Bond-slip behavior between pre-corroded rebar and steel fiber reinforced concrete

For the corroded reinforced concrete (RC) members repaired using steel fiber reinforced concrete (SFRC), bonding between corroded rebar and SFRC greatly affected the mechanical performance of repaired members. In the present paper, the central pull-out tests were carried out to investigate the bond behavior of SFRC and pre-corroded steel bar obtained in concrete specimens. The varied parameters included corrosion ratio and cover thickness to rebar diameter ratio (c/d). The experimental results revealed that the confinement and bridging action of fiber can improve the bond strength and transform the failure mode from splitting to pull-out or combined splitting and pull-out. Bond strength decreased with increasing corrosion ratio and decreasing c/d, whereas the residual bond strength remained no less than that of non-corroded rebar especially for specimens with a small c/d. Bond strength degradation, bond toughness variation and bond-slip descending behaviors with corrosion ratio were correlated to c/d and failing mode. A modified bond strength model considering the coupling effect of corrosion and c/d was proposed, and the calculated strength agreed well with the tested.