Bond behaviour of reinforcing bars in cracked concrete

Due to the relatively low tensile strength of concrete, cracks are inherent in reinforced concrete structures. A common cause of cracking is the corrosion of internal steel reinforcement, a deterioration process that can affect the bond behaviour and anchorage capacity of reinforcing bars. Corrosion leads to a reduction of the reinforcing bar diameter, the formation of a weak layer of corrosion products around the bar and expansive forces on the surrounding concrete (that can lead to cracking). In the past, the impact of corrosion on bond has been investigated by means of accelerated corrosion tests. However, the more fundamental impact of cracking as distinct from corrosion products on the bond reduction is still not fully understood.This study applies a novel test method to investigate the bond behaviour of reinforcing bars in cylindrical cracked reinforced concrete specimens. The influence of the number of cracks, crack orientation, confinement and concrete cover are investigated.The results indicate a significant loss of bond strength for single cracked specimens. This reduction becomes as high as 65% for double cracked specimens in the absence of confinement. It is shown that the crack orientation with respect to the rib pattern is of minor influence, but the concrete cover and confinement play a significant role in the obtained bond characteristics.