Acid Radical Tolerance of Silane Coatings on Calcium Silicate Hydrate Surfaces in Aggressive Environments: The Role of Nitrate/Sulfate Ratio

JL Jiang and SC Li and MH Wang and DS Hou and JH Hu and J Zhang and YJ Geng and HL Xie and MJ Hu and ZJ Liu, LANGMUIR, 39, 11304-11316 (2023).

DOI: 10.1021/acs.langmuir.3c00997

Silane is known as an effective coating for enhancingthe resistanceof concrete to harmful acids and radicals that are usually producedby the metabolism of microorganisms. However, the mechanism of silaneprotection is still unclear due to its nanoscale attributes. Here,the protective behavior of silane on the calcium silicate hydrate(C-S-H) surface is examined under the attack environmentof nitrate/sulfate ions using molecular dynamics simulations. Thefindings revealed that silane coating improved the resistance of C-S-Hto nitrate/sulfate ions. This resistance is considered the originof silane protection against harmful ion attacks. Further researchon the details of molecular structures suggests that the interactionbetween the oxygen in the silane molecule and the calcium in C-S-H,which can prevent the coordination of sulfate and nitrate to calciumon the C-S-H surface, is the cause of the silane molecules'strong adsorption. These results are also proved in terms of freeenergy, which found that the adsorption free energy on the C-S- Hsurface followed the order silane > sulfate > nitrate. Thisresearchconfirms the excellent protection performance of silane on the nanoscale.The revealed mechanism can be further used to help the developmentof high-performance composite coatings.

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