Electrochemical chloride removal in reinforced concrete structures: Improvement of effectiveness by simultaneous migration of silicate ion

Abstract

For rehabilitating the chloride contaminated concrete structure to extend its service life, an electrochemical chloride extraction (ECE) treatment with simultaneous migration of silicate ion was proposed. The electrochemical technique is capable of alienating the chloride ions from the reinforcement and simultaneous injecting SiO32− into the mortar to interact with Ca(OH)2, resulting in mortar desalination and densification. By a comparative experiment, the chloride extraction efficiency and corrosion properties of steel reinforcement in sodium chloride solution after the electrochemical treatment were investigated by chloride potentiometric titration, corrosion potential (Ecorr) and corrosion current density (Icorr) determined by electrochemical impendence spectroscopy (EIS). The microstructure of mortar after the electrochemical treatment was observed using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), differential thermo-gravimetric analysis (DTG) and X-ray diffraction (XRD). About 40–55% of initial chloride was removed from the mortar using a current density of 2A/m2. The electrochemical treatment can effectively prolong the initiation time of secondary corrosion for the steel reinforcement, due to the mortar densification by electro-migration of silicate ion.