Electrochemical chloride extraction for reinforced concrete: Effects of current densities and energization time

Reinforced concrete structures serving in marine environments are susceptible to deterioration and failure due to the attack of chloride ions. Electrochemical chloride extraction (ECE) treatment is an effective method to improve the durability of concrete by removing chloride ions from it. Current acts a critical role in the process of ECE treatment, and the efficacy of ECE treatment is highly dependent on the energization current and time. In this study, experiments were conducted systematically about the effect of different energization time (0, 7, 15, 30 days) and the energization current (0, 1, 2, 3 A/m 2 ) on concrete. In contrast to previous studies, which derived the change pattern of specimens after ECE treatment from single microscopic images, this study employed nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) to evaluate the efficacy of ECE treatment. These techniques were combined with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) for microscopic analysis. The correlations of the energization current and time with the dechlorination efficacy are elucidated in the study. The hydration products can be decomposed under excessive treatment time or current density and the optimal setting parameters are demonstrated, with the current density of 2A/m 2 on concrete for 30 days. The removal efficiency can reach 84 % near the cathode side.