Modeling time-dependent circumferential non-uniform corrosion of steel bars in concrete considering corrosion-induced cracking effects

Circumferential non-uniform corrosion of steel bars usually occurs in chloride contaminated RC structures and often lead to premature concrete cover cracking. This paper presents a numerical model developed to investigate the time-dependent process of non-uniform corrosion for steel bars at different locations in concrete. The model also considers the effects of longitudinal cracking on the chloride and oxygen diffusion. Corrosion is triggered around a steel bar once the chloride content reaches the chloride threshold at that point, which is determined based on chloride penetration. Thereafter, time-dependent corrosion rate around the circumferential surface of a steel bar is obtained through electrochemical theory, which make it possible to describe a cross-sectional corrosion profile showing the timeline of damage. A case study is developed to demonstrate the analysis procedure of the proposed time-dependent non-uniform corrosion model and to present the differences in the corrosion process between the side-located rebar and corner-located rebar. Then, the derived model can be partially verified with experimental results. In this research, the simulation results with the verified model indicates that the corrosion of side-located rebar at the top and bottom areas are more severe based on the effects of corrosion-induced cracking which allows more chloride penetration and oxygen diffusion. Also, the conducted parametric study shows that the time it takes to obtain the same critical corrosion angle increases with the increase of concrete cover thickness and steel bar diameter, but the safe time decreases with the increase of chloride penetration and oxygen diffusion coefficient.