smallest "gel" pores to the largest "capillary" pores. Some of the same characteristics exist. freezing characteristics. while Copyright by ASTM Int'l (all rights reserved). roughly a tenth that obtained with water vapor. which are on the average approximately parallel and about one to two water molecules in width.H gel") may constitute about 50 percent of the hydrated cement.. No further reproductions authorized. They consider that even a dense. Nevertheless it is reasonable to say that when the w/c ratio is higher than a minimum (about 0. The earliest estimates of the surface area of the solids in hardened cement paste were obtained by the vapor sorption method using water as the adsorbed species. the results were lower. and that any such distinction is arbitrary. When the same experiment was performed with nitrogen as the sorbed species. the smallest pores cannot be so investigated. which is the case for almost all concrete.S . The volume of the interlayer space. The presence of this water increases the elastic modulus of the material by as much as 100 percent. whereas the volume of the capillary space decreases with hydration. which may form crystals large enough to be visible in an optical microscope and which may constitute 25 percent of the hydrated cement.35). and then decreasing to the limit of the method. have not always shown good agreement.~) diameter. The values obtained were approximately 200 m 2 /g of dry solids. notably different from those of free water in bulk. .VERBECK ON PORE STRUCTURE 265 Sorption studies have shown a size distribution for the small pores from a lower limit of a few diameters of the water molecule throiagh a maximum volume of about 5 nm (50 . The overall average particle size of the elements of hydration is small. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Mercury intrusion data have failed to show any bimodality of the pore sizes in cement paste. At low w/c ratios the specific surface area is less than 1 m 2 / g of dry paste. for water in the capillary spaces. such as vapor pressure. although as mentioned previously. Another product of hydration of the calcium silicates is calcium hydroxide. extremely thin sheets that may be crumpled or rolled as foils. in each quantity of paste. increases with continued hydration of the cement.. It is a poorly crystalline material consisting of small. This discrepancy led to the advocacy of a different model for the structure of hardened cement paste. well-cured paste is capable of holding relatively large quantities of H 2 0 molecules that exist in spaces between layers of calcium silicate hydrate." The water molecules in these small spaces will have characteristics. which was set forth by Feldman and Sereda. but to a much lesser degree. and mobility. about 200 m 2 /g. areas are the "true" values.S . and that the nitrogen. The sensitivity of the material makes it desirable to investigate the pore structure in the wet state. concrete consistency. Low angle X-ray scattering has indicated that the specific surface area. water held either in the interlayer space or smaller capillary pores does not behave as normal free water. the C . including that within the "interlayer" spaces. The same technique gave specific surfaces of dried pastes roughly the same as those obtained with water vapor sorption..266 TESTS AND PROPERTIES OF CONCRETE at high w/c ratios.H gel is a material very sensitive to wetting and drying. The volume of the air voids in hardened concrete and the characteristics of the air-void system (void Copyright by ASTM Int'l (all rights reserved). The interlayer spaces retain most of their water even at relatively low humidities. not the water. whereas most of the capillary water is more volatile. The Powers model regards the surface areas obtained by water vapor sorption to be the "true" values and sees the nitrogen areas as lower because of steric or thermodynamic hindrance to the access of nitrogen to the whole surface. . size distribution of fine aggregate. is about 700 m 2 / g for water-saturated pastes. duration of mixing. as measured by nitrogen sorption. Those purposely entrained voids that have a significant effect on the resistance of the concrete to freezing and thawing and deicer scaling range from a few to several hundred micrometres in size. It is the capillary spaces with which the permeability of paste and concrete is associated most closely.. and so on. However. it is in the vicinity of 175 m 2 /g. for the water is these pores can move much more freely under hydrostatic pressure than can the interlayer water. So the Feldman-Sereda model considers that the "water" area includes interlayer spaces not accessible to nitrogen because of the specific attraction of water molecules to the silicate surfaces. Many of the accidentally entrapped voids can be seen with the unaided eye and may range in size up to several millimetres. The air voids may constitute from less than 1 to more than 10 percent of the concrete volume. major changes occur to the layered structure as it is dried or wetted. No further reproductions authorized. dispersed throughout the paste component. the volume and size depending upon several factors including the amount of air-entraining agent used. Air Voids Concrete normally contains air voids. these values must be taken only as rough indicators. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As previously noted. this is extremely difficult. The small air voids having a significant effect on concrete durability can be seen and studied using a microscope and a magnification in the range of approximately 30 to 150 diameters. accidently entrapped or purposely entrained. Inelastic neutron scattering has suggested that pore volumes measured by nitrogen absorption are realistic. Permeability of Concrete Interest in the permeability of concrete arises in connection with some proposed specific application of the concrete and. humidity differentials. it has been observed that many factors influence the rate of flow of water through the membrane. sawed. Although it is known that the observed rate of movement is dependent upon the characteristics of the membrane and the permeating materials. the treatment of the surfaces (as-cast. frequently heterogeneous. and solutions of different concentrations (osmotic effects) or at different temperatures. Approximately 75 percent of the concrete is aggregate. The cement paste component usually contains both extremely fine gel pores and the coarser but submicroscopic capillary spaces. The combined porosity of concrete (including the air voids) can be represented by the total capacity for evaporable water between the stages of complete saturation and dryness--dry except for the combined or nonevaporable water content of the cement hydrate. may result in emphasis of some particular aspect of concrete permeability. normally the coarsest of all. considering the relatively simple case of a hydrostatic water pressure differential across a membrane of concrete. Movement of water through concrete can be produced by various combinations of air or water pressure differentials. the quantitative value obtained may depend considerably upon details of the experimental conditions. Although these various pores and voids in concrete influence the physical properties of water contained therein. the air voids. the properties of the separate types of pores are not sufficiently different to permit their complete indentification in concrete. each component having its own characteristic pores. For example. or sand-blasted). In summary. concrete can be visualized as consisting of a heterogeneous mixture of components. Although these procedures may reveal the relative characteristics of the concretes involved. and spacing factor) can be determined in accordance with ASTM Recommended Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457). much more needs to be learned regarding these relationships. In terms of the other pores in the concrete. . Various tests have been devised to determine permeability. voids per inch of traverse. with an internal pore volume varying from almost 0 to 20 percent or more (most commonly about 1 to 5 percent). the measurement of inlet or outlet flow Copyright by ASTM Int'l (all rights reserved). the direction of permeation in relation to casting position (under-aggregate fissures). The prior curing history of concrete. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. therefore.VERBECK ON PORE STRUCTURE 267 size. carbonation. may constitute from less than 1 to more than 10 percent of the total volume of the concrete. the down-stream conditions (whether air or water). No further reproductions authorized. the pores ranging from relatively fine to coarse. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However.50. This large reduction in permeability is due to the drastic reduction in capillary size and volume that accompanies the decrease in w/c ratio. this "permeability" rapidly decreases with hydration. because of original w/c ratio and extent of cement hydration. and if the paste is of low permeability.60.8 w/c ratio may decrease a thousandfold between the curing ages of 7 days and 1 year. 6 months.4 weight. This attainment of discontinuity in the capillary system appears to occur when the total porosity (gel plus capillary) reaches approximately 50 percent.70 w/c ratio require approximately 3 days. and so on. 0. There is evidence that even when the capillary system becomes "discontinuous" (as measured by water permeability) there still remains some continuity in the large pore system. The permeability of cement paste appears to undergo a relatively abrupt reduction when. and the electrical conductivity between the membrane faces or factors that must be considered. All of the permeating water must pass through the paste component of the concrete (the continuous phase). has been observed to be as low as that of mature pastes of about Copyright by ASTM Int'l (all rights reserved). and 0. such as traprock or marble. All the capillary volume in fresh paste is capable of rapid transmission of water (as revealed by bleeding). Apparently the large capillary spaces necessary for the propagation of lee formation are not sufficiently numerous to influence significantly the permeability measurements. there is millionfold difference between the permeability of high-water-ratio paste at early age and that of well-cured low w/c ratio paste. The permeability of dense. The permeability of concrete to water under hydrostatic pressure will depend significantly upon the permeability of the cement paste component of the concrete. The hydrostatic water permeability (expressible in terms of Darcy's law) of a well-cured paste is reduced approximately a thousandfold by reduction in w/c ratios from 0.268 TESTS AND PROPERTIES OF CONCRETE or both. the nature and amount of solutes in water.40 0. providing the concrete is intact--not previously damaged by frost or rapid drying and not containing excessive under-aggregate fissures or honeycomb. admixtures.8 to 0. It has been estimated that cement pastes of 0. respectively. and 1 year of normal hydration. . At the present time the qualitative effects of many factors on the water permeability of concrete are known. No further reproductions authorized. the concrete will show similar characteristics. impervious aggregates. the test procedures commonly used for determination of the water permeability of concrete are probably sufficient to reveal relative differences in the permeability of concretes made with different water contents. The permeability of a paste of 0. This seems necessary in order to account for the spontaneous propagation of freezing in saturated pastes. Thus. in order to attain this condition. it attains the condition at which the capillary system becomes discontinuous due to blocking by increase in the concentration of the gel component in the paste. 14 days. Air voids in the concrete. namely.40 w/c ratio. air content. Absorption of Concrete The term "absorption" is usually applied to concrete in regard to the weight gain of partially dried specimens upon contact with or immersion in water. Capillarity can also produce liquid movement in concrete. other factors seldom do remain constant--it is commonly observed that air entrainment in most practical concretes will reduce segregation and bleeding and permit reductions in the w/c ratio. and so on. The absorption of concrete is measured by ASTM Test for Specific Gravity. can easily remove most of the aggregate water. do not impede movement of water. and Voids in Hardened Concrete (C 642). Obviously. Factors significantly influencing absorption are the curing history. cement type and fineness (particularly at early ages). should increase the permeability of saturated concrete roughly in proportion to their quantity. Because of its usually much finer pore structure. particularly the smaller voids. because they are much larger than the capillary and gel pores and.VERBECK ON PORE STRUCTURE 269 0. provided other factors remain constant. Copyright by ASTM Int'l (all rights reserved). if the aggregate is more or less permeable than the paste matrix.7 w/c ratio paste and about I percent for the granite. However. The ratio of the water absorbed to the dry weight is the absorption. . aggregate characteristics. No further reproductions authorized.paste surrounding the aggregate.70 w/c ratio. Absorption. Some granites have a permeability comparable to that of a mature paste of 0. their rate of absorption being slow because of their low water permeability. despite the enormous differences in porosity. may become filled with water. specimen size and shape. The coarse pores in' aggregate can become nearly filled with water only after a relatively high degree of saturation is established in the. The presence of water at one face of the concrete and unsaturated air at the other may give rise at the air interface to large negative pressures or capillary tensions (meniscus effects) that tend to draw the water through the concrete. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In this method the water absorbed by an oven-dried specimen is measured after 48 h immersion or after such immersion followed by 5 h in boiling water. hence. the air voids. about 50 percent for the 0. broken) surface carbonation. Such a process requires that the air in the void compressed by the absorption process must dissolve in the capillary water and slowly diffuse out of the specimen to permit filling of the void with liquid. w/c ratio. with the finer gel pores perhaps next. the permeability of concrete will be changed accordingly. with the result that the concrete may actually be more impermeable despite the presence of the air voids. During absorption it may be considered that the larger capillary spaces in the paste are the first to be wetted. the paste. if it is much below saturation. method of surface preparation (cast. Upon long-continued exposure to water. the existence of internal.270 TESTS AND PROPERTIES OF CONCRETE The absorption test is of value primarily as a basis of comparison of different concretes. pressures cannot be questioned. the so-called critical distance. therefore. without generating disruptive hydraulic pressure. Mechanical damage is caused by the inability of the system to achieve an equilibrium moisture distribution and by subsequent glassy ice formation. it would be associated with hydraulic pressures great enough to disrupt the concrete and cause a crack. Whatever the cause. The distress can arise in either the cement paste or the aggregate component of the concrete. If such movement was over a great enough distance. The water in the small pores cannot freeze at ordinary freezing temperatures. which could cause the unfrozen water to be forced ahead of the freezing front due to the volume increase experienced by water on freezing. With an appreciation of these factors. In terms of this hydraulic pressure hypothesis. This unfrozen water will then migrate to the ice in larger pores and cause expansive pressures. Powers later advanced the concept of gel-water diffusion. Only that in the paste will be considered here. Frost Durability Concrete that has in its pores a relatively large amount of water is often damaged on exposure to cold temperatures by a process known as freezethaw action. Copyright by ASTM Int'l (all rights reserved). durability (freezable water content). is still a matter of debate and further research. Again. probably nonuniform. it is not surprising that only rough correlations are observed between the results and such parameters as w/c ratio. While no agreement has been reached as to the cause of the phenomenon. . the absorption in a gross manner being a function of the permeability and porosity of the specimen although influenced by many factors of test procedure. so that expansive pressures will not be generated. The first analysis of the freeze-thaw process was that of Powers. the role of the entrained air is to provide escape voids into which the unfrozen water can go without having traversed the critical distance and. and attack by aggressive solutions. or the extent to which each of the above processes contributes to the difficulty. owing to thermodynamic considerations based on the small pore size. The exact mechanism of freeze-thaw. Osmotic pressures from differences in concentrations of dissolved salts would be expected to augment these expansive pressures. His description involved freezing of water in the comparatively large pores. strength. moisture redistribution and. No further reproductions authorized. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. More recently Litvan has proposed a mechanism wherein the water in the small pores migrates to the ice already formed because of a vaporpressure differential that will develop between the two as the temperature falls below freezing. entrained air voids offer an alternative destination for the gel water. and their magnitudes are determined largely by. Naturally. The test methods for freeze-thaw durability of concrete are ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666) and Test for Critical Dilation of Concrete Specimens Subjected to Freezing (C671). But the only way to be sure that concrete exposed to moisture and freezing temperatures will be durable is to entrain a proper air void system by the use of an appropriate air-entraing agent. Excessive expansion or a large decrease in sonic modulus of elasticity are the usual indications of a nondurable concrete.VERBECK ON PORE STRUCTURE 271 consequently. the higher the w/c ratio.25 mm. are all related to. These stresses can be eliminated effectively by the presence of entrained air voids of proper size. the greater the strength. The well-known w/c ratio rule is merely an expression of this effect. Entrained air has little. most nonair-entrained concrete is inherently susceptible to frost damage. The effects of the aggregate are important. keep the concrete relatively dry. and spacing. no problem will occur. If the developed stresses exceed the tensile strength of the concrete. at which point the strength becomes zero. As a first approximation the rule Copyright by ASTM Int'l (all rights reserved). . In either of these test methods the concrete is frozen and its changes in dimension or in properties are measured. the greater will be the capillary porosity of the paste and. shrinkage. if proper drainage. such as strength.12 to 0. coatings. the rate of freezing. This critical distance has been verified experimentally and in practice. Another result of such studies is the existence of a critical total porosity of about 60 percent. Both theory and experiment lead to relationships that are either parabolic or exponential between the two. Mechanical Properties of Concrete The important mechanical properties of concrete. the lower the strength. This idea was first given quantitative expression by Powers in his gel/space ratio rule. and the distance the water has to migrate to achieve equilibrium. If the paste is so dense that only the smallest pores are present. To avoid the development of destructive internal pressures under most practical conditions. the higher the ratio of gel to space available for it. number. therefore. that is. use in preventing freeze-thaw trouble arising in the aggregate component. etc. the porosity of the concrete. if any. but less so than those of the cement paste. and creep. All porous materials have this same inverse dependency between strength and porosity. pore pressure generated will depend upon the amount of freezable water. the permeability of the paste. No further reproductions authorized. deterioration ensues. But since practical considerations of workability usually require higher w/c ratios. stiffness. it will probably be durable to ordinary freezing exposure. the separation between entrained air bubbles should be in the range of approximately 0. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Fifth International Symposiumon the Chemistry of Cement. Various mechanical and analytical problems confront investigators of this matter. This problem of the effective pore area in concrete is also of direct concern to the designers of gravity dams. on its important engineering and technological properties is greater than that of any other property of the material. cause damage. No further reproductions authorized. The strength of concrete depends of course to some extent on other factors--chemical composition of cement.272 TESTS AND PROPERTIES OF CONCRETE seems to hold as well for air voids as for the small pores. the total porosity is the important parameter. and unanimous agreement has not been reached concerning the effective pore area to water in mortar or. being greater with the cube of the gel/space ratio. as are also the quantitative relationships between the parameters that describe the pore system and the properties of the concrete it so strongly influences. Like the strength. reported values ranging from about 40 percent to almost 100 percent. Both Young's and the shear moduli of elasticity of pastes depend on the porosity. concrete. Effective Pore Area The magnitude of pore pressure that is required before destructive forces develop in the concrete is related to the effective area of the concrete over which they produce stress. Bibliography Symposia Proceedings. aggregate properties. The exact nature of the pore system and of the solids that frame it is still a matter of debate and ongoing research. and in particular that of the hardened cement paste component. whereas lower pore pressures operating over large areas of the concrete could produce forces above the inherent strength of the concrete and could. Tokyo. Copyright by ASTM Int'l (all rights reserved). depending upon the grade of materials studied and the method of analysis applied. That the effective pore area is high is not surprising when the high porosity and fine texture of the pores in concrete are considered. 1969. Concrete Association of Japan. Small and isolated pockets of high pressure might be accommodated by the concrete. they are controlled by all those things that result in different paste porosities--principaUy w/c ratio and duration of proper curing. therefore. . placement practices--but the main influence is the porosity of the paste. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Conclusion The influence of porosity of the concrete. Vol. p." Journal of Testing and Evaluation. Skalny. General R e v i e w s Copeland. and Diamond. 1971. Verbeck. Brunauer. D. Vol. "Capillary Porosity in Hardened Cement Paste.." Proceedings.. and Dolch." Proceedings. N. "Density and Porosity Studies of Hydrated Portland Cement. Proceedings. "Cement Paste Microstructure--An Overview at Several Levels. and Brownyard. p. 564. Powers." Proceedings. 1973. W. 1974. and Mann. Winslow. L. "Complete Pore Structure Analysis. 1973. Academia. Moscow. 3. T. F. 387. 1976. Academia. Vol. Valenta. "A Mercury Porosimetry Study of the Evaluation of Porosity in Portland Cement.. and Diamond. S. R... G. . L. Powers. "Structure and Properties of Hardened Cement Paste. Their Significance and Experimental Determination. p. Prague.. E. 234. H. and Verbeck. SP-47.. Tokyo." Cement Concrete Research. 577. J. and Odler. Copyright by ASTM Int'l (all rights reserved). 1975. 1974. Prague.. Sixth International Congress on the Chemistry of Cement.. Moscow. F. J. 1974. Moscow. Diamond." Proceedings. Tokyo. R. Vol. T. Skalny. "Changes to Structure of Hydrated Portland Cement on Drying and Rewetting Observed by Helium Flow Techniques. G.. International Symposium Rilem/ IUPAC. p. S. 5. 1. 1976. Sixth International Congress on the Chemistry of Cement. p. "Capillary Continuity or Discontinuity in Cement Pastes. 3. Cement Association of Japan. Academia. 933. C-3. 2. p. Cement and Concrete Association. Diamond. 3. Conference on Hydraulic Cement Pastes: Their Structure and Properties. I. National Bureau of Standards. Academia. S. 1. C. p.. p. 1969. Prague. Vol. M. 4. Fifth International Symposium on the Chemistry of Cement. and Helmuth. p. Prague. J. E. Durability of Concrete. Detroit. S. 1970. Porosity. 425. Winslow. 1973. T. 1973. "Studies of the Physical Properties of Hardened Portland Cement Paste.. 45. Copeland. 1969. Vol. Vol. 2. 1972. International Symposium Rilem/IUPAC. W. C." Journal Colloid Interface Science. Sheffield. 36. D. Feldman. "A Critical Comparison of Mercury Porisimetry and Capillary Condensation Pore Size Distributions of Portland Cement Pastes. "Pore Structure of Calcium Silicate Hydrates. Powers. R. and Sereda. R. J. F. Vol." Cement Technology.VERBECK ON PORE STRUCTURE 273 "Pore Structure and Properties of Materials. I. 43." Proceedings." Proceedings. "The Specific Surfaces of Hydrated Portland Cement Paste as Measured by Low-Angle X-Ray Scattering. 1. 1972. "Phase Composition of Hardened Cement Paste. p. C-101. O. p.. H. "Generalized Log-Normal Distribution of Pore Sizes in Hydrated Cement Paste.. Feldman. Sheffield. Washington. American Concrete Institute." Cement Concrete Research.. 1973. American Concrete Institute. Proceedings. Kondo." Journal. Vol. Vol.." Journal of Materials." Cement Concrete Research. Fifth International Symposium on the Chemistry of Cement.. A. Feldman. 1973. R. p." Journal Colloid Interface Science.. Portland Cement Association. T. L. Conference on Hydraulic Cement P~istes: Their Structure and Properties.." Proceedings. 38. P. F. Part 2. "Volume Change. Research Division Laboratories. Sixth International Congress on the Chemistry of Cement. Pore S t r u c t u r e o f H a r d e n e d C e m e n t Paste Auskern. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Cement and Concrete Association. 531. 1960. E-75. 5. N. 38. 1. Vol. p. 1972. C. and Horn." Proceedings. Fourth International Symposium on the Chemistry of Cement. 1973. L. "Discussions. 1. 1959.. S. 1947. Vol. and Helium Flow Studies of Hydrated Portland Cement. J. "Structures and Physical Properties of Cement Pastes. p.. S. Part 1." Proceedings. International Symposium Rilem/IUPAC. p. Cement Association of Japan.. "Physical Properties of Cement Paste. R. No further reproductions authorized. p." Proceedings. International Symposium Rilem/IUPAC.. p. M. Diamond. 74. "Main Properties of the Pore System on Non-Metallic Structural Materials." Proceedings. and Daimon. Feldman. and Odler. J. American Concrete Institute. "Strength and Porosity of Concrete.507.. Sun Apr 6 21:31:16 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Proceedings. P. Academia. 1975. and Effects of the Air-Void System in Concrete. and Feldman.." Highway Research Record. American Concrete Institute. 103. p.. 356. Special Report No. C.." Journal American Ceramic Society. Vol. T... Hoff. G. 2. A. "Method of Developing Relationships Between Mechanical Properties of Hardened Concrete. S. Fagerlund. Vol.. R. International Symposium Rilem/IUPAC. "The Protected Paste Volume Concept Using New Air-Void Measurement and Distribution Techniques. "A Study of Mechanical Properties of Autoclaved Calcium Silicate Systems. p. G. p. . Larson. MacInnis." Proceedings. 1973. and Beaudoin. Prague." Cement Concrete Research. Detroit. Vol. 135. American Concrete Institute. 1972. 55. "Phase Transitions of Adsorbates IV. C. 13. C. "Theory of Volume Changes in Hardened Portland Cement Paste During Freezing. 1966. p. 1969." Proceedings. Mielenz. 2. Evoluation. 1967. 1972. Vol... p. "Elastic Moduli of Hardened Portland Cement and Tricalcium Silicate Pastes: Effect of Porosity. 781. and Malloy..T h a w Durability Fagerlund." Durability of Concrete. p.. 4. 285. Powers." Journal of Materials. Cady. M e c h a n i c a l Properties Beaudoin. G. Detroit." Durability of Concrete. p. 1972. F. T. No further reproductions authorized. Vol. J. 261. 202. "Significance of Microhardness of Porous Inorganic Materials. "Freezing Effects in Concrete." Journal of Materials. Academia. 717. 95. C. Vol.. Powers.. Helmuth. 184. p. D. p. G." Cement Concrete Research. 1975. 1953. 1973. G. G. p. Mechanism of Frost Action in Hardened Cement Paste. p. pp. H.. 1973. "Pore Structure and Frost Durability. Vol. J. Highway Research Board. F-17. Sereda. 1. 5.. 70. 55. T. SP-47. Litvan. American Concrete Institute. 32. J. 1958. International Symposium Rilem/IUPAC. 91. Popovics.. p. "The Air Requirement of Frost-Resistant Concrete. Academia. S. C. A. Prague. 2." Proceedings. "Porosity-Strength Relationships for Cellular Concretes. 90. Prague. 1973. D. p. G. and Helmuth.274 TESTS AND PROPERTIES OF CONCRETE F r e e z e . 29. D-51. T . J. and Turk. Vol. J. F-3. Popovics. Copyright by ASTM Int'l (all rights reserved). D. 38." Proceedings.359. p. Powers. R. "Origin. P. "Pore Structure and Frost Susceptibility of Building Materials.. Proceedings. "Effect of Porosity on the Strength of Concrete. 1975." Proceedings. Vol. p. Litvan. J. Vol. International Symposium Rilem/IUPAC. R. "The Significance of Critical Degrees of Saturation at Freezing of Porous and Brittle Materials. et al. R. 1949. Highway Research Board." Cement Concrete Research. C. SP-47. The Pennsylvania State University. D. The costs associated with repair or replacement of concrete bridge decks damaged by reinforcement corrosion is. 16801. 2]. and cured. In addition to the loss of concrete cover. and shall be for years to come. University Park. Copyright9 1978 tobyLicense ASTM lntcrnational www. Sun Apr 6 21:41:47 EDT 2014 275 Downloaded/printed by Universidade do Gois pursuant Agreement. Mechanisms of Corrosion The corrosion of steel in concrete results from the development of electrochemical corrosion cells. IProfessor of civil engineering.STP169B-EB/Dec. Copyright by ASTM Int'l (all rights reserved). The common denominator is the presence of chlorides which result from the application of deicing salts in the former instance and from the environment in the latter. many show signs of deterioration in five years or less [3. consolidated.2 While highway bridges are expected to last 30 years or more. 2The italic numbers in brackets refer to the list of references appended to this paper. 2). This is the familiar "pot hole" on a concrete bridge deck (Fig.astm. a reinforced concrete member suffers structural damage due to loss of bond and to loss of steel cross section.org . No further reproductions authorized. 1). The electrical current involved may be induced. Pa. properly placed. both in terms of frequency of occurrence and magnitude of resultant damage. provides an environment that will normally prevent corrosion of embedded steel. Reinforced concrete highway structures (principally bridge decks) and structures exposed to seawater or marine atmospheric environments are most prone to this problem. a major maintenance expense for many highway agencies [1. The damage that ensues from corrosion of reinforcing steel is manifested in the later stages as spalling of the concrete cover between the steel and the nearest free surface. However. Cady ' Chapter 19--Corrosion of Reinforcing Steel Introduction High quality portland cement concrete. sometimes to the extent that structural failure occurs (Fig. the technical literature abounds with evidence of serious problems related to corrosion of reinforcing steel in concrete. 1978 P. 4]. It is the result of pressures generated in the concrete due to the volume increase associated with the conversion of steel to corrosion products. Faraday's constant. Copyright by ASTM Int'l (all rights reserved).. c. n u m b e r of chemical equivalents reacting. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. universal gas constant.c C + dD the electrochemical potential E=EoRT. . No further reproductions authorized. absolute temperature. 1--Typical pot hole on a bridge deck. d = molar quantities of reactants and products.276 TESTS AND PROPERTIES OF CONCRETE FIG. that is by stray electrical currents (rarely). (ac)C (aD) d where E~= R = T = n = F = a = standard electrode potential. and exponents a. activities of reactants (A and B) and products (C and D). b. but more commonly results from electrochemical potentials created within the concrete in accordance with the Nernst equation [5]. For the chemical reaction aA + b B . CADY ON CORROSION OF REINFORCING STEEL 277 FIG. Copyright by ASTM Int'l (all rights reserved). . No further reproductions authorized. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 2--Structural failure o f a reinforced concrete column due to corrosion o f reinforcing steel. . : ".'A "'"" . Copyright by ASTM Int'l (all rights reserved). the corrosion rate is governed by the current in accordance with Faraday's law r=kI where r = corrosion rate in weight loss per unit time.:'.:". they are probably limited to the following: (a) Differential aeration--differences in concentration of oxygen over the surface of the steel. 9 .. "'. 9 h:...'.': "n:.A:. ""'" :..-. 9 . 4 [6].Z.i . " "" .. :''" :.: ~" ."o ". however.. dissolved salts..... Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "~. For the specific case of steel in concrete.'. It is evi9 ~ .'. The corrosion cell is shown schematically in Fig. + FIG. (b) Differential ion concentration--differences in concentration of metal ions.: '" -'..A"" :" :.": :9." " " " " " -1 FIG. :'. .A'.'." ~'. k = the electrochemical equivalent (a constant).278 TESTS A N D PROPERTIES OF C O N C R E T E The presence of an electrical potential is a necessary prerequisite for the occurrence of corrosion9 However. ~ 9 : Z'""--'"""i 9 . and pH (alkalies and free lime) in the concrete in the vicinity of the steel9 (c) Differential surface properties--variations in the surface characteristics of the steel such as mill scale or breaks in coatings.:'. 4--Flow diagram showing the basic chemical reactions in the corrosion cell (after Erlin and Verbeck [6]).. and I = current. 9r 9 ." :a'.~"a :"" ~.. 9 ~ ~ ~ 9 . 3. 3--Schematic diagram of the corrosion cell. . and a flow diagram showing the chemical reactions in the corrosion cell is shown in Fig.'. = OH ~ . . No further reproductions authorized.:. F:-] + F-q+?Tq.".'. The electrochemical potentials that must be present to form the corrosion cells may be created in several different ways.:" ~""'-'" ~" . 9 ~ ".'.: : " A " : . Effect of Chloride Ion One of the reaction products in the hydration of portland cement is free lime which exists in concrete as crystals of calcium hydroxide. Because a portion of the chloride ions enter into chemical reaction with the alumina compounds in the hydrated cement (to be discussed later). 9]. the influence of chloride content in reducing the resistivity of concrete is minor. Hausman [8] probably established the lower limit for threshold chloride concentrations Copyright by ASTM Int'l (all rights reserved). Electrochemical production of gamma Fe203 then builds up the protective film thickness until it becomes impervious to ions. sodium chloride will tend to increase pH and calcium chloride will tend to decrease it [6. In the absence of oxygen. The presence of small quantities of alkalies (sodium and potassium oxides) in portland cement may raise the pH even higher [8]. The normally protective environment provided by concrete relative to corrosion of steel results from the formation of gamma ferric oxide (Fe2Oa). while iron and other cations (Ca + + and Na § ) will diffuse toward the cathode. the presence of chloride ion changes the situation. chloride ions also affect the pH which.5.CADY ON CORROSION OF REINFORCING STEEL 279 dent from these figures that hydroxyl ions and other anions present (such as chloride) will diffuse toward the anode during corrosion. water contained within the pore structure of concrete becomes buffered at least to the pH of saturated lime solution (about 12. Any breaks that occur in this protective film are quickly repaired in the presence of sufficiently high hydroxyl ion concentration. As mentioned previously. and passivity is restored [7]. Since diffusion of ions through the concrete is necessary for corrosion to occur. especially in comparison to the effect of moisture content [5]. The effects of chloride ion concentration on corrosion probability and rate are difficult to quantify because of the strong dependence on moisture content and availability of oxygen to depolarize the cathode.5)[6].5). polarization of the cathode by hydrogen released in electrolysis interferes with current flow and corrosion ceases. However. However. forming first ferrous hydroxide which then reacts with oxygen to form predominantly cubic FeaO4 and gamma Fe203. Finally. Finally. Also. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it follows that a continuous conductive moisture path must exist in the concrete between the anode and the cathode. it will be observed that oxygen and water must be available at the cathode. chloride salts being strong electrolytes increase the conductivity of the ground path enhancing the corrosion current. However. No further reproductions authorized. as noted previously. The main function of the chloride ion in promoting corrosion of reinforcing steel in concrete is to release ferrous ions at the anode though the formation of ferrous chloride. steel becomes passivated at pH values above 11. . Also. Therefore. influences corrosion. conditions must exist that will tend to break down the passivation of the steel that normally occurs in alkaline environments (pH > 11. / m 3 of concrete. led Stratfull et al [12] to conclude that the quantity of chloride ion associated with the incidence of active corrosion of steel in concrete is about 0. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) ions can produce similar results. but chloride ion activity at the corrosion threshold bears a constant ratio to hydroxyl ion activity of about 0.6. found a nearly linear inverse relationship up to a resistivity value of 60 000 fl-cm beyond which corrosion apparently does not occur. saturated lime solution. some showing signs of deterioration and others not. . For the typical range of concrete mixtures normally encountered. in comparing electrical resistivity of concrete with concrete deterioration produced by corrosion of reinforcing steel.5 to 13. Copyright by ASTM Int'l (all rights reserved).8 kg of chloride ion per cubic metre of concrete at pH values of 12. Detailed study of 21 bridge decks of ages varying from 6 to 23 years. corrosion of steel in concrete might not occur at the chloride ion threshold concentration predicted by Hausmann due to somewhat more limited ion mobility and limitations on the rate of diffusion of oxygen to the cathode in concrete as compared to oxygenated. chloride ion threshold concentrations required to initiate corrosion increase. as previously discussed. It should be reemphasized that while the threshold chloride concentration increases with increasing pH.2 to 2. Effect of Moisture Content The presence of moisture is not only a necessary prerequisite for the initiation of corrosion. With regard to corrosion threshold concentration of chloride ion in concrete. this represents corrosion threshold chloride contents ranging between 0. it may be stated that the onset of corrosion may occur at chloride ion concentrations as low as about 0. Other bridge deck studies revealed similar corrosion threshold values [13].280 TESTS AND PROPERTIES OF CONCRETE through experiments with oxygenated. using Hausmann's results as lower limits. moisture content is the primary rate determining factor in the corrosion process.9 kg CI . These values are in good agreement with those predicted by Hausmann. Hausmann [8] also indicates that bisulfide ( H S .11] revealed a value of 0. Stratfull [14]. this figure is in close agreement with the data cited previously. it is more sensitive to the moisture content [5]. It is generally contended that only ions of the halogen elements. of which the chloride ion is the only one of practical significance with respect to concrete.6 kg/m 3 of concrete. work carried out by the Federal Highway Administration [10. While resistivity is influenced by chloride content.7 and 0. Again. respectively.5.20 percent C I .2.based on the weight of cement in the concrete mixture. However. No further reproductions authorized. saturated lime solutions. He showed that as the pH increases above 11. are apparently capable of promoting corrosion of steel embedded in concrete. This is largely due to the effect of moisture content in reducing the resistivity of the concrete thereby increasing current flow--the determinant of corrosion rate. However. CADY ON CORROSION OF REINFORCING STEEL 281 Effect of Concrete Mixture Variables Properties of concrete that influence the alkalinity and the quantity or uptake and transmission of water.5 cm thick section. The permeability of concrete to chloride ions also increases with increasing w/c ratio. Verbeck [9] reported a threefold increase in permeability to chloride ion as the w/c ratio was increased from 0. and oxygen have already been discussed.5. the ion concentration decreases with depth of penetration in accordance with an exponential decay relationship. cm.44 (0. kg/m 3. Water/cement ratios normally used fall in the range 0. and admixtures.5 are very low and nearly constant [9. The coefficient of permeability of a mature paste with zero capillary porosity has been determined to be about 7 X 10 .724) s where C ---. with lower and upper practical limits of 0. For chloride ions that enter the concrete from a free surface.5 cm thick section. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Carbon dioxide reduces the pH by reacting with the free lime to form calcium carbonate.6. oxygen. aggregates. High permeability concretes permit ready access of moisture. No further reproductions authorized. Spellman and Straffull [19] found that the average chloride content versus depth for 16 heavily salted bridge decks in California could be approximated by the following equation C = 6.maximum depth below the surface for the 2. chloride ions. Water~Cement Ratio Water/cement ratio and curing (to be discussed later) are the primary determinants of permeability of concrete.6. chlorides.4 to 0.chloride content of a 2. 5 [17]. Copyright by ASTM Int'l (all rights reserved).4 to 0. This is illustrated in Fig. Above 0.n darcys [18]. and chlorides directly and profoundly affect corrosion of embedded steel. oxygen. and S ---. cement. This equation may be considered to represent the mean condition for bridge decks subject to heavy salt applications for about a 10-year period. The concrete mixture variables that affect these properties are water/cement (w/c) ratio. The permeabilities for well cured concretes with w/c ratios up to about 0. The functions of moisture.35 and 0.16]. The effect of the w/c ratio on permeability results from capillary porosity produced by excess mixing water over and above that required for hydration of cement particles. permeabilities increase exponentially with w/c ratio.15. The effect of reduction of pH on steel corrosion also has been discussed previously.5 by weight. and carbon dioxide to the embedded steel. . Berman and Chaiken [20] found the chloride concentration due to the penetration of a 1. permeability increases with increasing maximum size of the coarse aggregate for most mineral aggregate materials [16].65 Ratio FIG./ m a were found for w/c ratios of 0. at a depth of about 5 cm. % x 3- 1- 0 I .2.5 w/c than for 0. The calculated value using Straffull's equation for a 5-cm depth is 1. For example./ m a.0. All other factors being constant.50 Water / Cement I .S5 w .50. 0. S--Permeability versus w/c ratio for hydrated portland cement paste.282 TESTS AND PROPERTIES OF CONCRETE 6-~ 5. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.60 respectively.4 w/c.4 kg C1 .18 N calcium chloride solution at all values of time and depth to be consistently greater for concrete of 0. 1.40. average chloride contents of approximately 0.40 I . Aggregate The primary effect of the aggregate in concrete on corrosion of embedded steel relates to its effect on permeability. and 0.2 kg C l .60 ! . Clear [11] found that the chloride content at a given depth after 830 daily salt applications varied directly with w/c ratio. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. .45 I . and 2. In experiments with simulated bridge deck slabs. This is due to the fact that most mineral aggregates have permeability coefficients 10 to 1000 times greater than the permeabilities of cement pastes in the usual range of w/c ratios. oxygen. Because of this. However. Copyright by ASTM Int'l (all rights reserved). and may produce voids in the vicinity of reinforcing bars. and carbon dioxide from free surfaces to the vicinity of embedded steel is of considerably less importance than might be implied from their effect on permeability. Thus. chloride ion. the aggregates are generally unable to compete with the paste for available moisture on the basis of capillarity. This is due to the interference by the reinforcing mat to the sedimentation process that causes the segregation. However. the property of the cement that has the greatest influence on corrosion is the tricalcium aluminate content. High alkali content can help to retard corrosion through its effect on pH. The occurrence of areas of active corrosion at the locations of these voids is commonly observed. their effect in transmission of moisture. though it is generally minor in comparison to other variables. the aggregates may contribute to corrosion by supplying a source of chloride ions. chlorides. The reason for this is that the more or less continuous capillary porosity in the paste phase is generally composed of much smaller pore diameters than those of the aggregates. Segregation and bleeding will produce channels. high alkali contents may lead to difficulties with alkali-aggregate reactions. promoting the ingress of water. the physical and chemical properties of the cement can have an effect. horizontal concrete members (such as bridge decks) [21]. In rare instances. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Such mixtures will also frequently display a porous concrete zone at the level of the reinforcing steel in heavily reinforced. normal Type I portland cement (typically 12 percent tricalcium aluminate) is three to five times more effective in removing chloride ion than sulfate resisting Type V portland cement (typically 4 percent tricalcium aluminate) [9. and carbon dioxide. the tendency for corrosion to occur decreases with increasing tricalcium aluminate content of the cement. This is due to the fact that chloride ions react with the hydrated tricalcium sulfoaluminate hydrate in the hardened cement paste to produce tricalcium chloroaluminate. The gradation of the aggregates may have a significant effect on corrosion of embedded steel if gradations are such as to result in segregation and bleeding of the concrete mixture. All other factors equal. Fineness of the cement. . However.22]. Thus. In a practical sense. About the only role played by the aggregates in the transport process is to replenish moisture to the paste during periods of drying.CADY ON CORROSION OF REINFORCING STEEL 283 Since aggregates typically constitute about 70 percent of the volume of concrete. for example. it is evident that they play a major role in determining the permeability of concrete. Cement The effect of cement content on corrosion of embedded steel is negligible [11]. the capillary porosity of the paste phase constitutes the conduit system for the movement of moisture and dissolved solids and gases. No further reproductions authorized. can influence corrosion to the extent that it affects bleeding. oxygen. Generally speaking. oxygen. there is relatively little change in permeability with change in w/c ratio below about 0. Carbon dioxide accelerates the process by combining with the free lime (carbonation). and carbon dioxide to the site of embedded steel has the potential for profound affect on corrosion of the steel. it has been reported that pozzolans actually reduce corrosion.25]. No further reproductions authorized. and air entraining agents usually reduce the w/c ratio and may therefore be somewhat beneficial in retarding corrosion. One source reported that CaCl 2 additions greater than 0. However. per se. it would be expected that their effect would be relatively minor. thereby reducing the high pH necessary to maintain a passive environment. Of course. this has not been found to be the case [23]. consolidation. . all investigators seem to agree that CaC12 additions produce serious corrosion problems in prestressed and steam cured concretes. the addition of chlorides would be expected to increase corrosion. this is Copyright by ASTM Int'l (all rights reserved). Most of them are organic materials that have no effect. and lime-scavanging (pozzolanic). on corrosion. Also. set and early strength acceleration. water. and oxygen are prerequisites for establishing active corrosion. as mentioned previously. With ordinary reinforced concrete. Since. air entrainment. the water reducers. chloride ions. This apparent anomaly is probably due to the fact that pozzolans appreciably reduce the permeability of concrete and the removal of soluble constituents by soft or slightly acidic waters (effloresence). Pozzolans. depth of cover of the reinforcing steel would seem to be a design problem rather than construction related. On the contrary. and curing. plasticizers. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. especially in cold weather concreting operations. The three construction activities that have been found to be most critical with regard to corrosion are depth of cover of the reinforcing steel. which combine with the free lime liberated during the hydration of portland cement would be expected to increase the tendency for corrosion due to reduction in alkalinity. reports on the effect on steel corrosion of CaC12 additions at the recommended rate of 2 percent by weight of the cement content vary widely [5. chlorides. Cover of Reinforcing Steel At first thought. especially in steam cured concretes [24]. Calcium chloride (CaC12) is sometimes used as an accelerator.5 weight percent of the cement are seriously detrimental to corrosion resistance [26]. Effect of Construction Variables Any activity in the concrete construction process that may produce conditions that facilitate the movement of water. As mentioned previously. However. water reduction. plasticizing.5.284 TESTS AND PROPERTIES OF CONCRETE Admixtures A wide variety of admixtures are incorporated into concrete mixes for various purposes including set retardation. = time to deterioration of concrete continuously exposed to saline water. 6--Effect of insufficient reinforcing bar support on depth of cover. and chloride ion availability on time to corrosion. and 10 cm have been found to be necessary to protect reinforcing steel for w/c ratios of 0. Copyright by ASTM Int'l (all rights reserved). However. No further reproductions authorized.6 respectively [I1. concrete cover.21. However. Minimum cover depths of about 5.281.5. w/c ratio) of the concrete. In an attempt to quantify the effects of w/c ratio.5. It is obvious that thicker covers should be more effective in preventing corrosion. 7. years. but beyond 5 cm protection is reportedly not significantly improved [5].27]. Clear [tl] presented the following modification of a relationship originally developed by Stratfull Rt-- 4 1 S i 1. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. FIG. uncracked concrete to prevent reinforcing bar corrosion is usually considered to be 5 cm [15.22 K ~ (w/c) where R.CADY ON CORROSION OF REINFORCING STEEL 285 true. 0. 6.4. the fact that design and actual depths of cover do not always agree is illustrated in Fig. The minimum required depth of clear cover with sound. . the required minimum depth of cove~ depends on the permeability (that is. and 0. No further reproductions authorized. is not considered to be a problem at depths greater than 25 m m [9]. Even the highest quality concrete is of no value in retarding corrosion if cracks are available to admit chlorides. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Based on these findings. it was found that values of depth of cover were distributed approximately normally. The effect of carbonation in lowering pH.0 50 69 84 6. The existence of a zone of tensile stress in the plastic concrete above the reinforcing steel has been illustrated in photoplastic studies [30]. oxygen. K = chloride concentration of water. Cracking results from the interference to subsidence of fresh concrete presented by the reinforcing bars.30].0 7.0 5. Since the required depths of cover cited above are minimum values and since variations in actual depths of cover occur in practice. water. . Target Value. target or specified values must be somewhat greater than the minimum values. TABLE l--Percentage of steel protected (5 cm minimun cover) for various target values of cover. It has been found that values of concrete cover of 5 cm or more are sufficient to prevent subsidence cracking [21. one can readily calculate specified target cover values to assure that a given percentage of the steel will have concrete cover equal to or greater than the desired minimum value. ppm. Here. and w/c = water/cement ratio by weight.5 6.5 93 98 99 The generally accepted 5 cm minimum depth of cover for sound. An example of cracking over reinforcing resulting from shallow reinforcing bar cover is shown in Fig. under these conditions. uncracked concrete is based on permeability of chlorides. However. For example. The depth of cover of the reinforcing steel is of special significance in the case of horizontal slab concrete members (for example. if the minimum required cover is deemed to be 5 cm. cm Steel Protected. % S. conCopyright by ASTM Int'l (all rights reserved). as illustrated previously.27. cm. high quality. with the mean value close to the specified value and the standard deviation about 1 cm.286 TESTS AND PROPERTIES OF CONCRETE Si = depth of steel below surface. bridge decks).5 7. and carbon dioxide. the percentage of steel having a cover of at least 5 cm for various specified target cover values will be as given in Table 1. insufficient depths of cover have been observed to produce cracking of the concrete immediately above the steel reinforcing bars. Based on a study of 17 bridge decks in New Jersey [29]. 7. though considerably smaller. Insufficient consolidation provides channels of ingress for the ingredients of corrosion--water. and carbon dioxide--and when occurring as "honey combing" in the vicinity of the reinforcement promotes the formation of differential aeration corrosion cells. effects [30]. . oxygen. No further reproductions authorized. 7--Subsidence crack in fresh concrete due to shallow reinJorcement. For example. the permeability coefficient for cement paste after 1 day of hydration will be more than 25 000 times that for paste hydrated for 7 days Copyright by ASTM Int'l (all rights reserved). crete slump and diameter of the reinforcing bar also have significant. has a profound effect on corrosion. Curing The primary influence of curing is the effect that it has on permeability. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. normal construction practices cannot be relied upon to produce adequate consolidation. For concretes with slump values of 7. Consolidation The degree of consolidation of the concrete. chlorides.CADY ON CORROSION OF REINFORCING STEEL 287 FIG. In one series of tests [11] the chloride content at a depth of5 cm in the concrete was about 12 times greater for concrete that had been compacted from 92 to 94 percent of maximum density than it was for maximum density concrete of the same mix design.5 cm or more. good consolidation is easily achieved by internal vibration. with the lower slump concretes. especially in the vicinity of embedded steel. Ferrocement sections are reinforced considerably more heavily than ordinary reinforced concrete and the reinforcing steel has a much greater specific surface. The reinforcement typically consists of steel reinforcing bars (usually high strength) sandwiched between multiple layers of steel wire mesh. Spellman and Straffull [24] studied the effects of steam and water curing on the time to corrosion of embedded steel. In both instances exponential relationships were obtained. degree of consolidation. and permeability of the aggregates. Of course. It is rather surprising. it will be observed that water curing provides significantly greater resistance to corrosion than steam curing. in view of potential corrosion problems. then. The apparent lack of corrosion problems is attributed to use of zinc coated (galvanized) mesh. and the fact that water will be available in the capillary pores for some time after cessation of curing. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. One corrosion related problem has been encountered involving the evolution of hydrogen gas on plain steel reinforcing rods sandwiched between layers of galvanized steel mesh.0 for water curing. Copyright by ASTM Int'l (all rights reserved). and the hydrogen gas produced appreciably reduces the bond of the reinforcing bars and increases the porosity of the mortar in the vicinity of the bars. equaling 0. a = a constant. and b ---. . This results from the galvanic cell created by the use of dissimilar metals (iron and zinc).90 for water curing. The addition of chromic oxide at the rate of 300 ppm of the mixing water apparently will eliminate this problem [17].33 for steam curing. and 0. D = days of underwater curing following initial curing (steam or water). low w/c ratio concrete mortar in fabricating ferrocement sections.66 for steam curing.a constant. minimum cover depths may be as small as 3 mm. Ferrocement Ferrocement consists of very thin (1 to 4 cm) heavily reinforced concrete sections. Also. equaling 6. the effect of curing on the permeability of concrete will not be as pronounced as this because of the influence of bleeding.288 TESTS AND PROPERTIES OF CONCRETE [9]. that ferrocement is applied so extensively and successfully in the construction of boat hulls. and high cement factor. and 6. of the form p ~_ ( I D b where P = days to active corrosion potential for partial immersion in saturated sodium chloride solution. In general. No further reproductions authorized. where ample chlorides from deicing salts are frequently available.5 to 6. The difference is probably attributable to the higher quality concrete. however. Assessing Corrosion Probabilities Once corrosion of reinforcing steel has progressed to the stage where its effects are manifested by cracking and spalling of the concrete surface. . No further reproductions authorized. Like ferrocement. Reportedly. the high strength steels used in prestressing tendons and the high stress levels encountered in prestressed members can lead to a form of corrosion not found in ordinary reinforced concrete--stress corrosion cracking. somewhat lower levels of chloride exposure (except in marine environments). of those that might be expected to come into contact with prestressed concrete. is practically nonexistent. The chloride ion apparently does not promote stress corrosion cracking [5.4 cm long. reinforcement corrosion in prestressed concrete bridge members. the specific surface of the reinforcing steel is considerably greater than in conventional reinforced concrete. Prestressed Concrete The factors that affect the corrosion of reinforcing steel in ordinary reinforced concrete are equally active in prestressed concrete except they are somewhat more critical because of the smaller cross sections (larger specific surface) of the prestressing tendons [15].1 to 8 volume percent.50 mm in diameter by 2. However. However. Stress corrosion cracking is a brittle form of failure that occurs under the conditions cited above in the presence of certain ions. Stress corrosion cracking has produced catastrophic failure of prestressed concrete sludge storage tanks. and it is too early to make an assessment of their performance in this regard. it is Copyright by ASTM Int'l (all rights reserved). one laborabory study showed insignificant corrosion in 2 volume percent steel fiber reinforced concrete specimens subjected to 90 daily cycles of exposure to saturated salt water [31]. are incorporated at the rate of 0. In addition. commonly about 0.) [5]. less than 0. are nitrate (NOa-) and bisulfide ( H S .CADY ON CORROSION OF REINFORCING STEEL 289 Steel Fiber Reinforced Concrete Steel fiber reinforced concrete consists of concrete mixtures in which randomly oriented steel fibers. Fiber reinforced concretes have only recently (since 1972) been put to use under conditions were corrosion might tend to be a problem (highway and bridge deck overlays). Of course. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 9]. this is vastly superior service to that obtained from the bridge decks.007 percent of the prestressed bridges in the United States have shown any evidence of reinforcement corrosion and no catastrophic failures have occurred [5]. The most common ions known to promote this kind of corrosion.25 to 0. and reduced tendency for cracking in prestressed members. where hydrogen sulfide was present [32]. 1. A 5 cm outside diameter core bit will produce about 50 g of powdered sample for each 1. samples are removed between depths of 0. the probability of the presence of active corrosion increases with increasing chloride content above the threshold value. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A rapid field technique for in situ analysis of the chloride content of portland cement concrete has been described by Morrison et al [35]. No further reproductions authorized. Therefore. These are determination of chloride contents at the level of the reinforcing steel and the evaluation of electrical half-cell potentials of the reinforcing steel. Typically. often used in tandem. boiling.290 TESTS AND PROPERTIES OF CONCRETE usually too late to take corrective measures that provide any degree of permanency. The method recommended for analysis of chlorides was developed by Berman [34] and described in detail by Clear [33].4 to 5.9 cm diameter Copyright by ASTM Int'l (all rights reserved). . The combination solid state electrode (with built in reference electrode) is recommended [33]. A number of precautions must be observed to assure the accuracy of the results. It involves the use of a rotary hammer to drill and pulverize the concrete to various depths. Briefly.7 cm (nominal 5. determination of the chloride content in the vicinity of the reinforcing steel provides an indicator of the probability of active corrosion.2 kg/m 3 of concrete. The Federal Highway Administration has adopted a procedure utilizing these two techniques as a decision-making process for replacement or repair of concrete bridge decks [33].9 to 3.25 cm sample). and 4. Depth of the reinforcing steel is determined by means of a magnetic flux device that is calibrated specially to indicate concrete cover (Pachometer). Only 3 to 4 g are needed for chloride analysis. filtering.25 cm sampling depth. it involves digesting a weighed quantity of the pulverized sample in nitric acid. depending on the pH. Furthermore.0 cm sample).9 cm (nominal 1. Two techniques. Chloride Determinations As discussed earlier. The titration end point must be precisely determined and this is accomplished by means of a potentiometric method utilizing a chloride ion specific electrode. The simplest and most economical method for acquisition of samples for chloride analysis is the technique recommended by Clear [33].6 to 1. These include running blank specimens for calibration purposes and applying correction factors for variations in moisture and aggregate contents of the test samples [33].2 cm (nominal 2.50 cm sample). and titrating the filtrate with silver nitrate solution of known normality. The method involves using a chloride ion specific electrode in a 1.6 to 1. threshold values of chloride content at which corrosion of embedded steel may occur are in the range of 0. are currently employed to assess the probability of active corrosion in the absence of physical evidence at the surface of the concrete. The detailed procedures involved in the half-cell method are presented in the ASTM Test for Half Cell Potentials of Reinforcing Steel in Concrete (C 876). Protective Measures The first and most important line of defense against corrosion of steel in concrete is the exercise of sufficient care to assure that the steel has an adequate cover of high quality (high cement content). A number of reference electrodes are suitable for evaluating corrosion of steel in concrete.20 V (CSE) are considered to be indicative of passive conditions [28]. and readings less negative than --0.20 to --0. bridge decks subject to deicer salts or structures in marine environments). Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Electrical Hal. potential readings are taken to be negative values. No further reproductions authorized. and carbon dioxide. Plots of equipotential contours are then constructed to delineate areas of possible corrosion activity. water.35 V relative to the copper-copper sulfate half-cell (CSE) have been found to be indicative of active corrosion 95 percent of the time [33]. However. preventing the access of chlorides.CADY ON CORROSION OF REINFORCING STEEL 291 hole drilled in the concrete.0. additional protective measures may be warranted. . low permeability (low w/c ratio) concrete that has been consolidated adequately around the reinforcement.35 V (CSE) are inconclusive as regards corrosion. Furthermore. into which had been placed a specified quantity of borate-nitrate solution. water. and oxygen. Potentials in the range --0. Generically. the readings are only statistically related to corrosion activity. (b) those that seal the concrete. half-cell potential measurements are obtained on a predetermined grid pattern over the surface of the concrete. and (d) those that impose a protective current flow in opCopyright by ASTM Int'l (all rights reserved). (c) those that seal the surface of the reinforcing steel with a material impervious to chloride ions. Therefore. Half-cell potential readings do not measure the structural or physical condition of the concrete [36]. Potential readings more negative than -.f-Cell Potential As discussed previously. In practice. By convention. but either the copper-copper sulfate (CSE) or the saturated calomel (SCE) half-cell are most commonly used. the process of corrosion of steel in concrete involves the formation of galvanic corrosion cells due to the electrochemical processes of oxidation at anodic areas and reduction at cathodic areas on the embedded steel. oxygen. for structures in particularly hazardous environments relative to the potential for corrosion problems (for example. corrosion activity can be identified by its effect on the electrical potential of a reference electrode (half-cell) inserted in the galvanic corrosion circuit. these protective measures may be classified into four categories: (a) those that remove chloride ions or inhibit their corrosive action. Copyright by ASTM Int'l (all rights reserved). . and magnesium hydroxide) do not tend to bond to the steel very well. the use of corrosion inhibitors generally is not recommended. chlorides. render the entire surface of the steel cathodic). In briefly describing the protective measures that fall into each of the four generic categories. The electrical cost to remove 6 k g / m 3 of C1. or at least seriously retard. aluminium oxide. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.ions. the protective measures can be relegated to two functional classes: (a) those that must be instituted at the time the concrete is placed. Removal or Inhibition of Chloride Ions Two possible approaches exist for removal of chloride ions from concrete to arrest or prevent corrosion. Furthermore. the amount of inhibitor required increases with increasing chloride content. phosphates. Also. Obviously. For these reasons. One consists of forcing water through the concrete to flush out the CI. Those that interfere with the corrosion process by stifling reactions at the cathode (for example.was reported to be $0.37. No further reproductions authorized. some inhibitors seriously reduce the strength of concrete [41].48/m 2 on a concrete bridge deck. Simultaneous impregnation with a furfuralacetone mixture while removing chloride ions during electro-osmosis was shown to be capable of removing up to about 12 kg/m 3 of chloride ion and reducing the permeability of the concrete to about one-third that of untreated concrete [39]. and chromates). Of the many potential corrosion inhibitors tried.26. Concrete Sealants Concrete sealants are of two general classes--those that provide a barrier at the surface to prevent. 40-42]. it will be readily evident to which functional classification each belongs. The other possibility is to use electrochemical means. This technique has been successfully demonstrated in the field by at least two investigative teams [37-39]. oxygen and carbon dioxide to the interior of the concrete. calcium carbonate. Also. The use of corrosion inhibiting admixtures in concrete has produced. taking advantage of the migration of ions in a direct current electrical field (electro-osmosis).292 TESTS AND PROPERTIES OF CONCRETE position to the galvanic corrosion cell (that is. the first of these two functional classes cannot be applied after the fact to existing structures. and the effectiveness of inhibitors reportedly lasts for only a short time. the penetration of water. at best. can produce intensified localized corrosion if used in insufficient quantities. and (b) those that may be applied anytime after the concrete has hardened and cured. Attempts to do this have not been successful [37]. sodium benzoate and sodium nitrate generally are considered to be the most promising. uncertain results [9. Those that stifle the anodic reactions (alkalies. Waterproof membranes. No further reproductions authorized. Low w/c ratio ("Iowa Mix") and latex modified mortar were found in tests to substantially reduce (but not totally prevent) intrusion of chloride ions [11]. is partially blocked with polymeric materials introduced to the concrete mixture as a water-styrene butadiene emulsion. or by impregnating the capillary pores of the hardened concrete with a suitably inert material. In this type of concrete mixture. The other type of material used in thick layers of impervious concrete is latex modified mortar. First. However.32). Excellent success in preventing bridge deck damage due to rebut corrosion has been reported by the highway agencies in Iowa and Kansas. The latex modified mortar overlay has a relatively long and successful history in protection of bridge decks [38]. The earlier waterproofing materials were applied as liquids and were usually of the polyester resin or epoxy-modified coal tar variety. capillary porosity. low w/c ratio. by incorporating materials in the concrete mixture to block the capillary pores. place. protected from damage by asphaltic concrete wearing surfaces. high cement factor (486 kg/m 3) concrete mixture. The "Iowa" mix lacks the workability needed to be useful in reinforced concrete members. horizontal configurations and to date have been used primarily on bridge decks. thereby preventing ingress of corrosive elements and immobilizing any that may already be present. The special construction techniques and equipment required to handle. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the recent appearance on the market of a class of conCopyright by ASTM Int'l (all rights reserved). . Like waterproof membranes. overlays are largely applicable to large.8 to 6. The first of these techniques invokes the principle of the "Iowa" overlay concrete mixture. More recently. considerable care and attention must be focused on their installation to assure proper sealing.CADY ON CORROSION OF REINFORCING STEEL 293 and those that penetrate and seal the capillary pore system of the concrete. it is expensive in comparison to the other techniques of comparable service performance (low w/c ratio overlays and waterproof membranes). where low w/c ratio overlays have also been used since the early sixties. low w/c ratio (0. One technique calls for the use of a low slump. However.4 cm) overlays of impervious concrete constitute another means of sealing structural concrete. Sealing of the structural concrete itself may be accomplished by taking steps to reduce significantly the inherent capillary porosity of the concrete. (namely. especially at curbs and joints. the preformed sheet-type membrane has gained favor [43]. they constitute only an intermediate time range solution since their serviceability is limited to the life of the asphaltic concrete wearing surface (about 15 years) [37.38]. presently constitute the most widely used method of retarding corrosion of reinforcing steel in concrete bridge decks [38]. Thick (3. and finish this material were developed in Iowa where about 200 bridges have received overlays [37]. Second. There are two problems associated with the use of waterproof membranes on bridge decks. has been limited pending development of appropriate hardware and technique. such as sulfur [37]. Polymer impregnation involves removing the evaporable water from the concrete to the desired depth of impregnation. introducing a monomeric material into the concrete by soaking or application of moderate pressure. if impregnation is accomplished to sufficient depth to encompass the reinforcing steel.11]. . presumably. The wax. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. but. is currently under study. also acts to block admission of water and chlorides to capillary pores. The third method. Coatings of the barrier type interfere with the corrosion process by preventing the corrosive elements from coming into contact with the steel. The monomer most commonly used in the rather extensive research carried out in this area since the late sixties is methyl methacrylate [46]. melts at about 85~ Thus. chloride ions already present are immobilized. No data are available on the chloride transmission rates of such concretes. Also. but one study indicated that only certain powdered epoxies Copyright by ASTM Int'l (all rights reserved). blocking the pores. after the concrete has hardened.5 mm diameter) wax spheres in the concrete mixture. 48]. polymer impregnation has been shown to reduce intrusion by water and chlorides to exceedingly low levels [10. In addition to phenomenal improvement in the mechanical properties of the concrete. Organic materials of various types constitute the most extensively used group of barrier coatings. permeabilities to water and ions would be appreciably reduced at this level of w/c ratio [44].30 or lower. The aforementioned second procedure is similar in principle to the latex modified mortar overlay material. No further reproductions authorized.294 TESTS AND PROPERTIES OF CONCRETE crete admixtures termed "super water reducers" or "super plasticizers" permits the formulation of workable concrete mixtures having w/c ratios of 0. It is called "internally sealed" concrete and consists of incorPorating about 3 weight percent of tiny (average 0. which is a 25/75 blend of montan and paraffin. Reinforcing Bar Coatings In terms of their function in retarding or preventing corrosion. Epoxies and chlorinated rubber are reported to be suitable [47. reinforcing bar coatings may be divided into two classifications--barrier coatings and anodic coatings. but development still lags well behind the polymers. Field application of polymer impregnation. The potential application of lower cost impregnants. and polymerization of the monomer by the application of heat or gamma radiation. impregnation of hardened concrete with inert materials. but is sufficiently less expensive to warrant its use in structural concrete. however. In addition. it is heat treated causing the wax to melt and flow into the capillary pores where it solidifies upon cooling. the economies of this method remain to be demonstrated in the field. Tests have shown that internally sealed concrete is highly impermeable to water and salt and is capable of maintaining low corrosion potentials on encased reinforcing steel when the concrete is subject to ponding with salt water [45]. Those metals that are more noble than iron in the electrical potential scale (cathodic) can be used as barrier coatings provided that they do not corrode in the environment presented by salt contaminated concrete. In spite of the fact that cases of satisfactory performance of galvanized reinforcement in concrete for 30 years or more have been documented [5. although the corrosion products formed do not result in volume changes believed sufficient to cause disruption. Excessive voltages will result in softening of the concrete in the vicinity of the steel and resulting reduction of bond strength.52. Zinc itself is not resistant to corrosion in the presence of chloride and hydroxyl ions.]. This can be accomplished by applying direct electrical current or by using sacrificial anodes. This has led to some concern regarding the long term durability of galvanized rebars [38]. The most commonly used anodic coating is hot-dipped zinc (galvanizing). Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Cadmium. . The main problem involves controlling potentials and current densities over the entire surface of the reinforcing steel. This includes such metals as nickel and copper.CADY ON CORROSION OF REINFORCING STEEL 295 applied by electrostatic spray techniques provide the proper mechanical and chemical properties to withstand fabrication and handling and possess sufficient protective qualities [49]. They provide protection primarily as barriers. 37]. This layer acts as a large anode to distribute uniformly protective current to the reinforcement. However. in 1976 placed a moratorium on its use in bridge decks until adequate time has elapsed to evaluate the performance of the over 200 existing installations [50]. like zinc. Anodic coatings consist of those metals that are less noble than iron. Cathodic Protection Cathodic protection prevents corrosion of steel by supplying current flow that suppresses the galvanic corrosion cell through polarization of the steel surface.47]. it is expensive and toxic [40]. The success achieved in preventing corrosion of reinforcing steel in concrete by galvanizing is mixed. Tests have shown that this technique Copyright by ASTM Int'l (all rights reserved). their use is not recommended because very severe localized corrosion may occur at any breaks in the coating due to the large cathode/anode areal ratio that exists under such circumstances. However. Besides. these problems reportedly have been largely overcome by using a conductive asphaltic concrete containing coke breeze to cover the surface of the concrete. but also through sacrificial action where the coating presents a large anode-to-cathode ratio relative to breaks in the coating. the Federal Highway Administration. after analysis of data from many sources.40. No further reproductions authorized. Direct current cathodic protection of reinforcing steel in concrete has produced mixed results [5. has shown mixed results as an anodic coating for reinforcing steel [5. Sacrificial anodes generally are not considered to be practical for the protection of steel in concrete because voltages and current densities cannot be controlled [51]. .. C. and SpeUman. F. Aug.. "Corrosion Testing of Bridge Decks. and Copenhagen.296 TESTS AND PROPERTIES OF CONCRETE renders the reinforcement passive. Vol. [7] Lewis." Final Report. pp. R. J. [9] Verbeck. Vo.. U. F." Corrosion. Highway Research Board. 47-68. 15. National Cooperative Highway Research Program.. 1974. 1975. 1975. Project NR032 522. "Bridge Decks.. E. Summary of Protective Methods The current status of potential corrosion preventive procedures. D. and Chaiken. "Structure and Physical Properties of Hardened Portland Cement Paste." Public Roads. American Concrete Institute. Vol. However.. 1970. K. 1958. Jr. 38. A. 41.. pp. No. R. [14] Straffull. [3] Sandvig. 1975. L. A. No. 1975. April 1976.. American Concrete Institute. "Steel Corrosion in Concrete. "The Corrosion of Steel in a Reinforced Concrete Bridge. Copyright by ASTM Int'l (all rights reserved). K. 1973. SP-49. J. 328. G. T." Highway Research Record. 1975. "Reinforcing Bar Corrosion in Concrete: Effect of Special Treatments. D. No. B.. 50-59. R. G. Nov. 382t-388t." Corrosion of Metals in Concrete. No. G. R. SP-49. J. D." Corrosion. "Corrosion of Reinforcing Steel in Concrete in Marine Atmospheres.. American Concrete Institute." Corrosion of Metals in Concrete. 16-17. 60-65. 1970. 42. A. 15p. pp.." Technical Report No. No. A Cooperative Study by the Portland Cement Association and The Bureau of Public Roads in cooperation with 10 State Highway Agencies. J. R. 173t-178t. 7. A. 8. American Concrete Institute. 39-46. "Designing Bridge Decks that Won't Deteriorate. Nov. 71-82.S. "Chlorides and Bridge Deck Deterioration.. 1-6. along with pertinent selected references for each. T~ C. 21-38. J. 5P-49. and Cady. Concrete Manual.. H. pp." Civil Engineering. [5] Moore. No. and Oddmund. Jurkovich. K. pp. D. Superintendent of Documents. pp. June 1974." Civil Engineering.. pp. Klodt. "Deterioration of 249 Bridge Decks.. Vol. and Straffull.. FHWA-RD-76-70. 9-18.. No. "Corrosion of Metals in Concrete--Needed Research. 46-55. Highway Research Board. March 1957. "Durability of Bridge Decks. pp. A. Department of the Interior. "Mechanisms of Corrosion of Steel in Concrete. July 1959. 8th ed. "Protection of Steel in Prestressed Concrete Bridges.. [8] Hausmann. 1967. C. 6. P. [17] Christensen. 8. "Solving the Galvanic Cell Problem in FerroCement. [6] Erlin. W. July 1971. . [2] Godfrey. No. Washington. K. [19] Spellman. F. and Williamson. pp. pp. No. Vol. more time and experience are necessary to evaluate fully the attributes of this method. [18] Powers." Journal. References [1] Dallaire. "Effectiveness of Concrete Cover in Corrosion Protection of Reinforcing Steel. 1973. 38-49. and Hensen." Report 90. D. 1975. Transportation Research Board. D. is presented in Table 2. 1975. D. pp." Transportation Research Record. 43-48. Aug. [12] Stratfull." Highway Research Record. 1. 11. [13] Portland Cement Association. 19-23. 539. B. Office of Naval Research." Corrosion of Metals in Concrete. and Verbeck. pp. [11] Clear. 13. Vol. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. B. "Time-To-Corrosion of Reinforcing Steel in Concrete Slabs. R. even in chloride contaminated concrete [51].. SP-49. pp.. [15] Szilard. 2. American Ceramic Society. D. W. "Techniques for Retarding the Penetration of Deicers Into Cement Paste and Mortar." Corrosion of Metals in Concrete." Materials Protection. G. 3. L.. L. [4] Carrier. 423. [10] Clear. 43. [16] Bureau of Reclamation. "PennDOT Attacks Bridge Deck Durability Problem. W. 45. pp. Vol. [20] Berman." Highway Builder.. Federal Highway Administration. R." Report No. No further reproductions authorized. 46 37 37. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 40. Inhibitors (admixtures) 3. 49 5. 38. Cathodic protection impressed current Method X X X X X X X X X X X 10. Chloride removal Electrochemical + ion exchange 2. 43 X PostConstruction X Construction 37. Seal concrete (a) surface (i) membranes (ii) overlays low w/c ratio latex modified mortar (b) low w/c ratio concrete super water reducers (c) internally sealed concrete (d) impregnated concrete (i) polymers (ii) sulfur 4. 40. X X Doubtful X X Field Evaluation Potential Needs X X Research/ Development r . -< . 48. 1. 37. 37. 38 44 37. 37.41. 50 5. 42 References Apply TABLE 2--Status of potential corrosion preventive procedures. No further reproductions authorized. 38.. 37 X X X Promising 37.. 52 X X X X X X X X X X X X 10. 26.Copyright by ASTM Int'l (all rights reserved). 51. 38. 39 9. 11. 40. 38. 40. 47. 47. Reinforcing bar coatings (a) barrier--type (b) anodic--type 5. 37.4 I"11 I'-- m u) z -n m z -11 O --n O O o') O z O 3o 20 O O z (3 >. 38. 45 10. 11. 1976. E." Highway Research Record. 5P-49. "A Rapid Method for Studying Corrosion Inhibition of Steel in Concrete. FHWA-Ks-RD.. "Determination of Chloride in Hardened Portland Cement Paste. Section 1. [26] Gouda.. D." NCHRP Report 165." Special Report 116. L. and Development of Surface Spalls in Bridge Decks.. F. Kansas Department of Transportation. G. Vol. and Vallerga. 32-35. 1964." Transportation Research Record. H. and Butler." Materials Protection. American Concrete Institute. E. "Corrosion of Prestressed Concrete Tanks. E. L. H. and Wood. pp.. and Ryell... Y. Cover over Reinforcing Steel. 90-100. No. Vol. "Time to Corrosion of Reinforcing Steel in Concrete Slabs. W. 328. Highway Research Board. [43] VanTil. No. "Cracking of Fresh Concrete as Related to Reinforcement. [40] Gjr O. H. C. Special Report 119. 4. 500. Nov. 1975. American Concrete Institute. A.. pp. 1971..5." Corrosion of Metals in Concrete. R. [37] Manning. Vol. F. Vol. D. Sept." Transportation Research Record. "Control of Steel Corrosion in Concrete Sea Structures. Topeka. C. No. Ramamurti. 7.. Ontario Ministry of Transportation and Communications." Highway Research Record.. 3. 8. 1." Journal. 27-45.. 70. 423. No. 39. 1974. March 1976. H. [36] Stratfull. Transportation Research Board. pp. No. "Studies of the Relationships Among Crack Patterns. "Influence of the Cement on the Corrosion Behavior of Steel in Concrete. 1968. Nov. "Recommended Depth of Cover for Bridge Deck Steel.. April 1976. 1971. of Transportation. 24-31." Bridge Deterioration Study." Highway Research Record. [41] Griffin... No. D. 95-102. pp. [44] Anonymous. [39] Morrison. Great Britain. Highway Research Board. SP-49. Federal Highway Administration. pp. R.. [33] Clear. and Gilliland. J. 11. F." Admixtures in Concrete. E. No. FHWA-RD-74-5. 3-6. 500. 3. Federal Highway Administration. F. pp. E. W. 1976. 3. M. Special Report 119. Cady." Report No. Portland Cement Association.. Transportation Research Board. American Concrete Institute. No further reproductions authorized. C. and Gilliland." Report No. G. Carr." Report No.. 7. 1-9.298 TESTS AND PROPERTIES OF CONCRETE [21] Bukovatz. J. 1975. No. pp. R. "Pozzolans in Highway Concrete. [28] Clear. pp. "Weathering Test of Reinforced Concrete Slab With Various Depths of Steel. 1975. [23] Committee MC-BS. Section 4. 330-335. 75-2. Topeka. Mortar. Aug. [35] Morrison." Cement and Concrete Association. Feb. 16-24. FHWA-Ks-RD.. No. "Accelerators in Highway Concrete." Journal of Materials.. Transportation Research Board. [38] Hay. J. 1974." Journal. [30] Dakhil. K. "State-of-the-Art Report on Fiber Reinforced Concrete. 13-21. [34] Berman. Virmani. 1973. [22] Steinour. 1973. "Concrete Variables and Corrosion Testing. 74-1. Ill. Transportation Research Board. 72. [25] Committee MC-BS. 21-28. 142-147. J. R. 421-428. "Internally Sealed Concrete. Transportation Research Board. "Chloride Removal and Monomer Impregnation of Bridge Deck Concrete by Electro-Osmosis. pp. J. M... [29] Weed. D. B... 12-21." Report No. "Half-Cell Potentials and the Corrosion of Steel in Concrete. W. [45] Jenkins. P. pp. No. P. Virmani. Copyright by ASTM Int'l (all rights reserved).. 197. 1972. pp. . V. [32] Cornet. April 1976. [42] Craig. 729-744. No. H." Public Roads.." Report RR 203. Jan. pp.. "The Bridge Deck Problem--An Analysis of Potential Solutions. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1971." Admixtures in Concrete. G. Vol. Stratton. Kansas State Highway Commission. L. J. 1976. 1970. Sept. Skokie. [24] Spellman. B. "Corrosion Inhibitors for Reinforced Concrete. and Concrete. 1965. F. pp. 1964. FHWARD-75-20. G. pp. Jan. Transportation Research Board. "Durable Bridge Decks. Portland Cement Association Research and Development Laboratories.. 1974. J. 1973. [311 Committee 544. pp. Part 7. "'Effectiveness of Corrosion Inhibitors and Their Influence on The Physical Properties of Portland Cement Mortars." Bulletin 168. [27] Stark. A.. Vol. Y. R. R. Topeka. D. Transportation Research Board. G. "Rapid In Situ Determination of Chloride Ion in Portland Cement Concrete Bridge Decks. "Evaluation of Portland Cement Concrete for Permanent Bridge Deck Repair. K." Journal.. K. and Monfore.. E. "Superplasticizing Admixtures in Concrete. 433." Corrosion of Metals in Concrete. I. and Carrier. and Stratfull. 77-88. P. L. Kansas Dept. American Concrete Institute. "Waterproof Membranes for Protection of Concrete Bridge Decks. J.. pp. K. 36-44. [48] Clifton. [51] Stratfull. 1976. G. SP-49.. J.. Brookhaven National Laboratory. L. S00. "Use of Galvanized Rebars in Bridge Decks.. Beeghly. Dec. [52] Robinson. American Concrete Institute. E." FHWA Notice N 5140. R." Corrosion of Metals in Concrete. 1975. pp. and Kukacka. H. American Concrete Institute. SP-49." Corrosion of Metals in Concrete. 1975. R. Copyright by ASTM Int'l (all rights reserved). 1-15. G. Transportation Research Board. Beeghly. and Mathey. R. pp. H. F. pp. E. SP-49. [49] Pike. J.. "Concrete-Polymer Materials. F. pp. No. and Mathey.10.... G. American Concrete Institute. "Use of Coatings on Steel Embedded in Concrete. R. 103-113. "Protecting Reinforcing Bars from Corrosion with Epoxy Coatings. pp.. "Cathodic Protection of Steel in Concrete. . "Experimental Cathodic Protection of a Bridge Deck.." Corrosion of Metals in Concrete. [50] Federal Highway Administration. Clifton. T. 1974. 1974." Transportation Research Record. C..CADY ON CORROSION OF REINFORCING STEEL 299 [46] DePuy. [47] Backstrom. R. 500. 9 July. 1975. Transportation Research Board. G. Sun Apr 6 21:41:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Hay. R. No." Transportation Research Record." Fifth Topical Report. 1973. E. 115-132. W. "Nonmetallic Protective Coatings for Concrete Reinforcing Steel.. R.. 83-93. F. R. No further reproductions authorized. STP169B-EB/Dec. liquid water. Copyright by ASTM Int'l (all rights reserved). which are sometimes used in conjunction with concrete. 2Consultant. 1978 Bernard Erlin ~and H u b e r t Woods 2 Chapter 20--Corrosion of Embedded Materials Other than Reinforcing Steel Introduction This chapter deals with materials. Jalisco. As the title of this chapter implies. special alloys of iron. Ill. Any concrete is never truly dry because it contains air and that air will hold moisture in vapor form. because of the chemical nature of the cement paste. and among the organic materials are a variety of plastics. and tin. A general condition necessary for the chemical degradation of any materials in concrete is exposure to moisture. emphasis will be given to the possible degradable aspects relative to their use. asbestos. so information about some fibers has been included. That moisture can be water vapor.OFg Copyright9 1978tobyLicense ASTM International .petrographer. air in concrete will contain sufIPresident. and wood and similar cellulosic materials. Among the metals are aluminum. For example. 60062. Sun Apr 6 21:41:46 EDT 2014 300 Downloaded/printed by Universidade do Gois pursuant Agreement. Hime Associates. copper and copper alloys.astIII. Fiber-reinforced concrete is gaining in use. No further reproductions authorized. among the inorganic materials are glass. stellite. other than conventional reinforcing steel. Inc. lead.. and concrete. Monel metal. Www. and a short discussion on that aspect precedes the discussions of material behavior. and the fact that most concrete contains some unhydrated cement. silver. and conditions that may render them serviceable or unserviceable. Erlin. General Condition Moisture is usually necessary for the chemical degradation of any material. Mexico. zinc. or solutions of which water is a component. Northbrook. and inorganic and organic substances. The materials to be described include metals. CaCO3 + SiO2 + x H 2 0 Concrete is wet when mixed and for some time after setting. The time required for concrete to dry to various internal humidity levels is not commonly appreciated. 3 This table shows that at an environmental relative humidity of 50 percent. . the vapor pressure for the paste at equilibrium.. thus aiding any tendency for electrochemical corrosion. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 301 ficient moisture to maintain a relative humidity of about 80 percent. Furthermore. and 240 days drying time was required to reach 75 TABLE 1--Rates of drying 15 by 90 by 90-cm (6 by 36 by 36-in. days Environmental RH 10 35 50 75 a 90% RH 75% RH 50% RH 18 30 36 36 80 110 240 . and of any soluble corrosion products away from the metal. carbonation of the portland cement paste will generate moisture due to the release of hydrate water when carbonation products are formed. No further reproductions authorized. a Drying Time to Reach Various Relative Humidities in the Concrete Slab at Middepth.. 620 840 . although a concrete may be relatively dry. 3The italic numbers in brackets refer to the list of references appended to this paper. Thus.) slabs of normal weight concrete. alkalies. It also increases the electrical conductivity of the concrete. and chlorides toward metal. The free moisture in wet concrete provides an aqueous medium which facilitates transport of soluble chemical substances. but even at low external humidity a long drying time may be required to lower the internal humidity to a point where corrosion is unlikely. The rate of drying also depends on external humidity. . concrete exposed continuously or frequently to a damp environment may remain wet enough to support any corrosion that may occur. Copyright by ASTM Int'l (all rights reserved). . calcium hydroxide. 36 days drying time was required to lower the middepth relative humidity to 90 percent. .) slabs of normal weight concrete are shown in Table 1 ll]. of course. . From Ref 1. such as the following CaSiO2 9 x H 2 0 + CO2 -. concrete which will eventually be dry may be internally wet long enough to promote serious corrosion of susceptible metals. depending principally on the quality of the concrete and the distance through which free water must move to an external surface where it can evaporate. The rates of drying of 15 by 90 by 90 cm (6 by 36 by 36 in. such as oxygen. . such as reinforcing steel which is connected (coupled) to the aluminum. such as beams and columns. because of its lesser surface area exposed to the alkalies. prolonged periods. Materials in " d r y " concrete are relatively immune to chemical degradation. the relative humidity at a point only 1. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. other conditions being favorable. No further reproductions authorized. One reaction product is hydrogen gas. Wright [3] has described a case of corrosion of sufficient severity to cause collapse of aluminum conduit in reinforced concrete containing calcium chloride.302 TESTS AND PROPERTIES OF CONCRETE percent. if at all. and for this reason aluminum powder sometimes is used in concrete to form extremely lightweight cellular concrete. however. will dry more slowly than thin sections. Concrete made with lightweight aggregates dries more slowly than that made with normal weight aggregates. at 90 percent relative humidity and probably at 75 percent relative humidity. Several dozen additional cases of concrete cracking due to corrosion of embedded aluminum conduit and posts. may be required before outward manifestations may become noticeable.9 cm ( 90 in. Corrosion of aluminum balusters embedded in concrete have been reported [5]. Additional tests showed that when the middepth relative humidity reached 90 percent. Aluminum in rod. but it seems almost certain that such corrosion could proceed. though at a much lower rate. or floor slabs not on the ground. Aluminum Aluminum has been given widespread attention because it has been the cause of numerous problems in the past. it has been shown that the situation can be worse if the concrete contains calcium chloride and much worse if it also contains steel. and thicker sections. . In every case chloride was present in Copyright by ASTM Int'l (all rights reserved). sheet. as long as 50 years or more. which prompted laboratory studies designed to describe conditions necessary for corrosion. The moisture condition of concrete required to support active electrochemical corrosion of aluminum and other susceptible metals is not known with any accuracy. and an instance of extensive concrete spalling over aluminum conduit in Washington Stadium has been published [4]. or pipe form will react much less vigorously than will the powdered metal. However. and window frames in contact with the concrete have occurred. Tests carried out by Jones and Tarleton [2] indicate that the corrosion of aluminum embedded in plain concrete can crack the concrete under unfavorable circumstances. Aluminum reacts in fresh concrete principally with alkali hydroxides derived from the cement.) from an exposed face was 87 percent. and methods for circumventing the corrosion. In smaller amounts the powder provides a slight expansion of grout such as that used for bedding machinery base plates. such as walls. Various amounts of calcium chloride were used.) concrete cubes were prepared using cements of high and low alkali contents. containing pieces of nominally t.) from one face. alkali content of cement. coupling of steel and aluminum. The cubes were removed from their molds at Copyright by ASTM Int'l (all rights reserved). The laboratory investigations by Monfore and Ost [6] show that calcium chloride concentration. 1--Concrete spalled by corroding aluminum conduit (from Ref S). FIG. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 303 amounts of at least about 1A weight percent of cement. 1.) aluminum conduit embedded 1. and the ratio of steel area to aluminum area are all interrelated in the corrosion of the aluminum and the subsequent cracking of concrete. externally connected for some tests and not connected for others. . No further reproductions authorized. 15-cm (6-in.25-cm (1/2-in. An example of concrete spalls over corroded aluminum conduit is shown in Fig. C-shaped sheets of mild steel were also embedded in the cubes. In their studies.25 cm (1/2-in. 16 0.09 0. Z E~ "tJ Go 0 .. No further reproductions authorized.09 0..6 2. . uncoupled coupled coupled coupled coupled coupled uncoupled uncoupled uncoupled uncoupled uncoupled uncoupled Electrodes no crack no crack no crack 5 4 3 3 3 no crack no crack no crack no crack no crack no crack Days to Cracking 0.07 0.3 2.92 1.10 0.04 0.2 1.04 Loss in Surface Thickness.4 0. % 0 2 2 4 4 4 0 2 2 4 4 4 0 4 .24 Cement C Ratio of Steel Area to Aluminum Area 28 14 28 7 14 28 28 14 28 7 14 28 0 0 CaCI2-2H20.. Cement Alkalies as Na20.07 0.Copyright by ASTM Int'l (all rights reserved). % 0. a =0 I'rl ---I m O O O co m "rl --4 O --r m 60 -4 r ).07 0. mils b TABLE 2--Corrosion o f 6063 aluminum conduit embedded in 15-cm (6-in.. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) concrete cubes stored at 50 percent relative humidity f o r 28 days. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized.Cj0~ 97VlEI31VI~ O3OO:181~3 :IO NOISOEIEIOO NO SOOOM ONV NI7EI3 ~~o~888oo8~8o88 x K o~" ~o II -" Copyright by ASTM Int'l (all rights reserved). . With 2 or 4 percent calcium chloride present. but metal losses in these cubes were as high as. considerable galvanic currents were found to flow in the circuit connecting the aluminum and steel. 4. and then stored at 23~ (73~ and S0 percent relative humidity for 28 days. ~ 40 9 "~ \. Exposure to a damper atmosphere might have brought about sufficiently more corrosion to have caused cracking. 2--Effect of calcium chloride on galvanic currents (from R e f 5). . S.306 TESTS AND PROPERTIES OF CONCRETE 24 h. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and with metals coupled. 2. 3. Copyright by ASTM Int'l (all rights reserved). cleaned. and invariably increased as the amount of calcium chloride increased. corrosion was a little greater with the higher alkali cement. The cubes that cracked did so within 7 days.2H20. or higher than. corrosion generally increased with the increasing ratio of steel area to aluminum area. Some measured currents as a function of time and calcium chloride content are shown in Fig. All cubes that cracked contained calcium chloride. The principal results are given in Table 2. straight lines were obtained with slopes I l ~120 Steel oreo/oluminum oreo = 28 Cement D. When the total electrical flow during 28 days (in ampere hours per unit area of aluminum) was plotted against the amount of corrosion as loss in thickness. the corrosion was greatest with the high alkali cement. and weighed. 2. !~. No further reproductions authorized.89~ olkolies o j\ 80 LIJ e:" ~_ a~ ~. 6. by weight of cement) did not crack. colciurn chloride 4% . and with metals coupled. 0. 9 2% o 0 0 I0 20 50 TIME. Several important findings can be noted in these results. The cubes containing 1 percent flake calcium chloride (CaCI2. With calcium chloride present.. In the case of coupled metals. They were observed regularly for cracks. With no calcium chloride and no coupling. The effect of progressively increased calcium chloride contents in increasing the current flow at all periods (up to end of test at 28 days) is evident. those in other cubes which cracked. After 28 days the aluminum pieces were removed. coated with a curing compound. 1. DAYS FIG. 1 percent flake calcium chloride to 8 days with 5. (b) the cause of corrosion of the aluminum was due unquestionably to galvanic cells activated when chlorides were present in the concrete.89 percent alkalies and containing 4 percent calcium chloride by weight of cement. The results are shown in Table 3. the cubes did not crack when no calcium chloride was used. concrete cubes containing 4 percent calcium chloride and steel coupled to the aluminum. and (d) there was an enrichment of chloride at the aluminum conduit surface.. aFrom Ref 5. a Protective Coating Material Thickness. and alkyd and phenolic materials.) concrete cubes by Wright and Jenks [7]. With coupled steel and aluminum (area ratio 10:1).5 2.47 nil nil nil Conversion factors--1 mil = 2.1 0.7 percent flake calcium chloride. Lacquer C and bituminous coatings A and D were all effective in preventing both corrosion and cracking. Tests somewhat similar to those reported by Monfore and Ost were carried out on 31-cm (12-in. 1 in. milsb None Silicone Lacquer B Lacquer C Bitumen A Bitumen D . Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.2S-cm (lA-in. mils Days to Cracking Loss in Surface Thickness. Copyright by ASTM Int'l (all rights reserved). certain metallic pigmented coatings. the slope being greater for the higher amounts of calcium chloride. Other tests [8] indicated that resistance to galvanic corrosion was provided by the following coatings: certain bitumuls. TABLE 3--Effect of protective coatings on corrosion o f aluminum conduit embedded for 28 davs in 6-in. No further reproductions authorized.. . bCalculated from weight losses. Tests [6] were made to determine the effectiveness of several different coatings applied to the aluminum before embedment in 1.) concrete cubes made with cement of 0. but did crack at various ages from 61 days with 1.54 • 10-s m.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 307 depending on the amount of calcium chloride used..5 cm.. which is also referred to as intergranular corrosion. 1 2 5 15 3 2 no crack no crack no crack no crack 2. = 2. cracks did not occur in the encasing concrete when chlorides were not present. (c) the corrosion of the aluminum was of the cubic type. These show that a silicone coating was ineffective and that Lacquer B prevented cracking within 28 days but permitted some corrosion. epoxies: fluidized-bed plastics. . McGeary [8] also found that: (a) for aluminum conduit coupled to steel. If the dampness persists. Bituminous coatings have been used successfully. but in contact with d a m p concrete it is attacked by the calcium hydroxide in the concrete and becomes converted to lead oxide or to a mixture of lead oxides. The role of the chloride appears to be that of an electrolyte. Lead partially embedded in concrete and thus partially exposed to the air is susceptible to corrosion because of the differential electrical potential that results. There appears little. (c) patch with epoxy or epoxy polysulfide systems. Calcium chloride should not be used in concrete in which aluminum will be used. if any. The results of these various investigations and field observations show that reinforced concrete is likely to crack and spaU from corrosion of uninsulated aluminum embedded therein if an appreciable amount of calcium chloride is present. and it therefore seems prudent not to use aluminum in concrete in or near seawater. the attack will continue. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. may be destroyed in a few years. The air-exposed portion in the presence of water will become cathodic with respect to the embedded portion which will become anodic. likelihood of concrete itself being damaged by corrosion of lead because of the softness of the metal. Copyright by ASTM Int'l (all rights reserved). Synthetic plastic and other organic coatings or sleeves. Lead Lead has a high resistance to certain chemical actions. Insulating coatings for aluminum to be used in concrete are commercially practical. If the lead is coupled to reinforcing steel in the concrete. . it seems evident that the latter would also facilitate corrosion of aluminum. and a galvanic cell is formed. and (d) engage an experienced patching specialist to complete the repairs.308 TESTS AND PROPERTIES OF CONCRETE McGeary [8] found the following to be effective repair procedures for concrete cracked because of corroded aluminum: (a) remove all loose concrete. which are themselves unaffected by damp concrete. In view of chemical similarities between calcium chloride and sodium chloride. A protective coating or covering always should be used when lead pipe or cable sheaths are to be embedded in concrete. Obviously. other salts which hydrolize and provide a strong electrolyte can be damaging also. (b) remove all corrosion products adjacent to the embedded aluminum surface. and a lead pipe. a necessary part of the galvanic cell. No further reproductions authorized. Corrosion and deterioration of the embedded lead will result. or both. are suggested. galvanic cell action may accelerate the attack [9]. for example. Sodium chloride is the principal constituent of sea salt. in which case the rate of corrosion may be several millimetres per year. When copper is connected to steel reinforcement. Zinc Zinc reacts chemically with alkaline materials. bronzes. Copyright by ASTM Int'l (all rights reserved). Thus it is desirable to insulate the copper with suitable coatings. Both satisfactory and unsatisfactory performances have been reported. red brass. aluminum-bronze. consequently. the concrete played in these cases. .CaZnO2 + H2 (1) When zinc is used in concrete it is practically always as a coating for st'eel. No further reproductions authorized. The products of reaction are not voluminous and. but normally in concrete the reaction is superficial and may be beneficial to bond of zinccoated (galvanized) steel. Very little systematic work has been reported on the behavior of copper and its alloys in or in contact with concrete. Copper pipes are used successfully in concrete except under the unusual circumstance where ammonia is present [15]. or they are close to each other. Very small amounts of ammonia and possibly nitrates can cause stress corrosion cracking. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. but as such phenomena can occur under circumstances unrelated to concrete. probably because these metals have given satisfactory service under such conditions. and coppersilicon alloys have good resistance to corrosion in concrete [11]. corrosion of the steel due to galvanic action is likely to occur.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 309 Copper and Copper Alloys Copper will not corrode in concrete unless soluble chlorides are present. if any. galvanized steel reinforcement has been used in concrete exposed in marine and other environments where chlorides are present (for example. Galvanized reinforcing steel has not always been successful in stopping corrosion of the steel and thus conflicting reports result [12-14].~ ported that brass wall ties have failed by stress corrosion and that manganese bronze bolts have sheared below their ultimate strength. Copper. Although good concrete normally provides a nearly ideal environment for protecting embedded steel from corrosion. Figure 3 shows one instance of multiple perforation and corrosion of such sheets under a roof slab [15]. Galvanized corrugated steel sheets often are used as permanent bottom forms for concrete roof or floor construction. it is not clear what role. The primary chemical reaction with calcium hydroxide is Zn + Ca (OH)2 -. and an electrolyte such as chloride is present. It is re. damaging stresses are not created. bridge decks). brass. The chemical reaction is probably Zn + CaC12 + 2H20 -. It is probable that this reaction could not take place at first but only after local depletion of calcium hydroxide by the reaction expressed in Eq 1. The dips are solutions of sodium or potassium dichromate acidified with sulfuric acid.7 to 4. Most of the corroded spots were dry to the touch. Further investigation of this and other similar cases showed that in each instance calcium chloride was used in the concrete and may be presumed to have abetted the corrosion by chemical action on the zinc and by increasing the electrical conductivity of the concrete to corrosion currents. and the corrosion will result in pitting of the surface.CaZnO2 + 2HC1 + FI2 (2) As this action produces hydrochloric acid. zinc. for example. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). Analysis of the corrosion protuberances indicated the presence of iron. It is also advisable to keep chloride-containing solutions from permeating the concrete. in conjunction with precast or cast-inplace concrete may show surface disfiguration due to the contact of the zinc with alkalies from the portland cement paste. Admixtures containing chloride as a major active component should not be used in concrete that will be exposed to moisture and contains or is in contact with galvanic steel. 3--Corrosion and perJoration of galvanized steel from under concrete slab (from R e f 15). zinccoated steel used. Corrosion of zinc can result when contact with relatively fresh concrete occurs. .8. it may well explain the observed acidity of the corrosion product. but some were moist and had pH values of 2. and chloride.310 TESTS AND PROPERTIES OF CONCRETE FIG. definitely in the acid range. Thus. Passivation of the zinc by use of chromate dips has been reported to be effective in protecting galvanized products. has a tendency to stick to the forms. such as previously described. alloyed cast iron. Whenever glass is to be used in concrete. chromenickel. silver. and as frameless windows or lights. iron-chrome-nickel alloys. Prisms cut from the panels and tested using accelerated methods in the laboratory had expansions of 0. the corrosion resistance of these materials becomes questionable if chlorides are present in the concrete or in solutions that permeate the concrete [17]. as wall blocks or tile. The resistance of some of these metals to corrosion in concrete may be affected seriously by the presence of "corrosion promoters" such as soluble chlorides. No further reproductions authorized. I9] used for decorative or aesthetic purposes. Before glass is used in portland cement concrete. nickel. has been described as a satisfactory method for avoiding that problem. chrome-nickel steels. Other reports [20] have also indicated the deleterious behavior of reactive glass. . and tin [11]. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. chromiumaluminum-silicon steels. Special circumstances might justify the use of these more costly metals.2 percent after 3 months of test. Glass Glass sometimes is embedded in mortar or concrete as artificial aggregate [18. The glass aggregate removed from the concrete. For example. Other Metals The following metals have been reported to have good resistance to corrosion in concrete: stainless steels. The warping was due to the expansion of the facing against the nonexpansive concrete backing.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 311 Concrete. as reinforcing as a substitute for steel. stellite. waste bottle glass used as aggregate in a decorative concrete facing of outside-exposed precast concrete panels caused sufficient expansions to warp the panels. in which galvanized reinforcing steel is located close to galvanized forms. Some glasses are reactive with alkalies in portland cement paste and the resulting expansion may cause severe damage to the glass or the concrete or both [20]. Monel metal. Nickel and cadmium-coated steel will not corrode in chloride-free concrete if the coatings are continuous [16]. tested using the procedures in the ASTM Test for Potential Reactivity of Aggregates (Chemical Method) (C 289) was found to be deleteriously reactive. However. Monel metal and Type 316 stainless steel are wellknown for their resistance to sodium chloride and other constituents of seawater and should work well in concrete. it is mandatory that the glass be tested to ensure that it will be chemically stable in concrete and not cause expansions due to alkali-silica reactivity. it should be tested Copyright by ASTM Int'l (all rights reserved). cast silicon-iron. A chromate treatment. and timbers have been embedded in or placed in intimate contact with concrete in composite constructions. or fibers in concrete commonly results in very slow setting and abnormally low strength because of interference with normal setting and hardening processes by carbohydrates. Addition of hydrated lime to the mixture in an amount equivalent to onethird to one-half of the cement by volume has been found effective in overcoming this action [22]. and specifically those given in Paragraph X1. wood chips. and possibly other substances in the wood.312 TESTS AND PROPERTIES OF CONCRETE using the methods provided in the Appendix of ASTM Specification for Concrete Aggregates (C 33). The use of fresh untreated sawdust.1. Among materials prepared for use in concrete is wood (includes bamboo. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.3 of the ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (MortarBar Method) (C 227). Problems incidental to the use of natural-cellulosic materials have included adverse effects of sugars on concrete setting and degradation of the fibers due to the high alkalinity of concrete. and wood fibers have been incorporated in mortars and concretes. Wood Current trends in the use of new or unusual materials in concrete are due to the emphasis on conservation of energy and the utilization of wastes and by-products. Further.2 of ASTM Test C 289 and Paragraph X1. tannins. . No further reproductions authorized. wood pulp. Softwoods generally give less trouble in this respect than hardwoods. These factors are perhaps foremost in precluding the use of many cellulosic materials. cotton. high differential thermal coefficients of expansion of some of these materials and unaccommodative volume changes can cause cracks to develop. Nondeleteriously reactive glass for use in concrete is manufactured and thus available for use in concrete. Additional problems incidental to the use of natural-cellulosic materials include swelling with moisture absorption and subsequent shrinkage. Many admixtures and wood treatments have been proposed or used to circumvent the influence of wood constituents on setting and hardening. or carbonation of the portland cement paste [21] are possible ways for improving their utilization. jute. The treatment is usually effective with mixed softwoods. fibers. bark. Sawdust. and rice stalks and hulls). and chemical degradation due to contact with calcium hydroxide. The amount of such substances differs with wood species and from time-to-time and place-of-origin within a single species.1. Prior treatment of the cellulosic materials such as impregnation or coating techniques. except when a high proportion of larch or Douglas fir is present. Copyright by ASTM Int'l (all rights reserved). The principal chemicals in concrete which could conceivably attack plastics are calcium hydroxide. and polytetrafluoroethylene. Types I and II. treating with 37 percent aluminum chloride solution or 50 percent zinc chloride solution in a rotary barrel with beater. Some of these methods involve encasement of the wood particles or of the finished product in a material of low permeability to moisture. to a smaller extent of lignin. Various methods have been employed to lessen the changes in volume consequent upon changes in moisture. Other treatments which have been suggested include soaking in sodium silicate solution. conduit shields. With woods of high tannin or carbohydrate content. chairs. and joint fillers. No further reproductions authorized. styrene copolymer rubber-resin blends poly(vinyl chlorides). to the amount of 5 percent of the cement. (c) reboiling with a solution of ferrous sulfate (2 percent) in water. and potassium hydroxide. chiefly of pentosans. and their compatibility with concrete is thus important. or simply on change in external humidity. is sometimes added as well as hydrated lime. than concrete made with mineral aggregates. Plastics The use of plastics in concrete and concrete construction has increased significantly. If the element is restrained. (b) draining and washing with water.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 313 Calcium chloride. The most suitable wood for embedment is said to be pine or fir. Concrete made with wood aggregate has considerably greater volume change on wetting and drying. The pretreatments mentioned previously have only a small influence on these volume changes. waterstops. sheaths. and least of all of cellulose. Copyright by ASTM Int'l (all rights reserved). preferably of a type with high resinous content [23]. and (d) draining and rewashing. Plastic products are now being used as pipes. If drying is not uniform. sodium hydroxide. A treatment found by Parker [22] to be effective with all woods tried. It is said that the harm is done by calcium hydroxide which causes dissolution of lipins and decomposition. the element may warp. moistening the wood with 1 percent sulfuric acid for 4 to 14 h. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. .consists of the following consecutive steps: (a) boiling sawdust in water. Timbers embedded in concrete sometimes have been observed to deteriorate. then neutralizing with milk of lime. the addition of lime with or without calcium chloride is not effective. but the details of such treatments and the results achieved have not been revealed in general. drying may lead to cracking. The following plastic groups have excellent resistance to all three of these alkalies at 24~ (75~ [24]: polyethylene. and they provide a similar service. etc. pavements. glass. slabs.) Pipes. rock slope stabilization. fence posts. they must enhance the physical attributes of concrete. and increased fracture resistance. Applications of fiberreinforced concrete are shown in Table 4. garden units.314 TESTS AND PROPERTIES OF CONCRETE Another source [25] provides the following information on the resistance of plastics to strong alkalies: Class of Material Resistance Polyethylene Polymethyl methacrylate Polypropylene Polystyrene Polystyrene acrylonifrile Polytetrafluoroethylene Polytrifluorochloroethylene Poly(vinyl chloride) and poly(vinylchloride) vinyl acetate (rigid) Polyvinylchloride and polyvinylchloride vinyl acetate (plasticized) Saran (monofilament grade) Epoxy (unfilled) Melamine (formaldehyde) Phenol (formaldehyde) Polyester styrene-alkyd Urea (formaldehyde) excellent poor excellent to good excellent good to excellent excellent excellent excellent fair to good fair to good excellent poor poor poor poor Fibers In a broad sense. steps. For fibers to be useful and effective. cellulose. pavements Miscellaneous small precast items (burial vaults. industrial floors Maintenance and repairs to dams. dolosse. street. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. pile caps. and be durable. Type of Fiber steel steel steel. No further reproductions authorized. Among the desirable characteristics that fibers can impart to concrete are flexural strength. Industrial floors. structural bridge deck elements. piles. polypropylene . and airfield pavements. sluices. building panels Copyright by ASTM Int'l (all rights reserved). slab overlays. boats. highway. resistance to fatigue and impact. sheets. fibers used for reinforcing concrete are small versions of conventional steel reinforcement. overlays. etc. boards. panels. tunnel linings. culverts. pavement. Type of Use Cast-in-place and precast bridge deck units. bridges. poles. A state-of-the-art report on TABLE 4--Some applications of fibers in concrete. glass glass asbestos. can suffer reductions in strength [29. Steel fibers have also been produced as crimped or deformed fibers so that mechanical interlock is present in addition to chemical bond. polyethylene. Rusting of fibers and the surface region of concrete generally occurs. However. and thus the durability of concrete made with steel fibers and used in environments chemically aggressive to the steel may be poor.30]. nylon. asbestos. Glass Glass fibers can be sensitive to alkalies in portland cement paste (see Copyright by ASTM Int'l (all rights reserved). . chloride in an amount equivalent to a purposeful chloride addition (for example. 1 percent calcium chloride by weight of cement) was present in the concrete to which a topping shake had been applied. polypropylene. but little is given regarding corrosion characteristics of embedded materials. Organic fibers are considered to rely upon mechanical interlock. rusting will be initiated at locations where steel is exposed in the cracks. Among the materials that have been used as fibers in concrete are steel. and the concrete should have as low a permeability as workability and w/c ratio will permit. This situation points out the desirability for avoiding the use of chloride either as a component of the original concrete mix. steel-reinforced concrete used for pavements. The results of unpublished studies of steel-fiber reinforced beams in a simulated seawater environment for 8 years have revealed that rusting of fibers to depths of 0. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) have occurred [31]. to develop adhesion to the cement matrix. Steel fibers and steel filings are used in proprietary floor toppings to enhance wear characteristics. The amount of metal used is significantly greater than for fiber-reinforced concrete. However. chlorides should not be a component of admixtures used in fiber-reinforced concrete. and other similar usages where chloride deicing agents are employed. bridge decks. Obviously. Instances have occurred where deterioration of the surfaces have resulted because of rusting of the steel. it has been reported that outside-exposed. steel fibers are subject to the same type of corrosion as reinforcing steel.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 315 fiber-reinforced concrete was prepared by the American Concrete Institute [26]. No further reproductions authorized.34 cm (1/16 in. and carbon. and steel and glass upon chemical interactions. and the rusting is not progressive [31]. Steel Good durability of steel-fiber reinforced concrete has been reported [27.28]. such as is desirable in warehouses. If cracks are present. The deterioration of the steel is enhanced particularly by chlorides. glass. In one such case. or as an application to concrete surfaces. Asbestos Asbestos has been used in conjunction with portland cement since about 1900. Organic Materials Polymer fibers such as nylon and polypropylene improve impact strength of concrete but not tensile or flexural strength because they have a low modulus of elasticity. The embrittlement associated with that exposure is thought to result because of reformation of cement hydration products in and tightly around the fibers so that fiber encasement is enhanced and failures are due to fracture rather than pullout of the fibers [35]. however. and alkalies. and low lime calcium silicate hydrates [39]. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Although the durability of the embedded asbestos fibers is not considered a problem. The chemical reactions have been found to be surfacial and occur on fiber surfaces and on cleavage planes. Asbestos minerals are naturally occurring and include a variety of different materials that fall into two groups: amphibole and chrysotile. magnesium carbonate. and iron which may substitute freely for each other. That explanation does not entirely satisfy all aspects of the situation. magnesium silicate hydrates. and further research is needed [36. Copyright by ASTM Int'l (all rights reserved). some corrosion of the fibers may occur after prolonged periods because of chemical reactions with calcium hydroxide in the portland cement paste. The alteration of the asbestos fibers does not adversely affect properties of the concrete because the alteration of the fibers is restricted to only its surface. . No further reproductions authorized. and early work using glass fibers reflected the adverse effects of alkali-silica reactivity [32]. The asbestos minerals may differ in composition but have the common composition of magnesium silicate. Glass fibers have been developed that are resistant to alkali degradation and are now available [33. reformation of the portland cement matrix may cause the concrete to become brittle with age [38].34]. These new fibers are formulated with zirconia and are particularly resistant to alkali attack. These fibers by themselves are reported to perform satisfactorily in concrete. Corrosion products are probably magnesium hydroxide. magnesium.316 TESTS AND PROPERTIES OF CONCRETE discussion under "Glass"). These tests are gratifying because they also demonstrate that the loss of fracture resistance caused by chemical changes within glass-fiber reinforced concrete (which occurs prior to 5-year exposures in wet environments) may be as dramatic as previously experienced. however.37]. and concretes made with these fibers are reported to retain their strength properties when stored in a variety of environments for periods of about 5 years (the tests are still in progress). Other polymer fibers having a high modulus of elasticity are apparently becoming available. Jan. Because the concrete has seen prior service in a given e x p o s u r e a n d environm e n t for lengthy periods does not necessarily m e a n t h a t as concrete aggregate in o t h e r service a n d exposures it will p e r f o r m similarly. 1970. L.. .. Vol. Canada. aggregates for use in concrete m u s t possess certain necessary physical a n d chemical characteristics. 1965. the old concrete is crushed and g r a d e d . 9. D. No..ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 317 Concrete The c u r r e n t e m p h a s i s on recycling of m a t e r i a l s . C o n c r e t e m a d e with a chloride a d d i t i o n . References [1] Abrams. a n d used either alone or b l e n d e d with other aggregates [40-42]. F. pp. W. "Corrosion of Aluminum Conduit in Concrete. and Costello. F o r such use." Journal. 28-29. and Tarleton. 7. and Ost. Building Research Station. [2] Jones. will p r o b a b l y r e s p o n d differently. "Effect of Embedding Aluminum and Aluminum Alloys in Building Materials. T h e concrete m a d e with concrete aggregates has h a d p r i n c i p a l use as a base for concrete m a d e with conventional aggregates. "An Unusual Case of Corrosion of Aluminum Conduit in Concrete. G. and where chemically u n s t a b l e aggregates are present. These are b u t two examples t h a t d e m o n s t r a t e the need for establishing new specifications a n d requirements to ensure t h a t concrete m a d e with recycled concrete will provide a d e q u a t e service. of t h a t for conventional concrete [43]. nothing has been r e p o r t e d r e g a r d i n g the physical or c h e m i c a l stability of such aggregates. pp. 31-34. its compressive strength is a b o u t 75 percent. 9. could p r o m o t e c o r r o s i o n of reinforcing steel. A l t h o u g h the w o r k a b i l i t y of concrete m a d e with recycled aggregates is a b o u t t h a t of concrete m a d e with conventional aggregates." Research Paper 36. Vol. T. [4] Anonymous. [3] Wright. if used in reinforced n o n c h l o r i d e . Borje. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Concrete from an elevated structure where the exposure has been dry. 1965. Sept. Aside from t h a t work." Engineering News-Record. such as those r e q u i r e d in A S T M Specification C 33. 11. F o r e x a m p l e ." Materials Protection and Performance. has resulted in the use o f old concrete as aggregates for new concrete. No. Oct." Portland Cement Association. D. Vol. J. pp." Engineering Journal. when used in a moist e n v i r o n m e n t .c o n t a i n i n g concrete. "Concrete Drying Methods and Their Effect on Fire Resistance. 1955. No further reproductions authorized. 10. E. pp. 1. E. 172. London. a n d the raising of old concrete structures a n d pavements.. Great Britain Department of Scientific and Industrial Research. A. R. 1357-1362. No. S. 1963. "Spalled Concrete Traced to Conduit. a n d its m o d u l u s of elasticity is a b o u t 60 percent. 38. Copyright by ASTM Int'l (all rights reserved). 10-22. Buck r e p o r t e d t h a t concrete m a d e with recycled aggregate h a d resistance to cyclic freezing [44]. M. [6] Monfore. Research and Development Bulletin 181. and Orals. Vol. Studies of recycled concrete aggregate is thus m e a g e r a n d the subject certainly merits c o n s i d e r a b l e a n d extensive work. 12 March 1964. J. No. E. Portland Cement Association. Research and Development Laboratories. [5] Copenhagen. "Corrosion of Aluminum Alloy Balusters in a Reinforced Concrete Bridge. Naval Civil Engineering Laboratory. 13-16. Corrosion Guide. and Hans. D. Vol. now with Materials Laboratory. No further reproductions authorized. E. [I0] Halstead. 50-56. No. "Use of Galvanized Rebars in Bridge Decks. 1976. F. G. Vol. 27. Reinhold..." Concrete Construction. Australia Commonwealth Scientific and Industrial Research Organization. New York. Title No. Paper No. J." Materials Systems and Science Division of the Construction Engineering Research Laboratory. Dec. 593-596. Washington. C. F. 1975 (unpublished). 1963." Materials Performance. Oct." Portland Cement Association. Plastics for Corrosion-Resistant Applications. William." Metaux & Corrosion. Vol.. Vol. 1974. 11. 22. H.369. Louis. [14] Anonymous. Handbook of Chemistry and Physics. New York. New York. pp. Task 03. 1964. American Concrete Institute. [11] Rabald. Journal Structural Division. J. [23] Dominik. [26] ACI Committee 544. "State-of-the-Art Report on Fiber Reinforced Concrete.. [25] Anonymous. D. M. K... Vol. 1955." Journal. "Corrosion of Galvanized Steel in Contact with Concrete Containing Calcium Chloride. 1. 16. "Sawdust-Cement and Other Sawdust Building Products. Federal Highway Administration... Port Hueneme. M. [12] Stark. S." Chemistry and Industry." Proceedings. "Attack on Glass Wall Tiles by Portland Cement. pp. 70-65. National Association of Corrosion Engineers. [24] Seymour.. Inc. B. Division of Building Research. Vol. p. "Guide to Durable Concrete. [27] Shroff. E. 9. Sept. Inc.. pp. 13th Annual Conference. . Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Przemsyl Cheniczny. Elsevier Publishing Co. [21] Anonymous. C. 89 (ST 5). Great Britain Cement and Concrete Association. [9] Anonymous. private communications.. [18] Anonymous. "Fiber Reinforced Concrete. Reprinted from Chemistry and Industry. "A Status Report on Fiber Reinforced Concretes. 348. [291 Bateson. 74-82. pp. Feb. "Effectiveness of Zinc Coatings on Reinforcing Steel in Concrete Exposed to a Marine Environment. Vol." Journal. "Corrosion of Nonferrous Metals in Contact with Concrete. [19] Johnson. pp. July 1977. 14 Aug. 1977. Nov. 1132-1137. 1977. Chemical Rubber Company. 117-132. American Concrete Institute. "Action of Cement on Wood. 1973. H. 729-744. 247-264." Technical Note N-1032. I.Y. pp.." Reprint No." Journal of Testing and Evaluation. French Patent No. 38. Jan. 140. St. 44.. U." Concrete Construction. [15] Mange. 9 July 1976. 1947. and June 1971.. 1966. and Jenks. pp. 48." Notice. Tex. t957. N. [17] ACI Committee 201. Sept. W. Feb. 2.S. E.C. [30] Project OK1. D. The Corrosion of Metals in Contact with Concrete. L. [31] Lankard. Clarkson College of Technology. pp. 1975.415. H. Houston." Journal. R. Work Unit 006. Copyright by ASTM Int'l (all rights reserved). Sidney. "Performance of Aluminum in Concrete Containing Chlorides. 36. T. and Obszarski. Ohio. 1956.. and Steiner. 25 (282). 5.. American Society of Corrosion Engineers. [8] McGeary. E. D." Centre de Recherehes de Pont-a-Morisson. 1957. No. "Corrosion of Metals in Buildings. March 1976.. [22] Parker. "'Strength of Steel Fiber Reinforced Concrete Exposed to a Salt Water Environment. pp. June 1970. 1949. pp. "Waste Materials in Concrete. P. T.318 TESTS AND PROPERTIES OF CONCRETE [7] Wright. July 1969.. Vol. 1949. [16] Freedman. 591-592. No. 1951. "Corrosion Behavior of Cracked Fibrous Concrete." Preprint.. [28] Anonymous. 344-350.. Cleveland. W." MS thesis. 63. American Concrete Institute. 1966. Mo. 372-376." Concrete Construction Engineering. "Accelerating Reactions of the Corrosion of Lead in Cement. Technical Note. E. B. Dodero. "Galvanic Corrosion in Concrete Containing Calcium Chloride. NACE Annual Conference." Report S-41..10. "Waste Glass as Coarse Aggregate for Concrete." Modern Concrete. p. "Corrosion of Lead by Cement. 1959-1960. 41st ed. 24 Aug. No. pp. Oct. "The Effect of a Corrosive Environment on the Properties of Steel Fiber Reinforced Portland Cement. [20] Waters. 1971. Proceedings. [13] Griffin. 1938. David and Perenchio. formerly Battelle Memorial Institute. R. 1970. "The Performance of Galvanized Reinforcement in Concrete Bridge Decks. Potsdam. " Concrete Products." HRB NCHRP. RILEM. R. Feb." Precast Concrete. . "The Strengths of Cements Reinforced with Glass Fibers. 8. A. p. 7. M. No." Journal. 1975." Symposium on Fiber Reinforced Cement and Concrete. "Properties of Fiber Cement Composites. 30-33. "Stronger Market Seen for Glass-Figer Concrete. "Recycled Concrete. 430. Vol. 15.. 22. No. [40] Anonymous." Symposium on Fiber Reinforced Cement and Concrete. Oct. E. Jan. [41] Anonymous. 373-376. 80. Project 4-10. G. 1-8. J. Ralph. No. "Recycled Slab is New Runway Base. and Diamond. 23-30. March 1969. American Concrete Institute. pp. pp. 6. "Rubble Recycling Saves Time. S." Magazine of Concrete Research." Rock Products. pp. 10. A. No. pp. Aug. 315-325. No.. 1971. F. Vol. pp. "Waste Concrete as Aggregate for New Concrete. and the Environment. Final Report. "Validity of Flexural Strength Reduction as an Indication of Alkali Attack on Glass in Fibre Reinforced Cement Composites." Highway and Heavy Construction." Precast Concrete. May 1977. 1976. 120. 42-44. 1975.. [42] Anonymous.. S. RILEM. [34] Tallentire. Sun Apr 6 21:41:46 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Promising Replacements for Conventional Aggregates for Highway Use. Copyright by ASTM Int'l (all rights reserved). "Glass Fibre Cement Applications. "Reusing Concrete. pp. Jan." Symposium on Fiber Reinforced Cement and Concrete. June 1971. Vol. [38] Anonymous. "Investigation on the 'Corrosion' of Asbestos Fibers in Asbestos Cement Sheets Weathered for Long Times. No further reproductions authorized. July 1977. 269-276. A. 21. 95-97. B." Engineering News-Record. 1975. Lazlo. 1975." Highway Research Record. [39] Opoczky. 186. pp.. D. No. [33] Ironman. 549-551. pp. 107-108. pp. and Ali. University of Illinois. 1977. RILEM. [36] Majundar. et al. "Developments in Fiber Composites. A. [44] Buck. [35] Grimer. pp. Ludmilla and Pentek. J. 279-313. 74.ERLIN AND WOODS ON CORROSION OF EMBEDDED MATERIALS 319 [32] Marek. Vol. Energy. [371 Cohen. 66. 1977. No. Vol. 1973. Sidney. Vol. [43] Frondistou-Yamas. pp. Pullout tests are generally satisfactory for measuring the relative bond values of bars with different deformations. Lu~ ~ Chapter 21 Bond with Reinforcing Steel Introduction Early experimenters and designers of reinforced concrete recognized that slip of the reinforcement had to be prevented in order to develop adequate bond and shear strengths and maintain the integrity of reinforced concrete members.A. Copyright9 1978tobyLicense ASTM International www. 2The italic numbers in brackets refer to the list of references appended to this paper. The first comprehensive series of bond tests was conducted by Abrams [112 who employed both pullouts and beam specimens and measured the slip with care. Bond strength is determined using either beam or pullout specimens. This investigation laid the foundation for many subsequent studies which finally culminated in the adoption of ASTM Tentative Specifications for Minimum Requirements for the Deformations of Deformed Steel Bars for Concrete Reinforcement (A 305) in 1956. 53223. or it may be defined as the average bond stress from a point of m a x i m u m tension to the end of the bar. experience has shown that bond values derived from pullout tests cannot be applied in general 1Vice president. No further reproductions authorized. Sun Apr 6 21:43:32 EDT 2014 320 Downloaded/printed by Universidade do Gois pursuant Agreement.STP169B-EB/Dec. Tests for Flexurai and Anchorage Bond in Beams Bond stress in a beam may be defined either as the nominal "flexural bond" [2] value calculated from the expression u = V/~ojd. The latter has been termed "anchorage" or "development bond. Wis." and it is generally considered to be more meaningful than the "flexural" bond value. Copyright by ASTM Int'l (all rights reserved).org .. 1978 L. Computerized Structural Design.astm. Brown Deer. This standard defined the minimum requirements for deformed reinforcing bars as we know them today. Inc. However. Mains observed in his study of distribution of tensile and bond stresses along reinforcing bars that the tensile stress distribution curves for the beams and pullouts were quite similar when plotted to the same scale and with the free end of the beam bar coincident with the free end of the pullout bar. The ACI Building Code for reinforced concrete (ACI Standard Code Requirements for Reinforced Concrete (318)) adopted in 1951 incorporated new provisions which increased the allowable bond for deformed bars in beams and slabs from 0. with a maximum of 2.LUTZ ON BOND WITH REINFORCING STEEL 321 to design of reinforced concrete beams and that beam tests are necessary to develop design criteria. The establishment of minimum requirements for the deformation of deformed reinforcing bars led to a substantial increase in working bond stress for deformed bars conforming to requirements of ASTM Specification A 305. there is a basic difference in the cracking phenomena. This code also recognized for the first time the difference between top and bottom bars.10 of the 28-day compressive strength. Transverse cracks are absent entirely in pullout specimens and the cracking is confined to longitudinal splitting.4 MPa (350 psi). while in the beam specimens both the concrete and the reinforcement are in tension. The difference between bond values obtained from pullouts and beams are due primarily to the different crack patterns which develop in the two types of specimens. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As the steel stresses increase. . The bonding in the portion of the beam between the support and the nearest transverse crack is probably the only bonding that the pullout specimen properly models according to work done by Mains [3]. Although longitudinal cracks develop along the reinforcing bars (as the stresses increase and slip becomes appreciable) in both beams and pullouts. transverse cracks develop. and each new transverse crack tends to initiate a new longitudinal crack. The test procedure was later adopted by the American Concrete Institute as ACI Test Procedure to Determine Relative Bond Value of Reinforcing Bars (208-58) (discontinued). Although the test procedure and the test beams described in ACI Standard Copyright by ASTM Int'l (all rights reserved). The allowable bond stress for top bars was reduced to 70 percent of the bond for bottom bars. 6]. This procedure was extensively used in bond studies [5. In pullout specimens the concrete is in compression. This test procedure included length of embedment and position of bar as cast (top or bottom) as parameters.05 to 0. This standard did not include any minimum performance criteria since its primary purpose was to establish relative bond values for different bars. The Bond Stress Committee of the American Concrete Institute (ACI) in its report of February 1945 [4] described a test procedure providing a uniform basis for comparison of bond values of different reinforcing bars. No further reproductions authorized. as cast. which culminated in development of ASTM Specification A 305 covering the geometric requirements for deformed bars. 1 was designed to permit the measurement of the average value of bond stress a n d t h e slip at both the loaded and free ends of the portion of the bar between the supports and the load points.). 2 was designed to place the development length of the test bar. described in the report of ACI Committee 408 on Bond and Development of Reinforcements [8]. both investigations showed that the ultimate bond stress is proportional to Copyright by ASTM Int'l (all rights reserved). and test bar placement are all fixed. Nos. a beam specimen and a test procedure were developed [7]. The test beam shown in Fig. The beam shown in Fig. The test beam illustrated in Fig. In order to study the effect of the various parameters on the bond values of deformed bars in simply supported beams subjected to concentrated loads. in a negative moment region between the point of inflection and the point where the other bars were cut off. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This arrangement permitted the calculation of the maximum steel stress and the average bond stress in a given development length of the bar. designated as L. The dimensions of the beam specimen were varied in order to study the effect of the bar cover and beam width.9] were concerned with different critical sections of beams. the standard was rather restrictive since it limited bars to one size. In spite of the differences in the specimens. and the embedment length to a m a x i m u m of 406 m m (16 in. and in this sense they may be considered as supplementing each other. The beam was provided with T-shaped ends in order to shift the reactions to points where they would not contribute to the restraint of longitudinal splitting. Another type of beam specimen designed for investigating bond in the areas of bar cutoffs and points of inflection was used in a bond study which included bar sizes from Nos. were included in a subsequent study by the same author [10]. the beam test still is not truly representative of the real-life beam. 1 was designed to investigate the bond at the support. concrete to one strength. Although this standardized beam is fine for providing comparison of test results. was intended to provide greater flexibility in the design of the recommended specimen and test procedure in order to permit the use of bars of different diameters. two additional bar sizes. 2 was concerned with the bond at the point of inflection and the section where tension bars terminate within a span. stirrup reinforcement. more than one strength of concrete. while the beam in Fig. and the longer lengths of embedment needed to develop the high-yield stresses of modern deformed bars.322 TESTS AND PROPERTIES OF CONCRETE 208 served their purpose well. and slip measurements were made at each load point plane. . The two bond investigations described elsewhere [7. 14 and 18. This test beam still has drawbacks in that the beam size. 3 to 11 [9]. which represent a considerable departure from the ACI Standard 208. No further reproductions authorized. This bond specimen also was intended to provide a research tool yielding data that readily could be translated into design criteria. A strip of metal embedded in the concrete directly opposite each load point assured formation of a crack at that plane. This procedure. . / l ! ~. 14S and 18S). 4 . w h e r e f ' c is the 28-day compressive strength of concrete. replaced by ASTM Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement (A 615)) (Nos. STEEL i ' .TT . .. . the bond stress for top-cast bars was limited to 70 percent of the bond stress used for bottom and vertically cast bars. An upper limit of bond stress in ACI Standard 318 functioned as the ultimate bond stress for the smaller reinforcing bars.. Position of the bar in the beam was also a factor influencing the bond stress. ~ff~[and inversely proportional to the bar diameter when other factors were constant. No further reproductions authorized.. --E- . ~ I 323 r~"DIA HOLE~ . REINFORCING . I I I i I Ia. 1--Bond test beam recommended by ACI Committee 408 in 1964. . . L . The parameter alone was used in an expression for the tension bars conforming to ASTM Specification for Special Large Size Deformed Billet-Steel Bars for Concrete Reinforcement (A 408) (discontinued.~ ~. . Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.4 _ll . ' rrJ . L I iI. . . An ultimate bond stress for reinforcing bars in compression was also in ACI Standard 318. . This relationship was recognized by the ACI in the formulation of the allowable bond stresses in the ACI Standard 318 for bars with sizes and deformations conforming to ASTM Specification A 305. STRI r' = 2 5 . LOADED PLAN RUBBER TEST 1 I 'I .i.. Copyright by ASTM Int'l (all rights reserved).~ _ t. I i I TUBING BAR 1 I I a.LUTZ O N B O N D WITH ~I" r .~ ELEVATION FIG. . Anchorage or development bond was considered of such importance relative to flexural bond that all bond provisions were presented in terms of development length rather than bond stress. the development lengths were 20 percent longer than those calculated using the provisions of ACI Standard 318-63. . 1 . . ' 1 PLAN = " ~-iS'T. . 14 and 18 bars. J I J. top-casting of the reinforcing bar. The development length expressions are based on the bond stress expressions of ACI Standard 318-63 and consequently involve the same variables. this was done due to the observation that closely spaced bars. . constituted a real problem at the bond stress levels of ACI Standard 318-63. . use of lightweight concrete. . . t t ELEVATION FIG. 1. For the larger bars up to No.. .. The development lengths calculated are modified for various situations.324 TESTS AND PROPERTIES OF CONCRETE L "t z l . .. 11. Secondly. .-L. The development length for top bars still represents a 70 percent Copyright by ASTM Int'l (all rights reserved). These situations which modify the development length are an indication of the areas of current thinking or research in bond. or both. for example. .. which are quite typical. 2--University of Texas beam. . and use of reinforcing bars with yield strengths greater than 414 MPa (60 ksi).-~I I I ~--J J .. . Three such areas are as follows. . Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. large spacing of the bars. No further reproductions authorized.. separate expressions for development length which are proportional to yield strength and inversely proportional to ~ c are used. the development length is proportional to bar area and yield stress and inversely proportional to x/f'c. . L ~ i I . .~ . -~. . . . As a result the development length of small bars is proportional to the bar diameter and the yield stress. . . . For Nos. Two basic changes were reflected by the bond provisions which were in ACI Standard 318-71 [11].-4" ~. Besides being cheaper than the Texas beam (Fig. Both beams could be used to test bond development in the overhanging portions at each end. 4(b). Recent bond testing has made use of two different specimens which are shown in Figs. it has flexibility of load application as the relationships of bond wiih shear. The development length also appears to be appreciably influenced by the spacing of reinforcing bars.13].LUTZ ON BOND WITH REINFORCING STEEL 325 effectiveness in bond relative to bottom bars. 3 II I JACK I F I G . Much is being learned about Item 3 above. so that in the near future the effects of bar spacing. 2. 3--Stub-cantilever beam used at West Virginia University. there is evidence that for the low-slump concretes now being used. 3 and 4. 4 allow a number of different tests to be run on the same type of beam. The Stub-cantilever beam which is shown in Fig. concrete cover and conCopyright by ASTM Int'l (all rights reserved). No further reproductions authorized. and the confinement of a reinforcing bar by lateral ties [12. 4(a) while a pair of top bar embedment tests can be conducted with the beam in Fig. the concrete cover of a bar. the bond reduction is not as large as indicated initially [5. 2). and dowel forces can be varied easily. In each case. 6]. the beam size and the number and arrangement of reinforcing bars are being varied. However. has been used in several research projects [14-16]. The development length of reinforcing bars has been found not to be directly proportional to the yield strength. The symmetrical beams shown in Fig. The bond effectiveness decreases as the yield strength increases in a bar [12]. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . A splice test can be conducted using the beam in Fig. moment. 3. (c) confinement of the splice by some form of lateral Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement..L_I. STARTER7 . The research work [17-19] which has led to the splice provisions in ACI Standards 318-63 and 318-71 have emphasized the following factors which influence the lap splice length required: (a) the increase of spacing between lapped splices decreases the splice length required. 4--Symmetrical beams. . . t t (B) FIG.] t (A) METAL CRACK r"r"r "rr + I i i i i I L. 1 L .326 TESTS AND PROPERTIES OF CONCRETE . Bond of Lapped Splices One of the areas of application in which bond plays a critical role is in the tensile lapped splices.13]. LAP -I - t . No further reproductions authorized. (b) an increase in concrete cover over the splice decreases the required splice length. finement by lateral ties may be explicit variables in development length expressions as are now being suggested by recent work [12. . Longitudinal splitting is produced in the splice length with increase in bar stress and is the basic cause for failure of lapped splices. Test data on tensile lapped splices are somewhat limited relative to data available on development. Considerable variation in the anchorage length and the shape of bond stress distribution curves were noted for wires of different diameters and different surface conditions of the wire ranging from rusted to lubricated. The code provisions for splices have always differed considerably from the development length provisions. the tendons function to some extent as ordinary reinforcing bars and bond stresses develop in accordance with shears and moments in the beam. Tests of beams prestressed by pretensioning indicated that as cracks occurred the flexural bond stresses increased Copyright by ASTM Int'l (all rights reserved). the recent work referred to previously [12] which is attempting to express explicitly the effects of concrete cover. . An exception is the work by Ferguson and Briceno [20] and Ferguson and Krishnaswamy [21] where the splice is in varying moment region as produced by a single concentrated load on a simple beam span. and (d) the length of splice required increases as the tensile force requirement increases. unless lateral reinforcement of a certain amount is used. The second type of bond stresses in prestressed concrete is brought about by flexural action. In this case.LUTZ ON BOND WITH REINFORCING STEEL 327 reinforcement decreases the required splice length. When a prestressed beam is subjected to flexure." In a study of the nature of bond in pretensioned prestressed concrete. One type of bond known as "prestress transfer bond" is developed at the ends of concrete members prestressed by the pretensioning method. These bond stresses which are associated with flexural cracking are commonly referred to as "flexural bond stresses. Tests of splices have been conducted primarily in test setups which place the spliced bars in a constant moment region as illustrated in Fig. the steel stresses at cracked sections increase rapidly and bond stresses increase accordingly. tension in the steel is transferred to the surrounding concrete primarily by friction which is made possible by the normal force produced by the Poisson effect. as well as the interaction between prestress transfer bond and flexural bond. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 4(a). or lateral swelling of the steel in the transfer zone. prior to cracking of concrete the stresses in the prestressing steel change quite slowly and the bond stresses are low. No further reproductions authorized. The code provisions reflect these points by increasing the required splice length as the percentage of spliced bars is increased and the level of stress in the bars is increased. As cracking occurs. Bond in Prestressed Concrete The bond between tensioned tendons and concrete plays a dual role in prestressed concrete beams. However. and confinement by lateral ties has indicated that the expression for development length works equally well for splice length. bar spacing. However. Janney [22] investigated the variation of the prestress transfer bond with various parameters. The splice length is increased if the spacing is less than a certain value. Additional work ~related to development length and bond performance of pretensioning strand appears in other references [24-27]. suggested a set of equations that would limit fp. a transfer bond length and a flexural bond length respectively as follows: ld -~.fe db _if. Martin and Scott [25]. No further reproductions authorized. and composed of two parts. Chi and Copyright by ASTM Int'l (all rights reserved). for example. MPa. position of the strand. the diameter of the bars. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Most bond testing of prestressed strand is done by concentrated loading on simple span prestressed members. the flexural bond capability is reduced considerably near the ends of the beam. of three-wire and seven-wire pretensioning strand based primarily on the work of Hanson and Kaar [23] appears in the ACI Standards 318-63 and 318-71. In recent years considerable research was carried out with new types of high-strength deformed reinforcing bars to study the mechanism of cracking and to determine the effect of such parameters as diameter of bars. and cross-sectional dimensions of beams on the width and spacing of cracks.685 lf-. As a result. a bond failure may be expected when the flexural bond stress wave reaches the anchorage zone. db. Janney [22] demonstrated this phenomenon by strain measurements in the posttensioned beams. An expression for development length. Little is known at present how the size of member. The length is proportional to strand diameter. Influence of Bond in Control of Cracking and Deflections The efficient and economical use of high-yield strength reinforcement is limited by the necessity of avoiding excessively wide cracks which may be objectionable from the standpoint of appearance or lead to corrosion of reinforcement. -._(fp. and presented a formula relating the average width of cracks to the computed stress in the reinforcement.e = effective stress in prestressing steel after losses. Clark [28] investigated these variables in a comprehensive series of tests of beams and slabs. ratio of reinforcement. As the diameter is reduced and radial pressure is relieved by the sharp increase in tension in the tendon after cracking. ld in millimetres.fse) db1 where f. even prior to reaching the free end of the tendon.328 TESTS AND PROPERTIES OF CONCRETE sharply and the bond stress "wave" progressed from the cracked midsection toward the ends of the beam. and fp. . = calculated stress in prestressing steel at design load. if the full development length could not be achieved in a particular situation. MPa. The equation considers failure to occur at the onset of general bond slippage.3. and the ratio of reinforcement. and spacing of the strand may influence the bond integrity. References [1] Abrams. A statistical study conducted by Gergely and Lutz [34] of beam crack width data from several investigations revealed that the bar stress. Copyright by ASTM Int'l (all rights reserved). the direct relationship between the bond strength and both the spacing and the width of tensile cracks. "Measurement of the Distribution of Tensile and Bond Stresses Along Reinforcing Bars.31]. Vol. Acknowledgments Acknowledgment is given to David Watstein of the National Bureau of Standards whose article on "Bond With Reinforcing Steel" formed the basis of this updated article on the same topic. A tension specimen devised to measure the bonding efficiency of a bar [33] gave values which correlated well with the spacing and width of cracks observed in an independent set of long axially reinforced tension specimens. In other words. 1913..LUTZ ON BOND WITH REINFORCING STEEL 329 Kirstein [29] made use of Clark's data in addition to their own to develop a simplified formula for the width of crack. 60. reduction of the slip between the concrete and the reinforcement along the entire length of the b e a m does increase the beam stiffness. by means of tension tests of axially reinforced cylindrical specimens. [3] Mains. The bonding efficiency of reinforcing bars also affects the rigidity of flexural members because the quality of bond affects the contribution of the concrete between tensile cracks which in turn improves the stiffness of the beam." Journal. p. The papers which discuss the various parameters affecting the distribution of strain between cracks and their effect on the flexural stiffness are by Soretz [36]. Nov. Baker et al [37]." Bulletin No. taking into account the distance from the bar surface to the nearest beam surface as a parameter. concrete cover. American Concrete Institute. The crack width expression recommended by Gergely and Lutz formed the basis of the parameter used in ACI Standard 318 to control the distribution of reinforcement (and crack width) in beams and one-way slabs. [2] "ACI Standard Building Code Requirements for Reinforced Concrete (ACI 318-63). 225. and area of concrete surrounding a reinforcing bar were the primary variables affecting crack width.. 1951." Journal. and Watstein and Seese [33] have demonstrated. . M. University of Illinois. Dec. Urbana. The resistance of the concrete between tensile cracks to flexure was considered at length in the 1957 RILEM Symposium on Bond and Crack Formation in Reinforced Concrete [35]. No further reproductions authorized. R. and Murashev [38]. "Tests of Bond Between Concrete and Steel. D. Vol. June 1963. Ill.. American Concrete Institute. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 71. Similar conclusions were reached by Broms [30. The earlier studies by Watstein and Parsons [32]. 48. 61. and Thompson. p. J. M. 1975.330 TESTS AND PROPERTIES OF CONCRETE [4] "Report of ACI Committee 208. N. E. 54. J." Report to the Bureau of Public Roads of the U. R. Prestressed Concrete Institute. Department of Structural Engineering. Vol. p. [16] Mirza. April 1969. National Bureau of Standards. American Concrete Institute. Y. N. Detroit. Portland Cement Association. E. National Bureau of Standards. and Breen. [7] Mathey. 50. Torsion. Development Department Bulletin D28. [6] Clark. 71-94. [5] Clark. American Concrete Institute. Proceedings. The University of Texas at Austin. G. American Concrete Institute. 62. American Concrete Institute. 1071. P. 41." Journal. C. P. p. A. Dec. Federal Clearinghouse No. E. Feb. Sept. P. D. P. American Concrete Institute Convention. Jan. Oct. H. 55." Journal of Research." Research Report 113-3. Vol. and Hsu. 17 March 1977.. Calif. P. Center for Highway Research.. C. 273. A." Journal. [14] Wilhelm. pp.. W. 201. Oct.. [11] ACI Committee 318. 37. Vol. J. 1965. 1959. M. May 1954. 52. Department of Transportation. [10] Ferguson. J. 1. S.. pp. "The Strength of Anchored Bars: A Reevaluation of Test Data on Development Length and Splices. "Nature of Bond in Pretensioned Prestressed Concrete. "Investigation of Bond in Reinforced Concrete Models-Eccentric Pullout Test. Department of Civil Engineering. American Concrete Institute. No. Portland Cement Association. Proceedings." Journal of Research. July 1962. American Concrete Institute. A.. "Tensile Lap Splices--Part 1: Retaining Wall Type. S.. P. Varying Moment Zone." presented at the Interaction Between Steel and Concrete Symposium. 689. E. W. "Flexural Bond Tests of Pretensioned Prestressed Beams. No. 62. Center for Highway Research. American Concrete Institute. S. 43. No. [23] Hanson. West Virginia University. "Development Length of Large High-Strength Reinforcing Bars. [20] Ferguson. and Lee. The University of Texas at Austin.. [17] Chamberlin. J. Jan. and Kaar. 1946. Jan. 717." Journal. March 1961. (plus cumulative supplement issued annually). and Thompson... [15] Gergely." Journal. 1969.. p. 47-67. and Breen. Vol. J.. J. H. "Building Code Requirements for Reinforced Concrete (ACI 318-71)." Journal. p. Coimbatore. "Influence of Concrete Strength on Strand Transfer Length. L. 129.. P. p. RP 1755." Civil Engineering Studies Report No. 1971. American Concrete Institute. O.S. T. [12] Orangun. Kemp. p. [8] "Report of ACI Committee 408. [18] Chinn. "Comparative Bond Efficiency of Deformed Concrete Reinforcing Bars. 783-803. American Concrete Institute. Cornell University. J. 1965." Journal. and Bond in Reinforced and Prestressed Concrete." Journal. and Briceno.. Iirsa." Journal. M. "Lapped Splices in Reinforced Concrete Beams. Ferguson." Journal.. N. L. N. "Lapped Splices for High Strength Reinforcing Bars. J. T. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. American Concrete Institute.. Vol.. Proposed Test Procedure to Determine Relative Bond Value of Reinforcing Bars. Vol. July 1959.. April 1971.. R. Vol: 59. and Mass. M. Jan. A. International Conference on Shear. and Thompson. Vol.. W. O. 8." Preliminary Review Copy. N. [19] Ferguson. "Splitting Cracks Along the Main Reinforcement in Concrete Members. PB-200635. W. 1949. 1945. P. "Spacing of Spliced Bars in Beams. and Wilhelm.. M. Vol.. Feb. "Investigation of Bond in Beam and Pullout Specimens with High-Yield-Strength Deformed Bars. LaFraugh. Dec.. 887. Vol. [24] Kaar. 7. P. [9] Ferguson. M. 1971. Vol.. Vol. Proceedings. 1964. No further reproductions authorized. 1955. M. "Bond of Concrete Reinforcing Bars. and Watstein. [22] Janney.. "Influence of Deformation Height and Spacing on the Bond Characteristics of Steel Reinforcing Bars. 1963. 57. [21] Ferguson. M." Proceedings. RP 2050.. The University of Texas at Austin. Also. India. A Guide for Determination of Bond Strength in Beam Specimens. Feb.. San Diego. Center for Highway Research.. J. "An Investigation of the Parameters Influencing Bond Cracking." Research Report 113-2. pp. Copyright by ASTM Int'l (all rights reserved). Research Report 154-3F. "Development Length of High Strength Reinforcing Bars in Bond. 1958. Development Department Bulletin DT1. P. R.. P." Journal. Also." American Concrete Institute. . C. [13] Kemp. and Krishnaswamy. Vo]." Journal. 2013. J. "Tensile Lap Splices--Part 2: Design Recommendations for Retaining Wall Splices and Large Bar Splices. RILEM. Stockholm. [38] Murashev. A. 41. V. and Parsons. and Lutz. [33] Watstein. Vol. Detroit.. D. Vol..." Journal American Concrete Institute. RILEM. and Lutz." Journal. 31. "Effects of Arrangement of Reinforcement on Crack Width and Spacing of Reintorced Concrete Members. 1976.. L. L. 1976.5] Symposium on Bond and Crack Formation in Reinforced Concrete.. 1965. RILEM. 1957. and Kirstein. National Bureau of Standards. L. "Width and Spacing of Tensile Cracks in Axially Reinforced Concrete Cylinders. Prestressed Concrete Institute. 1965. and Control q/" Cracking in Concrete. . Vol. No further reproductions authorized. B. [36] Soretz. F. pp. 11. 453.. A. [29] Chi. J. L. G. M. Mechanism. Stockholm. and Anderson. 52. July 1943. 62.. [37} Baker. American Concrete Institute No. Vol. 851. Jr. [3. 1957." Journal.. and McCrate. J." Journal." Vol. T. "Effect of Type of Bar on Width of Cracks in Reinforced Concrete Subjected to Tension. R. April 1956. P.." Symposium on Bond and Crack Formation. Nov. E... p. 1977. R. Stockholm. Oct. "An Assurance Criterion for Flexural Bond in Pretensioned Hollow Core Units. Aug. E. "'The Deformation of Cracked Rectangular Reinforced Concrete Beams." Symposium on Bond and Crack Formation. "Maximum Crack Width in Reinforced Concrete Flexural Members. 1957. Stockholm. 73. p. No. American Concrete Institute. P. American Concrete Institute. N. and Flexural Rigidity of. Aug. 22.LUTZ ON BOND WITH REINFORCING STEEL 331 [25] Martin. American Concrete Institute." Journal. A. "Development of Prestressing Strand in Pretensioned Members. Vol. A. p. A. D. Copyright by ASTM Int'l (all rights reserved). R. RILEM. [30] Broms. and Seese. Ashdown. 1." Journal. H. R. SP-20. A. American Concrete Institute. RP 1545. Jan. "Flexural Cracks in Reinforced Concrete Beams. No. and Scott. Vol. 457. [31] Broms. I. "Crack Width and Crack Spacing in Reinforced Concrete Members. p. Sun Apr 6 21:43:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Causes. Reinforced Concrete Members in Flexure. [28] Clark. [34] Gergely. [32] Watstein. [27] Salmons... D. "Factors Affecting the Stiffness of Reinforced Concrete Beams. A. p. "Bond Characteristics of Untensioned Prestressing Strand. 10. Feb: 1945.." Jourm~l. L. Vol. B. "Cracking in Reinforced Concrete Flexural Members. 1968." Symposium on Bond and Crack Formation. D. and Wildt. 54. 73. "Calculation of Crack Width in. N." Journal oJ" Research. 1-17. 293. L. American Concrete Institute. S. April 1958. [26] Anderson. A..-Feb.. 865. 1957. O. according to American Concrete Institute Standard on Nomenclature (ACI 116). Copyright by ASTM Int'l (all rights reserved). mixture proportioning. This process 1Head. Lane1 Chapter 22 Abrasion Resistance Introduction This paper reviews the effects of important factors such as strength of concrete. Copyright9 1978 tobyLicense ASTM International www. finishing procedures.STP169B-EB/Dec. Sun Apr 6 21:43:33 EDT 2014 332 Downloaded/printed by Universidade do Gois pursuant Agreement. Newly revised or developed ASTM standards. Abrasion resistance. Definitions The complex nature of the wear process is demonstrated by the multiplicity of definitions found in technical literature that attempt to describe the mechanical action that takes place under various categories of inadvertent particle removal. 1978 R. the wear is called impact erosion or impingement erosion. ASTM Definitions of Terms Relating to Erosion by Cavitation and Impingement (G 40) defines abrasion as wear by displacement of materials from a solid surface due to hard particles or hard protuberances sliding along the surface. is the ability of a surface to resist being worn away by rubbing and friction. Repeated collapse of cavities near a concrete surface causes pitting. No further reproductions authorized. Erosive wear is loss of material from a solid surface due to contact with a fluid which contains solid particles. Tenn.astm. When the relative motion of the solid particles is nearly normal to the solid surface. When the relative motion of the solid particles is nearly parallel to the solid surface. 37902. selection of concrete-making materials. Cavitation erosion is the wear of a solid body moving relative to a liquid in a region of collapsing vapor bubbles resulting in high impact.org . the wear is called abrasive erosion. Tennessee Valley Authority. Test for Abrasion Resistance of Concrete by Sandblasting (C 418) and Test for Abrasion Resistance of Horizontal Concrete Surfaces (C 779). Materials Engineering Laboratory. on the other hand. and surface treatment on the wear resistance of concrete surfaces as determined by recent research. Knoxville. provide test procedures for various types of wear simulating erosive or abrasive actions. Compressive Strength Witte and Backstrom [3]. surface deterioration may take place. or cutting from mechanical or hydraulic forces. or rock carried by the water. inadequate bond strength of the aggregate. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Such wear may be imposed by abrasive materials carried by wind or water flowing at various velocities. sliding. impact. A brief discussion of significant factors relative to concrete resistance to wear may illustrate the importance of the proper selection. concrete of higher strength may show reduced wear resistance if given an ordinary commercial finish. or may result from foot or vehicular traffic. Depending on the strength of the paste and subsequently on the bond and hardness of the aggregate. Conversely. as researchers before and after them.LANE ON ABRASION RESISTANCE 333 should not be confused with cavitation referring only to the formation and collapse of cavities within a fluid.5 MPa (5000 psi) concrete develops twice as much resistance to abrasion or erosion as 20. the coarse aggregate ultimately is exposed. Factors Affecting Abrasion Resistance Materials related factors which may reduce the resistance of concrete to abrasive action should be considered in the design and construction of concrete surfaces which are to withstand wear due to rubbing. As the paste is worn away. or overmanipulation of the plastic concrete surface.2 Studies on cavitation [2] disclosed that while good quality concrete withstands the flow of clear water at high velocities. Copyright by ASTM Int'l (all rights reserved). improper curing or finishing.7 MPa (3000 psi) concrete [4]. scouring. composition. it will not resist severe forces of cavitation or the wearing and grinding action of sand. A minimum requirement of six bags of cement per 335 kg/m 3 (yd 3) has been commonly accepted for concrete subject to abrasion. soft or resilient aggregate. cavitation. which initially resists abrasive forces. experience shows that the wear resistance of concrete of low to medium compressive strength can be improved appreciably by providing a hard troweled finish. However. 2The italic numbers in brackets refer to the list of referencesappended to this paper. scraping. percussion. Frequently the failure of concrete to resist abrasion can be traced to cumulative effects such as inadequate compressive strength. consider the compressive strength the most important factor responsible for the abrasion resistance of concrete. attrition. Reducing the wear resistance of concrete involves the surficial hardened cement paste. No further reproductions authorized. gravel. . Studies indicated 34. excessive air content or slump. gouging. and application of concrete based on the specific type of service condition. The ACI has published a committee report on the subject of concrete resistance to erosion as it relates to hydraulic structures which is an excellent source of information on this subject [1]. it is less resistant to the forces of abrasion. As the exposure to abrasion becomes more severe. 50) and 150/zm (No. the maximum-size aggregate should be limited to 10 or 13 mm (3/8 or tA in. good quality aggregates meeting the requirements of ASTM Specification for Concrete Aggregates (C 33) are generally acceptable. have investigated specifically abrasion characteristics of stone. Jackson and Pauls [10].to subangular-shaped aggregate is known to improve bond. regulates the water requirements for placing and finishing and has a direct influence on the wear resistance of concrete. hard coarse aggregates such as traprock. No further reproductions authorized. the effect of aggregate on wear resistance is reduced greatly. including air-entraining and waterCopyright by ASTM Int'l (all rights reserved). above this strength level. usually resulting in reduced wear. granite. Other studies have shown that while concrete of compressive strength below 55. the resistance can be increased appreciably by the use of dense. usually 19 to 39 mm (3/4 to 1~/2 in. Schuman and Tucker [7] point out that the shape of aggregate particles. silica.). or metallic aggregate near the surface.). 100) sieves in the concrete mix. abrasion resistance and compressive strength vary inversely with the void-cement ratio. Several researchers. . Angular. in concrete carrying light to medium traffic whereas for heavy dtity concrete surfaces. While mortar is more resistant to the forces of cavitation than concrete of the same strength.334 TESTS AND PROPERTIES OF CONCRETE The significance of the void-cement system on the durability of concrete was pointed out in extensive studies by Mielenz et al [5]. ACI Standard on Construction of Concrete Floors (302) recommends the use of the largest size aggregate permissable. Aggregate Selection Next in importance is the quality of the fine and coarse aggregates. Admixtures The effects of various admixtures. rounded or angular. or ASTM Test for Resistance to Abrasion of Small Size Coarse Aggregate by Use of the Los Angeles Machine (C 131).2 MPa (8000 psi) is greatly benefited by the use of hard aggregate. Pogany [11] states the rate of wear of concrete generally is not affected by the aggregate provided the coarse aggregate is equal or superior to the mortar matrix. Generally speaking. among them Scripture et al [8]. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Abrams [9]. it is advisable to reduce the amount of material passing the 300/zm (No. Smith [6] suggests that although no conclusive correlation exists between abrasion resistance and the quality of the coarse aggregate as determined by either the ASTM Test for Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate (C 88). Heavy duty floors and slabs exposed to more severe abrasive action demand well-graded hard mineral aggregates. For concrete subject to light to medium abrasion. Both the steel trowel and hard-steel trowel produce smooth surfaces. Step-by-step procedures for 7 classes of floors including consolidation and finishing are comprehensively described in a committee report of ACI 302 [14]. Bureau of Reclamation confirm Copyright by ASTM Int'l (all rights reserved). commercial. so will the resistance of concrete to abrasion. closing any existing imperfections and providing excellent resistance to abrasion. and hard-steel trowel finishes. the surface is blade-floated. (b) industrial. and upon stiffening. on the wear resistance of concrete could not be established conclusively on the basis of the review literature. Combining these demands in one application. The key to durable. floating or troweling the surface while bleeding water is present. he demonstrates that a deferred topping finish from which surface water is removed by a vibratory absorption process yields highest abrasion resistance. Concrete not severely exposed to freezing and thawing or ice removal agents should be placed at air contents not exceeding 3 percent to avert any reduction in wear resistance [13]. tend to produce a concrete of improved wear resistance.LANE ON ABRASION RESISTANCE 335 reducing admixtures and retarders. troweled. that is. This report requires floor classes 4 through 7 to be given special consideration when exposed to abrasive conditions and are classified as (a) light duty. In this investigation. cleanable concrete slabs according to Ytterberg [16] can be found in proper finishing procedures and in a reduction in the w/c ratio. Finishing techniques are also compared with wear resistance of concrete in a study by Fentress [15]. Water-reducing agents.S. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The wood float tends to tear the surface and to displace the aggregate. No further reproductions authorized. The general trend in most studies reflects an increase in abrasion loss proportional to increases in air content for any given water/cement (w/c) ratio [12]. magnesium float. causes a rough-textured surface and a lowering in wear resistance. Finishing Procedures Wear resistance of a floor is also affected by the construction techniques applied. abrasion forces were imparted on wood float. . by virtue of their positive effect on the w/c ratio and consequently on increases in strength. One plot shows greater wear loss due to a float finish as compared with a steel trowel finish. with delayed finishing. The technique requires that after the water of workability has been removed. Abrasion tests carried out by the U. industrial. In this comparative study the deferred topping exceeded by far a monolithic application in wear resistance. The same effect is shown when comparing premature finishing on abrasion. As the compressive strength is adversely affected by increased air contents. steel trowel. despite ease of finishing. and (c) heavy duty industrial. The magnesium float. General illustration of the effect of finishing techniques on abrasion resistance is given in the appendix of ACI 302. Well-cured concrete can produce a surface up to twice as wear-resistant as a surface cured for only 3 days. curing should start as soon as possible after the concrete has been finished and shall be continued preferably for a minimum of 14 days. The dry coating is power-floated and then steel troweled into the surface without the use of additional water to produce a hard. Mayberry's studies also confirm appreciably higher wear resistance of concrete for emulsion cured bridge decks [20]. and surface treatments using linseed oil. Curing In constructing concrete floors and slabs the quality of the concrete operation determines the properties of the surface. The use of steel fiber-reinforced concrete and topping mixes have recently been used with some success for airport runway pavements. A laboratory program conducted by the California Division of Highways [19] considers the effect on abrasion of such variables as slump. and incremental curing. . For poorly-cured or porous concrete surfaces. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. but the limited data indicates abrasion resistance is increased somewhat. The application of a curing compound immediately after finishing creates abrasion resistance approximately equivalent to that attained after 7 days of curing by water spray and continuous dampness. Copyright by ASTM Int'l (all rights reserved). Relatively few wear tests have been conducted on this type of surface. especially for surfaces composed of leaner concrete. Test data indicate among these variables that the greatest abrasion losses encountered were associated with less than adequate curing procedures. at least 5 days of curing at concrete temperatures of 21~ (70~ or higher are required and a minimum of 7 days at temperatures of 10 to 21~ (50 to 70~ to assure adequate abrasion resistance [14]. curing. A correlation of curing time and wear reported by Sawyer [18] involved a series of tests comprising a wide range of cement contents. Wearing surfaces can be improved by the use of dust coats or "dry shakes" consisting of dry cement or cement-aggregate mixtures sprinkled on the surface just prior to initial set. beneficial effects from treatment with linseed oil are demonstrated by an increase in abrasion resistance of as much as 30 percent. w/c ratios.336 TESTS AND PROPERTIES OF CONCRETE that vacuum-treated concrete surfaces are in fact considerably more resistant to abrasive forces than surfaces with either nontreated lean or richer concrete [17]. Pockets of bleed water should be absorbed before adding the dust coat and the troweling operation carefully supervised. From this study it is apparent that marked improvement in abrasion resistance can be expected with extended curing time. For concrete floor and slab construction using Type I portland cement. finishing. dense topping layer. ACI Durability of Concrete (201) suggests that for maximum durability and abrasion resistance. No further reproductions authorized. reliance was placed initially on the use of rattlers which provide abrasive action based on the tumbling of steel balls impacting a test surface [27]. ASTM Test for Abrasion Resistance of Concrete by Sandblasting (C 418) Copyright by ASTM Int'l (all rights reserved). Paints and coatings used to seal concrete surfaces and to protect the concrete from the attack of the environment or chemicals [23] possess only limited wear resistance and any test simulation to evaluate their effectiveness is difficult. some coatings. Preceding any standardization of laboratory methods or of testing machines. if properly bonded remain fairly resilient and effective in protecting concrete from erosive and abrasive actions. Treatment with fluorosilicates densities and hardens surfaces and improves abrasion resistance but the improvement by the two types of fluorosilicates is not of equal magnitude [22]. The Corps of Engineers Method of Test for Resistance of Concrete or Mortar Surfaces to Abrasion (CRD C 52) describes a drill press-type rotating cutter device. No further reproductions authorized.8-MPa (5000 to 6500 psi) compressive strength. However. particularly in strength and abrasion resistance due to impregnation and in-place polymerization of monomers in overlays and in mature concrete. Abrasion Test Procedures The techniques and test methods that have been employed for over a century to evaluate the resistance of concrete to abrasion. Numerous modified versions of the rattler principle continued to be the dominant test procedure along with the revolving metal disk pressed against a small concrete specimen [28]. . sodium silicate. The drill press-type abrasion machine [29] in modified form still is used by highway departments and enjoys some popularity because of its simple design. Concrete of 34. among them vinyls and heavy rubber.5 to 44. erosion. Liquid treatment of floor topping surfaces is less successful and improvements have proved of little significance. Experimental studies by Krukar and Cook [25] and by Dikeon [26] also demonstrated remarkable improvements in concrete properties. treated with polymer showed considerable increase in wear resistance. gums and waxes) serve to prolong the life of older floors and are considered an emergency measure for treatment of deficiencies in relatively pervious and soft surfaces which wear and dust rapidly [21]. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the zinc fluorosilicate shows greater resistance to impact type wear as imposed by the dressing wheel type machine. or cavitation have attempted with varied success to reproduce the typical forces detrimental to concrete surfaces. While the magnesium fluorosilicate is more resistant to rubbing action simulated best by a revolving disk-type abrasion machine.LANE ON ABRASION RESISTANCE 337 Floor Hardeners and Surface Treatment Certain chemicals (magnesium and zinc fluorosilicates. Polymer impregnated concrete for highway bridges was investigated by the University of Texas [24]. nonair-entrained. This procedure was revised in 1964 calling for the explicit use of silica sand which allows for closer control of the abrasive action. q J i :J I i \CONTROL VALVE FIG. . This permits accurate measurement of abrasion by volume displacement and replaces the old weight-loss determination. discontinued). The 1958 standard specified carborundum or silica sand. ables as gradation of the silica sand.13 on Methods of Testing Concrete for Resistance to Abrasion from the original Ruemelin blast cabinet equipped with an injector-type blast gun with high velocity air jet (Fig. The 1976 revision specifies the use of oil-base modeling clay of known specific gravity for the filling of voids in the abraded concrete surface. . . .03. . Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The modified clay filler method is similar to a procedure that evaluates floor and patio brick developed for ASTM Specifications for Required Safe Crushing Strengths for Sewer Pipe to Carry Loads from Ditch Fillings (C 15. The sandblast method closely reproduces wear conditions existing in hydraulic structures subject to abrasive materials carried by Copyright by ASTM Int'l (all rights reserved). . air pressure.COMP AIR CONN. The control over such vari- L[.~I QQ ===LOADING DOOR=:= m 9 g ~=1 i I L. . rate of feed of the abrasive. This procedure was modified by ASTM Subcommittee C09.- .. . 1). No further reproductions authorized. Rushing [30] compared the 1958 and 1964 procedures of ASTM Test C 418 in a 1968 laboratory study and found the later revision to permit a more accurate determination of abrasion loss. distance of the nozzle from the surface. and the area of the shielded surface is critical.338 TESTS AND PROPERTIES OF CONCRETE dates back to 1958 and is based on the principle of producing abrasion by sandblasting. 1--Sand blast cabinet. plane surface produced by disk abrasion is explained by the movement of the disks across the test surface causing the entrapped irregularly-shaped particles beneath to slide rather than to roll thus cutting the surface by friction (Fig. etc. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.13 initiated a number of major test programs conducted by independent laboratories. among them curing compounds. No further reproductions authorized. 3). 2) introduces frictional forces by rubbing and grinding. and coatings where the performance of the protective "skin" is critical. specimens are brushed clean. or impact are imposed by the disk's action. this machine provides the most reproducible results. Cleveland. 4) imparts high concentrated compressive forces with high impact stresses. Among the three standard methods. For almost two decades ASTM Test C 418 remained the only specified standard for testing concrete resistance to abrasion. leading to the selection of three abrasion machines and their inclusion in one ASTM standard. concrete stilling basins. with a depth micrometer. After every 15 min. Sliding and scuffing is accomplished by rotating steel disks in conjunction with abrasive grit. A supply of 60 mesh silica carbide abrasive is fed to the disks at a rate of 4 to 6 g/min. . ASTM Test for Abrasion Resistance of Horizontal Concrete Surfaces (C 779) covers three testing procedures: (a) the revolving disk machine. The disk machine was redesigned by Master Builders Company. 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 which became exposed as the depth of wear increased. The dressing wheel machine is not Copyright by ASTM Int'l (all rights reserved). and is essentially patterned after a machine developed by the National Bureau of Standards. Davis and Troxell [31] report the depth of wear for periods of 30 to 60 rain to be about the same for ordinary slabs as for heavy duty concrete surfaces. All three machines are portable and adaptable for laboratory and in-place field abrasion testing. In principle the dressing wheel follows the design of a machine described in the Corps of Engineers Specification CRD C 52 and was modified by the Kalman Floor Company. spillways. tunnels. The results of these comparative programs established such parameters as severity and reproducibility. (b) the dressing wheel.Y.LANE ON ABRASION RESISTANCE 339 water flowing at low to medium velocities. The revolving disk machine (Fig. In contrast to the disks the dressing wheel machine (Fig. N. etc. From 1964 through 1971. No high compressive stresses. Wear is measured after 30 and 60 min. and (c) the ball bearing machine. structures thus affected include piers. The smooth. White Plains. fracture. Subcommittee C09. The characteristics and applications of each machine are discussed briefly. respectively. Ohio.03. hardeners. Other applications of this test are relevant to the determination of the effectiveness of surface treatments. 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. However. The coeffiCopyright by ASTM Int'l (all rights reserved). Yet approximately equal depths of wear are obtained from both machines for the same test period when hard troweled finished floors are tested. 5). On ordinary finished concrete slabs the dressing wheels produce a depth of wear more than double that obtained with the disk machine for the same test duration. 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 stone and mortar which are abraded more quickly (Fig. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. unlike the steel disk machine in appearance except for three sets of seven dressing wheels mounted on horizontal shafts which take the place of the three rotating steel disks. no abrasive material is employed with this machine. . No further reproductions authorized. Initial and intermediate measurements of the test path are taken with a depth micrometer. 2--Revolving d&k machine.340 TESTS AND PROPERTIES OF CONCRETE FIG. 2 mm Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. During the test. and high speed constitutes the abrasive action of the ball bearing machine (Fig. and cutting action of steel wheels or the effect of resilient wheels with embedded nails or stones. pounding. cient of variation established by the Berkeley study for slabs abraded with the dressing wheel machine is several times as great as that for the revolving disk machine. Abrasion of concrete induced by the dressing wheel machine closely simulates the rolling. Repeated "dynamic" loading through strong impact. the machine operates on the principle of a series of eight ball bearings rotating under load at a speed of 1000 rpm and using water as a cutting aid. compressive forces. 6). Designed by Baker [3]. 3--Rotating disk after 120 rain of abrasion. No further reproductions authorized. rolling.LANE ON ABRASION RESISTANCE 341 FIG. ." Readings are continued for a total of 1200 s or until a maximum depth of 3. wear readings are taken every 50 s with a dial micrometer mounted directly to the supporting shaft allowing readings "on the fly. These results are essentially concurrent with a parallel study conducted in the PCA laboratories [32]. (0. . Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) slabs of the same age. No further reproductions authorized.0 m by 92-mm (4 ft by 10 ft by s/a-in. each of a different type of floor construction (see Table 1). Comparison of ASTM Test C 779 Abrasion Test Machines The relative performance of the three abrasion testing machines on four different floor types can be illustrated by the results of a program including abrasion tests on 305 by 305-mm (12 by 12-in.) or 120 mils is reached. Copyright by ASTM Int'l (all rights reserved). 4--Dressing wheel machine. The effects of the ball bearing machine on concrete surfaces indicate abrasive action becomes progressively more severe as the test continues due to soft and hard spots causing the core barrel to bounce to high angular speed (Fig.342 TESTS AND PROPERTIES OF CONCRETE FIG. also producing the highest standard deviation among the three procedures.12 in.2 m by 3. 7).) samples cut from ibur 1. 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. In its abrasive severity the ball bearing machine exceeds both the revolving disk and the dressing wheel. 9 mm (5/8 in. S--Dressing wheel machine wear path.) base slab with 15. No further reproductions authorized.LANE ON ABRASION RESISTANCE FIG.) maximum and final topping of grit size traprock worked into paste monolithic with cast-on iron filings and carbon black worked into paste 76-ram (3-in.) thick low water ratio ordinary commercial hard steel trowel 3 4 Copyright by ASTM Int'l (all rights reserved). hard steel trowel hard steel trowel 343 . TABLE 1--Composition of various concrete floor slabs and finishing applications. 9. Slab Type Finish 1 2 monolithic monolithic with cast-on traprock. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5 mm (3/8 in. 8) with the standard deviation as ordinate versus depth of abrasion as abscissa.344 TESTS AND PROPERTIES OF CONCRETE FIG. the highest deviation is attributed to the ball bearing machine and the lowest deviation--with exception of slab 4--is noted for the revolving disk machine. No further reproductions authorized. or sealing compounds. 10 illustrates possible applications of the four standard procedures for various categories of wear. are shown in Fig. curing. results are plotted (Fig. Characteristically. It is apparent from this graph that the more parallel the plotted graph line is to the abscissa the more reproducible is the test method. For a comparison of the effect of the three test methods on the four slabs. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As a general trend. . Fig. The quality of workmanship is disclosed by the shape of the middle third of the curve and the final third is indicative of the quality of the aggregate. Typical relationships between depth of abrasion versus time. 6--Ball bearing machine. Serving as a general guide. the first third of any curve reflects the influence of paste strength. 9. for any test procedure. This tabulation attempts to correlate severity of in-place wear with the abrasive action Copyright by ASTM Int'l (all rights reserved). 7--Ball bearing machine cutting head and wear path. . However. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it is necessary to bear in mind that there is overlapping in the type of abrasion imparted by these test applications and that a specific service condition may be reproduced by more than one procedure. revolving disks. No further reproductions authorized. through attrition. While all types of wear can be simulated by abrasion machines with a fair degree of realism. impact. and steel balls and failure to replace them regularly as specified. cutting. the rate of wear differs for various types of in-place abrasion and simulated testing is accelerated. of necessity. More severe abrasion due to percussion. loss in test accuracy may develop due to factors in the techniques: (1) rapid wear of dressing wheels. or rolling creates erratic action and is less conducive to reproducibility. for instance. Reproducibility Repeatability of test results will depend largely on the relative uniformity and consistent quality of surface texture and hardness of the concrete.LANE ON ABRASION RESISTANCE 345 FIG. (2) failure to remove dust and loose-abraded material regularly from the Copyright by ASTM Int'l (all rights reserved). In addition. particular with each of the test methods. Experience with testing of abrasion demonstrates relatively good reproducibility over a fairly wide range of concrete surface types and conditions when the abrasive action is moderate. J z IO0 z / / / / F- / J / W W r~ rY rr" .. I 0 O 0 O9 J ILl 80 A B R A S I O N .0 2 <~ I-.. 