Abstract: This paper presented the performance of mortar exposed to chloride solution.Effect of mineral admixture on chloride binding capacity was studied through testing the free chloride concentration and total chloride ion concentration of mortar specimens after soaking in sodium chloride solution.The result shows that the chloride binding capacity of mortar is improved with the increase of the content of mineral admixture.Chloride ions diffusion coefficient is measured according to RCM method, and results indicate that both of fly ash and slag can improve the resistance of chloride ions penetration, and the effect of slag on the improvement of chloride ion permeability is more significant.Change of porosity is also deduced based on chloride crystal, dissolution of Ca(OH)2 and Friedel's salt, and it showes porosity increased due to chloride solution, while mineral admixture can diminish this influence.

Key words: chloride ions concentration;chloride ions diffusion;porosity