Development of high-strength and high-ductility ECC with saturated multiple cracking based on the flaw effect of coarse river sand

This study developed a high-strength and high-ductility engineered cementitious composite (HSHD-ECC) using coarse river sand (RS) for the first time. Within this newly developed ECC, saturated multiple cracking was achieved based on the flaw effect of coarse RS. The maximum size (4,750 μm) of RS was almost 20 times that of ultrafine silica sand (USS) in conventional ECC. The compressive strength of river sand HSHD-ECCs exceeded 115 MPa. Moreover, the tensile strength and strain were more than 12 MPa and 9%, respectively. More importantly, fully distributed microcracks with spacing less than 1.3 mm could be observed on the RS-HSHD-ECCs. The pseudo-strain-hardening (PSH) index and PSH intensity were calculated to theoretically explain saturated multiple cracking and high ductility behavior. Also, it was found that coarse RS can be regarded as a flaw in HSHD-ECC and thus tailor the pre-existing flaw in the matrix. The agreement between theory analysis and experiments showed that coarse RS was preferable for application in HSHD-ECC to achieve the saturated multiple cracking and high ductility.