Experimental and analytical investigation of bond behaviour between steel bars and steel-fibre-reinforced recycled aggregate concrete

Abstract In this study, the bond behaviour between steel bars and steel-fibre-reinforced recycled aggregate concrete (SFRAC) is investigated using 27 pull-out tests. The main test parameters include concrete strength grade, recycled coarse aggregate replacement ratio, steel fibre volume fraction, and bonded length. Based on the test results, the failure mode, bond strength, and bond stress-slip curves of the SFRAC bond specimens were analysed. The results indicated that the ultimate and residual bond strengths between the SFRAC and steel bars tended to increase with the concrete strength grade within the tested range, and decreased as the RCA replacement ratio increased from 0% to 100%. The addition of the steel fibres substantially improved the residual bond strength. Scanning electron microscopy was performed to characterise the bonding mechanism of the steel fibres on the concrete and the microstructure of the interfacial transition zone of the SFRAC. Furthermore, an analytical model to simulate the bond-slip relationship was established through data fitting. Finally, finite element simulations were performed using the ABAQUS software, and the results of the experiments and simulations were compared. The results showed that the proposed model exhibits high accuracy and can be used to simulate the bond behaviour between steel bars and SFRAC.