Experiment and molecular dynamics study on the mechanism for hydrophobic impregnation in cement-based materials: A case of octadecane carboxylic acid
JZ Chen and Y Zhang and DS Hou and J Yu and TJ Zhao and B Yin, CONSTRUCTION AND BUILDING MATERIALS, 229, 116871 (2019).
A novel method that specimen is impregnated with octadecane carboxylic acid (OCA) solution is proposed to prevent water and ions from penetrating into concrete/mortar. Molecular dynamics is utilized to model capillary absorption in calcium silicate hydrate (C-S-H) channel to reveal related mechanism. The simplified model of decane carboxylic acid (DCA), coating on C-S-H channel and DCA mixed in solution, is used in the simulation. While the hydrophilic functional terminal of DCA chain is bridged to surface calcium in C-S-H, the other hydrophobic end diffuses free in the solution. The reduction of capillary transport rate induced by DCA is mainly due to two reasons. (1) DCA coating decreases the hydrophilicity of the channel; (2) Aqueous ions accumulate around DCA, forming huge DCA-based clusters and blocking the transport channel. This study can contribute to development of water repellent materials in durability design of cement-based materials. (C) 2019 Elsevier Ltd. All rights reserved.
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