Theoretical Evaluation of Diffusion Coefficient of Chloride Ion in Mortar from Mobility

Abstract

Many researchers have been trying to evaluate the diffusion coefficient of chloride ion in concrete by using qualitative and quantitative electromigration tests. Up to now, however, there has been no sufficient method to closely determine the diffusion coefficient of chloride ion through electromigration tests. This paper investigates the diffusion coefficient of chloride ion in mortar by mobility through an electromigration test. The concept of Einstein's equation, which can relate the diffusion coefficient of the chloride ion and the mobility in an ideal solution with very low concentration, is adapted. Then, for compensating the influence of the concentrations, the Debye-Huckel theory is used. For considering the effect of other existing ions, namely, OH-, Na+, and K+, the electrical neutrality is taken into account. Therefore, using Einstein's equation, the Debye-Huckel theory, and electrical neutrality, the diffusion coefficient of chloride ion can be calculated theoretically from the mobility. The correctness of the calculation is checked by a series of tests.