Effect of bidirectional electromigration rehabilitation on corroded reinforcement and surrounding concrete in chloride contaminated concrete

Abstract

Chlorides in marine environment are the major factors induced durability issues of concrete structures. Electrochemical methods are reported to efficiently solve these problems due to the intrusion of chloride salts. In this study, an electric field of different durations and different current densities were applied between the rebar cathode and the external anode to migrate the triethylenetetramine (TETA) corrosion inhibitor into the specimens. The linear polarization method was used to measure the corrosion condition of steel bars. Electrochemical impedance spectroscopy (EIS) was used to measure the impedance changes in reinforced concrete specimens. The concentrations of corrosion inhibitors and chloride ions were measured for different depths of the concrete cover. The scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) were used to determine concrete morphology and pore structure, respectively. The results showed that the bidirectional electromigration treatment increased the resistance of the concrete cover and recovered the corrosion potential of the steel bars to a lower level. With the increase in treatment time or current density, the chloride content in the concrete cover decreased, whereas the concentration of corrosion inhibitor in the specimen rose. The porosity evolved from micropores (0.001–0.1 μm) to mesopores (0.1–1 μm) in the concrete cover. Rehabilitation resulted in the hydration products being decomposed at the cathode and aggregated at the anode.