The diffusion coefficient of chloride ion is one of the most important parameters to estimate the durability of concrete structures.Recently,therefore,many electro-migration tests methods have been developed to evaluate the diffusivity of chloride ion in concrete.In this comparative study chloride migration was studied by means of three different methods.Results of the rapid chloride migration test,the alternating current test,and the simple diffusion cell are presented and discussed.The experimental results show that in water saturated condition,the diffusion coefficient of chloride ion depends on the porosity and pore structure of concrete.It turns out that the rapid chloride migration test overestimates chloride penetration by a factor of nearly four.Electrical conductivity as measured with the alternating current test is not a direct indication of chloride diffusion.The simple diffusion cell provides us with most reliable values to predict chloride diffusion in concrete.Results of the simple diffusion test may provide a basis for correction of results obtained by electro-migration methods.
