Compressive Behavior Of Engineered Cementitious Composites Under High Strain-rate Loading

As a type a cementitious composites proposed in 1990s,engineered cementitious composites(ECC)aroused much interest as its unique tensile properties and crack-control ability.Till now,much effort has been put on the theoretical research and basic mechanical properties.However,there are few studies about the dynamic mechanical properties of ECC under impact loading.Therefore,this paper focuses on investigating the dynamic mechanical properties of ECC by experiment.This paper first introduced the theoretical and experimental research done by former researchers.About theoretical research,the design concept and theory are discussed in detail and two important design principles(strength rule and energy rule)are explained.About experimental research,the basic mechanical properties,the anti-fatigue property,crack propagation property as well as thermal property are reviewed in different sections.Besides,the practical application of ECC is listed.The experimental device for the dynamic properties study of ECC was Split Hopkinson Pressure Bar(SHPB).The basic principle of SHPB device and the calculating formulas of stress,strain and strain rate of the specimens are introduced.The raw materials to prepare ECC specimens are also introduced.Three mix proportions of ECC are designed while the fluidity and compressive strength of each kind of ECC are measured.The impact experiment under three groups of air pressure(0.9MPa,1.2MPa and 1.5MPa)was carried out by the 100mm diameter Hopkinson rod on the ECC blocks with 92mm in diameter.Diagrams of the original waveforms have high repeatability and the initial fluctuation becomes more obvious with the increase of air pressure.By comparing the dynamic average stress-strain curve of each specimen,the dynamic mechanical properties of ECC were obviously different from the static performance.The dynamic compressive strength,peak strain,average strain rate and secant modulus can be obtained from the stress-strain curve.Three types of ECC show similar mechanical properties,which means the change of water and superplasticizer content cannot change the properties.Comparing ECC with concrete,the property of ECC is like high-strength concrete and the integrity of ECC is better.Besides,ECC is more sensitive than concrete.