A Numerical study for Chloride Migration in Concrete Under Electrochemical Repair Process

Electrochemical repair is one of the most effective methods of removing chloride from offshore engineering structures to improve their durability. The diffusion of chloride and electrochemical repair are key stages in this process. In this paper, a new numerical chloride migration-diffusion model is established by using Nernst-Planck equation. The distributions of free chloride ions in concrete in the stage of free chloride diffusion and the stage of electrochemical repair are simulated, and the effects of external potential and cathode position on electrochemical repair efficiency are analyzed. The numerical results show that electrochemical repair can effectively remove chloride ions from concrete. After 12 weeks of the electrochemical repair, the electrochemical repair efficiency is more than 66%. With the increase of repair time, the increase amplitude of electrochemical repair efficiency decreases gradually. In the initial stage of electrochemical repair, the chloride concentration on reinforcing bar surface decreases rapidly. After 4 weeks of electrochemical repair, the chloride concentration tends to be stable. As external potential increases, the electrochemical repair efficiency is also improved, and the chloride concentration on reinforcing bar surface decreases rapidly. When the cathodes are set on both sides of the concrete, the electrochemical repair time should be extended, and external potential should be increased to achieve better repair effect.