Effects of Interface Orientations on Bond Strength between Old Conventional Concrete and New Self-Consolidating Concrete

An experimental test was presented to study the effects of interface orientations on bond strength between old conventional concrete (CC) and new self-consolidating concrete (SCC). A total of 90 specimens were designed and tested using a direct shear test setup. The substrate CC was cast first and exposed to a carbonation chamber for the simulation of aged concrete. The new SCC was then cast on the aged concrete with different mold arrangements to simulate side, bottom, and top bonding interfaces. Effects of bonding interface orientation, concrete strength, and interface treatment on bond strength were clarified. Furthermore, the tested results were compared with the predictions of design codes to verify the applicability of design codes on the cases with different orientations of bonding interface. Results show that interface orientation significantly affects the bond strength between old CC and new SCC. Top bonding interface leads to highest bond strength, followed by side and bottom bonding interfaces. The average reductions of bond strength caused by side and bottom bonding interfaces, respectivety, are 6% and 57% compared to top bonding interface.