ABSTRACT
The error function solution of Fick’s second law assumes the constant surface chloride concentration, when it is used to calculate the apparent average chloride diffusion coefficient in concrete during the exposure period. However, the surface chloride concentration in concrete often vary with time. The purpose of this study is to investigate the effect of time dependent surface chloride concentration on apparent average chloride diffusion coefficient. A finite element analysis method was employed to simulate the chloride diffusion in concrete, which considering the time dependent surface chloride concentration and instantaneous chloride diffusion coefficient simultaneously. Then the chloride profiles were obtained at various exposure time, by which the apparent average chloride diffusion coefficient would be calculated. Meanwhile, the influences of various kinds of time-varying models of surface chloride concentration on the apparent average chloride diffusion coefficient were investigated. Finally, the rationality of the finite element analysis results was verified by comparing with field exposure test results. Results show that the time dependent surface chloride concentration has significant effect on the apparent average chloride diffusion coefficient.
