Bond-slip model of corroded plain round bars in low-strength concrete under cyclic and monotonic loading

Abstract

The effect of corrosion on the overall behavior of beam-type bond-slip samples constructed from low-strength concrete and plain round bars was examined in this study. First, a set of nominally identical specimens underwent testing under both monotonic and cyclic loading, and subsequently, the bond-slip interaction was assessed for each individual sample. The observed failure mode for plain round bars was direct pullout without concrete splitting apart, characterized by the loss of cohesion between the rebar and the adjacent concrete surface. Then, an analytical relationship was established by fitting a curve to the average experimental data using the method of least squares. Corrosion-degradation in the bond stress was considered by incorporating an exponential component into the equation of the reference bond-slip curve (i.e., null corrosion). Besides, the degradation in bond strength was predicted as a function of corrosion level, which is in the form of an exponential curve. The maximum surface crack width, an easily quantified variable on-site, was correlated with the bond strength of corroded bars. The regression analysis successfully established the optimal relationship between the maximum surface crack width and the corrosion level in an exponential form as well. Notably, the majority of the data in all cases fell within the 95% confidence interval.