THE RELATIONSHIP BETWEEN CHLORIDE DIFFUSION AND MIGRATION COEFFICIENTS IN CONCRETE

摘要

Chloride diffusion coefficient is an indicator of the chloride resistance of concrete andservice life prediction of concrete structure subjected to chloride environment. Many methodshave been developed to measure the chloride transport in concrete. Based on the driving force,these methods can be classified into diffusion test and migration test. In terms of the change inchloride concentration in concrete, they can be classified into steady-state andnon-steady-state testing. However, different methods give different results. This makes thecomparison of all these results difficult. In this paper, the relationship betweennon-steady-state migration test (Dnssm), steady-state migration (Dssm) test and non-steady-statediffusion (Dnssd) test were investigated. Dnssm was determined by NT build 492, breakthroughtime method and the methods proposed by Castellote, respectively. Dssm was determined byupstream method proposed by Truc and downstream method (NT build 355), respectively.Dnssd was determined according to NT build 443. Four different concretes, containing variousmineral admixtures and with water/binder ratio of 0.48, were used for study. A same chlorideconcentration of l mol/l, was used for all the tests. The results indicated that all thenon-steady-state testing methods gave the same order of the chloride resistance of concretesalthough the diffusion/migration coefficients were somewhat different. Both NT build 492and method proposed by Castellote gave a good estimation of diffusion coefficient.Breakthrough time method underestimated chloride diffusion coefficient. Steady-statemigration coefficient was one order of magnitude lower than non-steady-state migrationcoefficients obtained from other methods. Steady-state migration coefficient obtained fromupstream method was higher than that obtained from NT build 355.