Comparison of Three Different Methods for Measuring Chloride Transport in Predamaged Concretes

Abstract

Chloride transport is an important subject for the durability of steel-reinforced concrete structures in chloride-laden environments. There are several different types of tests for determination of the chloride-transport properties of concretes. The understanding of the differences between these tests is critical for choosing the most suitable type of test. Besides, there are different factors affecting the chloride transport in concrete, such as the water/binder (w/b) ratio, cement type or mineral additives, and the stress levels (since concrete structures are designed to withstand different loads). This work aims to evaluate the applicability and feasibility of different chloride-transport tests on concretes predamaged by compression. Moreover, the combined effect of predamage caused by different stress levels and the concrete mix design (w/b ratio, mineral additives) on chloride transport in concrete were investigated. The results show that the chloride profiles and the chloride diffusion coefficients in the chloride sorption + diffusion tests are much higher than those in the chloride diffusion tests, especially for the concretes subjected to higher stress levels. This indicates that the effect of sorption on the increase of chloride ingress into concrete is more significant when the concrete has more microcracks. Sorption was found to have minimum influence on the surface chloride content. The chloride migration coefficients were found to be higher than the chloride diffusion coefficients, especially for the concretes with a higher stress level. The partial replacement of ordinary Portland cement (OPC) with ground granulated blast-furnace slag (GGBS) can significantly reduce the detrimental effects caused by the high stress levels on chloride transport in all three methods.