Investigation of interface shear properties and mechanical model between ECC and concrete

Abstract This paper reveals an investigation of the influences of ECC mixture construction method (i.e., common casting and spraying ECC), ECC strength grade, interface roughness of concrete substrate, and polyvinyl alcohol (PVA) fiber type on shear properties of ECC-to-concrete interface. The test results show that two failure modes of interface shear failure and ECC failure were observed. The roughness degree of concrete substrate had a strong effect on the failure mode, while ECC strength grade, ECC mixture construction method, and PVA fiber type had almost no influence on the failure mode. The shear load-slip curves of all specimens were basically similar. Compared to the casting ECC, the spraying ECC had an obvious decreasing effect on interface shear strength. The ECC strength grade and roughness degree of concrete substrate had a significant influence on interface shear strength, and higher ECC compressive strength and coarser interface could cause higher interface shear strength. On the contrary, PVA fiber type had a slight influence on interface shear strength. Based on the micro-bonding mechanism and test results of shear load-slip curves, a shear strength mechanical model and a shear stress-slip model of ECC-to-concrete interface were proposed to predict interface shear strength and shear stress-slip curve, respectively.