Performance improvement of electrochemical chloride extraction for concrete structures

Abstract

The purpose of this study was to investigate methods for improving the performance of Electrochemical Chloride Extraction, an electrochemical treatment used for repairing concrete structures under active chloride induced corrosion. The lack of international standards was noticed. In addition, the main results obtained by the literature review showed that regarding the influence of the treatment setup, the electrolyte choice and the mix design, in terms of binder type, appeared as major factor on the efficiency of treatment and yet uncovered completely. The maximum amount of charge passed was found to be from 1500 to 2000 A-h/m2 while the optimal value for current density appears to be 2 A/m2. The anode system appeared to have negligible effects on the efficiency of treatment. Notwithstanding, titanium mesh is still the safest option as the anode, considering its inert characteristics and noble nature. Furthermore, by the experiments results it was seen that considering different electrolytes, Lithium Borate appeared to be the most efficient to extract chlorides from concrete while Calcium Hydroxide had better performance on restoring the passive state after corrosion, healing the structure at another level, filling up possible cracks. Therefore, depending on the main goal of the treatment, different electrolytes show better performances. After defining an optimal setup for ECE, the application of the treatment to different binders was addressed and, it was observed that the greater removal of bound chlorides was perceived for GGBS. This result confirmed the previous hypothesis in other works that the higher level of chloride removal for GGBS and ternary mixes at the steel depth may be attributed to the lower immobility of bound chlorides in those mixes, which would mean a higher portion of physically adsorbed chlorides by hydration products and those can turn into mobile easily under electric charge. Lastly, suggestions were made concerning the unification of standards about an optimal setup for treatment, on the grounds on increasing efficiency of chloride removal and saving up on costs of corrosion mitigation.