8--Abrasive effects of the three test methods in A S T M Test C 799 on various floor finishes (see Table 1). MILS SLAB I000 60 J / f / )0 F- / .1 IO0 20 ABRASION.. REVOLVING WHEELS DISKS FIG.0 I-- p / / r~ <~ I-co Z / 0. DEPTH 3 40 OF NO.346 TESTS AND PROPERTIES SLAB NO. No further reproductions authorized. .-~ / t0 / a nr" o Z r~ (Z /J // 1. MILS DEPTH 40 OF 60 80 IO0 A B R A S I O N . Copyright by ASTM Int'l (all rights reserved). 2 I000 co .. MILS SLAB NO.--.0 0.'-.co Ico 1. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.1 20 DEPTH 40 OF 60 80 1. 4 / / )00 / I00 0 l== o I00 co.. /. OF CONCRETE I SLAB IO00 NO.0 / t O I 20 DEPTH 40 OF 60 80 I00 20 A B R A S I O N . MILS LEGEND : ---- BALL BEARING DRESSING .z IO0 0 0 I-- 1. Conclusion Concrete materials are susceptible to deterioration due to abrasive action of environmental and man-made factors. and (6) insufficient number of wear readings. test surface. (2) evaluate specific effects of variables such as concrete-making materials. (5) arbitrary increase in the length of test or flow of sand. 50 60 90 f _J 25 Z 0 II1 50 u_ 0 I 75 n w O [00 FIG. or accept the quality of concrete surfaces. curing or finishing procedures. curing. 9--Typical time. (3) improper selection of a representative test area or specimen. increasing in order with dressing wheels and ball bearings. surface hardeners. the standard deviations shown in Fig. coatings or dust-coating materials. depth (abrasion) curves. (4) differences in age levels of concrete at which test results are compared. and finishing procedures are the basic requirements applying to any concrete subjected to abrasion from wind or water-borne particles or vehicular traffic on floors and pavements. In addition. 8 indicate the lowest coefficient of variation is obtained with the revolving disk method. Effects of variables on reduced wear resistance of concrete have proved to be cumulative which may explain why only certain portions of a concrete surface may fail in resisting abrasion while the remainder gives satisfactory performance. No further reproductions authorized. intrinsic conditions related to properties of concrete and construction techniques contribute to the reduction in wear resistance.LANE ON ABRASION RESISTANCE 347 TIME. M[N. predict. . Proper mixture design and selection of concrete-making materials. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Abrasion testing of concrete in-place or in the laboratory according to ASTM standard procedures will serve to (1) evaluate. Excluding the above variables. (3) compare various types of Copyright by ASTM Int'l (all rights reserved). -'" ETC. \\</. / IiEAk:Y STEEL AND TRAC!I VEIIICLES TIRE CtU\INS HEi\V~" RACKS. . ]ETC. - FIG. No further reproductions authorized.348 TESTS AND PROPERTIES OF CONCRETE ASTH C 779 PROCEDURE ~fPE OF D~AR ABRASIVE EROSION IMPACT EROSION CAVITATION (HYDRAULIC & WIND BLOWN) LIGHT & Dff[DILrM ]~AFFIC HEAVY TIRE AND STEEL ~qiEEL TRAFFIC MOVING OF >FO. the absence of standard criteria for wear of concrete surfaces prevents specifications of quality in terms of abrasion resistance. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Until recently the problem of evaluating the wear resistance of concrete was compounded by the absence of standard testing procedures and machines.~ /. lO--Applications of test procedures. The lack of sufficiently large populations of test data based on the proper methodology in the past has hampered the preparation of precision statements for these procedures. and (4) verify products or systems to meet specifications. RACKS. At present. concrete surfaces under simulated abrasion conditions. ASTM Tests C 418 and C 779 offer four distinct procedures which simulate various degrees of severity and types of abrasive or erosive forces to determine depth of wear or the loss of volume of the abraded material. Future concern of research dealing with procedures for testing abrasion resistance should be with the fact that these allow only an evaluation of a measure of relative quality without any defined acceptable or unacceptable limits. Copyright by ASTM Int'l (all rights reserved). Peoria. 1955." Agriculture Research Service. and Effects of the Air Void System in Concrete. 57.. 1956." Materials and Research Department. and Mather. 24. pp. 1966. [8] Scripture. [9] Abrams. Abrasion of Concrete. "Effect of Aggregate Quality on Resistance of Concrete to Abrasion. D. 1013. "Slab Construction Practices Compared by Wear Tests. H. American Concrete Institute. 1947. R. Vol. Proceedings. 1958. 1973. 864. Vol. Vol. [10] Jackson. W. Copyright by ASTM Int'l (all rights reserved). p. Vol. "Floor Aggregates. 2. [17] U. [24] Fowler." Proceedings. H. No further reproductions authorized. 141-172. Houston. Benedict.. Vol. 1305-1392. [3] Witte and Backstrom. [20] Mayberry. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Erosion of Concrete by Cavitation and Solids in Flowing Water. 114-1.. RP 1252. D. "Wear Test of Concrete. p. 522. J." Proceedings. [5] Mielenz. "The Effect of Various Surface Treatments Using Magnesium and Zinc Fluorosilicate Crystals on Abrasion Resistance of Concrete Surfaces. ASTM STP 169. [12] Kennedy. 51." Proceedings. Part II. C 445. F. No. W. Journal. L. and Paul. C 819. [7] Schuman.." Journal. F.. L. K. L. et al. [6] Smith. [14] ACI Committee 302. "Wear Resistance of Industrial Floors of Portland Cement Concrete. 1967. A. American Concrete Institute. J. Maine. 24. 1954. 55.. Proceedings. Evolution. pp. California Division of Highways. 21. pp. J. Feb. 1935. M&R 250908-1.. [13] ACI Committee 201. ASTM STP 205. No. L. 1971. "Accelerated Wear Tests of Concrete Pavements. B. . Dec. Bureau of Reclamation. Report No. Dec.S. A. National Bureau of Standards. Blake. Journal. Dean. and Tucker.S. 1957. 63. American Concrete Institute." Research Paper No. Bureau of Reclamation. p. 1921. 3. pp. 12. 1951. 1-4. [21] Portland Cement Association. July 1973.. p." Journal. [16] Ytterberg." Concrete Laboratory Report. and Bryant. Vol. Detroit. No. and Pauls. [11] Pogany. p. "Wear Test on Concrete Using the German Standard Method of Test and Machine." Concrete Laboratory Report No. U. University of Texas. 50. "Correlation Between Laboratory Accelerated Freezing and Thawing and Weathering at Treat Island. Proceedings.. American Concrete Institute.. American Concrete Institute. W. 1969. Abrasion Resistance. 163-174. Title 50-18. American Society of Civil Engineers.S. 12. T.. (ACI 302-69). American Society for Testing and Materials. No. "Linseed Oil Emulsion for Bridge Decks. J." Zement. Vol.LANE ON ABRASION RESISTANCE 349 References [l] ACI Committee 210. C. "Surface Treatments tor Concrete Floors.. [15] Fentress." Proceedings. H." Chapter 4. D. C-342. D. Department of Agriculture.. T. 27. Bureau of Reclamation. E. M. Jan.. "Polymer Impregnated Concrete for Highway Application.. "Determining the Abrasion Resistance of Concrete From That of the Mortar and Aggregates." Cement and Concrete. American Concrete Institute. Austin. 1952.." Laboratory Report No." Proceedings. Feb.S. 1971. Vol. American Society for Testing and Materials. R. D. [19] Spellman. and Prior." Concrete Intbrmation ST-37. L. Sept. [18] Sawyer. 52. "A Portable Apparatus for Determining the Relative Wear Resistance of Concrete Floors.. 1143-1153. [22] U. 59. Vol. Vol. S. and Ames.. American Society tbr Testing and Materials. E. American Concrete Institute. Recommended Practice for Concrete Floor and Slab Construction. 1956. I11. F. W. Erosion Resistance of Concrete in Hydraulic Structures (ACI 210-55). 1924." ACI 515. 1962. [4] Kennedy. [2] U. [23] ACI "Guide for the Protection of Concrete Against Chemical Attack by Means of Coatings and Other Corrosion-Resistant Materials. "Factors Affecting Durability of Concrete Surfaces.." Proceedings. American Society tor Testing and Materials. No. Center for Highway Research. Civil Engineering." Journal. "Some Properties Affecting the Abrasion Resistance of Air-Entrained Concrete.. Significance of Tests and Properties of Concrete and Concrete-Making Materials. E. "Durability of Concrete in Service. American Concrete Institute. Vol. Detroit. Jr. 1954. T. 1141. "Origin. Proceedings. "Erosion Resistance Tests of Concrete and Protective Coatings. BRPD-3-7. R." Research Report No. " Proceedings.. A. Vol. C. [30] Rushing." Washington State University. T. July 1970. Feb. Engineers. Skokie. C. 1970... E. p." Research and Development Laboratories. "Apparatus for Testing the Hardness of Materials.. 1925. No further reproductions authorized. p." Chemical Abstracts. June 1968. and Brinkerhoff. 1338. . R.. C. B. 1944. H. [26} Dikeon. "The Effect of Studded Tires on Different Pavement and Surface Texture. I11. 5750. Jan. Bureau of Reclamation. Portland Cement Association. [28] Guttman. 1936... G. March 1970.. P. H.. Vol. H." U. 38." Chem&alAbstracts. San Francisco. "Concrete Wear Study. and Troxell. J. Copyright by ASTM Int'l (all rights reserved). unpublished report. R. H. H. [33] Baker. [29] Haris. "Radiation Polymerization of Monomers. p. Oct.350 TESTS AND PROPERTIES OF CONCRETE {25] Krukar. "Cooperative Study on Methods of Testing for Abrasion of Concrete Floor Surfaces. "Description and Development of a Bearing Abrasion Test Machine.S. unpublished report. "Abrasion Tests on Concrete. and Cook. Inc. Highway Research Board.. J. unpublished report. 127. M." Chin and Hensolt. 1973. 1964. Berkeley. Louisiana Department of Highways. Sun Apr 6 21:43:33 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Report PB 183410. [31] Davis. [32] Klieger. E. [27] Scofield. 30. "Significance of Talbot Jones Rattler as Test for Concrete in Road Slabs.. "Methods of Testing Concrete for Resistance to Abrasion-Cooperative Testing Program. D." University of California. Perhaps the most comprehensive treatment of the influence of aggregates on resistance to freezing and thawing is that of Larson et al [7]. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. The report of ACI Committee 201 on Durability of Concrete [10] contains valuable recommendations for production of concrete to provide resistance to the various destructive processes encountered in field exposures. 2The italic numbers in brackets refer to the list of referencesappended to this paper. Virginia Highway and Transportation Research 'Council. A monograph by Woods [5] presents a comprehensive picture of durability. and one by Cordon [6] discusses freezing and thawing in detail.org . Charlottesville. Sun Apr 6 21:43:34 EDT 2014 351 Downloaded/printed by Universidade do Gois pursuant Agreement. An extensive annotated bibliography on concrete durability published by the Highway Research Board (HRB) in 1957 [8] with a supplement in 1966 [9] contains 534 citations. The published literature on the subject is extensive and only a somewhat superficial treatment can be given in a brief paper. In the absence of contact with aggressive fluids or incorporation of aggregates susceptible to detrimental expansion by reaction with alkalies in cement.astm. The reader should consult the similar papers in earlier editions of this special technical publication by Scholer [1.determined by its ability to withstand the effects of freezing and thawing in the presence of moisture. 1978 H o w a r d Newlon. Va. and Arni [4]. the resistance of concrete to weathering is. The ACI Symposium [11] on durability of concrete contains 17 papers on various theoretical and operational aspects of producing durable concrete. 3Attack by aggressive fluids and cement aggregate reactions are treated elsewhere in this publication. Jr. Unfortunately this bibliography has not been updated. 2 Powers [3].2]. 3 The testing of concrete for resistance to freezing and thawing had its genesis in similar tests on building stones reported as early as 1837 by Vicat 1Associate head. 22903.STP169B-EB/Dec. Copyright9 1978tobyLicense ASTM International www. t Chapter 23 Resistance to Weathering Introduction The purpose of this paper is to discuss the significance of currently standardized testing procedures for evaluating the resistance of concrete to weathering under service conditions. With the recognition that tests conducted in a variety of freezers designed for other purposes naturally gave variable results. several agencies such as the U. Of the currently standardized methods. ASTM Recommended Practice for Evaluation of Frost Resistance of Coarse Aggregates in Air-Entrained Concrete by Critical Dilation Procedures (C 682) describes the use of ASTM Test C 671 to evaluate the influence of coarse aggregates on the resistance of concrete to freezing and thawing. These efforts marked the beginning of a systematic quest for standardization and an understanding of factors influencing the resistance of concrete to freezing and thawing. Two older freezing and thawing methods have been discontinued. Portland Cement Association. ASTM Test for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (C 672) provides a procedure for evaluating the effect of deicing chemicals on concrete and the effectiveness of modifications of the concrete or of surface coatings in mitigating Copyright by ASTM Int'l (all rights reserved). but when freezing equipment became commercially available for food processing in the 1930s the reporting of such testing increased. It was only natural that the advent of "artificial stone" in the form of portland cement concrete would result in corresponding evaluations. several petrographic procedures are standardized that provide invaluable information for predicting the resistance of concrete to freezing and thawing and for interpreting the results of exposure in either the laboratory or under field conditions. Bureau of Public Roads. and Procedure B in which the specimens freeze in air and thaw in water.352 TESTS AND PROPERTIES OF CONCRETE [12]. is a consolidation of two earlier methods (ASTM C 290 and C 291) and provides for two procedures: Procedure A in which both freezing and thawing occurs with the specimens surrounded by water. Corps of Engineers. ASTM Test for Critical Dilation of Concrete Specimens Subjected to Freezing (C 671) employs a single cycle of cooling through the freezing point with specimens that are continuously wet. Few published tests from the nineteenth century survive. Bureau of Reclamation. Descriptions of some of this equipment will be found in reports by the agencies [3-8]. ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666) covers the exposure of specimens to cyclic freezing and thawing. This test was developed to accommodate certain theoretical criticisms of the cyclic method. . the most widely used of those available.S. The presently standardized methods as well as those discontinued have evolved over a period of about 50 years and reflect the inevitable compromise between the need for rapid assessment of resistance to weathering and the difficulty of translating the results from accelerated laboratory testing to the varied conditions encountered in field exposures. No further reproductions authorized. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and the National Sand and Gravel Association constructed specialized equipment for testing concrete by freezing and thawing. This test. In addition. There are currently three standard test methods and one recommended practice under the jurisdiction of ASTM Committee C-9 on Concrete and Concrete Aggregates intended to aid in evaluating the resistance of concrete to freezing and thawing. " In 1856 Joseph Henry reported testing by 50 cycles of freezing and thawing. the sulfate of soda. The first two cooperative test series were conducted betbre any methods were standardized. various tests of stone. were dropped because of lack of use. The 1944 series of tests used concrete specimens.S. Two of the initially approved standards were discontinued in 1971. accelerated laboratory testing greatly increased. In 1951 ASTM Committee C-9 on Concrete and Concrete Aggregates formed Subcommittee III-O on Resistance to Weathering (presently C09.NEWLON ON RESISTANCE TO WEATHERING 353 the detrimental influence of such chemicals. samples of marble used in the extension of the U. concrete. in his famous "Treatise on Calcareous Mortars and Cements. The reader should consult the cited references for additional information on these subjects. . While an extensive discussion of the theory and historical development of freezing and thawing tests is beyond the scope of this summary. While much is still to be learned. Both of these series emphasized the necessity for carefully regulating the methods of making and curing the specimens. These methods. an extensive body of knowledge has been developed that permits evaluations of concrete to aid in minimizing premature deteriorations from environmental factors. No further reproductions authorized. which provided for one cycle every 24 h.03. In 1936 [23]. (ASTM Test for Resistance of Concrete Specimens to Slow Freezing and Thawing in Water or Brine (C 292). the degree of saturation of the aggregates at the time of mixing the concrete. Vicat. In 1928 Grun [21] in Europe and Scholer [22] in the United States reported results from accelerated freezing and thawing of concrete in the laboratory. Following Scholer's initial paper.15) with the major responsibility for proposing methods for evaluating the resistance to freezing and thawing of aggregates in concrete Copyright by ASTM Int'l (all rights reserved). Capitol [20]. that of an easily crystallizable salt. a brief treatment is necessary. brick. the air content of the specimens. and ASTM Test for Resistance of Concrete Specimens to Slow Freezing in Air and Thawing in Water (C 310)). and again in 1959 [25] the HRB Committee on Durability of Concrete reported results of cooperative freezing and thawing tests designed to identify factors that influence resistance of concrete to freezing and thawing. Historical Evolution As early as 1837. 1944 [24]. and other porous materials were reported. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The 1936 series concentrated upon the influence of cement using mortar prisms incorporating ten commercial cements. These tests were conducted "by substituting for the expansive force of the congealing water. During the two decades before and those after the turn of the twentieth century. and the degree of saturation of the concrete at the time of freezing." reported the results from experiments by Brard [19] to distinguish the building stones that were injured by frost from those that were not [12]. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. one with good quality coarse aggregate and deficient air entrainment. Only the slow freezing in air and thawing in water method (ASTM Test 310) was able to discriminate adequately between concretes of low durability. No further reproductions authorized. These methods were largely representative of the methods and procedures then in use by the membership of Subcommittee III-O. 2. 13 laboratories participated using three conerete formulations representing a concrete with good quality coarse aggregate and adequate air entrainment." One of the difficulties with the four methods which was emphasized especially by the HRB cooperative programs was poor repeatability and reproducibility of results within and between laboratories. The general characteristics of the methods are reflected in their titles: ASTM Test for Resistance of Concrete Specimens to Rapid Freezing and Thawing in Water (C 290). The two slow tests were adopted to cover tests usually conducted in conventional freezers with manual transfer of specimens between the freezing chamber and thawing tank. Arni [4] summarized the general conclusions from the 1944 and 1954 test series as follows: "1.(C 310). These methods were dropped in 1971 since neither was in general use nor required by any other ASTM specification. soon after standardization of the four methods.354 TESTS AND PROPERTIES OF CONCRETE and standardizing the methods of tests. 3. reported in 1959 [25]. 4. In 1971 the two rapid tests (ASTM C 290 and C 291) were combined as two procedures (A and B) in a single test (ASTM C 666). In these tests deterioration of specimens is evaluated by the resonant frequency method (ASTM Test for Fundamental Transverse Longitudinal and Torsional Frequencies of Concrete Specimens (C 215)). Good Copyright by ASTM Int'l (all rights reserved). Rapid freezing and thawing in water (ASTM Test C 290) appeared to do the best job of detecting a difference between concretes both of which had high durability. . produced failure in fewer cycles. initiated in 1954. in 1952 and 1953 ASTM approved four tentative test methods that later became standards. ASTM Test for Resistance of Concrete to Slow Freezing and Thawing in Water or Brine (C 292). Rapid freezing was more severe than slow freezing when done in air but not when done in water. In the third cooperative test series. the four methods tended to rate different concretes in the same order of durability when there was a significant difference. and ASTM Test for Resistance of Concrete Specimens to Slow Freezing in Air and Thawing in Water . In general. Drawing heavily upon the results of the HRB cooperative test series and the experience of several laboratories that had developed specialized equipment for conducting freezing and thawing tests. Methods involving freezing in water were more severe. 5. that is. ASTM Test for Resistance of Concrete Specimens to Rapid Freezing in Air and Thawing in Water (C 291). than were those involving freezing in air. and one with poor quality coarse aggregate and adequate air entrainment. led in 1971 to standardization of ASTM Test C 672. The literature survey prepared by Larson et al as part of the research is a particularly valuable reference on all aspects of freezing and thawing studies related to aggregates [7]. Of the methods. As an outgrowth of this work. Critical saturation was defined when specimens exposed to continuous soaking and subjected to a cycle of cooling through the freezing point exhibited dilation greater than a specified value. as discussed later. No further reproductions authorized.NEWLON ON RESISTANCE TO WEATHERING 355 reproducibility generally was obtained only for concretes which were very high or very low in durability. particularly by Powers [27]. As noted earlier. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. in 1971 ASTM Test C 671 was approved along with ASTM Recommended Practice C 682. The method uses blocks fabricated to permit ponding of water on surfaces that are subjected to freezing and thawing in the presence of various deicing agents. However. in an unpublished report the subcommittee did outline procedures for using ASTM Test C 290 if evaluations of coarse aggregates were required [26]. In 1961 the subcommittee reported t h a t standardization of such tests was not warranted because of the high levels of variability associated with the existing methods. but the essential elements of the method are those that have been used for more than a century. Copyright by ASTM Int'l (all rights reserved). a wide spread in results was obtained. According to Stark [30] aggregates susceptible to causing distress in concrete pavements can be identified by freezing and thawing of concrete in water at a rate of two cycles per day. This method was first used by the California Department of Highways [28] and later was refined and extensively evaluated by Larson and his co-workers [29]. Lack of a standardized test method for evaluating resistance to freezing and thawing of coarse aggregates in concrete coupled with theoretically based criticisms of the cyclic methods. led to the development of methods designed to determine the length of time required for an aggregate to become critically saturated in concrete. More recently. agencies studying "D-cracking" of concrete have generally found a modification of the older procedure (ASTM Test C 666) to be useful in identifying coarse aggregates susceptible to this type of deterioration. particularly on highway and bridge deck pavements. Concern with surface mortar deterioration or deicer scaling. For concretes in the middle range. ASTM Test C 666 continues to be the most widely used. . While the variabilities are large in the middle range they are amenable to establishing a precision statement which has been incorporated in ASTM Test C 666 as discussed later. Subcommittee III-O was formed initially in 1951 wih the primary mission of developing freezing and thawing tests to be applied to the evaluation of coarse aggregates. which provides guidelines for applying ASTM Test C 671 to the evaluation of coarse aggregates. Specialized equipment is commercially available for conducting the tests under controlled conditions. which combined features of methods that had been developed and used by various agencies for a number of years. hence the designation "osmotic pressure hypothesis. Powers' initial studies suggested that the hypothesis advanced by Taber [34] to explain frost heaving of soils did not apply to mature concrete. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. are required to account for the behavior of concrete subjected to freezing and thawing. By this hypothesis." Powers. and that this process was reproduced artificially in the laboratory environment. This flow generates stress somewhat like osmotic pressures. Since the resistance to flow at a given rate is proportional to the length of the flow path. but by the segregation of ice into layers which enlarge as unfrozen water is drawn toward the region of freezing rather than forced away from it. the air bubbles were conceived as spaces into which the excess water produced by freezing could be expelled without generating destructive pressures. with some modification.356 TESTS AND PROPERTIES OF CONCRETE Theoretical Considerations Cyclic freezing and thawing tests were developed on a pragmatic rather than a theoretical basis. in a recent summary of his and other research [37]. Powers and his co-workers. when the flow path exceeds a critical length. Studies by Verbeck and Landgren [35] as well as those of Powers [36] make clear that the paste and aggregate should be considered separately when explaining the resistance of concrete to freezing and thawing. the stress is produced not by hydraulic pressure. the pressure exceeds the strength of the paste. As the water freezes. The theory was amplified in 1948 [32] to explain the beneficial influence of entrained air. According to this theory. This concept is called the hydraulic pressure theory. The temperature at which water freezes in various pores within the paste decreases with the size of the pore so that even if the concrete is at a uniform temperature throughout. the water will be at various stages of conversion to ice. a value that was approximately the same as that suggested by Mielenz and his co-workers from experimental studies [33]. the solution in the pore becomes more concentrated. The existence of solutions of various concentrations in the pores of the paste causes unfrozen water to move to the site of freezing in order to lower the concentration made higher at the freezing site than the more dilute solution of the unfrozen water. This is because the paste not only may become critically saturated by moisture from external sources but also must withstand pressure generated by water expelled from the aggregate particles during freezing. the pressure being due to the viscous resistance of such flow through the permeable structure of the concrete. advanced the hypothesis that the destructive stress is produced by the flow of displaced water away from the region of freezing. concludes that in general all three of the theories. It was assumed that the destruction resulted from the 9 percent volume expansion accompanying the conversion of water to ice. Powers calculated a critical thickness of the order of 0.25 mm (0. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved).). .01 in. Such flow would occur when the water content exceeds the critical saturation point. from their comprehensive study of the structure of cement paste in 1945 [31]. and between 356 and 406 mm (14 to 16 in. For Procedure A.4 to --17. flow of water from areas of lower to those of higher concentrations generate stresses such as were described earlier. while for Procedure B not less than 20 percent of the time is used for thawing. while in Procedure B the specimens freeze in air and thaw in water. the thawing portion is not less than 25 percent of the total cycles. The conventionally accepted term of testing is 300 cycles.8~ (40 to 0~ and raising it from --17. The method is designated as "rapid" because it permits alternately lowering the temperature of specimens from 4.1~ (37 to 3~ shall be not less than one half of the length of the cooling period. The specimens are normally prisms not less than 76 mm (3 in. For Procedure A both freezing and thawing occur with the specimens surrounded by water. Rapid Freezing and Thawing Tests In 1971 ASTM Tests C 290 and C 291 were combined as Procedures A and B in ASTM Test C 666.8~ (3 to 37~ shall be not less than one half of the length of the heating period. The requirements for Procedure A are met by confining the specimen and surrounding water in a suitable container. found that deterioration was greater for intermediate concentrations of deicing chemical (3 percent to 4 percent) than for lower or higher concentrations (to 16 percent). Copyright by ASTM Int'l (all rights reserved). and the time required for the temperature at the center of any single specimen to be raised from --16." or surface mortar deterioration. which can be obtained in 25 to 50 days.) long.8 to 4. Browne and Cady [38] have recently summarized these theories and their own experiments.) in width and depth. Thus a minimum of 6 and a maximum of 12 complete cycles may be achieved during a 24-h period. scaling results from freezing and thawing. the mechanism is probably most influenced by concentration gradients.4~ (0 to 40~ in not less than 2 nor more than 4 h. For Procedure A each specimen is surrounded by approximately 3 mm (1/8 in. . Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Verbeck and Klieger [39]. while in Procedure B the specimen is surrounded completely by air during the freezing phase of the cycle and by water during the thawing phase. in work confirmed by others. Various theories have been advanced to explain the increased severity of the damage as compared with freezing and thawing in water.1 to 2. Such findings can be explained by generation of osmotic-like pressures accompanying the movement of water between areas of varying concentrations. Except where the concentration of deicing chemicals is high enough to cause chemical attack. No further reproductions authorized.) of water during the freezing and thawing cycles. The time required for the temperature at the center of any single specimen to be reduced from 2.8 to --16. localized failures of the exposed surfaces occur that is called "scaling. In addition to the lowering of the freezing temperature that accompanies increased deicer concentration.NEWLON ON RESISTANCE TO WEATHERING 357 When freezing and thawing takes place in the presence of deicing chemica]s.) nor more than 137 mm (5 in. Although definitive answers have not been obtained. and M = specified number of cycles at which the exposure is to be terminated. The durability factor is calculated as DF = PN/M where D F -----durability factor of the specimen. In recent years. While some aspects of these machines have been subjected to criticism. -----relative dynamic modulus of elasticity. P = relative dynamic modulus of elasticity at N cycles.358 TESTS AND PROPERTIES OF CONCRETE During the early years of testing by freezing and thawing. While this assumption is not true in many cases because of disintegration. after c cycles of freezing and thawing.8~ (42 +_ 5~ Calculation of Pc assumes that the weight and dimensions of the specimens remain constant throughout the test. Copyright by ASTM Int'l (all rights reserved). The fundamental transverse frequencies are determined at intervals not exceeding 36 cycles of exposure and used to calculate the relative dynamic modulus of elasticity P~ = (hi2) \--~--/ • 100 where P.6 +__ 2. whichever is less. Custom-built freezers can hold 100 specimens. n = fundamental transverse frequency at 0 cycles of freezing and thawing. in percent. Deterioration of specimens is determined by the resonant frequency method. . the test is usually used to make comparisons between the relative dynamic moduli of specimens and Pc is adequate for the purpose. several types of equipment have become available commercially that meet the requirements for ASTM Test C 666. percent.. laboratories constructed specialized equipment. N = number of cycles at which P reaches the specified minimum value for discontinuing the test or the specified number of cycles at which the exposure is to be terminated. ASTM Test C 215. The fundamental transverse frequency is determined with the specimens at a temperature of 5. they meet the needs for rapid testing within practical limits. and nt = fundamental transverse frequency after c cycles of freezing and thawing. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. These handle from 20 to 60 specimens. but is consistent with recently published precision values. In both admixture specifications. with appropriate recognition of the variability of the test method. The value of 80 was established before levels of precision were established for ASTM Test C 666. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.NEWLON ON RESISTANCE TO WEATHERING 359 Because of the danger of damage to specimen containers and other parts of the equipment. Neither procedure is intended to provide a quantitative measure of the length of service that may be expected from a specific type of concrete. the performance requirement is stated in terms of a "relative durability factor" calculated as DF (or D F O = P N / 3 0 0 and RDF = (DF/DFO • 100 where durability factor of the concrete containing the admixture under test." Procedure A is currently required in three ASTM specifications. ASTM Specification for Air-Entraining Admixtures for Concrete (C 260). = durability factor of the concrete containing a reference admixture (or in the case of ASTM Specification C 494. -----number of cycles at which P reaches 60 percent. The scope of ASTM Test C 666 states that "both procedures are intended for use in determining the effects of variations in the properties of concrete on the resistance of the concrete to the freezing and thawing cycles specified in the particular procedures. namely. testing usually is terminated when the "relative dynamic modulus of elasticity falls below 50 percent. and ASTM Specification for Lightweight Aggregates for Structural Concrete (C 330). and = relative durability factor. . The value of 80 is not intended to permit poorer performance than the reference concrete. = relative dynamic modulus of elasticity in percent of the dynamic modulus of elasticity at zero cycles (values of P will be 60 or greater since the test is to be terminated when P falls below 60 percent). but rather to assure the same level of performance. One criticism of rapid freezing and thawing tests has been variability of the Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. or 300 if P does not reach 60 percent prior to the end of the test (300 cycles). DF = DF1 P N RDF Both ASTM Specifications C 260 and C 494 require that the relative durability factor of the concrete containing the admixture under test be at least 80 when compared with the reference concrete. ASTM Specification for Chemical Admixtures for Concrete (C 494). only an approved airentraining admixture). 2 17.6 0. No further reproductions authorized.4 5.8 9.4 6. . Procedure A Range of Average Durability Factor Standard Deviation (1S) 0 to 5 5 to 10 10 to 20 20 to 30 30 to 50 50 to 70 70 to 80 80 to 90 90 to 95 Above 95 0.8 4. As noted.Within-laboratory precisions for averages of 6 beams tested in accordance with A S T M Standard C 666.6 2.9 1.8 Acceptable Range (D2S) 1.15 reviewed the data from major published studies. as described by Arni [40]. The specification states that "in the absence of a proven record of satisfactory durability in structural concrete. lightweight aggregates may be required to pass a concrete freezing and thawing test satisfactory to the purchaser. cedures A and B.7 14.7 6.3 6." ASTM Test C 666 is listed as a method of sampling and testing in ASTM Specification for Concrete Aggregates (C 33). but is not mentioned elsewhere in the document.3 0.4 1.6 1.0 3.4 12.5 2.2 7.8 6. the primary measure of deterioration is the relative dynamic Copyright by ASTM Int'l (all rights reserved). Statistical analyses of these data.9 0. ASTM Subcommittee C09.2 6.4 4.3 Procedure B Standard Deviation (1S) 0.3 8. In response to the requirement by ASTM for precision statements in all test methods.2 4.8 23.3 4. In 1976 a precision statement was added to ASTM Test C 666 for expected within batch precision for both Pro. Values for standard deviation (1S) and acceptable range (D2S) as defined by ASTM Recommended Practice for Preparing Precision Statements for Test Methods for Construction Materials (C 670) are given in Tables 2 and 3 of ASTM Test C 666 for ranges of average durability factor in ten increments and numbers of specimens averaged from 2 through 6. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.3 0.4 3.2 19. While Procedure A of ASTM Test C 666 is specified in ASTM Specification C 330. showed that the variability was primarily a function of the level of durability factor of the concrete for the ranges of N and P normally used.7 3.4 Acceptable Range (D2S) 0. no values are given.3 These values confirm the long recognized facts that the variability is less for very good or very poor concrete than for concretes of intermediate durability and that results from Procedure A are somewhat less variable than those obtained from Procedure B.1 13. TABLE 1-.7 7.4 1.7 18.360 TESTS AND PROPERTIES OF CONCRETE results both within and between laboratories.03. Values for 6 specimens (as required by ASTM Specifications C 260 and C 494) are given in Table 1.7 2.5 2. One important influence that is not covered in ASTM Test C 666 is the effect of the container used to hold the specimen during testing with Procedure A. and the manner and extent to which the properties measured are related to freezing-and-thawing damage. can cause excessive damage to rigid metal containers.NEWLON ON RESISTANCE TO WEATHERING 361 modulus calculated from determinations of resonant transverse frequency. A note states that "for Procedure A. No further reproductions authorized. are matters of disagreement. the particular measure used often depends on the philosophy of the laboratory using it and on the particular purpose for which the tests are being made. Length change is based upon the fact that internal damage is accompanied by expansion rather than contraction during cooling or by a permanent dilation after a freezing and thawing cycle. particularly in equipment that uses air rather than a liquid as the heat transfer medium. or corners." This situation is particularly noticeable when the specimens are exposed with the long dimension vertical. in containers. especially under natural conditions. Various adjustments have been made to mitigate this problem. while weight loss reflects primarily surface mortar deterioration. ASTM Subcommittee C09. and possibly to the specimens therein. which presently requires weight and resonant frequency determinations.15 is considering adding requirements for length change measurements to ASTM Test C 666. Thus. Ice forms quickly on the open top rather than uniformly along the long dimension of the container. or inclusion of a rubber ball in the bottom of containers to absorb the pres- Copyright by ASTM Int'l (all rights reserved). including exposure of the specimens in containers with the long dimensions horizontal to provide a larger open area. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as discussed by Powers [27]. Experience has indicated that ice or water pressure. inclusion of flexible windows. .03. Either weight loss due to sloughing or reduction in resonant frequency may occur without accompanying length change. Two other characteristics that are commonly used are weight loss and length change. The question of which measure of deterioration is best to use is complicated by the facts that the different available tests measure different things. Results of tests during which bulging or other distortion of containers occurs should be interpreted with caution. Pressures from continued conversion of water between the specimen and container cannot be relived with consequent bulging of the container. this requirement contemplates that the specimen and the surrounding water will be kept in a suitable container while in the freezing-and-thawing apparatus. during freezing tests. Determination of reductions in tensile or compressive strength have been used infrequently because such testing is destructive. Weight loss measures loss of material or sloughing from the surface of the specimens. Resonant frequency and expansion reflect internal disruptions that are caused by unsound aggregates or deficient air void characteristics. and in Procedure A weight loss often occurs without a reduction in resonant frequency or expansion. Because the testing is initiated at a fixed age. That the degree of restraint offered by the container influences the number of cycles required to reach a specified level of relative dynamic modulus is clear as shown by Cook [41]. Experience with testing of specimens from hardened concrete is limited. Buck et al [42] reported tests indicating that because of its relationship with the amount of freezable water. They cited earlier work by Klieger [43]. But accommodating the many possible variations of saturation that might be encountered is impractical so that the most consistently reproducible condition is that of continued moist curing. The mixing procedures referenced in ASTM Method for Making and Curing Concrete Test Specimens in the Laboratory (C 192) require that coarse aggregates be immersed for 24 h prior to mixing.362 TESTS AND PROPERTIES OF CONCRETE sures. since it is difficult to resaturate concrete that has undergone some drying. There is not a great body of data on the influence on resistance to freezing and thawing of strength at the time that exposure begins. All of these have been reported to overcome the problem by some and not by others. who found that the number of cycles necessary to reach a given level of durability factor was increased dramatically when the specimens were tested in rubber containers as compared with containers made of steel. . Copyright by ASTM Int'l (all rights reserved). a given level of maturity (strength) was necessary to provide an acceptable degree of frost resistance as indicated by a durability factor of 50 for concrete containing satisfactory aggregates and entrained air. This influence is minimized when the evaluations are made by comparing concretes made with similar materials as required in ASTM Specifications C 260 and C 494. who reported similar findings in his studies of salt scaling. considerable variation of strength at the time of exposure to freezing and thawing may be encountered with cements of different strength gain characteristics for concrete with sound aggregates and satisfactory air void characteristics. Even a brief period of drying greatly improves resistance to freezing and thawing. Consideration of strength at the time of initial freezing is particularly important in testing concrete made with blended cements and pozzolanic admixtures that gain strength more slowly than concrete without such admixtures. Cyclic freezing and thawing methods were developed and applied only for laboratory mixed concrete until 1975. Another important influence on the results is the degree of saturation of the concrete and the aggregates both at the time of mixing and throughout the course of the testing. ASTM Test C 666 and the specifications citing its use require that testing begin after 14 days of moist curing. Thus the comparatively high degree of internal saturation and the early age at which testing begins result in a relatively severe test when compared with field exposures in which a period of drying normally occurs before exposure to freezing and thawing. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. when they were extended to cores or prisms cut from hardened concrete. No further reproductions authorized. The aggregates judged acceptable by the California procedure would have been rejected by other conventionally accepted criteria. and performance criteria. The method was used to evaluate several aggregates for a major highway construction project. testing and measuring techniques. Highly frost-resistant concrete may never exhibit critical Copyright by ASTM Int'l (all rights reserved). A typical plot of length change versus temperature is shown in Fig.NEWLON ON RESISTANCE TO WEATHERING 363 Dilation Methods In 1955 Powers published a critical review of existing cyclic methods for freezing and thawing tests [27]. . As opposed to a single durability factor. the time to critical saturation could be more readily interpreted for various field exposures. He was particularly critical of what he considered unrealistically high freezing rates of from 6 to 60~ (10 to 100~ as compared with natural cooling rates that seldom exceed 3~ (5~ He also noted the significance of moisture conditioning of aggregates and concretes in test methods which generally provided for only saturated concrete as compared with natural exposures where some seasonal drying is possible. Concrete subject to frost damage should reach some critical saturation level. Critical dilation is defined as a sharp increase (by a factor of 2 or more) between dilations on successive cycles. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5~ (5 ___ 1 ~ During the cooling cycle the specimen is placed in a strain frame to permit measurement of length change. The length of time required to become critically saturated would be compared with the field exposures to be encountered. Prior to critical saturation the length change will proceed along the dashed curve without dilation.7 ___ 9~ (35 ___ 2~ At two-week intervals the specimens are cooled in water-saturated kerosene at a rate of 2. The performance of this concrete has been reported as satisfactory after 15 years of service. He stated that durability was not a measureable property but that expansion occurring during a slow cooling cycle when the concrete or its aggregates became critically saturated was measurable and would provide an indication of potential resistance to damage by freezing and thawing. No further reproductions authorized. 1. This method provides for cylindrical specimens 75 mm (3 in. The California Division of Highways was first to report. in 1961. They developed specimen preparation and conditioning methods. If the period during which freezing would be expected was less than the time to reach critical saturation.) long that are stored in water at 1. In 1971 ASTM Test C 671 was standardized.) in diameter and 150 mm (6 in. then no damage would be expected. He proposed that specimens be prepared and conditioned so as to simulate field conditions and then be subjected to periodic slow rate freezing and storage in water at low temperature between freezing exposures. a practical application of Power's proposed method [28]. The procedures proposed by Powers and the method developed in California were extensively studied and refined by Larson and others [29].8 _ 0. after which it would expand on freezing. In addition to ASTM Test C 671 criterion for critical dilation in terms of increase from one cycle to another. . (c) If the dilation is in the range between 0. the specimen may be regarded as frost resistant. that is.9 Z g 15z -600 T O -800 Z kd -J E" 25 (. dilation. ASTM Recommended Practice for Evaluation of Frost Resistance of Coarse Aggregates in Air-Entrained Concrete by Critical Dilation Procedures (C 682) was also standardized in 1971. (b) If the dilation is 0. largely because of Copyright by ASTM Int'l (all rights reserved). The procedures of ASTM Recommended Practice C 682 are extensive and complex. it will show some limited initial dilation as all moist specimens do. the specimen may be regarded as not frost resistant. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.005 percent ( = 50 millionths) or less.005 percent and 0. Procedures essentially in accordance with ASTM Test C 671 have been used by Buck [44] and he found that a specimen that is frost resistant will now show increasing dilation with continuously decreasing temperature. he suggested that a criterion for critical dilation applicable to results of a single test be as follows: (a) If the dilation is 0. that is. significant storage capacity is required. ASTM Test C 671 and Recommended Practice C 682 have not been used extensively.TESTS AND PROPERTIES OF CONCRETE 364 200 -400 w t.9 Z bJ . but dilation will not continue throughout the cooling. This practice is based largely upon the work of Larson and his co-workers. No further reproductions authorized.J G o ~ 35 :E 5 I o I I 2 TIME 3 (H) FIG. an additional cycle or more should be run.020 percent.020 percent ( = 200 millionths) or more. 1--Typical length change and temperature charts. Although the apparatus is comparatively inexpensive and larger numbers of specimens can be processed than with ASTM Test C 666 equipment. critical dilation has been exceeded. the dilation is not critical. surface treatment." However. The test is based upon experience of a number of agencies who used blocks fabricated to permit ponding of water on one surface which could be exposed to freezing and thawing in the presence of deicing agents. The specimens are placed in a freezing environment for 16 to 18 h and in Copyright by ASTM Int'l (all rights reserved). the procedures may be justified.) deep. Widespread scaling demonstrated that all of these requirements were not being met consistently and brought forth a plethora of remedial or preventive products including admixtures. including freezing of water and addition of the solid deicer. The test can be used to evaluate the effect of mix design. In 1971 ASTM Test C 672 was standardized. It is intended for use in evaluating the surface resistance qualitatively by visual examination.046 m 2 (72 in. It is not intended as a test method for durability of aggregates or other ingredients of concrete." While the complexity of the evaluation procedure limits its general applicability. 2) and be at least 75 mm (3 in. are allowed where there is need to evaluate the specific effect. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) of a solution of calcium chloride and water having a concentration such that each 100 ml of solution contains 4 g of anhydrous calcium chloride. Modifications of the deicer and application procedures. No further reproductions authorized. Reproducibility of overall test results is likely to be affected adversely by variability in aggregate moisture. with adequate entrained air and with adequate curing and a period of drying before the first application of deicing agents are essential in preventing damage [I0]. high quality concrete. The test "covers determination of the resistance of scaling of a horizontal concrete surface subject to freezing and thawing cycles in the presence of deicing chemicals. curing or other variables on resistance to scaling. It has long been known that dense. The method calls for covering the surface with approximately 6 mm (1A in. . it is noted that "aggregate moisture states other than dry or saturated are very difficult to maintain during preparation of specimens. It is suggested that aggregates and concrete be "maintained or brought to the moisture condition representative of that which might be expected in the field. and curing agents. The specimens are placed in a freezing space after moist curing for 14 days and air storage for 14 days. where large projects or economic consequences of detailed aggregate evaluation are warranted. Scaling Resistance In the early 1960s it became apparent that the increasing use of deicing chemicals as part of a "bare pavement" policy adopted for the nation's highways was being reflected in widespread surface scaling of pavements and bridge decks.NEWLON ON RESISTANCE TO WEATHERING 365 requirements designed to bracket a broad range of potential exposure conditions. surface treatments." The specimens must have a surface area of at least 0. Provisions are included for applications of protective coatings if desired at the age of 21 days. chemical attack and alkali aggregate reactions are treated elsewhere in this publication. Although cases have been reported where deterioration was attributed to aggregate with an abnormally low coefficient of thermal expansion [45] or where the freezing and thawing resistance was influenced by aggregates with different coefficients of thermal expansion [46. an adequate volume of entrained air with the proper void distribution and characteristics. Experience with ASTM Test C 672 has been generally satisfactory for evaluating the variables for which it was developed. No further reproductions authorized. As noted in the method the ratings are ranks. and every 25 cycles thereafter.366 TESTS AND PROPERTIES OF CONCRETE laboratory air for 6 to 8 h. Summary The resistance of concrete to weathering in the absence of chemical attack or detrimental cement-aggregate reactions depends upon its ability to resist freezing and thawing. it has been used for outdoor exposures as well. As noted. aggregates cracking from excessive drying shrinkage. the writer is not aware of cases where alternate wetting and drying per se has caused deterioration. effect on concrete durability within the normal temperature range. While the method describes laboratory procedures. 15. and an increased concentration of dissolved salts.47]. Research and experience have shown that resistance to freezing and thawing requires a low water/cement (w/c) ratio. if any. The specimens are rated visually according to a scale from 0 (no scaling) through 5 (severe scaling) after 5. Elevated temperatures such as are encountered in certain parts of nuclear construction are beyond the scope of this paper. even if air entrained. it is now generally believed that "thermal incompatibility" has a minor. Some investigators have weighed the detritus but this is not required by the method. . While wetting and drying induce variation in moisture content that influences the resistance to freezing and thawing. Dry concrete will withstand freezing and thawing indefinitely whereas highly saturated concrete. and exposures which reduce the opportunity for critical Copyright by ASTM Int'l (all rights reserved). 10. If groups of similar specimens are to be reported or compared with other groups. and as such may not be subjected appropriately to analyses based on the calculation of averages and standard deviations nor other techniques that assure continuous distributions. all of which reduce resistance to weathering. may be severely damaged by a few cycles. Other Weathering Processes Other weathering processes that have been suspected of causing deterioration include heating and cooling and wetting and drying. such nonparametric quantities as the median and range may be used. 25. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 56. T. Smith). [12] Vicat. L. Joseph. American Society for Testing and Materials. Dec. 1945.. 20/' Bibliography 38." Proceedings. 1966. C." Publication SP-47. [19] Brard. H. "Performance of Automatic Freezing-and-Thawing Apparatus for Testing Concrete. London. 1951.4. [5] Woods. 259. No further reproductions authorized. A S T M STP 169A. 1966. A S T M STP 169. American Concrete Institute. C. American Concrete Institute. 38. Vol. T. 45. J.. "Hardened Concrete. 1956. Foster. B.. [3] Powers." Report on Significance of Tests of Concrete and Concrete Aggregates. R. "Durability of Concrete Construction. Hericart de Thury. pp." Significance of Tests and Properties of Concrete and Concrete Aggregates. the currently approved standards are very useful when properly conducted and interpreted and have undoubtedly resulted in a significant improvement in the resistance of concrete to weathering from natural forces." (translated from the French by J. C. Copyright by ASTM Int'l (all rights reserved). Highway Research Board. "Freezing and Thawing of Concrete-Mechanisms and Control. [10] ACI Committee 201. American Society for Testing and Materials. "Automatic Freezing-and-Thawing Equipment for a Small Laboratory. [18] Cook.NEWLON ON RESISTANCE TO WEATHERING 367 saturation. 259. "Treatise on Calcareous Mortars and Cements. Annales de Chimie et de Physique. 1856." Proceedings. T. 46.S. American Society for Testing and Materials. References [1] Scholer. C." American Journal of Science. Highway Research Board. and Cook. While direct translation of results from laboratory freezing and thawing tests is difficult at best because of the variety of exposures encountered. Highway Research Board. Franzen M.. NAS-NRC Publication 768. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. K. 1960. 114] Wuerpel. 1964. [16] Arni.. [9] "Durability of Concrete: Physical Aspects: Supplement to Bibliography No." Proceedings. J. 3. L. Vol. American Society for Testing and Materials. [4] Arni. H.. [11] "Durability of Concrete.." ACI Monograph No. Brard for the Immediate Detection of Stones Unable to Resist the Action of Frost." Significance of Tests and Properties of Concrete and Concrete Aggregates. 1943. American Concrete Institute. 1946. A S T M STP 22. Vol. "Durability of Concrete. T. 1957. A S T M STP 169. T. 4. American Society for Testing and Materials. . "On the Mode of Testing Building Materials and an Account of the Marble Used in the Extension of the U. 51. 160-192. Capitol. Highway Research Board... Cady. W. Weale. 1837." Proceedings." Bibliography 20. [15] Walker. American Society for Testing and Materials. NAS-NRC Publication 493. P." Journal. American Society for Testing and Materials. 1966. Vol. [2] Scboler. 1955. H. 1975. "A Critical Review of Literature Treating Methods of Identifying Aggregates Subject to Destructive Volume Change When Frozen in Concrete and a Proposed Program of Research. "Automatic Equipment and Comparative Test Results for the Four ASTM Freezing-and-Thawing Methods for Concrete. A. 1968. J." Significance of Tests and Properties of Concrete attd Concrete-Making Materials. E. "Automatic Accelerated Freezing-and-Thawing Apparatus for Concrete.. H.. American Concrete Institute. W.... [7] Larson. D. A. Resistance to Weathering--General Aspects. Hubert. NAS-NRC Publication 768. "Automatic Equipment for Rapid Freezing-and-Thawing of Concrete in Water. Vol.. 1828. [20] Henry. H. E." ACI Monograph No. Vol." Bulletin No. American Society for Testing and Materials. and Bloem. and Clevenger. "Resistance to Weathering--Freezing and Thawing. H. {t3] "Symposium on Freezing-and-Thawing Tests of Concrete. [6] Cordon. NAS-NRC Publication 1333. Highway Research Board. A.." Special Report 80. [8] "Durability of Concrete: Physical Aspects." Bulletin No. 1977.. 72. "Resistance to Weathering. 1955. "Guide to Durable Concrete. and Reed. On the Method Proposed by Mr.. K. [17] Cordon. 1960. S. Highway Research Board." Durability of Concrete. Vol. American Concrete Institute. H.. 1975. C. J. "Investigations of Concrete in Freezing Chambers.. D. P. T. 1957." Living with Marginal Aggregates." Technical Report 6-784.. "Investigation of Concrete in Eisenhower and Snell Locks St. 1961. C." NCHRP Report No." Zement. 1976. American Concrete Institute. B. Vol. C. G. [41] Cook. July 1967. Copyright by ASTM Int'l (all rights reserved)." Bulletin 150. K. Burrows. Waterways Experiment Station. Lawrence Seaway. and Flack. G. C. 1936. 1928. H. "Freezing Effects in Concrete. Highway Research Board. Publication SP-47.." informal presentation. No. [39] Verbeck. "A Concrete Failure Attributed to Aggregate of Low Thermal Coefficient. [45] Pearson." Cement. "The Mechanism of Frost Action in Concrete. Committee on Durability of Concrete. Evolution and Effects of the Air Void System in Concrete. 53." Proceedings.368 TESTS AND PROPERTIES OF CONCRETE [21] Grun. Paul. E. [35] Verbeck. "Studies of 'Salt' Scaling of Concrete. T. 28. C. Session 13.. "Prediction of Concrete Durability from Thermal Tests of Aggregate. [37] Powers. National Sand and Gravel Association. "Tests for Freeze-Thaw Durability of Concrete Aggregates. and Oct. July 1958. 1960. "Effects of Fluid Circulation and Specimen Containers on the Severity of Freezing and Thawing Tests. D. S. R.. T.. American Society for Testing and Materials. American Concrete Institute. C. Vol. American Concrete Institute. Vol. 24. Feb.." Proceedings.. and Thornton.. 45. "Progress Report. 1958. 48. 1975." Proceedings. Vol. Sept." Technical Report C-76-4. B. "Characteristics and Utilization of Coarse Aggregates Associated with D-Cracking. Robert. "Thermal Expansion of Aggregates and Concrete Durability... American Society for Testing and Materials. American Concrete Institute. David. D. 55. L." Journal. T. J. . 1952. and Cady. Vicksburg. R. American Society for Testing and Materials. "'Investigation of Frost Resistance of Mortar and Concrete. P. E. 1957. [32] Powers. ASTM STP 597.. J. R. 1944." Special Report No. "The Mechanics of Frost Heaving. chairman." Bulletin 305. Stephen. 1969. Publication SP-47.. American Society for Testing and Materials." Proceedings.. "A Working Hypothesis for Further Studies of Frost Resistance of Concrete.. 1979. Annual Meeting of Highway Research Board.. [24] Withey. C. H." Proceedings. L. A. F.. [29] Larson. 3. [34] Taber. and Aggregates. 1945. and Spellman. T. 1959. and Cady. 1952. 66. [22] Scholer. W. Vol. [43] Klieger. "Curing Requirements for Scale Resistance of Concrete. [40] Arni. P.. 1963. 48. Highway Research Board.S. "Basic Considerations Pertaining to Freezing-and-Thawing Tests. 60." Proceedings. [42] Buck." Proceedings. "Identification of Frost-Susceptible Particles in Concrete Aggregates. 1953. "Report on Cooperative Freezing-and-Thawing Tests of Concrete. D. E. Highway Research Board. American Concrete Institute.. C. T. [27] Tremper. 38. 16. 47." Durability of Concrete. "Influence of Physical Characteristics of Aggregate on the Frost Resistance of Concrete. Jan. E. Army Engineer Waterways Experiment Station. Concrete. A. H." Journal. [47] Higginson. American Society for Testing and Materials. C. [36] Powers.. T. [30] Stark. P.... 29. Mather. "Some Accelerated Freezing and Thawing Tests. Sun Apr 6 21:43:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. to be published Jan. George and Landgren. "Durability Tests of Certain Portland Cements.. O. J." The Journal of Geology. H. Vol." Bulletin 150. B. Vol. p. "Origin.. [33] Mielenz. Highway Research Board. 17. [44] Buck.. [26] ASTM Committee C-9. "Deicer Scaling Mechanisms in Concrete. 1949. D. [23] Mattimore. [38] Browne. D. T. 1930. Highway Research Board." Proceedings. Jr. 1955." Stanton Walker Lecture No. "Precision Statements without an Interlaboratory Test Program. Aug. [27] Powers. E. U. and Klieger.. Vol. and Kretsinger. Highway Research Board. V. Minutes of December 1961 Meeting. Backstrom. 1928. Wolkodoff. H. No further reproductions authorized. [31] Powers.. Miss. [46] Callan." Proceedings.. 4. 1958. Vol. [25] Foster. Highway Research Board. 1965. Vol. "The Air-Requirement of Frost Resistant Concrete. M. chairman. D. STP169B-EB/Dec. 1978 L. usually of sodium. The lactic and acetic acid attacks are milder and can be minimized by good workmanship. T u t h i l l ~ Chapter 24--Resistance to Chemical Attack Introduction Fortunately most concrete in service is not subjected to chemical attack. No further reproductions authorized. California Department of Water Resources. Copyright by ASTM Int'l (all rights reserved). probably the best initial correctives are either an ample cement content with a lowwater content and water/cement (w/c) ratio or a cementitious mixture of portland cement and a good. shales. In the case of sewers. 95822. In addition to good workmanship. very little good-quality concrete has actually been destroyed or made unserviceable by leaching of lime from internal or external surfaces. Many field structures have become unserviceable from disintegration by sulfate salts. Calif. or possibly calcium. H. Although concrete is often disfigured by deposits of efflorescence [1] 2 as lime water leach reaches outside surfaces. Copyright9 1978tobyLicense ASTM International www. which exist naturally at varying intensity in many soils. Sulfate attack can completely disintegrate average concrete made with ordinary cement in a very few years (Figs. good concrete. Acid attack is commonly encountered in sewers above the flow line. 4) by using at least six sacks of Type V sulfate-resistant cement per cubic yard of concrete at the lowest practil Concrete engineering consultant. 2The italic numbers in brackets refer to the list of references appended to this paper. Sun Apr 6 21:43:35 EDT 2014 369 Downloaded/printed by Universidade do Gois pursuant Agreement. Concrete is generally less able to resist successfully corrosion of this kind than disintegration by other forces. and elsewhere. on floors of food processing plants.astm.org . formerly concrete engineer. and 3). active pozzolanic material to minimize permeability. This chemical attack can be controlled for many years (Fig. magnesium. little can be done about it directly but much can be done to prevent it by proper sewer design. and a good pozzolanic material added to the cement to make the lime less subject to attack by acids. and ground waters. attack on concrete is by sulfuric acid. 1. Sacramento. By chemical attack is meant leaching and acid or sulfate attack. 2. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). 2--Corrosion by suljhtes has completely disintegrated lower parts of this drop structure in a western canal.from sulfate attack. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . 1--This World War H air base barrack floor in a desert location showed distress in a few years.370 TESTS AND PROPERTIES OF CONCRETE FIG. FIG. Y D. No further reproductions authorized. Unk~s Type ~[ cement co~tains 5. YD. 4--The lower the percentage o[" tricalcium aluminate in the cement. WASHINGTON \ \ \ \ \ I \ \ z\ L .'/~5 $ACKS/ CU.5% C3A. but rising sulfate solutions caused exposed surfaces to spall away as salt co.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 371 FIG. and the richer the mix the better will be the resistance o['concrete to sulfate attack. 3--Concrete under ground was intact. Copyright by ASTM Int'l (all rights reserved). EXPANSIONOF3x3xl6-iNCHCONCRETEBARS DURING7-YEARS IN SOAPLAKE WATER (4. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. an txtro sock pen cu yotd wifl not produce sulfote r~sista~ce equQ{ to ~'hot developed by petter thon borderline Type v sulfote resistin~ cement~ It should be noted thor Q Type I! cement c o ~ i n in9 this omount of CIA is opprooching the moximum orr~unt Of 1his compound ollowed ton TylDeV. TYPE V 3 4 TYPE I I 5 6 TRIGALGIUM 7 ALUMINATE 8 (C3A) 9 rO II 12 tN P E R C E N T FIG.6%-Nae S04) COLUMBIA BASIN PRO~EGT. An extt'o sock of TypeVcement will inceeo~ s~Hote resistonce more l'hon 5 0 % \ \ .. _o e: 4.stals developed in concrete pores when moisture evaporated.5 SACKS/CU. . the entire flume interior was painted with a coal-tar-base paint which had performed best in tests of many paints and coatings previously tried in the flume. the later report [9] indicates that its severity was due to the poor quality of concrete at these locations. and consequently lime-hungry. Snow water in mountain streams and reservoirs is often particularly aggressive because it is unusually cold (calcium hydroxide is more soluble in cold than in warm water). contains carbon dioxide. Scandinavians report [9. retaining walls.10] serious attack and decay of this kind in dams and conduits for relatively lime-free water. At the surface the solution absorbs carbon dioxide which reacts Copyright by ASTM Int'l (all rights reserved). Even with this treatment. however. taking lime into solution and becoming saturated with it. . inside surfaces of concrete conduits. Attack by snow water has been noted in power flumes and lined canals carrying water from the California Sierras (see Fig. this report will proceed with a more detailed discussion of the significant aspects of how these chemical actions damage concrete. and other structures. flumes. 5). This lime is readily dissolved by water. An outstanding California example is the 24 km (15-mile) Tiger Creek flume of the Pacific Gas and Electric Co. As a result. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This produces a mild carbonic acid solution that has a higher capacity for dissolving lime than does pure water without it [1-81. the surface was found to be considerably roughened.372 TESTS AND PROPERTIES OF CONCRETE cable w/c ratio. and. abutments. troweled gunite using ordinary portland cement showed that it too was being attacked. A few years after construction in 1930. repainting was required after 8 years' service. pure. Leaching Hydrated lime is one of the compounds formed when cement and water combine in concrete. like most surface water. These are formed by water that has come through the concrete. and it was feared furthec deterioration would seriously reduce its capacity. particularly if the water is lime-free and contains dissolved carbon dioxide. either along cracks or joints or through porous areas. Objectionable results of leaching are not confined to surfaces in contact with pure mountain water. After a trial length that had been coated with well-cured. Much greater resistance can be obtained by substituting an effective pozzolan for 15 to 30 percent of the cement by weight. where ground water has access to the opposite side. what can be done to combat them. are often disfigured by lime deposits. and in some cases what tests can be used to measure the degree of attack or the success of corrective measures. With this summary of the general problem of chemical attack and the means for producing concrete to resist it. and canal linings develop a sandy appearance from having the cement matrix leached and weakened by contact with these lime-hungry waters. Exposed surfaces of tunnel linings. No further reproductions authorized. even when the reduced actual cement content (80 percent) is taken into consideration. it is to be expected that the leaching process will greatly subside" and be further inhibited by slower diffusion. An unpublished report by Stenzel for the Metropolitan Water District of Southern California in 1936 found for typical Types I. however. Investigators have attempted to measure the influence of cement composition and the use of pozzolanic material on the degree of leaching that may occur. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Use of: (a) aluminous cements.L i m e . it may be said that failures from this source are not likely to occur before those due to weathering and other causes. Stenzel further concluded: "Since the laboratory experiments indicate that the actual quantity of cement dissolved is of a low order of magnitude. definitely less than for the portland cement group. No further reproductions authorized.. (b) portland-blast furnace slag ceCopyright by ASTM Int'l (all rights reserved). II. 5 . From these observations and other studies of the problem. Although unsightly.h u n g ~ or slightly acid water has leached sur/uce mortar and exposed small aggregate on surfaces of this siphon inlet. The effect [for a portland-pozzolan cement] is. with the calcium hydroxide and causes precipitation of a white deposit of calcium carbonate." In 120 days of leach tests. the following ways to minimize leaching are recommended: 1. more than 20 percent less solids were dissolved from the mortar made with the 80-20 portland-pozzolan cement. and V cements that "the leaching effect is similar in nature and magnitude for all the cements studied." He added: "As the lime is exhausted from the rich surface layer of the concrete.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 373 FIG. . this kind of leaching rarely has detracted significantly from the basic serviceability of such structures made of good concrete. Unfortunately many existing systems are not amenable to such changes. and retard dissolving of cement increasingly after the surface has been leached. Acid Attack in Sewers Problems of acid attack above water levels in sewers usually are assumed to be the result of sulfuric acid formed from hydrogen sulfide gas. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. inhibit diffusion. however. 5. fluctuating only slightly above and below a pH of 7. which rises and combines with oxygen and with moisture condensed on upper surfaces of the sewer conduit [12]. 6. since the flow itself is not aggressive. 3. generated by bacteria from sulfur compounds in the sewage. Consideration of a provision for a protective coating of durable and effective surface sealing material. and curing so that hardened concrete free from permeable imperfections is ensured. problems of acid corrosion in the crown portions are best solved by design or operating modifications that result in the sewers running full or with ventilation at higher velocities. (c) portland-pozzolan cement with 20 to 30 percent of a good pozzolanic material that is strongly active in combining with lime to form insoluble lime silicates. Use of sufficient cement and a low w/c ratio to ensure good dense concrete together with air entrainment. Design and use of contraction and construction joints that are watertight and frequent enough to prevent intermediate cracking. to minimize permeability and capillarity. Proper control of concrete mixes. For most sewers. Copyright by ASTM Int'l (all rights reserved). This is not a direct attack of acid in the sewage. portland-cement concrete is not the proper material to use since none of the various compositions of portland cement are resistant to acid corrosion. 2. Lower temperatures also tend to reduce the production of acid-forming hydrogen sulfide gas [12]. When sewage is stagnant or moves slowly. No further reproductions authorized. provision for drainage facilities necessary to prevent water from standing behind structure walls. or (d) "low-lime" portland cement with less tricalcium silicate than dicalcium silicate." and Ref [11]. bacterial creation of the sulfide is often too rapid to be oxidized by air dissolved in the sewage.374 TESTS AND PROPERTIES OF CONCRETE ments. 4. and serious problems of acid corrosion exist in their crown portions (see Fig. When practical. placing procedures. 6). Predominance of certain industrial wastes in certain locations may change this significantly and present a special problem. particularly in water channels. if such can be found and reliably applied.0. Other materials or protective coverings or coatings should be employed. (See Portland Cement Association Bulletin "Effect of Various Substances on Concrete and Protective Treatments. in such aggressively corrosive situations. The fact should be faced that. Records indicate that the usual run of sewage and waste water averages very close to neutral. Where Required. . use of limestone or dolomite aggregate may be a desirable measure where concrete must be used in sewerage for reasons of design or otherwise.2.6 m m (2. The tests were made on 3 by 6-in. Hence. both plain and air-entrained concrete lost strength rapidly. found that in 5 percent solutions of sulfuric acid with a pH of 0. No further reproductions authorized.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 375 FIG. Investigators are continuing the search for materials or treatments that will make concrete a suitably resistant material to chemical attack.52. amounting to approximately 50 percent in 12 weeks' immersion. 9. but it is considered that this concentration provides a reliably indicative accelerated test of relative resistance to acid attack.14] that calcareous aggregate tends to neutralize acids in sewage and so reduces the rate of deterioration of concrete even though it will still be attacked. It is reported [13. Smith and Backstrom. 5 percent is much stronger than the acid solutions attacking sewers. 6--Disintegration of concrete in the crown qf'a sewer is caused by suljuric acid jormed as hydrogen su(tide gas rising from the sewage and combining with oxygen and moisture on the concrete. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Actually.1 m m ( 90 max aggregate.S. Copyright by ASTM Int'l (all rights reserved).). and a slump of about 68. and lost weight from progressive surface disintegration. cylinders of concrete having a w/c ratio of 0.7 in. in an unpublished report for the U. . ASTM Test for Chemical Resistance of Mortars (C 267) describes a test method which is essentially a description of methods used by most investigators. Bureau of Reclamation in 1952. it is persistent and can result in softening a working floor so that it wears rapidly and becomes uneven and unsatisfactory for smooth operation of wheeled trucks.6 mm (4-in. whereas depth does not. the results of tests are encouraging (Table 1). since loss varies with volume of the specimens. averaging a pH of 4. The water contained considerable aggressive carbonic acid [9]. Another soft English moor water was quite acidic. So far this treatment is applicable only to precast units. 101. Not all aggressive surface waters are sulfates. One English moor water was made weakly sulfuric acidic by contamination from a polluted industrial atmosphere and from pyrites in the soil [19]. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and it has the drawback of being so toxic that exceptional care would have to be exercised to protect workmen. and carts. probably due mainly to organic acids washed from peat. and shapes being exposed to various acid solutions for intervals between which surfaces were brushed to remove loosened or softened material [15. Many investigators have used immersed-storage and flow-over-the-surface tests with specimens of various materials. gave a significant indication of the degree of corrosion and the degree of resistance that may be expected. mixes. These observations suggest that need for precautions against acids may exist and must be recognized. sometimes collectively described as humic acid. A German investigator has reported initial encouraging results with a process called "Ocrat-Concrete" [17]. Copyright by ASTM Int'l (all rights reserved).9) is due to silage in concrete silos [15.5 has been destructive to somewhat porous concrete pipe. . Such methods are considered to be significant because they have pointed the way to other materials and practices which are giving far better service. No further reproductions authorized. When given proper time in the treatment. Exposed to a flow of this water for 4 years. sizes. Such tests. The treatment [18] consists of subjecting the concrete in a vacuum to the action of silicon tetrafluoride gas (SiF4): 2Ca(OH2 + SiF4 = 2CaF2 + Si(OH)4. However.) concrete cubes lost considerably more strength than would be indicated by their 4 percent loss in weight [20]. Although attack from these products is comparatively mild.16].376 TESTS AND PROPERTIES OF CONCRETE Results of these many research tests have identified materials and mixes that have not been resistant to various forms of chemical attack in service. the fluoride gas penetrates to some depth and provides more than a thin shell of resistance to acid attack. Another common area of acetic acid attack (pH 3.4 to 3. dollies. It is best that results be judged and compared from depth of scaling rather than from loss in weight. although they are the most common.4. Other Acid Attack Common among other acid attacks are lactic and acetic acids in dairy and fruit products spilled on concrete floors of food processing plants. when suitably representative of the nature of attack.16] Swedish moor water with pH values as low as 4. mix 1:3 by weight. Aged 6 Weeks TABLE 1252 3300 3357 4025 4395 1920 1721 2091 1465 2176 2247 384 569 626 1152 1195 411 484 455 427 612 583 destroyed after 5 h 2930 Compression Specimen 1707 1408 1408 1394 1565 1422 1380 1735 1579 1166 1180 754 1408 Tension Specimen 0.Copyright by ASTM Int'l (all rights reserved).040 0. plastic.q -1I-" I-" . and 1 psi = 6. psi Dycherhoff white cement. : 25. cured 3 days.. w/c ratio = 0.e. psi Strength after 6 weeks immersion in acids and sulfate solutions after ocrating at 28 days. psi Strength at 8 weeks. Portland cement and Rhein sand 0 to I/8-in.C o n c r e t e 7069 6472 4964 4592 5362 4893 4992 6429 5206 7368 8335 3001 6045 Compression Specimen .89 kPa. psi: sodium sulfate solution: portland cement portland-blast furnace slag 10 percent acetic acid solution: portland cement portland-blast furnace slag cement dycherhoff white cement lactic acid: portland cement portland-blast furnace slag cement dycherhoff white cement 5 percent hydrochloric acid: portland-blast furnace slag cement Removed in abrasion test.36. in. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. w/c ratio -..0. No further reproductions authorized. mix 1:3.4 ram. 30 percent max slag. mix 1:5 by weight. same materials: Strength at 6 weeks.4 r 0 --I -t r- (3 "I" m Z O ITI --I O 6O 2O m O Z C .061 711 Tension Specimen Ocrated Untreated o f u n t r e a t e d concrete a n d O c r a t .68.5 by weight. 1--Comparison Conversion factors -l in. earth moist: strength at 6 weeks. then air dried at 6 weeks.3/in.. psi Portland-blast furnace slag cement. impermeable concrete in welldesigned and well-drained structures.23] and imply. Among these same tests it may be noted that the portland-blast furnace slag cement mortar was improved in strength during 6 weeks of storage in these acid solutions. that it contributes nothing to acid resistance. the attack will be rapid and severe. Most investigators report best results with it in resistance to sulfates and sea water [12. This cement is being investigated as a means for creating a concrete resistant to acids. Dry concrete in dry sulfate-bearing soils will not be attacked. The American Concrete Pipe Association [22] reports results from tests in which pipe concrete with Type I cement was immersed for 9 months in acetic acid (pH = 2. where strong acid attack is expected. Clearly superior resistance was found in specimens in which 25 percent of the cement had been replaced with a calcined opaline shale pozzolan. this report suggests that reliance should not be placed on serviceability of such portland-pozzolan cement concrete if pH values of attacking acids are less than 5. Basically.5) after 6 months of water curing. much better serviceability may be expected. Average concrete with Type I cement has been completely disintegrated in only a very Copyright by ASTM Int'l (all rights reserved).0. Where saturation is continuous in strongly sulfatebearing ground water. This cement contained not over 30 percent slag. but tests by contemporary investigators give no indication that super-sulfated cement is resistant to acid attack [20]. the same recommendations made for resistance to leaching are suggested for best resistance to mild acids. or at least a protective surface treatment of proved effectiveness should be provided. no portland-cement concrete is acid-resistant. In 1927 Schlyter [21] recommended slag or aluminous cement for better acid resistance. It is even more severe where saturation and drying are frequently alternated. The degree and rate of this attack vary. there is great difference in the degree of resistance obtained in the wide range of cementing materials and workmanship used. and decreases as the amount of dry exposure increases. Super-sulfated cement is a mixture of granulated blast furnace slag with some anhydrite (calcium sulfate) and a small addition of lime or portland cement. 1-3). well-placed. . Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Sulfate Corrosion Some of the most spectacular chemical attacks encountered in concrete have been a result of sulfates in adjacent soil and ground water (see Figs.378 TESTS AND PROPERTIES OF CONCRETE The weakening effect of these acids on portland-cement mortar is noticeable in the strengths reported in the German data shown in Table 1 [16]. by omission of the subject. especially in sewers. In detail. However. However. When the most resistant cements are used in good. other materials should be used. However. These attacks increase as the concentration of sulfates in surrounding water increases. No further reproductions authorized. sulfate solution rises in the concrete. This is a concentration that is capable of a considerable degree of sulfate attack." Other investigators. By a wicking action. A less severe effect has been noted in some exposures where underground concrete was unaffected. as it evaporates from concrete in surfaces just above the ground. 4. These specimens contained a wide variety of cements. Both the manner of sulfate corrosion and one means of retarding it are mentioned in the following statement of Bogue [23]: "Since calcium sulfoaluminate forms most readily in concentrated solutions of Ca(OH)2. it is possible for it to become a saturated solution of gypsum which contains 1100 ppm SO4. Bureau of Reclamation. This is summarized in their University of Minnesota Technical Bulletin No. crystals of sulfoaluminate and sulfate develop in pores under the surface with sufficient force to flake off the concrete [24]. but some structure and canal locations are in soil containing appreciable amounts of calcium sulfate (gypsum). . but the surface of the concrete immediately above the ground was pitted and scaled away (see Fig. In arid climates. 3). although it is likely to be at a slower rate than with sodium sulfate because it has been determined that calcium sulfate reacts with hydrated tricaleium aluminate but not with hydrated lime or the hydrated silicates. "LongTime Tests of Concretes and Mortars Exposed to Sulfate Waters. similarly arrived at the same basic conclusion: that the lower the percentage of tricalcium aluminate in the cement. and as early as 1920 Miller commenced his lifelong study of this problem with Manson. 194. including the Portland Cement Association.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 379 few years when severely exposed in drainage pipe. and since the disintegration of cements in sulfate solutions is due chiefly to the formation of that salt. The widespread nature of the problem and the vigor of sulfate attack stimulated a search for means to combat it. Specimens ranged from half briquets of standard 20-30 Ottawa sand mortar to approximately 150 by 300 mm (6 by 12-in. sulfate attack on concrete may be negligible. these research tests involved exposure of concrete specimens immersed in sulfate waters. Essentially. Typical results of tests by the Bureau of Reclamation are plotted in Fig. The most common and aggressive sulfates are those of sodium and magnesium. pozzolanic materials. Because gypsum is relatively insoluble. floors. Copyright by ASTM Int'l (all rights reserved). the better would be the resistance of concrete to sulfate attack. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Presumably this implies that active silica or pozzolan is helpful in reducing the severity of sulfate attack by combining with Ca(OH)2 and making much of it insoluble. and lower parts of canal structures. the presence of active silica will retard the formation of the sulfoaluminate and thus delay the disintegration of the structure. the U. if ground water movements are sufficiently sluggish.) concrete cylinders and lengths of commercial precast concrete pipe. However.S. and the Metropolitan Water District of Southern California [25]. No further reproductions authorized. 4~ (130~ for 8 h. Results of the long-time exposure tests have proved quite significant in that concrete in service. made under normal exposure conditions. but it took many years to prove the relative merit of comparatively resistant materials and treatments. and curing found most resistant in these tests. are using currently an accelerated sulfate test for evaluating sulfate resistance of concretes. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Actually. . and complete failure of the concrete. in the long-time tests. indicated by a 40 percent reduction in dynamic modulus or an expansion of 0. The criterion of failure in this test is established as being a loss of 15 percent in dynamic modulus or an expansion of 0. Concentrations of sulfate were varied. internal disruption has definitely started. 4 is presented on this basis. from loss of strength compared to that of specimens stored in plain water. from significant loss of weight. "Summary of Sulfate Resisting Performance of Cements in the Long Time Study of the Portland Cement Association. 0. Information in Fig." reported in Ref 26. mixes.) specimens are alternately soaked in a 2. This test produces results comparable to those of the 21. No further reproductions authorized. the Bureau of Reclamation laboratories in Denver..5 percent being considered as complete failure. In these tests.10 percent correlates quite accurately with ultimate resistance performance. the conclusion is inescapable that low tricalcium aluminate content correlates positively and most reliably with greatest sulfate resistance.5 percent.380 TESTS AND PROPERTIES OF CONCRETE and admixtures in mortars and concretes of varying richness and curing. 33 of Ref 27. and effects of both sodium and magnesium sulfates were noted. from loss in dynamic modulus.1 percent solution of sodium sulfate (12 600 ppm SO4) at about 22. and in Miller's Table 6. complete failure being a loss of 40 percent. and exposure to drying were determined.8~ (73~ for 16 h and then dried in air at 54. At this point. "Summary of 122 Commercial Cements. and in many other such summaries. Effects of curing. such as in Lerch's Table 1. Indications from this accelerated test have been consistent with long-time results well established during the past 25 years. Consequently. it has been found that the time required to develop an expansion of 0. Although the low tricalcium aluminate in Type V cement is without doubt the most important factor in improving resistance of concrete to sulCopyright by ASTM Int'l (all rights reserved). In this test approximately 75 by 150 mm (3 by 6-in. and from obvious visual failure. Whenever sulfate resistance of a comprehensive range of cement compositions has been obtained and tabulated against the percent of tricalcium aluminate in each composition. it did not take long to identify unresisting concretes.1~ (70~ continuous soaking test in approximately one-sixth the time." p. Colo. Lack of resistance was evaluated: from expansion. is imminent.2 percent. has resisted sulfate attack far better than concrete made with most other cements. except for differences in the effects of pozzolanic materials and admixtures. temperature. made with the cements. greater or more prolonged resistance can be obtained with a somewhat less resistant composition of cement. with N-type pozzolans best results are more likely to result with only the 15 percent replacement [28]. since its combination with the lime is slow and will stop without moisture. 4.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 381 fates (Fig. 3. . if there is only one mill that can make the cement to those safer limits. as it is to specify limits that will provide all the sulfate resistance that can be put into the cement. in which less than 4 percent is tricalcium aluminate. 4. An additional hundredweight of Type V sulfate-resistant cement will increase resistance at least 50 percent as shown in Fig. 4). Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. later research investigation has shown that if arrangements can be made to use a suitable pozzolan. Among the N-type pozzolans. 2. Fig. Inasmuch as a chemical explanation for this is unlikely. makes the most sulfate-resistant portland cement. Accordingly. All otherwise acceptable flyashes tested have improved significantly (as much as tbur to ten fold [28.50 should be used. Precast units such as concrete pipe and block can be made appreciably Copyright by ASTM Int'l (all rights reserved). As noted in item 2 above. A low-lime and low-aluminate cement. A w/c ratio of not more than 0. No further reproductions authorized. perhaps to only one mill. The concrete should have an ample cement content. Specifications for sulfateresistant cement having these compound limits were written in 1934 for work in southern California [25]. equal to that provided by Type V cement with 4. having less than 50 percent tricalcium silicate and less than 12 percent tricalcium aluminate plus tetracalcium aluminoferrite. provided the pozzolan. those least effective were usually (but not always) those causing appreciably higher mixing water requirement. Pozzolan effectiveness is substantially greater the longer curing can be provided prior to sulfate exposure. it is considered to be due to the improvement in impermeability usually resulting from air entrainment of the concrete. however.5 percent of tricalcium aluminate. Air entrainment is generally recognized as being measurably beneficial to sulfate resistance. This is advisable even at a somewhat higher premium. An active pozzolanic material may be substituted for 15 to 30 percent by weight of the cement. It is also evident that sulfate resistance. with the exception of sub-bituminous and lignite flyashes [30].5 percent tricalcium aluminate. as most are. 5. there are several other provisions and precautions that will contribute materially to sulfate resistance: 1. is not obtained by using an additional hundredweight of Type II cement per cubic yard unless the Type lI cement contains less than 5. 5] the sulfate resistance of Type II and Type V cements [29]. It was felt that when long-range durability of concrete is at stake in an aggressive environment it is not as important to require composition limits that most manufacturers can meet. is one proved to be effective in increasing sulfate resistance of Type II and Type V cement. - io "/ 50 C0 70 OAYS M O I S T CURING 80 ~0 FIG. steam curing at 1 7 6 . i n c l u d i n g those m a d e with ordinary p o r t l a n d cements. I J / / o /'~emen't !zo io /i R--q. "f "~"~'~ Cement Z0 DAYS 30 DRYING 40 AFTER 28 M Hell briquettes m I% solufion of No2504 Type I cemenf-MWD Reporf~702 ""Ce e. as indicated by the data in Fig. C a l c i u m chloride reduces sulfate resistance regardless of the type of cement used. ing concrete several weeks alter good curing. .. 7. P r e s u m a b l y c a r b o n a t i o n occurring d u r i n g this period contributes to improved sulfate resistance.382 TESTS AND PROPERTIES OF CONCRETE more resistant by a period of several weeks of drying following good curing.. TABLE 2--Attack on concrete by waters containing sulfate (as S04). as it also improved resistance of leaching. It m u s t be recognized that the intensity of the corrosive sulfate attack will vary with the parts per million of sulfate (SO4) in water that wilt be in Copyright by ASTM Int'l (all rights reserved). 7--Resistance to sulfate corrosion is materially increased by do. 7 ~ (350~ or above greatly improves the resistance of specimens. 6. by reducing permeability. As indicated by Miller [27]. No further reproductions authorized. 7. 35 3c I Cement V-.t/ ..t C . Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Relative Degree of Sulfate Attack Minor Positive Severe Very severe Parts per million Sulfate (as SO4) in Water Least Resistant Cement Advisable 0 to 150 150 to 1 500 I 500 to t0 000 Type I or II Type I1 or V Type V or V + extra cement or a pozzolana Type V + extra cement + a pozzolan 10 000 or more " A pozzolan proved to increase effectivelysulfate resistance of Type V cement. After a decade of experience with this test it was noted that the results of such tests agree fairly well with the long-term behavior of cements in concrete in aggressive sulfate exposure. since on occasion cements having 6 to 9 percent tricalcium aluminate have been indicated by this test to be comparatively sulfate resisting. Prompt sulfate action is generated by mixing sufficient powdered calcium sulfate with the cement for it to contain 7. Subcommittee C01. preferably those mentioned in item 3 above.S. For purposes of acceptance testing and for comparing sulfate resistance of different cements. The work on this test has recently been reviewed by Mather [31]. Because such high values of C3A would raise serious doubts as to actual sulfate resistance. unless concrete is unusually Copyright by ASTM Int'l (all rights reserved). because the factor of time has not been taken otherwise clearly into consideration. Accordingly. The method is described in ASTM Test for Potential Expansion of Portland Cement Mortars Exposed to Sulfate (C 452). recommends somewhat the following schedule of cement types for appropriate resistance to the indicated degree of sulfate exposure (see Table 2).. the small fraction of extra cost for this more assured protection for each degree of severity of prospective attack could well be a wise investment. No further reproductions authorized. and because of the possibility that the service exposure may become more aggressive. p. In such a rapid physical attack. The U. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 8th ed.0 percent of SO3. an exposure of lesser degree may well have a cumulative greater effect in the long run. these salts have the effect of increasing the severity-of freezing-and-thawing cycles and. Actually this scaling is not primarily the result of chemical attack as evidenced by the considerable freedom from scaling obtained when concrete is amply air entrained. some feel that the results of this test can be used best only as a supplemental indication to compound composition requirements. Bureau of Reclamation Concrete Manual.29 on Sulfate Resistance of ASTM Committee C-1 on Cement has developed an expansion test which in 14 days reflects with fair reliability the resistance to sulfate attack which may be expected from the cement used to make up the test bars.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 383 contact with the subject concrete. As time goes on. In this modified table an alternative cement of superior resistance is shown for each degree of sulfate attack. the test would serve no reliable purpose as an acceptance test that is not served by simply specifying the compound composition requirements. Table 2. . At today's (1978) prices for concrete in place. Attack by Other Chemicals Most widespread among attacks by other chemicals is the scaling of concrete pavements and sidewalks caused by the use of sodium or calcium chloride to melt ice and snow in freezing weather. 11. but no better than could have been predicted at the start from the calculated CaA contents of the cements. . The additional precautions of good workmanship.4 to 50.8 mm (1 to 2.384 TESTS AND PROPERTIES OF CONCRETE resistant to such weathering. at a temperature of 143~ (290~ a brine as strong as synthetic sea water. and ample cover over reinforcing steel should largely offset the other recognized causes of failure of concrete in sea water. plants of larger capacity may utilize as much concrete as possible structurally. 12. or by the formation of chloro-aluminates under wetting and drying conditions. uncoated and untreated.) of additional sacrificial concrete. 4-7.S. sulfate constitutes a little over 2500 ppm of sea water. The U. is not suitable for conducting mineral-free distilled water or. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. alkali-aggregate reactivity contributed to failure. for desalination of return-flow Colorado River treaty water deliveries to Mexico. experience has shown that this result is largely prevented by using 5 to 7 percent of entrained air in the concrete.5 in. With increasing attention to conversion of saline water. This possibility has raised the question of the effect of hot sea water and of hot distilled water on concrete durability. have from 25. provided exposed surfaces for either.34].32]. by keeping slumps low. Concrete for the large plant to be built shortly at Yuma. and to freezing and thawing at tide and wave levels [2. such concrete is suitable at temperatures not exceeding 121~ (250~ where only in contact with distilled water vapor or with a sea water brine. 33. European literature speaks favorably of the performance of aluminous and slag cement and of portland-pozzolan combinations in sea water exposure [18. Since a pavement is disintegrated mainly by cycles of freezing and thawing. The physical actions involved in such weathering may be supplemented by leaching because of the greater solubility of calcium hydroxide in calcium or sodium chloride solutions. low w/c ratios. Bureau of Reclamation has conducted pertinent tests [35] and reports [36] that conventional portland cement concrete. Presumably by such chemical actions calcium chloride has caused disintegration of concrete where brine has dripped from refrigerating equipment and where no freezing was involved. No further reproductions authorized. a concentration that is regarded as sufficiently severe when found in ground water to warrant use of Type V sulfate-resistant cement and other precautions previously mentioned to secure sulfate resistance. However. In one notable example in southern California. surface disintegration results. will be used with the above limitations. Copyright by ASTM Int'l (all rights reserved). Ariz. . At temperatures of the brine below 93~ (200~ no sacrificial concrete need be used. air entrainment. Sea water is mentioned mainly to point out that most concrete failures in this connection have not been due to chemical attack of the sea water so much as to porosity which enhanced leaching and expansive corrosion of reinforcing bars. and by avoiding overmanipulation in finishing which brings water to the surface and works entrained air out of the concrete. This is covered in greater detail in other papers in this symposium.) cylinders of various cements and mixes in continuously flowing water at the job site for comparison with similar cylinders stored in fresh water. Bureau of Reclamation Concrete Laboratory for his considerable assistance in reviewing pertinent technical literature. Relation of Aggregates to Resistance to Chemical Attack Except in its relation to resistance to chemical attack.S. Appropriate warning is given that heat generated by Lumnite cement in confined massive placements may be formidable and objectionable unless precautions are taken to care for it. B. Acknowledgment The author is indebted to A. and no means are now known by which it can be made satisfactorily resistant. Recognition is made also of valuable work reported by contemporary investigators mentioned in the text and in the references. and Super. aggressive sulfate salts exist in this water and are responsible for the attack. Although some aggregates may be somewhat vulnerable. Evidently. Trass. as limestone. Indications from available records of experience are that aggregate is secondary in responsibility for lack of resistance to chemical attack. it is not the purpose of this paper to discuss the influence of aggregate on concrete durability. These cases should be recognized in advance. Conclusions This brief survey indicates that there are many resources in materials and benefits from careful workmanship which can be marshalled quite effectively against many kinds of chemical attack on concrete in service. there are certain exposures to which concrete is inherently unresistant." or mixes with flyash or pumicite substituted for part of the cement were even better than rich mixes and low w/c ratios. if the aggregate otherwise makes serviceable concrete. If the paste can be made resistant. is vulnerable to acid. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. the concrete will be resistant and serviceable. Arrangements were made to submerge approximately 150 by 300 m m (6 by 12-in. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. . for example. Crosby of the staff of the U.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 385 Sulfur water is an occasional source of concrete deterioration according to reported tests [3]. and other materials of proved resistance should be used. Results indicated that "the special cements--Lumnite. failure of concrete to resist chemical attack is primarily a failure of the cement paste. .. p. [17] Wittekind. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. C. American Society for Testing and Materials. June 1954. 1931. Vol.. Sept. 79-89. [20] Halstead. Vol. May 1950. ]26] Lerch. 1952. Zement. L.." Magazine of Concrete Research. 33. April 1949. 1936. 475. 17. 1. J. W. Manson.." Journal. [22} Davis. R. 5 Dec. [4] Terzaghi. American Concrete Pipe Association.. "Resistance of Cement to the Corrosive Action of Sodium Sulfate Solutions." Proceedings. June 1936. 35-45.. Kalk-Gips. Vot. Vot." Journal Institution of Structural Engineers. G. No further reproductions authorized. 1960. "Guide to Durable Concrete." Water and Sewage Works. "An Investigation of the Erosive Effect on Concrete of Soft Water of Low pH Value. . 46. "Concrete Deterioration in a Shipway. 6. 61. P. R. H. Proceedings. "Leaching of Lime from Concrete. H. "Concrete Deterioration Due to Carbonic Acid. "Concrete Exposed to Sulfur Water. Vol. [9} Granholm... 849.." Journal. "Long Time Tests of Concretes and Mortars Exposed to Sulfate Waters. F. 1954. "'Efflorescence. "Damage to Cement Structures. p. C. Sept." Journal. 1927." Journal. Vol. ]7] Tremper. Gothenburg." Journal." Journal. 36. H.. R.. 1977. Reinhold Publishing Corp. D. p. Journal of Sanitary Engineering Div. D. P. S." Journal. 83. R. [10] Hellstrom. American Concrete Institute. No. p.. 185. [8] Wolley. No. and Benton." Transactions. Feb. 587. American Concrete Institute. O. [24] Stutterheim. [21] Schlyter. 36. p. A." The Surveyor. 1043." Cement and Cement Manufacture. 1 Sept.. American Concrete Institute. L.. 1 Dec." Bulletin No. 473-475. Vol. pp. W." Proceedings. C. 210. 2nd ed.. 130.. and Rogers.. [21 Mather. "Decay and Repair of Concrete and Masonry Dams... 553. American Concrete Institute. E. June 1948. W. "The Effect of Acid Waters on Concrete. 1939. pp. 194. "Significance of Tests for Sulfate Resistance. R." Agriculture Engineering. Oct. American Society for Testing and Materials. 1961. G. Boston Society of CiviJ Engineers.. Nov. R. 2. 1954. G. 1961. R. 93. New York. "Long-Time Pipe Study. 1950. Porter. "Permeability. May 1951. Proceedings. [19] Lea. p. H. W. Vol. [27] Miller. E. M. Oct. 46. Stockholm. B.. 37. July 1952. 1951. No. "Leaching of Lime from Concrete. N.386 TESTS AND PROPERTIES OF CONCRETE References [1] Anderegg. Acid and Absorption Tests of Mortars Used in Dry Tamped Silo Staves. C." Technical Memorandum.Y." Journal. p. "Concrete for Long-time Service in Sulfate Environment. p. J." Bulletin No. American Concrete Institute.-Dec.. 136-160. 1955. [15] Hughes. 1944. K. p. Vol. 12. pp. [25] Tuthill. p. Vol. South African Council for Scientific and Industrial Research. "Leaching of Lime from Concrete... 44. [28] Kalousek. 1950. Vol. {18] German Patent No. C. University of Minnesota.. 2. Sweden. [131 Pomroy. 20. "Protection of Concrete Sewers in Presence of H~S.. American Concrete Institute. Vol. "Laboratory Tests of Concretes and Mortars Exposed to Weak Acids. D." Journal. [14] Swab. 1972. 225.. 753-755. Proceedings. E. 1944. [12] Hammerton.. L. Sweden. "Deterioration of Concrete Owing to Chemical Attack. p. pp. [3] Nelles. Dec.. Proceedings. American Concrete Institute. Proceedings. and Manson." Journal. T. 977. June 1940. Government Testing Station. Copyright by ASTM Int'l (all rights reserved). D. "The Corrosion of Cement and Concrete. pp. May 1933. F. D. Sept. National Building Research Institute. Chalmers University of Technology. [11] ACI Committee 201. [6} Terzaghi. I1. [5] Terzaghi." Bulletin. B. B. "The Deterioration of Concrete and Reinforced Concrete Due to Chemical and Natural Agencies."ASTM Bulletin No.. 28. The Chemistry of Portland Cement." Cement and Concrete Research. 46. American Concrete Institute. 1941. American Society of Chemical Engineers. American Concrete Institute.. N. Vol. Feb. Nov. 441. Feb. P.. [16] Miller. [23] Bogue.. "Pozzolanic-Material--with Special Reference to Their Use in Concrete Pipe. "Effects of H2S on Concrete Structures. F. K. J. L. 841. and Desch. R.." Research Report No. 1978. Backstrom. U.S. [32] Wakeman. and Whiteneck. H. C... H. [36] Backstrom.. P. American Concrete Institute. Sun Apr 6 21:43:35 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Tests and Evaluation of Portland and Blended Cements 1or Resistance to Sulfate Attack. R. [30] "Performance of Lignite and Subbituminous Fly Ash in Concrete. S. U. [31] Mather.. M.TUTHILL ON RESISTANCE TO CHEMICAL ATTACK 387 [29] "Fly Ash Increases Resistance of Concrete to Sulfate Attack.. Redmond. W. "Evaluation of Concrete and Related Materials for Desalination Plants.. Bibliography on Sulfate Resistance of Portland Cements. . C. 23.. [33] Lea. 1937. American Society for Testing and Materials. E. March 1971. with Abstracts. E. E.. "Use of Concrete in Marine Environments. E. J. Concretes and Mortars. Copyright by ASTM Int'l (all rights reserved)." Executive Summary (35). Vol.. 1976. April 1958. Bureau of Reclamation. [34] Miller. Dockweiler. London.. E. and Rubenstein. and Chen. June 1971... 1975. T.. Manson. U." REC-ERC-76-1. Bureau of Reclamation.. T." Cement Standards--Evolution and Trends. L. R.S. Backstrom. R. Bureau of Reclamation. Edward Arnold and Co. p.S. G. Bureau of Reclamation. Stover. J. H. April 1952. 54.." Journal. M. J. U. and Graham. D. A S T M STP 663. F. M. No further reproductions authorized. [35] Graham. American Society for Testing and Materials. "Evaluation of Concrete for Desalination Plants. Chemistry of Cement and Concrete. C. V. Jan.S." Report Rec-ERC-71-15. the main role of concrete in a fire is to protect any embedded steel for as long as possible against a rise in temperature to the point where its physical properties are reduced significantly. 1978 Peter Smith 1 Chapter 25 Resistance to High Temperatures Introduction One of the main reasons why portland cement concrete is so widely used in building construction is that it can help satisfy a cardinal need for public safety in face of the hazards of fire better than most of its competitors. to a maximum of 1260 ~ (2300 ~ after 8-h survival in ASTM Fire Tests of Building Construction and Materials (E 119). Engineering Research and Development Branch. Copyright by ASTM Int'l (all rights reserved). Concrete is incombustible and a reasonable insulator against the transmission of heat. These qualities alone help confine the fire and limit the extent of the damage. Ont. No further reproductions authorized. Ministry of Transportation and Communications. Usually only the ambient temperature regime is controlled in these tests.STP169B-EB/Dec.org . A temperature of 649 ~ (1200~ may be reached before 25 percent of the original compressive strength of a calcareous aggregate concrete is lost (the corresponding temperature for a siliceous aggregate concrete is about 427~ (800~ However. and (b) upon fire endurance ratings specified by the survival times of specific structural assemblies or components in standard laboratory fire tests. Copyright9 1978tobyLicense ASTM International www. Therefore. causing excessive structural deflections that might lead ultimately to collapse. Toronto. Canada. for example. Fifty percent of the yield strength of mild steel is lost by about 593 ~ (1100 ~ (the corresponding temperature in the case of the tensile strength of prestressing wire is about 427 ~ (800 ~ Every building code contains minimum fire protection requirements based on (a) a combination of knowledge of the physical properties and past experience of the behavior of various building materials when exposed to fire.. such tests do not provide much information about the effect ~Director. Sun Apr 6 21:43:36 EDT 2014 388 Downloaded/printed by Universidade do Gois pursuant Agreement. the essential engineering properties of the body of the concrete remain intact. and though the surface may crumble or spall.astm. Concretes made from normal constituent materials usually cannot provide for sustained performance at temperatures above 538~ (1000~ Copyright by ASTM Int'l (all rights reserved). then much more than mere survival needs to be known about the thermal and mechanical properties of steel and concrete at elevated temperatures. the resistance of the concrete is dependent on those properties that impart fire resistance with the added interest of the ease with which the concrete may vaporize. . its constituent materials. or those residual properties after slow or quench cooling. No further reproductions authorized. Secondly. sustained or repetitive temperatures. foundry floors. One such application is in prestressed nuclear reactor primary containment vessels where complex regimes of mechanical and thermal stress may occur in comparatively massive concrete sections. However. advanced industrial and military applications require a greater knowledge of the physical properties of various types of concrete under sustained or repetitive moderately high temperature regimes. experiments to determine the same properties at sustained high temperature require special equipment and measuring techniques. in the order of 66~ (150~ with local hot spots reaching 121 ~ (250 ~ For the ultimate doomsday accident where the reactor core melts. furnace and compressor supports at moderately high.SMITH ON RESISTANCE TO HIGH TEMPERATURES 389 of specific high temperatures on the properties of concrete. It is relatively easy to determine the residual properties by standard test methods and the results provide much of the information needed to determine what can be saved after a fire. in some cases up to 371~ (700~ without special forethought having been given to the properties of the concrete used. Concretes made with normal cements and aggregates have been used successfully over many years in locations such as soaking pits. Firstly. or reinforcing steel except in a very general way. To improve fire resistance when designing and building a new concrete structure or for assessing the condition and possibilities of repair of one damaged by fire. it is needed for computer-based modeling techniques of heat flow and structural behavior that offer great promise for extending the results of fire tests on discrete assemblies to the more general case and of demonstrating the beneficial effects of restraint and support that from unaffected cooler parts of the structure have on overall fire resistance. However. An objective in recent years has been to increase the operating temperatures within the concrete without the need for artificial cooling. some of the newer industrial applications do demand a detailed knowledge of the structural behavior of concrete at moderately high temperatures. Yet this kind of information has become increasingly in demand in recent years for two main reasons. While some investigations have pursued the subject up to 1000~ (1832~ in present practice design bulk concrete temperatures at failure (in order to still retain the reactor core) are in the range from 204 to 316~ (400 to 600~ though normal operating bulk concrete temperatures are considerably lower. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. and a rapid worsening in most mechanical properties of structural value. Endurance Standards. Generally speaking. flue. or refractory field require many other considerations to be taken into account. Many influencing factors. some not fully understood. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. (b) the depth of cover provided to any embedded steel. and kiln linings.390 TESTS AND PROPERTIES OF CONCRETE special concretes are necessary for use in furnace. Fire Testing. the end of structural usefulness of a particular concrete does not occur suddenly at a specific temperature. and Modeling In North America the fire resistance of building components is usually measured. Concrete manufacture by autoclaving or other processes involving high temperatures is excluded from the material presented. while light weight aggregate concretes may be useful for thermal insulation. thermal incompatibilities between paste and aggregate. above about 149~ (300OF) the progressive continuum of cement dehydration reactions. While not all of the information necessary for such uses of concrete is in the public domain. missile. ceramic bonds develop which might reestablish concrete as a useful engineering material. Fortunately for most needs. the engineering properties and behavior of concrete at these temperatures vary by only a few percentage points from those measured at room temperatures. enter the picture. By selection of the best combination of these for a particular application. and fire endurance is specified. and eventual physiochemical deterioration of the aggregate leads to high thermal stresses. Refractory concretes made with high alumina cements and heat resistant aggregates are capable of resisting sustained temperatures up to 1800 ~ (3272 ~ At temperatures approaching 1200~ (2192~ above the point where normal concretes have decomposed to mush. However. microcracking. on the basis of ASTM Test Copyright by ASTM Int'l (all rights reserved). significant improvements in overall fire resistance can be achieved. . an appreciation and references sufficient for a general understanding are given. and in reactor thermal and radiation shields. Reactor shields require heavy weight aggregate concretes. As yet this potential has received little attention beyond producing ceramic glazes by heating the faces of concrete units with an oxyacetylene flame. three of the most important factors are within control prior to placing concrete: (a) the structural system and design details chosen. The extreme case of high temperature use for normal concrete is probably scarificial exposure in some missile launching sites where temperatures of 2760~ (5000~ may be reached for a few moments. No further reproductions authorized. Specialized concrete applications such as those in the nuclear. as thermal insulation. Interest in the high tempeature behavior of structural concretes for most applications starts at a lower bound temperature of 100~ (212~ and immediately above as free water starts to be driven off. and (c) the type of coarse aggregate specified. Benjamin [3] reported on thermal factors arising from moisture content and type of aggregate. No further reproductions authorized. with improvements upon them being introduced as the development of knowledge and experience dictated. the more likely that it will be salvageable). Sheridan [4] discussed concrete as a protection for structural steel. and 1260~ (2300~ in 8 h (assuming an end point has not yet been reached). They include development of a passage for flames or gases through to the unheated side. Carlson [2] looked at the effect of moisture. spalling. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. surface temperature criteria. Both before. the first version of the standard fire tests was established in 1917. A standard fire exposure is defined by a time-temperature curve in which 538~ (1000~ is attained in 5 min. and lateral restraint as affecting fire endurance ratings. fire testing laboratories around the world have worked actively to evaluate new types of construction and improve fundamental knowledge. or 4-h rating). necessary to ensure saftety in a particular set of circumstances. specimen size. 2. Copyright by ASTM Int'l (all rights reserved). Fire endurance is then stated in terms of time to reach whichever end point occurs first (such as 1. is discussed later when the matter of moisture content in concrete is considered. cover to reinforcing steel. 927~ (1700~ in 1 h. Minimum specimen sizes (areas or lengths exposed) and a moisture condition requirement prior to testing are specified and superimposed loads may be added to simulate in-service conditions. . It must be emphasized that the prime purpose of fire tests and related criteria is to ensure safety of the building and occupants in case of fire and not to ensure structural survival or ease of repair after the fire (though obviously the more fire resistant the construction is. End point criteria in the test are intended to simulate modes of failure in an actual fire. The proceedings of that symposium provide a good opening to present day thinking on fire resistance through four comprehensive papers.SMITH ON RESISTANCE TO HIGH TEMPERATURES 391 E 119. One particular problem. the requirements and significance of such test procedures have been debated. and radiant heat. and columns are exposed on all faces. increase in temperature of steel or the unexposed surface due to heat transmission. restraint. 2The italic numbers in brackets refer to the list of references appended to this paper. In their literature survey Uddin and Culver [1] 2 cite 149 references covering the period from 1884 to 1961. Exposure to the furnace temperature is on one side only for slabs and walls. and ever since. are called forward in the applicable building code along with related design criteria. In the last decade. beams are exposed from beneath and from the sides. on structural factors such as concrete strength. the moisture conditioning of specimens prior to exposure to high temperature. 3. and failure to support load after hosing down. Troxell [5] addressed the special problems of prestressed concrete sections. when an American Concrete Institute Symposium was held. The appropriate fire endurance requirements. not later discussed. No further reproductions authorized. that is. The results are specific and particular to the component or assembly tested and cannot be extended with confidence to include even comparatively minor variations in the configuration tested. The regimes to be modeled are not simple.8]. and (6) thermal conductivity. (4) cover over reinforcing steel. there is a usually good agreement on the general trends reported. Uddin and Culver [1]. etc. Two general tests are useful in obtaining an understanding of the ob- Copyright by ASTM Int'l (all rights reserved). They are: (1) type of aggregate. However. with the advent of computers. taking material and structural parameters into account. However. where this is not essential. moisture content. specific heat. Behavior of Concrete In their review. by modifying the normal procedure or developing a new or indirect method through considerable ingenuity. while the actual numbers may differ. and mechanical properties are interactive in the concrete mass and the structural geometry may be complex. are specific to experimental techniques and support a general observation that a property that can easily be determined at normal temperatures by standard tests often can only be determined at elevated temperatures with difficulty. diffusivity. thermal. Throughout the discussion experimental techniques to measure various properties will be identified or. Most of these factors interrelate and the format has been adopted of first considering the influences of component materials and then considering the properties or particular problems of concrete at high temperature. Lastly. . many of the differences reported in measured values of various properties may be ascribed to differences in test conditions. mathematical models are being developed for the heat flow process in a variety of structural concrete units to establish temperature distributions and. As a result. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. reasonable calibration with actual fire tests is being achieved and the modeling approach is greatly increasing understanding of the interaction of material properties and the design and performance of concrete structures at elevated temperatures. (2) free moisture in the concrete. Two references [7. left to the details provided by the referenced sources. Accordingly. it is difficult during the test to simulate the beneficial effects of restraint by cooler parts of a concrete structure that are clear of the actual fire. to then predict fire endurance and structural behavior at high temperatures [6]. (5) modulus of elasticity. list six material properties as having particular influence on the high temperature performance of structural concrete. (3) stress levels in both steel and concrete.392 TESTS AND PROPERTIES OF CONCRETE The establishment of fire endurance ratings by means of standard fire tests is both expensive and time consuming. The overall pattern of their length change data confirms the complex superposition of dehydration shrinkage in the cement paste and expansion of the aggregate as being a major factor in high temperature performance of concrete. in practice these are little used for such benefit alone. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and calcined shaledust) [10]. Harmathy and Allen [9]. . The corresponding cooling curves demonstrate that most of the reactions and events that occur during heating are irreversible. Thermogravimetry tests provide insight into chemical reactions involving loss of weight while dilatometry tests that measure change of length may detect other reactions not necessarily accompanied by loss of weight. Influence of Cement Paste Choosing one portland cement over another will do little to improve the properties of concrete at high temperature. Then. This Harmathy and Allen attributed to the accommodating plasticity of the cement paste at high temperatures. and overlapping. The dehydration of calcium hydroxide to form the oxide is a relatively simple process occurring generally between 400 and 600 ~ (752 and 1112 ~ Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. silica flour. among other investigators. While a case may be made for using pozzolanic or blast furnace slag cements mainly because these produce lesser amounts of calcium oxide as a result of dehydration and also for using microfillers (fly ash. chemically bound water (nonevaporable) is released progressively from the complex system of low crystalline order. used such analysis to determine the overall stability of a variety of concretes and to pinpoint specific chemical and physical changes that occur with increasing temperature. did not cause a corresponding change in the concrete. and other hydrates in the cement paste and from the calcium hydroxide crystals formed when the cement originally hydrated. calcium silicate hydrates.SMITH ON RESISTANCE TO HIGH TEMPERATURES 393 served behavior of concrete at high temperatures. Cement dehydration or the decomposition of carbonate aggregate and the chemical stability of lightweight or siliceous aggregate concretes are very evident in their loss-of-weight test data. High alumina cements are used in refractory concretes but may not be appropriate for structural purposes because of the conversion phenomena which may occur under normal service conditions. The development of distress and the change for the worse in the thermal and mechanical properties of portland cement pastes that occurs with increasing temperature are the result of an uninterrupted series of physical-chemical reactions that are accompanied by shrinkage and microcracking. Desorption of what is commonly called evaporable water first takes place as the temperature increases. One important result from the change-of-length test was to show that the a-~ quartz transformation at 573 ~ (1063 ~ while certainly causing an increase in volume in siliceous aggregates. with the result that many investigators have confirmed that cement paste expands up to 100 ~ (212 ~ and then with further heating and loss of moisture. Total dehydration is only complete at 800~ (1472~ or above. The resulting influence for the worse in the mechanical properties of concrete with increasing temperature is clear. one of the causative mechanisms. and differential thermal analysis [9. 11]. Thermal conductivity of cement paste is also dehydration dependent. thermal conductivity is only half its value at room temperature. dilatometric. In addition to the effects of thermal incompatibilities. though separate data related to the paste component alone are sparse. Thermal expansion is additive to shrinkage due to dehydration. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. will rehydrate to calcium hydroxide with a disruptive 14 percent increase in volume. resulting in shrinkage that is irreversible. its temperature endpoint is probably about 538~ (1000~ After exposure to sustained temperatures of 649 to 816 ~ (1200 to 1500 ~ concrete is friable. Most of these decompositions are irreversible so damage to concrete from this cause at sustained high temperatures is essentially permanent. and. At 750~ (1382~ where the paste is much dryer and more porous.394 TESTS AND PROPERTIES OF CONCRETE Subsequently the calcium oxide thus formed. after cooling and in the presence of moisture. the decrease in evaporable and chemically bound water with progressive dehydration of the paste modifies the physical bonds existing initially in the concrete and promotes microcracking. the dehydration of the silicate hydrates and other compounds present. it contracts rapidly to a degree that more than equals the initial expansion. porous. through any intermediate stages. On the other hand. is a very important component to the overall behavior of concrete because of incompatibility with the same properties in the aggregates. thus for dehydrated cement paste to serve a useful present and future purpose. The stage reached at any given temperature is dependent also upon the rate of heating since all the reactions are not instantaneous. Above 500~ (932~ shrinkage again changes to expansion. . Many of the above events are evident in thermogravimetric. Zoldners' review of experimental thermal data [12] shows that the variation of thermal properties of the cement paste with temperature. No further reproductions authorized. Actual values of the apparent coefficient of contraction or expansion are time dependent as is dehydration. in particular thermal volume change. the lower the moisture content the lower the thermal conductivity. is more complicated and gradual and not fully understood. and (b) an apparent thermal expansion that is a hygrothermal contraction dependent on the internal transportation of moisture between various states in the capillaries and gel pores. usually can be taken apart with the fingers. There appear to be two components to thermal volume change of paste prior to decomposition: (a) a true thermal expansion that is essentially constant and reversible. Copyright by ASTM Int'l (all rights reserved). after cooling. SMITH ON RESISTANCE TO HIGH TEMPERATURES 395 Influence of Aggregates Unlike the situation with cements. The calcined material is also less dense and hence a better insulator. man-made or natural. . At higher temperatures other internal volume changes occur and the crystal form may be metastable. Furthermore. The first point is that carbonate aggregates are decomposed chemically by heat whereas siliceous aggregates in general are not. Most striking is the transformation of the quartz crystal from the a to [3 polymorph at 573 ~ (1063 ~ with an increase in volume. forms an inert insulative layer thus further retarding temperature rise in the concrete. Though not entirely justified by fact. shales. quartz has a much greater coefficient of thermal expansion than most other rocks up to 600~ ( l l 1 2 ~ The consequence in concrete is much greater thermal incompatibility between the cement paste and aggregate and hence greater internal thermal stresses. Between 660 to 979 ~ (1220 to 1795 ~ calcium carbonate breaks down into calcium oxide with the release of carbon dioxide. basic. they have serious deficiencies in their physical properties at high temperatures. the selection of one aggregate over another can have a great influence on the resistance of concrete to high temperature. many building codes and insurance rating handbooks group concretes into two or four classes of fire endurance rating depending on the aggregate used. calcareous. and this is discussed later when the spalling phenomena are considered. escaping from the surface of the concrete in considerable volume. Many people have ascribed a greater tendency to spalling for these reasons. the carbon dioxide. Furthermore. in particular the crystal form transformation. though siliceous aggregates may be chemically stable. Since the aggregate fraction is about 70 to 80 percent of the concrete and it dominates high temperature performance. No further reproductions authorized. Crushed firebrick and fused aluminum oxide (corundum) and other special aggregates used in refractory concretes are at the top of the line. On the other hand. Then in descending order of fire endurance come expanded slags. To summarize the pros and cons of carbonate and siliceous aggregates --on the whole. The advantages of lightweight aggregates. slates. and lastly siliceous aggregates. are discussed in connection with lightweight concrete and attention naturally focuses on the reasons for the significantly different behavior of calcareous and siliceous aggregates which are the most widely used in normal weight concretes. it is wise to look at some Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the benefit of carbonate aggregates is the positive one of being a better insulator. and clays. air-cooled slag. finely grained igneous rocks such as basalt. Magnesium carbonate is likewise decomposed between 741 and 838~ (1365 and 1540~ Both reactions are endothermic thus absorbing heat and delaying temperature rise in the concrete. Most rocks contain different minerals and crystal forms and. reviewed by Zoldners [I2] probably provide the most recent complete sets of data available on rock thermal expansions up to 1000~ (1832~ For most rocks. An amorphous mineral can have a much lower coefficient of expansion than the same mineral when crystallized and again this is reflected in rocks. basalt. Igneous rocks such as granites. gneisses. A rock of only one mineral type usually has the average coefficient of expansion of the individual crystals. have composite complex coefficient of thermal expansion that are nonlinear with temperature and. while anorthosite. sandstone. Upon heating. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. that is. However. quartz. on mineral composition and structure. and barite rocks.396 TESTS AND PROPERTIES OF CONCRETE of the thermal properties of rocks in more detail before turning to concrete. and a strong influence of the presence or Copyright by ASTM Int'l (all rights reserved). At normal temperature the highest values of thermal conductivity are associated with silica-rich rocks such as quartzites and sandstones. The "ideal" aggregate from a thermal conductivity point of view would seem to require an amorphous microstructure and porous macrostructure. mineral composition is the dominant factor and therefore it is reasonably possible to compute the coefficient of thermal expansion of composite rocks from the weighted average of that of the individual minerals. and rhyolites have intermediate values as do limestones and dolomites. a specification best met by lightweight aggregates. a thermal expansion as close to that of the paste as possible in order to minimize development of parasitic thermal stresses. and through the orientation of the crystals this is reflected in the rocks formed from them. where the rock is porous. and a high specific heat to absorb heat. Canada. are also moisture content dependent. and limestone show relatively little change. Thermal expansion of aggregates at high temperatures depends. anorthosite. The desirable properties in case of fire are low thermal conductivity that delays temperature rise. . Low values are found in basalt. Studies by Mines Branch. in some cases by as much as 50 percent between 100 and 573 ~ (212 and 1063 ~ Mirkovich [13] provides experimental values over the range from 100 to 800~ (212 to 1472~ He found the greatest decrease in thermal conductivity occurs with those rock types that show the greatest thermal expansions. dolerite. No further reproductions authorized. and granite. as it does at more normal temperatures. expanding differently in different directions. Some minerals are anisotropic. thermal conductivities decline (with the exception of amorphous and monoerystalline rocks). the rate of thermal elongation is many times greater at the 500~ (932~ mark and above than at room temperatures. This connection between thermal conductivity and expansion is ascribed by Zoldners [12] to the fact that higher thermal expansion stresses cause more microcracking of crystals and loosening of grains resulting in increased rock porosity and hence decreased thermal conductivity. therefore. continuity over supports or providing restraint of members. Hot-rolled steel reinforcing bars show a linear decrease in yield strength with increase in temperature up to about 370~ (700~ amounting to about 15 percent. Sands. After that the decrease is more Copyright by ASTM Int'l (all rights reserved). . among other factors. and zeolite inclusions in basalt are unstable at temperatures as low as 300~ (572~ because they contain hydrous minerals that dissociate readily. Such systems include continuous slabs or beams. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and plates that are less prone to collapse than statically determinate structures such as simply supported beams. and Fillers (812-51)). Further changes involving sudden volume increases may occur at higher temperatures and contribute to the generally less desirable performance of siliceous aggregates. Of all the rocks examined in this test series. However. arches. frames. No further reproductions authorized. the test does not appear to have been applied to portland cement concrete aggregates. and employing statically indeterminate structural systems. The ultimate moment capacity of a normally reinforced concrete section at a particular temperature is a direct function of the steel yield strength. Calcium carbonate rocks show contraction after about 900~ (1652~ and dolomites after about 800~ (1472~ (on decomposition to the oxides).SMITH ON RESISTANCE TO HIGH TEMPERATURES 397 absence of quartz is evident. Embedded Steel and the Influence of Structural Systems A prime objective in the design of fire-resistant structural concrete is to prevent collapse for as long as possible. From the measured values of strength reduction an ordering of various types of aggregate by merit was developed. anorthosite showed the best thermal stability up to 1000~ (1832~ Although basalt shows a similar low expansion up to 600~ ( l l 1 2 ~ this increases at higher temperatures and rapid expansion occurs above 900~ (1652~ One general point to note is that fine grained rocks generally seem more durable than coarse grained ones. Unheated and heated aggregates (after 1 day at 250~ (482~ or 15 min at 500~ (932~ or 2 min at 1000~ (1832~ were tested by Shergold [14] in a modified aggregate crushing and impact test (British Standard Sampling and Testing of Mineral Aggregates. A high expansion rate after 650~ (1202~ is stated to possibly indicate a high biotite mica content. This requires keeping any embedded steel as coot as possible for as long as possible. A few rock types such as phonolite. This ordering appears to be in general agreement with that of the other investigations referenced previously. tinguaite. One surprisingly simple test for the overall durability of an aggregate was developed for use in determining the resistance of aggregates to high temperatures during the drying process prior to the proportioning and mixing of bituminous concrete. An abrupt leveling of the expansion curve at about 600 ~ (1112 ~ indicates the presence of quartz (after the 573 ~ (1063~ inversion). However. Changes in the coefficient of thermal expansion of steel at high temperatures are related to changes in the phase and crystal composition of the steel. The coefficient of thermal expansion of steel varies with temperature in a dissimilar manner to that of concrete at very high temperatures. especially in simply supported members.) cover would reach over 427~ (800~ whereas with 50-mm cover (2-in. concern was expressed that the thinner concrete sections would offer less protection to the steel tendons. For the same normal weight concrete exposed in a standard fire test for 1 h steel with only 25-mm (1-in. but is generally close to that of concrete where compatibility is critical at lower temperatures. Similar orders of limitation on steel temperature with increased cover are applicable to other periods of fire exposure. or slightly higher than. No further reproductions authorized. This effect and the difference in coefficients of thermal expansion may adversely affect the local bond of concrete to steel at higher temperatures. high-carbon steel and then stress relieved.) the steel temperature would be about 204 ~ (400~ With 7S-ram (3-in. Thereafter it declines. Fire protection requirements relating to structural steel encased in concrete are covered in Ref 4. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and the steel temperature then rapidly becomes high enough to dehydrate the cement paste. whitish. When prestressed concrete first came to the fore. A S0-percent loss in yield strength Copyright by ASTM Int'l (all rights reserved). It was thought that this could result in excessive deflections and earlier failure than with normal reinforced concrete. steel that has remained encased in concrete will recover much of its lost strength on cooling and only exposed reinforcement that has become distorted and twisted will usually need replacing or supplementing. Both the coefficient of thermal expansion and the thermal conductivity of steel influence the performance of the surrounding concrete in a fire.398 TESTS AND PROPERTIES OF CONCRETE rapid and reaches 50 percent by about 593~ (1100~ Less than 20 percent of the original yield strength remains at 760 ~ (1400 ~ The length of time before steel reaches a critical temperature in a fire depends on the amount of cover to the steel and on the insulative properties of the concrete. Up to about 316~ (600~ the bond strength between steel and concrete is the same as. porous layer is evident surrounding reinforcing steel embedded in otherwise sound concrete. The influence of cover is striking. The thermal conductivity of steel is much greater than that of concrete and sometimes after a fire a thin. resulting in direct loss of prestress and relaxation of steel stress at high temperatures [5]. . Above about 260 ~ (500~ the loss of tensile strength is greater than that for normal reinforcing steel. High tensile prestressing wire and strand is cold drawn from hot-rolled. The coefficient increases with temperature up to 649~ (1200~ decreases to zero in the range up to 816~ (1S00~ and then increases again.) cover the steel would probably be hardly warm to the touch. at room temperature. Usually this happens if part of the bar has become exposed to the heat source (as by spalling). Further discussion of design philosophy by Gibbons is found in Ref 15. or bond strength are available. prestressed. and shows some-modest advantages in high temperature performance. each concrete. Variables include: (a) whether the concrete is restrained or not during heating. when a prestressed tendon is heated. It should be emphasized that there is no one critical temperature or condition at which embedded steel (normal reinforcement. stress relaxation also reduces the prestressing force and substantial relaxation losses may remain after cooling. While little data directly related to tensile. or after heating and cooling. and (e) whether it is quenched or allowed to cool slowly. will have different strength values at different temperatures. and applicable material properties offers promise that the rational design of concrete structures for a particular high temperature resistance may soon become as routine as any other design task. No further reproductions authorized. much of the direct tensile strength loss is recovered. and ultimate collapse of a member. depends on the circumstances of the superimposed conditions. (d) whether it is tested while hot or after cooling. The dead and live load intensity. deflection. depending on the behavior of the cement paste and aggregates. (c) whether the concrete is subject to thermal cycling. Actual fire experience and numerous studies of prestressed concrete structural assemblies in standard fire tests result in a well placed confidence in the high-temperature performance of prestressed concrete provided its singular features in this respect are taken into account during design and construction. shear. In addition. Uddin and Culver [1] published a state-of-the-art review in 1975 on the effects of elevated temperatures on structural members. and member restraint all influence the outcome in terms of the distortion. A combination of established engineering principles. . Treated "stabilized" wire or strand now coming into wider use has improved relaxation properties. Strength--Compressive and Flexurai The observed strength of the same concrete when heated to a particular temperature. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. compressive and Copyright by ASTM Int'l (all rights reserved).SMITH ON RESISTANCE TO HIGH TEMPERATURES 399 of prestressing steel occurs at about 427~ (800~ whereas this loss is only reached with hot-rolled reinforcing bars at a higher temperature of about 593~ ( l l 0 0 ~ High strength alloy steel bars used in some prestressing systems reach the 50-percent loss level at about 565 ~ (1050 ~ On cooling. or structural steel) suddenly fails. discussion of their paper in 1976 added a further 21 references. computerbased modeling of temperature-structural regimes. structural indeterminacy. continuity. However. While the 246 references cited are only up to 1971. Standard references in design handbooks cover the properties of structural and reinforcing steel at high temperatures. (b) whether free moisture is contained or not during heating. ) siliceous aggregate) cylinders with maturities of from 42 to 227 days conditioned at 24 ~ (75~ and 55 to 60 percent relative humidity. Using such apparatus and 75 by 150-mm (3 • 6 in. and (4) the original strength of the concrete had little effect on the percent reductions in strength observed. for siliceous aggregate concrete the corresponding temperature was 427~ (800~ (2) when loaded during heating. the ends of which usually are machined flat. (3) residual strengths after cooling were a little lower than the corresponding hot compressive strength.) concrete (10-ram (3/a-in. Temperatures are measured and controlled by surface or embedded thermocouples. For purposes of a general understanding only the more recent and significant studies have been referenced. Where length changes as well as strength are to be measured. and light-weight (expanded shale) aggregates. it is probably the most investigated property at high temperature. In summary. the compressive strength is important and specific data are needed if fire endurance is to be improved by these means. Copyright by ASTM Int'l (all rights reserved).) cylinders. Concrete specimens (cy]inders) have varied in size from 50 mm (2 in. However in the design of complex frames and continuous or restraine~t members. The testing regimes included heating without load and testing while hot. Because compressive strength is one of the prime qualities by which concrete is judged. his results showed: (1) carbonate and sanded lightweight aggregate concrete retained more than 75 percent of original strength up to 649~ (1200~ when heated unstressed and tested hot. and testing after slowly cooling.) length to 100 mm (4 in. To maintain uniform temperature conditions. siliceous. . In simply supported members. differences in the strength of concrete in the compressive zone have relatively minor consequences and do not affect fire endurance. Usually the specimen is heated by means of an electrically or gas heated furnace which jackets the concrete cylinder. No further reproductions authorized.) diameter and 100 mm (4 in.). Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.400 TESTS AND PROPERTIES OF CONCRETE flexural concrete strengths at elevated temperatures have been studied widely. Turning to Malhotra [17]. Access to earlier work is by Ref 1. heating at three stress levels and testing while hot. then extension rods or optical devices may be used to bring the gage points outside the furnace.) by 200 mm (8 in. load is applied from the testing machine platens through preloaded cement-asbestos disks above and beneath steel cylinders. Abrams [16] determined the compressive strength of concrete between 93 and 871 ~ (200 to 1600~ for concretes in the strength range of 23 to 45 MPa (3300 to 6500 psi) that contain carbonate. who tested 50 by 100-mm (2 by 4 in. Various techniques have been used to modify the compressive strength testing procedure used at normal temperatures (ASTM Test for Compressive Strength of Cylindrical Concrete Specimens (C 39)) to permit testing at high temperatures in the usual type of universal testing machine. compressive strengths were 5 to 25 percent higher but were not affected by the applied stress level. For Copyright by ASTM Int'l (all rights reserved). If concrete specimens are quenched.SMITH ON RESISTANCE TO HIGH TEMPERATURES 401 provides the following observations on some additional factors: (1) aggregate/cement ratio had little bearing on changes in coriapressive strength up to 204~ (400~ however. They were a gravel comprised mainly of a mixture of metamorphic and granitic igneous rock. as may happen to actual concrete hosed down with water during a fire. His tests also confirmed those of Abrams with respect to the benefit of the concrete being under compressive stress (in the order of design stress) when heated.65 had little influence on reduction of compressive strength of concrete (up to 593~ (1100~ in his tests).16] bare also noted in certain conditions of test. and an expanded slag. . the decline of flexural strength is much greater than that of compressive strength. and (3) above 525~ (977~ the expanded slag aggregate concrete outperformed the others whereas below that temperature it was equal or inferior in compressive strength. The observation about an increase in strength in the lower range of temperature is an interesting one that other investigators [10. This he attributed to thermal shock. He also recorded an additional reduction of compressive strength of about 20 percent in specimens tested after cooling. up to about 500~ (932~ there is a greater reduction in residual compressive strength than when slowly cooled. and (2) water/cement (w/c) ratios in the range from 0. (2) the sandstone aggregate concrete showed a significant strength gain up to about 300~ (572~ after which deterioration was rapid. a relatively pure sandstone. at 400~ (752~ only 85 percent of the initial strength remained as compared with over 95 percent for the limestone. a high-calcium.37 to 0. Speaking generally. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. fine-grained limestone. No further reproductions authorized. Zoldner's [18] results include the effect of four different aggregate types on compressive strength at elevated temperatures. His conclusions provide three additional pieces of information in addition to generally agreeing with Abrams [16]: (1) the crystalline igneous and metamorphic rock gravel aggregate deteriorated more rapidly than did the limestone aggregate concrete. The commonest procedure for determining flexural strength appears to be a modification of three-point loading of small beams along the lines of ASTM Test for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)(C 78) [18. He also noted a harder outer shell in cylinders quenched due to rehydration of the cement. above this temperature lean mixes showed a proportionally smaller reduction in compressive strength than occurred with richer mixtures. and that at higher temperatures this largely eliminated the difference in strength between quenched and slowly cooled specimens.19]. then as Zoldners [18] showed. The decreases observed in flexural strength are not necessarily of the same order and magnitude as those for compressive strength of concrete of the same mix proportions and containing the same constituents [18]. Poisson's Ratio. made up to 400~ (752~ that for a given mortar or concrete (with siliceous aggregates). the value of E after cooling was essentially the same as that prevailing at the high test temperature. Marechal [21] also calculated Poisson's ratio. crushed rock aggregate (mainly porphyry and quartzite). and gravel aggregate (siliceous and siliceous limestone) at one cement factor and found the reduction in this modulus to be aggregate dependent. In general terms. or by displacement measurements as by Sullivan and Poucher [19] on concrete specimens heated within a furnace. At high temperatures the value of E.34 X 10 -6 and final values at 760~ (1400~ of from 0. Copyright by ASTM Int'l (all rights reserved). Sullivan and Poucher [19] noted in their tests.30 X 10 -6 some benefit was found in low w/c ratios and air drying. and age. and Bulk Modulus The ratio of stress to strain is one of the most important of concrete structural parameters. Because of sensitivity complications in the test procedure the results were erratic but a general tendency to decline with increasing temperature was apparent. Philleo [20] noted that the value of E depended on initial w/c ratio. . thus determining that the reduction in E with increasing temperature is a permanent one. but more hopefully found only a 50 percent flexural strength reduction with limestone aggregate concrete at 400~ (752~ (a reduction level which he found to occur at over 600~ ( l i 1 2 ~ in the case of compression). Sullivan and Poucher [19] found the flexural strength of a siliceous aggregate concrete at 400~ (752~ varied from 25 percent to 0 percent of the original strength. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the modulus of elasticity. Marechal [21] looked at the variation of E with temperature for expanded clay. No further reproductions authorized. in the above order. curing regime. He made further calculations for the bulk modulus K which declined with temperature in a curve parallelling that for E.91 to 2. Modulus of Elasticity. there is a decrease in E in the order of 10 to lS percent between initial values at room temperature and those at 100~ (212~ E then remains relatively constant up to 300~ (572~ after which a progressive decline sets in so that by 538~ (1000~ it is only half or less than half of that before heating. Between unheated values for calcareous gravel aggregate concrete ranging from 3.20 to 7. may be obtained dynamically as by Philleo [20]. up to 400~ (752~ Philleo [20] was able to compute Poisson's ratio since he measured both flexural and torsional frequencies of vibration. Zoldners [18] obtained similar results.402 TESTS AND PROPERTIES OF CONCRETE example. Again quenching resulted in greater strength losses than occurred when specimens were tested hot. but did so directly from the longitudinal axial load and measured transverse strain data and a similar decline was found after the evaporable water had been driven off. 32. and 649~ (75. 316. and 1200~ respectively. Dependence on creep on moisture content is stressed by Marechal [24]. He also found that (a) the latter affects the creep rate more than the temperature. Cruz [22] also carried out exploratory stress relaxation tests under constant strain over a 5-h period. At 300~ (572~ they measured creep rates in concrete at three times those at 125~ (257~ and above 400~ (752~ they observed that creep increased very rapidly at low stress levels as a plastic stage was reached. (b) there was a nonlinear relationship between creep and stress level. Thermal Properties The basic thermal properties of concern to the behavior of concrete at elevated temperatures are: thermal conductivity (the ability of the material to conduct heat. and for fire resistance design. but the creep rate was higher when the concrete was subject to both high temperature and a high stress-to-strength ratio. Higher creep rates occur in saturated or sealed specimens for which a fully accepted explanation does not exist.SMITH ON RESISTANCE TO HIGH TEMPERATURES 403 Creep Data on inelastic behavior of concrete at high temperature is essential for nuclear applications. Copyright by ASTM Int'l (all rights reserved). Obviously. there is scope for more refined understanding of the viscoelastic properties of concrete at elevated temperatures if the practical effects are to be predicted by theoretical analysis supported by test data. since long term behavior under complex mechanical thermal loadings is involved. Recent investigations of concrete under transient high temperature conditions. and (c) with a lower w/c ratio. If inelastic behavior is not taken into account and if only data secured on small specimens are used. a ratio of the flux of the heat to the temperature gradient). Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. including time-dependent effects such as creep and relaxation. creep was less. A study by Wang [23] of high strength concretes 38 and 46 MPa (5500 and 6700 psi) containing quartz gravel aggregate over the temperature range from 93 to 427~ (200 to 800~ showed that the shape of creeptime curves was the same as at room temperature. . Stress was reduced by 2. confirm that a very complex pattern of behavior probably exists [25]. A first step in overcoming the continuing elusiveness of creep at high temperature was to devise apparatus for measuring it as reported by Cruz [22]. No further reproductions authorized. if the effects of restraint are to be taken into accout. 600. overestimations of the affected parameters will occur. while the reverse was true below 200~ (392~ to the development of microcracking between aggregate and paste. and 74 percent at 24. In addition to creep tests. Sullivan and Poucher [19] attributed the fact that creep rates for concrete above 200~ (392~ were higher than those for mortar. cement pastes. while overridden to some extent by the greater contribution of the aggregate fraction to the overall apparent specific heat of concrete. and Specific Heat Thermal conductivity and diffusivity of a mixture such as concrete are not additives of the properties of the constituents and there are difficulties in experimental determination at a given elevated temperature. Data from Harmathy (and Allen) [11. However. though other physiochemical changes also contribute. Thermal Conductivity. must be taken into account if reasonably accurate results are to be attained in heat flow model studies. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Transient methods. and the two more widely understood parameters of specific heat and the coefficient of thermal expansion. A. it is essential to stress a number of very significant differences between the thermal behavior of concrete. and aggregates at elevated temperatures as compared with those at more normal temperatures. both of which exist side by side in a nonhomogeneous material such as concrete.9] and other investigators show Copyright by ASTM Int'l (all rights reserved). Difficulties also plague direct measurement of true specific heat at elevated temperatures. Diffusivity. . However.404 TESTS AND PROPERTIES OF CONCRETE thermal diffusivity (the rate at which temperature changes can take place). and the other on the time-temperature rise response to heat pulses to determine difussivity. "Thermal Properties" by J. Rhodes. also present problems. Equilibrium at the test temperature is disturbed in making the determination by standard physical methods and chemical dehydration reactions take place in the cement phase which may add or subtract heat. a self-defeating state of affairs. One is based on fitting a temperature distribution curve used (assuming linear heat flow) to determine all thermal properties. such as the hot wire method. Harmathy [27] offers two variable state methods which appear to overcome the various problems associated with other methods. These properties and test methods are more fully discussed in the chapter. No further reproductions authorized. which also contains tables summarizing experimental values (also given in Ref 12). Thompson [26] discusses the shortcomings of steady state methods such as the hot plate (ASTM Test for Steady-State Thermal Transmission Properties by Means of the Guarded Hot Plate (C 177)) or hot box (ASTM Test for Thermal Conductance and Transmittance of Built-up Sections by Means of the Guarded Hot Box (C 236)) standards and indicates that meaningful determination would only be possible after moisture equilibrium is reached. since the hot wire does not present a surface of constant flux and the initial temperature rise in the wire in a region of high conductivity will be less than in a region of low conductivity. mortars. Experimental errors are greater. Such latent heat effects. Both are accompanied by the necessary mathematical interpretations. These are due principally to accompanying moisture migration-desorption. Values reported in Ref 9 for a range of concretes over a temperature range from normal ambient to 650~ (1202~ show a slight trend to higher values with higher temperature. Harmathy and Allen [9] confirm this order of reduction and find that all thermal diffusivities became approximately equal at about 600~ (1112 ~ whereas at lower temperatures there was considerable difference between Iightweight aggregate and normal weight aggregate concretes. Moisture content has a significant role in heat conduction in concrete until dehydration is complete after which. Fortunately. including the contribution from moisture present. For normal weight concretes. and with decomposition of the constituents. . thermal diffusivity (h). the now dry. and specific heat (c) are simply related by the expression k ---. both thermal conductivity and diffusivity show considerable decrease at high temperature.SMITH ON RESISTANCE TO HIGH TEMPERATURES 405 considerable dispersion in values for the specific heat of concrete. porous. with the relatively small variation in specific heat with temperature. The greater the moisture content the greater the thermal conductivity according to data summarized by Zoldners [12]. in general. Harada et ai [28] cite a 50-percent decrease at 800~ (1472~ as compared with thermal conductivity at room temperature. did not merge the aggregate groups at the upper temperature. This is most apparent between a dry lightweight concrete and a normal weight concrete. A high specific heat. and specific heat) are important to overall behavior of concrete at elevated temperature because they essentially determine the inward progression of Copyright by ASTM Int'l (all rights reserved). thermal conductivity (k). a 20-percent increase in thermal conductivity was noted assuming both were consolidated fully. No further reproductions authorized. This is not surprising in view of the experimental difficulties encountered but. specific heat appears to be insensitive to the aggregate used or to the mix proportions of the concrete. Their data on conductivity. normal weight concrete becomes a much better heat insulator than at lower temperatures. diffusivity. density of the concrete is an important overall parameter when low density is due to air voids.hcp where p is the density. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. has the advantage of taking up more heat and delaying temperature rise in a fire. Conductivity and diffusivity hence vary in step and. From an examination of ]6 concretes made with Type 1 cement and a range of aggregates and processes used in the manufacture of concrete masonry units. while showing a similar trend. The three thermal properties so far discussed (conductivity. For a lean concrete as compared with a rich one. The lightweight aggregates showed lower diffusivities and less reduction with increase in temperature than did concretes of normal weight. volume changes due to chemical reactions. concrete shows thermal expansion in linear up to about 260~ (500~ then after a transition period there is a further iinearity about 427~ (800~ but at a higher coefficient. in nuclear reactors where significant temperature gradients are a feature of normal operations. . As already discussed. probably due to a permanent dilation as a result of decomposition. after completion of dehydration. There are three components of volume change in concrete at elevated temperatures to consider. On the microscale they influence the thermal incompatibilities that occur between the cement paste and aggregates due to differential thermal volume changes. clear of the furnace containing the specimen.406 TESTS AND PROPERTIES OF CONCRETE temperature rise into concrete and hence the extent of damage that may occur to steel or concrete in a fire. Unless relieved by creep or plasticity in the paste. Zoldners [12] summarizes data from other investigations which show that the thermal coefficient of expansion of concrete is in approximate proportion to the weighted value of those of the aggregates once initial shrinkage of the cement paste due to dehydration has occurred. Thermal Volume Change and Thermal Incompatibilities The observed thermal expansion in concrete is an additive of those of the components. As well as true thermal volume changes. for example. Looking at Philleo's data [20] for a calcareous aggregate. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. also occur. Above 538~ (1000~ the coefficient is again lower. decomposition of calcium hydroxide or rchydration of the lime. A point of particular interest in this data is that the expansion curve for limestone aggregate concrete is very close to that of mild steel over the temperature range up to 700~ (1292~ Between the "best" natural Copyright by ASTM Int'l (all rights reserved). the thermal expansion of the paste is highly dependent on moisture content while that of the aggregate is highly dependent on mineral composition. these parasitic thermal stresses may be very high. They are also important in heat flow calculations necessary in the design of structures for performance at elevated temperatures as. the transition in quartz crystals. No further reproductions authorized. Philleo's experimental technique seems fairly typical of those used to secure such data. The coefficient of thermal expansion of concrete with increasing temperature thus tends to approach asymptotically that of the rock type in the aggregate [28]. The term "thermal incompatibility" is used widely to describe those differential volume changes which result in differential strains and hence stresses between aggregate particles and paste and between the constituent minerals of each. The horizontal displacement between two wires hung vertically from gage points on a horizontal concrete beam is measured at the test temperatures. and changes in physical form of the component materials. for example. for example. As compared with concretes containing limestone aggregate and a variety of portland and high alumina cements. No doubt. Philleo's work [20] did include three cement factors and corresponding w/c ratios. as will be discussed. Specimens having a higher w/c ratio and lower cement factor tended to have the higher coefficients. though at different rates. No further reproductions authorized. if not as yet fully explained. These data are for only one cement factor. it is not surprising that the effect of more than one thermal cycle has only really been addressed after interest arose in using concrete in nuclear reactor vessels. The effect of thermal cycling on strength has been investigated by Camp- Copyright by ASTM Int'l (all rights reserved). one w/c ratio. Crispino [32] pursued an investigation to find the best combination of thermally compatible materials that would hence give good performance as a structuraI concrete for nuclear reactor pressure vessels at high temperature under thermal cycling.SMITH ON RESISTANCE TO HIGH TEMPERATURES 407 rock aggregate concrete investigated. While the cement paste is shrinking as dehydration proceeds. effect on the mechanical properties of concrete in which. Further reading is provided by Dougill [30]. the coefficient of thermal expansion was halved [28]. Above 427~ (800~ these variables and initial curing (moist or air dried) had little effect. After dehydration is complete. . the aggregate is expanding. in the case of an expanded slag or shale lightweight concrete. moisture effects may play a substantial role. there is a clear. Thermal Cycling Since most investigations in the past have addressed fire resistance. a slight overall contraction with an almost constant coefficient up to 900~ (1652~ In all cases an initial shrinkage up to about 300~ (572~ is noted. however. below 260~ (500~ all these variables did affect the coefficient values to a greater extent. As a result. he found barytes aggregate with portland cement far superior. thermodynamic based theories that fully account for the role water and a variety of physico-chemica! phenomena play will be forthcoming one day in a graduate thesis. Considerable hypothesizing continues toward a full explanation of the behavior of concrete at all temperatures with respect to thermal properties. Zoldners' own data [18] show a very rapid expansion above about 400~ (752~ for a predominately metamorphic and igneous gravel aggregate concrete and for a sandstone aggregate concrete. he provided full data on most mechanical properties up to 500 ~ (932 ~ The importance of thermal incompatibilities and the resulting thermal strains and stresses cannot be overemphasized. andesite and limestone or sandstone concrete. However. and one aggregate/cement ratio. as compared with limestone aggregate concrete and. both are expanding. In addition to documenting the thermal properties. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and firebrick aggregate concretes up to 302~ (STS~ and noted a progressive deterioration with increasing number of thermal cycles though most of the loss occurred in the first few cycles. Behavior Mechanisms and Influence of Moisture Content The stresses from thermal loadings due to overall expansion or contraction.408 TESTS AND PROPERTIES OF CONCRETE bell-Allen and Desai [31] and Campbell-Allen et al [32] who compared the compressive strengths of linestone.32]. For a constant moisture condition (sealed) of the concrete its thermal coefficient of expansion decreased during thermal cycling to 143~ (300~ A similar decrease was observed for concretes which successively dried out during thermal exposure. After the first thermal cycle (21 to 143 to 21~ (70 to 300 to 70~ of the concrete in a moist condition. Polivka et al [33] examined concrete that allowed moisture a controlled escape or sealed it in. In examining the significance of data from thermal cycling and sustained high temperature tests. when added to those arising from mechanical loadings. and thermal volume change is also important in nuclear applications of concrete. determine the imposed total stress levels in the concrete. expecially where thermal cycling occurs. However. a significant residual expansion was observed. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. are dependent on time or the rate of temperature increase.31. over durations up to 14 days of thermal exposure cycling up to 143~ (300~ They showed that: 1. 2. The interrelationship of thermal cycling. thermal stresses on a smaller scale between particles determine the resisting strength. compressive or tensile. moisture content. and this expansion successively increased with the number of cycles. of the concrete and the effect on other mechanical properties such as the various moduli. . Thermal strain incompatibilities and the resulting parasitic thermal stresses are thus critical to performance of concrete at high temperature. No further reproductions authorized. Thus investigators have explained their observations on compressive strength changes with temperature in general terms of the changes in physical properties of the cement and aggregate and the thermal incompatibilities between these components with temperature. expanded shale. From petroCopyright by ASTM Int'l (all rights reserved). the nature of the thermal regime must be considered since many of the reactions influencing the measured thermal and mechanical properties including the internal transport or the explusion of water. This was also true for concrete specimens that were permitted to lose moisture during thermal exposure. A larger permanent expansion was observed for concretes of high moisture contents than for those of lower moisture contents. Similar effects are observed with flexural strengths and modulus of elasticity attributable to incompatible dimensional changes between cement paste and aggregate and to observed microcracking [19. etc. quench heating and cooling. Deterioration of structural properties under both moisture conditions (sealed and unsealed) can be expected from any test variable that can produce large temperature differentials in the concrete on heating (for example. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. lime-rich calcium silicate hydrates producing lower strength. Poisson's ratio. and relaxation of bonds. Whereas small defects would have little effect on compressive strength. The advantage in compressive strength where the concrete is preloaded in compression is ascribed to the suppression of thermal microcracking in the cement paste and the increase in compressive strength at moderately high temperatures has been attributed by Zoldners [18] to "a heat stimulated cement hydration and densiflcation of the cement gel due to the loss of absorbed water. microcracking. 2. use of very large specimens. For concrete that is heated slowly at atmospheric pressure. 1. First. Zoldners [18] attributed the greater reductions in flexural strength as compared with compressive strength at the same temperature to microcracking. and bulk modulus K with increase in temperature follow the general pattern for reduction in compressive strength. Since the reductions in modulus of elasticity.SMITH ON RESISTANCE TO HIGH TEMPERATURES 409 graphic examination.) While their data strongly support the role of moisture content in influencing mechanical properties of concrete at moderately high temperatures. Lankard et al [34] reviewed existing data secured on specimens at elevated temperatures from which moisture could escape. these have usually likewise been put down to thermal incompatibilities. they do provide somewhat of a challenge to the views expressed by others on the role of microcracking. the primary factor influencing changes in the structural properties is the hydrothermal reactions that can occur in the cement phase and that convert the original highly cementitious calcium silicate hydrates into crystalline. they would immediately show up as a reduction in flexural strength. 4. . No further reproductions authorized. and probably most important. made their own tests on both sealed and unsealed specimens up to 260~ (500~ and provided this summary. the influence of heat exposure per se on the structural properties of concrete is critically dependent on the moisture content of the concrete at the time of heating and is quite different for concrete in which the moisture is free to evaporate as compared to concrete sealed against moisture loss. 3. For concrete slowly heated at saturated steam pressures. Copyright by ASTM Int'l (all rights reserved). the primary factor influencing changes in the structural properties is the loss of free water. Abrams [16] draws attention to microcracking and deterioration in aggregate to paste bond. Partial loss of chemically combined water (dehydration of hydrated cement phases) occurs above 121~ (250~ and primarily affects the flexural strength." From his pulse velocity measurements. In "saturated steam" conditions. Polivka et al [33] established that at 143~ (300~ a maximum reduction in strength and stiffness. once dehydration proceeds to a significant loss of other forms of water and to decomposition of the cement hydration products. occurred at an intermediate moisture content corresponding to about a 50percent loss of the free water in the concrete. in the order of 75 and 55 percent respectively.410 TESTS AND PROPERTIES OF CONCRETE For unsealed specimens they noted the microcrack system was no worse after careful heating. This observation helps to explain that compressive strength decline is not significant below 260~ (500~ (and in some cases may even increase) provided all the free water is removed on heating. It also adds to the usual explanation of the development of flaws and stress concentrations around flaws to account for the reduction in tensile strength with temperature being greater than that for compressive strength. However. The removal of free. sometimes accompanied by spalling in which moisture expulsion plays a significant role. . and once aggregate deterioration and thermal incompatibilities increase with increasing temperature. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Lankard et al [34] found a continual and much greater decline in compressive strength and modulus of elasticity up to 260~ (500~ Compressive strength at the upper temperature was only 50 percent of original while the modulus of elasticity fell to only 31 Copyright by ASTM Int'l (all rights reserved). moisture is usually free to be progressively driven off from the concrete. nonload bearing water also appears to account for the observed behavior of the independence of the reduction in modulus of elasticity with temperature at moderately high temperatures. in a fire. even where it is cool and open on the other. possibly not as bad as that in the original concrete. The justifications for this are that most tests at normal temperature are made on small specimens and. But it does appear that the presence or lack of free water is the controlling parameter at lower temperatures. Most of the data so far discussed on the thermal and mechanical properties of concrete have been secured by testing small unsealed specimens. No further reproductions authorized. then these latter mechanisms appear to account fully for the observed behavior. However. nuclear reactor shields and primary containment vessels present a different set of conditions in which the concrete essentially is sealed against moisture loss. The prestressed concrete sections tend to be massive and concrete may be hot and sealed by a steel liner on one side. In hot sealed areas the exposure conditions may be quite akin to autoclaving mature concrete and. In this case they considered that the benefit of free water removal is offset by the loss of chemically bound water which reduces the critical stress requirements for tensile failure. with chemical and mineralogical changes in the component phases of the concrete and restriction on the mobility of moisture. there is a greater reduction with temperature in the physical properties of concrete than occurs when the moisture is freely driven off. the quartz volume change may not be as significant as earlier thought. Because it influences almost every parameter of concrete behavior. this apparent lack of control is the real situation when mature or young concrete is exposed to fire and sometimes it spalls and sometimes it does not. No further reproductions authorized. For many years direct thermal causes. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. While it is still not possible to cover every circumstance of possible moisture condition in a standard test. the present requirements are an improvement and save time and money. or pores if the water was not present. are known to lead to lower strengths. they determined from X-ray analysis the presence of new. Natural drying has been replaced with a specified conditioning regime of relative humidity and temperature and moisture content at the start of the test. particularly at arris. There are two possible causes of such spalling: thermal incompatibilities and moisture entrapment. The contraction of cement paste is due to the expulsion of free water and while water is a relatively poor direct conductor of heat as compared with aggregate. in particular such things as the 2. if they occur in autoclaved products. thus making for more rapid inward progress of the heat into the concrete and increasing the probability of embedded steel being adversely affected. more highly crystalline. capillaries. is an evident feature of most fire damaged concrete. In observations of the composition of the hydrated cement phases under these sealed heated conditions. Many of the disparities in the results of physical tests for strength and other properties in the investigations referenced are probably explained by lack of control on the moisture parameter and the temperature gradient in the concrete. including spalling. However. and uniformity of moisture content in the concrete prior to fire tests has been of long standing concern. probably lime-rich calcium silicate hydrates some of which. especially if it becomes exposed. Spalling and Cracking Spalling of concrete surfaces. The amount of free water in concrete also has a major influence on thermal properties. This led to investigations and proposals to modify ASTM Test E 119 by preconditioning the specimens [35]. control. Experienced investigators such as Harmathy and Allen state Copyright by ASTM Int'l (all rights reserved). it is a many times better conductor of heat than is the air which would be occupying voids. The worst consequence of this process is that it opens up fresh surfaces to the heat source. However.4 percent increase in volume of quartz at 573~ (1063~ were considered a main contributing factor. No doubt the active debate and investigation into the role of moisture in concrete at elevated temperatures under both actual exposure conditions and in laboratory test conditions will continue the drive to further refine fire tests and develop better models to predict heat flow and structural behavior.SMITH ON RESISTANCE TO HIGH TEMPERATURES 411 percent of the original value. . the existing large vapor pressure differential would move the "moisture clog region" towards the colder region and the pressure buildup would level off). No further reproductions authorized. the vapor can only leave through the dry layer. A simple view is that the disruptive pressure causing spalling is the result of rapid heating with sufficient moisture present to produce saturated or superheated steam. The resulting thermal stresses may be sufficient to induce cracking. Thermal cracking may range from crazing on the surface and microcracking to deeper and substantial spalling or cracks of structural significance at locations where overall structural deformations or thermal stresses exceed the tensile capacity of the concrete. Moisture entrapment now is identified [36. As moisture is desorped in a layer adjacent to the heated surface. intensified desorption at the frontal plane and vapor pressure build-up. Shorter and Harmathy [37] offer an explanation called "moisture clog spalling" along the following lines. this does not appear to be an adequate explanation and it is worthwhile to examine a more plausible explanation in some detail. then the moisture in the concrete is most beneficial. It seems that by the temperature necessary for quartz expansion to occur the plasticity of the paste is great enough to accommodate the expansion. expanding and meeting increasing flow resistance as it goes. The absorption of heat associated with the desorption of moisture checks the rise in temperature in the concrete. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . Data on the thermal properties of cement paste. and concrete emphasize the thermal contraction and expansion strain incompatibilities that develop with increasing temperature.37] as predominate at least in the earlier stages of spalling deterioration. However. the vapor migrates toward the colder region and is readsorbed. and between the hotter and cooler parts of the concrete itself. In establishing an overall picture of the effects of moisture on the fire resistance of concrete. within and between the constituents.412 TESTS AND PROPERTIES OF CONCRETE they have never identified spalling due to this cause [9]. aggregates. if resistance of the pores to moisture flow was not too high. a very steep temperature gradient develops across the dry layer resulting in a high rate of heat flow. through sudden pop-outs of siliceous aggregate particles at or near the surface will likely occur. High moisture contents are conducive to spalling but if spalling did not take place (because. Because the concrete to the rear is saturated. As the thickness of the dry layer increases a completely saturated layer builds up at some distance in from the exposed face and later a sharply defined front forms between the two layers. Harmathy [37] stressed two very important practical points. If the permeability of the material is low the pressure build up at the front continues until a tensile spall occurs separating the dry layers from the rest. Planes of weakness Copyright by ASTM Int'l (all rights reserved). As the temperature of the exposed surface increases. and because of thermal shock. Sometimes it appears as though additional spalling occurs as the concrete cools down. a first step is to try to obtain an estimate of the temperature reached and its duration and hence a first estimate of the likely remaining properties of the concrete. similar metallographic methods may be useful. No further reproductions authorized. and reduced tensile and compressive strength of concrete when simultaneously exposed to tensile and compressive stresses (from the longitudinal prestress). Investigation of Fire Damage Once the structure is safe to enter after the fire. Though the effect of the temperature on normal reinforcing steel is not so critical. As temperature increases the color of siliceous or limestone aggregate concrete changes through pink or red to gray at about 600~ (ll12~ to buff at about 900~ (1652~ Harmathy [41] proposes thermogravimetric and dilatometric testing of samples secured within a day or two of the fire as a means of determining a temperature history inwardly into the concrete. The appearance of the concrete can also provide important evidence [39. these processes are not rapid and most likely the apparent spalling is simply the falling away of already loosened pieces of concrete.SMITH ON RESISTANCE TO HIGH TEMPERATURES 413 may also develop at the level of the reinforcing steel. Many circumstantial clues may be found by sifting through the debris and identifying the remains of common objects that have known melting points. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Permanent color changes may accompany dehydration of the cement paste. The approach is based on the fact that the continuum of reactions in the cement paste remains frozen at the temperature level reached (for at least a few days) and by comparison with a reference sample of unaffected concrete or standard data this temperature marker can be identified. Selvaggio and Carlson [38] in fire tests of prestressed concrete beams observed some cases of longitudinal tensile splitting through the full depth of the flanges and webs when the temperature at the level of the steel tendons was as low as 149~ (300~ By analysis they established that the differentia] thermal expansion between concrete and embedded steel can be a source of tangential tensile (bursting) stresses of considerable magnitude. a high modulus of elasticity. While the normal contractions are opposed by a volume increase if moisture is present to rehydrate the calcium hydroxide. . Copyright by ASTM Int'l (all rights reserved). Abrams and Erlin [42] provides a method based on examining the microstructure and microhardness of prestressing steel for estimating the temperature reached in a fire and hence its remaining tensile strength.40]. together with factors originating from the steel arrangement and moisture expulsion. if the surface of the concrete is quenched with water. Two concrete factors were considered to contribute to lack of resistance to these stresses. and its chemically stable vesicular and glassy (amorphous) composition. Where doubt still exists after the structural analysis or repairs have been completed. compressive. material. confirmatory fullscale load tests can be made. slags. and thermal studies made by Harmathy and Allen [9] on concrete used in masonry units confirm the reasons why concretes made from lightweight aggregates have superior heat resistance to normal weight concretes. 500.414 TESTS AND PROPERTIES OF CONCRETE Once the likely temperature regime has been established. The account by Fruchtbaum [44] in 1941 remains as a classic and that by Eisiner. the capacity of the aggregate to retain moisture. 932. Moreno. 700. perlites. slates. and 1000~ (572. Zoldners (and Wilson) [I0. . The merits they impart appear to be due to their significantly lower thermal diffusiveness (up to 600~ (1112~ and thermal conductivities (at all temperatures). or micas and natural pumice or scoria) aid in the endurance of concrete to high temperatures. and structural evaluation techniques and restoration methods available to examine young concrete damage in construction fires. Confirmation of the residual engineering properties of the concrete and steel after cooling can be determined by securing samples for standard laboratory testing. the available data on the engineering properties of the concrete and steel at either the elevated temperature reached or after cooling can be incorporated in the appropriate structural analysis to determine respectively the mode of failure or if the structure should be demolished or can be repaired. among others. and flexural strength determinations made after cooling that all lightweight (expanded shale and Copyright by ASTM Int'l (all rights reserved). dilatometric. Numerous accounts of investigations and repair of fire damage to mature concrete have been published (Ref 40 provides an excellent general review). Lightweight aggregates (man-made expanded shales. and Parma [45] of the 1973 Avianca fire is typical of the advances incorporated in such investigations in recent years to match the greater sophistication of concrete constructions.18] among others. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. points out that the compatibility in relative stiffnesses between the cement paste and lightweight aggregates is also beneficial. Lightweight Aggregate Concrete The thermogravimetric. have looked at the residual engineering properties of lightweight concretes after exposure to temperatures of 300. He further noted a good bond strength between paste and aggregate. clays. Standard methods for in situ nondestructive testing such as ultrasonic pulse velocity measurements can be used to help delineate the damaged areas and compare the properties in situ of the affected concrete with that untouched by the fire. Abrams [I6]. Smith [43] described the investigative. and 1832~ and after cycling 5 or 25 times from 100 to 300~ (212 to 572~ They concluded from ultrasonic pulse velocity. No further reproductions authorized. 1292. by using high alumina cement rather than portland or blended cements. and calcined shale dust) as 20 or 40-percent cement replacements did improve the heat resistance of the concretes up to 500~ (932~ In all cases where microfillers were used. Desov et al [46] reported reductions of up to 40 percent in hot tested specimens after heating to 350~ (662~ for between 3 and 7 h. As with normal weight concrete. Heavyweight Aggregate Concrete Heavyweight concrete is used for radiation shielding in nuclear reactors. as aggregate [47]. can be made with high alumina cements and common refractory materials. This shielding is usually in the shape of a hollow cylinder or sphere. the improvement in residual flexural strength was in the range of 10 to 20 percent though similar improvements were not always noted in compressive strength. thermal gradients induce moisture migrations. such as crushed firebrick. The pulse velocity measurements. in monolithic linings for kilns. By using aggregates such as fused aluminum oxide with a cement that is essentially calcium aluminate. This type of concrete will be stable and retain considerable strength at dry heat temperatures of up to 1300~ (2372~ because ceramic bonds have replaced the hydraulic bonds which were lost during desiccation. In summarizing the results of compressive strength of limonite. silica flour. and combination thereof. Residual strengths for all lightweight concretes were reduced to about 80 percent by heating to 300~ (572~ and to about 45 percent by heating to 700~ (1292~ as compared with the unheated reference concretes. Since failure is largely because of the deterioration of the cement paste matrix. insulating lightweight refractory concretes good up to about 950~ (1742~ can be made. Refractory Concretes Concretes used to withstand prolonged high temperatures. They also found that although there was no advantage in using Type 1S (blended portland blast furnace slag) cement as compared with a normal Type 1 cement. No further reproductions authorized. serpentine. generally supported the conclusions drawn from the strength data. and complex triaxial stresses can occur. magnetite and steel punchings. portland cement concretes. service temperatures for a refractory conCopyright by ASTM Int'l (all rights reserved).SMITH ON RESISTANCE TO HIGH TEMPERATURES 415 slag) concrete stood up to the effects of high temperature better than did semi-lightweight concrete. taken to be an indicator of porosity and microcracking in the matrix. for example. these effects were ascribed to differences in thermal expansion between the cement paste and aggregates and to the dehydration of the paste. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . the addition of microfillers (fly ash. After heating to 1000~ (1832~ residual strengths were negligible. Under moderately high operating temperatures. No further reproductions authorized. last for only a few seconds. Concluding Remarks Concrete has a longstanding and justified reputation as a fire resistant material. Tail and higher wing mountings in more recent planes have largely removed the problem from the practical sphere and a 1953 paper by Bishop [49] remains definitive. The conditions though extreme. References cited to studies in connection with both fire resistance and nuclear reactors show that in the last decade striking advances have been made in our understanding of the mechanism and consequences of these phenomena on the thermal and mechanical properties of concrete at high temperatures. however. it is known that the solutions tried include sacrificial concrete and protective shields including ceramic ablative shields. warm-up aprons. howbeit with long recognized room for improvement in testing methods [50]. involving temperatures of about 2760~ (5000~ and velocities over 2438 m/s (8000 ft/s). thermodynamic explanations that tie together all the aspects of the very complex viscoelastic. Development of temperature regime-structural behavior models and greater understanding of material properties are leading to significant improvements in the specification and design for fire endurance based on updated standard fire tests [51].416 TESTS AND PROPERTIES OF CONCRETE crete can be as high as 1800~ (3272~ A 1978 report by ACI Committee 347 [48] provides a definitive discussion of refractory concrete properties for those having deeper interest. there was considerable concern that the hot blast might be damaging to concrete test cells. