Interfacial shear properties between water-castable engineered cementitious composites (WECC) and concrete substrate

Abstract

To characterize the shear performance and bonding mechanism of the interface between a water-castable engineered cementitious composite (WECC) and the concrete substrate, single-sided shear tests were conducted. The effects of age (3 days, 7 days, 14 days, and 28 days) and roughness (0 mm, 0.91 mm, and 1.87 mm) on the macroscopic performance of the interface were studied. Computed tomography (CT) was used to quantitatively analyze the changes in the mesoscopic void structure of the three interfaces at different ages, and scanning electron microscopy (SEM) was used to analyze the microscopic structure and hydration products of the interfaces. A three-zone, double-layer, two-interface bonding model for WECC–concrete substrate interfaces in water media is established, elucidating the bonding mechanism. On the basis of the CT test results and single-sided shear test results, an interfacial shear stressslip model and a peak shear stress prediction model including macro- and mesoscale parameters are developed. As the roughness and age increase, the interfacial peak shear stress gradually increases. When the roughness is 1.87 mm, the interfacial peak shear stress is the highest. The interfacial peak shear stress of W1.87–28 is 60.65 % greater than that of W1.87–14 and 34.25 % greater than that of W0.91–28. The results reveal the structure of the interface between WECC and concrete panels and provide early-age interfacial bonding data for WECC reinforcement projects.