Chloride Extraction and Realkalization of Reinforced Concrete Stop Steel Corrosion

Abstract

Chloride extraction and realkalization are nondestructive, electrochemical treatments to halt and prevent corrosion in chloride-contaminated and carbonated concrete, respectively. The process actually removes chloride ions from the contaminated concrete by the principle of ion migration while at the same time raising the pH of the carbonated concrete through electro-osmosis. Concrete to be treated is first tested to determine the level of chloride contamination. Then, after preparing the surface, a steel or titanium mesh electrode is attached to the structure. The electrode is embedded in a nontoxic biodegradable electrolytic media. Next, electric contacts are established between the attached electrode and the steel reinforcement bars (rebars) inside the concrete. When an electric field is applied, chloride ions migrate away from the rebars and towards the externally attached electrode, eventually ending up in the temporary electrolytic media, which is then discarded. Simultaneously, alkali ions migrate from the electrolyte into the concrete, raising its pH to the original levels. The passivating layer of the rebars is thus reestablished to protect them from corrosion.