Concentration dependence of diffusion and migration of chloride ions - Part 2. Experimental evaluations

This paper series includes two parts: (1) theoretical considerations and (2 ) experimental evaluations. In Part 1, the chloride ion diffusion and migra tion processes in a pure solution system as well as in a solution-concrete system have been theoretically analyzed. The relationships between differen t diffusion coefficients from the conventional diffusion or migration tests have been established. In this, the second part, the parameters influencin g the "effective" diffusion coefficient, such as activity coefficient, coun ter-electrical field, and the friction coefficient due to the ionic interac tion, are quantitatively evaluated with available experimental data. The re sults show that the concentration dependence of chloride diffusion and migr ation can be quantitatively described by two decisive parameters: K-tau and f; the former describes the effect of counter-electrical field and the lat ter describes the friction effect. The theories fit the experimental data f airly well. Some phenomena of ion diffusion in concrete can be explained by these theories, such as the differences in diffusion coefficient between d iffusion and migration tests and between cations and anions. (C) 1999 Elsev ier Science Ltd. All rights reserved.