The vertical Non-uniform corrosion of Reinforced concrete exposed to the marine environments

Abstract

Reinforced concrete (RC) structures usually are exposed to a wide variety of combined actions, which may cause various damages to the structures. The main objective of this study is to investigate the vertical non-uniform corrosion of reinforcement bar in concrete that was exposed to the marine environments. The concrete embedding rebar electrodes array (CRA) was designed and made based on the wire beam electrode (WBE). To simulate the submerged, tidal and splash marine environments, the marine environment simulation equipment (MESE) was set up. Electrochemical behaviors of rebar electrodes were characterized using the WBE method, linear polarization (LP) technique and electrochemical impedance spectroscopy (EIS). To monitor the carbonation and chloride ion penetration of concrete, the pH and chloride ion profiles of the concretes were analyzed. The vertical non-uniform corrosion of rebars was caused by the difference of oxygen concentration, moisture content, free chloride content and pH value in vertical direction. The macroscopic galvanic corrosion between the splash zone rebars and the tidal zone rebars was inhibited and the galvanic corrosion between the adjacent rebars was promoted by the high resistivity of the splash concrete. The concrete carbonation was a metathesis reaction between the bicarbonate ion (HCO3−) of seawater and the alkaline hydration products of concrete in the marine environments.