Quantification methods for chloride binding in Portland cement and limestone systems

This paper presents a comparison of methods to quantify the chloride binding capacity for cementitious materials composed of Ordinary Portland Cement (OPC) and Limestone (LS, 0 to 55% replacement). Physical and chemical chloride bindings were investigated to better understand the binding capacity of the different systems and to provide basic information for modelling. Cement pastes samples were exposed to a 0.5 M NaCl solution and their chloride contents were quantified as free ions in pore solution, chemically bound ions in AFm phases, and physically bound ions on Calcium-Aluminum-Silicate-Hydrates (C-A-S--H). Notably, the study showed that (1) considering a solid solution between Friedel's salt and Hemicarboaluminate (He) was necessary for the quantification of chemically bound chlorides in limestone blended system and (2) an accurate estimation of the C-A-S-H content was critical for quantifying physically bound chlorides.