Concrete cover cracking under chloride-induced time-varying non-uniform steel corrosion

Chloride-induced steel corrosion is the main influential factor of the safety and durability of reinforced concrete (RC) structures. Recently, the issue of chloride-induced steel corrosion for RC structures has attracted more and more attentions. However, with the progression of the research, some faults on the fundamental assumptions and mechanism have also been found. For example, the distribution of corrosion products in natural environment is more prone to be non-uniform rather than to be uniform, and the actual rust distribution of corrosion product is not time-invariant but time-varying. Therefore, in this study, a 2D chloride diffusion analysis for the case of concrete with a single rebar was first investigated with Fick's second law. Based on this, corrosion initiation time at each position around the steel cross section can be obtained, and time-varying non-uniform corrosion depth around the steel cross section at any time was calculated by multiplying the time-varying corrosion rate and corrosion time. Then, a numerical model was developed to study the concrete cover cracking under the time-varying non-uniform reinforcement corrosion. Four crack propagation paths were predefined in the model, including vertical and horizontal direction. And cohesive elements were introduced to simulate the crack evolution along these two directions. The numerical model was verified with the experimental results. The influence of environmental parameters, concrete cover depth, and rebar diameter on the evolution of concrete cover cracking was also investigated. The present research will be helpful to the life prediction of RC structures.