Residual bond strength in reinforced concrete cracked by expansion agent filled pipe simulating rebar corrosion

･This study empirically investigates the bond strength degradation in cracked concrete. The combined effects of concrete cracking and cross-sectional reduction of stirrups on bond capacity are considered.
･Bond strength decreases when the induced crack width increases.
･We also propose to estimate bond strength degradation as a function of the induced crack width and stirrup ratio.

Abstract

In corroded reinforced concrete, the volume of steel increases due to expansive corrosion products, leading to cracking of concrete. As a result, the bond capacity between concrete and rebar gradually decreases. Previously, the author explored bond deterioration owing to corrosion-related cracking using a novel crack simulation approach. To simulate the volumetric expansion of the rebar due to corrosion, an aluminum pipe is inserted into the concrete and filled with an expansion agent. However, the previous study did not consider the important effect of stirrups that provide confinement and improve bond strength. To address this limitation, pull-out tests were performed on 48 cracked specimens to investigate bond deterioration considering the influence of crack width and stirrup. It is concluded that the induced cracks without corrosion products can measure the exclusive result of corrosion of the rebar itself. After cover cracking, stirrups become the primary confinement source and can help reduce bond deterioration. Finally, an empirical formula was proposed to evaluate the bond strength degradation with induced crack width and stirrups being the main parameters. Comparisons with various experimental results of corroded specimens confirm that the proposed formula can give satisfactory predictions.

Benefit

Cracks in concrete are the most readily available clues for assessing the degree of deterioration of concrete structures. The results of this study demonstrated that such cracks could be artificially reproduced, and that the degradation of concrete could be predicted from these cracks.