Evaluation of the bond performance between non-uniformly corroded bimetallic steel bars and concrete

Corrosion of steel bars inevitably exists in reinforced concrete structures, which significantly affects the bonding performance between steel bars and concrete. Due to the protection of concrete, the steel bars in structures usually undergo non-uniform corrosion. However, previous studies on bonding properties were mainly based on uniform corrosion, limiting the accuracy of structural safety assessment. In this study, the bond performance between an innovative corrosion-resistant bimetallic steel bar and seawater concrete (BSBSC) after corrosion was evaluated. An accelerated corrosion method was designed to obtain uniform and non-uniform corrosion BSBSC specimens, and the bond pull-out tests of 44 BSBSC specimens were carried out. The experimental results indicate that, compared with uniform corrosion, non-uniform corrosion specimens have larger widths of rust expansion cracks under similar corrosion degrees. The bond strength of BSBSCs with uniform corrosion can increase by up to 45.85 % at the initial stage of corrosion. Meanwhile, the bond stress of BSBSCs with non-uniform corrosion decreases significantly even at a relatively low corrosion degree. Non-uniform corrosion has a more significant impact on the bond slip. When the corrosion degree exceeds 1 %, bond slip is close to 0. A bond stress-slip constitutive model was proposed, which can predict the bond behavior within the corrosion degree range of 1–15 %. Based on the experimental and theoretical analysis results, the modification of bond anchorage length in the current code was proposed to take the influence of non-uniform corrosion into account.