Abstract: According to the chloride ion transmission mechanism, the chloride convection-diffusion control equation in unsaturated concrete was derived by considering the difference of moisture transmission the dry-wet alternate process. The results of model calculation have a good correlation with the measured results. The calculation results show that the free chloride ion concentration with increase with the increase of dry-wet cycles, the convection zone depth, surface chloride ion concentration and peak chlorine ion concentration increases with dry-wet cycles and gradually stabilized. The regression equations of each index were obtained.

Key words: unsaturated concrete;chloride;convection zone depth;surface chloride ion concentration