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. moisture-dependent behavior pattern in concrete at elevated temperatures still are awaited. Copyright by ASTM Int'l (all rights reserved). full physico-chemical. and runway ends. The launching of rockets from pads or underground silos for space exploration or military purposes presents another aspect of the hot blast problem and is one for which all the answers have not yet reached the public domain. However. Deficiencies in concrete performance at elevated temperatures arising from moisture effects and thermal incompatibilities long have been recognized also [50]. However. . and the choice between sacrificing the concrete or trying to shield it is one of cost and convenience. Elevated Temperature Coupled with Blast At the time of the introduction of jet aircraft into service. temperatures of 677~ (1250~ occur and this may be as high at 1927~ (3500~ where afterburners are used. The velocity of the attendant hot blast has been estimated at 1067 m/s (3500 ft/s) and the impingement of this on the concrete was particularly exaggerated by the downward inclination and low slung engines on many early jet aircraft. Immediately at the jet exhaust. ." Journal of the Structural Division." Proceedings. A. [18] Zoldners. 1973." Publication SP-5. "Compressive Strength of Concrete at Temperatures of 1600~ '' Publication SP-25. pp. 1973. pp. pp. American Concrete Institute. P. T. T.." Journal of Materials. p." Fire Technology. 25. American Concrete Institute. 685.. American Concrete Institute. American Concrete Institute.. [22] Cruz." Publication SP-5. "Experimental Study Relating Thermal Conductivity to Thermal Piercing of Rocks. [21] Marechal. 1087-1108. and Polivka. pp." Journal. Vol. "Thermal Properties of Concrete at Elevated Temperatures." Publication SP-34. pp. American Concrete Institute. 1-32. Vol. M. 1377-1419. E." Roads and Road Construction. ST7. 102-108. 5... 1976. 1972. "The Influence of Temperature on the Physical Properties of Concrete and Mortar in the Range 20~ to 400~ '' Publication SP-25." International Journal of Rock Mechanics in Mining Sciences (England). No. pp. 102. American Society for Testing and Materials. L. 101. [12] Zoldners. R.. 1962. "Fire Endurance Testing Procedures.. Vol. American Society of Civil Engineers. G. pp. 36-42. "Fire Resistance with Concrete as Protection." Publication SP-39-9. pp. 51-63. 1971. American Concrete Institute. V. N. Vol. pp. 161-163. E. G. Vol. "Fire Resistance of Reinforced Concrete. pp. C. STI2. American Concrete Institute. and Lin. "Apparatus for Compression Tests on Concrete at High Temperatures." Magazine of Concrete Research. T. W. pp. 85-94." Publication SP-25. Proceedings. pp. 59-86. B. No. pp. [6] Salse. I. pp. 102.. and Poacher. ST6. 857-864.. March 1970. [15] Gibbons. Vol. American Society of Civil Engineers. F. 1972. 83. "The Effect of Temperature on the Compressive Strength of Concrete. "Some Aspects of Structural Fire Resistance of Concrete. M. 1960. 1971. 31.. "Structural Fire Resistance of Concrete. 149-177. "Thermal Properties of Selected Masonry Concrete Units. N.. Proceedings. Research and Development Laboratory.. 54. July 1975. C. and Culver. P. 1. American Concrete Institute." Journal VTO. [9] Harmathy. 47-74. Vol. G. American Concrete Institute. "Fire Resistance of Prestressed Concrete. [13] Mirkovich. J. "The Effect of High Temperatures on Concrete Incorporating Different Aggregates. November 1975.. R. J. [5] Troxell. 205-218.. 10. [14] Shergold. 1971. 43-55. American Concrete Institute. January 1976. R. "Thermal Properties of Concrete under Sustained Elevated Temperatures. 1968. 1968. A. [3] Benjamin. p. p.. No. J. June 1976. 1. "The Effect of High Temperatures on the Strength of Road Making Aggregates. [16] Abrams.SMITH ON RESISTANCE TO HIGH TEMPERATURES 417 References [1] Uddin. pp. W. A. "Apparatus for Measuring Creep of Concrete at High Temperature. 3. "Effects of Elevated Temperatures on Structural Members. [10] Zoldners. C. Vol. 61-68. pp. M." Journal. A. pp. 1962. 7. V.. 5. [11] Harmathy. [19] Sullivan. No. 10. 8. April 1958. Vol. 1956.. and Wilson." Publication SP-34.. R. 132-142. No. 3-22. June 1953. 1268. H." Magazine of Concrete Research. March 1976. 102. Z. and Allen. pp. pp. S. No. C. "Variations in the Modulus of Elasticity and Poisson's Ratio with Temperature. Portland Cement Association." Publication SP-5. G. Vol. [20] Philleo. Dec.. J. [8] Purkiss. 60.. "Effect of Sustained and Cyclic Temperature Exposure on Lightweight Concrete. Feb. [17] Malhotra. June 1973. American Concrete Institute." Publication SP-5." Journal of the Structural Division: Proceedings. "Instrumentation and Techniques for Study of Concrete Properties at Elevated Temperatures. 1971. Sept. 1962. C. 495-503. Vol. and Dougill. H. C. 2376. Bresler. 103-135. 2463-2464 and Discussion ST3. Z. S. V. American Concrete Institute. pp. Vol. pp. pp. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1962. [4] Sheridan. [2] Carlson. T.. V. Vol. Copyright by ASTM Int'l (all rights reserved). pp. 23. T. No further reproductions authorized. 25-39. 1531-1549 and Errata STll. L... "Some Physical Properties of Concrete at High Temperatures. No. 33-58. N.. G. [7] Bertero. F.. London.... 387-400.418 TESTS AND PROPERTIES OF CONCRETE [23] Wang.. VII.." National Building Studies. [25] Schneider. F. 6. 1." Three part series on "Repair of Fire Damage. pp. D. M. [31] Campbell-Allen. D.. 1967. Study B." Concrete Construction. New York. T. 1972. Vol. Vol. Fe'd6ration Internationale de la Precontrainte. and Erlin. 1. "Some Effects of Thermal Volume Changes on the Properties and Behaviour of Concrete. C. [26] Thompson. "An Investigation of the Effect of Elevated Temperatures on Concrete for Reactor Vessels. M. "Creep of Concrete at Elevated Temperatures. 6. "Physical Properties of Concrete under Nonsteady State Condition. Influence of Aggregate and Load Intensity. American Society for Testing and Materials.. London. American Society for Testing and Materials." Proceedings. 1974. M. Fondriest. [37] Harmathy. Vol. IV. 65-77. Portland Cement Association. 1. [33] Polivka. International Conference on Mechanical Behaviour of Material. 203-213.. No. pp. June 1972. "Variable-State Methods of Measuring the Thermal Properties of Solids. No.. Congress. No. R. 1968. and Desai. Vol. [24] Marechal. B. "Investigation and Repair of Damage to Concrete Caused by Formwork and Copyright by ASTM Int'l (all rights reserved). American Concrete Institute. Z. and Orels. C. 17. 65.. 45-49. W." Publication SP-34. pp... 74-94. No." Nuclear Engineering and Design (Amsterdam). E. pp. V. Vol. "Effect of Moisture on the Fire Endurance of Building Elements. and 6. "Estimating Post Fire Strength and Exposure Temperature of Prestressing Steel by a Metallographic Method.." Publication SP-27. pp. Takeda. T. 1971. 1965. 4. Vol. and Roger. 1968. 1971. [34] Lankard. 59-102. S. T. Part 2--The Visible Changes in Concrete or Mortar Exposed to High Temperature. [41] Harmathy." ASTM STP 385.. D.. "Creep of Concrete as a Function of Temperature. G. and Furumura. Vol." Magazine of Concrete Research. No. pp." Proceedings. Evaluating Fire Damage to Concrete Structures and Reinstating Fire Damaged Structures. E. D." Publication SP-34. "Effects of Moisture Content on Structural Properties of Portland Cement Concrete Exposed to Temperatures up to 500~ '' Publication SP-25. 62.. "'Strength Elasticity and Thermal Properties of Concrete Subjected to Elevated Temperatures. "A Note on Difficulties of Measuring the Thermal Conductivity of Concrete. H. J. International Conference on the Structure of Concrete. [42] Abrams. H. No further reproductions authorized. N. May. No." Journal. and Snyder. 20. [43] Smith. 11. E. Nov. pp. 2. . Deutscher Ausschuss f'tir Stahlbeton. P. Vol. April 1964. [28] Harada. Bertero. American Concrete Institute. Z. E.. E. Z. Portland Cement Association. 1950. [30] Dougill. 1972. American Concrete Institute. 35. pp. Birkimer. 377-406." Journal of Applied Physics. 52-73." (in German). March 1968. [39] Bessey. S. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement..." ASTM STP 385. American Concrete Institute... S. [32] Campbell-Allen. 959-1064." Publication SP-34. pp. P. [40] "Concrete Structures after Fires. [35] Abrams. C. [38] Selvaggio." Journal. E. M. V. No. April. H248. J. S.. and Carlson. 443-479... Research and Development Laboratory. "Explosive Spalling Occurring in Reinforced and Prestressed Concrete Structural Members of Normal Dense Concrete Under Fire Attack. 41-64. "Fire Resistance of Prestressed Concrete Beams. J. W. Jan.. pp. [27] Harmathy. L. HMSO. 1972. "Studies of the Technology of Concretes Under Thermal Conditions. Technical Paper 4." Proceedings.." 1964. "The Influence of Aggregate on the Behaviour of Concrete at Elevated Temperatures. C. 9.. "Concrete Drying Methods and Their Effect on Fire Resistance. 1975. Vol. pp. U. No. and Gjorv.. S. 4.. "Investigation on Building Fires. 3. F." Journal. "Determining the Temperature History of Concrete Constructions Following Fire Exposure. American Concrete Institute. Sept. T. American Concrete Institute. J. 1967. M. pp. "The Effect of Moisture Content on the Mechanical Behaviour of Concrete Exposed to Elevated Temperatures. [36] Meyer. L." Nuclear Structural Engineering (Amsterdam). O. 1964. 382-388. Low. D. pp. 1972. [29] Crispino. Ottens C. Yamane. 1965. 23-33. 547-564. L. Research and Development Laboratory. pp. No further reproductions authorized. "High-Temperature Behavior of Aluminous Cement Concrete Containing Different Aggregate. 63. 1099-1153. Vol." Proceedings. R. Supplement No. 1943. D." Journal. American Concrete Institute. New York. 1953. 1963. pp. Investigation Conducted by the Bureau of Yards and Docks. Jan. 37.. 11.. 43. Eisiner. Fruchtbaum. No. K.. "Fire Performance Ratings 1977. 423-434.. N. 60. Columbia. Desov. pp. A. V. E.. C.. Menzel.. American Society of Civil Engineers. "Fire Damage to General Mills Building and Its Repair. G. 1977. "Cube and Prism Strength of Concrete at Elevated Temperatures. Fe'de'ration Internationale de la Precontrainte. J. Separate 317. 966-995. A. "Lessons from the Avianca Fire in Bogota. American Concrete Institute. . and Milovaniov. Proceedings...SMITH ON RESISTANCE TO HIGH TEMPERATURES [44] [45] [46] [47] [48] [49] [50] I51] 419 Falsework Fire. 1978 Refractory Concrete Report by Committee 347. 3. Proceedings. Nov. Copyright by ASTM Int'l (all rights reserved). American Society for Testing and Materials. American Concrete Institute. Zoldners. M. Vol." National Research Council of Canada. 1963." Proceedings. American Concrete Institute. Malhotra. Oct. No. H. VII Congress. "Tests of the Fire Resistance and Thermal Properties of Solid Concrete Slabs and Their Significance.. J. 1974. A. pp. American Society for Testing and Materials. 1941." Proceedings. and Parma. D. Nekrasov. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1535-1566. to be published." Proceedings. A. pp. 201-252. C." Publication SP-34. Bishop. pp. G. National Building Code of Canada." Journal. and Wilson. 2. Moreno. Vol. "The Effect of Jet Aircraft on Airforce Pavements. S. Ottawa... Vol. J. 1Professor of civil engineering. Universityof California. but it also has the advantage of being a material that can be cast into any desired homogeneous structural shape. which is about 50 percent higher than the unit weight of conventional concrete.STP169B-EB/Dec. nuclear power plants. 1978 M i l o s P o E v k a 1 a n d H. they can be produced with densities up to about 5300 k g / m 3 (330 lb/ft 3) using iron as both fine and coarse aggregate. For certain types of biological shields there is a need to include materials of low atomic weight in the concrete. 99352. S. Such high-density concretes. At the present time there are two standards. ASTM Specification for Aggregates for Radiation-Shielding Concrete (C 637) and ASTM Descriptive Nomenclature of Constituents of Aggregates for Radiation-Shielding Concrete (C 638). produced by the use of heavy aggregates. Calif. Wash. 2Consulting engineer. the reduction in the thickness of the shield is accomplished by the use of high-density concretes.org . Conventional concrete of sufficient thickness can be and is being used for such purposes. concrete is not only economical. Concrete is now commonly used for shielding of atomic research facilities. Inc. Davis ~ Chapter 26--Radiation Effects and Shielding Introduction Portland cement concrete is an ideal material for use in construction of radiation shields. Copyright9 1978tobyLicense ASTM International www. However. However. will usually have a unit weight ranging from 3350 to 3850 k g / m 3 (210 to 240 lb/ft3). United Nuclear Industries. Although there are other materials that could be employed for radiation shielding purposes. In addition. that pertain to concrete-making materials for biological shielding. Copyright by ASTM Int'l (all rights reserved). and for radiation medical and research units or equipment. Richland.astm. No further reproductions authorized. Specific references to some of these standards and to their applicability are covered later herein. 94720. several of the existing ASTM standards pertaining to concrete and concrete-making materials are applicable to shielding concretes. Sun Apr 6 21:43:36 EDT 2014 420 Downloaded/printed by Universidade do Gois pursuant Agreement. Berkeley. where usable space is a major consideration.. It is also investigating boron-containing aggregates and their potential use in shielding concrete.3 Electromagnetic Waves Of the electromagnetic waves. This research subcommittee was established for the purpose of carrying out a study and research on the general problem of concrete for radiation shielding. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. in 1965. Recognition by ASTM Committee C-9 on Concrete and Concrete Aggregates of the significance of concrete for radiation shielding as an engineering material is evidenced by the activities of its Subcommittee C9.02. the committee acquired information which was made available to the profession at a symposium held at Gatlinburg. Copyright by ASTM Int'l (all rights reserved).and gamma rays are the only types that require shielding for protection of personnel. After a 3-year study. . Gamma rays are identical with X-rays except for the source. is appropriately referenced. Tenn. Types of Radiation There are two general classes of radiation that are considered in the design of biological shields: (a) electromagnetic waves and (b) nuclear particles [1].POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 421 Extensive literature is available on the subject of concrete for radiation shielding. Currently. high-frequency waves known as X. This paper consists of a review and discussion of radiation shielding and of properties of concrete and concrete-making materials for shielding purposes and of their effects and significance. Gamma rays are given off spontaneously from naturally occurring heavy elements or from lighter elements produced in atomic piles or by accelerators [2]. The work of other writers on the subject. the high-energy. This symposium was sponsored jointly with the Shielding Division of the American Nuclear Society. the subcommittee is preparing a specification covering test methods for materials and procedures associated with the preplaced-aggregate method for constructing radiation-shielding structures.08 on Concrete for Radiation Shielding. Pertinent papers were reviewed and are cited in the list of references. Both X-rays and gamma rays have a high power of penetration but can be adequately absorbed by an appropriate thickness of concrete shield. No further reproductions authorized. Nuclear Particles Nuclear particles consisting of nuclei of atoms or fragments thereof. when used. 3The italic numbers in brackets refer to the list of referencesappended to this paper. The subcommittee prepared ASTM Standards C 637 and C 638 and is responsible for revision of these standards as required. concrete was used successfully as a shield against radioactivity in structures enclosing areas where low levels of gamma radioactivity are measured. there is also the problem of designing shields which will minimize the socalled "background" radioactivity. Shielding Problems As discussed above. although accelerated protons at high-energy levels may require heavy shielding comparable to that required for neutrons of equal energies. The magnitudes of radiation must be determined. Protons and alpha and beta particles carry electrical charges which interact with the electrical field surrounding the atoms of the shielding material. that is. . the heavy particles of atomic nuclei. of intermediate neutrons between 0. Tolerance Levels Concrete shields are installed to protect personnel from radiation emitted by nuclear reactors.5 eV. The energy range of fast neutrons is between 10 000 and 10 000 000 eV. intermediate (epithermal). Neutrons have high powers of penetration but do not follow a defined path through a given material. No further reproductions authorized. They are slowed down only on collision with atomic nuclei. They generally do not constitute a separate shielding problem. As reported by Wollenberg and Smith [5]. protons. all but the neutrons possess an electrical charge. and alpha and beta particles. nuclear explosions. 4]. Such concretes must not only provide a shield from extraneous radioactivity. accelerators. but the concrete itself must be low in radioactivity.S and 10 000 eV and of thermal neutrons less than 0. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A shield adequate to reduce gamma radiation is normally also sufficient for protons Copyright by ASTM Int'l (all rights reserved). Neutrons are classified as fast. the principal types of radiation requiring consideration in the design of a shield are gamma rays and neutrons. do not carry an electrical charge and thus are unaffected by electrical fields surrounding atoms. Low Background Concrete In addition to the use of concrete shields as protection from radiation. thus decreasing the energy of the particle. Of these. and some medical and research units or equipment. low-background counting facilities. and slow (thermal) neutrons. Neutrons.422 TESTS AND PROPERTIES OF CONCRETE include neutrons. Information on the tolerance levels for gamma rays and neutrons was published by the National Bureau of Standards [3. using theoretical calculations and experimental data. to design properly a biological shield that will ensure that the level of radiation on the outside of the shield is maintained below the maximum permissible intensity. but neutrons and gammas are not equally attenuated by the same materials. high density and low cost are of prime importance. Thus. Hydrogen is effective in this action.2 million volt gamma ray. Almost any material of sufficient thickness can serve satisfactorily as a shield. Neutron and Gamma Ray Shielding Neutron Shielding--For an efficient neutron shield it is often desirable to incorporate three classes of materials. materials of low atomic weight. Most materials attenuate gamma radiation primarily by the Compton scattering process [2] with the attenuation being approximately proportional to the mass of the material in the radiation path. Finally. to slow down further the moderately fast neutrons through elastic collisions. whose atomic mass is 56.POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 423 and alpha and beta particles. For the second case. Copyright by ASTM Int'l (all rights reserved). the general shielding problem resolves itself into attenuation of neutrons and gammas. Gamma Ray Shielding--Gamma radiation may originate inside the shield through neutron capture as well as from the primary source behind the shield. has not only a very high cross section (absorbing power) for neutrons. but emits gamma rays of only 0. Boron. The shield should contain some heavy material. preferably hydrogen. The gamma rays given off during absorption of neutrons are a factor in the required shield thickness. especially hydrogen (for reducing neutrons of intermediate range to the thermal range). which requires considerable shielding itself. . Shielding Requirements Concrete shields are usually of two distinct types: (a) those required to attenuate gamma radiation only and (b) those required to attenuate fast neutrons and associated gamma radiation [7]. it is necessary to remove the slow. it is desirable to have materials of high or medium atomic mass (to slow down fast neutrons). on the other hand. and finally materials for absorbing thermal neutrons. These heavy elements slow down the fast neutrons by inelastic collisions. or elements of higher atomic number. such as iron. because different materials of the same mass have approximately equal protective properties against gamma radiation [6]. It is desirable to have light elements. thermal neutrons by absorption. No further reproductions authorized. Hydrogen is particularly effective because it weighs about the same as a neutron. These requirements for a neutron shield are summarized in more detail by Henrie [8]. For the first case. For these reasons boron-containing materials are often used in neutron shields.0478 million volts. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Attenuation of only the high-energy gamma radiation (1 to 10 000 000 V) is discussed here but not that of the lower energy X-rays. but in the process emits a 2. but very little influenced by the type of material. No further reproductions authorized. The thickness of the concrete shield will vary depending on the type of nuclear unit but may range up to 1. concrete with silica aggregate is about one half oxygen. manganese. in which case the required thickness will vary almost directly with the density. The efficiency of a concrete shield of given thickness depends mainly on its density and uniformity.424 TESTS AND PROPERTIES OF CONCRETE Shielding Ability of Concrete Concrete is an excellent shielding material that possesses the needed characteristics for both neutron and g a m m a ray attenuation. has satisfactory mechanical properties. slowing down fast neutrons. In some cases. contained in chemically combined form in the hydrated cement.8 to 2. and others [7]. such as removable shielding plugs. The density of concrete can be controlled within wide limits by selection of appropriate heavy aggregates. cobalt. Intensity of g a m m a radiation rather than of neutrons often determines the thickness of the shield. Since concrete is a mixture of hydrogen and other light nuclei. The desired uniformity of the shielding quality requires that the concrete form a homogeneous mass with uniform distribution of the aggregate particles. Troublesome elements include vanadium. Materials used in a shield should not be subject to decomposition or weakening under the influence of radiation. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. materials that become highly reactive when exposed to intense thermal neutron radiation should be avoided. chromium. conventional concrete will provide a most economical shield. The hydrogen and oxygen. The oxygen may also be present in the concrete in another form in addition to water. and can be produced within a relatively wide range of density. . If there are no space limitations. Excessive settling. and nuclei of higher atomic number. segregation. it is efficient in absorbing gammas. moderate the neutron flux satisfactorily. Mather [9] reports that data reviewed indicate that the radiation stability of concrete is adequate for most applications. and absorbing resonance and slow neutrons [9]. or formation of pockets during placing may cause excessive radiation to penetrate such faulty sections. Conventional concrete has been used to provide radiation shielding. Also the ease of construction makes concrete an especially suitable material for radiation shielding. and has a relatively low initial as well as maintenance cost. Also concrete containing potentially deleteriously reactive cement-aggregate combinations should be avoided. Aggregates for Shielding Concrete Concrete shields may be small structures housing a research nuclear unit or may be massive monolithic structures or structures consisting of precast assembled elements of various sizes. Copyright by ASTM Int'l (all rights reserved).4 m (6 to 8 it). however. ferrophosphorus. magnetite. Composition In general. Types Naturally occurring iron ores. and barite. and borocalcite have been used. manufactured iron and steel. magnetite ore from Wyoming has an iron content of about 50 percent. ferrophosphorus. In such cases the shielding ability of the concrete is increased by increasing its density and in the case of neutron shields by including a sufficient amount of light elements. The increase in the density of the concrete is accomplished by the use of heavy aggregates. . Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. such as naturally occurring iron ores. The specific gravity Copyright by ASTM Int'l (all rights reserved). and borates such as colemanite.POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 425 Frequently. Aggregates containing bound water are sometimes added to the mix to shield against fast neutrons. hydrous ores including goethite. and bauxite. Along with hematite. manufactured iron and steel. They include hydrous-iron ores. To improve neutron attenuation. The manufactured heavy aggregates listed in Table 1 (except for the boron additives) are only used when the required concrete density is greater than about 4000 kg/m 3 (250 lb/ft 3) [10]. and ilmenite. it is desired to produce concrete of improved properties with respect to shielding ability. and barite are the major heavy aggregates that have been used to increase the density of concrete. chemical limitations may be applied. For example. Information on conventional concrete and concrete-making materials is covered thoroughly by the various papers of this publication. As a control of the uniformity of the high density of some of these aggregates. Natural iron ore aggregates can produce concrete densities up to 3850 kg/m z (240 lb/ft3). or bauxite. serpentine. while ilmenite ore from Quebec has an iron content of only 38 percent. limonite. For example.10] is given in Table 1. boron frit. Also. boron-containing admixtures are sometimes added to the concrete. these are used chiefly for gamma attenuation. especially when space limitations require that the thickness of the shield be reduced. to shield against neutrons. The remainder of this paper will refer to concretes whose properties were enhanced with respect to their shielding ability. while the iron content of magnetite and limonite aggregate should be in excess of 60 and 55 percent. the exact chemical composition of heavy aggregates is not critical as long as the required density is met. A listing of these aggregates as prepared by Davis [7. barite ore should have a barium sulfate content greater than 90 percent. such limits will greatly depend on the economy of using easily available materials which may justify using lower values. However. serpentine. The most commonly used have been barite. Included in this table are boron-containing additives used in neutron shields. respectively. 4 to 2. W o l l e n b e r g a n d S m i t h [5] indicate t h a t serpentinized u l t r a m a f i c rock is the most suitable source of l o w . C o m p o s i t i o n of aggregates b e c o m e s very i m p o r t a n t when they are to be used in l o w .5 to 2.6) (2.0) (7. T h e d e s i r e d increase in hydroCopyright by ASTM Int'l (all rights reserved).6) (4.3) [15 to 25%] b (2.4 to 2.7 to 3.0) (2. a n d t h o r i u m . Natural Mineral Local sand and gravel calcareous siliceous basaltic Hydrous ore bauxite serpentine goethite limonite Heavy ore barite magnetite ilmenite hematite Boron additives calcium borates borocalcite colemanite gerstley borate (2. bWater of hydration is indicated in [ ].5 to 7. of both of these a g g r e g a t e s is in excess of 4.5 to 2.m a k i n g materials.5.4) (2.8) (2.4) Manufactured Crushed aggregates heavy slags ferrophosphorus ferrosilicon Metallic iron products sheared bars steel punching iron shot Boron additives boron frit ferroboron borated diatomaceous earth boron carbide (-5.b a c k g r o u n d counting facilities r e q u i r i n g aggregates having low levels of n a t u r a l g a m m a activity.b a c k g r o u n d aggregate. To require the iron content to be 55 p e r c e n t or g r e a t e r would e l i m i n a t e these two reliable sources o f heavy aggregate [10].8) [8 to 12%] (4.426 TESTS AND PROPERTIES OF CONCRETE TABLE 1--Aggregates used in shielding concrete.3 to 2.10] gives representative values of a b s o r p t i o n factors for various aggregates a n d o t h e r c o n c r e t e .6) (5.8 to 6.7)~ (2.3) (6.0) aSpecific gravity is shown in ( ) .7 to 7.8) (7. Also the heavier elements are more effective in a b s o r b i n g fast n e u t r o n s by inelastic collisions t h a n are the lighter ones.6) [10 to 13%] (3.0) ( . density is not the only factor to consider in the selection of an aggregate for a n e u t r o n concrete shield.1.0 to 4. No further reproductions authorized.2 to 4.8 to 2. Radiation A t t e n u a t i o n a n d A b s o r p t i o n The c a p a c i t y of the various heavy aggregates to a b s o r b g a m m a rays is almost directly p r o p o r t i o n a l to their density.0) (5.4 to 3.1) (1. . However. u r a n i u m . Based on extensive studies.5 to 7. Davis [7. O f p r i m a r y c o n c e r n are the concentrations of p o t a s s i u m . Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. whereas serpentine is good up to at least 400~ (750~ Measurement and Significance of Properties Members of Subcommittee C9. However. and treats several of the important constituents of heavy aggregates. Based on results of a limited study made by Dolch. However. These materials contain a high percentage of water of hydration (fixed water content) as shown in Table 1. A discussion follows of some of the important properties and their significance. Nomenclature and Mineralogy--ASTM Descriptive Nomenclature of Constituents of Natural Mineral Aggregates (C 294) does not include a number of the more probable constituents of heavy aggregates.02. tested according to ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227).POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 427 gen content. which were large enough to cause the combination to be regarded as alkali reactive. containing barite aggregate and high-alkali Type I cement. Limonite and goethite are reliable sources of hydrogen as long as shield temperatures do not exceed 200~ (390 ~F)." Chemical Properties--Raphael [12] has reported expansions of mortar bars. such as iron oxides. required to slow down fast neutrons. for the information of Subcommittee C9. present special problems. Mather [11] states: "The high-density aggregates. presence of such organic impurities should be checked for by the use of ASTM Test for Copyright by ASTM Int'l (all rights reserved).02.08. and aggregates containing water that are used in shielding concrete. on heating of the concrete some of this fixed water in the aggregate may be lost [10]. ASTM Test C 227 is applicable to heavy aggregates.08 chose to prepare a new document (ASTM Method C 638) rather than request revision of ASTM Method C 294. . only in their capacity as accessory constituents of rocks in use as normal aggregates. can be accomplished by the use of hydrous ores. it appears that ASTM Test for Potential Reactivity of Aggregates (Chemical Method) (C 289) is also applicable to heavy aggregates. Most of the pertinent existing standards are applicable in their present form. Members of Subcommittee ASTM C9. can be useful. These expansions might have been caused by reactive silica or by calcium sulfate in the aggregate. Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The origin of the majority of deposits of heavy aggregates makes the presence of organic impurities very unlikely.02. No further reproductions authorized.08 of ASTM Committee C-9 have made an evaluation of ASTM standards on aggregates with regard to their applicability to heavy aggregates. but they are still problems in which petrographic identification of reactive substances. ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295) applies to aggregates for shielding concrete as well as it does to other aggregates. or substances likely to produce problems in concrete production and placement. 428 TESTS AND PROPERTIES OF CONCRETE Organic Impurities in Sands for Concrete (C 40). If such a test is included in a specification for heavy aggregate it should contain an explanation similar to that given for lightweight aggregates, ASTM Specification for Lightweight Aggregates for Structural Concrete (C 330), as follows: "Heavy aggregates that, upon being subjected to the test for organic impurities, produce a color darker than the standard shall be rejected, unless it can be demonstrated that the discoloration is due to small quantities of materials not harmful to the concrete." Deleterious Constituents--ASTM standards for deleterit, us constituents of aggregates include tests for clay lumps (ASTM Test for Clay Lumps and Friable Particles in Aggregates (C 142)) and lightweight pieces (ASTM Test for Lightweight Pieces in Aggregates (C 123)) are applicable to, and can be used in specifications for, heavy aggregates. However, the test for hardness (ASTM Test for Scratch Hardness of Coarse Aggregate Particles (C 235)), when applied to heavy aggregates, needs some interpretation. The hardness of the minerals magnetite, hematitie, and ilmenite, which produce ores of high specific gravity (4.2 to 4.8) is about 5 to 6 on Mohs' scale. Barite ore, which has a specific gravity of 4.0 to 4.5, has a Mohs' hardness (of the mineral) of only 2.5 to 3.5. The Mohs' hardness of calcite, by definition, is 3. Thus if ASTM Test C 235 is intended to classify calcite as just barely harder than "soft," it would be expected to classify barite sometimes as "hard" and sometimes as "soft." Therefore, it would not be reasonable to ask for a barite aggregate under a specification that includes a limit of soft particles, as is the case of ASTM Specification for Concrete Aggregates (C 33), for particles scratched by the ASTM Test C 235. For these reasons, it is necessary to use careful judgment in the application of ASTM Test C 235 to heavy aggregates. Gradation--The gradation requirements of heavy aggregates can be within the limits given in ASTM Specification C 33. The sample of heavy aggregate used in the sieve analysis should be greater in weight than the samples specified in ASTM Test for Sieve or Screen Analysis of Fine and Coarse Aggregates (C 136). This increase in weight should be obtained by multiplying the specified weight (ASTM Test C 136) by the ratio of the specific gravity of the heavy aggregate to that of ordinary aggregate (for which a value of 2.65 may be assumed). Unit WeightwThe unit weight of heavy aggregates can be determined by the procedures of ASTM Test for Unit Weight of Aggregate (C 29). However, it might be desirable to employ larger capacity measures than those specified in ASTM Test for Unit Weight of Aggregate (C 29). For example, a 0.03 m 3 (1 ft 3) capacity measure is much too small for 100-mm (4-in.) aggregate. Also, the use of a vibrating table in lieu of rodding (ASTM Test C 29) is suggested as a better procedure for heavy aggregates. Specific Gravity--In the design of a concrete shield the unit weight Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 429 selected for the concrete is of primary importance. The specific gravity of the aggregate is the major factor influencing unit weight and is, therefore, of considerable significance in specifications for heavy aggregates. The specific gravity, for both fine and coarse aggregate, is determined on a saturated surface-dry basis in accordance with appropriate sections of ASTM Test for Specific Gravity and Absorption of Coarse Aggregates (C 127) and ASTM Test for Specific Gravity and Absorption (C 128). Again, the sample weights should be increased according to the procedure described earlier under Gradation. To produce concrete weighing 3700 to 3850 kg/m ~ (230 to 240 lb/ft 3) the aggregate must have a specific gravity of 4.5 or greater. To produce concrete weighing around 4800 kg/m ~, (300 lb/ftJ), the aggregate must have a specific gravity of 6.0 or greater. It is necessary in specifications for heavy aggregate to give the minimum values of specific gravity. Davis [10] gives the following minimum values: limonite or goethite 3.25, magnetite 4.50, ferrophosphorus 6.10 for fine, and 5.90 for coarse aggregate. The range of specific gravities of the various aggregates used in shielding concrete is given in Table 1. Resistance to Abrasion--The resistance of heavy aggregates to abrasion and their tendency to fracture during handling and mixing varies considerably, and allowances must be made for the natural characteristics of the heavy ores being used [10]. Magnetite and ilmenite, which can be purchased in satisfactory gradings, are harder than barite and the hydrous ores, goethite and limonite, and are less prone to produce excess fines during handling and mixing [9]. Since concrete shields are generally not subjected to severe abrasion, aggregates which do not pass the abrasion resistance requirement of ASTM Specification C 33 (maximum abrasion loss of 50 percent) may be used, provided these aggregates produce concrete of otherwise satisfactory properties. Concrete for Radiation Shielding The special concretes used for the construction of shielding structures are distinguished from conventional concretes primarily by their higher density, obtained through the use of heavy aggregates, and in some eases by containing boron additives to improve attenuation of neutrons [13]. The practices to be employed in the proportioning, mixing, and curing of the shielding concretes are basically the same as those used for conventional concretes. Test methods used for the evaluation of the properties of fresh and hardened conventional concretes are discussed in this publication by various authors. In this paper only the special properties of shielding concretes, some of which are of less consequence in conventional concrete structures, are discussed. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 430 TESTS AND PROPERTIES OF CONCRETE Special Properties and Their Significance In the selection of mix proportions for a concrete to be used for shielding purposes several properties need special consideration. They include the workability and setting characteristics of the fresh concrete and the density and strength of the hardened concrete. The effects of high-temperature exposure and thermal cycling on the properties of hardened concrete also need to be considered. Workability--To facilitate the proper placing of concrete in forms (frequently of complex shape and containing many embedded items) and to ensure the integrity of the concrete in the shield (avoiding segregation and cold joints), the concrete mix must be extremely workable. Because heavy aggregate mixes tend to be harsh, more fine aggregate is usually used than in conventional concrete, and the sand frequently contains a high percentage (10 to 16 percent) of material passing the No. 100 sieve [7,10]. Cement contents of the concrete are usually high 350 to 450 kg/m a (560 to 750 lb/yd 3) and even higher, because of desired workability or fixed water content. Frequently, when a shield includes closely spaced reinforcement or a high concentration of embedded items, it becomes necessary to employ other than conventional methods of placing, such as the preplaced-aggregate method. Setting Characteristics--The setting characteristics of a concrete need to be considered when boron additivies are used in neutron shields, since some of these borates may adversely affect the setting and strength properties of the concrete. As discussed earlier, boron is an efficient element in shielding against neutrons. However, most naturally occurring borates like colemanite and borocalcite are somewhat soluble, and borate solutions are powerful retarders of the set of concrete and also of the rate of strength gain [8, 9]. In addition, borate ores frequently contain impurities that either tend to reduce the ultimate strength of concrete or cause erratic setting behavior or both. Henri [8] discussed the influence of boron-containing additivies, such as colemanite, borocalcite, and boron frit, on the setting characteristics of concrete. Colemanite is generally considered the poorest of the three in this regard. However, it has the advantage of being more economical in some geographical areas. It contains about 10 percent boron. Borocalcite is a calcium borate similar to colemanite and contains about 13 percent boron. It also causes erratic setting characteristics of the concrete. To reduce the effect of these naturally occurring borates, all the fines passing a No. 30 sieve are usually eliminated. This lessens the exposed surface area of a given weight of the material and thereby reduces its solubility. These materials were used successfully in concretes, frequently in conjunction with calcium chloride (about 1 percent by weight of cement) to overcome the retardation. Low-sodium boron frits are an excellent source of boron (about 18 perCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 431 cent) and have little effect on the setting characteristics of concretes. These materials, being refined products produced by fusion of different compounds, may be more costly than the naturally occurring borates. It is highly desirable that prior to the use of borate additives a thorough evaluation of their effects on the properties of concrete, especially setting characteristics, be made. Density--Though the density or unit weight of the concrete used in a shield is a major consideration, the designer also must consider all of the shielding characteristics of the concrete, as well as cost and construction problems. As stated earlier, conventional concrete (weighing say, 2400 kg/m 3 (150 lb/ft 3) provides the most economical and is the most commonly used shielding material. Only due to limited space or other conditions of construction will concretes of higher densities be employed. The density of the concrete is governed principally by the specific gravity of its aggregate, as previously discussed. The density is also influenced by the cement, water, and air content of the concrete mix. ASTM Test for Unit Weight, Yield, and Air Content (Gravimetric) of Concrete (C 138) is applicable to the determination of the unit weight of shielding concrete. Typical ranges of densities commonly specified for concretes made with some of the heavy aggregates are listed in Table 2. TABLE 2--Densities of shielding concretes commonly specifiedfor given heavy aggregates. Type of Aggregate Density, Ib/ft 3 Barite Magnetite Ilmenite Ferrophosphorus Barite and boron additive Magnetite and boron additive 215 220 220 285 200 210 to to to to to to 225 235 240 300 215 225 Density, kg/m 3 3450 3500 3500 4550 3200 3350 to to to to to to 3600 3750 3850 4800 3450 3600 Densities of about 5300 kg/m 3 (330 lb/ft 3) can be produced when using iron as both fine and coarse aggregate. Densities other than those shown in Table 2 can be obtained by the use of various combinations of natural or manufactured aggregates. References included with this paper give the properties of many typical concrete mixes containing heavy aggregates. Strength--Although structural strength may be a requirement for highdensity shielding concrete, this property usually causes no problem because sections are thick and the mixes have high cement content [14]. For structural shielding concrete, 21 to 35 MPa (3000 to 5000 psi) compressive strength is usually sufficient; for massive walls, 14 MPa (2000 psi) is adequate. However, concrete for radiation shielding must have adequate Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 432 TESTS AND PROPERTIES OF CONCRETE strength to resist cracking during its service life. Some of the strengthdetermining properties of hardened concrete are discussed by Lott and Kesler [15]. In a study by the Corps of Engineers [9,16], it is shown that highstrength concrete can be made using materials that provide high density. The high-density, high-strength concrete produced for this investigation was made with a Type I portland cement, using magnetite or ilmenite aggregate of 12.5 mm (or 11/2 in.) 37.5 mm maximum size. The concretes had cement contents of 430 to 575 kg/m 3 (720 to 970 lb/ft3), water/ cement (w/c) ratios of 0.30 and 0.35 by weight, and slumps of about 12.5 mm (1/2 in.). The unit weight of these concretes was about 3700 kg/m 3 (230 lb/ft3). The compressive strengths at 7 days were in the range 52 to 65 MPa (7600 to 9400 psi), at 28 days, 62 to 76 MPa (9000 to 11 000 psi), and at 90 days, 69 to 83 MPa (10 000 to 12 000 psi). It is concluded in this study [9,16], that although no new technology is needed to produce uniform high-density concrete of high strength, adherence to the best practices in production and control of such concretes is absolutely essential. Effects of High-Temperature Exposure--The influence of high temperature and thermal cycling on properties of concretes are of major importance in the design of concrete shielding structures [17]. These effects of temperature were studied by Davis [ 7,13.17,18], and the following evaluation of effects of temperature is taken from a recent paper [18]. Fortunately, from a strength standpoint, concrete in a reactor shield is usually over 6 or 9 months old before it is subjected to nuclear heating and is, therefore, mature in hydration and strength. The loss in compressive strength that occurs when mature concrete is subjected to high temperatures ranges from 20 to 50 percent, even when the concrete is heated as high as 320 or 430~ (600 or 800~ for long periods. However, for important structural members, concrete should not be exposed continuously to temperatures much above 260 to 320~ (500 to 600~ Concrete is almost completely dehydrated when heated above 430~ (800~ If made with heat-resistant aggregates, it may still retain 25 to 50 percent of its strength at temperatures as high as 700 or 760~ (1300 or 1400~ On the other hand, if unstable aggregates or high w/c ratios (over 0.60 by weight) are used in the mix, deterioration at temperatures above 320 to 430~ (600 to 800~ may be appreciable. If the concrete is subjected to wide and frequent fluctuations in temperature, the loss of strength of the concrete may be several times as great as that observed for concrete exposed to a constant high temperature. If concrete contains special aggregates, such as limonite or serpentine, to provide hydrogen for neutron attentuation, the temperatures will be limited to a safe value below that which dehydrates the aggregate: about 180 to 200~ (350 to 400~ in the case of limonite or as high as 370~ (700~ for serpentine. On the other hand, the maximum temperature in a Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. POLIVKA AND DAVIS ON RADIATION EFFECTS AND SHIELDING 433 concrete shielding structure may be limited to less than 90~ (200~ to minimize moisture loss, temperature gradients, or surface cracking. Davis [17] shows that at high temperatures, tensile, flexural, and bond strength are affected more than compressive strength. In most shielding structures, thermal effects are of prime consideration in design. References [1] Callan, E. J., "Concrete for Radiation Shielding," Proceedings, American Concrete Institute, Vol. 50, 1954, pp. 17-44. [2] Foster, B. E., "Absorption by Concrete of X rays and Gamma Rays," Proceedings. American Concrete Institute, Vol. 50, 1954, pp. 45-63. [3] "Permissible Dose from External Sources of Ionizing Radiation," NBS Handbook 59, National Bureau of Standards, 24 Sept. 1954, and insert dated 8 Jan. 1957. t4] "Protection Against Neutron Radiation Up to 30 Million Electronvolts," NBS Handbook 63. National Bureau of Standards, 22 Nov. 1957. [5] Wollenberg, H. A. and Smith, A. R., "Low-Background Concrete," Transactions, American Nuclear Society, Vol. 8, No. 1, May, 1965, p. 183 (summary only). Paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. Also in report form: UCRL-11674, Lawrence Radiation Laboratory, University of California, Berkeley, Calif., 18 Sept. 1964. [6] Komarovskii, A. N., "Shielding Materials for Nuclear Reactors," translated from Russian by V. M. Newton, Pergamon Press, London, 1961, p. 145. [7] Davis, H. S., "Concrete for Shielding, Nuclear Radiations," Progress Report, Committee on Nuclear Structures and Materials, Proceedings. American Society of Civil Engineers, Vol. 88, No. ST 1, Feb. 1962, Part I, Paper 3062, 1962. [8] Henri, J. O., "Properties of Nuclear Shielding Concrete," Proceedings, American Concrete Institute, Vol. 56, 1960, pp. 37-46. [9] "High-Strength, High-Density Concrete," Technical Report No. 6-635, Corps of Engineers, Waterways Experiment Station, Nov. 1963, p. 65. [10] Davis, H. S., "Aggregates for Radiation-Shielding Concrete," Transactions, American Nuclear Society, Vol. 8, No. 1, May 1965, p. 178 (summary only), paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. Full text published by ASTM in Materials Research and Standards. Vol. 7, No. 11, Nov. 1967. [11] Mather, K., "Application of Petrography to Radiation-Shielding Concrete," Transactions. American Nuclear Society, Vol. 8, No. 1, May 1965, pp. 177-178, paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. [12] Raphael, J. M., "Structural Properties of Magnetite Concrete," Proceedings, American Society of Civil Engineers, Vol. 84, No. ST 1, Jan. 1958, Paper 1511, 1958. [13] Davis, H. S., "High-Density Concrete for Shielding Atomic Energy Plants," Proceedings, American Concrete Institute, Vol. 54, 1958, pp. 965-977. [14] Washington, W. O., "Design Requirements of Shielding Concrete," Transactions, American Nuclear Society, Vol. 8, No. 1, May 1965, pp. 176-177 (summary only), paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. [15] Lott, J. L. and Kesler, C. E., "Problems of Hardened Concrete," Transactions, American Nuclear Society, Vol. 8, No. 1, May 1965, pp. 178-179 (summary only), paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. [16] Mather, Katharine, "High Strength, High Density Concrete," Proceedings, American Concrete Institute, Vol. 62, 1965, pp. 951-962. [t 7] Davis, H. S., "Thermal Considerations in the Design of Concrete Shields," Proceedings, American Society of Civil Engineers, Vol. 84, No. ST 5, Sept. 1958, Paper 1755. 1958. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 434 TESTS AND PROPERTIES OF CONCRETE [18] Davis, H. S., "Effects of High-Temperature Exposure of Concrete," Transactions. American Nuclear Society, Vol. 8, No. 1, May 1965, p. 182 (summary only), paper presented at the 1965 annual meeting of the American Nuclear Society, Gatlinburg, Tenn., 1965. Full text published by ASTM in Materials Research and Standards, Vol. 7, No. 10, Oct. 1967. Bibliography "Concrete for Nuclear Reactors, Vol. I, II and llI," Publication SP-34, American Concrete Institute, 1972. (Includes 75 papers presented at an international seminar on concrete for nuclear reactors, Berlin, 5-9 Oct. 1970. Several of the papers were prepared and presented by members of ASTM Committee C-9. Davis, H. S., "Concrete Shields--Their Preparation and Use," General Electric Review, Vol. 59, No. 6, June 1956, pp. 43-45. Davis, H. S., "High-Density Concrete for Reactor Construction," Civil Engineering, Vol. 26, No. 6, June 1956, pp. 52-56. Davis, H. S., Brown, F. L., and Witter, H. C., "Properties of High-Density Concrete Made with Iron Aggregate," Proceedings, American Concrete Institute, Vol. 52, 1956, pp. 705726. Davis, H. S., "Cement and Aggregates for Shielding in Atomic Energy Plants," Mining Engineering, Vol. 9, No. S, May 1957, pp. 544-548. Davis, H. S. and Borge, O. E., "High-Density Concrete Made with Hydrous-Iron Aggregates," Proceedings, American Concrete Institute, Vol. 55, 1959, pp. 1141-1147. "Engineering Compendium on Radiation Shielding, Vol. II Shielding Materials," International Atomic Energy Agency, Springer-Verlag, Berlin, 1975. Polivka, M., "Annotated Bibliography on Concrete for Radiation Shielding," Concrete for Nuclear Reactors, Vol. III, Publication SP-34, American Concrete Institute, 1972, pp. 16391731. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. STP169B-EB/Dec. 1978 S. B. H e l m s ~ Chapter 27 Weight Air Content and Unit Terminology The density of concrete is the mass of the solid per unit of volume and, considering weight synonymous to mass, the term unit weight can be used to signify density expressed as kilograms per cubic metre (or pounds per cubic foot). In engineering and scientific work, density of substances is frequently indicated as grams per cubic centimetre and when the numbers so expressed are listed without stating the units they may be assumed equal to the specific gravity for all practical purposes. In the technology of concrete and aggregates, where the specific gravity is known, 1000 is the practical multiplier used to determine the unit weight in kilograms per cubic metre (or 62.4 in lb/ft3). As an example, "solid unit weights" of aggregates derived from these multipliers are used in mix design procedures involving the summation of solid volumes of the mix components. Air content is expressed as percent by volume irrespective of the size distribution of the minute air voids beneficially incorporated in air-entrained concrete by air-entraining agents. Determining Test Values The measurement of density of hardened concrete is based on procedures that are simple and direct, using samples such as molded specimens, drilled cores, or portions taken from hardened structures and trimmed to cylinders or prisms of sufficient size to be representative. It is reasonable to require unit weight by displacement measurement to be reported to the nearest 1.6 kg/m 3 (0.1 lb/ft 3) and within an accuracy of 0.1 percent. Accurate weighings are used in determinations by displacement techniques such as suspended-immersed methods, or by weight-inI Materials engineer, Bechtel Power Corp., Gaithersburg, Md. 20760. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 435 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978 tobyLicense ASTM International www.astm.org 436 TESTS AND PROPERTIES OF CONCRETE air of the sample divided by its volume as calculated from measured dimensions. This latter procedure is especially adaptable for determinations on dry specimens using precise measurements of linear dimensions within an accuracy of 0.2 percent. The apparatus and instruments used for these purposes are familiar and it is unnecessary to describe the detailed procedures commonly used or to comment on their significance. In contrast, the accepted techniques for determination of air content, after concrete has set, require specialized equipment and sophisticated techniques if exact information is desired. Where an estimated air content will suffice to differentiate, or to be indicative of the general level of air content, less discriminating methods may be used which are predicated on precise density measurement, specific gravities of the concrete constituents, and known or determined percentages of the ingredients. While methods for unit weight are traditional, those for air content have developed since the time the advantages of entrained air were recognized, as the means for studying the effects of air content on other properties and especially the resistance to frost action. Representative Densities and Ranges of Porosity The unit weight block diagram was developed to describe the principal types of concrete which are of commercial significance. Figure 1 shows these in one illustration which serves to indicate the scope of this paper, insofar as air content and unit weight should be considered, whereas the other characteristics of concrete in certain other major categories (such as cellular, lightweight, radiation shielding) are covered separately as topics of special interest in this publication. Figure 1 does not delineate exact limits because such variables as moisture content and richness of mix have an appreciable effect on the density. Hardened unit weight exceeds the respective fresh unit weight due to the influences of absorption, bleeding (water gain), and settlement. Voids in vesicular aggregates contribute to reduced density but are not considered to be part of the air content charted on the figure. The arbitrary dividing lines between zones were drawn to correspond to available data in published references. For purposes of this discussion, concretes are classified on the "block diagram" according to the air content as: "non-AE" 0 to 2 percent, "air entrained" 2 to 10 percent, and "aerated" from 10 to 30 percent air. Other subclasses, according to unit weight, are: "lightweight" 320 to 1922 kg/m ~ (20 to 120 lb), "normal weight" 1922 to 2643 k g / m 3 (120 to 165 lb), and "heavyweight" 2643 to 5286 kg/m 3 (165 to 330 lb/ft3). Influences of moisture content and variations of aggregate physical properties affecting concrete density were not considered critical in constructing the block diagram which serves a descriptive purpose. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 437 HELMS ON AIR CONTENT AND UNIT WEIGHT ] ~Stee] ~ --Steel 500~ Shot. Punchings & Magnetite Aggregate 1 coarse & Magnetite fine --Steel coarse & Limonite fine l ~ ~Eerro Alleys 5286 --Iron & Limonice --lron OIe & S t e e I 400 Punchings --Magnetite coarse and fine f~ / B a r i t e Aggregate - USBR Design --H,,dreus Iron Aggregate - NPDL Design --llmenice Aggregate - HEPC Design 300 e~ Natural Heavy Iron Ores ~ M i c h i g a n Limonite Aggregate CO3~ACTED PIPE centrifugated, ~ S S L CONCRETE and ASBESTOS CEMENT PIPE 2000 ~SONRY ~ORTAR CUBES 1922 PASTE-FOAM-ORAVEL 10 STRUCTURAL LI~I~T .~'LIGHT 1000 ~-643 E~A~ED AGGRE~TE FILL CONCRETE WT. BLOCK EXPANDED AGGRECATE "low fines" Concrete i Pumice H ~ | I L ~ N LIGHT ~ . ] MIXTURES including[ I Perlite-Sand Blends INSULTING P ~ S T E R S I Wermiculite and I Perlfte MORTARS [- . . . . . . . --_~ .~ 320 non air entraineo AE , l ~ . - - - - c o n c r e t r ~ ~ir entrained aerated mixtures mortars ~0 AIR C O ~ E ~ , m , 2O per cen~ & 30 FIG. 1--Unitwe~htblock d~gram. Review of Principles of Density Feret [1] 2 represented the "density" of mortar as the total volume of the solid particles per unit of volume. This was similar to the current application of the method of absolute volumes involved both in proportioning methods and in the analysis of the physical constants of concrete. Detailed discussions of the validity of the relationships established by Feret are included in Refs 2 and 3. After the relationship between water content and richness of mix was established by Abrams' water/cement (w/c) ratio, Talbot and Richart [4] utilized the concept of the cement/space ratio which now may be applied in evaluating data of air-entrained and lightweight concrete. Their Fig. 12 [4] applicable to their Series 2-G mortars and concretes, made with Wabash 2The italic numbers in brackets refer to the list of references appended to this paper. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 438 TESTS AND PROPERTIES OF CONCRETE River aggregates, shows a linear relationship between the unit weight of concrete and the voids as represented by the line unit weight, k g / m 3 = 16.02[167(1-v-c) + 193c + 55v] or unit weight, lb/ft a : 167(1-v-c) + 193c + 55v This line closely fitted all experimental points plotted for these materials; v and c are absolute volumes of voids and cement, v being the sum of water and air voids. Talbot and Richart recognized that levels of water content affected compressive strength at a given ratio and employed a strength reduction curve to normalize their charts of compressive strength versus cement/space ratio. The effect of air voids on unit weight is more pronounced than that of water voids, and changes of unit weight are therefore indicative of the air content of air-entrained concrete. Feret [5] distinguished between "airentrained" in mortar, water voids, and cavities quite a long time ago. Heretofore there has been no method to distinguish and discriminate the different types and sizes of air voids in freshly mixed concrete; in 1969 a technique was developed to facilitate such distinction. The device called void spacing indicator [6, 7] was introduced for studying the quality of the entrained air system in plastic concrete and was shown to be a valuable indicator of the frost resistance of the hardened concrete. The cement/space ratio concept advanced by Talbot and Richart was utilized by Morris [8] who developed a mortar voids methods for designing concretes. Illustrations in Morris' paper correlate strength with the cement/ space ratio as shown in the original Bulletin No. 137 [4]. Such concepts were extended to the design of air entrained concrete mixtures by Thornburn [9]. Charts of the type used by Morris have unique utility in establishing strength versus voids correlations in presentation of design data for the lightweight insulating or aerated classes described by Fig. 1. Effect of Aggregate Density Condensed data from Bureau of Reclamation reports [10] presented in Table 1 show the variation of concrete unit weight, in round numbers, as attributable to specific gravity of the aggregate used in the mix. For structural concrete the values usually range from 2371 to 2435 kg/m 3 (148 to 152 lb/ft 3) with 2403 (150) being the reasonable assumption for dead load, whereas it can range as high as 2499 k g / m 3 (156 lb/ft 3) in massive construction using larger maximum size aggregate. Effect of Paste Content and Degree of Compaction Cement pastes in the practical range of 0.019 to 0.034 m 3 (5 to 9 gal) Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. HELMS ON AIR CONTENT AND UNIT WEIGHT ,= < [.. E~E~ Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 439 440 TESTS AND PROPERTIES OF CONCRETE of water per sack of cement, or w/c ratio of 0.44 to 0.80, have air-free unit weights from 1602 to 1922 kg/m 3 (100 to 120 lb/ft 3). Since normal aggregates usually range from about 2563 to 2803 kg/m 3 (160 to 175 lb/ft3), it is clear that a reduction of paste volume by substitution of aggregate will increase the unit weight. Table 2, which applies to mass concrete, is included as an example of increased unit weight due to reduction of the amount of paste or mortar in the mixture. In mixtures of stiffer consistency, of 50 mm (2 in.) slump or less, the degree of compaction as effected by vibration would have a more pronounced effect. Important factors in the consolidation of concrete are reviewed in the report of ACI Committee 309 [11]. Some applicable test results given in the paper by Grieb et al [12] are shown in condensed form in Table 3. By using vibration to facilitate compaction it is practical to lower the sand proportion and reduce the slump required for proper placing. Each of these changes permits lower water content and thereby increases unit weight. With improved densification and adjustment of mix proportions, as described, the mortar or paste will be of better quality and show higher strength for a given cement content. The advantage of proper compaction of concrete in the field is as obvious as the adverse effects of incomplete or improper consolidation. The ACI 309 report cites the benefits of vibration and revibration in elimination of entrapped water under aggregate particles, and under steel reinforcement, and the elimination of extraneous air voids, to improve bond. Published results [11] on effects of overvibration have shown that it can reduce entrained air to low levels; however, it was found that extra vibration to eliminate undesired large voids "will not damage the parameters of the air void system . . . essential to best durability if the concrete initially contains the amount of air recommended in ACI 211-73. While half of the initial air could be lost due to overvibration, the requirements for frost resistance apparently would still be met unless the initial air content was lower than that prescribed in ACI 211 Recommended Practice." Recognition of Advantages of Entrained Air A study launched about 1935 [13] showed that cores from certain experimental pavements having high resistance to freezing and thawing contained portland cement that had been blended with either of two natural cements which happened to contain about 0.07 percent of fat or grease. Lowered unit weight was the clue leading to understanding that resistant slabs contained larger amounts of entrained air than did nonresistant slabs, and studies of air entraining materials were started. It has been stated [14] that the first work correlating freezing-and-thawing tests with air content was reported by the Portland Cement Association in June 1938. But the term "air-entraining cement" was not introduced until after their Study of Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. h2.98 1:2.80:1.05 1:2.79:2.65 1:2.46:4,26 1:2.34:6.07 No. 4 (4.8 mm) 3/8 in. (9 mm) 90 in. (19 mm) 11/2 in. (38 mm) 3 in. (76 mm) 3.6 3.8 3 3.4 3,2 (91) (96) (76) (86) (81) Slump, in. (ram) 42.9 36.7 30.1 26.5 22.4 Volume % of Paste b Vibrated 137.2 141.8 148.0 152.9 154.6 137.7 140.6 149.2 155.1 158.1 2198 2272 2371 2449 2477 2206 2252 2390 2485 2533 lb/ft 3 kg/m 3 Rodded Vibrated Rodded Vibrated 2360 2480 2450 2440 2280 2400 2590 2480 2400 2140 psi Rodded Vibrated 16.27 17.10 16.89 16.82 15.72 16.55 17.86 17.10 16.55 14.75 MPa Rodded Vibrated 7 Day Compressive Strength aCondensed from Table 61 Bureau of Reclamation, Bulletin 4, Cement and Concrete Investigations, Boulder Canyon Project. b Water/cement ratio 0.56 by weight. Weight Proportions Maximum Sieve Size of Aggregate Unit Weight TABLE 2--Unit weight and strength of hand rodded and vibrated specimens data from mass concrete investigations, a I ill 0 --r c z -q > z c~ m z -H z O O 6O O Z > m t- Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. "Mix No. 2 results. bFor six cited tests of representative retarders. 150.3 150.1 147.0 145.3 151.1 149.9 149.0 153.5 152.5 152.2 150.8 153.8 152.1 152.5 5 8 11 12 19 21 Average b Nonvibrated lb/ft 3 Vibrated No. Retarder 2459 2443 2438 2416 2464 2436 2443 Vibrated Unit Weight of Hardened Concrete 2407 2404 2355 2327 2420 2401 2386 kg/m 3 Nonvibrated 6500 6050 6240 5690 6170 6210 . . . psi . . . 44.8 41.7 43.0 39.2 42.5 42.8 MPa/m 2 Vibrated Cylinders 1 1 2 16 2 5 4.5 Increase Due To Vibration, % Compressive Strength T A B L E 3--Data representative o f Grieb's Table 10, R e f 12. Effect o f delayed vibration on compressive strength o f concrete at 28 days. a -I I'1"1 0 0 Z 0 O .-fl (,9 O -o m 33 "O 2~ Z m o~ --4 co 4~ Ix) J~ HELMS ON AIR CONTENT AND UNIT WEIGHT 443 Cement Performance was instituted in 1941, when these were known as "treated" cements. Improved scaling resistance of pavements made with "treated" cement was attributed to entrained air by Moore [15] who stated: "Both Vinsol resin and tallow reduce the unit weight of concrete by introducing air, uniformly distributed throughout the mass in microscopic voids . . . . The reduction in compressive strength and unit weight of concrete which accompanies the increase in resistance to freezing and thawing may appear disturbing at first thought for it has generally been accepted that the denser and stronger the concrete, the greater its durability [16]. The belief that durability increases with strength is undoubtedly true up to the point where requirements for good concrete are satisfied, but beyond this point the theory that strength is an index of durability may not be true." Vollmer [17] utilized fresh unit weight data to show the effect of calcium chloride admixture on the calculated air content of concretes made with Vinsol resin cement and concluded that use of calcium chloride reduced air. However, more refined tests by Pigman [18], Gonnerman [19], and others [20] have shown that entrained air is increased slightly by the incorporation of calcium chloride. The density of saturated hardened concrete is consistently found to exceed that of the respective fresh concrete. This is probably attributable to two effects combined; a small reduction in the air content is usually experienced and higher water content can result from prolonged moist curing or resaturation. Therefore, the fresh unit weight should not be used as the basis of absolute volume calculations for air content of the cured concrete unless approximate values for air will suffice. Data selected from Tables 5 and 6 of Bugg's paper [21], while seemingly contradictory to the foregoing statement, are of interest as listed in Table 4. The mixtures had 76 to 102 mm (3 to 4 in.) slump and contained 335 kg/m 3 (6 sacks) of Type 1 cement. The unit weight relationships could have been affected by variations of coarse aggregate in samples, bleeding tendency, degree of compaction, curing, and moisture condition of beams at time of measurement. The fact that the sets of unit weight data for several mixes agree Closely could be misleading, since unit weight of moistcured specimens should be higher than that of fresh mix. In a few cases a surprising difference in unit weight is shown, corresponding to higher computed air in hardened mix, because of variations such as loss of moisture. See Table 11 of Ref 12. Axon [22] listed the changes in weight of hardened concretes containing varying amounts of entrained air during the progress of moist curing, water curing, and air curing; beams gained approximately 0.5 percent in weight in 28 days of water curing and were shown to lose from 2 to 2.7 percent in weight during 2 weeks of air drying. Since sonic E is a function of the true density of the specimen, E values in the last column of Table 4 show a reasonable relationship to hardened unit weight. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. Moisture Condition, Prior to Batching vacuum saturated vacuum saturated immersed 24 h immersed 24 h vacuum saturated vacuum saturated immersed 24 h immersed 24 h vacuum saturated vacuum saturated Type, and Characteristics Limestone 67-25 0.7 % absorption gravel 79-IG 1.6% absorption gravel 79-IG 1.8% absorption gravel 82-IG 1.8% absorption gravel 82-1G 2.5 % absorption Coarse Aggregate 3.3 0.6 3.6 0.3 3.6 0.3 4.0 0.9 4.8 0.5 Air Content, Percent 148.8 152.8 150.1 153.9 150.1 154.6 146.1 150.9 144.4 151.0 2383 2448 2404 2465 2404 2476 2340 2417 2313 2419 Fresh Concrete Unit Weight lb/ft 3 kg/m 3 149.7 154.1 148.9 153.6 145.1 149.9 143.8 149.8 152.8 148.8 2383 2448 2398 2468 2385 2460 2324 2401 2303 2399 Cured Unit Weight lb/ft 3 kg/m 3 825 865 800 830 755 870 680 735 645 725 5.69 5.96 5.52 5.72 5.21 6.00 4.69 5.07 4.45 5.00 Flexural Strength psi MPa At Age 28 Days 5.52 5.99 5.77 6.04 5.68 6.11 5.59 6.00 5.25 6.00 38.1 41.3 39.8 41.6 39.2 42.1 38.5 41.4 36.2 41.4 S o n i c E X 10 - 6 psi kPa TABLE 4--Unit weights of fresh concrete and (76 by 102 by 406 ram) (3 by 4 by 16 in. ) size hardened beams, after Bugg [21]. m .-1 m o 0 z 0 O 11 O "o ill z13 -13 -n z --I o') .Ix Several papers in the 1947 ASTM Symposium on Measurement of Entrained Air [23] listed data for volumetric method versus the gravimetric (unit weight). No further reproductions authorized.) in length.HELMS ON AIR CONTENT AND UNIT WEIGHT 445 It is also of interest that Bugg studied similar concretes with air contents ranging up to 7. provided the specimen is representative of known mix proportions and is in a saturated state. Seventy-two hours of oven drying with subsequent 48-h resaturation of specimens is essential to conduct tests according to the procedure deve. Kennedy's discussion [25] indicated his appreciation of this method.) beam specimens molded from the test concretes. operating at a test pressure of 34. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Measurement of Air Content of Hardened Concrete The simplest estimate of total amount of air in concrete can be derived from unit weight. Copyright by ASTM Int'l (all rights reserved).) diameter cores were omitted for brevity.5 MPa (5000 psi) to determine air content of hardened concrete. 871]. Erlin [27] modified this apparatus to eliminate using a testing machine to apply high pressure. Figure 3 of Swanberg's paper [23. p. In checking hardened concrete for the presence of entrained air. 102-mm (4 in.) in diameter and 254 mm (10 in. it is not always essential to determine the size distribution of air voids when one is primarily interested in knowing the amount of air contained. and comparisons of cylindrical specimens have shown reasonable agreement with air contents determined by microscopical means. This meter is an excellent means of differentiating between concretes of different air contents.loped at Illinois Division of Highways laboratory under Larsen and Blandin. . Some data for 51-mm (2 in. The equipment accommodates drilled cores up to 127 mm (5 in. Most published gravimetric tests apply to fresh concrete. on the assumption the void sizes are normal.) diameter cores were the size usually tested in the high pressure meter. Results for the original fresh mix are compared in Table 5 to cores drilled from hardened 152 by 152 by 760-mm (6 by 6 by 30-in. However. 74] used unit weight test data to substantiate results by the pressure method. and Table X in Gregg's paper [24. p. such as in correlation studies of pavement construction. Additional Illinois Division of Highways data obtained under conditions of laboratory control are given in Table 5. Other tests at Waterways Experiment Station [26] have shown the high pressure meter to be a satisfactory tool for such tests. Development of the high pressure air meter was recounted by Lindsay [25] who reported the successful application of a high pressure meter of special design.5 percent and concluded that no significant increases in freezing-and-thawing durability occurred with air contents in excess of 3 percent except when very porous aggregates were placed in concrete in a highly saturated condition. 6 2. When the foregoing values were applied in calculations.8 3. In U.5 6.8 4.3 5. values for laboratory concrete in plastic state and the same concrete in the hardened state. computed from absolute volumes.8 3.3 3.7 0. after Dykins and Blandin [28]. data were presented on changes in weight (water absorbed) and unit weight in curing prior to freezing-and-thawing tests.3 F H I J 0.0 0.0 3.6 2.8 7.5 ~ushedStone ~ a ~ e A ~ r e g a t e 0.5 5. on this basis. No further reproductions authorized.5 7. % Subgroup Individual Core Determinations Average Air Concent.2 2. % Hardened Concrete Plastic Concrete GravelCoarseAggrega~ A C D E 0.7 3.9 4.8 3. Sweet [29] pointed out that the air volume in hardened material may differ from the volume of air entrained in fresh mix. concrete volume.6 5.4 2.2 4.1 0.7 4. the agreement with the pressure test method provided evidence of accuracy.4 6.S.6 4. the time concrete displacement data were obtained.0 4. Compilations of the State of Illinois have indicated this difference can range from a few tenths of a percent up to nearly 1. . would account for the differences found. changes in theoretical unit weight of concrete with time.7 Loss of Entrained Air as Shown by Tests on Hardened Concrete Whereas tests under closely controlled conditions result in good agreement between measured air contents in fresh and hardened states.446 TESTS AND PROPERTIES OF CONCRETE TABLE 5--Air meter test comparisons.5 6.1 t. Searching for an explanation for about 20 percent less air in hardened concrete.2 0.9 0. due to changes in water content.9 0. 4-in (102-mm) diameter cores only. (Selected data from Ref 28 Table 2. In a series of Copyright by ASTM Int'l (all rights reserved).0 percent at 28 days.9 0.0 percent to 2.9 4.0 percent air. as shown in Table 6.5 4.3 1.) Air Content in Hardened Concrete. declared that use of such specific gravity as indicated for 72 h. due to hydration. were also recognized.6 6.4 2. it is generally accepted that a loss of entrained air will be experienced between the mixing of concrete and finally placing it in the forms. In his ASTM paper [30].6 5. after allowance was made for water lost in molding.8 0.7 2. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.2 1. Bureau of Reclamation tests made at about the same time.4 2.5 2. and it was shown [29] that the average air content fell from an initial value of 3.1 1.0 0. and specific volume of ingredients. Bloem and Walker [31] studied the apparent specific gravity of cement in water versus time and. 1 percent measured by pressure meter on the fresh mix. studied air-entrained pastes during setting. No further reproductions authorized. and stability of entrained air during hardening of the mixture. interesting facts were presented on the evolution of the air void system and the possible changes which take place in freshly mixed concrete. In one of his experiments.HELMS ON AIR CONTENT AND UNIT WEIGHT 447 TABLE 6--Changes in theoretical unit weight of concrete with time. Time After Mixing. making compariCopyright by ASTM Int'l (all rights reserved). it is practically impossible to determine the size distribution of air voids in tests of fresh concrete. using a neutralized Vinsol resin air-entraining agent. Part I [33].5 to 1. includes data for concrete specimens containing two superior air entraining agents and shows the air content of hardened mixture 0. Their Table 4.4 2395 2409 2417 2422 2425 a See chart on Fig.1 percent lower than the 5. Part I of the series covered the action of air bubbles in freshly mixed concrete. comprising a treatise on factors governing size.4 150. Verbeck [36] applied the camera-lucida method successfully by tracing the voids on an enlargement of a microscopic view at a magnification of about 100 diameters to determine air content at desired locations within a specimen. Powers [35] provides a practical insight regarding the cited papers and other related references for those who need to apply the principles of studies such as these in further investigations. Quantitative Estimate of Air Content by ASTM Recommended Practice Several techniques have been developed for hardened material which are based on inspection of polished sections. referencing the papers by Mielenz et al. Otherwise. h 0 1 2 3 4 Theoretical Unit Weight ~ lb/ft a kg/m 3 149. By this work Bruere has provided a means whereby the size distribution of air voids in fresh concrete may be studied by arresting the fresh void system (introducing an agent which induces quick set) then using microscopical methods developed for samples of hardened concrete.9 151.2 151. the conclusion based on Bruere's paste data was that rearrangement of bubble sizes and solution of air from small bubbles were negligible in the period during which airentrained pastes are fluid prior to setting. While the case for paste-aggregate combinations was not studied. the bubble systems of pastes of normal and accelerated setting characteristics were compared. Bruere [34]. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5 150. . distribution. ACI articles by Mielenz et al [33]. 2 of Ref 32. better perception at higher magnification will substantially increase the microscopically determined air. C 823. it is conducted regularly in research studies and has proven to be a practical method for study on job concrete. and spacing of air voids present. then traversing the prepared surface under a microscope to determine the relative amount. and is extensive. 132 and p. locating a typical field for scanning. the Missouri Highway Department. Stated briefly.3.02 in. effect of magnification. Copyright by ASTM Int'l (all rights reserved). this is discussed by other authors in this publication. the average void-to-void distance should be 0.) or less. (The nature and size range of air voids in Types I and IA cement concretes were shown clearly in cameralucida drawings in Klieger's [37] paper. Section 5. In this way the air voids are shadowed and recognizable down to 15 #m size or less. These procedures require skill and experience to achieve desired accuracy. shallow because the cut surface may be close to the bottom of the void. size. Although this procedure requires precision and capable technicians. The results reported by Warren [39] at the University of Wisconsin include photomicrographs of carefully polished interior sections of air-entrained concrete magnified to 40 diameters. 4For details see ASTM Standards C 457. Powers was able to advance the theory of permissible spacing to show that. Voids filled with fluorescent dye in Canada balsam were photographed in ultraviolet light. The ability to distinguish air voids is dependent on the qualities of the ground surface. and the operator's skill using stereoscopic binocular with the surface illuminated from one direction at a low angle.5 mm (0. Table 5. calculated from measurements by the plane intercept method.3 With the additional evidence provided by new techniques [38] for determining the nature of air voids. No further reproductions authorized. as is seen in Table 7 herein.448 TESTS AND PROPERTIES OF CONCRETE sons with other methods. The recommended practice includes specific instructions for proper conduct of the microscopical examination with numerous notes explaining special details. for high resistance to freezing and thawing in cement pastes. ASTM Recommended Practice for Microscopical Determination of AirVoid Content and Parameters of the Air-Void System in Hardened Concrete (C 457) has provisions for both linear traverse and modified pointcount methods. the technique is based on preparation of representative plane interior surfaces by sawing and fine grinding on suitable laps. 787. Section 11. and elsewhere were meeting the need for specialized microscopical examination of hardened air-entrained concrete.2. In determinations of void systems of high specific surface. The ASTM 3See p. An interesting feature of Verbeck's paper was the tabulation of size and volume of voids. . Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) The published discussion of Verbeck's paper and subsequent developments have shown that skilled technicians at the laboratories of the Corps of Engineers. 4 low incident light (around 30 deg from horizontal) also aids in detecting air voids. Void properties. are interesting because those introduced by two accepted air-entraining agents had essentially the same specific surface. and C 586. 004 in.1 5.0567 0. about 0.Copyright by ASTM Int'l (all rights reserved). b m m Net air content.5 140.0604 0.1 (2292) 7 sacks (390) 29. % Average diameter of voids.6 5.118 5.~ -7 sacks (390) Neutralized Vinsol Resin Admixture ~Defined as surface area of voids per cubic millimetre air in concrete.39 0.3 142.113 5. Specific surface of voids. Curves showed the average diameter of air voids was only slightly affected by cement content and angularity of coarse aggregate.33 0.100 5.43 0. At a given cement content. lb/ft 3 ( k g / m 3) Type I Cement Concrete Mixes Darex Air Entraining Admixture TABLE 7--Void properties in 76-mm (3-in. at air content of 7 percent.0669 0.5 143.)slump air-entrained gravel concretes (after Warren [39]).0536 0.0 5.1 (2260) 4 sacks (223) 39.18 0. bOne half average m a x i m u m distance from void to void within paste.-4 m c z z E2 z -4 m z 3o (3 O -1m rE 6o O Z . No further reproductions authorized.2 141.094 5. . the air voids were more numerous and smaller in the concrete with higher cement content. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. % Fresh unit weight. a m m 2 Air content.4 5. Photographs showed.Ix r -r .8 (99~. pressure meter.3 (2248) 4 sacks (223) 39. the listed data show little difference between concretes made with the two agents. Cement Factor: ( k g / m 3) 28. m m Void spacing factor. .a). present problems in surface preparation. the air-void content.450 TESTS AND PROPERTIES OF CONCRETE Recommended Practice C 457 procedures are the available methods for the determination of A. p. " .5 percent air. . at very high air content the bubbles tend to coalesce. Air determined microscopically to be approximately 30 percent. in order tO minimize the sacrifice of mechanical properties and ensure satisfactory durability. . Figure 2 is a photo- FIG. According to Mielenz and Wolkodoff [33]. the specific surface of air voids. micrograph of a concrete containing air voids at the high level of 30 percent which would be prohibitive from the structural standpoint but commonplace if cellular concrete were desired. This figure forms an interesting contrast with the illstrations presented by Mielenz et al [33. or weak for other reasons. No further reproductions authorized. Contrast of Purpose for Higher Levels of Air Incorporated in Concrete Usually the amount of entrained air in hardened concrete is intended to be within the range of 3 to 7 percent in the form of minute air voids of high specific surface. the computed spacing factor. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.2/ in. ranging from 275 t o 550 cm 2/cm3 (700 to 1400 in. On the other hand. 1958. and Z. and the thin septa and ridges between the voids are easily lost Copyright by ASTM Int'l (all rights reserved). Polished sections of concrete with high air content. Aug. the inclusion of air in excess of 8 percent will markedly reduce compressive strength. Part 2. a. 262] to show normal void systems of concrete with 3. 2--Concrete containing excessive entrained air (X15). . When batch proportions and weights of ingredients are accurately known. 1. Thus there are two main purposes for incorporating air in concrete. Such predictions are dependent on the accumulation of data pertaining to equilibrium air dry weight at a given relative humidity. some predictions of the air dry unit weight can be made or calculated by making certain assumptions.2 mm (0. 1. Large amounts of air. and other minor factors. the air content is determinable by the method of absolute volumes--deducting the volume of component ingredients from the calculated volume of the batch.008 in. or as entrapped air. in the range of 10 to 30 percent or more air content. Referring to the "non-AE" subclass mentioned earlier. The amount of incidentally entrained air is dependent on mix proportions. Yield. however. too. In normal weight concrete this "incidental" entrained air is less than 2 percent. No further reproductions authorized. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. If properly controlled. To a certain extent air dry unit weight values. As mentioned in an introductory paragraph of this paper. the smaller amount of air present in non-air-entrained concretes is known as incidental air. 2. aggregate absorption. or accidental air.HELMS ON AIR CONTENT AND UNIT WEIGHT 451 during grinding. organic impurities. although higher values may result from inadequate compaction. the voids will be of high specific surface and provide the required spacing factor of 0. are useful in dead-load computations. and Air Content (Gravimetric) of Concrete (C 138) to determine the unit weight of freshly mixed concrete. Similar displacement procedures are available for tests of concrete masonry units under ASTM Method of Sampling and Testing Concrete Masonry Units (C 140).) or less. introduced by aeration or generation of gas. in the explanation of Fig. and improved workability. amount of fines. Theoretical weight per cubic metre (cubic foot) was mentioned previously. Air entrainment for frost resistance. For purposes of insulation and weight reduction the void size is not as critical as in structural applications. ASTM Test for Unit Weight of Structural Lightweight Concrete (C 567) includes the testing of hardened concrete by determining the air dry weight of standard 152 by 305-mm (6 by 12-in." adding the thought that these factors would impair the accuracy of the linear traverse technique. Determination of Unit Weight Using Standardized Procedures Calibrated standard cylindrical measures are used under ASTM Test for Unit Weight. primarily to reduce the density of the concrete product. Notably the procedure given in Section 4 of this test is applicable to normal weight concrete specimens. specimen volume is determined in ASTM Test C 567 by making suspended-immersed weighings. while fictitious in nature. Where composition is known. ASTM Method C 140 Copyright by ASTM Int'l (all rights reserved). . aggregate particle shape.) cylinders moist cured 7 days and air dried at 50 percent relative humidity for 21 days. shown in Table 8 representing a wider variety of proportions. this principle has been used to indicate the absence of entrained air. traced the relationships of voids. and air content-it is appropriate to emphasize that air-entraining cement will increase consolidation of concrete block mixtures of dry tamp consistency.) maximum crushed stone concrete with different sands and cements. density. the absorption of concrete is primarily dependent on the quantity and quality of paste or mortar component and. as in the case of a lightweight concrete masonry unit. for given materials. No further reproductions authorized. unless the specimen is not immersed for the required 24-h period. The selected results show reduction of absorption in lean mixes where there was a marked reduction of mixing water when air was entrained. where increased drainage time of 5 to 10 min could have the effect of reducing the apparent volume of the specimen by 1 or 2 percent. Having obtained physical data on a given concrete sample. In discussing the reabsorption of water. the 1-min drain time tends to increase the calculated volume of a porous concrete. Table V of Ref 2 included interesting saturated surface dry unit weight and absorption data of resaturated air dry concrete. Axon [41] developed and published a procedure for determination of air content and estimation of original unit water content based on physical and microscopical methods. are of interest because the sand was reduced to compensate for the increased amounts of air. Hansen [42] published data showing the effects of overrodding on 63-mm (2i/2 in. and since the proportions of dry solids are determinable. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. absorption is a useful criterion of quality. Swayze [45] mentioned this in an article in Civil Engineering when "treated" cement Copyright by ASTM Int'l (all rights reserved). an analytical approach can be made according to the method of absolute volumes by establishing the proportions and specific gravity of ingredients. On the other hand. .452 TESTS AND PROPERTIES OF CONCRETE specifies a draining period of I rain which is required to properly calculate the effective specimen volume. Entrained Air and Related Properties Though affected by coarse aggregate character. The short period required for completing the "saturated surface dry" and "immersed" weighings minimizes the possibility of error in determined volume due to further reabsorption. In our experience. the concrete may be disassembled after dehydration at 600~ in the manner described by Blackman [40]. incidentally. By measuring the volume and weight of a suitable resaturated specimen. Following the line of paradoxes expressed in Gilkey's speech [44] which. Klieger's data [43]. including air-entraining cement. The same type displacement procedures may be used to determine volume and unit weight of specimens of various sizes obtained from hardened concrete according to ASTM Method of Obtaining and Testing Drilled Cores and Sawed Beams of Concrete (C 42). as abridged from Hansen's paper. unit air and water contents may be calculated with reasonable accuracy. .5 in.1 2.. 1% in.5 in.. (mm) 4-Sack a Mixes 223 k g / m 3 1.6 1.2 90 in.Copyright by ASTM Int'l (all rights reserved). Gravel Gravel Stone Stone Type I Type IA Type I Type 1A 6 (152) 6 (152) 3 (76) 3 (76) 4.5 .0 1.7 1. 1. (38 ram) max 2.. (19 mm) max 2% in.2 1.3 2. in..2 1.6 1.4 3.5 in. (38 ram) max . (63 ram) max 51/2-Sack a Mixes 307 k g / m 3 90 in..7 1.77 k g / m 3. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.6 2.5 1.7 2.6 1. Coarse Aggregate Cement Slump.4 3. Values for kg cement/m 3 shown in parentheses.4 2. 1. No further reproductions authorized. (63 ram) max O'1 Ga 1" m Z C > z o z -H m z -H O O O z "1" m v- .2 2. (63 ram) max 2.5 in.6 1.7 2.4 1. by 72-h Resaturation of Air-Dry Concrete TABLE 8--Absorption of air-dry concrete (after Klieger [43]).6 3.1 90 in. %.2 1.7 2.. (38 ram) max 7-Sack a Mixes 390 k g / m 3 Absorption. (19 ram) max 1..1 1. .5 3. (19 mm) max a l sack/yd 3 : 55..1 1.9 2. Varied Amounts of Voids and Special Purpose Concretes Methods used in commercial practice for imparting dense structure to concrete by manipulative means include: (1) production of hard floor finishes from dry-tamped concrete using power floats [48]. 503. usually made with lightweight aggregates. Whereas. Low specific weight is dependent on the presence of voids. whether formed by air or water. to manufacture cellular products. In the range of lowest density concretes. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Copyright by ASTM Int'l (all rights reserved). the plotted thermal conductivity in Kluge's [52] Fig. and in Canada. The criterion of strength/weight ratio may be used. The principle of "no fines" concrete [51] could even be modified to the use of lightweight aggregate and foamed paste to produce a variety of densities down to the low limit. an intended use for thermal insulation often makes strength a secondary consideration. Foamed concretes that use large amounts of air-entraining agent as well as gas concretes are likely to show high shrinkage. to make lightweight compositions. Erratic behavior of aluminum powder dependent on the sensitivity to chemical properties of cement. could cause an inordinately high air content. in dry tamp concrete. (2) densification of initially overwet concrete by vacuum techniques to achieve high early strength. and stabilization by autoclaving is desirable. Although slight advantages can be claimed for certain aggregates in weaker. Aluminum powder has been used for many years in other countries such as Sweden. are among the factors to be considered in controlling manufacture. to rate the efficiency of compositions of similar unit weight. however. leaner mixtures. in plastic concrete. and (4) manufacture of lightweight masonry units [49]. (3) making of concrete pipe by spinning and packer methods. including a double dosage of dry powdered air-entraining agent which. Various reports have traced the development of the use of gas-forming agents. No further reproductions authorized. Lightweight cellular concrete [50] is discussed more fully in the paper by Lewis 5 in this publication. such as aluminum powder and hydrogen peroxide. The insulating characteristics of low density concrete may be correlated closely with the unit weight of the oven dry specimens and the compressive strength with air dry density.454 TESTS AND PROPERTIES OF CONCRETE was being introduced to the block industry. 14 permits 5See p. Manufacturing problems and economic factors are reasons for their not gaining acceptance here. and Helms and Bowman [46] presented quantitative data. Results supporting this principle were given in Table 6 of Ref 47 for laboratory specimens containing expanded slag aggregate. and difficulty in distributing the powder to get uniform results. but these products have never proved feasible for production in our country. . increased compaction was experienced. as holes in honeycomb or as pores in the aggregate. HELMS ON AIR CONTENT AND UNIT WEIGHT 455 citation of K values which could be assumed applicable to any oven-dry lightweight concrete mix with low unit weight. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Revised compositional data selected from the final mixtures.36 a Slight advantages for certain combinations could be overshadowed by the effect of small amounts of moisture retained by air dry specimens. Much ordinary concrete.5 W/m. No further reproductions authorized. The special concretes used for radiation shielding require dense aggregate materials such as iron ores. and usually either an airentraining agent or a fine plasticizing admixture. In conclusion. the utilization of heavy aggregate because of its weight is of direct engineering importance.~ 0. is dependent on its relatively high mass for its usefulness.5 2.7 1. TABLE 9--K values for oven-dry lightweight concrete. since cement content is reflected only as weight. 420 Copyright by ASTM Int'l (all rights reserved)./h-ft 2. the mixtures described contained iron ore and steel punchings which have been used as aggregates for radiation shielding. Results for 40 test combinations are shown which included three aggregate samples. c Results tabulated by Brewer [54] tend to confirm the above portrayal of the thermal conductivity of low density concrete. it should be mentioned that unit weight tests are the time6See p. Oven-Dry" Unit Weight of Concrete lb/ft 3 20 42 55 70 (kg/m 3) (320) (673) (881) (1121) Conservation Maximum Thermal K Valueh"~ btu. three volume proportions of aggregate. counterweights. for this purpose Callan [56] described high unit weight concretes in the range of 3604 to 4406 k g / m 3 (225 to 275 lb/ft3).29 0.10 0. 3 illustrate the relations of voids to weight and total solid volume to compressive strength.K 0. used in gravity dams. listed in Table 10. in. Keyser [55] studied heavy aggregate concrete for making counterweights as far back as 1932.0 2. At the other extreme. The plotted data of expanded perlite concretes in Fig. In order to avoid segregation the quantity of mortar used was only slightly greater than that required to fill the voids in the coarse aggregates. The curve of strength versus solids has limitations. This topic is covered adequately in Polivka's paper 6 in this volume. but it has unique applicability in the extreme range of high voids. are of historical interest. . and some foundations. as shown in 'Table 9. Concrete in the weight range above 4005 k g / m 3 (250 lb/ft 3) has been used extensively for permanent ballast in ships [57]. bLess conservativevalues may be found elsewhere [53]. lock walls. Although not directed toward nuclear application.22 0. Copyright by ASTM Int'l (all rights reserved). Type IIl cement insulating concrete made with expanded perlite aggregate. to calculate this information from weight and displacement or weight and dimensions of hardened specimens.. and Air Content (Gravimetric) of Concrete (C 138). 600 9 40Q \ _.0 . .. as for the data plotted in Fig. Yield..) m 600 9.. 9 25 9 %..( 9 "~"~ ~ so~ o. \ 9 .( \oo.0 8.7 and sometimes it is expedient. The determination of yield and interdependent unit contents of cement and water is necessary in both laboratory and field for the proper control of concrete mixtures. 4.Q_ s 200 -~. 400 \ \ 9 ~ 350 20 "70 "' 75 80 '"" Pet Ccnf Voids FIG. 3. honored basis for determination of yield.456 TESTS AND PROPERTIES OF CONCRETE 65O 40 ..4 (... 3--Relationship of unit weight and strength to percent voids. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized.<-- 2...( 9 X% 7. 7Measured by ASTM Test for Unit Weight. 8 lb/ft 3 29.Copyright by ASTM Int'l (all rights reserved). Compressive strength. . (6 to 16 m m ) thick. 13 19. 28 days Design unit weight Unit weight.5 334 188 227 520 1594 1515 4378 kg/m 3 563 317 383 876 2687 2553 7379 Ib/yd 3 11 2190 psi 273.6 271. No further reproductions authorized.0 MPa 4378 4303 kg/m 3 "9"6"5 1901 989 4378 334 188 kg/m 3 kg/m 3 4260 psi 272. . (13 to 25 ram) in diameter and 1/4 to s/8 in. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. .0 272. Quantities per Cubic Yard or per Cubic Metre TABLE l O--A bridged average data from Keyser's Table 1 [55].4 MPa psi 2230 4378 4333 kg/m 3 lb/ft 3 273. oil and rust free. 28 days age Cement Water Sand Fine iron ore Coarse iron ore Rivet punchings v Total Reference Mix No. bSized 1/2 to 1 in.3 268. Value for kg c e m e n t / m 3 shown in parentheses. 3487 2069 2342 1390 7360 4367 lb/yd 3 14 (38-mm )-max iron ore concretes.77 k g / m 3. z u m z o 0 z :12 60 O z --ira .6 lb/ft 3 1"6"27 3204 1667 7378 563 317 lb/yd J a 1 sack yd 3 = 55.1 15. .4 4~ -1--I m c z ).4 MPa 4367 4354 kg/m 3 563 334 224 133 744 441 . probably no-slump. . 6-sack a (335 kg/m 3) 1 89 t- O'1 ".3 270.1 MPa 4373 4359 kg/m 3 "46"8 1584 1821 4373 "789 2670 3069 7371 lb/ft 3 334 166 kg/m J 563 280 lb/yd 3 12 2750 psi 273. 15. Vol. 1949." Bulletin No. 1940. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Journal. Research Report No. C. G. Sept." Pit and Quarry. Proceedings. University of Illinois.. Vol. No further reproductions authorized. and Woolf. "Concretes Containing Air-Entraining Agents.. p. Urbana. June 1970. "Pavement Scaling Successfully Checked. June 1969. p. Vol. A. E. [12] Grieb. "Vacuum Method of Measuring Air Content of Fresh Concrete. 136. 1938. [14] Avery.. I11. M. 1955. 121. [21] Bugg." Journal.. Ira. 1604. F. 2. [13] Paul.. p. 12." Significance of Test and Properties of Concrete and Concrete Aggregates. Vol. 58. 893. 59. discussion. p. 38." Journal. June 1944. F. H. 156." Journal. H. [11] ACI Committee 309. REFERENCES [1] Feret." Research ReportNo. Texas A & M University. Table 4. 1934). p. [17l Vollmer. [9] Thornburn." Transactions. 40. "Portland Cement Association.. American Society of Civil Engineers.. 68. "Air Void Systems in Ready-Mixed Concrete. (An account of Kansas Highway Department experience. "Effect of CaC12 on Water Requirement. L. ASTM STP 169. the size of voids is of little consequence if they are uniformly distributed throughout the mix. 1892. 23. 1971. W. Dec. 1961. R.. [15] Moore. 492. and Richart. Engineering Experiment Station. L. 1871. D. O. H. 208. Highway Research Board. 1 Feb. 61. 6. and Ivey. [4] Talbot. Proceedings. Portland Cement Association. U.. "Air Content and Unit Weight. p. American Society for Testing and Materials. 27. "Water Cement Ratio Versus Strength etc. American Concrete Institute. No. G. P.. Vol. and it has been realized for many years that if air is efficiently dispersed into the finest attainable size a smaller amount will be required for durability with subsequently less effect on strength." Proceedings. B. Proceedings. 15] Feret. L. Part 2. D. 45 Years of Outstanding Service to Industry." Proceedings. P. p. 137. Copyright by ASTM Int'l (all rights reserved). Nov. D. L.. 1941. Werner. and Journal of Materials. R. p. p. H. p. [19] Gonnerman. W. 2. American Society for Testing and Materials. "Effect of Pellet and Flake Forms of Calcium Chloride in Concrete. Vol. No. p." Bulletin 75. 29. 103-3. [2] Helms. 87. 34. 7th ed.S.. T." TTI. Research Report. 1953. 1943. 1897. Feb." Proceedings... Aggregates. [3] Woods. F. Dec. 154.. [7] Ivey. 1947. S. M. . p. Feb. "Water-Reducing Retarders for Concrete--Physical Tests. [8] Morris. "The Laws of Proportioning Concrete." Journal. "Chloride Salts Resistant Concrete in Pavements. [20] McCall.. Vol. N. 1932.458 TESTS AND PROPERTIES OF CONCRETE When air is incorporated for the purpose of reducing density. discussion. "Sur la Compacite (Density) des Mortars Hydrauliques. "The Mortar Voids Method of Designing Concrete Mixtures. 1961. Vol. 509. Hubert.. 144. R. p. 296. "The Strength of Concrete--Its Relation to the Cement. American Concrete Institute. [6] Torrans. T. and Torrans. p. July 1947. 921. O. [18] Pigman. Highway Research Board." Proceedings. [16] Jackson. L.. to 31 July 1943. Proceedings.. H. 1907. Highway Research Board. 4. "Annales des Ponts et Chausses" and Bulletin de la Societe d'Encouragement pour l'Industrie Nationale. American Concrete Institute. 103-4F. 49. p. and Water. Bureau of Reclamation." Engineering News-Record. Vol. June 1969. American Concrete Institute. But the size of air voids entrained to improve durability is extremely important. 10 Oct. 31... p. Vol. E. S. Specific Weight and Compressive Strength of Concrete Made with Plain and Treated Cement. H. No. J. "The Design of Concrete Mixes Containing Entrained Air. [10] Concrete Manual. "Effect of Air Entrainment on the Durability Characteristics of Concrete Aggregates. "The Void Spacing Indicator. Vol. J. Voh S." Public Roads. American Concrete Institute. and Claus. 1923. "Recommended Practice for Consolidation of Concrete." Vol. 9. p. American Association of Highway Officials of the North Atlantic States. . Dec. May 1947. and Reagel. p. 918. "Research on Concrete Durability as Affected by Coarse Aggregates. p. F. Ky. H. Proceedings." Proceedings." (Series 66) Journal. Highway Research Board. 629. H. 434.. "A Method of Estimating the Original Mix Composition of Hardened Concrete Using Physical Tests.. p." Proceedings.. J.. S. 45. C. W. also discussion. 1964. Vol. 187. 1025. S. Vol. Research Department. E. E.. 28. May 1949. 1947." Journal. Klieger. "Rearrangement of Bubble Sizes in Air-Entrained Cement Pastes During Setting. H. C. Oct." Bulletin No. 1962).. Concrete. C. 1068.. Blackman. O.. Highway Research Record 62. Waterways Experiment Station. Vol. also discussion. Bruere. Pirtz." Proceedings." Proceedings. Cement." Bulletin No. Vol. F. A.. 18. (Journal. "Linear Traverse Technique for Measurement of Air in Hardened Concrete. American Concrete Institute. "Studies of Concrete Containing Entrained Air. S. 988. Gregg. "Effect of Air-Entrapping Portland Ce- [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] ment on the Resistance to Freezing and Thawing of Concrete Containing Inferior Coarse Aggregate. S. P.. "Method of Estimating Water Content of Concrete at the Time of Hardening.. J. Backstrom. 981.. Oct. Klein. Proceedings. Verbeck. Lexington.. "Effect of Entrained Air on Concrete with 'Sand-Gravel' Aggregates. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Powers.. p. p. Vol. Vol. 1948. H. including: T. F. L. 1958. No further reproductions authorized. 35. Cements. Brewer. Bloem. p. 117. T. p. Brown. 12. 42. American Concrete Institute. D.HELMS ON AIR CONTENT AND UNIT WEIGHT 459 [22] Axon. T. American Society for Testing and Materials. 533.. July 1958. G. H." Report No.. C-431. Vol.. 43. p. Portland Cement Association.. 70. and Flack. 55. . 1965. McCoy. 424. C. Willis. "Field and Laboratory Air-Content Studies of SaltDamaged Concrete Structures. Hansen. 1962. W.884. J. 1962. V. Portland Cement Association. Army Corps of Engineers. 48. 1950. 50. 60. Mielenz. E. "Loss of Entrained Air in Freshly Mixed Concrete and Effect on Properties of Hardened Concrete.. Bureau of Reclamation. American Society for Testing and Materials. and Blandin. Oct." Journal. "Air-Entrained Concrete (Durability). 222. Dykins. Vol. C. E. p. p. Kennedy. American Society for Testing and Materials. 149. and Effects of the Air Void System in Concrete. Engineering Experiment Station." Bulletin 174. 6-286. E. Vol. Swanberg. E. 43. "Experiments with Air Entrained in Cement Concrete.. David. "Illinois Develops High Pressure Air Meter for Determining the Air Content of Hardened Concrete. F. U. Highway Research Board. Highway Research Board. J. W. pp. 1943. Research Department. p. 5. Axon. Publication 1246. Concrete. and Pearson. 95. Evolution. American Concrete Institute.. Sept. Sweet. 3." Australian Journal of Applied Science. B. 1948. Wolkodoff. 1947. American Concrete Institute. Vol. and Pierson. J." Proceedings.S. V. R. B. and Epoxy Bonding. and Walker. Alexander. Proceedings. Proceedings. L.. Jan. 1948. "Air Content of Concrete by a High-Pressure Method. L.. Thomas. Characteristics of Air Void Systems. H. W.S." Research on Aggregate. Sweet. J. L.. p. 1946. D. "Topics in Concrete Technology 4. Erlin.. Entrained Air in Unhardened Concrete. No." Bulletin 149. Symposium on Measurement of Entrained Air in Concrete. "The Camera-Lucida Method for Measuring Air Voids in Hardened Concrete. E. "Determination of the Properties of Air Voids in Concrete. Jr. G. B. Part I. 871. M. American Concrete Institute. University of Kentucky.. Cordon. C. C. Proceedings. Highway Research Board. No. Proceedings. June. Vol.. 1952. O. discussion. A. Vol. U. and discussion by T. p. Dec.. March 1954. "High Pressure Test for Determining Air Content of Hardened Concrete. 894. Lindsay." Journal. 1956. S. 62. Warren. Vol." WES Miscellaneous Paper No. American Concrete Institute. and Manipulation Upon the Resistance Copyright by ASTM Int'l (all rights reserved).. Vol. 47.. 47. Kennedy. Journal. Materials Laboratories. "Origin. American Society for Testing and Materials. Proceedings. Sept." Journal. 1953. Schweizer. B. p. T." Journal. 13. "Influence of Sands. U. p. C. ASTM STP 169A. "High Strength Air-Entrained Concrete.. June 1971." Magazine of Concrete Research. 121. 1953. Fig. No." Journal. Colin. L.. P. Valore. May 1949. M. No further reproductions authorized. June 1954. Harland. Vol. [47] Helms. 68. "Designing Concrete for Weight of 271 Pounds Per Cubic Foot. and Mclnnis.. American Concrete Institute. Copyright by ASTM Int'l (all rights reserved). . 3." Joint Research Lab Publication No. also discussion. "Lightweight Concrete's Place in the Insulation Spectrum. 91. 2. C. "Concrete for Radiation Shielding. Sept. p. 1. 302. 1939. Building Materials and Structures Report BMS 96.. G. p. Vol." CivilEngineering. E. "Effect of Entrained Air on Strength and Durability of Concrete Made with Various Maximum Sizes of Aggregates. 833. American Concrete Institute. 45. No. pp. p. P. Proceedings. Vol. J." Proceedings. "Compaction of Concrete Slabs by Vibration. 525. No. Portland Cement Association Research and Development Laboratories. J. American Concrete Institute. S0. Voi. "Mechanism of Frost Damage in Hardened Cement Paste. B. p. "Porosity-Strength Considerations for Cellular Concrete. March 1974. 28. p. 6. [48] Klock. 16." Proceedings. F. Jan. and Woodworth. and Bowman. [45] Swayze. Proceedings. H. 34. B. 105. 51. [44] Gilkey.. American Concrete Institute. C. Jan. Journal. Kraft. 1943. Vol.. 462. [56] Callan. R. Proceedings. E. [57] Journal of Commerce. p. 309. 1951. Jan. "Relation of Heat Flow Factors to the Unit Weight of Concrete. No. B. Proceedings. "Less Sand and Water in Air-Entraining Batches Improves Concrete. May. "Method of Making Vibrated Dry-Tamp Concrete Cylinders Applied to Tests of Lightweight Aggregate and Block Mixtures. J. American Concrete Institute. "Tests on Concrete Masonry Units Using Tamping and Vibration Molding Methods. 4. American Concrete Institute. R.. 1942. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 573. Vol. April 1961. C. [43] Klieger. "Effect of Vibration on Air Content of Cement Mortar and Concrete." Journal. R. L*. 50. p. also discussion. S. Proceedings.. Proceedings. R. G.. 31. "Water Cement Ratio Versus Strength--Another Look. 13. April 1950." Journal. [49] Wendt. American Concrete Institute." Cement and Concrete Research. M. American Society for Testing and Materials. p.. [50] Valore. 19 Dec. [52] Kluge. 1972. Hogberg." Concrete (London). W. Vol. Sparks.. "The Zig-Zag Course of Concrete Progress. Hoff. Vol. March 1968. [55] Keyser. "Lightweight-Aggregate Concrete.. P. National Sand and Gravel Association and National Ready Mixed Concrete Association.. American Concrete Institute. 17.." Journal. D. [53] Neher. Highway Research Board. and Green. Vol. Vol. April 1932. p..817. p.460 TESTS AND PROPERTIES OF CONCRETE of Concrete to Freezing and Thawing. also discussion. p. 1955.. C. 1975.. "Air Replaces Sand in 'No-Fines' Concrete." Journal. Proceedings. p. "Cellular Concretes. American Concrete Institute. 51.. 57. Proceedings. Nov." Journal. p. Vol. 1969. Proceedings." Journal. 46. 725. June 1966." Significance of Test and Properties of Concrete and Concrete Aggregates. C. C.. p. "Air Content and Unit Weight. American Concrete Institute. 1951. 177. 68. Forder. Sept. "Monolithic and Bonded Floor Finishes. Gilkey. Proceedings. MCORA. 27. [46] Helms. p. 36. M.. A. A. Vol. Vol. Proceedings. further studies. 7. p. 17.." (in Swedish) Nordisk Betong. 2. Bibliography Beaudoin. Vol. 625. p. C." Journal. Vol. Jr. H. p. Gaynor. Vol. 1184. K. 1287. No. June 1951. E. 47. American Concrete Institute. [51] Petersen. D. S. 773. 139. W. 1967." Journal. June 1949. Cubes and Beams." Journal. 55. H. No. J. M. 45. American Concrete Institute. 95." Cement and Concrete Research. July 1946.. "A Radio-active Method for Measuring Variation in Density in Concrete Cores. Vol. 39. [54] Brewer. M. 1966. 1952. 1942. J." Journal. L. p. Vol. 1.. M." Journal. 28. Vol. Nov. National Bureau Standards. and Tuma. p. Vot. 5. 6." 1958. Highway Research Board. 665. P. p. D. "Measuring Concrete Density by Gamma Ray Transmission.HELMS ON AIR CONTENT AND UNIT WEIGHT 461 Larson. 1. Proceedings." Journal.. 1965. "Note on Density of Concrete as Affected by Variations in Properties and Proportions of Ingredients. Feb. 1968. No. March 1967. 2. O. 285. MTRSA. P. Vol. 19. H. T. p. and Ivey. Copyright by ASTM Int'l (all rights reserved). Torrans. 10.. J.. May 1949. Vol. American Concrete Institute. K. No. No. . and Malloy. Sept. Larson. 8. Proceedings. D. p. Vol. p." Highway Research Record. 8. 45. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Protected Paste Volume Concept Using New Air-Void Measurement and Distribution Techniques. No further reproductions authorized. 202. "Method of Test for Air Content of Hardened Concrete. "Systems Approach to Analysis of Hardened Concrete. Lewis. "Air Void Systems Affected by Chemical Admixtures and Mixing Methods.68. 38. p. Vol.." Journal of Materials. 107. June 1965. U." Materials Research and Standards. 2. 1971. D. and Cady." Construction Review (Australia) Vol.." Materials Research and Standards. Vellines. CRD-C83-58. K. Oct. "Concrete Control on a Major Project. "A Method for Determining the Air Content of Fresh and Hardened Concrete. Cady." Journal. p. D. L. D. P. No. MTRSA.S. 1. 68. R. and Ason. S. American Concrete Institute. Preiss. JMLSA. and Cooper. No.. p.. R. Riley. Army Corps of Engineers.. 9. P. T. No.. National Research Council. 226. J. B. T. 21. G. a smaller sample is often all that is available. The state of the art and science of the analysis of concrete for its components was well detailed by Minnick [i]2 in the previous edition of this book (ASTM STP 169. except for one recently developed technique that at least requires only a minimum of effort (see Maleic Acid Method section). To such an end this chapter is written. 111. Concrete specimens should be secured to represent each area in question. T h a t review concluded that " . Where possible." there are many occasions when a knowledge of the cement factor is desirable. Northbrook.STP169B-EB/Dec. Copyright by ASTM Int'l (all rights reserved). the situation has scarcely improved.org . 2The italic numbers in brackets refer to the list of references appended to this paper.astm. 1978 W. . the analyst who can report not only the data but also estimates of the error and its direction is of inestimable value." Unfortunately. the chemical procedure has not yielded a high degree of accuracy.4). However. Determination of Cement Content Sample Selection A sampling program should be carefully designed to provide the desired information. No further reproductions authorized. specimens of acceptable concrete should also be obtained so that comparisons of determined cement contents can be made. Although such requests may often be poor substitutes for the far better "Determine why this concrete performed badly. Hime Associates. . hopefully obviating aggregate interference. Conl Vice president. Although several 4-kg (10-1b) specimens are required if strict adherence is made to ASTM Test for Cement Content of Hardened Portland Cement Concrete (C 85).60062. Erlin. It may prove quite satisfactory if it is cut from a concrete core or cylinder. Sun Apr 6 21:43:38 EDT 2014 462 Downloaded/printed by Universidade do Gois pursuant Agreement. H i m e I Chapter 28 Cement Content Introduction Analyses for cement content are requested frequently by those who have encountered concrete that has shown low strength or other improper performance. Copyright9 1978tobyLicense ASTM International www. HIME ON CEMENT CONTENT 463 crete portions obtained by hammering or by selection from rubble are undesirable as they are likely to reflect a loss of the mortar fraction.. An unanticipated positive error may thus occur. Excellent tables detailing the acid solubility of aggregates were given in Minnick's [1] review. fine grinding should be avoided if aggregate correction procedures are not to be used. at least in their surface regions. Sample Preparation The pulverization operation should not lead to significant loss of fine material. If several 4-kg (10-1b) specimens are not available. The method determines acid-soluble silica and calcium (generally soluble calcium is equivalent to total calcium) by straightforward. A magnet may be used to remove any iron contaminant introduced by steel disks. often major. Unfortunately an error. the size of the aggregate should dictate the sample weight. That method. and interfere with the silica procedure. has been cited in specifications of many countries and has been evaluated by dozens of investigators [3-6]. Assuming a 4-kg (10-1b) minimum sample requirement for a 25-mm (1-in. Copyright by ASTM Int'l (all rights reserved). "wet chemical" techniques of analysis.T h e original 1954 version Of ASTM Test C 85 was based on determinations of soluble silica and calcium in the concrete.5 4 . with alkalies from the portland cement fraction. forming acid-soluble silicates. be chosen in direct proportion to the aggregate size. . or a modification of it. An analytical sample that just passes a 30-mesh screen will usually permit complete cement solubility while minimizing aggregate interference. occurs if the aggregate fraction contains calcareous and siliceous components that are soluble under the conditions of the test. If soluble silica or lime is to be determined. are soluble or partly soluble in acid. and assumes them to be entirely due to the portland cement component. the sample weight for other sizes of aggregate might. Cement Content Analysis Procedures Methods Based on Soluble Silica or Lime A S T M Test C 8 5 . such as limestone or dolomite. but quite lengthy. except quartz. nor gain from the grinding device itself. All calcareous aggregates. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) top-sized aggregate. if necessary. crushers. as suggested as early as 1924 by Kriege [2]. or disk pulverizers. No further reproductions authorized. Many siliceous aggregates. One phenomenon has been overlooked by other investigators: siliceous aggregates that were originally insoluble in acid may have reacted. interfere with the calcium procedure. 200 sieve. 2. It is nearly impossible to duplicate these parameters. has dissolved. and in the sand fraction. and thus unidentical solubilities. The hardness and initial size of the concrete fragments being analyzed will not be the same as those of the virgin aggregate particles. the temperature of the acid. The coarse fraction of the concrete is treated with acid to dissolve the cement adhering to the aggregate. for the sand fraction. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Composition may thus vary. This procedure. However. Numerous investigations of the errors due to aggregate solubility have been made. Ford [4] and many others have found that a cement content determination will generally provide a high result without aggregate corrections. 50 sieve is used. Under the most favorable conditions. 3. Thus. but none of the aggregate. Correction errors may arise for any of a number of reasons. can provide excellent results for most samples and is the method of choice for research purposes. and thus identical grinding. in the hands of an expert analyst. No further reproductions authorized. a 10 percent error should be assumed. This is especially true when the analysis is performed by an inexperienced analyst. Additionally. and a low result when corrections are applied. or even grinding to pass a given sieve. may produce quite unidentical particle sizes. and the particle size of the aggregate. 6 sieve is used. using the aggregate in the sample itself. may differ significantly. This layer is removed by Copyright by ASTM Int'l (all rights reserved). For the cement-sand. An exact timing is an impossibility with calcareous aggregates. and guilt on an innocent concrete producer. a generally infrequent situation. It is difficult to stop this treatment at the precise moment when all the cement. 1. only that portion retained on the No. especially the latter. their final particle sizes. Such corrections may themselves be in error due to the fact that their magnitude depends upon an assumption of aggregate proportions. and thus their acidsolubilities. the correction procedure can lead to overcorrection for aggregate solubility. Additionally. the solubility of siliceous aggregates may vary greatly with the time of treatment with the acid. A S T M Test C 85-66--The current version of ASTM Test C 85 differs from the original one (1954) in that it provides correction procedures for aggregate interference.464 TESTS AND PROPERTIES OF CONCRETE Corrections for aggregate interference in the ASTM Test C 85-54 procedure can be made if the original aggregate is available for analysis. . it is possible that doubt may be cast on good concrete. The fine fraction is divided into two parts to determine soluble silica and lime in the cement-sand combination. material passing the No. although both parts are further ground to pass a No. Both the coarse and fine aggregate may have reacted with the cement alkalies to produce a layer now soluble in acid. and consequently a low cement content. 82 3.85 3.12 16. Determined Acid Digestion Period SiO2.38 18. 2. and 20 min. Additionally. The soluble silica procedure of ASTM Test C 85-66 is followed.62 TABLE 2--Silica data f o r concrete containing no soluble siliceous aggregate. but for 10. Tables 1 and 2 present the data for TABLE 1--Silica data f o r concrete containing partially soluble siliceous aggregate.93 4.0689 0. g SiO2.0825 3. respectively. % Portland Cement. a method has been developed to provide determined cement contents at or above the actual level.HIME ON CEMENT CONTENT 465 the process that produces the aggregate fraction used for the correction analysis. Determined Acid Digestion Period SiO2. Siliceous aggregates that are partially acidsoluble are revealed by this treatment. calcareous aggregate and most quartz aggregates). 1. The concrete specimen is ground to just pass a 30-mesh screen (by limiting grinding time and size of charge). In the author's laboratory. 15. . If the silica contents increase with time. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.38 18.0771 0.71 19. an estimate of the magnitude of (positive) error is possible. Author's Procedure--"Negative" errors (underestimation of true cement content value) can cause undue hardship to a concrete producer and may lead to a false interpretation of the cause of improper concrete performance. The method is essentially as follows. Copyright by ASTM Int'l (all rights reserved). Indeed.33 18. g SiO2. % 10 min IS rain 20 min 0.24 such an aggregate.44 3. No further reproductions authorized. % 10min 15min 20min 0.0764 0.0767 3. % Portland Cement. European practice is to employ a short digestion procedure with ice-cold 80-percent hydrochloric acid ("Florentin" acid) to minimize aggregate solubility. Thus.19 18. except that the three portions are not each digested for 15 min. a method that minimizes such errors has frequent application. the 10-min data usually provide the most accurate results. and for an aggregate containing no soluble siliceous material (for example.0786 0. aggregate. a clay) contains water or other substances volatile at 600~ (for example. The use of the 14. Because sulfate contents of cement. vary from less than 2 percent to almost 4 percent. This method provides results within 24 h. a 30 percent error can result from this factor alone. The method can prove a helpful "backup" to confirm other data. or.5 percent. 4. and usually an unacceptable burden in the latter. and could cause very significant errors. Unpublished work by Pistilli [9] at the Portland Cement Association found that this interference could be minimized by reducing the maleic acid concentration from 20 to 14. and since they do not provide a direct determination of cement content. Unfortunately. cement content can be determined through analyses for sulfate. the sulfate content of the cement must be known or estimated--an infrequent event in the former case. as SO3. Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. air. and water contents of hardened concrete.5 percent maleic acid concentration. Negative errors can arise if the aggregate (for example. More extensive investigations have shown that fly ash. or if the cement paste had carbonated (masonry mortars are often extensively carbonated). providing results within 1 h. and requires only about 2 man-hours. . The methods have not found wide usage since they require special equipment and expertise. An atomic absorption procedure employing a nitrous oxide flame and cement standards has proven excellent for this determination. and thus did not interfere. Data from the method must thus be used with care. found that most calcareous and some siliceous aggregates were partially soluble. Sulfate Method--As presented by Kossivas [10] and several others. its speed and simplicity recommend it highly. organics). and a water-correction ignition temperature of only 520~ are suggested. or suggest the need for additional work. Clemena [8]. in an extensive test of the method. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. a unique situation. the method is remarkably free of interference. Although the authors found that most aggregates were insoluble in maleic acid solution. and some other aggregates can lead to error. any rapid. but rather of cement paste. Maleic Acid Method--A method based on the solubility of hydrated cement in a methanolic maleic acid solution was developed by Tabikh et al [7]. Microscopic Methods--Polivka et al [11] and Axon [12] have presented methods for the determination of cement. Since few aggregates contain sulfate. The fraction of cement by weight is multiplied by the determined or estimated unit weight to provide the cement factor.466 TESTS AND PROPERTIES OF CONCRETE 3. alternatively. However. accurate method for calcium may be employed. The soluble calcium oxide procedure of ASTM Test C 85-66 is followed. slag. Mielenz [14. and others. Additives and Admixtures The chloride content of concrete can be determined by acid extraction and potentiometric titration. Since the methods do provide information on all the major concrete components. and the accuracy of such estimates is open to question. . relatively inexpensive method utilizing a silver electrode has been described by Hime [20]. for triethanolamine by Connolly and Hime [26]. nuclear devices that determine calcium or silicon automatically have been proposed by Covaut and Poovey [18]. Determination of Other Concrete Components Although an extended discussion of methods for other components of concrete is beyond the scope of this chapter. A chloride electrode method developed by Berman [21] is the basis of most governmental analyses in connection with bridge deck corrosion.17]. For large-scale projects.15]. Copyright by ASTM Int'l (all rights reserved). aggregate. for polyhydroxycarboxylic acids by Frederick and Ellis [25]. and are not only subject to the same interferences as the soluble silica and calcium methods. No further reproductions authorized. Iddings et al [19]. Methods for several types of retarders were also given by Halstead and Chaiken [27]. but also to all forms of siliceous and calcareous aggregates. air voids. procedures for lignosulfonates were developed by Hime et al [22] and Kroome [23]. A general discussion was given by Hime et al [22]. and for vinsol resin by Hime et al [22] and Kroome [23]. These devices are extremely costly. admixtures. and Erlin [16.HIME ON CEMENT CONTENT 467 The proportion of cement in the paste fraction must be estimated. been developed. Methods that have been found to be especially applicable are as follows. In the hands of petrographers well versed in concrete and concrete-making materials. Miscellaneous Methods--Many other methods for cement content have been presented. for sugars by Shima and Nishi [24]. Methods of detailed petrographic techniques for the analyses of concrete and the wealth of information that can be obtained are aptly given by Mather [13]. they can have important value in concrete investigations. and water. Methods for several organic additives and admixtures have. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A rugged. the petrographic techniques and information thereby obtained are extremely useful to the chemical analyst in his understanding of the potential error to which his analytical results are susceptible. the analyst charged with a determination of cement content should be aware that analyses can also be made for additives. but none has attained popularity nor shown promise except in limited applications. 326-339. ." Engineering NewsRecord. often an approximation at best." Proceedings. 1924. J. pp. [3] "Cement Content Determination and Reactive Aggregate Cooperative Tests. or by microscopic methods such as those of Polivka et al [11] and Axon [12]. No further reproductions authorized. p. Water content also has been estimated by the microscopic techniques of Axon [12]. H. F. calcium hydroxide). No. as acid-insoluble residue for certain siliceous aggregates... "Determining the Cement Content of Concrete. 282-285. unfortunately. Copyright by ASTM Int'l (all rights reserved). In favorable cases. pp. Methods of analyses of concrete and many other cement products have been presented in books by the Society of Chemical Industry [31] and Figg and Bowden [32]. 892. For non-air-entrained concrete. Blackman [28] and Brown [29] have presented an applicable method determining original water as the sum of combined water and water calculated as having led to development of voids. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. [21 Kriege. General Reference Works Methods of analysis of cements and concrete were presented by Hime in a chapter of Encyclopedia of Industrial Chemical Analysis [30]. 1966. Vol. 1952. 21. free water can be determined as loss at 110~ and combined water as loss from 110 to 1000~ correcting for carbon dioxide as determined by any usual technique. American Society for Testing and Materials. the determination of the water content of hardened concrete is of academic interest only. A S T M STP i69A.468 TESTS AND PROPERTIES OF CONCRETE Air Voids The air void content of concrete is determined by point count or linear traverse methods in accordance with ASTM Recommended Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457). American Society for Testing and Materials. Vol. 52." Concrete and Concrete Making Materials. The latter contains a bibliography of 193 references. Aggregate The aggregate content of concrete can be determined by difference (100 percent less cement and water). The determination of original mix water is of much greater importance but. 92. "Cement Content. Differential thermal analysis and thermogravimetric analysis techniques generally allow assignment of water to specific substances (for example. Water Generally. References [1] Minnick. L. pp. C. "Cement Content Determination in Hardened Concrete." Reviews in Engineering Geology. Inc." Analytical Techniques for Hydraulic Cement and Concrete. "Analytical Techniques for Hydraulic Cement and Concrete. W.. [24] Shima.. April 1952. pp. "Use of Neutron Activation to Determine Cement Content of Portland Cement Concrete. [14] Mielenz. "Analysis of Hardened Concrete. Teiji. F. "Diagnosing Concrete Failures. M. No further reproductions authorized. G. D. A. American Society for Testing and Materials. R. A S T M STP 395. 1955. Grace and Company. 1962. Portland Cement Association. 1971.. 1964. 962-974.. [17] Erlin. K. Chapter 40. II. M. 135-152. [10] Kossivas. [11] Polivka.. 47-52. [6] Forss.. 125-143. pp. p. . 14. "Determination of the Cement Content of Hardened Concrete by Selective Solution. pp.. G.. pp. "A Physical Method for Determining the Composition of Hardened Concrete. Ara. 29-37. 3A. 1970. [16] Erlin. pp. "Determination of Chloride in Hardened Portland Cement Paste.. 1963. F. W. Ed. G. Copyright by ASTM Int'l (all rights reserved). Kelly. E." Highway Research Record 370. 1." Observations of the Performance of Concrete in Service. University of Maryland. 1966. 1-7. H. Vol. 132-134. W. A S T M STP 169. H. "Cement Content of Hardened Concrete. 1969. 1966. C. A.." HRB Bulletin 268." A S T M STP 395." in Standard Methods of Chemical Analysis. 1976. W. 1972. 1966. American Society for Testing and Materials. 2. [15] Mielenz. 62. D.. "A Method of Estimating the Original Mix Composition of Hardened Concrete Using Physical Tests. Vol. Ill." Special Report 106. 1972." presented at Cement Chemist's Seminar. R. C.. 1964. Highway Research Board. [12] Axon. American Society for Testing and Materials. 330-335. Vol. Portland Cement Association." Bulletin. American Society for Testing and Materials. A S T M STP 205. 18-29. 221. [21] Berman. M. Skokie. A S T M STP 169A. Highway Research Board. Bernard. A. F. "Nuclear Techniques for Cement Determination. 1956.. [9] Pistilli. American Society for Testing and Materials. pp. American Society for Testing ~ind Materials." Publication 1022. and Woods. and Poovey. J. 61. "A Method of Detecting and Determining Lignin Compounds in Mortars and Concrete. [13] Mather.. "Portland Cement.C. 3-17. W. [19] Iddings. W. pp. pp... Washington. "A Method for the Determination of Cement Content in Concrete. D. [7] Tabikh." Significance of Tests and Properties of Concrete and Concrete-Making Materials. Vol.. Katharine. 106-109 (Chemical Abstract. Bernard. pp. 3. pp. W. J. L. Vol.. pp." presented at Rock Products Chemical Research Seminar. Perez." Journal of Materials. Mortar and Concrete. American Society for Testing and Materials.. 1970. 1 Oct. Ikuo and Nishi. 23. pp. J. "Study of Methods for the Determination of the Portland Cement Content of Hardened Concrete." Nordish Betong.. Vol. Kiessel. also Research Department Bulletin 193. [22] Hime. and Schaefer." Papers on Cement and Concrete. pp. Mivelaz.HIME ON CEMENT CONTENT 469 [4] Ford. No. F. 1. 17. Van Nostrand Company. Washington.. "Determination of Saccharose in Hydrated Cement. Stanton Walker Lecture Series on the Material Sciences.C. 1962. [23] Kroome. G." Report on Significance of Tests of Concrete and Concrete Aggregates. F. 7. 21-26." Semento Gijutsu Nempo. No. "Petrography Applied to Portland Cement. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. R. 76-76. O. 5344b)." Lecture No. 1-38. Arman. June-Sept. Vol. Welcher. 1969. "Petrographic Examination (Hardened Concrete). G. Bengt. [20] Hime... Balchunas. No. O. 1971. pp. H.. C. Vol." Magazine of Concrete Research.. Chicago.. pp. Highway Research Board. "Cement Content of Hardened Concrete. [5] Kriege. and Connolly. D.. "Analytical Techniques. Available NTIS PB-213-855.." Proceedings. B. 1-29. L. A. [18] Covault. E. 118-130. D. 18 Nov. 1966. C. 1962. Geological Society of America. Highway Research Board. 1068-1080. September. M." Virginia Highway Research Council. [8] Clemena. A. W. "Methods Used in Petrographic Studies of Concrete.. and Best. D. 7. [26] Connolly. Society of Chemical Industry. 1957. Wiley. T. 533-541. [30] Hime. W. pp. ." Encyclopedia of Industrial Chemical Analysis. pp. B. 1964. 1961. pp.. pp.. 94-155. New York. pp. March 1968. W." Materials Reseaeh and Standards. 1954. 1971. "Determination of a Polyhydroxy Carboxylic Acid Retarder in Hardened Concrete. Vol.. W. Oct. 741-746. No. W. 1976. American Concrete Institute. D. S. 6. 31. 50. 14-18. "Cements. W. L.. Vol. and Chaiken. "Analysis of Concrete for Triethanolamine. G. 126-135. 9. Vol. 8.. Vol. [28] Blackman. 18. Vol.470 TESTS AND PROPERTIES OF CONCRETE [25] Frederick. J." SCI Monograph No. A. [29] Brown. 1970. R.. [31] "Analysis of Calcareous Materials. "Method for Estimating Water Content of Concrete at the Time of Hardening. Vol. J. and Ellis. S. J." Public Roads." Cement and Concrete Research. J. and Bowden. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Mortars and Concrete. Copyright by ASTM Int'l (all rights reserved). Her Majesty's Stationery Office. [27] Halstead. 6. G. W." Journal of Applied Chemistry. No further reproductions authorized. and Hime. J. [32] Figg. "A Tentative Method for the Determination of the Original Water/ Cement Ratio of Hardened Concrete." Proceedings. "Water-Reducing Retarders for Concrete--Chemical and Spectral Analyses. The Analysis of Concretes.. pp. 565-572. By 1950 the industry used a third of the cement produced in the United States and today it uses about two-thirds of that produced. 2 The American Society for Testing and Materials (ASTM) has maintained ASTM Specification for Ready Mixed Concrete (C 94) since 1933 and ASTM Specification for Concrete Made by Volumetric Batching and Continuous Mixing (C 685) since 1971. This discussion will be supplemented by background information on the industry.2].astm. The interested reader should recognize that within the past 10 or 15 years there has been a tremendous increase in the use of ready-mixed concrete in the industrial nations in the rest of the world. operating procedures. History of the Industry The first concrete mixed off-site and delivered to the job may have been furnished in about 1913 but. That percentage doubled and tripled during World War II. This paper will review requirements of these two specifications and their relationship to other more general concrete specifications and codes. The references are intended to identify additional information in particular subject areas. Sun Apr 6 21:31:15 EDT 2014 471 Downloaded/printed by Universidade do Gois pursuant Agreement. ready-mixed concrete was not a recognizable industry until the late 1920s when the first revolving drum agitators and mixers were developed [3]. Copyright by ASTM Int'l (all rights reserved).org . and special problems and circumstances. 29448.C. Giant Portland and Masonry Cement Co. 2The italic numbers in brackets refer to the list of references appended to this paper. No further reproductions authorized. The peak production oc1Vice president of engineering and research. D. G a y n o r 1 Chapter 29--Ready-Mixed Concrete Introduction Ready-mixed concrete is concrete manufactured for delivery to a purchaser in a plastic and unhardened state [1. the industry used only about 5 percent of the portland cement produced. 1978 R. Foreign literature is an increasingly important source of information on ready-mixed concrete. Copyright9 1978 tobyLicense ASTM lntcrnational www.. The discussion represents procedures and conditions in the United States and Canada. S. Harleyville. In 1933 when the first ASTM specification appeared.STP169B-EB/Dec. Specifications ASTM Specifications C 94 and C 685 are specifications for the material freshly mixed concrete. specifying agency. A 1971 Bureau of Census survey of employment revealed that 40 percent of the companies had less than 7 employees. They address the separate and joint responsibilities of the various parties in a typical job--the owner. Included are the basic elements of both prescription and performance specifications. The industry started as small individual family-owned businesses. antitrust laws and regulations produce a diffusion of economic power in the ready-mixed concrete industry that is unlike that in most other industrialized nations. No further reproductions authorized. By the end of 1977 the volume should be about 15 percent above 1975 levels but still substantially under the 1973 level. . These facts and the U. In the recent recession the volume dropped to 131. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Industry surveys [4. An estimate of total employment in the industry in 1975 was 80 000 [6].472 TESTS AND PROPERTIES OF CONCRETE curred in 1973 when a total of 174 • 106 m 3 (228 • 106 yd3) were produced. and deliver the concrete. Few companies operate in more than one or two geographical areas. and the mixing and delivery operation.5] have consistently shown that the 10 percent of largest companies produce well over half of the total volume of readymixed concrete. 75 percent less than 18 and 94 percent of the companies less than 50 employees. Under certain prescriptive alternatives where strength is not specified. the contractor who must place it. the batch plant. American Concrete Institute (ACI) Specifications for Structural Concrete for Buildings (ACI 301) is intended to cover all of the usual requirements for cast-in-place concrete for buildings and should be used essentially by referCopyright by ASTM Int'l (all rights reserved). contractor. The responsibility for acceptable performance of concrete in place is divided inevitably between the concrete producer who must deliver acceptable material. These two ASTM specifications are meant to be incorporated by reference in the general job specifications. The requirements govern measuring of materials. and ready-mixed concrete producer.5 • 106 m 3 (172 X l0 s yd3) in 1975. Although it is difficult to identify all of the small companies it appears that there are about 5000 companies in the industry and perhaps 8 to 10 thousand plants. As yet there are no significant national chains. and the specifier who must structure appropriate specifications and plans. Included is the basis or unit of purchase--the cubic yard-and the appropriate test method. mix. Since strength test results are weighted heavily in the acceptance of the material and since strength is not usually determined until the concrete has been in the structure for 28 days. it is considered prudent to regulate further the procedures used to proportion.S. procedural and compositional requirements are necessary. Appropriate test methods are defined. It has retained much of that character. batch. The check list covers only the physical facilities. The requirements for mix design approval. generally for the protection of the public interest. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Increasingly. In the past 10 or 15 years there has been a gradual change away from the prescription to the performance or strength specification in large or important work. Conformance to the check list is required by ACI 301 and several highway or transportation departments and is often used in nuclear work. or actual performance of the total operation. mixing. which is now used in about 12 percent of the concrete. not personnel. testing. the sections of ASTM Specification C 94 dealing with materials. and delivery of ready-mixed concrete is by reference to ASTM Specification C 94. A company interested in certification must retain the services of a registered professional engineer to perform the inspection and to certify that the facilities met requirements at the time they were inspected. One additional factor has been that the mix design and proportioning expertise has been with the specifying agencies or commercial testing laboratories employed by them. procedures. It is a system for establishing the adequacy of the production facilities in a readymixed concrete operation. and evaluation are not used in AC1301. In this instance the Building Code is designed for inclusion in local or state building codes. the concrete industry is moving increasingly to the performance approach. are evidence of this increased interest in performance specifications. In preparing both ASTM Specifications C 94 and C 685 the ASTM Committee has produced a compromise of requirements somewhere between the needs of the small project where no job specifications are prepared and for large projects where specifiers provide detailed specifications requiring highly specialized procedures tailored to specific job conditions. and evaluation of both ACI 301 and ACI 318 differ in important respects from those in the ASTM specifications for ready-mixed concrete. ready-mixed concrete producers are assuming technical responsibility. Although there will always be a need for prescriptive specifications for small work. This writer believes that conditions will change rapidly in the future. No further reproductions authorized. . The batching. The acceptance of water-reducing admixtures which are now used in about 50 percent of the concrete and the recent interest in the use of fly ash. testing. An additional document that falls in the general classification of a specification is the National Ready Mixed Concrete Association (NRMCA) Check List for Certification of Ready Mixed Concrete Production Facilities [7]. The ACI Building Code Requirements for Reinforced Concrete (ACI 318) is another example of the use of ASTM Specification C 94 by reference. Therefore. A section of ASTM Specification C 94 states that when requirements of the job specifications conflict with requirements of ASTM Specification C 94 the job specifications govern.GAYNOR ON READY-MIXED CONCRETE 473 ence. proportioning. Two factors have been principally responsible for this trend--the difficulty of obtaining competent testing services and the almost complete reliance on strength tests made 28 days after the concrete has been placed in the structure. Copyright by ASTM Int'l (all rights reserved). ASTM Specification C 94 defines three basic types of ready-mixed concrete operations and ASTM Specification C 685 includes the fourth. volumetric proportioning equipment. The technology in the area of batch equipment and automation has been developing at an exponential rate and "automation" and the associated controls will be discussed in some detail. and contamination. and continuous rather than batch-type mixing equipment. The ASTM Specification C 685 system is generally known by the name of the only equipment currently available for this process--the Concrete Mobile. Owners will have to continue to perform acceptance testing but inevitably the amount of such testing done will be reduced as the quality of the information from the concrete producers improves. delivery to the job. and aggregates. Operating Procedures Operating procedures are considered to include materials handling. weather. the prescriptive requirements must be reduced or eliminated and the concrete producer must be able to change materials and proportions rapidly in response to varying materials. Central mixed concrete is mixed completely in a central mixer and transported in a revolving drum agitator (that is. That is. weighing. Mixing. The available equipment consists of truck mounted material bins. dump crete). The requirements of the NRMCA check list [7] outline the objectives and leave to the inspecting engineer's judgment the question of the adequacy of the system. mixer). Shrink-mixed concrete is partially mixed in a central mixer with the final mixing and transportation in a revolving drum truck mixer. Truckmixed concrete is mixed and delivered in a revolving drum truck mixer. They will rely on accelerated strength testing procedures which will estimate 28-day strengths at 1 or 2 days and they will insist on accurate uniformity information from suppliers of cement. and final discharge into the contractor's placing equipment. Materials Handling Aggregates--The objectives of a well-designed aggregate storage and handling system are to provide an adequate supply and to prevent segregation. General precautions are described in ACI Recommended Practice for Measuring. ASTM Specification C 94 has no specific requirements in this area. an agitator. No further reproductions authorized. mixing. charging the mixer. job conditions. TransCopyright by ASTM Int'l (all rights reserved). . Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. breakage. or a nonagitating unit (that is. admixtures. fly ash.474 TESTS AND PROPERTIES OF CONCRETE Ready-mixed concrete producers will become increasingly responsible for self-inspection systems--quality control testing. One additional change will be necessary if the system is to evolve. and acceptance testing procedures used for or by the owner. Generally. Precise shutoff of gates is more difficult to achieve and therefore cement should be weighed first and the fly ash last in a cumulative butcher. Some operators will not store fly ash in multicompartment bins adjacent to cement because of the possibility of conrumination. screws. plugging. the plant will include some relatively large secondary storage at the site in stockpiles. Bin gates. large silos. Low pressure air pads are necessary at the bottom of most bins to ensure flowability. Cernentitious Materials--Most cement is delivered by truck and is blown into overhead storage with pneumatic pumps. poor flowability is likely to be associated with Copyright by ASTM Int'l (all rights reserved). Where the degradation and breakage produce detrimental clay or claylike fines rehandling and stockpiling must be minimized. No further reproductions authorized. In some instances. When fly ash is delivered by truck the fill pipe connections should be reversed or of a different design so it will be impossible to blow fly ash into a cement bin. and flowability has always presented problems in handling cement and fly ash is not immune to these difficulties.GAYNOR ON READY-MIXED CONCRETE 475 porting. A number of problems recur. This procedure should be necessary only when excessive detrimental fines are generated in handling. Multicompartment cement silos must be inspected carefully for small openings in seams. Fly ash flows through small openings and cracks in bin partitions and gates much more easily then cement. and air slides deserve close attention to ensure accurate and complete cutoff during weighing operations. To avoid excessive variations in moisture content this material will have to be elevated by the loader operator so that it can drain or it must be blended with drier material as it is transferred to overhead storage. Aggregates are moved from secondary to primary storage on belts. specifying agencies have required "finish screening" of coarse aggregate with rinse water as it goes into the primary or overhead storage. Bag filters are used to handle the excess air. Adequate pressure relief valves and bin level indicators are necessary to protect the filters. Primary or overhead storage is needed to supply the weigh hoppers or aggregate batchers. rotary feeders. Further. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. When coarse aggregates are produced in a dry process and they either contain fine material or degrade in handling. Contamination of cement with fly ash has presented serious problems. generally in the West. The principles of building and reclaiming materials from stockpiles is discussed in Refs 9 and 10. it is probably more important in warm dry climates where slab concretes tend to develop plastic or other early cracking. A similar condition occurs with moisture in the lower portions of a stockpile. . with rubber tired loaders or combinations of these. Packing. barges. or even rail cars.S. and Placing Concrete (ACI 304) and the U. This is generally above the batcher and the materials flow by gravity to the weigh hoppers. the fines tend to accumulate in the lower portions of the pile and the loader operator must exercise care in reclaiming these portions of the stockpile. Bureau of Reclamation Concrete Manual [8]. With fly ash. 2 in the NRMCA Check List [7] and 0. Under ASTM Standard C 685 cement and aggregates are measured by bulk volume. Specifications for most scales or weigh batchers contain two kinds of tolerances-scale accuracy and batehing accuracy tolerances. admixtures must be protected from freezing and tanks and supply lines suitably protected. calibrated containers. Liquid admixtures are measured by volume in a variety of meters and other positive displacement devices. Admixtures--Most liquid chemical admixtures are furnished in bulk from the supplier and stored in tanks ranging from about 2 to 8 m 3 (500 to 2000 gal). In some equipment a load cell is used to replace the dial or beam as the indicating device. No further reproductions authorized. Many. Materials such as cement and aggregates are generally weighed. or an increase in coarse fractions. and sometimes even with calibrated timers. Somewhat more liberal tolerances are permitted for secondary devices such as slave dials or recorders. increased moisture content.476 TESTS AND PROPERTIES OF CONCRETE increased carbon. Water is sometimes weighed on a scale but most of the time it is measured by volume in a meter. Scale calibration procedures vary widely between different agencies and Copyright by ASTM Int'l (all rights reserved). Use of timers should be prohibited. The scale accuracy tolerances are applicable during calibration and are designed to ensure that accurate equipment is used.4 in ASTM Specification C 94. Measuring Materials--Batching The various specification requirements for batching systems are designed to accomplish one or more objectives. if not most. The batching tolerances generally apply to the indication of the primary or master device. As with cement and aggregates. care must be exercised to ensure that the material is placed in the proper tank. although in special circumstances. lightweight aggregates may be measured by bulk volume. except perhaps for calcium chloride solutions. Scales or Weigh Batchers A scale consists of a container generally suspended at the four corners and transmitting reduced loads through a system of levels to a calibrated beam or dial indicating device. The scale accuracy as a percentage of the total capacity of the scale is 0. The primary concern is the quality of the product. 0. Batching accuracy tolerances are much more liberal and are intended to govern under operating conditions where it is not practical to require the scale to come to static equilibrium. Important secondary objectives are to see that the customer also obtains the quantity of concrete ordered and the quantities of cement and admixtures where those are a part of the purchase agreement. . Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.1 in NBS Handbook 44 [i1] and CPMB Standards [12]. The general rationale is that most automation is able to compensate for material falling into the batcher to about 0. Often individual batchers were needed to increase batching speed. Below 30 percent of scale capacity ASTM Specification C 94 requires overweighing cement by up to 4 percent. The reason is that batches may require small additions of tempering water and it is unrealistic to require measurement to within a few millilitres. These were found principally in large dam projects. Generally the tolerances are ___1 percent for cement. and each aggregate size. the scales are checked by alternatively placing the weights on the scale and adding 227 kg (500 Ib) of material to the hopper. including ice. large aggregate batchers can be checked quite rapidly with such large individual test weights. and CPMB standards. No further reproductions authorized. Dial scales can be checked with reduced loads within the lever system. On aggregate batchers the tolerances are generally 2 percent for individual batchers and 1 percent of the cumulative weights for cumulative batchers. Generally these tolerances are stated as a percent of the total water in the batch. ASTM Specification C 94 requires that "adequate standard test weights" be available and the NRMCA Check List requires 227 kg (500 lb) of test weights. Occasionally very large individual test weights up to 2250 to 4500 kg (5 000 to 10 000 lb) each are available. Again the 0. and prohibits weighing cement on the same scale as aggregates. ASTM Specification C 94 permits cumulative weighing of cement and fly ash or pozzolans if the pozzolan is weighed last.5 percent. Generally. Table 1 is a summary of batching accuracy requirements of ASTM Specification C 94.3 percent scale capacity restriction becomes equal to 1 percent of the amount being weighed at 30 percent of capacity and 2 percent at 15 percent of scale capacity. When there is sufficient access and suitable capacity hangars. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.GAYNOR ON READY-MIXED CONCRETE 477 are not highly standardized. Currently available automation weighs rapidly and there is little need for individual batchers. but not with aggregates. Aggregates may be weighed either cumulatively or individually. Some specifications require individual batchers for cement. NRMCA check list. Observation of batch operators on manual scales suggests that they generally are able to weigh to about this same 3 scale divsion. fly ash. The CPMB standards which are for the Copyright by ASTM Int'l (all rights reserved). The check list and CPMB standards set a tolerance of ___0.3 percent of capacity without unduly slowing down the operation.3 percent of scale capacity which of course equals 1 percent of the amount being weighed at 30 percent of scale capacity. The tolerances on measuring water by weight or volume are generally _ 1 percent except that the NRMCA check list permits _ 1. Both ASTM Specification C 94 and the CPMB standards add the clarifying statement that the tolerance is _ 1 percent of the required cumulative weight. etc. checking the scale within each of the four quadrants. . ASTM Specification C 94 permits weighing cement and pozzolans on the same scale. moisture on the aggregates. This is about 3 scale divisions on a typical dial scale. 3 b +2 r _0.f + 0 . ---+1. aPercent of required cumulative weight. % by weight or volume 3.d CPMB a Dec.3 b -+ 2 c . --+3 or +--0. 1977..ix ". Admixtures a.3b or • dose per sack (the larger) _+3c or _+ dose per sack -+1 c or + 0 . total mixing water in 4. Cement above 30 b below 30 b 2. Cpercent of amount weighed or measured. % +1 e -+ 1 c'd -+ 1 c ASTM Specification C 94. ice. and water batched from plant and mixers.. .. /'Percent of scale capacity.4 m o 0 z 0 -n "12 ~o 0 13 m z oo --4 m . b.5e or --+ 3. % aNote that tare compensated controls are required to meet tolerances for individual rather than cumulative batchers.3 b +1 a +0..3 b -+1 c. fContains requirements on aggregate moisture compensation and slump control. individual batchers above 15 b below 15 b b. m --.7 litre (1 gal) (the larger) --0. Water a. 3 b (the larger) _+1 c or 3.1 d +0.B a t c h i n g accuracy r e q u i r e m e n t . + 4 c NRMCA Check List. 3 b or 3 d (the smaller) -+3 e +-.Copyright by ASTM Int'l (all rights reserved)...4 O0 . by volume -+ 2 c +0.7 litre (1 gad (the larger) +0. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.3 b --0.3 b -+ 1 d b. by weight • -----3 or + dose per sack (the larger) same as by volume or + dose per sack (the larger) same as by volume . Aggregates a. cumulative batchers above 30 b below 30/' Material TABLE 1 .. No further reproductions authorized. ePercent of total mixing water required in the batch including water on aggregates. added by weight by volume 1. At low flow rates meters are likely to be less accurate. No further reproductions authorized. The early devices were graduated tubes operated manually. 8 mm 3 ( + 1 gad for volumetric batchers. that valves will not leak. The principal purpose is to provide improved control of yield.GAYNOR ON READY-MIXED CONCRETE 479 equipment require somewhat different minimum tolerances for weigh batchers--___0. A few producers have found that control of structural lightweight aggregate concrete is improved if the coarse aggregate is batched by bulk volume instead of by weight. but the initial cost is much less. Most systems include a sight glass or other means of checking the amount batched which is visible to the batchman.3 mm 3 (4 oz) and when they are used for small batches it may be necessary to dilute concentrated admixture solutions. . Some available admixture dispensers have a discrete pulse rate of 0. The aggregate feeder consists of adjustable gates near the bottom of the bin with a belt that Copyright by ASTM Int'l (all rights reserved). The meters used are generally accurate to -t-3. Volumetric Batching for Water or Admixtures Although water weigh batchers are more reliable than water meters. Timers depended heavily on constant pressure and freedom from build-up in lines or valves. Volumetric Batching of Solids Generally batching by bulk volume is prohibited under ASTM Specification C 94 and required under ASTM Specification C 685. they are used in about 20 percent of the plants. Space limitations are a consideration. A few producers have built specially calibrated weigh hoppers and other devices to be able to batch a constant bulk volume of the material.3 percent of scale capacity and + 3 . The currently available equipment includes a vane feeder for cement with vibrators and other devices to ensure constant calibration. A great variety of volumetric dispersing systems have been used ranging from simple pumps and timers to positive displacement devices which can be equipped to record the amount batched.8 mm 3 (___1 gal). With certain lightweight coarse aggregates specific gravities vary widely and batching by weight produces significant variations in yield. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The arrangement of the admixture piping system is of great importance and deserves careful attention to ensure that variable amounts of material are not trapped in the lines. Meters require more frequent calibration and attention. and that the amount of admixture measured actually is placed in each batch. Some dispensers will handle several different admixture solutions and are provided with a water flush between measurements. Batching tolerances for admixtures are generally ___3 percent or an amount necessary to dose a sack of cement. ASTM Specification C 685 requires volumetric measurement of materials and continuous mixing. Timer systems are permitted only for calcium chloride in the NRMCA check list. and (d) prevent discharge until the material is within tolerances. when actuated. No further reproductions authorized. Interlocks other than those for the individual batchers is optional.480 TESTS AND PROPERTIES OF CONCRETE pushes aggregate up against the gates. starts the weighing operation and stops automatically when the required weight has been reached. but the following have been selected in the CPMB standard: 1. An automatic batching system consists of the required combination of individual weigh batchers and volumetric devices the controls of which are all automatic. A relatively new type of control made possible by microprocessors and computers is the tare compensated control which treats the start of each weighing operation as zero. . The number of combinations of these various types of batchers and the interlocks that are provided are almost endless. (c) prevent discharge if the charging gate is open. A manual control is one that is actuated manually with the accuracy dependent on the operator's visual observation. 3. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A semiautomatic batcher is one that. Batching Systems and Controls The CPMB standards provide convenient consistent terminology to define batching systems and controls. (b) prevent charging if the discharge gate is open. 4. In this system cumulative batchers are required to meet batching accuracy tolerances for individual material batchers in the CPMB standards. An automatic batcher starts and stops automatically and includes interlocks to (a) prevent charging until the scale returns to zero. The speed of the belt and rotation of the cement feeder are coordinated and operate at constant speed. Batching systems consist of the required combination of individual batchers meeting the requirements for semiautomatic. Additionally: (a) All must be actuated by a single starting mechanism. A "semiautomatic interlocked" control is similar but is furnished with an interlock to prevent batcher discharge until the required material is within tolerances. A semiautomatic batching system is one that contains the necessary individual weigh batchers and volumetric devices (if water or admixture is measured volumetrically) the controls of which are either semiautomatic interlocked or automatic or a combination of these. Lean mixes are produced by increasing the aggregate gate openings. The degree of interlocking is optional. 2. Water or Copyright by ASTM Int'l (all rights reserved). A manual system consists of a combination of manual batchers except that admixture or water batchers may have semiautomatic or automatic controls. or automatic controls. semiautomatic interlocked. A partially automatic system is one with at least one control for cement or aggregate batchers which is semiautomatic or automatic and the system does not meet requirements for semiautomatic or automatic systems. TABLE 2--Equipment and operating procedures in NRMCA certified plants. NOTE--The number of plants certified has varied from 400 to 620. Part of the difference is due to the fact that plants remain in service for a long time and that in 1966 automated plants had been available for only a relatively limited period. Later precision potentiometers Copyright by ASTM Int'l (all rights reserved). Plants. and water Total 1966 1970 1973 1977 83 15 2 80 19 1 75 23 3 71 27 2 54 45 26 10 17 47 1.481 GAYNOR ON READY-MIXED CONCRETE admixtures not batched at the same time as other ingredients may have separate starting mechanisms.. A review of the plants currently certified under the NRMCA check list in Table 2 shows a steady decline in manual batching since 1966. Batching Manual Partially automatic Semiautomatic Automatic 3. 1 1 1 "5 " 5 2 9 12 1 8 10 1 19 21 . manual batching has remained fairly constant at about 20 percent in this period. Figures for 1977 may not be representative of the industry since they include a reasonably large number of plants on nuclear projects where sophisticated equipment is required. No further reproductions authorized. ii" 25 ii 34 36 10 21 33 . Recording Cement only Cement and aggregate Cement and aggregate Cement. aggregate.. Based on the estimated purchases of equipment in Table 3. . % Mixing. Discharge of any weighed ingredient may not start until all weighed ingredients have been batched. (b) Each batcher must return to zero tolerance and volumetric devices must signal empty and reset to start. In a manual system a beam poise is positioned on a lever or the operator simple observes a dial scale. In an early semiautomatic control a reed switch was attached to a dial scale pointer and magnets were positioned around the dial face. Other systems used various mechanical limit switches and other devices to sense beam balance or position. Weight Setting--The question of how the required weight is to be designated is one that has undergone significant development in the past 10 years. % of plants Truck mixing Central mixing Shrink mixing 2. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. (c) Discharge of any ingredient may not start until all individual batchers have been cleared of the previous batch and returned to zero within tolerance. 482 TESTS AND PROPERTIES OF CONCRETE TABLE 3--Types o f equipment purchased by ready-mixed concrete producers in 1966 and 1976. were attached to the pointer shaft on a dial scale and various systems used to measure or match the voltage produced. This has greatly facilitated the use of punched cards. Equipment in use at any given time may be quite different.6 m 3 (10 yd 3) total b. % Estimated Purchases 1.9 m 3 (9yd 3) 7. % a. hydraulic direct drive 1966 1976 20 4 76 100 18 32 50 100 21 79 100 12 88 100 10 30 60 100 23 77 100 22 21 57 100 11 38 28 12 9 2 100 6. total 2. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. under 5. manual b. chain drive. Control panels with provisions for preset mixes were popular. m 3 (yd 3) 5.1 m 3 (8yd ~) 6. partial and semiautomatic a c. by weight b. but the percent of manual batchers has been relatively constant. automatic a d. Copyright by ASTM Int'l (all rights reserved). power take-off b. by volume c. More recently the development of low cost microprocessors and computers promises to permit an even greater range of available options where mix formulations can be stored in memory.0 (7.9) 64 36 N N 33 65 aChanges in the definitions of automatic systems make comparisons between 1966 and 1977 data uncertain.6 m 3 (10yd 3) over 7. mixer size.8) 1 5 40 27 22 5 100 6. No further reproductions authorized. Truck mixers a. chain drive. hydraulic c.3 m ~ (7 yd 3) 5. The development of reliable low cost digital volt meters has greatly simplified and reduced the cost of converting a voltage into a digital indication. Values are for equipment purchased in the indicated year.8 (8.3 m 3 (7 yd 3) 6. Water batching. Plant types. These presets were potentiometers incorporated in the panel to produce a reference voltage to be matched during batching. Mixer drive type a. avg capacity. % a. % a(1) central and shrink mixing (2) truck mixing (3) total b(1) permanent (2) portable (3) mobile (4) total 4. total 3. . Automation of batehing. The master scale is required to be accurate to 0.2 percent of scale capacity in the NRMCA check list. Although such provisions are viewed with some skepticism by specifying agencies. Another not so obvious reason is to correct out-of-specification batches or to add materials to returned concrete. Virtually all automated batching systems include provisions to switch to manual control. The digital volt meter and cathode ray tube (CRT) display will further increase the use of remote indicators. the required information is seldom available in sufficient time to make such calculations worthwhile. Graphical recorders. anticipate the correct amount. and shut off flow with increased precision avoiding the usual system of gate chatter to achieve final tolerance. The importance of use or reuse of returned concrete and the precautions that should be observed will be discussed in a later section.1 percent of capacity.GAYNOR ON READY-MIXED CONCRETE 483 The use of the term "computer" controlled or operated in descriptions of batching systems has a certain popular appeal. The scale monitors or slave dials are required to repeat the indication of the master scale within ___0. Recorders The use of recorders is increasing.2 percent of scale capacity. because of more limited resolution. The significance of control of the sequence and rate of discharge of batchers is discussed in a later section. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Although Table 1 may overestimate the use of recorders in the industry it shows a dramatic increase from 5 to 21 Copyright by ASTM Int'l (all rights reserved). The automation required protection from dirt and dust and often the plant operator's station is air conditioned with rugs on the floor and windows to observe the operations. Correspondingly this has increased the need for remote indication. but there are practical limitations that must be recognized. . the provisions are necessary to permit weighing small batches and permit operation in case of malfunction of the automatic system. scale followers. A computer can also sense the rate of discharge of material from a batcher and control that rate instead of relying on preset combinations of limit switches or predetermined average settings.25 percent for digital readout. must register within 2 percent of scale capacity. The tolerance is increased to 4-0. Remote Indicators The development of punch card automated plants has done much to improve working conditions for the plant operator. A related item is that digital recorders are required to reproduce the (master) scale reading within 0. or slave dials. No further reproductions authorized. Here the computer can sense flow rates of material into the scale. A few plants have been built where a computer has been used to control and speed up the weighing operations. Although it is theoretically possible to proportion mixes to produce the required strength. the CPMB studies of economic factors [13. Graphical recorders were first used on large projects where large numbers of identical batches were produced. In a low profile plant the aggregate batcher is at ground level and materials are elevated on a belt for charging either a truck or stationary central mixer. demand. More recently digital recorders have been most popular. More recently the amount of information recorded has greatly increased. inspection for gross errors was easy and rapid. blade life. The cement batcher can be located either near the aggregate batcher to discharge on to the belt or it Copyright by ASTM Int'l (all rights reserved). The traditional permanent plant has bins. Data on truck utilization can be made available to customers to help increase their efficiency on the job. This record was of relatively little immediate value except that after a problem was detected the record could be inspected to see if batching was correct. (c) Time of day to the nearest minute and date. central mixing has increased between 1965 and 1977 from 15 to 27 percent. . Mixing Concrete As outlined earlier there are three general types of conventional readymixed concrete operations: truck mixing. and (c) sand moisture setting. Increasingly digital recorders are being used to prepart delivery tickets. Early recorders were used only for cement or aggregates.14] show that the decision to use central or truck mixing will depend upon a large number of other variables such as the market area. (b) size of batch. The low profile plant is another important development. Under these conditions.484 TESTS AND PROPERTIES OF CONCRETE percent of the plants in the period from 1966 to 1977. Additional data on truck operation are being used to help the dispatching and truck scheduling. Later specifications required recordation of presence or absence of admixtures. No further reproductions authorized. Shrink mixing is reported at about 2 percent. and (d) empty balance of scales and meters. batchers. central mixers. Estimates of the sales of central and shrink mixing plants in 1966 and 1976 are less--12 and 23 percent respectively. Additional information may include (a) identity of each material. keep inventory. (b) batch count or identification. Significant growth in popularity of central mix plants in the industry is apparent. and truck utilization. Within the technical community the advantage of central mixing over truck mixing is improved control of quality. central mixing. and holding hoppers stacked one above the other so that materials flow vertically by gravity throughout the batching and charging operation. However. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The minimum is generally (a) batch weights or volumes of materials required. Early models produced a sequential record on a tape. and shrink mixing. Because of the long life of such equipment the real percentages of central mix plants in the industry are even lower. Table 2 shows that of the plants certified under the check list. and input data directly to accounting for billing. The other fact that may not always be appreciated is that considerable additional mixing is accomplished in the process of discharging and handling the concrete for placement in the work [18]. hydraulic motor. Table 3 shows that the average size of mixers purchased has increased from 6 to about 7m 3 (8 to about 9 gal 3) since 1966. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). Most of the other major truck mixer manufacturers have or are producing units of this type. The advantage of the front discharge is that with controls in the cab the driver can position the truck and chute during placement. Most of the early units were built under the Rite-Way patents. It is obvious that the primary function of any concrete mixer is to blend uniformly the separate ingredients. batching techniques. for the moment. The front discharge unit has been produced for perhaps 15 years. Both are inclined axis mixers.GAYNOR ON READY-MIXED CONCRETE 485 can be located at the elevated end of the belt to discharge cement into the truck or central mixer. Strehlow [15] discusses equipment. In 1966 the move had just started away from mechanical power take off. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. That improper handling can produce segregation in the structure is common experience. Pictures of these and other early designs are given in Ref 5. Under favorable circumstances this can eliminate the need for a man to handle the chutes. Chute handling devices have also been developed for rear discharge units. Very few have been produced since 1966 and they have not been a real factor since perhaps the mid to late 1950s.17]. Perhaps a hundred horizontal axis truck mixers are still in use. and chain drive was just beginning. volumetric batching and continuous mixing under ASTM Specification C 685. The other big change in truck mixers has been in the method of powering the mixer. The rear discharge inclined axis mixer predominates. A principal disadvantage of the front discharge has been the difficulty of adapting it to a standard truck design and the lack of flexibility in locating the mixer on the truck frame to comply with the weight laws of the various states. The use of a hydraulic pump. there are two types of revolving drum truck mixers in use today--rear discharge and front discharge. and other factors which affect efficient production of concrete in different plant configurations. The fact that may not have always been obvious is that the method and sequence of charging both central and truck mixers is of great importance in determining whether the concrete will be mixed [16.6m 3(8 and 10 yd3). but may be overemphasized. . At this time they account for 1 to 5 percent of the total truck mixers in use. The predominant sizes sold are between 6 and 7. That system of drive shafts and universal joints was a major maintenance item. Truck Mixing Revolving Drum Truck Mixers--Excluding. Coarse aggregate and some of the water should start ahead of sand and cement. Discharge rate of the low slump models is satisfactory at slumps down to perhaps 3.) but may be marginal at 2. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. cement.8 cm (llA in. Most manufacturers rate capacity as an agitator somewhat less than the 80 percent maximum because often the unit will not hold that amount of concrete without spillage.5 m 3 (790 to 201A yd3). the drum became larger and the angle of inclination of the axis of the drum decreased. The effects of these variables are discussed in detail in Refs 17 and 19. Although initial costs are higher maintenance and down time are reduced. Generally about one fourth to one third of the water must be added to the discharge end of the drum after all other ingredients have been charged. When used as an agitator the maximum is 80 percent of gross drum volume. Low slump mixers have discharge openings up to 107 or 122 cm (42 or 48 in. the theoretical optimum that blends water.). particularly sand and cement. and aggregate from start to finish may produce headpacks.9 to 15. The handling of the water deserves special attention.5 cm (1 in. If not Copyright by ASTM Int'l (all rights reserved). mixing revolutions or mixing speed. The Truck Mixer Manufacturer's Bureau Standards [18] list standard mixer sizes from 4. In most loadings the probability of head packs is decreased by placing some coarse aggregate and water in the drum before sand and cement. and poor mixing. The other innovation that has been established is the paving or low slump mixer. The problem with low slump models is that the volume of high slump concrete they will hold without spillage is reduced. Cement-last loadings were typical in two-stop plants where the aggregates were charged first and the truck driven to a second station for cement.5 m 3 (6 to 15 yd3) with corresponding maximum permissible ratings as agitators from 5. The traditional or standard truck mixer has 92 cm (36 in. As mixer size increased. The degree to which spillage is a problem depends upon the terrain and concrete slump.). in the head of the drum during charging [20]. cement balls. However.6 to 11. Under ASTM Specification C 94 the capacity of a truck mixer is limited to 63 percent of gross drum volume.486 TESTS AND PROPERTIES OF CONCRETE The direct hydraulic drive which eliminates the chain and associated maintenance problems was widely available only 3 or 4 years ago and in that short time it has become the accepted system. Charging Truck Mixers--Procedures used to charge the ingredients into a truck mixer are more important to efficient mixing than any of the other variables such as batch size. Handling of the water is reasonably flexible except that it cannot be batched entirely first or last.) diameter rear opening. No further reproductions authorized. . depending on the application. This and the increased size of the discharge opening reduced the amount of high slump concrete a mixer would hold. Certain variations of ribbon loadings are generally best. In some situations it will be advantageous to add about one fourth of the water after all solids have been charged. All loadings must be designed to avoid packing of material. To be successful. Many producers mix for 125 or 150 revolutions as their standard procedure. At 18 to 22 rpm only 4 or 5 revolutions may be sufficient. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This is to limit grinding of soft aggregates and other undesirable effects on concrete in hot weather.GAYNOR ON READY-MIXED CONCRETE 487 handled correctly cement-last loadings can cause problems. . in spite of the evidence that under optimum conditions a half or a third that number should be adequate.8 mm (86 and 94 in. With optimum charging sequences most mixers will be able to produce uniformly mixed concrete in 30 or 40 revolutions. Until recently maximum mixing speeds were at 10 or 12 rpm (or drum speeds of 1. The NRMCA researches [17] showed that between 4 and 12 or 14 rpm drum speed had little effect. At present the maximum diameter of drums in use are between 325. For slurry mixing all added water is batched first followed by the cement. A variety of other loadings involving sandwiching cement between aggregates and double batching work well if the aforementioned principles are followed. It is essential that about one fourth of the water be batched last after all the cement is in.). but less than 6 rpm.5 and 355. This will continue to be true only as long as current maximum highway truck width limits apply. coarse aggregate and some water should be charged first. particularly when superplasticizing admixtures are used. ASTM Specification C 94 contains these numbers. depending upon the mixer used and its condition. High mixing speeds are particularly important in the incorporation of tempering water. Slump loss tends to be increased with increased mixing revolutions. although it is time consuming. Mixing revolutions can be either highly important or irrelevant. Tests show that this is necessary at drum speeds less than about 12 or 14 rpm. ASTM Specification C 94 limits the total number of revolutions to a maximum of 300. The slurry is mixed for perhaps a minute and then the aggregates added. but at higher speeds up to about 22 or 23 rpm mixing could be improved dramatically. This water can come from the water nozzle in the discharge end of the drum.75 ft/s) at the maximum diameter). Generally a minimum of 70 and a maximum of 100 revolutions at mixing speed are specified. Cement-first loadings do not work. However. slurry mixing does work well. In practice a uniform number of revolutions should be used. If the charging procedure is poor additional revolutions at mixing speed are generally of little benefit. No further reproductions authorized. but the wording of the section is such that some members of the responsible subcommittee feel that these limits apply only when uniformity tests are to be made. The TMMB standards [21] require mixing speeds more than 6. In no instance was mixing poorer at 18 or 20 rpm than at 12 rpm. but less than 18 rpm and agitating speeds more than 2. Many specifications require a minimum of 30 revolutions.15 m/s (3. This loading will give excellent uniformity and will be free of cement balls [20]. Another advantage receiving more attention is the atCopyright by ASTM Int'l (all rights reserved). Procedures for charging central mixers are quite different from those necessary for truck mixers. Nontilting Mixer--This is a revolving drum mixer which charges. Rapid wear and difficulties with high slump concrete restrained its use.4 m 3 (41/z yd 3) are available. The reason is that a revolving drum central mixer Copyright by ASTM Int'l (all rights reserved). The final observation on factors that affect mixing uniformity is that batch size is not a critical variable. Sizes range from 1. If this continues. Also if efficient charging sequences are used and mixing is good at capacity then a 0. 2. Rapid mixing and low overall height are significant advantages. The mixing compartment may be stationary or rotate. 1. sizes from 0. Tilting Mixers--These are revolving drum mixers that discharge by tilting about a horizontal axis at right angles to the axis of the drum. 4. These are most popular today. It does a better job of mixing very dry concretes than drum type mixers [23].5 to l l . mixes. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. generally in sizes from 0.24]. S m 3 (2 to 15 yd3). This mixer has a horizontal cylindrical mixing compartment with blades rotating about the horizontal axis. Its capacity is about 30 percent of gross drum volume and is available. . Central Plant or Stationary Mixers The Plant Mixer Manufacturers Division Standards [22] defines four types of concrete plant mixers. They indicate that to minimize mixing time the sequence and rates of material flow during charging must be balanced carefully to approach uniform blending of all ingredients. only recently has equipment designed for use in ready-mixed concrete plants been available.75 or 1.75 to 3.~ yd3). No further reproductions authorized. Although it may be too early to determine. Rated capacity ranges from 30 to 45 percent of gross drum volume. Vertical Shaft Mixers--This mixer has an annular mixing compartment with rotating blades or paddles. Horizontal Shaft Mixer~--Although horizontal shaft mixers are not new.4 m 3 (1 to 41. The drum axis can be either horizontal or at an angle to the horizontal..75 to 7 m 3 (1 to 9 yd 3) and larger may be feasible. Sizes up to about 3.488 TESTS AND PROPERTIES OF CONCRETE tempt to limit revolutions to minimize wear on the blades and drum. Particular care must be taken to blend the water uniformly throughout the charging period. efficient loading with a short remix on arrival at the job instead of agitating the concrete during delivery should become more popular. Charging Central Mixers--Comprehensive studies of effect of charging sequence have been made by FHWA on the large tilting mixers used for highway concretes [18. This is the "pan' mixer popular in concrete plants 5 to 10 years ago. 3.5m ~ (1 or 2 yd 3) increase over mixer capacity will not adversely affect uniformity in most available equipment. If mixing is poor at capacity then reducing batch size 0.75 or 1. and discharges with the axis of the drum horizontal.5 m 3 (1 or 2 yd 3) is not likely to improve mixing. GAYNOR ON READY-MIXED CONCRETE 489 is much less full than a truck mixer and therefore blading and mixing action is quite different. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The spiral blades must force concrete down the outside of the truck mixer drum and establish a return flow to the discharge end of the drum along the central axis. The calculated volume is compared to the output meter on the unit. The aggregate belt is geared to the rotation of a vane feeder for cement. In a truck mixer there is very little folding action. coarse aggregate. The aggregate bins have a belt at the bottom with calibrated gates. cement. probably to obtain a more stable indication of slump. Production rate is inversely proportional to cement content. Volumetric Batching and Continuous Mixing The only available equipment in the United States which produces concrete under ASTM Specification C 685 is the "Concrete Mobile. The units are available in sizes from 3 to 9 m 3 (4 to 12 yd3). Rarely are mixing times longer than 60 s required and in many instances 45 s is sufficient." The equipment is truck or trailer mounted and consists of bins for sand. materials are fed into a rubber lined auger mixer.06 m 3 (2 ft 3) of concrete and mixing time is about 15 or 20 s. . water and admixtures are proportioned with flow meters. Under ASTM Specification C 685 calibration and mixer uniformity tests are required at 6-month intervals. generally where the amount of concrete required is relatively limited. most often they have been purchased by companies catering to the small volume Copyright by ASTM Int'l (all rights reserved). In somewhat larger work where requirements are less than 23 or 30 m3/h (30 or 40 yd3/h) it has been used as a job site mixing plant. This is likely more prevalent in low slump concrete and in concretes hauled in nonagitating equipment. Slump is readily adjustable and the unit can be started and stopped as concrete is needed. Experience with mixer uniformity tests suggests that 90 s would be conservative for all large central mixers. Difficulties with excessive air content have been noted where discharge was delayed more than about 60 s longer than the regular 45 to 75 s mixing time. For mixing. Mixing Time--ASTM Specification C 94 and the Corps of Engineers [25] require mixing time in a central mixer of I min for the first cubic yard and 15 s for each additional cubic yard. Washout tests can be used to check quality of fine and coarse aggregates. No further reproductions authorized. The unit is versatile and has been used in a variety of work. Although conventional readymixed concrete producers have incorporated these units in their fleets. Under this formula a 7 m 3 (9 yd 3) mix would require 3 min. Commercial ready-mixed concrete plants tend to use somewhat longer times. Yield is checked by weighing output of the unit over a convenient interval and determining the unit weight of the concrete. The mixer holds about 0. Reduced mixing time is permitted when acceptable uniformity is demonstrated. Many highway departments use either 60 or 45 s as the minimum permitted. and water. Once sand is stockpiled it will drain to a reasonably stable value between 6 and 8 percent in about 4 to 6 h depending upon sand grading. and over 102 mm (4 in. 51 to 102 mm (2 to 4 in. truck utilization. the number of units in the field is thought to be about 3 or 4 percent of the total truck mixer fleet.) and excessively low slump batches that were difficult to consolidate were used to provide a margin for the higher slump batches that might be encountered later.38 mm (1 1/2 in. There is a gradual increase in strength the longer concrete is mixed but only if no water is added and workability is sufficient to mold acceptable specimens. Control of Slump and Water Content--ASTM Specification C 94 contains tolerances on slumps of less than 51 mm (2 in.) -4.). No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). Most sands are produced at moisture contents of 10 to 15 percent. Most concrete plants contain electric moisture meters which provide a reasonably accurate indication of sand moisture. and by contractors for special work.) higher slump if the average slump or the average of the most recent 10 batches is less than specified. tempering. The key to slump control is to provide aggregate handling and storage facilities which provide uniform moisture in the sand at levels less than about 8 percent.490 TESTS AND PROPERTIES OF CONCRETE market. slump. The units do encounter problems with false setting cements because of the very short mixing time. by city maintenance departments. . The fundamental fact is that strength decreases when water is added to concrete or when the mixing water content is increased. The available research data are extensive [26-35]. but not the other aspects such as dispatching.). This has created problems in mass concrete where the minimum slump is 50 mm (2 in.) +_ 13 mm (1/2 in.) -4. concrete strengths are improved.). Although no data are available. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Calibration checks should be made daily. These meters will not work if the sand contains small amounts of dissolved salts and when the sand approaches saturation they give spurious readings. slump decreases continuously with time. Therefore. It specifies maximum slumps of 102 or 127 mm (4 or 5 in. The quality issues relate to measurement and control of mixing water. ACI Specification for Structural Concrete for Buildings (ACI 301) has a more realistic approach. and customer service which are of great importance to the contractor and producer alike. Also.) and permits use of batches of up to 25 mm (1 in. The placement of electrodes in weigh hoppers or overhead bins deserve close attention. retempering and their effects on strength and other properties or characteristics. Delivery and Delivery Time This discussion will cover delivery as it affects quality.25 mm (1 in. The outstanding advantage of the unit is that it produces freshly mixed concrete. water ratio. (6) variations in time of addition of admixtures. Although they are expensive they are much more accurate and calibration is stable [36] over long periods of time.). but when 8 percent is specified the variation of air content with slump is appreciable [37]. Control of slump is simplified greatly. The amount of water required to produce a given slump varies from dayto-day and on the same day. The effects are generally manageable at target air contents of about 4 percent. at a given water ratio.) are generally more sensitive. (5) slight changes in cement and admixture properties. The significance of variations in coarse aggregate grading. (4) temperature. The solution lies in use of the statistical approach to w/c ratio specifications which recognizes inherent variability and which encourages use of an average w/c ratio well below the intended maximum. (2) accuracy of hatching water. