Experimental study of dynamic bond behaviour between corroded steel reinforcement and concrete

Corrosion damage of steel reinforcement is detrimental to the load-carrying capacity of reinforced concrete structures because it not only reduces the cross sectional area and strength of reinforcement bars, but also weakens the bond between reinforcement and concrete. Many studies have investigated the effects of corrosion on reinforcement loss and static bond strength between reinforcement and concrete, but no study of the influence of corrosion damage on dynamic bond strength has been reported yet. In this study, laboratory tests were conducted to investigate the effect of corrosion on the bond behaviour between steel reinforcement and concrete subjected to high rate dynamic load. Accelerated corrosion damage was induced to steel bars embedded in concrete specimens under laboratory condition. The bond parameters of steel reinforcement and concrete including the ultimate bonding load and bond-slip relationship corresponding to the various strain rates and corrosion degrees were obtained through dynamic pull-out tests. The empirical formulae of dynamic increase factors (DIFs) of the ultimate bonding strength corresponding to different corrosion levels and strain rates were proposed. The experimental results show that the strain rate effect on bonding behaviour is prominent irre-spective of the corrosion level. The increase in the ultimate bonding strength with strain rate for the heavily corroded reinforcement (eta = 5 %-10 %) is more prominent than that for the slightly corroded reinforcement (eta = 0 %-5%). The decrease in the ultimate pull-out force caused by the corrosion damage at high strain rate is more pronounced than that at low strain rate. Corrosion-induced crack and the tensile strength of concrete have significant effect on both the static and dynamic bond behaviours. The results presented in the paper can be used for better modelling and prediction of the responses of corroded reinforced concrete structures subjected to dynamic loads.