Evaluation of Rapid Chloride Permeability Test (RCPT) Results for Concrete Containing Mineral Admixtures

Abstract

The correlation between the charge passed data derived from rapid chloride permeability test (RCPT) and the chloride penetration coefficient K derived through 90-day soaking test for the concrete containing mineral admixture is elucidated. For this purpose, concrete specimens containing varying proportions and fineness of mineral admixtures, such as ground granulated blast-furnace slag (GGBFS) and silica fume (SF), and moist-cured for different periods, were subjected to a 90-day soaking test and a RCPT. To supplement the results, the electrical resistivity and compressive strengths of concrete mixtures were also evaluated. For the majority of mixtures containing SF and GGBFS, the chloride penetration coefficient K and the charge passed data were following different trends. This suggests that the charge passed and K are the independent properties of concrete controlled by different factors. The charge passed depends on the microstructure and the pore fluid conductivity (especially OH-negative ions) of the concrete, while K depends primarily on the microstructure of the concrete. Furthermore, the charge passed through SF and GGBFS concrete was shown decreasing exponentially with increasing electrical resistivity of the mixture. Thus, the charge passed through the concrete mixture containing SF and GGBFS can be used as a measure of the overall conductivity of concrete, rather than as a measure of the resistance of chloride penetration. The charge passed was shown to be related to the compressive strength of SF and GGBFS concrete; the compressive strength increases linearly with the charge passed decreasing.