TIME/DEPTH DEPENDENT DIFFUSION-COVECTION MODEL OF CHLORIDE WITH TRANSPORTATION IN CONCRETE STRUCTURES WITH CHLORIDE-BINDING ISOTHERMS

Ion transport through a hydrated cement system often becomes a principal factor to degrade concrete in a chlorideladen environments. Based on the transport mechanism of chloride ion, an analytical solution of mathematical model for predicting chloride penetration into concrete structures was herein derived: The model consists of both the diffusion of chloride due to concentration gradient and the convection of chloride due to moisture transport. The model also depends on temperature, age, relative humidity, and chloride binding. Based on both the diffusion coefficient and the mean velocity with time/depth dependence, an analytical solution of the mathematical model developed by previous researchers was solemnly derived and used to predict the properties of concrete structures contaminated by chloride. The chloride penetration decreases as the time-dependence ratio increases. The amount of chloride accumulated in concrete increases as the relative humidity increases. Moreover, the proposed model may be effectively used for the practical evaluation and design for durability of concrete structures.