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and amount of mixing. This results from the fact that coarse gradings are similar to large maximum size materials. In air-entrained mixes the problem is complicated greatly by the fact that an increase in slump is likely to be accompanied by a corresponding increase in air content. within specifications. Most producers find it necessary to rinse off the rear fins between loads with the mixer washed out only at the end of the day. . and (7) changes in aggregate grading within specification limits.GAYNOR ON READY-MIXED CONCRETE 491 Although not widely used. The situation is analogous to that for strength were the statistical approach is widely accepted. The argument of slump control versus water/cement (w/c) ratio control continues. neutron moisture meters have been available for 6 or 8 years. No further reproductions authorized. and strength have been studied in some detail [38. This is recognized to vary with mix design and slump range. (3) interdependence of slump and air content. Hot weather and unusual mix designs may require washing and discharge of wash water after every load. Central mix plants with tilting mixers generally are equipped with ammeters or watt meters which give good indications of the slump. A few producers find that on short hauls it is not necessary to wash out between loads. Pollution control regulations make it increasingly difficult to wash out after every load. Measurement and control of reused water and wash water from the previous batch continues to be a problem. Readings are affected by both batch size and the characteristics of the particular mix design. on slump. strength decreases with increased maximum size (or a coarser Copyright by ASTM Int'l (all rights reserved).) or even 130 mm (5 in. delivery time. In controlling slump in the field it is generally assumed that the addition of about 5 litre/m 3 (1 gal/yd 3) will increase slump about 25 mm (1 in. That is. Both studies show that under these conditions production of uniform slump concrete will produce more uniform strength than production of uniform w/c ratio concrete. 39]. Some of the factors are: (1) errors in methods of measuring moisture (testing errors). The middle range of slumps around 75 to 100 mm (3 to 4 in.). Again this is critical in concretes with slumps up to about 100 mm (4 in. 492 TESTS AND PROPERTIES OF CONCRETE grading). the average w/c ratio would have to be about 0. One proposal was to delete Item 4 containing the 11A-h limit since if no water is added concrete strength improves with time. One is to use cooled concrete and the other is to produce an initial slump of 50 or 75 mm (2 or 3 in. Both readymixed producers and inspection agencies favor reliance on fixed time limits. Discharge must be complete within 11/2 h or 300 revolutions but (a) these limits can be waived if the concrete can be placed without addition of water.45 to avoid rejection of more than about 5 percent of the batches. This is roughly equivalent to a standard deviation of 10 litre/m 3 (2 gal/yda). The subcommittee which has jurisdiction over the standard has discussed.) required. The producer is responsible for slump for 20 min after arrival at the job site. The time limit should be to the start of discharge rather than completion of discharge. When concrete is central mixed or truck mixed in the yard. . Tempering water can be added only (a) on arrival at the job site. ASTM Specification C 94 has controlled tempering and retempering by the following: 1. This means that if the specifications call for a maximum w/c ratio of 0. Another proposal was to provide reduced times in hot weather and increased time in cold weather or if special batching procedures were used to keep cement dry. No other proposal has been acceptable nor is it likely that the present text would be acceptable to a sufficient majority if it was not already in the standard.) and temper it on arrival at the job to the 130 mm (5 in. and (b) in hot weather a time less than 11/2 h may be specified by the purchaser.50. Control of Tempering and Retempering Since 1968. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Data [35] suggest that it is better to retemper than to send out high slump in anticipation of the slump loss.03. balloted. In truck mix operations there are several alternatives. but increases with a decrease in water required to provide a given slump. and (b) and when the slump is less than specified. all of which delay Copyright by ASTM Int'l (all rights reserved). slump loss starts early and there are only two possible methods of extending available delivery time. In very tightly controlled jobs the standard deviation of w/c ratio is likely to be about 0. Two changes should be made in the current provisions. No further reproductions authorized. 3. 4. Meininger [27] provides data and reviews the effect of batching procedures on available delivery time and retempering. The absolute prohibition of later addition of tempering water should be relaxed to permit up to about 5 or 71/2 litre/m 3(1 or 11/2 gal/yda). and reballoted a variety of changes in these sections. 2. No water may be added at any later time. Recently instances of serious rapid loss of air has been reported in the field on concretes made with fly ash. An attrition test procedure [42] has been employed by the NRMCA laboratory to discover other similar instances. Limited tests show adequate durability and infer maintenance of adequate air void characteristics. Meininger [28] shows that when cement is ribboned with damp aggregate it is wetted and results are similar to those that would be obtained from mixing concrete at the plant. In one instance grinding released active clay minerals which increased mixing water requirement and greatly accelerated slump loss. 33]. Precautions to be observed to obtain adequate mixing with cement-last loading were discussed earlier. Grinding of aggregates during mixing has been discussed. There has been considerable recent interest in the properties of cement. 42]. but unfortunately no tests have been reported. (c) trying a 1 to 5 min delayed addition of a half dose of retarder. the drum stopped and the cement loaded on top of the aggregate without turning the drum. The implication is that perhaps half of the cement stayed dry. This was the standard procedure fnr horizontal axis mixers and is practical for the small percentage of inclined axis mixers which have quick release batches. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Other characteristics of the ash are likely of importance. grinding is mostly in the sand sizes. The other obvious alternative that should be considered is the location of a cement bin or a complete plant on the job site where a long haul is anticipated. 40] show that cement can be loaded into a still drum of the normal inclined axis mixer and that the cement is not wetted significantly. (b) removing the admixture. Rapid slump loss can be rather complex but is more prevalent in hot weather and generally due to an unfortunate combination of cement and admixture properties. The big change came when aggregates and part of the water were batched first. The stability of the air content under prolonged mixing has been studied on several occasions and generally the loss of air has generally been less than about 20 percent of the initial amount after 11/2 to 2 h of mixing and agitation. Later tests [34. The problems have been experienced with fly ashes with ignition losses of about 5 percent. On several occasions researchers have speculated that continued mixing would grind the cement.GAYNOR ON READY-MIXED CONCRETE 493 mixing until arrival on the job and are designed to keep a portion of the cement dry. The possible solutions include (a) changing brands of cement. 41. Delays exceeding 12 h reduced strength only 5 to 8 percent. (d) increasing gypsum content. and cement-admixture combinations that can affect rate of slump loss [23. When cement was loaded as the last ingredient it was expedient to slow the drum to 4 or 5 rpm when the cement was loaded. Tests show that because of the surface area. but relatively little quantitative data are available [26. . ConCopyright by ASTM Int'l (all rights reserved). In this instance only 3 or 4 drum revolutions were required to load the cement and delaying mixing was of significant benefit. 32. No further reproductions authorized. (e) changing admixture. It should be noted that for high strength mixes where long delivery times cannot be avoided. or additional cement. Although all are important the first three can be solved only by using cool concrete. To provide ice the producer must install a slinger to crush or chip the block ice. (3) increase rate of slump loss. summer concretes might be 2. The report of ACI Committee 207 [43] contains much useful information. an increase in cement content may actually reduce strength levels.494 TESTS AND PROPERTIES OF CONCRETE cretes made with other similar fly ashes have retained adequate air contents for periods as long as 6 or 7 h. Typically. Hot and Cold Weather Concrete The report of ACI Committee 305 on Hot Weather Concrete published in 1977 [40] and the report of Committee 306 on Cold Weather Concreting to be published in early 1978 as ACI Recommended Practice for Cold Weather Concreting (ACI 306) provide timely information which will not be covered here. It is not unusual to have to haul ice 160 km (i00 miles) or more. In certain massive structures it may be more economical to use moderate heat cement and use reinforcing to control crack widths. Block ice is in short supply during hot weather in all parts of the country. Strength problems are more prevalent in hot weather than cold. specifiers are imposing 32. . fly ash. Installation of water chillers for mixing water may be a more economical solution where a reduction in concrete temperature of 4 to 6~ (about 7 to 10~ will be sufficient. ice or cooled water is practical since the refrigeration facilities can be included in the plant. The decreased strength levels in hot weather are likely the combined results of (1) higher concrete temperatures reducing strength levels. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In very large jobs. No further reproductions authorized. Several years ago it appeared that use of liquid nitrogen to cool mixing Copyright by ASTM Int'l (all rights reserved). reducing delivery time or increasing the potential strength level by using admixtures.2~ (90~ temperature limits for usual construction and 15 to 24~ (60 to 7S~ temperatures for massive concrete in hot weather. Increasingly. refrigerated storage at the site.15 MPa (400 or 600 psi) lower. (b) increased rate of moisture loss. Producers who keep good records know that as the weather warms up strength results decrease. and (c) failure to start moist curing promptly on receipt at the laboratory at one day. and (4) nonstandard testing procedures in part related to increased construction activity: (a) initial curing exceeding the 15 to 27~ (60 to 80~ specified.75 or 4. and one or more refrigerated trailers to transport the ice. requiring more tempering water. In small jobs where the demand is more sporadic it is much more difficult. (2) higher temperatures increasing mixing water requirement. water. However. 3. In recent years producers have not been able to discharge wash water into streams or from their property. 4. It should be done only with the full knowledge of the purchaser. The cement. and various rotary scrubbers. Copyright by ASTM Int'l (all rights reserved). Control is assured by maintaining a specific gravity of about 1. Rarely do these systems solve the troublesome problems of disposal of cement slurry or aggregates. No further reproductions authorized. drag tanks. This has renewed interest in devices for reclaiming and reusing returned concrete and wash water. with increased cost and demand few installations have been made in recent years. The paper by Parker and Slimak [45] summarizes the situation. . In it. Some of the solutions include: 1. Fresh water is used in these operations and the aggregates are returned for use in concrete. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. returned concrete is screened and washed to remove aggregate. Construction of waste separation facilities which separate aggregates and reuse wash water for washing out equipment and for reuse as mixing water in concrete. A blower at the lower end of the pipe provides the draft with the burner installed near the top of the silo. In this portion of the system the attempt is to produce as dilute a slurry as possible by adding the maximum amount of clean water. Often it will not be possible to reduce water use sufficiently to avoid the need for disposal of at least some water. and some sand fines are collected in a circulatory system to be reused as mixing water in subsequent batches. This requires control and centralized authority in the plant to avoid using too much returned concrete or concrete that is too old or using it in important construction. Incorporating returned concrete into subsequent batches of lower strength concrete. In large mass pours preparation of smaller alternative work that can be placed if there is a breakdown or form failure after eight or ten trucks have been batched and are on the way to the job. In cold weather it is generally necessary to heat aggregates and water by one of several available methods [44]. Reshipping returned concrete seems to be a fact of life since between 2 and 4 percent of the total volume shipped is going to be returned.03. unless additional modifications are made. 2. Other less elaborate systems include pits and sloping slabs. Working closely with job superintendents to minimize overordering. One method of heating aggregates in silos that does not appear to have been previously described is the use of a burner or pipe or pipes located down through the center of the silo. Reuse of Wash Water as Mixing Water in Concrete Disposal of returned concrete has always been a problem for the industry.GAYNOR ON READY-MIXED CONCRETE 495 water would be economic. One of the most advanced systems originated in California [46]. manufacturing. If they are batched into wash water required dosages may increase dramatically. The available data indicate no adverse effects due to the use of wash water [47. to avoid an excessive number of tests less than f ' . The probability of tests less than fc' under current ACI 318 procedures ranges from about 3. Included also is a list of optional chemical requirements that may be specified. For this reason the average strength must exceed the specified strength. StrengthTesting When strength is used as a basis for acceptance for the concrete. The admixture can be batched on the sand or into a limited quantity of clean regular water. ASTM Specification C 94 and ACI standards require tests of standard moist cured 152 by 305 mm (6 by 12 in.5 to 9 percent or in other words the required overdesign Copyright by ASTM Int'l (all rights reserved). 48]. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. The application of the normal probability distribution and statistical procedures are accepted widely. Tests for mortar strength and time of set are required weekly for the first month and monthly thereafter as long as test results are satisfactory. care must be exercised in batching admixtures. There are two acceptance criteria in ASTM Specification C 94 which are similar to those which appeared in ACI 318 and ACI 301 prior to 1971 or 1972. The amount higher ranges from 2. protection. Under ASTM Specification C 94 and ACI 318 trucks are sampled a minimum of once a day for each class of concrete furnished and once for each 115 m 3 (150 yd 3) of concrete delivered each day. f j . but not for acceptance of the potential strength of the concrete delivered. .45 MPa (500 psi) belowfc'. (2) sulfates--5000 ppm. Job cured specimens are often used to assess the adequacy of curing. Results of strength tests vary because of variations in materials. reinforced in moist environments--1000 ppm). (3) total solids--50 000 ppm. and strength development in the structure.) cylinders. No further reproductions authorized. For structures designed by the ultimate strength method or for prestressed concrete not more than 10 percent of individual tests are to have values less than f " and the average of any three consecutive tests must exceed f ' .75 MPa (about 400 psi) to perhaps 8.496 TESTS AND PROPERTIES OF CONCRETE Recently revisions to ASTM Specification C 94 were adopted to permit reuse of wash water as mixing water for concrete. The limits are: (1) chlorides (prestressed--500 ppm. and (4) alkalies--600 ppm. For working stress and other structures the averages of six consecutive tests must exceed fc' and not more than 20 percent of tests can be less t h a n f L In ACI 301 and ACI 318 these earlier requirements were changed to require averages of three consecutive to exceed fc' with no individual tests more than 3. and in testing procedures.27 MPa (1200 psi) or more. Failure to Meet Strength Requirements The consequences of a failure to meet strength requirements varies greatly. Since ACI 318 is a code document it addresses the question of structural adequacy and public safety. The average can come from the recording of 30 tests or can be determined by preparatory laboratory batches. If no suitable record of 30 tests is available the required overdesign is 8. 2." Tests of cores may be required "if the likelihood of low strength concrete is confirmed and computations indicate that the load-carrying capacity may have been significantly reduced. No formalized mix design submission or approval procedure is included in ASTM Specification C 94.45 MPa (500 psi) below f~' "steps shall be taken to assure that the load-carrying capacity of the structure is not jeopardized. The ACI standard then specifies over design ranging from 2. Identify a mix design which will provide the average strength determined above. . ASTM Specification C 94 provides information on the average strength necessary to meet the acceptance criteria depending upon the coefficient of variation of the operation. They are subject to great differences in interpretation. appoint an arbitration panel.27 MPa (400 to 1200 psi) for standard deviation from 2 to 4 MPa (300 to 600 psi). 1.75 to 8. The current ACI procedures which produce from 3.45 MPa (500 psi) belowfL Further when individual tests are more than 3. The recommendation is that the average strength of the concrete be at that level which will limit the probability tests less than the design strength to 5 percent." Cores can be tested wet or dry depending on moisture condition in the structure and results are considered satisfactory if the average of three Copyright by ASTM Int'l (all rights reserved). These mix qualification procedures only recently are being used widely.27 MPa (1200 psi). The generalized procedure for mix approval is as follows.5 to 9 percent of tests less than fc' are in reasonable agreement with the recommendations of the CEB-CIB-FIP-Rilem Committee on Statistical Quality Control of the Quality of Concrete [49]. In 1971 and 1972 the ACI standards adopted the acceptance criteria described above and required mix submission procedures that emphasized the use of prior experience with similar mixtures. A 1977 revision requires steps to be taken to improve the average strength level when either of the two criteria are not met--average of three consecutive or individual tests more than 3. ASTM Specification C 94 suggests that the manufacturer and purchaser confer and if they cannot agree. No further reproductions authorized. Determine the standard deviation from one or more groups of a total of 30 tests on "similar" concretes. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The recent article by Peters [50] discusses some of these difficulties.GAYNOR ON READY-MIXED CONCRETE 497 is somewhat larger than in ASTM Specification C 94 for ultimate strength or prestressed structures. but ultimately they are more or less arbitrary. Copyright by ASTM Int'l (all rights reserved). A number of graduated penalty functions have been used. First. No further reproductions authorized.75fc'. engineering judgment was relied upon to determine the nature and amount of corrective action required in any given instance. the contractor should be penalized in proportion to that loss in value. determining the practical consequences of a failure to meet a strength specification and controlling the risk associated with any specified level of quality. References 51 and 52 are useful and an extensive annotated bibliography is being prepared by ACI Committee 214. Load tests of the structure are suggested as an additional step if structural adequacy remains in doubt.498 TESTS AND PROPERTIES OF CONCRETE cores equals 0. For the highway department it presumably reduces the decisions to a mathematical formula and removes them from the political or judgmental arena. Willenbroc and Kopac [54] discuss four approaches and recommend procedures for developing three of them. The potential advantage for the concrete producer that is rarely realized is that it permits a calculation of the level of risk associated with the quality level supplied. instead of relying on fixed levels of strength that are either acceptable or unacceptable they have instituted graduated reduced payment clauses for strengths less than some specific level. Under traditional specifications. For the contractor and ready-mixed concrete producer it creates a great many problems. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Naturally. Although each application seems to be somewhat different at least two factors are common. at some strength levels the concrete will be unacceptable and must be removed. A large body of significant information has been published in the past 15 years on the testing and interpretation of core tests. The only reliable response is to furnish an excessive strength margin. Future Developments in Acceptance and Quality Control Testing Significant developments are being made in the application of statistical principles to the problems of judging compliance with strength specifications. The theory is that a minor deviation below specified levels will reduce the service life or increase required maintenance and. Too often the concrete producer is asked to accept reduced payments based on the cost of concrete in place which is often three to eight times the price he receives at the end of the chute. . therefore. Unfortunately this holds little appeal for the producer since in most circumstances the uncertainties in the testing and in his ability to control constituent materials and production do not permit predictable control of the risk involved.85f" with no cores less than 0. The Federal Highway Administration and a number of state transportation departments have been moving vigorously toward something which comes under the general label of "Statistically Oriented End Result Specifications" [53]. This objective is rarely achieved because of the difficulty of quantifying the unknown. It remains to be seen if it will ever be possible to develop penalty functions which are equitable to both the owner and contractor. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and accelerated strength testing have great potential for reducing and quantifying the risks assumed by producers. The BRMCA "Scheme" does quantify the risk of failure to meet specification requirements. The "Authorization Scheme" covers personnel. England. Predicted 28-day strengths are based either on the 7-day results or 1-day accelerated tests [56].. Control charts. Increasingly sophisticated automation and recording devices will be more reliable and efficient and reduce batching errors to the practical minimum. highway department attempt to address this problem. contractors. the problems of obtaining accurate testing and of deciding what to do when test results fail to conform to specifications continue to create problems for specifiers. operating procedures. No further reproductions authorized. and producers. A rise or fall in the accumulated sum indicates actual values consistently above or below the target values. With well conceived educational programs. In other instances separate acceptance testing is done by the specifying agency. contractors. however.S. improved testing. and (3) the difference between the predicted and actual 28-day strengths. materials. Another important development is the "Authorization Scheme" of the British Ready Mixed Concrete Association (BRMCA) [55]. Cumulative sum or Cusum charts are developed by plotting the accumulated differences between the actual values and the target or expected average values. are maintained for: (1) the difference between the target 28-day strength and the 28-day strength predicted from the accelerated tests. One practical result is to shift the burden of the routine testing to the contractor. but as in commercial work in this country the consequences of a failure are not quantified. The emerging reduced payment clauses in U.GAYNOR ON READY-MIXED CONCRETE 499 The second issue in the move to oriented statistically end result specification is to require specific quality control by the contractor. quality control. Developments in specification. are also used for acceptance. (2) the difference between the assumed standard deviation and that estimated from successive pairs of results. made under surveillance of highway department inspectors. Closure The quality of ready-mixed concrete continues to improve. based on the Cusum method developed by Ready Mixed Concrete Ltd. In some instances. plant and equipment. When significant changes occur. and owners alike. . and Copyright by ASTM Int'l (all rights reserved). and quality control procedures. Recent developments greatly reduce the volume of testing that has to be done to establish the correlation between results of accelerated and standard 28-day procedures. the contractors quality control tests. cement content is modified to maintain target or acceptable values. 5. 3273. May 1966. [20] "Cement Balls or Lumps in Freshly Mixed Concrete--Causes and Cures. 1971.S. W. "The Relationship Between Mixing Time and Type of Concrete Mixer. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. [3] "Pictorial History of the Ready Mixed Concrete Industry. U. Bureau of Public Roads. p. National Bureau of Standards. M. June 1974. American Concrete Institute. "A Study of Mixing Performance of Large Central Plant Concrete Mixers.." Modern Concrete. [10] Miller-Warden Associates. [15] Strehlow." Publication SP 19. [4] "NRMCA Production and Value Survey. C. 296.. [25] "Standard Practice for Concrete. Change 3. p. Swedish Cement and Concrete Research Institute. National Ready Mixed Concrete Association. Office of the Chief of Engineers. [6] Levine. 1964. [23] Johansson. [24] Bozarth. 1977. 41. 1973. p. [8] Concrete Manual. 112. 41. p.. Sec. "Stockpiling of Aggregate for Gradation Uniformity. 1974. Highway Research Board. [16] Bloem.C. pp. Bureau of Public Roads. pp. I. 103. [12] "Concrete Plant Standards of the Concrete Plant Manufacturers Bureau. [11] NBS Handbook 44. "Mixing Concrete in a Truck Mixer. Office of Research and Development. 320. E.8. and Gaynor. References [1] "Cement and Concrete Terminology. R. 44 (out-of-print). July 1966. 21." Proceedings." CPMB Publication No. [5] "NRMCA Industry Data Survey.500 TESTS AND PROPERTIES OF CONCRETE improved quality control of constituent materials the incidence of defective concrete can be reduced. "Abstract of Mixing Concrete in a Truck Mixer." Research and Development Report. M." National Ready Mixed Concrete Association. 103. U. D. 24. Washington. [14] "A Study of Economic Factors of Central Mixing in the Production of Ready Mixed Concrete. 92. July 1967. 1 Jan. [18] Bozarth." NRMCA Technical Information Letter No. [21] TMMB Standards of the Truck Mixer Manufacturers Bureau. 1 Nov.2. R. R. 16 March 1973. 148. Jan.." National Ready Mixed Concrete Association. Federal Highway Administration. [13] "CPMB Does Cost Survey on Central Versus Transit Mixing. Revision.." NCHRP Report 46. and Grieb. D. [2] "Standard Industrial Classification Manual-1972. [7] NRMCA Check List for "Certification of Ready Mixed Concrete Production Facilities.5 and T. 8th ed. No further reproductions authorized. "Factors Affecting the Homogeneity of Ready Mixed Concrete. E. L. and Mullarky. 11 April 1975. F. pp. [19] Mullarky. D. Department of Transportation. 1975. NSGA Circular No. T. Department of the Army. Arne. National Ready Mixed Concrete Association. 25. 42. pp. National Ready Mixed Concrete Association. 1972 through 1975. Dec." 3rd. pp. Bureau of Reclamation. W.. 1976. "Case Study of Influence of Imbalances in Charging of Cement and Water on Mixing Performance of an 8-Cubic Yard Central Plant Mixer. 1967. 99. . 1976.. Nov. D. J. Sid. 33. W. Granley. R. D.. Department of Commerce. June 1976. Concrete Plant Manufacturers Bureau. 9th rev. p.. (annually through 1970). "Economic Indicators for the Concrete Industry. 1 July 1973. National Ready Mixed Concrete Association. Copyright by ASTM Int'l (all rights reserved)." EM 1t10-2-2000. [22] Concrete Plant Standards of the Plant Mixer Manufacturers Division. 1967. "Effects of Different Methods of Stockpiling and Handling Aggregates." NRMCA Technical Information Letter No." NRMCA Publication No.. [9] Warden. Phase 1.." Research and Development Report. 102. J. 1975." National Ready Mixed Concrete Association. p." Concrete Products. Vol. 141. 1971. [17] Gaynor. 4th rev.." CPMB. B. and Gaynor. June 1969. I. p.S. Washington...3." Sixth Revision. F. p.." SIC No.C. "Concrete Plant Production. D." National Ready Mixed Concrete Association. " NRMCA Technical Information Letter No. Vol. 4-12. W. [41] Slater. p. . R." NRMCA Publication No. American Concrete Institute. 150. April 1976. 1977. ll. R. 295. P. S. 9. F. 810 and Discussion. 1977. Part 2.. S. 461. 510-533." Journal. and Waller. pp. "Slump Loss Caused by Admixtures. 18. L. p. Dan. No. C. (Also Joint Highway Research Project. American Concrete Institute. "Tests of Concrete Conveyed from a Central Mixing Plant. American Concrete Institute. L. Highway Research Board 1973..) [40] ACI Committee 305. F. D. 74. p.) [39] Baker. "Evaluation of Construction Control Procedures. No. 72.03." Journal. M.. [43] "Effect of Restraint." Proceedings. p. and Hoadley. No. "Mix Time and Retempering Studies on Ready Mixed Concrete. Vol. No further reproductions authorized. W. 317-332. p.. Highway Research Board. National Ready Mixed Concrete Association. and Smith. R." 16 June 1975. [38] Hudson. 20910. and Gaynor. 526. 1977.. National Ready Mixed Concrete Association. September 1967. Vol. [46] Harger. 6 Feb. 107.. 291-295. "Effect of Variations in Coarse Aggregate Gradation on Properties of Portland Cement Concrete. F. 97-110. D. July 18.. 1963.. Aug. No. 7. M. D. 10.GAYNOR ON READY-MIXED CONCRETE 501 [26] Gaynor. Vol. Vol. [31] Tuthill. [47] Unpublished memorandum from R.. R.. [36] Ullman. 12. D. 361-368. 74. pp. No.. M.. 1968. R. 1973. (Chapter 2 "Study of Effect of Variations in Gradation of Coarse Aggregate on Characteristics of Portland Cement Concrete. D. P. 7. Bailey. Purdue University and Indiana Highway Commission. pp.." NRMCA Publication 131. March 1961. 4. 69. Sept. pp." Journal. July 1977. 70. "A System for 100 Percent Recycling of Returned Concrete. F. "Hot Weather Concreting. 1931. C. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. National Ready Mixed Concrete Association. A. [30] Beaufait. 900 Spring Street. [331 Hershey." Journal. pp. American Concrete Institute. National Ready Mixed Concrete Association. S. National Ready Mixed Concrete Association. W." NRMCA Publication No. Md. pp. p. [34[ Gaynor. June 1975." TRB Record 564. Aug. [28] Meininger. 8. p. 57." Journal. "Control of Air Content in Concrete--An Outline. D. [42] Davis. 1969. 294. W. Transportation Research Board. 70. No. "C 94 and C 685 Requirements for Quality of Mixing Water.. No. National Ready Mixed Concrete Association. ACI. R. and Reinforcement on Cracking of Massive Concrete. pp.. R. Vol. Vol. No. Silver Spring. F. [44] "Cold Weather Ready Mixed Concrete. Gaynor to ASTM Subcommittee C09. 233. G. [45] Parker.. Vol." Journal. "Effect of a Delay Between Batching and Mixing on Concrete Strength. Volume Change.. National Ready Mixed Concrete Association. "Waste Treatment and Disposal Costs for the Ready Mixed Concrete Industry. C. 72." National Ready Mixed Concrete Association. December 1973. pp. H. and Shah. No. and Scholer. B.." Highway Research Record 441. "Case of Abnormally Slow Hardening Concrete for Tunnel Lining. 7. Adams." Journal. p." NRMCA Publication 111." Journal of Materials. 9.. 19..09 Methods of Testing and Specifications for Ready Mixed Concrete. "Study of ASTM Limits on Delivery Time. "Importance of Petrographic Analysis and Special Tests Not Usually Required in Judging Quality of Concrete Sand." pp. C. "Properties and Possible Recycling of Copyright by ASTM Int'l (all rights reserved)." NCHRP Report No. H. May 1973. R. p. 17. "Nuclear Moisture Meters for Sand. Mielenz. Problems-Practices. 130. 445-470. 1973. Richard C. 1969. [27] Meininger. [48] Pistilli. American Concrete Institute. 8. R. R.. 31..." Journal. "Effects of Prolonged Mixing on Properties of Concrete. F. "Retempering a Prolonged-Mixed Concrete with Admixtures in Hot Weather. [37] Gaynor. R. 73. A. W. 74. Peterson. [32] "Concrete Admixtures. Vol. and Slimak. 333. C. Journal. S. 8 Feb. Young and Daugherty and Kowaleski). American Concrete Institute. N. American Society for Testing and Materials. and Polivka. H. T. Vol. [29] Ravina. G. E. 1091-1109.. pp.. American Concrete Institute. "Concrete Slump Loss. American Society for Testing and Materials. [35] Previte. American Concrete Institute. No." NRMCA Technical Information Letter No. p. October 1975." NRMCA Technical Information Letter No. 6. "Shrinkage Compensated Cement and the Ready Mixed Concrete Producer. July 1973. 1976 (papers by Green. 8. March 1975. 281-287. D. 38. "A Cusum-Controlled Accelerated Curing System for Concrete Strength Forecasting.. Transportation Research Board." NCHRP Synthesis No. pp. N. 147. Stockholm." Journal American Concrete Institute. 1975. 3. Copyright by ASTM Int'l (all rights reserved). and Warren. 4. RILEM. p. RILEM. No. p. May 1975. Willenbrock. 249. Sept. 1." Materials and Structures. Recommended Principles for the Control of Quality and the Judgement of Acceptability of Concrete. 40.." Cement and Concrete Research. "One Look at Concrete Compressive Strength. "Concrete Quality--A Producer Looks at the Building Code Requirements. 1971.. Grant. 5. Pennsylvania Transportation Institute. British Ready Mixed Concrete Association.-Dec. "A Methodology for the Development of Price Adjustment Systems for Statistically Based Restricted Performance Specifications." ERMC077 Congress. Part IV of BRMCA Code for Ready Mixed Concrete. A. Jack H. 1976. Vol. T. No further reproductions authorized." Materials and Structures. "Recommendations for Estimation of Quality of Concrete in Finished Structures. and Kopac. Sun Apr 6 21:31:15 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Nov. 1976. P. 387-403. Oct. p. June 1977. R. 1974. 24. D. 74-27 (1). Vol. "Statistically Oriented End-Result Specifications.-Oct. Oct. 1977." Research Report No. No. Nov. p. 47. National Ready Mixed Concrete Association." NRMCA Publication No. May 1975. Petersons. N. J. 501. Gaynor. 169. BRMCA Authorization Scheme. Peter A..502 [49] [50] [51] [52] [53] [54] [55] [56] TESTS AND PROPERTIES OF CONCRETE Solid Waste from Ready Mixed Concrete. . Project No.. Peters. No. Sun Apr 6 21:43:38 EDT 2014 503 Downloaded/printed by Universidade do Gois pursuant Agreement. air-cooled blast-furnace slag. 3. with the light weight produced by high air contents or specially graded aggregates having little or no fine material or both. and crushed stone) may be produced by several methods: 1. No fines or "popcorn" concrete. Either lightweight or normal weight aggregates may be used. National Slag Association. Cellular or foam concrete. with strength being of lesser importance. W . 1978 D. 22314. where the light weight is caused primarily by inclusion of a large amount of air or gas. 2.STP169B-EB/Dec. L e w i s 1 Chapter 30--Lightweight Concrete and Aggregates Introduction Both "lightweight concrete" and "lightweight aggregate" are general terms which include a wide variety of products and are frequently subject to varying definitions. either with or without other ingredients such as sand or pozzolanic fines. (b) masonry units requiring moderate strength with light weight and good insulation properties. which is comparable to conventional concrete except for the use of lightweight materials as all or part of the aggregate. Va. No further reproductions authorized.astm. Applications include: (a) structural concrete for use in buildings and bridge decks. Alexandria. Lightweight aggregates of various types have been used for many years. Concrete lighter in weight than that usually obtained with "normal weight" aggregates (gravel. A suitable foam or foaming agent is combined with cement and water.org . Lightweight aggregate concrete. Copyright9 1978tobyLicense ASTM International www. 1Chiefengineer. where weight reduction produces design economies and other characteristics desired are the same as for conventional concretes made with normal weight aggregates. and (c) insulation or fill uses where light weight and a high degree of insulation are required. Copyright by ASTM Int'l (all rights reserved). usually 25 percent or more. Lightweight concretes produced by these various methods may range in unit weight from 240 to 320 k g / m 3 (15 to 20 lb/ft 3) to weights only slightly less than those of conventional concretes. cellular. the various kinds of lightweight aggregates are discussed here on the basis of the ASTM specifications in which they are included. processed lightweight aggregates are produced from clay. 2The italic numbers in brackets refer to the list of referencesappended to this paper. respectively. scoria. by-product materials include cinders. These are frequently based on original source. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. expanding. is that having air-dry unit weights of 1840 kg/m 3 (I15 lb/ft a) or less and made with lightweight aggregates as all or a major part of the aggregate. Copyright by ASTM Int'l (all rights reserved). slate. Types of Lightweight Aggregates Various methods have been used to classify lightweight concrete aggregates into general types. clays. and granular inorganic material as follows: "aggregates prepared by expanding. and fly ash. Therefore. vermiculite. or sintering. 2 The artificial aggregates are either by-products of an industrial operation or specially processed by calcining. No further reproductions authorized. Some of the materials may be placed in more than one of the type groups. The inorganic or mineral materials are the only ones that have been used to any significant extent and are the only materials covered by current ASTM specifications for lightweight aggregates. In this classification system. The most common method of making lightweight concrete in the United States is the use of lightweight mineral aggregates. pumice may be used either in its natural state or after heat processing (calcining). shales. diatomite. or sintering products such as blast furnace slag. clay. and slates are natural materials that are always heat processed during production of lightweight aggregates. . It seems most reasonable to classify lightweight aggregate materials for discussion purposes on the basis of their end use under ASTM specifications. Discussion of lightweight aggregates is confined to the major types of inorganic aggregates covered by current ASTM specifications. Lightweight Aggregates for Structural Concrete ASTM Specification for Lightweight Aggregates for Structural Concrete (C 330) covers two general types of lightweight. blast-furnace slag and fly ash are by-products that are processed for use as lightweight aggregates by expanding and sintering. calcining. as discussed in this paper. For example. fly ash. shale. perlite. blast-furnace slag. Lightweight concrete. as either natural or artificial materials [1]. with some use of cellular concretes for insulating and fill purposes.504 TESTS AND PROPERTIES OF CONCRETE and in the past 25 years they have become an important factor in the concrete construction industry. Both mineral (inorganic) and vegetable (organic) materials of many varieties have been considered and tested for use as lightweight aggregates. and tuff are natural aggregates. such materials as pumice. Expanded shales. and the natural scorias and pumices are the materials usually considered for structural lightweight concrete usage. crushed. Fly ash is processed for use as a lightweight aggregate by mixing with sufficient moisture to permit it to be either pelletized or extruded to form spherical or cylindrical shapes that can then be sintered. therefore. are used in the majority of current structural applications. and gases released within the material cause it to expand to form a lightweight. scoria. smooth particle shapes. ." A number of different methods for accomplishing and controlling the expansion have been used [2-4]. clays. Lightweight aggregates of this type were introduced in the United States about the time of World War I and later came into widespread use due to rising demands for lightweight concrete and widespread distribution of suitable raw materials. Carbon present Copyright by ASTM Int'l (all rights reserved). since no significant differences appear to exist due to the particular classification of the raw material used. producing aggregate with relatively smooth particle surfaces.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 505 shale or slate. Sintered materials are produced on a traveling grate over which suitable raw material mixed with small amounts of fuel has been spread evenly. then crushed and screened. or tuff. with production of the pelletized materials beginning in 1969. cellular structure. referred to as "coated" aggregates. the raw material is heated to a plastic state in the kiln. slates and blast-furnace slags. The aggregates are produced either by the rotary kiln or sintering processes. Expanded slags have been produced in North America since the late 1920s. In the rotary kiln process. and aggregates prepared by processing natural materials. and slates are generally treated as a single type. Expanded slag is produced by controlled processing and cooling of molten blast-furnace slag to obtain a lightweight cellular "clinker" or pellet. or with water and other agents such as steam or compressed air or both. Commercial production of fly ash as a lightweight aggregate has been developed in the past decade. material is sized before expansion. and slates are the most readily available in many geographic areas and. Slags and the natural aggregates are more limited in their areas of availability. and screened. Of these aggregates. clays. ASTM Definition of Terms Relating to Concrete and Concrete Aggregates (C 125) defines expanded blast-furnace slag as "the lightweight cellular material obtained by controlled processing of molten blast-furnace slag with water. Following expansion. In a variation of this process. the material is cooled. the expanded shales. such as pumice. No significant difference in product characteristics results from the various processes except the pellet form which has lower internal absorption and rounded." Expanded shales. which is subsequently crushed and screened to the required size. The fuel is ignited under an "ignition hood" and continues to burn as the grate moves over blowers. No further reproductions authorized. The clinker is allowed to cool. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Some use has been made of diatomite. clays. and is imported from Mediterranean sources for occasional use in East Coast areas. Christensen [5] summarized their characteristics. Cinders (referred to as "clinker" in Great Britain) are the residue of high temperature combustion of coal or coke." these materials from industrial.50 Btu 9in." or "steam cinders. uses. and limited applications in concrete masonry units constitute the only commercial use for cinders in concrete at the present time. they are covered in the following section on insulating concretes. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. k. Scoria is a volcanic "cinder" with its pores chiefly in the form of vesicules instead of the more tubelike. including possible effects from deleterious materials present in some sources. Commercially. ." "boiler cinders. power plant. Since the primary use for perlite and vermiculite is in insulating concrete. Dwindling supplies have resulted in greatly decreased usage. Lightweight Aggregates for Concrete Masonry Units ASTM Specification for Lightweight Aggregates for Concrete Masonry Units (C 331) includes all lightweight aggregates described above and. K (0. cinders and the expanded perlites and vermiculites. which generally produce concrete weighing from 240 to 800 kg/m 3 (15 to 50 lb/ft a) and having a thermal conductivity. and performance in 1931. crushed and screened to proper size./h 9ft 2. ~ while Group Copyright by ASTM Int'l (all rights reserved). Fine aggregate sizes can be produced by crushing after sintering and cooling. of 0. The weaker materials (including tufts) are sometimes benefited by calcination at a temperature near incipient fusion. widely varying in strength and porosity characteristics. It is available in a number of localities in the Western states. Lightweight Aggregates for Insulating Concrete ASTM Specification for Lightweight Aggregates for Insulating Concrete (C 332) covers those aggregates considered satisfactory for the manufacture of lightweight concrete not exposed to the weather and for which the primary consideration is the thermal insulating properties of the concrete. True pumice is a spongy lava from which steam or gas escaped while it was still molten. interconnected pores of the pumices. volcanic ash naturally cemented together (more properly designated as tuff) is sometimes referred to as pumice. No further reproductions authorized.06 to 0.506 TESTS AND PROPERTIES OF CONCRETE in the fly ash forms all or a large p a r t of the fuel required after ignition. lightweight materials of volcanic origin. in addition. and steam locomotive boilers were probably the first lightweight aggregates used in the United States. Known as "industrial cinders.45 to 1.22 W / m . Pumice and scoria are cellular. They are divided into two groups: Group I includes such materials as expanded perlite and vermiculite. There are many deposits of pumice in the Western states. " thus excluding from consideration such materials as seaweed. generates steam causing disruptive expansion and breakage into small expanded particles. Insulating concrete (ASTM Specification C 332) is presumed to be protected from weathering.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 507 II includes the same materials as those covered under ASTM Specification C 330 for structural concrete (described above). Specific requirements are discussed below under the individual characteristics. thermal conductivity is specified.) for the same aggregates.15 to 0. Group II aggregates are expected to result in concrete weighing from 720 to 1440 k g / m 3 (45 to 90 lb/ft 3) and having thermal conductivities of 0. cork. .i n . When usec~ in concrete primarily for insulation purposes.5 mm (1A in. straw. / h" ft2~ Perlite is a volcanic glass which contains sufficient combined water that. while ASTM Specifications C 331 and C 332 restrict top size to 12. Lightweight Aggregate Specifications and Tests The characteristics of lightweight aggregates covered by the current ASTM specifications are discussed in the following sections. which have not been extensively used in this country [6].) nominal maximum size are given in ASTM Specification C 330. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. however. No further reproductions authorized. when it is heated quickly.05 to 3. Vermiculite is a micaceous mineral that forms another extremely lightweight aggregate when subjected to sudden heating.43 W / m . and durability requirements are omitted.K (1. The specifications are not restricted to these particular aggregates. however. Conversion to steam of layers of combined water in the laminated structure of the mineral produces an "exfoliated" or expanded lightweight aggregate. Both include limitations on deleterious substances and various concrete-making properties.0 mm (1 in. Most lightweight aggregates are available only in sizes smaller than 19. Under controlled kiln conditions an aggregate of high internal void content and very low unit weight is produced.0 mm Copyright by ASTM Int'l (all rights reserved). ASTM Specifications C 330 and C 331 are quite similar in requirements.00 B t u . Grading Each specification tabulates requirements for gradation of the aggregates. Composition All specifications stipulate that "the aggregates shall be composed predominantly of lightweight cellular and granular inorganic material. and sawdust. Coarse aggregate gradings up to 25. General types of materials considered to be acceptable are enumerated and the aforementioned aggregates are listed as examples. slates. cinders. of the material used for the determination of unit weight.1 ft a) or more. and the sieving time is limited to 5 min. ASTM Specification C 331 provides that the gradation requirements may be waived to produce special characteristics in masonry units. In general.) while perlites and vermiculites are normally supplied only in 4. shales. Maximum values only are applied to Copyright by ASTM Int'l (all rights reserved).75 mm (No. and natural lightweights must have dry loose unit weights not greater than 880 kg/m 3 (55 lb/ft 3) for the coarse aggregates. Minimum unit weights of 120 and 96 kg/m 3 (7189 and 6 lb/ft 3) are stipulated for perlite and vermiculite. respectively. and 1040 kg/m 3 (65 lb/ft 3) for combinations of the coarse and fine when marketed as a single grading. weak. acoustical. Special gradings are stipulated in ASTM Specification C 332 for these two aggregates. the gradings in ASTM Specifications C 330 and C 331 are similar to those for normal weight aggregates (ASTM Specification for Concrete Aggregates (C 33)) except for somewhat larger amounts of material passing the smaller sieve sizes. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. such as texture. . 1120 k g / m 3 (70 lb/ft 3) for the fine aggregate. strength. or thermal insulating properties. 4) or smaller top size gradations. except that oven-dry aggregate is tested. fly ashes. clays. respectively. Uniformity of Grading Variations in grading of lightweight aggregates may not only affect water demand and strength characteristics of concrete but will also change the unit weight because of differing specific gravities for various sizes of particles. The ASTM specifications for lightweight aggregates provide that the maximum variation in fineness modulus shall not be greater than 7 percent from that of the sample submitted for acceptance tests. Size of the test sample for coarse aggregate is set at 2830 cm 3 (0. and friable materials. This provision applies to both the coarse and fine aggregates. Expanded slags. to avoid excessively expanded. Maximum dry loose unit weights for perlite and vermiculite are 196 and 160 k g / m 3 (12 and 10 lb/ft3). These modifications are intended to prevent blinding of the smaller sieves with an excessive volume of material and breakage of the more friable aggregates during the sieving operation. except that the test sample of fine aggregate is reduced in size. Unit Weight All lightweight aggregates are subject to unit weight limitations. unless it can be demonstrated that the resultant concrete will have the required characteristics.508 TESTS AND PROPERTIES OF CONCRETE ( 90 in. Grading is determined in accordance with ASTM Test for Sieve or Screen Analysis of Fine and Coarse Aggregates (C 136). The tests are conducted in accordance with the ASTM Test for Unit Weight of Aggregate (C 29) using the shoveling procedure. A table provides weights for the test samples as determined by the fine aggregate unit weight. weight. the specifications provide limits and specify a test procedure to evaluate the potential degree of staining from the aggregate. However. the specifications require that the unit weight of successive aggregate shipments shall not differ by more than 10 percent from that of the sample submitted for acceptance tests. Of course. Organic impurities are tested for by ASTM Test for Organic Impurities in Sands for Concrete (C 40). correlations of aggregate and concrete unit weights are very general in nature. yield. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. To provide control of uniformity in use. enclosed in filter paper cups." Staining of concrete surfaces may result from use of lightweight aggregates that contain excessive amounts of iron or iron compounds. Deleterious Substances A number of materials are considered to be potentially deleterious in lightweight aggregates used in structural concrete or masonry units. to steam for 16 h. since particle shape and gradation differences may cause large variations in the voids between aggregate particles in the test. The test is conducted in accordance with ASTM Test for Staining Materials in Lightweight Concrete Aggregates (C 641). but are not included in the insulating concrete aggregate specifications (ASTM Specification C 332). . Accordingly. The unit weight test furnishes a control over the maximum unit weight or density of lightweight aggregates and. Aggregates producing a color darker than the standard are subjected to rejection. and consists essentially of exposing aggregate samples. "unless it can be demonstrated that the discoloration is due to small quantities of materials not harmful to concrete. provides some idea of the weight characteristics of concrete in which they might be used. and strength of the concrete in which the aggregate is used. specific gravity or density of the mineral material. Uniformity of Unit Weight Unit weight of a lightweight aggregate will be affected by changes in gradation. unit weight. No further reproductions authorized. since excessively light and weak aggregates of these types would be excluded from use either by failure to comply with other specification requirements or by the need for excessively high cement contents and the high concrete unit weights resulting from degradation. The degree of staining is evaluated either by visual comparison of the Copyright by ASTM Int'l (all rights reserved).LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 509 the materials used in structural concrete and masonry units. the variations will be reflected in the water requirements. therefore. they are subject to limitations in ASTM Specifications C 330 and C 331. and in the particle shape or surface texture. Although it is not a serious problem with the commonly used materials. The test method and specification limits are based entirely on extensive studies of cinder aggregates by Seaton [7]. ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295) is useful in this regard. popouts. Adequate evaluation of the effects of unburned or underburned lumps and development of a suitable test procedure for identifying them remains an unsolved problem. since both structural concrete and masonry unit performance could be adversely affected by lack of desirable properties in these respects. Loss on ignition of lightweight aggregates is limited to S percent for all materials covered by ASTM Specifications C 330 and C 331.5 mg or more." The limitation is based apparently on unproven fears that residual unburned fuels in sintered or rotary kiln products might be deleterious. Clay lumps are limited to 2 percent by weight of the aggregate in both ASTM Specifications C 330 and C 331. the importance of both strength and lightness Copyright by ASTM Int'l (all rights reserved). Originally intended as a limit on the amount of "unburned or underburned lumps in expanded clay. Concrete-Making Properties Properties of the lightweight aggregates. No specific test procedure is required. No further reproductions authorized." it is doubtful that such lumps are sufficiently friable or soft after 24-h immersion to be broken by finger pressure as stipulated in the test method. nor is any reference made to such tests. dependent upon the primary use and desirable characteristics of the concrete. Requirements for drying shrinkage. are specified indirectly in terms of their performance in concrete. The test method used is ASTM Test for Clay Lumps and Friable Particles in Aggregates (C 142). but appear to be serving a useful purpose applied to all lightweight aggregates. except cinders which are limited to 35 percent (ASTM Specification C 331).510 TESTS AND PROPERTIES OF CONCRETE stains on the filter paper with photographic reference standards provided in the test method or by chemical determination of the amount of ferric oxide (Fe203) deposited on the filter papers from 200 g of the aggregate tested. These specification requirements are varied. Such materials are not considered to be deleterious. Aggregates having a visual classification of "heavy stain" or darker are required to be tested by the chemical procedure and rejected if the Fe203 is 1. The specification wording was changed from "unburned or underburned" to "clay" lumps. In ASTM Specification C 330. that some lightweight aggregates may be partially hydrated during production or naturally contain innocuous carbonates or water of crystalization that would contribute to the loss on ignition. . Attention is called to the fact. other than those described previously. in notes. and durability are listed in ASTM Specifications C 330 and C 331. and the notes state that "consideration should be given to the type of material when evaluating the product in terms of ignition loss. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and the restriction is probably useful only for detecting contamination of the aggregate. shale or slate aggregates. A much more realistic test procedure and limits can be found in the American Association of State Highway and Transportation Officials (AASHTO) Specification for Lightweight Aggregates for Structural Concrete. ASTM Specifications C 330 and C 331 stipulate Copyright by ASTM Int'l (all rights reserved). The present requirement for a 100-day test (after fabrication of the specimens) is excessively time consuming as well as unrealistic with respect to the concrete used.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 511 of weight are recognized by suitable limitations. Popouts in lightweight concrete are comparatively rare. when encountered. To date. the slump (and the water/cement (w/c) ratio) are far from any used in this application. The AASHTO test uses proportions similar to those proposed for field use and limits shrinkage to 0. No popouts. limits are imposed on these characteristics in ASTM Specification C 332. Initial length measurements are made after 7 days moist storage with final shrinkage measurements at the age of 100 days after storage at 50 percent relative humidity. occur as a result of hydration or oxidation or both. For insulating concrete. loose volumes.10 percent in ASTM Specifications C 330 and C 331 when determined in accordance with procedures outlined in the specifications. No further reproductions authorized.). The need for specifications of this nature should be examined carefully. Durability of both structural concrete and masonry units is important for those structures and structural elements exposed to weathering. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No data correlating results of this test with actual performance are known to exist. lightweight aggregate concretes have been found to have drying shrinkage values no greater than those of some natural aggregate concretes [9]. Under some conditions. but may be caused occasionally by such materials as unhydrated pieces of hard-burned lime or magnesia. lightweight and low thermal conductivity are of primary importance. To test for such materials. Drying shrinkage is limited to 0. rather than as a result of freezing and thawing action which is responsible for most popouts with natural aggregates.07 percent after 28 days storage at 37. or unstable iron compounds. The concrete proportions used bear no resemblance to actual mixes of structural lightweight concrete. as determined by visual inspection of the autoclaved specimens. are permitted under either ASTM Specifications C 330 or C 331. no specific procedures or specification limits have been developed to measure this attribute. The popouts. with sufficient water to produce a slump of 50 to 76 mm (2 to 3 in.8~ (100~ and 32 percent relative humidity. concrete specimens are prepared in the same manner as outlined above for the shrinkage test. ASTM Test for Length Change of Hardened Cement Mortar and Concrete (C 157) is followed using fixed proportions of one part cement to six parts aggregate by dry. calcium sulfate. while the cement/aggregate ratio could be similar to that of some concrete masonry units. The specimens are cured and tested in accordance with ASTM Test for Autoclave Expansion of Portland Cement (C 151). and more realistic procedures adopted if they are to be used for acceptance testing. M 195 [8]. . The requirements were originally on the basis of all lightweight aggregate only.3 MPa (305 to 334 psi) for the sand/lightweight mixes. The specification. and 115 lb/ft 3) for sand/lightweight aggregate concretes. using 150 by 300-mm (6 by 12-in. and 110 lb/ft 3) for concrete made with all lightweight aggregate. Required 28-day splitting tensile strength values range from 2. 1680.) cylinders. Later investigations [10] demonstrated that absorption did not correlate with resistance to freezing and thawing and. with the permissible values varying with the unit weight and strength values. the specifications do note that materials that Copyright by ASTM Int'l (all rights reserved).512 TESTS AND PROPERTIES OF CONCRETE that "in the absence of a proven record of satisfactory durability" the lightweight aggregates "may be required to pass a concrete freezing and thawing test satisfactory to the purchaser. Both compressive and splitting tensile strengths are specified. 110. as originally adopted. Curing may be either in accordance with ASTM Method C 192 or the drying procedure used in the unit weight test may be used. with the minimum values required increasing as the 28-day air dry unit weight increases. leading to the higher requirements in ASTM Specification C 330 than for the all lightweight mixes. The method requires the testing of air-dry specimens which has been shown by extensive testing to produce lower strengths than continuous moist curing [12. but have more recently been modified to include use of natural sand fine aggregate with lightweight coarse aggregates. However. The test is run in accordance with ASTM Test for Splitting Tensile Strength of Cylindrical Concrete Specimens (C 496).2 MPa (290 to 319 psi) for all lightweight aggregate mixes and from 2. Strength and unit weight requirements for structural concretes made with the lightweight aggregates are included in ASTM Specification C 330. and 1840 kg/m a (105. Air dry weight ranges in ASTM Specification C 330 are 1600. 1680. included limitations on the absorption of the lightweight concretes. . moist cured for 7 days and stored for 21 days at 23~ (73~ and 50 percent relative humidity. and 1760 kg/m a (100. No further reproductions authorized. Compressive strengths (28 days) required range from 17 to 28 MPa (2500 to 4000 psi) for the lightest to heaviest weight range in both all lightweight and sand/lightweight mixtures." Details of the test procedures and the evaulation of results are left to the discretion of the purchaser. 1760. the requirements were deleted. This research has also shown higher splitting tensile strengths for the mixes containing natural sand fine aggregates.0 to 2. Specimens are made in accordance with ASTM Making and Curing Concrete Test Specimens in the Laboratory (C 192). Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. differing from compressive strength in this respect.13].1 to 2. therefore. Unit weight is determined by ASTM Test for Unit Weight of Structural Lightweight Concrete (C 567). 105. Investigations have shown that these differences in curing have no significant effect on the 28-day compressive strength of structural lightweight concretes [11]. The unit weight thus obtained is an air-dried value that more closely corresponds to the weight in actual service than would the plastic unit weights. Curing is for 7 days in the moist room followed by 21 days at 50 percent relative humidity with subsequent oven drying. The report of ACI Committee 213. Unit weight is determined by weighing and measuring the dimensions of specimens having a volume of not less than 2360 cm 3 (144 in. The test conditions serve principally to permit general classification and comparison of materials and to provide a standardized reference condition. and the use of oven-dried specimens does not duplicate conditions of actual use. some increases in both weight and thermal conductivity should be expected from residual moisture in the job concretes. The lightweight aggregates are not required to meet each of the strength and unit weight levels when used in concrete. and natural lightweight aggregates. The lightweight materials used for structural concrete and masonry units have demonstrated through experience that the degradation or breakdown during mixing and placing is not excessive and need not be a matter of Copyright by ASTM Int'l (all rights reserved).43 W / m . Oven-dried specimens are used for both thermal conductivity and unit weight tests on the insulating concretes. and to 0./h-ft2OF) for those weighing up to 1440 kg/m 3 (90 lb/ft3). Thermal conductivity values are determined in accordance with ASTM Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate (C 177). K (1. Miscellaneous Test and Properties In addition to the tests and properties included in the lightweight aggregate specifications and described previously several others are of interest either because they are utilized in mix design and control or in specifications for normal weight aggregates. K (3. Thermal conductivity values specified in ASTM Specification C 332 for insulating concretes are limited to a maximum of 0.3). "Guide for Structural Lightweight Aggregate Concrete. . The specification stipulates that it "shall be possible to produce structural concrete" that will satisfy the requirements of "one or more" of these categories. Under conditions prevailing in actual use.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 513 do not meet the splitting tensile strength requirement may still be used if the structural design is suitably modified. slags.50 Btu 9in. The lighter concretes are those made with perlites and vermiculites. No further reproductions authorized.0 Btu in. Strength of the aggregate particles undoubtedly influences the properties of concrete made with them but is not usually included in specifications./h 9ft2~ for concrete having an oven-dry unit weight of 800 kg/m a (S0 lb/ft a) or less. Moisture content of insulating materials affects both the thermal conductivity and unit weight." includes discussion of many such properties and comparisons with those of normal weight concretes. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the heavier weights are those usually resulting from use of expanded shales.22 W / m . Bulk specific gravities of lightweight aggregates are much lower than those of normal weight aggregates." The inherent characteristics of the aggregates and of the concretes made with them may also serve to reduce effects of such reaction--high porosity. and slates may react as natural pozzolans and could act to inhibit alkali aggregate reactions. However. Glassy phases of blast furnace slag are not deleteriously reactive [14] and in various investigations [15. Absorption and specific gravity test results for lightweight aggregates are quite different from those for normal weight aggregates. and the specifications do not require that tests for chemical reactivity be applied to them. and high creep in low-strength insulating concretes might preyent structural damage in situations where normal weight concretes would be in distress.16] have been shown to be effective inhibitors of such reactions. . In addition to the methods provided in ASTM Test for Specific Gravity and Absorption of Coarse Aggregate (C 127) and Test for Specific Gravity and Absorption of Fine Aggregate (C 128). special techniques have been used by the U. breakdown and degradation in handling is likely to be somewhat greater for the lightweights. the highly irregular and vesicular surfaces of most lightweight aggregates makes surface drying difficult and uncertain. the weaker lightweight aggregates are not capable of making the strength requirements for concrete included in ASTM Specification C 330. Attempts to correlate abrasion or crushing strength tests [6] of the aggregates with properties of the resulting concretes have been successful only in a very general manner. while absorptions are higher. Chemical reactions of lightweight aggregates have not been a problem. Ranges of both bulk specific gravity and absorption for various types of lightweight aggregates have been summarized by Washa [6]. No further reproductions authorized.S.514 TESTS AND PROPERTIES OF CONCRETE concern with aggregates meeting the specification requirements for other properties. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Therefore. Mielenz [14] reports potentialities for alkali-aggregate reaction with some natural lightweight aggregates and expanded perlites but notes that the "volume change will not necessarily cause structural distress if appropriately accommodated in the design. low modulus of elasticity. clays. Bureau of Reclamation [6]. The fines in expanded shales. In general. with resulting questionable validity of the absorption and specific gravity values. Saxer [17] and the Portland Cement Association [11] for determining the absorption Copyright by ASTM Int'l (all rights reserved). Although the strength of lightweight aggregates covers a wide range and undoubtedly overlaps the strength range for natural aggregates. For a given type of lightweight aggregate (produced from similar raw materials) the strength of the aggregate varies roughly with the unit weight. the average is probably somewhat less than that for natural aggregates. Perlites and vermiculites are much weaker structurally than the expanded or sintered aggregates but are employed only in the very light insulating concretes where high strength is not a requirement. Variations in specific gravity with size of particle lead to the need for higher percentages of fine material than are usually considered desirable for normal weight concretes. since accurate information on bulk saturated-surface dry specific gravity is seldom available. Instead. The proportions of fine and coarse aggregates and the cement and water requirements are estimated or based on previous experience with the particular aggregate. specific gravity. it has been shown [20] that specific gravity of lightweight aggregates increases with decreasing particle size. No further reproductions authorized. Higher specific gravities for the small sizes may also increase tendencies toward segregation during transportation and handling. or to decrease unit weights in insulating and fill concrete uses. Unit weight and air content of the mix are determined. changes in gradation would be expected to change the specific gravity and absorption values. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Recommended Practice for Selecting Proportions for Structural Lightweight Concrete.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 515 and specific gravity of lightweight aggregates. However. to provide improved resistance to weathering. the total moisture content is used in mix control and can be determined by procedures outlined in ASTM Test for Total Moisture Content of Aggregates by Drying (C 566). Therefore. proportioned on the basis of cement content at the required consistency. Surface moisture tests." describes such procedures in detail. and free moisture means that net w/c ratios cannot be established with sufficient reliability for use as a basis of mix proportioning. The dry loose unit weights and moisture contents of the aggregates are determined and the first mix made on the basis of the estimated proportions and sufficient water to obtain the desired slump. vesicular-surfaced particles. no method is widely used and such tests are not usually conducted on lightweight aggregates. Plastic Lightweight Concrete Mix Proportioning The principles of mix proportioning usually applied to normal weight concretes are generally difficult to use with lightweight aggregates. such as ASTM Test for Surface Moisture in Fine Aggregate (C 70). The lack of accurate values for absorption. are of little value with lightweight aggregates. ACI Committee 211 report. Since weights of all Copyright by ASTM Int'l (all rights reserved). Other test methods have been proposed by Helms and Bowman [18] and Landgren [19]. While the natural aggregates do not usually exhibit any significant changes in specific gravity with varying size of particle. Lightweight concrete mix designs are established usually by trial mixes. Keeping the aggregate damp and handling in separated sizes are often recommended to minimize these tendencies. . Optimum air contents are usually somewhat higher than for normal weight concretes to avoid workability problems from the angular. ) slump does not indicate the same workability or placeability for a lightCopyright by ASTM Int'l (all rights reserved). This is not a true specific gravity value. The test results are not directly comparable to those obtained with normal weight aggregates. that is. gradation.516 TESTS AND PROPERTIES OF CONCRETE materials in the mix and the specific gravities of all except the lightweight aggregates are known. a "specific gravity factor" for the aggregate can be calculated. Final mix design is on the basis of dry. and the balance of the mixing water. Plastic Concrete Tests Tests of plastic or freshly mixed concretes conducted by standard procedures are confined principally to the structural lightweight concrete mixes. Control of lightweight mixes is obtained by keeping the cement content. air-entraining agent. and so on should be avoided to minimize such tendencies. and the lightness of the larger particles causes them to float to the surface where they may interfere with finishing operations. the aggregate is added last to minimize degradation. slump. usually two or more minutes for structural mixes and four or more minutes for masonry unit mixes. a 75-mm (3-in. Mixing is then continued as required for homogeneity. checks of moisture content. Overmanipulation. Overwet lightweight mixes tend to segregate. and volume of dry aggregate per cubic metre (yard) constant. Workability is determined by means of ASTM Test for Slump of Portland Cement Concrete (C 143). . slump. A common practice for structural and masonry unit concretes is to mix the aggregates and about two thirds of the required mixing water for periods up to 1 min prior to the addition of the cement. and air content tests of the fresh concrete will determine if changes in aggregate weight have occurred and if the proper cement content is being used. If a change in aggregate weight has occurred. and unit weight of the aggregate can be made to determine causes of the change. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A pycnometer method for determining a specific gravity factor developed and reported by Land~ gren et al [21] may be used. excessive vibration. Unit weight. total water necessary to provide the desired slump. Mixing Procedures and Control Mixing procedures for lightweight concretes may vary with the different types of aggregates. since the proportions of free and absorbed water are unknown. No further reproductions authorized. The slump should not only be maintained as consistent as possible but also kept as low as is practical for the placing conditions. but it provides a useful value for adjusting mix proportions for additional trial batches. For some insulating concretes. loose volume of aggregate per cubic metre (yard). and the cement content necessary to obtain the required strength. and the producers' recommendations should be followed. while in others special tests particularly suited to lightweight concrete characteristics are used. Hardened Lightweight Concrete Earlier published information on the characteristics and properties of lightweight concretes (and lightweight aggregates) was summarized by Washa [6]. Porosity characteristics and difficulties in specific gravity determinations of lightweight aggregate make both the pressure and gravimetric methods very inaccurate when used on lightweight concretes. tests for properties of lightweight concretes are the same as those for concretes of normal weight. is the recommended procedure. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. presumed to be comparable to weight in service. lightweight concretes are often economical in use principally because of the weight savings involved. However. Kluge [22]. No further reproductions authorized. Structural lightweight concretes are covered in detail in the ACI Committee 213 report. With lightweight concretes. the last three of these covering lightweight structural concrete." Unit Weight Except in special design circumstances. . "Guide for Structural Lightweight Concrete. and insulating concretes. The calculations shown in the method for gravimetric air content are not applicable to lightweight mixes. Unit weight of freshly mixed structural lightweight concrete is important in determining yield and controlling mix proportions. respectively. therefore. Yield. and Air Content (Gravimetric) of Concrete (C 138) is used. ASTM Test for Unit Weight. Carlson [23]. and Valore [24]. due to the lesser weight of concrete causing distortion of the mass upon removal of the slump cone. ASTM Test C 173 volumetric method gives the most reliable results for air content of lightweight concretes and. Specifications for lightweight structural concrete usually stipulate a maximum unit weight in an air-dry condition. provides a procedure for determining this Copyright by ASTM Int'l (all rights reserved).LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 517 weight concrete as it would for a normal weight mix. since holes left by rodding do not fill as readily as in the case of normal weight mixes. In many cases. Air content of lightweight concretes is determined by ASTM Test for Air Content of Freshly Mixed Concrete by the Volumetric Method (C 173). This method is applicable to any type of aggregate. tapping the sides of the measure to remove air bubbles is particularly important. the unit weight of hardened normal weight concrete is seldom of interest. For the same workability. masonry units. ASTM Test for Unit Weight of Structural Lightweight Concrete (C 567). whereas pressure methods are accurate only for denser aggregates where proper correction for air within the aggregate particles can be made readily. because the total absolute volume of the mix ingredients cannot be determined accurately. a lightweight mix would have a lower slump. Specifications usually require the lightweight concretes to have the same compressive strengths as would be required for normal weight concretes in structural and masonry unit uses. aggregate characteristics. Specimens are 75 by 150-mm (3 by 6-in) cylinders. In some cases. cement content. insulating concretes are not required to produce high compressive strengths and frequently are in the range of 1. . with curing consisting of 7 days moist. while those made with other types of lightweight aggregates are usually in the range of 800 to 1440 kg/m 3 (50 to 90 lb/ft3).4 to 5. Insulating concretes made with perlite or vermiculite aggregates or cellular concretes may range from 240 to 800 k g / m 3 (15 to 50 lb/ft 3). Unit weights of insulating concretes are usually determined in an ovendry condition. and 3 days in an oven at 60~ (140~ Moisture content Copyright by ASTM Int'l (all rights reserved). Standard procedures for making. and all other factors that affect strength of any concrete. ASTM Test for Compressive Strength of Lightweight Insulating Concrete (C 495) covers the procedures for testing fresh concretes weighing less than 800 kg/m 3 (50 lb/ft3). Although higher cement contents are required with some lightweight aggregates to obtain these equivalent strengths. densities above these values may be economical for use. No further reproductions authorized. 18 days at 50 percent relative humidity. using the oven-dry weight and dimensions of companion specimens to those subjected to either thermal conductivity or compressive strength tests. Unit weight of concrete in masonry units is an oven-dry basis for all aggregates.6 MPa (200 to 800 psi). Compressive strength of both lightweight structural and masonry unit concretes are determined by the same procedures used for testing normal weight concretes. It is quite low for insulating and fill concretes while structural concretes compare quite favorably with excellent quality conventional concretes. In contrast.518 TESTS AND PROPERTIES OF CONCRETE value. Although tests in an air-dry condition are stipulated in ASTM Specification C 330 for evaluation of unit weight and splitting tensile strength and may be used for compressive strength tests to evaluate lightweight aggregates. curing. Strength Properties The strength of lightweight concretes varies with unit weight. and testing normal weight concretes are used for these purposes. many of them have essentially the same cement factorstrength relationships as do high-quality normal weight aggregates. these procedures are not intended for use in job control or acceptance testing of lightweight concretes. ASTM Sampling and Testing Concrete Masonry Units is used. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. with lightweight units having concrete weights usually in the range of 1200 to 1760 kg/m a (75 to 110 lb/ft3). The usual range of air-dry unit weight values for structural lightweight concrete is from 1360 to 1840 kg/m 3 (85 to 115 lb/ft3). are used.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 519 has a large effect on the strength of insulating concrete. A similar test condition is stipulated for determining compressive strength of hardened insulating concrete. The standard test procedures. using the standard test procedures employed for normal weight materials. Tensile strength of lightweight structural concrete is determined by ASTM Test C 496. and Testing Specimens from Hardened Lightweight Insulating Concrete for Compressive Strength (C 513)). Flexural strength tests are sometimes conducted on structural lightweight concretes. The influence of unit weight is apparently the reason for the lower E values of lightweight concretes. Copyright by ASTM Int'l (all rights reserved). The ratio of flexural strength to compressive strength is usually somewhat higher for the lightweight concretes than for regular concrete mixes [25]. For lightweight concretes. using cubes cut from structures in place (ASTM Securing. Tendencies of some insulating concretes to crack if dried rapidly led to the use of relatively low-temperature oven drying preceded by a period of air drying. such comparsions have usually been based on comparative tests using only one normal weight aggregate. and complete saturation would not represent its "in service" condition. . Building Code Requirements for Reinforced Concrete. The current ACI Standard 318 uses this relationship to obtain design values for lightweight structural concretes in the absence of actual test values. The value varies with both unit weight and strength. Plastic Properties and Creep These tests on lightweight concretes are confined usually to the structural concretes. ASTM Test for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression (C 469) and ASTM Test for Creep of Concrete in Compression (C 512). Although the average lightweight concrete may have greater creep than the average normal weight concrete. However. Pauw [27] developed a relationship between modulus of elasticity. the method provides that the test be run on air-dried cylinders for evaluation in accordance with ACI Standard 318. Better correlation of diagonal tensile strengths with air-dry tensile strengths than with tests of moist cured specimens has been shown [26]. Preparing. the variations found in both types result in considerable overlap in the ranges of values. and strength that appears applicable to both lightweight and normal weight concretes. The modulus of elasticity is usually lower than that of normal weight concrete of the same strength. No further reproductions authorized. frequently of higher than average quality. Some investigations [11] have shown lightweight structural concretes to have higher creep values than normal weight mixes. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The oven-dry test requirement was selected as a reproducible condition that would provide reasonably realistic values. unit weight. masonry units about one fifth. and masonry units [29. as noted previously. type of aggregate is also a significant factor. Bond with Reinforcing Steel Bond characteristics of lightweight structural concretes may be evaluated by means of ASTM Test for Comparing Concretes on the Basis of the Bond Copyright by ASTM Int'l (all rights reserved). as discussed previously under the specifications for lightweight aggregates for insulating concrete. fireproofing. some of the structural lightweight concretes have drying shrinkage characteristics that fall in the range found in concretes made with regular aggregates. Lightweight concretes are generally capable of undergoing greater deformation before cracking than regular concrete. However. tensile strength. In both cases. except in the case of lightweight masonry units where the value is usually smaller.520 TESTS AND PROPERTIES OF CONCRETE Volume Change The volume change of lightweight concretes is usually somewhat greater than that of normal weight concrete having similar cement contents.) of lightweight concrete is the equivalent of about 75 mm (3 in. the type of aggregate has a significant effect upon the fire resistance of the concrete. Shrinkage tests may be conducted in accordance with ASTM Test C 157 although. and creep characteristics. Thermal Conductivity The thermal conductivity of lightweight concrete varies primarily with unit weight. Volume changes due to temperature variations are quite similar to those of regular concretes. however. High drying shrinkage alone is not indicative of increased cracking tendencies. Tests are conducted usually by ASTM Test C 177. Fire Resistance Lightweight concretes offer greater fire resistance than do normal weight concretes in structural uses. since resistance to cracking is also dependent upon modulus of elasticity. Comparison of the results of standard fire tests on lightweight and normal weight concretes indicates that 50 mm (2 in. No further reproductions authorized. . Values of thermal conductivity of lightweight concretes indicate that structural concretes have about one third. this test has been modified in some details for use in determining the concrete making properties of lightweight aggregates (ASTM Specification C 330). Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.30].) thickness of normal weight concretes. of course. The coefficient of thermal expansion is about the same for lightweight and normal weight concretes. and insulating concretes about one tenth of the thermal conductivities of regular concretes. as shown by Foxhall [28]. Tests reported by Shideler [11] show bond strengths of lightweight concrete to be essentially the same as those of normal weight concrete. Acoustic Properties Sound absorption properties of building materials are of interest in control of air-borne noise in many structures. Porosity is an important factor in the sound absorbing properties. No correlation of absorption with any significant or desirable property of the concretes has been shown to exist. specifications for concrete masonry units do include such limitations where exposure to weathering is involved. . Lightweight aggregates of the types now commonly employed in structural concrete have been in use many years without any evidence of ill effects on the reinforcing steel. low-quality concrete exposed to moist conditions. but excellent records in many places led Christensen [5] to the conclusion that corrosion of the reinforcing steel was associated principally with the use of porous and permeable. generally more absorptive aggregates. and no limits are placed on lightweight structural or insulating concretes. Cinder concrete used in the past was questioned in this respect. However.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 521 Developed with Reinforcing Steel (C 234). influence on rusting of the reinforcement. and exposure conditions constituted the important factors. Corrosion of Reinforcing Steel Both natural and manufactured lightweight aggregates are free from any corrosive effects on reinforcing steel. if any. on a volume basis. are permitted higher absorption values than heavier units containing denser aggregates. due to the wide differences in unit weights of the concretes. and concrete masonry units are employed frequently in such uses. As a result of corrosion tests and experience. For valid comparison of absorption values they must be expressed as percentages by volume rather than by weight. Lightweight aggregates apparently contribute to sound absorbing efficiency in masonry units [23]. Masonry units made with the lighter weight.) of concrete over the steel [31] has shown no evidence of corrosion. are varied with both severity of exposure and with the unit weight of concrete in current specifications. quality of the concrete. Absorption The water absorption of lightweight concretes is greater than that of concretes made with normal weight aggregates. generally Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Some lightweight concrete exposed to seawater for long periods and with less than 25 mm (1 in. and that thickness of cover. The maximum permissible absorptions. Short [32] concluded that aggregate type (dense or lightweight) had little. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. Thus insulating concretes are very easily sawed with the lightweight structural concretes being somewhat more difficult to saw or nail. "Lightweight Concrete and Aggregates. The literature seems devoid of any authenticated field cases where lack of durability has been caused by use of lightweight aggregate concrete. New York. [2] Miller. . R. In general. W. No further reproductions authorized. should preclude the use of such aggregates. The drying shrinkage test included in the lightweight aggregate specifications. continuous pores through such units tend to provide lower resistance to sound transmission through walls. There would appear to be little difference between sound transmission through walls of lightweight structural concrete. 238-249. Copyright by ASTM Int'l (all rights reserved). this phase of lightweight concrete durability is deserving of additional research and investigation. and walls of normal weight concrete. or of lightweight masonry units sealed by painting or plastering. A S T M STP 169. pp. 27-28 May 1953. Yo." General Meeting. E. W. N. Such particles could retain sufficient clay-like characteristics to cause high drying shrinkage and detrimental volume changes from alternate wetting and drying in structural concrete. the better the nailability and sawability. References [1] Davis. properly proportioned mixes show excellent durability. It seems that the possible use of lightweight aggregates containing excessive amounts of unburned or underburned particles of clay or shale is the greatest potential danger to durability in lightweight structural concretes. 1955. American Iron and Steel Institute. particularly compared to those made with very hard.522 TESTS AND PROPERTIES OF CONCRETE showing higher efficiency than normal weight concrete units.. and Kelly. American Society for Testing and Materials. Durability Although laboratory studies have shown that some lightweight structural concretes with inadequate entrained air [10] and lightweight masonry units made with lean mixes [33] can be destroyed by artificial cycles of freezing and thawing. R.. the lower the unit weight. natural aggregates. "Expanded Blast Furnace Slag for Use as a Lightweight Concrete Aggregate. However. Nailability and Sawability Lightweight concretes are more readily nailable and can be sawed more easily than normal weight concretes." Significance of Tests and Properties of Concrete and Concrete Aggregates. ASTM Specification C 330. J. The field performance of all types of lightweight concrete appears to have been generally excellent from the standpoint of resistance to the effects of weathering. American Concrete Institute. 545-552. [5] Christensen." Journal. A. W. pp.. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vol. T W." Journal American Concrete Institute." Journal American Concrete Institute." Journal. R. [16] Pepper. A. "An Improved Procedure for Proportioning Mixes of Structural Lightweight Concrete. L.. 383-402. 1952. Proceedings." Journal. W. [12] Pfeifer... C. Jr.. G.. J. American Concrete Institute. No. 59. Vol. Department of Energy. 53. 1969. 1178-1202." Research and Development Bulletin.. 1956. pp. 1. [8] American Association of State Highway and Transportation Officials. 1964. "Fly Ash Aggregate Lightweight Concrete. U. Oct. American Concrete Institute. [21] Landgren. H. Proceedings.. 846-865. 253-273. Vol." Sept. [9] Reichard." Journal. pp. 8-9 Nov. 299-328. [13] Pfeifer. "Petrographic Examination. 64. D. 1962. pp. "Tests of Lightweight-Aggregate Concrete Designed Copyright by ASTM Int'l (all rights reserved). pp. [14] Mielenz. . Proceedings. "Determining the Water Absorption of Coarse Lightweight Aggregates for Concrete. J. [4] Emery.. American Concrete Institute. 44-47.. W. 47. 57.LEWIS ON LIGHTWEIGHT CONCRETE AND AGGREGATES 523 [3] Lewis. Cotsworth.. 1959. [6J Washa. A.01T. Leonard and Mather. Proceedings. Jan. Paul and Hanson. Proceedings. pp. Portland Cement Association. 1041-1053.." Significance of Tests and Properties of Concrete and Concrete Aggregates. D. S. July 1967. and Cordon. 53. Vol. Proceedings.. Vol. "Extension of Testing Techniques for Determining Absorption of Fine Lightweight Aggregate. Research and Development Laboratories. American Society for Testing and Materials. No further reproductions authorized. Federico. S. pp. "Pelletized Blast Furnace Slag. Nov. 384-392. 53. "Structural Lightweight-Aggregate Concrete. 1956. 361-380. pp. J.. and Bowman.. Sept. C. 779-796. 62. R. W. [7] Seaton.. and Pfeifer. R. ASTM STP 169. "Insulating Concretes. pp. 491-508. Paper 4." Proceedings. No. [24] Valore. American Concrete Institute. Vol. 375-382." Journal American Concrete Institute. H. Proceedings. Vol. "Study of Causes and Prevention of Staining and Popouts in Cinder Concrete. 1976. 59. pp. and Hooton. J. Einar. Vol. "Lightweight Aggregates for Concrete Masonry Units. "Effectiveness of Mineral Admixtures in preventing Excessive Expansion of Concrete Due to Alkali-Aggregate Reaction." Proceedings." Journal. R.1. March 1951. 44. W. B.. D. R. Vol. pp. pp. L. pp. American Concrete Institute. pp.. Jan. F. [18] Helms. [ll] Shideler. J. Oct. pp. "Cinders as Concrete Aggregate. Vol. pp... Proceedings." Proceedings. 54. Vol. 53. American Society for Testing and Materials..." Journal American Concrete Institute Feb. pp. J. [10] Klieger. "Lightweight Concrete Made with Expanded Blast Furnace Slag. American Society for Testing and Materials." Journal." Bulletin 184. RD003. 619-633. Portland Cement Association. Nov.. [22] Kluge. Proceedings. C. American Society for Testing and Materials. 1974." Journal. 1957. 583-646. 78-79. P. pp. Bryant." Rock Products. Robert. 1961. "Variations in Density of Lightweight Concrete Aggregates. 7. Vol. "Creep and Drying Shrinkage of Lightweight and Normal-Weight Concretes. [20] Sweet. S. 1948. Hanson. No. 5." Journal. C. Proceedings Vol. Proceedings. Mines and Resources of Canada. S. Vol. W. 509-532. "Properties of Lightweight Aggregates and Lightweight Concretes. 64. [23] Carlson. [25] Price. 27.. W. W. [17] Saxer. D. 47-65. 1958. "A Direct Method of Determining Absorption and Specific Gravity of Aggregates. Nov. 4 March 1964. "Sand Replacement in Structural Lightweight Concrete-Splitting Tensile Strength. "Alkali-Aggregate Expansion Corrected with Portland-Slag Cement. 1956." National Bureau of Standards Monograph 74. G. 7. Vol. D. 87. Vol. A. [15] Barona de la O. American Concrete Institute. 434-437. R. 1931. "Freezing and Thawing Tests of Lightweight Aggregate Concrete. 1955. Seminar on Energy and Resource Conservation in the Cement and Concrete Industry. May 1956. [19] Landgren." Proceedings. 1956.. pp. Oct. May 1965. Department of Commerce. 55. "Lightweight-Aggregate Concrete for Structural Use. "Standard Specifications for Transportation Materials. J.. Jan. pp. No. [26] Hanson.." The Reinforced Concrete Review. American Concrete Institute. R. "The Use of Lightweight Concrete tbr Reinforced Concrete Construction. 5. [28] Foxhall." Concrete. 36. pp. 25-39. 1-37. 38-42. 121-163. Vol." Journal American Concrete Institute. Vol. pp." Heating and Ventilating. "Concrete Ship Resists Sea Water for 34 Years. pp.. 47. "Tests on Concrete Masonry Units Using Tamping and Vibration Molding Methods. A.. American Concrete Institute. [30] Copeland. pp." Concrete Products.. Vol. 1964. 84-85. 1959. [31] Willson. "Tensile Strength and Diagonal Tension Resistance of Structural Lightweight Concrete. "Heat Transmission of Lightweight Aggregate Concretes. 57. Sun Apr 6 21:43:38 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Journal American Concrete Institute.. 1939. Reinforced Concrete Association. W. 141-175. 1962. B. 3. Proceedings. pp. July 1961. F. 5. "C/M and Fire Resistance. K. No. 5. A. London. M. I.524 TESTS AND PROPERTIES OF CONCRETE for Monolithic Construction. Copyright by ASTM Int'l (all rights reserved). p. Vol. 67." Symposium on Fire Resistance of Concrete. Proceedings. A. Nov. 1954. Vol. "Fire Resistance of Reinforced Concrete. "Static Modulus of Elasticity of Concrete as Affected by Density. [29] Benjamin. E. 1. Sept. 11. Publication SP-5. Vol. C. Nov. Proceedings. April 1949. and Woodworth. No." Journal. Vol." Journal American Concrete Institute. pp. 62. No further reproductions authorized. 581-600. No. . Dec. 58. Proceeding. [33] Wendt. 45. May 1950. pp.. P. 679-687. Vol. 1960. Adrian. [27] Pauw. [32] Short. anchoring poles carrying telephone cables and transmission lines. Texas Industries. Some products introduce the ingredients into the package separately without prior mixture. 76010. While this represents an important market. Combined Materials for Mortar and Concrete (C 387) in 1956 and during subsequent revisions of that specification covering these materials which will be discussed later in this paper.org . the scope of use has expanded far beyond it. Combined Materials for Mortar and Concrete The Products Packaged. Carter ~ Chapter 31--Packaged. 1Manager of quality assurance. Arlington. Dry. 1978 A. as well as some supermarkets. varying in mass from 5 to 41 kg (10 to 90 lb) generally are available at the producing plant. Dry. Public utilities are regular customers. using the concrete or mortar for a variety of purposes including patching of sidewalks and pavements after installation of pipe or conduit.STP169B-EB/Dec. Sun Apr 6 21:45:31 EDT 2014 525 Downloaded/printed by Universidade do Gois pursuant Agreement.. Tex. the buying public has become increasingly specification conscious. No further reproductions authorized. signals. and so on. and hardware stores.astm. dry. setting signs. Copyright by ASTM Int'l (all rights reserved). Industry makes use of the products for repairs and maintenance requiring relatively small quantities of materials. Still others package the cement separate from the aggregates. The packages. Inc. Copyright9 1978 tobyLicense ASTM International www. The general trend is to mix the various ingredients thoroughly before packaging in moisture-resistant multiwall paper bags. C. building supply. Since the original publication of ASTM Specification for Packaged. Use of the Products The original developer of the packaged materials for concrete and mortar visualized the principal user as the "do-it-yourself' homeowner. Highway departments and railroads use them for patching. combined materials for mortar and concrete are combinations of cementing materials and aggregates which require only mixing with proper quantities of water to be ready for use. 2) 70 70 70 aLightweight concrete using normal weight sand may contain some portion of lightweight fines. . Quality Control A most important step in the direction of standardization and quality control was taken when Subcommittee C09. . No further reproductions authorized. TABLE 1--Physical requirements. .17 on Method of Testing and Specifications for Packaged. In other cases. (b) net weight in each bag. (3) a high-strength concrete-sand mortar. Copyright by ASTM Int'l (all rights reserved). psi (MPa) Water RetenKind of Material Concrete high-early strength normal strength normal weight lightweight using normal weight sand a lightweight High-strength mortar Mortar for unit masonry Type M Type S Type N tion.. This was published as tentative in 1956. For masonry mortars.7) 3500(24. Minimum compressive strength is specified for each product. Dry.2) 2500(17. (2) two classes of normalweight concrete. (c) yield in cubic metres or square metres per 25.1) 2500(17. adopted as standard in 1960. This specification now requires that cements.1) 3500(24. and (4) four classes of mortar for unit masonry.2) 3500(24. The specification also covers container construction. 2500(17.2) 3000(20.) of thickness.. minimum water retention is also specified (see Table 1). min. Combined Materials for Mortars and Concrete of ASTM Committee C-9 on Concrete and Concrete Aggregates developed ASTM Specification C 387. concrete in quantities of several cubic metres up to several hundred cubic metres has been used in locations inaccessible to ordinary transport.2) 1800(12..2) 3500(24. Compressive Strength.1) .1) 5000(34.. 2500(17. and aggregates.03.4) 750(5... and that there be printed on the bag: (a) kind and type of material used. and further revised in subsequent years... admixtures. % 3 days 7 days 28 days 2500(17. min. and requires that all packages be identified as conforming to ASTM Specification C 387. They cover: (1) two classes of lightweight concrete.526 TESTS AND PROPERTIES OF CONCRETE and for other work too numerous to list.5) . and also test methods conform with applicable ASTM standards.4 m (1 in. and (d) amount of water recommended for mixing. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. minimum strength requirements for lightweight concretes were increased to equal those for normal-weight concretes in Table 1. The principal purpose of such revisions has been to clarify statements in the specification. No further reproductions authorized. Department of Civil Engineering. A. ASTM is so organized that recommendations from any source will be considered by the sponsoring committee. the producer and consumer of packaged materials for mortar and concrete have a useful tool for bringing about standardization and improvement of products. Louis. In addition. and longtime member of ASTM Committee C-9. Brust. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The writer has endeavored to update the chapter in this revision. Frequent revisions of the original 1956 specification indicate the widespread interest in the subject. A product made with the letter and spirit of this specification will be a good product. rather than to make any great changes in its original requirements. W. Significance of ASTM Specification C 387 In ASTM Specification C 387. Copyright by ASTM Int'l (all rights reserved). The responsible producer may be presumed to comply with the basic requirements of ASTM Specification C 387 and to use the procedures outlined to study his products and to develop higher and more uniform quality. Both producer and consumer should scrutinize ASTM Specification C 387 to determine what changes or additions seem to be desirable. There is now little need to accept anything less.CARTER ON MATERIALS FOR MORTAR AND CONCRETE 527 In 1975 the scope of ASTM Specification C 387 was revised to include descriptions of intended uses of dry-packaged mortars and concretes as an aid to the consumer. Further changes undoubtedly will be made in the future.. St. now retired. Acknowledgments The original author of this chapter was Prof. Washington University. Mo. . The consumer should be encouraged to require that the product be certified to comply with ASTM Specification C 387. As an alternative to blending the fine and coarse aggregate. 2The italic numbers in brackets refer to the list of references appended to this paper. The drying shrinkage of PA concrete is less than that of conventionally placed concrete with similar material proportions [2]. representing roughly 60 percent of the total concrete volume. This is due apparently to the point-to-point contact of coarse aggregate particles.astm. L a m b e r t o n 1 Chapter 32--Preplaced Aggregate Concrete Introduction The term "preplaced aggregate" (PA) concrete describes a method of placing gap graded concrete. patent [1] 2 was issued in 1943. and for high density biological shielding [7]. The process was developed by Wertz to whom a U. While the two-step placement procedure would increase costs over that of conventional methods in a great majority of routine concrete work.org .. The coarse aggregate fraction can be preplaced either very rapidly with bulk handling equipment or slowly and carefully by hand labor. Ohio 44114. cement. and water and placing the mixture in a form. in heavily reinforced structures [6]. No further reproductions authorized.STP169B-EB/Dec. Because of this low shrinkage characteristic. Copyright by ASTM Int'l (all rights reserved). 1978 B. IVice President. Intrusion-Prepakt. A . 4]. The method is now widely accepted for other specialized applications such as placement of mass concrete under water [5]. it has the advantage of permitting placement of coarse aggregate. coarse aggregate is preplaced in the form and a structural grout is injected into the coarse aggregate mass in such a way as to fill void spaces where it hardens to form dense homogeneous concrete. particularly railroad bridge piers and tunnel linings [3. it was first used as a method of repairing concrete and masonry structures. Cleveland. in a timed sequence independent of mixing and placing cementitious constituents. The method is particularly applicable to placement of concrete in structures containing a profusion of inserted fixtures [8]. Sun Apr 6 21:45:31 EDT 2014 528 Downloaded/printed by Universidade do Gois pursuant Agreement. Copyright9 1978 tobyLicense ASTM International www.S. Engineering. depending on the application. followed by grout injection at a time convenient to the overall construction schedule. Inc. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Actually a highly fluent structural mortar. Grout used in PA concrete work is a structural material. is essential to successful execution of the work. Excess fines will increase water requirement and so reduce compressive strength and increase drying shrinkage. Substitution in the range of 15 to 35 percent by weight of portland cement is common. admixtures. As indicated in Table 2. Either natural or manufactured sand may be used. Since the specific gravity of this material is appreciably less than that of cement. Fly ash is also less effective than cement in chemically fixing water and so is undesirable in shielding subject to high neutron flux which is more effectively attenuated by hydrogen atoms. Grading 2 of ASTM Specification C 637. somewhat finer grading is required where high-density sand is used or where coarse aggregate grading is finer than normal. The same working stresses used in conventional concrete design are applicable to PA concrete. Copyright by ASTM Int'l (all rights reserved). . Gap graded fine aggregate may cause excessive bleeding. although the former is usually preferable from the standpoint of pumpability. It is customary practice to substitute pozzolanic quality fly ash for part of the portland cement. sand. Fly ash should meet the Class F requirements of the ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618). Injected into coarse aggregate. and improved resistance to chemical attack. Fine aggregate. fly ash is particularly beneficial in the PA concrete process in that it improves pumpability and retards initial set. the grading is equally suitable for use with normal-density aggregates. Cementing materials suitable for use in conventionally placed concrete may be used with equal confidence for placement by the PA concrete method. A typical gradation appears in Table 2. Oversize material will cause obstruction of the void channels in the coarse aggregate mass. No further reproductions authorized. partial replacement of cement with fly ash causes a slight reduction in unit weight of the concrete. it produces concrete comparable in strength and other physical characteristics to that mixed and placed by conventional methods. Although described in this specification in connection with high-density aggregate for biological shielding. and water which is injected into the coarse aggregate mass is referred to as "grout. properly graded. it bears no resemblance to the low strength. Grading 1 of ASTM Specification for Aggregates for Radiation-Shielding Concrete (C 637).LAMBERTON ON PREPLACED AGGREGATE CONCRETE 529 Materials The slurry containing a mixture of portland cement. reduced permeability. In addition to the beneficial properties normally imparted by any pozzolan to portland cement concrete such as lower heat generation. generally high water/cement (w/c) ratio grouts which are pressure injected into soil or rock formations to increase strength or reduce permeability. Fly ash is often omitted when concrete is to be used for high density biological shielding. 530 TESTS AND PROPERTIES OF CONCRETE Coarse aggregate grading is far less critical than is fine aggregate grading. section thickness.). it is common practice to scalp coarse aggregate on a 20-mm (3/4-in. In the absence of very closely spaced reinforcing or restricted form configuration. The only absolute requirements are that it be (a) free of surface dust which would prevent bond of grout to the aggregate particles.S. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) wash screen. and within the tight confines of complex formwork characteristic of most shielding installations. There is no practical limit for maximum aggregate size other than that imposed by handling equipment. (b) sufficiently saturated that it will not absorb water from the grout and so cause premature thickening. The advantage of the method for this type of work is two-fold. Although the economies of aggregate manufacture often preclude such a blend. No further reproductions authorized. to cause expansion of the grout prior to initial set in an amount sufficient to more than offset setting shrinkage of the grout which would otherwise take place beneath coarse aggregate particles. The particles should be of such toughness and hardness that they do not fracture or degrade during transport and placement into the forms. most importantly. Groutfluidifier is required on all PA concrete work to promote fluidity of the grout mixture and. for example. Grading 1 of ASTM Specification C 637. and (c) of such a grading that grout will flow readily by gravity alone through the void system. Normal aggregate grading limits for most structural applications are shown in Table 2. Extra caution must be exercised during placement to avoid degrading friable aggregate.) aggregate with 200 to 300-m (8 to 12-in. Grout fluidifier is customarily used as a commercially preblended material conforming to U. .) aggregate. and spacing of reinforcing bars and embedments. The heavy particles of mineral ore or steel punchings or a blend of these coarse aggregates is placed in the form with no possibility of segregation such as may occur when coarse aggregate and grout is combined in a plastic mass and placed by conventional methods. A trommel type screen is generally more effective than a deck screen in washing the aggregate particles to the required surface cleanliness. consideration should be given to extreme gap grading of the coarse aggregate such as a blend of 20 to 40-mm ( 90 to 11A-in. void contents as low as 32 percent have been reported for such a grading. A wide variety of high density aggregate. while mansized pieces of waste rock may be used for deep mine concreting. Aggregate graded within these limits will exhibit a void content in the range of 43 to 48 percent. both fine and coarse as described in ASTM Specification C 637. have been placed by the PA concrete method which is suited particularly for construction of high-density biological shielding. closely spaced reinforcing. Second. the method is well suited to concrete placement around multiple embedments. Where minimum grout consumption is desired. Army Corps of Engineers SpecificaCopyright by ASTM Int'l (all rights reserved). Aggregate for mass concrete work such as bridge piers may be graded from 25 to 150 mm (1 to 6 in. bleeding tends to increase. For typical structural applications. Specifications Specifications for PA concrete placement vary widely in detail depending on job complexity. and a chemical buffer to assure properly timed reaction of the aluminum powder with the alkalies of the cement. grout Copyright by ASTM Int'l (all rights reserved). For difficult projects such as large heavily reinforced structures or biological shielding.43 to 0. An air-entraining agent or air-entrained cement should not be used routinely in the PA concrete process. Army Corps of Engineers Method of Selecting Proportions for Intrusion Grout Mixtures (CRD-C 85). proportions are normally in the range of 2:1:3 to 4:1:5 by weight in which the ratio represents. It contains a water-reducing agent. a suspending agent. At a slow expansion rate. at 21~ (70~ it is approximately S0 percent complete in 1 h and 95 percent complete in 3 h. performance type specifications normally are employed. fly ash. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. For mass concrete applications the ratio of cementing materials to sand may be reduced to as low as 1:2. The release of hydrogen bubbles and the expansive reaction have an effect similar to that of an air-entraining agent with respect to freeze-thaw durability. Performance of grout fluidifier in combination with job cement should be determined. the weights of cement. therefore. However.S. the alkali content of which is less than 0. The ratio of water to cementing materials (cement plus fly ash) is in the range of 0. . where freeze-thaw conditions are severe and a specific minimum air content is required. If the expansion time is more rapid. grout insert spacing. Grout mix proportions may be selected in accordance with U.40. For routine structural repair of concrete or masonry.47. and the product custom formulated by the manufacturer if necessary when use of cement is anticipated. and sand. setting forth not only compressive strength required but aggregate composition and grading. This reaction results in the formation of hydrogen gas to expand the fluid grout. an air content determination should be made using grout fluidifier and job cement and an air-entraining agent incorporated in the grout mix if required. grout mixing and pumping time is shortened unnecessarily. This gas-forming reaction should be so timed that. Since the expansive characteristic of the grout is dependent on the alkali content of the cement. aluminum powder. specifications may be entirely of the prescription type. No further reproductions authorized. Grout fluidifier is added in an amount equal to 1 percent by weight of the cementing materials. Further decrease in this ratio is usually precluded by pumpability limitations. it may be depressed when the standard grout fluidifier formulation is used with low alkali cements.LAMBERTON ON PREPLACED AGGREGATE CONCRETE 531 tion for Grout Fluidifier (CRD-C 566). respectively. requiring only that a minimum stipulated compressive strength be exhibited by test cylinders and that good construction practice be followed in accordance with such accepted publications as ACI Standard 304 [9]. usually in the range of 5 to 8 percent. They should not only call for specific gravity limitations but also carefully describe sampling procedure with respect to quantity represented by each sample. Aggregates may be blended continuously by strear/aing through metering gates onto a belt ahead of a washing screen which completes the blending process. although particular care should be exercised with the softer natural minerals such as geothite and limonite. and allowance must be made for a loss of some of this friable material in the blending operation. placement temperature. and in-place density. or they may be batch blended by a few rotations in a concrete mixer followed by washing and screening. Temperatures at the time of grout injection are often of great importance where minimum thermal shrinkage is an important consideration. frequency of sampling. the two materials must be inspected separately and the final blend again inspected for particle size gradation and homogeneity of the blend. in practice either type of blending operation causes some size degradation of the more friable of the two aggregate fractions. All high-density aggregate should be weighed before placement and sampled frequently to determine unit density and void content. although a tolerance of _+2 percent is a more common limitation. Where watertight steel forms are used. with conformance sampling and testing performed at the job site. All aggregates described in ASTM Method 638 are suitable for placement by the PA concrete method. No further reproductions authorized.532 TESTS AND PROPERTIES OF CONCRETE surface monitoring procedures. consideration should be given to reclaiming undersize material and incorporating it in concrete to be placed by conventional methods. The aggregate may be precooled in the form by flooding it with chilled water or Copyright by ASTM Int'l (all rights reserved). If the aggregate is relatively friable and breakage during transit is high. void content of the entire coarse aggregate mass may be determined in-place by metering water into and out of the aggregate-filled forms. . Although the latter method may appear to be somewhat more accurate. and the location where tests are to be performed. calculations can be made to determine required grout density. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. such as a combination of iron ore and steel punchings. Where blended aggregates are to be used. High-density aggregates typically used in PA concrete construction are described in the ASTM Descriptive Nomenclature of Constituents of Aggregates for Radiation-Shielding Concrete (C 638) and typical specifications for these aggregates are presented in ASTM Specification 637. Ferrophosphorous varies widely in hardness and some of it may be so soft and friable as to be unsuitable for placement by the PA concrete method. Based on these determinations. Aggregates should always be tested prior to shipment. All of these materials are obviously far more expensive than normal density aggregate and purchase specifications for these materials should be written with particular care. Using careful testing and sampling procedures it is possible to specify in-place density of concrete placed by the PA concrete method as close as ___1 percent. Fluid grout characteristics are always routinely tested during any placement by the PA concrete method. Using such methods. Specifications usually require grout consistency to be controlled within a range of • 2 of a stipulated value. particularly for deep mass concrete placements. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Army Corps of Engineers Method of Test for Flow of Grout Mixtures (CRD-C 79) should be made routinely at about 2-h intervals. often no more than once a day.S.) [9].). as well as location and spacing of grout insert pipes and vent pipes. expansion Copyright by ASTM Int'l (all rights reserved). Army Corps of Engineers Method of Test for Expansion of Grout Mixtures (CRD-C 81) is performed less frequently. Short voltage pulses are transmitted on electrically calibrated detector wires located within the aggregate mass and the pulse reflections assembled and displayed on an oscilloscope. Using this technique. The utility and significance of the test procedure is greatly enhanced if observations are made of both total grout expansion and accumulated bleed water at four 15-rain intervals following mixing and at 30-min intervals thereafter until all expansion has ceased. in which a float on the end of a' line is dropped into the sounding well and the depth to the grout surface physically measured. For critical applications. Although with normal cement and at normal temperature.LAMBERTON ON PREPLACED AGGREGATE CONCRETE 533 covering the coarse aggregate with flaked ice and allowing the ice to melt and drip down through the aggregate mass. No further reproductions authorized. The Time Domain Reflectometer provides a more accurate means of determining grout surface location in a nonflooded aggregate mass. in combination with precooling the grout ingredients and using ice in the mixing water. location to the grout surface can be determined with an accuracy of about ___300 mm (12 in. . This test requires only observation of total grout expansion 3 h after mixing.7-mm (1A-in.S. location of grout surface can be determined with sufficient accuracy by simply observing grout or moisture seepage through the forms or through insert or inspection holes drilled in the side of the forms. Slotted sounding wells may also be used. For routine repair work and for many structural concrete applications.) coarse aggregate. Measurements of grout viscosity or flow. Grout or water around the sensor wires alters the impedance permitting an experienced operator to locate the grout surface with an accuracy of about ___80 mm (_-+-3 in. location and frequency of sounding wells may be specified.) orifice in accordance with U. The test for expansion in accordance with U.) coarse aggregate and the lower end of the range required for plus 12 mm (189 in. Typical consistencies range from 21 to 30 s with the upper end of the range suitable for use with plus 20 mm ( 90 in. permits placement temperatures to be achieved within the range of 5 _ 3 ~ (40 _____5~ Grout surface monitoring is of particular importance in ensuring complete penetration of all voids within the coarse aggregate mass and complete contact with embedments and penetrations. This test is analagous to the slump test for conventionally placed concrete. measuring the time in seconds for discharge of 1725 cm 3 of grout through a 12. is reported as the volume of bleed water (total volume minus grout volume) divided by initial volume. is calculated as total volume minus initial volume divided by initial volume.) prisms are cut on which final acceptance tests are performed. No further reproductions authorized. cores extracted from conventionally placed concrete should be of a diameter equal to at least four times that of the maximum coarse aggregate particle size. covered only with a thin layer of structural mortar. including grout and accumulated bleed water.) test cylinder will result in an erroneously low figure. This procedure is particularly important in counterweight construction where excessive density may be as objectionable as deficient density. nondestructive testing procedures such as the Schmidt hammer and the Windsor probe should be used and interpreted with particular caution. Discrepancies in test results might be expected. Before any adjustment is made to the mix design.534 TESTS AND PROPERTIES OF CONCRETE is virtually complete at 3 h. 100 by 100 by 150 mm (4 by 4 by 6-in. at the aforementioned intervals. two notes of caution are in order. fractions of an inch away. and grout consistency are all strongly influenced by the effectiveness of mixing equipment and procedures. Grout bleeding. performed on the structural mortar. Expansion. Secondly. In accordance with good practice. expressed in percent. Copyright by ASTM Int'l (all rights reserved). grout expansion. Density determinations on the standard 150 by 300-mm (6 by 12-in. The observer should then note and report not only the total volume of the specimen. for example. However. but the total volume of grout and the total volume of bleed water. Hardened concrete placed by the PA method is evaluated by the same methods employed with conventionally placed concrete. expansion may continue as long as 4 h at lower temperatures and with some low alkali cements. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Density of hardened concrete is normally determined by casting test cylinders in accordance with Corps of Engineers Specifications CRD-C 84. Following the procedures of CRD-C 81. This limitation on minimum core diameter is even more important with PA concrete by reason of the fact that there is a higher percentage of large aggregate particles with a correspondingly greater possibility that these particles will be torn loose from the grout matrix. approximately 800 cm 3 of fresh grout are placed in a 1000-cm 3 graduate. such tests may show a substantial variation in strength between what is essentially a test on an aggregate particle and another test. From these test cylinders. on attempting to determine 28-day strength on concrete placed by the PA method using very dense aggregate and grout with a relatively high percentage of fly ash replacement of the cement. Because of the fact that densely packed large coarse aggregate particles are in close proximity to the formed surface. expressed in percent. Bleeding. . adequacy of the mixing procedure should be evaluated carefully. B. No. B. 93-103.110. pp. J. B. Eerdmans Publishing Co. [7] Davis." Journal. pp. April 1967. pp. 421-444. Nov. Oct. Aug.. F. 2. 1969. 6." Journal. 34... "Mackinac Bridge Pier Construction. 1955." Civil Engineering. No. [2] "Investigation of the Suitability of Prepakt Concrete for Mass and Reinforced Concrete Structures.." Journal American Concrete Institute. pp. 1957. No. 7. E. No. Vol. Davis. L. 155-172. Oak Ridge National Laboratory. S. B. "Report on Design and Placement Techniques of Barytes Concrete for Reactor Biological Shielding. Proceedings. Lamberton. April 1950. H. Sun Apr 6 21:45:31 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Dec. Yuzo and Moriguchi. A. G. May 1954. Oct.. 204-212. American Concrete Institute. 1960. No. 60-65. R." Journal. "Prepakt Method of Concrete Repair. 66." Patent No. 43. No. "Process for Filling Cavities. 4. Steinman. Wm. pp. Jamesen." Report No. 581-595. No further reproductions authorized. Proceedings Vol. R. pp. [6] Klein. 3. E.. and Haltenhoff. . C. 965-977. Proceedings Vol.. Proceedings Vol. "Design and Construction of a Fully VibrationControlled Forging Hammer Foundation. G. T." Journal. "Placing Concrete in Deep Mines. C. "High-Density Concrete for Shielding Atomic Energy Plants. April 1948.. Vol. J.. [3] Davis. M. Copyright by ASTM Int'l (all rights reserved). Downs. Davis.. and Wendell. pp. 37-39. W. "Strengths of Prepacked Concrete and Reinforced Concrete Beams. American Concrete Institute. 1739. [8] Tirpak. "Preplaced Aggregate Concrete for Structural and Mass Concrete.313. Proceedings. Davis. March 1970. Proceedings. E. May 1958. Part 14.. U. E. 8.. pp. D. Jr. Bibliography Akatsuka. No." Journal..S. American Concrete Institute. "Floating Caisson Facilitates Repair of Grand Coulee Spillway Bucket.. A. R. 45-48. E. "QA Put to Work on the PCRV.. E. L. March 1947. 44.. 52. No.LAMBERTON ON PREPLACED AGGREGATE CONCRETE 535 Closure The PA concrete process is an internationally accepted method of concrete placement appropriate to certain specialized construction problems." Journal. 813-826. June 1955.. p. and Nulands. 446-449." Nucleonics. S. Test methods for evaluating the properties of the fresh grout and coarse aggregate fractions employed in this method are well established. [4] Keats. pp. Miracle Bridge at Mackinac. American Concrete Institute. 29." Journal. Proceedings Vol. 1953." Journal. pp. Jan. pp. H. 64. 1956.. E." Power Engineering. Army Corps of Engineers. C. Proceedings Vol. 1975.. D. 1951." Technical Memorandum No. D. and Crockett. No. 57. 28. Olds. [5] Davis. References [1] Wertz. "How to Choose and Place Mixes for High Density Concrete.. S.. "The Maintenance and Reconstruction of Concrete Tunnel Linings with Treated Mortar and Special Concrete. A. Johnson. 11. 2. 35-39. Vol. U. R. Several additional test methods and specifications were prepared by a subcommittee of ASTM Committee C-9 on Concrete and Concrete Aggregates and will be published in the Annual Book of A S T M Standards. "Kemano Penstock Tunnel Liner Backfilled with Prepacked Concrete. pp. 9 March 1943. American Concrete Institute.S. pp. F. G. 633-667.. pp. Jr. 1956. American Concrete Institute. Department of the Interior. 6-330. 5. 24. 785-797. 8th Ed. V. "Restoration of Barker Dam. Concrete Manual. [9] ACI Committee 304." Civil Engineering. American Concrete Institute. American Concrete Institute. 10. 287-308. Proceedings Vol. pp. Cleveland.S. Sun Apr 6 21:45:34 EDT 2014 539 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and quality control of aggregates. hardness. and the presence of contaminating substances is determined. the method is progressively being applied more widely. selection. all aggregates used in concrete construction by the Bureau of Reclamation. 2The italic numbers in brackets refer to the list of referencesappended to this paper.S. and may be obtained through some commercial laboratories. the physical and chemical attributes of each. surface texture. are described. testing. differential thermal analysis. 1978 R. Ohio 44118. Copyright by ASTM Int'l (all rights reserved).org . have been examined petrographically as a part of the basis for their selection [1]. Martin Marietta. Mielenz Chapter 33mPetrographic Examination Introduction Petrographic examination of concrete aggregate is visual examination and analysis in terms of both lithology and properties of the individual particles. Since 1936. By petrographic examination. such as particle shape. the ASTM accepted a Tentative Recommended Practice for 1Vice president. Petrographic examination of aggregates is performed also by several other agencies of the U. Department of the Interior. or electron microscopy is used to supplement the examination with optical microscopes. Master Builders Division. and specifications governing acceptance are based upon the results [3]. pore characteristics. government and state highway departments. and potential alkali reactivity. In 1952. C. X-ray diffraction. research and development. less commonly. Copyright9 1978by ASTMInternational www. coatings are identified and described. As will be discussed subsequently. No further reproductions authorized. The procedure requires use of a hand lens and petrographic and stereoscopic microscopes.STP169B-EB/Dec. U. Coarse aggregates proposed for use in either portlandcement concrete or bituminous concrete are examined by petrographic methods in laboratories of the Ministry of Transportation and Communications-Ontario.2 The method has been applied similarly by the Corps of Engineers since before 1940 [2]. petrographic examination contributes in several ways to the investigation.astm. Consequently. the relative abundance of specific types of rocks and minerals is established. petrographic examination establishes the fundamental nature of aggregates so that aggregates from unfamiliar sources can be compared Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Petrographic examination is cited in the ASTM Specification for Concrete Aggregates (C 33). and heating-cooling. Purpose of the Petrographic Examination of Concrete Aggregates Preliminary Determination of Quality Preliminary petrographic examination of concrete aggregate is performed either in the field or in the laboratory as an adjunct to geologic examination. Minor modifications were made in 1964 and 1965. and use of concrete aggregate. Second. the examination reveals the composition and physical and chemical characteristics of the constituents. . By revealing variations in the material. Techniques of the examination are treated briefly because instructions have been published [1-10] and are included in ASTM Recommended Practice C 295. First. blast-furnace slag. Also. The abundant data obtained and the rapidity with which petrographic examination can be completed justify more general use of the method in investigation. Probable performance of concrete aggregate is estimated in two general ways by petrographic examination. wetting-drying. exploration. the probable response of the aggregate to such phenomena as attack by cement alkalies.540 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Petrographic Examination of Aggregates for Concrete (C 295). The rapidity with which the petrographic examination predicts potential alkali reactivity of aggregate is especially valuable because of the long time commonly required by tests of concrete or mortar. freezing-thawing. sand. crushed stone. examination of exposures or core from pilot drill holes establishes the minimum program of exploration and sampling necessary for acceptance or rejection of the deposit. usually can be estimated. which was adopted as a standard in 1954. From this information. and sampling. the preliminary petrographic examination indicates the relative quality of aggregates from alternate sites. and the most common types of lightweight aggregate. Establishing Properties and Probable Performance Petrographic examination is primarily a supplement to the acceptance tests. This paper summarizes the objectives and applications of petrographic examination of aggregates with reference to gravel. The examination assists the geologist or materials engineer in determining the extent to which consideration of an undeveloped deposit is justified. selection. manufacture. yet produces objectionable popouts in pavements after exposure for two winters (Fig. shale. FIG. even though the materials come from new sources.MIELENZ ON PETROGRAPHIC EXAMINATION 541 with aggregates upon which information is available. or subjected to special tests. or conversely. and of particles producing popouts during service has identified the unsound rock types. 1). Mich. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This application is discussed below. By relating the sample to aggregates previously used in construction. . abrasion resistance. meets usual specification requirements for soundness. No further reproductions authorized. rejected. For example. Petrographic examination of aggregate may be a part of an investigation of concrete constructions as described in the Copyright by ASTM Int'l (all rights reserved). 1--Popouts produced by claystone. and chert in concrete pavement near Jackson. Petrographic examination of the gravel Courtesyof MichiganState HighwayDept. aggregate indicated to be sound in standard tests might be found unsatisfactory for the intended use. Correlation o f S a m p l e s with Aggregates Previously Tested or Used Detailed petrographic examination is the only test that permits comparison and correlation of samples with aggregates previously used or tested. Mich. gravel in certain deposits near Jackson. Thus. aggregate indicated to be unsound by standard tests may be found adequate. in the light of other data. whether the aggregate should be accepted. data and experience previously obtained by use and long-time tests of similar aggregates can be applied in the selection of materials proposed for current work. Examination of proposed materials will demonstrate the presence or absence of these rock types and thus will indicate. and content of soft particles. Such substances as clay. usually are not determined. . For example. and soluble salts. Consequently. Selecting and Interpreting Other Tests All properties of aggregates influencing performance of concrete ordinarily are not evaluated by test before selection of the aggregate to be used in the work. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. coal. Contamination introduced by containers may invalidate samples. petroleum products. or wastes. vegetable matter. it is worthwhile to apply a test by which the relative significance of such properties can be determined and the need for supplementary quantitative tests indicated. For example. Incomplete processing of synthetic aggregates may contaminate the finished product with raw or partially fired raw materials or coal (Fig. Copyright by ASTM Int'l (all rights reserved). yet expand in freezing and thawing? Is it the result of alkali-aggregate reaction? Is failure in the soundness or abrasion test the result of 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 potentiallly deleterious and extraneous substances can be detected and determined quantitatively. Other properties. such as coatings. Such factors as thermal properties and volume change with wetting-drying rarely are determined. Petrographic examination aids interpretation of other tests. or refractories containing calcium or magnesium oxides are especially important. Undesirable substances inherent in the material.542 TESTS AND PROPERTIES OF CONCRETE AGGREGATES ASTM Recommended Practice for Examination and Sampling of Hardened Concrete in Constructions (C 823). such as whether it was obtained from an approved or disapproved source. soil. are the particles identified as clay lumps in accordance with ASTM Test for Clay Lumps and Friable Particles in Aggregates (C 142) indeed clay lumps or are they merely friable or pulverulent particles? What is the cause of unexpected failure of concrete specimens in freezing and thawing? Is it the presence of unsound particles which do not disintegrate in the surface soundness test. coal. such as from overburden or from trucks or railroad cars not properly cleaned of previous cargo. plant remains. primarily because of cost and time required. clay. 2). may decrease the quality' of aggregate markedly. the examination may be applied to determine the source of aggregate used in constructions. industrial products. are detected easily and can be determined quantitatively by petrographic methods. such as chemical reactivity or effect of the aggregate on the freezing-thawing resistance of concrete. Inadvertent contamination with natural substances. such as coal. shales. Their properties then can be evaluated and compared with properties of the remainder of the aggregate. 2--Coal in sintered clay before crushing ( X2. Determining Effects of Processing Petrographic examination aids in production and processing of aggregate.S. Microscopical examination will reveal the presence of raw or underburned materials. or production of rock dust. or high in magnetic susceptibility. . Comparison can be based on particle shape. If the undesirable particles are unusually soft. such as expanded shale or clay.MIELENZ ON PETROGRAPHIC EXAMINATION 543 Courtesy of Bureau of Reclamation. and clays whose crystal structure was not destroyed by the calcination. and contaminants. alkali-reactive phases. By petrographic examination. the undesirable particles can be identified and separated. slag. friable. and similar materials have been fired. the trace of the differential thermal Copyright by ASTM Int'l (all rights reserved). Department of the Interior FIG. The feasibility of beneficiation by removal of unsound or deleterious constituents depends on the properties of the particles and their abundance. U. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. free lime (CaO). No further reproductions authorized. content of unsound or chemically reactive constituents. lightweight. and other types. dense. presence of coatings. separation may be feasible on a commercial scale. The relative merit of alternative processing methods and equipment can be determined quickly by comparison of the original material with the processed aggregate. perlite. Reduced one half for reproduction. slate. such as periclase (MgO). X-ray diffraction analysis is the most dependable means to identify and determine quantitatively the proportion of crystalline phases. Petrographic examination can be used to control the manufacture of synthetic aggregate. 7). Differential thermal analysis can be used to estimate the effective temperature to which clays. or alkali reactive materials. or chemically deleterious materials should be estimated from measurements made at exposures. and detailed notes made at the site should relate each sample to a particular zone and portion of the deposit or rock ledge. or synthetic aggregate. unsuitable. crushed stone. or (c) drilled core. If the deposit or rock exposure is variable. (b) stone in quarried blocks and irregular pieces. sand. such as gravel.) sieve is to be used in the work. Performance of the Petrographic Examination Samples for Petrographic Examination Samples of aggregate for petrographic examination should be representative of the source. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. detailed examination in the field may be warranted if aggregate retained on the 75-ram (3-in. Chips from cobbles not adequately identified in the field should be taken to the laboratory for further study. Examination in the Field Petrographic analysis of samples in the field usually is qualitative or only semiquantitative because lack of facilities makes detailed work difficult. fractured. Samples supplied to the laboratory comprise: (a) granular materials. For granular materials. . inasmuch as a representative sample of this size fraction necessarily weighs a hundred or more kilograms and transportation of the sample to the laboratory is costly. Recommended procedures for sampling and for preparation of the sample for analysis are covered by ASTM Methods of Sampling Aggregates (D 75) and ASTM Recommended Practice (C 295). However. Examination in the Laboratory Petrographic examination of aggregate in the laboratory may be brief or detailed. The preliminary examination should not replace the quantitative analysis included in the program of acceptance tests. the examination should be performed on all size fractions inCopyright by ASTM Int'l (all rights reserved). These notes and the results of the tests on the samples will be the basis for operation of the deposit inasmuch as it may be desirable to waste or avoid zones or portions containing inferior. The relative proportion of unsound. slag. Brief examination indicates the relative merit of materials from alternate sources and supplies justification for abandonment or continued investigation of undeveloped deposits.544 TESTS AND PROPERTIES OF CONCRETE AGGREGATES curves for the raw and fired product will coincide above the effective temperature achieved in the firing operation. samples should be selected from each zone. No further reproductions authorized. capillary suction against the tongue. 200 (75-/~m) Sieve in Mineral Aggregates by Washing (C 117).6 kg 1. (2) resonance when struck. Size Fraction. granularity. .2 kg 0. Copyright by ASTM Int'l (all rights reserved). 30) sieve are best identified. The analysis can be made conveniently by traversing a representative portion of each fraction by means of a mechanical stage and microscope assembly like that employed in the point-count procedure according to ASTM Recommended Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457) (Fig. TABLE 1--Minimum representative sample size. or swelling.18 to 0. Details of procedure are outlined by K.5 to 4. No further reproductions authorized. 3). (3) ease of fracturing. The fractions are quartered or. 16 to 30) (No. (4) nature of the fracture surface and fracture fillings. (5) odor on fresh fracture. 30 to 50) (No. such as absorption of droplets on fresh fracture.34 kg (57 lb) (19 lb) (2. Specially calibrated and fabricated cups holding 100 grains in the various size fractions have proved convenient in the petrographic laboratory of the Bureau of Reclamation for obtaining the small samples of fine aggregate for the analysis.30 to 0. The sample of each size fraction should comprise a minimum of 300 particles. (8) reaction to water. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.0066 g Samples for petrographic examination are obtained by sieving in accordance with the ASTM Test for Sieve or Screen Analysis of Fine and Coarse Aggregates (C 136) and ASTM Test for Materials Finer Than No.15 (3 to 11/2) (11/2 to 3/4) (3/4 to 3/8) (3/8 to 3/16) (No. For natural sand and gravel and crushed stone.30 0. During the analysis. 4 to 8) (No. examined. such as porosity. Mather [2] and in ASTM Recommended Practice C 295.75 4.18 1.75 to 2. helpful clues to identity and physical condition can be obtained by noting such features as: (1) friability or pulverence in the fingers.36 2.75 lb) 15 g 2.60 to 0.033 g 0. Fractions retained on the 600-~m (No. split repeatedly on an appropriate riffle. (6) color and its variation.MIELENZ ON PETROGRAPHIC EXAMINATION 545 cluded in the aggregate.28 g 0. and (9) differential attack by acids or other media. for fine aggregate.60 0. mm (in. or lamination. (7) internal structure.5 9. 50 to 100) Weight of 300 Particles 26 kg 8. slaking.6 Ib) (0. evolution of air on immersion. the minimum representative samples are shown in Table 1.) 90 to 38 38 to 19 19 to 9. 8 to 16) (No.36 to 1. and counted under the stereoscopic microscope. softening.1 g 0. Mather and B. 3--Performing the petrographic examination of fine aggregate with stereoscopic microscope. However. The mineralogic composition of finer fractions usually is determined most easily and accurately in immersion oils under the petrographic microscope. better continuity in description of physical characteristics of the particles is obtained if analysis of fractions passing the 600-/zm (No. preparation of plane surfaces by sawing and lapping. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. mechanical stage. 4). . with or without etching or staining. Such examination should be supplemented by microscopical examination of grain mounts in immersion oils. supplemented by use of oil immersion mounts of granular material. The results may be Copyright by ASTM Int'l (all rights reserved). Thin sections or polished surfaces. X-ray diffraction and differential thermal analysis may be required to identify or determine quantitatively constituents that are very finely divided or dispersed through particles of aggregates (Fig. No further reproductions authorized. 30) sieve and retained on the 150-/~m (No. They usually are employed in the study of quarried stone. commonly is preferable because of the larger area made available for examination or analysis. 100) sieve is performed under the stereoscopic microscope.546 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. analysis is performed on at least three size fractions of coarse aggregate and five size fractions of the fine aggregate. However. and tally counter. usually are used in analysis of blast-furnace slag. Thin sections occasionally are necessary in examination of natural aggregate. Ordinarily. .MIELENZ ON PETROGRAPHIC EXAMINATION L 547 i '. Kaolinite is indicated by the endotherm (downward shift) at 990 to 1025 ~ Nontronite is revealed by endotherms at 100 to 350~ and 450 to 550~ lllite produces the small endotherms at 100 to 200~ and 500 to 615~ Organic matter produces large exotherms at 430 to 500~ or 440 to 600~ Pyrite develops a marked exotherm at 400 to 485~ used to compute the petrographic composition of the aggregate in any gradation comprising the analyzed fractions.. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement....Limestone with Drganic .nine L 9Altered Diabose nontion~ --I X/x~ :i I . U."~~e w l t h Organ.te I Sisga Oom. Occasionally.S. 30) sieve.Colombio.' ChickemaugoDam. the composition by count usually differs greatly from the composition by weight. but for the finer fractions.Tenn er l l. Analysis by count is the more appropriate determination technically because the influence of Copyright by ASTM Int'l (all rights reserved)../] near Kansas City. 4--Typical differential thermal analysis records obtained on concrete aggregates.j.te with pyri!e /" Cripple Creek. No further reproductions authorized. consistent analyses of all fractions of fine and coarse aggregate can be reported only by count.Phon]l. Numerical results of the analysis may be expressed by weight or count for particles retained on the 600-#m (No. one analysis may be performed on a graded aggregate.-Sandstone w~th kaolin. Consequently.~ matter k.SA b canto. the results are based only upon count of grains unless a correction factor is applied. For such an analysis. . Department of the Interior FIG.. Kansas I .Cola i i J Heating Rate II~ IO0 200 300 I 400 I 500 i 600 I 700 TEMPERATURE-DE6 C 800 900 IOOO ilao Courtesy of the Bureau of Reclamation. Petrographic criteria useful in detecting dolomitic rocks that are potentially susceptible to a deleterious degree of alkali-carbonate reacCopyright by ASTM Int'l (all rights reserved). and Mielenz [10. No further reproductions authorized. . Hansen [11].12]. permeability. the petrographic analysis is more rapid if the relative proportion of the several rock types or facies is determined by weight. However. Observations Included in the Petrographic Examination In reporting the results of the petrographic examination.8]. the accuracy and precision of analysis by weight are affected adversely by unavoidable loss of rock substance when the particles must be broken to allow identification of rock and mineral types and description of physical condition. softening and distintegration with wetting or wetting and drying Thermal properties Strength and elasticity Density Hardness Chemical activity Solubility Oxidation.548 TESTS AND PROPERTIES OF CONCRETE AGGREGATES particles of given type upon performance of concrete depends primarily upon their frequency and distribution in the mass. A simple test to detect forms of pyrite that are likely to oxidize while enclosed in concrete was devised by Midgley [13] and is discussed more generally by Mielenz [12]. Specifications on lithologic composition preferably are expressed as percentage by count of particles. Swenson and Chaly [9]. the petrographer should supply information on the following subjects as necessary to evaluation of the aggregate: Mineralogic and lithologic composition Particle shape Surface texture Internal fracturing Coatings Porosity. Details of calculating and reporting are summarized in ASTM Recommended Practice C 295. and carbonation Alkali-silica reactivity Alkali-carbonate reactivity Sulfates Sulfides Cation exchange reactions Organic Substances The significance of these properties is discussed by Rhoades and Mielenz [7. hydration. and absorption Volume change. When applied to coarse aggregate only. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.MIELENZ ON PETROGRAPHIC EXAMINATION 549 tivity are described by Hadley [14]. Coatings should be reported and evaluated separately because coatings usually are confined to portions of a deposit and. and (3) poor. if appropriate. or hydrating portland cement while enclosed in concrete or mortar under ordinary conditions. water. for crushed stone. . particle shape should be considered apart from other aspects of physical quality because particle shape commonly is subject to control or modification by processing of the aggregate. Unless Copyright by ASTM Int'l (all rights reserved). If other test data are available or if the particles can be compared petrographically with previously tested materials. and the surface texture is relatively rough. capillary absorption small to moderate. FairwParticles exhibit one or two of the following qualities: firm to friable. Condition of the Particles The following classification of properties is useful in cataloging the physical and chemical condition and particles constituting and aggregate. the properties can be evaluated semiquantitatively or quantitatively. the nature and abundance of coatings vary with processing methods and equipment. No further reproductions authorized. Satisfactory--Particles are hard to firm and relatively free from fractures. Physical condition is defined by three terms: (1) satisfactory. Poor--Particles exhibit one or more of the following qualities: friable to pulverulent. interfere with the normal course of hydration of portland cement. chemical stability in concrete is designated by two terms: (1) innocuous and (2) deleterious. Similarly. slake when wetted and dried. coefficient of thermal expansion approaching zero or being negative in one or more directions. Gillot [15] and others [16-20]. Deleterious--Particles contain one or more constituents in significant proportion which are known to either react chemically under conditions ordinarily prevailing in portland-cement concrete or mortar in such a manner as to produce significant volume change. highly fractured. surface relatively smooth and impermeable. It is intended that the aforementioned properties be determined qualitatively by observation of the mineralogic composition and texture of the particles or by simple tests. moderately fractured. (2) fair. very low compressibility. combine three or more qualities indicated under "fair. marked volume change with wetting and drying. capillary absorption is very small or absent. capillary absorption high. DolarMantuani [21] describes alkali-silica reactivity of argillites and graywackes. or supply substances that might produce harmful effects upon mortar or concrete." Innocuous--Particles contain no constitutents which will dissolve or react chemically to a significant extent with constitutents of the atmosphere. in lakes or marine basins. sand and gravel are more or less complex mixtures of different kinds of rocks and minerals. The analysis was obtained because the aggregate apparently delayed or prevented development of specified strength by the concrete under certain conditions." The measurement should be made in accordance with definitions of these terms as they appear in ASTM Definition of Terms Relating to Concrete and Concrete Aggregates (C 125). All are based upon samples received as a part of engineering investigations. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) sieve. deposits of sand and gravel usually vary vertically by stratification and laterally because of the lenticular nature of zones or strata." The summary of physical and chemical quality is included in a separate tabulation. but the inclusion of pertinent description facilitates interpretation of the analysis. particles whose length is more than five times their width should be designated as "elongated pieces. In the tabulation. The format accords with ASTM Recommended Practice C 295. Consequently. Summarizing the Petrographic Examination Tables 2 through 5 exemplify a variety of forms in which the petrographic analysis may be reported." and those having a ratio of width to thickness greater than five should be designated as "flat pieces. . Table 5 is an analysis of a sample representing a commercial crushed stone coarse aggregate passing the 38-mm (11A-in. moderately weathered or fraetured. The tabulation could be simplified by cataloging the rock types into major and secondary classifications. It departs somewhat from the format recommended in ASTM Recommended Practice C 295.550 TESTS AND PROPERTIES OF CONCRETE AGGREGATES otherwise defined by applicable specifications. Table 2 is in the form generally employed by the Bureau of Reclamation [22]. Table 3 is the analysis of the sand produced with the gravel whose composition is summarized in Table 2. The tabulations always are accompanied by appropriate discussion and supplementary description. or by wind or glaciers on the earth's surface. Table 4 is similar except that the designations of quality are not used because they are inappropriate for description of lightweight aggregate. such as "granite: fresh. deeply weathered. The concrete-making qualities of the aggreCopyright by ASTM Int'l (all rights reserved). Petrographic Examination of Natural Aggregates Examination of Natural Aggregates in the Field Sand and gravel result from weathering and natural abrasion and impacting of rock and the deposition of the resulting particles along streams. Moreover. No further reproductions authorized. the denotation of "innocuous" and "deleterious" is restricted to potential deleterious alkali reactivity because the significance of the sulfides and organic matter in the stone could not be evaluated. Examination in the field should indicate the lateral and vertical extent and the physical nature of the coatings.MIELENZ ON PETROGRAPHIC EXAMINATION 551 gate are influenced by these changes. Identification of such Courtesy of the Michigan State HighwayDept. near Charlesvoix. S--Cobbles of argillaceous limestone disrupted by freezing-thawing in the deposit. Water-soluble salts in coatings or ground water also may be revealed by efflorescence at or near the surface of the deposit. particles will aid evaluation of the petrographic examination performed in the laboratory. Close observation of gravel and sand exposed on the surface of the deposit commonly will reveal unsound particles which slake or fracture with freezing-thawing or wetting-drying (Fig. Representative specimens of particles affected by freezing and thawing should be packaged separately and transmitted to the laboratory with samples of the gravel and sand. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). In interpreting the effects of natural freezing and thawing. Weathering of gravel and sand after formation of the deposit is common on terraces and at lower levels of deposits along existing stream channels. Deposits of sand and gravel commonly are changed by deposition of mineral matter from ground water or by weathering of particles. The examination should indicate the extent and distribution of such weathering. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. clay. Observation of natural disintegration forewarns of possible difficulty in service. . Areas of the deposit free from coatings and zones so heavily coated as to preclude processing should be delineated. Examination in the field also should reveal the variability of the sand and gravel with reference to unsound or deleterious particles. FIG. the consequences of particle size should be evaluated [23]. Mich. Their presence forewarns of the need for quantitative determination of their concentration in the aggregate. and organic matter. 5). 0..5 3/4 to 3/8 in.2 48.6 .. 29.2 0.0 Weathered granite 40. 11/2 to Granite Rock Types 0.8 Rhyolite porphyry 6..Copyright by ASTM Int'l (all rights reserved). fractured.-) O m "O m O "I~ Z (D -q m . 17. Size Fraction. includes some free quartz Description of Rock Types TABLE 2--Example of tabulation of a petrographic analysis of gravel. porphyritic. 8. rounded to fragmental pink.1 1. fractured and weathered weathered.3 1..0 3/4 in. weathered.4 Coarse-grained granite 0.2 .9 6. 0.2 Andesite porphyry . Sample No. m fi-) &-) m n'i (3 0 Z (. Deeply weathered granite 12. fair fair satisfactory satisfactory fair satisfactory poor fair satisfactory Physical Quality innocuous innocuous innocuous innocuous innocuous innocuous innocuous innocuous innocuous Chemical Quality rn ).. to green medium.7 Fractured coarse-grained granite o. rounded. Plant.6 3/8 to 3/16 in. slightly friable. includes some free quartz mierocrystalline..to fine-grained. black. Company...4 . 0. rounded.1 0. microcrystalline pink.o Weathered andesite porphyry Basalt 2.5 17. rounded to fragmental fractured. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Colo. white to brown microcrystalline.1 . rounded to fragmental fractured. No further reproductions authorized.2 0. tan. percent by weight a as above. porphyritic. near Denver. 1 Quartzose sandstone 1. .3 32. . massive hard.2 Granite gneiss 2. rounded.3 0. Con version f a c t o r s . and 1 lb = 0.6 Milky quartz 0.0 lb of 11/2 to 3/4-in. . banded.2 15.5 fine-grained. pink to gray medium.- 0. platy.8 Quartzite 2.8 10. fine. hard. smooth fine-grained.7 7.45 kg. . hard. 1 in. brown.to fine-grained. . quartzose soft. fractured aBased upon analysis of 19. 0.0 6. No further reproductions authorized. brittle. . rounded as above. 2. .2 Deeply weathered gneiss Fractured schist 2.. and 0.4 m m .2 Schist 0. massive to schistose massive. .2 2. .. porphyritic. absorptive.4 0. massive. dense. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . aggregate. firm to hard porous.7 Ib of 3/4 to 3/8-in.to medium-grained as above.2 ..0 0. intensely fractured to friable hornblende schists. hard.4 Diorite innocuous Innocuous innocuous Innocuous fair poor satisfactory fair satisfactory poor fair satisfactory fair deleterious Innocuous Innocuous Innocuous Innocuous Innocuous innocuous satisfactory satisfactory innocuous satisfactory 03 01 Ga z 5 z "l- "O N O Z "O m :IJ O O :D z m rm . gray cryptocrystalline.~ 0. hard.3 Weathered gneiss 2..5 . 0. fractured to slightly friable as above. ..80 lb of 3/8 to 3/16-in.1 0.2 2.4 .2 Shale Rhyolite 0.. = 25.Copyright by ASTM Int'l (all rights reserved). 0. 0.8 14.4 Ferruginous sandstone . .0 0. No.2 15. Passing No. .. "016 0.6 11.. a n d on the d i s t r i b u t i o n of constituents by size fractions shown at the left above.2 3..3 Sc pc 17. 1.9 34.. .1 . Basalt Sericite schist Quartz and quartzite Feldspar Claystone Chalcedonic chert Mica H o r n b l e n d e . 50-100 No. . 2.. .2 3.3 1.5 . . . .2 .6 2.0 .n .5 2.3 4.5 . . .. D = potentially chemically deleterious. 100. .2 813 li12 43. ...0 . 100. . ..... 28.0 2.0 .8 23. zircon. . .8 0. . . 8-16 . .0 16. i 1. 100200 . . .. .0 .8 6. percent T A B L E 3--Example of tabulation of a petrographic analysis of natural sand.2 65. .. .7 51.2 . . 100. ..3 Tc C h e m i c a l Quality In W h o l e S a m p l e b a Based on count of 500 particles in each sieve fraction. .2 15. 013 .6 . .4 0. . "915 59... . .. .8 1.. . 21.8 G r a n i t e a n d g r a n i t e gneiss Pegmatite Rhyolite tuff Constituents No. b Based on g r a d a t i o n of the s a m p l e received.3 No. .3 4.8 . Fc Physical Q u a l i t y 98. No further reproductions authorized. 16-30 a 82. . 313 0.8 11.2 0. 30-50 .. .4 0.0 .0 2. . .4 . .6 11. Total .7 11.0 16. .7 51.6 28.. . . . ..2 .2 0. as N u m b e r of Particles. P = poor.6 51.. . ..5 . .. .... Plant. 200 4..9 I00.8 4.2 1...3 "3. . .7 . No. . F = fair. .0 33.0 iii 012 .7 41. . Colo. S a m p l e No. 100.6 0. garnet. .. 0.1 .9 No. etc .3 . Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. i12 .7 51. .. 4-8 In Size F r a c t i o n s I n d i c a t e d A m o u n t .7 0. "" '3.. 100. .. . ---I m (D :D m 0 0 0 z 0 :D m --4 m o~ O --i1 0 -o m z o -o --4 m O~ --4 (D 01 t.8 0. . .4 .1 48.. . 10. C o m p a n y n e a r Denver. c s = satisfactory.2 ic 1.2 13..0 2....0 0.6 0.5 8. .8 10.. .1 9.1 9.0 18. T = total of c o n s t i t u e n t in whore sample.. 24.2 0. . . . I = chemically innocuous. .0 16.. 34. Dc 100. .0 9. ..8 1. 100. . " "1.. . ..Copyright by ASTM Int'l (all rights reserved). 4 . 100.0 1. .0 0. 1. .6 . 4-8 . .4 7.6 .. Plant. 100.2 1. vesicular particles Red to tan. . friable vesicular.4 .0 . Total .4 7.1 0.7 32.0 "b:8 0. 25.. .8 7. 29. . 30-50 .8 1. bricklike particles Gray to black.8 . . 9.3 0.6 7.0 12.7 13. 50-100 100..3 . friable vesicular. fragile. b Based on gradation of the sample received.2 .0 .9 20... . . Company Sample No. . vesicular particles Red to brown. 21. 46. dense hard. vesicular particles Black to gray.6 4. firm to fragile vesicular. . In Size Fractions Indicated a Amount. hard vesicular. many slake in water not vesicular.2 42.1 4. . 1. . 16-30 .2 No. . .0 0. .. friable.1 Granite Sandstone Coal 1.7 . 100.0 30. . 9. many slake in water not vesicular.2 23.0 "i11 1. . 62.Copyright by ASTM Int'l (all rights reserved).8 23. 'oi1 .8 2.4 2.1 1. . Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. contain coal hard. Gray to pink.6 3/8 to 3/16 in. 100 .8 22. . . .7 100. percent TABLE 4--Example of tabulation of a petrographic analysis of expanded clay aggregate.9 .5 No. .7 .1 21.4 0. .1 No. ol ida O! z z x /: ffl O -o a- m :13 O fi3 20 z N O z m /-rtl . fine-grained hard to friable not vesicular.0 o. '21s 2.2 No. 100. 3. . vesicular particles Red to tan.0 . Black to gray. I00. .0 '210 7. as Number of Particles.0 "119 4.4 Passing No. .6 64.3 .8 0. . No further reproductions authorized.. 8.0 . bricklike particles Gray to pink.4 0. 0.5 26. and on the distribution of constituents by size fractions shown at left above.2 25. 20..5 1. . .0 No. . . 8-16 . 24. . bricklike particles Constituent 3/4 to 3/8 in.8 . . SS. hard a Based on count of 500 particles in each size fraction.0 . . .1 0. . 15.2 44. .0 1. 36. .8 0. 44. friable particles 100.8 .4 In whole sample b Remarks not vesicular.0 100.4 0. . 33..9 56.9 0. No further reproductions authorized. ..total of constituent in the sample..1 2..0 0. 1. a Plant.. slightly porous....2 Sc 40..1 .2 33.4 . sparse organic m a t t e r with pyrite a n d m a r c a s i t e Description of the Rock Type or Facies 59. . coarse.4 2. fine-grained. b Based u p o n analysis of 25.1 .2 4. percent by weight b T A B L E 5--Example o f tabulation o f a petrographic analysis o f crushed stone coarse aggregate. F = fair.2 33.9 ... c s = satisfactory.3 0.1 1.2 Tc ..1 0. iron sulfides a n d organic m a t t e r a b u n d a n t white to gray. 2....2 Dc Ic C h e m i c a l Quality a S a m p l e g r a d e d in accordance with specifications of the State Highway Dept. 4 aggregate for concrete highway pavement.1 1. for 11/2 in. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.9 2.g r a i n e d l a m i n a t e d . Company S a m p l e No.1 4.Copyright by ASTM Int'l (all rights reserved). soft to friable. . I :-.D "11 ITI Q m -4 ITI 0 z 0 O "11 :IJ O "u m :lJ -t -u z -I -I m O1 t~ O~ .0 4.7 "0. contains sparse organic m a t t e r with pyrite a n d m a r c a s i t e g r a y to buff. particles of zones of chalcedony evident conchoidal fracture. organic d o l o m i t i c limestone Soft dolomitic limestone Dense dolomitic limestone Rock Type or Facies Physical Quality A m o u n t . 9 56.. T :. m t. Fe .. P = poor. D = potentially deleteriously alkali reactive...1 .1 100. same as above except c o n t a i n i n g one or more seams of iron sulfides a n d organic matter white to gray. .0 2.not deleteriously a l k a l i reactive. pc 98.1 0.0 1. dense includes also g r a i n s of q u a r t z a n d feldspar gray to buff.4 2..9 lb of a g g r e g a t e split from the sample. Total Chalcedonic chert Sandstone Chalcedonic limestone Limestone L a m i n a t e d limestone Soft.to m e d i u m .. to No. . 56.. abundance. The location of many known deposits of alkali reactive natural aggregate in western United States has been reported by Holland and Cook [25]. Fraser et al [26] have provided a detailed study of composition of ehalcedonic cherts in relation to their reactivity with alkaline solutions. petrographic examination commonly is time consuming. and (S) the possible qualitative contribution of particles of the several types of properties of concrete (Tables 1 and 2). glassy to cryptocrystalline rhyolites. (4) particle shape. Occasional basalts contain glass whose index of refraction is less than 1. and soluble phosphates have been identified [8. thus eliminating the need for tedious examination sufficient to effect a separation. Natural aggregate may contain more than 20 rock and mineral types. Consequently. chalcedony. slates. and latites--of similar composition and physical condition might be combined. causing softening and absorptivity in the superficial portion of the particles. and granite gneisses--or rhyolites. and their tufts.24]. Weathering in the deposit is especially significant because the alteration affects most or all particles. No further reproductions authorized. Alkali-reactive dolomitic rocks may occur as Copyright by ASTM Int'l (all rights reserved). alkali and alkali-earth sulfates. probable potential chemical reactivity. physical properties. dacites. opal. (2) the abundance of particles in various physical conditions and degrees of chemical reactivity. Coatings usually are composed of silt. manganiferous substances. and calcium carbonate. The petrographic examination should reveal the composition. latites. granites. For example. but organic matter. clay. Based upon the similarity in composition and probable performance in concrete. at least certain artificial siliceous glasses. abundance. tridymite. and cristobalite. two or more rock types commonly can be combined into a single category with considerable saving in time and without loss in validity of the analysis. Gravel and sand potentially susceptible to the alkali-silica reaction occur along many important rivers in the United States and have been responsible for serious distress in many concrete structures (Fig. . and graywackes. argillites. (3) the composition. or may be developed by weathering in the deposit. frequency. quartz monzonites.535 and palagonite may be partially altered to opal.MIELENZ ON PETROGRAPHIC EXAMINATION 557 Examination of Natural Aggregates in the Laboratories Samples and data from the field should be examined to determine: (1) the abundance of individual lithologic or mineralogic types. and certain phyllites. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This action decreases both the bond with cement and the strength and durability of the concrete. and andesites. and physical nature of coatings. Coatings on gravel and sand vary from minute spots and films to a cement which produces zones of sandstone or conglomerate in the deposit. Soft and altered particles may be original constituents of sand and gravel. 6). iron oxides. opal. and the ease with which the coatings are removed by impact and abrasion. dacites. The known alkali reactive substances are the silica minerals. Especially in warm humid areas. For example.. and rock may vary widely in porosity. AmlZ I r .. I ~. ~ "~c')~q 7 " ~ L .S ..15]. degree of fracturing...~l.___ 9 . _o._. Certain zones may contain deleterious or unsound substances. leached. Petrographic E x a m i n a t i o n of Crushed Stone Examination o f S t o n e in t h e F i e l d Rock formations are massive or stratified. and partially decomposed near the surface. Any rock containing a significant proportion of these substances is potentially deleteriously reactive. 6--Location of structures in the United States known to be affected by alkali-aggregate reaction in concrete. constituents of natural aggregates. or local shearing. rock formations commonly are fractured. such as chalcedonic or opaline chert and clay or shale in limestone or dolomite.. 'S<A_ ' .. or chemical reactivity.:.. Rock formations commonly contain zones of faulting.558 TESTS AND PROPERTIES OF CONCRETE AGGREGATES ! #7. the strata can occur in any attitude with respect to the horizontal.- _ Section of river carrying reactive sand or gravel • Source of reactive crushed stone 9 Structure affected by alkali-silica reaction O Structure affected by alkali-carbonate reaction FIG.. . and sources of crushed stone subject to alkali-carbonate reaction. sources of sand or gravel subject to alkali-silica reaction. hardness. )-__ A.. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the alkali reactivity of dolomitic limestones typically varies widely even within the same quarry when deleterious facies are present [14. toughness.. . . within which the materials are fractured or chemically decomposed. No further reproductions authorized. ... Copyright by ASTM Int'l (all rights reserved).o. jointing. Shale. should be recognized in any evaluation of such observations [23]. quarried faces or other excavations. Disintegration of rock on natural exposure commonly does not coincide with results of the sulfate soundness test [27]. ballast. Observation of such disintegration indicates unsoundness of stone in at least portions of a quarry. including deeply altered basalts and diabases containing nontronite. Department of the Interior FIG. crushed stone aggregates commonly are complex petrographically. Similar effects occur if the zeolites leonharditelaumontite constitute a significant proportion of the rock. Consequently. This survey may reveal lithologic varieties which have failed in the natural exposure to freezing-thawing or wetting-drying or to oxidation and hydration (Fig. 7). 7--Disintegration of argillaceous facies of limestone used as riprap at Chickamauga Dam. . E x a m i n a t i o n o f C r u s h e d S t o n e in the L a b o r a t o r y As is indicated above. Soluble salts usually will be revealed by efflorescence at exposed surfaces. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. may slake and fracture during brief exposure even though they appear sound when excavated.MIELENZ ON PETROGRAPHIC EXAMINATION 559 These features should be discovered by geologic and petrographic examination of natural exposures. claystone.S. and drilled core. and argillaceous rocks. No further reproductions authorized. and masonry. they are especially common in diorites and quartz diorites. riprap. Copyright by ASTM Int'l (all rights reserved). they should be examined in the detail required for natural aggregate (Table 5). Tenn. The significance of size of fragments Courtesy of the Bureau of Reclamation U. Petrographic examination in the field should include exposures of geologic formations and stone used in the area for fill. 8). Quantitative petrographic analysis can be made on calcareous rocks by preparing plane surfaces by sawing and lapping. Webster Dam. The examination should establish the relative abundance of individual rock types or facies (Fig. 9). 8--Crushed limestone aggregate containing seams and pieces of illite shale. This technique can be applied to calcareous aggregates in hardened concrete (Fig. and siliceous sand or silt. 61 percent. chert. .560 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Petrographic examination of stone in the form of quarried blocks or irregular pieces should include inspection of the entire sample. ( X 89 ).S. Department of the Interior FIG. Quantitative analysis can be made similarly on prepared surfaces of quartzose and feldspathic rocks following etching by 1189 to 2 min immersion in hydrofluoric acid (HF) (Fig. Specimens representative of each type should be obtained by sawing or coring of typical pieces. Courtesy of the Bureau of Reclamation. the manufactured aggregate produced should be examined to determine Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. The etched surface can be analyzed by point-count or linear traverse in general accord with procedures given in ASTM Recommended Practice C 457. 5 percent by weight. fair. 10). If the sample of stone was submitted for crushing tests in the laboratory. followed by etching. such as clay. Thirty seconds of immersion in 10-percent hydrochloric acid (HC1) will provide adequate differential attack on calcite and dolomite and will expose noncalcareous constituents. poor. detailed petrographic examination. these specimens serve for special tests. The physical quality was indicated as follows: satisfactory. U. and reference. 34 percent. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Kan. The core should be Copyright by ASTM Int'l (all rights reserved). inasmuch as such zones commonly represent fractured. the effects of natural fracturing. if unsound or deleterious particles constitute 10 percent of the finished aggregate. For example. Especial attention must be given to sections in which core loss was high or complete. These features should be correlated with the processing equipment and methods employed.MIELENZ ON PETROGRAPHIC EXAMINATION 561 FIG. distribution of unsound or deleterious substances in the size fractions. If the samples are in the form of drilled core. Reduced one half for reproduction. was this proportion derived from approximately one piece in ten of the original sample. No further reproductions authorized. Inspection of the stone prior to processing is important because only thus can the examination of the finished aggregate be interpreted fully. . 9--Concrete containing dolomitic limestone coarse aggregate (a) beJbre and (b) after etching for 30 s in lO-percent HC1. altered. and internal texture on particle size and shape. the latter suggests that the material should not be used as aggregate in permanent construction. and the abundance and composition of crusher dust. frequency of fractures and seams within the particles. or does a typical piece of the stone contain approximately 10 percent of unsound material? The former possibility suggests that the quarry should be examined to determine whether the unsound zones can be avoided or wasted. or otherwise unsound rock. ( X 10). jointing. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Scattered crystals in the etched areas on the lapped surfaces of the aggregate particles are dolomite. the entire length of core should be examined and compared with logs available from the driller and geologist. as necessary. soluble salts. content of clay and shale. which is Copyright by ASTM Int'l (all rights reserved). dark areas are augite in the etched surface (• tO). Petrographic Examination of Blast. both in depth and laterally. These observations should be correlated from hole to hole so that the variation in lithology or quality of the rock. The examination is facilitated by sawing and lapping of the core along the length. such as sulfides. . Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. is established. and presence of deleterious substances. lO--Augite gabbro (a) before and (b) after 189 rain etching by concentrated HF. The quality of the aggregate to be expected from the formation represented by the cores also will be indicated by petrographic examination of aggregate produced from cores in the laboratory. to establish variations in lithology. and petrographic microscope. White areas are plagioclase feldspar. frequency and intensity of fracturing. stereoscopic microscope.562 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. Reduced one half for reproduction. No further reproductions authorized. with or without etching or staining. consisting essentially of silicates and aluminosilicates of calcium and of other cations. and alkali reactive substances.Furnace Slag Blast-Furnace Slag Blast-furnace slag is the nonmetallic product. regardless of rock type. examined by means of the hand lens. crystals occur individually or in clusters scattered through the glass matrix.S. Three general types of blastfurnace slag are used for concrete aggregates. Abrasion resistance relates to glass content and the condition of internal stress [30]. the surface texture of which is pitted. namely. Incipient crystallization produces brown or opaque areas in thin sections (Fig. However.29]. air-cooled slag. Well-granulated slag is substantially all glass. Air-cooled slag is more or less well crystallized. Courtesyof the Bureau of Reclamation.MIELENZ ON PETROGRAPHIC EXAMINATION 563 developed simultaneously with iron in a blast furnace (see ASTM Definition C 125). In addition to the indicated microscopical methods. crushed stone. . granulated slag. rough. the two-dimensional aspect simplifies quantitative estimation of composition. Petrographic examination of lightweight or expanded slag will be discussed in a later section. Copyright by ASTM Int'l (all rights reserved). 11). The dark areas are concentrations of microcrystalline melilite and merwinite. 11--Photomicrograph of granulated blast-furnace slag. Crystals range from submicroscopic to several millimetres in size. or conchoidal. depending primarily upon the method of disposal employed at the steel plant. Properties of blast-furnace slag as concrete aggregate have been reported by Gutt et al [28. and lightweight slag [30]. being preferred by some petrographers because the surfaces are easy to prepare in sizes larger than thin sections. Department of the Interior FIG. Note the vesicles (bubbles) in glass phase (white) (XS0). No further reproductions authorized. examination of polished and etched surfaces in reflected light is a valuable technique. and manufactured sand are applicable.U. the instructions provided for examination of ledge rock. Such slag crushes to angular and approximately equidimensional pieces. and microchemical tests can be used to identify various phases in the section under study. Performance o f the Petrographic E x a m i n a t i o n o f Blast-Furnace Slag The procedure for petrographic examination of blast-furnace slag is not included specifically in ASTM Recommended Practice C 295. Reduced one halffor reproduction. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. surface texture. More than 20 compounds have been identified in blast-furnace slag (Table 6). The inversion ordinarily takes place before the slag has cooled. Dicalcium silicate can be identified microscopically in slag by Copyright by ASTM Int'l (all rights reserved). causes "dusting" or "blowing" of slag [30. a mottled aspect is produced on the surface of damp concrete [12]. occasionally. In less severe occurrences. or by chilling the molten slag so that the compound does not crystallize [30]. MgO.564 TESTS AND PROPERTIES OF CONCRETE AGGREGATES The petrographic examination of blast-furnace slag aggregate should include description of the various types of slag as well as of contaminating substances. fl. Sulfides released into the cement paste matrix produce innocuous greenish staining of the interior of concrete. and the disintegrated material is removed by screening in the production of coarse aggregate. Each type should be studied in some detail to assure identification of potentially deleterious compounds. Gypsum commonly forms a blast-furnace slag by weathering and may result in sulfate attack on the cement paste matrix in concrete in service. or presence of products of weathering. High-lime blast-furnace slags commonly contain one or more forms of calcium disilicate (~. the disintegration takes place slowly. and Snow [34. No further reproductions authorized. Inversion of fl-dicalcium silicate to the ~. and thus unsuitable for concrete aggregate. but even well-crystallized slag rarely contains more than five compounds (Table 7). Sulfides of manganous manganese and ferrous iron are common. . or merwinite. rapid cooling ordinarily arrests the compound in the fl modification. a compound of variable composition between akermanite (2CaO. color. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. vesicularity. Nurse and Midgley [32]. producing pieces that are partly or wholly weak and friable. and in standard works on mineralogy. forsterite. The typical constituent of blast-furnace slag is melilite.2SiO2) and gehlenite (2CaO. or 3. Insley and Frechette [33].-dicalcium silicate. Calcium sulfide almost always is present in small proportion. depending upon particle shape.AI203-SiO2).35]. Presence of colloidal sulfides is suggested by yellow or brown coloration of the glass phase [30]. crystallinity. This action of dicalcium silicate can be avoided by maintaining a ratio of CaO to SiO2 in the slag sufficiently low to prevent formation of the compound.SiOD. Magnesium-containing blast-furnace slags usually include monticellite. Pseudowollastonite and anorthite are of common occurrence. The slag constituent usually can be segregated into two or more varieties.36]. forms of 2CaO. X-ray diffraction methods are necessary if crystalline phases are submicroscopic and are a great aid to a petrographer who is developing experience independently in this field. Properties and techniques for identification of these compounds are summarized by Rigby [31]. Several original constituents of blast-furnace slag may be deleterious to the performance of concrete. with the accompanying 10-percent increase in volume of the crystals. If air-cooled slag is poured in thin layers. Gehlenite Akermanite Pseudowollastonite Wollastonite Bredigite Larrlite 7-dicalcium silicate Olivine Merwinite Rankinite Monticellite Pyroxene Diopside Enstatite Clinoenstatite Compound TABLE 6--Compounds occurring in blast-furnace slag.q :]0 O Q m f. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.-I z -o I z N O Z -u Ill . A120 3" 3 SiO 2 CaS FeS MnS (Mg. frl . SiO 2 72CAO 9SiO 2 2(Mg. A120 3"2SIO 2 MgO CaO Chemical Formula oldhamite ferrous sulfide m a n g a n o u s sulfide spinel anorthite periclase lime Compound 2CaO.(Mg. A120 3" SiO 2 2CaO.A120 3 2 MgO. McCaffery et al [38]. primarily Nurse and Midgley [32]. MgO. 2SiO 2 3CaO. SiO 2 fl2CaO. Fe)O.SiO 2 MgO..2SiO 2 CaO.SiO 2 Chemical Formula a Compiled from several sources. MgO. SiO 2 A120 3" SiO 2 3A120 3. A120 3 CaO.2SiO 2 2CaO. Fe)O-SiO2 3CaO. No further reproductions authorized..Copyright by ASTM Int'l (all rights reserved). SiO 2 ~ ' 2 C a O . 2MgO.2SiO 2 ctCaO. Fe)O. SiO 2 flCaO. 2SiO 2 MgO. 2A120 3"5SiO 2 cristobalite calcium aluminate cordierite siUimanite mullite madisonite CaO. and American Concrete Institute Committee 201 [40]. SiO 2 CaO.. a Grl O) O~ z . MgO. -4 r . No further reproductions authorized. a --4 I"11 00 fi3 Q 20 m 60 0 -11 0 0 z 0 20 m -4 X C:7 "13 20 0 "o m 20 --4 m o9 Go .Copyright by ASTM Int'l (all rights reserved). A l 2 0 3 9Si02 produced by crystallization of blast furnace slag. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. b Key: C2AS = gehlenite -~ Dolomite Limestone F l u x Stone X X C2S X C3S2 X X X X C3MS2 CMS2 = diopside CMS = monticellite CAS2 = a n o r t h i t e C352 = r a n k i n i t e CAMS2 = merwinite M A = spinel X X CS X X X X X x MA X X X CMS MxS = forsterite MS : e n s t a t i t e M g O = periclase X X X CMS2 C o m b i n a t i o n of C o m p o u n d s b X X X X x X CAS2 X X X X M2S X MS X MgO T A B L E 7--Most frequently occurring combinations o f compounds of CaO. M g O . X X X x X X X X x X f melilite C2MS2 = a k e r m a n i t e J C2S : d i c a l c i u m silicate CS = wollastonite or pseudowollastonite X X X X X C2MS2 C~AS a After Nurse a n d Midgley [32]. coke. their absence or presence and abundance should be established by the petrographic examination. and incompletely fused fluxstone. 3 Nevertheless. or swelling). namely. manganese oxide (MnO).37]. and friability. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and rock particles. softness. Shale. Copyright by ASTM Int'l (all rights reserved). slaking. iron carbide. Particles of expanded material may be segregated on the basis of particle shape. occurrence of efflorescence. and Slate Petrographic examination of lightweight aggregate should include segregation of the particles into as many categories as required to describe the sample adequately (Table 4). The petrographic examination supplements standard tests in distinguishing clayey particles from "clay lumps" determined in accordance with ASTM Test C 142. coal." vesicularity. These compounds are deleterious because of the increase in solid volume resulting from hydration or carbonation in place. basic open-hearth slags commonly contain free oxides that are subject to hydration in portland-cementconcrete. friability. its abundance should be determined. No further reproductions authorized. Scattered crystals of/3-dicalcium silicate commonly are stable in blast-furnace slag and so are innocuous. The last is important because delayed hydration and carbonation of free lime and magnesia may produce expansion of the concrete and popouts. a solid solution of magnesium oxide (MgO). and reaction to water (softening. development of a coating or "skin. blast-furnace slag [32. Cristobalite has been reported as a constituent of blast-furnace slag [38]. This compound is potentially alkali reactive. Free lime (CaO) and magnesia (MgO) are extremely rare as constituents of air-cooled blast-furnace slag and are not likely to form either as a primary phase or devitrification product in granulated. Metallic iron and iron carbides rust by oxidation and hydration if exposed at the surface of concrete. free lime (CaO) and magnesiowl]stite.MIELENZ ON PETROGRAPHIC EXAMINATION 567 special techniques [36]. Contaminating substances whose presence or absence should be established by petrographic examination are metallic iron. and ferrous oxide (FeO). . The composition and content of raw material commonly can be established most easily and accurately by X-ray diffraction or differential thermal analysis. if identified. absorptivity. The individual types of particles also should be analyzed petrographically 3Unlike blast-furnace slags. Petrographic Examination of Lightweight Concrete Aggregates Expanded Clay. The glass phase of normal blast-furnace slag is not deleteriously reactive with cement alkalies. Other materials to be identified and determined quantitatively are underburned or raw material. density. These should be separated on the basis of porosity. surface texture. Incompletely expanded particles and particles not expanded should be distinguished from vesicular ones. friability. Extraneous or contaminating substances are primarily dense particles of volcanic rock and organic matter. such as dense slag. Scoria is a highly porous and vesicular volcanic rock in which the vesicles typically are rounded or elliptical in cross section. fracturing. surface texture. Cinders Cinders used as concrete aggregate are the residue from high-temperature combustion of coal and coke in industrial furnaces. effects of weathering in stockpiles. sulfates. 12). and coke. Pumice. Petrographic examination also assists selection of raw materials. coatings. Petrographic examination should determine the physical nature of the cinder particles on the basis of composition. coal. specific gravity. and content of contaminating substances. scoria. . the interstitial glass occurring as thin films (Fig. Pumice is a very highly porous and vesicular volcanic rock composed largely of natural glass drawn into approximately parallel or loosely entwined fibers and tubes. development of manufacturing methods and equipment and process control. Scoria. particle shape. surface texture. The petrographic examination should describe the aggregate in terms of the nature of the expanded particles. and potential alkali reactivity. including their particle shape. tuff. friability or softness. Tuff.568 TESTS AND PROPERTIES OF CONCRETE AGGREGATES to establish the presence of free magnesia or lime. These result mainly from decomposition of calcium and magnesium carbonates in the feed during firing. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. weathering. Tuff is a general term designating consolidated volcanic ash of any lithologic type or physical character. friability or softness. porosity or vesicularity. and volcanic cinder used for lightweight aggregate are naturally occurring porous or vesicular volcanic materials. predominantly ranging from 4 to 32 mm in diameter. Petrographic examination of these types of aggregate includes segregation of the particles on the basis of particle shape. They may produce distress or popouts in concrete or concrete p r o d u c t s unless the aggregate is water. secondary deposits in voids. Especial attention should be given to identification of sulfides. No further reproductions authorized.or steam-cured prior to use [39]. Volcanic cinder is a loose accumulation of highly vesicular (scoriaceous) fragments of lava. Expanded Blast-Furnace Slag Expanded blast-furnace slag is produced by carefully controlled intermingling or molten slag and water or steam in one of several ways [30]. In production of lightweight aggregate. Copyright by ASTM Int'l (all rights reserved). and Volcanic Cinder Pumice. softness. and surface texture. For example.400 percent under the same conditions. Department of the Interior FIG. The type and relative proportion of the materials can be established by petrographic examination. No further reproductions authorized. in spite of alkali-silica reaction and formation of alkalic silica gel in highly porous pumice and tuff. The pieces are black. yet the specimen contained abundant alkalic silica gel [41].535 to 1.. gray. a very highly porous rhyolite tuff from Hideaway Park.570 probably is alkali reactive. containing abundant tridymite caused only 0. A similar but dense tuff from near Castle Rock. glass whose index is in the range 1. Opal. and reddish brown. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Volcanic glass with an index of refraction less than 1.041 percent expansion of a high-alkali cement mortar during one year of moist storage in accordance with ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227). and cause disruption into small pieces. produced an expansion of 0. vesiculate the rock. and cristobalite are also common alkali-reactive constituents of volcanic aggregates. Copyright by ASTM Int'l (all rights reserved). . Reduced one half for reproduction. chalcedony. The product is known commercially as perlite.. Note the rounded vesicles. However. two types of volcanic materials are intermixed occasionally for economy or to control gradation or unit weight.MIELENZ ON PETROGRAPHIC EXAMINATION 569 Courtesy of the Bureau of Reclamation.535 is potentially deleteriously reactive with cement alkalies. certain obsidians and pitchstones release gases which. Perlite When heated rapidly to fusion. expansion usually is prevented by the abundant voids into which the hydrating gel can escape without development of excessive stress in the mortar. U. Colo. being trapped within the molten glass. tridymite. 12--Typical basaltic scoria aggregate (natural size). Colo.S. depending upon mineralogic properties and purity and the conditions of firing. and volcanic ash are present in widely differing proportions. However. Perlite may contain particles of dense volcanic rock or individual crystals. During petrographic examination.and low-alkali cement [42. composition. porous and absorptive. with both high. The degree of expansion varies widely. Applied in the field. These differ significantly within individual samples from some sources. and potential alkali reactivity. vermiculite.43]. Fine sand. the particles of vermiculite are segregated by degree of expansion.570 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Petrographic examination should indicate the composition of the aggregate in terms of particle shape. the method aids exploration and sampling and permits preliminary evaluation of materials from alternative sources. Finely divided opal and opaline skeletons of diatoms are the predominant constituents. . and ranges from firm to pulverulent. especially from marginal deposits where the vermiculite grades into hydrobiotite or biotite. Exfoliated Vermiculite Exfoliated vermiculite is produced by rapid heating of the micaceous mineral. Detailed exCopyright by ASTM Int'l (all rights reserved). surface texture. Diatomite Crushed and sized natural diatomite typically is soft. silt. density. No further reproductions authorized. typical perlite is potentially reactive with cement alkalies. Such volume change will not necessarily cause structural distress if appropriately accommodated in the design. At least certain diatomites produce significant expansion of mortars stored in accordance with ASTM Test C 227.43]. friability or fragility. and fragility of the expanded crystals. Conclusion Petrographic examination should be included in the investigation and testing of concrete aggregate for use in permanent construction. