Chloride sorption by C-S-H quantified by SEM-EDX image analysis

The validation of reactive transport models requires the understanding and quantification of the chloride sorption by C-S-H, but the experimental methods are lacking. In this paper, we use SEM-EDX hypermaps to quantify the chloride sorption in hydrated an C3S paste, after equilibrium in solutions of chloride salts (NaCl, KCl, CaCl2, MgCl2), with and without the addition of sodium hydroxide. The errors and uncertainties of the method are analysed to demonstrate the relevance of the method. We first show that the detected chloride contents are not related to alkali salts precipitation. Then, we illustrate a small correlation between the chloride sorption and the calcium concentration in the pore solution. Finally, a comparison between our method and the water-soluble chloride content shows that a fraction of the sorbed chloride is not extracted by the later method.