Coupling effect of corrosion damage on chloride ions diffusion in cement based materials

Abstract The durability of concrete structures in marine environment depends on the migration speed of chloride ions in concrete. If the reinforced steel bars in these structures are attacked by chloride ions and begin to rust, these are considered as failure. In general, the diffusion of chloride ions in concrete is analyzed by solving the diffusion equation based on Fick’s law. In the equation, the diffusion coefficient is assumed to be constant. However, novel studies have shown that corrosion damage could take place in concrete due to the formation of Friedel’s salt during the diffusion process. The evolution of corrosion damage not only causes the diffusion coefficient to be a function of time, but also speeds up the migration of chloride ions. This can decrease the durability of concrete structures. However, few related researches have been reported. Close attention to this study was paid to the coupling effect between corrosion damage and the migration of chloride ions. The variation of porosity of cement based materials due to chemical reaction, physical absorption, continued hydration, and corrosion damage was investigated. Then, a new diffusion equation was derived by considering these factors. By virtue of the numerical method, the spatial-temporal distribution of corrosion damage was evaluated, and its effect on the migration of chloride ions was numerically discussed. These results show that corrosion damage could significantly affect the diffusion of chloride ions.