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Being composed of volcanic glass. Also to be reported is intermixture of the vermiculite with particles of rocks and minerals occurring with the vermiculite in the deposit. elasticity of brittleness of the flakes. clay. Release of combined water expands with crystals-like an accordian--increasing the volume to as much as 30 times its original size. although significant expansion may not occur because of the porosity of the particles. laboratory tests demonstrate that certain perlites produce significant expansion of mortar stored in accordance with ASTM Test C 227 in combination with either highalkali or low-alkali cement [42. gravel." Record No. [12] Mielenz. C. Validity of the results depends u p o n the t r a i n i n g a n d experience of the petrographer. Woda. E. 1946. [20] Buck. p. Vol. C. 40. E. 395. E. 525. 3.. Transactions. Bulletin. "15 Years of Living at Kingston With a Reactive Carbonate Rock.. 19. 43. C. p. R. E. p. [19] Ozol. "Anhydrous Minerals and Organic Materials As Sources of Distress in Concrete. R. 1967. A. 36. p. (2) c o m p a r i n g the aggregate with aggregates for which service records or previous tests are available. 1964. p. pp. 462. E. Vol. American Society for Testing and Materials. W. p. [2] Mather. 10. 1071. 268. 987. American Concrete Institute. L. R. [21] Dolar-Mantuani." Research Record No. R. "Bridge Deck Deterioration Promoted by AlkaliCarbonate Reaction: A Documented Example. Highway Research Board. Proceedings. C. A S T M STP 83.. 99-117. and Brownridge. p. 55-63. D. 1958. H. 1974. and Koniuszy. 1956. and Witte. "An Engineering Method of Petrographic Analysis for Coarse Aggregate Quality. 1963. with proper t r a i n i n g a n d the adoption of u n i f o r m techniques a n d n o m e n c l a t u r e .. A. M. Proceedings. 309. F.. 1948. 1974. Vol.. R... No further reproductions authorized. p.. Katharine and Mather. [13] Midgley. Proceedings. Roger and Mielenz. [11] Hansen.. 525. J.MIELENZ ON PETROGRAPHIC EXAMINATION 571 a m i n a t i o n of aggregate in the laboratory s u p p l e m e n t s the s t a n d a r d acceptance tests. 13. especially by (1) detecting adverse properties. "Control of Reactive Carbonate Rocks in Concrete.. P. crushed stone. Transportation Research Board. 525. [3] Bayne. R. [5] Rexford. [10] Mielenz. [7] Rhoades. [15] Gillot. 1958. The methods can be applied effectively to sand. Vol." Research Report No. D. C. 42. J. [16] Swenson.. R. 54. a n d (5) d e t e r m i n i n g the efficiency a n d relative merit of processing a n d m a n u f a c t u r i n g methods. Vol. V. Highway Research Board. Metallurgical. [8] Rhoades. Bulletin. p.. and Newlon. C. [6] Mielenz. Highway Research Board. 1974. American Society for Testing and Materials. G. p. Proceedings. L. [14] Hadley. G. p. Geological Societyof America. "Petrographic Examination of Concrete Aggregate to Determine Potential Alkali Reactivity.. Sulfates or Sulfides. subjective elements in the e x a m i n a t i o n are not significant." presented at the 36th Convention Canadian Good Roads Association. 95-104. "Alkali-Silica-Reactive Rocks in the Canadian Shield. Highway Research Board. P. B. Transportation Research Board. D. "The Uhthoff Quarry Alkali Carbonate Rock Reaction: A Laboratory and Field Performance Study. 1969. 8. H." Technical Report C-75-3. 13-16 Sept." Record No. Vol. [17] Smith. [4] Mielenz. J. Proceedings. Chojnacki. U. 1946. 1188. L. 1948. Mineral Aggregates." Research Report 18-C. (4) detecting c o n t a m i n a t i o n . Army Engineer Waterways Experiment Station. p. G. "Reactions of Aggregates Involving Solubility. [9] Swenson. 1975. 48. 187.. GeologicalSociety of America. No. Bryant. Vol. Concrete Research.. 1961. R. . and Chaly. 5"7. 1954.. American Institute of Mining.. 50. slag. and Gillot. 43. However. 23-27. References [1] Mielenz. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. C. pp.. Transportation Research Board. 20. Roger and Mielenz. Vol. (3) e x p l a i n i n g results of tests a n d justifying special tests as required. G. Oxidation." Record No. pp.S. W. p. pp. p. 1964. 43-54. pp. 1955. 759. Banff. 1950. 581. 1288. [18] Ryell. and Petroleum Engineers. Alberta. 1. H.. Jr. P." Record No. Copyright by ASTM Int'l (all rights reserved).. C.. 1950.. Vol. American Society of Testing and Materials. 29. Transportation Research Board. Concrete Research. American Concrete Institute. 75. Proceedings. C.. a n d n a t u r a l or synthetic lightweight aggregate.. American Society for Testing and Materials. p. W. Vol. Vol. 305. G. 2. 1947. Rock Products. 2167. 299. U. A. Vol. Proceedings of the 4th International Symposium on Chemistry of Cement. W. R... and Cook.. G. No. R. R. E. A. 1949. Greene. W.. "The Risk of Unsoundness Due to Periclase in High Magnesia Blast Furnace Slags. 581. Vol. 57. 1942. Bureau of Reclamation. Technical Publications No.. p. [24] Goldbeck. T. 211. 1927.S. 45. Department of the Interior. 1967.. L. G. 1933. V. [26] Fraser. 1035.. and Runner. Iron and Steel Institute. H. Processing. The Thin Section Mineralogy of Ceramic Materials. Concrete Research. Rock Products. F. 19. A. No. American Concrete Institute. Microscopy of Ceramics and Cements. 12.S. B. American Ceramic Society. "Alkali Reactivity of Natural Aggregates in Western United States. G. B.S. 8th ed. 1953. 9. T. Leo. British Ceramic Research Association.. 60.661. Journal. and Frechette. Cordon. and Petroleum Engineers.. American Institute of Mining. . J.. Metallurgical and Petroleum Engineers. Academic Press. W." Monograph 43. [28] Gutt. Oesterle. J. H. H." Laboratory Report No. 1967. 1972. R. [42] Hickey. "The Mineralogy of Blast Furnace Slag. [35] Snow. E. S. 83-94. 146. Proceedings. Proceedings. H. p. 44. R. S. [34] Snow. G. 1953. Vol. Vol.. W. and Schapiro." Mining Engineer. [30] Josephson. [40] "Committee 201 Report on Blast Furnace Slag as Concrete Aggregate. [23] Verbeck.. C. Journal. 1951.. 1960... R. W. No further reproductions authorized. N. 1954. pp. p. [31] Rigby. W.. D." Circular 468. Vol. "Iron Blast Furnace Slag: Production. Illinois State Geological Survey. 1953. and Uses.. Harvey. R.. W. U. Inc. Metallurgical. F." Proceedings. 27." Silicates Industriels. [43] Price... Vol. American Institute of Mining. American Society for Testing and Materials.. C. Proceedings. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. K. "Properties of Chert Related to Its Reactivity in an Alkaline Environment. Vol. American Concrete Institute. National Bureau of Standards. G.. Vol. Vol. Proceedings. 183. R.. Technical Publication No. 479. H. and Gutt. Department of the Interior. W. 2rid ed. Bureau of Mines. 991. [27] Loughtin. "Properties of Concrete Made With Typical Lightweight Aggregates--Housing and Home Finance Agency Research Program. F. A. Y. and Benton. J.. 16. C-385. [41] Mielenz. [38] McCaffery. p. and Newman. Jr. New York. W. and Price. and Heigold. Concrete Research. p. 104. D. and Ryder. D.. G.. R. 17 March 1928.572 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [22] Concrete Manual. 1955. 19. 1960. 1930-1931.Y. Highway Research Board.. Vol. 19. 1948.. 71-82. 193. 1949. No. 50. p. T. Properties. 36. [37] Stutterheim. Jr. Vol. and Cordon. [33] Insley. Sillers.. 1948. M.. [29] Everett. and Landgren..... 31. and Midgley. 1975. Copyright by ASTM Int'l (all rights reserved). R.. American Concrete Institute." Bulletin No. W. [25] Holland. 2. 1063. p. [39] Nordberg. Bror. p. [36] Parker. p. N. U.. Part 1. [32] Nurse. Kinniburgh. pp. p. 7. P. H. Department of the Interior. pp.. 21. Bureau of Reclamation. astm. although aggregates with discontinuous or gap grading have sometimes been used to advantage [26-28]. but the grading limits discussed are applicable to lightweight and heavyweight aggregates as well. screen analysis. of which concrete is composed. 2The italic numbers in brackets refer to the list of references appended to this paper. and mechanical analysis are terms used synonymously in referring to the gradation of aggregate. one with circular apertures is a screen. This paper is concerned mainly with normal weight aggregates. mounted in a suitable frame or holder for use in separating material according to size. with regularly spaced apertures of uniform size. No further reproductions authorized. However. Calif. H.STP169B-EB/Dec. because aggregate. Copyright by ASTM Int'l (all rights reserved). fit together as absolute volumes and in no other way. 92653. and the effects of entrained air and amount of cementitious material contained in the concrete [1-25]. none of these has been accepted as being universally applicable. Sieve analysis. differences in particle shape and texture of the aggregates. Laguna Hills. an apparatus with square openings is a sieve. A sieve is defined as a metallic plate or sheet. water. because of economic consideration. or other similar device. and entrained air. 1978 W. is usually undesirable. or coarse aggregate having a large deficiency or excess of any size fraction. Price I Chapter 34--Grading Introduction The influence of aggregate gradings on the properties of concrete has been extensively discussed in the technical literature during the past 125 years and many methods for arriving at " o p t i m u m " or "ideal" gradings have been presented. in mechanical analysis. Copyright9 1978tobyLicense ASTM International www. Nomenclature The particle size distribution of aggregate as determined by separation with standard sieves is known as its gradation. 1Consulting engineer. 2 Experience has demonstrated that either very fine or very coarse sand. cement. a woven wire cloth.org . Sun Apr 6 21:45:34 EDT 2014 573 Downloaded/printed by Universidade do Gois pursuant Agreement. 6 (No.36 (No. such as 9. because of their pronounced effect on the slump and workability of the concrete. 9. 38.). with the U.4). No further reproductions authorized.50). and 1189 in.574 TESTS AND PROPERTIES OF CONCRETE AGGREGATES ASTM Specification for Wire-Cloth Sieves for Testing Purposes (E 11) lists dimensions for the standard sieves in metric units.). 76 (3 in.4) size. lines on a graph can be spaced at constant intervals to represent the successive sizes and the fineness modulus can be computed. This separation for recombining in the desired proportions in the concrete mixture pays dividends through the ease with which the resulting uniform workable mixture can be placed and the savings in cement that is realized. The fineness modulus of fine aggregate is determined by using the cumulative percentages of material retained on sieves below the 4. The fineness modulus is an empirical factor used to indicate the coarseness or fineness of the material.75 (No.). Uniformity of concrete is of such importance that some specifications for large jobs require that the grading of fine aggregate shall be controlled. Although many different gradings have been found to produce suitable concrete. This is recognized in grading specifications.).15 (No. also used for separating coarse aggregate are: 12. so that the fineness moduli of at least 9 out of 10 consecutive test samples of the fine aggregate as delivered to the mixer shall not vary more than 0.1 mm (3/8. and dividing the sum by 100. The fine aggregate must be separated from the coarse aggregate and the coarse aggregate separated into sizes as listed in Table 2 of ASTM Specifications for Concrete Aggregates (C 33). Table 2 of ASTM Specification C 33 lists the amount of undersize and overCopyright by ASTM Int'l (all rights reserved).3 (No. The fineness modulus of fine aggregate usually falls between 2.S.). 25 (1 in. with its coarseness increasing as the fineness modulus becomes larger. The U.) Under such a system employing a log scale. and 90 (31/2 in.).18 (No.1 (1 t/2 in. Size Separation The gradings of sand and gravel deposits and the crusher product of quarried material seldom occur in desirable percentages to produce uniform workability and economical strong concrete. 2.). It is obtained by adding the total percentages of a sample of the aggregate retained on each of a specified series of sieves. 19.). 0. and 38. 63 (21A in.5 (1/2 in. Metric units for sieve openings will be used in this paper. 3A.5.S. Perfect separation of the aggregate at the processing plant cannot be accomplished at reasonable cost. A convenient system of expressing the gradation of aggregate is one in which the consecutive sieve openings are constantly doubled. Other sieves.20 from the average of the 10 samples [28].16). customary units shown in parentheses.3 and 3. standard sieve sizes of this series in millimetres are: 0.1. and 150 (6 in. 4. 50 (2 in.5 (3/8 in.8).).75 (No.100). 0. 19 ( 90 in.).30). . the gradings cannot vary suddenly or widely during concreting operations. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1. Because of the segregation which usually occurs in handling. Maximum Size Aggregate The amount of water per unit volume of concrete required to produce a given slump decreases as the maximum size aggregate increases.). The condition is further aggravated by breakage and segregation which occurs in the larger sizes of coarse aggregate during stockpiling and handling. At the 28 Mpa (4061 psi) level. and 9.2 of Building Code Requirements for Reinforced Concrete Copyright by ASTM Int'l (all rights reserved). Some have found it economical to finish-screen the aggregate just before it goes into the batching bins. Under such conditions it is difficult to obtain uniformly workable concrete.) size.PRICE ON GRADING 575 size permitted in each size fraction of coarse aggregate.5 mm (1/2 in.5 mm (3/s to 189 in. smaller maximum size aggregates must be used for most efficient use of cement with 37.75 to 19 mm (3/16to 90 in. there seems to be no advantage in using maximum size aggregate below the 12. and in this fraction it is common practice to extend the size from 4. as shown in Table 1. it is not possible to obtain strengths above a practical level of 35 MPa (5076 psi) with the entrained air contents listed in Table 1 [33].) for the 35 MPa (5076 psi) level. No further reproductions authorized. acceptable separation can be assured.29].5 to 12. This practice is generally followed except for the finest size of coarse aggregate where the ratio is usually increased above the 2 to 1 figure. . 19 mm ( 90 in. 31].) for strength above 42 MPa (6092 psi) [28. no cementitious material can be saved by using aggregate above 76 mm (3 in. Also. and where this is done. the cementitious content of the concrete can be progressively reduced as the maximum size aggregate is increased while maintaining a constant water/cement ratio and strength. A large particle of aggregate has less area for bonding with the mortar than an equal weight of smaller aggregate particles and it is for this reason it is not possible to obtain high strengths with large maximum size aggregate [32]. In Section 3. segregation will occur in the stockpiling and batching operations. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Segregation in such finer size fractions may be very pronounced. It has been found that where there is an excessive amount of either undersize or oversize.3. Lenses of fines which form in large stockpiles are another constant source of trouble. with portions of the material that reach the mixer containing a preponderance of fines below the 9. As the strength level is increased. In the production of high strength concrete above 42 MPa (6092 psi). it is desirable that the ratio of the size openings of the upper and lower screens which determine any size fraction be not greater than 2 to 1.) for the 42 MPa (6092 psi) level.) size [30.5 mm (11/2 in.5 mm (3/s in. For compressive strengths below 21 MPa (3046 psi). Breakage and segregation can be minimized through careful and proper handling of the aggregate. and slugs of fine or coarse material will reach the mixer.) in size. 5 177 334 40 1 37.. CApproximate percentage of fine aggregate of total aggregate by absolute volume.75 m m (sand) TABLE 1--Mortar requirements for workable concrete with various maximum aggregate sizes. Quantities listed can be reduced significantly through the addition of a water-reducing admixture.5 m m 148 279 34 4 168 316 37 0.3 76 m m 118 222 25 3 139 262 28 0. bCement required in kilograms per cubic metre for 0.rl O~ .53 water/cement ratio by weight.2 150 m m ~Approximate amount of mixing water in kilograms per cubic metre required for 7S-mm slump with well shaped angular coarse aggregate. %d Water. 276 520 100 6 245 462 100 13 M a x i m u m Size Aggregate Water. 4.5 160 302 34 0.2.5 m m 19 m m 202 382 49 2 192 362 S0 7 177 334 45 6 Air-Entrained Concrete 216 406 54 2. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.3 of ACI Recommended Practice for Selecting Proportions for Normal and Heavy Weight Concrete (ACI 211.r) --4 I11 t. No further reproductions authorized. k g / m 3b Fine aggregate.-I Z 0 "0 -.1). --I rrl o) rl-I "-i1 m -4 m C') 0 Z C) 0 0 "0 m -n . k g / m 3b Fine aggregate.5 25 m m 157 296 37 4. dRecommended average total percentage of entrained air required for frost resistance from Table 5. %d 201 380 58 8 228 430 62 3 9.5 m m 169 318 40 5 192 360 44 1.5 Nonair-Entrained Concrete 12. %c Entrapped air. %c Total air.5 50 m m 139 262 31 3. k g / m 3" Cement.Copyright by ASTM Int'l (all rights reserved). k g / m 3a Cement.4 (. or if an approved mineral admixture is used to supply the deficiency in fines passing these sieves." From the limitation on maximum size aggregate set by ACI 318. for any given set of materials and air content. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. except for massive sections of concrete. or in nonair-entrained concrete containing more than 307 kg/m 3 of cement. The coarse sand results in harshness. respectively.1 mm (11/2 in. and the fine sand requires a comparatively large amount of water to produce the necessary fluidity and also tends to cause segregation. Also. workability and methods of consolidation are such that the concrete can be placed without honeycomb or void. If the mortar is workable and satisfactory in other respects. in the judgment of the engineer.PRICE ON GRADING 577 (ACI 318). No further reproductions authorized. should be satisfactory for most concretes. some economies can be realized. by using 150 mm (6 in.) accomplishes little or no saving in cost or improvement in the characteristics of the concrete.3 and 0. it is usually possible to secure workable concrete by using enough mortar to fill the voids among the coarse aggregate particles and separate them so that there is ample room for them to move in the mortar without interference. These limitations may be waived if. one third of the depth of slabs.) maximum size aggregate. shown in Table 2 of this paper. bleeding. it can be seen that. the maximum size aggregate will usually be below 38. For the lean. It can be seen from the foregoing discussion that grading of aggregate has a marked influence on the strength of concrete. the strength will vary in accordance with the water/cement ratio law. nor three fourths of minimum clear spacing between individual reinforcing bars or bundles of bars or pretensioning tendons or post-tensioning ducts. 50 and 100) sieves may be reduced to 5 and 0. with other advantages of lower heat generation and shrinkage. . if the aggregate is to be used in air-entrained concrete containing more than 251 kg/m 3 of cement. Experience has shown that usually very coarse sand or very fine sand is unsatisfactory for concrete mixtures. The use of cobbles larger than 150 mm (6 in. Grading of Fine Aggregate The grading of fine aggregate has a much greater effect on workability of concrete than does the grading of the coarse aggregate [34]. and for a constant grading. ASTM Specification C 33 also requires that fine aggregate shall have not more than 45 percent retained between any two consecutive sieves of those shown in the Copyright by ASTM Int'l (all rights reserved). But. and segregation. the physical characteristics of the aggregate have a pronounced effect on the strength of concrete.15 mm (Nos. it is stated: "The nominal maximum size of the aggregate shall not be larger than one fifth of the narrowest dimension between sides of forms. Fine aggregate gradings falling within the specification limits of ASTM Specification C 33. low-strength concrete used in the interior of thick concrete dams.). Under these specifications the minimum percentage of material passing the 0. .-d m ~) 0 Z 0 0 CO -11 0"u m -n z o m t. m m 50 to 85 1..50) 2 to 10 0.5(3/8 in.6 (No.16) TABLE 2 .3 (No.8) aThese percentages can be modified as explained in the text. 100 Percent passing by weight a 95 to 100 4.) Sieve Size.Copyright by ASTM Int'l (all rights reserved).18 (No.15 (No. 9.G r a d i n g limits f o r f i n e aggregate.30) 10 to 30 0. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.q ~ Co .75 (No. No further reproductions authorized. 25 to 60 0.36 (No.4) 80 to 100 2.100) m fi) -n m fi) m . On large jobs involving many thousands of cubic metres (yards) of concrete. and that the fineness modulus shall be not less than 2.15 mm (Nos. In one case this "chattering" was eliminated by increasing the amount of material passing the 0. However. it has been found that a coarse sand with a fineness modulus of around 3. No further reproductions authorized. It is sometimes difficult to finish a floor because of the grading of the sand which causes "chattering" or waves to form under the trowel.S0) sieve.3 and 0.0 produced the best workability and highest compressive strength [30].3 mm (No. It has already been mentioned that ASTM Specification C 33 permits a reduction in the minimum amount of material passing the 0.50) sieve from 12 to 18 percent and the amount passing the 0. It is practicable to make size separation of the coarser material by screening at comparatively small expense and to recombine the separated sizes in desired proportions. Fine aggregates having gradings outside ASTM Specification C 33 have produced satisfactory concrete in some instances. .3 mm (No. The sand must be well graded and somewhat on the fine side.) size. In general. Coarse Aggregate As a rule it is less difficult to provide satisfactory grading in coarse aggregate than in sand. it is stressed that regardless of the grading selected it must be maintained within certain limits without sudden variations if satisfactory economical concrete is to be produced. Concrete for pumping must be very workable.PRICE ON GRADING 579 table. Table 3 shows the approximate ranges over which it will usually be practicable to vary the relative proportions of size Copyright by ASTM Int'l (all rights reserved).3 nor more than 3.200) sieve from 1 to 4 percent. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as has been discussed under Size Separation. it is recommended that the average grading as produced from the deposit or quarry without blending or wasting to bring it within some predetermined limits be tried in trial mixes to determine whether the aggregate can be used without expensive processing. manufactured sands require more fines than natural sands for equal workability [21]. with 15 to 30 percent passing the 0. but where the behavior of an available sand having a grading falling outside accepted limits is unknown. with high sand contents and preferably with aggregate graded below the 25 mm (1 in.1. On the other hand. 50 and 100) sieves from that shown in Table 2 in the ease of rich or airentrained mixes. increased percentages of these sizes may be desirable in the ease of the lean concrete used in mass construction.075 mm (No. and where the size of the job does not warrant the expense of trial mixes before specifications are written. For the high cement contents used in the production of high-strength concrete. it is recommended that an accepted specification such as ASTM Specification C 33 be used. 75 to 95 TABLE 3--Approxirnate ranges in grading o f gravel coarse aggregates f o r various m a x i m u m sizes (in millimetres).) 150 (6 in.5 to 19 Fine Percentages Reduced to Cleanly Separated Basis 27 15 10 8 to to to to 45 25 15 15 4.1 (1% in. mm 19 (% in. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) 38.) 75 (3 in.1 55 30 15 12 to to to to 73 35 25 20 9. Cobbles 75 to 150 0 0 0 20 to 35 Maximum Size Aggregate in Concrete.1 to 75 0 40 to 55 20 to 40 20 to 30 Medium 19 to 38.Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized.-I or) -I m Go O1 tX~ 0 . "-4 m Go "n m -i1 rn --4 rn z O I"11 O~ O -o ::]o 0 "o rn :]0 o z .) 0 0 20 to 40 20 to 32 Coarse 38. . Air Entrainment and Grading Purposefully entrained air in concrete materially improves the resistance of concrete to frost action. uniform concrete cannot be produced with pit-run or Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The effect of the finely dispersed air bubbles obtained through the use of air-entrained agents is entirely different from that of the larger air voids which result from poorly graded aggregates. Although grading of aggregate has a pronounced effect on the strength of concrete and small maximum size aggregate must be used for efficient production of high-strength concrete. Coarse. 4. 3.). it is sometimes possible to use a coarser or finer grading or a jump grading and obtain concrete of satisfactory workability with the proper amounts of entrained air. the larger voids do not improve the quality of the concrete and contribute to poor workability and segregation. In addition to a reduction in the amount of fine aggregate which may be accomplished for a given set of materials and grading. but unless trial mixes are made beforehand to determine whether they can be used. as already mentioned. the use of cobbles larger than 150 mm (6 in. air content. improves its workability. Economical. and gap gradings have produced satisfactorily workable concrete under certain conditions. In general. but it is recommended where such aggregates are being considered that they be tried in trial mixes before the usual specifications are relaxed or changed. more poorly graded aggregates can be used for air-entrained concrete. and cement content on the resulting characteristics of the concrete. No further reproductions authorized.PRICE ON GRADING 581 fractions of coarse aggregate for concretes having various maximum sizes of aggregates and for optimum sand percentages. Conclusions 1. the effect of particle shape and surface texture of the aggregate.5 and 225 mm (3/8 and 9 in. fine.) accomplishes little or no saving in cement and involves difficulties in handling and placing procedures. but none has been universally accepted because of economic considerations. Workable and placeable concretes have been made with aggregates graded up to every maximum size between 9. 2. it is recommended that gradings be required to meet a specification such as ASTM Specification C 33. and reduces segregation in the mix. ASTM Specification C 33 recognizes the effect of entrained air on workability and permits a smaller percentage of fines for air-entrained concrete. the strength of concrete for any given set of materials and grading will follow the water/cement ratio law. Many methods have been proposed for arriving at an "ideal" grading. however. Table 1 shows the reduction in fine-aggregate percentages which may be realized through the use of air entrainment in concrete. C. E. p. and Thompson. "The Strength of Concrete and Its Relation to the Cement. . L. H. March. American Concrete Institute. Washington. Journal. D.. and Gruenwald. 1947. R. R. Vol. 1951. J. American Concrete Institute. 29 Dec. "Grading of Mineral Aggregates for Portland Cement Concrete and Mortars. No further reproductions authorized. A. [14] Weymouth. pp. [21] Tyler." Mineral Aggregates. E. I. Engineering and Construction Department. 59. 1918. C. p. p. American Society for Testing and Materials. N. Part 2. p. E. p. [3] Feret. G. N. Vol.. Vol. "Strength and Other Properties of Concrete as Affected by Materials and Methods of Preparation. Chicago. 1943. W.." Technical Paper No. A. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. 1897. B. R. Sept. [4] Mercer. "The Properties of Concrete Mixes.. [2] Wright. F. [15] Weymouth. 1907. C. National Bureau of Standards.. Vol. Lewis Institute. 444. Tennessee Valley Authority. [13] Weymouth. Aggregate. "Designing Workable Concrete. H. 1. G. A.. D. Copyright by ASTM Int'l (all rights reserved). Proceedings. "Relation of Aggregates to Concrete. A. [20] Blanks. p. 36." Journal. [16] Walker... Stanton and Bloem. 1948. April 1940. "The Laws of Proportioning Concrete. A. R. p. p. 354. and Gates. "Effects of Particle Interference in Mortars and Concretes. 58. "Proportioning of Mortars and Concretes by Surface Area of Aggregates. 1845." Rock Products. 1963. B. Vol. "Effect of Aggregate Size on Properties of Concrete. "Size.. 235.. 818. 844-51. C." Bulletin No. F. A S T M STP 83. F. 1928. Structural Materials Research Laboratory.." Transactions." Proceedings. 67... 1919. 25 Feb." Bulletin No. [18] Walker." Proceedings. M. American Concrete Institute... Part 2. 1923. S. 19. Corps of Engineers. (Ref 11)." Bulletin. J. "Some Theoretical Studies on Proportioning Concrete by the Method of Surface Areas of Aggregates. 1938. [12] Walker. Ill. June 1929..582 TESTS AND PROPERTIES OF CONCRETE AGGREGATES crusher-run aggregate." A S T M STP 22. J. W. [11] Swayze... [10] Abrams. American Society of Civil Engineers. 1933. and it is necessary that the aggregate be separated into its component sizes so that it can be combined in the concrete mixture within the limits of variation permitted by the specification." Engineering News--Record. L.. G. Vidal. B." Journal American Concrete Institute. L. R. 92. Symposium on Mass Concrete. Dec. A.... S.. 1937. E. B.. L. Melbourne Technical College Press. Wallace. 1960. [7] Talbot. Vol. and Ore. F." Proceedings. "Concreting of Norris Dam. S. E. "A Study of Fine Aggregate in Freshly Mixed Mortars and Concretes. "Concrete Mix Design--A Modification of the Fineness Modulus Method. [6] Wig. H. Oct. American Society for Testing and Materials. discussion of paper by Swayze and Gruenwald.. 433. 137. p. Williams. American Society for Testing and Materials." Public Roads. Surface Texture. "Design of Concrete Mixtures.. The Law of Grading for Concrete Aggregates. National Sand and Gravel Association. 18. "Effect of Type and Gradation of Coarse Aggregate Upon Strength of Concrete. 43. [22] Gilkey.. G. and Grading of Aggregates. 2." Bulletin No. Sept. E. American Society for Testing and Materials. 829.. E. and Bartel." Journal. Part 2. F. Vol." Publication SP-6. H. 43. American Society for Testing and Materials. C. N. M. [17] "Standard Guide Specifications for Concrete. and Richart. [19] Kellerman. W.. 26. and Water. Shape. 134. "Effect of Aggregate Size on Properties of Concrete. Treatise on Mortars. G. and Russell. [8] Edwards. Price.4.. 38. W. W. References [1] Price. M. D. 1947. Proceedings. Bulletin de la Socidtd d'Encouragement pour l'Industrie Nationale. University of Illinois. 1938. Proceedings. [23] Higginson. p. [5] Fuller." Department of the Army. American Concrete Institute. [9] Young. Vol. "High Strength Air Entrained Concrete. 1967. 5. U." Journal. "Proposed Synthesis of Gap-Graded Shrinkage-Compensating Concrete. p. [32] "Tentative Interim Report on High Strength Concretes. 1943. 951.. Sun Apr 6 21:45:34 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. 64. p. No. [30] Schmidt. American Concrete Institute. S. Department of the Interior. 17. 48. [28] Concrete Manual 8th ed. p.. R. "Grading and Surface Area (of Aggregates). Proceedings.C. Rue de Teheran.4. A. [27] Li. Vol. Copyright by ASTM Int'l (all rights reserved). Vol. American Concrete Institute. American Society for Testing and Materials. p. 1029.. 62. W. March 1968. Proceedings. Vol. p. 1955." ASTM STP 169. Oct 1967. Bulletin 18. [29] Cordon. p. Sept. D. American Concrete Institute. Shu-tien. 45. Vol." Journal.S. Proceedings. and Gillespie.. L. Proceedings. May 1975. [26] Mercer. 1966. 274. 654. B. 11. Bureau of Reclamation. Aug. H. A. [31] Mather." ASTM'STP 169. "9000 psi Concrete--Why? Why not?" Civil Engineering. Washington. 39. [25] Price. Paris VIII. 60. [34] Guide and Recommendations on Aggregates for Concrete for Large Dams." Journal. Proceedings. p. H. [33] Gaynor. D.. p. W. H. 1963. American Society for Testing and Materials. "High-Strength. 556.. High-Density Concrete. Katharine. France. Aug. William and Hoffman. W. Vol." Publication No. "Grading and Surface Area (of Aggregates). E. ." Journal American Concrete Institute. National Sand and Gravel Association and National Ready Mixed Concrete Association. 64." Journal American Concrete Institute. 1965.PRICE ON GRADING 583 [24] Price. Feb. 404. Commission Internationale Des Grand Barrages. 309. "Gap Grading for Concrete Aggregates. "Variables in Concrete Aggregates and Portland Cement Paste Which Influence the Strength of Concrete. No further reproductions authorized. the coarse and fine aggregate particles. surface area. Surface Texture. clay lumps and friable particles. the amount of surface area caused by the kind and degree of relief. beneficial. if present. Differences in particle shape and surface texture. No further reproductions authorized. Ozol 1 Chapter 35 Shape. prior to the application of the test procedure for their determination. Surface Area. In the hardened concrete. and Coatings Introduction The equidimensionality and angularity of coarse and fine aggregate particles. the degree of adhesion between the particles and cement paste. and the chemical and physical nature of coatings. as between different rock types. and in combination. surface texture. 2 1Principal research scientist. chemical stability of the aggregates. and coatings on. Copyright by ASTM Int'l (all rights reserved). Coatings can also be innocuous or. Their effects may relate to adhesion between particles and matrix. are all characteristics that significantly affect the properties of both fresh and hardened concrete. Md. the shape of the relief and the degree of relief on their surfaces. surface area of. the ingredient proportions. composition. Those properties are influenced individually. or chemical. angularity. and deleteriouslyalkali-reactivesubstances. the elasticity. Copyright9 1978tobyLicense ASTM International www. in turn.STP169B-EB/Dec. Martin Marietta Laboratories. will affect the bulk void contents and frictional properties of the aggregates and. the specification does have limitations on certain substances which. 2Organic impurities. and the mechanical behavior of the cement-aggregate interface. materials finer than 75 /~m (No. Baltimore. and the distribution of stresses within the concrete are influenced by: particle orientation. depending on their physical nature and mineral. conceivably. A. and contribution of excess material to the plastic concrete mixture.org . However. 21227. 200) sieve. the compressive and flexural strength. surface texture. and economy of the unhardened concrete mixtures made from them. by the equidimensionality. mechanical properties. might have been present originally as coatings. 1978 M. ASTM Specification for Concrete Aggregates (C 33) does not explicitly contain any limitations on shape. Sun Apr 6 21:45:36 EDT 2014 584 Downloaded/printed by Universidade do Gois pursuant Agreement. Coatings can be responsible for various detrimental physical or chemical effects in both plastic and hardened concrete. and coatings.astm. where conditions favor. the development of such tests would further the widest and best utilization of aggregates that vary in those properties. solid waste. fine aggregate. for example. their identification by standard mineralogical techniques. Taken altogether. or ought to be. ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295). and surface area [3-9]. surface morphology. individually or in bulk. most siliceous natural sands and gravels. and surface area. roundness. caliper [1. the foregoing will be germane and comple3 The italic numbers in brackets refer to the list of references appended to this paper. void content. and entrained air for the most economical mixture for a particular purpose will work toward the fullest utilization of the natural geological materials resource. Moreover. may need mixture proportions (that is. There are no ASTM standard test methods for determining the surface area of particles. the shape of the aggregate particles has been intentionally or incidentally a factor. Copyright by ASTM Int'l (all rights reserved). and particle sphericity and angularity. it does not necessarily follow that this aspect of the specification will. changed when sufficient accumulated research and testing information are available from which to extract and organize numerical limits on those properties for specification purposes. demonstrate that concrete suitable to a purpose can be made with coarse and fine aggregates of very different sphericity. for example. surface texture. Rather. water. for example. combining admixtures as needed) tailored to the aggregate characteristics. cement.OZOL ON SHAPE 585 The ASTM Test for Index of Aggregate Particle Shape and Texture (D 3398) is used for determining a numerical index of aggregate particle shape and (surface) texture based on the weighted average void content of specified sizes which have been subjected to two different compactive efforts. if they are. The background research and comparisons. No further reproductions authorized. Thus. ASTM Test D 3398) method. investigations in past years. particle shape.2] 3) or indirect (for example. Concrete made with coarse or fine aggregates of rough surface textures with less equidimensionality and greater angularity than. surface texture. as measured by any present direct (for example. calls for the determination of whether exterior coatings are present on aggregate particles and. . which often are of irregular texture and shape. The exercise of that tailoring for the determination of the most suitable grading and proportions of coarse aggregate. in which. although present ASTM standards mention almost no tests useful for the comparative performance evaluation of aggregates differing in particle shape. alternative. which will have been prerequisite to test development. or other unconventional materials. surface texture. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. will in turn help to elucidate further the relationships between concrete properties and the aggregate properties of surface area. it will lead to the best use of substitute. Although present ASTM specifications are silent regarding any quantitative limits to be placed on. need to be reexamined with respect to those properties in light of their anticipated future value [I0]. And. but in principle having a subtle correlation: the kind of intrinsic coating present on a particle and its shape. is a quantity that is fixed by shape and surface texture when the sizes of the particles are fixed. in that a process which affects the expression of one property may. roundness. The surface texture and the amount of surface area present may then have controlled both the volume of the coating and the degree of adherence of the coating to the particle at the same time that other geological factors specific' to the deposit determined the mineralogy or chemistry of the coating. Coatings are a separate issue. The surface area of an individual particle. promote or inhibit development of the others. concurrently. Theoretical Discussions The concept of particle shape incorporates three geometrical ideas. which are distinct and separately definable properties in the abstract or mathematical sense. The fundamental attributes of particle geometry are shape and surface texture. all of which would have the same surface texture--if shaped by the same tools and methods. The discussion of shape herein is concerned with shape from the standpoint of particle proportions and overall object geometry. in principle. and area (especially with regard to crushed stone). the stone or aggregate material could be carved or "sculpted" into any shape. and area can each be related back to the geology of the deposit (especially with regard to sands and gravels). both natural and artificial. They may be linked properties in the geological sense. based on the degree to which the volume of a par- Copyright by ASTM Int'l (all rights reserved). No further reproductions authorized. the subject of surface texture is treated separately. namely. sphericity. and form. That is. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. in practice unrelated to questions of particle shape. or the total surface area of an aggregate. Sphericity is a measure of how nearly equal are the three axes or dimensions of a particle. One investigator [11] includes a fourth property. surface texture. which will address the concerns of interested agencies and individuals that "good" aggregates are becoming less available and that therefore aggregate materials. surface texture. surface features ( = surface texture) under the broad heading of particle morphology. heretofore considered marginal in various physical and chemical properties. Shape Definitions. .586 TESTS AND PROPERTIES OF CONCRETE AGGREGATES mentary activites. insofar as the surface texture of a rock particle is more particularly a function of the way the intrinsic mineralogical properties cause the material to fracture or to be modified by chemical or physical weathering. where lip = actual volume of the particle. then. and S is the actual surface area of the particle itself. is the volume of the circumscribing sphere of diameter De. If s is the surface area of a hypothetical sphere of the same volume as a particle. calculated from the direct measurement of Des.0. That relation derives from the expression--developed by Wadell [13] and taken as the fundamental equation--relating the volumes in question. Sphericity and roundness can be visualized conveniently. 4 that is. 3 sphericity = "~/-Vp/Vcs. The spheres may or may not be concentric. S(r = ~Vp/V~s -- r/6D. the sphericity. and short axes of the particle. but not defined rigorously. medium. the ratio s / S is the sphericity [13] ( = 1 for a spherical particle and ---. and Ve. the diameter of the sphere of volume Ves is Des. = D n/Dc~ . 3 ~.806 for a cube). Vp may be measured by displacement in water. where D. = 4The diameter of the sphere of volume Vp is D. the particle itself is a sphere with both a roundness and sphericity of 1--the maximum value. and De. by the analogy of an irregular solid within which is a sphere of the largest possible size and around which is a sphere of the smallest possible size. or of the smallest circumscribing ellipsoid. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. / D c s . When the spheres coincide. 7r/6D ~s3 Copyright by ASTM Int'l (all rights reserved). Roundness is a measure of the sharpness of the edges and corners of a fragment. is the diameter of a sphere of the same volume as the particle (nominal diameter).. since a sphere has the least surface for a given volume. and Vc. Proportions or dimensions are more directly determined than surface areas. Form or shape factor distinguishes between particles of the same numerical sphericity but of different axial proportions. and an expression more practically suited to measurement is: Sphericity ff = D .OZOL ON SHAPE 587 ticle fills the volume of a circumscribed sphere whose diameter is the maximum dimension of the particle. have been proposed and used for sphericity. No further reproductions authorized. D.. may be calculated from Vp ( D . almost all based on the geometric properties of a sphere as the standard reference form. or the degree to which the contour of a particle fits the curvature of the largest sphere that can be contained within the particle. is the diameter of the circumscribing sphere (equals the largest dimension of the particle) [14]. The form of Folk [11] or the alternative shape factor of Aschenbrenner [12] is a measure of the relation between the three dimensions of a particle based on ratios between the proportions of the long. Various alternative mathematical expressions. The congruence of the particle boundary to the inner sphere is an indication of roundness and its coincidence to the outer sphere. ~b = 3~ (Tr/6)l'i's(Tr/6)13 = 3 ~ i.716 since De. and D. I = x/3. and s are considered to be determined by direct measurement (that is.9 if l.96. Vp Vcs D. Use of the cube root of the volumetric ratio gives a sphericity value of 0.0 0..1 0. in hydrodynamic behavior. and short (s) dimensions (as if the particle were enclosed in a circumscribing triaxial ellipsoid rather than a sphere) to approximate D . and s are measured from the circumscribing ellipsoid which in this case is a sphere. bDiameter of sphere of volume Vcs. T/~BLE l--Wadell sphericity values corresponding to the ratio Vp/Vcs. Table 1 illustrates that for some values of Vp relative to Vcs at the unit volume.. Note that from S = D . the long diagonal of the cube.9 1. i. is equal to v~. the sphericity is "high" for particles that occupy only a small fraction of Vc. By the Krumbein formula. i. the same measurement may be accomplished without direct physical determination of V.. intermediate (i). the sphericity of a cube is around 0. .984 1. Sneed and Folk [16] define another measure of sphericity that relates particularly to settling behavior in a fluid.24 Wadell Sphericity S = Dn/D~s Vp/vcs 0. a cube has a sphericity of 0. Since particles tend to orient.6) and is 1.24 1.794 0. faithful only as Vp approaches V.9 "Diameter of sphere of volume Vp. or ~Vp/V. .1 0. 3 and to define sphericity as S.0 if l.sl2 Literal interpretation of the numerical value of sphericity as the simple proportion to which the volume of an irregular object fills its circumscribing sphere is. = ~f6Y~r. s : x/2.24 1.5 0.5 0.. but Folk [11] points out that a rod settles faster than a disk of the same volume although the respective Wadell sphericity values might indicate the opposite. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Settling velocity is supposed to increase with particle sphericity.5 0. For low relative values of Vp. with the maximum projection area. but may possibly be of some relevance regarding particle behavior in plastic concrete.46 for a particle that is only one tenth of the volume of the circumscribing sphere. Krumbein [15] used the product of the long (l)..464 0. / D . Essentially..0 1..197 1. i is ~ 1. the plane with the l and i axes perpendicular to the direction of motion of the fluid.806)." Dcsb 0. No further reproductions authorized. by the above definitions.575 0.588 TESTS AND PROPERTIES OF CONCRETE AGGREGATES ~rVJ0.0 1. they define maximum projection sphericity as: Copyright by ASTM Int'l (all rights reserved). A flat oblate form with two dimensions very much longer than the third may have the same numerical sphericity value as a long prolate form with two dimensions very much shorter than the third (Fig. . and size of fragments.TABouR~ L~I IV ~!ii~!i::e d Roller ]0 Rod . for a mathematically detailed exact method for characterization of grain shape. may be used to calculate the Riley Sphericity = D~Di/Dc where Di is the diameter of the largest inscribed circle. oblate. 1).0 jSHORT I _I~ERMEDlATE FIG.20].i. No further reproductions authorized. A projection. when used in conjunction with the Wadell Sphericity. and by Ehrlich and Weinberg [18]. or cross section. -Fl~: ='andElong~ 12~ ~.. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The evaluation of sphericity ( = equidimensionality) by the volumetric approach does not yield.0 z S __ 2~m III -. This formula compares the maximum projection area of a given particle with the maximum projection area of a sphere of the same volume. I Bladed. especially at low numerical sphericities. unique values for particles of decidedly different geometric proportions. Copyright by ASTM Int'l (all rights reserved).OZOL ON SHAPE 589 ~ss27~. and bladed forms is made possible by means of manipulations of the axial lengths or proportions of the particle. Distinction between the prolate. as in a petrographic thinsection. which. Maximum projection sphericity was used in a convenient method developed by Burke and Freeth [17] for determination of shape. and others [19. Synonomous descriptive terms are given for the four shape categories. of a particle.=. equant. and Dc is the diameter of the smallest circumscribing circle [21]. The hyperboloid arc is a line of equal (Wadell) sphericity. 1--Shape categories of Zingg (~-IV) defined by ratio of two thirds for i/l and s/i. can uniquely define 1. sphericity. Sneed and Folk [16]. Values of F > 1 represent prolate forms with i approaching s. strictly speaking. or of the circumscribing triaxial ellipsoid of the Krumbein formula. which then is equal to ls/i 2. equidimensional. and a cube is used as the illustration of the zero roundness but high sphericity analog of the sphere. excluding roundness and surface texture.590 TESTS AND PROPERTIES OF CONCRETE AGGREGATES the particle geometry. No further reproductions authorized. it is more convenient to use the two-dimensional projection or section of the particle (as in Riley Sphericity). plot s/l versus (l -. Roundness. roundness. Note in Fig. a cube is not. For measurements. 1 that rounded and unrounded ( = zero roundness) versions of the illustrated forms may have the same sphericity and shape values. can define four shape categories when fixed values are assigned to those ratios. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or to the nominal radius of the particle. that is reflected in its Wadell Sphericity value as calculated by the volumetric method. values o f f < 1 represent oblate forms with i approaching l.i)/ (l -. This additional idea permits the gross particle geometry. and short (s) axes of the particle. the shape factor of Aschenbrenner [12]. using a triangular diagram. 3). The ratio value used by Zingg. Although the forms within the upper right cell of the shape category diagram are designated by some authors as equant. ideally is the ratio of the average radius of curvature of the corners and edges of a particle to the radius of the maximum inscribed sphere. The ratio p / q is defined as the shape factor. and the resulting shape classes are illustrated in Fig. which would be defined by the intersection of a sphericity curve with a point of given i/l and s/i values. is the average radius of curvature of all the corners divided by the radius of the largest inscribed circle: p = E (ri/R)/N. and s/i the flatness ratio. not easily measured accurately. or equiaxial. And non-orthogonal forms with planar surfaces intersecting in sharp obtuse or acute angles also have roundnesses close to zero with radii of curvature that are small and. to be completely specified by (Wadell) Sphericity and (Aschenbrenner) shape factor (see Fig. intermediate (i). F. Pettijohn [23] points out that a cylinder capped by two hemispheres also has a roundness of 1. A sphere has a roundness of 1. and the four shape classes of Zingg [22]. p. q.s) (Fig. 2). and that is the basis of the definition. Asehenbrenner [12] designed i/l the elongation ration. Thus. producing a different scheme for the combined specification of form and sphericity. more importantly. quantitative roundness measurements Copyright by ASTM Int'l (all rights reserved). For that reason. as defined by Wadell [13]. equidimensional. or angularity. when plotted versus the short to the intermediate intercept ratio (s/i). Zingg showed that the ratio of the intermediate to the long intercept (i/l). may be used in various ways to define the related measures of f o r m of Sneed and Folk [16]. 1. 2/3. . All orthogonal forms have a roundness of zero because of their infinitely small radii of curvature. the long (l). That is. Shapes o f particles falling at various points on the triangle are illustrated by a series of blocks with axes of the correct ratio.. 2--Particle shape as deft'ned by Wadell sphericity (~b).67 ELONGATE L-'I/L.73 BLADES ~ .. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement..~(~l~ ~ ~ .50 ----.4 ~.--.-------i(~ EJongaled) 0' 591 ~F : 1. ~ / I/'X\\\k"x /% 'U tJ6 (Fiat and ... COMPACT / <>-/ ... ~ -= sphericity.. Copyright by ASTM Int'l (all rights reserved). o.8 :]. l//U(' i'L'}(\\\~ \ ~ 't/\ ~ ' ~ -~ o.aF : 1.------.S. and Asehenbrenner shape factor (F).~..00 . 3--Form triangle. ? "~ \ 1 .OZOL ON SHAPE Disks IFiat) Spherical (Neither Flat nor Elongated). all blocks have the same volume. p = sii FIG. From Sneed and Folk [16].F = 3. No further reproductions authorized.6 :0. PLATY .~ 0.~ FIG... Independence o f the concepts o f sphericity and f o r m may be demonstrated by following an isosphericity contour f r o m the disklike extreme at the left to the rod-like extreme at the right. .2: ~ 0..Rods (Elongated) ~______.01 'FLATNESS RATIO.00 . the ratio of the average radius of curvature of the protrusions and convexities of the particle to the radius of its maximum inscribed circle.5 0 or 0. 4).i . . Copyright by ASTM Int'l (all rights reserved). for example. In principle.23]. sphericity and roundness are unrelated geometrically. . 0 0. No further reproductions authorized. Generally. in natural sediments--of the same sort as natural sand and gravel deposits used for aggregate--investigations have found sphericity and roundness to be correlated closely and also each to be a function of size. but the relation statistically is such that. though not necessarily to the same degree.0' 03 lID -'l- ~ o. . The better rounded grains are the more spherical. or both. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.592 TESTS AND PROPERTIES OF CONCRETE AGGREGATES at a level of accuracy and reproducibility that can discriminate realistically small differences in roundness would best be done on sections or projections that do not have sharp corners but do have a degree of roundness to begin with.9 ROUNDNESS FIG. but the same natural forces that produce roundness also produce sphericity. Then the definition might be better worded as: " .9 >0 t~ hi "1- IP (~ 0." Roundness and sphericity evaluations of individual particles are obtained more commonly by use of visual guides which may assign numerical values or descriptive terms. and. a sphericity increase of 15 percent might coincide with a roundness increase of 125 percent [23]. in plotting roundness versus sphericity. coarser grains round easier than finer ones. 4--Visual chart for estimating roundness and sphericity of particles [24]. to silhouette charts or photographic charts for both pebbles and sand grains (Fig. a small change in sphericity is correlated with a large change in roundness. and roundness increases with size [11.3 ~ o. the original particle shape is controlled by largerscale structural features of the bed rock. shaly partings. the result of factors associated with transportation and abrasion and. The form (including shape factor of Aschenbrenner) and sphericity of both sands and gravels and crushed stone are primarily the result of: (1) the degree of anisotropy of the material (the result of bedding planes. the abrasion. mineral cleavage. which were then exploited by glacial action. schistosity. In the case of natural sands. stream action. Secondarily. etc. for crushed stone. all at the same starting sphericity. Experiments by Thiel [25] on the abrasion of coarse and fine sand-sized materials. gyratory. that is. the more flat or elongated the product--slightly more so if the machine is of the compression (jaw. including two gravels and three crushed stones. schistosity. the greater the reduction ratio. That effect is less pronounced with impact. faults. and the final shapes of the particles are influenced strongly by preferred orientations of any sort contributing to anisotropy. In a study of the shape of various. Generally. . Equigranular rocks with no preferred orientations tend to yield more cubical particles on crushing. additionally. the original particle shape. as supplied. The characteristics of crushing equipment also influence the particle shape of the rock being crushed. and mechanical (frost) and chemical weathering. type machines. With crushed stone. they are. attrition. In the case of gravels. and Copyright by ASTM Int'l (all rights reserved). showed at the conclusion a clear correlation between size and sphericity. for sands and gravels. or cone crusher) type. or impeller. the result of the action of crushing and sizing equipment on the shot rock of the muck pile. fractures. cleavage. Most of the shot rock requires further size reduction by crushing. No further reproductions authorized. and bedding planes. its shape prior to transportation. Rocks with bedding. are a function of the size and frequency of the cracks initiated by the action of shock waves on the smaller-scale flaws and discontinuities of the rock--approximately of the order of magnitude of the grain sizes. the analogous "original" particle shape is that produced by blasting of the bedrock. Conway [26] found that sphericity for all increased with increasing sieve size. the shape prior to the action of agents inducing roundness and sphericity.) and (2) the original shape of the particle. mineral cleavage. that is. rubbing. coarse aggregates. chipping. Rounding of sand and gravel particles is chiefly the result of those geologic factors that were of secondary importance in contributing to their form and sphericity. was probably most strongly controlled by its mineral grain shape in the parent material. that is. which would produce more nearly cubical particles at equivalent throughputs. may yield particles more elongated or flattened than equidimensional.OZOL ON SHAPE 593 Sphericity increases with size but the relationship in naturally occurring materials is less pronounced than with crushed materials. etc.. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. such as joints. Those shapes are a complex function of the influence of the large-scale structural features of the bedrock but. following an earlier reported procedure of Huang [29]. Measurement Methods that have been used at large for obtaining a particle shape evaluation. (6) measurement of the radii.7. all edges sharp. which would tend to induce fracturing.78 and of roundness from 33. the sand with the lowest sphericity had a roundness of 49. respectively. most of the methods used are based on the principle that the volume of voids in the aggregation changes according to the axial ratios of the individual particles. When it has been desired to evaluate the shape of individual aggregate particles in concrete research and technology. 66. Chamberlin [30] determined sphericities according to Krumbein's formula for 25 sands by using a petrographic microscope to measure the lengths of the principle axes of 100 particles from the No. and 100 according to whether the particles had. radii of curvature. by rectangular openings (actually or in effect). No further reproductions authorized.594 TESTS AND PROPERTIES OF CONCRETE AGGREGATES (possibly) solution incident to their transportation and to the site of deposition. When it has been desired to obtain an evaluation of the overall. (4) measuring the time required for material to pass through an orifice. (5) determination of the surface area to volume ratio. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.7. as developed by the Corps of Engineers [1] Copyright by ASTM Int'l (all rights reserved). (3) sieving. of a fraction that has been sieved by square openings. The sphericity may be determined by the application of Wadell's defining equation.74. The volume also changes according to particle angularities and ~urface textures. <50 percent of edges rounded. The proportional calipers. and that aspect has been examined by Tons and Goetz [27] and Ishai [28] and is discussed later. The roundability of particular mineral or rock fragments depends directly on their hardness and toughness and inversely on the presence of cleavage or cracks. the methods used mostly have been based on measurement of particle dimensions rather than their volumes.1 to 55.68 to 0. include: (1) visual comparison of the particle silhouette or photograph with standard shapes. or photographs of particles. >50 percent of edges rounded. . or statistical. 33. 14 • 28 size fraction of each. He determined the average roundness value for the same fraction of the sands by assigning roundness values of 0. shape characteristic of an aggregate. with individually measured long dimensions and weights of the particles and volume calculated from the bulk specific gravity of the aggregate. and diameters of particles. The sand with the highest sphericity had the lowest roundness. or all edges rounded. the highest roundness sand had a sphericity of 0. Conway [26] used this procedure on coarse aggregates. (2) measurement of the percentage of voids at one or more compactive efforts. or index. The range of sphericity was from 0. negating what rounding had been accomplished. Laughlin [32] evaluated sand "shape" by a straightforward application of Wadell's roundness formula. In those devices.55 for a crushed chert and an artificially rounded limestone. They are tested likewise for length (elongation) against a distance of 1. of slightly different construction. . The results were expressed as the statistical correlation of each grain to the most similar standard shape.6 times the mean of the upper and lower sieves of the particular fraction. 8. Burke and Freeth [17] used projected silhouettes of gravel particles placed on a grid to measure dimensions for calculation of maximum projection sphericity. there is a Corps of Engineers method [31] that uses a stereoscopic microscope and requires the determination of length. and 100) sieves. respectively.028 by 0. and elongated particles in. The specification requires that the sum of the flakiness and elongation indexes not exceed 35 percent.36 mm.).0949 and 0. and thickness of 300 particles in each mesh size. Particles in each size fraction of the sieved aggregate are gaged for thickness (flakiness) by determining whether whey will pass through an elongate slot 0. 50. and 150 /zm (Nos. is essentially an individual particle measurement and defines both a flakiness and elongation index.14 in. The weight percent of the material passing the flakiness gage is the flakiness index. width. as well as to the shape that the total sample most nearly resembled. 8 by No. Heigold and Lamar [35] experimented with a novel method.18 mm (0. A method used by the Ohio Department of Highways [34] is similar in concept. Flat. measure particles individually.36 by 1. 16. respectively. The length of the minor axis was obtained by rotating the fragment about its major axis until the minimum silhouette width was seen. CorreCopyright by ASTM Int'l (all rights reserved). and the weight percent not passing the elongation gage is the elongation index. 30. Particles with length to width (l/w) or width to thickness (w/t) greater than three are classed as elongated or fiat.0474 in. 600/~m.34 to 0. 300 #m.556 mm (0. Methods for Sampling and Testing of Mineral Aggregates. The method for particle shape determination in British Standard 812. Sands and Fillers. respectively) fraction are determined by passing the material over a sieve with 0. the other automatically closes to a multiple of the measuring jaw. They measured the intercepts of photographic silhouettes of 10 by 14 mesh grains of calcite and 17 different limestones on a radial grid of 16 equally spaced rays (diameters) and used a computer to compare data obtained with reference data on a variety of geometrical standards. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.OZOL ON SHAPE 595 and Schulze [2]. using enlarged photographs of grains retained on 2.8 times the mean of the sieves using pegs which are set the prescribed distance apart on a board. His values ranged from 0. 16 (square openings 2. thin. when one dimension of the particle is gaged by one set of jaws. which depends on availability of computer data processing.7112 by 3. the No.18 mm. based on Markwick [33]. the same criteria are applied to the results of the proportional caliper tests on coarse particles. No further reproductions authorized. For fine aggregate. for example. 1.) rectangular openings. A different graphical approach was employed by Mackey [36] who compared the outline of the particle to that of a perfect ellipsoid and assessed the angularity of its periphery by assigning values to interior angles of points and angles subtended by arcs. or the standard shapes of Rittenhouse [41]. The method was applied to determine the effect of particle orientation on the measurement of the shape and texture of particles exposed in precisely oriented sections of two concrete prisms made with elongated glass rods and natural gravel.20] developed a further modification of the Fourier m e t h o d of Ehrlich and Weinberg to express more precisely the total roughness of the particle profile as the sum of two separately measurable shape and texture factors. Depending on the object sizes. as the coarse aggregates. sphericity and shape factor. such as Fig. No further reproductions authorized. . elongated and smooth shape. the result is expressed as a shape equation. The image is displayed on a cathode ray tube. Czarnecka and Gillot [19. roundness or form was not attempted. Copyright by ASTM Int'l (all rights reserved). for example. utilizing coordinates of peripheral points. the values do not differ significantly for differently oriented sections of the concrete prism. Where the aggregate has an "extreme. When the shape of the particles does not induce their preferred orientation. a two-dimensional chart. or to photographs and silhouettes of coarse or fine aggregates.(or smaller-) sized materials. the orientation of the particle cross section affects the values of the shape and roughness coefficients. Automatic image analysis is applicable to sand. They carried out a Fourier series expansion of the radius about the center of the mass. the estimation of sphericity and form would require the same assumptions as the estimation of sphericity from. respectively. is assumed. the method assesses mainly angularity and roughness. the image for processing is obtained by a television camera attached to a microscope or to a low-magnification macro lens." that is. 4. and values accumulated for the various curves and angles of the particle outline are subtracted from that value to give the shape factor for the grain in question. The necessary equipment is marketed by several microscope or instrument manufacturers. scanning lines and the gray scale of the image are the basic measuring tools. A related and mathematically more elaborate approach was developed by Ehrlich and Weinberg [18] to describe grain shape. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.596 TESTS AND PROPERTIES OF CONCRETE AGGREGATES lation of the results with other existing measures of sphericity. Since a gross particle geometry. coarse aggregate sizes. The estimation of roundness by this technique presents no theoretical problems. that is. and measurements of both shape and volumetric parameters are obtained by a variety of electronic manipulations. The shape factor of the reference ellipsoid is 1. Computer processing for automated analysis of grain images is described by Mueller and Hunn [37] and others [38-40]. The measurements were made on the twodimensional maximum-projection-area-grain shape.0 by definition. The specific gravity of the sands must be known or determined. . Bulk methods for particle shape measurement are applied with equal convenience to both coarse and fine sizes. and 30 by 50. sand) which was 1. Values for various kinds of sands--natural sand. Wills used equal amounts of three sizes: 8 by 16. the highest was 1. for a natural silica sand and a crushed stone sand.) diameter orifice with that of a standard smooth.57 (flow rate = 19. Huang [29]. On the basis that the interparticle friction of aggregates of irregular particle shape (low roundness and high roughness) is great compared to the internal friction of aggregations of smooth. are done most conveniently on coarse aggregates. Wills [6]. The flow rate of the sands (R).4 to 23. rounded sand of the same size. was 1. .0 by definition. produced by vibrating the loosely compacted sample. produced by the fall of the material from the orifice into the container. Bennett and Katakkar [46] used the method in a study of 12 sands. and Ishai and Tons [28]. For the fine aggregate tests. A representative suite of time index values was obtained with this method by Malhotra [45] for nine natural and seven crushed sands. and then at dense compaction. The lowest time index.. The greater the departure from equidimensionality and roundness.05 (flow rate = 13.525-mm (3/8-in. Shergold [44]. for practical reasons. Rex and Peck [43] developed a test for comparing the flow time of a fixed quantity of unknown sand through a 9. combined. ON SHAPE 597 Direct physical measurements on individual particles. is determined and expressed as a time index: Runk. Their results. and experimentally prepared sands--ranged from 48 to 59 percent [42]. and g : bulk specific gravity of the aggregate. The size fractions used are 8 by 16. determined independently on coarse particles of the same rock. respectively.. No further reproductions authorized. the higher the void content. who collected the samples for void content determinations by means of the orifice flow method of Rex and Peck [43]. spherical particles. 16 by 30. applied to both coarse and fine aggregates. A similar method. for a rounded natural sand. expressed as s/lO0 cm 3 of solid sand volume rather than as time index. v = volume of cylinder (cm3).i s used as an index of particle shape. in s/100 cm 3 of absolute sand volume. excluding the standard (Ottowa I11. replenishing with additional aggreCopyright by ASTM Int'l (all rights reserved). In the National Crushed Stone Association method. . was used by Wills [6]. Void contents were determined by weighing each size first at loose compaction. ranged from 15. The percent voids = 100 (1 -. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.7. Rex and Peck [43]. stone sand. for a laboratory-crushed coarse grained granite.OZOI.(w/v. . the percentage of voids in specified size fractions (each tested separately) in a loosely compacted condition--produced when the sand falls into a cylindrical cont a i n e r .g)) where w = weight of sand in cylinder.3). the value reported is the average of the determinations on the three fractions. 16 by 30. Illustrating that category of test method are those used by Gray and the National Crushed Stone Association [42]. and 30 by 50.9). /Rstandard. where w = weight of dry aggregate in the test cylinder.weight of water to fill cylinder. the percentage of voids for each fraction is obtained by filling the mold in three courses. Void content at dense compaction was determined independently by ASTM Test for Voids in Aggregate for Concrete (C 30). 3/4 by 1/2 in.75 mm (1 by 3/4 in.25 Vlo -.48]. No further reproductions authorized. The coarse aggregate samples for testing contained equal amounts of four sizes: 25. . Void values at loose compaction ranged from 50 percent for a partially crushed mica schist sand to 40 percent for a well-rounded smooth glacial sand. S ---.( W / S . generally after Huang [29. The correlation between the two methods was excellent (coefficient >0. was constructed.) high).g)]. The particle index. respectively.1 mm. relates the two void percentages by the expression Ia = 1. a large cone (571. and determining the net weight of the aggregate.0.525 to 4.5 mm (22 1/2 in. Percentage of voids is calculated from: V. 19. and V = volume of mold (ml).7 by 9.7 mm. After the sample is separated into nine sizes between 19.9). 200) and the bulk dry sp gr of each size is determined.) and 75 #m (No. A related technique by Shergold [44] computes angularity number: A N = 33-.. 12. the opposite was true for smoother rounded materials for both coarse and fine aggregates. c ---. percent = [1 -. Wills expressed orifice flow rate results in terms of time/absolute volume of material rather than as the time index of Rex and Peck [43]. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.598 TESTS AND PROPERTIES OF CONCRETE AGGREGATES gate.4 by 19. Void contents at loose compaction ranged from 47 percent for crushed limerock to 39 percent for a smooth-surfaced. each rodded by 10 strokes. V)] • 100. the index (Ia) obtained is a function of the original percentage of voids and the change in the percentage of voids produced in a single-sized sample at two compactive efforts. and 3/8 to No.525 ram. 4). the value found by Shergold for very well-rounded. and 9. whereas.1 by 12.(w/c. For assessing particle shape and surface textures of coarse aggregates. sufficient to hold approximately 59 kg (130 lb) of sample.0.100 [1 -. singlesized beach gravel. In ASTM Test D 3398.32. At dense compaction. well-rounded gravel. the same materials were 41 percent and 32 percent. voids at dense compaction were 42 and 33 percent. The same procedure is repeated with 50 strokes to obtain the higher degree of compaction. angular aggregates had the highest orifice flow times and void contents.25 Vs0 . The constant 32 was derived empirically and represents the porosity of smooth uniformly sized spheres at zero compactive effort. roughtextured. A test method based on void content and orifice flow similar to the NCSA and Wills methods is used in New Zealand [47] and employs the complete gradation of the sand.bulk sp gr. The A N thus indicates the percentage voids ratio in excess of 33 percent. respectively. and again striking off and weighing. where W is net weight of aggregate at either 10 or S0 tampings per layer. 1/2 by 3/8 in.05 mm (3/4 in. Bennett and Katakkar [49] measured the (Shergold) Copyright by ASTM Int'l (all rights reserved).. and g is apparent sp gr of the aggregate../~. An aggregate of rough-textured but equidimensional particles could conceivably have the same void content as an aggregate of flat and elongated but smooth-surfaced particles. However. An advantage of measurements of individual particle-shape characteristics is that the kind of deviation from equidimensionality may be isolated and identified as to size fraction and lithology. In British Standard 812. there is evidence that the dominant characteristic affecting void volume in the Shergold procedure. and by analogy in the Huang method. "Geometry of irregular particles can be characterized satisfactorily by an ellipsoid. or combined coarse and fine aggregate. for natural quartz sand and crushed stone sand (presumably igneous rock). Although it nominally expresses aggregate angularity. recalling the definition for sphericity of Krumbein [15]. The A N values ranged from 15 to 30. V = volume of cylinder. and surface texture may yield the same numerical void content. is particle angularity [50. No further reproductions authorized. However." They illustrate Copyright by ASTM Int'l (all rights reserved). and S = sp gr of aggregate.27]. form (or shape factor). Bennett and Katakkar [49] stated that the three measures--time of flow. as well as to their sphericity and form (or shape factor). the method for A N is drived from Shergold's work but calculates the angularity number by the formula: A N = 67--100 [A/(V • S)] where A = mean mass of compacted aggregate in cylinder. . but all evidently more angular than the most angular reported by Shergold. and specific surface--were closely interrelated. the product always includes contributions traceable to angularity and surface texture of the particles. the Shergold procedure basically assesses the same sort of property as the previously described particle shape tests which used void content or flow time. basically void content methods.44. However. bears directly on the mortar or paste requirement. Tons and Goetz [27]. Numerous combinations of sphericity. state. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No matter what the form of the results of all these methods.OZOL ON SHAPE 599 angularity number for twelve sands of different geological and shape characteristics. angularity number. should that be desired. do not conveniently allow that distinction. Explicit relationships quantifying the extent to which surface texture and the three attributes of particle geometry separately influence the voids ratio of an aggregate do not yet exist. The bulk methods. roundness. bulk methods of particle shape evaluation are germane to the practical task of proportioning the ingredients for concrete because the voids ratio of the particular coarse aggregate. and any one may be considered to be a satisfactory index of particle shape. respectively. Aggregates H and E have almost the same characteristics except for roughness factor. which has next to the highest void content in the suite. it may be reasoned that particle angularity--the presence of (sharp) edges and corners--is a more important determinant of bulk void content than axial proportions or surface texture. No further reproductions authorized. CAngularity number (percent voids minus 33) ranged from 1 to 10 in [50.6 4. crushed granite A.51. but A produced the lowest void content in the suite because it is more rounded. angularity numbers. bAverage elongation index.2 to 16. 5 l ] . Data excerpted from Kaplan [ 5 0 .600 TESTS AND PROPERTIES OF CONCRETE AGGREGATES mathematically that one-size ellipsoids pack like spheres. Theoretical Considerations Surface texture of an aggregate particle is the degree to which the surface may be defined relative to arbitrary numbers as being rough or smooth (loosely referring to the height of the asperities) or coarse grained or fine Copyright by ASTM Int'l (all rights reserved).4 2. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. may be examined to deduce the stronger influence of a factor other than particle proportions on the aggregate void contents (see Table 2). It follows that flatness. indicating that surface texture did not contribute to A N of H. crushed basalt F~ Eb E + F AN c RoughnessFactord 9 8 34 31 !8 24 42 42 27 32 76 73 9 1 9 9 16. who measured the elongation. flakiness. On the basis of the above information. and rough particles are also angular.6 in Refs 50. and surface texture for a suite of 13 coarse aggregates.1 aAverage flakiness index. dMethod of Wright [52] ranged from 2. elongated. but changing roundness had a direct effect. dimensional and flat and elongated particles may produce equivalent void contents. Surface Texture and Surface Area Definitions. Aggregate A is more flat and elongated than K.2 13. and rough surface coincide with high void contents only when the flat. It is evident from comparing aggregates K and E that both equiTABLE 2--Angularity number versus properties of aggregates. natural quartzite gravel E.51]. Aggregate K. . elongation. Shergold's measurements [44] showed that decreasing the average sphericity of an aggregate by increasing the amount of flat particles from 20 to 40 percent produced little change in the percentage of voids. crushed flint gravel H. thus producing voids percents i d e n t i c a l to those of spheres for each of the three ideal states of packing. also called roughness or rugosity.414 ( : x/2. where A is the true (real) surface area. and the base of the large triangle appeared as a smooth line. include the lateral and vertical periodicity or irregularity of the roughness. Additional elements of surface texture. P = profile line. that is. In this illustration R : 1. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. is in Ref 55. have more surface area than a smooth surface of equivalent dimensions--it may or may not. and (2) the amount of surface area per unit of dimensional or projected area. The latter property. then roughness factor R =. 5--Independence of roughness and surface area: illustration of roughness factor. A more elaborate demonstration of the independence of roughness and surface area. A rough surface (in the sense of degree of relief) does not. The two properties are not related functionally but depend on the relative amplitude and frequency of the asperities on the surfaces being compared. If the total length of the profile of the larger triangles represents A. ipso facto. Profile P2 is both rougher and has more profile line (surface area) than P3.OZOL ON SHAPE 601 grained (loosely referring to their spacing). geometric. For example. but almost invariably involves some measure of the deviation of a profile of the surface from a hypothetical reference surface.P / L : A / a . R = A / a . 12 LI. Copyright by ASTM Int'l (all rights reserved). By projecting the sides of the smaller triangles to intersect the legs of the larger enclosing triangle (left) it is seen by inspection that the total profile length of the smaller triangles equals the profile of the enclosing triangle. If the smaller triangles were microscopic. the asperities are twice as high. 54] as the roughness factor. since all triangles are 45 deg). ~I" ~T LT hi L FIG. the roughness of segment L~ is greater I. as well as their morphology. the result would be exactly the same. Two independent geometric properties are the basic components of surface texture: (1) the degree of the surface relief. has been defined by Wenzel [53. using three dimensional models. is variously defined depending on the intended use of the information. in terms of their reliefs. in Fig. The criterion by which one surface is designated rougher than another. and a is the apparent or projected area. but the lengths of their profile lines (P1 and P2) are exactly the same. the statistics of the height distribution of the population of asperities and their frequency of occurrence over an area. No further reproductions authorized. or cross-sectional area. that is. 5. and L represents the projected. a. the true surface area. than L2. Ll = L2. not easily incorporated into a concise comprehensive definition. although it is the ratio of areas. . Alternatively.54]. 6). They distinguish between waviness ( : unevenness) and roughness: Copyright by ASTM Int'l (all rights reserved). the mean surface line is defined to be parallel to the surface and at a depth such that it divides the peaks and valleys of the profile into equal areas. . The simple arithmetic or center line average (CLA) may be used. K z = 0. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Lines connecting the peaks of the asperities. 6--Mathematical definitions for numerical evaluation of surface texture [55]. or both the peaks and valleys separately.0~5 dx~ (C) [" P. have been used for other numerical definitions (Fig.602 TESTS AND PROPERTIES OF CONCRETE AGGREGATES For example. averaging the height and depth of numerous equally spaced ordinates. A roughness value is determined from the mean surface line by P. ~ R Swedish gondord oppoims KI =0. the use of the root mean square (RMS) average will emphasize the maximum peak to valley relief and will identify a surface with a wide statistical range of ordinate measurements (peak to valley heights) as being rougher than one with a smaller range but with the same CLA height. Another analytical treatment of a roughness profile is used by Wright [52] and Orchard [56] generally after the method of Kramrisch [57].10 /~'T =~Lyd-x Avg Depth FIG. No further reproductions authorized. and is essentially the two-dimensional analog of the roughness factor of Wenzel [53. Alternatively. The latter ratio corresponds to the roughness factor of Wenzel [53. can have the same average depth. Vp. 58]. waviness is the undulatory or long wave irregularity (Fig. Tons and Goetz [27] and Ishai and Tons [28] present theoretical and experimental approaches for expressing the geometric irregularity attributable to shape. Orchard [56] favors the profile length per unit of center line ( = mean surface line). . and the profile length per asperity. T--Analytical treatment of roughness profile. permit unique numerical descriptions of surface topography [59. and surface texture in a unified characteristic related to individual particles and to their packing behavior in bulk. CLA or RMS height.56]. are obtained by intersecting the magnified profile with chords of varying lengths. Profiles of widely differing surfaces. Loosely packed particles are in contact with each other primarily at the high spots of their individual surface roughnesses. it is stated by the authors. further refinement and sophistication of the mathematical treatment of roughness profiles has been done which. 7(a)) on which is superimposed the short wavelength irregularity or "roughness" (Fig. the roughness line may be obtained with a map measuring wheel. No further reproductions authorized. is defined as the volume enclosed by a dimensionless membrane that connects the peaks of the surface asperities (Fig. 7(b)) to produce the resulting texture (Fig. 8). or the ratio of the roughness line to the unevenness line. the roughness line. angularity. 7(c)). but is that plus the volume of the depressions between the high Copyright by ASTM Int'l (all rights reserved). A theoretical particle volume. The difference between the two lengths. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or if its length is considered to correspond to the projected or geometric surface. the ratio of the difference to the unevenness line. In view of that. The lengths of the unevenness line and of the profile. is used as a measure of texture. do not provide a unique quantitative assessment of the surface roughness [58.59. Therefore.OZOL ON SHAPE 603 (cx) FIG. and therefore those. as easily obtained criteria for routine determinations. the packing volume. that is.54] as the unevenness line flattens. or related common measures. the more mechanically significant space occupied by an irregular particle within a mass of adjacent particles is not just its solid volume. markedly different in asperity shape and coarseness. (Wenzel [53. in the calculation of the specific rugosity. Gp = W/Vp. Vp may be calculated from Gp = W/Vp. where W is the dry weight of the particle. where Gp. is the known packing specific gravity of a standard smooth-surfaced spherical aggregate (marbles). The Gp is further utilized. + S. The Gp. R. and r~Wx and ~W.28] state that in this way all the geometric irregularity factors are accounted for and unified as the total surface voids under the packing volume membrane. the degree to which test particles are irregular compared to smooth uniform spheres. If G. is numerically the lowest of all the commonly used specific gravities. Gap. The test which was developed.. is known.54]) component of surface texture.. which expresses the volume of the surface voids of the particle as a percent of the Vp of the particle or.) 9 G.p.i. There may now be defined a packing specific gravity. are the respective weights of the unknown and the standard materials which occupy the same volume in bulk. to provide a better and more refined distinction between different types of geometric characteristics. 8--Particle packing volume and macro-surface voids and micro-surface voids enclosed by packing volume membrane [28]. ~" FIG. and the roughness factor. . Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The total surface area of an aggregate of particles is controlled by their size.x = (r~Wx/r. No further reproductions authorized. The Gp of a solid.604 TESTS A N D PROPERTIES OF CONCRETE AGGREGATES Macro-Surface Voids Volume " Membrane ' ~ ~ . Sty can be partitioned into macrosurface voids and microsurface voids.. An unknown packing specific gravity (Gpx) for an aggregation of one-size particles is found from the relation G. spots or asperities. The authors [27. The surface of the gross geometric particle shape. smooth-surfaced sphere is equal to its apparent specific gravity. S~. "the pouring test. which are the points of contact with the neighboring particles.W. as defined and obtained by this method. that Copyright by ASTM Int'l (all rights reserved). with the G.. where W equals the dry weight of the particle.. Sty = S." is similar in operation to the void content determination for a one-size material. volumetrically. shape (d/). that is asphalt residue. No further reproductions authorized. is termed the specific surface area (Powers [60]) or the "membrane" surface area (Tons and Goetz [27]). by this method. It would appear that direct assessment and comparison of roughness could be accomplished by electron microscopical techniques which can both construct the surface roughness and concurrently analyze it by computer [63]. that is. Wright [52] makes a thin section of an aggregate particle embedded in resin and traces the profile of the magnified (• 125) image of the interface. divided by its "membrane". a hypothetically smooth surface. has been described by Orchard et al [61]. termed rugosity. Specific surface is also applied to results of direct physical determinations of true. the surface area. Rugosity. The authors found that. equals the volume of asphalt remaining on the particle (cubic centimetres). expressed per unit weight (cm2/gm) or volume (cm2/cm3). The technique used by Boyde [64] on canine dental enamel and sandpaper would be applicable to rock surfaces. the rugosity increased very little with increase in Vp. for example. Surface texture may be evaluated by indirect methods. the Talysurf machine. the geometric surface area by definition. This method was used by Kaplan [51] on 13 coarse aggregates used in concrete. surface area by sorption (BET) or permeability (Carman-Kozeny) methods. The weight of a fine powder used to "level" a unit area of surface roughness also may be used. the rugosity increased with the particle Vp. The result. Tons and Goetz [27] determined the volume between asperities. An electromechanieal stylus apparatus especially for rock and aggregate surfaces. approach on flat sawn rock slabs [65]. or geometric. holding size constant. That area. that is. Measurement of the resistance to air flow between a rock surface and an elastic membrane held against it at a given pressure has been used as a measure of roughness [66]. also may be influenced by angularity. area (square centimetres) calculated from particle dimensions. For a rounded gravel. . Bikerman used a similar. between the packing volume membrane and the particle surface. or available. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. for crushed limestone and gravel. Scrivener and Hudson [62] describe a method for obtaining the profile length of coarse surface textures using a device with spring-loaded probes. that due to sphericity (~b). corresponds to the dimensional or projected area in the definition of R. by coating particles with asphalt and then removing the excess down to the roughness peaks. Measurement Profiles for analysis can be generated by electromechanical stylus devices used for the investigation of metal surfaces. which directly determines profile length per unit of center line length. Copyright by ASTM Int'l (all rights reserved). diminishes as the particle shape approaches equidimensionality.OZOL ON SHAPE 605 is. For R of 1. Direct determination of true surface area may be done by adsorption methods. is based on the principle of weighing the amount of adsorbed substance directly on the substrate [69].S. . specific surface area may be physically determined directly from measurements of permeability--the loss of head and rate of flow--of a liquid through a column of single-sized particles. The above applications concern external surface. cross section of a small cylinder) would need to be coated with platinum.S. or sieve analysis. . determined specific areas (square centimetres/cubic centimetres) for nine sizes each of crushed granite.) 19 by 12. the sands with the highest and lowest values. rounded gravel. using Gibbs Adsorption Isotherm. . the (geometric) specific area may be estimated from the particle size. Without benefit of direct physical determination. --7. using this method.8 by 1. The coarse sizes of the irregular gravel had values similar to the rounded gravel. . TABLE 3--Specific surfaces obtainedfrom Refs 49 and 68. Standard BET methods [70] can be. used in electrochemical research for determination of true surface area of electrodes [71] might be possible. It is applicable to larger samples and can be used for finding Wenzel's roughness factor.1 1/2 times that of the rounded gravel for any particular size. The same method was used by Bennett and Katakkar [49] on one size each (B. as for scanning electron microscopy.7 mm (aA by 1/2) 2. and usually are. . and bulk Copyright by ASTM Int'l (all rights reserved). Determination of true surface area of rock specimens by the differential capacity method. cm-1 B. with the result expressed as area/unit weight. and surface not to be included in the measurement (sides and bottom) would need to be masked or insulated.5 50 98.14) from twelve fine aggregates which were then used in concrete. which were also used in concrete. . applied to fine particles. Patat's method. Specific Surface. Shacklock and Walker [68]. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and irregular gravel. The rock surface (for example.606 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Based on the theory of Carman [67].63 56.5 Crushed Sandstone b Natural Silica Sand b . q. The granite had a specific surface . Illustrative values of specific surfaces obtained from [49] and [68] are shown in Table 3.12 5. b Ref 49. the adsorption and permeability methods are also used for determination of the internal surface area of the total pore volume. 60 42 a Ref 68. Size mm (in.47 6.4 mm (7 by 14) Rounded Gravel a Irregular Gravel a Crushed Granite ~ 4. No further reproductions authorized. texture involves the following factors: (1) degree of crystallinity ( = mineral composition in the context of surface texture). Stamenkovic [72] gives a table for the surface area. each with its own characteristic cleavage or fracture.) where P~. In contrast. the simplified equation for area of a prolate spheroid may be used [27]. If sphericity (~b) is known. Surface Textures of Rocks As used in the petrographic sense to describe an interior cross section of a rock. 9 and 10). with strong cleavages. shales.. are the solid volume fractions or the weight fractions if the specific gravity is the same for all sizes. may have very rough or rugose surfaces. porosities < 5 percent. the particular size. The surface texture should be considered to be very much controlled by those same factors. or other sorts of preferred orientations of the minerals. or expanded slags. that is. i. tuff. specific surface (cmZ/cm 3) can be estimated from sieve analysis by: cm2/cm a : (558/~b) (Pl q. the character of which is mainly attributable to their intergranular voids. Certain rocks. scoria. If !. which are used in various locales for aggregate. P2. for example. . or various-for example. and (3) the shape and relative sizes and arrangement of the mineral grains. The surface features of sands and gravels are rather different and bear the results Copyright by ASTM Int'l (all rights reserved).OZOL ON SHAPE 607 specific gravity (neglecting angularity and assuming a spherical shape). or slates. The specific surface of spheres for Group 1 (100 • 200 B. sieves) is 558 [60]. as in pumice. and distribution of voids in a porous surface may be more important for the bond and other mechanical properties of the interface than the absolute numerical value of the porosity. Most rocks that are used for concrete aggregate are not intrinsically very porous. slags. P3. Also contributing to surface texture and therefore surface properties. and bioclastic limestones. (2) grain size. equigranular textures.1/2P2 d. in' square foot per pound. and arrangement of places in the rock where there is no mineral matter. or the formula used by Chamberlin [30]: cm2/cm 3 = 2/i (i/l + i/s + 1). are measured. for example. but the surface porosity will have the same numerical value and directly affect the surface texture of the aggregate. as with other textural elements. Again. of various size fractions.S.1/4P3 + 1/8P4. a granite--reflecting the irregular grain boundaries and size and shapes of several minerals. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. a fair amount of regularity or periodicity may be present on broken surfaces of sedimentary or metamorphic rocks (Figs. shape. shape. are the size. The petrographic factors shaping surface texture are perhaps more germane to the production of texture on crushed stone surfaces. and s. No further reproductions authorized. the voids or pores intrinsic to the rock or artificial aggregate that become voids or pores in the surface when the rock is broken. axes for a particle. The (micro) surface texture of aggregates may be random. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. for mechanical interlock. and so forth. indentations. pores. etching. pits. and thus with surfaces which. to some extent.I n fresh concrete the particle shape. and surface texture of the aggregate affect the volume of cement paste that must be used first to fill the voids in the aggregate and then to provide sufficient extra volume of cement paste to "float" the aggregate and provide the mass with enough plasticity to achieve thorough mixing and dispersion of the ingredients. No further reproductions authorized. Pennsylvania. precipitation. of preferential solution.608 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. in concrete. and usually by not more than 3 percent when no air-entraining Copyright by ASTM Int'l (all rights reserved). 11 and 12 that. Note sharp asperities and ridges Jormed by intersections and edges of cleavage planes. it is obvious from Figs. etc... on a microscale. quartz sand grains can have surfaces with abundant projections. 5 #m across. 9--Fracture surface of crystalline dolomite rock used as aggregate. angularity. Although having less vertical relief. Effects and Significance of Properties Plastic C o n c r e t e S h a p e a n d T e x t u r e . grooves. Ledger fbrmation. Powers [74] has noted that the volume of concrete exceeds the volume of the compacted aggregate by between 3 and 10 percent. are also significant for adhesion and. leaching. Field is 17. . lO--Fraeture surface of pure.51].5 ~m across. . and Kaplan [50. the average difference encountered should be less because of the unlikelihood that two aggregates being compared would be at the opposite extremes of the shape and surface texture spectrum. because fewer coarse aggregate particles can be packed. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In any case. Field is 17. agent is used. fine-grained limestone used as aggregate. it may be estimated that. whatever the paste Copyright by ASTM Int'l (all rights reserved).OZOL ON SHAPE 609 FIG. may be investigated experimentally or empirically for either the workability as the variable or the properties of the concrete at a given workability and cement paste volume as the variable. the maximum range in void content at dense compaction between aggregates at the extremes of the shape and texture spectrum might be around 8 to 9 percentage points. the "sufficient extra volume of paste" needed for workability would be that volume equal to 3 or somewhat greater percent of the outside volume of the aggregate mass. No further reproductions authorized. and irregularly shaped aggregates would be those requiring the relatively higher excess paste volumes. Therefore. Note equigranular texture. Concretes with angular. St. Paul Formation. Pennsylvania. depending on the amounts and proportions of the cement and water. without interference. In practice. From data in Wills [6]. Shergold [44]. rougher. in concrete when the particle shape is irregular than when it is spherical. The effect of the shape characteristics of the aggregate on the workability of the concrete and the concomittant effects on the hardened concrete. at a given grading of combined aggregate. 8 kg (220 lb) of water and 261.39 bags/yd3).1 kg (300 lb) and 356. 11--Deep surjace etching on silt grain from consolidated deposit. it may be calculated from quantities reported by Blanks [ 75] that there was about an 8 percentage point difference in paste volume required--the undifferentiated amount for both void filling and workability--between two concretes with the same maximum size coarse aggregate 38. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.50).4 kg/m 3 (6. but one made with a "well rounded" and the other with a "harsh and angular" sand. .). For example. Field 68 gm across.6 kg/m 3 (4. working to the same w/c ratio (0. the second 136. volume needed for satisfying the two requirements of void filling and workability. it is evident that it may be achieved by adjusting the quantities of cement and water to either maintain the same water/cement (w/c) ratio or to increase or decrease it.69 bags/yd 3) of cement. No further reproductions authorized. Atlas of Quartz Sand Surface Textures [73] used with permission. The first concrete needed 99.1 mm (11/2 in.610 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. USSR. Note extensive surface pitting and etching with occasional deeper pores. Copyright by ASTM Int'l (all rights reserved). three crushed limestones (one artificially rounded). The roundness values ranged from 0.57 and 6. Atlas of Quartz Sand Surface Textures [73] used with permission. the respective w/c ratios of the concretes at 7. The water requirement to produce the same mortar flow (100 percent) for the most rounded sand (0.55) was 84 percent of that for the least rounded (0. and one hammermilled chert were graded to the same fineness modulus and used in concrete with fixed coarse aggregate and cement 334. but allowing the effect of particle shape and surface texture on the plasticity of a mortar mix at constant sand gradation Copyright by ASTM Int'l (all rights reserved).) according to the measured (Wadell) roundness values of his sands. Roslyn.00.6 kg/m 3 (6 bags/yd 3) content. No further reproductions authorized. 12--Quartz crystal growth on sand grain f r o m beneath till. USA. Alternatively.34 (chert). Not varying anything. one natural.) slump were 5.55 (rounded limestone) to 0.Y. Five sands. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Crystal faces have Jormed as upturned cleavage plates.62-cm (3-in.OZOL ON SHAPE 611 FIG. l"4. Laughlin [32] determined the varying water requirement to provide a constant mortar flow (100 percent) and concrete slump (3 in.34). . by precipitation. Field is ~ 150 tzm across. Data for the concretes containing the coarse aggregates with the highest and lowest void contents. at constant grading and cement content. (Incidentally. are shown in Table 4.9 MPa ( . with which the other materials were combined as coarse and fine categories. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and 76. found that the flow of mortars (of exactly the same mix proportions) was related inversely to the time indexes of the sands. and that that index is a satisfactory method for determining shape and water requirement. 117 percent for Leighton Buzzard (a rounded natural) sand. time index 1.5 percent for a crushed coarse-grained granite. Other factors. coarse and fine. One. with their companion fine aggregates. void content and orifice flow measurements demonstrated that the fine and coarse aggregates from the same source had similar particle shapes.7 litre (1 to 11A gal) increase was associated with a similar voids increase of the coarse aggregate. using the time index of Rex and Peck [43] as a measure of the particle shape and surface texture of nine natural and seven crushed sands. A 4-percent increase in fine aggregate voids caused a 14. No further reproductions authorized.) The experimental design permitted a noteworthy distinction to be made between the separate effects on water demand and strength of the fine and coarse aggregates. Overall. whereas.00. time index 1.8 to 5. a natural quartz sand with a companion gravel. Previously cited works and others lead naturally to the question of which of the shape or surface properties of aggregates has the greater effect on Copyright by ASTM Int'l (all rights reserved). on the concrete mixing water demand at constant cement content and. only a part of the variation in compressive strength was attributable to variation in mixing water requirement. Allowing the w/c ratio to change. Fine aggregates influenced compressive strength almost entirely through their effect on mixing water demand. and the strengths of the hardened concretes decreased as the water requirement increased. He concluded that the water requirement for constant flow would vary as the time index.1000 psi)--while a 3.612 TESTS AND PROPERTIES OF CONCRETE AGGREGATES and mix proportions to be expressed. in turn. The fine aggregates had a much greater effect on concrete mixing water demand and strength than did their coarse companions. time index 1. on the strength of the concrete.9 litre/m 3 (3 gal/yd 3) increase in water demand--which lowered compressive strength 6. . for example.05. for the coarse aggregates. Malhotra [45].57. elasticity. was used for control aggregates. the mixing water required to maintain a given slump increased directly with the percent voids of the aggregates. or bond strength with cement paste of the coarse aggregate. Wills [6] showed the direct influence of aggregate particle shape on the void content of the aggregate and. through the mixing water demand. mineralogy. The flow was 125 percent for the mortar with the standard (highly spherical and well-rounded) Ottawa sand. The nine aggregates used by Wills had companion coarse and fine fractions from the same source. were suggested as being as important as the particle shape which had controlled the percent voids and water demand. 6) Slump.0 Sand.4 (640) 4. No further reproductions authorized. MPa (psi) TABLE 4 .8 (690) Flexural Strength.D a t a f o r the concretes containing the coarse aggregates with the highest a n d lowest void contents [6].0 (38.3 (5270) 39..) 36. kg/m 3 (bags/yd 3) 306.Copyright by ASTM Int'l (all rights reserved).4 190.45) Voids percent CA (1 in max) dense compaction 41.49) 304. 28 days.3 (5700) Compressive 4. percent of Aggregate 88.4 (3.5) 91.9 (3. o~ 6o ol 0 z o~ "1" t'- 0 N 0 .2 (5. mm (in.2) 160.1 41.0 (32.0 (5.6 33.2) Water. Cement. kg/m 3 (gal/yd 3) 33. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 07 in compacting factor. Copyright by ASTM Int'l (all rights reserved).922) and therefore only flakiness was used in the statistical analyses. the minimum intercept depends on several factors. it is more important to use aggregates that have low angularity than low flakiness. and using the same natural sand fine aggregate in all mixes. 29 percent of the variation in workability was due to flakiness and 59 percent to angularity. have the greatest effect on workability.614 TESTS AND PROPERTIES OF CONCRETE AGGREGATES workability. if workability is a concern. and seems to be independent of the particle shape of the coarse aggregate. . Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and Kaplan concluded that changes in surface texture have no appreciable effect on the workability of the concrete. an increase of 10 in the flakiness index would cause a reduction of about 0.) below which the workability of the concrete is inadequate.8 mm (0. and gravel--but with the same grading and mixture proportions.4 by the method of Wright [52]) no statistical relation could be established between it and the compacting factor. Holding grading. crushed stone. It was earlier noted that angularity appears to have the greatest effect on void content. but the conclusions regarding flakiness also apply to elongation. Although there was a wide range in the surface texture of the aggregates (roughness factors from 2.15 in. Popovics [76] reached a similar conclusion regarding the greater importance of angularity than shape. No further reproductions authorized. elongation. Popovics SElongation was found to be well correlated with flakiness (0. It was found that the average mortar intercept was related inversely to the angularity number in concretes made with aggregates of (visibly) different particle shapes--crushed reef shell. Rather. he gave approximate quantitative relationships for estimating the compacting factor from flakiness index and angularity number. angularity. All the concretes had sufficient mortar to fill the voids. If angularity and flakiness are varied separately: at constant flakiness an increase of 10 in the A N would cause a reduction of about 0. From studies of hardened concrete. such as the method of compaction and grading of the sand.1 to 16. Based on the average mortar intercept--the measured distance along a random line of the mortar layer between coarse aggregate particles--as a criterion of workability. and w/c ratios constant. Kaplan [50] investigated the separate effects of flakiness. he found that changes in the angularity of coarse aggregates. and surface texture of 13 coarse aggregates. his results indicated that: there exists a minimum value for the average mortar layer intercept 3. while at constant angularity. There was some correlation between flakiness s and angularity but when the two were analyzed together statistically. with changes in flakiness and elongation having decidedly less effect. as measured by the AN. separately or together. and aggregate to cement. Kaplan suggested that. on the workability of concrete as measured by the compacting factor [British Standard on Methods of Testing Concrete (1881)].01. Abrams and others earlier had observed that surface area of aggregate varied widely without appreciable difference in concrete strength. For 25 sands for which he had measured sphericity. the compacting factor increased as specific surface decreased. and crushed granite. However. Excerpted data from Chamberlin [30] show. Surface Area--The relation between the physically-measured (permeability method) specific surface of aggregate and concrete workability was examined by Shacklock and Walker [68] for mixes made with rounded gravel.OZOL ON SHAPE 615 considered that the results supported the Shergold test method for the measurement of angularity number. They concluded that "the workability of the various mixes was closely related to the specific surface of the fine aggregate. and roundness. even allowing for substantial error in the determination of surface area and sphericity. since AN and flow time were very closely correlated with specific surface and varied directly with it. respectively). . Chamberlin [30] determined the water required to bring mortars. the relation was less direct. to a predetermined consistency as measured by penetration of a standard cone. No further reproductions authorized. that the sand with the highest water requirement did not have the highest specific surface but had the lowest roundness. The sand with the highest roundness had next to the lowest water requirement (in source data as well) but had a mid-value for specific surface (see Table 5). a similar conclusion could be drawn with respect to those properties. They found that the "effective" w/c 6 ratio for a particular workability was directly proportional to the mean specific surface for mixes that were oversanded. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. He suggested that. Copyright by ASTM Int'l (all rights reserved). And for mixes of coarser gradings. They also determined void contents (angularity numbers) and orifice flow times for a single size of the twelve sands. irregular gravel. and calculated (geometric) specific surface.49 and 0." that is. and had noted that water required to produce a given consistency depended largely on the character of the aggregate apart from its surface area. Bennett and Katakkar [49] similarly measured the specific surface of twelve sands which were used in concrete at a fixed gradation with a standard coarse aggregate and fixed w/c and aggregate/cement ratios. at a constant workability. for example. Similarly. Introduction of roundness improved correlation with sphericity only slightly. the relationship appeared to be inverted: a higher w/c ratio being required. as the specific surface decreased. ~The "effective" w/c ratio takes into account the absorption and specific gravity of the aggregate. But for mixes of normal gradings.63. variations in surface texture of the sands exerted a considerable influence on the water requirement variation. He found that variations in water requirement were correlated only partially with specific surface and sphericity (coefficients of 0. mixed to constant volumetric proportion between cement and saturated surface dry sand. 7 8. according to decrease in particle diameter. Sand No. The void volume of an aggregate of one-size spheres is the same for the same mode of packing (for example.W a t e r requirement versus sand surface and geometry.7 35. increases (after void volume is deducted) in the same proportion as surface area increases. It has never been shown that the extra paste requirement. each requiring separation and lubrication and thereby constituting a greater total paste volume demand.68 0. if for coating of surface area. It is not clear then how surface area alone leads to the requirement for greater paste volume.7 51.74 0. If it may be presumed that the minimum paste thickness requirement for separation is proportional to that contact area. ml 25 24 18 7 2 0. there are many more such contacts in an aggregate of smaller spheres.67 7. than an aggregate of larger spheres of the same total solid volume of material. Copyright by ASTM Int'l (all rights reserved).59 7.14 7.78 0. ~ Sphericity Roundness Specific Surface Water Requirement. it is experienced in the mixing of concrete that. as a practical necessity. Although the surface area of the smaller spheres will be greater.16 8. where the particles are of different kinds and also differ in angularity and sphericity. . all of it must be coated if the 26 percent void volume of the aggregation is filled completely. other things being equal. the paste requirement increases as the particle sizes of aggregates of the same kind decrease. The point contact area between two (ideal) spheres is the same whether the spheres are small or large. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it appears that the higher paste requirement associated with higher specific surface for particles of the same size fractions.72 0. rhombohedral ~ 26 percent) whether the spheres are small or large. But. The table is constructed from the highest and lowest values for each property independently.616 TESTS AND PROPERTIES OF CONCRETE AGGREGATES TABLE S .7 55. It is suggested rather that it is the greater number of points of contact between the greater number of particles. This is said to occur because of the increased surface area of the aggregate to be coated. comprising the same total solid volume of material that require separation and therefore demand the higher paste requirement.77 33.1 49. with the corresponding values for the other properties. then. that is. Regarding increase of surface area as a consequence of decreasing particle size. could be attributed just as easily to increase in void volume. No further reproductions authorized. the minimum paste thickness requirement per contact is the same whether the spheres are small or large. Regarding differences in surface area between aggregates of the same size..36 233 215 201 191 189 ~Ref 30. flexural strength is more affected by those properties than compressive strength. The elasticity of the aggregate was the single most important factor affecting flexural strength. Kaplan's data showed that. which were used both uncrushed and crushed. and flakiness and elongation indexes. it was concluded that surface texture was the most important aggregate property influencing compressive strength. the effect becomes more significant as the strength level of the concrete increases. It must be presumed that explanations as to why rougher texture and increased angularity contribute to concrete strength at equivalent mixture Copyright by ASTM Int'l (all rights reserved). From regression analyses on all of the data. the crushed condition of the same gravel produced higher strength in 41 cases. For the intermediate mixture (cement/aggregate by weight : 1:7. while altogether the data demonstrate the same effects caused by lithology controlling the shape and texture. Flakiness and angularity together accounted for only slightly more variance than angularity alone. the highest and lowest compressive (with corresponding flexural) and flexural (with corresponding compressive) strengths with the aggregate shape and texture values are shown in Table 6. that is. with the effect increasing as strength increased. For the concretes with the crushed and uncrushed natural gravels. lower strength in eleven. And. except that surface texture had the dominant effect for the concrete at the highest strength level. w/c = 0. surface textures. These isolated data illustrate effects on concrete strength due to shape and texture independent of the intrinsic lithologic properties of mineral chemistry and modulus of elasticity. the rougher the texture.OZOL ON SHAPE 617 Hardened Concrete Apart from the effects they exert on the strength of hardened concrete.53. followed by shape and surface. The variance due to each of the properties as a percentage of the total variance accounted for by their effect on the concrete strength. Kaplan [51] used 13 coarse aggregates with both differences and similarities in angularity numbers. the greater the strength.60) at 28 days. . and four types of crushed stone. differences in particle shape and surface texture directly influence the strength of hardened concrete of the same mixture proportions. was given for the average of all concrete mixes. No further reproductions authorized. as shown in Table 7. according to Kaplan's results [51]. and flakiness with angularity. These included three natural gravels. out of a total of 54 pairs of tests (27 each) of compressive and flexural strength covering different mixture proportions and ages. by means of their effects on the required paste volume and the proportions of cement and water for a given workability. which were incorporated into three basic mixtures of different aggregate/cement and w/c ratios. The angularity number was used in the regression analyses to represent the shape properties because it had been shown that elongation was well correlated with flakiness. and equal strength in two. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. MPa (psi) Strength.7 (5910) 44.8 (5480) 3. 40. CAngularity number (percent voids--33) ranged from 1 to 10 for the 13 CA's.65 5. H.8 (6500) 47..55 (530) (795) (740) (660) Compressivea Flexural a Strength. natural quartzite gravel crushed limestone crushed basalt crushed flint gravel Aggregate 31 34 26 8 Flakiness b 24 33 42 42 Elongation b TABLE 6 . AN C 4.0 13.6 (6910) 37.6 for the 13 CA's. dMethod of Wright [52] ranged from 2. A.48 5. E.4 10. b British Standard 812. N. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.10 4.Copyright by ASTM Int'l (all rights reserved).C o n c r e t e strength versus coarse aggregate shape a n d surface texture.2 Roughness Factor d (Surface Texture) O~ -4 m (O m :IJ ~3 h3 m -4 I'll 0 0 z 0 O -I1 m l[ -o ~o O -o rn z ~D -4 co -4 m Oo .2 to 16. MPa (psi) a28 day.1 2. The elimination of adhesion between the mortar and the coarse aggregate reduced compressive strength by an average of about 23 percent. Tensile strength was less affected. A possible explanation is Copyright by ASTM Int'l (all rights reserved). but in this case with the strength of the bondless concrete increasing with age as a percent of the control. or reduction. Patten [77] investigated the relative contributions of adhesion and "keying. the total adhesive force is the product of: (1) the specific adhesion. at seven days to 27 percent difference at six months. Studies focusing further on the components of the adhesive force making up the percent contribution of adhesion to bond strength endeavor to test the interface in as pure a state of tension as possible to avoid mechanical contributions. and (2) the amount of surface area available for bonding over which the adhesive force acts. Different rocks have been observed to have different tensile bond strengths to cement paste [81-84]. The object was to eliminate adhesive bonds without affecting the mechanical interlock. Under conditions of tension. At 6 months. in the high strength series. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the splitting tensile strength of the concrete with the "bondless" aggregate was 92 percent of the strength of the concrete with the untreated aggregate. or physical keying. No further reproductions authorized." or mechanical interlock. whereas at 7 days it was 79 percent. between the aggregate and the mortar. and an untreated condition. ranging from 6 to 28 percent difference. Various specimen configurations and techniques for measuring aggregate-cement bond strength have been reviewed by Alexander et al [81].OZOL ON SHAPE 619 TABLE 7--Proportional contribution of shape. Investigations along similar lines have been conducted by Darwin and Slate [78] and others [79. Compared to the control. by compressive and tensile strength measurements of concrete at five different ages in which the same coarse aggregate had been used in both a "bondless. percent. due both to particle shape (geometric area) and roughness factor (true surface area per unit of geometric area). the strength of the adhesive force per unit area of surface from whatever physicochemical mechanism it derives. . of the FollowingProperties Flexura] strength Compressivestrength Shape SurfaceTextUre Modulusof Elasticity 31 22 26 44 43 34 proportions will involve the contributions of: (1) mechanical interlock (due to the surface relief) and (2) total surface area available for adherence of the cement paste." or surface-treated. the strength of the bondless concrete decreased with age from 19 percent difference. the coarse aggregate was coated with a mold release agent.80]. that is. texture and modulus of elasticity to concrete strength [51]. Relative Effect. with an average reduction of about 17 percent. 3. similar to the failure of a poorly adhering coating. authors have reported achieving satisfactory workability at acceptable w/c ratios or strengths. Elongated or flaky particles may affect durability adversely if they are oriented parallel to the concrete. made concretes of adequate workability and a w/c ratio of 0. and some degree of angularity and surface roughness. for example.2 MPa (2500 psi) compressive. they thereby affect. pavement. Adequate workability was achieved. bleeding. The particle shape of the shell coarse aggregate was described as highly unfavorable because of extreme angularity: angularity numbers determined were in the range of 26 to 30. and 2. calcite. For either of these possibilities.6 k g / m a (6 bags/yd a) cement and suitable amounts of flyash and air entrainment. an alternative hypothesis to explain differences in bond strength between different rock types is that surfaces of different lithologies have different roughness factors and therefore present different true surface areas available for bonding [87]. in addition to compressive strength. based on experimental work. drying-shrinkage. and angularity of aggregates have been noted. Copyright by ASTM Int'l (all rights reserved). Undesirable effects of flatness. elongation. for example. concrete has been fabricated with aggregates of low sphericity. As a consequence of their influence on the water content necessary to obtain suitable consistency. The flecking. using aggregates of which 50 to 90 percent were fiat or elongated or both.6. No further reproductions authorized. may induce structural weakness within the concrete if they are so oriented as to be loaded as columns in compression [88].620 TESTS AND PROPERTIES OF CONCRETE AGGREGATES that the bond is chemical and its specific adhesion differs significantly according to the particular chemistry of the mineral surface [85]. In certain instances where. Flat particles may cause uneconomic grading and.07 MPa (300 psi) splitting-tensile were obtained at 28 days. is due to the stronger bond between the mortar and the upper mineral surface than within the mineral itself [91]. with good cleavage directions oriented parallel to the surface. The mortar cover over fiat coarse aggregate particles oriented parallel to the pavement surface may "fleck o f f ' when the particle surface is micaeous or contains other minerals.79 MPa (550 psi) fiexural. Highly angular and flat and elongated particles are more subject to fracturing and change in gradation by generation of fines than similar amounts of rounded spherical particles. (by weight) 60 percent crushed reef shell coarse aggregate and 40 percent beach sand fine aggregate with 334. Alternative possibilities are that (1) the bond is chemical but its specific adhesion on the smallest unit area basis does not differ greatly between minerals. or (2) the bond is physical [86]. deriving from the same sorts of forces that hold materials together in general. and durability of the concrete--especially freeze-thaw durability if excessive bleeding has caused the formation of channels. for exploratory or practical reasons. and air voids having been trapped underneath. and strengths of 17. Mercer [92]. Good bond may be inhibited [89] and any pores formed may be exploited subsequently by weathering [90]. . Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Popovics [3] made concretes using. surface with bleed water. for example. 4 and 0. secondarily deposited CaCO3 may occur as an overgrowth on pebbles or grains of limestone or quartz. or closely related species of minerals may be at the same time major components of the rock comprising the aggregate and also coatings on its particles.2 and 68. Coatings may occur on sand and gravel. sand and gravel and crushed stone. Probably only two materials. For example. that is. Corresponding slumps were between 3.1 and 5. Similarly.5 and 5. or artificial aggregates alike. the Copyright by ASTM Int'l (all rights reserved). and more prone to degrade than the particle interior.52. The same substance may be both a coating and a granular component. to the extent that it is present as both adhering and discrete material.5.8 in.3. blebs. No further reproductions authorized.3 and 4.1 cm (2. and 29.9 in. which are also chemically SiO2. petrographic examination [93]. secondarily deposited opal. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. are volumetrically important in this dual behavior. calcium carbonate (CaCO3) and silica (SiOz).. Corresponding compressive and flexural strengths were 34.31 MPa (5000 and 800. .1 ml/kg (3 oz/bag)). or on other rock types. of the two main categories of aggregates most commonly used. and 4220 and 770 psi). patches. The w/c ratios were varied between 0. causing the formation of a "rind" which may be softer.OZOL ON SHAPE 621 Concretes were made by MeGhee [5] using a crushed slate coarse aggregate which had flakiness and elongation indexes of 57. Identification and Composition The most specific method of identifying the nature and extent of coatings present on concrete aggregate particles is by direct. namely. chemically SiO2 may occur as a coating on pebbles of quartz or quartzite. more absorptive. respectively. In general.) without a water-reducing admixture and 7. what is for all intents and purposes a kind of coating may result from weathering and leaching of the particle surface. Minerals in this category are those which are both major rock-forming minerals and occasional "coating formers" on particles of the same or of different mineralogy. Their chemical and mineralogical nature may differ according to those generic categories of aggregate. Coatings Definition Coatings are adhering materials which may be cemented strongly or weakly to the particle surface and which are present as layers.3 and 1.8 cm (1. respectively [26]. Further. In sands and gravels.) with the admixture (2. crushed stone. Adequate workability was achieved without deviation from the proportions derived from the standard ACI method. or individual grains over large or sometimes only very small portions of the surface of coarse or fine aggregate particles. the same. silt. storage. Goldbeck [94] reported that a decrease of 1. asphalt.622 TESTS AND PROPERTIES OF CONCRETE AGGREGATES former would be the more likely to have any coatings present that are intrinsic to the materials--as a consequence of factors related to the particular geology of their formation. and organic matter. may become coatings on those aggregates at some stage of manufacturing. iron oxides. and organic matter may be intrinsic coatings on particles of the deposit in situ. gypsum. thenardite (Na2SO4). clay. but especially during transportation. it may happen that dust of fracture-individual particles of which may be in the clay and silt sizes--adheres to and coats portions of the aggregate particles. solvents. misenite (KHSO4). Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Therefore. In the case of both coarse and fine crushed stone aggregates that are processed incompletely or improperly. of the same mineralogy as the rock deposit being produced. that intrinsic mineral coatings will not be present as they may be in the unconsolidated or loosely consolidated deposits from which sand and gravel are processed. and phosphates. Both crushed stone and sand and gravel after manufacturing. and sulfates other than gypsum. it is in the nature of the integral bedrock deposit and the subsequent quarrying and crushing operations that continually expose fresh surfaces. the coating/particle interface may be predisposed to separate as in the case of bond failure between Copyright by ASTM Int'l (all rights reserved). in the hardened concrete. by definition. alkali sulfates. that is. In the case of crushed stone. it is less likely that the coatings will be of the natural mineral type as for sand and gravel in situ. they are bonded more strongly to the cement paste than they are to the host particle. Later contamination which may form coatings on crushed coarse and fine aggregate and sand and gravel can be portland cement. through carelessness or oversight. opal. for example.a n d increase water demand--dust of fracture is not clay in the mineralogical sense but rather. are vulnerable to contamination by materials which may adhere to portions of individual particles and form coatings.5 percent flexural and up to 2 percent compressive strength can be caused per percent of dust. those which might occur as coatings on sand and gravel due to deposition or precipitation from waters. In this case. or other organic materials. No further reproductions authorized. Substances in this class. Other substances such as clay. In that case. Although undesirable because it may become an unanticipated and unwelcome contribution to the gradat i o n . Sigrlig~cance Adherent cemented coatings can be detrimental physically if. oils. materials found as coatings on crushed stone are more likely to be silt. but also. are therefore mostly mineral in nature and may include calcium carbonate. or transportation subsequent to extraction. . or other substances not intrinsic to the deposit which have come in contact with the material after extraction and crushing. OZOL ON SHAPE 623 the particle/paste (or mortar) interface. materials present as coatings will cause the same variety of effects as if they were present other than as coatings. opal. Siliceous coatings of. Bedrock. for example. They are in the long r u n . Despite the investment of energy in the manufacture of portland cement. and (4) innocuous chemically and as strongly bonded to the host particle as is the coating to the paste or mortar--in which case they are innocuous physically as well. portland cement concrete requires the minimum of energy consumption for its production relative to all other major construction materials. (3) innocuous chemically but bonded less strongly to their host particle in the hardened concrete than to the enclosing paste or mortar. Conclusion Insofar as the naturally rounded mineral aggregates. thereby constituting a bond or joint more prone to failure under physical stress than other paste aggregate interfaces without interposed coatings. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It is doubtful that nature is manufacturing sand and gravel at the quite remarkable rate at which convenient sand and gravel deposits are being used up in rapidly developing parts of the world. Chlorides and sulfates can cause efflorescence and staining on concrete surfaces and corrosion of reinforcing steel. they may be: (1) composed of a deleterious or innocuous soluble substance which dissolves during mixing of the concrete. will impair the bond between cement paste and aggregate. Therefore.a n d in the short run for certain localities at present-a fixed resource. No further reproductions authorized. but removable. suitable for the manufacture of portland cement and for the production of mineral aggregate is. as well as interfering with bonding as previously described. depending on the alkali content of the cement and other factors [96]. and so forth. virtually inexhaustible. it is the case geologically that the primary material is the more abundant and the derived material the more exhaustible. are products derived from parent bedrocks. increasing water demand. Wright [95] says that this effect is more likely to occur with natural sands than with crushed stone sands. . except lumber. To summarize the behavior of coatings on coarse or fine aggregate particles. may be susceptible to alkali-silica reaction. geologically speaking. dirt. Iron sulfides and other iron compounds can cause rust stains on concrete surfaces. Soluble. Organic materials may retard the setting of cement. sands and gravels. if clayey. thereby altering the gradation somewhat and. (2) composed of an innocuous or tolerable substance that is insoluble. In a related manner. it is reasonable to forecast increasing use of concrete as a building material with increasing use of aggregates other than sand Copyright by ASTM Int'l (all rights reserved). poorly adhering dust. or chemically reactive.. Soft coatings may cause surface pitting and reduced abrasion resistance of the hardened concrete. clay. 2 metric tons (919 a n d 1058 million tons). April 1954. Sandor.. Drawer M. "Lightweight Aggregate Particle Shape Effect on Structural Concrete. K. Vicksburg. M. Shape and Roundness of Rock Particles. [2] Schulze. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. H. t h e yearly t o n n a g e o f sand a n d gravel has exceeded the p r o d u c t i o n of c r u s h e d stone. A b o u t 1972.1 a n d 952. Miss." Virginia Highway Research Council. Vol. American Society for Testing and Materials.. 1976. R. 71.6 a n d 885.. 40. 443-451. and Ozol. No. Hemphill's.. Va. 1949. Copyright by ASTM Int'l (all rights reserved). C. B. S. [4] Johnston. Highway Research Board.. 1956. 97-113. Jr. M. [10} Living with Marginal Aggregates. American Concrete Institute. 1953. T h e increasing use of crushed stone for b o t h coarse a n d fine aggregate. No further reproductions authorized. "How Aggregate Particle Shape Influences Concrete Mixing Water Requirement and Strength.. [9] Buck. H. pp. Vol. 1976. H. 2.. [12] Aschenbrenner. pp. [5] McGhee. Army Engineers Waterways Experiment Station." Journal of Materials. A.. 827." Journal of Sedimentary Petrology.S. A S T M STP 597." Journal. References [1] "Method of Test for Flat and Elongated Particles in Coarse Aggregate.. . a n d area. along with p e r h a p s recycled concrete a n d other recycled materials. No. 344-350. Vol. Handbook for Concrete and Cement. American Society for Testing and Materials. 2. Petrology of Sedimentary Rocks." Journal of Testing and Evaluation. March 1974. 822. 15-31. "Influence of the Grading of Aggregates on Concrete Mix Proportions. "An Evaulation of A Slate Aggregate for Use in Concrete." HRB Record No. they exhibit less variety in the expression of those p r o p e r t i e s a n d raise fewer questions." Road Abstracts. 1966.. "Rapid Method for Particle Shape Determination and Suggestions for Definition of Ordinary and High-Quality Chippings. 1952.. C. D.. (Historically. K. for crushed stone. Texas. [8] Imbert. Acknowledgments T h e a u t h o r wishes to express his g r a t i t u d e a n d a p p r e c i a t i o n to Bryant M a t h e r for his review of the m a n u s c r i p t a n d v a l u a b l e suggestions. [3] Popovics. 1932. 26. University Station. [t31 Wadell. Jr.. Austin. D. No. May 1977. [11] Folk. "A New Method of Expressing Particle Sphericity.. "Recycled Concrete as a Source of Aggregate. in t h e U n i t e d States. pp. H. pp. 3. I. a crossover p o i n t was reached: in 1972 a n d 1973 the totals for s a n d a n d gravel p r o d u c t i o n were." Designation CRD-C 119-48-52-53. American Concrete Institute. pp.624 TESTS AND PROPERTIES OF CONCRETE AGGREGATES a n d gravel. "Volume. texture.6 metric tons (914 a n d 984 million tons). Vol. 21. By their n a t u r e . 4." Living with Marginal Aggregates. No. 1968. A. [7] Wills. Vol.. 1967. 1973. D. American Society for Testing and Materials. Charlottesville. a n d surface a r e a will be m o r e p r o m i n e n t considerations in the future. 843-865. "Waste Glass as Coarse Aggregates for Concrete." Journal. L. Nov. [6] Wills. A S T M STP 597. texture. M. C." Journal of Geology. respectively. Vol. Dec. U. "Reef Shell Beach Sand Concrete. 441. 4. It is the case t h a t the n a t u r a l l y r o u n d e d aggregates are easier to work with a n d have p r e s e n t e d little technical challenge with respect to shape. forecasts t h a t the effects a n d significance of shape. Bd. Miss. "Measurement of Shape Characteristics of Coarse Aggregates. pp. 114 . 1. 5. American Society for Testing and Materials. [30] Chamberlin. 2nd ed.. E. and Goetz... L. 94-97. A." Industrial Minerals Notes 41. C. [35] Heigold. Section M-2." Industrial Research. Highway Research Board. NRC 1968. R. 1970. and Hunn. Freeman. 1941. 1937. Construction and Materials Specifications." Road Research Bulletin No. A. T. T. 1962. 414. Particle Shape for Sand Used in Portland Cement Concrete. 1941.. No further reproductions authorized. [28] Ishai. Va.. and Freeth. Feb." Sehweiz. No. 4.." Journal of Geology. R. Illinois State Geological Survey.. D. "Limestone Fine Aggregate in Portland Concrete. 1. [20] Czarnecka.. W. A. Waterways Experiment Station. 1935. L. H." Proceedings. p. I. pp. "Influence of Natural Sand Fine Aggregate on Some Properties of Hardened Concrete Mortar. 1966. "Projection Sphericity. [15] Krumbein. and Lamar. H. pp.OZOL ON SHAPE 625 [14] Wadell." Civil Engineering and Public Works Review. "'A Rapid Method for the Determination of Shape. 10. Ilan and Tons. "'The Shape of Road Aggregates and its Measurement. "Bertrag zur Schlotteranalyse. No. 211-214. 132] Laughlin. and Gillott. N. 1969. No.. E. "An Exact Method for Characterization of Grain Shape. pp." HRB Record No." Journal of Testing and Evaluation. Mineralog. 91-93.. 43. P." Journal of Sedimentary Petrology. 2. E. Vol. and Sloss.. July 1977. 1958. J. Handbook for Concrete and Cement. pp. D. [18] Ehrlich. Vol.. 2." lndustrialResearch... F.C. June 1977. [36] Mackey.. C... pp. [17] Burke. H. N." Designation CRD-C 120-55. 2. Sphericity and Size of Gravel Fragments. Copyright by ASTM Int'l (all rights reserved)." Highway Materials Research Laboratory. 1965. W. 1957. E. Feb. New York. G. Vol. D. Wash. Shape and Roundness of Quartz Particles. No. 250-280. Nov. E. "A Modified Fourier Method of Shape and Surface Texture Analysis of Planar Sections of Particles. Petrog.. J. E. 39. American Society for Testing and Materials. 6472." Journal of Sedimentary Petrology. E. H." Journal of Testing and Evaluation. March 1970. H. Vol. pp. London. 39-140. [331 Markwiek. 11." HRB Record No.11. D. HMSD. 1961. Aug. Ky. 15. C. 11.. J. [26] Conway. 299-302. S. Charlottesville. No. pp. "Concept and Test Method for a Unified Characterization of the Geometric Irregularity of Aggregate Particles. 124. ..S. V. [24] Krumhein. 1955. [34] State of Ohio Department of Highways. Vol." Virginia Highway Research Council.150. Highway Research Board. [38] Ryland. 205-212. 2. 797-798. 1223-1242. and Gillott. Vol. W. R. J. pp. 103-124. W. "The Measurement of Particle Shape. 4. Vol.4. [23] Pettijohn. 236.." Journal of Sedhnentary Petrology. "The Effect of Orientation on the Analysis of Shape and Texture of Concrete Aggregates by the Modified Fourier Method. E.. No. E. [25] Thiel. [31] "Method of Test for Flat and Elongated Particles in Fine Aggregate. G. E. 703. Sedimentary Rocks. and Stevens. [37] Mueller." Journal of Sedimentary Petrology. 1974. [21] Riley. 1977.. W. [16] Sneed. Lexington.. T. Stratigraphy and Sedimentation. "Volume... 1960. [19] Czarneeka. July 1977. Army Engineers. and Folk. D. U. "Pebbles in the Lower Colorado River. Mitt. C. "Image Analysis Automates Microscopy. VoI. "Measurement of Geological Significance of Shape and Roundness of Sedimentary Particles. pp. 1968. "Texture Analyzer-System. 66. B. pp.. "The Relative Resistance to Abrasion of Mineral Gains of Sand Size. Jan. 5. [22] Zingg. pp. pp.. Aggregates for Concrete. No. and Weinberg." Journal of Geology. 1935. No. Vol." Journal of Sedimentary Petrology. "Two-Dimensional Shape of Sand Made by Crushing Illinois Limestones of Different Textures. P. Harker and Bros. 1956. 60. pp. 62. Vol. 40. "A Test for Evaluating the Geometric Characteristics of Coarse Aggregate Particles. [27] Tons. American Society for Testing and Materials. [29] Huang. "Packing Volume Concept for Aggregates. Y.." Journal of Testing and Evaluation. 3-15. K. R. W. J. Vol. Texas--A Study in Particle Morphogenesis. 5. 292-298. Vicksburg. Vol. American Society for Testing and Materials. R. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. E. 1943. E. April. 1466. Dec.. 3rd ed. Dec. E. R.. Vol. p. 79. Aug. [54] Wenzel. Nov. London. No. R." Proceedings.. [43] Rex. Ernst Leitz.. [41] Rittenhouse. M. G. Wangorsch ed. F. F. 7. 1965. 5th Conference of the Australian Road Research Board. H. "Surface Roughness and Contact Angle. H.. "Surface Texture in Relation to Adhesive Bonding. I11. S.. 1974. 1964. pp. G.. Yandell. "Flexural and Compressive Strength of Concrete as Affected by the Properties of Coarse Aggregates. N. 1955. 1953.. Vol. "Topics in Concrete Technology: 1." Industrial and Engineering Chemistry. Vol. 1964. No. 29. Vol. 14. T. N. F. "Surface Topography Description and Measurement. 1976. 28. [51] Kaplan. "Zur Rauhigkeitzbestimmung yon Gesteinbruchflacher... London." Journal of Sedimentary Petrology. pp. O. No. 7th Annual SEM Symposium. Vol. 10. 1967." Magazine of Concrete Research. Vol. No.." Geologie und Bauwesen.. No. No. Vol. [53] Wenzel." Wear." Journal. D." Magazine of Concrete Research. and Peck. 656-658. . H. Vol. American Concrete Institute. Vol." Symposium on Properties of Surface.. "A Quick Method of Measuring the Surface Texture of Aggregate. American Society of Mechanical Engineers 1-23. F. [40] Kanin. "The Effects of the Properties of Coarse Aggregates on the Workability of Concrete. [47] Clelland. [44] Shergold. Miller.." Journal of Physical and Colloid Chemistry. Wiley. "Resistance of Solid Surfaces to Wetting by Water. Wellington. N. Jan. 53. 4. [60] Powers. A. 1964.. G. V. P. J. Geometric Properties of Particles and Aggregates." Scientific and Technical Information. British Granite and Whinstone Federation." Journal. Vol. 46.. "A Visual Method of Estimating Two Dimensional Sphericity. Vol.. [46] Bennett." Public Roads.." Proceedings. pp. 6. 1971. 118-120. W. J. W. [48] Huang. No further reproductions authorized. 325-341. 1956. New Zealand. X. "A Comparative Study of Twelve Types of Sand used as Fine Aggregate in Concrete. Y. 29. J.. 63-74. 30. 33-59.. N." Journal of Materials." The Microscope. Central Laboratories. "A Stereo-Plotting Device for SEM Micrographs and a Real Time 3-D System for the SEM. 2. 1962. pp. Ministry of Works. pp.Y. F. 1. C. American Society for Testing and Materials.. 1968. J. 1958. "Correlation Between Particle Shape and Surface Texture of Fine Aggregates and Their Water Requirement. 13.." Materials Research and Standards. p. Chicago.. Copyright by ASTM Int'l (all rights reserved). p. "A Modification of the AASHO Road Test Serviceability Tridex Formula. [59] Myers. 19.626 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [39] Haun. "A Comparative Study of Twelve Types of Sand Used as Fine Aggregate in Concrete. 81-111. [56] Orchard. 2. J. "Stone Sand. [58] Wallach. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. [42] Gray. National Crushed Stone Association. 1949. D. 13." Concrete Technology." Magazine of Concrete Research. [63] Boyde.." Journal. and Bell. M. N. W. A. R. [57] Kramrisch. M... and Katakkar. 4. A. "Characterization of Surface Roughness.. [62] Scrivener. IITRA. S. pp. F." Engineering Bulletin No. "The Percentage Voids in Compacted Gravel as a Measure of Its Angularity. [55] Marian. 11. "Sand for Concrete--A New Test Method... Part 5. 1969." Surface Mechanics. 2-15. 1193-1208. [50] Kaplan. and Rzeznik. Kluge. 5. F. Spring. pp. Vol. Vol. W. American Society for Testing and Materials.. 3. "A Method of Measuring the Surface Texture of Aggregate. E. B. Wetzlar." Journal. 1965. J. and Hudson. 1963." HHR No. [49] Bennett." New Zealand Standards Bulletin No. E. May 1959. "An Improved Particle Index Test for the Evaluation of Geometric Characteristics of Aggregates. M. 93. "An Instrument for Automatic Image Analysis. Portland Cement Association Research and Development Laboratories. and Katakkar.. 1936. "A Laboratory Test to Evaluate the Shape and Surface Texture of Fine Aggregate Particles. 5. R. J. [52] Wright.. British Granite and Whinstone Federation. "Properties and Testing of Aggregates. [45] Malhotra. "A New Electro-Optical System for Quantitative Image Analysis. [61] Orchard. Symposium Volume. Vol. and Lye. 182189. F. pp. 1935. pp. E. 1963. H. F.. 3. Aug. American Society for Testing and Materials. W. G. 1. A S T M STP 340. pp. 988. No. 5. W. [77] Patten. Vol. of Technology. "Strength of the Cement Aggregate Bond. IITRA." Revue des Materiaux de Construction. A. E. "Mineralogical Contribution to the Study of Adhesion Between the Hydrated Constituents of Cement and the Embedded Material. 1958. American Concrete Institute. 1. "Good Concrete Depends on Good Aggregate. 225-234.." Technion. "Adhesion of Asphalt to Stone. D... Vol. 5.. Sept. P. Y.. J. [76] Popovics... CV-223 (1967) in Hebrew. 1971." Materiaux et Constructions. Aug. No. Society of the Chemical Industry. 346-349. Emmett. Sept. "Critical Stress Volume Change and Microcracking of Concrete. 4. and Livneh. Vol.. No. J. Nov. Shklarsky.OZOL ON SHAPE 627 [64] Boyde. 1970. O.C. Jan. F. Wardlaw. 1968. T. [84] Alexander. M. H. 1961.. Prague.. pp. Vol. ." Civil Engineering Transactions. No.. H. Israel Inst. M. "High Strength and Water Impermeability of Concrete as a Function of Surface Area Aggregate. and Nielsen. {67} Carman. American Concrete Institute. and Slate. [71] Brodd. B. The Institution of Engineers. p. 1. 86-98." Proceedings. P. Chicago. No further reproductions authorized. "Die Adsorption yon Makromolektilen.. No. London. [87] Ozol. "The Significance of the Aggregate-Cement Bond for the Durability of Concrete. and Chandra. 4. Vol. March 1970. A.." Journal of Materials." Indian Concrete Journal. W. "The Determination of the Specific Surface of Powders. T. American Concrete Institute. R. O. July-Aug. Vol. 770781. F. 1973. D. 309. 66. 1973.. and Jeffery. J. No. and Walker. pp. "The Nature of the Bond Between Different Types of Aggregates and Portland Cement. Civil Engineering Department. S. R. J. 9. F. Vol. Ill. 1957. Vol. July 1938.. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement... 1959. 377-390. [65] Bikerman. F. 1961. S. [70] Brunauer. "Tensile Bond Strength between Aggregate and Cement Paste or Mortar. "Modal Determination of the Effect of Bond Between Coarse Aggregate and Mortar on the Compressive Strength of Concrete.. T. [72] Stamenkovic. C. 1938. "Effect of Paste-Aggregate Bond Strength on Behavior of Concrete. No. J. 53-87. P. P. pp. [73] Krinsley. International Conference on the Structure of Concrete. Vol. T. Durabilite des Betons. [81] Alexander. Journal. "Polarization Capacity at Solid Electrodes and True Surface Area Values. and Gilbert. "Photogrammetry of Stereo Pair SEM Images Using Separate Measurements from the Two Images. "The Effects of Adhesive Bond Between Coarse Aggregate and Mortar on the Physical Properties of Concrete.. Atlas of Quartz Sand Surface Textures. D. 65. Report No. [79] Shah. Australia. 1973. 56. 69-72. 12. No.. Electrochemical Society. pp. D. 1956. Washington. pp. "Aggregate-Cement Bond. 59-81. E. 60.. [66] Gur. 7." Research Report R64-3. S. B. "Influence of Particle Shape on the Properties of Crusher Graded Aggregates. P. 104. Uber Eine Neue Meszmethode. Vol. [75] Blanks. S. Cement and Concrete Association. J. "The Nature of Concrete. Cambridge University Press. [82] Hsu." MakroMolekulare Chemie." Civil Engineering." Journal. and Sept. O. "Adsorption of Gases in Multi-molecular Layers. M. "Aggregate Grading and the Internal Structure of Concrete. 1964. C. Sandor. [78] Darwin. pp. pp. 9. J. and Schliebener." Journal. "The Specific Surface of Concrete Aggregates and its Relation to the Workability of Concrete.. April 1963.. 57. 155-172. Vol." Proceedings.. W." Journal.. 441. 91-98.. 1965.. American Chemical Society. N. and Hackerman.. J. Highway Research Board. C. [74] Powers. [85] Farran. pp. No. pp. F. Nakladatelstoi Ceskoslovenske Akademie red. Sept. and Teller. 122. C. "The Portland Cement Aggregate Bond--Influence of Surface Area of the Copyright by ASTM Int'l (all rights reserved). American Concrete Institute. M. [86] Chatterji. 1969. K. K." HRB Record No. 60. American Society for Testing and Materials. 7th Annual SEM Symposium. W. and Slate." Research Report No. [80] Nepper-Christensen. pp. Massachusetts Institute of Technology. 3. 191-209. pp. Cement Paste Strength and the Strength of Concrete." Journal. I. 45." Colloque International. 651-655. C. Proceedings. Vol. pp. J. 643-68. 1974. [69] Patat. 1966. and pp.." Journal. 5." Significance of Tests and Properties of Concrete and Concrete Making Materials. R. [831 Valenta. 64-66. 1952. A. [68} Shacklock. No.. H." Journal. A S T M STP 169A... 14. and Doornkamp. Vol. Part 1. Vol. A S T M STP 169A. Virginia Highway Research Council.. 1952. Vol. M. F. 115. "Modern Concepts Applied to Concrete Aggregates. 301. American Society for Testing and Materials. Copyright by ASTM Int'l (all rights reserved). 1929. 381-403. "Effect of Particle Orientation Upon Compressive Strength Results." Pit and Quarry. 10. C. 1966." Proceedings. 111-112. B. L.. 1966." Proceedings." Pit and Quarry. No. 1966. June 1952. J. "Observations on the Use of Foliated Rocks for Coarse Aggregate in Paving Concrete. [93] Mielenz. pp." Transactions. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. pp. 1931. R. A S T M STP 169A. C.. [88] Mercer. 44. 1950. "The Properties and Specification of Aggregates for Concrete. Vol. American Society for Testing and Materials. 29. [9l] Ozol. 132. A. [95] Wright. H. 212. p. [96] Hansen. ASCE. Sept." Report No. [90] Scholer. [92] Mercer. [94] Goldbeck. 11. "A Digest of a Report on Effect of Stone Dust on the Properties of Concrete. T. p. B.628 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Coarse Aggregate as a Function of Lithology." Significance of Tests and Properties of Concrete and Concrete Making Materials. W. June 1972." Proceedings. American Society for Testing and Materials. A. .. 487-496. Highway Research Board. R.. Vol. 71-R40. F. P. "Petrographic Examination. 1962. "Aggregate Particle Shape Determination.. L. pp.. 3.. Sept. 45. "The Chemical Reactions. No." Significance of Tests and Properties of Concrete and Concrete Making Materials.. [89] Blanks. "Durability of Concrete. p. 2nd Forum on Geology of Industrial Minerals." The Quarry Managers 'Journal. C. Civil Engineering Department. (3) the specific gravity in order to convert volume to weight.astm. Copyright by ASTM Int'l (all rights reserved). G. density. 1978 W. numbers must be found to describe the aggregates for design and for specification purposes. For most aggregates. absorption. and (5) the surface moisture because mixing water must be adjusted to compensate for it. 27650. unit weight. the properties that lend themselves readily to determination are specific gravity. American Association of State Highway and Transportation Officials. Generally. and grada1professor. Density. Mullen i Chapter 36--Weight.C. sometimes with pores and wrinkles or crevices that hold water. and the tests that find substantial use are fairly simple. Because the particles do not fit together nicely. Raleigh. North Carolina State University. tests for aggregate properties are logical and based upon sound physical principles. (4) the absorption because it affects the specific gravity that is used. Copyright9 1978tobyLicense ASTM International www. spaces called voids are left between them and the whole pile contains water in the pores and on the surface of each particle. and Surface Moisture Introduction Aggregates in stockpiles are collections of various sizes of irregularly shaped particles often with rough or convoluted surfaces. (2) the volume that solids will contribute to the concrete mix. five factors must be determined: (1) the volume of voids in order to fill them with paste and to float the particles apart with an excess of paste. Sun Apr 6 21:45:36 EDT 2014 629 Downloaded/printed by Universidade do Gois pursuant Agreement. N.org . including use in portland cement concrete. In order to use these aggregates as the largest part of a concrete mixture. since most concrete is batched by weight. For construction purposes. such as those published by The American Society for Testing and Materials.STP169B-EB/Dec. Absorption. even when located on the edge of the African desert. To accomplish this identification. they are fairly well codified to meet the testing and specification needs for most construction work. and others. No further reproductions authorized. The tools for this identification are provided to the construction industry through standard specifications and methods of test. aggregates often are identified by physical properties and by gradation. when. specific gravity. . For many lightweight or highly porous aggregates. minerology. but for a given aggregate the values are relatively stable for design purposes. or. Such numbers are unit weight. Testing for production is an aid to control of quality in the world of commerce. Testing for research is an aid to understanding in the solution of problems. size. gradation. using simple equipment and procedures and without unnecessary requirements for precision. it may be insufficient statistically to give a value that is reliable. without companion tests. absorption. If the end is accomplished without detriment to any of the parties participating or affected. The values that are obtained for physical properties vary with aggregate source. if possible. All aggregates are different when we examine them closely enough. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. specific gravity and absorption are not determined as readily for normal or heavyweight aggregates due to their highly vesicular nature and due to inability to distinguish between surface roughness or rugosity and surface porosity. Fortunately." A single test may be worthless if it determines a value that has no use. These numbers should be determined simply. such arguments consume valuable time in standardization committee work and bring to mind the Lilliputian political parties [1] 2 who were divided into "big enders" and "little enders" over which end of an egg to open. Unfortunately. it did not matter as long as the egg could be opened. voids. in truth. and so on. The only variable quantity that is needed regularly in concrete mixture production is the free or surface moisture and this value usually is not required until after mix proportions have been established. it may be harmful if it furnishes an erroneous value that is believed. density. it is possible to arrive at workable concrete mix proportions without knowing aggregate specific gravity through the use of density or yield trial batching. Copyright by ASTM Int'l (all rights reserved). shape and surface texture. A Philosophy of Aggregate Tests A "single test" is not worth a thousand "expert opinions. An example of confusion is the running controversy over use of the terms density and specific gravity where the purists would have us use density in place of specific gravity. but to 2The italic numbers in brackets refer to the list of referencesappended to this paper. Testing requirements for research and for production must not be confused. What is needed from aggregate tests are numbers describing properties of aggregates that may be used for design purposes or for acceptance. range of gradation. Gradation and unit weights are determined easily for almost all aggregates. then the use of specific gravity is perfectly legitimate. No further reproductions authorized. It does not really matter which term is applied as long as the designer or buyer or seller is comfortable with the term and finds it useful in his work.630 TESTS AND PROPERTIES OF CONCRETE AGGREGATES tion. Aggregate Configuration It is generally recognized that aggregate particles come in various sizes that are described for engineering identification purposes by separation on square opening sieves. and angular aggregates produced as gravel. Rugosity has been described by Tons and Goetz [4] as the asphalt holding capacity or the surface roughness of aggregate particles when an asphalt coating is applied and then literally scraped off. the surface. Aggregate particle surfaces vary from smooth sometimes glassy to rough irregular surfaces. Sometimes the crystal structure of ledge rock is such that for a particular size all particles may be single crystals with cleavage planes as surfaces. There are rounded. Such an aggregate containing single feldspar crystals was recently encountered in North Carolina [2]. and crushed stones with varying degrees of rounding of the corners and edges. water. . Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or glacial transportation. ABSORPTION. Kummer and Meyer [7] in their work on skid resisCopyright by ASTM Int'l (all rights reserved). We must stand far enough away in testing to see only those properties that are important in our work. and surface texture or roughness. Tons and Ishai [5] describe a concept and test method for geometric irregularity of aggregate particles that includes microvoids. Shape and surface texture of aggregate particles have been discussed by Mather [6] using the terms sphericity. 1 and 2. The rugosity is indexed to the volume of asphalt held by the surface which represents the amount of material that must be applied to "smooth up". DENSITY. Crushed stones produced directly from ledge rock by and large have rough surfaces. No further reproductions authorized. and packing voids as seen in Figs. and roughness as descripters. subangular. angularity. roundness. Calcite crystals have been known to break out as single particles [3]. crushed gravel. It also is recognized that aggregates having the same size designation may vary widely in shape. The rugosity also can be an index of possible surface interlock between adjacent aggregate particles and of the frictional resistance to movement of one surface past another when in contact. macrovoids. As a general rule natural gravels and sands tend to have smooth surfaces from polishing during wind. AND MOISTURE 631 describe these differences may not be necessary for use of the aggregates in construction. Fortunately most of the ASTM tests that will be discussed here attack the opening of the egg and leave the question of which end of the egg to approach to be considered only when it truly makes a difference in the value to be obtained from the test. Minerology and porosity of the source rock as well as natural polishing contribute to the final surface texture. The textures of slags and lightweight aggregates may vary from glassy to extremely rough depending upon the processing method. To do otherwise will result in unnecessarily complicated tests that probably will not find wide usage.MULLEN ON WEIGHT. smoothness. No further reproductions authorized.~. Porosity / FIG. the degree of compaction obtained. Visual evidence of differences in aggregate mobility between particles of different shapes and texture is shown in Fig.. and geometric irregularity of aggregate particles.EffectiveVolumeMembrane Asphalt/ ~ '~ ~ Apporent Volume Membrane Absorphon "~ "~ ..) tance treat surface texture of pavements and. 1--Packing volume. (From Ishai and Tons IS].. . by inference.. Goldbeck and Gray [8] in their application of the b/bo concept for concrete mixture design account for differences in aggregate mobility as Copyright by ASTM Int'l (all rights reserved).~ V o i d s ImpermeobletoWoter Surface Voids r ~ . Aggregate mobility affects the energy required for compaction of aggregates and.. fine. of aggregates in certain types of pavements using smooth. and gritty for sharpness of texture as shown in Fig.~ / . ~ Impermeable to/ Asphalt FIG. the ease with which aggregate particles move past one another when manipulated.~ ~___. in a standard compaction procedure. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.~Ao. Shape and texture affect aggregate mobility.632 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Macro-Surface Voids ~ -f Packing /-/ Volume Membrane Pocknig ~'~E ~ j " ~ . 2--Volumetric characteristics of an aggregate surface pore.) Micro Surface ~ Voids Macro Surface ~ Voids ~ / ~ f " -- ~o\~ . and coarse for size or depth of texture and smooth. packing porosity. The mobility of an aggregate affects the workability of fresh concrete as well as the quantity of coarse aggregate that may be used.~ . rounded. 4 where it is possible to form a pile of unconfined crushed stone several particles deep while unconfined glass marbles can be piled only one particle deep. 3. (From Ishai and Tons [5]. _ ~ __ ~ MaximumVolume Membrane (Mix) PackingVolume Membrane Bulk VolumeMembrane ~ . ROUNDED (~) COARSE TEXTURED. No further reproductions authorized. the surface area will double as the Copyright by ASTM Int'l (all rights reserved). 4--Aggregate mobility affected by shape and surface texture (photo).) FIG. GRITTY (~ COARSE TEXTURED. AND MOISTURE 633 (~ SMOOTH (~ FINE TEXTURED. absorption. reflected in the dry rodded unit weight of coarse aggregate. . DENSITY. a measure of packing density. (After Kummer and Meyer [6]. ROUNDED ~) FINE TEXTURED. GRITTY FIG.MULLEN ON WEIGHT. If size of aggregate and range of sizes of aggregate are considered as part of aggregate configuration. For a given weight of aggregate. sometimes for specific gravity. and for free or surface moisture. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 3--Surface textures. then both affect the values obtained for unit weight. ABSORPTION. surface area increases dramatically. A=24 V=l A=12 V=I A=6 FIG. Particle shape affects surface area with a sphere having the most efficient containment of volume and flats and flakes having the least efficient containment. No further reproductions authorized. one size spheres have voids less than 30 percent while angular particles produce packings with voids that often exceed 50 percent. the relationship between particle size is not quite as straightforward for different shaped aggregates as in the case of the cubes illustrated in Figs.91 If flat and elongated particles are considered. When packings of these geometric shapes are studied. . Classic studies in this area are those by Fuller and Thompson [9] and by Weymouth [10].634 TESTS AND PROPERTIES OF CONCRETE AGGREGATES particle size is halved. Copyright by ASTM Int'l (all rights reserved). Put differently. This concept is illustrated in Figs. For geometric shapes of equal sieve size. Due to the use of square opening sieves. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 5 and 6 by subdividing a one unit cube of aggregate. the following relations for surface areas for equal absolute volumes hold: spheres 1 cubes 1 pyramids 1. S--Surface area versus particle size at equal volumes. 5 and 6. the amount of surface intersecting internal pores allowing absorption is doubled as is the surface area to hold a given film thickness of surface water. It is well known that packings of particles containing a range of particle sizes result in reduced void contents in keeping with the presence of particles small enough to fit into the voids between larger particles. Neither unit weight nor voids are defined in ASTM Definitions of Terms Relating to Concrete and Concrete Aggregates (C 125). called voids. unit weight and voids are complimentary. when one increases the other decreases. That specific gravity may be affected by particle size is evident with some lightweight aggregates where specific gravity tends to increase as particles become smaller due to elimination of vesicules by crushing. being made up of irregularly shaped particles. No further reproductions authorized. good measure pressed down. For with the same measure that ye mete withal it shall be measured to you again. do not fit together nicely with the result that spaces are left between the particles. 6--Size surface area relationships. AND MOISTURE 635 /. Brink and Timms [1l] describe unit weight as follows: "The unit weight of a concrete aggregate is the weight of a unit Copyright by ASTM Int'l (all rights reserved). Voids are usually expressed as percent of volume of a packing arrangement as described above. ." Aggregates. Unit Weight and Voids Historically. These spaces. One such reference to a "compacted" unit measure from Luke 6:38 in the King James translation of the Bible follows: "Give and it shall be given unto you. that is. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and running over.8_ Ld UJ 24_ h r 12_ 67 ! 1 1/8 1/4 I ! 112 I 7 PARTICLE S I Z E FIG. are affected by the shape of the particles. and the orientation or packing arrangement of the particles. unit weights and unit measures have been with us almost since recorded history. For aggregate packings. DENSITY. and shaken together. shall men give unto your bosom.MULLEN ON WEIGHT. but both are the subject of ASTM Standards. the size distribution of the particles. ABSORPTION. Standard unit weight measurements are obtained on aggregates dried to essentially constant weight at 105 to l l 0 ~ (221 to 230~ Copyright by ASTM Int'l (all rights reserved). Compaction is accomplished by rodding for aggregates that are 11/2 in. (40 mm) maximum size aggregate. When specific gravity is 2. When the test is performed properly. Maximum size is defined in ASTM Definition C 125 as the smallest sieve opening through which the entire amount of aggregate is required to pass. (40 mm) maximum sized aggregate can be compared to a sample size of 16 kg (36 lb) specified for this same aggregate size in ASTM Test for Sieve or Screen Analysis of Fine and Coarse Aggregates (C 136) if calculations are made assuming values for specific gravity and voids. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The purpose of the test is to determine the weight that will be contained in the measure of known volume. For smaller maximum sized aggregates volume calibrated measures having nominal volumes of I/2. (40 mm) maximum size and smaller and by jigging for aggregates that are larger than 11/2 in.3 lb). the results of repeated tests on the same sample by the same operator should be reproducible within 1 percent. The sample weight contained in a given measure will vary with the density of packing and the specific gravity. For the 4 in. The sample size for a 11/~ in.70 and voids are 45 percent. ASTM Test for Unit Weight of Aggregate (C 29) provides for determination of unit weights of aggregates of maximum size of 4 in. Loose unit weights are determined by a shoveling-filling procedure without compaction. ASTM Test C 29 provides for compact and loose unit weight determinations. . and 1/10ft 3 are variously specified. (100 mm) and smaller. the measure is filled in three layers with the first two layers leveled with the fingers and the third layer placed to overflowing with the surface leveled using a straightedge or the fingers in such a way as to balance projections and depressions in the final surface. In both cases. (100 mm) maximum size.636 TESTS AND PROPERTIES OF CONCRETE AGGREGATES volume of representative particles. then the sample weight for the 1/2 ft 3 foot measure is calculated to be 21 kg (or 46. The number of aggregate particles will vary with the density of packing for a given maximum size and gradation meaning that the number of particles in the packing will be affected by the particle shape. In the case of 1 89 in. a volume calibrated container (a measure) having a nominal capacity of one cubic foot is specified thereby determining the sample size by volume. (40 mm) maximum size as these larger aggregates do not lend themselves to compaction by rodding. %. "Representative particles" is a synonym for representative sample. somewhat larger than that required for ASTM Test C 136. a sample of sufficient size to represent the stockpile or barge or bin or other supply of aggregate to be tested." Accordingly unit weight has been expressed in terms of pounds per cubic foot when these units are in use and in kilograms per cubic metre in the International System of Units (SI) and in keeping with ASTM Metric Practice (E 380). No further reproductions authorized. the 89 ft 3 measure is the smallest that may be used. as will the unit weight and voids. . DENSITY. changes in unit weight are indicative of changes in angularity or in gradation or of changes in both. r from balance capacity required by ASTM Test C 29. as small particles fill the spaces between larger particles. and heavyweight. greatest increase in unit weight of concrete over aggregate weight will occur when b / b o = 1 or with preplaced aggregates. air cooled slag. (b) graded aggregates pack more densely than one sized aggregates. aggregates may be classified into nonstructural or insulating lightweight. In terms of unit weight.13]. ASTM Specification for Lightweight Aggregatesfor Structural Concrete (C 330). AND MOISTURE 637 The unit weight or dry rodded unit weight as it is often called for compacted aggregate is directly useful in concrete mixture design where the b / b o method as applied by Goldbeck and Gray [8] and its variations are used [12. No further reproductions authorized. July 1968. and ASTM Test for Unit Weight of Aggregate (C 29). Due to the presence of aggregate voids. gradation and compaction and some rules of thumb apply as follows: (a) rounded particles pack more closely and have fewer voids than angular particles. ASTM Specification for Lightweight Aggregatesfor Concrete Masonry Units (C 331). ASTM C 29c PcAb aASTM Specification for Lightweight Aggregates for Insulating Concrete (C 332). As b / b o decreases below 1. For a given aggregate source. unit weights of concretes using the aggregates will almost always be greater than the aggregate unit weights. For aggregate of a given specific gravity voids will vary inversely as the unit weight. bDesign and Control of Concrete Mixtures. and (c) voids decrease with compaction effort that brings about most favorable particle orientation. structural lightweight. the unit weight of concrete will also decrease for these higher specific gravity aggregates. Table 1 contains unit weight ranges for these aggregate classifications as found in ASTM or other references [12]. Copyright by ASTM Int'l (all rights reserved). Increases will be greatest when grout or mortar has a higher specific gravity than the aggregate especially if the b / b o value is less than one. Some measure of unit weight is particularly useful in grouting of preplaced aggregate where work may be completely underground or underwater or obscured from visual control in some other way. Voids are affected by aggregate shape. normal weight. ABSORPTION. In the case of aggregates with specific gravities greater than the grout or mortar specific gravity. ASTM Specificationfor Concrete Aggregates(C 33).MULLEN ON WEIGHT. Portland Cement Association. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Aggregate Classification Insulating Lightweight for masonry Lightweight for concrete Air cooled slag Normal weight Heavy weight Unit Weight Range Compaction lb/ft 3 (kg/m 3) Mode 6 to 12 (96 to 196) 55 to 70 (880 to 1120) 55 to 70 (880 to 1120) > 70 (> 1120) 75 to 110 (1200 to 1760) 110 to 290 (1760 to 4640) dry loose dry loose dry loose compacted compacted compacted Unit Weight Source ASTM C 332a ASTM C 331a ASTM C 330a ASTM C 33 a PCA b. TABLE 1--Unit weight classification for aggregates. 355 • 100 where A = bulk specific gravity of aggregate. In cases of this type where normal equipment is not available. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.355 = weight in pounds per ft a of water at 62~ (16. (63. In both cases. and 62. (736 mm) inside diameter pipe piling. The effect of overestimating the voids would have been to allow the grout pool to rise above the aggregate surface. and this situation would have resulted in dropping aggregate through water and grout as new increments of aggregate were added. it is a simple matter to compute an estimate of specific gravity. churning and Copyright by ASTM Int'l (all rights reserved). The effect of underestimating voids would have been to allow the grout pipe to be pulled out of the grout pool as pipe sections were removed resulting in mixing grout and water together in the piling.638 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Voids expressed in percent are determined using ASTM Test for Voids in Aggregate for Concrete (C 30). all of these quantities can be estimated and checked frequently if a carpenter and platform scales are available. No further reproductions authorized. % = (A • 62. voids. aggregate. B = unit weight of the aggregate. The box is then filled level full with water to determine the voids volume from the added water weight.B A X 62.7~ Sometimes in construction. A tightly constructed cubic foot box is placed on the platform scales previously leveled. Aggregate barged to the site from two sources was dropped into the pilings in increments using a clam shell and a hopper funnel. The voids were checked barge by barge using a cubic foot plywood box and a platform scale. It was necessary to know the voids in the aggregates to control the grout level in the preplaced aggregates to keep the grout pipe below the surface of the grout pool and the grout pool below the surface of the preplaced aggregates. and specific gravities will be unknown and field estimates are desired. With volumes of box. followed by weight of box filled with aggregates compacted in the manner that represents use. unit weights. During the construction of the cast-in-place concrete pilings for the main piers of the Tappan Zee Bridge [14] it was necessary to know the voids of preplaced aggregates in the pilings that extended to rock about --300 ft (--90 m) and were cut off below water at about --20 ft (--6 m). ASTM Test C 30 is actually a calculation method using the formula Voids.355) -. . Weight of box is obtained. Actually the testing is accomplished using ASTM Test C 29 for unit weight and either ASTM Test for Specific Gravity and Absorption of Coarse Aggregate (C 127) or ASTM Test for Specific Gravity and Absorption of Fine Aggregate (C 128) to obtain the bulk specific gravity. and voids known. a variation that if ignored could have affected by several feet the calculated level of the grout pool in a 280 ft (85 m) long 29 in.5 mm) nominal maximum sized aggregate. Voids ranged from 45 to 53 percent for 21/2 in. Copyright by ASTM Int'l (all rights reserved). the two methods for coarse and fine aggregates. 7--Specific gravity determination schemes.MULLEN ON WEIGHT. grout levels were verified using an hydrometer with a specific gravity of 1. WEIGHT IN AIR [A] SPECIFIC G R A V I T Y WEIGHT IN WATER [B] = A A-B /. The hydrometer would float on grout having a specific gravity of 2. 7. DENSITY. Within 50 ft (15 m) of the surface. Overflow devices have been used also where the water displaced by aggregate may be caught and weighed.06 and sink through river water. There are a number of ways to determine specific gravity. . the method employed involves determination of weight in air and determination of volume of water displaced.~ WATER WEIGHT GRADUATION LINE AGGREGATE AGGREGATE WEIGHT c SPECIFIC AND WATER D GRAVITY = E D C§ D-E FIG. but the two approaches above are the basis for ASTM Tests C 127 and C 128. ABSORPTION. No further reproductions authorized. Specific Gravity and Absorption Specific gravity is defined as the ratio of the weight of a given volume of material to the weight of an equal volume of water.5 on a sounding line. AND MOISTURE 639 mixing of water into the grout would have resulted in weakened concrete at the affected locations. Usually for aggregates. a dimensionless number. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The two basic schemes for making the water displacement determination are shown in Fig. but all involve some measurement of weight and volume. Porosity as it increases becomes extremely important in specific gravity determinations to the point that with some highly vesicular aggregates. there are two moisture conditions that enter into specific gravity calculations though. However. 8. and the volume excluding the pores that will be smaller than the bulk volume by the volume of the permeable pores. the volume including permeable pores known as the bulk volume. Therefore specific gravity determinations must be and are temperature related and surface porosity must be treated to account for volume of permeable pores. Copyright by ASTM Int'l (all rights reserved). There are two volumes that may be determined. bulk dry and saturated surface dry.FREE WATER (~~FILM SSD+FREE WATER 9 PORES EMPTY 9 PORES SATURATED 9 PORESSATURATED 9 SURFACE DRY 9 SURFACE DRY 9 SURFACEWET 9 LIGHTER C O L O R 9 LIGHTER COLOR 9 DARKER COLOR 9 FINE A G G R E G A T E FLOWS 9 FINE A G G R E G A T E FLOWS 9 FINE AGGREGATE CLINGS FIG. As shown in Fig. 8 and the schemes illustrated in Fig. The reason for this problem is that it is almost impossible to determine either of the two volumes needed for the calculations. three specific gravities are determined as follows using ASTM Tests C 127 and C 128. specific gravity determinations. 7 because of aggregate surface and internal porosity and rugosity and because water varies in density with temperature. Using the volumes and weights shown in Fig. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . are approximations at best. 7. As a result of treatment of permeable porosity and its water content we have not one but three specific gravity values that are determined for both fine and coarse aggregates.640 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Specific gravity determinations are not quite as simple as indicated in Fig. 8 illustrating the presence of permeable pores and varying moisture contents. three moisture condi- ~ BULK DRY ABLE PORE ABSORBED WATER SSD ~_. tions may actually exist under test conditions. No further reproductions authorized. A schematic aggregate particle is shown in Fig. 8--Aggregate moisture conditions. The Manual of Concrete Testing [15] contains the same cautions indicating that the 24-h period is not always long enough for resaturation to occur. Absorption is expressed as a percentage of the oven dry weight. In both ASTM Tests C 127 and C 128 an SSD sample is weighed in air. the aggregate must be brought to a saturated surface dry (SSD) condition. while the free water is variable and a property of the aggregate only in that the capacity to carry free water is related to aggregate surface area. If there are any permeable pores. bulk specific gravity--where the oven dry weight is used with the volume that includes the permeable pores. Additionally. bulk specific gravity (saturated surface dry basis)--where the weight of the aggregate including weight of water in permeable pores is used with the volume including the volume of the permeable pores. drying is accomplished by gentle manipulation under a warm air current until particles when molded into a cone shape will not retain the shape when the mold is removed. If there are any permeable pores. AND MOISTURE 641 1. absorption is generally higher for fine aggregates than for coarse aggregates. For coarse aggregate. In order to determine absorption. Both methods include a precautionary note indicating that when concrete is proportioned using naturally moist aggregates that oven drying and resaturation for 24 h may yield specific gravity and absorption values that are too low for their intended use. . The key to recognition of the change from surface wet to SSD is that a color change will occur from dark to light in all aggregates when the surface water film is gone. No further reproductions authorized. For fine aggregates. the apparent specific gravity will be higher than either of the other two specific gravities. Absorbed water is the unbound water contained in the permeable pores of the aggregate particles that may be driven offby oven drying at 100 to 110~ The water carried by an aggregate that is not contained in the pores is surface water or free water. DENSITY. The difference in the two waters is that absorption is a property of the aggregate. Both ASTM Tests C 127 and C 128 require that aggregates be oven dried and resaturated for 24 h before specific gravity determinations are made. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Copyright by ASTM Int'l (all rights reserved). Because of the surface area per unit volume of material. particles are dried in a towel until all visible surface water films are removed. ABSORPTION.MULLEN ON WEIGHT. for similar minerals. 3. ASTM Tests C 127 and C 128 prescribe the means for drying aggregates from a free surface moisture condition back to a SSD condition. excluding the volume of permeable pores. the bulk specific gravity (SSD Basis) will be higher than the bulk specific gravity. 2. fine aggregate particles will no longer cling together when SSD. apparent specific gravity--where the oven dry weight of aggregate is used with the volume. Then the measurement must be made quickly for the SSD condition is transient in a drying atmosphere. then in water to determine its SSD volume followed by drying at 100 to 110~ to constant weight to determine the absorbed water weight and by calculation its volume. adjustments were made in the presaturated procedure for subsequent days of concreting. but free water was present in such quantity that it was draining through the stockpile.642 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Crushed angular particles generally have higher absorptions than smooth rounded particles because the surface area is higher. Absorptions may range from a fraction of one percent for silica gravels and some granitic rocks to several percent for some limestones. No further reproductions authorized. The original specifications read that the stockpiles would be sprinkled for 24 h immediately prior to use. range from about 1. In batching concrete. As lighter weight particles are often porous. The adjustment required that stockpiles be sprinkled for 24 h but that sprinkling be discontinued at least 24 h before the stockpile was to be used to allow free water moisture to stabilize before use. For heavyweight concretes. . most aggregates are in an SSD plus moisture condition. One trend that is an exception to the general rule is for lightweight fine aggregates to have lower absorptions than lightweight coarse aggregates. The importance of absorption varies with magnitude of absorption. In ASTM Test for Lightweight Pieces in Aggregates (C 123). Specific gravities give us the means to convert weights to absolute or solid volumes for proportioning.8 to 5. lightweight coarse and fine aggregates were presaturated by sprinkling the stockpiles. Presaturation was successful. One has to be particularly careful with lightweight aggregates and probably the best practice is to presaturate the aggregates before batching. On the Tappan Zee Bridge [16]. moisture adjustments were made on practically every batch to compensate for free water changes. aggregates are separated at a given specific gravity according to whether they float or sink in a liquid of given specific gravity. Among normal weight aggregates. aggregates can absorb mixing water and affect the workability of the mixtures. In order to produce concretes of certain unit weights. aggregates and air contents must be varied as cement and water specific gravities are constants for all practical purposes. the test is conducted with the aggregates in an SSD condition to prevent the heavy liquid being absorbed by the aggregates. lighter weight or lower specific gravity particles are sometimes of questionable durability in concrete mixes. Obviously.7 down to less than one for some expanded slags.0 specific gravity range while light aggregate specific gravities. high specific gravity minerals such as iron ores and barites in the 3. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Normal weight concretes are made with aggregates in the 2. Needless to say.2 specific gravity range are used. Structural lightweight aggregates may reach 10 to 15 percent absorption while nonstructural lightweights may exceed 100 percent absorption.4 to 3. when they can be determined. Ropke [17] reported a quick Copyright by ASTM Int'l (all rights reserved). If this is not the case. Sometimes steel punchings are used. Water was being batched by weight and on the first day of concreting. porous aggregates will have higher absorptions than nonporous aggregates. Specific gravities also can be used for identification or acceptance purposes. The percentage of such quick drying particles in the sample was determined and the sample was rejected outright or accepted for further testing on the basis of this preliminary test. an unstable moisture content is indicated with water actually draining through the stockpile or bin. mortars. spread it on the floor. It is best to allow any stockpile to drain and to reach a stable moisture content before use in concrete. If higher free moisture percentages are encountered. By and large in concrete proportioning. The free moisture is almost always expressed as a percentage of the bulk or oven dry weight. At this time. It is difficult to distinguish between free and absorbed moisture of lightweight aggregates so that use of total moisture is often a better means of controlling consistency of lightweight concretes. No further reproductions authorized. it will range from near zero to a maximum of 1 or 2 percent on normal weight aggregates. AND MOISTURE 643 field laboratory test that he used in prospecting for glacial gravels in an area of upstate New York where lightweight particles could be a problem. Surface water is part of the mixing water in concrete mixes. Surface Moisture Surface or free moisture is that water carried on the surface of an aggregate that is available for lubrication or mixing water and for hydration or chemical reaction with the cement. specific gravity is used and is applied to the individual components of concrete: aggregates. All aggregates stored in outside stockpiles will carry free or surface moisture. The porous lighter weight particles dried almost immediately as evidenced by color change because they absorbed the surface water. As noted in earlier paragraphs. For coarse aggregates. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ABSORPTION. and concretes are described by using weights or weight per unit volume. Fine aggregate free moistures range from 3 to 8 or 9 percent with 4 to 6 percent being about normal. Fluctuating surface moisture contents make water adjustments difficult and consistency control exacting. lightweight aggregates may have moisture contents in excess of 100 percent in some cases. ASTM Test for Total Moisture Content of Aggregate by Drying (C 566) is used for fine and coarse aggregates. and doused it with a bucket of water. mostly absorbed. true density or mass per unit volume seldom is used to describe concrete or aggregates. Density Scientifically. Mixtures of these individual particles into pastes. density is defined as the mass of a unit volume of a material. A few words were written in the introduction about the use of density instead of specific gravity. Free moisture is a variable quantity that must be determined at time of use. and water. DENSITY. cement. . He took an oven dried sample of gravel.MULLEN ON WEIGHT. The total moisture is determined by drying a moist sample of appropriate size for the aggregate size at 100 to 110~ Copyright by ASTM Int'l (all rights reserved). a gas stove. No further reproductions authorized. Problems with moisture sensors. One is the use of the Speedy Moisture Tester that has powdered carbide to generate gas from the free water on a fine aggregate sample in a closed chamber. This moisture condition is defined in the method as thoroughly dry. Weights are determined to the nearest 0. aggregate weight and mix water adjustments are made automatically while in less sophisticated plants. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and all reach-in moisture sampling schemes for that matter. Usually adjustments are made to the nearest 1 percent of free water content. Control of changes in surface moisture is possible to a certain extent and should be undertaken where possible. this type of problem calculation can be readily put into nomograph form for rapid graphical solutions. stockpiles will have a moisture gradient from top to bottom so that systematic removal of material from a Copyright by ASTM Int'l (all rights reserved). Location of sensors and sample vents is important to ensure that representative samples are taken. Knowledge of and adjustment for surface moisture is the key to successful consistency control in concrete batching and mixing operations. Using ASTM Test for Surface Moisture in Fine Aggregate (C 70). the surface or free moisture is determined using a displacement scheme.1 percent additional loss in weight. Gasoline stoves are not recommended because they are a possible fire hazard. From the volume and the weight. Temperature is not controlled in ASTM Test C 70. the method is used to determine the volume of a weighed wet sample including the surface moisture. Free moisture percent is calculated from the total moisture percent by subtracting the percent absorption. In effect. then free surface moisture is present and the proportions by weight of water and aggregate to produce the specific gravity can be calculated. or a gasoline stove. In some cases. Temperatures in these frying pan methods often exceed the 100 to l l 0~ drying temperature specified in ASTM Test C 566 which make it possible to complete a test in 10 to 20 min. For example. are that sampling may be from dead areas in the bins rather than from the aggregate flow stream. If the sample specific gravity is less than the bulk specific gravity (SSD Basis) of the aggregate. manual adjustments are set up by the batch plant operator. More and more batch plants are being equipped with electronic moisture sensors placed into the aggregate bins with readout on the batching console. they can be converted to percent free moisture based upon SSD aggregate. the specific gravity of the mixed aggregate and surface water sample can be calculated. This gas generated causes the pressure in the chamber to rise and this can be read on a pressure gage as free moisture expressed as a percentage of the wet sample weight. Once the weights are known. For a given aggregate. Another method is to dry the sample in a frying pan over a hot plate.1 percent. There are other methods of determining free moisture in the field with varying accuracy. The carbide does not generate gas from absorbed water and a test can be completed in a minute or two.644 TESTS AND PROPERTIES OF CONCRETE AGGREGATES until further drying produces less than 0. . J. unless b i n s are heated. Egons and Goetz. July 1968. DC. A. Illinois. and Surface Moisture. DC.. pp. 1933. Vol. A. Ilan and Ton. ignited the b a t c h plant. Gullivers Travels. [11] Brink. Vol. G. C. N. G. A S T M STP 169." Rock Products. 1968. National Crushed Stone Association. Aug. p. American Society for Testing and Materials. HighwayResearch Board. and Durability. Bryant. K. "'LightweightConcrete Deck for Tappan Zee Main Spans. E. Washington. Bins left filled overnight will have a c o n c e n t r a t i o n of m o i s t u r e at the discharge gate m a k i n g it necessary to treat the first few b a t c h e s for moisture a d j u s t m e n t s at the start of work on a n individual basis to ensure consistency control. 29.Y. H. 1968. Part 1. Madigan-Hyland Consulting Engineers.." Transactions. 1907. H. Copyright by ASTM Int'l (all rights reserved). E... Absorption.Y." Final Report. W. "A Concrete Failure Attributed to Aggregate of Low Thermal Coefficient. 631. Portland Cement Association. "A Method of Proportioning Concrete for Strength. C. W. [2] Mullen. American Society for Testing and Materials. 67. "Tentative Skid Resistance Requirements For Main Rural Highways. [17] Ropke. A. p. 1957-1959. and Timms. [15] Annual Book of A S T M Standards. 685-694. pp. G.. . G. Dec. p. W. Avoid the experience of the b a t c h p l a n t operator in upstate New York who when faced with frozen b i n s poured gasoline into the tops of the bins a n d ignited it to thaw the aggregates [18]. American Society for Testing and Materials. American Concrete Institute. "Packing Volume Concept for Aggregates. N. and Gray." BHR Report No. and Meyer. [18] Mullen. No further reproductions authorized. Jonathan.. "Weight. and Whitfield. G.. ABSORPTION. [8] Goldbeck. American Concrete Institute. "Construction Diaries--Berkshire Thruway." NCHRP Report 37. Washington.. 25 Feb. Egons.. 1967. [4] Tons. William B. 235. Jack. 11. 1957. "Surface Wear and Skid Resistance of Portland Cement Concrete Pavements. Surface Texture. and Thompson. [7] Kummer. W." Proceedings. 1952-1955. 26. A S T M STP 169A. American Society of Civil Engineers.4. J. and Coatings.. 1942." Significance of Tests and Properties of Concrete and Concrete-Making Materials. T. Density." Madigan-Hyland Consulting Engineers. "Shape.. p.1-74). 38. DENSITY. [6] Mather. a n d b u r n e d it to the g r o u n d . American Concrete Institute. L. AND MOISTURE 645 stockpile will allow moisture contents to change gradually. Workability. Part 14. p. 1966. W. 415. [9] Fuller. 1977.. W. R. T h e aggregates were thawed b u t the gasoline r a n from the b o t t o m of the bins. [16] Mullen. "Concept and Test Method for a Unified Characterization of the Geometric Irregularity of Aggregate Particles. Skokie. J. Construction Diaries--Tappan Zee Bridge. "The Laws of Proportioning Concrete. 1977. private communication. Sun Apr 6 21:45:36 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Engineering Bulletin No. 1975. [13] "Recommended Practice for SelectionProportions for Normal and HeavyweightConcrete" (ACI 211. I n freezing weather. Jan. 55. 1966. 1976. E. North Carolina State University. Sanford. llth Edition. [12] Design and Control of Concrete Mixtures. aggregates will freeze together if b i n s are left filled over night. [5] Ishai. "Effect of Particle Interference in Mortars and Concrete. Manual of Concrete Practice. Project ERSD 110-74-3.." Significance of Tests and Properties of Concrete and Concrete-Making Materials. [10] Weymouth. [3] Pearson. References [1] Swift.MULLEN ON WEIGHT. W. [14] Mullen. p. G. 76-96. 