Corrosion of reinforcing steel exposed to chloride leads to the degradation of steel-reinforced concrete structures. Electrochemical chloride removal (ECR) has proven to be a non-destructive and cost-effective rehabilitation technique for reinforced concrete structures. Most studies have focused on chloride attack, with free chloride removal efficiency used as the primary index to measure ECR performance. Hence, we focused on the influence of ECR on bound chloride ions under the combined effect of chloride and sulfate. The instability of bound chloride ions was investigated through macroscopic experiments, whereas the underlying mechanism was revealed using XRD and TG-DTG analyses. In addition, a three-dimensional ECR simulation was developed using the finite element method. Both free and bound chloride ion concentrations decreased over the experimental period, with the rate of decrease being higher during the first 4 weeks than during the subsequent 4 weeks. The decomposition of C–S–H gel and the desorption of physically adsorbed chloride ions played a leading role in the release of bound chloride ions, whereas the contribution of Friedel’s salt was comparatively minor. The three-dimensional finite element simulation demonstrated that ECR can effectively remove chloride ions from concrete and that the longer the treatment time, the greater the effect.
Yu et al. (Sat,) studied this question.