Molecular insights into the adsorption of chloride ions in calcium silicate hydrate gels: The synergistic effect of calcium to silicon ratio and sulfate ion
N Wang and RQ Zhao and L Zhang and XM Guan, MICROPOROUS AND MESOPOROUS MATERIALS, 345, 112248 (2022).
Corrosion of steel bars by chloride ions is one of the main reasons for determining the service life of marine concrete. In this work, the effects of calcium to silicon (C/S) ratio and SO42-concentration on Cl- adsorption in calcium silicate hydrate (C-S-H) gels were systematically studied by molecular dynamics simulations. Atomic-scale results show that higher C/S ratio induces more Cl- adsorption. The presence of SO42-not only reduces the Cl- adsorption but also buffers the adsorption caused by increasing C/S ratio. The Cl- adsorption is caused by the attraction of interlayer Ca (Cah) and hydroxyl groups in low C/S gel, while in high C/S ratio C-S-H gel is mainly contributed by Cah. More Cl- adsorption at the C-S-H interface ensures less Cl- accumulation in zones surrounding the reinforcement. The insights into ion adsorption behaviour should provide useful information for prolonging the durability of marine concrete by designing appropriate compositions.
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