Determining the steady-state chloride migration coefficient of ITZ in mortar by using the accelerated chloride migration test

Abstract

In this study, an electrochemical technique is applied to accelerate chloride ion migration in mortar to estimate its transport properties. The steady-state chloride migration coefficient of mortar was determined experimentally as a function of the aggregate volume fraction to investigate the effect of aggregate content. The influence of the aggregate–cement paste interfacial transition zone (ITZ) on the steady-state chloride migration behavior in mortar was investigated using a three-phase model. The three-phase material was composed of cement paste matrix, aggregate, and ITZ. The chloride diffusion is considered to take place in the cement paste and the ITZ phases. The chloride flow is controlled by dilution in the cement paste, and the chloride flow is controlled by the combining effects of tortuosity and dilution in the ITZ. The experimental results are fitted with the three-phase model. Based on the experimental and regression analytical results, the approximate chloride migration coefficient of ITZ with different assumed thicknesses of ITZ is determined.