432.." Proceedings. Highway Research Program. Highway Research Board.." Journal of Testing and Evaluation. STP169B-EB/Dec. 1978 W. The ratio of the weight of water to that of dry solids is the absorption. Such confusion in terminology is unfortunate. Sun Apr 6 21:31:13 EDT 2014 646 Downloaded/printed by Universidade do Gois pursuant Agreement. absorption. These properties include density. The purpose of this article is to discuss the parameters related to the pore system of an aggregate. 2 It is not intended to repeat details needlessly. not that between pieces. Liquids.astm. Definitions Concrete aggregates have a bulk volume that is the sum of the volume of their solids and that of their voids or pores. The porosity and the degree of saturation control the various densities. Ind. Copyright by ASTM Int'l (all rights reserved). strength. and Gases (E 12). and freezethaw resistance. the methods for their measurement. Copyright9 1978tobyLicense ASTM International www. Dolch Chapter 37 Porosity Introduction Most of the important properties of concrete aggregates are influenced strongly by the volume and dimensions of the internal pore system of the material. No further reproductions authorized. the properties that describe a pore system in a porous solid are the size distribution and shape of the pores. 2The italic numbers in brackets refer to the list of references appended to this paper. Purdue University. The ratio of the volume of contained water to volume of voids is the saturation of the void system. Lafayette. 47907. 2]. Other than total volume of voids. School of Civil Engineering. the latter of which is measured by ASTM Test for Voids in Aggregate for Concrete (C 30).org . and the properties of the aggregate and concrete they so strongly influence. The voids will be either empty or will contain water. lProfessor of engineering materials. L. which are defined by ASTM Definitions of Terms Relating to Density and Specific Gravity of Solids. This void volume is that within the piece of aggregate. but to emphasize subsequent developments. The porosity is the ratio of the volume of voids to the bulk volume. Many of these topics were covered in earlier papers of which this is the successor [i. the relationship can be expressed in two ways. sometimes of several sizes. Most often that basis is unit weight of solids. the permeability is a function only of the pore structure and not of the fluid. etc. The size of a pore cannot be defined exactly in any way that is useful. Generally speaking. So defined.DOLCH ON POROSITY 647 These are known collectively as the pore structure. For practical purposes Copyright by ASTM Int'l (all rights reserved). in any event. For example the hydraulic radius of a round pore is one fourth of its diameter. Therefore. plotted against pore size. If there are various volumes of pores of various sizes. to distinguish it from any portion that is enclosed completely by solids. but bulk volume. . the differential way of plotting the data shows nothing that is not also evident from the integral curve. are also used. gas or liquid. get larger and smaller. or the proportion of pore volume of a given size. size distributions of aggregate materials usually are presented as a cumulative curve. The solids in a porous body are more or less finely divided.. void volume. see Refs 3 and 4. go this way and that. is the differential pore size distribution. a simpler concept that can be described and analyzed and whose properties can be determined. In most porous solids the walls of the pores twist and turn. flows through a porous solid. By far the most commonly used model has been a bundle of round tubes. When a fluid. the absorptivity is defined as the square of the ratio of the volume of liquid absorbed to the cross sectional area that it penetrates in unit time. The extent to which these properties correspond to their counterparts measured on the real material is the degree of success of the model. A plot of the volume of voids that are smaller (or larger) than a given size is the cumulative or integral pore size distribution. Measurement Methods Porosity The pore space that is interconnected and connected to the outside surfaces of the piece is sometimes called the effective porosity. The slope of this curve. No further reproductions authorized. Another way of expressing pore size is by the hydraulic radius. If the porous solid is absorbing the fluid by capillarity. the permeability is defined as the volume flow rate of a fluid of unit viscosity that permeates a sample of unit cross-sectional area under a unit pressure gradient. For a discussion of models. which is defined as the cross sectional area of a pore space divided by its perimeter. The differential curve is also likely to emphasize unimportant aspects and is. The inability to describe such a system in detail results in the use of a model. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The specific surface (area) is the area of the solid surfaces on some unit basis. suitable only for a relatively small range of pore sizes--say two orders of magnitude. 648 TEST AND PROPERTIES OF CONCRETE AGGREGATES with aggregates. and the volume of solids and true density can be determined. The usual stereographic procedures of point counting. the permeability. and the pressure on the system is measured before and after the change. Pore Structure Pore structure refers to the combined aspects of pore size distribution and pore shape. but it is tedious and has the major disadvantage that a lower size limit is imposed by the resolution of the microscope. The method has been used on aggregates [10]. linear traverse. So pores smaller than about 1/~m will not be seen at all and cannot be included in the measured porosity. Pycnometric methods can be used to determine the effective porosity if a gas. since the amount of liquid absorbed depends on how it was taken up and. this is an unimportant distinction. This is completely unwarranted. because it is not adsorbed appreciably by the solid surfaces. Examples of such equipment are given in Refs 5 and 6. is used. or the absorptivity. even this does not result in complete saturation with most aggregates and cannot be used as a measure of total porosity. The gas is usually air. Effective porosity can also be determined with the so-called McLeod gage porosimeter [7. and any that is not can be considered part of the solid. An average or "equivalent" pore size can be determined by measuring the specific surface. but helium may be better. Porosity also can be determined microscopically by examination of a polished section or a thin section. Many aggregates have major portions of their porosity in sizes smaller than this. The volume of voids is determined directly by measuring the volume of this air. ASTM Recommended Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457) is an adaptation of this method. or ASTM Test for Specific Gravity and Absorption of Fine Aggregate (C 128). or areal measurement are used [9]. and for most of them the method is unsuitable. . Copyright by ASTM Int'l (all rights reserved). the saturation is hardly ever complete. No further reproductions authorized. in any event. since most aggregates have a completely interconnected pore space. In the past. a common way to measure porosity was to assume that the volume of absorbed liquid (usually water) equals the volume of voids.8] in which a dry sample immersed in mercury has the air in its voids removed by expansion and collected. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Boyle's law is assumed. The former is the "twenty-four hour" absorption and is the more common. The volume of a chamber containing the dry solid is changed by a known amount. The latter is called the "vacuum absorption". An independent measure of the bulk density permits calculation of the porosity. The two exposures that are most common are a 24-h soaking in water or a period of evacuation of the dry solid by an aspirator followed by admission of water and soaking. The absorption of an aggregate is measured by ASTM Test for Specific Gravity and Absorption of Coarse Aggregate (C 127). rather than a liquid. The most commonly used theory is the BET [15]. which has two properties of most real porous media: an irregular pore shape and a flow path that is tortuous. It is related to the rate at which a liquid. always less than unity. hydraulic radius. for example. No further reproductions authorized. so this pore "size" can be determined. The vapor adsorption method also is used to determine pore size distribuCopyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. cylindrical pores. has been shown to correlate well with the conventional adsorption value. the surface surrounding the effective porosity. The method obviously measures only the solid surface that is contacted by the vapor. but the method is not accurate for a material with a wide range of pore sizes. A variant [22]. The absorptivity was defined by Powers and Brownyard [21]. The sorption data are then interpreted in the light of one of several theories to allow calculation of the specific surface. in Refs 11 through 13. The method has the advantage of ease and simplicity. For solids with a comparatively small specific surface.DOLCH ON POROSITY 649 The equivalent pore size is related to the porosity-to-specific surface ratio. in which the time is measured for the complete absorption of a small water drop placed on the surface of the rock. that is. The permeability method has been used on some aggregate materials [19. that is. the greater the retardation and the smaller the measured permeability. The permeability method of determining pore size depends on the retardation of the flow of a fluid (liquid or gas) passing through the material by drag on the pore walls. . The most important way of determining the specific surface is by the method of vapor phase adsorption. The technique involves measuring the amount of vapor adsorbed or taken up by the solid on its surfaces as a function of the ambient pressure of the vapor. etc. A general discussion of the sorption method is in the book by Gregg and Sing [16]. There are several ways to measure it. usually water. slits. In the use of the permeability method it is necessary to assume or to measure the degree of tortuosity of the flow path of the permeating fluid. The method has the same uncertainties as the permeability method with an additional one that depends on the influence of the degree of saturation. A round tube or a hydraulic radius model is then used to calculate a pore size for the sample [19]. The vapors most often used are nitrogen with the sample at the temperature of liquid nitrogen or water vapor at room temperature. One of the most common is that of Kozeny.20]. The book by Carman [I 7] is a good summary of the subject. The experimental techniques can be found. the use of krypton may be advantageous [14]. The analysis of such a model shows the permeability to be proportional to the porosity and the square of the hydraulic radius. The smaller the pore. The form of the relationship depends on the pore model that is used. is imbibed by capillarity into the dry porous solid. Translations of permeability measurements into pore sizes depend on the analysis of some model for the porous medium. perhaps the electrical analog method is best [18]. as are most aggregate materials. Of course. who also covered other methods for the determination of pore structure. . a pore size distribution obtained by this method is weighted towards smaller pore sizes. A problem with the method is that the product of the surface tension of the Copyright by ASTM Int'l (all rights reserved). the whole void volume will be recorded as being the size of the entrance. The second major way of determining the pore size distribution of a porous solid is by mercury porosimetry. These data can be used then to construct a pore size distribution curve. according to the usual capillary pressure relationship. The data are obtained from the comparatively high vapor pressure portion of the sorption experiment. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A summary of this work is given in Ref 27. So in calculating a pore size distribution a choice must be made of which set of data to use. with several forms of commercial apparatus available. the lower the vapor pressure the smaller the capillary size. The method consists of immersing an evacuated porous sample in mercury. it is recognized that this is not really correct for most porous solids and. A general review of the method is given by Rootare [29]. The amount is always larger for the latter case. And so a cumulative pore size distribution curve can be generated. The size of the pores is related inversely to the pressure required to cause entry of the mercury. Therefore. who has analyzed a variety of pore shapes in terms of the kind of sorption hysteresis they produce. The sizes of pores that can be investigated range from a lower value of perhaps several molecular diameters to an upper one of several hundred micrometres. specifically. if a void has an entrance that is smaller than its body (a socalled "ink-bottle" pore). which results in a hysteresis of the sorption isotherm data. The ways to do this have been reviewed by Linsen and van den Heuvel [23] and by Dullien and Batra [24]. The choice is determined largely by the pore shape that is appropriate. The volume of pores of any size increment is the amount of mercury forced in over the corresponding pressure range. The subject has been investigated by de Boer [25]. No further reproductions authorized. and then forcing the mercury into the pores by the application of increasing pressure. The relationship between the pore size in which capillary condensate exists and the ambient vapor pressure is given by the Kelvin equation. This is the region in which bulk liquid is present in the pores by the process of capillary condensation. A general review is given by Everett [26]. Brunauer and his colleagues have devised a method for the complete analysis of pore size distributions that does not assume a shape for most of the size range. It is necessary to make a correction for the thickness of film already adsorbed on the pore walls. The idea was developed by Ritter and Drake [28] and has since become almost a standard method. The model implicit in the usual analysis is an assembly of round tubes of various sizes.650 TEST AND PROPERTIES OF CONCRETE AGGREGATES tions and to gain some insight into the shape of the pores in a porous medium. The amount of vapor taken up by the solid at a given vapor pressure depends on whether vapor is being added to or removed from the solid. The influence on density is of importance in such matters as mix proportioning. . the porosity of a concrete aggregate affects the behavior of the concrete for one or both of two reasons--either because the pore space decreases the volume of solids in bulk volume of the aggregate or. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. usually on other materials. Other things being equal. The porosity of aggregates also affects their other mechanical properties. more importantly. such as modulus of elasticity and Poisson's ratio. the abrasion resistance of the aggregate will be smaller the greater its porosity. Winslow and Diamond [30] measured this product of the surface tension and cosine of contact angle by drilling small holes of accurately measured size in the material and measuring the pressure needed to cause the mercury to enter them. The effects of the first of these are mostly obvious. the strength and. In an investigation of the pore structure of hardened cement paste. consequently. Any mixing water that is Copyright by ASTM Int'l (all rights reserved). This property is recognized to be of importance in determining the degree of breakdown an aggregate can be expected to undergo during mixing of concrete or compaction of base course. No further reproductions authorized. Porosity is important to questions of proportioning concrete because of its control over the absorption of the aggregate. and the strength of the paste aggregate bond are more important [37]. This influence is probably not simply one of a reduced cross section to bear the load. Except for those that are grossly weak. and ASTM Test for Resistance to Abrasion of Small Size Coarse Aggregate by Use of the Los Angeles Machine (C 131) are part of many aggregate specifications. the strength of the aggregate is not considered to be a primary factor governing the strength of concrete. The strength of the cement paste. which is related intimately to its own porosity. These properties in turn are important to the same properties of the concrete. because the pore space permits the ingress and retention of water or aggressive solutions. Significance of Porosity of Aggregates Broadly speaking. ballast.DOLCH ON POROSITY 651 liquid and the cosine of the contact angle it makes with the solid must be known in order to calculate the pore size. Little has been done on this last question. The mercury porosimetry method has been used on a wide variety of solids [29]. and so on. but it is logical to assume that the roughness and the porosity of the surface of the aggregate play an influential part in the development of the interfacial bond with the paste [38]. ASTM Test for Resistance to Abrasion of Large Size Coarse Aggregate by Use of the Los Angeles Machine (C 535). Most users of the method have assumed values of the contact angle that were obtained by early workers. Abrasion resistance is an important property of aggregates that is related to strength and porosity. Applications to concrete aggregates have been reported [31-36]. which are additive functions of the properties of its constituents. basically because by shrinking the aggregate fails to restrain the shrinking of the paste [39]. They Copyright by ASTM Int'l (all rights reserved). an inhomogeneous material. fashion by the application of relatively small correction factors. And. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. of course. except possibly for the influence of clay minerals. therefore. While the absorption value is not.652 TEST AND PROPERTIES OF CONCRETE AGGREGATES abstracted by the aggregate during mixing and placement must be considered in the mix proportions. even though in those days the effects of freezing and thawing were compounded with those from other kinds of difficulties. it still stands. a saturation of greater than about ninety percent should be necessary for trouble to develop. few generalizations can be stated concerning the types of materials that may be particularly subject to this difficulty. It should be remembered that. A few aggregates undergo excessive volume change themselves on wetting and drying and. and field performance of the aggregate in pavement concrete. The degree of saturation hypothesis is the basis for a widespread dependence on absorption tests to indicate an aggregate's probable performance. No further reproductions authorized. Indeed there is some question of how much the subsequent work on test methods has improved upon it [42]. if approximate. although this mechanism has been amplified by subsequent work. can contribute greatly to the shrinkage. It was recognized long ago that the coarse aggregate component had an important effect on the durability of concrete pavements [40]. Study of frost durability of aggregates in concrete has been given impetus by the growing scarcity of "good" aggregates and the necessity to use material that would have been rejected in former days. to be a fairly useful indication of the likelihood of trouble. The so-called "degree of saturation" hypothesis was the earliest attempt to explain these effects. particularly under vacuum conditions. Usually this is done in an effective. If the degree of saturation of an aggregate particle is less than somewhere in the region of 90 percent. there will be no damage to the concrete from this source. Foremost in the list of significant effects that the porosity of aggregates has on the properties of concrete is freezing-and-thawing durability. Little work has been done on these aggregates. for most aggregates of the usual compositions and porosities the absorption is good enough. Since water expands on freezing by about ten percent. as saturation is determined ordinarily. . The modern understanding of the freeze-thaw durability of aggregates in concrete stems from the analysis of Verbeck and Landgren [43]. and. such as most gravels. as precise an indicator as is the saturation. But in the proportioning of lightweight aggregate concrete the needed correction factor frequently becomes large and indeterminate because of the large absorption that can occur with lightweight aggregate. Early work [41] did indeed show a reasonable correlation with saturation attainable by the aggregate. especially considering the simplicity of the test method. may have some individual pieces critically saturated although the value determined on the overall sample may be considerably lower. Nevertheless. This critical porosity is in the region of a fraction of a percent. yet they still produce nondurable concrete. The result of this less-than-satisfactory situation has been that freezing tests of concrete containing the aggregate in question have been considered superior to tests on the aggregate alone. No further reproductions authorized. low permeabilities. the predictions of freeze-thaw durability has been the subject of much research. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. which includes a bibliography of the work that led to its development. which has a small critical distance. the expansion will be so small as to cause no difficulty. The reason advanced is that unfrozen water forced out of the aggregate piece has nowhere to go but into the paste. . Unconfined freeze-thaw testing is useful only for those aggregates with small critical distances that exhibit internal failure. therefore. part remaining in the concrete and the other part coming out with the flake of mortar. the critical distances in finely pored rocks. rather than within the aggregate. Such materials cannot fail internally by the hydraulic pressure mechanism. the porosity is small enough that even if it is saturated and the water freezes.). In the first. and better than sulfate soundness tests.008 in. called elastic accommodation. and again there is a size effect. The development of such testing is covered in another chapter in this volume. are in the small coarse aggregate size range. the failure is within the piece of aggregate. Recent studies have confirmed this maximum size effect. therefore. Some rocks are of such a low porosity. with permeabilities so large that their critical distances are many centimetres (inches) or even metres (feet). Therefore. The critical distance in a hardened cement paste is of the order of 0. freezing should produce failure within the aggregate. The second class of aggregates is those with small pores and. with larger-size coarse aggregate being more deleterious. so failure occurs there. if a piece of such a material is larger than this size and is critically saturated. Owing to its importance. The expansion of the water in forming ice forces unfrozen water ahead of the freezing front. such as many cherts and shales.DOLCH ON POROSITY 653 discussed three classes of behavior. The third class of aggregates is those with larger pores and. and they should be immune from freeze-thaw trouble. Such behavior is characteristic of those materials that produce pop-outs. pressures large enough to fracture the matrix will be developed. a test that could be performed on the aggregate alone is still Copyright by ASTM Int'l (all rights reserved). Analysis of this mechanism shows that entrained air in the paste provides hardly any help. which now seems well established [45-47]. If this flow must traverse a distance larger than a critical maximum. The current standard is ASTM Recommended Practice for Evaluation of Frost Resistance of Coarse Aggregate in Air-Entrained Concrete by Critical Dilation Procedures (C 682). The mode of action is based on the hydraulic pressure hypothesis of Powers [44] for frost damage in hardened cement paste.20 mm (0. The upshot of most of the early work was that absorption and saturation were fair indicators of potential durability performance. although the limited further testing of the idea [50] seems to show the hydraulic pressure hypothesis to be more important. The same piece of questionable aggregate near the surface of a slab may not pop out if the overlying paste is dense and impermeable.654 TEST AND PROPERTIES OF CONCRETE AGGREGATES desirable. Logically. Early studies [10] also showed that nondurable aggregates seem to have a comparatively large proportion of small pores. 1955.. that the aggregate's properties are not the only determinant factors. References [1] Lewis. p. and Dolch. It has long been considered that the details of the pore structure of the aggregate should be the most important factor in whether it will be durable or nondurable to frost in concrete. The primary variable is the permeability of the paste and the degree to which it permits water to enter and reach critical saturation in aggregate pieces. so failure from this source does not occur. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This mechanism has some aspects of theories that have been advanced for freezing action in hardened cement paste [49]. No further reproductions authorized. of course. Recent work has shown a good correlation between laboratory and field freeze thaw durability of an aggregate in concrete and a factor combining its total porosity and median pore size. The tool most used so far has been mercury porosimetry. Dunn and Hudec [48] measured the frozen water in cold aggregate samples and found that in nondurable materials only a little water became frozen. they postulated expansion processes that did not depend on conversion of the water to ice. . W. D. even assuming the concrete to be properly air-entrained. Therefore. W. These properties are related to the absorptivity. Some work has been interpreted as showing that mechanisms other than ice-expansion and hydraulic pressure are important in freeze-thaw. 303. a nondurable aggregate would comparatively rapidly acquire a high degree of saturation and retain it more tenaciously. More work on the relationship between an aggregate's pore structure and its durability to freeze-thaw remains to be done. and that the nature of the concrete plays a role in the durability question. and may have pertinence for rocks containing large clay components. but the results of most of the studies that have been done [31-36] have been neither clear-cut nor unanimous in their conclusions. It would seem that this matter could be settled by the determination of pore-size distributions of a variety of aggregate materials. "Porosity and Absorption. Copyright by ASTM Int'l (all rights reserved). It should be recognized. American Society for Testing and Materials. with higher porosities and smaller pore sizes being worse [51]. Limited work [8] did show that nondurable aggregates had higher absorptivities and larger rates of saturation increase when imbibing water by capillarity. but will if that paste is more porous and permeable because of a higher water/cement ratio. L." A S T M S T P 169. E. [19] Dolch. 1. "Permeability and Absorptivity of Indiana Limestone Coarse Aggregates.. 90." Thesis. Vol. 1922. Emmett. Prague.. H. and Sing." Proceedings.. "The Shapes of Capillaries. E.. 1938. p. Vol.. H. M. 5. 60. 1. C-3. W. and Brownyard. "Correlation Between Absorption of Single Aggregate Particles by Water-Drop Test and Immersion Tests. R. Prague. 988. [15] Brunauer. and Batra. and Honig. New York. I. [17] Carman. and Willingham. 112. 1967. 1967. and Bunting. 48. Vol. L. "Application of Electrical Resistivity Measurements to Problems of Fluid Flow in Porous Media. American Society for Testing and Materials. A. Butterworth.. 1973. [12] Joy. [5] Washburn. A. RILEM/IUPAC Conference on Pore Structure and Properties of Materials. [7] Washburn. [18] Wyllie. 1943. "Complete Pore Structure Analysis.. S. PhysicalAdsorption of Gases.. N. R. [6] Schumb. p. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Chapter 35. W. 59. J. Ed. [20] Huang. "Adsorption of Gases in Multimolecular Layers. Purdue University. American Chemical Society." Vacuum.. 1967." Proceedings. American Society for Testing and Materials." Proceedings. and Teller. Prague. Surface Area and Porosity. New York. Vol. Eds. Pittsburgh. S. p. L. M. 1922. p. Washington. and Crowell. 1204.. P. 1970.. 1973. Part A. C. "Studies of the Physical Properties of Hardened Portland Cement Paste. and Wakao. 65. H." in The Structure and Properties of Porous Materials. C. A. [24] Dullien...." Journal. [23] Linsen. New York. Vol. 1957. 1962. 2. N. Marcel Dekker. G. "Porosity. 527.. p. "A Helium Densitometer for Use with Powdered Materials. P.. [21] Powers. Pa. Flood. D. Beckwith. [25] deBoer. L. 5. V.. Butterworth. 1554. 1952." RILEM International Symposium on Durability of Concrete... J. E. 1953. [9] DeHoff. Vol. p. E. J. and van den Heuvel. and Rhines. London. [10] Sweet. H. Vol. p. H. Ludmila. and Odler.. American Chemical Society. Academic Press. "Studies of Limestone Aggregates by Fluid-Flow Methods. W. 309. S. 865. No further reproductions authorized. W." Special Report No. Vol. American Association of Petroleum Geologists. A. 67. Academia. [14] Beebe. [11] Young... E. C. American Ceramic Society. and Drake. 1947. L. L. A." Journal. Stone. Everett and F. [22] Dolar-Mantuani. B. A-27. American Ceramic Society. D. Academia. S. A.. C. T. Vol. J. 3. Vol. New York. Flow of Gases Through Porous Media. "Porosity VII--The Determination of the Porosity of Highly Vitrified Bodies. B. W. A." Journal. "Porosity 6--The Determination of Porosity by the Method of Gas Expansion. The Physics of Flow Through Porous Media. "Adsorption Hysteresis. Sherwood. C. p. Skalny. E. "Methods and Techniques for the Determination of Specific Surface by Gas Adsorption. F. Vol. p. "The Determination of Small Surface Areas by Krypton Adsorption at Low Temperatures.. American Society for Testing and Materials. Vol. [16] Gregg. 254.. 1.. T." Mellon Institute of Industrial Research." Bulletin. S. [4] Proceedings." Proceedings. McGraw Hill. N. [26] Everett. Macmillan. p. S. 1956.. E. Flood Ed. "Pore Structures. p. Vol... Highway Research Board." Journal. Vol. Marcel Dekker. 1692. M. 1955. "Determination of the Structure of Porous Media. H.. 1966. "The Assembly.. W. "Pore Size Distribution in Porous Materials--Pressure Copyright by ASTM Int'l (all rights reserved)." The Solid-Gas Interface. R. T. 1959. Academic Press. and Spangler.. 1945. 1956. S.. F." A S T M S T P 169A. W. W. "Determination of Mean Pore Radii in Mineral Aggregates Using Permeability Measurements. E." in The Solid-Gas Interface. 443.. [3] Scheidegger. p. 1968. A. D. 43. American Chemical Society.DOLCH ON POROSITY 655 [2] Dolch. "Research on Concrete Durability as Affected by Coarse Aggregate." Journal.. Calibration and Operation of a Gas Adsorption Apparatus. K. p. [28] Ritter. and Rittner. Quantitative Microscopy. Chapter 36. M. [27] Brunauer.. 359. p. and Bunting. p. D. . 1970. p. 36. 1966. 1. 68. N. [8] Dolch.. K. B. C. S. 1958. New York. J. London. American Concrete Institute. American Chemical Society. J. L." in Flow Through Porous Media. New York. A. Adsorption. E. RILEM/IUPAC Conference on Pore Structure and Properties of Materials. 219. J. 1948. B. P. [13] Faeth. and Meininger. p. J.. and Kamada. C. B. 1970. p... "A Short Literature Review of Mercury Porosimetry as a Method of [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] Measuring Pore-Size Distributions in Porous Materials.. H. and Teske.. C. T. 1969. J. 1973.. Virginia Highway Research Council. "Influence of Physical Characteristics of Aggregates on Frost Resistance of Concrete.. Report No. Sturman. J. American Ceramic Society." Industrial and Engineering Chemistry.. 1. and Hudec. Lewis.. New York State Department of Public Works. 1967." Proceedings. Vol. and Klieger. 1972.. D. Sun Apr 6 21:31:13 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Vol." Bulletin 239. Vol.. Powers. and Lau. Hsu. 60. 3. Y. "The Role of Mortar-Aggregate Bond in the Strength of Concrete." Journal of Research." Record No. No further reproductions authorized." thesis. [29] Rootare.. 1063. p. Portland Cement Association Research and Development Laboratories. Prague. p. C. "A Working Hypothesis for Further Studies of Frost Resistance of Concrete. Dunn. E. 155. American Concrete Institute. 3. Vol. 1978... J. 1964. 1945. Cady. "Relationship of Pore-Size Distribution and Other Rock Properties of Serviceability of Some Carbonate Aggregates. Vol. p. 1968. 38. D. and Winter. P. 2. Highway Research Board. 55. P. Vol. Highway Research Board. 196. 71-R39.. p." Journal of Materials. G." Journal of Materials. Sherwood. 1972. Slate. "The Influence of Pore Structure of Concrete Made With Absorptive Aggregates on the Frost Durability of Concrete. D. D. Vol. Kaneuji.. M. and Erlin. S. p. p. p. 33.. H. Ill. Litvan. F.. Monfore. 564. Roper. Vol. B-129. P. "A Mercury Porosimetry Study of the Evolution of Porosity in Portland Cement. Highway Research Board. Vol. Woods. 41. 5. American Concrete Institute. "Microcracking of Plain Concrete and the Shape of the Stress-Strain Curve. . 441. N. Vol. Analytical Edition. 226. 6." Proceedings.656 TEST AND PROPERTIES OF CONCRETE AGGREGATES Porosimeter and Determination of Complete Macropore-Size Distributions. Part 2.." Portland Cement Association. and Shelburne. American Society for Testing and Materials. Huang.. 144. "Effect of Maximum Size of Coarse Aggregate on D-Cracking in Concrete Pavements". and Woods. R. H. P. 24. and Hsieh. F-4S.. and Modry. D. G.. R." Proceedings. 1964. p. p. "The Influence of Clays on Water and Ice in Rock Pores. American Concrete Institute. Purdue University. 1973. 210. E. K. J. J. "Mechanism of Frost Action in Concrete Aggregates. Purdue University.. RILEM/IUPAC Conference on Pore Structure and Properties of Materials.. 60. 1965. Winslow. Highway Research Board. D.. 25. "Pavement Blowups Correlated with Source of Coarse Aggregate. p. University of Maryland." Proceedings. "D-Cracking of Concrete Pavements in Ohio.. Makoto. "Relationship Between Aggregate Pore Characteristics and Durability of Concrete Exposed to Freezing and Thawing. Vol. Highway Research Board. Sweet. and McShee. 1960. T. 25. Scholer. "Research as Related to the Development of Aggregate Specifications.. S. MacInnis. J.. W. 147. 35th Annual Road School. G. K. and Diamond. p. F. T. W. p. L. 1960. H. Koh." Journal. Stark. C. Record No. 41. E. 209. Gaynor. Skokie. 1970. P." Record No. Copyright by ASTM Int'l (all rights reserved). 1967.. M. "Maximum Aggregate Size Effect on Frost Resistance of Concrete." Record No. "Phase Transitions of Adsorbates IV--Mechanism of Frost Action in Hardened Cement Paste. B. O. C. 2." Report RR 65-5. 1949." RILEM International Symposium on Durability of Concrete. 1963. 1946.. and Landgren. No. 4. "Correlation Between the Pore Size Distributions and Freeze Thaw Durability of Coarse Aggregates in Concrete. G. "Petrographic Studies on Concrete Containing Shrinking Aggregate. R. No. Klieger. Verbeck. K. T. 108. and Lemish. thesis. C. p. 245. S. Meininger." Proceedings. R.. E. R. Highway Research Board." Proceedings. H. 1971. Cox. Hiltrop. Lange. "Investigation of Aggregate Durability in Concrete. C. 1968. Stark. Vol. 17. 1945... G. 782. G. Dudash. p. C.. W." Proceedings. R." Aminco Laboratory News. Vol. 68. and a Discussion of Possible Sources of Errors in This Method. 294. B.. 1974.. "Determination ofthe Frost Resistance of Limestone Aggregates in the Light of Porosity Investigations. Walker. 20910. consequently. C. the lithology of the particles and. Examples include pavements and slabs exposed to heavy traffic and hydraulic structures subject to eroding forces of moving water and sediment material. No further reproductions authorized. must possess a reasonably high degree of inherent strength. In many crushed stone aggregates and some sands and gravels. National Sand and Gravel Association. Copyright9 1978tobyLicense ASTM International www. and wearing actions to which it may be exposed both in concrete production operations and. the static and dynamic stresses.org . A small percentage of weak particles in most inI Director of engineering research. National Ready Mixed ConcreteAssociation. In end uses such as beams. walls. Strength. and Related Properties Introduction Aggregates for use in concrete. and other mostly structural or architectural elements the only real strength property needed of the aggregate after the concrete is in place is that necessary to give the concrete enough strength to resist the distributed service loads. Some recognition must be given to the consideration of an aggregate as a whole versus the properties of the individual particles present. SilverSpring. Other uses may expose aggregate near or at the surface to a variety of localized impact and abrasive stresses which will be of overriding importance in aggregate evaluation and selection. Toughness. tenacity.astm. and stability to resist. impacts. ultimately. without detrimental degradation. great variations may exist among the mineral and rock particles involved. Actions involved in production are fairly predictable.STP169B-EB/Dec. those in service may be less predictable. M e i n i n g e r ~ Chapter 38 Abrasion Resistance. in concrete in service. footings. Md. Copyright by ASTM Int'l (all rights reserved). covered slabs. and to a large extent the individual constituent particles. columns. In other cases. Sun Apr 6 21:45:30 EDT 2014 657 Downloaded/printed by Universidade do Gois pursuant Agreement. their mechanical properties show little variation. In many uses of concrete the roughest treatment to which an aggregate may be subjected in terms of mechanical forces and attrition is in the concrete production process. 1978 R. In some cases special aggregates. mineral. Here the particles are expected to possess enough strength and rigidity to carry the stresses without mechanical breakdown or excessive deformation--for usual aggregates and typical stress levels in concrete this is no problem. is the production of very high strength concrete--higher than 35 or 70 MPa (S000 or 10 000 psi). yielding. These weaker materials are used because of economic reasons or to produce concrete of lighter unit weight. An exception. either dry or in the presence of water. Surface actions are of two basic modes--impact and rubbing. Examples are lightweight aggregates. for the relative hardnesses involved.658 TESTS AND PROPERTIES OF CONCRETE AGGREGATES stances is not objectionable and may be thought of as an impurity or deleterious substance and therefore not properly the subject of this discussion. Concrete carrying a distributed static or dynamic load. . can be an important factor. An example is high velocity hydraulic structures where high surface strength and very accurate surface alignment is needed to resist cavitation damage which can spread rapidly once started. These weaker or less abrasion resistant particles allowed in small percentages may cause a slight increase of fines during mixing or may contribute to occasional surface imperfections not particularly harmful to overall performance. and not subjected to local stress concentrations. however. damage can be inflicted by the movement of particles or objects on the surface under enough load to cause identation. and volcanic cinders sometimes used in concrete. In other instances. aggregate materials are used which possess compressive strength of the same order of magnitude as the concrete in which they are used. or debonding of aggregate particles. Materials with good impact resistance are said to possess good toughness. the amount of material removed by such Copyright by ASTM Int'l (all rights reserved). abrasion. These loadings or actions usually are applied to the surface of the concrete so that only the properties of the aggregate at or near the surface are of any substantial importance in determining whether the long term performance of the concrete will be acceptable. In some cases. Impact. and other wearing actions. No further reproductions authorized. Impact is where hard particles or objects impinge against the concrete surface with enough momentum to cause shattering. attrition. concrete mixtures. or synthetic materials making up aggregates are usually much stronger in compression or tension than the concrete. limerock materials used in Florida. where high strength aggregate materials will probably be required. eliminating even very small percentages of friable or weak particles is desired. or coatings may be used at the surface to improve the surface properties locally. and the weakest link in the system is the bond between the paste and aggregate. In other words. The rock. requires aggregate that will bond with the surrounding cement paste permitting the transfer of stress through the aggregate particles. scuffing. In the rubbing or scratching mode. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and therefore cause scratching or gouging as movement occurs. Scratches and gouges from relatively large particles or objects are on a macroscopic scale and are termed wear. Distributed Stress--The sections on "Strength of Aggregate Material" and "Elastic Properties" apply to distributed stress. are quite often made in connection with rock mechanics investigations for foundations. will wear away a significant quantity of surface mortar exposing more and more coarse aggregate with time. there are several problems involved in translating this information to the behavior of aggregate in concrete: (1) the conditions of confinement in concrete are certainly different than that of unconfined tests and triaxial tests may not truly represent the situation in concrete. A section on "Impact Resistance and Toughness" is also included. .MEININGER ON PHYSICAL PROPERTIES 659 action. 3. aggregates that allow rapid polishing can contribute to low skid resistance of wet surfaces. Strength of Aggregate Material Measurements of unconfined and confined compressive (or crushing) strength of rock and mineral specimens drilled or sawn from rock ledges. and any aggregate specifications. Certain inferences can be drawn from these data as to the nature and distribution of the strengths of the materials constituting aggregate particles. or shear stress. Copyright by ASTM Int'l (all rights reserved). The arrangement of the discussion in this chapter is based on the types of action concrete and aggregate might be expected to resist: (1) distributed stress of the noninstantaneous type whether it is compression. and occasionally other types of service. and (3) scratching and rubbing actions which on a macro scale produce wear and on a micro scale involve polishing. There is an element of impact in these tests as well as surface attrition and leaching of fines. if repeated over and over again. Rubbing or scratching action from much smaller particles--on a microscopic scale--does not have the capacity to remove much material but it can cause a polishing action at the surface. and Skid Resistance" is included along with a section on "Wet Abrasion and Attrition Tests" which is a more specialized topic pertaining to testing of aggregates wet rather than dry. 2. or in some instances cobbles or boulders from gravel deposits. tunnels. In highway uses. and various mining applications. relating to the three general classes of mechanical action. The main divisions which follow are organized with the purpose of discussing the significance and measurement of aggregate properties. and (3) rock properties are most often reported for specimens that have a minimum of flaws. Impact--The section on "The Los Angeles Abrasion Test" is included under impact since the test involves mostly impact with some wearing attrition. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. (2) strength tests of rock specimens usually involve measures to distribute the stress evenly over the entire cross section. Scratching and Rubbing--A section on "Hardness. (2) instantaneous impact loadings where significant momentum is involved. tension. 1. whereas in concrete localized stress concentrations may develop due to the nonhomogeneous nature of the concrete. Wear. No further reproductions authorized. However. the strength of an individual aggregate particle can be influenced greatly by defects in the particle.2 to 11. The assumption can be made that the strength of the rock materials in gravels is similar to that of the rock materials from which the gravels were derived. and like all brittle materials relatively weak in tension. Compressive strength increases with confinement and both elastic and plastic deformations occur.7 MPa (900 to 1700 psi). that their strength characteristics may be an important limitation on the properties of concrete made 2The italic numbers in brackets refer to the list of referencesappended to this paper. and for a quartzite source. Bond [9] shows compressive strengths of small cubes and cylinders cut from rock material. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and fissures. granite. compressive strengths of 105 to 200 MPa (15 000 to 29 000 psi) and tensile strengths of 2. for rock from which crushed stone coarse aggregates are made. limestone. The great bulk of the strength data available is for stone materials where specimens of the required size can be obtained and usually the material is less variable. and basalt aggregates and obtained compressive strengths ranging from about 160 MPa (23 000 psi) for the gravel and the granite on the low end to 305 MPa (44 000 psi) for the basalt on the high end. Gravel deposits on the other hand present difficult problems in attempting to measure strength. for a limestone source. over 70 MPa (10 000 psi). Strength specimens can only be cut from sizes larger than used in many products and the lithology of many gravel deposits is quite variable. There is also some. From the foregoing it is apparent that the great majority of the aggregatemaking rock materials are strong in compression. He also reports compressive strength results from one gravel source ranging from 165 to 235 MPa (24 000 to 34 000 psi). proportion of aggregates used for concrete that are weak enough. There are many sources for data on compressive strength of rock and in some cases tensile strength or modulus of elasticity [2-10]. Tests of two types of rock used as aggregate by Iyer et al [8] yielded. probably fairly small. No further reproductions authorized. .660 TESTS AND PROPERTIES OF CONCRETE AGGREGATES cracks.8 MPa (1100 to 2300 psi). only about 60 results indicated compressive strength levels of about 70 MPa (10 000 psi) or less. necessitating the testing of a large number of specimens to get meaningful results. The basalt had a tensile strength of 15. limestone. These values represent ranges from a number of sources. less than 70 MPa (10 000 psi). compressive strengths of 340 to 470 MPa (49 000 to 68 000 psi) and tensile strengths of 7. However. For limestone the values ranged from 90 to 270 MPa (13 000 to 39 000 psi). Of the almost 1000 compressive strengths reported by Woolf. The tensile strength measured for the gravel.2 MPa (300 to 900 psi). Kaplan [5] tested gravel.1 to 6. and for granite 85 to 275 MPa (12 000 to 40 000 psi).6 to 15. in his state-by-state summary [2].2 MPa (2200 psi). Copyright by ASTM Int'l (all rights reserved). and granite ranged from about 6. for traprock 10S to 235 MPa (15 000 to 34 000 psi). Udd [1] 2 gives a review of the methods used in testing rock and some examples of the range and variability of results. texture. The 10-percent fines value is conversely the load in kilonewtons needed to produce 10-percent fines as defined in the crushing value test. Crushing value is simply the percentage of fines generated which pass the 2. Fundamental strength tests of specimens cut from aggregate materials are not used for the specification or qualification of coarse aggregates for concrete. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Kaplan [5] in using a number of strong aggregate materials in concrete concluded that "no relationship between the strength of the coarse aggregate and the strength of concrete was established.12] that aggregate strength need only be of the same order of magnitude as the concrete strength needed. These are the "Crushing Value" and the "Ten Percent Fines Value" both of which are run on 10 to 14 mm aggregate particles placed in a confining base." Johnston [3] using a 48 MPa (6900 psi) sandstone coarse aggregate in concrete and Collins and Hsu [7] using a 28 MPa (4000 psi) oolite coarse aggregate in concrete were both able to produce concrete over 40 MPa (6000 psi) at 28 days age. In Britain two strength tests run on a collection of particles are detailed in the British Standard for Concrete Aggregates B5812-75. It is recognized that coarse aggregate to mortar bond is extremely important to concrete strength and that a reasonably high strength aggregate with excellent bonding characteristics is necessary in the production of very high strength concrete over 35 or 40 MPa (5000 or 6000 psi). The strength of individual fine aggregate particles is apparently not too important as long as some minimum level is achieved. The influence of fine aggregate on concrete strength is almost exclusively through its shape. This finding should not be taken to mean that aggregates of low strength will not affect concrete strength. Kaplan also found that the relationship also held for rock tensile and flexural strength. Tanigawa [13] in his model analysis with various aggregate and mortar strengths concluded that the best results in terms of delay in formation of bond cracks at the coarse aggregate-mortar interface were obtained when the aggregate and mortar were about the same strength. Bond is not as important with fine aggregate because of its large surface area-to-volume ratio.MEININGER ON PHYSICAL PROPERTIES 661 with these materials. principally so that it does not break down and create excess fines and surface area during concrete production. Figure ! shows that the British crushing value has a reasonably good relationship with rock compressive strength.36 mm sieve when a load of 400 kN is imposed on the collection of particles. no static load type of strength indicator is generally used in the United States or Canada. The crushing value normally is used for high-strength aggregate materials where excessive fines are not produced under the stipulated load. as does broad experience with lightweight structural aggregates and experience using volcanic cinders and coral in concrete. [11. These data suggest. at least for the fairly strong aggregate materials that he Copyright by ASTM Int'l (all rights reserved). . As a matter of fact. For weak and lower quality aggregates the 10percent fines value is preferred [14]. No further reproductions authorized. and grading effects on mixing water demand needed for workability. OOO .000 4~ dk~ qJ 30.000 ~ o s 0 o t. The significance of strength tests of aggregates is not well established. . investigated. There are no ASTM test methods or specification requirements in this area. The influence of aggregate source on concrete modulus of elasticity is determined normally by testing concrete mixtures containing each of the Copyright by ASTM Int'l (all rights reserved).000. did find a trend toward weaker concrete at the same water/cement ratio for aggregates with lower compressive strength and high British crushing values. Johnston.0 Crushlnoj 30 40 EO Value of A99recjate F I G .~o0 qj 150 ~J Q u~ v) 0j t cL - 20. 1--Relationship between rock compressivestrength and the British crushing value of aggregate derivedfrom the rock. ~kSO ft. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. . O0 0 -~-o o 0 ~ 0 0 I0 British 2. The usual practice is to evaluate the aggregates' performance in concrete to see if it will produce concrete of the needed strength. 500 40.662 TESTS AND PROPERTIES OF CONCRETE AGGREGATES 9 K=plan | dohnst'on 50. Aggregate strength may be an indicator of other aggregate properties. Elastic Properties Modulus of elasticity and related values such as the Poisson's ratio of concrete aggregates is not included in aggregate specifications and there are no ASTM aggregate test methods designed to yield this information. but relationships have not been established. with the weaker aggregates that he investigated.j I0. the dynamic values are higher. As a matter of fact. Figure 2 gives an indication of the range of Young's modulus of elasticity for various rock types. and 207 X 103 MPa (2. have a curved stress-strain curve when the stress exceeds about 30 percent of ultimate strength. No further reproductions authorized. . This is due to the formation of bond cracks and slipping at the aggregate paste interface. stress-strain curves for stone [6] and for cement paste [23. of necessity.8. on the other hand. Concrete and mortar. and there has been shown to be a good linear relationship between dynamic and static values determined in the laboratory. Generally.15. shows data where aggregates with E values of about 14. various assumptions. Both in compression and tension. 9.MEININGER ON PHYSICAL PROPERTIES 663 aggregates. 6. A number of investigators have also determined rock modulus of elasticity in connection with researches of aggregate and concrete properties [3. 62. 34. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As is the case for compressive strength a good deal of information from rock mechanics investigations is available concerning rock deposits [1. 5. An example of this is contained in Houghton's paper [17] where natural rounded aggregate with an E of about 41 400 MPa (6 x 106 psi) produced concrete with E ranging from 28 000 to 34 000 MPa (4 to 5 • 106 psi) at 90 days compared to a quarried aggregate with an E of about 62 000 MPa (9 X 106 psi) which produced concrete with an E of 21 000 to 28 000 MPa (3 to 4 X 106 psi). and 30 X 106 psi) were used in different proportions in concrete indicating "that the modulus of elasticity of concrete is a function of the elastic moduli of the constituents.17]. Copyright by ASTM Int'l (all rights reserved). Because of this and because unknown factors can affect the influence of the pasteaggregate bond on the stress-strain curve there is no simple relationship between aggregate modulus of elasticity and concrete modulus of elasticity. 11. There has been a good deal of activity in the more theoretical area of developing equations to predict the resulting modulus of elasticity of a composite material from a knowledge of the elastic properties of the aggregate and the matrix [18-22]. but little is known about the elastic properties of gravel or sand particles other than what can be inferred from tests of parent rock material.5. Both static and dynamic E data are included. An increase or decrease in the modulus of either the aggregate or matrix constituent will produce a corresponding effect on the concrete. A direct linear relationship has also been found between rock compressive strength and modulus of elasticity [15. however." The equations advanced by Hirsch and others are complex and include. 76. 7. With a curved stressstrain curve the modulus of elasticity computed for the concrete will vary depending on which of the several recognized definitions is used.16]. it does not always hold that an increase in aggregate modulus of elasticity will increase the E of the concrete even if the properties of the paste are held relatively constant. Hirsch [22].16].24] are normally fairly straight lines indicating that the aggregate and matrix are reasonably elastic. Houghton [17] discusses the concept of predicting the tensile strain capacity of mass concrete so that tensile strains caused by thermal volume changes can be accommodated by the concrete without cracking. 0 o STATICALLY DETERMINED ~o ooo 9 DYNAMrCALLY DETERMINED SCHIST SHALE 9 9 SHONKINITE SILTSTONE SKARN SLATE SYENITE TACTITE TUFF 9 o ~ o Q o e o 99 I 0 I I 1 [ . The values are somewhat lower than the corresponding compression values. GRANITE GREENSTONE H E M A T I T E ORE HORNSTONE JASPILITE bJ (3.5 DO ORE o ?" t~" META-RHYOLITE MONZONITE PEGMATITE PHYLLITE PORPHYRY PYROXENITE QUARTZ QUARTZITE SALT 9 o 9 "" O0 SANDSTONE ~ o ~ " 8. )F- LIMESTONE L) O 0C MARLSTONE MAGNETITE MARBLE o ONE VALUE AT 29.0 ONE VALUE AT 20. No further reproductions authorized. From Ref 1. ~.1 psi • 6895 MPa. Relationships with age Copyright by ASTM Int'l (all rights reserved).=~ 0 0 0=o 9149 ~ 9 9 o . 2--Relationship between rock type and Young's modulus.= 9 =.~. ...~. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.oo~ 9 o~ Dee 9 .24] gives values of tensile modulus of elasticity of rock. ~. I I I I 5 YOUNG'S I I0 MODULUS I I I 1 ] I I I 15 I 20 ( p s i x 10 6) FIG..... Johnston [3.664 TESTS A N D PROPERTIES OF C O N C R E T E A G G R E G A T E S AMPHIBOLITE ARGILLITE BASALT BORAX CHALK CHERT CONGLOMERATE DIABASE DIORITE DOLOMITE EPIDOSITE GABBRO GNEISS . 1 0 6 -~ Less work has been done on the tensile modulus of elasticity..~9oz~. * . Los Angeles Abrasion The Los Angeles abrasion test--ASTM Test for Resistance to Abrasion of Small Size Aggregate by Use of the Los Angeles Machine (C 131) and ASTM Test for Resistance to Abrasion of Large Size Coarse Aggregate by Use of the Los Angeles Machine (C 535)--is accepted and used almost universally in the United States as a specification qualification test for coarse aggregate for concrete. The stiffness of an aggregate can have an important effect on the drying shrinkage and creep of concrete and mortar. Philleo [27] indicates that except for cases in which the creep of the aggregate itself is a factor. over 70 MPa (10 000 psi) compressive strength. the influence of the aggregate on creep of concrete is confined to the elastic constants and the concentration of the aggregate in the concrete. Lott and Kesler concluded in their studies of crack propagation in plain concrete [18] that cracks are arrested only when the E of the aggregate is greater than the E of the paste.21. Brandon [6]. Abrasion Test has supplanted the older Deval Abrasion Tests--ASTM D 2 and D 289--which have been withdrawn Copyright by ASTM Int'l (all rights reserved). Poisson's ratio averaged about 0. A. Creep is a third factor which enters into the estimate when stress is applied slowly. which is usually not the case. After freezing only the wet limestone showed a significant reduction in E to about 62 000 MPa (9 X 106 psi). Weaker rocks of the sandstone. It is also used widely around the world to evaluate aggregates. Poisson's ratio ranged from about 0. .05 and one 32 MPa (4600 psi) sandstone had a Poisson's ratio of 0. For the strong rocks. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.04 to 0. one 90 MPa (13 000 psi) conglomerate had a Poisson's ratio of 0.30 for the limestone.08 for several sandstones and quartzites to values over 0. Counter to the general trend. Hobbs [25] for concrete and Chamberlin [26] for mortar show a relationship of decreased drying shrinkage with increasing aggregate modulus of elasticity.14 for the quartzite and 0. and granite varieties ranged from 0. graywacke. Iyer et al [8] measured E and Poisson's ratio on aggregate rock material both wet and dry and before and after 100 cycles of freezing and thawing. basalt. No further reproductions authorized. The L. Before freezing E was about 80 000 MPa (11 to 12 • 106 psi) for both the quartzite and limestone rock.06 and 0. Hansen [10] gives measurements of the complete range of mechanical properties of three aggregates and discusses the procedures used in testing very small specimens.20 for a variety of rock types. gives values for Poisson's ratio at stress levels well below half of ultimate strength.MEININGER ON PHYSICAL PROPERTIES 665 for tensile strength and modulus of elasticity enter into the determination of strain capacity for rapidly loaded concrete. Chamberlin estimated the E of sands from dynamic E measurements on mortar. He was able to use the relative effective elastic modulus as a quality indicator which correlated with sand equivalent.13. along with compressive and tensile strength of rock. Abrasion Test. A. or graded aggregate with an abrasive charge of steel spheres (ASTM Methods D 289). and D. ASTM Test C 535. At first it provided for testing only 38. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The required charge of nominal 420-g steel spheres is also indicated in Table 1. 4 sizes were added (Gradings C and D). .) and No. Briefly the method is a dry abrasion and impact test which involves placing a sample of aggregate and a charge of steel balls into a hollow steel cylinder that is 508 m m (20 in. The L. and has a single rigid steel shelf extending 89 m m (31/2 in. is discussed in more detail by Woolf [28]. Loss values are higher and encompass a larger range than that of the Deval Test.5 m m (3/8 in. Abrasion Test was developed to overcome some of the defects found in the Deval test. 12) sieve. The cylinder is rotated at 30 to 33 r p m for 500 revolutions. in a cast iron cylinder for 10 000 revolutions. for them.w i t h an increased sample size from 5000 to 10 000 g and a doubling of the number of revolutions from 500 to 1000 for these larger sizes.). This was an attempt to obtain generally corresponding percentages of wear for each grading when a material of uniform quality was tested. and G ) .0 m m (11/2 or aA in.1 m m (11A in. which consisted of tumbling cubical pieces of rock (ASTM Methods D 2).666 TESTS AND PROPERTIES OF CONCRETE AGGREGATES as ASTM standards. The L. The Deval Tests are still on the books as AASHTO standards and are referenced in a few specifications in the United States. F. Such uniformity of results was usually obtained for Gradings A. Later 9.) maximum size aggregates (Gradings A and B). The precision statement recently added to ASTM Method C 131 is based Copyright by ASTM Int'l (all rights reserved). 50 m m (2 in. The method was revised in 1976 to add a precision statement.70 m m (No.) m a x i m u m size grading (Gradings E. No further reproductions authorized. A.2. ASTM Test C 131. A nominal 5000-g sample is used for the nominal gradings given in Table 1. was first adopted as a tentative ASTM standard in 1937.) long and 711 m m (28 in. is closed on the ends. within a reasonable margin of error.). however. But in view of its declining use in favor of the L. B. A large number of flat or elongated pieces might also cause this ratio to increase. For a detailed description of the equipment and procedures see ASTM Test C 131. and a second narrower 38. expressed as a percentage of the original weight. Abrasion Test the Deval Test will not be discussed further here. In 1947 a revision was prepared to add three more gradings for large aggregate sizes--75 m m (3 in. agreement was found in some instances and contrary data in other cases: To clarify the situation in 1964 and 1965 the larger sizes were deleted from ASTM Test C 131 and a new method was adopted.) in diameter.. For the larger gradings. Often the loss is determined at 100 and 500 revolutions.) into the chamber. The Deval Test. For a uniform material the ratio of the loss after 100 revolutions to the loss after 500 revolutions should not greatly exceed 0. It is much quicker to prepare a sample and obtain the resulting losses. Percent loss or wear is obtained as the difference between the original sample weight and the amount of the final sample coarser than the 1.1 or 19. A. C. . Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 4) 6.75 mm (1/4 to T A B L E 1 . No. . . . . g . . .) 9. .q m O "0 m "In F"O o "0 -T . .) 1 in. . D .Copyright by ASTM Int'l (all rights reserved). .1 to 25. o f Steel Spheres F~ z . .) 19. 1250 3/4 in. .S a m p l e grading and steel sphere charge. 1250 ..5 m m (3/4 to . 4 to 6 8 12 11 No. 1/2 in. .3 to 4. . . . . 8) 4 .. . . . .5 to 9.) 12.0 mm (1 to 38. . .0 to 12. . .< O IT1 z z . 5000 .5 m m (1/2 t o . .5 to 6. . A S T M Test C 131. . 7 5 to 2. . ..0 mm (U/2 to . . No. . . . .0 to 25.36 mm (No. . . .3 m m (3/8 to W e i g h t in E a c h Sieve F r a c t i o n . 2500 . No further reproductions authorized. 1250 2500 3/8 in. . . 1250 2500 . . 2500 1/4 in. .) A B C Grading 19.. F. this method is not utilized as much as ASTM Test C 131.) maximum size aggregate samples distributed to a large number of laboratories throughout the United States by the AASHTO Materials Reference Laboratory. and 3 correspond to the E.5 percent and single operator coefficient of variation 2. Even though it is widely used in specifications. For this reason desirable specification limits for larger sizes may not necessarily be the same as those judged to be needed for the smaller sizes of coarse aggregate. On the other hand. softer minerals will be more susceptible to surface wearing. and G gradings deleted from ASTM Test C 131. They are given in Table 2 with the required charge of steel spheres.0 mm (3A in. In another precision investigation within one state the data show a higher level of variability on samples having a loss of 13 to 18 percent [29]. A. Unfortunately no data are available at this time to use in the development of a precision statement. Caution should be exercised in comparing values obtained from ASTM Tests C 131 and C 535. even though they are strong. Judgment may be needed in establishing limits for different circumstances. Present Gradings 1. They may give different results for similar materials. The samples were tested by both ASTM and AASHTO procedures which differ only in minor respects for this particular test. To some extent harder rocks and minerals. Multilaboratory coefficient of variation was found to be 4. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and an indication of uniformity can be obtained by comparing the loss after 200 revolutions with that after 1000 revolutions. The ratio should not be greatly different from 0. A. No further reproductions authorized. Due to the limited application of large size aggregate in construction today. These data are based on samples ranging in loss from 10 to 45 percent. due to the lack of enough significantly explicit data Copyright by ASTM Int'l (all rights reserved). abrasion loss cannot be consistently related to the performance of concrete. .70 mm (No. 12) sieve. Test is the result of impact and surface abrasion. Loss is again determined using the 1. at least during early revolutions of the drum before any fines are created which might tend to cushion the impact forces. abrasion limits have to be ignored. the L. ASTM Specification for Concrete Aggregates (C 33) now includes a modular format where many of the required properties of coarse aggregates are varied depending on severity of exposure to weather and the end use of the concrete.2 for uniform material. tend to shatter more than softer materials which can better absorb the force. Wear or loss in the L. The same equipment is used for ASTM Test C 535. Note that 10 000-g samples are used and that 1000 revolutions of the drum are used. 2.0 percent. and the product of the degradation action in that case may be more of a dust rather than the larger angular pieces resulting from the shattering of hard pieces. However. and. L. Impact probably causes more loss.668 TESTS AND PROPERTIES OF CONCRETE AGGREGATES on 19. in some cases where aggregate performance is acceptable in concrete. A. No further reproductions authorized. . . Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 5000 5000 50 to 38..) 5"000 5000 38.1 to 25 m m (11/2 to 1 in. .. .. of Steel Spheres O~ O~ r m co -11 0 "13 m -n p- 0 09 "1" . 63 t o 5 0 m m (21/2 to 2 in.. . .. 5000 25 to 19 m m (1 to 90 in. .S a m p l e grading and steel sphere charge. 1 2 3 Grading 2500 . .1 m m (2 to lt/2 in.) W e i g h t in E a c h Sieve Fraction. g T A B L E 2 . .< 0 z m m z z G) m . 75 to 63 mra (3 to 21/z in. . .Copyright by ASTM Int'l (all rights reserved). 2500 . . A S T M Test C 535. .) .) 12 12 12 No.) . . but they did find that high L. . Walker and Bloem did not detect any dependence of concrete compressive streng~th on L. A. values. A. judgment provisions such as the following in ASTM Specification C 33 have had to be inserted in many specifications to allow use of known satisfactory materials: "Coarse aggregates having test results exceeding the limits specified . Smith [30] used coarse aggregates in concrete with L. A. A. laboratory studies reported by BIoem and Gaynor [32] failed to show such a relationship with strength. abrasion loss were blended to produce a range of L. A. A. The most significant correlations with concrete abrasion resistance were with concrete strength and water/cement (w/c) ratio. Copyright by ASTM Int'l (all rights reserved). A. abrasion losses. Jumper blended San Fernando Valley aggregate to obtain L. He found no significant correlation between L. Bartel and Walker [35] and Walker [36] showed a slight drop-off of compressive and flexural strength with increased L. abrasion losses did lower flexural strength with the aggregates studied. the limit has been set at 50 percent for all categories. This study included 56 coarse aggregates. (2) dressing wheel. did show some correlation of reductions in L. abrasion test has been correlated by Woolf [31] with the strength of concrete prepared with a wide variety of aggregates. Jumper [33] and Walker and Bloem [34]. A. No further reproductions authorized. in researches where aggregates of high and low L. .670 TESTS AND PROPERTIES OF CONCRETE AGGREGATES relating concrete performance with L. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . loss or wear is to be determined using the grading most nearly corresponding to the grading to be used in the concrete. and (3) the Ruemelin shot blast apparatus. A. abrasion losses ranging from 13 to 39 percent. provided that the aggregate produces concrete having satisfactory characteristics when tested in the laboratory. values from 42 to 58 percent. A. may be accepted provided that concrete made with similar aggregate from the same source has given satisfactory service . A. Above that strength no coarse aggregate effect could be detected. The soft limestone did decrease the concrete abrasion resistance at strengths below 55 MPa (8000 psi). abrasion loss at 500 revolutions or 100 revolutions. The loss in the L." ASTM Specification C 33 specifies requirements for a wide range of aggregate sizes. or in the absence of a demonstrable service record. In addition. . Over that range the decrease in compressive strength for constant cement factor concrete was from about 27 to 23 MPa (3900 to 3300 psi). In its place a minimum compact unit weight is required. A. . abrasion loss. With respect to the freezing and thawing durability of aggregates tested in concrete specimens. abrasion requirement. The determination of which grading of ASTM Tests C 131 or C 535 is to be used to test an aggregate product is based on the requirement that the L. A. abrasion wear value. However. A. abrasion values with increased strength. loss and the abrasion of concrete using three different test procedures: (1) Davis steel ball. Crushed air-cooled blast-furnace slag is excluded from the L. Gaynor and Meininger [37] did not find a relationship between concrete durability and L. No good correlations with field performance were found for basalts in terms of L. abrasion losses of rounded and crushed particles from the same parent rock do not vary much. A. The lowest L. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The carbonates and basalts were intermediate. on the average. Hobeda [39] shows a good relationship between the British crushing value and the L. These data represent tests of aggregates from a number of states. For igneous and metamorphic rocks L. A. A.70 mm (No. abrasion loss in two figures apparently originally appearing in a 1948 British paper by Shergold.70 mm (No. Percent loss increased in a straight line relationship with number of revolutions. 80) dust. He developed a sandblast test which was able to discriminate quality better. an empirical number derived from field service. In comprehensive research into aggregate degradation. and 46 percent L. Copyright by ASTM Int'l (all rights reserved). A. 12) sieve but comparatively low values of minus 180/zm (No. 80) sieve plus A. A. and a good relationship between L. A.70 mm (No. 28. West and his co-authors concluded that for carbonate rocks there was a good relationship between degradation value. but the spread of the data was large. Also particles in the larger sizes were marked and identified. loss. The granite and gneiss category had high loss through the 1. Sandstones gave a comparatively high amount of dust for the corresponding loss percentages through the 1. 12) sieve. and the particles held their angularity longer than did the fine grained limestone which suffered more surface loss by wear. versus percent loss determined in the traditional manner on the 1. losses. Fine and coarse grained limestone aggregates were tested in Grading A with the loss and gradation of the sample determined after each 50-revolution increment. Figure 3 shows percent minus the 180/zm (No. Woolf presents some data [28] showing that L. and L. which is the amount of dust lost in the test. A. No further reproductions authorized. abrasion correlated with the empirical degradation value and grain size. A. abrasion loss. 12) sieve. The highest loss gravel was the least effective in transferring load. A. A. More breakage of the coarse grained material occurred in the larger sizes. He found a relationship of loss in the sandblast test with porosity of the lightweight aggregate. Machine.MEININGER ON PHYSICAL PROPERTIES 671 Nowlen [38] in research into the effectiveness of aggregate interlock in concrete pavement joints compared the performance of three gravels with 17. Houston [40] experimented with the use of the L. A. respectively. abrasion and unconfined freeze-thaw deterioration. Larger grain size rock showed higher L. . The Los Angeles abrasion test has not been used widely for lightweight aggregates. Lines have been added to show the average trends for various rock classifications. loss material proved to be most effective in transferring load from one slab to another in repetitive loading tests. abrasion test for evaluating the quality of lightweight synthetic aggregates. West et al [41] studied the mechanism of abrasion in the L. abrasion loss. Hobeda also reports correlations with the Swedish impact test. if = . . all states. . / = w to 20 . Woolf [28] discusses the now withdrawn ASTM Method D-3 for toughness of rock which involved an empirical test to determine the distance in centimeters through which a 2-kg h a m m e r falls to cause failure of a small cylinder drilled from the aggregate material. A. 9 § OIABASE D MARBLE I0 20 30 MINUS 80 + A AFTER TEST (%) 40 3--Production of fines versus L. No further reproductions authorized.672 TESTS AND PROPERTIES OF CONCRETE AGGREGATES & 70 60 / A / / / / 50 Oj 40 9 0 ..~. .. A.'~ V .. Woolf [28] discusses the Jackson Impact Test in which an aggregate particle is rested on a rigid lower steel ball and a guided upper ball is allowed to fall on t h e particle. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Abrasion Test there is no impact or toughness test for concrete aggregate in regular use in the United States.9 10 0 CARBONATES SANDSTONES ~ . From R e f 41.~. Britain. abrasion loss. Toughness values for a wide variety of rock are tabulated in Ref 2. With respect to concrete aggregate. / .0 / W U ~" FIG.- 9 GRANITE a GNEISS 8 9 BASALT ---. Impact Resistance and Toughness Other than the L. .: / z o. Two concepts--whether or not the particle fractures and the Copyright by ASTM Int'l (all rights reserved). toughness is usually considered the resistance of the material to failure by impact. and Scandinavian countries for aggregate evaluation. There are however tests of this type used in Europe. ) material subjected to 15 blows by a 14-kg hammer falling 380 mm). Woolf [42] indicates that some hard but brittle particles also broke in the device. the L. (6) L. A. A. 12 steel spheres). suggesting that further strict standardization of procedures may be necessary. (10) Modified Marshall Impact (8. with 200 blows). This showed that the limits allowed in the United States are broad. Abrasion Test. Abrasion (Grading B). abrasion loss usually specified in the United States with equivalent L. The eleven procedures studied in detail were: (1) German Impact (sample in 8 to 12. A. High variation of results were found for the L. up to 40 to 50 percent loss. He found that even though the methods use different loads and procedures the tests characterize "the same or at least similar properties of the aggregates." Good correlation was found between all the tests run in the same laboratory. Woolf also reported other impact methods tried in an attempt to identify soft particles. (same as 5 except smaller sample). (3) L. and (d) a bag abrasion method where particles were placed in a cloth bag and swung against an anvil or hit with a rubber mallet. the British Impact Test (British Standard 812) and a modified Marshall Impact Test. or brittleness values as they Copyright by ASTM Int'l (all rights reserved). A. (7) Deval (Grading D of old ASTM Standard D 289). (Grading C). . Hobeda [44.5 to 9. Kohler compared L. No further reproductions authorized.5 mm (1/2 to 3/8 in.5 mm (5/16 to 1/2 in.0 to 12. (b) calibrated blows with a hand hammer where the type of fracture of the particles was examined (hard materials yielded sharp edged fragments and soft pieces tended to crush). None of the impact type tests did a very consistent job of identifying inferior material in samples of hard quartz gravel to which soft pieces were added. (Grading D). 5000-g sample.)). A.5 mm. (c) blows with a rubber mallet. weighing 260 times the specific gravity in grams. (9) British Impact (British Standard 812. and German Impact Tests when tests were run in different laboratories. bituminous mixtures. limits comparable to the French and German requirements. These comparisons were made for aggregates used in surface courses.MEININGER ON PHYSICAL PROPERTIES 673 height of drop needed to cause fracture--have been used in an attempt to measure soft particles in aggregate. A. 12. including: (a) a rotary machine which slung individual particles against a steel plate. Different size balls have been tried in this test. A. (5) L. A. Kohler [43] in a comprehensive study reported to the Highway Research Board in 1972 compared the results of aggregates tested by the German Impact Test. (4) L. compared to more restrictive equivalent values of 20 to 30 percent maximum loss for French and German specifications. A.7 in. A. and (11) Modified Marshall Impact (same as 10 except sample of 400 g). when comparing impact. (8) Deval (Grading E). (2) L.45] found a relationship between the Swedish impact test and L. and base courses.) aggregate. abrasion.5 mm range subjected to 10 blows with a 50 kg (110-1b) hammer from a height of 500 mm (19. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Machine used with German Grading (8 to 12. the Deval Abrasion Test. 140 versus 165 MPa (20 000 versus 24 000 psi). Good correlations are shown between impact value and crushing value. traprock. Low values were obtained from a number of limestones. In the intermediate to high range a wide variety of rock types and gravels were represented: limestone. A. The aggregate materials included in this study mainly had mica occurring in small flakes. and a sandstone. Bond [9]. In other related research Kauranne [47] found a good correlation between the Swedish impact value and L. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The crater depth and volume was measured and found to correlate well with Copyright by ASTM Int'l (all rights reserved). a traprock. . Rad [48] recently investigated a weight-drop test procedure to measure a coefficient or rock strength based on impacting an aggregate sample with a 2. A. The great disparity in L. sandstone.5-kg weight falling from a height of 56 cm. the Swedish indicate that they have found no correlation between i m p a c t resistance test results of aggregate and wear of aggregates subjected to studded tires in a road simulator. Mexico. It was found somewhat remarkable that mica increased toughness in laboratory tests in view of the known poor performance of mica-rich materials in road surfacings. loss of 46 percent were tested. A.674 TESTS AND PROPERTIES OF CONCRETE AGGREGATES are sometimes called. In the World Road Conference Report. loss of 26 percent and a granite-gneiss with an L. run on both dry and soaked aggregates." Two crushed stones. which in turn are less susceptible than flat or long aggregates. 4). and the coefficients of rock strength by the proposed test were close also. Usually there is very little rebound using this procedure. 1975. granite pebbles. and several ores. Another interesting research on impact resistance of rock was conducted by Singh [49] in which pellets were fired at rock at high velocity. British crushing values were also determined on particles in the 8 to 11. Pilot experiments showed that "rounded aggregates are less susceptible to breaking than sharp aggregates. a marble-limestone with an L. abrasion loss. Also there was a tendency for higher abrasion losses in crushed gravels with increasing percentage of quartz and feldspar and decreasing percentages of mica. Unconfined compressive strengths were fairly close. Aggregate abrasion value by the method contained in British Standard 812 showed much better correlation with road simulator wear (see Fig.3 mm size fraction. in the investigation of tests which might be useful as an indicator of crushing resistance of rock under impact. granite. and gabbro diorite. Mica percentages varied from about 5 to 25 percent. No further reproductions authorized. A. respectively. Pendulum devices were studied. However. rhyolite. In most cases soaking the samples had little effect on the impact of crushing values. developed a test which avoided the traditional drop-weight methods. These relationships do not hold up as well for stones. abrasion loss in this case is apparently due to the greater brittleness of the granite-gneiss. The highest impact resistance was obtained from several granites. some aggregates--those with a large proportion of mica or secondary hygroscopic minerals--did show crushing and impact values which indicated deterioration. For concrete aggregate at least minimal impact resistance is required to prevent undesirable breakdown in aggregate handling and hatching Copyright by ASTM Int'l (all rights reserved)..R e l a t i o n s h i p o f aggregate i m p a c t a n d abrasion values to wear caused by s t u d d e d tires." Rock tested ranged in compressive strength from 28 to 393 MPa (4 000 to 57 000 psi) with corresponding ranges in tensile strength and modulus of elasticity. "Among the rock properties to which rock damage is correlated are shore scleroscope hardness and tensile strength.MEININGER ON PHYSICAL PROPERTIES 675 5"0 40 q oQ 30 t 20 L I0 .?- W e a r ~n R o a d 3 S~mulator 4 5" ~ mm FIG. total energy input and impact pressure.2 :g m (5 L t~ < -tcJ ~oo . Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.< E E ~ 7O0 j 6~ . . F r o m R e f 45. 4 .j r f 400 300 L 200 o'n I00 -- O / . No further reproductions authorized. . Rate of cutting or drilling. Rebound Hardness--Shore scleroscope. unlike metals. and more recently the scratch hardness test developed by Woolf Copyright by ASTM Int'l (all rights reserved). and granite aggregates. apparently due to better bond between m o l a r and aggregate. basalt. then no test was specified for a time.676 TESTS AND PROPERTIES OF CONCRETE AGGREGATES operations. No further reproductions authorized. Hardness. Cracks were through the coarse aggregate particles. and gouging actions. Swiss rebound hammer. such as those which might be imposed on an industrial floor or from sediment loads in large hydraulic structures. There are many potential ways of measuring the hardness [53]. cracks indicated failure in the bond zone. Stiffler has observed that. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Mineral and rock materials when subjected to rubbing. are worn down due to the scratching and pitting that occurs. 1. Hardness is an often used term in describing desirable aggregate properties. Wear. there are few applications of concrete where surface aggregates may be exposed to severe impact loadings. First the Douglass particle strength test was used. This is apparently due to mineral grains or particles being pulled from the matrix. scratching with brass (ASTM Recommended Practice for Estimating Scratch Hardness of Coarse Aggregate Particles (C 851)) or steel [42]. There is a history of ASTM Specification for Concrete Aggregates (C 33) having a limit on "soft particles" [55]. particularly with the aid of an abrasive. 3. Sandhu's data on the number of drop hammer blows to failure of concrete cubes with various aggregates show that a crushed limestone and a crushed brick aggregate gave better relative impact resistance. Beyond that. but there has been little agreement as to how measurements should be made and whether hardness should be a property which is specified for concrete aggregates. Scratch Hardness--Moh's hardness scale. Sandhu [51] reports that impact resistance of concrete is mainly affected by concrete compressive and tensile strength although there is some indication that at the same concrete strength level angular aggregates and those with rougher surface texture may perform better in impact. Wear or Abrasion Hardness--Dorry hardness where a core of rock is subjected to wear with an abrasive on a revolving horizontal wheel [42] and British aggregate abrasion value (British Standard 812). minerals are pitted as well. scratching. Neville [50] in discussing the impact strength of concrete discusses pile driving and accidental impacts. 5. Skid Resistance "Hardness is the single most important characteristic that controls aggregate wear" according to Stiffler [52]. Indentation Hardness--Vicker's hardness number which is the load divided by the projected area of the indentation. 4. Rockwell hardness [54]. 2. For gravel. which just scratch when subjected to the movement of an abrasive on the surface under a load. Hardness Unconfined Compressive Strength.. or scratches are smoothed and polished gradually.7) 57 (8. and the action is such that any texture such as existing pits. such as typical road grit at 10 to 40 #m. He also established correlations for strength and modulus of elasticity versus the product of rock hardness times unit weight.1) 178 (25. . Polishing is a special form of wear where abrasive size is quite small.4) 61 (8. using the shore scleroscope and the Schmidt hammer as measures of hardness.2) 77 (ll.8) 308 (44. ASTM Test for Scratch Hardness of Coarse Aggregate Particles (C 235) has been withdrawn.7) Saturated 24 (3. This can happen particularly to exposed cement paste and the top surfaces of fine or coarse aggregate particles.. In most. Initially the hardness of the fine aggregate is important. Table 3 presents some of the data. Harvey et al [54] was able to relate hardness of limestone by the Rockwell procedure to sulfate soundness. strength and hardness decreased going from dry to saturated rock. particularly lower strength concrete.1) Schmidt Dry 13 30 15 24 13 20 27 32 Saturated . The procedure is now covered in ASTM Recommended Practice C 851 which is not intended for specification purposes. 27 . As a general rule concrete strength has been found to be the most significant factor in rate of wear of concrete [56]. It is any removal of Copyright by ASTM Int'l (all rights reserved). but TABLE 3--Effect of water on rock strength and hardness.677 MEININGER ON PHYSICAL PROPERTIES [42] has been used. percussion or the like" [57]. scraping. 26 "2'2" 25 31 Shore Dry Saturated 18 85 47 90 23 39 88 101 10 84 26 84 16 43 80 93 not all cases. Michalopoulos et al [4] studied the effect of water on the strength and hardness of rocks.5) 168 (24.7) 242 (35. but fine and coarse aggregate may be an important factor in some instances for concrete surfaces subjected to heavy traffic or abrasive forces.5) 19b (28.5) 47 (6.8) 253 (36.3) 20 (2. gouges.9) 157 (22.. Wear is "waste or diminish by continual attrition. No further reproductions authorized..9) 217 (31. Because of the difficulty of applying this procedure in a meaningful and consistent way to the specification of aggregates. Avg MPa (ksi) Dry Sandstone Granite Tonalite Granite Limestone Limestone Granite Granite 31 (4. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ASTM Specification C 33 now has no limits on soft particles and no other provisions referring to hardness.8) 75 (10. The coarse aggregate will become involved only if there is enough loss of elevation to expose a significant amount of the coarse particles. ) occur in normal rolling tires. In the studded tire road simulator it was determined that wear of pavements was not related to aggregate impact resistance but to the wet abrasion test value with a load of 12. with an abrasive supplied to simulate road grit. Hobeda's [45] abrasion by wet and dry methods. and solid rubber tires. the widespread use of studs in tires for winter traction caused a sharp rise in wear of road surfaces.678 TESTS AND PROPERTIES OF CONCRETE AGGREGATES particles that produce shape changes on a microscopic or macroscopic scale [52]. In a review of pavement wear testing Stiffler reports that sliding movements between rubber and pavement of up to 6. Regeneration of the surface can occur when two components of differing hardness are present and particles of the weaker softer material wear faster causing the harder material to protrude and eventually be undercut and torn out leaving an unpolished surface. wears along with the paste in these tests. The mechanism of concrete wear can vary [30]. first in the Scandinavian countries and later elsewhere. The least studded tire wear Copyright by ASTM Int'l (all rights reserved). Wear of highway pavements is due in large measure to the fine mineral abrasive present on the pavements. Road wear then decreased to only a minimal problem with the use of pneumatic tires. For example. slag.4 m m (1A in.5 kg on the samples (Fig. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. or rubber on mineral aggregate samples. Therefore. Studded tires have also been an important factor in road wear. iron wheels. 6). harder aggregates retard abrasion loss and stand out from the surface. mullite. In wear studies of minerals with three different fine abrasives of varying hardness it was found that wear rate corresponded fairly well with Vicker's hardness for calcium carbonate (both impure (i) and crystalline (c)). No further reproductions authorized. The reverse is true for a shot blast test where the limestone cushioned the abrasive shot and decreased the wear compared to more brittle aggregate. using a modified British abrasion test on a horizontal turntable with an abrasive. Friction forces of tire on pavement is made up of two components: (1) adhesion at contact and (2) plowing displacement of softer material by harder. During the first decades of this century. . on the other hand. and silicon dioxide (both crystalline (c) and fused ( f ) ) (see Fig. 4). With the phasing out of the studs in many areas this factor should diminish. Polishing occurs when a fine abrasive is used and the surface is made up of materials of similar hardness. Using higher pressure on the specimen caused intensive microcracking of the mineral specimens which allows moisture to penetrate. many pavement wear researchers utilize a wearing mode of rubber on pavement specimens. road wear was substantially due to horses' hooves. in concrete abrasion tests using the steel balls or dressing wheel. In the 1960s. Figure 5 shows the scratching and pitting action caused by wear of minerals. showed increased abrasion loss with moisture for most materials. A softer limestone aggregate. Copyright by ASTM Int'l (all rights reserved). From R e f S2. No further reproductions authorized. 679 . S--Microphotographs of several worn minerals.MEININGER ON PHYSICAL PROPERTIES FIG. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. They discussed some German wear data which showed 2. In concrete containing a sand with a substantial amount of soft minerals.3 Copyright by ASTM Int'l (all rights reserved). wear of both the matrix and the overall pavement was reduced. Smith found that in an area where almost a third of the passenger vehicles were equipped with studs.1 to 0.5 to 7. From Ref 52. and the most for micaceous gneiss and limestone. When a 100-percent silica sand was used with the harder traprock. Preus [60] in reporting test track studies showed that studs produced more than 100 times as much wear as regular tires even when sand and salt are applied to the surface. Pavements with aggregates of similar hardness to the matrix showed uniform wear. No further reproductions authorized. and concrete compressive strength was not significant for the materials used. pavements with traprock and limestone coarse aggregates wore at about the same overall rate even though the mechanism was somewhat different. In Canada and the United States [58-61] studded tire wear was studied intensively. was found for fine grained quartzites and diabase.5 mm (0. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . Rosenthal et al [61] show photos of stud wear marks. With harder aggregates the matrix was preferentially worn down around them until the particles were dislodged by the studs because of lack of embedment. It was determined that studded tires did not change the skid resistance much. They confirmed that studs tend to skid over hard aggregate and leave grooves in softer material.680 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. size of coarse aggregate. Other aggregate types. over the winter of 1969-70. wear on both portland cement concrete and bituminous concrete approached 5 to 8 mm in one season. Keyser found that the age of the mortar and whether or not limestone coarse aggregate was used were significant factors in studded tire wear studies. 6--Wear inversely proportional to hardnessfor Si02 abrasive. For a granite aggregate there was an inverse relationship between wear resistance and skid resistance. skid resistance increased as absorption and surface capacity of the particles increased. The lightweight fines did wear faster. that the energy needed to turn a rubber tire against a fixed concrete specimen decreased markedly as the siliceous particle count in the fine aggregate was decreased below 25 percent. for sandstone. A number of other laboratory procedures for evaluating pavement materials and mixtures for polishing are currently in use or under investigation. Some highway agencies have advocated the use of ASTM Test for Insoluble Residue in Carbonate Aggregates (D 3042). For carbonate aggregates. a direct relationship between sand-size. Degree of polish is measured with the British portable tester (ASTM Test for Measuring Pavement Surface Frictional Properties Using the British Portable Tester (E 303)). Skid resistance of pavement surfaces in wet weather depends on microtexture and. and one mountain gravel. A higher insoluble residue indicates a higher percentage of harder and perhaps more polish resistant minerals." ASTM Recommended Practice for Accelerated Polishing of Aggregates Using the British Wheel (D 3319).MEININGER ON PHYSICAL PROPERTIES 681 in. and silica or lightweight fine aggregate. Microtexture is controlled by the polishing tendency of the exposed cement paste or aggregate surfaces. residue. Deceleration areas showed the most wear. MuUen and Dahir [64] studied the wearing and polishing characteristics of a number of aggregate sources. Colley et al [63] in tests at the Portland Cement Association showed. The procedure involves polishing oriented coarse aggregate particles held by an epoxy backing using a rotating rubber tire running against the specimens which are around the perimeter of a second wheel. low skid resistances have been found [63]. No further reproductions authorized. For concrete pavements exposed to normal traffic wear which does not expose much coarse aggregate during the life of the pavement. acid-insoluble. on macrotexture if significant speeds are involved. . ASTM Specification C 33 contains the warning that "Certain manufactured sands produce slippery pavement surfaces and should be investigated for acceptance before use. They found no general correlation of properties for all aggregates. Abrasive and water are fed onto the tire specimen interface at a constant rate.) of pavement wear after only 27 000 passes of studded tire cars. and. is similar to the polishing value determination in British Standard 812 for coarse aggregate. it is the fine aggregate which tends to control the polishing rate and microtexture [46]. also. In other studies where calcareous fine aggregates were used in concrete. silica gravel and limestone coarse aggregates. Franklin Copyright by ASTM Int'l (all rights reserved). after polishing. found good skid resistance in all cases. Macrotexture is controlled by finishing operations and it is important in removing excess water from between the tire and pavement. and skid resistance was implied. Meyer [62] in using a number of concrete finishing textures. as a tool in selecting fine or coarse carbonate aggregates for use in surface courses. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. synthetic aggregate. Woolf [67] in 1966 briefly described the then fairly new California durability index test for fine and coarse aggregate which measured the tendency of an aggregate to break Copyright by ASTM Int'l (all rights reserved). Conversely for soft dolomite and limestone fine aggregates the particles were worn flush with the cement paste during the dry wearing cycle. The effect was much greater when the coarse aggregate was exposed.682 TESTS AND PROPERTIES OF CONCRETE AGGREGATES and Calder [46] report results of skid resistance research using several types of fine aggregate which are in decreasing order of performance: (1) calcined bauxite fines with both good polishing and abrasion resistance. For concrete where little coarse aggregate was exposed the effect was slight. and. and somewhat more severe than typical road action. Figure 7 shows how the British polished stone value (British Standard 812) of coarse aggregate affected the skid resistance of pavement surfaces after the 55-h wear and polish treatment. both tined and brushed mortar surfaces were included. No further reproductions authorized. although. It is more severe than the polish stone value device. Wet Durability and Attrition Tests In recent years there has been increased interest in abrasion and attrition procedures run in a wet environment. Highest losses in skid resistance consistently occurred with limestone coarse aggregate. current values are reported as still being adequate for most of these pavements. and (4) a carbonate fine aggregate with both poor polishing and abrasion performance. Studies of 31 concrete pavements in the United States [66] showed an average 20 percent reduction in skid resistance over 5 years. (3) a flint sand with poor polish resistance but good abrasion resistance. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. (2) a gritty sandstone material with good polish resistance but poor abrasion resistance. Coarse aggregate characteristics may become more important relative to concrete skid resistance if practices now in use in Europe are adopted more widely. Polish is evaluated with the British portable skid tester and texture wear by the sand patch test. The other is brushing away the mortar to expose coarse aggregate on the wearing surface to give more macro texture. . They use a dry wearing cycle of 50 h with a small flint gravel as an abrasive followed by 5 h of wet polishing with a fine emery abrasive. Weller and Maynard [65] at the British Road Laboratory have developed an accelerated wear machine for pavement samples. One includes sprinkling a skid resistance wearing surface aggregate on the top of fresh concrete just prior to finishing. The most important characteristic of the sands tested is hardness. the skid numbers of the pavement surfaces containing the soft fine aggregate were lowest after dry wearing and improved during wet polishing. Harder sands stood out from the surface and showed higher skid resistance after dry wearing than after wet polishing. since portland cement paste polishes more during the dry cycle and gains skid resistance during wet polishing. abrasion (a dry test) was used by the great majority. The L. and mixing which could affect concrete properties such as strength and water requirement. For concrete aggregates the principal value of such tests are identification of aggregates which may create undesirable fines during handling. Brushed concrete -o ~ v u~ 10- 020- I 30 I ~. It has been known that some aggregates degrade in a different manner in the presence of water than that exhibited in dry test methods [68]. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A. a number also indicated use of some type of wet abrasion or attrition procedure including: California Durability Copyright by ASTM Int'l (all rights reserved).0 [ 50 [ 60 I 70 I 80 Polished stone value FIG. . down into plastic clay-like fines. Highway Research Board Circular 144 [69] indicates use by state transportation agencies of various test methods relating to aggregate durability (other than freezing and thawing). These tests perhaps have more significance for base courses and aggregate surfaced roads where the possibility of interparticle movement in the presence of water may occur over the period of service of the material. No further reproductions authorized. 7--The effect o f polished stone value on the skid resistance value after wear and polish.MEININGER ON PHYSICAL PROPERTIES 683 60- "o 50 /- u 0 40 t" 30 c cl / / s 20 Exposed stone 1 Tined concrete i. batching. From R e f 65. however. and the sand Copyright by ASTM Int'l (all rights reserved).8. A. Washington Degradation Procedure. 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. A. showed a somewhat high sediment height in the wet L. and 1.0. A crushed graywacke aggregate with moderate dry L. the Oregon Air Test. Some materials showed marked differences compared to dry abrasion. machine. 73] have tried modified L. and Modified L.684 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Index (AASHTO T 210. He describes the Idaho degradation test which involves: wet tumbling in a glass jar. He experimented with different procedures designed to detect comminution degradation and alteration degradation. In Sweden a wet degradation test was performed in a rotary device [44]. A. Others [41. and good skid resistance. No further reproductions authorized. abrasion test and an extended 4-h test without the steel balls. loss. abrasion tests with water. Breese [73] gives a good history of the development of wet abrasion tests in the Western United States. . Almost all agencies reported some degradation problems. A. abrasion procedure was used in a National Cooperative Highway Research Project in the United States [71]. Idaho Degradation. and sediment heights in a sedimentation column were much greater after the wet attrition. Helm in Idaho [74] found little production of plastic fines in a modified dry L. The aggregates were crushed basalt. A wet test was also run which tended to accelerate the production of plastic fines. and the sediment height after the second 250 revolutions with water present correlated favorably with sediment height for the same material tested by the Washington Degradation Test. A modified wet L.0. The Larson proposal was to develop specification limits for loss after 250 dry revolutions and for sediment height after an additional 250 revolutions with water present. abrasion tests using water. test and in the California and Washington durability tests. A. A. Larson et al proposed a modified L. A few relied on petrographic analysis to identify mineral constitutents which are associated with rapid weathering. but it was found messy to clean out the drum of the L. Fines from the standard L. a pit-run river gravel. In many cases minus 75 #m (No. procedure. Plasticity index of the fines produced from the extended test were respectively 6. test consisting of 250 dry revolutions followed by 250 wet revolutions with performance being evaluated after both the wet and dry periods. Ekse et al [72] compared properties of fines produced from a standard L. Percent loss after 250 dry revolutions correlated well with the standard S00 revolution value. test were found to be nonplastic. A. A. A. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 72. and a crushed river gravel all from sources in the State of Washington. A. 200) amounts were more than double compared to dry attrition. Nevada Air Test. 2. an ASTM Standard is in preparation by Committee D-4 on Road and Paving Materials). in most cases the problems were termed moderate. with initial and final gradations. the Washington Degradation Test was one of the tests which interested these researchers. The value obtained is very dependent on the surface area of the charge and finer samples will indicate more degradation. The durability index test starts with a washed sample and then measures the quality of the fines generated from interparticle abrasion during a wet agitation period. Degradation or attrition of aggregates during mixing and agitating of concrete has been the subject of a number of investigations [80-83]. A. abrasion and sulfate soundness procedures. A. L. abrasion. In studies by Slater and more recently by Gaynor and by McKisson it was Copyright by ASTM Int'l (all rights reserved). At Purdue the Swiss Hammer was found to be a potentially useful toel in identifying hard shales. Weathered basalt was found to produce lower durability results than fresh basalt.5 and the multilaboratory standard deviation is 2 to 5. as an impact test. These aggregates contained altered minerals which contributed to rapid weathering. . tends to pulverize the rock and produces fines which in many cases are unlike those resulting from normal construction and service degradation. No further reproductions authorized. abrasion test and which gave good results in the Washington Test. A. Goonewardane [79] in recent work with the Washington degradation test looked into sources of variation. There is little correlation between durability index and L. The precision of the fine and coarse California durability tests [29] is fairly good with the standard deviation increasing with decreasing index values. A. In addition to the Washington Test. The single-operator standard deviation is about 1. He concluded that both surface attrition and leaching of clays from the aggregate pores were involved in the test. cleanness value. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The California durability index for fine and coarse aggregate [78] was developed to measure breakdown during construction and normal use under traffic conditions.5 to 3. good indications of performance were the ultrasonic disaggregation test and the ethylene glycol soak test used by the Corps of Engineers. In studies in Pennsylvania and Indiana [76. It is intended to complement the sand equivalent. It is stated that it is not presently anticipated that the test will be specified for concrete or asphalt surfacing aggregate. 77] to help identify the properties of shales which might help determine suitability for its use in embankment or as a granular material. Figure 8 shows California durability index values versus L.MEININGER ON PHYSICAL PROPERTIES 685 equivalent test to evaluate performance. Aggregate quality improved with repeated agitation cycles as found by Hveem [78]. High rebound readings were obtained for two shales which showed less than 40 percent loss in the L. Minor [75] describes the development of the Washington degradation test which was prompted by the poor performance of several basalt crushed stones and volcanic gravels which gave losses in the standard L. abrasion test ranging from 12 to 50. Amount of increase in aggregate surface area was judged to be a key characteristic. abrasion which. A. little change was noted in the coarse aggregate grading. 8--L. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. 100) sizes of about 6 percent in 160 min. in the discussion of that paper. ..85].. and 2 h and 40 min. 100) material of almost 12 percent in 2 h in one study.. In 2 h of mixing in a laboratory mixer.!T i ~ I olo BY'I I DURABILITY i I I Io 20 30 LART-% Loss at 5 0 0 rll t TEST I 40 . Hard quartz sand only caused an increase of 1 percent in the same 160-min mixing period. and Tuthill and Adams.. in another case. No further reproductions authorized. caused an increase in minus 150/~m (No.f I I t i 1 I . 100) material generated from the fine aggregate depended on aggregate hardness. II--I Z'~ "-" l . Several tests have been developed to measure the propensity of fine aggregates to degrade due to attrition during concrete mixing [82.. report data using a vane type attrition chamber.. identified that during prolonged mixing the fine aggregate with its much greater surface area tended to break down by attrition much more readily than the coarse aggregate. in one case. 60 Revolulions Less Durable -. From R e f 78. Davis et al. .r . 84.. The amount of minus 150 #m (No. x bJ o Z ). In the other study a soft limestone sand caused an increase in minus 150/~m (No.. A fine aggregate known to break down.686 TESTS AND PROPERTIES OF Inn CONCRETE l GEND t AGGREGATES I i II aGGREGATE ( ~ x #4)i IREGATE (~14 x 2 0 0 ) ~ . 50 i- A. mounted in a drill press and turned Copyright by ASTM Int'l (all rights reserved).J m (]c tl a [ "-IE~. FIG.. abrasion loss versus California durability index. '.. No further reproductions authorized.MEININGER ON PHYSICAL PROPERTIES 687 at 800 rpm. They used a 1000-g sample of aggregate. ASTM Test for Clay Lumps and Friable Particles in Aggregates (C 142). strength. has been withdrawn and is no longer referenced in ASTM concrete aggregate specifications. which detects particles which can be broken between the fingers after soaking. the Deval Abrasion Test. Meininger [85] reported on research conducted in the NSGANRMCA Joint Research Laboratory using the same attrition chamber but reducing the sample size to 500 g for increased convenience and also to spread the results out more. Abrasion Test for coarse aggregate which is used in ASTM Specification C 33 and ASTM Specification for Aggregates for Radiation-Shielding Concrete (C 637) as well as in a large number of agency specifications. He investigated a number of basalt fine aggregates and found that those causing rapid slump loss in concrete yielded more than 8 or 9 percent minus 75 #m (No. Impact on Specifications Tests which measure directly abrasion. . 200) sizes generated by the attrition test and the decrease in fineness modulus for a number of aggregates. Table 4 shows results of percent minus 75 #m (No. however. Values for 1000-g samples and 500-g samples are both reported. A. It has been reissued as a recommended practice. These sands also had high magnesium sulfate soundness losses. has been withdrawn as an ASTM standard although it is still an AASHTO Standard. ASTM Test C 235. At least one state still uses the Deval Test. the 500-g results have been found to be roughly double the loss for 1000-g samples in terms of generation of minus 75 /~m (No. or toughness characteristics of an aggregate are not generally referenced in specifications for concrete aggregates in the United States. is used in a number of ASTM aggregate specifications to detect extremely weak particles. Copyright by ASTM Int'l (all rights reserved). Since grading affects the results it has been found that the use of several standard gradings is the best practice. 200) fines in the shaker test. to evaluate fine aggregate attrition. Abrasion Test. A. The scratch hardness test method. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The one exception is the L. 200) when a coarser grading is tested. A. Abrasion are also used widely in other countries as indicators of aggregate quality. 10 percent fines value. The Deval and L. Higgs reports another approach to the same problem [84] using a paint shaker to attrition a 1000-g regraded sample of fine aggregate. The predecessor of the L. One sand which produced 6 percent fines in the test caused some problems on a construction project with increased aggregate fines. There appears to be a difference in the approach taken in the United States and Canada with respect to using aggregate strength and impact tests in specifications as compared to European and British practices which do utilize tests such as the crushing value. 2 2.20 0.56 0. 1 Coarse-No.95 0.25 0.4 3.20 0. % Fine Aggregate Source Decrease in Fineness Modulus Minus 75 tzm (No. 1 Coarse-No. 2 Medium-No.1 14. 2 0.7 5.3 5.89 0.6 15.4 3. 0.4 2. 2 Medium-No.18 5.76 1.4 5. 1 Coarse-No. silica sand silica sand silica sand silica sand silica sand river sand manufactured limestone some mica manufactured sand occasional strength problems some mica some mica manufactured s a n d commercial sand angular river sand angular river sand strength problems slump loss problems silica sand silica sand silica sand commercial sand commercial sand commercial sand small amount shale Remarks -I m 6o m G~ I"11 -I ill 0 0 z 0 0 "13 60 m "11 -I 0 "U Z --t ITI 60 "--4 60 O~ t~o Oo . 1 Coarse-No.35 1. 1 Coarse-No.0 4.4 1. 1 Coarse-No.2 16.77 0.81 0.2 23.2 Absorption. l Coarse-No.5 1.5 5.11 0.9 6.Copyright by ASTM Int'l (all rights reserved).41 0.0 16.1 5.9 10.8 14. 1 Coarse-No. 1 Coarse-No. 2 Medium-No.4 2. 1 Coarse-No. 1 Coarse-No.9 1. 1 Coarse-No.3 3. 200) Generated Coarse-No.78 0.7 3. 1 Coarse-No. NSGA-NRMCA Joint Research Laborato~ Test Fine Aggregate Grading b Attrition Test Results T A B L E 4--Tests of fine aggregate in vane-type attrition chamber.07 0. 1 Coarse-No.3 3. 2 Medium-No. 2 Medium-No. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.9 6. No further reproductions authorized. 1 Coarse-No.94 0.4 5154 4957A 4957C 5160A 4954 5076 4621 5160B 5044A 4957B 4989A 4989B 5044D 5075 5044C 5044B 5019B 4933 5154 4965 5160A 5065B 5065A "5168B 5016B 1. 1 Medium-No.55 0.67 0.16 0. 1 Coarse-No.2 22.40 0.25 0.22 0.9 0.9 1.3 11.0 500-g Sample a.3 12.19 0.6 8.7 3.3 1. 2 Medium-No.01 0.8 5.27 0.1 2. 1 Coarse-No.6 12.6 3.6 24. Coarse-No. lO00-g Sample a.9 1. 5016C 5117 5016A 5065C 5160B 4621 5065A 5065B 5065C 4621 O~ O0 r "o 212 0 "o m ~o ---I t'3 w- -o -r .. Medium-No.22 0.19 0. Medium-No. 2 Fine-No.< 0 Z ITI z 7 fi3 m 2o . % Passing No. 200 material generated in the test. Medium-No. Medium-No.90 7. 2A3 Fine-No. 2A3 Fine-No.8 4. lower strength small amount shale commercial sand small amount shale commercial sand some mica manufactured limestone commercial sand commercial sand commercial sand manufactured limestone 100 100 100 100 100 These are the sand gradings prior to the attrition test. Medium-No. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.24 0. 2 approximate 80 88 100 100 87 50 74 80 85 70 25 49 50 60 52 10 20 20 30 15 2 5 0 10 2 0 0 0 0 1 OThe 500-g sample has been shown to yield attrition results at least 50 percent higher than results obtained with the 1000-g s a m p l e . 4 No.20 0.0 4.18 0...2 2. 3 Medium-No.36 0. 2 Fine-No.0 2.4 6.31 2 2 2 2 2 2 2 2 2 2 2 0.2 1.Copyright by ASTM Int'l (all rights reserved). Medium-No.7 J B C D E F G H 1 L K Good Poor 0.8 1. No further reproductions authorized.22 0. Medium-No. . 2 approximate Medium-No. Tuthill and A d a m s Data [82] Medium-No. 2A3 Fine-No.8 2. . 1 Medium-No.52 6 18 lO00-g S a m p l e a.19 0.b o t h in terms of decrease in fineness modulus and minus No. 200 i14 ..16 0. 100 No. lower strength sticky concrete.64 0. Medium-No.44 0. and Polivka Data [82] Medium-No.3 1.2 0.7 1.7 4. 2 Medium-No.9 9..10 0.21 0.14 0.4 . 2 approximate 0.6 1.3 8.16 0..3 2.0 9. Medium-No.2 Medium-No. 2 Medium-No.18 0.20 0. 8 No. b Gradings. 2 Medium-No. 2 Medium-No.20 0.27 3 6 6 6 6 6 6 6 6 8 9 6. Medium-No. 30 No.3 2.22 0. 0. iii 0..5 2.. Davis. 50 No.1 7. 3 acceptable sand slump loss problems satisfactory sand satisfactory sand satisfactory sand satisfactory sand satisfactory sand satisfactory sand satisfactory sand satisfactory sand satisfactory sand sticky concrete. Mielenz.. 2 Medium-No. 2A3 Fine-No.1 l 0. 16 No.. .. [5] Kaplan. "Influence of Water on Hardness Strength." Journal. 1953. "Durability Tests on Some Aggregate for Concrete. 1. T. and Triandafilidis. American Society for Testing and Materials. G. March 1977. Sept. P. O. J. References [1] Udd. "Properties of Florida-Oolite Concrete. S.. [3] Johnston. Rahn. or strength properties are required.. 1. E." Journal of Testing and Evaluation. and Remarkrishnam.690 TESTS AND PROPERTIES OF CONCRETE AGGREGATES and impact value as potential specification tests.. D. Quite often these methods might be used to evaluate the performance of alternative aggregate sources as well as various mix proportions. "Physical Properties of Rocks and Probable Applications. 1965. American Society for Testing and Materials. For example. 1946. "Crushing Tests by Pressure and Impact. "Results of Physical Tests of Road-Building Aggregate. March 1970. [6] Brandon. 593. p. strength. C. and Hsu." Report REC-ERC-74-10. [7] Collins. E. 13. Construction Division. American Institute of Mining and Metallurgical Engineers. [9] Bond." Bulletin. Concluding Remarks There is a good deal of history and data available concerning the measurement of physical properties of aggregates and attempts to relate these properties with concrete properties. No. second.. 114. p. ASTM Test for Abrasion Resistance of Concrete by Sandblasting (C 418) and ASTM Test for Abrasion Resistance of Horizontal Concrete Surfaces (C 779) cover the abrasion testing of concretes by four procedures depending on anticipated service condition--sandblasting. 1975. impact. [4] Micbalopoulos. J. With respect to aggregate strength. May 1959. ASTM Specification for Lightweight Aggregate for Structural Concrete (C 330) and ASTM Specification for Lightweight Aggregates for Concrete Masonry Units (C 331). revolving disks. and Compressibility of Rock. J. p. Vol." Magazine of Concrete Research. . and ball bearings. or toughness properties are needed. rely more on past service record and judgment for those aggregates which have performed satisfactorily. Winter 1976. "Rock Mechanics Properties of Typical Foundation Rocks. American Concrete Institute. require the aggregate to be of sufficient strength to yield certain minimum compressive and tensile splitting values when used in concrete." Technical Publication No." A S T M STP 373. C. 1895. F. Copyright by ASTM Int'l (all rights reserved). American Society of Civil Engineers. In North America the practice is to. dressing wheel. "Strength and Deformation of Concrete in Uniaxial Tension and Compression. p. the evaluation and testing of concrete containing alternative materials remains the best approach to assuring performance when special abrasion.. However. Bureau of Reclamation. 1974. J. "Flexural and Compressive Strength of Concrete as Affected by the Properties of Coarse Aggregate. 141. M. p. p. D. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. T. R. 1193. first. No further reproductions authorized. [8] Iyer. [2] Woolf." Bureau of Public Roads. to test the properties of concrete made with the aggregate in question if special abrasion. Association of Engineering Geologists.." Journal. C. F. A. and. [18] Lott. W." Report LR 293. "The Precision of Selected Aggregate Test Methods." Manuscript 4035. p. E. L. 563. Pergamon Press. p. 18. No.. and Haas." Testing Techniques for Rock Mechanics. .. W. R." Series 88 and 107." Quarterly Journal of Engineering Geology. L." Cement and Concrete Research. Highway Research Board. No. J. National Sand and Gravel Association. 69. F. and Tubey. [23] Shah. 1968. 1975. A S T M STP 402. T." Journal. [22] Hirsch. W. [13] Tanigawa. Young's Modulus. 1976. Highway Research Board. and Bloem. "Modulus of Elasticity of Concrete Affected by Elastic Moduli of Cement Paste Matrix and Aggregate.S.. W. K. p. "Deformation of Concrete and Its Constituent Materials in Uniaxial Tension. "The Effective Modulus of Rock as a Composite Material. [21] Hansen. [20] Hobbs. E. C. 1956. [25] Hobbs. and Kesler. "Effects of Aggregate Properties on Strength of Concrete. Shrinkage and Thermal Expansion of Concrete Upon Aggregate Volume Concentration... 350.. 66. [24] Johnston. J. Jan. 691. C. D. Dec. [19] Ko." Proceedings. Transportation Research Board. G. 1963. p. American Concrete Institute. 539.. Oct. [26] Chamberlin. [1l] Ross. J." A S T M STP 169 and 169A. K. "Influence of Aggregate and Voids on Modulus of Elasticity of Concrete." Journal. [17] Houghton. 1958. University of Arizona. J." TRB Record No. "Research on Low-Grade and Unsound Aggregates." Cement and Concrete." HRB Special Report 90. 1970. "Coral and Coral Concrete. 531. "The Dependence of the Bulk Modulus. "Determination of the Mechanical Properties of Three Concrete Aggregates Using Small Scale Test Specimens. L. "Crack Propagation in Plain Concrete. A.. Strength. 1972. and Ames. M. and Winter." International Journal of Rock Mechanics and Mineral Sciences. 1976.. [14] Hosking. 1969. "Arizona Volcanic Cinder Concrete--A Comparative Study. 679. J. D. Naval Civil Engineering Laboratory. "Can Research in Volume Change Assist the Designer. [29] Benson. E. Cement Mortar. American Concrete Institute. Hardness. American Society for Testing and Materials." Journal. distributed with NSGA T. and Elastic Properties.. 068. P. [31] Woolf. 193. W.. Feb. p. C. American Concrete Institute. S. 1. American Concrete Institute. E. "Effect of Soft Sandstone in Coarse Aggregate on Properties of Concrete. "Effect of Aggregate Quality on Resistance of Concrete to Abrasion. Abrasion. 324. [28] Woolf. A. "Rattler Losses Correlated with Compressive Strength of Concrete. 1966. K. [12] Lorman. March 1962. 133. 85. p." SP-20... 1974. A. D. C. Sept. "Influence of Natural Sand Fine Aggregate on Some Properties of Hardened Concrete Mortar. No further reproductions authorized. U. p. Copyright by ASTM Int'l (all rights reserved). 10.. T. D. D... [34] Walker." HRB Record No. D. "Model Analysis of Fracture and Failure of Concrete as a Composite Material. 427. Pergamon Press. [30] Smith. 9." HRB Record No. and Gaynor.L.." Technical Report No. P. American Concrete Institute.. Sept. L. 1966. "Deformation Moduli of Rock. "Determining the Tensile Strain Capacity of Mass Concrete.. p. 1976. 5. 124. 1965.I." Journal.MEININGER ON PHYSICAL PROPERTIES 691 [10] Hansen. 1959.. 1966." Journal." Bulletin No.. 204. O. D. p. P. Dec. p. W. 1977. p. p. [27] Philleo. p. Engineering Experiment Station. 1974. p. Highway Research Board. W. Highway Research Board. and Kienow. B. American Concrete Institute. p.. Y. 91. 1937. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 445. O. E. Herbert. "The Relation Between Los Angeles Abrasion Test Results and the Service Records of Coarse Aggregates. "Inelastic Behavior and Fracture of Concrete. Vol. G. Great Britain. A S T M STP 205.. R. "A Review of the Geological Factors Influencing the Mechanical Properties of Road Surface Aggregates. Transportation Research Board. 1949.. p. 1969. [15] Clark. W. and Cement Paste. R. "Influence of Aggregate Restraint on Shrinkage of Concrete. L. American Concrete Institute. American Society for Testing and Materials. 72. H." Journal. "Toughness. p. D.. R. C. 7. [16] Hartley.." TRB Record 613. 1960. [32] Bloem. and Beardsley. Road Research Laboratory. American Concrete Institute." Technical Report TRA 43Z Cement and Concrete Association. S. R. C.. [33] Jumper. 1955 and 1966. D. D. Highway Research Board. 1974. M.. 1967.. 1972.. G. C. F. 1974.. and Schonfeld. Transportation and Road Research. K. N. Benedict. 1975. Statens Vaginstitut. M." Significance of Tests and Properties of Concrete and Concrete-Making Materials. A. ITT Research Institute. N." Series 62. National Sand and Gravel Association. p. F.. p. 1944. 17.." Report No. No further reproductions authorized. O. D." Report J-15. 1966. W. "The Concept of Hardness as Applied to Mineral Aggregates. J. "Investigation of Aggregate Durability in Concrete." Final Report NCHRP Project 4-2... "Comparative Investigations of International Test Methods for SmallSized Coarse Aggregates. N. "Bergmaterial Till Vagbyggnad. P.." Journal of Testing and Evaluation. Highway Research Board. 6. "Degradation of Aggregates. Stiffler. [49] Singh. D. S. E. 1966. "Relation Between Wear and Physical Properties of Roadstones. Commission Geologique de Finlande. 1964." Journal. 1969. Illinois State Geological Survey... [40] Houston. P. G. M. J. [44] Hobeda. [41] West. "The Skidding Resistance of Concrete--The Effect of Materials Under Site Conditions. Stockholm. . R.. R. and Wiskocil. S. (PB 190 965). "A Sandblast Abrasion Test for Synthetic Aggregate Evaluation. R. [46] Franklin." HRB Record No. "Abrasion Resistance. Dec. Purdue University School of Engineering." HRB Special Report 101. Guntram." Laboratory Report 640. 1971. 84. 1969. Highway Research Board. 305. J. American Society for Testing and Materials.." Illinois Minerals Note 54.. and Calder. 13. [38] Nowlen. D. "Properties of Carbonate Rocks Affecting Soundness of Aggregate." Bulletin No. "On the Abrasion and Impact Strength of Gravel and Rocks in Finland. T. [57] Prior. F. [43] Kohler. 1. 412. National Swedish Road and Traffic Institute. p. 1975. [52] Stiffler." 29th Annual Meeting of the National Sand and Gravel Association. K. T. R. Nov. American Concrete Institute. "Resistance of Concrete to Impact Loading. p. J. Kalevi. [36] Walker. [54] Harvey. F. Pennsylvania State University Joint Road Friction Program and Automotive Safety Research Program. B. 243.. Peet. 1971. Peet. p.L. S. "Concrete-Making Properties of Gravels from Southwestern United States. 25.. B.692 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [35] Bartel. W. R. [42] Woolf. Stockholm. M. [56] Scripture. 1953. E. distributed with NSGA T. E.. "Rock Breakage by Pellet Impact. S. "A Simple Technique for Determining Relative Strength of Aggregates. 1951. 477. Johnson." ASTM Materials Research and Standards.4.. A S T M STP 169. Jr. FRA-RT-70-29. Aug. 196.I. p. 1967. American Concrete Institute. Highway Research Board. and Bryant. Fraser. and Walker. "Floor Aggregates. 48. McGraw-Hill. R. "Hardened Concrete--Physical and Mechanical Aspects. Smith. [50] Neville. Portland Cement Association Research and Development Laboratories. E. 352. C.. W. 196. 1969. Mexico. Nov. E. United Kingdom. p... A." HRB Record No. and Meininger." Crushed Stone Journal.." HRB Record No. p. "The Flexural Strength of Concrete. [51] Sandhu.." HRB Record No.. T..Y. Sept. 2. Troxell. [47] Kauranne. 169. 1954. May 1963. [58] Smith. R. [48] Rad." Indian Concrete Journal.. J.. [53] Davis.. Copyright by ASTM Int'l (all rights reserved)." Monograph No.. D. The Testing and Inspection of Engineering Materials. S. [37] Gaynor. W. [45] Hobeda. 1946. comments at World Road Conference. Highway Research Board. "Influence of Moisture on the Strength and Wearing Properties of Road Aggregate. 1970. and Aughenbaugh. "Mineral Wear in Relation to Pavement Slipperiness. American Society for Testing and Materials. and Baxter. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Peet. Feb. [39] Hobeda. E. "Methods for the Determination of Soft Pieces in Aggregate. 42. "Influence of Aggregate Properties on Effectiveness of Interlock Joints in Concrete Pavements." No. "Studies of Studded-Tire Damage and Performance in Ontario During the Winter of 1969-70. and Renninger. May 1968. No. Also.. J. R." Special Report No. 1970.. H. [55] Gray." Journal. and the Iowa State University Press. American Society for Testing and Materials. H. H. and Shumway. Vallerga. 122. [72] Ekse. Vol.. Idaho. 2. R. [60] Preus. Christensen. E. D... 1974. S.. H." Symposium on Road and Paving Materials. [77] Chapman.. and Nowlen." HRB Record No. D.. 1959. 1971. 4. W.. "Weathering Study of Some Aggregates... Highway Research Board. [76] Reidenouer. p. p. L. Mathiowetz. L. 1. Results Digest No." Pennsylvania Department of Transportation. June 1970." Record No. K. Jan. 353. National Ready Mixed Concrete Association. 1964.. 75-11. Journal. [68] Melville. [67] Woolf. C. Vol." Transportation Engineering." Publication No. Bureau of Materials. R.. W. R. 119. University of Nevada. "Effect of Prolonged Mixing on the Properties of Concrete. 3rd Annual Engineering Geology and Soils Engineering Symposium. 16." HRB Special Report No. and Research. p. J. and Elastic Properties. R. C. Jr. Nov. July 1973. Strength. 1966. Aug. "Skid Resistance and Wear Properties of Aggregates for Paving Mixtures.. 352.. Cart. L. "Degradation of Mineral Aggregate. T." HRB-NCHRP Report No. [73] Breese. Highway Research Board. "Shale Suitability--Phase II-Final Report. "Modification of the Standard Los Angeles Abrasion Test. 461. Joint Highway Research Project. 1967. p. American Society for Testing and Materials. 1966. O. Civil Engineering Department. "Wearability of P C Concrete Pavement Finishes. 1969." Proceedings." North Carolina State University Highway Research Program Interim Report." Journal of Testing and Evaluation. 1969. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1976. D. "Requirements for Wear-Resistant and Skid Resistant Highway Pavement Surfaces. R. 5. 1970. 1963. Highway Research Board. C.. C-1308. 719... Highway Research Board. 238. P. G. [62] Meyer. p. [70] Vantil. D. No. [75] Minor. [71] Larson. [65] Weller. "Factors Affecting Skid Resistance and Safety of Concrete Pavements. p.. p. R. 89. p. C." reviewed in TRBNCHRP Research. 1977. [74] Helm.. J. "Degrading of Aggregate by Attrition in a Concrete Mixer... Highway Research Board. Copyright by ASTM Int'l (all rights reserved). J. B. [82] Davis. 1959.. Boise. 28. P.. 3.4." Circular No. "Toughness. E." Report No. "Behavior of Aggregate in the Washington Degradation Test. 80. and Dahir. "Analysis of Questionnaire on Aggregate Degradation. "Importance of Petrographic Analysis and Special Tests Not Usually Required in Judging Quality of Concrete Sand. A. R. British Road Research Laboratory. [61] Rosenthal. [78] Hveem.. Milos. P. HRB Record No." Significance of Tests and Properties of Concrete and Concrete-Making Materials. and Maynard. . R. and Hilliard. and Morris." HRB Record No. W. 170. [64] Mullen. D." Proceedings. P. 1. C. Geiger. 61. D. "Shale Classification Tests and Systems--A Comparative Study. 1975. H. J. No further reproductions authorized. "Influence of Materials and Mix Design on the Skid Resistance Value and Texture Depth of Concrete." Report No. K. N. 111.. Mielenz. E. April 1965." Report No. M. 62. P. J. B. Sept.. 101.. 1969." Journal of Materials. R. M. Sept. 109. April 1974. G. "An Investigation of the Variation of Degradation-Susceptibility Within An Aggregate Source.MEININGER ON PHYSICAL PROPERTIES 693 [59] Keyser. "Resistance of Various Types of Bituminous Concrete and Cement Concrete to Wear by Studded Tires. A S T M STP No. and Howe. L. et al. Testing. Discussion of Ref 59. [81] Gaynor. 1971. and Smith. 1971.. 352.. L.. Bureau of Reclamation. 1948. "A Test for Production of Plastic Fines in the Process of Degradation of Mineral Aggregates." Circular No. LR 334. [63] Colley. p. No. A.. p. D. 31. "A Durability Test for Aggregates. p. E. [69] Hendrickson. H. R. J. M. and Polivka. J. 277. and Smith. Hardness. "Evaluation of Studded Tires. A. (PB 197 625). A S T M STP 277. "Degradation Characteristics of Selected Nevada Mineral Aggregates. H." Engineering Report No. American Society for Testing and Materials. A S T M STP 169. Abrasion. American Society for Testing and Materials. B. [80] McKisson. American Society of Civil Engineers. E. Highway Research Board. F. 144. June 1975. G. Vol. C..." Symposium on Road and Paving Materials.. [66] "Surface Wear of Portland Cement Concrete Pavements. Highway Research Board. American Society for Testing and Materials. [79] Goonewardane. R. 16. Transportation Research Board. 301." Proceedings. L. R. A." H R B Record No. W. l. Winter 1975. "Erosion Resistance of Concrete in Hydraulic Structures.R. "Aggregate Degradation During Mixing." Report 201.. Copyright by ASTM Int'l (all rights reserved). "A Review of European Practice for Laboratory Evaluation of Aggregate Polishing Characteristics. "Rock Penetration as a Test of Physical Properties. R. ACI Committee 210. Bibliography ACI Committee 201. H. p. "Predetermining the Polish Resistance of Limestone Aggregates. 1970. No further reproductions authorized. Association of Engineering Geologists. 1947.. American Concrete Institute. p. [84] Higgs. I. p. 1969. F. Sun Apr 6 21:45:30 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Tests of Concrete Conveyed from A Central Mixing Plant. 1931." Bulletin. p. E. 57.. [85] Meininger. "Erosion of Concrete by Cavitation and Solids in Flowing Water. Highway Research Board. 341... J. Fourth Annual Engineering Geology and Soils Engineering Symposium. No. p. Part 2. B. and Mahone. 15. Byrne. W.. 12.. 510. Howard. 1977." Proceedings. W. American Concrete Institute. 3rd Annual Engineering Geology and Soils Engineering Symposium." National Ready Mixed Concrete Association Convention. Moscow.herwood. D. Vol. p." Proceedings. V. C.. R. 173. . Price. "Montmorillonite in Concrete Aggregate Sands. C. Boise." H R B Record No. Olsen. American Society for Testing and Materials. 43. T. Highway Research Board. '.694 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [83] Slater. Vol. 1965. and Simms. W." Report 210. C. "Durability of Concrete in Service. D. Idaho. and Hoover. 1962.. Idaho. American Concrete Institute. 341. N. 1966. 1009. Haye.." Proceedings. "Investigation of Test Methods to Determine Basalt Aggregate Breakdown. E. p. This may be because the significance of thermal properties is not as apparent. K . C o o k 1 Chapter 39--Thermal Properties Introduction The thermal properties of concrete aggregates are of greater or lesser concern to the user. Examples of where knowledge of thermal properties are of greater concern are in the design of massive structures. and the like. z The need for a better understanding of the effects of the thermal 1Consulting engineer. 2See p. Concrete. Copyright9 1978tobyLicense ASTM International www. An understanding of the effects of the thermal properties of aggregates on the properties of concrete can have an effect on improving concrete quality and in some instances may well be mandatory. Except for thermal coefficient of expansion. The significance of tests of thermal properties of concrete is discussed in another paper in this publication. warehouses. Sun Apr 6 21:45:32 EDT 2014 695 Downloaded/printed by Universidade do Gois pursuant Agreement. 1978 H. the discussion in this paper is confined to the significance of tests of thermal properties of the aggregates. 242. No further reproductions authorized. The attention that has been given to the thermal properties of concrete aggregates is not as great as the amount of research and the volume of testing performed in connection with other properties of aggregate. Copyright by ASTM Int'l (all rights reserved). Insofar as possible. such as dams. pavements. such as office buildings. seldom are considered.STP169B-EB/Dec. where thermal and volume stability are important and in lightweight concrete structures where insulating value is a primary factor.astm. and in many instances the effects do not appear to be as important as the effects of other properties of aggregates. Ohio 44114. Cleveland. in some instances it has been necessary to discuss briefly the thermal properties of the concrete as affected by the aggregates. A discussion of the significance of the thermal characteristics of concrete aggregates is further complicated by the effect of the relationship between the thermal properties of the concrete as a whole and the thermal properties of the component materials. the thermal properties of the aggregates used in normal concrete structures. however.org . depending upon the nature of the concrete structure and the exposure to which it is subjected. Refs 5 to 15 list more values than most of the others.9 • 10-6/~ (5.4 • 10-6/~ to 12. whereas other thermal properties are usually of concern only in special instances. The thermal properties of aggregate referenced in the literature are thermal coefficient of expansion. particularly with respect to the volume change of concrete as affected by the aggregates.9 • 10-6/~ (4. and they are discussed here in that order. as evidenced by the fact that the great majority of available references deal with thermal expansion. The significance of other thermal properties has been given much less attention than has thermal expansion. Hydrated cement pastes may range from 10. 226. It should be noted that Ref 15 is concerned completely with the thermal coefficient of expansion of portland cement rather than aggregates. and other factors. the mixture proportions.6 / ~ 14. particularly the thermal coefficient of expansion on the durability of concrete. Scholer [3].8 • 10-~/~ (6 • 10-6/~ to 16.8 • 10-6/~ (3. Undoubtedly the reason for this is that the thermal expansion of aggregate and hence of concrete is important from the standpoint of structural design in all concrete structures. are discussed in a paper on volume change in this publication . is by Hallock [4] and is entitled. 4See p. specific heat. has been expressed by Allen [l]. It is included because a discussion of the thermal properties of concrete aggregates would not be complete without some information on the thermal properties of the cements with which they are used. .0 • 10-6/~ (7. "Preliminary Notes on the Coefficients of Thermal Expansion of Certain Rocks. and others. included in this paper. An average value for the linear thermal coefficient of expansion of concrete may be taken as 9. and thermal diffusivity. particularly in massive structures.2 • 10-6/~ (9 • 10-6/~ and mortars from about 7." Some aspects of this property.4 Numerical Values for Thermal Coefficients of Expansion Although values for the thermal coefficients of expansion of aggregates from specific locations are contained in nearly all of the references listed and are available from many other sources.6 • 10-6/~ (7.2 • 1 0 . Thermal Coefficient of Expansion The earliest reference to work on this subject. thermal conductivity.0 X 10-6/~ Mitchell [5] has found that at early ages or at certain critical saturations the 3The italic numbers in brackets refer to the list of referencesappended to this paper. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. appropriately enough.a Woolf [2].8 • 10-~/~ depending upon the type and quantities of the aggregates. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved).5 X 10-6/~ but the range may be from about5.696 TESTS AND PROPERTIES OF CONCRETE AGGREGATES characteristics of aggregates. 4 • 10-6/~ for some samples of near cement specimens.9 • 10-6/~ [13]. report the results of heating and cooling concrete specimens over the temperature range of 4.4 to 60~ (40 to 140~ at various rates. It is for this reason that the cubical expansion of rocks and minerals is not always related directly to the linear expansion. particularly under severe exposure conditions or under rapid temperature changes.3 • 10-6/~ parallel to its C axis and --4. on the other hand. Pearson [16] attributes a concrete failure to the use of an aggregate of low-thermal coefficient subject to severe frost action.6 • 10-6/~ perpendicular to this direction.3 • 10-6/~ (12. which has a linear thermal coefficient of expansion of 25.8 X 10-~/~ (14. He reports values as high as 22.7 • 10-6/~ (--2. Subsequent laboratory investigations described in the paper and in a subsequent paper [17] included freezing-andthawing tests of concrete containing aggregates of both low and high thermal coefficients. and concretes having higher coefficients of expansion were less resistant to temperature changes than concretes with lower coefficients. Effect of Thermal Expansion There seems to be fairly general agreement that the thermal expansion of the aggregate has an effect on the durability of concrete.COOK ON THERMAL PROPERTIES 697 linear thermal coefficient of expansion of cement pastes may be somewhat higher than those reported above. It should be kept in mind that some minerals exhibit anisotropic characteristics or the property of expanding more in one direction or parallel to one crystall6graphic axis than another. Walker et al [18].5 • 10-6/~ about 16. and this possibility should be kept in mind when investigating the thermal properties of aggregates. The anomalous results obtained by Pearson and by Walker et al perhaps may be explained by the fact that the concrete in Pearson's studies was subjected to temperatures below the freezCopyright by ASTM Int'l (all rights reserved).0 • 10-6/~ (8. The most notable example is calcite. The agreement as to whether a high or a low coefficient of expansion is most desirable is not so general." It also was determined that the thermal coefficients of expansion of concrete and mortar containing different aggregates varied approximately in proportion to the thermal coefficient and quantity of aggregate in the mixture. . Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The linear thermal coefficient of expansion of common rocks ranges from about 0. The indications were that the concretes containing the aggregates of low thermal coefficient failed much more rapidly under the freezing cycle employed. He indicates that variation of thermal expansion of neat cement is related to the amount and characteristics of the gel and to an optimum (or pessimum) moisture condition producing maximum thermal expansion. No further reproductions authorized.9 • 10-6/~ (0. They found that "changes in temperature were destructive to the concrete with sudden changes in temperature being much more severe than slower ones. In one of the earliest papers on the subject. Potash feldspars are another groups of minerals exhibiting anisotropy. .21] has statistically analyzed 78 combinations of aggregate in concrete with respect to durability in freezing and thawing and differences in thermal expansion between the coarse aggregate and the mortar. Walker et al [18] found no relationship between resistance of concrete to temperature changes and differences between thermal coefficients of aggregates and mortar. private communication. One of Koenitzer's conclusions was that the elastic and thermal expansion properties for any one material vary with the conditions of test. Copyright by ASTM Int'l (all rights reserved). but the low thermal expansion apparently introduced no adverse effects. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. J. The U. whereas the results of the other workers were based on experiments above the freezing temperature. He coneludes that. state among other conclusions that. Tl~is aggregate was predominately basalt with a thermal expansion of about 7. Again Callan's work is based on studies over the freezing-and-thawing range.5 • 10-6/~ (2.2 • 10-6/~ C (4 • 10-6/~ s The Bureau of Reclamation also found [6] in the Kansas-Nebraska area that replacement of part of the aggregate with limestone. It should be noted that the addition of limestone was for the purpose of inhibiting cement-aggregate reaction. No further reproductions authorized. in attempting to correlate laboratory-accelerated freezing and thawing with natural weathering at Treat Island. while there appears to be a correlation between the resistance of concrete to freezing and thawing and differences in thermal exs L. Where the differences between these coefficients exceeds 5. whereas that used by the other workers was not. Me. and the improvement in durability probably was primarily because of the inhibition of this reaction. Smith [23] presents calculations to indicate the potential magnitude of physical incompatibility of the matrix and aggregate in concrete based on differences in thermal expansion.5 • 10-6/~ greatly increased the durability of the concrete in which it was used.7~ (9 to 80~ 29. who obtained coefficients of linear expansion of several concretes and the aggregates used in them over temperature ranges of -12. Callan [20. The above is conjecture but is somewhat supported by Koenitzer [19]. Swenson and Chaly [22] include some discussion of the effect of thermal coefficient of expansion of the aggregates on concrete durability and caution against the possible deleterious effects if large differences are observed. which had a thermal expansion averaging 4.8 to 26. Kennedy and Mather [24].0 • 10-6/~ caution should be used in the selection of the aggregate combination for highly durable concrete.S. where the difference between coefficients of expansion of coarse aggregate and mortar is large..4 to 88~ (85 to 190~ and -128 to 88~ (9 to 190~ in both moist and dry conditions.4 • 10-6/~ (3. the greatest variation being caused by freezing. the durability of the concrete may be considerably lower than would be predicted from the results of the usual acceptance tests.698 TESTS AND PROPERTIES OF CONCRETE AGGREGATES ing point. Mitchell. Bureau of Reclamation's experience with aggregate at Grand Coulee Dam Showed an extremely high resistance to freezing and thawing. This range is usually 55 ~ (100~ or more because the change in unit length per degree is extremely small. The Bureau of Reclamation reports [14] that at a temperature of 572. as yet. for example. although. this means of multiplying the change in unit length is not available for determining the linear expansion of fine aggregate. Seemingly. The method described by Willis and DeReus [26] is an example of measurements made over a considerable temperature range with the use of an optical lever. . The preceding discussion has dealt with the effects of thermal expansion of aggregates over termperature ranges that can occur under natural exposure conditions. 50 mm (2 in.85 percent. Much less is known about these effects under more extreme ranges as.) diameter cores.COOK ON THERMAL PROPERTIES 699 pansion between the coarse aggregate and the mortar. The specimens were 25. the size of a representative specimen that can be obtained from a coarse aggregate rapidly approaches a practical maximum. The majority of the test methods are based on the measurement of linear expansion over a temperature range. the proven correlation in actual field experience is not strong. Copyright by ASTM Int'l (all rights reserved). Except in the case of a crushed aggregate of sufficient uniformity to permit obtaining a larger specimen that will be representative of the sand sizes. 74.) long. Endell [25] has reported the results of experiments to determine the structural and expansion changes of concrete aggregates with temperatures up to 1200~ (2192~ These are considered to be highly specialized conditions and are not discussed further here.4-mm (1-in. and the multiplication of the change over a substantial temperature range greatly increases the facility and precision of the measurements. Likewise. there is the possibility of difficulty under unusual situations but sound engineering judgment would not dictate unusual precautions as being necessary with normal concrete and normal aggregate. the longer the specimen the greater is the accuracy and precision of the determination. The above discussion of potential imcompatibility between the matrix and the aggregate of concrete has serious implications. However. 6 Methods of Determining Thermal Expansion of Aggregates Several ingenious methods have been developed for determining the thermal coefficient of expansion of coarse aggregate. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Another device that has been used to obtain additional multiplication of the length change is the optical lever.7~ (1063 ~ quartz changes state and suddenly expands 0. No further reproductions authorized. under the conditions that may exist in burning buildings. drilled from the aggregate specimens to be tested and placed in a 6See p. but are discussed further in another paper in this publication. usually producing a disruptive effect at the suface of concrete in which it is used. the correlation is probably usually of lesser importance than other characteristics of the concrete. 1. none of the above methods are readily adaptable to the determination of the thermal coefficient of expansion of this type of material. the results obtained include the effect of the length change contributed by the cement. The purpose of this requirement is to determine if anisotropy or preferred crystal orientation exist. Because of the size and usually heterogeneous nature of fine aggregate. Detailed descriptions of the apparatus.3.) lever arm. The strain gages are then mounted so as to measure strain in each of the three directions. on a vertical scale placed 6.7 to 57. having a 25. by means of a precise level. This method employs specimens from 25. the preparation of specimens.8~ (140 + 5~ The vertical movement of the specimen as the temperature was varied was measured by reading the image reflected by the mirror of the optical lever. Of course.7~ (37 --2 3~ to 60 + 2. The usual approach has been to determine the linear expansion of mortar bars containing the fine aggregate.4-mm (1-in. the only measurements required are the weight of the water Copyright by ASTM Int'l (all rights reserved). Verbeck and Hass [30] have developed a dilatometer method for determining the thermal coefficient of expansion which is particularly adaptable for use with fine aggregate. The flask is filled with aggregate and water and the apparatus allowed to come to equilibrium at one of the controlling electrical contacts.700 TESTS AND PROPERTIES OF CONCRETE AGGREGATES controlled-temperature oil bath with a range of 2. After proper calibration.78 4.6 • 10-V~ (2.2 ~ (35 to 135~ This method requires that the piece of aggregate be sliced in three mutually perpendicular directions. two of these directions to lie in the major structural plane of the rock. if such plane can be located. and the test procedure are also given by Johnson and Parsons [8].0 X 10-7/~ Another method is the interferometer method described by Merritt [27] and modified by Saunders [28]. A third method for determining the thermal coefficient of expansion of coarse aggregate is that developed by the Corps of Engineers [21.1 m (20 ft) from the mirror. The details of the method are well described in the reference. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. .) in size coated with wax and held in fulcrum-type extensometer frames. Also the current method used by the Bureau of Reclamation and described by Mitchell [5] is avaiable.4 to 76. Measurements are made with electromagnetic strain gages with electronic indicators while the specimen is immersed in a circulating ethylene glycol solution held at the desired temperature.2 mm (1 to 3 in. The equilibrium temperature is noted and the procedure repeated at the other electrical contact.29] in which an SR-4 strain gage is bonded to a prepared piece of aggregate and readings taken over a temperature range of 1. No further reproductions authorized. It is reported that consideration of the possible errors involved in the measurements indicates that the calculated coefficients are probably accurate to 4. The method determines the cubical thermal coefficient of expansion from which the linear expansion may be calculated. The apparatus consists of a 1-1itre dilatometer flask to which is attached a capillary-bulb arrangement containing electrical contacts spaced over a calibrated volume. Its SI units are joules per kilogram kelvin 7and U. Specific heat is the amount of heat required to raise the temperature of a unit mass of material one unit of temperature. No further reproductions authorized. Thermal conductivity is also of importance in lightweight concrete for insulation purposes. customary units are square feet per hour. Copyright by ASTM Int'l (all rights reserved). Reference 31 indicates the application of these data in connection with computing concrete placement temperatures and designing cooling systems. the user should be sure of the particular units used in calculations. Since thermal conductivity usually varies directly with density. and Specific Heat Thermal conductivity. The same type of measurements and calculations would apply equally to other massive structures. It has been indicated by some [32-34] that thermal diffusivity may have an important effect on concrete durability. customary units are Btu per lb per ~ Thermal Conductivity of Lightweight Aggregates One of the more useful properties of lightweight concrete is its low thermal conductivity. . and all three normally are determined only for concrete as used in massive structures. and others. In the interpretation or comparison of thermal values. measured as the rate of heat flow through a body of unit thickness and unit area with a unit temperature difference between two surfaces. the calorie gram (IT). Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as indicated by Tyner [35]. thermal diffusivity.S. customary units as Btu/ft-h-~ Thermal diffusivity is defined as the thermal conductivity divided by the specific heat and density and is a physical property of the material which determines the time rate of change of temperature of any point within a body. Davis and Kelly [36] also state that "the presence 7Users of the SI systemshould be aware that there are several "metric" units which havebeen used alternatively. Thermal Diffusivity.COOK ON THERMAL PROPERTIES 701 placed in the flask and the temperature needed to produce an expansion equivalent to the volume between the electrical contacts.S. For the same reason. This method offers a tool for determining directly the average thermal expansion properties of the smaller aggregate sizes that have not been available heretofore. He reports that in a 1:5 mixture of Florida limerock concrete an increase of moisture from 0 to 5 percent increases the thermal conductivity by 23 percent and an increase f r o m 0 to 10 percent increases the conductivity by 46 percent. the calorie kilogram. and in other thermal calculations aimed at reducing thermal volume change and thus cracking in large dams. moisture has a tremendous effect on thermal conductivity. there are the calorie gram. aggregates of low density produce concrete of lower conductivity.S. and specific heat are largely interrelated. normally is expressed in calculations for concrete in the SI system as watts per metre kelvin or the U. Its SI units are square metres per second 7 and U. Thermal conductivity. for example. Thermal Conductivity. under conditions of continuous or intermittent exposure to moisture. but they indicate that the reduction seems to be influenced more by the reduction in the density of the concrete than by the characteristics of the aggregate. it is believed that such a combination would result in higher thermal stresses than those existing in homogeneous bodies. While the relationship of reduced thermal conductivity with reduced density holds generally for normal and lightweight aggregates. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Nothstine [33] and Weiner [34] have reported the results of their approach to the problem. the body can be thought of as being thermally homogeneous. . exposed to natural freezing and thawing accompanied by thermal shock and characterized by bond failure and internal expansion. hence. and the density of the material influence the temperature distribution and the thermal stresses during the transient period only in a certain combination known as the thermal diffusivity. if a high degree of insulation is desired. an aggregate (and concrete) of relatively low absorption should be used. Copyright by ASTM Int'l (all rights reserved). He attributes the failure to the relatively high thermal coefficient of expansion of ]the concrete. specific heat. resulting in differential volume change." Kluge et al [37] and Price and Cordon [38] also have found pronounced reductions in the thermal conductivity of concrete containing lightweight aggregate. The increases in diffusivity ranged from 20 to 59 percent for saturations of less than 5 percent. being higher than the mortar. Since a difference in diffusivities would result in different rates of diffusion of heat through the aggregate and cement.702 TESTS AND PROPERTIES OF CONCRETE AGGREGATES of a small amount of moisture in the interior of a lightweight concrete greatly increases its thermal conductivity. The authors of the references cited essentially agreed that the thermal diffusivity of the aggregates apparently has an effect on the durability of concrete but that further work is needed to determine the significance of the effect and to find a practical means for using this knowledge to improve concrete durability. responds more quickly to temperature changes. If in a mixture such as concrete the thermal diffusivities and conductivities are the same for each material. Thermal Diffusivity Investigations have indicated that the normal diffusivity of the aggregate may have an influence on the durability of the concrete in which it is used. Thomson [32] states that for a given body with specified boundary conditions the thermal stresses depend on certain physical properties of the materials. Fox and Dolch [40] in an investigation of four limestones found a large change in the thermal diffusivity with a relatively small degree of saturation. and to the diffusivity of the gravel which. investigations of barite for use in concrete for radiation shielding by Witte and Backstrom [39] indicate its thermal conductivity to be somewhat lower than normal concrete aggregate. Weiner's work was instigated by the failure of a gravel concrete. In a homogenous body such physical properties as thermal conductivity. which is responsible for surface stress. No further reproductions authorized. Depending upon the degree of accuracy desired. but in most cases they may be used with aggregates if properly modified with respect to specimen size and shape. the conductivity and diffusivity of aggregate cannot be obtained indirectly by determining these properties of the concrete and mortar. k (Btu/lb-~ and = density in kg/m 3 (lb/ft3). Methods of Test for Conductivity.specific heat in J/kg. it is customary to determine diffusivity and specific heat and calculate conductivity or to determine conductivity and specific heat and calculate diffusivity. then changing the surface temperature. Whether conductivity is determined directly and diffusivity calculated. as a matter of practical convenience. thermal diffusivity. and by refining the instrumentation. This is possible because the formula includes all three values. Copyright by ASTM Int'l (all rights reserved). Some of the test methods included in the references to this paper are based on determinations made on concrete specimens.hcp where k h c p = thermal conductivity in w/re. precise equipment. refinements can be made by grinding the specimen to a sphere. for example. or vice versa. and the density. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Thomson [32]. permits solving the equation for the unknown property. The specific heat of the aggregate contributes materially to the specific heat of the concrete [31]. and knowing the values for any two. However. and Specific Heat Methods are available for the direct determination of thermal conductivity. The formula is k =. All of the methods depend basically on obtaining time-temperature differential curves between the temperatures at the center and the surface of a specimen by starting at essentially equilibrium temperature. and specific heat. . and a capable operator. k (Btu/ft-h-~ = thermal diffusivity in mE/s (ft2/h). is largely a matter of the most convenient equipment setup available and the preference of the laboratory doing the work. Since the conductivity of a mixture is not an additive function of the constituents [41]. No further reproductions authorized. The determination is by no means routine in nature and requires careful experimentation. ---. Diffusivity. The Corps of Engineers [29].COOK ON THERMAL PROPERTIES 703 Specific Heat of Aggregates Specific heat is of considerable importance in connection with the calculations involved in the control of placement temperatures and the limiting of thermal volume change of mass concrete. and Fox and Dolch [40] describe methods for the direct determination of diffusivity of stone and concrete. and plotting the time-temperature curve until equilibrium conditions are obtained at the new surface temperature. Since the equipment is designed for use with a flat specimen either square or round. It is a calorimetric procedure wherein the net heat required to raise the temperature of a specimen of known weight a given amount is measUred. and some aspects of the problem are controversial. There appears to be no doubt that the normal properties of the aggregates. ASTM STP 83. H. specimen size and shape." Mineral Aggregates. Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and. particularly thermal expansion. References [1] Allen.. 221. . The ultimate solution must be based on the performance of aggregates of known thermal properties in concrete. American Society for Testing and Materials. American Society for Testing and Materials. instrumentation. 1948. D. C. the major difficulty is to separate the effects of the thermal properties of the aggregates from the numerous other variables existing in the concrete. O. This procedure probably could be used for coarse aggregate provided a specimen of the required size and shape could be fabricated from a large rock specimen. have an effect on the durability and other qualities of concrete. "Influence of Mineral Aggregates on the Strength and Durability of Concrete. as is normal in this field of investigation. "Needed Research. Other references may be found appended to many of the references cited here. A S T M STP 83. Investigations reported to date do not present a clearcut picture of the effects that might be expected. p. it is not adapted easily to precise determinations of the conductivity of such materials as concrete aggregates. [3] Scholer. No further reproductions authorized. The Bureau of Reclamation [43] has developed a method for the determination of the thermal conductivity of concrete by the use of a 203 by 406-ram (8 by 16-in. both to resolve existing controversy and to improve concrete further as a construction material.42]." Report of Significance of Tests of Concrete and Copyright by ASTM Int'l (all rights reserved). References 44-52 provide additional background information on the theory and mathematics of thermal tests. "Durability of Concrete. C.704 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Thermal conductivity when measured directly is determined by ASTM Test for Steady-State Thermal Transmission Properties by Means of the Guarded Hot Plate (C 177) or similar methods [35. H. Conclusions Test methods are available which when used with proper attention to procedure. The specific heat of aggregate usually is determined by a procedure known as the method of mixtures [29].. 153. [2] Woolf. p.) hollow cylindrical concrete specimen. 1948." Mineral Aggregates. There is a real need for additional research work on the subject.. For this reason it is generally considered better to determine diffusivity and calculate conductivity for such materials. and technique are entirely adequate for the determination of the thermal properties of aggregates. COOK ON THERMAL PROPERTIES 705 Concrete Aggregates, A S T M STP 22,4, American Society for Testing and Materials, 1943, p. 29. [4] Hallock, W., "Preliminary Notes on the Coefficients of Thermal Expansion of Certain Rocks," Bulletin No. 78, U.S. Geological Survey, 1891. [5] Mitchell, L. J., "Thermal Expansion Tests on Aggregates, Neat Cements and Concrete," Proceedings, American Society for Testing and Materials, Vol. 53, 1953, p. 963. [6] "A Study of Cement-Aggregate-Incompatibility in the Kansas-Nebraska Area," Report C-964, U.S. Bureau of Reclamation. [7] Griffith, J. H., "Thermal Expansion of Typical American Rocks," Bulletin No. 128. Iowa Engineering Experiment Station, 1936. [8] Johnson, W. H, and Parsons, W. H., "Thermal Expansion of Concrete Aggregate Material," Journal of Research, RP 1578, National Bureau of Standards, Vol. 32, 1944, p. 101. [9] Parsons, W. H. and Johnson, W. H., "Factors Affecting the Thermal Expansion of Concrete Aggregate Materials," Journal, American Concrete Institute, April 1944; Proceedings, Vol. 40, p. 457. [10] "Laboratory Investigations of Certain Limestone Aggregates for Concrete," Technical Memorandum No. 6-371, Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, Miss., Oct. 1953. [11] "Test Data on Concrete Aggregates in Continental United States," Technical Memorandum No. 6-370, Vols. 1-5, Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, Miss., Sept. 1953. [12] Rhoades, R. and Mielenz, R. C., "Petrography of Concrete Aggregate," Journal, American Concrete Institute, June 1946; Proceedings, Vol. 42, p. 581. [13] Rhoades, R. and Mielenz, R. C., "Petrographic and Mineralogic Characteristics of Aggregates," MineralAggregates, A S T M STP 83. American Society for Testing and Materials, 1948, p. 20. [14] Concrete Manual, U.S. Bureau of Reclamation, 7th ed., 1963, p. 60. [15] Meyers, S. L., "Thermal Coefficient of Expansion of Portland Cement," Industrial and Engineering Chemistry, Vol. 32, Aug. 1940, p. 1107. [16] Pearson, J. C., "A Concrete Failure Attributed to Aggregate of Low Thermal Coefficient," Journal, American Concrete Institute, June 1942; Proceedings, Vol. 38, p. 36-41. [17] Pearson, J. C., "Supplementary Data on the Effect of Concrete Aggregate Having a Low Thermal Coefficient of Expansion," Journal, American Concrete Institute, Sept. 1943; Proceedings, Vol. 40, p. 33. [18] Walker, S., Bloem, D. L., and Mullen, W. G., "Effects of Temperature Changes on Concrete as Influenced by Aggregates," Journal, American Concrete Institute, April 1952; Proceedings, Vol. 48, p. 661, [19] Koenitzer, L. H., "Elastic and Thermal Expansion Properties of Concrete as Affected by Similar Properties of the Aggregate," Proceedings, American Society tbr Testing and Materials, Vol. 36, Part 2, 1936, p. 393. [20] Callan, E( J., "Thermal Expansion of Aggregates and Concrete Durability," Journal, American Concrete Institute, Feb. 1952; Proceedings, Vol. 48, p. 485; discussion, Journal, American Concrete Institute, Dec. 1952; Proceedings, Vol. 48, p. 504-511. [21] Callan, E. J., "The Relation of Thermal Expansion of Aggregates to the Durability of Concrete," Bulletin No. 34, Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, Miss., Feb. 1950. [22] Swenson, E. G. and Chaly, V., "Basis for Classifying Deleterious Characteristics of Concrete Aggregate Materials," Journal, American Concrete Institute, May 1956; Proceedings. Vol. 52, p. 987. [23] Smith, G. M., "Physical Incompatibility of Matrix and Aggregate in Concrete," Journal, American Concrete Institute, March 1956; Proceedings, Vol. 52, p. 791. [24] Kennedy, T. B., and Mather, K., "Correlation Between Laboratory Accelerated Freezing and Thawing and Weathering at Treat Island, Maine," Journal, American Concrete Institute, Oct. 1953, Proceedings, Vol. 50, p. 141. [25] Endell, K., "Experiments on Concrete Aggregate Materials to Determine Structural and Linear Expansion Changes with Temperatures up to 1200~ '' Ernst and Sohn, Berlin; (revised) Tonindustrie-Zeitung, Vol. 53, 1929, p. 1472; Ceramic Abstracts, Vol. 9, 1930, p. 159; Chemical Abstracts, Vol. 24, p. 2265. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 706 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [26] Willis, T. F. and DeReus, M. E., "Thermal Volume Change and Elasticity of Aggregates and Their Effect on Concrete," Proceedings, American Society for Testing and Materials, Vol. 39, 1939, p. 919. [27] Merritt, G. E., "The Interference Method of Measuring Thermal Expansion," Journal of Research, RP 515, National Bureau of Standards, Vol. 10, 1933, p. 591. [28] Saunders, J. B., "Improved lnterferometric Procedure with Application to Expansion Measurements," Journal of Research. RP 1227, National Bureau of Standards, Vol. 23, 1939, p. 179. [29] Handbook for Concrete and Cement. Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, Miss., 1949. [30] Verbeck, G. J. and Haas, W. E., "Dilatometer Method for Determination of Thermal Coefficient of Expansion of Fine and Coarse Aggregate," Proceedings. Highway Research Board, Vol. 30, 1950, p. 187. [31] "Cement and Concrete Investigations," Boulder Canyon Project Final Reports, Part 7; "Thermal Properties of Concrete," Bulletin No. l, Bureau of Reclamation, 1940. [32] Thomson, W. T., "A Method of Measuring Thermal Diffusivity and Conductivity of Stone and Concrete," Proceedings. American Society for Testing and Materials, Vol. 40, 1940, p. 1073; discussion, p. 1081. [33] Nothstine, L. V., "Thermal Diffusivity and Modulus of Elasticity in Relation to the Durability of Concrete," Kansas State College, Manhattan, Kan., 1940. [34] Weiner, A., "A Study of the Influence of Thermal Properties of the Durability of Concrete," Journal, American Concrete Institute, May 1947; Proceedings, Vol. 43, p. 997. [35] Tyner, M., "Effect of Moisture on Thermal Conductivity of Limerock Concrete," Journal, American Concrete Institute, Sept. 1946; Proceedings, Vol. 43, p. 9. [36] Davis, R. E. and Kelly, J. W., "Lightweight Aggregates," Mineral Aggregates, A S T M STP 83, American Society for Testing and Materials, 1948, p. 160. [37] Kluge, R. W., Sparks, M. M., and Tuma, E. C., "Lightweight-Aggregate Concrete," Journal, American Concrete Institute, May 1949; Proceedings, Vol. 45, p. 625. [38] Price, W. H. and Cordon, W. A., "Tests of Lightweight-Aggregate Concrete Designed for Monolithic Construction," Journal, American Concrete Institute, April 1949; Proceedings. Vol. 45, p. 581. [39] Witte, L. P. and Backstrom, J. E., "Properties of Heavy Concrete Made with Barite Aggregates," Journal, American Concrete Institute, Sept. 1954; Proceedings. Vol. 51, p. 65. [40] Fox, R. G., Jr. and Dolch, W. L., "A Technique for the Determination of a Thermal Characteristic of Stone," Proceedings, Highway Research Board, Vol. 30, 1950, p. 180. [41] Austin, J. B., "Factors Influencing the Thermal Conductivity of Non-Metallic Materials," Thermal Insulation Materials, A S T M ST,~ 39, American Society for Testing and Materials, 1939, p. 17. [42] "Projected Testing Method for Conductivity of Materials," Bulletin No. I9, International Association of Testing and Research Laboratories for Materials and Structures, RILEM, Nov. 1954, p. 3. [43] Materials Laboratory Procedures Manual. U.S. Bureau of Reclamation, 1951. [44] Shack, Alfred, translated from the German by Hans Goldschmidt and E. P. Partridge, Industrial Heat Transfer, Wiley, New York, 1933. [45] McAdams, W. H., Heat Transmission, McGraw-Hill, New York, 1942. [46] Carslaw, H. S. and Jaeger, J. C., Conduction of Heat in Solids, Oxford University Press, London, 1947. [47] Clark, H., "The Effects of Simple Compressing and Wetting on the Thermal Conductivity of Rocks," Transactions. American Geophysical Union, Part 3, 1941, p. 543; Chemical Abstracts, Vol. 36, 1942, p. 2820. [481 Clark, H. and Birch, F., "Thermal Conductivities of Rocks and Its Dependence Upon Temperature and Composition," American Journal of Science, Vol. 238, 1940, p. 529; ChemicalAbstracts. Vol. 34, 1940, p. 7796. [49] Ingersoll, L. R., Zobel, O. J., and Ingersoll, A. C., Heat Conduction with Engineering and Geological Applications, McGraw-Hill, New York, 1948. ]50] Jakob, M., Heat Transfer. Wiley, New York, 1949, Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. COOK ON THERMAL PROPERTIES 707 [51] Niven, C. D., "Thermal Conductivities of Some Sedimentary Rocks," Canadian Journal of Research, Vol. 18, 1940, p. 132; ChemicalAbstracts, Vol. 28, 1934, p. 7455. [52] Kingery, W. D. and McQuarrie, M. C., "Concepts of Measurements'and Factors Affecting Thermal Conductivity of Ceramic Materials, Journal, American Ceramic Society, Vol. 37, No. 2, Part 2, Feb. 1954, p. 67. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:32 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. STP169B-EB/Dec. 1978 Sidney D i a m o n d 1 Chapter 40, Chemical Reactions Other than Carbonate Reactions Introduction The proper role of aggregates in concrete is usually perceived as mechanical, rather than chemical. Aggregates are selected on the basis of their favorable physical properties, and unless something unusual occurs, they are supposed to remain inert and unreactive chemically. However, a growing body of experimental evidence indicates that even in "normal" concrete a certain amount of chemical reaction must be occurring between the aggregate grains and the surrounding cement paste, if only at the interface. Direct microscopical evidence of interfacial chemical responses [1-3] 2 is complemented by reports of differences in behavior of otherwise identical concretes made with aggregates of different chemical character, for example, carbonate aggregates as compared to siliceous aggregates [4, 5]. Thus the usual assumption about the chemical inertness of aggregates under normal circumstances is not correct. This situation is perhaps less surprising when considered in terms of the chemical environment that exists within concrete. Recent research in which the pore solution has been expressed from hardened cement pastes [6, 7] and mortars [8, 9] made from even moderate alkali-content cements reveals that the environment surrounding the aggregates is one in which the pH is considerably higher than often realized. Values of pH as high as 13.5 or more are not unusual; further, the alkali concentration often approaches 1 N, and may exceed it. It is becoming apparent that aggregates in concrete are exposed over most of their service life to small amounts of highly concentrated alkali hydroxide solutions containing little dissolved calcium, even though the solutions are saturated with respect to calcium hydroxide. Such solutions constitute lProfessor of engineering materials, Purdue University, West Lafayette, Inc. 47907. 2The italic numbers in brackets refer to the list of references appended to this paper. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 7O8 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978 tobyLicense ASTM International www.astm.org DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 709 a much more aggressive environment than the conditions with which aggregate rocks have come to equilibrium during their geochemical history. Under these circumstances the idea that most aggregates in concrete undergo at least surface chemical reactions is not surprising. However, we are concerned here not with interfacial reactions, but with the effects of bulk chemical reactions in which significant portions of at least some aggregate grains are transformed chemically to reaction products, which may be deleterious and cause distress in concrete. Consideration of these matters would be facilitated, in the writer's opinion, if a clear distinction is recogized between the aggregate reactions per se and any expansion, cracking, strength loss, or other deleterious effect that may occur as a secondary consequence of such reaction. The same reaction may produce a deleterious secondary effect in some circumstances and not in others. Most known aggregate reactions in concrete are brought about in response to the alkaline character of the pore solution and are properly designated as "alkali-aggregate" reactions. Such reactions are known to occur with at least two distinct kinds of aggregates--those that are largely composed of silica (or siliceous minerals or glasses) and those that are largely composed of carbonates, particularly dolomitic carbonates. Considerations relating to the latter, the "alkali-carbonate" reactions, are specifically excluded from this paper, and are covered elsewhere in this volume. With respect to noncarbonate alkali reactions, Gillott [10] has suggested that a distinction be drawn between reactions involving the various forms of silica (opal, chalcedony, chert, flint, tridymite, cristobalite, microcrystalline, or strained quartz, etc.) for which the designation "alkali-silica" reactions would be reserved, and another class of reactions involving complex rock types having as active components various layer-lattice and other silicate minerals, such reactions being called "alkali-silicate" reactions. The rocks in question include graywackes, phyllites, siltstones, argillites, arenites, and others. The distinction is not clear-cut, because many of these rocks include fine quartz as well as the silicate minerals, and some contain dolomitic grains. The utility of setting up a separate category of "alkali-silicate" reactions is not universally accepted [11]. In addition to these reactions specifically attributed to the alkaline character of the pore solutions in concrete, other reactions can occur with specific components of certain aggregates that can produce deleterious consequences. These have been discussed in some detail by Hansen [12]. The specific reactions involved include delayed hydration of periclase (MgO), of various iron oxide constituents, and even of calcium oxide (CaO), which is an occasional constituent of slags and expanded shales [13]. These cause distress resulting from the enlargement of the individual grains. Other sources of distress include various ferrous sulfides that can oxidize and expand [14]; dehydrated clays and some zeolites that can undergo hydration and expand; and anCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 710 TESTS AND PROPERTIES OF CONCRETE AGGREGATES hydrite, formed in some expanded shale and expanded clay aggregates, which can hydrate to gypsum and cause problems both by direct expansion pressure and by subsequent formation of secondary ettringite. Discussion of these reactions also might lead to the consideration of problems associated with contamination of aggregate materials by various soluble salts, a related problem and one of much current concern in Middle Eastern countries. However, such problems are outside of the intended scope of the present paper. In fact, the available information on occurrences of nonalkaline reactions in general is so meager that these will not be discussed further, and the .remainder of this paper will be concerned exclusively with the alkali reactions. Mechanisms Responsible for Distress Associated with Alkali-Silica Attack The writer has recently reviewed certain aspects of this subject [15,16]. Most of the available information on noncarbonate alkali-aggregate attack has been gathered in terms of reaction and distress with silica-bearing aggregate. It is presumed that the slower and perhaps more complicated reactions that occur with the silicate rocks are at least generally similar to what occurs with the silica aggregates. The practical consequences of alkali-silica attack are that the affected structure or structural members: (1) are placed under expansive stresses, (2) expand, (3) crack, (4) lose strength, and (S) by virtue of cracks reaching the exterior, become exposed to further deterioration from external sources. An additional consequence of importance in some cases is that the external appearance of the affected structure is degraded by deposits of alkali-silica sols which bleed to the outside, carbonate, and leave patchy white deposits. The problems generated by alkali-aggregate attack range from the purely cosmetic to the complete failure of the structure and the necessity for its replacement. The time scale involved may be rapid (of the order of several months to only a few years), or it may be slow (of the order of 30 years or more). In the latter case the distress may be evident at a fairly early age but progress only slowly, or it may appear suddenly without warning many years after the structure has been placed in service. Alkali-silica reactions and distress have been observed in many countries, and probably exist unnoticed or unremarked in many others. While a typical map cracking pattern often occurs at the exposed surface of the concrete, other causes of distress in concrete may generate similar signs. In some occurrences it is difficult or impossible to decide whether alkali reactions are the primary cause of the problem, since distress due to shrinkage, sea water attack, freezing and thawing, or sulfate attack from other sources may also be present. Significant contributions to this difficult problem of field recognition have been made by Idorn [17] in his systematic survey and analyCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 711 sis of the causes of distress in Danish concrete structures, and by Mielenz [18] in his detailed discussion of the microscopic aspects of the problem. The broad outlines of the mechanism responsible for the distress are generally agreed on by most investigators, but a number of the details remain to be settled. The affected (silica) aggregates react in situ with the alkaline solutions in such a manner that they are converted to alkali silica glasses or relatively dry gels. If free water is available, it is absorbed by these gels, which then swell and generate the expansive forces that do the damage. Both coarse and fine aggregate grains may be affected. In some cases it is clear that only part of a grain is affected, the remainder being resistant to the reaction. Furthermore, a full gamut of different responses have been observed when distressed concrete is examined petrographically. Some affected aggregates retain their apparent rigidity and most of their original microscopic features, and merely expand. Other aggregates seem to convert completely to gelatinous products in situ--they exert enough expansive stress on their surroundings to have caused cracks in the surrounding cement paste matrix, but if dried specimens are examined the altered residual "grain" is seen to have shrunk away from the original contact with the paste, and may display shrinkage cracks. If water is easily available, the reaction products may grow progressively more hydrated and convert gradually to fluid sols and even to solutions. These may run through previously generated cracks and sometimes accumulate in void spaces. Hansen [19] and other workers believe that such isolated pockets of reaction product sol will exert further expansive stresses by drawing in additional water through the "membrane" of cement paste surrounding them, that is, by osmotic action. In any event, the fundamental action of the initial mechanically competent reaction products in attracting water and swelling is osmotic in character, the reaction product gel itself constituting in effect a "virtual" membrane. Osmotic action with self-constrained gels does not require an intact membrane to surround the gel, and is continued even after cracks develop in the concrete. The expansion and cracking that constitute the deleterious features of the attack are not invariable consequences of the occurrence of the alkali-silica reaction. Under many circumstances reaction does not lead to distress. This may come about if the concrete is sufficiently porous to provide local accommodation for the expansive effect; if it is under a sufficiently strong compressive loading so that the expansive stresses produced are overbalanced; if the available water is too limited in amount to produce the requisite swelling of the reaction product; if the character of the reaction product produced is such that the gel converts rapidly to a sol at relatively low water content and hence ceases to exert expansive stresses; perhaps if the reaction product is soon converted to a calcium alkali-silicate gel of limited swelling ability; or for various other reasons not fully understood. Furthermore, it is well established that although considerable reaction may Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 712 TESTS AND PROPERTIES OF CONCRETE AGGREGATES occur, expansion and distress may not be severe if the fraction of aggregate present that is sensitive to alkaline attack is either much smaller than or much larger than some "pessimum" proportion, or conversely, if the alkali content of the pore fluid is much less or much greater than some "pessimum" amount. A reliable and simple means of detecting reaction independently of the distress it may cause would be helpful in distinguishing cases where no alkali reaction has occurred from those where reaction has occurred but has not led to visible distress in the particular concrete. In the latter instance, changes in such things as the alkali content of the cement, the cement content of the mix, or the conditions of exposure may convert the aggregate from a seemingly innocuous one to a deleterious one. Methods of Avoiding Alkali Aggregate Reaction Problems Avoiding the deleterious consequences of alkali-aggregate reactions in concrete is not particularly complicated in principle. The entire gamut of techniques ordinarily practiced can be summarized as follows 1. Do not use reactive aggregates. 2. Do not use cement with a high content of alkalies. 3. When bringing possibly reactive aggregate and high alkali cement together for economic or other reasons, use an admixture (pozzolan) which experience or specific tests indicate will mitigate the deleterious consequences of any reaction that may develop. ASTM standardization activities have been addressed to each of these aspects. The resulting set of practices, with a few exceptions, has been successful in preventing large scale damage to concrete in the past. Whether it will continue to do so in the future is open to question. Methods of Avoiding the Use of Reactive Aggregates To avoid the use of reactive aggregate it is necessary to know which aggregates are reactive. The first line of defense, and the one technique practiced to the exclusion of all others by probably the great majority of concrete producers, is simply to use aggregate of known satisfactory service record. This usually works well if there is such aggregate available and economically competitive in the area, assuming that the currently available aggregate is really the same as the aggregate on which the service record is based (new faces are constantly opened up in any active quarry), and assuming that relevant parameters of the concrete being produced are similar to those for the concrete on which the service record is based. These parameters include the alkali content of the cement to be used, the richness of the mix (that is, the amount of cement added per unit volume), and the possibility of additional alkali being brought Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 713 in from sources external to the concrete during its exposure. It should be apparent that satisfactory service from a quarry under one set of conditions is in itself no guarantee of continued satisfactory service if either the actual rock or the conditions of use have changed materially. The second way in which the use of reactive aggregate can be avoided is simply to "inspect" the aggregate and reject any that inspection discloses as being reactive. Unfortunately, "inspection" for the presence of reactive components in aggregate cannot be carried out satisfactorily by means available to most aggregate or concrete producers. In order to have much chance of screening out deleterious aggregate "inspection" really entails one or more of the following: (a) a complete petrographic examination by a petrographer familiar with the problem, (b) a chemical test requiring analytical chemical facilities and some laboratory expertise, and (c) a "proof test" where one mixes high alkali cement with the aggregate and waits to see if expansion will take place. All these approaches have been the subjects of ASTM standardization activity. The ASTM Recommended Practice for Petrographic Examination of Aggregate for Concrete (C 295) provides specific and helpful information with reference to such important matters as sampling techniques and details of what should be determined in examination of natural sands and gravels, of drilled cores, of ledge rock, etc. No attempt is made to provide criteria for the recognition of individual minerals or rock constituents, this being assumed to be part of the professional equipment of the petrographer. Unfortunately, in applying this recommended practice to the recognition of reactive components in concrete aggregates, the petrographer has certain practical problems to overcome. Some components, for example opal or chalcedony, are clearly deleterious and can be recognized readily. Other components, for example cherts, may be deleterious in some cases and not in others. Quartz, close to being present universally, may be deleterious in microcrystalline or cryptocrystalline sizes, especially when strained, and reports are accumulating that even strained megascopic quartz may sometimes be reactive, but not always. The petrographer has a considerable problem with silicate rocks that sometimes exhibit alkali-silicate responses, again, not with any great degree of predictability. Dolar-Mantuani [20] has provided guidance in such decisions. A related difficulty has to do with proportions of possibly reactive components that might be present. One of the peculiar features of the alkaliaggregate problem is the existence of the "pessimum proportion" phenomenon. Aggregates with a proportion of reactive component much higher than the pessimum, and with the reactive species thus readily detectable by the petrographer, would in fact be less deleterious than aggregate containing a much smaller content of the same species, which might escape detection. The ultimate in this unusual state of affairs must surely be the aggregate Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 714 TESTS AND PROPERTIES OF CONCRETE AGGREGATES responsible for the cracking and distress observed in the Vale de la Mare Dam on the Island of Jersey. The reactive component (beekite, an opalchalcedony complex) is ascertained reliably to make up perhaps 0.02 percent of the total aggregate [21]. The second line of defense in screening out reactive aggregate is the chemical test, often designated the "quick chemical test" for its most desirable attribute. This test, the ASTM Test for Potential Reactivity of Aggregates (Chemical Method) (C 289), is based originally on research carried out by Mielenz et al at the Bureau of Reclamation [22]. The idea is that one distinguishes between a "deleteriously reactive" rock and an "innocuous" rock by crushing the rock to standard size (150 to 300 #m), immersing it in a 1 N sodium hydroxide solution, and "cooking" it in a sealed container at 80~ for 24 h. The resulting suspension is then filtered, and the filtrate is analyzed for two parameters: the amount of silica dissolved in it, and the reduction in the original hydroxide ion concentration due to reaction with the granular rock. Roughly speaking, deleterious rocks are those with which unit reduction in alkalinity is accompanied by at least unit production of soluble silica; conversely, innocuous rocks are considered to be those with which either little or no reduction in hydroxide concentration occurs (that is, little reaction takes place), or else rocks with which significant reduction in hydroxide ion concentration is observed, but accompanied by a less-thanequivalent production of soluble silica. As currently specified, the reduction in OH-ion concentration, Re, is plotted on a linear ordinate against the concentration of soluble silica, Sc on a logarithmic abscissa, and a standard line, modified from the original 1:1 correspondence on the basis of experience with mortar bar testing and field service reports, is used to separate "innocuous" aggregates from those not considered innocuous. Such a chart is shown in Fig. 1. In the current version of the test method, the aggregates not considered innocuous are further subdivided into those considered "potentially deleterious" and those considered "deleterious." Somewhat paradoxically, the "potentially deleterious" aggregates are those with which a large reduction of OH-concentration is accompanied by a correspondingly large (or larger) production of soluble silica, that is, a great amount of reaction of the type with which we are concerned has taken place. The aggregates considered "deleterious" on the other hand have shown only a modest lowering of the OH-ion concentration accompanying a considerable production of silica. The rationale is based generally on the idea that aggregates that show extensive reaction in the test are likely to contain greater than the pessimum proportion of reactive constituents, and so are capable of causing serious distress only if diluted with additional unreactive material [23]. In any event, the subdivision seems to be backed up by mortar-bar results attesting to its validity. The results of the quick chemical test may be anomalous if certain conCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 715 stituents that react with the alkaline solution differently from the susceptible silica or siliceous components of concern are present. The presence of magnesium or ferrous carbonates (dolomite, magnesite, or siderite) or of serpentine in the aggregate is known to result in unusually large reductions in OHconcentration and also restrictions on the amount of soluble silica that would otherwise be produced, thus perturbing the interpretation of the quick chemical test. The presence of calcite has been said to cause difficulties in some circumstances, and there may be other unknown aggregate constituents that also interfere. Thus it is often desirable to combine the quick chemical test with at least some petrographic examination to be sure that known or suspected components that may result in anomalous interpretations are absent. It should be understood that the quick chemical test involves reaction conditions (temperature and pressure) different from those at which concrete undergoes alkali-aggregate reaction in the field, and is in no sense a predictor of the extent of expansion which a given"deleterious" aggregate might produce in a given concrete. Nevertheless it appears to serve its designated purpose well, at least with respect to the alkali-silica reaction. It is appreciated particularly where quick decision is required, the results being obtainable in a few working days. Perhaps the screening method most closely related to the actual behavior of field concrete is the method whereby mortar bars consisting of the aggregate and a highly alkaline cement are prepared and, exposed to controlled temperature and humidity, and the resulting expansion, if any, is measured. Such a scheme is the basis of ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227). In this method a procedure is prescribed for preparing mortar bars using a specified gradation of fine aggregate and a reference cement of high alkali content (or alternatively, the contemplated job cement). The mortar bars are stored in special containers designed to maintain a 100 percent relative humidity atmosphere at a slightly elevated temperature (37.8~ and their lengths are measured at intervals to monitor the rate and extent of any expansion occurring. Coarse aggregate to be tested for alkali reactivity is first crushed to the specified fine aggregate gradation. Cement-aggregate combinations that show expansions greater than 0.10 percent in 6 months under this regime "usually should be considered capable of harmful reactivity." Combinations which show expansions of 0.05 percent at 3 months are considered "potentially capable of harmful reactivity." A somewhat different set of exposure conditions is prescribed for mortar bars in an alternative mortar-bar test, ASTM Test for Potential Volume Change of Cement-Aggregate Combinations (C 342). This test is said to have particular applicability to certain cement aggregate combinations common in Oklahoma, Kansas, Nebraska, and Iowa. A variant form of reaction has been reported from this region, which is characterized by a hot, dry environCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 716 TESTS AND PROPERTIES OF CONCRETE AGGREGATES 700 9 o 600 _ --. Aggregates causing m o r t a r expane~on more than 0.1 percent in o year * h e n used with a cement c o n t a i n i n g 1.38 per cent a l k a l i e s , A g g r e g a t e s causing rttortar exDan$1on tess t h a n 0.1 p e r c e n t in o year | under some condifions, Aggregates for which mortar expansion data are not a v a i l a b l e but which ate indicoter to be d e l e t e r l o u ~ by petrographic examination. - Boundary which are indicated to be innocuous by pe, r o g r o p h i c e x o m i n a t l o n llne b e t w e e n innocuous and d e l e t e r i o u s a~gregotes. 