Analytical and experimental investigation of the bond behavior of confined high-strength recycled aggregate concrete

Abstract

This study investigates the bond behavior between 600 MPa grade reinforcement and high-strength recycled aggregate concrete (RAC) by carrying out 22 beam tests. Test parameters include the recycled coarse aggregate (RCA) replacement ratio, reinforcement diameter, concrete cover thickness, stirrup ratio, concrete strength and the addition of steel fibers. The influences of different parameters on the failure modes, bond-slip curves and bond strength are discussed. The results indicate that the RCA replacement ratio has little effect on the failure mode and the bond-slip curve, while the bond strength decreases with its increase. Similar to normal aggregate concrete, the bond strength is positively correlated with f′c1/2. Increasing the concrete cover thickness or the stirrup ratio can significantly improve the bond strength and decrease the crack width. The addition of steel fibers can avoid specimen splitting, but this addition will disturb the reinforcement-concrete interface, which has little effect on the bond strength of 50 MPa grade RAC, however, the addition slightly increases the bond strength of 70 MPa grade RAC. The design bond strength of steel fiber concrete should not be lower than the design bond strength of plain concrete with the same compressive strength. The splitting failure of specimens is further classified, and the effective confinement Factor K for predicting the failure mode is presented. In view of different confinement conditions, bond-slip models between the 600 MPa grade reinforcement and high-strength recycled concrete are established.