Effect of pH on Desorption of Bound Chlorides in Cement Pastes Containing Granulated Blast-Furnace Slag

This study aims to investigate the kinetics of chloride desorption in ordinary Portland cement (OPC) pastes containing ground granulated blast-furnace slag (GGBFS) upon exposure to an acidic environment with low pH levels. The desorption of bound chlorides in this study was examined using paste samples with a water-to-binder ratio of 0.4 and at two GGBFS replacement levels, 25% and 50%. Initially, the pastes were exposed to three different salt solutions composed of sodium chloride, calcium chloride, and magnesium chloride to assess their chloride binding capacity. Then, various volumes of nitric acid were added to the salt solution, and the amount of released bound chlorides was quantified at acid-to-paste sample mass ratios of 4%, 8%, 11%, 15%, and 19%. The results revealed that the incorporation of GGBFS increased the chloride binding capacity of the paste samples and their resistance to chloride desorption compared to their OPC counterparts. Additionally, the pH of the exposure solution, the cation of chloride salt, and GGBFS replacement level also influenced the extent of chloride desorption.