500 "•400 ? .g. ~ 300 C g o a~ i ~1oo o a.5 5.o Quantity FIG. 7.5 ~o Sc-Dissolved z5 5o Silica 75~oo (millimoles z5o soo rso ,ooo 25oo per l i t e r ) 1--Decision chart for interpretation of the results of A S T M Test C 289, ment much of the year, and where much of the available aggregate is in the form of relatively fine gravel, necessitating concrete mix designs of higher than usual cement content. The reaction under these circumstances appears to be characteristically slow and unspectacular in early years, but to result eventually in severe map cracking, expansion, and degradation. ASTM Test C 342 (based originally on the work of Conrow [24]) prescribes curing the mortar bars in water at room temperature (23~ up to 28 days, followed by a week of curing at an elevated temperature (55~ with the humidity Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 717 maintained at 100 percent relative humidity, then a week of drying in a drying oven at the same temperature, and finally a return to the original 23 ~ water-curing conditions. Subsequently the expansion is monitored at periodic intervals. Criteria are provided in the Appendix to ASTM Specification for Concrete Aggregates (C 33), indicating that aggregate-cement combinations producing expansion equaling or exceeding 0.200 percent at 1 year may be considered unsatisfactory. The ASTM mortar-bar tests described above have a long history of use in the United States, and most concrete technologists feel that they are successful and reliable as indicators of deleteriously expansive aggregates. However, other researchers, particularly many technologists from outside the United States, are concerned that mortar bars may lack a sufficiently close correspondence to field concrete to be entirely reliable, and have developed concrete prism tests for what are considered more realistic assays of possibly deleterious aggregates. Current German practice uses concrete prisms (cubes) 30 cm on a side, and Dahms [25] reported that not only are the cube expansions different from those of mortar bars, but the shape and dimensions of the concrete prisms themselves significantly affect the results, "for example, no expansions or only very small ones could be found in (concrete) beams, yet the 30-cm sized cubes showed quite substantial cracks and precipitations of alkali silicate gel." Difficulties with ASTM Test C 227 mortar bars and a preference for concrete prisms have also been expressed by Canadian researchers [26]; this is true especially when considering rocks susceptible to the less-wellunderstood "alkali-silicate" reactions. Further, these researchers suggest that the expansion "schedule" specified in ASTM Test C 227 (0.1 percent at 6 months or 0.05 percent at 3 months) is not appropriate for the alkalisilicate reacting rocks, which take longer to expand. Limitation on the Alkali Content o f the Cement The second general way of staying out of trouble with alkali-silica reactions is to avoid the use of high-alkali cement, thus limiting the amount of alkali that would be expected to be brought into the pore solution of the resulting concrete. The ASTM Specification for Portland Cement (C 150) suggests that a limit of 0.60 percent on the total alkali content (percent Na20 plus 0.658 percent K20) may be specified when the cement is to be used in concrete with aggregates that may be deleteriously reactive. The value of 0.60 percent was arrived at empirically by correlation with field indications of distress, and seems to be a reasonable figure. However, the specification does not take into account the proportion of cement to be used in a particular concrete. Clearly a 446 kg/m 3 (750 lb/yd 3) mix design will result in incorporating more than half again as much alkali in a unit volume of concrete as will a 307 k g / m 3 (420 lb/yd 3) Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 718 TESTS AND PROPERTIES OF CONCRETE AGGREGATES mix design, and will have a proportionately higher potential for chemical attack. Further, limiting the alkali content of the cement does not guard against the potential introduction of additional alkalies from other sources--sea water, deicing salts, etc. Finally, the value of the alkali content limitation specified ceases when it becomes impossible or uneconomical for the cement producer to provide cement that meets the limit. With the growth of energy constraints, dry process kilns, often with suspension preheaters, are replacing older designs, and these energy-efficient kilns provide only limited ability to reduce excess alkali in the raw mix by venting. This development, combined with the increasing tendency to recycle alkali-rich waste cement dust to the raw mix has resulted in a progressive increase in alkali contents of most cements in recent years. It seems likely that only those few suppliers blessed with low alkali raw materials will be able to offer cement that complies with the 0.60 percent alkali limitation for the indefinite future. Use of Pozzolanic or Other Admixtures to Mitigate the Effects of AlkaliAggregate Reactions Experience has indicated that introduction of significant proportions of certain pozzolanic materials, as a substitute reactant that combines with the alkali solution more rapidly than the deleterious aggregate and which produces reaction products without deleterious consequences, can prevent distress in concrete. Deciding what constitutes an appropriate pozzolan for this purpose is the function of a special mortar-bar testing procedure described in ASTM Test for the Effectiveness of Mineral Admixtures in Preventing Excess Expansion of Concrete Due to Alkali Aggregate Reaction (C 441). The procedure is based on the mortar-bar test of ASTM Test C 227, except that the aggregate used is a specified gradation of highly reactive borosilicate glass rather than an aggregate to be tested for its potential reactivity. The glass is combined in a mortar with a high alkali reference cement (alkali content of at least 1.0 percent). Control mortar bars are prepared without admixture; test mortar bars prepared at the same time contain 25 percent less cement than the control mix, and incorporate an amount of the test pozzolan of the same volume as that of the cement removed. Control and test bars are maintained at 37.8~ and 100 percent relative humidity, and are measured at 14 days. The beneficial effect of the admixture (if any) is displayed in terms of the reduction in expansion of the test mortar bars over that of the control, reduction of 75 percent or more being deemed satisfactory. In a variant of the test method, Section 4.3 of ASTM Test C 227 prescribes that the contemplated job cement be used instead of a reference high-alkali cement, and that the contemplated pozzolan be used in the amount proposed for use on the job. For this "job mix" mortar, a limitation in expansion of 0.02 percent over the 14 day period is specified. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE 719 ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618) lists the 75 percent reduction in expansion of the test mortar as compared with the control mortar, and the 0.02 percent maximum expansion of the "job mix" mortar as optional requirements for pozzolans, to be applied at the purchaser's request. ASTM Specification C 618 indicates that the test for mortar-bar expansion of the "job mix" mortar is to be preferred over that for reduction of expansion with a reference cement, if the portland cement to be used in the work is known and available. The use of other than pozzolanic admixtures to mitigate the effects of alkali-aggregate reactions is not addressed by an ASTM specification, but evidence in the literature suggests that small quantities of lithium salts added as admixtures reduce expansions of reactive combinations significantly [27]. The possible use of barium salts also has been suggested, but the latter will precipitate a highly insoluble barium sulfate instantly on addition to suspensions of ordinary gypsum-containing portland cement. The experimental work in which the beneficial effects of barium salts were described [28] was carried out with gypsum-free ground clinker specially prepared for the purpose. Another significant possibility for the mitigation of the deleterious effects of alkali reaction is the possible use of pozzolanic cement or of blast-furnace slag cement. Present specifications for such blended hydraulic cements (such as ASTM Specification for Hydraulic Cements (C 595)) make only passing reference to alkali reactions, but considerable European experience attests to the potential value of at least some such blended cement products in controlling the deleterious consequences of alkali reactivity. Concluding Remarks All sources of available information about trends in the cement industry suggest that the drift to higher alkali contents in most portland cements will continue in the foreseeable future. This comes at a time when high quality aggregates with proven service records are becoming progressively more difficult to obtain in many areas due to various factors, but particularly to urban restrictions on continued operation of aggregate sources. While the trend does not seem to have caused a noteworthy upsurge in alkali-related problems in the recent past, scattered reports of such problems continue. It is probably too soon for occurrences of distress associated with the recent upsurge in alkali contents of portland cements to have manifested themselves, since a lag time of a number of years before such distress is noted would be expected. Nevertheless, it would not be surprising if a number of recently completed structures eventually show such distress, especially where adherence to the optional limitation of 0.6 percent total alkali content is not traditionally practiced. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 720 TESTS AND PROPERTIES OF CONCRETE AGGREGATES T h e r e has b e e n an i n c r e a s e of r e s e a r c h in d e f i n i n g t h e d e t a i l s o f a l k a l i attack under various circumstances, and the summary of one and the c o m p l e t e p u b l i s h e d p r o c e e d i n g s o f two o t h e r r e c e n t i n t e r n a t i o n a l conf e r e n c e s on t h e q u e s t i o n are now a v a i l a b l e [29,30]. It is h o p e d t h a t cont i n u e d r e s e a r c h on t h e s u b j e c t will b e f r u i t f u l in d e v e l o p i n g e n h a n c e d m e t h o d s of r e c o g n i z i n g a n d c o p i n g with t h e p r o b l e m . Acknowledgments T h e w r i t e r is p l e a s e d to a c k n o w l e d g e his d e b t to G u n n a r I d o r n , K a t h a r i n e a n d B r y a n t M a t h e r , a n d Bill D o l c h - - f r i e n d s a n d c o l l e a g u e s w h o h a v e prov i d e d i n f o r m a t i o n , c o n v e r s a t i o n , a n d g u i d a n c e with r e s p e c t to alkalia g g r e g a t e p r o b l e m s o v e r a n u m b e r of years. References [1] Barnes, B. D., "Morphology of the Paste-Aggregate Interface," Ph.D. thesis, School of Civil Engineering, Purdue University, West Lafayette, Ind., Jan. 1976. [2] Farran, J. et al, "Etude de l'Aureole de Transition Existant entre les Granulats d'un Mortier et la Masse de la pate de Ciment Hydrate," Liaisons de Contact dans les Materiaux Composites Utilises en Genie Civil, RILEM International Colloquium, Vol. 1, Toulouse, France, 1972, pp. 60-76. [3] Javelas, R., Maso, J. C., and Ollivier, J. P., Cement and Concrete Research, Vol. 4, No. 2, March 1974, pp. 167-175. [4] Alexander, K. M., Wardlaw, J., and Gilbert, D. J., "Aggregate Cement Bond, Cement Paste Strength, and the Strength of Concrete," International Conference on the Structure of Concrete, London, 1965, pp. 59-81. [5] Scholer, C. F., RecordNo. 210, Highway Research Board, 1967, pp. 108-117. [6] Longuet, P., Burglen, L,, and Zelwer, A., Revue des Materiaux, No. 676, 1973, pp. 35-41. 17] Abbassi, Gh., Revue des Materiaux. No. 691, Nov.-Dec. 1974, pp. 315-322. [8] Barneyback, R. S. and Diamond, S., "Preliminary Studies on Pore Solutions Expressed from Alkali Silica Reactive Mortars," Annual Meeting, American Ceramic Society, May 1976. Abstract, Bulletin, American Ceramic Society, Vol. 55, No. 4, April 1976, p. 407. [9] Diamond, S. and Barneyback, R. S., Proceedings, 1976 Alkali Symposium, The Effect of Alkalies on the Properties of Concrete, Cement and Concrete Association, London, 1977, in press. [10] Gillott, J. E., "Practical Implications of the Mechanisms of Alkali-Aggregate Reactions," Symposium on Alkali-Aggregate Reaction, Preventative Measures, Reykjavik, Iceland, Aug. 1975, pp. 213-230. [11] Mather, B., Cement and Concrete Research, Vol. 6, No. 6, Nov. 1976, pp. 813-814. [12] Hansen, W. C., "Chemical Reactions," Significance of Tests and Properties of Concrete and Concrete-Making Materials, A S T M STP 169 A. American Society for Testing and Materials, 1966, pp. 487-496. [13] Hansen, W. C., "Anhydrous Minerals and Organic Materials as Sources of Distress in Concrete," Record No. 43, Highway Research Board, 1964, pp. 1-7. [14] Mielenz, R. C., "Reactions of Aggregates Involving Solubility Oxidation, Sulfates, or Sulfides," Record No. 43, Highway Research Board, 1964, pp. 8-18. [15] Diamond, S., Cement and Concrete Research, Vol. 5, No. 4, July 1975, pp. 329-346. [16] Diamond, S., Cement and Concrete Research, Vol. 6, No. 4, July 1976, pp. 549-560. [17] Idorn, G. M., "Durability of Concrete Structures in Denmark," Technical University of Denmark, Copenhagen, Jan. 1967. [18] Mielenz, R. C., "Cracking of Concrete Related to the Alkali-Silica Reaction," DisCopyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DIAMOND ON CHEMICAL REACTIONS OTHER THAN CARBONATE [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] 721 eussion presented at the U.S.-Japan Joint Seminar on Research on Basic Properties of Various Concretes, Tokyo, Jan. 1968. Hansen, W. C., Cement and Concrete Research, Vol. 6, No. 2, March 1976, pp. 323-325. Dolar-Mantuani, L., "Petrographic Investigation of Alkali-Reactive Silicate Rocks in Several Structures," Proceedings, 1976 Alkali Symposium, London, A. B. Poole, ed., Cement and Concrete Association, 1977, in press. Midgley, H. G., "The Identification of Opal and Chalcedony in Rocks, and Methods of Estimating the Quantity Present," Proceedings, 1976 Alkali Symposium, London, A. B. Poole, Ed., Cement and Concrete Association, 1977, in press. Mielenz, R. C., Greene, K. T., and Benton, E. J., Journal, American Concrete Institute, Vol. 19, No. 3, Nov. 1947, pp. 193-224. Mielenz, R. C. and Witte, L. P., Proceedings, American Society for Testing and Materials, Vol. 48, 1948, pp. 1071-1103. Conrow, A. D., Proceedings, American Society for Testing and Materials, Vol. 52, 1952, pp. t205-1227. Dahms, J., "Influences on the Alkali Aggregate Reaction Under Field Conditions," Proceedings. 1976 Alkali Symposium, London, A. B. Poole, Ed., Cement and Concrete Association, 1977, in press. Grattan-Bellew, P. and Litvan, G. G., "Testing Canadian Aggregates for Alkali Expansivity," Proceedings. 1976 Alkali Symposium, London, A. B. Poole, Ed., Cement and Concrete Association, 1977, in press. McCoy, W. J. and Caldwell, A. G., Journal, American Concrete Institute, Proceedings. Vol. 47, 1951, pp. 693-706. Hansen, W. C., Journal, American Concrete Institute; Proceedings, Vol. 31, 1960, pp. 881-883. Asgeirrsson, H., Ed., Symposium on Alkali Aggregate Reaction--Preventative Measures, Icelandic Building Research Institute, Reykjavik, Iceland, 1975. Poole, A. B., Ed., Proceedings. 1976 Alkali Symposium, London, Cement and Concrete Association, 1977, in press. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:45:41 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. N. innocuous. Charlottesville. Virginia Highway Research Council. No further reproductions authorized. 2The italic numbers in brackets refer to the list of references appended to this paper. This environment is always at least as alkaline as a saturated solution of calcium hydroxide and may for certain sources of cement exceed this alkalinity [1].OI'g Copyright9 1978tobyLicense ASTM International . probable cause. Www.astIII. W a l k e r ~ Chapter 41--Chemical Reactions of Carbonate Aggregates in Cement Paste Introduction It has long been recognized that no aggregate is completely inert in the environment of portland cement paste. Carbonate aggregate reactions may be beneficial. The most common beneficial reactions are those of enhancement of the bond of the aggregate to the paste by the epitactic overgrowth of the calcium hydroxide of the cement paste on the calcium carbonate crystals of limestone and dolostone aggregates [2. Va. 1978 H. Copyright by ASTM Int'l (all rights reserved). 22903. Dedolomitization can be an innocuous reaction but in specific kinds of carbonate rocks it can result in expansion of the aggregate particles and destructive expansion of the concrete in which it is used. Sun Apr 6 21:47:47 EDT 2014 722 Downloaded/printed by Universidade do Gois pursuant Agreement. Usually these rims will show a different solubility in acid than does the center of the aggregate particle.STP169B-EB/Dec. It is now considered that such rims are generally innocuous and occasionally may indicate a reaction which strengthens the bond. The most deleterious of the chemical reactions occurring between carbonate aggregates and cement paste is the expansive dedolomitization reaction. The production of rims of discoloration within the aggregate particle has been associated with concretes showing distress as well as with good durable concretes. IMaterials research petrographer. 2 We only need to consider those reactions which take place at a rate sufficient to affect the concrete during its normal life span. The expansive dedolomitization reaction. or deleterious. and suggested means of control will be the major subject of this p a p e r .3]. its occurrence. as Axon and Lind [9] have stated. or both. is first manifested in the field by many of the same evidences of expansion that have been found to be associated with the expansive alkali-silica aggregate reactions [10. and the presence of the distinctive "pattern" or " m a p " cracking on surfaces. Consequently any factor contributing to concrete deterioration cannot be ignored. but rather that their deleterious nature is due to excess porosity. lack of freeze thaw durability. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as it is frequently called.11].13]. However. are not basically chemically reactive. Copyright by ASTM Int'l (all rights reserved). Examination of the expanded portions of the concrete yields little positive evidence of the reaction." Expansive Dedolomitization Reaction Evidences The expansive dedolomitizafion reaction or expansive alkali-carbonate reaction. No further reproductions authorized. or they may be visible only when the surface is moistened with water. The cracks may be severe and may extend more than two thirds of the way through the slab. lack of cohesiveness on wetting and drying. The concrete in the surface areas between the cracks generally retains its integrity and apparently is unaffected by the reaction. Expansive carbonate reactions produced in laboratory fabricated mortar bars and concrete bars have shown instances of peripheral cracking and other cracking within the aggregate particles [12. These evidences include the closing of joints and the squeezing out of joint filler materials. The cracking of the paste is not distinctive but is common and does generally connect aggregate particles to each other or to the surface. . or the presence of expanding clay minerals. and pavement blow-ups [6-8]. "Factors both physical and chemical which cause deterioration of concrete tend to work concurrently and not independently. The typical cracks occur in the surface of the concrete that has not been as affected by the expansion as has the portion of the concrete in contact with the soil or other moisture source. There is no clear cut evidence such as the silica gel in the alkali-silica reaction. distress due to weathered materials [5]. The pattern cracking is pseudo-hexagonal and to the geologist is reminiscent of the sort of cracking usually associated with mud cracks and columnar jointing. lack of physical stability. the buckling of adjacent members. the crushing of weaker concretes. Occasionally certain surface cracks may be traced to a typical carbonate coarse aggregate particle. with certain materials greatly increase the rate of deterioration of concrete by frost action. For example a slight amount of alkali carbonate or alkali silica reaction may.WALKER ON ALKALI-CARBONATE REACTIONS 723 It is generally considered that kinds of carbonate aggregates which have been associated with D-cracking [4]. which are shrinkage phenomena. There are no characteristic reaction products discernible by visual inspections or microscopical examination. with finely disseminated clay material.724 TESTS AND PROPERTIES OF CONCRETE AGGREGATES The expansion of the aggregate particles in cement paste can be illustrated by the results obtained by treatment of samples of carbonate rocks in solutions of sodium hydroxide over a period of 1 year as shown in Fig. . .2 ~" / 0 '. most importantly. good physical properties [14]. . conchoidal fracture and frequently for dark color.. . . and of Middle Ordivician age [10. Hand specimens are noted for fine grain. Ozol. The microstructure of the alkali-expansive carbonate rocks is made up of small rhombs of dolomite. . and Sherwood's study of test methods. . 2.0 ~ . . ' 9 J ~ 0.0 ~ ~ 12-9 --UNRESTRAINED . . . . This texture is illustrated in Fig.15].4 12~9 0. Characteristics of the Expansive Carbonates The expansive alkali-carbonate rocks reaction was reported first by Swenson in 1957 [10]. generally under 25 #m in diameter set in matrixes of calcite micrite. . . . The deleterious nature of this aggregate could not be detected by any of the ASTM tests or procedures available at that time. . 1 from Newlon. The matrixes of these rocks generally appear dark and murky in standard thickness (30-#m) petrographic sections..~ . with high alkali cements. The acid insoluble residue and carbonate analyses of this limestone are shown in Table 1. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ~ ~ . Ont. Copyright by ASTM Int'l (all rights reserved). .f~. He discovered that the severe distress found in the concrete of the Kingston. in the presence of moisture.9 16 24 32 40 48 WEEKS FIG. RESTRAINED / O~ / . 1--Length changeof typical rock prisms [12]. and. with low porosity. at high temperatures. No further reproductions authorized. . .NOTE C H A N G E " ~---~ ~ IN S C A L E ~ 1 / ~. Testing in specimens of concrete (as detailed below) showed that the expansion was greatest with large size aggregate. . . 6. grain size 2 to 6/~m (mostly aphanocrystalline). area could be attributed to a specific argillaceous dolomitic limestone. 8 ~i 15. . 3.18] Gull River Ontario Lake Expanders [15] Virginia Late Expander [12] FIG. Acid Insoluble Residue.16] Virginia Early Expanders [17. Hadley [16] reported on studies of similar aggregates from Iowa. Newlon and Sherwood [17. No further reproductions authorized. at least small areas of the texture described above [10. Swenson and Gillott [14] theorized that the rare occurrence of carbonate rocks with nearly equal proportions of calcite and dolomite might indicate a "constitutional instability" which made it possible for these rocks to react with the Copyright by ASTM Int'l (all rights reserved). The typical compositions of these aggregates are shown in Table 1. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Illinois. and Indiana. % Dolomite % of Total Carbonate S to 15 10 to 20 about 50 40 to 60 13 to 29 21 to 49 33 46 to 73 75 to 87 over 90 Kingston Early Expanders [10.14. whenever they occur. It was noted that the particular composition of the carbonate rock that was found to be most reactive was uncommon in nature. Illinois & Indiana Early Expanders [20.16-18]. It can be shown that the majority of the expansive alkali-reactive carbonate rocks.15] Iowa.18] found expansive alkalireactive rocks in Virginia.14. have in common. and shown in Fig.WALKER ON ALKALI-CARBONATE REACTIONS 725 Table l--Composition of the alkali-reactive expansive carbonate rocks. that is rhombs of dolomite "floating" in a silty and clayey mi-' crite sized calcite matrix and that those areas have a composition that includes high amounts of acid-insoluble residue and approximately equal amounts of calcite and dolomite. 2--Typical texture of alkali-reactive carbonate rock [12]. speaking of the conditions of carbonate deposition states. Reactions of the Alkali-Expansive Carbonate Rocks Hadley [16. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.20] proposed that the following reaction had taken place in the expanding carbonate rocks exposed to alkali solutions CaMg(CO3)2 + 2 M O H = Mg(OH)2 + CaCO3 + M2CO3 in which M represents potassium. 3 . . or lithium. Steidtmann [19].. " Thus. Most carbonate rocks perform very well in portland cement concrete. No further reproductions authorized. " . . we can assume that this intermediate composition cannot be expected to occur in uniform lithologies of wide extent but will occur only within isolated areas of a time zone or facies.A vein of reactive texture surrounded by innocuous texture. the margin between dolomite and limestone bearing conditions is a narrow one and hence near the critical stage slight changes in chemical conditions may completely change the nature of d e p o s i t i o n . cement alkalies. There is only a very limited type of narrow distribution that will react expansively with the alkalies which may be found in cements. . the Copyright by ASTM Int'l (all rights reserved). .726 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. The rock is alkalireactive [12]. In concrete. . sodium. 22]. brucite. No further reproductions authorized. detected by Hadley [16]. It was found that the rate of dedolomitization was highest when the calcite to dolomite ratio was nearly equal to one [11. The hydrotalcite-sjogrenite minerals possibly may help promote the water absorption and expansion.WALKER ON ALKALI-CARBONATE REACTIONS 727 alkali carbonate produced by this reaction will react with hydration products of portland cement. Later work by Walker [13] and Buck [28] indicated the formation of layer minerals of the hydrotalcite or sjogrenite groups. Buck and Mather [25] found that dedolomitization occurred only with the expansive rocks and never with the nonexpansive ones. for example Na2CO3 "1. in the concrete. Seligman [21] has pointed out that the reaction producing the carbo-aluminate end-product.Ca(OH)2 = 2NaOH + CaCO3 This last reaction indicates that the sodium hydroxide could have been regenerated until all the dolomite had reacted or all the alkali had been used up in secondary reactions.17. or in Hadley's dolomite crystal [16]. namely alkali-carbonates. Hadley found that a large dolomite rhomb mounted in a strain gage and immersed in 3 M NaOH expanded about 0. Feldman and Sereda [26] postulated that an expanding water absorbing substance formed in conjunction with the dedolomitization reaction. are well documented by X-ray diffraction analyses of reacted limestones. Hansen [22] has theorized that the dolomite is more expansive with sodium hydroxide than with the other common alkalies because the sodium ions penetrating the dolomite lattice form sodium carbonate hydrated with ten molecules of water before the crystal structure disintegrates into solution.16. . However. these mineral groups are related closely to and often occur with brucite. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In nature.15 percent in 100 days. All limestones whose composition approached this ratio reacted with alkalies when the rock was finely ground. lithium carbonate requires still less space because it does not form a hydrate. Gillott [27] found evidence of water uptake by dedolomitized rock. would also regenerate the alkalies and thus further the dedolomitization. The reactions and the end products. or both. and calcite. the reactions are a volume by volume replacement and cannot explain the observed final expansion found in the limestones. The dolomitic rocks which exhibited stable size and those that shrunk also dedolomitized [24]. However. Lemish and Moore showed that the same dedolomitization reactions occurred in all dolomitic rocks when in the presence of alkalies. Copyright by ASTM Int'l (all rights reserved). potassium carbonate requires less space because it hydrates with only two water molecules. only those rocks with the typical fine-grained texture including dolomite rhombs in an argillaceous calcite micrite reacted to the alkali when in an unground state [23]. Theorizing that the dolomite crystals were formed under conditions of great pressure. Other studies [13] have shown that. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. It is thought by many that the alteration of the dolomite Copyright by ASTM Int'l (all rights reserved). Such zones have not been observed in the dolomite rhombs of the expansive rocks of Virginia. Once the dolomite is removed or disrupted by dedolomitization. the presence of illite. The influence of texture was confirmed by the fact that expansions were greater with the more coarsely crushed samples. whereas the brucite can occur within the reacted rocks.29]. It was determined that expansions of more than 7 percent were obtained in some instances. No further reproductions authorized. and that the rock material absorbed water while expanding. Sherwood and Newlon [23] showed that powdered samples of the reactive rocks react with strong concentrations of NaOH and form brucite (MgOH) and gaylussite (CaNa2(CO3)2 9 5H20). the authors thought that the included clay would be free of water and in an active state.728 TESTS AND PROPERTIES OF CONCRETE AGGREGATES The clay minerals. It has been postulated that the clays weaken the strueture of the rock to the point that the expansion of the included dolomite crystals is not restrained and becomes expressed externally to the extent that even the surrounding concrete is expanded [11. They postulated that the cloudy material is a clay. the clay absorbs water and causes expansion. and the results observed with the various alkalies. His data suggest that only certain limited combinations of textural properties and dolomite versus calcite content can produce the requirements for detrimentally expansive carbonate rocks. Swenson and Gillott [27.31] investigated the expansion of powdered samples of the reactive rocks in alkaline solutions by means of special compression cells and dilatometers. did not have sufficient internal textural rigidity to expand under a restraining force of about the same magnitude as would be found in concrete paste. Despite detailed work performed by numerous investigators the exact mechanism causing the expansion of these dolomitic rocks when exposed to highly alkaline environment is still to be determined. are always found in alkaliexpansive limestones. the gaylussite can be precipitated from the solutions in which prisms of reactive carbonate have been stored for expansion testing. Swenson and Gillott noted that the dolomite crystals in the rocks causing expansion at Kingston are zoned by the inclusion of growth rings containing a cloudy material [31. that rate and expansion varied with the particle size. known to expand in alkali solutions. most particularly illite.32]. Brucite and gaylussite have been found at the surface of rock samples which have reacted with NaOH in certain studies [24]. Any proposed mechanism must account for the roles of the required texture. the calcitedolomite ratio. This theory must be considered in the light of Hilton's work [30] in which it was shown that certain porous argillaceous limestones. . This process may cause a portion of the expansion in those rocks in which the cloudy zones appear. 015 percent at 84 days.34].03 percent at 1 year.34] was closer to the method of the Canadian standard CSA A 23. commonly used to detect the alkali-silica reaction. He found that aggregate which produced definite deterioration in the field produced only slight expansions in the mortar bars.75 mm (No. The data for the later ages are preferred.0 mm (3A in. et al [35]. The Canadian test uses aggregate specifically proportioned into three sizes between 25.24.) in size can be used in the same grading as will be used in the final mixture. Test Methods Older Methods--ASTM Test for Potential Reactivity of Aggregates (Chemical Method) (C 289) is not appropriate for reactive carbonate rocks because it was specifically designed to detect the amount of silica reacted with the cement alkalies. that is. The method will be titled "Test for Length Change of Concrete Due to Alkali Carbonate Rock Reaction.02 on Chemical Reactions of Portland Cement Concrete. and 0. and Newlon et al [12]. Aggregates less than 19.) bars of concrete. The alkali content is augmented by the addition of reagent grade sodium Copyright by ASTM Int'l (all rights reserved).0 mm (1 in.2. The present state of the draft indicates that the specimens shall be classified as potentially reactive if the expansion equals or exceeds 0. using various cements and storing the specimens in a very moist environment. The method accelerates the reaction by the type of storage conditions only. 75 by 75 by 280-mm (3 by 3 by 11-in.) and 4. The method is in draft form under the jurisdiction of ASTM Subcommittee C09." The advantage of this proposed method is that it can use the ingredients in the proportions proposed for structural and for paving concrete to be used in constructions. No further reproductions authorized. The method used by Smith [33. 0. was too slow and interpreted improperly to detect the deleteriously expansive alkali-carbonate reactive rocks. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Determination of Length Change of Concretes--The practice of using the length change bars of concrete as a method of test for alkali-carbonate reactive aggregate was begun by Swenson [10] and later reported by Smith [33. Ryell. it produced insufficient expansion to be classed as reactive by the criteria in use for alkali-silica reactive aggregates. .025 percent at 180 days. 4 sieve) and a standard cement. Basically the method tests aggregate in small.02. Swenson [IO] found that the m o r t a r bar test method (ASTM Test for Potential Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227)).WALKER ON ALKALI-CARBONATE REACTIONS 729 crystals by the dedolomitization reaction must in carbonate rocks of the proper texture and composition allow the alkalies greater access to the interstitial illite as well as to any other included clays. Test for Alkali Aggregate Reaction. The bars are measured for length change at regular intervals and the percentage change is calculated. however. The test method states: "Appreciable expansion should indicate the need for further testing. quantitative predictions of concrete expansion in service solely from results of this test method are not yet possible (ASTM Test C 586). . Usually expansive tendencies are evident after 28 days of immersion in alkali.) cross section. it is recommended that the rock cylinder method be used only as a screening method and that quantitative data be obtained from tests in concrete such as the concrete bar method outlined above or ASTM Test for Copyright by ASTM Int'l (all rights reserved). Measurements of the length of each specimen of aggregate are made with a special length comparator at intervals of 1 week for the first month and every 4 weeks thereafter. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . The use of high alkali cement had the intention to speed up the reaction but the addition of sodium hydroxide solution may change the reaction because of the greater availability of alkalies from the hydroxide than would occur in field concrete. From this point of view. Smith [34] indicated that beams which had expanded more than 0. Determination of Length Change of Aggregate Rock--Hadley [20] developed a test for the expansion of the aggregate itself which has become ASTM Test for Potential Alkali Reactivity of Carbonate Rocks for Concrete Aggregates (Rock Cylinder Method) (C 586)." Thus. the preparation of a large number of concrete mixtures. This test is commented on by Dolar-Mantuani [36] as follows: " T h e great advantage of the test is that the aggregate is tested in the coarse aggregate size embedded in concrete paste. it appears that expansions in excess of 0. .730 TESTS AND PROPERTIES OF CONCRETE AGGREGATES hydroxide so that the alkali content of the mixture shall be 1 percent by weight of the cement with the Na20 equivalent calculated as Na20 + 0. exceptions to this have been noted. In the light of current knowledge." Despite the possibility that the chemical reaction may be accelerated when the aggregate is of small size and has more surface area.1 percent are indicative of chemical reactions and should warrant additional testing preferably in concrete. the expansion has bee'n shown to be accentuated by larger size aggregate by both Swenson an(: Gillott [14] and Newlon et al [12].658 • K20. . Thus the concrete bar method of de~ecting expansive alkali-carbonate aggregate reactivity avoids the possible diminution of the expansive effect of crushing the aggregate to sand size as would be required for the testing of the aggregate in mortar bars of 25 by 25 mm (1 by 1 in. this method measures the change in length of small (approximately 35 mm long) right circular cylinders (originally four-sided prisms) of aggregate rock as they are altered by soaking in individual containers of 1 N sodium hydroxide solution. and the long storage required for the bulky specimens may make this test method prohibitively expensive for use in any survey of a large number of carbonate aggregate quarries. the added alkali is a possible disadvantage. No further reproductions authorized.02 percent at 84 days were considered to contain deleteriously expansive reactive aggregate. The collection of large size aggregate samples. thus is very similar to the real field conditions of the mix. In essence. Various dyes may prove useful.40 percent. by staining and volumetric analyses of the thin section. Copyright by ASTM Int'l (all rights reserved). with sufficient experience. These rocks were first noted by Dolar-Mantuani [15] during studies of the Gull River carbonate rocks in which she used the rock cylinder test. The textural classification of the aggregate is. the texture determination can be used as a method of screening out all the possible potentially deleteriously expansive carbonate aggregates. and (2) all limestones which dedolomitize in an alkaline environment possess the characteristic texture and composition. The reactive texture frequently may be recognized by a petrographer. Minor-expansion group--expansion from 0. showing expansion in 2 to 5 weeks. (See ASTM Recommended Practice for Petrographic Examination of Aggregates for Concrete (C 295).10 to 0." These authors go on to point out that rocks which possess the characteristic texture and composition may be deleteriously expansive when embedded in concrete and that all rocks which have shown themselves to be deleteriously expansive do possess the characteristic texture and composition over at least small portions of their volume. No further reproductions authorized. 2. Alternatively. 3.) It has been shown that the most expansive rocks are those with between 10 and 30 percent acid-insoluble components and a calcite to dolomite ratio approaching unity. Late-major-expansion group--expansion of at least 0. various methods of instrumental analysis of the elemental composition may be used. The expansive aggregates studied were grouped into three classes: 1.40 percent.39 percent. after which the length of the cylinders either remained more or less constant or increased at a very slow rate. therefore. This group usually reached its maximum expansion in 10 to 40 weeks. 18 [reprinted here as Fig. Petrographic Examination--Newlon et al [12] state that there are no known exceptions to the following: "(1) All limestones which possess the characteristic texture and composition as described in ASTM C 294 and described above and shown in Fig. Early-major-expansion group--expansion of at least 0. This texture is best observed and defined by a trained petrographer examining standard (or somewhat thinner) petrographic thin sections of the rocks in question by means of a polarizing microscope with standard equipment. often accompanied by an analysis of the mineral phases by X-ray diffraction. . Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Late Expanders The exceptions to the ability of the rock cylinder test to indicate alkaliexpansive carbonate rocks within 28 days are the rocks known as late expanders. Thus.WALKER ON ALKALI-CARBONATE REACTIONS 731 Length Change of Hardened Cement Mortar and Concrete (C 157) modified by the substitution of moist storage for dry storage. 2] will react or dedolomitize in an alkaline environment. by examination of polished or finely ground surfaces of rock which have been subjected to a light acid etch. The texture was of rhombs of dolomite floating in a clayey. when tested by ASTM Test C 586. 4) among the 22 aggregate samples for a comparison study of the various test methods. but the ground mass was not as fine-grained as in the early expanders and was composed of interlocking dolomite as well as calcite. The late expanding rocks are reported to have continued expanding for five years [37. No further reproductions authorized. 4--Texture of late expanding carbonate rock from Virginia [12]. Newlon et al [12] found only one such aggregate (Fig. of at least 0. Later work by Dolar-Mantuani [37] defined the late expansive group as those rocks which. the rock cylinder method. have a shrinkage period of at least 10 weeks.732 TESTS AND PROPERTIES OF CONCRETE AGGREGATES starting to expand after 25 weeks (in one case after more than one year) and continuing to expand for the full testing period [15]. While intensive studies have been made of this type of rock by Dolar-Mantuani (1964). . These rocks were characterized as having acid-insoluble residues of from 21 to 49 percent and carbonate contents containing 75 to 87 percent dolomite. fine-grained ground mass. The single FIG. and silica minerals. Copyright by ASTM Int'l (all rights reserved). clay. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.03 percent and a later minimum expansion to 0. These authors state: "Sample 13-1 was a delayed expander whose expansion was not reflected in the concrete. these have been limited to studies of rock without parallel studies of concrete.20 percent.38] and some of them have expanded for 11 years (personal communication). At 4 weeks the cylinder had expanded close to 0. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. bedding surfaces. at least up to 5 years in service" In this regard. Entire beds of strata may be dolomitized evenly or the changes may take place only along certain cracks. Dolomitization is an uneven process. However. No further reproductions authorized. The remainder of the rock was pure lithographic limestone. At this time the stylolitic end broke off. Dolar-Mantuani [15] describes the expansive behavior of a rock cylinder of variable texture which was tested under ASTM Test C 586.7 percent insoluble residue. The late expanders may be prevented from expressing their expansion in concrete by the strength of the more hydrated concrete of ages greater than 10 weeks. Rock Variability The expansion for the wide variety of compositions and for the range of exansive behaviors found in the aggregate from one lithologic unit. If the expansion is sufficiently slow. even though only a small portion of the length was involved. The pointed end of the little cylinder contained a stylolite with reactive texture. the concrete may adjust to the changing aggregate by creep and autogenous healing [39].WALKER ON ALKALI-CARBONATE REACTIONS 733 sample in this project obviously does not permit generalization but it sugt gests that the delayed expansive tendency in rocks is not manifested in concrete. it should be noted that Smith found no reason to test concrete prisms more than 84 days after studying the results obtained with concrete specimens of nearly 7 years of age [34]. The shortened cylinder was repointed. . The conditions of deposition often undergo a continuous and variable set of changes during the entire history of deposition of the sediments which make up one small piece of rock.1 percent dolomite and only 4. Thus. or stylolites. fissures. One portion of a rock may be a pure aphanoerystalline micrite with no insolubles and another portion may contain veins and stylolites high in acid insolubles with included dolomite rhombs in a typical reactive texture. The cylinder represented a limestone which contained only 4. the possibility of these rocks contributing to the deterioration of concrete at later ages must not be disregarded entirely. Submarine slumping of unconsolidated sediments can mix these deposits. soaked in 1 N sodium hydroxide solution. The expansion had been produced entirely by the small amount of material in the narrow stylolite. Figure 3 shows a similar seam with reactive texture in a thin section of the Virginia aggregate. and testing was resumed. from one quarry is accounted for by the fact that rocks are heterogeneous in nature.5 percent. The specimen showed no further expansion. More and greater changes must be considered as the sample size increases. Copyright by ASTM Int'l (all rights reserved). the small amount of dolomite and the insoluble residue were arranged in a texture that caused the rock to expand significantly. )" The authors further explain that the Stage II sampling must be arranged in accordance with the specific sort of variability that the rocks exhibit in the particular quarry sampled. then less than 15 percent of the the total aggregate. 4.. Use and Control of Expansive Carbonate Aggregates The precautions necessary once an aggregate has been identified as being potentially deleteriously expansive have been reported by Smith [33. Selective Quarrying--Avoid using a rock determined to be potentially reactive in the fabrication of portland cement concrete. Experience has shown that a minimum of 5 samples and an average of approximately 10 samples per quarry will give a preliminary indication of the amount of reactive materials present. 1. it should be diluted either naturally or by artificial means until the coarse aggregate contains less than 20 percent potentially reactive material. Sampling is the most complex aspect of the evaluation of prospective quarry sites or producing quarries for potential reactivity. In part they conclude: "The sampling plan should have two stages. This complexity results from the cohabitation and interbedding of reactive and non reactive rocks in what are designated as single lithologic units by conventional geologic criteria. .34]. if both the coarse and the fine are reactive. the expansion appears to be in direct proportion to the diameter of the aggregate particles and the smallest feasible size of the reactive aggregate should be used. Dilution--If it is not economically feasible to avoid the use of the potentially reactive material. more detailed sampling procedure (Stage II) would be used where warranted for quarries shown in the Stage I sampling to contain significant amounts of reactive rock .734 TESTS AND PROPERTIES OF CONCRETE AGGREGATES The sampling problem is dealt with in detail by Newlon et al [40]. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Smaller Aggregate Size--Although the size of the aggregate does not slow the chemical reactions involved. . In general these writers are in agreement and they have enumerated the following procedures. A second.) 2. Extremely reactive materials should be present in less quantity and slightly reactive materials may somewhat exceed this amount.. . (Such aggregate will normally be acceptable for use as a base material or in bituminous concrete. 3.43]. and Newlon et al [40. Swenson [42]. No further reproductions authorized. . they believe that the sampling instructions contained in ASTM Recommended Practice C 295 closely describe the requirements. It is often not economically feasible to obtain a cement with such a low alkali content that Copyright by ASTM Int'l (all rights reserved). In general. Low Alkali Cement--The expansion of these rocks has been shown to increase with the amount of alkali in the cement. The first. screening (Stage I) would furnish sufficient information to establish either the absence or presence of reactive rock within a quarry. Mather [41]. (Stage I sampling. or. or preliminary. the structure or pavement should be designed to accommodate small amounts of expansion. The concrete surface shown has been lapped smooth to enhance detail and contrast. Copyright by ASTM Int'l (all rights reserved). 5.WALKER ON ALKALI-CARBONATE REACTIONS 735 the most reactive of carbonate aggregate will show no expansion. If the discolored rim is wholly or partially less soluble than the interior of the aggregate. Determination of whether such interior aggregate rims are positive or negative is accomplished by subjecting a smoothly sawn or smoothly lapped surface of the concrete to a hydrochloric acid etch. Rim Forming Aggregates Rims Within the Aggregate Rims occur within certain carbonate aggregate particles which have reacted with the surrounding cement paste. Low alkali cement may become harder to obtain under environmental control procedures of cement production. Although rims are thought of generally as a product of a chemical reaction of the carbonate aggregate with the alkalies of the cement.95 percent Na20 (equivalent). Consideration should be given to unsightly cracking that may occur on surfaces exposed to public view. Rims which are more soluble than the interior of the aggregate are classified as being negative. that is expansion joints. 7. Prohibit Use--If none of control measures 1 through 6 can be applied in an economically feasible regime that controls the expansion. With the most reactive rock 0.4 percent alkaline can be sufficient to create expansion and should be used only in conjunction with other control measures. etc. Design Considerations--If known potentially reactive aggregate is to be used. 6. the use of the potentially reactive carbonate rock under consideration must be prohibited. Figure 6 shows the same aggregate after use in a concrete bar made with cement containing 0. it is considered to be a positive rim. . surface finely lapped. Protection from Moisture--Because the reaction takes place only in the presence of moisture. should be used.. Figure 5 shows this dark discoloration on particles of a reactive Virginia aggregate after moist storage of a concrete bar fabricated with high alkali cement containing 0. They may be observed as dark discolorations at the very edges of the particles or very slightly inside the edges. the potenially reactive rock used with a moderately low alkali cement should be protected from ground moisture with a vapor barrier. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it sometimes happens that they are more pronounced visually in low alkali concrete than in high alkali [12. Evidence of the presence of a rim is destroyed completely on some aggregates by the action of the acid.44]. No further reproductions authorized.43 percent Na20 (equivalent). It is clear from the work of Bisque and Lemish [29. Devonian age. acid-resistant rims had developed on the aggregate while it had been embedded in concrete. Iowa) which had been used in concretes showing premature distress. When samples of the concretes were sawn and etched. . Cedar Valley formation. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The source of silica for the enrichment of the rim was shown not to be the quartz of the fine aggregate [46]. Positive Rims--The first investigation of positive rims was conducted by Lemish et al [50] and by Bisque and Lemish [29. No further reproductions authorized.D a r k rims f o r m e d on a Virginia reactive aggregate embedded in a concrete bar fabricated with high alkali cement and subjected to moist storage [12]. These changes led the authors to conclude that a chemical reaction and accompanying transfer of material had occurred.46].45. Copyright by ASTM Int'l (all rights reserved). but was variously thought to be either the paste itself [29. Illitic clay was found to be a necessary mineralogical constituent of the rim-forming carbonate rocks [45].46] and Lemish [47] that dedolomitization accompanied the rimforming process. it was found that the dark rim was less soluble than either the interior of the aggregate or a very narrow layer of the aggregate at the contact with the cement paste. S .. The rims were duplicated on Glory aggregate in the laboratory in a silica solution at pH 12. The dark.736 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. Various chemical experiments and analyses suggested that the rims may have become enriched in silica.46] who found dark rims on aggregate particles from the Glory Quarry (Rapid member. and a high loss under freeze-thaw testing [50. It is this lack of strength development which has been thought to be the cause of the deterioration specifically associated with the Glory aggregate.1 mm) calcite.WALKER ON ALKALI-CARBONATE REACTIONS 737 FIG. It was shown that the growth of the positive reaction shells was not accompanied by excessive expansion of test bars of concrete [45]. aggregate [48] were associated with the retardation of strength development which normally accompanies the continuing hydration of concrete as it matures.reaction rims were first shown by Mather Copyright by ASTM Int'l (all rights reserved). insoluble residue of 10 to 14 percent. No further reproductions authorized.0 to 0. but which has not been thought to be associated with all positive rim-forming aggregates. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 6 . very fine (0. It is not known if there is any correlation between the susceptibility to frost and the rim-forming process. a texture of dolomite crystals set in a matrix of medium to coarsely crystalline (1. Negative RimsmNegative . but testing did indicate that the Glory aggregate [45] and Jeffersonville...W i d e rims f o r m e d on a Virginia Reactive aggregate (same aggregate as in Fig. . 5) embedded in a concrete bar fabricated with low alkali cement and subjected to moist storage [12] or the well distributed particles of silica minerals in the carbonate coarse aggregate [48 ]. Some of the rim-forming aggregates were earlier found by Sweet [49] to be highly susceptible to frost damage. The lithology of the Rapid member typically possessed high.51].1 mm) porosity. Ind. It should be noted also that no effects. To date there is only one type of chemical reaction that is known generally to cause premature deterioration of concrete pavements and structures. These may take the form of lobes of carbonation or areas low in calcium hydroxide extending out into the paste. This is the expansive alkali-dedolomitization reaction. (See also Hadley [21]. [reprinted here as Fig. and that two of these reached expansions in excess of 0. Exterior Rims Discolorations of the mortar surrounding aggregate particles occur in some cases [50. A check for rim vs expansion showed that six of the 25 rimmed rocks also expanded. Sherwood and Newlon tested 224 samples from 43 quarries for rim formation by embedding cubes of the test rock in mortar bars which were then stored over water for 8 weeks [53]. The composition of the rim-forming rocks and the type of rims formed can be seen in Fig. The reaction does not seem to cause any kind of deterioration. 7]. have been proven attributable to rim growth at this time. 8] shows a negative and a positive rim from this group . They seem to be associated generally with aggregates which form positive rims. These mortar rims or lobes are not known to be indicative of any particular deleterious reaction with carbonate aggregates. No further reproductions authorized.52. Copyright by ASTM Int'l (all rights reserved).738 TESTS AND PROPERTIES OF CONCRETE AGGREGATES et al [52].1 percent after six months. . . and (c) the limited evidence in the case of positive rims points to compositions high in dolomite." Further investigations by Buck [44] of the aggregates observed to have negative reaction rims in the Milford D a m investigations [52] confirmed the fact that this type of reaction occurs in high calcite rocks. They sometimes occurred in acid etched concrete samples as negative areas surrounding less soluble aggregate centers.54]. 9. (a) the negative rims were virtually limited to high calcite rocks. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. All but two of these were negative rims. . The reaction is most active in high alkali cements and occurs expansively with only a very restricted type of rock. In fact. (b) the insoluble residue contents are generally low.) Sherwood and Newlon [53] reported: "Evidence of rims was found in 25 of the 224 cubes. Synopsis The chemical reactions which take place between carbonate aggregates and portland cement paste are many and varied. no relationship between rim growth and expansion appears to exist. Buck thought that the reaction might take place in a wide variety of carbonate aggregates and might be responsible for the observed increase with time of the strength of the bond between carbonate aggregate and concrete paste. . either deleterious or beneficial. Because the percentage of the rim growing rocks that expanded is about the same as the percentage of all the samples that expanded. Figure 10 [reprinted here as Fig. 1960. American Society for Testing and Materials. American Society for Testing and Materials. 1956. pp. a substantial amount of illite. Katharine and Mielenz.02 appears to offer the most dependable means of evaluating the susceptibility of cement-aggregate combinations to expansive effects of this reaction. 7--Composition of rim-forming rocks [18]. C. W. [2] Lerch. R. "Chemical Reactions. A S T M STP 169A. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Thus." Significance of Tests and Properties of Concrete and Concrete Making Materials." Proceedings. 39. selective quarrying is often a preferred method of dealing with them when they occur. "Chemical Reactions. Vol. No further reproductions authorized. References [1] Hansen. 1960.02. C. Highway Research Board. "Cooperative Examination of Cores from the McPherson Test Road. P e t r o g r a p h i c examination (ASTM Recommended Practice C 295) and the rock cylinder method (ASTM Test C 586) are valuable screening procedures to detect aggregate materials that are potentially susceptible to the alkali-carbonate rock reaction...WALKER ON ALKALI-CARBONATE REACTIONS LEGEND INSOLUBLE RESIDUE / k o ClearlyDefined / ~ Negative Rim / L~ Passible / / Negative Rim * Clearly Defined Positive Rim 9 Passible 739 / / / \ \ Po DOLOMITE CALCITE FIG. Copyright by ASTM Int'l (all rights reserved). They have most often been found in Ordovician formations. Rocks of this composition can occur in any of the carbonate sequences. The rocks contain nearly equal amounts of calcite and dolomite." Significance of Tests and Properties of Concrete and Concrete Making Materials. The expansive alkali-reactive carbonate rocks occur in relatively small quantities in limited areas or time zones. 205-216. . A S T M STP 169. William. and possess a texture of dolomite rhombs in "dirty" micrite. [3] Mather. A test method for length change of concrete prisms being developed by ASTM Subcommittee C09. 740 TESTS AND PROPERTIES OF CONCRETE AGGREGATES FIG. 8--Close-up photos o f sawed cubes comparing acid etched and non-etched halves. Part (A ) shows a negative rim and part (B) a positive rim [18]. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. WALKER ON ALKALI-CARBONATE REACTIONS 741 [4] Bukovatz, J. E., Crumpton, C. F., and Worley, H. E., "Kansas Concrete Pavement Performance as Related to D-Cracking," Cement Aggregate Reactions, Record No. 525, Transportation Research Board, 1974, pp. 1-8. [5] Roy, C. J., Thomas, L. A., Weissman, R. C., and Schneider, R. C., "Geologic Factors Related to Quality of Limestone Aggregates," Proceedings, Highway Research Board, Vol. 34, 1955, pp. 400-411. [6] Moyer, R. A., "An Eleven-Year Study of the Expansion and Contraction of a Section of Concrete Pavement," Proceedings, Highway Research Board, Vol. 25, 1945, pp. 71-81. [7] Woods, K. B., Sweet, H. S., and Shelburne, T. E., "Pavement Blowups Correlated with Source of Coarse Aggregate," Proceedings, Highway Research Board, Vol. 25, 1945, pp. 147-168. [8] Sweet, H. S. and Woods, K. B., "Evaluation of Aggregate Preformance in Pavement Concrete," Journal, American Concrete Institute, Vol. 19, No. 10, June 1948, pp. 10331040. [9] Axon, E. O. and Lind, Junior, "Alkali-Carbonate ReactivitymAn Academic or a Practical Problem," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 114-125, [10] Swenson, E. G., "A Reactive Aggregate Undetected by ASTM Tests," Bulletin No. 57, American Society for Testing and Materials, 1957, pp. 48-51. [1l] Hadley, D. W., "Alkali Reactivity of Dolomitic Carbonate Rocks," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 1-19. [12] Newlon, H. H., Ozol, Michael, and Sherwood, W. C., "Potentially Reactive Carbonate Rocks," An Evaluation of Several Methods for Detecting Alkali-Carbonate Reaction, Progress Report No. 5, Virginia Highway Research Council, 71-R33, May 1972. [13] Walker, H. N., "Reaction Products in Expansion Test Specimens of Carbonate Aggregates," Cement-Aggregate Reactions, Record No. 525, Transportation Research Board, 1974, pp. 28-37. [14] Swenson, E. G. and Gillott, J. E., "Characteristics of Kingston Carbonate Rock Reaction," Concrete Quality Control, Aggregate Characteristics and the Cement Aggregate Reaction, Bulletin No. 275, Highway Research Board, 1960, pp. 18-31. [15] Dolar-Mantuani, L. M. M., "Expansion of Gull River Carbonate Rocks in Sodium Hydroxide," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 178-195. [16] Hadley, D. W., "Alkali Reactivity of Carbonate Rocks--Expansion and Dedolomitization," Proceedings, Highway Research Board, Vol. 40, 1961, pp. 462-474. [17] Newlon, H. H. and Sherwood, W. C., "An Occurrence of Alkali-Reactive Carbonate Rock in Virginia," Carbonate Aggregate and Steam Curing of Concrete, Bulletin No. 355, Highway Research Board, 1962, pp. 27-44. [18] Sherwood, W. C. and Newlon, H. H., Jr., "A Survey for Reactive Carbonate Aggregates in Virginia," Record No. 45, Highway Research Board, 1964, p. 222. [19] Steidtmann, Edward, "The Origin of Dolomite as Disclosed by Stains and Other Methods," Bulletin, American Geological Society, Vol. 28, June 1917, pp. 431-450. [20] Hadley, D. W., "Alkali-Reactive Carbonate Rocks in Indiana--A Pilot Regional Investigation," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 196-221. [21] Seligmann, Paul, "General Discussion," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, p. 111. [22] Hansen, W. C., "General Discussion," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, p. 110. [23] Sherwood, W. C. and Newlon, H. H., Jr., "Studies on the Mechanisms of AlkaliCarbonate Reactions--Part I, Chemical Reactions," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 41-56. [24] Lemish, John and Moore, W. J., "Carbonate Aggregate Reactions--Recent Study and an Approach to the Problem," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 57-71. [25] Buck, A. D. and Matber, K., "Brucite Formation in Carbonate Rock Prisms," Miscellaneous Paper No. 6-867, U.S. Army Engineer Waterways Experiment Station, Corps of Engineers, Vicksburg, Miss., Jan. 1967. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 742 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [26] Feldman, R. F. and Sereda, P. J., "Characteristics of Sorption and Expansion Isotherms of Reaction Limestone Aggregate," Journal, Vol. 58, No. 2, Aug. 1961, pp. 203-214. [27] Gillott, J. E., "Mechanism and Kinetics of Expansion in the Alkali-Carbonate Rock Reaction," Canadian Journal of Earth Sciences, Vol. 1, No. 2, 1964, pp. 121-145. [28] Buck, A. D., "Control of Reactive Carbonate Rocks in Concrete," Technical Report C-75-3, U.S. Army Engineer Waterways Experiment Station, Corps of Engineers, 1975. [29] Bisque, R. E. and Lemish, John, "Chemical Characteristics of Some Carbonate Aggregate as Related to Durability of Concrete," Air Voids in Concrete and Characteristics of Aggregate, Bulletin No. 196, Highway Research Board, 1958, pp. 29-45. [30] Hilton, M. H., "Expansion of Reactive Carbonate Rocks Under Restraint," CementAggregate Reactions, Record No. 525, Transportation Research Board, 1974, pp. 9-22. [31] Swenson, E. G. and Gillott, J, E., "Alkali-Carbonate Rock Reaction," Cement Aggregate Reactionsl Record No. 525, Transportation Research Board, 1974, pp. 21-40. [32] Swenson, E. G. and Gillott, J. E., "Alkali Reactivity of Dolomitic Limestone Aggregate," Magazine of Concrete Research, Vol. 19, No. 59, June 1967, pp. 95-104. [33] Smith, P., "Learning to Live with a Reactive Carbonate Rock," Symposium on AlkaliCarbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 23-27. [34] Smith, P., "15 Years of Living at Kingston with a Reactive Carbonate Rock," Cement Aggregate Reactions, Record No. 525, Transportation Research Board, 1974, pp. 23-27. [35] Ryell, J., Chojnacki, B., Woda, G., and Koniuszy, Z. D., "The Uhthoff Quarry AlkaliCarbonate Rock Reaction--A Laboratory and Field Performance Study," Cement Aggregate Reactions, Record No. 525, Transportation Research Board, 1974, pp. 43-54. [36] Dolar-Mantuani, L. M. M., Draft of "Manual of Petrographic Analysis of Concrete Aggregates," unpublished. [37] Dolar-Mantuani, L. M. M., "Late-Expansion Alkali-Reactive Carbonate Rocks," Mineral Aggregates, Record No. 353, Highway Research Board, 1971, pp. 1-14. [38] Dolar-Mantuani, L. M. M., "Alkali-Silica-Reactive Rocks in the Canadian Shield," Portland Cement Concrete, Record No. 268, Highway Research Board, 1969, pp. 99-117. [39] Gillott, J. D. and Swenson, E. G., "The Mechanism of the Alkali-Carbonate Rocks Reaction," Quarterly Journal of Geology, Vol. 2, pp. 7-23. [40] Newlon, H. H., Sherwood, W. C. and Ozol, M. A., "Potentially Reactive Carbonate Rocks," A Strategy for Use and Control of Potentially Reactive Carbonate Rocks, including an Annotated Bibliography of Virginia Research, Progress Report No. 8, Virginia Highway Research Council, 71-R41, 1971. [41] Mather, Bryant, "Development in Specification and Control," Cement Aggregate Reactions, Record No, 525, Transportation Research Board, 1974, pp. 38-42. [42] Swenson, E. G., "Interaction of Concrete Aggregates and Portland Cement--Situation in Canada," Engineering Journal, Vol. 55, No. 5, 1972, pp. 34-39, [43] Newlon, H. H. and Sherwood, W. C., "Methods for Reducing Expansion of Concrete Caused by Alkali-Carbonate Rock Reaction," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 134-150. [44] Buck, A. D., "Investigation of a Reaction Involving Non-Dolomitic Limestone Aggregate in Concrete," Miscellaneous Paper No. 6-724, U.S. Army Engineer Waterways Experiment Station Corps of Engineers, 1965. [45] Bisque, R. E. and Lemish, John, "Effect of Illitic Clay on Chemical Stability of Carbonate Aggregates," Concrete Qualiy Control, Aggregate Characteristics and the Cement Aggregate Reaction, Bulletin No. 275, Highway Research Board, 1960, pp. 32-38. [46] Bisque, R. E. and Lemish, John, "Silification of Carbonate Aggregates in Concrete," Physical and Chemical Properties of Cement and Aggregate in Concrete, Bulletin No. 239, Highway Research Board, 1960, pp. 41-55. [47] Lemish, John, "Research on Carbonate Aggregate Reactions in Concrete," Transactions, American Institute of Mining, Metallurgical, and Petroleum Engineers, Vol. 220, 1961, pp. 195-198. [48] Lemish, John, Harwood, R. J., Hiltrop, C. L., and Werner, M, A., "Compositional Variations Associated with Carbonate Aggregate Reactions," Properties of Concrete, Record No. 3, Highway Research Board, 1963, pp. 1-8. [49] Sweet, H. S., "Research on Concrete Durability as Affected by Coarse Aggregate," Proceedings, American Society for Testing and Materials, Vol. 48, 1948, pp. 988-1017. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. WALKER ON ALKALI-CARBONATE REACTIONS 743 [50] Lemish, John, Rush, F. E., and Hiltrop, C. L., "Relationship of Physical Properties of Some Iowa Aggregates to Durability of Concrete," Air Voids in. Concrete and Characteristics of Aggregate, Bulletin No. 196, Highway Research Board, 1958, pp. 1-16. [51] Hiltrop, C. L. and Lemish, John, "Relationship of Pore-Size Distribution and Other Rock Properties to Serviceability of Some Carbonate Aggregates," Physical and Chemical Properties of Cement and Aggregate in Concrete, Bulletin No. 239, Highway Research Board, 1960, pp. 1-23, [52] Mather, K., Luke, W. I., and Mather, B., "Aggregate Investigations, Milford Dam, Kansas--Examination of Cores from Concrete Structures," Technical Report No. 6-629, U.S. Army Engineer Waterways Experiment Station Corps of Engineers, June 1963. [53] Sherwood, W. C. and Newlon, H. H., "A Survey for Reactive Carbonate Aggregates in Virginia," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 222-233. [54] Mather, Katherine, Buck, A. D., and Luke, W. I., "Alkali-Silica and Alkali-Carbonate Reactivity of Some Aggregates from South Dakota, Kansas, and Missouri," Symposium on Alkali-Carbonate Rock Reactions, Record No. 45, Highway Research Board, 1964, pp. 72-109. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. STP169B-EB/Dec. 1978 L. D o l a r - M a n t u a n i ~ Chapter 42--Soundness and Deleterious Substances Introduction During the past 100 or more years many tests have been developed and applied to assess the quality of concrete aggregates. This paper is a discussion of the significance of five aggregate quality tests currently in use. One of them, the sulfate soundness test (ASTM Test for Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate (C 88)), is perhaps the most widely used of all methods for determining the overall quality of aggregate. The other four tests are used to determine the presence of specific harmful particles or substances which influence the mix proportions of fresh concrete or its early stage hardening, or which damage the concrete surface under specific circumstances. Nomenclature A terminology has grown up over the years for describing the assessment of aggregate quality. As is common with most terminologies that grow with time, not all authors use the same terms with the same meaning. The two terms used in association with the materials and tests discussed here are "soundness" and "deleterious" and different authors have assigned different meaning to these terms. The sulfate soundness test is designed to predict the overall performance of an aggregate in concrete. Bloem [112 used "soundness" as a general term to describe an aggregate as a whole and uses "deleterious substances" to describe individual particles or contaminants that are harmful to concrete. The use of the terms "soundness" and "deleterious" in this way causes some difficulties. In some literature on concrete technology "sound" and "unsound" are used to describe chemical properties only. Consideration IConsultant petrologist, Toronto, Ontario, Canada M6M 4Z2. 2The italic numbers in brackets refer to the list of references appended to this paper. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 744 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978tobyLicense ASTM International www.astm.org DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 745 should be given to omitting the term soundness from the ASTM C 88 sulfate test which is identified adequately by the word sulfate. Actually, the test measures the unsound and not the sound aggregate constituents. It is not easy to find agreement on the meaning of "deleterious." Bloem used it to mean specific, mainly physically undesirable, characteristics of an aggregate. Petrographers usually use deleterious, and its opposite innocuous, to refer to chemical properties of individual particles. (See Rhoades and Mielenz [2] and for wider definitions see Mielenz [3,4] and in the present publication.) A detailed classification of harmful substances, based on published literature, was proposed by Swenson and Chaly [5]. They use "deleterious" to mean any quality of an aggregate that is harmful to concrete. In this paper, the term "harmful" will be used to mean detrimental to concrete in the broad sense. Sulfate Test Although individual particles behave differently in concrete, it is desirable to have general criteria for the acceptance of an aggregate. It is convenient to test representative aggregate samples to obtain data that show a meaningful relationship between the test results and the quality of concrete made from the aggregate. No satisfactory single test accomplishes this. The most frequently used method for measuring overall aggregate quality and its performance in concrete is ASTM Test C 88. This test was first published in 1931 as a tentative ASTM method and was approved as a standard method in 1963. The scope is given as follows: "This method covers the testing of aggregates to determine their resistance to disintegration by saturated solutions of sodium sulfate or magnesium sulfate. It furnishes information helpful in judging the soundness of aggregates subject to weathering action, particularly when adequate information is not available from service records of the material exposed to actual weathering conditions." The sulfate test is carried out by soaking a sample of each fraction in saturated sodium or magnesium sulfate solution and then oven drying. Magnesium sulfate generally is more destructive than the sodium salt. The growth of salt crystals in the pores of the particles was thought originally to produce disruptive internal forces similar to the action of freezing in water. After 5 or 10 cycles of soaking and drying, the amount of the material that has been broken or disintegrated is determined by weighing the coarse aggregate fractions retained on sieves with openings five sixths of the original ones. The fine aggregate is sieved on the original sieves. The sulfate loss is expressed as the weighted sum of the difference between the first and second weighing of each fraction. T h e physical damage produced during the test includes crumbling, flaking, splitting, cracking, and granular disintegration of the aggregate Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 746 TESTS AND PROPERTIES OF CONCRETE AGGREGATES particles. To investigate the damage in more detail, after each immersion, the fraction retained on a 19.0-mm (3A-in.) sieve is examined visually with or without a lens. After the test the damaged particles are counted and the smaller size fractions of coarse aggregate are examined to determine if there is excessive particle splitting. Shaly and other weak, flat particles may split, producing thin flat particles of approximately the same sieve size as the original particles before testing. The weight of such physically damaged particles probably should be added to the loss. Since the aggregate is washed before testing, the fines and soluble materials are not included in the loss (see ASTM Test for Materials Finer than No. 200 (75-/~m) Sieve in Mineral Aggregates by Washing (C 117)). A petrographic examination of the coarse aggregate before and after the test gives information about the weakness and strength of the rock varieties in the aggregate. An examination of the "loss" passing the after-test sieves and retained in the pan of each fraction may help to characterize the objectionable aggregate, especially the shales and other argillaceous rocks [6]. Interpretation of Sulfate Tests Although the scope of the method refers to weathering, with no mention of frost action, the test results usually are interpreted in terms of the behavior of aggregates exposed to frost action. Explanations of the mechanism by which the sulfate test disrupts rock particles have been given by many authors but there is no general agreement [7-11]. Some research workers [8] have published data on the properties of the sulfate solutions and observations of the behavior of the sodium and magnesium salts as they pass through various stages of crystallization and dehydration. It is generally agreed that alternative soaking in sulfate solution and oven drying causes salt to accumulate in the pores and cracks in the rocks. At some number of alternations, the quantity of salt reaches an amount which on rehydration during the next soaking cannot be accommodated in the pores of some particles and exerts disruptive pressures. Bloem discussed the properties of the two salt solutions and pointed out that the magnesium solution is more aggressive than the sodium solution because there is a greater weight and volume of magnesium salts than sodium salts in solution. There is evidence that destructive forces other than the pressure produced by crystal growth must be involved in the sulfate test. Wuerpel [I0] found the loss to be approximately proportional to the number of cycles. Appreciable losses have occurred when the test was run with distilled water instead of sulfate solution, indicating that simple wetting and drying or heating and cooling disrupts the particles [8]. Hudec and Rogers [12] found that destruction in the sulfate test was related to the quantity of water adsorbed by carbonate rocks. These results indicate that wetting and drying is also a Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 747 destructive force in the sulfate test. Finally, the severity of the test increases when the drying time is extended beyond that needed to dehydrate the crystals, indicating damage from prolonged heating. During the early development of the sulfate test, it was suggested that the loss depends more on the number of pores than on their size and distribution [13-19]. The damage to concrete due to freezing depends on the pore structure, elastic properties, size, and water saturation of the aggregate particles [12-22] as well as the properties of the other ingredients, their proportions, and the severity of the exposure, to mention a few factors. Details of frost action are discussed elsewhere in this publication. Various authors have emphasized that there is little or no theoretical or experimental support for the assumption that the sulfate test simulates exposure to freezing and thawing in concrete or gives a reliable indication of field performance [17,13,14,23]. On the other hand, statistical analysis by Vollick and SkiUman [24] based on 70 samples did indicate a correlation between the freeze-thaw durability of air-entrained concrete and the soundness of coarse aggregate as measured by the sodium sulfate test. However, the wide scatter obtained shows that the durability is influenced by other factors that are not measured by the sulfate test. Quoting selected papers, starting with the first description of sulfate solution used for aggregates by Brard (1829), Mather [25] concludes "that many fundamental aspects of the physical and chemical effects of the phenomena associated with the formation of hydrated sulfates in aggregates are still poorly understood." This is still true today. Chamberlin a has pointed out repeatedly that the fine aggregate particle size is smaller than the critical size for frost damage in most materials and therefore sulfate test results on fine aggregates require an entirely different interpretation than the results on coarse aggregates. From examples of his and other's investigations it can be concluded that high magnesium sulfate losses for fine aggregates correlate with properties such as low density, high absorption and attrition, low resistance to abrasion, and low modulus of elasticity [17,26-29]. These test results agree with the general petrographic findings that deeply altered and in situ weathered rocks consisting of detrimental constituents having a physically poor texture, break down on further weathering into sand fractions which are compositionally or texturally detrimental, or both, to concrete. This usually is reflected in the coarser sand fractions by the presence of poor rock particles and in the finer fractions by concentrations of harmful mineral grains. After a critical review of the literature treating methods of identifying aggregates subject to destructive volume change when frozen in concrete, Larsen et al [30] conclude that the sulfate test is too sensitive to test variables and does not measure or reflect the susceptibility of aggregates to aChamberlin, W. P., personal communication. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 748 TESTS AND PROPERTIES OF CONCRETE AGGREGATES damage by freezing and thawing. They recommend therefore that "no further research effort should be devoted to sodium or magnesium sulfate soundness tests and these should be deleted from specifications as soon as suitable replacements are available." However, it seems rather unwise to eliminate these tests, which are probably the most widely used for concrete aggregates and which have been used for most major constructions on this continent. It is the author's opinion that the test does indicate weaknesses in aggregates. If the specification limits are used carefully together with sound engineering judgment, the test is certainly useful because of the relatively short time needed to perform it. The value of the test may be enhanced by petrographic examination of the aggregate after testing to identify better the weaknesses in the particles. Reproducibility of Sulfate Tests After various researchers [8-10,15,31] showed that many details of the equipment and technique affect the test results, the equipment and procedures were defined more closely to give better reproducibility. Several suggestions by Wuerpel [11], Paul [31] and Woolf [32,33] for changes were incorporated in the reviews of the test method; the last was as recently as 1973 in the Annual Book of A S T M Standards. These changes improved the reproducibility both within and between laboratories. But the failure in many cases to obtain results of even comparable magnitude probably stems from three causes: (1) inability to prepare truly representative specimens especially for the coarser fractions of lithologically complex aggregates [34]; (2) differences in following the procedures, such as extra drying to obtain constant weight; and (3) deviations from the prescribed method, such as shortening the initial or final drying period before weighing. A great principal difficulty in obtaining comparable results is the number of different alternative procedures permitted in the method. Either sodium or magnesium solutions can be used and either 5 or 10 immersion cycles. Trends associated with the various optional procedures have been identified [35]. Although they do not permit translation of results obtained with one type of salt or number of cycles to another, they do indicate approximate degrees of severity in a statistical sense. For fine aggregates, magnesium sulfate is consistently more severe than sodium sulfate, producing losses about twice as great. For coarse aggregate, magnesium sulfate is usually the more severe but the difference is smaller, and for many individual aggregates, may be reversed. Losses at 10 cycles average about 50 percent higher than at five cycles for either type of salt and for both coarse and fine aggregate. The 1976 Annual Book of A S T M Standards seems to Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 749 favor the magnesium over the sodium solution. This is probably because the magnesium sulfate solubility is less sensitive to temperature changes than is the solubility of sodium sulfate [11.31]. Laboratories using sodium sulfate are hesitant to switch to magnesium because it would reduce the value of accumulated results, particularly where earlier results from the same deposit are used for comparison. It has been suggested that the sulfate test might be used to accept aggregates but not to reject them [33], the assumption being that aggregates that withstand the test are good while those that break down may or may not be bad. Unfortunately, the test is not reliable even to that extent. Certain aggregates with an extremely fine pore structure show almost no loss in the sulfate test but disrupt concrete when frozen in a saturated condition. Conversely, certain highly porous aggregates disintegrate in the sulfate test but produce concrete with good resistance to freezing and thawing. Vollick and Skillman [24] report that durable concrete was produced with aggregates having as much as 32 percent loss in the sodium sulfate solution. A low sulfate test is usually, but not always, evidence of good durability, whereas a high loss places the aggregate in a questionable category until performance data become available. A recommendation that sulfate testing be simplified by testing one fraction each of the coarse and fine aggregates was not accepted for ASTM Test C 88. It was rejected because no one size fraction adequately represents the quality of a graded aggregate. This is evident from petrographic examination of numerous samples [37]. Conversely, the N.Y. State Department of Transportation tests the 25.4 to 12.7-mm (1 to 1/2-in.) fraction only for acceptance and as an indication of uniformity of aggregate supplies. This simplified test (NYSDOT 208 A-76) is considered very helpful in the dayto-day operation of the state transportation department. 4 Specification Limits The lack of correlation between the sulfate loss and the performance of aggregates in field or laboratory concrete, militates against setting inflexible acceptance limits for the sulfate loss and disregarding judgment in interpreting the results [1]. In ASTM Specification for Concrete Aggregates (C 33), limits are specified for magnesium and sodium sulfate losses for fine aggregates. For coarse aggregates the sulfate test can be omitted for certain types of concrete and for concrete placed in certain locations. The specifications also contains escape clauses for certain cases in which the aggregate fails to meet the requirements. 4Toung, G. D., personal communication. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 750 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Precision Statement Precision indexes, based on the latest data supplied by ASTM Subcommittee C09.03.05 on Methods of Testing and Specifications for Physical Characteristics of Concrete Aggregates (19 June 1974): for coarse aggregates having weighted average sulfate losses in a range of 6 to 16 percent for sodium and 9 to 20 percent for magnesium sulfate are given in Table 1. Available data thus still discourage any attempt to estimate the laboratoryto-laboratory reproducibility of sulfate test results. Bloem's paper [1] includes within-laboratory-single-operator data on 5-cycle sodium and magnesium sulfate tests made in triplicate on 36 fine aggregates and 56 coarse aggregates [38]. The results are given in Table 2. To the extent that these data apply generally, which assumes meticulous attention to all testing detail, duplicate determinations by one operator within one laboratory should be expected to yield numerical losses checking within about 4 for coarse aggregate and 1.5 for fine aggregate 95 percent of the time. Other Tests for Soundness Absorption Test Because of the unsatisfactory correlation between the sulfate test results and the overall performance of aggregates in concrete, it has been suggested that the absorption test, which measures pore volume directly, gives better correlation with the resistance of concrete to laboratory freezing and thawing than the sulfate test [18,19]. Unconfined Freeze- Thaw Test To replace the sulfate test with the freeze-thaw test on unconfined aggregates seemed to be a logical change to obtain values that more closely indicate the susceptibility of aggregates to frost action. Over the years, many attempts have been made to improve the correlation between the laboratory freeze-thaw test results and the performance of aggregates in concrete. Variables investigated include sample type and size, pretest treatment, rate and conditions of freezing and thawing, different numbers of cycles, and the addition of a small volume of alcohol, usually 0.5 percent [39], to the water. Various investigators have reported a general correlation between aggregate freeze-thaw resistance and other tests including absorption and sulfate loss. Some have expressed confidence in the ability of these tests to predict field performance. For instance, the N.Y. Statement Department of Highways successfully uses a laboratory freeze-thaw test (NYSDOT 208) or the magnesium sulfate test (NYSDOT 207) for acceptance Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 751 TABLE ] --Precision statement for sulfate losses:a Multilaboratory sodium sulfate magnesium sulfate Single operator sodium sulfate magnesium sulfate Maximum Coefficient of Variation (1S %), max, % Maximum Difference between two Tests (D2S%), b percent of avg 43 35 131 99 23 I1 64 30 ~These numbers represent, respectively, the 1S% maximum and D2S% maximum limits as described in ASTM Recommended Practice for Preparing Precision Statements for Test Methods for Construction Materials (C 670). bD2S is the difference 2-sigma limit: difference equalled or exceeded in only S percent of cases. TABLE 2--Percentage of coefficient or variation. Type of Test Coarse Aggregate" Fine Aggregateb 14.5 12.4 3.9 6.0 Five-cycle magnesium sulfate Five-cycle sodium sulfate "Fixed grading, 25-ram (I-in.) maximum size. bTypical concrete gradings; loss weighted in accordance with individual grading. of aggregates. However, a g g r e g a t e rejection m a y require showing, by a p e t r o g r a p h i c identification, t h a t failed particles have a known unsatisfactory p e r f o r m a n c e record in concrete structures (see footnote 4). A l t h o u g h the results from the freeze-thaw test correlate only poorly in the statistical sense with the results from the New York State or A S T M M e t h o d C 88 m a g n e s i u m sulfate tests, all t h r e e p r o c e d u r e s (with their a c c e p t a n c e criteria) tend to accept or reject the s a m e m a t e r i a l s (see footnote 3). Verbeck [20] a n d m a n y others have p o i n t e d out t h a t the destructive effects of particles freezing in concrete c a n n o t be s i m u l a t e d by freezing aggregate in an u n c o n f i n e d state. This is relevant for coarse aggregate fractions but, as m e n t i o n e d above, C h a m b e r l i n points out t h a t these mechanisms generally do not a p p l y to the small particles of fine aggregates. His thesis a b o u t the different position of fine a g g r e g a t e c o m p a r e d to t h a t of coarse aggregate suggests t h a t the physical a n d other p r o p e r t i e s of m a n y n a t u r a l sands have a high degree of m u t u a l correlation [26]. C o n f i n e d Freeze- T h a w Tests F r e e z e - t h a w tests on aggregates in the confined state in concrete is the most satisfactory m e t h o d for p r e d i c t i n g the field p e r f o r m a n c e o f concrete aggregates. These m e t h o d s are discussed elsewhere in this p u b l i c a t i o n . Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 752 TESTS AND PROPERTIES OF CONCRETE AGGREGATES Copper Nitrate Test The copper nitrate test is performed by first immersing the aggregate in one normal copper nitrate solution for 16 h (overnight) and then in strong ammonia for about 2 min and finally washing carefully in tap water. The one normal solution is prepared by dissolving 250 g of hydrated copper nitrate, (Cu(NO3)2.3H20) in 1 litre of distilled water. This test was used to obtain data on harmful aggregates consisting of varieties of argillaceous rocks and shales [40]. The prolonged copper nitrate test proved to be a good indicator of the presence of harmful argillaceous impurities in carbonate rocks and sandstones, and of the presence of harmful shale particles. The damage to the aggregate particles is similar to that produced by the sodium sulfate test. The quality assessment is based on scaling, flaking, splitting, cracking, exfoliation, and disintegration of argillaceous concentrations. There is no acceptance limits for this test because the complex copper nitrate coating on the carbonates prevents evaluation of the damage by weight [6]. Correlation of Losses with Petrographic Characteristics Fourteen samples of pure and argillaceous dolostones from a quarry were subjected to the magnesium sulfate test after being petrographically examined by Woda. s The number of particles in the 16.0 to 12.5-mm (1/2 to 5/8-in.) and 12.5 to 9.5-mm (5/8 to 3/8-in.) size fractions were counted before and after testing and the losses were calculated by weight, and particle count. The correlation among values of sulfate losses, acid insoluble residues, and absorption, all of which were low, was good for the group of pure dolostones. For the group of argillaceous dolostones the correlation was also good for the average values of these parameters, all of which were high, but it was mostly poor for each of the single samples in the argillaceous group. The loss values by particle count averaged 13 percent (based on weight loss) lower than those by weight. Lithology of Harmful Substances Harmful substances can be classified in four groups according to their composition or physical properties. 1. "Clay and silt" refers to incoherent finely disseminated materials finer than 75 #m (No. 200 sieve). This includes the fine materials that occur in lenses and layers in gravel and sand deposits and the fracture fines produced by crushing gravel and rocks. Fracture fines include crusher fines consisting of grains smaller than 75 #m and crusher dust which, before washing, usually adheres to the surfaces of the crushed particles. Large SWoda, G., personal communication. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 753 amounts of dust are produced when shales, argillaceous limestones, dolostones, some sandstones and similar rocks are crushed. 2. The term "clay lumps" means lumps of clay in the aggregate which remain cohesive during processing and are not disseminated throughout the aggregate. These lumps would have to be dispersed mechanically to produce fines. The lumps contain silt or very fine sand and often are held together by clay. They do not disintegrate easily during the mixing and placing of concrete. Clay lumps and lumps of clayey silt held together by ice may survive the processing of a concrete mix. Clay lumps lose some material during processand handling, as do friable and intensely physically weathered particles. This increases the amount of fines in the concrete mix. 3. "Friable" and "soft" particles, and "lightweight" pieces, including porous chert, are usually distinctly or deeply weathered rocks or mineral agglomerations. Friable and soft particles are characterized by a poor bond between the grains. The difference between friable and soft particles is that individual mineral grains are detached easily from friable particles of any rock or mineral aggregation while soft particles consist of relatively soft mineral constituents that are structurally weak and have a low compressive and tensile strengths, and may be partly friable. Examples are micaceous minerals and gypsum [41]. Soft particles usually lose material in bits and pieces but may also lose mineral grains. Deeply weathered rocks, such as some granites and gneisses, ochers, earthy varieties of weathered iron oxides, and incompletely cemented sand- or pebble-sized particles, are designated as friable material, whereas weathered shales, soft limestones, dolostones, and sandstones with an argillaceous or limonitic matrix lacking proper cementitious properties are designated as soft or rather weak particles. Lightweight pieces include highly porous particles of rocks and minerals which float on a liquid with a density of 2.0. These particles lack frost resistance because they are saturated with water easily. The flotation test also separates pieces of coal and lignite, both of which have very low densities. Varieties of very porous weathered chert with a relatively low density are objectionable as constituents of concrete aggregates. A density of 2.40 is used to separate the usually harmful chert varieties from the harmless ones. Some aggregate particles may consist of weathered, porous, and frost susceptible chert together with its host rock limestone or dolostone. These may have a higher density and still be harmful [42]. 4. "Organic impurities" may consist of coal, lignite, plant roots, twigs, and other vegetable and animal materials. A distinction is made between discrete pieces of impurities, such as coal and lignite, and minute particles of coal and lignite finely disseminated throughout the aggregate. Organic matter, mainly tannins and compounds derived from the decay of vegetables or animal matter, may occur as contaminants in particles or as particle Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 754 TESTS AND PROPERTIES OF CONCRETE AGGREGATES coatings. Organic matter which occurs in argillaceous concentrations in sedimentary rocks usually is not determined by the test for organic impurities but it does influence the quality of an aggregate. Effect of Harmful Substances on Concrete Large amounts of fines (material finer than 75 /~m) in an aggregate increase the water requirement of concrete resulting in excessive drying shrinkage and low strength of the hardened concrete [43]. The adverse effect on concrete is greater when the fines contain clay minerals, particularly those of the swelling group such as montmorillonite, smectite, and nontronite. These minerals increase the amount of volume change in the hardened concrete and cause the formation of microcracks [44,45]. Fines in a sand that contained an unusually large proportion of nontronite, in addition to increasing the water requirement, caused very rapid early stiff. ening of the concrete mix [27]. Finely divided, dispersed clayey material in the small amounts frequently found in aggregates usually is not harmful. When clay lumps survive mixing and placing, and occur at the surface of hardened concrete, they may breakdown from freezing and thawing, wetting and drying, or wear and cause unsightly surface pits and popouts. Friable and soft particles break down easily into numerous smaller pieces. Depending upon the number of very friable particles, concrete deterioration may be general but is more often localized in the form of surface pitting or scaling [15]. Large quantities of soft particles cause a reduction in strength. Smaller quantities significantly lower the abrasion resistance of concrete surfaces exposed to severe attrition and impact. Very low density particles usually are considered unsound [46-50]. Very porous rocks, such as intensely weathered chert, friable siltstones, and dolostones, are easily saturated with water but disruption on freezing depends on many other factors [20]. Organic impurities consisting principally of tannins retard the hardening and reduce concrete strength, particularly at early ages [23,51,52]. Minute grains of finely divided coal or lignite, in sufficient quantities, will retard hardening [51], but coal and lignite are usually present as small particles which may cause localized pitting, popouts, and staining of concrete surfaces marring its appearance [15]. Coal may be sensitive to frost. Anthracite is chemically inert, but could cause surface blemishes. Brown lignite coal, fossilized wood, tall oil residues, and pine oil contain materials which readily disperse in the alkaline solution present in concrete causing dark brown local stains and weak zones. They complicate the painting of concrete surfaces. There is no simple way of separating such compounds from aggregates [53]. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 755 Tests for Harmful Substances The tests discussed below are designed to determine if potentially harmful substances occur in sufficient amounts to be harmful in a particular construction. Generally accepted limits for these substances are given in ASTM Specification C 33. Clay, Silt, and Crusher Fines ASTM Test C 117 determines the amount of fines in concrete aggregates. Particles dispersed by the wash water and water soluble materials are removed from the sample during the test. It is assumed that particles which disintegrate during washing will disintegrate during mixing of the concrete. The test does not indicate the presence of the detrimental swelling clay minerals. This information must be obtained by X-ray diffractometry or other suitable methods. ASTM Specification C 33 recognizes that the dust from nonargillaceous rocks is less detrimental than clay. The limits are increased when the fines consist "of the dust of fracture, especially free from clay or shale." Various other tests have been developed which are reported to indicate reliably the potential harmfulness of clay constituents in concrete aggregate [44]. Sand-equivalent and sedimentation tests evaluate the clay in terms of the extent to which a water suspension of the aggregate will settle in a prescribed time period. According to Gaynor [54], based on examinations of 130 samples, there is almost no correlation between the sand equivalent value and the amount of minus 75 #m material in the sand. Others have reported that the tests correlate well with the mixing water requirement of concrete which, in turn, affects shrinkage and strength. It might be surmised that, in view of the many factors which affect mixing water requirements, aggregates should be evaluated for this effect by direct comparisons in concrete mixes [1]. Experiments to determine the precision of ASTM Test C 117 have shown that the results of two properly conducted tests from two different laboratories should not differ by' more than 0.6 percent and those conducted by the same operator on the same coarse aggregate by not more than 0.3 percent. Clay Lumps and Friable Particles ASTM Test C 142 has changed over the past ten years from "Test for Clay Lumps in Natural Aggregates" (C 142-64T), to "Test for Friable Particles in Aggregates" (C 142-67), and finally to "Test for Clay Lumps and Friable Particles (C 142-71). It applies only to agglomerations and weathered particles which may be expected to remain at least partially Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 756 TESTS AND PROPERTIES OF CONCRETE AGGREGATES intact during the concrete mixing. Therefore, the test is performed after the sample has been tested foi" materials finer than 75 #m and the original fines have been washed from the sample. The remainder, which is broken down with the fingers and removed from the sample by wet-screening on sieves whose openings are slightly smaller than those of the original sieves, is classified as clay lumps and friable particles which are less detrimental than fines. The maximum amounts permitted in concrete mixtures is 1 percent for fines and 2 to 10 percent for clay lumps and friable particles (ASTM Specification C 33). The friable particles that break down during the wet-screening in ASTM Test C 117 are also expected to break down during concrete mixing. For this reason, the total amount allowed of material finer than 75 #m, in an aggregate is specified. Lightweight Pieces ASTM Test for Lightweight Pieces in Aggregate (C 123) uses heavy liquids of suitable density to separate low density particles. The samples are immersed in the heavy liquids in the saturated surface dry condition, a condition which is not obtained easily, neither for very fine-grained fractions nor for very large coarse fractions. Coal and lignite particles are separated by a liquid having a density of 2.0. They are distinguished from other low density, mostly deep weathered rock particles, by their brownish-black or black color, following the direction given in ASTM Specification C 33. Very finely divided coal or lignite is detected by the test for organic impurities. Potentially physically harmful chert is very porous and lighter than harmless dense chert. Potentially detrimental chert is distinguished by its saturated surface dry density, which is specified as less than 2.40 (ASTM Specification C 33). Formerly, to distinguish harmful chert, an option was given to use a saturated surface-dry density of less than 2.35, or 5 cycles of the sulfate test or S0 cycles of the freeze-thaw test at --17.8~ (0~ and 4.4~ (40~ emphasizing the frost susceptibility of such chert particles. Whereas lignite and coal may be separated by the less hazardous zinc chloride solution, the requirement of a heavy liquid density of 2.40 for chert means that toxic liquids must be used. Experiments have shown that sand-sized particles of chert which were detrimental in coarse aggregate size, did not damage concrete subjected to the freeze-thaw test (ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666, Procedure B)) rapid freezing in air and thawing in water [55]. The vulnerability of chert particles depends on the pore structure which relates approximately to density. Porous chert is limited to from 3 to 8 percent (ASTM Specification C 33) for aggregates in which chert appears as a minor constituent. The test for lightweight pieces Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 757 is repeatable within about 10 percent (95 percent probability level) on duplicate portions of the same sample [32]. Soft Particles It is difficult to distinguish clearly between soft and friable particles. Since 1949, soft particles have been identified by ASTM Test for Scratch Hardness of Coarse Aggregate Particles (C 235). The test has been discontinued as a standard but retained as ASTM Recommended Practice C 851. The reason for discontinuing it as a test method was the lack of consistency in results and the poor correlation of the results with concrete strength, even when the aggregate contained a high percentage of "soft" particles [15]. Soft particles sometimes were determined by visual examination but the results were poor because of the different impression of softness by each observer. Mobs hardness scale for mineral grains also has been applied for determining the hardness of rock particles, but is quite inappropriate for this purpose. The test for soft particles, using a brass pencil of specified hardness to scratch the particles is useful for quick cursory checking a sample in the field or in the laboratory before the more adequate Los Angeles abrasion test is performed (ASTM Test for Resistance to Abrasion of Small Size Coarse Aggregate by Use of the Los Angeles Machine (C 131) and ASTM Test for Resistance to Abrasion of Large Size Coarse Aggregate by Use of the Los Angeles Machine (C 535)). It is also useful in petrographic examination of physically unsatisfactory aggregate. Organic Impurities The colorimetric test for organic matter, ASTM Test for Organic Impurities in Sands for Concrete (C 40), detects harmful organic substances but unfortunately also reacts with other organic substances, such as bits of wood, which in limited amounts do not affect strength or setting time adversely. Therefore, a negative test is normally conclusive evidence that the aggregate is free from harmful organic matter, but a positive reaction (dark color) may not forebode difficulty. Some sands contain organic coatings which produce "accidental" air entrainment in a concrete mixture [36]. These volatile products derived from the anoxemic decomposition of organic matter from underlying clay beds cannot be detected by the sodium hydroxide color test. The colorimetric test is employed as a warning only and should be checked by mortar strength and setting time tests. ASTM Test for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar (C 87) uses as the basis of comparison the suspect sand after it has been Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 758 TESTS AND PROPERTIES OF CONCRETE AGGREGATES treated to remove the organic matter. Presumably, the only difference between the test and reference mortars is the organic matter in the former. The colorimetric test gives a highly reliable and reproducible indication of organic matter in sand. The check for effect on mortar strength by ASTM Test C 87 is subject to the problems of strength testing, which is discussed elsewhere. ASTM Specification C 33 allows the mortar strength ratio to be as low as 95 percent. The slight reduction allows for unavoidable testing variation. Petrographic Examinations (Addendum) Harmful substances, which occur in discrete particles, large enough to be handled, such as coal, lignite, and friable particles, can be identified most efficiently by petrographic methods. Petrographic examination 6 gives numerical data for aggregate particles consisting of harmful substances or containing them in amounts sufficient to influence the concrete quality adversely. It does not give numbers corresponding to the specified limits obtained by technological tests. The petrographic examination cannot be used for determining either the amounts of organic materials coating aggregate particles or finely disseminated minute particles of coal and lignite, nor can it be used to determine the exact amounts of clayey material in the fraction finer than 75/~m (No. 200 sieve size). However, it does identify the clay minerals. The importance of detailed petrographic examination of aggregates from areas without a service record is emphasized in a paper by Davis et al [27]. Conclusion When the sulfate test was first developed it was thought that it would help to separate aggregates susceptible to frost action from those which are resistant to it. Today the significance of the test is still evaluated by comparing the results with those from laboratory freeze-thaw tests and with the general field performance of the aggregate. The correlation with field performance and laboratory freeze-thaw results is frequently poor. Many users claim that the test is unsatisfactory while others say they obtain satisfactory results which are useful for selecting and assessing concrete aggregates. Suggestions have been made to replace the sulfate test with the freezethaw test on unconfined aggregate. This suggestion was rejected on the grounds that the test results would not reflect the performance of aggregates confined in concrete. Some researchers who recommend elimination of ASTM Test C 88 do not consider the vast number of test results available for which the aggregate behavior in concrete is known. The test is one 6See p. 539. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 759 of those often used for assessing a d e p o s i t p r i o r to t a k i n g an option for p u r c h a s e of an aggregate source. In the tests for h a r m f u l a g g r e g a t e substances clay a n d silt, clay lumps, a n d friable particles, lightweight pieces a n d o r g a n i c c o n t a m i n a n t s are included. Some of these substances increase the w a t e r r e q u i r e m e n t thereby r e d u c i n g strength a n d d u r a b i l i t y o f concrete; some m a y influence the setting time of a concrete mix, aggravate drying s h r i n k a g e (swelling clay minerals), or cause surface stains, pits a n d popouts. Finely d i s s e m i n a t e d clay a n d silt in aggregates are more d e t r i m e n t a l t h a n clay l u m p s a n d friable particles. This is reflected in the specification limits. T h e organic i m p u r i t i e s are detected readily a n d their influence on concrete strength should be checked by A S T M Test C 87. T h e test for soft particles ( A S T M Test C 235) is no longer a s t a n d a r d a c c e p t a n c e test b e c a u s e of the lesser i m p o r t a n c e of soft particles except where good a b r a s i o n resistance is required. It gives a quick p r e l i m i n a r y indication of the presence of particles which m a y be classified as soft. The general opinion seems to be t h a t the s t a n d a r d tests for h a r m f u l substances are useful, satisfactory, easy a n d quick to perform. By following up the test results a n d e l i m i n a t i n g or r e d u c i n g the a m o u n t s o f h a r m f u l m a t e r i a l s some basic concrete p r o b l e m s can be avoided. References [1] Bloem, D. L., "Soundness and Deleterious Substances," Significance of Tests and Properties of Concrete and Concrete Making Materials, ASTM STP 169A. American Society for Testing and Materials, 1966, pp. 497-512. [2] Rhoades, R. and Mielenz, R. C., "Petrography of Concrete Aggregates," Proceedings, American Concrete Institute, Vol. 42, 1946, p. 581. [3] Mielenz, R. C., "Petrographic Examination of Concrete Aggregate," Proceedings, American Society for Testing and Materials, Vol. 54, 1954, pp. 1188-1218. [4] Mielenz, R. C., "Petrographic Examination," Significance of Tests and Propert&s of Concrete and Concrete Making Materials, ASTM STP 169A, American Society for Testing and Materials, 1966, pp. 381-403. [5] Swenson, E. G. and Chaly, V., "Basis for Classifying Deleterious Characteristics of Concrete Aggregate Materials," Proceedings, American Concrete Institute, Vol. 52, pp. 987-1002; Journal, May 1956. [6] Dolar-Mantuani, L., "A Guide to Petrographic Evaluation of Natural Concrete Aggregates," in manuscript prepared for print. [7] McCown, V., "The Significance of Sodium Sulfate and Freezing and Thawing Tests on Mineral Aggregates," Proceedings, Highway Research Board, Vol. 11, 1931, p. 312. [8] Garrity, L. V. and Kriege, H. F., "Studies of Accelerated Soundness Tests," Proceedings, Highway Research Board, Vol. 15, 1935, p. 237. [9] Walker, S. and Proudley, C, E., "Studies of Sodium and Magnesium Sulfate Soundness Tests," Proceedings, American Society for Testing and Materials, Vol. 36, Part 1, 1936, p. 327. [10] Wuerpel, C. E., "Factors Affecting the Testing of Concrete Aggregate Durability," Proceedings, American Society for Testing and Materials, Vol. 38, Part 1, 1938, p. 327. [11] Wuerpel, C. E., "Modified Procedure for Testing Aggregate Soundness by Use of Magnesium Sulfate," Proceedings, American Society for Testing and Materials, Vol. 39, 1939, p. 882. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. 760 TESTS AND PROPERTIES OF CONCRETE AGGREGATES [12] Hudec, P. P. and Rogers, C. A., "The Influence of Rock Type, Clay Content and Dominant Cation on the Water Sorption Capacity of Carbonate Rocks," Abstract of paper presented at Geological Society of Canada, Annual Meeting, Edmonton, May 1976. [13] Woolf, D. O., "Relation Between Sodium Sulfate Soundness Tests and Absorption of Sedimentary Rock," Public Roads, Dec. 1927, p. 225. [14] Cantrill, C. and Campbell, L., "Selected Aggregates for Concrete Pavement Based on Service Records," Proceedings, American Society for Testing and Materials, Vol. 39, 1939, p. 937. [15] Walker, S. and Bloem, D. L., "The Problem of Deleterious Particles in Aggregates," Circular No. 35, National Sand and Gravel Association, 1950. [16] Adams, A. and Pratt, H. A., "A Comparison of Absorption and Soundness Tests on Main Sands," Proceedings, American Society for Testing and Materials, Vol. 45, 1945, p. 771. [17] Mather, Katharine, "Relation of Absorption and Sulfate Test Results of Concrete Sands," Bulletin No. 144, American Society for Testing and Materials, Jan. 1947, p. 26. [18] Bloem, D. L., "Review of Current and Projected Researches," report to Annual Convention, National Sand and Gravel Association and National Ready Mixed Concrete Association, Chicago, I11., Feb. 1960. [19] Sweet, H., "Chert as a Deleterious Constituent in Indiana Aggregates," Proceedings, Highway Research Board, Vol. 20, 1940, p. 599. [20] Verbeck, G. and Landgren, R., "Influence of Physical Characteristics of Aggregates on Frost Resistance of Concrete," Proceedings, American Society for Testing and Materials, Vol. 60, 1960, p. 1063. [21] Litvan, G. G., "Phase Transitions of Adsorbates, 4. Mechanism of Frost Action in Hardened Cement Paste," Journal. American Ceramic Society, Vol. 55, No. 1, Jan. 1972, pp. 38-42. [22] Litvan, G. G., "Frost Action in Cement Paste," Materials and Structures, No. 34, JulyAug. 1973, p. 6. [23] Lang, F. C., "Deleterious Substances in Concrete Aggregates," Bulletin. National Sand and Gravel Association, April 1931; Circular No. 10, National Sand and Gravel Association, May 1931. [24] Vollick, C. A. and Skillman, E. I., "Correlation of Sodium Sulfate Soundness of Coarse Aggregate with Durability and Compressive Strength of Air-Entrained Concrete," Proceedings, American Society for Testing and Materials, Vol. 52, 1952, p. 1159. [25] Mather, B., "Sulfate Soundness, Sulfate Attack and Expansive Cement in Concrete," International Symposium on Durability of Concrete--1969, RILEM Preliminary Report, Part 2, C209-C220. [26] Chamberlin, W. P., "Influence of Natural Sand Fine Aggregate on Some Properties of Hardened Concrete Mortar," Report No. 24, Highway Research Board, 1966, pp. 18-40. [27] Davis, R. E., Mielenz, R. C., and Polivka, M., "Importance of Petrographic Analysis and Special Tests Not Usually Required in Judging Quality of Concrete Sand," Journal of Materials, American Society for Testing and Materials, Vol. 2, No. 3, 1967, pp. 461-486. [28] Chamberlin, W. P., "Importance of Petrographic Analysis and Special Tests Not Usually Required in Judging Quality of Concrete Sand: A Discussion," Journal of Materials, American Society for Testing and Materials, Vol. 2, No. 3, 1967, pp. 482-483. [29] Tuthill, L. H. and Adams, R. F., "Importance of Petrographic Analysis and Special Tests Not Usually Required in Judging Quality of Concrete Sand: A Discussion," Journal of Materials. American Society for Testing and Materials, Vol. 2, No. 3, 1967, pp. 480-482. [30] Larsen, T., Cady, P., Franzen, M., and Reed, J., "A Critical Review of Literature Treating Methods of Identifying Aggregates Subject to Destructive Volume Change When Frozen in Concrete and a Proposed Program of Research," Research Special Report No. 80, Highway Research Board, 1964, p. 81. [31] Paul, I., "Magnesium Sulfate Accelerated Soundness Test on Concrete Aggregates," Proceedings, Highway Research Board, Vol. 12, 1932, p. 319. [32] Woolf, D. O., "Improvement in the Uniformity of the Accelerated Soundness Test of Coarse Aggregate," Bulletin No. 213, American Society for Testing and Materials, Jan. 1953, p. 42. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. DOLAR-MANTUANI ON SOUNDNESS AND DELETERIOUS SUBSTANCES 761 [33] Woolf, D. O., "An Improved Sulfate Soundness Test for Aggregates," Bulletin No. 213, American Society for Testing and Materials, April 1956, p. 77. [34] Alexander, M. L., "An Evaluation of the Effect of Sampling on the Repeatability of the Sodium Sulfate Soundness Test," California Department of Transportation, Dec. 1975, p. 20. [35] Bloem, D. L., "Sulfate Soundness Test Relationship," report to Subcommittee III-e of ASTM Committee C-9, 23 Sept. 1958. [36] MacNaughton, M. F. and Herbich, J. B., "Accidental Air in Concrete," Proceedings, American Concrete Institute, Vol. 51, 1955-1956, pp. 273-284. [37] Dolar-Mantuani, L., "Petrographic Examination of Natural Concrete Aggregates," Record No. 120, Highway Research Board, 1966, pp. 7-17. [38] Bloem, D. L. and Gaynor, R. D., "Effect of Aggregate Properties on Strength of Concrete," Journal, American Concrete Institute, Oct. 1963; Proceedings. Vol. 60, p. 1429. [39] Brink, H. R., "Rapid Freezing and Thawing Test for Aggregate," Bulletin No. 201, Highway Research Board, 1958. [40] Dolar-Mantuani, L., "Concrete Aggregate Examination by Prolonged Copper Nitrate Staining Method," Ontario Hydro Research News, Vol. 14, No. 2, Second Quarter, 1962, pp. 2-14. [4l] Lang, F. C., "Deleterious Substances," Significance of Tests of Concrete and Concrete Aggregates, A S T M STP 22 A, American Society for Testing and Materials, 2nd ed., 1943, pp. 138-144. [42] Dolar-Mantuani, L., "Harmful Constituents in Natural Concrete Aggregates in Ontario," Proceedings, 24th International Geological Congress, Montreal, Section 13, 1972, pp. 227-234. [43] Powers, T. C., The Properties of Fresh Concrete, Wiley, New York, 1968. [44] Temper, B. and Haskel, W. E., "The Effect of Clay on the Quality of Concrete Aggregates," California Highways and Public Works, Vol. 34, Nov.-Dec. 1955; Highway Research Abstracts, Vol. 26, No. 2, Feb. 1956, p. 30. [45] Lyse, I., "Tests Indicate Effect of Fine Clay in Concrete," Engineering News Record, Vol. 113, 23 Aug. 1934, p. 233. [46] Lang, F. C., "Summary of Tests on Effect of Shale in Gravel on Compressive Strength of Concrete," Proceedings. American Concrete Institute, Vol. 23, 1927, p. 592. [47] Walker, S. and Proudley, C. E., "Shale in Concrete Aggregates," Proceedings, Highway Research Board, Vol. 12, 1932, p. 273. [48] Litehiser, R. R., "The Effect of Deleterious Materials in Aggregates for Concrete," Circular No. 16. National Sand and Gravel Association, 1938. [49] Walker, Stanton and Bloem, D. L., "Effect on Heavy-Media Processing on Quality of Gravel," Circular No. 55, National Sand and Gravel Association, 1953. [50] Higginson, E. C. and Wallace, G. B., "Control Testing for Separation of Lightweight Material from Aggregate," Bulletin No. 243, American Society for Testing and Materials, Jan. 1960, p. 60. [51] Freeman, P. J., "Effect of Coal and Lignite in Sand for Concrete," Proceedings. American Society for Testing and Materials, Vol. 29, Part I, 1929, p. 328. [52] Mather, B., "Testing of Fine Aggregate for Organic Impurities and Compressive Strength in Mortars," Bulletin No. 178, American Society for Testing and Materials, Dec. 1951, p. 35. [53] "Impurities in Aggregates for Concrete," Advisory Note No. 18, Cement and Concrete Association, London, 1969. [54] Gaynor, R. D., "Investigation of Concrete Sands," Technical In)brmation Letter No. 266, National Sand and Gravel Association, 13 May 1968, p. 24. [55] Bloem, D. L., "Factors Affecting Freezing-and-Thawing Resistance of Chert Gravel Concrete," Research Report No. 18, Highway Research Board, 1963, pp. 48-60. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. STP169B-EB/Dec. 1978 W. J. M c C o y 1 Chapter 43--Mixing and Curing Water for Concrete Introduction This paper is concerned primarily with the significance of tests of various types of waters for mixing and curing concrete and makes no attempt to include the effect of quantity of mixing water. Almost all natural waters, fresh waters, and waters treated for municipal use are satisfactory as mixing water for concrete if they have no pronounced odor or taste. Because of this very little attention is usually given to the water used in concrete, a practice that is in contrast to the frequent checking of the cement and aggregate components of the concrete mix. Mixing Water A popular criterion as to the suitability of water for mixing concrete is the classical expression, "If water is fit to drink it is all right for making concrete." This does not appear to be the best basis for evaluation, since some waters containing small amounts of sugars or citrate flavoring would be suitable for drinking but not mixing concrete [1]$ and, conversely, water siutable for making concrete may not necessarily be fit for drinking. In an attempt to be more realistic some concrete specification writers attempt to insure that water used in making concrete is suitable by requiring that it be clean and free from deleterious materials. Some specifications require that if the water is not obtained from a source that has proved satisfactory, the strength of concrete or mortar made with the questionable water should be compared with similar concrete or mortar made with water known to be suitable. The Corps of Engineers, U.S. Army Specifications [2], in addition to a general description of acceptable water also states that if the pH of water lies between 6.0 and 8.0 and the water is free from orIDirector, Cement Technology, Master Builders, Cleveland, Ohio 44118. 2The italic numbers in brackets refer to the list of references appended to this paper. Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:33:06 EDT 2014 765 Downloaded/printed by Universidade do Gois pursuant Agreement. No further reproductions authorized. Copyright9 1978tobyLicense ASTM International www.astm.org 766 TESTS AND PROPERTIES OF OTHER MATERIALS ganic matter, it may be regarded as safe for use in mixing concrete. (An exception to this is the case where sodium sulfates or other natural salts are present in excessive amounts.) These specifications also state that if water is of questionable quality it should be tested in mortar cubes for which the 7 and 28 day compressive strengths should equal at least 90 percent of that of companion test specimens in which distilled water is used before it is judged to be acceptable [3]. Other than comparative tests of this type, no special test has been developed for determining the quality of mixing water, and, hence it is difficult for the man in the field to judge the fitness of water for use in concrete [4]. The two principal questions regarding mixing water appear to be how do impurities in the water affect the concrete and what degree of impurity is permissible? The following discussion is a resum6 of available information on these two items. Effect of Impurities in Mixing Water The most extensive series of tests on this subject was conducted by Abrams [5]. Approximately 6000 mortar and concrete specimens representing 68 different water samples were tested in this investigation. Among the waters tested were sea and alkali waters, bog waters, mine and mineral waters, and waters containing sewage and solutions of salt. Tests with fresh waters and distilled water were included for comparative purposes. Setting time tests on cement and concrete strength tests from 3 days to 2.33 years were conducted for each of the various water samples. Some of the more significant conclusions based on these data are as follows: 1. The time of setting of portland cement mixes containing impure mixing waters was about the same as those observed with the use of clean fresh waters with only a few exceptions. In most instances the waters giving low relative compressive strength of concrete caused slow setting, but, generally speaking, the tests showed that time of setting is not a satisfactory test for suitability of a water for mixing concrete. 2. None of the waters caused unsoundness of the neat portland cement pat when tested over boiling water. 3. In spite of the wide variation in the origin and type of waters used, most of the samples gave good results in concrete due to the fact that the quantities of injurious impurities present were quite small. 4. The quality of mixing water is best measured by the ratio of the 28 day concrete or mortar strength to that of similar mixes with pure water. Waters giving strength-ratios which are below 85 percent in general should be considered unsatisfactory. 5. Neither odor nor color is an indication of quality of water for mixing concrete. Waters which were most unpromising in appearance gave good Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. MCCOY ON MIXING AND CURING WATER FOR CONCRETE 767 results. Distilled waters gave concrete strengths essentially the same as other fresh waters. 6. Based on a minimum strength-ratio of 85 percent as compared to that observed with pure water, the following samples were found to be unsuitable for mixing concrete: acid water, lime soak water from tannery waste, carbonated mineral water discharge from galvanizing plants, water containing over 3 percent of sodium chloride or 3.5 percent of sulfates, and water containing sugar or similar compounds. The concentration of total dissolved solids in these waters was over 6000 ppm except for the highly carbonated water which contained 2140 ppm total solids. These data support one of the principal reasons for the general suitability of drinking water, for few municipal waters contain as much as 2000 ppm of dissolved solids and most contain far less than 1000 ppm. For drinking waters, 1000 ppm is the maximum permissible in some specifications [6]. Very few natural waters other than sea water contain more than 5000 ppm of dissolved solids [7,8]. 7. Based on the minimum strength-ratio of 85 percent, the following waters were found to be suitable for mixing concrete: (a) bog and marsh water; (b) waters with a maximum concentration of 1 percent SO4; (c) sea water, but not for reinforced concrete; (d) alkali water with a maximum of 0.15 percent Na2SO4 or NaCI; (e) pumpage water from coal and gypsum mines; and (j) waste water from slaughterhouses, breweries, gas plants, and paint and soap factories. Many of the specifications for water for mixing concrete, especially those which require that it be potable, would have excluded nearly all of the above waters, but contrary to this rather general opinion, the test data show that the use of many of the polluted types of water did not result in any appreciable detrimental effect to the concrete. The important question is not whether impurities are present, but do impurities occur in injurious quantities? It should be noted that the conclusions in Paragraph 7 are based entirely on tests of specific samples from the indicated sources, and it should not be assumed that all waters of the type described would be innocuous when used as mixing water. Typical analyses of natural fresh water as reported by the U.S. Geological Survey are given in Table 1. Collins [9] reports that these analyses represent public water supplies used by about 45 percent of the cities of the United States that have a population of more than 20 000. A concrete manual [10] published in Denmark in 1944 points out that humic acid and other organic acids should be avoided because their presence means a danger to the stability of concrete. An article appearing in a 1947 issue of the British publication Concrete and Constructional Engineering [11] discusses the harmful effects of using acid waters in concrete and claims that the harmful effects of organic acid Copyright by ASTM Int'l (all rights reserved); Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. cement content. The amount of sugar that can cause these different effects varies with the other factors involved.8 1.0 34.0 27.0 9.0 0. Sugar is probably the organic contaminant that causes the most concern. With still larger amounts the cement becomes quick setting and strengths are reduced for markedly for 28 days and probably permanently.0 0. The later strengths. Kleinlogel [12] in his book Influences on Concrete states that mixing water should not contain humus. and early strengths such as those for two and three days (or even seven days) are severely reduced.52 564.S. provided proper curing is maintained as required.0 434.768 TESTS AND PROPERTIES OF OTHER MATERIALS TABLE 1--Typical analyses of city watersupplies (ppm)a Analysis Number 1 3 5 Silica (SiO2) Iron (Fe) Calcium (Ca) Magnesium (Mg) Sodium (Na) Potassium (K) Bicarbonate (HCO3) Sulfate (SO4) Chloride (CI) Nitrate (NO3) Total dissolved soilds 2.0 0.6 13. sulfur.2 983. Steinour [15] explains that.0 10. although sugar as a contaminant in the field has gained a bad reputation as a retarder and strength reducer.1 165.0 11.0 9.4 0. are increased.0 0.0 aTaken from Collins [9].0 22.0 84.0 280. although the smaller amounts retard the setting.5 1. such as the composition of the cement. . they increase the strength development.02 36. A recent article in the Indian Concrete Journal [13] contains a tabulation of maximum limits for impurities in mixing water which is summarized in Table 2.7 2.0 18.7 0. or at least not affected adversely.2 119.0 6 9.0 183.54 31.08 3. however.0 0. No further reproductions authorized.0 8. or industrial wastes containing fat or acid.0 22.14 5.0 2.4 215.0 0.7 14.0 334. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.2 96.4 0. coal particles.8 549. The limits for suspended particles in Table 2 agree with the requirements of the U.1 6.09 92.0 13.0 7 22. With larger amounts the setting is further retarded.0 12.0 8. and ambient conditions.0 9. are not evident as soon as those of mineral acids. the English article [11] also states that seawater with a maximum Copyright by ASTM Int'l (all rights reserved).0 121.4 339. while deleterious salts have a greater effect on strength at an early age than at later ages. Use of Sea Water in Mixing Concrete In addition to the supporting reference previously mentioned in Abrams' paper [5].4 1.0 0.2 1. peat fiber. Bureau of Reclamation [14] which has a turbidity limit of 2000 ppm for mixing water. these judgments need qualification. Laboratory tests have shown that. Iron salts Sodium iodate. and 90 day compressive strength tests of concrete mixed with fresh water and with seawater. in reinforced concrete. Calciumchloride 6.S. an effect that can be avoided by the use of a higher cement content. Steinour [15] states the use of seawater may cause a moderate reduction in ultimate strength. 8. Sodium and potassium carbonates and bicarbonates 2. The Indian Concrete Journal article [13] pointed out that concrete made with seawater may have higher early strength than normal concrete. Impurity 1. the risk of corrosion of the steel is increased. 9. Calciumand magnesium bicarbonates 5. A paper by Liebs in the German publication Bautechnik [16] contains the results of comparative 7. and. phosphate arsenate and borate Sodiumsulfide Hydrochloricand sulfuric acids Sodiumhydroxide 11. but strengths at later ages (after 28 days) may be lower. No further reproductions authorized.5% by weight of cement is set not affected 2 000 ppm concentration of salts of the order of 3. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. of concrete although it may lead to corrosion of reinforcement. Sodiumchloride 3. Dempsey [19] describes construction of military bases in Bermuda using Copyright by ASTM Int'l (all rights reserved). Most engineers are of the opinion that seawater should not be used for mixing reinforced concrete. Seawater definitely should not be used for making prestressed concrete. . Salt and suspended particles Maximum Tolerance Concentration 1 000 ppm 20 000 ppm 10 000 ppm 400 ppm of bicarbonate ion 2% by weight of cement in plain concrete 40 000 ppm 500 ppm even 100 ppm warrants testing 10 000 ppm 0. 10.MCCOY ON MIXING AND CURING WATER FOR CONCRETE 769 TABLE2--Tolerable concentrations of impurities in mixing water. He also notes that concrete in which seawater is used as mixing water is sound but its use may cause efflorescence or dampness. There are several references in the literature which indicate that salt water has been used in mixing plain concrete without incurring trouble at later periods. Sodiumsulfate 4. The data show that the seawater concrete had about 6 to 8 percent lower strength than the fresh water concrete. Hadley [17] points out that the seawater was used in the concrete mix for the foundation of the lighthouse at the extremity of the Los Angeles breakwater which was built by the U. Engineer Corps in 1910 and that 25 years later it was examined and found to be in good condition with sharp edged corners and no disintegration.5 percent does not appreciably reduce the strength. 7. Much of the concrete in the Florida East Coast Railway was mixed with sea water with no detrimental effect due to its use [18]. 28. No efflorescence was observed. however. In some instances the staining or discoloration of the surface of concrete from curing water would not be TABLE 3--Effect of algae in mixing water on air content and strength of concrete.0 7. No further reproductions authorized. Effect of Algae in Mixing Water on Air Content and Strength of Concrete A rather extensive series of laboratory tests reported by Doell [20] has shown that the use of water containing algae had the unusual effect of entraining considerable quantities of air in concrete mixes with an accompanying decrease in strength. especially if water satisfactory for use in mixing concrete is employed.770 TESTS AND PROPERTIES OF OTHER MATERIALS coral aggregate and concludes that seawater seems to be satisfactory for making reinforced concrete and causes no problem beyond an acceleration in stiffening of the mix. one of the important aspects of these data is that considerable quantities of air can be entrained in concrete by the use of mix water containing algae.6 33.5 to 3 in.6 6. MPa (psi) none (control) 0.0 mm ( 90 maximum size aggregate concrete having a water/cement ratio of 0. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. % Compressive Strength.03 (4840) (4040) (3320) (2470) .30 (4830) Copyright by ASTM Int'l (all rights reserved). Mix Number 10 8 7 5 9 Algae in Mix Water. The latter possibility is unlikely. No harmful effect on the durability of reinforced concrete had occurred at the end of four years.9 10.09 0.75 17. 2. 28 day. % Air in Concrete.15 0. with the ratio of coarse to fine aggregate constant. The data in Table 3 were extracted from Doell's paper and are based on tests with 19. Curing Water There are two primary considerations with regard to the suitability of water for curing concrete.5 and a slump of 38. In addition to the detrimental effect on strength.86 22.). Effect of Hardness of Mixing Water on Air Content of Concrete Wuerpel [21] reports data on a series of air determination tests with waters of various degrees of hardness which show that the air content was not affected by the amount of hardness in the water.03 0.2 33. One is the possibility that it might contain impurities that would cause staining and the other is that it might contain aggressive impurities that would be capable of attacking or causing deterioration of the concrete.23 2.2 mm (1.1 to 76.37 27. In some cases 0. relatively low concentrations of these impurities may cause staining. and. Army [23].06 ppm of iron gave a moderate rust colored stain. No cleaning is required of surfaces which will subsequently be stained when the structure is in service. since considerably more water was evaporated over a unit area than would be the case in most instances in the field. Copyright by ASTM Int'l (all rights reserved). show that there is not a consistent relation between dissolved iron content and degree of staining. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.6 mm (4-in. U. The Complete Method can be used to evaluate those sources that the Preliminary Method indicates to be promising. . This method of test outlines three procedures for evaluating the staining properties of water proposed for use in curing concrete. However.04 ppm produced considerable brownish black stain. Generally speaking. The test results by each of these three methods are evaluated by visual observation.S. For these surfaces the contractor has the option of using nonstraining water or of cleaning the surface after completion of moist curing.S. U.858 m 2 (20-ft 2) slab of concrete with the test water under maximum exposure to the sun with the test slab placed at a slight angle to keep it in a wet condition with a minimum runoff.) watch glass in the surface of a neat white cement or plaster of Paris specimen. In the Complete Method. Army [22]. It is advisable to use a performance type test procedure. however. an example of which is Test Method CRD-C 401-57 of the Corps of Engineers.08 ppm of iron resulted in only a slight discoloration. the conditions of these tests were such as to accentuate the staining properties of the water. No further reproductions authorized. waters with 0. especially if the concrete is subjected to prolonged wetting by runoff of curing water from other portions of the structure [2].MCCOY ON MIXING AND CURING WATER FOR CONCRETE 771 objectionable. The most common cause of staining is usually a relatively high concentration of iron or organic matter in the water.35 litres (3 gal) of test water drips on to a mortar specimen exposed to heat lamps and forced circulation of air. 11. With respect to organic impurities in water. while 0. The Field Method is intended as a means of evaluating the water finally selected for use and involves the curing of a 1. Test data included in an unpublished Waterways Experiment Station Miscellaneous Paper by the Corps of Engineers. The latest Corps of Engineers Standard Practice Manual for Concrete [24] notes that the Standard Guide Specifications do not require that water be nonstaining. it is virtually impossible to determine from a chemical analysis if the water would cause objectionable staining when used for curing concrete. in other cases. the manual does clearly state that there must be no permanent staining of surfaces where appearance is important. The Preliminary Method is intended for use in selecting sources that are worthy of more complete investigation and consists of evaporating 3000 ml of the test water in the concave area formed by the impression of a 101. " Bulletin No. In the case of seawater. which upon casual examination would be judged to be unsuitable because of color. N. would be found to be satisfactory when tested in mortar or concrete since in many instances the strength would be greater than 85 to 90 percent of the strength of comparative specimens made with pure waters. March 1929. or contamination with impurities as in the case of marsh water. [4] Bauer.. "Effect of Sugar of Concrete in Large Scale Trial. [5] Abrams. 1946. . a strength reduction ranging from 8 to 15 percent can be expected depending on job conditions. 2730. D." Public Roads. Aug. Many waters. the suggested performance tests [21] will determine if a water possesses any potential staining qualities. pp. [8] Giesecke. G. but algae can entrain air and significantly reduce strength. "Effect of Alkalies on Strength of Mortar. M. 473. [6] Public Health Service Drinking Water Standard. Army. Organic matter or iron in the curing water can cause staining or discoloration of concrete. The hardness of water does not affect air content of concrete. but this is rather uncommon especially where a relatively small volume of water is used. "Effects of Various Salts in the Mixing on the Compressive Strength of Mortar. F..." CRD-C 406. American Concrete Institute. alkaline sulfate waters. U.. E.. "Tests of Impure Waters for Mixing Concrete. and Parkinson. 25-27. p. Washington. New York." Proceedings. seawater ordinarily is not recommended for use as mixing water in reinforced concrete. [2] "Requirements for Water for Use in Mixing or Curing Concrete. C. Handbook for Concrete and Cement. [3] "Method of Test for Compressive Strength of Mortar for Use in Evaluating Water for Mixing Concrete. D.772 TESTS AND PROPERTIES OF OTHER MATERIALS Summary Mixing Water The significance of the foregoing information presented indicates that any naturally occurring or municipal supply waters suitable for drinking purposes can be used as mixing water for concrete and that most naturally occurring waters ordinarily used for industrial purposes are satisfactory. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Curing Water It is improbable that a water used for curing would attack concrete if it were of the type suitable for use as mixing water. 1949. 1924. Department of Health Service. odor. Plain Concrete. 82. No further reproductions authorized. Engineering Research Series.. and water containing industrial wastes. [7] Proudley. 3rd ed. University of Texas. 20. E. Army.S. Vol. Copyright by ASTM Int'l (all rights reserved). A. however. McGraw-Hill. E. 1924.. Corps of Engineers." CRD-C 400.S. A. E. Vol. 442-86. p. 1927. C. however. Handbook for Concrete and Cement. References [1] Clair. U. Corps of Engineers. U. pp." Engineering NewsRecord.S. 5. 36. 1963. 333-342. Vol. pp. Sun Apr 6 21:33:06 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Influence of Mixing Water Hardness on Air Entrainment. Army. 2. Corps of Engineers. No.S. [13] "Requirements of Mixing Water for Concrete. "Concrete Mix Water-How Impure Can It Be?" Journal. 44-197.S. 3. 44. American Society for Testing and Materials. Portland Cement Association. March 1963. 1940. pp. [19] Dempsey. Copyright by ASTM Int'l (all rights reserved). "Letter to Editor.S." Title No. Standard Practice for Concrete." Concrete and Constructional Engineering . No further reproductions authorized. 42. Influences on Concrete." Proceedings.. . "Typical Water Analyses for Classification with Reference to Industrial Use. [23] "Method of Test for the Staining Properties of Water. 1963. Research and Development Laboratories. p. [11] "Water for Making Concrete. London. E. 1949. Vol. [12] Kleinlogel. "Coral and Salt Water as Concrete Materials. 315-316. 113." Waterways Experiment Station Miscellaneous Paper. American Concrete Institute.. D. p. [24] Engineer Manual. [20] Doell." CRD-C 401-57. Bureau of Reclamation. pp. Corps of Engineers. H. 39. "The Effect of Algae Infested Water on the Strength of Concrete. May 1935.. W. Army. [15] Steinour. U. U. pp.. [21] Wuerpel. 1944. Denmark. 158. 25. [17] Hadley. and Nielsen. Dec. Vol." Indian Concrete Journal." Proceedings. 1948. U. No. American Concrete Institute. 98. G. Vol. Corps of Engineers. 1954. A. C. B. pp. Army. Department of Interior.. [10] Plum. Handbook for Concrete and Cement. pp. p. pp... 1057-1061. Vol. 1951. 1953. Vol." Engineering News-Record. J." Proceedings. p. p. W. pp.S. [22] "Water for Use in Mixing or Curing Concrete. N. H. H.MCCOY ON MIXING AND CURING WATER FOR CONCRETE 773 [9] Collins. 313-314. Homer." Bulletin No. reprinted from an editorial "Water for Making Concrete." Proceedings." Proceedings. 48. American Concrete Institute. 74. New York. Proceedings. Frederick Ungar Publishing Co. 401. p.. [14] Concrete Manual. unpublished." Bautechnik. 165. 1947.. 38. 416-16. American Concrete Institute. [18] "Job Problems and Practice. 716-717. "The Change of Strength of Concrete by Using Sea Water for Mixing and Making Additions to Concrete. "Concrete Manual. 42. U. C. Vol. 1960. 95. 1944. [16] Liebs. 1946. Christiani. 32-50. 10. 44. American Concrete Institute. Copenhagen. EM 1110-2-2000. "curing is the process of maintaining a satisfactory moisture content and a favorable temperature in concrete during the period immediately following placement so that hydration of the cement may continue until the desired properties are developed to a sufficient degree to meet the requirements of service" [1]. No further reproductions authorized. Pittsburgh. low resistance to abrasion. Inadequate or improper curing may result in the physical disruption of the hydration cement gel products or in a low extent of cement gel formation (hydration). 15216. Numerous studies have shown that improper curing results in a variety of undesirable effects. Generally. moist environments having moderately low temperatures provide optimum curing conditions. These conditions allow the cement to hydrate to the fullest extent possible within the physical-chemical limitations which always constrain complete hydration. "use" must be considered in the definition. Pa. Carrier 1 Chapter 44--Curing Materials Introduction Environment adjacent to and within a freshly placed mass of portland cement concrete has a profound influence on the ultimate strength and durability which the concrete will exhibit. Curing requirements may differ substantially depending on the ultimate use intended for the concrete. and other properties--it is usually desirable to advance hydration to the maximum extent possible through maintenance of a favorable curing environment. As a minimum. structural concrete as used in beams. high permeability. dusting. Copyright by ASTM Int'l (all rights reserved). (generally moderate to high surface tVice president. 2The italic numbers in brackets refer to the list of referencesappended to this paper.org . Hence. Temperature and moisture are the two most significant environmental properties. scaling. E. such as lower strength.astm. etc. Sun Apr 6 21:31:11 EDT 2014 774 Downloaded/printed by Universidade do Gois pursuant Agreement. cement factor. columns. and low resistance to weathering. Copyright9 1978tobyLicense ASTM lntcrnational www. Ackenheiland Associates. several types of cracking.2 Examples of uses which differ significantly from the standpoint of curing requirements are mass concrete as used in dams (a relatively small surface area per unit volume of concrete). or both. For a given concrete--one having a fixed water/cement (w/c) ratio.STP169B-EB/Dec. 1978 R. minimal strength is required. High surface strength resists abrasion. The rate of hydration reaction is controlled to a large extent by temperature. refrigerant systems consisting of coolant pipes are placed in the fresh concrete during placement of massive pours. nonmassive placements having large exposure areas (for example. In the Hoover Dam. Cooling water at 10~ (50~ and lower was circulated through the tubing as soon as placement was complete. Heat liberation. Thus. strength is perhaps the most important and desired property. In massive construction. the expanding ice in the plastic concrete causes a permanent increase in the Copyright by ASTM Int'l (all rights reserved). The desired service properties of these three types of concrete are also widely different.5 m (5 ft) left of concrete. There are a number of physical factors which influence the selection and specification of the curing process and materials. In structural concrete. If this water freezes. Similarly. In short. It is important to ensure that freezing does not occur to fresh concrete. for example.CARRIER ON CURING MATERIALS 775 area per unit volume of concrete).75 m (5. normally amounts to about 100 cal/g of cement. At temperatures near or slightly below 0~ (32 ~ the rate of hydration and thus early strength gain is nil. First. this amount of heat can be reduced to 60 to 70 cal/g by reducing the cement factor and percentage of high-heatproducing cement compounds. uniform strength is the principal requirement. . Two conditions are necessary in order for damage to occur. In highway or floor slab concrete. For mass concrete. Frequently. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the concrete must be at an early enough stage of curing to still contain large quantities of bulk or uncombined water. Curing must be such that hydration proceeds relatively quickly and uniformly throughout the entire cross section of beams and columns. tricalcium silicate and tricalcium aluminate. commonly referred to as the heat of hydration. Temperature Effects Hydration of cement is an exothermic process. the concrete temperature. Adequate curing is particularly important for the cement which surrounds the reinforcing steel. No further reproductions authorized. and highways or floor slabs (high surface area per unit volume of concrete). Apart from the uses of concrete described above. cracking.5 cm (1 in. loops of 2. a wide range of acceptable curing methods and materials presently are being used.75 ft) on center for each 1. but low heat of hydration is important. not the air temperature. must drop below 0~ (32~ Second. Adequate curing of interior concrete in a mass concrete structure is virtually ensured since it is surrounded by additional concrete.) 14 gage tubing were spaced 1. thin floor slabs) may remain plastic for much longer than normal periods at these temperatures. and weathering. curing requirements as specified in construction practice may differ markedly due to the differing intended uses of concrete. several of the more important physical properties which affect and are affected by the curing process are dealt with below. the hydration reaction.776 TESTS AND PROPERTIES OF OTHER MATERIALS porosity of the concrete. to maintain adequate temperatures in curing concrete and to minimize evaporative losses. In this case. as measured by the number of cycles to a 25 percent weight loss. This may occur when the heat of hydration for a relatively Copyright by ASTM Int'l (all rights reserved). foundations. As hydration of freshly mixed concrete progresses. and the like can cause overheating damage to concrete. damage may result. a minimum initial curing time of at least 36 h at 20~ (68~ is necessary. Should this chemically free water then be subjected to freezing. if fresh concrete has been maintained for several days at lower temperatures prior to freezing. the ice crystals which form may disrupt the hydration products which have formed. Another common misconception relative to winter concreting is that there is no danger of freezing of fresh concrete which has cured for several days. If the temperature of fresh concrete of typical mix proportions has been maintained at or above about 13 ~ (55~ for several days prior to freezing. No further reproductions authorized. Durability. being retarded by low temperatures. provided that no additional water is supplied to the curing concrete. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. A common misconception relative to winter concreting is that calcium chloride (dissolved in the mix water at the rate of not more than two percent by weight of cement) acts as an antifreeze. there is little danger of detectible strength loss due to freezing. Rather. Insulation in winter concreting of certain members such as bridge piers. The modulus of rupture may also be reduced by as much as half the normal value. water quantities. Probably more damage occurs due to curing at too high a temperature than too low. For virtually no change in flexural strength. Freezing after a minimum curing period of 24 h at 20 ~ (68 ~ causes only slight reductions in the compressive strength. may be reduced by more than half. has consumed very little of the original mix water. Generally the insulation blankets currently in use serve two purposes. Where ambient temperatures fall below 5~ (40~ insulation is considered desirable by many specifying agencies. However. The mechanisms. However. Prolongation of freezing conditions can result in excessive heaving in the concrete. hastening the hydration reaction if and only/fthe temperature of the mixture is well above freezing. even in winter concreting. some free water becomes combined chemically with the cement and some is drawn into smaller capillary spaces. thereby diminishing the ultimate strength. . it acts as an accelerator. Early frost damage in concrete can result in the loss of about half of the compressive strength. and curing periods associated with early freezing problems have been the subject of numerous research projects [2]. the ultimate temperature below freezing is not related to the magnitude of damage except with respect to the extent of concrete affected. thus reducing the strength and durability of the concrete. The temperature at which this capillary water freezes becomes progressively lower as the capillary diameter decreases. This is not to say that it is not desirable to both insulate and heat concrete placed in the winter. It is also important that there be no interruption in the availability of water to hydrating particles during the early curing period. Cement gel precipitates only into water-filled space. These techniques do not replace the need for insulation. Ordinarily the temperature of curing concrete should not exceed about 71~ (160~ High temperatures may cause rapid evaporation of the mix water (appears as drying of exposed edges of the member). This is demonstrated most obviously by the inability of cement gel to fill air cavities such as entrained air bubbles in concrete. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. As shown in Fig. curing practices should be such as to keep concrete as nearly saturated as possible until the originally water-filled space has become filled with hydration products. mix water and sometimes aggregates are heated prior to mixing with cement.CARRIER ON CURING MATERIALS 777 massive placement is contained too tightly within the insulation blankets. . This allows a more uniform initiation of the hydration reaction and may be particularly valuable for structural concretes. Evaporative sprays over aggregate stockpiles or ice melted in the mix water are used where the combined effects of solar exposure and heat of hydration raise concrete temperatures to about 40~ (100~ or higher. and random cracking are also related to high early temperatures. if not uniform throughout the curing mass. once the capillary Copyright by ASTM Int'l (all rights reserved). cracking occurs. Apparently. 2. Also high temperatures. mix water frequently is cooled to avoid problems associated with rapid set. The important criterion is that concrete temperature be maintained in the range of 5 to 71~ (40 to 160~ In addition to insulation for winter concreting. For hot weather concretes exposed to solar radiation. if curing water is denied for a period sufficient to allow curing concrete to dry. No further reproductions authorized. Moisture Effects The precise mechanism by which hydrating cement gains strength is still incompletely understood. Hence. excessive shrinkage. Flash set. even after long periods of subsequent moist curing. If large variations occur before the concrete has developed sufficient strength to resist the resulting thermal stresses. it never again regains the strength of continuously moist cured concrete. Figure 1 shows some general relationships between strength at various ages for different curing temperatures. may cause physical disruption. It is known that cement gel is the precipitated product formed during the chemical combination of cement and water. The optimum curing temperature is usually considered about 32~ (73 ~ Curing at lower temperatures may give slightly higher 28-day compressive strengths whereas curing at higher temperatures may increase the early strength at the expense of 28-day and ultimate strength. thus curtailing the hydration reaction in those areas. 3) and is negligible below 0. / .Ploced And Cured M o i s t At Tempero lures Indicoted ' 0 u 0 I 3 7 28 AGE OF T E S T . . DAYS FIG. self-desiccation which is caused by the consumption of water during hydration occurs. a~ ~ . m ~ 30 i/ (n ILl a. 20 > .. Generally.. plus the curing water which must be added to keep the cement saturated. the volume of mix water added to concrete is sufficient to allow adequate curing.~-- - / ~ _ _ .80 is relatively low (see Fig.. ' " ' // / I0 / .~_. 80 / . n.. For maximum hydration. 9O ~z tu u . I10 C3 ~00 . No further reproductions authorized.80 of the saturation pressure (or about 80 percent internal relative humidity). Design and Control of Concrete Mixtures).-s-s ~ . concrete must be kept saturated or as nearly so as is practical. / Concrete Mixed.- '" . . Air dried concrete cylinders are approximately 15 to 30 percent stronger than the same concrete when saturated (either before drying or after being soaked for 15 to 30 hours). continuity to interior areas of hydrating cement is broken. Powers [3] and others [4-6] have shown that portland cement virtually stops hydrating when concrete dries to the point where the internal relative vapor pressure falls below about 0. Copyright by ASTM Int'l (all rights reserved).30. In some respects.. . 1--Relationships between strength and curing age for concrete cured at various temperatures (from Portland Cement Association Manual. 5 0 li: ~or) o 40 ~f[. . ..44 g of water per gram of cement.30 and 0. it is never again fully regained by the addition of moisture. self-desiccation is desirable. If no curing water is added.+#~~//:"""+P uJ j- = == . Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ~ -~--.~f w 70 '8 "1- 60 "z .oso___ _ _ .' . Maximum hydration for an average cement (which is usually distinct from complete hydration) requires about 0.778 TESTS A N D PROPERTIES OF OTHER MATERIALS >. The hydration rate for relative vapor pressures between 0. J ~.. autogenous healing is enhanced. especially where concrete members are in contact with soil. but results achieved over the years have proven satisfactory.9 Z I. Water in larger capillaries is consumed by self-desiccation. Membrane curing does not assure as full an extent of hydration as water or moist curing. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ~.~. Another phenomenon. .. Copyright by ASTM Int'l (all rights reserved)..Z hi U ~ 140 12: W Q. 2--Strength of concrete increases while moisture and unhydrated cement are still available. Membrane curing has also become much more economical than the former wet covering techniques for many continuous-production concrete uses such as highways. MOIS" CURED.. Efforts to prohibit the evaporative losses of large quantities of mix water during the early stages of curing by the application of membrane coatings are desirable..- ~ ~ f ] / ... 0 U ~'" ~Z 1 2 0 . Note delayed strength rise when moist curing is resumed (from Portland Cement Association Manual./ //< 100 | 3: (.R 2B DJYS IN AIR ~. IN AIR . known as autogenous healing. for example) may occur late in the life of the concrete member due to hydrating of previously unhydrated cement. FTER I YEA IN AIR.. [/ 3 -.4O o 0 W 9 20 0 O 50 IOO 150 200 250 AGE AT TEST-DAYS 3OO 350 400 0 S. The remaining water is drawn preferentially into the smaller capillaries where it is much less susceptible to freezing. No further reproductions authorized. Design and Control of Concrete Mixtures). If substantial quantities of unhydrated cement are available because of early cessation of the hydration reaction. is enhanced by selfdesiccation of curing concrete. IST CURI!D AFTER IONTHS N AIR MOI!|T CURl O _________- NTIRE T ME AFT '.CARRIER ON CURING MATERIALS 779 Q 1%1 tlL 0 MOIST C JRED ENTIRE T I M E ' ~ 160 I.J FIG. Autogenous "healing" across fine cracks or in weakly bonded areas within the matrix (between cement paste and aggregate. One final advantage of selfdesiccation is the improvement in freeze-thaw resistance.I e: 60 ] ::~. .08 w . Absorbent forming materials may be sprayed with a hydrophobic material or oiled to retard moisture loss. c9 20 Z w U >m Q.36 IZ bJ . Moisture losses other than the physical and chemical uptake of water by the hydration process occur by evaporation. . 0 ..EVAPORATED WAT ER (. bleeding..32 . absorption by certain forming materials.12 Z ILl Fn. No further reproductions authorized.- ./. 20 40 60 RE LATIVE HUMIDITY 80 I00 3--Amounts of water taken up by dry cement exposed to water vapor 6 months (from Ref 4). Evaporation may be controlled by reducing exposed surface Copyright by ASTM Int'l (all rights reserved).2 4 f. excessive bleeding may render a freshly applied membrane-forming compound ineffective by disrupting the continuity of the membrane. u u. For example.~ 28 "~ O T A L WATER N O N .780 TESTS AND PROPERTIES OF OTHER MATERIALS . and by gravity-induced flow. D . Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement..04 / 0 0 FIG.40 .) n. Control of each of these losses may be achieved by a different technique.9 tr "Q_ ' . Methods of Curing Three general methods for curing are in common use in the field: (a) low permeability sheet materials. and low relative humidity) the internal relative humidity 5 cm (2 in. These facilities usually include temperature control intended to accelerate the hydration process. Drying shrinkage cracks are a random pattern though they frequently reflect edge drying.) below exposed concrete surfaces remained sufficiently high to allow curing to proceed for at least 28 days (see Fig. and are relatively short. Low permeability sheet materials and membrane-forming compounds are Copyright by ASTM Int'l (all rights reserved). the upper 0. The most significant single factor affecting the magnitude of volume change and associated cracking in concrete is moisture content. Not all curing concretes require additional effort by man. have relatively wide openings at the exposed concrete surface. However. sheet material) beneath the fresh concrete. Concrete curing behind forms. weathering. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. gravity and bleeding losses may be controlled most effectively by altering mixture proportions. Early volume changes due to bleeding are usually not serious (excluding prestressed concrete) since significant stresses cannot develop in plastic concrete. (b) low permeability membrane-forming films. They are usually good indicators of inadequate early curing. Gravity losses may be partially controlled by placing an underlayment barrier (for example. for example. This experiment points out the importance of adequate curing for surface concrete which. fog sprays used on bridge decks). especially where a set retarder has been used in the concrete. Temperatures are raised at a uniform rate of not more than about 20~ (40~ for larger units and about 3S~ (6S~ for smaller sizes until a maximum of 71~ (160~ is reached.CARRIER ON CURING MATERIALS 781 area (for example. or other deteriorative mechanisms. typically does not require additional moisture. they are caused by rapid drying of fresh concrete surfaces. No further reproductions authorized.) of concrete dried to the point where curing activity virtually ceased in slightly more than 1 day. consists of immersion in lagoons or placement in enclosures maintained at high relative humidity. Plastic shrinkage cracks are relatively shallow. used extensively at concrete products manufacturing plants. in service. 4). with sheet coverings) or by increasing the relative humidity in the air immediately adjacent to the concrete member (for example. usually of polymer materials. As their name implies. and (c) wet coverings such as burlap or wet sprays. Research has shown that cracks associated with early volume change can be greatly reduced through adequate curing. is exposed to abrasion. high early evaporative losses. Conversely. However. Studies [8] show that even for moderately severe exposures (high temperatures. particularly from high unit water content mixes can cause drying shrinkage and plastic shrinkage cracks.65 cm (1A in. . sprayed or otherwise applied like paints. A fourth method. high wind velocity. such as polyethylene or combinations of plastic with fibers or fabric for strength. ~'0o10 11 NOTE: 100% = 200sq. most curing compounds flake off (with the possible exception of asphalt emulsion or similar flexible coatings). It also may provide some temperature control. It is applied either immediately after casting fresh concrete. . . or fog sprays frequently are used where the strength of the surface concrete may be critical to the life of the entire structure. Plastic films. . 4--Moisture distribution with depth at 28 days for specimens sprayed with various applications of white pigmented curing compound and subjected to a severe exposure (from Ref8). Some of these sheet materials have a burlap-like texture on their underside. Copyright by ASTM Int'l (all rights reserved). White sheet coverings and white pigmented curing compounds usually are specified for concrete exposed to solar radiation. 20 o/ t I I ! '/. After several months. reinforced with fibers and treated to reduce shrinkage. is effective in retarding moisture loss.782 TESTS A N D PROPERTIES OF OTHER MATERIALS I00 so .V~ DEPTH BELOW SURFACE I 2 (INCHES) FIG. Wet coverings. . i . such as for concrete bridge decks. rt.- a ~ ~ - - .oo ~ " > < " ~ S ~ ' . or it may be applied subsequent to a preliminary wet curing by fog spray or wet burlap.lgal. No further reproductions authorized. depending on the use and exposure of the sprayed surfaces. Temperature control for concrete placed in the summer months or in warm climates is achieved commonly through the use of white or reflecting curing materials. soaker hoses. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement./ 40 ~ j ~ ' IX/ ~ . They dry rapidly resulting in a continuous film which retards moisture egress from the curing concrete. . Liquid membrane-forming compounds typically are sprayed on exposed surfaces of freshly placed concrete after the water sheen has disappeared.-V. are used in the same manner as water resistant paper products. V. used principally where the supply of water is limited or where an excessive investment in piping or water trucking is required to maintain wet coverings. Water resistant paper. there is a trade off between reflectance and moisture retention properties. produce concrete having superior strengths. At least one state highway department has attempted to measure the field application rate by laying an absorbent fiat-lying paper material of known weight on the pavement just prior to passage of the curing compound spraying machine. white pigmented and clear or translucent. It is most difficult to determine the field application rate for sprayed compounds. Copyright by ASTM Int'l (all rights reserved). but becomes inconspicuous after a week's exposure or less in sunlight. Excessive bleeding can also disrupt the continuity of an otherwise appropriately applied membrane. the wet curing methods. Hence. Experiments [8] show that for lightly textured surfaces. however. It is generally fairly easy to detect nonuniform applications of white pigmented curing compounds by the alternating white and gray colors of freshly sprayed surfaces. allowing small quantities of mix water to escape from the hydrating concrete. . The moisture-retaining effectiveness of sprayed membranes is not as heavily dependent on the application rate as it is on the constituent ingredients of the film and the continuity of coverage the film exhibits on a microscopic scale.CARRIER ON CURING MATERIALS 783 Effectiveness of Curing Methods Of the three curing methods cited. thus rendering it ineffective in moisture retention. After spraying the surface. No further reproductions authorized. if properly carried out. No widely accepted standard test is available.) or greater. at least for depths of 2. applications of from one half to two times the normal application rate of white pigmented curing compound are effective in maintaining the 28-day internal relative humidity of curing concrete at or above the 80 percent level. this method is used rarely. The dye is readily visible immediately after spraying. Two types of compounds are used widely. Still another method suggests visually comparing the whiteness of field sprayed concrete with that of a laboratory prepared mortar plaque sprayed at the specified rate. To aid in determining uniformity of coverage of clear or translucent compounds--for that matter to aid the person doing the spraying in differentiating what has been sprayed and what has not--a fugitive dye is frequently added. Sheet materials and membrane films each have finite permeability. Sheet materials and membrane-forming compounds are not as effective principally because less moisture is available to promote hydration. excessive pigmenting of the membrane vehicle may reduce moisture retention efficiency.5 cm (1 in. While solar reflectance is desirable in some instances. the sprayed paper is weighed again to determine the application rate. If applied too early--before the water sheen has disappeared--the membrane becomes scaly and exhibits discontinuities upon drying. Experience has shown that the time of application may affect moisture retention properties more significantly than the thickness of the film. In practice. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. made with standardized mix proportions and mixing procedures. polyethylene film. . ASTM Test for Water Retention by Concrete Curing Materials (C 156) provides a laboratory technique for estimating the efficiency of membrane-forming compounds and sheet materials. Sheet materials are laid over the surface of the plaque and sealed at the edges with a sealing compound. each allow a maximum moisture loss of 0.4 ___ 3~ 50 percent relative humidity. Acceptable compounds must possess a certain long term pigment settling resistance and must adhere to but not be deleterious to concrete surfaces. membrane curing compounds must dry to the touch after a 4-h exposure at 23 + 1. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Minimum tensile strength properties and minimum percent elongation are specified.7~ (73. In this test. A minimum percentage reflectance is specified for white or reflecting sheets and compounds as tested by ASTM Test for 45-deg. are finished so that their surfaces have a very light texture. Each of these are in common use. moisture loss is measured by weight for a freshly mixed mortar plaque specimen subjected to 72 h of exposure in a cabinet held at 37. Further. compounds must not be tacky or track off concrete when walked upon after 12 h. This is particularly true for concrete members which do not lie horizontally or for those with deep textures such as is now done in pavement construction.055 g/cm 2 through the membrane during the aforementioned 72-h test.8 ___ 1. and ASTM Tests for Tensile Properties of Thin Plastic Sheeting (D 882). Membrane compounds must have a consistency which allows them to be sprayed readily at 4 ~ (40 ~ These test methods are intended principally to assess the characteristics of Copyright by ASTM Int'l (all rights reserved). and white burlap-polyethylene.1~ (100 ___ 2~ and a relative humidity of 32 +_ 2 percent. No further reproductions authorized. Tests and Their Significance Water retention capability is perhaps the most significant property of a curing material. These properties are tested according to ASTM Tests for Wet Tensile Breaking Strength for Paper and Paper Products (D 829). Curing compounds are sprayed or brushed on the surface at the rate of 0. and ASTM Specification for Liquid Membrane Forming Compounds for Curing Concrete (C 309). curing period. 0-deg Directional Reflectance of Opaque Specimens by Filter Photometry (E 97).784 TESTS AND PROPERTIES OF OTHER MATERIALS Other properties which may affect a membrane's effectiveness are its viscosity. Both resin and petroleum or natural (the so-called "wax bases") vehicle solids are used. The same plaque specimens are used for testing the moisture retention efficiency of sheet materials. and an air velocity of approximately 183 m/min (600 ft/min) passing horizontally across the specimens. The mortar plaques. In addition to the above described water retention and reflectance criteria. Curing compounds may flow from the ridges of the texture to the sag areas.2 dm3/m2 (1 gal/200 ft2). and sag characteristics. ASTM Specification C 171 identifies three types of sheet materials: waterproof paper. ASTM Specification for Sheet Materials for Curing Compounds (C 171). The tests are significant only as base or minimum criteria for curing materials. and the texture and exposure conditions of the concrete surface to which curing materials are being applied. (b) No curing. Many variables affect the field performance of curing materials. the condition and age of the surface concrete at the time of application of membrane-forming compounds. No widely accepted standard test is available for testing the moisture retention performance of concrete constructed in the field. 5--Two specimens made from same concrete mix showing the effects of curing on abrasion resistance of concrete (from Ref 9). the air flow under or around sheet materials (particularly at edges or corners). Evidence suggests that even the application of a second coat of curing compound on heavily textured surfaces may not assure adequate moisture retention. Among the most important are the type of water used with wet curing methods. FIG. Sound judgment by knowledgeable and experienced concrete specialists must be exercised to achieve strong durable concrete. but has not gained wide acceptance. particularly where surface properties are important. (a) Membrane curing compound. Figure 5 profoundly demonstrates the importance of curing for surface concrete. .CARRIER ON CURING MATERIALS 785 concrete curing materials. the heat transmission/absorption properties of sheet material or insulation/curing materials. The fact that a particular curing material is acceptable by ASTM standards does not ensure that its performance in the field will be adequate. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Copyright by ASTM Int'l (all rights reserved). A small surface mounted device for visually estimating relative humidity through color change at the surface of concrete members has been proposed [8]. They do not provide information on whether curing of field constructed members is adequate. For example. a membraneforming compound may perform adequately on a pavement having its surface prepared with a burlap drag but inadequately on rougher pavement surfaces prepared with a rake of textured float. No further reproductions authorized. Abrasion tests and impact or penetration resistance may provide valuable performance information as to the adequacy of curing at the surface. pp.. pp. [5] Rodt. 178-188.. Vol. Vol. V. [2] Cady.. and Prior. 7. D. pp. Portland Cement Association. Hochschule Leoben. p. Springfield. E. "Abrasion of Resistance." Pennsylvania State University Special Report No. R.. 1955. "Evaluating Effectiveness of Concrete Curing Compounds." Significance of Tests and Properties of Concrete and Concrete Aggregates A S T M STP 169. Hi~ttenmiinn Jahrb. 25. No. and Cady. 69. T. 5. . American Society for Testing and Materials. American Society for Testing and Materials. 1. Vol. D. PB 183-602. [8] Carrier.." Journal of Research. No. March 1962. C. Highway Research Board. 163-174. 27.786 TESTS AND PROPERTIES OF OTHER MATERIALS References [1] "Curing of Concrete Pavement. and Carrier. R. revised edition. 520. 1947. 14. M." Current Road Problems. J. p. No further reproductions authorized. U. L. Copyright by ASTM Int'l (all rights reserved). 2. [9] Kennedy. 2. National Bureau of Standards. [4] Jesser. Va. Clearinghouse.. 1940. and Berg. H. 75. Zement. 1925. E. 294-302. 403-416. G. T-12. No. R. C. L. 1927. 1952.. Vol. pp. P. [71 "Design and Control of Concrete Mixtures. "A Discussion of Cement Hydration in Relation to Curing of Concrete. June 1970. "Method for Determining the Moisture Condition in Hardened Concrete. p. Vol. [6] Gause.. and Tucker." Proceedings. rnontan." Bulletin No. Sun Apr 6 21:31:11 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. "Methods For Analysis of Hardened Concrete: Early Frost Damage. P. [3] Powers. 1-R Highway Research Board." Journal of Materials. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:47:39 EDT 2014 787 Downloaded/printed by Universidade do Gois pursuant Agreement. This report is concerned with the class of materials. In these early instances. Concrete Materials Research Department. particularly when chemical deicers are being used. Research and Development Laboratories.org . Portland Cement Association. Materials similar to presently used additions are called air-entraining admixtures when added with the other concrete ingredients at the time of mixing." Other investigators [2-6] came to similar conclusions during the late thirties and early forties. 2 The following paragraph from Gonnerman's report is of particular significance. 60076. the air entrainment was not intentional but resulted from the pre~ence of the crusher oil or the use of the tallow as a grinding aid during the production of the cement. how can they be 1Director. What are these materials. but they did show clearly that portland cement that inadvertently contained "crusher oil" reduced surface scaling as did many of the blends of portland and natural cement that contained tallow added during grinding of the natural cement. "These projects (test roads constructed in 1935-1937) revealed no relationship between surface scaling and composition of the cement. These were the forerunners of the materials now used to produce air-entraining cements and called additions.STP169B-EB/Dec. 1978 Paul KEeger 1 Chapter 45--Air-Entraining Admixtures Introduction The use of intentional air entrainment in concrete is a well-established means of greatly enhancing the ability of concrete to resist the potentially destructive effect of freezing and thawing. Its use should be mandatory when concrete is to be exposed to such an environment. Laboratory tests disclosed that the beneficial effect of the crusher oil and tallow was due entirely to the additional air entrapped in the concrete by these air-entraining agents. both as to the process of entraining air and enhancing durability. Skokie.astm. No further reproductions authorized. A thorough survey of the early development of air entrainment is presented by Gonnerman [1]. 2The italic number in brackets refer to the list of references appended to this paper. as on pavements and bridge decks. Ill. Copyright9 1978tobyLicense ASTM International www. how do they function. Entrained Air Voids--Air voids resulting from the use of intentional air entrainment. but the following definitions appear appropriate. (3) salts of sulfonated lignin (paper pulp industry). (See ASTM Definition of Terms Relating to Concrete and Concrete Aggregates (C 125) for the definition of an admixture. Entrained Air--The air. Such voids are generally spherical in shape and considerably smaller than the natural air voids. (2) synthetic detergents (petroleum fractions). the use of which results in intentional air entrainment. or to be interground with. made up of discrete air voids. (See ASTM Definition of Terms Relating to Hydraulic Cement (C 219) for a definition of an addition. hydraulic cement. (6) fatty and resinous acids and their salts (paper pulp and animal hide processing). which becomes part. This listing is by no means complete. (4) salts of petroleum acids (petroleum refining). Such voids are larger than those resulting from intentional air entrainment and are at times referred to as natural air voids.) Air-Entraining Agent--A material the use of which results in intentional air entrainment when included in a mixture. Air-Entraining Admixture--A material added to cementitious mixtures at the time materials are batched for mixing. Air Entrainment--The introduction of air in the form of discrete air voids or bubbles dispersed throughout the mixture as a result of the use of air-entraining agents.788 TESTS AND PROPERTIES OF OTHER MATERIALS specified and tested to ensure adequate performance? These are some of the questions which we will attempt to answer in this chapter. In an extensive evaluation program. Materials Used as Air-Entraining Admixtures T h e r e are many materials capable of functioning as air-entraining admixtures. No further reproductions authorized. Definitions It will be helpful to define certain of the terms used in discussing air entrainment. a term that should be used only when it is intended to refer to materials that can be used both as airentraining additions or admixtures. the Bureau of Public Roads [7] separated 27 commercial air-entraining admixtures submitted for test into the following classifications: (1) salts of wood resins (pine wood stumps). and (7) organic salts of sulfonated hydrocarbons (petroleum Copyright by ASTM Int'l (all rights reserved). . (5) salts of proteinaceous materials (processing of animal hides). Entrapped Air Voids--Air voids not resulting from intentional air entrainment. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.) Air-Entraining Addition--Air-entraining material interground with. of a mixture during the process of air entrainment. 9]. plasticity and workability are increased. thus reducing segregation. and bleeding is reduced. to the use of intentionally entrained air. Powers showed that the air voids must be well distributed throughout the matrix (cement-water paste component) and sufficient in number so that each void provides protection to the cement paste surrounding it. 4 were in flake form. can be used to entrain gas bubbles in cementitious mixtures but are not considered as acceptable air-entraining admixtures. and the protected volumes overlap to leave no unprotected paste. Each void provides space into which the excess water can move during freezing. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No further reproductions authorized. . These and other advantages are discussed in detail in a number of the appended references. such as hydrogen peroxide and powdered aluminum metal.05 percent of active ingredient by weight of the cement. 17 were liquids. This work developed the concept of internal hydraulic pressure created by the resistance to flow or movement of excess water volume produced during the freezing process as being the mechanism responsible for distress. Uniformity of placement and consolidation can be achieved more readily. Generally. and the voids should be sufficiently close to one another so as to avoid high internal hydraulic pressure in the paste during movement of water to the air void. the intentionally entrained air must have certain characteristics. in addition to Copyright by ASTM Int'l (all rights reserved). only small quantities of air-entraining admixtures are required to entrain the desired amount of air. S were powders. for example [8. Not only is the total volume of importance.) There are numerous other advantages. since they do not produce an air void system which will enhance resistance to freezing and thawing. For example. enabling a reduction in water content. and 1 was semisolid. also. Function of Entrained Air The major reason for the use of intentionally entrained air is to provide concrete with a high degree of resistance to freezing and thawing and the use of chemical deicers. (The discussion to follow will also be applicable to the use of air-entraining cements. To keep this internal pressure below the tensile or rupture strength of the paste. Some materials. Later work by Powers and Helmuth [13] indicated that. To achieve the improvement in frost resistance. but more importantly the size and distribution of the air voids must be such as to provide efficient protection to the cement paste. Of these 27 materials. Powers ~ [10-12] contributions to the understanding of how entrained air functions in providing increased frost resistance have been outstanding. in which the air-entraining agent or material is used as an addition during the grinding of the cement clinker. These are of the order of 0.KLIEGER ON AIR-ENTRAINING MIXTURES 789 refining). the air content (composed of entrapped air voids which are too large to be effective with respect to improving frost resistance or workability but which are included necessarily when air content is expressed in volumetric terms) may range up to as high as 1.006 to 0.01 in. As the maximum size of coarse aggregate increases and consistency and cement content held constant. Table 1 shows this effect of maximum size of aggregate on the optimum air content. Powers [11] developed the concept of void spacing factor to characterize an air-void system and analyzed laboratory freezing and thawing data available at that time to show that the void spacing factor for frost resistance should be about 0.790 TESTS AND PROPERTIES OF OTHER MATERIALS the generation of hydraulic pressure during freezing. the air content of the mortar fraction is essentially constant at about 9 percent. This led to the specification that such concrete should contain 4. For these concretes.5 percent and composed of relatively large and ineffective air voids. during the freezing process.203 mm (0. This is an indication of the distance water would have to travel. These and other tests [16] called attention to the need for different volumetric air-content requirements for concretes made with different maximum sizes of coarse aggregate. along with void spacing factors. and thus avoids the development of these expansive forces.1 mm (1189 in.) is required for extreme exposures.5 ___ 1. another important factor may be the diffusion of gel water to capillary cavities contributing to the growth of ice bodies in these cavities resulting in the development of expansive forces. In such concretes without intentional air entrainment. Field and laboratory tests indicated that when such concretes were provided with about 3 percent additional entrained air the resistance to freezing and thawing and deicer chemicals was enhanced greatly. More recent work by Mielenz et al about 0. therefore. . less mortar is required in the mixture [15].5 percent air.) and that the average amount of entrapped air would be about 1. This factor may be of significance in nonair-entrained concrete.1 mm (11/2 in. The presence of an adequate air-void system provides spaces containing ice which competes with the ice in the capillary cavities for this unfrozen gel water.152 to 0. to reach a protective air void. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Although the total air contents of the mixtures shown in Table 1 vary through a wide range.0 percent. Most of the early field and laboratory work on air-entrained Concretes dealt with paving-type concrete in which the coarse aggregate was generally about 38. No further reproductions authorized. The void spacing factor is defined by Powers as the average maximum distance from a point in the cement paste to the nearest air void.0 or 2.) maximum size.3 . Extensive freezing and thawing tests by Klieger [15] provided further substantiation of the void spacing factor concept. the provision of an additional . 0 Copyright by ASTM Int'l (all rights reserved). or less. based on the premise that the coarse aggregate would have a maximum size of 38.008 in. change in total concrete air content with change in maximum size of coarse aggregate is to be expected. .5 8.7 14.007) (0. b Calculated as follows Mortar air content.178 0.5 4.0 Cement Content: (658 lbs/yd 3) 63.008) (0.5 No.5 5.008) (0.7 16.2 19.203 0.5 12.67 0. 4 (21/2) (11/2) (3/4) (3/8) (No.4 23.008) (0.42 0.3 16.007) (0.0 9.1 9.58 0.0 6. mm (in.0 10. %b BubbleSpacing Factor.203 0. % Mortar Air Content.5 4.8 19.6 10.330 0.013) (0.75 0. % = Paste air content. and A = volume of air.8 8.0 9.2 9.3 8.8 26.1 9.4 a Optimum determined from relation between expansion during 300 cycles of freezing and thawing and air content of concrete. 4 (21/2) (11/2) (3/4) (3/8) (No.1 19.38 0.67 0.7 9.2 8.203 (0.) Total Air Content. 4) 4.5 38.009) (0.178 0. Max Size of Aggregate.9 19.5 38.305 (0.5 4.5 8. W = volume of net mixing water.2 31.1 9. of R e f 15).5 No.178 0. 33. No further reproductions authorized.229 0. percent of intentionally entrained air by the use of an air-entraining adm i x t u r e p r o v i d e d a n a i r . mm (in.1 19.9 11.011) (0.3 8.91 0.KLIEGER ON AIR-ENTRAINING MIXTURES 791 TABLE 1--Characteristics of concretes at aptimum a a& content (Tables 17 and 18.152 (0.5 18.5 18.006) 0.5 38.5 8. 4) 4.330 0. S p e c i f i c a t i o n s b a s e d o n v o l u m e o f e n t r a i n e d a i r still r e m a i n t h e o n l y Copyright by ASTM Int'l (all rights reserved).5 5.6 0.36 0.1 8.203 0.53 0.47 0.36 0. by Weight Cement Content: (376 lbs/yd 3) 63.4 16.5 7.42 0. 4 (21/2) (11/2) (3/4) (3/8) (No.5 No.) c Net w/c Ratio. S = absolute volume of fine aggregate (saturated surface dry).007) (0.42 0.5J Cement Content: (517 lbs/yd 3) 63.012) 0.4 9.1 12.305 0.5 5.56 0.012) (0.0 14.v o i d s y s t e m well d i s t r i b u t e d t h r o u g h o u t t h e m a t r i x and containing a sufficient number of air voids to meet the void spacing f a c t o r r e q u i r e m e n t s w h i c h l a t e r s t u d i e s d e m o n s t r a t e d as n e c e s s a r y .0 16.008) 0. % = • C+W+S+A A C+W+A • 100 100 where C = absolute volume of cement.7 23. CCalculated from linear traverse data using method outlined in Bulletin No.009) (0. %b Paste Air Content.013) (0.279 0. Portland Cement Association Ill].229 0.5 9. 4) 4. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.1 19. Section -08c.S. Copyright by ASTM Int'l (all rights reserved).) square mesh sieve shall be between 4 and 7 percent of the volume of the concrete based on measurements made on concrete immediately after discharge from the mixer. it was a recognition of the need for considering the effect of the maximum size of coarse aggregate on the required air content of concrete. it is indeed fortunate that concretes having total air contents in the range of the optimum air contents shown in Table 1 will have the proper size and distribution of air voids when the air-entraining admixture used meets the requirements of ASTM Specification for Air-Entraining Admixtures for Concrete (C 260)." Although this was directed primarily to mass concrete. A nonair-entrained concrete was also included in these tests. and Spacing Factor of the Air-Void System in Hardened Concrete (C 457). Army. Not having such a test method available. can be seen in the results of a study made in the laboratories of the Portland Cement Association. the air content. and number of voids per lineal inch of traverse were determined on the hardened concretes as described in ASTM Recommended Practice for Microscopical Determination of Air-Void Content.1-mm (ll/5-in. rather than on the size and distribution of the air voids in the cement-paste matrix. CE 1401. October 1953. Examples of such use are found in American Concrete Institute (ACI) Standard Recommended Practice for Selecting Proportions for Concrete (ACI 211. U. It would be highly desirable to have a test method available that could provide a measure of size and distribution of air voids within a few minutes after completion of mixing. void spacing factor. In addition to the determination of air content of the freshly mixed concrete as de cribed in ASTM Test for Air Content of Freshly Mixed Concrete by the Pressure Method (C 231).01. until a means is developed for readily determining other air void parameters directly on the freshly mixed concrete in the field. Guide Specifications for Concrete. . the Corps of Engineers. specific surface. despite the fact that other parameters are of more importance than volume alone. states: "The total calculated air content of that portion of the concrete containing aggregate smaller than the 38.792 TESTS AND PROPERTIES OF OTHER MATERIALS practical way of specifying intentionally entrained air. Additional refinements of the technique enabled the determination of the total number of air voids per unit volume. and the Bureau of Reclamation. Specifications and control tests will continue to be based on the volume of air entrained in the concrete. Specific Surface. No further reproductions authorized. The importance of size and distribution of air voids.S. Air-entrained concretes were prepared using an acceptable proprietary air-entraining admixture and four nonproprietary materials which exhibited a potential for entraining air. as contrasted with total volume of voids alone. Army.1) and specifications of agencies such as the Corps of Engineers. