Study on bond performance, flexural and crack extension behavior of base concrete prisms strengthen with strain-hardening cementitious composites (SHCC) using DIC technology

Strain-hardening cementitious composites (SHCC) have become one of the important materials for repairing damaged structures due to their excellent mechanical properties. In this study, the flexural strength of four composite specimens which were reinforced by SHCC layers of various thicknesses was tested under four-point bending tests. At the same time, crack extension behavior and surface strain distribution development of the SHCC-reinforced composite specimens was studied by using digital image correlation (DIC) technology. Then, a new method called relative deformation difference ratio (RDDR) was proposed to evaluate the bond performance between the old and new materials based on the deformation response under loading. The test result illustrates that the SHCC reinforcement layer can significantly improve the flexural strength and deformability of the base concrete prism. However, due to the significant difference of mechanical properties between the reinforcement material and old material, if the reinforcement layer is too thick, the deformation difference between the two materials increases under loading, which would weaken the interface properties and reduce the composite structural strength. The proposed RDDR method effectively reflects the bond performance of the two materials. The findings of this study could support future research and repair applications using SHCC.