SEMINAR REPORT ON ³BENDABLE CONCRETE´PRESENTED BY CHITARI NAGESH BABASAHEB I ST ± SEM M.TECH. IN STRUCTURAL ENGINEERING BASAVESHWAR ENGINEERING COLLEGE BAGALKOT ABSTRACT Engineered Cementitious Composites (ECC) is an ultra-ductile fiber reinforced ultracementitious material that embodies a micromechanics based design concept. concept. The tensile ductility and self-controlled selftight crack width characteristics are conducive to enhancing structural safety under severe loading, and durability under normal service loading. loading. The cost of ECC is currently about three times that of normal concrete per cubic yard. yard. However, a number of commercial projects in Japan and Australia have already demonstrated that initial construction cost saving can be achieved when ECC is used, through smaller structural member size, reduced or eliminated steel reinforcement, elimination of other structural protective systems, and faster construction offered by the unique fresh and hardened properties of ECC . fieldductile concrete that has the potential to significantly contribute to enhancing infrastructure safety. ECC is a field-ready compelling. These properties of ECC and its applications are reviewed in the seminar work. The advantages offered by ECC over conventional concrete become even more compelling. durability and sustainability. sustainability. work. . However. and these improvements are already emerging in limited forms. in some ways drastically.INTRODUCTION Demands on Future Concrete: Concrete:Concrete is ubiquitous. ubiquitous. the mechanical properties and functional characteristics of concrete will have to be improved. material. more than one ton per capita of concrete is cast for infrastructure construction worldwide. forms. concrete is an excellent construction material. measures. By many worldwide. . Annually. roadways and bridges. . In boundaries. which see no national boundaries. some cases. currently facing three major challenges 1) Brittle failure under severe loading:loading: Infrastructures are subjected to severe natural loadings such as earthquakes. bridges.These advancements are needed to address deficiencies in concrete infrastructure. serious damages have occurred to infrastructures including buildings. loading. and core crushing resulting in subsequent collapse of bridge piers or columns in soft first stories in buildings. cover spalling. bond splitting. e. 2)Deterioration under normal service loading:loading: .g. the magnitude of this problem in terms of dollar cost dwarfs those associated with failure due to severe loading. Deterioration is not as dramatic as collapse of infrastructure. buildings. Infrastructure failure can often be traced to brittle fracture of concrete. years. problems. impacts. . Globally.A major cause of lack of durability of reinforced concrete structure may be traced to cracking of concrete which may lead to steel reinforcement corrosion and other problems. 3) Lack of sustainability of RC structures:structures: The sustainability of RC infrastructure has come into question in recent years. the huge flow of material driven by concrete production causes significant societal and environmental impacts. infrastructure. thus providing service life significantly higher than current infrastructure. safety.1) Highly ductile: . thus providing infrastructure safety.with durable: . 2) ability to withstand mechanical and environmental loads under normal service conditions.With ability to ³yield´ ductile: like a metal when overloaded. Highly durable: . even under severe impact load or large imposed deformation. construction and use. realized. while retaining all other advantages. environment. If concrete behaves like steel in tension (highly ductile). thus ensuring harmonious interaction between the built and the natural environment.minimize natural sustainable: resource use and pollution emission. end of life demolition) of an infrastructure. . during the full life cycle (material production. concrete structures with enhanced serviceability and safety can be readily realized.3) Highly sustainable: . . loading. Which have 500 times more resistant to cracking and 40 percent lighter in weight. weight.ENGINEERED CEMENTITIOUS COMPOSITE Concrete also known as Engineered Cementitious Composites (ECC) is a fiber reinforced cement based composite material systematically engineered to achieve high ductility under tensile and shear loading. durability. volume. infrastructure. Recent research indicates that ECC holds promise in enhancing the safety.By employing micromechanics-based micromechanicsmaterial design. and sustainability of infrastructure. maximum ductility in excess of 3% under uniaxial tensile loading can be attained with only 2% fiber content by volume. . Figure 1 shows a typical uniaxial tensile stressstress-strain curve of a ECC containing 2% Poly Vinyl Alcohol (PVA) fiber.01 . Properties of PVA fibers Length (mm) Diameter ( m) Volume fraction (%) Elastic modulus (GPa) Fiber strength (MPa) Interfacial bond strength (MPa) 12 40 2 40 1600 2. The properties of PVA fibers are given in the table below. Typical tensile stress-strain curve and crack width development of ECC. . . micro-fibers are added the resulting composite maintains self-consolidating characteristics during casting and ductile behavior after hardening.Making of ECC ECC is made with ingredients typically found in concrete. Instead. fly ash. However. including cement. and no air entrainment is necessary. no coarse aggregate are employed. sand. and super plasticizer. multiple micro racks form when the composite material is overloaded beyond the elastic state (pseudo-yielding). As a result. mortar matrix and the interface between them interact under mechanical loading. and the propagating micro cracks maintain very tight cracks width in accordance with the tailored nature of the bridging fibers . Instead. brittle fracture failure is eliminated.The components in an ECC mix design is based on micromechanics on how the fiber. FLOW CHART OF IMPORTANT ELEMENT OF ECC . In addition to collapse resistance.PROPERTIES OF ECC Safety:. . Its implementation eases the adoption of new high performance material such as ECC. Billington in reviewing this subject suggested that the use of ECC could lead to highly damage tolerant structures with limited residual crack widths such that postearthquake repair costs could be minimized.A major driver of next generation infrastructure resistant to seismic loading is performance-based earthquake engineering. under combined environmental and mechanical loads. These cracks are exacerbated by fatigue loading due to moving traffic. is complex. deterioration often begins with cracking due to thermal movements or restrained drying or autogenously shrinkage cracking.Durability The cause of infrastructure deterioration. . In bridges and roadways. Damage behavior . 5 in unaxial tension.Grey no indicate data normalized by number of cracks. .Crack width evaluation of link slab specimen during fatigue test Coefficient of permeability versus crack width for ECC & reinforced mortar series prestrained to 1. Micro cell & Micro cell corrosion rate measured for 1) rc 2)RECC along the reinforcement bar length Failure mode of a) concrete b) ECC . the amount spalling. . Additionally. shear.APPLICATIONS Earthquake resistant structures:structures: The no of experiments confirm significant improvements in damage tolerance. of steel shear reinforcement can be drastically reduced since ECC remains highly ductile in shear. suppressing many of the commonly observed failure modes in RC such as cover spalling. Freezeaccelerated weather exposure. and wheel load abrasion and wear tests. fatigue. and significantly delay corrosion of reinforcing steel. spalling. . Freeze-thaw exposure.Durable and sustainable infrastructure Structures have enhanced durability when applying ECC. the ductility of ECC minimizes the potential for cover spalling. all indicate high ECC material durability self± self± controlled tight crack widths reduce transport of water and corrosives through the cover . Furthermore. Uses of ECC in Field MIHARA BRIDGE JAPAN . . Hand finishing of ECC link slab on Grove Street Bridge Project Patch repair on a bridge deck. unlimited beyond 1. Fine Fine aggregates and Matrix aggregates and Cement Cement Controlled for matrix toughness.Comparison between ECC. fine sand. and HPFRCC Properties FRC Common HPFRCC ECC Mechanical Properties Strain-softening: Strain-hardening: Strain-hardening: Tensile strain 0.1% <1. Cement. Fly ash.5% strain Typically < 100 micrometers during strain-hardening Coarse aggregates. 8% max Typically several Crack width Unlimited hundred micrometers. FRC. .5% >3% (typical). Use high Vf minimize Vf for cost and process ability Any type. Vf usually less than 2%. df for steel > 5%. Vf usually Fiber Mostly steel. Vf usually Tailored. polymer fibers .Properties FRC Common HPFRCC ECC Chemical and frictional Interface Not controlled Not controlled bonds controlled for bridging properties Micromechanics based. df ~ 150 ~ 500 micrometer micrometer FRC:.High Performance Fiber Reinforced Cement Concrete . Design Methodology N.FIBER REINFORCED CONCRETE HPFRCC:. df < 50 micrometer less than 2%.A. fiber. composites. rate. . and interface properties to exhibit strain-hardening and strainmultiple cracking behaviors in the composites.MODERN TECHNIQUES Spray able ECC Technology :-In the development concept of spray able ECC. micromechanics is adapted to properly select the matrix. the fluid properties are controlled by the rheological process design to develop flocculations between cementitious particles at a proper rate. Within the pre-determined premicromechanical constraints. Lightweight ECC Technology .