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The results of these measurements and the performance of the concretes when frozen and thawed while immersed in water are shown in Table 2. For example. Entrained Air Content. U. 2 None A B D E Fa 1. 3) Concrete.1 4.9 Air.031 0.787 0.1 4.130 0.10% Expansion -.2/in. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.193 0.. 19 29 39 82 t00 550 Freezing and Thawing Cycles for 0.11) (0.) 11 889 15 236 18 897 16 377 22 716 38 976 (302) (387) (480) (416) (577) (990) Specific Surface.o x --I r" -n rn Go m z z 63 m --4 -n z rn Z O 63 m I-- 7~ .26) (0.) 0. Air Content.0) (4.220 0.378 (0. 1.013) (0.006) Void Spacing Factor. % 0.8 6.201 0.013) (0. (ASTM C 231).1) (9.D r.152 (0.9) (3.4 t.330 0.22) (0.Copyright by ASTM Int'l (all rights reserved).6) Number of Voids/ mm (in.8 5.5 3. No further reproductions authorized.1 3.79) No. mm (in.330 0.8) (4. m2/m 3 (in.0 6.0 5.010) (0. 3) of air a A commercial air-entraining admixture meeting the requirements of ASTM Specification C 260.031) (0. millions Air-Void Characteristics (ASTM Recommended Practice C 457) TABLE 2--Influence of air-void characteristics on resistance of concrete to freezing and thawing.254 0.78) (3.2 3.009) (0.0 5. % AirEntraining Admixture 4 881 6 712 13 425 15 866 47 598 231 279 (0. of Voids/m 3 (in.157 0.3) (5.08) (0. rate of shearing action. (6) temperature of the mixture.17-19] have made significant contributions to the understanding of the mechanism by which airentraining admixtures function and the influence of a number of different variables. the calcium salt of the active constituent in the admixture may be only slightly soluble in water. (2) the presence of other chemical admixtures. No further reproductions authorized. that is. . Bruere [19] has shown that such changes do not take place to any signifiCopyright by ASTM Int'l (all rights reserved).794 TESTS AND PROPERTIES OF OTHER MATERIALS It is apparent from these data that an air-entraining admixture must not only be capable of entraining some volume of air but also that the air void system must be characterized by a large number of small. well distributed air voids in order to provide a high degree of frost resistance. Many calcium salts of sulfonic acids are soluble in water and many air-entraining admixtures in which the surface-active constituent is a sulfonate would not form such precipitated films around the air bubbles. Admixtures which produce a relatively insoluble precipitate in portland cement concrete include sodium soaps of wood resin. some of which are: (1) concentration of the air-entraining admixture and its influence on surface tension. Mielenz and his co-workers dealt extensively with the origin. such as water reducers and retarders. (3) time of mixing. and (8) the gradation of the solids in the mixture. and effects of the air-void system in concrete. air-entraining admixtures are positively adsorbed at air-water interfaces and that the surface tension of the water is decreased about 25 percent. Factors Influencing Amount and Character of Entrained Air The works of Mielenz et al [14] and Bruere [9. This adsorption at air-water interfaces produces a "film" of air-entraining admixture which influences the air-retention properties of discrete bubbles formed during mixing. (7) water cement (w/c) ratio and water content of the mixture. Mielenz et al [14] have concluded from theoretical considerations of pressure in air voids due to hydrostatic pressure of overlying concrete and the curvature of the air-water interface (that is. (5) consistency of mixture. They showed that in the concentrations normally used in concrete. or fatty acid. such as neutralized Vinsol resin and sodium abietate. (4) speed of mixing. including the cement. However. the film at the air-water interface may include a precipitated solid or gelatinous film enclosing each air bubble. evolution. For some air-entraining admixtures. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The amount and character of the air entrained in concrete is influenced by numerous factors. In such instances. or triethanolamine salts of sulfonic acid. Their tests on air-water foams and dilute cement pastes tended to corroborate these conclusions. rosin. bubble size) and the solubility of air bubbles in water that both the total volume of air and the size distribution of the air bubbles can change in the unhardened concrete due to interchange of air between bubbles and dissolution of air. sodium soaps of lignin derivatives. but concretes made with them illustrate the importance of the distribution of the air as compared with simple volume. number of air voids per unit volume. and compaction. Part of the differences occur during the mixing operation and part during handling. although such interchange is of significance during the mixing process and may be for a few minutes thereafter. All of these factors will be operative during the mixing operation. (2) the elasticity of the film at the air-water interface.. Fine Aggregate--Changes in grading of sand may alter the volume and nature of air in the mortar [20]. Such sands are relatively rare. . increase the specific surface of the air-void system." Cement--As the cement content increases. and decrease the spacing factor. such as water reducers or retarders. . Further information on the influence of numerous variables on the characteristics of air entrained in concrete is of interest and is presented in the following paragraphs.KLIEGER ON AIR-ENTRAINING MIXTURES 795 cant degree in air-entrained pastes after cessation of mixing. and spacing factors. In the richer mixes. Appreciable increase in the quantity of very fine particles of sand will decrease the amount of entrained air and may reduce the maximum and median size of the individual air bubbles [21]. The potential importance of these differences with respect to freezing and thawing durability was illustrated by the data in Table 2. (3) transmission of air across the air-water interface. and (4) adhesion of the air bubbles to particles of cement or aggregate. At the same volumetric air content. Macnaughton suggests [22] this type of entrained air be termed "accidental air" and since "it may be unstable in nature and vary in size. The presence of other chemical admixtures. Sands have been reported as containing organic matter difficult to remove by ordinary measures which cause entrainment of large quantities of air in concrete. 'entrained air'. Appreciable increase in the quantity of the middle sizes of sand will tend to increase the air in the mortar. placing. Type and Amount of Air-Entraining Admixture Mielenz and his co-workers theorize that the type of organic material which constitutes the active ingredient in the air-entraining admixture influences the amount and character of entrained air voids by its effect on: (1) surface tension. Sand gradation is of more importance in leaner mixes. [it] should not be confused w i t h . the influence of gradation on entrained air is not as marked.. . Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the air-entraining potential Copyright by ASTM Int'l (all rights reserved). different air-entraining admixtures will produce air-void systems having different specific surfaces. may result in a synergistic effect which operates to increase the amount of air entrained significantly. No further reproductions authorized. Increasing the amount of acceptable air-entraining admixtures will increase the volume of air-entrained. The amount of air entrained by any given mixer will decrease appreciably as the blades become worn. or as the mixing action is impaired if hardened mortar is allowed to accumulate in the drum and on the blades. The larger natural voids are expelled most readily [14. If vibration is applied as it should be. Moderately small bubbles may tend to work upward if the vibration is intense and prolonged. No further reproductions authorized. air entrainment varies inversely with temperature [8. and a transit mixer may develop significant differences in the volume of air entrained in a given concrete mixture.26].0 percent. that the critically important spacing of small entrained-air bubbles in the matrix is disturbed very little. is not harmed by prolonged agitation. Consistency--Within the normally used range. A stationary mixer. after which the air content may remain approximately constant for a considerable period before it begins to drop off. Nondegradable detergents present in water can result in excessively high and variable air contents. The reduction in air may result from an increase in very fine particles in the mixture with prolonged mixing action or simply from an increase in the ratio of air-escape to foamgeneration in the latter portion of the mixing period. less air will be entrained at 310. The air content will increase with increased time of mixing up to about 2 min in stationary [8] or paving mixers (and to about 15 min in most transit mixers). Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. even by intense vibration. Temperature--For a constant amount of air-entraining admixture.23.9 K (100~ than at 294. and an increase in the fineness of cement will result in a decrease of the air entrained in the mortar [2325]. the specific surface of the air voids generally decreases and the spacing factor increases [14].24] Vibration--Intensive internal vibration applied to concrete will cause air bubbles to rise to the surface and be expelled. An increase in entrained air will occur if the mixer is loaded to less than rated capacity. increase in initial slump is accompanied by an increase in air content in concrete mixtures [8. with just enough intensity Copyright by ASTM Int'l (all rights reserved).27-29]. Portland Cement Association tests of transit-mixed concrete indicate that the air void system. Some regular (nonair-entraining) cements naturally entrain more air than others. everything else being equal. however.25]. a paving mixer. as characterized by specific surface and spacing factor.3 K (70~ and more will be entrained at 277. Mixing--The effect of mixing action on the amount of air entrained varies with the type and the condition of the mixer [8.6 K (40~ In other words.796 TESTS AND PROPERTIES OF OTHER MATERIALS of an admixture will tend to diminish. Although the volume of air entrained may increase. and a decrease will result from overloading the mixer. and these require less air-entraining admixture to develop a given mortar air content. Water--Increase in w/c ratio is likely to result in an increase in air content. There is increasing evidence. Work by Klieger [16] indicates that the optimum mortar air content remains at about 9. . in this case the added air is in the form of relatively large natural voids. The effect becomes marked with fly ash as the carbon content increases. as with many of the other variations in concrete. or condition of the air-entraining admixture itself. This last cause. Copyright by ASTM Int'l (all rights reserved). For field control purposes. In some instances externally applied vigorous vibration may cause an increase in air content. no such method has yet been developed. Yield. and if the mixture is designed properly. largely inhibiting air entrainment. Calcium chloride can be used successfully with air-entraining admixtures. evaluation must continue for the most part along the indirect lines of volume of air in the total mixture. Work under way in the research laboratories of the Portland Cement Association [30] and elsewhere points toward advances in the comprehension of the mechanics of air entrainment which should further establish this major advance in the technology of concrete. Unfortunately. however. finely divided admixtures such as fly ash or bentonite will reduce the air content. the ideal test would be one which could measure these characteristics in the freshly mixed concrete. For the time being. some tests have indicated that when the inhibiting reaction does not take place. On the other hand. Methods for Determining Air-Void Characteristics Freshly Mixed Concrete Since parameters such as specific surface and spacing factor of entrained air are more reliable criteria of effectiveness than the volume of entrained air. as noted earlier. Any influence which would maintain or even actually improve the distribution of the bubbles within the matrix or increase the ratio of airboundary surface to air volume would be desirable. a rapid chemical reaction may occur between the two. type. However. It is certain that an improved surface-to-volume ratio would reduce considerably the total volume of air needed to be entrained compared with what is now considered normal for optimum results. The gravimetric method described in ASTM Test for Unit Weight. No further reproductions authorized. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. presently available test techniques can determine with reasonable accuracy only the volume of entrained air. One of the most frequent and pronounced causes for variations in air content results from variation in the amount. but if added in direct contact with certain common admixtures. removal of the effective portion of the entrained air will not occur. .KLIEGER ON AIR-ENTRAINING MIXTURES 797 and duration to effect consolidation. Especial care must be taken when other chemical admixtures are used in conjunction with airentraining admixtures. is a function in turn of the alertness and adequacy of the control and inspection given the work. the air content may be increased about 1 percent. Admixtures--Solid. specific surface. is a simple test to make. Based on Boyle's law. Hardened Concrete The important characteristics of the entrained-air voids can be determined most readily in hardened concrete by microscopical examination of sawed and ground surfaces of the hardened concrete. by this method. Additional refinements of the linear traverse equipment enable the measurement of chord size distribution of air voids from which the total number of air voids per unit volume can be calculated. Mielenz and his co-workers [14] show the results of measurements of air- Copyright by ASTM Int'l (all rights reserved). This technique eliminates the possibility of significant errors in differentiating between air in the aggregate particles and air in the paste. .8 mm (2 in. The volumetric method described in ASTM Test for Air Content of Freshly Mixed Concrete by the Volumetric Method (C 173) is most useful for determining the air contents of concretes made with lightweight aggregates [32]. as shown in Table 2. and spacing factor of air voids by either a linear traverse method or a modified point-count method. The most widely used method is that described in ASTM Test C 231 which is a procedure for determining the air content of freshly mixed concrete by application of pressure. that at a constant temperature the volume of a given quantity of any gas varies inversely with the pressure to which the gas is subjected. It is based on the relation of actual to calculated air-free unit weight of the concrete and produces reasonably accurate results when aggregates of relatively uniform specific gravity are used.798 TESTS AND PROPERTIES OF OTHER MATERIALS and Air Content (Gravimetric) of Concrete (C 138).) in maximum size. the larger particles may be removed by hand and the effect of such a removal calculated in arriving at the total air content [31]. errors attributable to inadeate sampling may be introduced where the specific gravities of the fine and coarse aggregate differ materially or where either aggregate is itself composed of particles of materially differing densities. However. No further reproductions authorized. When larger aggregate is used. There are a number of pressure meters on the market which. Large errors will be introduced where highly vesicular or porous aggregates are used due to the impracticability of differentiating between the air in the aggregate particles and the entrained air in the paste. Passing samples of freshly mixed concrete over a sieve to exclude large particles may lead to important errors resulting from loss of air during the screening operation. the method is generally adequate for use with all ordinary types of mortar or concrete containing reasonably dense aggregate. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. produce satisfactory results with concrete mixtures containing aggregate up to about 50. ASTM Recommended Practice C 457 is a procedure for determining the total air volume. the Scope of ASTM Method C 233 acknowledges that the "tests are based on arbitrary stipulations permitting highly standardized testing in the laboratory and are not intended to simulate actual job conditions. has provided a means for evaluating air-entraining admixtures on a per- Copyright by ASTM Int'l (all rights reserved). ASTM Specification C 260 evaluates the effects which any given airentraining admixture under test may exert on the bleeding. This specification. it will be reasonable to expect that the quantity of the airentraining admixture represented by the sample will develop satisfactory entrainment of air in field concrete without deleterious effects. and (2) that the admixture contains nothing which will have a deleterious chemical effect on such mixtures. No further reproductions authorized. The criteria of ASTM Specification C 260 are assumed to afford assurance that if. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. resistance to freezing and thawing. strength of bond to steel. Although such measurements are time consuming. the particular sample of the admixture under test exerts satisfactory influence on certain properties of the laboratory concrete. However. and the length change on drying of a concrete mixture in comparison with a similar concrete mixture containing a reference air-entraini n g admixture. under the particular conditions of the specified mixtures and conditions in ASTM Method C 233. Current Specifications for Air-Entraining Admixtures It was realized rather early in the development of air entrainment that the size and distribution of the air voids could be expected to be of major importance with respect to the effectiveness of the entrained air in enhancing durability." All of the elaborate testing required by ASTM Specification C 260 reduces simply to a very indirect method of determining whether: (1) the particular admixture under test will produce relatively stable air voids which will become widely dispersed throughout the matrix of f e l d mortar or concrete so as to produce an air-void system having the proper characteristics for enhancing durability. a performance type specification was developed in 1950 by ASTM. The methods by which these effects may be tested are given in ASTM Testing Air-Entraining Admixtures for Concrete (C 233). Since there was no ready and reliable means for determining these air-void characteristics and since there was a need to evaluate the influence of these air-entraining materials on other concrete properties.KLIEGER ON AIR-ENTRAINING MIXTURES 799 void characteristics of cores taken from a wide variety of structures. compressive and flexural strength. while rather elaborate. they can provide reassuring evidence of the effectiveness of the air-entraining admixture in providing the desired air-void system. The volume of air in hardened concrete can also be determined by a high pressure method developed by the Illinois Highway Department [33]. with its attendant test methods. . discussion." Proceedings. American Society for Testing and Materials.. American Concrete Institute. pp. In this respect.. 1954. further information is needed on the accuracy and reproducibility of the method. 1941. W. Oct.. "History of Air-Entraining Cements. H. A.. however. in almost all cases. 1939. ASTM Recommended Practice C 457 provides the means for such a comparison. J. American Concrete Institute. No. 329-350. The wide variet~ ch~. 1938. D. can be supplanted by an examination of the characteristics of the air-void system produced by the admixture under test and a comparison with the system produced by the reference admixture. such as slump. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. . "More Durable Concrete With Treated Cement." Public Roads. [6] Hansen. "Experimental Test Data in Connection with the Development of Chloride Resisting Concrete by the Use of Treated Portland Cements and Blends with Natural Cements. B. discussion. 1954. 351-353. [4] Kellerman. 580-1 to 580-5. bleeding. about the optimum air-void system in the matrix when the total air contents shown in Table 1 are present in the concretes.800 TESTS AND PROPERTIES OF OTHER MATERIALS formance basis. 268-278. 243-245." Engineering NewsRecord." Proceedings. Vol. it is fortunate that the simple air-entraining admixtures available so economically in the United States appear to produce. C. W. "The Effect of Using a Blend of Portland and Natural Cement on Physical Properties of Mortar and Concrete.nically of materials which can function as satisfactory air-entraining admixtures precludes the inclusion of chemical requirements. A. which is responsible for the various ASTM specifications and test methods to which this report has referred. 946-949.. W. F. 19 June 1941. No further reproductions authorized. Vol. Copyright by ASTM Int'l (all rights reserved). pp. Feb. and Chaiken." Proceedings. 67-89. M. Vol. Concrete Briefs. pp. 561-578. pp. and strength. 27. pp. "Chemical Analysis and Sources of Air-Entraining Admixtures for Concrete. Until that time." 17th Annual Proceedings. 52-61. Such information is being developed by ASTM Committee C-9 on Concrete and Concrete Aggregates. Aug. [7] Halstead.. C. Vol. G. pp. pp. 58. 35. In recognition of the fact that the tests required are elaborate and timeconsuming and that consequently they may not be performed as often as desirable to ensure conformance. 12. Feb. however. References [1] Gonnerman. 126. ASTM Specification C 260 contains a section on Optional Uniformity Requirements which can be invoked to ensure that subsequent shipments are identical to the sample tested for performance. 1961. and Runner. which are probably the most costly and time-consuming part of the testing procedure." Consulting Engineer. 38.. A. "Air-Entrained Concrete. F. Association of Highway Officials of the North Atlantic States. the job performance of an air-entraining admixture must still be based on the direct measurement of "total air content" and on its effect on other readily measured properties. A further consideration which is receiving attention is the possibility that the freezing and thawing tests. E. [2] Swayze. "Durability of Concrete Pavement-Experience in New York State. A Look at the Record. pp. Vol. pp. [5] Lawton. [3l Anderson. Vol. Research and Development Laboratory. Vol. Nov.KLIEGER ON AIR-ENTRAINING MIXTURES 801 [8] Lerch. 55. F.. Proceedings. [12] Powers." Australian Journal of Applied Science. 50. [24] Scripture. A. pp. Contains extensive bibliography to 1950. No. 1949. Bulletin No. Vol." Proceedings. American Concrete Institute. 13. [10] Powers." Mining Engineering. American Concrete Institute. W." Proceedings." Proceedings. 289-294. Proceedings. 1949. Vol. Portland Cement Association. and Herbich. 29. "A Working Hypothesis for Further Studies of Frost Resistance of Concrete. 45.. "Some Factors Affecting Air Entrainment. American Concrete Institute. 45. F." Journal. Journal. Proceedings. Research and Development Laboratory. 1954. Highway Research Board. Vol. [16] Klieger." Journal. "Void Spacing as a Basis for Producing Air-Entrained Concrete. May 1954. "Rearrangement of Bubble Sizes in Air-Entrained Cement Pastes During Setting... 32.. pp. 177-201." Proceedings. 205-210. 1951.. [13] Powers. M. Copyright by ASTM Int'l (all rights reserved). 1958. 1953. [19] Bruere.. [15] KIieger. Part 1--Entrained Air in Unhardened Concrete. D. [23] Scripture. [11] Powers. Vol. and Effects of the Air Void System in Concrete." Journal. F. Vol. J. 5. American Concrete Institute. American Concrete Institute. and Bryant. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1962. H. Highway Research Board. E. Vol. Bulletin No. and Litwinowicz. 1022-1028. Portland Cement Association. Jr. "Influence of Size Grading of Sand on Air Entrainment. Vol. W. [21] Mather. 1950. 741-760.. H. American Concrete Institute. "Crushed Limestone Aggregates for Concrete. Jr. Supplement. 3. 11. Vol. 55. Metallurgical. 1958. T. J. cement factor. No." Journal. American Concrete Institute. 1945. Proceedings. pp.. Vol. C. C. Discussion by R. G. and Flack. and Helmuth.. 41. Vol. and sand to total aggregate ratio of the concrete mixture. 33. Proceedings. C. [20] Scripture. L. W. 78-86.." Australian Journal of Applied Science. Powers." Journal. [18] Bruere. T. Jr. and Litwinowicz. pp. Nov. J. Vol.. American Concrete Institute." Journal. "Theory of Volume Changes in Hardened Portland Cement Paste During Freezing." Research Laboratories of the Portland Cement Association. and T. Portland Cement Association." Journal.. Nov. Douglas McHenry. G. "Effect of Temperature and Surface Area of the Cement on Air Entrainment. Proceedings. 12. American Institute of Mining. 1945. "'Accidental' Air in Concrete. pp. E. Bulletin No.. F. 31. 41. 433-442. [9] Bruere. 36164. T. March 1961. Paul. 217-228. J. [14] Mielenz. S. . 1958. Wokodoff. No. Terzaghi. B. G. Data on effects on air entrainment of variations in slump. V.. July 1958. Bulletin No. 184-211. 399-401. Highway Research Board. Hornihrook. 2. No. pp. Research Department. Vol. No further reproductions authorized. Bulletin No. Paul. C. Backstrom. "Relative Importance of Various Physical and Chemical Factors on Bubble Characteristics in Cement Paste. 77. A. "Effect of Entrained Air on Strength and Durability of Concrete Made with Various Maximum Sizes of Aggregate. E. B.. 55. 49. pp. and "Part 4--The Air Void System in Job Concrete. C. Oct. pp.. [17] Bruere. E. D. Oct. Portland Cement Association. 40. 222-227." Australian Journal of Applied Science. "Air-Entrainment in Concrete.. Vol. 272-1 to 272-20. 1960. M. T. 34. "Origin. Vol." Journal. 273-284. Collins. 1953. Brewer. W. W. TechnicaIPublicationNo.." Journal. M. M. pp. Research Department. Vol. 3. Portland Cement Association. 48. American Concrete Institute. Portland Cement Association. Katharine. Proceedings. "Part 2--Influence of Type and Amount of Air-Entraining Agent. Highway Research Board. Evolution. pp.. No. 55. 1960. Proceedings. Vol. "Basic Principles of Air-Entrained Concrete. Aug. "The Air Requirement of Frost-Resistant Concrete.. Research and Development Laboratories. 51. Benedict. R. "Effect of Type of Surface-Active Agent on Spacing Factors and Surface Areas of Entrained Bubbles in Cement Pastes. Feb.. Proceedings." Australian Journal of Applied Science. [22] Macnaughton. C. E. Bulletin No. pp. "Part 3--Influence of Water-Cement Ratio and Compaction. 46. American Concrete Institute. Vol. Research Department.. 1. M. "Further Studies on the Effect of Entrained Air on the Strength and Durability of Concrete Made With Various Maximum Sizes of Aggregates. E. pp. Proceedings. 11.4. Feb. 1948. Proceedings. 1955. William. pp. and Petroleum Engineers. G. 245-272." Journal. 1952. pp. R. Sept. March 1946. F. Proceedings. 929 for "Effect on Air Entrainment"). J. and Litwinowicz. Waterways Experiment Station. 1-18. Vol. 6-352. J. Bulletin No. "Particle Size of Dispersed Carbon Black Affects Entrainment of Air in Concrete. [31] "Handbook for Concrete and Cement. "Air Entrainment and Its Effect on the Design of Concrete Mixtures. "Effect of Vibration on Air Content of Mass Concrete. W. Jr. American Concrete Institute. 149-163. Waterways Experiment Station. H. American Concrete Institute. Experiences. E. Nov. 1948. May 1947. 653-662. Feb. 1954. Proceedings. pp. W. T. 47. American Concrete Institute. E. 49.. and Chaiken. Vol. 337-358. 909-920. 1949. "Effect of Entrained Air on Concrete Made with So-Called 'Sand Gravel' Aggregates." Journal. Vol. C. C. 3." Journal. pp. "Some Effects of Vibration and Handling on Concrete Containing Entrained Air. discussion by C." Air Entrainment in Concrete Design." Air Entrainment in Concrete Design." Journal. Bulletin No. B. F. and Litwinowicz. Vol. No. 259-267. Nov. "Air Entrainment and Resistance to Freezing and Thawing. Jackson.5. C. 268-278.. E. E. 16. 1964. A. "The Testing of Aggregates in Air-Entrained Concrete. 49. American Concrete Institute. 47. 144. June 1953. 1947. Proceedings. 832. pp. Portland Cement Association.. P. 469-488. F. 1950. Paul. Proceedings. Vol. pp. No. Scripture. pp. C. Blanks. and Cordon. [28] Crawley. Waterways Experiment Station." Journal. 3." Technical Memo No." Proceedings. No further reproductions authorized. p. Proceedings. 12. Wuerpel. American Concrete Institute. Vol. T. "Development and Study of Apparatus and Methods for the Determination of the Air Content of Fresh Concrete. S. Proceedings. Sept. Dec. Portland Cement Association. H. Proceedings. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Symposium on Measurement of Entrained Air in Concrete. F. J.. 27. S. 1956. W. (especially p. Proceedings. pp. 45. E. 12. pp. "Linear Traverse Technique for Measurement of Air in Hardened Concrete. "Chemical Analysis and Sources of AirEntraining Admixtures for Concrete." Public Roads. 45. Vol.. Halstead. "Entrained Air in Concrete. Vol. 1951. and Tests with AirEntraining Agents in Making Durable Concrete." Journal. October. Nov. "Effects of Mixing Time." Journal. Vol. Copyright by ASTM Int'l (all rights reserved).. 9. R. "Illinois Develops High Pressure Air Meter for Determining Air Content of Hardened Concrete.. No. 424-435. Klieger. 38.. Proceedings. 1053-1072. pp. 45. W." Pit and Quarry. 43. London. May 1953. Vol." Public Roads.. 1-12. 920-1 to 920-2. F. 1947. Lindsay. American Concrete Institute. 921-931. pp. No. Bernard. Bulletin No. 35. [29] Tuthill.802 TESTS AND PROPERTIES OF OTHER MATERIALS [25] Wright. June. 297-308. 1952.. See also "Investigation of Field Methods for Determining Air Content of Mass Concrete. 1947. Mather. Feb. March 1948. pp. "Evaluation of Air-Entraining Admixtures for Concrete. J. and Brand of Cement on Air Entrainment. American Concrete Institute. Part 1. A. Institute of Civil Engineers.. Vol. Research Department. Highway Research Board. pp. Research and Development Laboratories. Oct." Proceedings. 43.. 6. O. [26] Scripture. 41-56. 27. W. Vol. J. G. and Pierson. pp. "Practices. 48. Sept. Mardulier. Waterways Experiment [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] Station. Menzel. 18.. F. Bulletin No. pp. Vol. 117-124. Portland Cement Association Research and Development Laboratories. 1953. 22. 49. Feb. American Society for Testing and Materials. Vol.4. U. pp. pp." Journal. 35. . 1952.. J. pp. p. American Concrete Institute. Vol. L... W. Research Department. Benedict." Journal. "Topics in Concrete Technology and Mixtures Containing Intentionally Entrained Air. p.. Kennedy. No." CivilEngineering. Bulletin No. Size of Batch. 1954. 30. Portland Cement Association. "Vibration of Mass Concrete. [30] Powers. W." Method CRD-C 41-52. "The Application of Air-Entraining Agents in Concrete and Products. Proceedings. 1952. Research Department. American Concrete Institute. L. and Kennedy. [27] Higginson. Brown. May 1949. 2.. H." Journal. Brickett. Vol. Bryant. A. Vol. L. 30." Journal. D. and Timms. 305. Portland Cement Association. Research Department. ." Journal.. G. [51] Wuerpel. 1945. C. Bulletin No. Research Department. No further reproductions authorized. 496-498. J. 11. Vol. "The Camera Lucida Method for Measuring Air Voids in Hardened Concrete.. Vol. Second Interim Report. 43. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. American Society for Testing and Materials. Proceedings. Proceedings. 1025-1040. Portland Cement Association." Journal. 42. "Addition of Air-Entraining Agent at Concrete Mixer Advocated.. G. E. C. June 1946. Feb. [47] Taylor." Journal. Bulletin No. "Some Effects of Air-Entrainment and Coarse Aggregate Type on the Properties of Concrete.. Proceedings. Vol. American Concrete Institute. May 1947." Journal. 84. pp. Proceedings. C. D. G. E. [52] Verbeck. No. 44 (TP2S2). April 1947. pp. 44. p.C. "Determination of the Air Content of Mortars by the Pressure Method. "Effect of Carbon Black and Black Iron Oxide on the Air Content and Durability of Concrete. Part 2. 1946. [50] Wuerpel.. [49] Wuerpel. T. Concrete Research No. American Concrete Institute. Contains extensive bibliography up to 1945. Bulletin No. American Concrete Institute. Portland Cement Association. Copyright by ASTM Int'l (all rights reserved). 49-82. Research Department.. 613. p. "Field Use of Cement Containing Vinsol Resin. [48] Wuerpel. p.. 1948.KLIEGER ON AIR-ENTRAINING MIXTURES 803 [45] Symposium on Entrained Air in Concrete. Dec. Vol. Central Concrete Laboratory. Nov. 601. Journal. 15." Civil Engineering. Proceedings. Vol. Washington. American Concrete Institute. 27. 1946. "Laboratory Studies of Concrete Containing Air-Entraining Agents. American Concrete Institute. 23. Sept. 42. pp. 1945. Vol. [46] Taylor. C. T.." National Crushed Stone Association. 42. 16. 155. p." A S T M Bulletin No. E. E.5. It should be noted that many of these improvements may be obtained without the use of admixtures if proper steps are taken in the design of concrete for the desired uses. Copyright9 1978tobyLicense ASTM International www. Only mineral admixtures are discussed in this paper.STP169B-EB/Dec. However. resins. 1978 L. borax. such as calcium chloride. and reduction of expansion caused by reactive aggregate and alkalies in cement. A wide variety of materials are so classified. and artificial materials. Mineral admixtures include any essentially insoluble material other than cement and aggregate. Sun Apr 6 21:31:09 EDT 2014 804 Downloaded/printed by Universidade do Gois pursuant Agreement. therefore. sulfonated lignins. fats. They are finely divided and so form pastes to supplement portland cement paste. according to ASTM Definition of Terms Relating to Concrete and Concrete Aggregates (C 125). Sacramento. processed natural materials. oils. An admixture is defined as a material other than water. admixtures designed for specific uses may effect the desired improvements in properties at a lower cost. added resistance to freezing and thawing. Copyright by ASTM Int'l (all rights reserved). Calif. one of the matters of prime consideration. increased workability. and is added to the batch immediately before or during mixing. 95822. acceleration or retardation of hydration or setting.org . Mineral admixtures include natural materials. reduction in heat of hydration. H. in contrast to soluble substances which act as chemical accelerants or retardants during the hydration of portland cement or otherwise modify the properties of the mixture. which is used as an ingredient for concrete. increased impermeability. increased strength. inorganic compounds. and sodium silicate. 1Concrete engineeringconsultant. and finely divided minerals. aggregates. and hydraulic cement that is used as an ingredient of concrete or mortar and is added to the batch immediately before or during its mixing.astm. improved resistance to aggressive waters and soils. Among the effects sought are: reduction in bleeding. Economy is. No further reproductions authorized. T u t h i l l I Chapter 46--Mineral Admixtures Introduction Admixtures generally are used to provide an economical means of improving one or more properties of fresh or hardened concrete. Among these are organic compounds. and carbohydrates. such as triethanolamine. sodium carbonate. and volcanic ash. Increasing the ratio of surface area of solids to volume of water in the paste provides an effective method of reducing the degree of bleeding. powdered mineral admixtures have been used in concrete to improve workability and to alleviate bleeding. Their value is based upon their ability to form soft. The types of mineral admixtures used at the present time generally are limited to those having pozzolanic properties. This generally increases the stiffness of the paste and at a given slump effects a wider separation of the aggregate particles in the concrete. but it does somewhat reduce strength in other than lean concretes. These materials were used primarily to improve workability prior to the advent of the use of air-entraining agents. such as fly ash. ground quartz. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. hydrated lime. plastic pastes which separate and lubricate the aggregate particles in the fresh mortar or concrete mixture. Good admixtures will form pastes which contain a maximum proportion of solid matter and a minimum proportion of water. and stone dust. This requires that the mineral particles do not have unfavorable shapes and that the surface area is not too great. No further reproductions authorized.TUTHILL ON MINERAL ADMIXTURES 805 For years. thereby increasing the workability. Although the major portion of this paper is devoted to a discussion of properties. hydrated lime. diatomaceous earth. and talc. pozzolanic materials. air entrainment notably aids workability and reduces bleeding more uniformly and economically than do most of the mineral admixtures. a brief summary of the history and use of other mineral admixtures is presented. Materials . The ratio of surface area of solids to volume of water may be increased by increasing the cement content or by adding a suitable mineral admixture. except for pozzolans. calcined shale. they do not generally impart any benefits to concrete other than improved workability and reduced segregation. such as clay. Air entrainment also has a significant effect on increasing resistance to deterioration of concrete caused by freezing and thawing and has led to an almost complete elimination of the use of chemically inert mineral admixtures. methods of testing. talc. Although pozzolans are still used in some areas to supplement sand that is deficient in fines.for this purpose included cementitious materials. Williams [1] 2 compared 2The italic numbers in brackets refer to the list of references appended to this paper. Admixtures with Low Reactivity This type of admixture includes such materials as ordinary clay. Copyright by ASTM Int'l (all rights reserved). and inert materials. and blast-furnace slag. The "inert" mineral admixtures vary in their ability to increase workability and reduce bleeding. . since. ground limestone. hydraulic lime. and significance of specifications requirements for mineral admixtures having pozzolanic properties. bentonite. such as natural cement. although not used as admixtures to a great extent at the present time. However. This temperature is below the temperature required for the formation of tricalcium silicate and tricalcium aluminate in portland cement. and monocalcium silicate. . Because of its compound composition. natural cement produces concrete which develops strength slower than portland cement concrete. Cementitious Materials Cementitious materials used as admixtures include natural cements. He concluded that the relative efficiency of admixtures was indicated by the volume of paste produced by a given weight of each. hydraulic limes.806 TESTS AND PROPERTIES OF OTHER MATERIALS the workability afforded by several admixtures and attempted to gage the effect of each in resisting segregation in concrete. slag cements. there is no significant interaction between the hydration products of the portland cement and the natural cement. Natural cement-portland cement combinations simply alter the percentages of the hydraulic compounds present. Blast-Furnace Slag Granulated blast-furnace slag is a nonmetallic product consisting essentially of silicates and alumino-silicates of calcium that is developed simultaneously with iron in a blast furnace and is granulated by quenching the molten material in water or in steam. resulting in the changes in properties of concrete mentioned. Natural Cements The development of natural cements in a logical manner was started in Europe during the late 18th century. The percentages of these two compounds present in natural cements are dependent upon the quantity of lime present in the raw material. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Natural cement is the product obtained by finely pulverizing calcined argillaceous limestone (ASTM Specification for Natural Cement (C 10)). No further reproductions authorized. the intimately associated compounds of calcium and silicon found in natural cement rock will react at these lower temperatures to form dicalcium silicate. Natural cements are calcined at a temperature below 1000~ which is sufficient to drive off carbonic acid gas. However. may provide economical means of improving specific properties of concrete. concretes containing natural cement show a greater rate of strength gain at later ages. Some of these materials. the major compound in natural cement. When natural cement is used as an admixture in portland cement concrete. according to ASTM Copyright by ASTM Int'l (all rights reserved). and lower heat of hydration than do concretes containing Type I portland cement. and pulverized granulated blast-furnace slag. greater resistance to sulfate attack. and air. Blast furnace slags have both cementitious and pozzolanic properties. for use in the manufacture of portland blast-furnace slag cement. The use of blast furnace slag in combination with portland cement in concrete results in a reduction in the total percentage of uncombined calcium hydroxide present and an increase in the quantities of calcium silicates and aluminates as compared with a corresponding concrete containing straight portland cement. It should be noted that these advantages will be gained only under suitable curing conditions for the concrete and may vary Copyright by ASTM Int'l (all rights reserved). Such concrete will have a lower temperature rise. likely will exhibit decreased permeability. Although in practice blast-furnace slags generally are not used as admixtures. as compared to concrete containing a Type I portland cement. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.0 Granulated blast-furnace slag having a chemical composition within the following ranges generally will meet the requirements of the above formula: Silicon dioxide (SiO2) 30 to 40 percent Aluminum oxide (AI20a ) 8 to 18 percent Ferrous oxide (FeO) 0 to 1 percent Calcium oxide (CaO) 40 to 50 percent Magnesium oxide (MgO) 0 to 8 percent Manganic oxide (Mn2 03 ) 0 to 2 percent Sulfide sulfur (S) 0 to 2 percent The use of granulated blast furnace slag as a constituent of portland blast-furnace slag cement does not conform to the definition of an "admixture": that it is a material added to the batch immediately before or during mixing. their use as such would give results similar to those obtained by intergrinding with portland cement. The use of blast furnace slag as a cementitious material dates at least from 1774 when Loriot made a mortar using finely ground blast-furnace slag and slaked lime. Blast-furnace slag. and may exhibit increased strength at later ages and increased resistance to aggressive attack of sea water and natural acid waters. closer control of the desired properties of the concrete would result from the regulated additions at the mixer.TUTHILL ON MINERAL ADMIXTURES 807 Specification for Blended Hydraulic Cements (C 595). Portland blast-furnace slag cements have been used widely in Europe since about 1855. was required in the 1960 Federal Specification SS-C-197b [2] to comply with the following requirement for composition CaO + MgO + U3A1203 SiO2 + 2/3A1203 1. In addition. The use of blast-furnace slags as cementitious materials generally is limited at the present time to the manufacture of portland blastfurnace slag cements and slag cements. No further reproductions authorized. . may tend to inhibit expansion due to alkali-aggregate reaction. At later ages.0 SiO2 + V3AI203 The chemical requirements for the slag cement itself are directed toward limiting the quantities of certain compounds present." Slag cements have lower strengths than portland blast-furnace slag cements. Type S is defined as slag cement for use as a blend with portland cement in making concrete and as a blend with hydrated lime in making masonry mortar. Chemical requirements for slag cements are the same for both types. Slag Cement Slag cement is defined in previously mentioned ASTM Specification C 595 as the "finely divided material consisting essentially of an intimate and uniform blend of granulated blast-furnace slag and hydrated lime in which the slag constituent is at least 60 percent of the weight of the slag cement. No further reproductions authorized.0 2. most countries have abandoned production of this cement. max Loss on ignition. In the United States. ASTM Specification C 595 and the 1960 Federal specifications [3] cover two types of slag cements. The relative improvements are likely to be greater for concrete in which the cementitious material contains the largest proportion of the slag component. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. max Copyright by ASTM Int'l (all rights reserved). however.0 1. max Sulfide sulfur (S). they generally are used in combination with portland cement in concrete. 4. Economy is the primary advantage to be derived from the use of slag cement. Concrete containing this type of cement usually exhibits good resistance to sulfate attack and better plasticity than does corresponding straight portland cement concrete. the proportions usually used are about 50 percent slag cement and 50 percent portland cement. However. Because of their low strength. max Insoluble residue. These limits require the composition of the slag to conform to the following CaO + MgO + 1/3A1203 _> 1.0 percent percent percent percent . because it is relatively unstable in storage and is lower in strength-producing characteristics.0 4. The chemical requirements listed in ASTM Specification C 595 are as follows: Sulfur trioxide (SOa). Type SA is an air-entraining slag cement for the same uses as Type S.808 TESTS AND PROPERTIES OF OTHER MATERIALS greatly with the composition and fineness of the slag and the composition and fineness of the cement. Concrete containing slag cement in combination with portland cement gains strength slower and may have less temperature rise than corresponding straight portland cement concrete. Types S and SA. the strengths of slag cement-portland cement concrete which has been moist cured generally are comparable to straight portland cement concrete. 30 percent less at 0. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. have been used in the past as admixtures for concrete. the rapidity of slaking and the evolution of heat. hydraulic lime must also conform to physical requirements for fineness. Requirements for fineness are that not more than 0. are a maximum of 2 h for initial Copyright by ASTM Int'l (all rights reserved). Hydraulic Lime Hydraulic lime is obtained from the burning of limestone containing clay. is required to be between 16 and 26 percent. The physical test limits for slag cements require that the specific surface by the Blaine air permeability method be an average of not less that 4700 cm2/g with no single value being less than 4200 cm2/g.50 percent. These limits are as designated in ASTM Specification for Processing Additions for Use in the Manufacture of Hydraulic Cements (C 465). containing less than 1 to 2 percent silica and alumina. time of setting. The alumina and silica of the clay combine in some degree with the lime produced in the burning. and compressive strength. to hydraulic limes containing up to 25 percent of these constituents. The compressive strength requirements for Type S slag cement at 7 and 28 days' age are 600 and 1500 psi. 30 sieve and not more than 10 percent may be retained on a No. no appreciable immediate reaction occurs unless they are finely ground. which. which is characteristic of limes high in calcium oxide decreases until. The total of iron and aluminum oxides is limited to a maximum of 12 percent. Hydrated limes. This fineness which is approximately 50 percent higher than that found in most portland cements. The composition of limes may vary from high quality limes. along with iron and aluminum oxides.5 percent may be retained on a No. combines with the calcium and magnesium oxides and imparts the hydraulic properties to the lime. ASTM Specification for Hydraulic Hydrated Lime for Structural Purposes (C 141) requires that calcium and magnesium oxides comprise between 65 and 75 percent of the hydraulic hydrated lime. No further reproductions authorized. In addition to the chemical requirements. final set 1 h less at 7 h. the ASTM Specification C 595 requirements for slag cement are: (Vicat) initial set the same at 45 min. and carbon dioxide may not exceed 8 percent. and air content of mortar the same at 12 percent maximum for nonair-entraining cement but 3 percent less at 19 percent. with no lesser minimum limit. both with and without hydraulic properties. helps to improve the strength-producing properties of slag. soundness 0. respectively. soundness. and the resulting compounds are responsible for the hydraulic properties of the material. . time of setting limitations by the Gilmore needle test. The silica content. As the content of silica and alumina increases. with the limes having a high degree of hydraulic activity. As compared with requirements in ASTM Specification C 150 for portland cement.TUTHILL ON MINERAL ADMIXTURES 809 Specification C 595 also has limitations on the types and quantities of processing additions which may be interground with slag cements. 200 sieve. has continued intermittently since that time. The autoclave test for soundness permits not more than 1. The first large scale use of pozzolan in the United States took place in 1910 when a rhyolite tuff was used in the construction of the Los Angeles aqueduct.4 kPa (S00 psi) at 28 days' age. such as quartz even in finely divided form. Calcium hydroxide is liberated during the hydration of portland cement. hydraulic hydrated lime rarely is used as an admixture in concrete." which produced strengths in tension tests equal to straight portland cement at one year and gave greater strengths at five years' age. to between 15 and 40 percent. the compressive strength requirements are a minimum of 1723. chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties (ASTM Definition of Terms Relating to Hydraulic Cement (C 219)). in finely divided form and in the presence of moisture. it is agreed that the siliceous ingredient of a pozzolan should be in an amorphous or noncrystalline state. and. Such materials were used in a variety of constructions.0 percent expansion. except with curing at elevated temperatures. No further reproductions authorized. One of its principal uses is as an ingredient in masonry mortars. when employed solely for the purpose of improving workability. which were built by the Bureau of Reclamation between 1911 and 1916. especially considering modern specifications requirements. some of which are still in service. The early Greeks and Romans used pozzolans in combination with lime to improve the cementing qualities of lime. The amounts of pozzolan used in concrete has varied from 5 percent or less of the total cementitious material. such as glass. combine. primarily due to the lack of any real advantage being derived from such use. At the present time. they were interground with cement to produce"sand cements. This was followed by the use of ground granite in Arrowrock Dam and pulverized sandstone in Elephant Butte Dam. are considered to be quite inactive. opal. or thermally altered clay for best activity.810 TESTS AND PROPERTIES OF OTHER MATERIALS set. Although the degree of pozzolanic activity of the Arrowrock ground granite and Elephant Butte ground sandstone was very low. . Pozzolanic Materials The term "pozzolan" is employed to designate a siliceous or siliceous and aluminous material. Generally.6 kPa (250 psi) at 7 days' age and 3347. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. but slowly. and 24 h for final set. and pozzolans combine with this liberated calcium hydroxide to form stable cementitious compounds which contribute to strength and watertightness. which in itself possesses little or no cementitious value but will. with lime. particularly in mass concrete construction. The use of varying amounts of pozzolan in concrete. therefore. including the aqueducts of ancient Rome. Crystalline siliceous materials. when utilized Copyright by ASTM Int'l (all rights reserved). Natural pozzolans include such materials as some diatomaceous earths. alumina. moisture content.TUTHILL ON MINERAL ADMIXTURES 811 for its pozzolanic properties. usually the low carbon fly ashes of the United States require no further processing. Italian specifications require that the lowest quantity of pozzolan to be used with a cement be determined by the following composition ratio to which the cement-pozzolan mixture in total should agree SiO2 % + A1203% + Fe203 % >1 CaO% = Pozzolans are classified into two major groups: (1) raw or calcined natural and (2) artificial. and volcanic ashes or pumicites. the amount used generally ranges between about IS and 35 percent by weight of the total cementitious material. The spherical shape and texture of the low carbon fly ashes generally result in a reduced water requirement when used in concrete. The American Society for Testing and Materials. sulfur trioxide. Each may or may not require calcination. and exchangeable alkalies. an attempt is made to proportion the amounts used to obtain a balance between the total amount of silica. To conform to this principle. the cementitious properties being thereby more completely utilized. . Copyright by ASTM Int'l (all rights reserved). These compounds are magnesium oxide. The other main compounds present in pozzolans have maximum limits placed upon the quantities permitted to be present. the California Department of Water Resources. loss on ignition. as well as at least one state agency. aluminum oxide. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. have established specifications for pozzolans. and precipitated silica. are given in Table 2. most of the free lime in cements is combined with silicates and aluminates. in maximum and minimum values. Suitable fly ash has a lowcarbon content and a fineness usually about the same as that of portland cement. and ferric oxide. tufts. are given in Table 1 and physical requirements. Artificial pozzolans include the fine fly ash produced from the burning of powdered coal which is caught in electrostatic precipitators. where pozzolans interground with portland cement are used extensively. the federal agencies such as the Bureau of Reclamation and the Corps of Engineers. In the United States. depending upon its clay content or grinding or both in order to be suitable for use as pozzolan. These requirements provide for a minimum of 70 to 75 percent of the pozzolan to be composed of silicon dioxide. concrete containing most natural or calcined natural pozzolans requires more water than does the corresponding portland cement concrete. Chemical limitations. In Italy. No further reproductions authorized. In this way. Most of the fly ash particles are in the form of tiny glassy spheres. and iron oxide with the total amount of calcium oxide available in the cementpozzolan mixture. opaline cherts and shales. in percent. waterquenched boiler slag. On the other hand. 5 1. not more than than Compressive strength With portland cement. 0.0 3. 75 (900) 85 (900) 75 (800) 85 (800) 0. cm 2/ cm 3.. percent.0 1. 325 mesh sieve.020 0. Bureau of Reclamation and Corps of Engineers [4] Item Fineness Specific surface.812 TESTS AND PROPERTIES OF OTHER MATERIALS TABLE 1--Chemical requirementsfor pozzolans.0 5.03 0.50 0. .5 .0 . 28 days.0 3.0 5.. autoclave expansion.03 115 105 115 105 75 . 7 days.020 0.0 70. not more than Soundness.020 0. 4. 75 . 1. not more than Exchangeable alkalies as Na20.0 4.0 8.0 70. not morethan Water requirement. Bureau of Reclamation and Corps of Engineers Item Silicon dioxide (SiO2) + alum i n u m oxide (A1203) + ferrite oxide (Fe203) not less than Magnesium oxide (MgO). min M P a (psi) Increase in drying shrinkage of mortar bar. percent of control.03 0.50 Copyright by ASTM Int'l (all rights reserved).0 12.0 5...0 10.. Blaine air permeability apparatus. not less than Material retained on No. percent shrinkage of pozzolan bar minus percent shrinkage of control bar. .0 6.0 4. not more than Loss on ignition.0 70.020 0.50 0.. not more than Moisture content. not less than Mortar expansion at 14 days percent...5 2--Physical requirementsfor pozzolans..50 0. not more than ASTM Specification C 618 Natural (Type N) Fly Ash Natural (Type N) Fly Ash 12 000 6 500 12 000 6 500 20 34 .03 0. percent not more than Reduction of reactive expansion at 14 days. percent. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. percent. not more than TABLE ASTM Specification C 618 Natural Pozzolan Fly Ash Natural Pozzolan Fly Ash 70. not less than With lime. not more than Sulfur trioxide (SO3).0 3. No further reproductions authorized.0 3.0 5. 3). . Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. it is necessary to proportion the concrete mixes to provide higher early strengths. However. 1--Permeability of concrete with and without pozzolan. concretes containing some pozzolans under moist or mass curing conditions continue to gain in strength for a long period of time and may produce concretes whose strengths are equal to or substantially greater than the strength of corresponding straight portland cement concretes.4 70 to . 1) [5]. One method frequently used in certain localities to partially counteract the lower strength of portland cement-pozzolan concrete at early ages is the redesign of concrete mixtures to incorporate a greater amount of pozzolan in the mix than the cement it replaces [6. lower heat of hydration (Fig. Pozzolans lower the resistance of concrete to deterioration caused by freezing and thawing unless longer than usual moist curing is provided. Therefore.TUTHILL ON MINERAL ADMIXTURES 813 The principal technical benefits generally derived from the use of pozzolan in concrete are increased impermeability (Fig. No further reproductions authorized.7]. However. reduced alkali-aggregate expansion (Fig. Redesign of mixtures in this manner can be justified economically only in localities where the cost of the pozzolan is low enough to permit production of this concrete without an increase in cost. Copyright by ASTM Int'l (all rights reserved). paving and structural concrete generally require early strength properties comparable to those obtained in straight portland cement concrete. when pozzolan is used for these purposes. and improved workability. 2) [5]. One of the disadvantages of using pozzolan is that concrete containing pozzolan generally develops strength more slowly than portland cement concrete. 12 X 10 -4 i 35 o ' I --~ 9 i0 3o ~ 100% portland cement -8 25 ~ 20 "6 ~E . 400 450 500 ib/yd 3 concrete FIG.~- ~ 75% p o r t l a n d cement ! 25 tO 30% fly ash 5 200 250 300 350 Cementing Materials. this type of strength gain is satisfactory. which in most instances is not always practicable kg/m 3 40 X 10 -4 125 150 ' ' 175 200 225 ' I I o 250 I 275 [ . In mass concrete. under prolonged moist curing conditions. Pozzolanic activity index: Copyright by ASTM Int'l (all rights reserved). consequently it becomes amply and comparably durable. With recommended air entrainment.814 TESTS AND PROPERTIES OF OTHER MATERIALS 60 If. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. exposure ambients are sufficiently moist so much of the time that full natural curing and maturity of exposed pozzolan-cement concrete is sooner or later attained. during construction. by weighf. Conformance with the specifications limits listed in Table 2 generally will assure that pozzolan will impart the desired properties to concrete in which it is used. No further reproductions authorized. In most regions having enough freezing and thawing weather to affect durability. 0 "D 00 I 5 tO Age 15 in Days 20 25 50 0 FIG. Calcined Diafomaceous Shale replocemenf.30~. C . the California Department of Water Resources. A . However.N o Pozzolon replacement 13 . ~ 30 t) 15 ~7 Jo ~ 50 p 40 0 0 0 n- 2 tO E Y 3 Sacks of cemenfing maferial per cubic yard of concrete : A .30*/. Fly Ash replacemenf. r E u 5 0 . by w?. 2--Effect of pozzolan on temperature rise of concrete. any such effect on durability is likely to be small in comparison with the benefits of using pozzolan. many pozzolans have a beneficial effect on the durability of concrete as measured by freezing and thawing tests. to assure procurement of pozzolan of maximum effectiveness. one state agency. . However. improved the following four physical requirements in their specifications for N-type natural pozzolan as compared with corresponding requirement values shown in Table 2. The magnitude of the reduction is usually not large and varies with the pozzolan. 4 QUARTZ (CONTROL) 0. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. min.6 CALCINED 0.0. (Note.2 Nol~-reoc//ve 0. percentage of control With lime.2 0.6 FL:ASH 0.6 OIL -=: 0. The Copyright by ASTM Int'l (all rights reserved).'2 mortar in 25 by 25 by 278.TUTHILL ON MINERAL ADMIXTURES 815 ~ 0.5 0. at 28 days.2 X x '. ) bars sealed moist at IO0~ ) With portland cement.3 0. expansion after 15 months storage.1 0 0..5 NCALCINED 0.7 0. at 7 days. .7 0.1 0 0 6 12 18 6 t2 18 0 G 12 POZZOLAN REPLACING HIGH-ALKALI CEMENT. t8 F I G .7 I 0.5 CA LCI N E D PUMICITE I I ALCINED UE NTE 0. No further reproductions authorized. min percent 90 (1000) 110 85 The fineness requirement is important to assure that a uniform and sufficient surface area per unit quantity of material is present to react with the calcium hydroxide which is liberated during the hydration of cement." 1.5 CALCINED c 0. max.3 0.mm (1 by 1 by 11 88 in. 3--Effect of small proportions of pozzolans on chemical reactivity in mortar bars. percentage of control Reactivity with cement alkalies: Reduction of mortar expansion at 14 days.4 ~ 0. PERCENT BY W E I G H T . I Aggregole7 0 0.4 •X•'PUMICITE 0. min MPa (psi) Water requirement. The water requirement of concrete may also be increased by pozzolans of very high fineness. Copyright by ASTM Int'l (all rights reserved). require a larger amount of water in concrete for a given slump. since the value of a pozzolan when employed in combination with portland cement depends primarily upon its effect upon strength of concrete. as determined from tests on S0-mm (2-in. Methods of test in use for determination of fineness of pozzolans include specific surface (cm2/g or cm2/cm3 of solid volume) by Blaine air permeability apparatus. 325) mesh sieve. concrete containing optimum amounts of pozzolan frequently develops higher strengths (Fig. Coarse pozzolans of poor particle shape. the greater will be the drying skrinkage of the concrete in which it is used. The compressive strength of portland cement-pozzolan mortar is a property of considerable importance. with compressive strengths of a similar mortar containing the same portland cement without pozzolan. per cent of material retained on a (No. the difference in strength becomes progressively less as the age of the concrete increases. Coarse pozzolans of poor particle shape.816 TESTS AND PROPERTIES OF OTHER MATERIALS fineness of a pozzolan will affect its other properties. Sec. when fog-cured 28 days. at later ages. such as some of the coarse volcanic ashes. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. when used in large amounts. No further reproductions authorized. and calculated mean particle diameter. The greater the water requirement of a pozzolan. The contribution of a pozzolan to strength of concrete arises in the cohesion of the hydration products of cement pozzolan combinations and in the adhesion of the matrix to the grains of sand or other aggregate. Pozzolans will react with hydrated lime in the presence of moisture developing a "set" by the formation of cementitious products and increasing in strength to an extent that depends on the activity of the pozzolan. and. usually produce strengths which are lower than similarly cured concrete containing the same weight of portland cement only. the more rapid is the rate of chemical reaction and the greater is the proportion of the pozzolan which reacts. also contribute to bleeding in freshly mixed concrete.)-cube specimens. Concretes containing pozzolan. 4). such as some diatomites. The workability of concrete is decreased as the fineness is decreased. . 7). particularly volcanic glasses. primarily its strength producing ability. which test is considered effective in determining the total activity of pozzolan (ASTM Specification for Fly Ash and Other Pozzolans for Use with Lime (C 593). However. Another test used for determining the strength-producing properties of pozzolan is the test for compressive strength with lime. The slower strength-producing properties of portland cement-pozzolan concretes are considered to be due to the slow rate of reaction between the calcium hydroxide liberated as the cement hydrates and amorphous silica or siliceous glass to form silicates and aluminosilicates of lime that are not found in portland cement concretes which do not contain pozzolan. An evaluation of the compressive strength-producing properties of pozzolans is made by comparing the compressive strengths of portland cement-pozzolan mortars. The more finely ground a material is. Type 11. E--25 percent flyash pozzolan replacement by weight. A a n d B--470 lb cementitious material per cubic yard of concrete. the water requirement for concrete of a given consistency usually is changed. Cement A. Cement B. Therefore.O 35O 5000 300 4000 250 3000 200 ~ 150 2000 8 10. D a n d E--282 lb cementitious material per cubic yard of concrete.TUTHILL ON MINERAL ADMIXTURES 817 6000 J 40. Results of this test are generally reported after 7 days' age and. . Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. the lime-pozzolan test for compressive strength is also useful as a uniformity test for compressive strength after a source has been established. a direct relationship exists between water requirement and drying shrinkage. the greater the drying shrinkage. the greater the amount of water required. and fly ashes of low carbon content usually lower it slightly. C--30 percent N-type pozzolan replacement by weight. a lime pozzolan sand mortar is used to obtain an evaluation of the activity of the pozzolan without introducing other variables from portland cement. A high-water requirement will increase drying shrinkage of conCopyright by ASTM Int'l (all rights reserved). provide a more rapid evaluation of the strength-producing properties of a pozzolan than do portland cement-pozzolan strengths which generally are reported at 28 days' age. Natural pozzolans have a tendency to increase the water requirement. by weight. A--No pozzolan. 4--Effect of some pozzolans on compressive strength of concrete. As previously mentioned. No further reproductions authorized. However. C.15 percent N-type pozzolan replacement. Type II. When pozzolan is added to concrete as a partial cement replacement.0 50 0 0 7 2| 9! AGE. B . It is considered that the portland cement-pozzolan mortar test provides a more reliable indication of the actual performance to be expected from concrete containing a given pozzolan. therefore. D-No pozzolan.DAYS 365 O0 T30 F I G . Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.J= -400 . Pozzolan specifications limit the percent increase in both water requirement and drying shrinkage of mortar containing portland cement-pozzolan combinations over that of portland cement mortar without pozzolan. ~ . Figure 5 [5] shows the effect of various pozzolan replacements on drying shrinkage and autogenous length change of portland cement concrete. in Davis Dam (some parts without and some with) and in structures of the Delta-Mendota Canal (without) and of the California Aqueduct (with) which are in identical service conditions running parallel on the west side of the San Joaquin Valley. . such as strength. these greater laboratory shrinkage values for the N-type natural pozzolans are not always reflected in a visible additional amount of cracking in field structures. impermeability.no.o0 car. Both have cracks. and may harmfully affect other properties of concrete. It is not as if there were cracks in the pozzolan concrete and none in the concrete without it. b y w t .~ ' ~ ~ O F~ H . ~ -600 3 7 14 28 Age in Days ( L o q 90 Scale ) 180 E F G H 365 FIG.|_="-3 ~ zoo ~ ~'~ i'~~ ~Drying shrinkage at 50% relative humidity . This was noted where concrete with and without such pozzolan was examined particularly for this comparison. by wt. durability as measured by freezing and thawing.~ 9o days . 5--Drying shrinkage and autogenous length change of lO0 by 100 by 750-ram (4 by 4 by 30-in. Copyright by ASTM Int'l (all rights reserved). ~ ~ | B & F . No further reproductions authorized.cubic yard of concrete : ~ ~ A 8 E . ) bars of portland cement concrete with variouspozzolan replacements.5 0 % Fly Ash replacement.818 TESTS AND PROPERTIES OF OTHER MATERIALS crete.50% Calcined Shale replacement. which in turn will increase the amount of cracking which may occur. b y w t . .NO replacement I ~ ~ "-500 C & G .50% Pumice replocemenf. and sulfate resistance. However. to assure that the shrinkage characteristics of concrete containing pozzolan are not adversely affected to a harmful degree. If visible cracking is to be eliminated it will not be accomplished as much by choice of materials as it can be approached by judicious use of contraction joints and grooves. ~ c> 3 Sacks of cementi . some pozzolans were found to effectively reduce expansion caused by alkali aggregate reaction. is well worth considering and making if one of the values expected from use of a pozzolan is control of alkali-silica expansion. However. natural N-type pozzolans. reduced expansion very positively even with the highalkali cement and reactive aggregate. the considerable superior reduction of such expansion imparted by the Ntype. is generally used for this purpose. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. all the others except the pumicite.10 percent after 15 months of storage under conditions highly conducive to maximum alkali-silica expansion. Subsequently. Also it is shown by less reduction in expansion with 15 and 18 percent of the fly ash in the lower left unit and of the S-type pumicite in the lower right unit of Fig. this distinction between N-type and other pozzolans. One of the important benefits derived from the use of pozzolan is its effectiveness in controlling potentially disruptive expansion in concrete resulting from the formation of an alkali-silicate gel. All but the two just mentioned were nonfly ash. Initially. which is the product of reaction between certain types of mineral aggregates (cherts. Other pozzolans have little effect in controlling this expansion. opal. Accordingly. and so on) and the alkalies (sodium and potassium oxide) in cement. nonfly ash pozzolan is a much more important factor in its favor than its minor and seldom evident contribution to shrinkage is to the contrary. Therefore. which is not clearly made in some specifications. In general the N-type pozzolans will be found to be considerably superior to the S-type and fly ash pozzolans in their ability to reduce expansion due to the alkali-silica reaction. which is only slightly better than the fly ash in this respect. which measures the effectiveness of a pozzolan in reducing expansion of mortar made with high-alkali cement and reactive aggregate. An accelerated test (ASTM Test for Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method) (C 227)). except for the ground quartz. the only apparent methods of controlling alkali-aggregate reaction in concrete were to use low-alkali cements or to avoid the use of reactive aggregates. nonpozzolan control shown in the upper left unit of Fig. which only began to reduce expansion when used in amounts of 15 and 18 percent. it is necessary to test pozzolans individually in order to evaluate their ability to control this expansive reaction. At these amounts. No further reproductions authorized. 3. This is indicated in the absence of a value for minimum percent reduction in expansion allowed for fly ash by the ASTM and Federal specifications cited in Table 2. replacement of some portion of the cement with any pozzolan will have the effect of diluting the alkalies just Copyright by ASTM Int'l (all rights reserved). The amount of pozzolan needed in concrete to control reactive expansion will vary with the individual pozzolan. In this figure it will be noted that all these tests of different pozzolans were made with high-alkali cement.TUTHILL ON MINERAL ADMIXTURES 819 Moreover. to substantially less than 0. if any question of alkali-silica expansive reaction may be involved. aggregates. and with the alkali content of the cement. 3. . (5) Type I with fly ash. According to a wide range of long-time testing of sulfate resistance at the U. as required for portland cements. this does not mean that thereby Type I was made as resistant as Type V. indications are clear that greatly improved resistance to severe exposure to sulfates. is markedly improved sulfate resistance. The more severe the exposure. No further reproductions authorized. Through improved technology and a thorough knowledge of proper design of concrete mixes to meet specific Copyright by ASTM Int'l (all rights reserved). such tests require many months. "dead burnt" calcium oxide. all such good pozzolans materially improve the impermeability of the concrete so that it is less vulnerable to penetration of solutions carrying the sulfates. the greater was the benefit of the pozzolan in resisting it. or an excessive amount of sulfur trioxide. However. . The expansion of mortar bars determined by the autoclave soundness test. Another substantial benefit from the use of fly ash and N-type pozzolans meeting requirements of ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618). ACI Committee 212 [8] advises that pozzolans should not be used in amounts less than about 15 percent by weight of total cementitious material. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. These did as well as many of the fly ashes in air-entrained concrete. potential job cement and pozzolan should be tested for specific combined capability. As a safety precaution against the possibility of increased alkali-silica expansion in concretes containing small (pessimum) amounts of certain pozzolans less than 10 percent by weight of the cement. all types of cement are notably improved in this respect by pozzolans. Ideally. The order of resistance reported was (1) Type V with fly ash (greatest resistance). The potential danger of unsoundness occurring in concrete due to the presence in pozzolan of either the periclase form of magnesia. even several years. Unfortunately. (3) Type V.S. Whether or not such tests are made. (4) Type II. With 12 fly ashes tested there were two N-type pozzolans. of specimen exposure in strong sulfate solutions to make positive distinctions. Bureau of Reclamation. (6) Type I (least resistance). is the procedure used for evaluation of the effect of a pozzolan on soundness of concrete.820 TESTS AND PROPERTIES OF OTHER MATERIALS that much and to that extent cause some reduction in their reaction with silica aggregate. (2) Type II with fly ash (barely greater than Type V). No lignite and subbituminous fly ashes were included. will be obtained if 15 to 30 percent of the cement (preferably Type V) is replaced by weight with fly ash or N-type pozzolan meeting the requirements of ASTM Specification C 618. Much has been done in recent years toward the development and refinement of the use of mineral admixtures. Aside from their ability to combine with and thus deny lime for expansive combination with sulfates that penetrate the concrete. points out the importance of determining the characteristics of the" pozzolan in this regard. Later indications are that these do not reliably increase sulfate resistance. Bibliography Blanks. H. . New York. Bogue. Army. 1955. F. New York. 1. it is a n t i c i p a t e d t h a t the f u t u r e will c o n t i n u e to show m a r k e d i m p r o v e m e n t s in concrete technology. American Society for Testing and Materials. [4] "Pozzolan. 1963. Dec. 23. B a s e d u p o n p r e s e n t technological advances. N. Department of the Interior. p. "Application of Fly Ash for Lean Concrete Mixes.. [8] ACI Committee 212.. Vol. Del Instituto de Ingenieria. which have p r o v i d e d b e t t e r concrete a t lower cost. W.. Sec. Portland. American Concrete Institute. pp. G.2. and Washa. 1975." Federal Specification SS-C-218a. the p r e c e d i n g a u t h o r of this p a p e r in the 1966 edition of A S T M S T P 169A. 7th ed. [3] "Cement. 21 Nov. pp. for Use in Portland Cement Concrete. 1971.Y." Publicacion Numero 68. "Cooperative Tests of Fly Ash as an Admixture in Portland Cement Concrete. American Concrete Institute.. American Concrete Institute. New York. this i m p r o v e d technology has r e s u l t e d in m o r e e c o n o m i c a l a n d a d v a n t a g e o u s uses o f m i n e r a l a d m i x t u r e s . Reinhold Publishing Corp. [6] Lovewell. I n a d d i t i o n .. R. Dexheimer. "Use of Pozzolans in Concrete.. Vol. "The Technology of Cement and Concrete. "Pozzolans in Concrete Dams." Technical Report No. "Admixtures for Concrete. 6-445." Proceedings. 377. P r i n c i p a l differences are an u p d a t i n g of the various agency specifications a n d A S T M s t a n d a r d s m e n t i o n e d a n d f u r t h e r i n f o r m a t i o n r e g a r d i n g the i m p r o v e m e n t s i m p a r t e d to concrete by the various pozzolans.. H i g g i n s o n . and Kennedy. Corps of Engineers. G." Proceedings. Miss. R. Wiley. p a r t i c u l a r l y as to sulfate resistance a n d as to effective control of t h e alkali-silica reaction. 26 Sept.. H." Concrete Materials. 1093. Copyright by ASTM Int'l (all rights reserved). 6. Universidad Nacional Autonoma de Mexico. p.. E. Sept. [2] "Cement. C. Waterways Experiment Station. "Proportioning of Concrete Mixtures Using Fly Ash. U. 1958. 1956. 1958. 54." Federal Specification SS-C-197b. [5] Higginson.Y. 1955. which will u n d o u b t e d l y include f u r t h e r r e f i n e m e n t s in the use of m i n e r a l a d m i x t u r e s . L." Proceedings. E." Question No. 6th International Congress on Large Dams. "Manual de Control del Concreto. The Chemistry of Portland Cement. "Investigations of Portland Blast-Furnace Slag Cements. 1931. 27. M. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1960. 2 Dec. 97." Federal Specification SS-C-1960/5.." Report of Subcommittee III-h on Methods of Testing and Specifications for Admixtures. No further reproductions authorized. 1960. Vicksburg. Vol.. W. American Concrete Institute. 62. 44..S." Proceedings. C." Journal. 1950. Acknowledgments This writer wishes to give full credit to E. E. "Admixtures and Workability of Concrete. 1962. p. 1962. Concrete Manual. Proceedings. References [1] Williams.5. Vol. N. 810-820. American Society for Testing and Materials. 647. C.S. U. 46. R. Bureau of Reclamation.TUTHILL ON MINERAL ADMIXTURES 821 needs. 314-348. A.. A. R. 1944. Blast-Furnace Slag. T h e g r e a t m a j o r i t y o f its original content r e m a i n s u n c h a n g e d in this edition. Vol. Vol. the use of m a n y a d m i x t u r e s previously used has b e e n e l i m i n a t e d . H. Slag. [7] Frederick. Davis. H. pp.. Martin's Press Inc. S. F. American Society for Testing and Materials. . and Desch. A S T M STP 99. Sun Apr 6 21:31:09 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. NO.. 375-387. N. "Mineral Admixtures. Copyright by ASTM Int'l (all rights reserved). Meissner. C. C.Y. New York." Economic Geology. Vol. 1956. and Schieltz. M... C. K. N." Significance of Tests and Properties of Concrete and Concrete Aggregates. 3. H. R. The Chemistry of Cement and Concrete. Greene. Use of Pozzolanic Materials in Mortars and Concretes. St. A S T M STP 169.. 311-328. pp. Mielenz. 46. No further reproductions authorized. 1951. T.822 TESTS AND PROPERTIES OF OTHER MATERIALS Lea. American Society for Testing and Materials. 1950... "Natural Pozzolans for Concrete. 1956. 4 [2].astm. (4) pH of solution. entitled "Guide for Use of Admixtures in Concrete" [5]. Structures Laboratory. mortars. hence.STP169B-EB/Dec. Bruce Foster [3]. 1978 Bryant Mather 1 Chapter 47 Chemical Admixtures Preface The original version o f A S T M STP 169 [1] 2 published in 1956 did not have a chapter on "Chemical Admixtures" since at that time there was no ASTM standard covering chemical admixtures. U. It was prepared by Dr. No further reproductions authorized.S. In 1967. (10) infrared or X-ray spectra. Copyright9 1978tobyLicense ASTM International www. Vicksburg. The present chapter is an updating of Dr. there is a discussion of "Quality Control of Admixtures. liaison with the Transportation Research Board Committee A2E05 on Chemical Additions and Admixtures for Concrete and Subcommittee C09. in A S T M STP 169-. RILEM published "Proceedings. The ASTM Specification for Chemical Admixtures for Concrete (C 494) was originally issued in 1962 and." In this discussion there is a presentation of a series of 11 tests of the admixture itself. (9) density. 6. Miss. This committee which was organized in 1943 has functioned in close. Foster's paper. Army Engineer Waterways Experiment Station. (2) loss on ignition. or both. For a more comprehensive review of knowledge in this complex field. tests of the admixture in pastes. In Vol. 2 The italic numbers in brackets refer to the list of references appended to this paper.08 on Test Methods and Specifications for Admixtures for Concrete of ASTM Committee C-9 on Concrete and I Acting chief. (11) methods of identification indicated by the manufacturer. reference should be made to such of the following works as may be relevant. This discussion is limited to certain features of chemical admixtures regarded as most appropriate in the context of this volume. (8) color and odor. In 1971 the American Concrete Institute (ACI) published the fourth report of its Committee 212 on Admixtures for Concrete. 167-185. but informal. 39180. there was a chapter. Copyright by ASTM Int'l (all rights reserved). International Symposium on Admixtures for Mortar and Concrete" [4] held in Brussels. pp. The 11 tests mentioned are: (1) dry solid content. (7) specific surface (of powders). (5) surface tension of solution. Sun Apr 6 21:31:08 EDT 2014 823 Downloaded/printed by Universidade do Gois pursuant Agreement. (3) presence of sugar or chloride.03.org . (6) foam stability. issued in 1966. and concretes. reports of research. I6]. for which he gives references.824 TESTS AND PROPERTIES OF OTHER MATERIALS Concrete Aggregates. . entitled "Admixtures and Special Cements.11] of published work in the preceding year. prepared by Albert Joisel. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1969 [7]. and Vavrin [14]." He reported that in 1974 there were three review papers: Bonzel and Krumm. a water-reducing and retarding admixture as one that reduces the quantitiy of mixing water required to produce concrete of a given slump and retards the setting of concrete. modify the properties of the cement paste of hardened cement stone in a desired way. and a water-reducing and accelerating admixture as one that reduces the quantitiy of mixing water required to produce concrete of a given slump and accelerates the setting and early strength development of concrete. In 1973 a book entitled Admixtures for Concrete of 253 pages with text in parallel columns in English and French. and the state-of-the-art reviews sponsored by all three groups have been studied and used. Odler [I0] defines "chemical admixtures" as "inorganic or organic compounds which. in concrete technology. London." proceedings of a symposium organized jointly by the Concrete Society and the Cement Admixture Association. the Highway Research Board published the report on "Admixtures in Concrete. were published in 1974 discussing the effects of chlorides on hydration of portland cement and on the nature of the products formed." prepared by its Committee A2E05 [8]. Symposia. bibliographies. Most chemical admixtures react chemically with the cement in concrete. when added to portland cement in small amounts (usually less than one percent by weight of cement). [12] Ivanov et al [13]. Chemical admixtures of other types are classified and described in reports of the ACI [5. These five Copyright by ASTM Int'l (all rights reserved). Introduction Although all concrete admixtures are chemicals in a literal sense. an accelerating admixture as one that accelerates the setting and early strength development of concrete. was published [9]. Reviews covering significant portions of the area were distributed in 1970 as Part IV (V. with benefit. In 1975 and 1976 annual reviews were published [10. This discussion will be confined to set-controlling and water reducing admixtures. by convention." [6] and as "The Science of Admixtures. No further reproductions authorized. A review of the mechanism of acceleration by calcium chloride was given by Skalny and Maycock [15]. increases the time of setting) of concrete. A water-reducing admixture is defined as one that reduces the quantity of mixing water required to produce concrete of a given slump. Also in 1971. a retarding admixture as one that retards the setting (that is. by all three.IV) of the Proceedings of the Fifth International Symposium on the Chemistry of Cement. Odler [10] noted that 21 papers. the term "chemical admixture" is restricted to water-soluble substances other than those used solely for the purpose of air entrainment. 6 Nov. CH(SOaNa). Tuthill et al [25] and those who discussed their paper have reported excessive retardation when retarders Copyright by ASTM Int'l (all rights reserved). Therefore. formaldehyde and phenol. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Often. They also may be modified by the addition of an air-entraining admixture. a combination of anthranylic acid.7 X 106. while at the same time preserving the water-reducing properties. Polivka and Klein [24] reported that the effectiveness of the latter materials.B. or both. MATHER ON CHEMICAL ADMIXTURES 825 types of admixtures are referred to in ASTM Specification C 494 as Types A. Odler [11] reported that a series of additional compounds was described to be effective as water-reducing or plasticizing agents. among them: acrolein. glutamic acid amide. It is to be expected that the extent of any modification of setting time will depend upon the properties of the cement to which an admixture is added. The materials in widespread use as set-retarding and water-reducing admixtures in the United States in 1959 were classified by Prior and Adams [19] into four classes: (1) lignosulfonic acids and their salts. and a compound with the formula (NaO2). The accelerating admixture which has found greatest use is calcium chloride [16. The effect of calcium chloride on acceleration of strength development has been reported to vary with the cement with which it is used [18].23]. admixture of triethanolamine and gallic acid. or acceleration. D.20]. both from a waterreducing standpoint and from a retarding standpoint. No further reproductions authorized. The organic material triethanolamine also is used extensively but usually in combination with other materials. use of such materials also results in a lower water requirement to produce a given slump. no significant change in setting time. In each of these. B. while the behavior of concrete containing water-reducing retarders appears to be dependent even more upon the properties of the cement. polyacrylic and polymethacrylic acid or their alkali metal or ammonium salts. polyethylene-oxide with a molecular weight from 8 X l0 s to 6. polyglycerol. (2) modifications and derivatives of iignosulfonic acids and their salts. (3) hydroxylated carboxylic acids and their salts. respectively. Types of Materials and Their Action in Concrete Many materials. the discussion of accelerators will be confined primarily to calcium chloride. and little published information is available on its properties [21. and (4) modifications and derivatives of hydroxylated carboxylic acids and their salts. the primary component has both water-reducing and set-retarding properties. was greater with cements of low alkali and low C3A content. and E. where R is H or Me. when introduced into mortars or concretes have been found to modify the setting properties of portland cement [16-18].CHR(CO2Na). . C. In the formulation of products of Classes 2 and 4 these admixtures may be modified by the addition of other components to give various degrees of retardation. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. However. with no chloride added. working with cements little affected by the addition of either lignosulfonate or hydroxylated carboxylic admixtures. type of aggregate. which could be overcome by an increase in the sulfate content of the cement.08 on Admixtures for Concrete had a task group on chemical admixtures that was working on the modification of ASTM Copyright by ASTM Int'l (all rights reserved). and their capacity to enhance air entrainment and reduce water requirement. No further reproductions authorized. When two or more admixtures are added ~o a concrete mixture. they should be added separately during the mixing operation unless they have been shown to be compatible when added to the concrete as a single material. Water-reducing admixtures are effective with all types of portland cement. The water reduction found with lignosulfonate water-reducers may be contributed to by the air entrained by these materials. such as air-entraining agents or pozzolans. At the time or preparation of this paper (December 1976). when experience with specific admixture-cement combinations under similar job conditions is not available. Bruere [27] and Dodson and Farkas [28] have noted that the effect of water-reducing retarders depends in some cases on the time at which the retarder is added to the mixture. was increased greatly by a 2-min delay in their addition after mixing commenced. and the presence of other admixtures. Seligman and Greening [26] have reported on work that provides information on the chemistry of this phenomenon. even though the cement without the water-reducing retarder showed no early stiffening and had a normal setting time. but definite. The unfavorable behavior of some admixtures with certain cements and under certain conditions of use which have been reported is counterbalanced by a record of successful use under controlled conditions in many concreting operations. portland-pozzolan cement. the excess retardation was accompanied by stiffening. the amount of water reduction with a given admixture is also influenced by dosage. In addition to varying with the particular cement employed. amount over that required to produce the same slump. . ASTM Subcommittee C09. tests with specific materials should precede a decision for use in construction. Often. cement content.826 TESTS AND PROPERTIES OF OTHER MATERIALS were used with certain cements. Effects on Freshly Mixed Concrete Water Reduction The water reduction resulting from the use of traditional water-reducing admixtures ranges from 5 to 15 percent [29]. The addition of recommended amounts of calcium chloride has been found to reduce the water requirement by a small. Dodson and Farkas [28]. portland blast-furnace slag cement.03. and high alumina cement. found that the efficiency of the admixtures as retarders. MATHER ON CHEMICAL ADMIXTURES 827 Specification C 494 to deal with a number of products that had recently come on the market in the United States (principally from Europe and Japan) that permitted greater degrees of water reduction than referred to above. With either lignosulfonate or hydroxylated carboxylic admixtures. dosage. and can produce a very rapid set. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. nor does calcium chloride. Air-entraining properties may be incorporated in the modified materials of Classes 2 and 4 Copyright by ASTM Int'l (all rights reserved). Setting Time The magnitude of the effect on setting time of the addition of calcium chloride depends not only upon the dosage. provided that the allowable air content with lignosulfonate materials is not exceeded. but also upon the particular cement. Germany [31. the temperature. and other factors. so that less air-entraining agent is required when added to concrete containing one of these other admixtures. Classes 2 and 4 water reducers may be formulated to give no retardation or to produce acceleration. Overdosage may produce excessive setting times of 24 h or more. and other factors. at high temperatures. the degree of retardation can be controlled by varying the dosage. both effects being produced by the incorporation of a catalyst or an accelerator. or the United States [33].32]. Similarly. if the concrete finally sets and has been protected from drying. that is. It has been reported that some of these products provide the alteration of properties that characterizes their use for a relatively short period of time. ultimate strengths developed may be satisfactory if forms are left in place for a sufficient length of time. . Air Entrainment Lignosulfonate water-reducing retarders usually entrain 2 to 3 percent of air when used in normal dosages. all three materials enhance the effectiveness of air-entraining agents from the standpoint of volume of air produced. but also upon the temperature. as is also the case with very large dosage at normal temperatures. but in such cases. The hydroxylated carboxylic admixtures do not entrain air. These have been used to produce high-strength concrete by taking advantage of the opportunity they provide to lower the water/cement (w/c) ratio more than generally has been practical with more traditional water-reducing admixtures or to produce "flowing" concrete. The recommended maximum dosage has a substantial effect on setting time at normal temperatures. concrete of much greater slump. the retardation of setting time brought about by retarders is dependent not only upon the particular cement with which they are used. Such admixtures may be added to ready mixed concrete after arrival at the site for placement.B. No further reproductions authorized. The relevant available data may be located beginning with the work in the United Kingdom [30]. However. lignosulfonate water-reducers normally entrain some air. Bleeding Water-reducing admixtures that entrain air reduce bleeding. Copyright by ASTM Int'l (all rights reserved). . When the airentraining agent is not incorporated in another admixture by the manufacturer.828 TESTS AND PROPERTIES OF OTHER MATERIALS by the incorporation of a suitable air-entraining agent. The balance of the water reduction when using a lignosulfonate water reducer. the reduction being due to the entrained air and the lower content. Hydroxylated carboxylic water-reducing retarders have been reported to increase the rate and amount of bleeding. after mixing. As pointed out earlier. The percentage of strength gain at 3 and 7 days is usually higher than that at 28 days. it and other admixtures should be added to the concrete separately unless tests have shown that the two materials are compatible when added to the concrete as a single material. The portion of the water reduction attributable to the air content can. As pointed out above. the addition of a water-reducing admixture will give a high initial slump with the same w/c ratio and permit more slump loss before concrete becomes unworkable. However. No further reproductions authorized. in placing the concrete. Calcium chloride may result in early stiffening and in many cases. this increase in strength is generally greater than would be predicted from the reduction in w/c ratio. Further. Effects on Hardened Concrete Strength Usually compressive strength is increased 10 to 20 percent by use of a water-reducing admixture based on lignosulfonate or a salt of a hydroxylated carboxylic acid [16]. with suitable adjustment of the amount of sand. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. while tests up to 5 years in duration have shown a continued strength benefit. compensate largely or wholly for the loss of strength due to the entrained air. is not added until after mixing has commenced. Such bleeding has been suggested as being responsible for a portion of the strength increase observed with the use of these materials. therefore. Slump Loss Contrary to expectations. and the reduction produced by a hydroxylated carboxylic water reducer. water-reducing retarders usually have not been found effective in reducing slump loss resulting from substantial delays. are effective in increasing the 28-day strength over that which would be produced with similar concrete without admixtures. the use of retarders with some cements may actually produce an early stiffening. Tremper and Spellman. Resistance to Freezing and Thawing While the entrained-air void spacing obtained with Class 1 water-reducing retarders is slightly greater than that for an equivalent amount of entrained air produced by typical air-entraining admixtures. contamination of aggregate. except that the concrete matures more rapidly. found drying shrinkages of 8 to 17 percent greater than similar concrete without admixtures for one hydroxylated and two lignosulfonates. (approximately 75 by 75-mm) cross section made from a blend of Type II cements. Permeability The permeability of concrete is not changed significantly by any of the chemical materials. but the effect is less pronounced than that on compressive strength. Drying Shrinkage The available data on the effect of accelerators and retarders on drying shrinkage are conflicting.34-36]. The relative shrinkage where calcium chloride was added was found to be dependent on the SO3 content of the cement used. probably because of the influence of variations in test procedures employed. calcium chloride also shows maximum strength gain at early ages [34]. as measured by freezing and Copyright by ASTM Int'l (all rights reserved). The percent increase in shrinkage over the control concrete was usually higher for shorter than for longer drying periods. using concrete specimens of 3 by 3-in. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and choice of aggregate source. In assessing the importance of these figures it should be kept in mind that they are comparable in magnitude with effects which may be introduced through choice of cement. using various procedures and drying times. the performance of concrete containing water-reducing retarders. and dried at 50 percent relative humidity for 28 days. Flexural strength generally is improved by all of these admixtures. Accelerators are particularly effective at very early ages and at relatively low temperatures. Other investigators [22. . No further reproductions authorized. and calcium chloride may even cause some reduction in flexural strength at late ages. particularly with accelerators. choice of maximum aggregate size. MATHER ON CHEMICAL ADMIXTURES 829 In common with retarders. and shrinkages of 30 percent greater for calcium chloride. and in the case of accelerators may be affected less by failure to provide effective curing. Concrete with 2 percent calcium chloride has often been found to be stronger at 1 year than similar concrete without the admixture. [23].B. moist cured for 7 days. have reported drying shrinkage figures which are usually lower than those of Tremper and Spellman. often has been found to be better than concrete of the same air content. There is some evidence that retarding admixtures. in concrete in which dissimilar metals are imbedded. Copyright by ASTM Int'l (all rights reserved). By contrast. Also calcium chloride may bring about corrosion where elevated temperature is employed during curing [44]. chlorides should not be used in prestressed concrete [38-40].35]. and of adequate cover thickness. consolidated properly to form a continuous contact with the steel. through the use of water-reducing retarders [35]. This increase might be the result of the reduction in w/c ratio. 37]. and hence the resulting corrosion [411. . when used in conjunction with chlorides. but they may have a pronounced effect upon the rate at which the heat is liberated. or where galvanized forms are to be left in place [43]. either in the presence or absence of iceremoval salts. as would be expected from the earlier strength development. reduce the increased electrical conductivity which normally would result from use of the chlorides. have not been found to bring about corrosion. Calcium chloride has been found to improve the early resistance of concrete to freezing and thawing. If the concrete is proportioned properly.35. but the use of calcium chloride has been found to decrease somewhat the resistance of concrete to sulfates [32]. if any. The usual water-reducing retarders. stannous chloride [44]. another accelerator. effect on the total heat liberated during the hydration of cement [21. No further reproductions authorized. unless modified by the addition of chlorides. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Heat of Hydration The chemical admixtures have been shown to have little. in concrete where stray currents are present [41]. no corrosion problems normally are encountered. such as aluminum conduit and steel reinforcement [42]. Resistance to Sulfates Laboratory tests have shown some small improvement in sulfate resistance.830 TESTS AND PROPERTIES OF OTHER MATERIALS thawing tests. but to reduce somewhat the eventual durability of the fully cured concrete [34. Concrete containing calcium chloride liberates heat earlier. However. but without the water-reducing retarders. was found not to contribute to corrosion. when properly used. Corrosion of Metals The addition of calcium chloride to reinforced concrete has not been found to contribute significantly to corrosion of the reinforcing. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Retarders Retarders may be used to delay the setting of concrete during hot weather. and the latter figure should not be exceeded. Dosage In the case of water-reducing and retarding admixtures dosages required to produce specific results usually are recommended by the manufacturers. In other cases. In the first case the usual benefits accruing from the use of a lower w/c ratio normally will be obtained. Variation in the dosage often can be made to obtain the desired concrete properties under particular job conditions. 1. or a higher slump with delayed placing of the concrete. or to extend the vibration limit so that large members can be cast and consolidated without cold joints. MATHER ON CHEMICAL ADMIXTURES 831 Applications Water-Reducing Admixtures Water-reducing admixtures may be used with no change in cement content and slump to produce concrete with a lower w/c ratio. and without damage to the freshly placed concrete due to settlement of forms as concreting proceeds. It should provide test methods and specification limits by which the Copyright by ASTM Int'l (all rights reserved). Accelerators Accelerators have their primary application in cold weather concreting where they may be used to permit earlier starting of finishing operations. Increase in the dosage in a multipurpose material to obtain one particular effect might not be feasible because. as an example. the manufacturer may change the formulation of the admixture to suit the conditions under which it will be used.B. Specifications A specification for a concrete admixture should serve several purposes. No further reproductions authorized. and in certain cases. the application of insulation. or with reduced cement content and unchanged w/c ratio and slump. In the third application a reduced cost may result. may be obtained. In the second application easier placing of concrete. too much or too little air entrainment might result. and. reduce the time required for curing. with no change in cement content and w/c ratio to produce a higher slump. . and permit earlier removal of forms or loading of the concrete. in many cases an increase in strength greater than normally produced by the reduction in water possibly may result. Calcium chloride usually is added in amounts of 1 to 2 percent by weight of the cement. The complete sets of tests prescribed in ASTM Specification C 494 is so extensive. and air-entraining admixture proposed for the specific work. and slump in the job concrete as use of a new lot of admixture is started. These Copyright by ASTM Int'l (all rights reserved). One alternative to this type of test consists of watching the rate of hardening. appropriate test procedures for establishing the equivalence of materials from different lots. water requirement. 3. water requirement. Excessive drying shrinkage. 46]. and to some extent quantitative. 4. that it is unlikely that it will be performed more than a few times for any given admixture. . and setting time measure properties important in the use of chemical admixtures. Specifications should provide test procedures and test limits against which the material may be judged from the standpoint of not producing deleterious properties in the concrete. low resistance to freezing and thawing. both from the standpoint of composition and concentration. The specification requires the manufacturer to recommend. and blend of cement would perform satisfactorily with the other concrete ingredients on a particular job. Tests for strength. compositional analysis of water-reducing retarders may be obtained by infrared or ultraviolet absorption spectroscopy [45. tests be made using the cement. aggregates of specified grading. where practicable. and specific job conditions can be assessed. and requires such an extended period of time. It contains recommendations that can serve to assure that a particular admixture previously subjected to all the specification tests and found satisfactory when tested with specific aggregates. No further reproductions authorized. Recommended Practice for Selecting Proportions for Normal and Heavyweight Concrete. and excessive setting time are examples of such properties. and perhaps never for specific lots of materials used in construction work. and a few tests at temperatures anticipated in the field might be profitable. A test procedure is outlined using a blend of cement. to give the user some assurance that the material being used is uniform and is the same as that which was tested. air-entraining agent. and it recommends that. 2. The current version of the ASTM Specification C 494 recognizes each of these needs.832 TESTS AND PROPERTIES OF OTHER MATERIALS material to be tested may be judged as to its general ability to perform the functions for which it is purchased. A specification should provide a ready means of identifying materials in successive shipments. aggregates. upon request.1. Qualitative. The specification should provide procedures whereby the performance of a particular admixture with particular sources of cement and aggregate. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The materials covered by ASTM Specification C 494 are often found particularly useful at temperatures well below or above the laboratory temperature of 23~ (73~ required by the specification. while another involves laboratory concrete tests using the new batch and a reserve sample from the initial batch [47]. and mixture proportions based on ACI Standard 211. on the average." A S T M STP 169-. but as a practical matter. only 50 percent of the time. A S T M STP 169-. pp. "Classification and Definitions of Admixtures. American Society for Testing and Materials. including report of RILEM Working Group on Admixtures. For example.4. but substantial improvement can be achieved only by further reduction in the variance through better testing and test methods. The limits given in Table 1 of ASTM Specification C 494 take this factor into account by lowering the strength requirements and the water requirement by approximately 10 percent. .4. and they are subject to future change in the light of more extensive statistical considerations of the problem. [2] Significance of Tests and Properties of Concrete and Concrete-Making Materials. the specification has been undergoing constant improvement and clarification. 1967. B.. but also that of the control concrete without admixture. [4] Proceedings. [3] Foster. under the requirements of the specification. an admixture which actually caused a 10 percent reduction in strength would be rejected. increasing the number of specimens. or the use of more specimens.B. Since its introduction. Brussels. No further reproductions authorized. Protection to the consumer against acceptance of inferior products can be increased by improving test procedures so that the variance is lowered." Copyright by ASTM Int'l (all rights reserved). American Society for Testing and Materials. on the average. 1966. (1955) 1956. and the limit therefore is set at 120 percent of the control. an admixture which actually. and the test data should be available to the purchaser. will produce an increase of 20 percent in strength would fail to meet the specification requirement 50 percent of the time. less extensive tests might well be used for assessing the admixture's performance with the specific materials and conditions of given concrete work. E. 556-564. References [1] Significance of Tests and Properties of Concrete and Concrete Aggregates. if it is intended that a water-reducing admixture increase the 28-day compressive strength by 20 percent. or both. MATHER ON CHEMICAL ADMIXTURES 833 tests are desirable and necessary to establish the potential value of an admixture. 1966. RILEM. The balance between probability of accepting an inferior product and rejecting a satisfactory one can be adjusted within limits. However. allowance must be made not only for the statistical variation of test results on the concrete containing the admixture. and further revisions no doubt will be made. The rate of rejection for true strengths above or below this point depends on the standard deviation of the test data and the number of test specimens. In establishing specifications for concrete admixtures. 8. International Symposium on Admixtures for Mortar and Concrete. These figures were selected originally as a matter of good judgment. A S T M STP 169. Vol. American Society for Testing and Materials. "Chemical Admixtures. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The specification requirement for Type B (retarding) admixture that the strength of treated concrete at any age be at least 90 percent of that of the untreated control has the objective of requiring that there be no sacrifice in strength due to use of the admixture. M. [11] Odler. "Shrinkage of Concrete--Comparison of Laboratory and Field Performance. pp. 1964. A S T M STP 266. [23] Tremper.S.. American Ceramic Society. 1968. Cements Division. H. Vol. L. "Effects of Three Chemical Admixtures on the Properties of Concrete. "Calcium Chloride in Concrete. Nov. pp. 1960. and Lagoida. 1831." The Concrete Society. p. Bryant. 83-95. Tokyo. 1973. 1975. Pozzolans." Effect of Water Reducing and Set Retarding Admixtures on Properties of Concrete. H. 6-123. "Mechanisms of Acceleration by Calcium Chloride: A Review. S.. No.. L. London. [16] "Admixtures for Concrete. L. F. Highway Research Board. 60. Milos and Klein. 1828. R. 3. and Kalousek. "Importance of Mixing Sequence when Using Set-Retarding Agents with Portland Cement. A. 1943. 30. Vol. J." in Proceedings. Highway Research Board. Jumper. "Delayed Addition of Set-Retarding Admixtures to PortCopyright by ASTM Int'l (all rights reserved). Vol. Vol." Journal. 1974/75. American Society for Testing and Materials. "Admixtures. Highway Research Board. 1970. [21] Newman. Highway Research Board. 32-50.. and Farkas. p. 1-29. 3.. R.. U. Ivan." Beton Zhelezobeton." Miscellaneous Paper No. 6. [7] "The Science of Admixtures. 32. E. 1963. M. Vol. American Concrete Institute. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. No. 170. 4.. L. Bailey. [9] Joisel.. Retarders. [12] Bonzel. 1974. Chemical Publishing Co. [13] Ivanov." Cements Research Progress 1974. Paris.. American Concrete Institute. 30. S. "Introduction to Producers' Papers on Water-Reducing Admixtures and Set-Retarding Admixtures for Concrete. published by the author. The Chemistry of Cement and Concrete. "Effect of Chemical Additions on Hydration Processes and Hardening of Cement. E. Bailey and Spellman. J. 1975. F. V. 2-5." Record No. [22] Mather." Preprint 11. [17] Steinour. 68. p. F. N. H. pp. G. Paul and Greening. . "Concrete Additives. U. Research and Development Laboratories.. 281. C. [14] Vavrin.. Columbus. [19[ Prior. 79-91. Vol. 11. No. 199. p. 1974. G." Proceedings. Portland Cement Association. Corps of Engineers. "Effect of Water-Reducing Admixtures and SetRetarding Admixtures as Influenced by Portland Cement Composition.. Part 4. [18] Lea. pp." VDZ Zement Taschenbuch. American Concrete Institute. May 1956. Adams. 646-676. 1960. 1091. Sept. and Bailey Tremper. E. "Effects of Added Materials on Some Properties of Hydrating Portland Cement Clinkers. ASTM STP 266. 2. including "Use of Surface-Active Agents in Concrete. V. New York.. W." Journal. 62. B. and Adams. Tokyo. Cement Association of Japan. J." Special Report 119. Vol. [20] Vollmer. Proceedings." Effect of WaterReducing Admixtures and Set-Reducing Admixtures on Properties of Concrete. and Smith. 303-331. Batrakov. 1960. and Krumm.. [27] Bruere. pp. 1970. 57. p. p. Columbus. 57. Ohio. R. M. [24] Polivka. [15] Skalny. "Admixtures." Nature.834 TESTS AND PROPERTIES OF OTHER MATERIALS [5] "Guide for Use of Admixtures in Concrete. Wiesbaden-Berlin. [28] Dodson.. pp. 1963. p. Alexander. 80. 1976. 1974. Palmer. E. N. National Bureau of Standards. American Ceramic Society. "Studies of Early Hydration Reactions of Portland Cement by X-Ray Diffraction. E. Ohio.Y. No.. Proceedings. 3rd ed. Report No. 1963. 3. "A Case of Abnormally Slow Hardening Concrete for Tunnel Lining. A. Vol. p. H. p. pp.S." Journal.. 1952 (annotated). 1971. Air Entrainers. 124. G. N. American Society for Testing and Materials. D. discussion by K." Journal of Testing and Evaluation. Vol. Proceedings. Part 4.. March 1961. M. 1971.. 9.. Tokyo.. Proceedings. H. R. Army.. "Concrete Mix Water--How Impure Can it Be?" Journal. 1481-1524. [10] Odler. International Symposium on the Chemistry of Cement. Ivan. and Maycock. 3. V. Vol. M. C. The Organizing Committee." Cements Research Progress 1975. Cements Division..." Journal of Research. Blaine. "Additives for Concrete and Construction Mortar." Bibliography No. 13.. H. pp. Bauverlag GmbH. 1971. Admixtures for Cement (Les Adjuvants du Ciment). International Symposium on the Chemistry of Cement." Record No. F. [8] "Admixtures in Concrete-Accelerators. [6] "Admixtures and Special Cements. 57. Albert. [26] Seligman. Inc. Moscow. 5th International Symposium on The Chemistry of Cement. No further reproductions authorized.. Water Reducers. Proceedings. [25] Tuthill. and Ore. 7. No. A.. 39-42. Peter and Rixom." Proceedings. 1959. "Water-Reducing Retarders for Concrete-Chemical and Spectral Analyses. Sept. 1. American Society for Testing and Materials. Vicksburg." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. "Water-Reducing Retarders for Concrete. 1959. "Curing Requirement for Scale Resistance of Concrete. [32] "Flieszbeton. 31. Vol. Vol. 1960. American Society for Testing and Materials. W. 33.." Monograph 43. Proceedings. "Some Chemical Additions and Admixtures in Cement Paste and Concrete. 48. H. Nov. Set-Retarding Agents. G. [46] Halstead. L. 1955." Proceedings. 2. "Effect of Admixtures Electrolytic Corrosion of Steel Bars in Reinforced Concrete. 1957. 180. W.. Vol. "Corrosion of Galvanized Steel in Contact with Concrete Containing Calcium Chloride. M. Louis. p. 64. and Thorvaldson. Vol. American Concrete Institute." Concrete. T. p. American Concrete Institute. St. J. [30] Hewlett. Setsuji. pp. Bernard. National Bureau of Standards. p. J. . p. "Effects of Calcium Chloride on Prestressing Steel and X-Rays for Anchorage Lengths. "Corrosion Tests on Prestressed Concrete Wire and Strand. J. [29] Vollick. Vol. 97.. "Observations in Testing and Use of Water-Reducing Retarders.. [33] Tynes. and Hideshima. T. R. Yasuo.. "Structural and Lean Mass Concrete as Affected by Water-Reducing. and Woolf. C. Akihilo. T. p. No.. "Water-Soluble Plastics as Concrete Admixtures. 159." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. [38] Evans." USAEWES TR C-77-1." pages 327-350. p. R. p. [40] Godfrey. World Prestressed Conference. E. 150. S. "Effect of Water-Reducing Admixtures and Set-Retarding Admixtures on the Properties of Plastic Concrete. American Concrete Institute. "An Unusual Case of Corrosion of Aluminum Conduit in Concrete. "Corrosion of Prestressed Wire in Concrete. W. p... Mo. A S T M STP 266. [39] Monfore. 537. Nov. Wiesbaden-Berlin. 4th International Symposium on Chemistry of Cement. "Superplasticised Concrete. G." Proceedings.. Vol. 57. No. [34] Shideler.. 1964. p. American Society for Testing and Materials. MATHER ON CHEMICAL ADMIXTURES 835 land Cement Concrete. B. Werner. San Francisco. O. 1962.. [44] Vivian. 1960. E. pp. ASTM STP 266. 1961. [41] Kondo." 13th Annual Conference. E.. E.. C. pp. H." Journal. O. [36] Grieb. H. ASTM STP 266. J." Bulletin 310. 1960. 38. Bauverlag GmbH. 299-312. 1960. 1st International Congress on Polymer Concretes. 54. Takeda. "Detection of Lignosulfonate Retarder in Cement Suspensions and Pastes. London. G. D. Jr. 5. Vol. 2. Vol. Paper No. and Verbeck. Prestressed Concrete Institute. Adams. 431. 1960. April 1977. Proceedings. L. 1960. ]35] Wallace. p.. and Chaiken.." Bulletin No.." The Engineering Journal. H." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. R. [31] Sasse. Highway Research Board. [42] Wright. Proceedings." Journal. [47] Tuthill. Vol.. F.B. 56. E. Highway Research Board." Journal. 1976. "Calcium Chloride in Concrete. E.. 1957. No. 48-51." Effect of Water-Reducing and Set-Retarding Admixtures on Properties of Concrete. 1952. [45] Swenson. 816-829. Calif. American Society for Testing and Materials. J. A S T M STP 266. 1357. E. and Hemme. Copyright by ASTM Int'l (all rights reserved).. [37] Klieger. 38. pp. 1957. 491-516. 45. Paul. 909. American Concrete Institute. 4. Sun Apr 6 21:31:08 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. H." Journal. G. [43] Mange.. Roger. Proceedings. 1975. No further reproductions authorized. pp. Miss. 136. 1958. VDZ Zement Taschenbuch 1976/77. Proceedings. G. American Society for Testing and Materials." Public Roads. National Association of Corrosion Engineers. "Investigation of Proprietary Admixtures. abstract. strength. lprofessor emeritus of civil engineering. Ann Arbor. Universityof Michigan. Since density. No further reproductions authorized. L e g a t s k i ~ Chapter 48--Cellular Concrete Introduction The basic contribution of cellular concrete to the field of concrete technology is the ability to control the density of concrete over a wide range. The cell size varies approximately from 0.004 to 0. of course.).04 in. Copyright by ASTM Int'l (all rights reserved). Density control is achieved by adding a calculated amount of a proper foam to a slurry of water and cement. Sun Apr 6 21:47:39 EDT 2014 836 Downloaded/printed by Universidade do Gois pursuant Agreement. They consist of a system of macroscopic air cells uniformly distributed in either a matrix of cement paste or of aggregate and cement paste. The structural elements referred to above usually will be those which must resist modest loads on a relatively small span. The wet density range for cellular concrete mixes is usually considered to be from about 320 to 1920 kg/m 3 (20 to 120 Ib/ft3). during which periods the cells are separated. and member cross section may now be considered as variables. Examples of nonstructural cellular concretes of broad utility are those used primarily for insulation.org . General Cellular concretes are lightweight concretes. Mich. in addition. to discuss cellular concretes in general. for filling space. Copyright9 1978tobyLicense ASTM International www.STP169B-EB/Dec. M. the procedures for mix design. provide increased insulating value and reduced weight. with or without the addition of sand or other aggregate. Reducing the density of concrete by adding foam. 48104. their physical properties.10 to 1 mm (0. 1978 L.astm. coated with cement paste. It is the objective. The skin of the air cells must be tough and persistent in order to withstand the rigors of mixing and placing. thermal conductivity. and finally the range of their applications. and the concrete is pumped or transported to the casting position. is accompanied by reduction in all of the strength properties as well as a reduction in thermal conductivity. it becomes possible to select a concrete density and size of element that will satisfy strength requirements and. in this chapter. or both. LEGATSKI ON CELLULAR CONCRETE 837 In this discussion it is assumed that the air cells are preformed as foam and added to the slurry in the mixer. In reference to the density of cellular concrete. and A = weight of aggregate kg/m a (lb/yd a) of concrete. In the high-speed mixing method the volume of air cells produced depends on the amount and properties of the foam concentrate and the mixing time as well as the temperature of the water and other materials. the air-dry density of 152 by 305 mm (6 by 12 in. In practice the approximate wet density range is considered to be from 320 to 1920 kg/m a (20 to 120 lb/ft3). the water-cement (w/c) ratio. humidity. It is also possible to form the air cells in the slurry by chemical reaction or by vigorous mixing of the slurry with a proper foam concentrate in a high-speed mixer. the condition of the material in its place in the construction. Cylinders made.) of concrete whose wet density ranged from 480 to 575 kg/m 3 (30 to 36 lb/ft3). confusion can be avoided by always stating the moisture condition of the mix along with the density. For this purpose the oven-dry density may be calculated with sufficient accuracy from the mix data by assuming that the water required for hydration of the cement is 20 percent of the weight of the cement. . The air-dry density of cellular concrete probably represents. the wet density of the concrete. The oven-dry density. and the oven-dry density. There are no definite upper and lower limits of the wet density of cellular concrete mixes. The chemical reaction method of foaming is suited only to precasting and requires a large capital investment in plant. The change in density due to air-drying is a functio~ of temperature. for laboratory conditions: temperature 21 to 24~ (70 to 75~ relative humidity 50 percent and drying period 28 days. D. The significant moisture conditions are wet density (density of the fresh concrete). cured. The relation of air-dry density to wet density would therefore seem to be a complicated one. However. air-dry density (at stated age and curing condition). These latter cylinders were 76 by 152 mm (3 by 6 in. Oven-dry density of cellular concrete usually is used only for determination of thermal conductivity. Copyright by ASTM Int'l (all rights reserved). duration of the drying period. is calculated as follows D = 1.) cylinders is about 80 kg/m 3(5 lb/ft a) less than the wet density for cellular concretes of wet densities from 640 to 1920 kg/m a (40 to 120 lb/fta). No further reproductions authorized. and air-dried under job conditions in the west and southwest states have shown density losses up to about 160 kg/m 3 (10 lb/ft3). Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. as well as any other density measure. Consequently the control of batch density is difficult at best.2c + Akg/m3( 1"2c + A lb/ft3~ \ 27 / (1) where c = weight of cement kg/m 3 (lb/yd 3) of concrete. and the surface-area ratio of the element. These concretes are usually limited to a wet density range from about 800 to 1920 kg/m 3 (50 to 120 lb/ft3). . Modified Cellular Concretes--Any of the above types of cellular concrete mixtures can be modified beneficially by the use of additives. Lightweight Aggregate Cellular Concrete is similar to sanded cellular concrete but with lightweight aggregate replacing part of the sand. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.5 percent of the absolute volume of cement. The lightweight aggregates used should be of structural grade in order to increase the strength-density ratio. causing a modest level of prestress which partially compensates for the effects of drying shrinkage. based on effectiveness. Neat cement cellular concrete usually is limited to the low density range (wet density up to about 720 kg/m 3 (45 lb/ft3). Sanded Cellular Concrete is a cellular concrete that contains fine aggregate (sand) in addition to cement. water. water. and preformed foam.). (c) Expansive Additive--There are advantages to be gained by using an expansive additive or a shrinkage compensating cement in making reinforced cellular concrete members. A suggested lower limit for fiber glass. is a volume of glass fiber equal to about 0. The amount used is usually a compromise based on effectiveness. The following additives have been used successfully in cellular concrete. 2. desired or required workability of the concrete. (b) Chopped Fiber Glass--Alkali resistant fiber glass is added to low density cellular concrete to increase the tensile strength and thus help to control shrinkage cracking. any claimed advantage is questionable.75 to 1. The tendency of the member to expand is restrained by the reinforcing steel. the centroid of the area of reinforcing steel must be at or close enough to the centroid of the section to avoid unwanted curvature of the member due to eccentric prestress. and the cost. However. It contains no solid aggregates. No further reproductions authorized. (a) Cement Dispersing Agent--This additive acts to disperse the cement particles in the batch. The strength increase varies from about 10 percent at a wet density of 1440 kg/m 3 (90 lb/ft 3) to about 40 percent at a wet density of 1760 kg/m 3 (110 lb/ft3). 1. Neat Cement Cellular Concrete is made using portland cement. The upper length limit is related to the increasing difficulty of dispersing fibers in the mix as their length is increased. and preformed foam. The upper limit depends upon the projected use of the concrete. 3. and cost. its required workability. The lower limit length is based on bond with the cement paste.5 in. The range of fiber length is from about 20 to 40 mm (0. and to increase compressive strength especially for wet densities of 1440 kg/m 3 (90 lb/ft 3) and above. Copyright by ASTM Int'l (all rights reserved).838 TESTS AND PROPERTIES OF OTHER MATERIALS Types of Cellular Concretes The various kinds of cellular concretes may be classified and briefly described as follows. 4. Balanced against the dispersion problem. than stone aggregate concrete." Figure 1 shows a curve of compressive strength versus wet density (unit weight) for the cellular concrete mixes described above. are among the important advantages of cellular concrete. This additional variable is accompanied by advantages and disadvantages. Those at or above wet density 800 k g / m 3 (50 lb/ft 3) had a cement content of 390 k g / m 3 (658 lb/yd3). Sufficient test results have not been collected to document the compressive strength and other physical properties across the full density range. type and amount. which is 10 to 15 percent. there is a compensation for this disadvantage. All of the mixes were made with Type I cement. No further reproductions authorized. The principal disadvantage is at least an expected one--the strength properties are reduced by adding air cells (preformed foam) to reduce the density. from 320 to 1920 kg/m 3 (20 to 120 lb/ft3). However. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.carious additives. It can be considered as the price that must be paid for the ability to reduce both density and thermal conductivity by adding stable air cells. (c) aggregate. The lower densities and the accompanying lower values of thermal conductivity. including also all of the mixes modified by . the cellular concretes of lower density have very low tensile strength. Similar curves can be drawn for different cement factors and for various additives. and (/3 curing conditions. Compressive Strength The principal factors affecting the compressive strength of cellular concrete are: (a) density. However. .LEGATSKI ON CELLULAR CONCRETE 839 Physical Properties The density of cellular concrete may be varied over a wide range. The cement factor for neat cement mixes is calculated after selection of the w/c ratio. (d) total water content. The sanded mixes up to 1280 kg/m 3 (80 lb/ft 3) had no additives while those above 1360 kg/m 3 (85 lb/ft 3) contained a cement dispersing agent. The density is an additional variable encountered in working with cellular concrete. information is at hand 9(see appended figures) for neat cement cellular concretes up to wet density of 720 kg/m 3 (45 lb/ft 3) with no additives and sanded cellular concretes from 800 to 1920 k g / m 3 (50 to 120 lb/ft3). The modified cellular concrete mixes shown in Table 1 demonstrate that special admixtures can be quite beneficial in increasing the compressive strength. Thus the use of an additive such as chopped fiber glass to inCopyright by ASTM Int'l (all rights reserved). Therefore. Tensile Strength The tensile strength of cellular concrete bears about the same relation to its compressive strength as does stone aggregate concrete. as will be discussed under "Design of Mixes. (b) cement content. (e) additives. 3 by 17.) were used for shear tests.~ 20. Iblft 3 1--Compressive strength versus unit weight. 4 i 27. 5 bars embedded in the full length of Copyright by ASTM Int'l (all rights reserved).8s Ill ae I2 m Ill Z 1 - - E eL 6. Shown also is the nominal permissible ultimate shear stress for lightweight concrete according to American Concrete Institute (ACI) Building Code Requirements for Reinforced Concrete (ACI 318). . No further reproductions authorized. quite old and are the results of pull-out tests of No.).. They were reinforced with two No. Shear Strength Beam specimens of dimensions 14.5 by 127 cm (5 % by 6 7/a by 50 in.3 o z .6 DISPERSING I-. WEIGHT (WET).4 cm (36 in. 4 bars placed at an effective depth of 12.840 TESTS AND PROPERTIES OF OTHER MATERIALS 641 320 961 1282 SANDED 1602 1922kg/m3 MIXES SACKS~Y-D 3.) and were loaded at midspan. 4 and No. unfortunately. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 2 where the ultimate shear stress is plotted against the wet density of the concrete. Test results are shown in Fig. Bond Strength T h e data for bond strength are. crease tensile strength is common practice in the application of low density cellular concretes.7 7~ 13.9 0 20 30 40 50 60 70 80 90 100 110 20 UNIT FIG. Of course the fiber glass should be alkali-resistant. Comparison indicates that the ACI Code is applicable to cellular concrete. The beams were supported at a span of 91.7 cm (5 in. 0 176 o 0 442 805 416 lb/yd 3 Mix B 1630 460 a 3.) long Liquid latex Expansive additives Preformed foam Compressive strength Compressive strength (with no additives) lb/ft 3 kg/m 3 Item Mix A 0 105 0 0 262 1041 418 247 kg/m 3 65 lb/ft 3 TABLE 1--Typical modified cellular concrete mixes quantities are for 1 m 3 (1 yd3). Type I Water (total) Aggregate sand ceramic beads Additives fiber glass 25 m m (1 in.2 MN/m 2 co Fn . Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. ~These values are for a sanded mix.Copyright by ASTM Int'l (all rights reserved).8 550 0 0 0 0 3 0 51 694 429 45 721 412 255 lb/yd 3 Wet density Cement.-n 0 0 z c i-:IJ t'n r'i-- O Z O (9 f-/'11 .2 ~ psi 11. MN/m 2 psi 2 296 5 0 86 volume as required for density 3. No further reproductions authorized. / .Average Ultimate From Beam Tests /P" _ / of Cellular Concrete. 3 is intended as a reasonable approximation of the lower boundary of the test results.) cylinders of cellular concrete of various densities. In this statement the air cells are treated as aggregate. In a laboratory study of modulus of elasticity of cellular concretes whose density (wet) varied from 1281 to 1842 kg/m 3 (80 to 117 lb/ft 3) the measured Copyright by ASTM Int'l (all rights reserved).z A: .97 0 Z lm 130 120 /?~- 110 n' < 100 W Z 90 1/) /// o / V g 15% 0. 140 o e me / 0. It is reasonable to assume that cellular concrete should have a somewhat lower modulus of elasticity than concrete of the same density but made with a more rigid aggregate whose density is reduced by enclosed voids (manufactured lightweight aggregate). B: Permissible Shear Stress For ~ 1. 152 by 305-mm (6 by 12-in.842 TESTS A N D PROPERTIES OF OTHER MATERIALS 200 190 180 . 1281 1442 1602 I I r e1922 kg/m3 ~.170 o. Modulus of Elasticity The modulus of elasticity of cellular concrete is a function of its density and compressive strength. No further reproductions authorized. FIG. The dotted line in Fig. /~ o ~/~ 160 ' 150 I- 1762 Avg. It would seem that a new test series for development bond is needed. . Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 2--Shear strength versus 110 Ib/ft 3 120 unit weight.-15% ~ .24 Sand Lightweight Concrete f (ACl-318 71).69 / ~ ~ 8O I 70~ 6o! ~ 5O 70 80 UNIT ~c a 90 WEIGHT 100 (WET). . with Dispersing Agent.. -p ~ 600 i Z W E I. it was considered likely that the very low density concretes would be used principally for insulation and that there would be little Copyright by ASTM Int'l (all rights reserved). Points indicated on the graph by unshaded circles represent mixes without a dispersing agent. The equation selected to best interpret the trend of the test results is Ec = W 1. Most of the specimens tested were from mixes containing a cementdispersing agent. a-No.83 . .~ 9 -/ / _ _ db 4* 2. No further reproductions authorized.I . (wet density -. +-No. I" 4 5 4 5 Ba'r. The dotted lines on each side of the Ec line are intended as a guide by which to judge the scatter of data. Bar. 4.//~-.14 m o4 E Z #4+\ a Z 0 W 400 / 9 I# 4 o & #4+ O I 300 .6 x/j~" psi) (2) where W = (wet density . Iblft 3 F I G . The study was not extended to the densities below 1281 kg/m 3 (80 lb/ft 3) because.. and f~' = 28-day compressive strength. (W L5 • 28.5) lb/ft 3.J L ~' c~ / 1922 .LEGATSKI ON CELLULAR 843 CONCRETE kg/m 3 1282 1442 1602 1762 700 e .s • 37.+ with Dispersing A g e n t . Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.04 fx/~'--~2. at that time. . Bar. N / m 2 (psi). a-No. + No Dispersing Agent.80) kg/m 3.07 i 70 7'5 CELLULAR 80 85 CONCRETE 90 95 UNIT 100 105 WEIGHT 110 115 120 (WET).~ ~ ~" m 4.No.76 (Not more than 425) / 2.oo ~ .500 4. 3--Pull-out bond strength versus unit weight9 modulus was plotted against the measured density (wet) as shown in Fig. Bar. No Dispersing Agent. Copyright by ASTM Int'l (all rights reserved).5 0 76 80 86 UNIT 90 96 WEIGHT 100 105 (WET). The units of k are watts/metre-Kelvin or W / m k (BTU 9 in/h 9'.-'%~x__Ec 10% / 2 S~" " Ul Q O Z O ~ O .34 /g-o r Ec I/I . Strength . indicates that a single curve can be used to show the relation of thermal conductivity to oven-dry density for both cellular and other concretes whose density can be varied over a wide range. was developed from thermal conductivity tests on concrete made using no-fines gravel and lightweight manufactured aggregate. i i .I i 6.. *---Mixes containing a cement . i- ~ Ec+ 10% /"_" . D. 4--Modulus of elasticity versus unit weight. assembled from four sources. across unit area for unit difference of temperature.dispersing agent. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. This information. 1922 1762 . National Bureau of Standards curve. The dashed line. . That prediction is being proven false by a growing interest in low density cellular concrete to resist calculated loads. 5.5 1281 . .89 . through unit thickness.[ / / /7~ . ft 2 9 ~ Information from several sources is included in Fig.45 0.24 13. T h e r m a l Conductivity. 5.. The test results plotted represent determinations of thermal conductivity of cellular concretes for a limited range of densities from the sources noted on Fig. / / ~~.79 "9" 10. ? o v- 2 1442 .i ul - 1 . / >. interest in their stiffness. 110 116 Iblft 120 0 3 FIG.6 9 / / 17. 6 v ~ I w = Unit Weight (wet)-5 pcf" f'c = Comp./ _\ 1. / y ~. kg/m31602 .844 TESTS AND PROPERTIES OF OTHER MATERIALS 2. --///I --. ec= W '5 2 8 . No further reproductions authorized. / 3. k The thermal conductivity of a material is the time rate of transfer of heat by conduction. 04 ft3/min) (5) Also required is an approximate or trial value of w/c by weight.454 m3/min (16. foam volume/air volume ---. Copyright by ASTM Int'l (all rights reserved). Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. S--Thermal conductivity versus density.05 k g / m 3 (2. No further reproductions authorized.288 = 0 Ib/ft 3 25 40 60 80 100 120 k g / m 3 400 644 961 1281 1602 1922 140 2242 DENSITY (OVEN DRY) FIG.I Rensseioer tests // o Pittsburgh Testing Lob. Design of Mixes Following are two examples of mix designs. and Example 2 is for a sanded cellular concrete mix.75 lb/ft 3) (4) foam rate = 0.577 ~II I ua I 9I. . Example 1 is for a neat cement cellular concrete mix.of Michigan tests >-P > 8. It is necessary to have at hand the foam gun calibration.1.442 " Univ. Use Type I cement and w/c = 0. 1 (SI Units) Design a neat cement cellular concrete mix to have a wet density of 641 k g / m 3. This consists of the following factors.LEGATSKI ON CELLULAR CONCRETE 10' Notional Bureau of Standards curve for No-fines gravel and lightweight aggregate concrete ~ 1. 1.865 O . Example No.en I" // I II 2 ~ 0. " ~ /i D To= 845 i/ / 11 // tests * ~ s 0. values for which are taken from a calibration test.57. Table 2 may be used as a guide.154 B /. 0.05 (3) unit weight of foam = 44. 0 1 • 1000 A b s o l u t e v o l u m e -----0 . 0 0 0 0 Air volume required = 0. f o r 1 m 3 o f c o n c r e t e .2032 m 3 1 min 29 s *See Eqs 3 to 5. 3 6 2 1 1 m 3 ~--.57 = 408.6379 • 1.3 kg/m 3 of concrete. is Cement Net water F o a m v o l u m e -----0 .3 408. 6 6 9 8 m 3 Foam time 408.48 0.5 = 203.48 m i n = 1 r a i n 2 9 s T h e t r i a l m i x .59 C a l c u l a t e w e i g h t o f c e m e n t . 6 6 9 8 • 4 4 . 0 5 * = 2 9 .15 • 1000 _ 232.05" = 0. Calculate the weights and absolute volumes of materials for 1 m a of concrete Absolute m3 Weight.57 • 408. No further reproductions authorized.7 1 -.57 0.58 0. .6698 m 3 W e i g h t o f w a t e r in f o a m = 0 .1295 3.49 0.1 . c.53 0. 1 = 0.846 TESTS AND PROPERTIES OF OTHER MATERIALS TABLE 2--Trial guide of w/c by weight.2 kg = 0.0.2032 m 3 F o a m t i m e r e q u i r e d = 0 . r e q u i r e d f o r 1 m 3 c + (w/c)c = 641 from which c = 641/1. Copyright by ASTM Int'l (all rights reserved).7 -. 5 k g / m 3 o f c o n c r e t e Net water added at mixer = 232. k g Cement Water (total) =0. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.2326 • 641.3 kg 203.29.3 • Volume.6379 m 3 Foam volume = 0. Wet Density of Concrete kg/m 3 641 721 961 1281 1602 1922 lb/ft 3 Trial Value of w/c for Type I Cement 40 45 60 80 100 120 0. 6 6 9 8 / 0 .2 kg = 0. 4 5 4 * = 1. 57 = 688 l b / y d 3 of concrete.08 ft 3 W e i g h t o f water in f o a m = 18. Calculate weight o f c e m e n t .05" = 18.218 • 1. No further reproductions authorized.282 1080 62.04" = 1.218 ft 3 F o a m volume = 17.127 min = 1 m i n 08 s T h e trial mix.7 l b / y d 3 o f concrete Net water a d d e d at m i x e r = 392 . Use T y p e I cement a n d w / c = 0. I (U. Use T y p e I cement. e. lb Cement W a t e r (total) = 0. Customary Units) Design a n e a t c e m e n t cellular concrete mix with a wet density of 40 l b / f t 3. i t 3 Weight.4 392 1 3. Calculate the weights a n d absolute volumes of the m a t e r i a l s for 1 m 3 of concrete Copyright by ASTM Int'l (all rights reserved).3 lb = 41 gal F o a m t i m e r e q u i r e d = 18.57 • 688 1 688 • 3.15 • 62. r e q u i r e d for 1 yd 3 C+(w/c) c =40 • 27= 1080 where c = 1080/1.08/16. 418. Calculate the weights a n d absolute volumes of m a t e r i a l s for 1 yd 3 of concrete. 2 (SI Units) Design a cellular concrete mix to have a wet density of 1602 k g / m 3.08 ft 3 Foam time 1 m i n 08 s Example No. for 1 yd 3 of concrete is Cement 688 lb Net water 342. a s s u m e the sand contains 2 weight p e r c e n t moisture.49. Absolute Volume. .4 A b s o l u t e volume = 9.57.46.26 k g / m 3 .LEGATSKI ON CELLULAR CONCRETE 847 Example No. S.08 • 2.7 = 342.3 lb = 41 gal F o a m volume = 18. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.75* = 49.000 - Air volume r e q u i r e d = 17. e s t i m a t e w / c = 0.782 1 yd 3 = 27.500 X 6. 02 X 990.67 1.05* -= 13.0. Calculate the weights a n d a b s o l u t e volumes o f the m a t e r i a l s for 1 yd 3 of concrete.0.0000 Air volume r e q u i r e d = 0.26 Net water a d d e d 158.3162 m 3 W e i g h t of water in f o a m ---.46 X 418. is Cement 418.80 --. 4 5 4 " = 0. for 1 m3 of concrete. A d d to s a n d an a m o u n t equal to weight o f s a n d moisture: 990.05" = 0.158.67 kg -.23 = 19.6965 min = 0 rain 42 s T h e trial mix.40 X C a l c i u m ligno-sulfanate 1.5 sacks p e r yd 3.93 kg kg kg kg S u m o f weights = 1602.0 990.77 W e i g h t of 1 m 3 S a n d (dry) 1 3.S.65 X 1000 A b s o l u t e volume = 0.3162 X 44.03 kg F o a m t i m e r e q u i r e d ---.3737 2.1587 m 3 S a n d correction.80 = 1010.0. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.11 Calcium ligno-sulfanate S a n d (with 2 p e r c e n t water) 1010.3011 • 1.26 • W a t e r (total) = 0.1924 neglect = 1602. 3 1 6 2 / 0 . No further reproductions authorized. sand c o n t a i n s 2 percent moisture.23 + 19.0.3011 m 3 F o a m V o l u m e = 0. Use Type I cement.11 611.1328 . Use 1A lb of c a l c i u m lignosulfanate per sack o f cement. E s t i m a t e w/c = 0.26 = 192.00 k g / m 3 Example No.46. Copyright by ASTM Int'l (all rights reserved).15 • 1000 1 1 • 1000 = 0.03 F o a m t i m e = 0 min 42 s W e i g h t of f o a m water 13. 7.13.40 .93 ...93 k g / m 3 o f concrete Correction for s a n d moisture = 0. 2 ( U. m 3 Weight.848 TESTS AND PROPERTIES OF OTHER MATERIALS Absolute Volume. Customary Units) Design a cellular concrete mix to have a wet density of 100 l b / f t 3.0 . kg Cement 418.6989 1 m 3 = 1.23 X 1 . .80 Net water a d d e d as mixer = 192.19. 587 = 5.75* = 23.05" = 8.33. If Type III cement is used. Copyright by ASTM Int'l (all rights reserved).4 lb = 32.4 lb = 32.02 X 1668.5 -.092 Absolute volume = 18.8 ---.5 X 94 Water 705 X 0. After the concrete has been pumped into place most of the accidental air will have been removed. If fiber glass is added.124 ft 3 Foam volume ---. Also account for weight and volume of fiber in calculations.02 or more.8 lb versus 2700 lb. . depending on amount of fiber.3 -.3 X 62.04 = 0. for 1 yd 3 of concrete.3 lb Water in foam 23.0 1 Sand (dry) 1668. Mixes designed according to the above procedures will often have a wet density about 48 k g / m 3 (3 lb/ft 3) below the design density.4 lb Net water added at mixer = 324. This is largely due to the presence of accidentally entrapped air in the mix.46 Calcium ligno-sulfanate 1 3.4 = 267.33. increase w/c by 0. check Foam time 0 rain 32 s Notes on Mix Design 1.4-. f l 3 Weight. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.9 1031.5318 min = 0 min 32 s Add to sand an amount equal to weight of moisture in the sand = 168.1 gal Foam time required = 8.197 Weight of 1 yd 3 = .53 ft 3 Weight of water in foam = 8.8.53/16.LEGATSKI ON CELLULAR CONCRETE Absolute Volume.05.15 X 62.0 lb 2676.1 gal Calcium ligno-sulfanate 1.4 1. lb Cement 7.23.9 lb Sand (moist) 1702.8 X 2. 2.4 1 324.124 X 1.4 = 1702 = total weight of sand The trial mix.03 to 0. 2 7 X 100 2700.65 X 62.53 X 2.000 Air volume required = 8.876 1 yd 3 : 27.2 705 X 849 -- 3.8 + 33. If the concrete is placed by means other than pumping a minor correction can be made in the design to account for about 2 percent of the volume.5 lb/yd 3 of concrete Correction for moisture in sand: 0. 3. is Cement 705 lb Water 267.10.5 2699. No further reproductions authorized. increase w/c about 0. ASTM/ANSI Method C 796. in particular. and foam. the factors that can influence physical properties are reduced to a minimum. with no support other than the water. the floor fills being about 1682 kg/m3/(105 lb/ft 3) and the roof fills being about 561 k g / m 3 (35 lb/ft3). the low density cellular concrete must float indefinitely. . For this kind of system. Thus. Three guides also have been developed from 1967 to 1975 by the ACI Copyright by ASTM Int'l (all rights reserved). This standard. The present applications are limited almost entirely to nonstructural uses because of the general lack of published information on properties of cellular concrete. The ASTM Specification for Foaming Agents Used in Making Preformed Foam for Cellular Concrete (C 869) was published in 1977. Cellular concrete of various unit weights for different parts of the structure has been used successfully to build a three-story apartment house in Honolulu. it is necessary to use a foam chemical which produces a foam made up of a discrete bubble system. which permits casting low density cellular concrete in large floating fabric envelopes of controlled thickness. No further reproductions authorized.850 TESTS AND PROPERTIES OF OTHER MATERIALS Applications The number and kinds of applications for cellular concrete seem to be limited only be one's imagination. The test batch contains only cement. The unit envelopes then are fastened together after curing to form a floating cover for reservoirs to minimize algae growth and evaporation loss. Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. These applications are near the opposite ends of the density range. Cellular concrete at a low density has been used recently as a road fill on bridge approaches over a very poor subgrade which could not support an earth fill. Cellular concrete has many uses in construction of all types. It is used widely as a sound insulating fill in floors and as a heat insulating fill in roofs. A system has been designed and tested. The envelopes are filled while floating on the water. This specification assigns limits to the physical properties of the test batch used in ASTM Method C 796 making it possible to specify the quality of the foaming chemical. Standards ASTM Testing Foaming Agents for Use in Producing Cellular Concrete Using Preformed Foam (C 796) now has also been designated an American National Standard by ANSI. It can also be used as floats on water if care is taken to use a foam chemical which produces a discrete bubble system. water. In other words. It is expected that a demonstration house will be built soon in Michigan. is significant because it provides a method of testing foaming chemicals (foam concentrates) by measuring common physical properties of a standard test batch of cellular concrete made using the foam chemical to be tested. This is the basic reason for developing both ASTM Method C 796 and the ASTM Specification C 869. and Wall Units (ACI 65-38). Sun Apr 6 21:47:39 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. with Compressive Strengths Less than 2500 psi (ACI 72-7). (2) Guide for Low Density Precast Concrete Floor.LEGATSKI ON CELLULAR CONCRETE 851 which are applicable to cellular concrete. . Copyright by ASTM Int'l (all rights reserved). and for Aggregate Concretes Above 50 lb/ft 3. Roof. and (3) Guide for Cellular Concrete Above 50 lb/ft 3. They are: (1) Guide for Cast-inPlace Low Density Concrete (ACI 64-44). No further reproductions authorized. However.org . Copyright by ASTM Int'l (all rights reserved). and Sealing of Concrete Introduction Concrete is one of the most durable materials of construction. Augusta. or both. patching. and sealing of concrete include epoxy resins.2 and all chemical attack requires the presence of water [2]. (2) adhesives. There is no frost damage to concrete if it is dry [1]. No further reproductions authorized. 1978 R.J. coatings quite often are applied to concrete to prevent ingress of the solution. linseed oil. Since such attack can only occur in a wet environment. Copyright9 1978tobyLicense ASTM lntcrnational www. urethanes. For these uses the epoxy resin systems have proven to be the most versatile. silicones.astm. Penetration of concrete by water or injurious solutions is especially severe where the concrete is exposed to alternate cycles of wetting and drying or freezing and thawing. N. it can be attacked both physically and chemically by certain injurious solutions including acids. acrylics. because concrete is inherently porous and alkaline. and water. oil-based paints. Absorption and subsequent chemical or physical attack also can be reduced by polymer impregnation [3] or by inclusion of the polymer in the plastic-concrete mixture in the form of a latex or unreacted premixed epoxy resin and curing agent [4]. salts. 2The italic numbers in brackets refer to the list of references appended to this paper. 1Construction materials consultantl RR 1.STP169B-EB/Dec. Organic materials which have been used for bonding. 07822. polyvinyls. Bonding and Patching Materials Materials in common use for bonding and patching of concrete fall into three general groups: (1) bonding admixtures. Patching. and (3) resinous mortars. bitumens. Sun Apr 6 21:47:45 EDT 2014 852 Downloaded/printed by Universidade do Gois pursuant Agreement. J. Schutz Chapter 49--Organic Materials for Bonding. and so-called rubberbased coatings. or (3) used in a similar manner with concrete or mortar containing the latex as an admixture. patching. These resins are mixed with a curing agent immediately prior to use. grade. They will be resistant to alkalies. These admixtures are latices of either acrylic. these latices must be used at a concentration of at least 12 percent polymer solids based on the cement content. The epoxy resins cure by cross-linking. Patching. are used universally. and oils. The inclusion of the latex as an admixture in the mortar or concrete will improve both freeze/thaw and chemical resistance. Adhesives. A specification is available for epoxy resin systems for use with concrete. No further reproductions authorized. or polyamides. and overlaying concrete. The cured-resin systems will have tensile strengths and compressive strengths between 10 and 20 times that of good concrete. mild acids. liquid low-molecularweight epoxy resins of the bisphenol A type. or polyvinyl acetate. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. and Overlaying Materials Epoxy resins are the most widely used organic systems for bonding. the working time of such mortars and concretes is extremely short--the latex will tend to coalesce in 10 to 20 min depending on the type. solvents. . For these purposes. and other factors. These curing agents are generally of the chemical groups such as amines. and care should be taken in choosing the proper latex in areas where the installation will be subject to excessive moisture or weathering. (2) mixed with portland cement in sand and applied as a bonding grout for conventional mortar or concrete. These admixtures are generally used in one of three methods: (1) applied directly as an adhesive. namely. This specification classifies epoxy resin systems by type. These latices may be water-reemulsifiable after hardening of the concrete. Suitable systems are available for use as adhesives for bonding new plastic mortar or concrete to existing hardened concrete and also as binders for the manufacture of resinous mortar and concrete patches or overlays. ASTM Specification for Epoxy Resin Base Bonding Systems for Concrete (C 881). The water resistance of the butadiene styrenes and acrylic latices is generally good while the polyvinyl acetate latices are generally inferior. and color based on the following uses: (1) bonding hardened concrete and Copyright by ASTM Int'l (all rights reserved). However.SCHUTZ ON ORGANIC MATERIALS FOR COATING CONCRETE 853 Admbctures Admixtures used to improve the adhesion of plastic mortar or concrete to hardened concrete are classified by the American Concrete Institute (ACI) as bonding admixtures. In order to be effective as an admixture. reaction products of bisphenol A epichlorohydrin. therefore. curing shrinkage is much less here than in those resin systems such as the polyesters which cure by polymerization. class. polyamines. temperature. Handling beyond that time generally results in profuse cracking on drying. butadiene styrene. Component B shall contain one or more curing agents which. Each type is divided into three grades based upon its flow characteristics. After 14 days' curing. the overlay and block are cycled 5 times between 77 • 5 ~ (25 + 2.6 • 2~ and 73. Grade III is for nonsagging applications. It also requires that the epoxy resins shall be furnished in two components for combining immediately prior to use. Component A shall contain a bisphenol A. and as a binder in epoxy mortar or epoxy concrete. gel time.854 TESTS AND PROPERTIES OF OTHER MATERIALS other materials to concrete. (3 mm) thick film of the epoxy resin under test is cast on a glass plate and cycled 10 times between 124. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.1 ___ 1. A strength of 10 MPa (1500 psi) based on the elliptical area (glue line) is considered satisfactory. In the thin glue lines usually used. and plastic or hardened concrete is bonded to the original hardened concrete using an epoxy-resin adhesive. will cause the system to harden. ASTM Bond Strength of Epoxy Resin Systems Used with Concrete (C 882) covers the test method developed by Kriegh and Nordby for determining the bond strength of epoxy resin systems to concrete. bond strength. ASTM specifications are available for testing the suitability of epoxy resin systems for use with concrete. After 14 days cure. a standard concrete cylinder is cast or cut at a 60-deg angle. .7~ Any crack or delamination of the system is considered a failure. compressive strength. a J/8 in. No further reproductions authorized. A suitable inert filler may be incorporated uniformly in one or both components. ASTM Effective Shrinkage of Epoxy Resin Systems Used with Concrete (C 883) determines whether or not an epoxy resin system will have excess volume changes on curing. In this test method. that is. and (3) bonding skid-resistant materials to hardened concrete. the composite cylinder is tested in compression. In this test method. creep.8~ and --6 + 3 ~ (--21.6~ (51. Grade II has moderate viscosity. consistency.4 _ 1. Epoxy-resin systems when used as adhesives have a relatively high elastic modulus. (2) bonding freshly placed concrete to hardened concrete. the resin system is considered unsuitable for use with concrete. since a structural bond is required in most adhesive applications.8~ (23 • I~ If the shrinkage is such that the glass plate breaks. and percent of volatile matter.9 + 3. This specification defines an epoxy resin as a resin that contains or did contain epoxy groups that are principally responsible for its reaction. on mixing with Component A. Grade I has low viscosity. thick layer of epoxy resin sand mortar is cast on a standard concrete block. The specification stipulates limits for viscosity. ASTM Thermal Compatibility Between Concrete and Epoxy Resin Overlay (C 884) is a test method in which a 1/2 in. the differences in linear thermal coefficient of expansion between the epoxy resin and the concrete is inconsequential because the total tensile strength of the thin glue line (1 mm or Copyright by ASTM Int'l (all rights reserved). epichlorohydrin epoxy resin with or without a reactive diluent. 1--The effect of changes in the sand aggregate-binder ratio on the thermal coefficient of an epoxy system. Figure 1 illustrates the effect of aggregate loading on linear coefficient of expansion of several epoxy-resin systems [7]. . When applied in layers 40 mm (1189 in. Copyright by ASTM Int'l (all rights reserved). a resin with a low modulus of elasticity must be used._ -80 42 -70~ 36 30 E -50 E x 24 '~ ~ 18 ~[_ ~ -40 x Sand-filledepoxy E Lq> -30 ~:= . creep of the epoxy resin is not a problem because the effective modulus of elasticity of a material in a thin glue line will be extremely high [6]. Therefore. Some epoxy-resin systems are sensitive to water before cure. and foreign material and coated with the epoxy-resin adhesive to prevent further corrosion.SCHUTZ ON ORGANIC MATERIALS FOR COATING CONCRETE 855 less) is less than the tensile strength of the concrete. they can only be used under dry conditions. or spray to properly prepared concrete surfaces. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. oil. For applications as an adhesive._o -20 o~ 12 I. Epoxy-resin systems are also available which will not only cure under wet conditions. it is desirable to include coarse aggregate in the system. and these dry conditions must be maintained at least until initial cure of the system. the steel should be cleaned of rust.- -10 "~ Concrete !o 1 2 3 4 5 6 7 8 9 e-- 10 Aggregate-binderratio FIG.) or greater in thickness. Epoxy-resin systems are used quite commonly as the sole binder for mortar and concrete patches and overlays. Since such patches and overlays are generally thick. both for reasons of economy and thermal compatibility. The epoxy-resin systems may be applied by brush. roller. the differences in thermal coefficient of expansion between the thick resin mortar and the base concrete will result in failure of the overlay or patch by shearing of the concrete adjacent to the resinous mortar or concrete. In thin glue lines. Where reinforcing steel is exposed. No further reproductions authorized. the epoxy resin should contain no solvent since solvent may be entrapped during cure and cause both a rubbery cure and later shrinkage of the adhesive. but will u. If high-modulus binders are used. but are attacked readily by solvents. Voids in excess of 12 percent will result in a permeable mass with resultant poor chemical and freeze-thaw resistance. Copyright by ASTM Int'l (all rights reserved). Coatings and Impregnations Bituminous materials include both asphaltic.856 TESTS AND PROPERTIES OF OTHER MATERIALS displace water from the surface. Coal-tar coatings possess a high degree of water resistance and should be considered wherever continuous immersion is encountered. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. When formulated with epoxyresin systems. It stresses the necessity for preparing the concrete surface to be treated before application of the resin system. and (2) the surface must be clean. asphaltic coatings may be permeable to water. the forms should be coated with polyethylene rather than oil. Where large cavities are to be repaired by use of an epoxy-resin concrete. Oil may be absorbed into the resin impairing the cure of the system. since the resin systems are sticky and viscous. Patching and other repairs using these systems can be carried out even under water. the most economical method is to prepack aggregates into the void and then inject the epoxy resin as a grout from the bottom of the void. unless they are specially formulated. However. This report should be studied by those planning to use these materials. The total voids in the system should be less than 12 percent by volume. grease. waxes. that is. Asphaltic coatings generally are used to protect foundations.and coal-tar-based materials. . The most common use for coal-tar coatings is for protection of underground pipelines. basements. or other contaminants. Coal-tar coatings have a tendency to crack and craze when exposed to ultraviolet light or high temperature. Asphalts are resistant to many mildly corrosive materials. When using forms for epoxy resin mortar or concrete. excellent long-term performance has been recorded. No further reproductions authorized. Two surface conditions must be met if an application is to be successful: (1) the surface must be strong and sound. There is considerable difference between asphalts and coal tars. and similar structures from water. and gasoline. oils. ACI Committee 403 has issued a guide covering the use of epoxy resin in concrete construction [7]. the sand/aggregate ratio is usually the reverse of that which would be used for portland cement concrete. Further. such as residues of curing compounds. free of oil. Proportioning epoxy-resin mortar or concrete follows the same guidelines as proportioning portland cement concrete mixtures. or polishes that may have been applied to the surface of the concrete. This approach displaces air in the case of water-sensitive systems or it displaces water in the event the repair is made under water with a waterinsensitive system. . Two types of latices in common use are acrylic and polyvinylacetate latices. kerosene. Moisture behind an oleo-resinous paint will cause premature failure due to blistering and flaking [9]. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. When heavily filled or pigmented. Oleo-Resinous Paints Oleo-resinous paints. No further reproductions authorized. are only capable of satisfactory performance when applied to dry. Since these latices are water-based. The solution types are more economical and more widely used. and trisodium phosphate in water. The solution type is a mixture of raw or polymerized (boiled) linseed oil and solvent usually in a 50-percent concentration.1 and 3. the acrylic gives the best results on exterior exposure due to their superior ultraviolet resistance. therefore. This may be either the solution or emulsion type. On evaporation of the solvent or water.2 mm (5 and 125 mils). poor durability. Total coating thickness for either system will vary between 0. The use of linseed oil impregnations is especially desirable where the concrete is suspected of having a low air content and. Oleo-Resinous Materials Penetrating Sealers Numerous tests carried out by state highway departments and private laboratories indicate that one of the most efficient penetrating sealers is linseed oil [8]. Such reinforcing also increases their thickness and boosts both impermeability and service life. Latex Coatings Latex coatings are relatively insensitive to dampness and alkalinity and have become the most widely used coatings for interior and exterior concrete surfaces.). The emulsion type contains polymerized linseed oil. and presence of vapor pressure does not result in failure. While both are suitable for interior concrete coatings. they form permeable coatings. The protective effect is obtained from penetration of the linseed oil into the concrete to a depth of approximately 3 mm (l/a in. They have limited resistance to moisture. well-aged concrete (3 to 12 months). the linseed oil oxidizes and an effective seal is developed. surface dampness is not a problem. Copyright by ASTM Int'l (all rights reserved). detergent.SCHUTZ ON ORGANIC MATERIALS FOR COATING CONCRETE 857 Bituminous coatings may be used with reinforcing fabric and tape to increase their resistance to impact on backfilling and handling. while attractive in appearance. chlorosulfonated polyethylene. Silicones Silicone resins in solvent solution or in aqueous solution as alkali metal methyl siliconates impart water repellency to concrete and masonry surfaces. Although these systems do not actually harden the concrete surface. The new acrylic-amine epoxy-resin systems exhibit good resistance to ultraviolet radiation and may be used in both interior and exterior applications. they are not quite as chemically resistant as the conventional epoxy-resin systems. Applied after the concrete has hardened. and similar contaminants tend to wash off architectural concrete. . or 100-percent solids systems. these chlorinated rubber coatings retain moisture efficiently and aid in curing the concrete. dirt. they are not suitable as exterior architectural coatings. the epoxy-resin-based coatings have proven very successful. or acrylic amine systems [9]. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Copyright by ASTM Int'l (all rights reserved). Chlorinated-rubber-based clear coatings are used as both curing compounds and so-called floor hardeners. and epoxy resins. chlorinated rubber. styrene-butadiene. For interior use for protection where aggressive solutions are encountered. polyamide. These may be either polyamine. The alkali metal methyl siliconates are more effective on calcareous surfaces than the solvent-borne silicone resins. the polyurethane. Both types are flooded onto the surface in dilute solutions containing 3 to 6-percent silicone solids. 2 to 5 years being average. amine adduct. They may be applied as solvent solutions. The service life of these impregnations is rather short. water-based. These materials have not proven effective in protecting nondurable concrete from freezing and thawing damage. The polyurethane-based coatings exhibit extremely good scuff and abrasion resistance and form the basis for many coatings for concrete floors. Due to the water repellency imparted by the silicones.858 TESTS AND PROPERTIES OF OTHER MATERIALS Synthetic-Resin Coatings Synthetic-resin coatings other than latex-based coatings which are successfully used for concrete are generally applied as solvent solutions and include: coumarone-indene. The most commonly used materials in this group are the so-called chlorinated-rubber-based coatings. soot. and the epoxy-resin-based coatings. No further reproductions authorized. they do protect the concrete from abrasion and subsequent dusting. polyurethane. They often are used in conjunction with an epoxy-resin based prime coat. neoprene. usually 24 h after placing the concrete. Because these epoxy-resin systems will tend to chalk. However. [5] Kriegh. P. G. 1950. No further reproductions authorized. D. Bureau of Reclamation. 1971.S. and Use. March 1976. American Concrete Institute. 21 Nov. R. D. Sauer." Journal. "Durability of Concrete Construction." ACI Monograph 4. U. [6] Schultz. E. G." American Concrete Institute. Sun Apr 6 21:47:45 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.. Title No. Department of Commerce.. Copyright by ASTM Int'l (all rights reserved).. "Polymer Cement Concrete. "Organic Coatings: Properties. J. Selection.SCHUTZ ON ORGANIC MATERIALS FOR COATING CONCRETE 859 References [1] Woods. J." Third Topical Report. 1968." Chemical Week. and Sun. A." Building Sc&nce Series 7. [7] "Use of Epoxies with Concrete. "Methods of Evaluation of Epoxy Compounds Used for Bonding Concrete. 47. [8] "Linseed Oil in Road Up. Part 3. A.. American Concrete Institute. J. Influences on Concrete. Frederick Ungar Publishing Company." Manual of Concrete Practice. Feb.. 1968. A. 1964. p. American Concrete Institute. F. Brookhaven National Laboratory. "Epoxy Adhesives in Prestressed and Precast Concrete Bridge Construction. No. [3] "Concrete-Polymer Materials. and Nordby.. M." Epoxies with Concrete. 503-1.. [9] Roberts. Hubert. 73-14. [4] Nawy. Nov. . 1975. [2] Kleinlogel. Jan. SP-21. American Concrete Institute. Permeability of the aggregate void system should be low enough to prevent permeation by water or cement paste under pressure. cementing materials.2]. Valore. upon the interstitial void structure and the ways in which they affect pumpability of concrete are beyond the scope of this paper. C. or aggregates. it is an objective in proportioning the ingredients of concrete to obtain a blend of solid materials. Ridgewood. which. Valore Research Associates. will have an interstitial void structure of minimum volume. To achieve that end. 07450. Surface area should be low enough to permit the use of economical amounts of cement and suitable water/cement (w/c) ratios to provide a volume of paste sufficient to saturate the aggregate voids and form workable cohesive concrete. The latter requirements would appear to be contradictory since permeability of a bed of granular solids is inversely related to its surface area.STP169B-EB/Dec. For more specific information. when consolidated. Copyright by ASTM Int'l (all rights reserved). reference is made to a study by Kempster and its elaboration in Guide to Concrete P u m p i n g of the British Building Research Establishment (BRE) [1. ~ Chapter 50 Concrete Pumpability Aids for Introduction An essential requirement of concrete for any use is that it be transported from mixer to forms without separation of water. Sun Apr 6 21:47:47 EDT 2014 860 Downloaded/printed by Universidade do Gois pursuant Agreement. 1978 R. 2The italic numbers in brackets refer to the list of referencesappended to this paper. Freshly mixed concrete is a suspension of solids in water of which only l Principal. with sufficient retention of consistency to permit economical consolidation. Discussion of the details of the influence of specific size gradings and particle shape of aggregates. No further reproductions authorized. and relatively low permeability and surface area.org . from the finest cement grain to the largest particle of coarse aggregate. the price for failure to achieve them is failure to achieve pumpability. 2 These references describe direct measurements in the laboratory of aggregate void volume and water permeability. In pumped concrete these general requirements become critically important. Jr.J.N.astm. Copyright9 1978tobyLicense ASTM International www. the concrete mixtures generally were pumpable. 100 sieve) aggregate. pumpable.VALORE ON PUMPABILITY AIDS FOR CONCRETE 861 the latter is inherently pumpable. when the volume of cement was equal to or greater than the aggregate interstitial void volume. Admixtures Pumpability aids for concrete are admixtures whose sole or primary function is the improvement of pumpability. Pumping can be impaired. it is shown that. that is. Exceptions were mixtures in which the volumes of total fines. . The British Guide illustrates effects on pumpability. 1. "movable. 1--Dewatering of concrete under pressure in pipeline. Kempster and the British Guide defined optimum relationships between total aggregate interstitial void volume and cement contents for pumpable concrete [1. however. Pumpable concrete must be mobile or workable enough to be moved through changes in shape and direction of lines without a buildup of excessive pressure. they will not normally be Particle Uigration of High Fr~cfional Aesistance Courtesy American Concrete Institute FIG. not only of aggregate void volumes and cement contents. 3"Mobile" means "movable" while one definition for the word "stable" is "difficult to move. Also it must be sufficiently stable or cohesive to resist separation or segregation of its constituents under the pressures of pumping. No further reproductions authorized. This is illustrated in Fig.2].3 Forced bleeding of water or cement paste from concrete under pressure is an example of segregation which. can make pumping impossible. were excessively high." These terms are not opposites in the present context. consisting of cement plus minus 150-#m (No." Copyright by ASTM Int'l (all rights reserved). when contents of cement and other subsieve fines are excessive. From Browne and B a m f orth [3]. in laboratory trials. The workable and cohesive pumpable concrete possesses a sufficient volume of cement paste to act as a lubricant between concrete and walls of the line to reduce frictional resistance.concrete is an internally stable mixture that is pumpable. but also of size of voids as influenced by particle gradation and shape. in excess. Using the expedient of considering the density of dry portland cement to be 1440 k g / m 3 (90 lb/ft3). Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. The following list is based in part on that draft. and other cellulose gums 2. The Standards Association of Australia has classified thickening admixtures for concrete and mortar [4]. Therefore the objective is to prevent dewatering of the paste under pressure of pumping. Since the objective is to inhibit forced bleeding of water from cement paste or permeation of paste through interstitial aggregate voids. the desired inhibition of segregation must not be obtained at a cost of decreased mobility. Therefore the function of the pumpability admixture is that of imparting water retentivity to the cement paste under forces tending to separate water. ethyl. Polyethylene oxides 3. while providing undiminished brushability and integrity of the applied coating. or can improve pumpability of marginally pumpable concretes. The requirements in pumped concrete are analogous. hydroxyethyl. of obtaining satisfactory aggregate interstitial void volume and individual void size when using available materials.862 TESTS AND PROPERTIES OF OTHER MATERIALS used in concrete that is not pumped or in concrete that can be readily pumped. The primary purpose of using admixtures to enhance pumpability of concrete is to overcome difficulties. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Cellulose derivatives (methyl. Dewatering has two cumulatively adverse effects: it decreases mobility of the concrete and depletes the lubricating fluid. unpumpable concretes pumpable. unavoidable at reasonable cost. As in the use of any ingredient in concrete. but not all. Pumpability admixtures can make some. Polyacrylamides Copyright by ASTM Int'l (all rights reserved). Water-soluble synthetic and natural organic polymers which increase the viscosity of water: 1. In masonry mortars. and minimize rapid absorption of vehicle into substrate. No further reproductions authorized. the objective is economic. as shown by the BRE experiments. they serve as suspending aids for inorganic pigments and fillers. Under optimum conditions. In polymer-latex and other paints. thickening agents provide water retentivity and retention of plasticity against the forces of suction of porous brick or concrete block. these agents impart a degree of thixotropy to suspensions of mineral solids in water: stability of the suspension at rest and compliability when worked upon. . The principle involved in virtually all of the admixtures marketed for improving the pumpability of concrete is that of thickening or increasing the viscosity of water. permeability of the void structure is effectively reduced by increasing the viscosity of the permeating fluid. Acrylic polymers 4. A. prevent running on vertical surfaces. Other examples are provided by synthetic polyelectrolytes which act as flocculents or thickeners. various raw or calcined pozzolanic materials 2. cement composition. and other factors change. Gum arabic is a powerful water reducer for gypsum hemihydrate plasters but in portland cement pastes it can produce a virtual glue-like stickiness. depending upon dosage levels. some of which are listed in McCutcheon's Functional Materials [5]. D. Fly ash. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 4. various rock dusts This list does not include all of the possibilities. Organic flocculents: 1. Classification may be misleading since the performance of a given admixture can change drastically when dosage rates. 863 Carboxyvinyl polymers Natural water-soluble gums Starches Polyvinyl alcohol B. 6. 1. Bentonites and organic-modified bentonites Pyrogenic silicas Milled asbestos and silica-coated milled asbestos Asbestos short fibers and other fibrous materials E. Finely divided inorganic materials which supplement cement in cement paste. it is held that these admixtures are effective in pumped concrete because they lower bleeding capacity or total bleeding. . asphalt. They can function as thickeners or flocculents. Natural water-soluble gums C. depending upon dosage levels and other factors. When used in small amounts of 0. These agents and some of the synthetic materials also can have dispersing or water-reducing effects. 8. High-surface area inorganic materials: 1. Emulsions of various organic materials: paraffin. No further reproductions authorized. Carboxyl-containing styrene copolymers 2.05 percent of cement weight. Nevertheless. 3. 2. and acrylic and other polymers. Other problems with the listing given above occur with the natural gums (algins. It would appear to be highly undesirable to induce flocculation and increase bleeding in pumped concrete. coal tar. Natural or precipitated calcium carbonates. 7. despite causing increases in initial rates of bleeding [4]. Copyright by ASTM Int'l (all rights reserved).01 to 0. larger amounts produce thickening which may or may not disappear upon prolonged mixing. An example is provided by the polyethylene oxides. Other synthetic polyelectrolytes 3. arabic). mixing temperature and time. Smaller amounts make water slipperier.VALORE ON PUMPABILITY AIDS FOR CONCRETE 5. Hydrated lime 3. tragacanth. they improve pumpability. These types of agents are not considered specifically. to control air content. No further reproductions authorized. lignosulfonates and their derivatives. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. For dosage of methyl or hydroxyethyl cellulose of 0.864 TESTS AND PROPERTIES OF OTHER MATERIALS Factors to consider in the use of emulsions (paraffins.1 percent or more. in this paper. in combination with other agents introduced for the specific purpose of improving pumpability. no increase in water may be required. Many of the thickening agents cause entrainment of air. the particular concrete system in which a pumpability admixture is incorporated must be evaluated in terms of side effects upon the fresh and hardened concrete in addition to assessing the effectiveness of the admixture in performing its intended function. and other set-retarding or water-reducing admixtures. especially for higher concentrations of pumpability admixture in mortars and concretes. By using a suitable dispersant in combination with a thickening agent. tributyl phosphate) may need to be used. Many of the synthetic and natural organic thickening agents retard the setting of portland cement pastes. and any effect that changes the characteristics of the hardened concrete. by weight of portland cement. Side Effects A side effect of a concrete pumpability admixture is any effect that it has on fresh concrete other than that on pumpability. Since the main effect of a water thickener is to increase viscosity. In such cases. Copyright by ASTM Int'l (all rights reserved). they will be present in many cases. The omission here is deliberate because a substantial proportion of concrete that is to be pumped in North America will be specified as air-entrained concrete and will probably also contain a water-reducing or set-retarding admixture. . Both types of paraffin emulsion are considered to be useful in Australian concrete technology. In any case. the listing given above does not include air-entraining agents or surface-active agents widely used in concrete such as hydroxylated carboxylic acid derivatives. Evaluation of and experience with these admixtures are well established and specifications and testing methods for them are well known. formaldehyde-condensed naphthalene sulfonates and melamine polymers. some thickeners act as dispersants of solid particles. a defoamer (for example. evaluation of effects of such combinations on pumpability and other properties of concrete will be required in order to determine whether or not adverse interactions occur between admixtures. retardation may be substantial. polymers) is whether they function in the desired way in cement paste by remaining stable or by breaking of the emulsion. Therefore. Despite their inclusion in the BRE Guide. as pumping aids. substantial thickening can increase water requirements with the usual consequence of reduced strength. such admixtures may be considered to be normal constituents of concrete. At certain dosage levels. The apparatus is shown in Fig. windy. small-scale test methods are needed. and concretes. in determining the bleeding characteristics of concrete. The water retention test method for masonry mortars in ASTM Specification for Masonry Cement (C 91) provides information that will not necessarily predict working properties of a mortar with a highly absorptive concrete block in dry. If pumpability of concrete containing such admixtures cannot be tested directly in the laboratory. In order to evaluate admixtures for pumping concrete in the laboratory. Copyright by ASTM Int'l (all rights reserved). 3. Bleeding Tests Several test methods provide data on bleeding of cement pastes. No further reproductions authorized. reliably predicting pumpability have yet been devised .VALORE ON PUMPABILITY AIDS FOR CONCRETE 865 Test Methods The BRE Guide contains the statement: "No methods o f . . . . This is to say that pumpability of a given concrete cannot be evaluated without pumping trials. ASTM Test for Bleeding of Cement Pastes and Mortars (C 243) based on a carbon tetrachloride displacement method developed by Valore et al [6] provides data on initial bleeding rate and bleeding capacity and was used successfully. . including effects of aggregate interference in causing internal bleeding. In this and the Valore et al studies. ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666) provides results that show the relative ability of specific concrete specimens to survive a specified regimen in a particular type of machine. The situation is not much different with evaluation of some of the other properties of concrete and mortar. In general. 2. the pumping action is itself the crucial test. the test methods are satisfactory if results provide a reasonably accurate indication of performance. when modified. mortars. a number of other properties of mortars or concretes which correlate in some degree with pumpability can be determined to provide indirect indications of effectiveness of the admixtures. . and hot weather. Correlation of such results with durability in service is not perfect. In pumping concrete. and it is not necessary to wait for years for confirmation of laboratory test results as may be required to learn the actual durability of concrete in service. . Ritchie [7] adapted the carbon tetrachloride displacement method to testing of concrete mixtures with apparatus depicted in Fig. it was concluded that only by obtaining bleeding data for concrete and for the corresponding cement paste can a complete picture of the potential dewatering of concrete be seen. " Inquiries by the present author of specialists in pumping concrete have elicited general agreement with that statement. Similarly. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. 1.1. 2--Carbon tetrachloride displacement bleeding test apparatus. From Ritchie [7]. 3--Carbon tetrachloride displacement bleeding test apparatus modified for tests of concrete. . Water seal --~ Burette tube-'P Collected bleeding water Carbon letrachloride Pycnometer jar $ompll of r paste or concrete I~'ii:1 Courtesy American Society of Civil Engineers FIG.1 I 1 0 1 2 I I I 5 4 5 i INCHES FIG. No further reproductions authorized. Copyright by ASTM Int'l (all rights reserved). From Valore et al [6]. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.866 TESTS AND PROPERTIES OF OTHER MATERIALS H I d E . . 4--Filter-presses of O. and by the American Petroleum Institute in a fluid-loss test of oil-well cements and cement additives (API Recommended Practice for Testing Oil-Well Cements and Cement Additives. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. These methods are based on the use of a filter press. Browne and Bamforth [3] described a new pressure bleeding test and apparatus for the purpose of establishing pumpability of concrete. Fluid Loss Test (API RP 10B)).5 MPa (500 psi) by the piston. filter presses of 0.li Ill tll "-"iF-o" Courtesy Fisher Scientific C o m p a n y FIG. support. 1. is said to correlate directly with pumpability for concrete of a given slump. 1. No further reproductions authorized. III . An air-tight fitting containing an inlet is attached to the top of the cylinder and a gas or liquid is introduced through the inlet. 5. The authors developed a calibration curve of (V~40 -. and 3 litre capacity are shown in Fig. minus that collected at 10 s (V~0). 4.12. A drawing reproduced from the paper is shown in Fig. The concrete sample is subjected to a pressure of 3. A vertical cylindrical container with a filter. The volume of bleeding water collected at 140 s (V140). This was interpreted as showing that concretes that dewater quickly (in the first 10 s) under pressure tend to be unpumpable.VALORE ON PUMPABILITY AIDS FOR CONCRETE 867 Test methods which cover determination of water loss under pressure have been applied by Schupack [8] to portland cement grouts for posttensioned tendons in concrete structures. The pressure then can be increased gradually or in increments and the volume of water forced from the grout can be collected and measured.Vl0) versus slump which forms a line of demarcation between zones of "pumpability" and "unpumpability.11 lit ." Results of this work tend to negate the principles involved in using flocculating admixtures to improve pumpability by increasing initial bleeding rates and decreasing bleeding capacities. and 3-litre capacities9 Copyright by ASTM Int'l (all rights reserved). and fluid outlet at the bottom is filled with grout. actuated by a hydraulic jack. ~ hi' . . 12. .."-'"~'.~':b-"'r '~ Concrete Sample -~"--"----7"--~ -" / '\ . i'. in order to show effects of admixtures. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. Gray [9] developed a laboratory procedure for comparing pumpability of concrete mixtures which involved pumping concrete samples upward through a 1.~--. and fly Copyright by ASTM Int'l (all rights reserved). Colibrofed Cyl I'..ce. Other Tests A water-retentivity test for masonry cement mortars (ASTM Specification C 91) has been mentioned. paraffin emulsion. and included mixtures containing methyl cellulose. Measuring ~-'~ Cylinder 5OMes.... 5--Pressure bleeding test of concrete devised by Browne and Bamforth [3]. No further reproductions authorized.J I ..Piston l~r"2")~:~. It combines a type of forced bleeding under a small partial vacuum with a measure of workability retention. Test mortars were made with natural sands and fine lightweight aggregates.. \ II Gauze Rei'oinin~ --~ ' ~ Plate FIG.Top Cop ~..868 TESTS AND PROPERTIES OF OTHER Iflllf ~Ukt (~( MATERIALS Double Acting IJHJIH ydroulic ..lf Ij . ..2 m (4 ft) vertical section of pipe with a curved offset of 305 mm (12 in..d .iJ~a .L J. Rubber "0" Ri no s 125 ram. Tests could be conducted on mortars or concretes especially proportioned to have lower than optimum pumpability. '1 r Bose inder i i ..) and measuring the pressure required to move the concrete. using a flow table.. combining measures of bleeding rates and capacities under pressure with some measure of the decrease in workability accompanying dewatering of test samples.. respectively. Tanaka [10] and Ozaki and Emura [11] presented results of pumping tests on lightweight aggregate mortars and concretes. The testing arrangement is shown in Fig. The principles involved might well be applied to development of tests of pumpability admixtures. 6..Diameter Cyhader ' ~--.Gouz... rates of pumping were reduced when methyl cellulose or paraffin emulsion were used and increased when fly ash was used in mortar mixtures at dosage levels required to prevent segregation. ash. Evaluation of pumpability was based on the rate of pumping in litres per minute with equipment not otherwise described. with three pressure measuring stations to Copyright by ASTM Int'l (all rights reserved). In pumping tests of lightweight concretes pressures were measured at several stations in a U-shaped pumping circuit about 45 m (150 ft) in length. about 23 m (75 ft) in length. No further reproductions authorized. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. because of the space required. Kempster [12] described a similar but smaller concrete pumping circuit. it is not well-suited for use as a laboratory method for evaluating admixtures. Lightweight mortars were more difficult to pump than sand mortars.VALORE ON PUMPABILITY AIDS FOR CONCRETE 869 I11 To Voct Purn FIG. . Slump and flow were measured before and after pumping. The admixtures used were found to reduce segregation. The testing set-up provided a good indication of pumpability in the field but. 6--Schematic drawing of pumping apparatus for concrete. due to Gray [9]. ge Distance A. segregation. 8.B:1. Grouts. A study in progress by Lane [14] involves a small pumping circuit suitable for laboratory installation.870 TESTS AND PROPERTIES OF OTHER MATERIALS determine the effects of aggregate interstitial void size and total volume and to evaluate the effectiveness of admixtures on unpumpable or marginally pumpable concretes.t Strain gouge "C' ~{ ~. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement.~m Distance I1 _ C : 10 m pump CourtesyBritish BuildingResearchEstablishment FIG. Kempster [13] also studied effects of sand gradation and admixtures on the pumpability of mortars. Copyright by ASTM Int'l (all rights reserved). shear resistance. has reappeared in recent years in testing concretes containing "superplasticizers" or high-dosage water reducers [15]. mortars. but the methods were not very discriminatory. Many papers have been published on various aspects of workability of concrete.. 7mPurnpingcircuit used by Kempster [12]. and stickiness test methods that showed recognition of important aspects of workability. and concretes are being tested for pumping characteristics with this equipment. Slump and remolding (Vebe) tests have survived and the flow test.~u. Results of Kempster's tests are summarized in Refs 1 and 2. Herschel and Pisapia [16] developed harshness. The voidmeter developed in Kempster's studies is shown in Fig. 9auge los . .Flexible rubber pipe Im Reduction pipes $fraln g. No further reproductions authorized. widely used in testing of mortars. 7. The pumping circuit is shown in Fig. . The question then becomes one of asking. seem to make it a simple matter to proportion pumpable concretes. mortars. Kempster.~ '-. .s o . Reservoir Position 2~. Measurement of workability of concrete appears to be a necessary adjunct to bleeding or dewatering tests. .. or for that matter.. No further reproductions authorized. their main area of use in marginally pumpable or "somewhat" nonpumpable mixtures requires that standard test mortars or concretes be formulated with inherently mediocre or poorer levels of pumpability. It has been recognized that precise prediction of pumpability characteristics of concrete in the field may not be attainable with presently known bench-scale laboratory methods. Admixtures for pumping of concrete might be evaluated indirectly by means of determination of their effects on initial bleeding rates and bleeding capacities of cement pastes. The principles affecting pumpability. Since admixtures for improving pumpability need not be used in concrete that can be pumped readily. concretes or mortars lacking in pumpability. J II Courtesy American Concrete Institute FIG.:~.qDJZ Lid ~[~ Aggregate [I 9 . Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement. In this discussion it has been assumed that proportioning of concrete mixtures for pumping has been done properly with the materials at hand. . . can an admixture Copyright by ASTM Int'l (all rights reserved). From paper by Browne and Bamforth [3].VALORE ON PUMPABILITY AIDS FOR CONCRETE 871 Reservoir Position| ~ Inilio! wole~_Level Meosuring Tube~ Col ibroted Scote~ ~Top ir-tight .~. Conclusion Admixtures for pumping concrete and potential methods for evaluating them have been described.--. . or concretes under pressure. when everything else possible has been done and the concrete still cannot be pumped. 8--Voidmeter developed by Kempster [12]. as elucidated by Browne and Bamforth.-. and others. using methods now available. Vol. Ridgewood.. Vol. [6] Valore. [9] Gray. Mortars. W. Y. [2] Crowe. [15] "Superplasticising Admixtures in Concrete. R. Vol." Proceedings.1967. Vol. Vol. and Blaine." McCutcheon Division. 92. 1949.. 1969. Bowling. of pumpability in the field. 228. American Concrete Institute. "Pumpable Concrete. New York.. p.. "Development of a Water-Retentive Grouting Aid to Control the Bleed in Cement Grout Used for Post-Tensioning. 1-14. 641. No. E. Proceedings.. R. H.. May 1968. J." FIP Seventh Congress. 17-35. MC Publishing Co. American Society for Testing and Materials. and Concretes. No further reproductions authorized. "On the Artificial Lightweight Aggregate Mortar-Mesalite Mortar. Onoda Cement Company. Sun Apr 6 21:47:47 EDT 2014 Downloaded/printed by Universidade do Gois pursuant to License Agreement." Journal of Research. New Jersey. 1974. B. London. "Factors of Workability of Portland Cement Concrete." Proceedings. 193-203. . CO 1. "Information on Thickening Admixtures for Use in Concrete and Mortar.. pp. M.. "The Direct and Continuous Measurement of Bleeding in Portland Cement-Water Mixtures. Slough.. [10] Tanaka. "Stability of Fresh Concrete Mixes. Dec. [5] "Functional Materials. E." Journal. Current Papers." Standards Association of Australia. [7] Ritchie.872 TESTS AND PROPERTIES OF OTHER MATERIALS help? To answer that question.."PumpabilityofMortars. Vol. and Pisapia. [16] Herschel. 1974. 62. pp. 49." Journal. 20. 1977. even if indirect. unpublished. [13] Kempster. K. L. American Concrete Institute. and Fillers. [8] Schupack. Sands. Potential side effects of concrete pumping admixtures of air entrainment and retardation of set have been mentioned. P. "Laboratory Procedure for Comparing Pumpability of Concrete Mixtures. Feb. 62 (in Japanese.. "Lightweight Aggregate Concrete Placing with Pump Method. May-June 1936. Unpublished Report on Study of Pumpability of Grouts. and Emura. [11] Ozaki. Building Research Establishment. I. E. p.. Copyright by ASTM Int'l (all rights reserved). Tenn." Proceedings. Vol. American Society of Mechanical Engineers. "Tests to Establish Concrete Pumpability. p. Jr. English translation arranged by subcommittee)."ContractJournal. DR 73146.. [4] Committee BD/33-Concrete Admixtures.. May4. F. 217. B. American Society for Testing and Materials. No. Miscellaneous Publication." Contract Journal. Aug.. E.. Jan. Tennessee Valley Authority. 1969. Department of the Environment. Wexham Springs.. 21. Draft for Comment. R. May 1977. 5. "Measuring Void Content: New Apparatus for Aggregates. O. 28. [3] Browne." Building Research Station. G. a test method or combination of test methods is required that will provide some indication. E. 409. p. 1962. No. Knoxville. Onoda Cement Company. Guide to Concrete Pumping. 93 (in Japanese. A." Journal of Research. Tests for these characteristics are now incorporated in specifications for admixtures for concrete and need not be repeated in a specification for pumping admixtures. 1976. Proceedings Vol. 1975. [14] Lane. W.. 73. A. pp. J. October 1973. and Bamforth. 964. 27 March 1969. Vol. CP 29/69. [12] Kempster. Journal of Construction Division." Cement and Concrete Association. R. pp. 74. E. Her Majesty's Stationery Office 1972. D. 32. England. 1966. 891-908. p. References [1] Kempster. p. English translation arranged by subcommittee). C.
Report "ASTM (1978) - Significance of Tests and Properties of Concrete and Concrete-making Materials"