Impact Mechanism of Water Saturation and Loading Rate on the Dynamic Tensile Properties of ECC

Water saturation has a significant impact on the dynamic tensile properties of engineering cementitious composites (ECC). In this paper, vacuum water saturation equipment is used to saturate ECC rapidly, reducing the effect of secondary hydration of cement. Dynamic tensile tests at four strain loading rates (2×10−5 s−1, 10−4 s−1, 10−3 s−1, 10−2 s−1) were performed in three saturated states (dry, semisaturated, and saturated) using the mechanical testing and simulation system. The results show that, under the same strain rate, the higher the water content of the specimen, the higher the ECC ductility, and the more fiber pull-out at the main crack section, while with the increase of loading rate, the three water content specimens are characterized by decreasing number of cracks and decreasing ductility. With the same saturated state of the ECC, the crack initiation strength, tensile strength, and elastic modulus increase with the increase of the loading rate, and the higher the water content, the greater the value of dynamic increase factor (DIF), and the higher the strain rate sensitivity; further, the DIF value of tensile strength is higher than the DIF value of crack initiation strength. For the same water-saturated ECC, the crack initiation strain and ultimate tensile strain decreased with the increase of loading rate, the higher the water content, the smaller the dynamic reduction factor (DRF) value, the higher the strain rate sensitivity; further, the DRF value of the ultimate tensile strain is lower than the DRF value of the crack initiation strain. Also, it was found that the strain rate sensitivity of ECC was lower than that of plain concrete compared to plain concrete.