A novel method for assessing C-S-H chloride adsorption in cement pastes

The binding of chloride can retard the penetration process and is of important significance for the durability of concrete structures. The previous researches calculated the content of C-S-H absorbed chloride mainly through chemical synthesized C-S-H and thermodynamic modeling, rather than in real cement pastes. This study proposed a feasible method for assessing C-S-H adsorbed chloride in real cement pastes by utilizing the order of decomposition of Friedel's salt, Kuzel's salt and C-S-H gel during carbonation and the significant content difference between them. All the parameters used for analysis were obtained experimentally, and thus have high reliability. The content of bound chloride adsorbed on C-S-H and combined in Friedel's salt was determined with this novel method in pastes under two different exposure conditions. The results show that the adsorption amount of chloride within W50-N and W50-C on C-S-H of per unit mass is 0.00418 g and 0.00588 g separately, and the ratio of C-S-H adsorbed chloride to the total bound chloride in pastes is 49.1% and 46.0% respectively. (C) 2019 Elsevier Ltd. All rights reserved.