Research on Salt Corrosion Resistance of Lithium-Based Protective Coating on Mortar Substrate

The present study concerns hydrophobic surface treatments with silane-based coating on concrete surfaces against external ionic transport. The nano-modification and organic-inorganic modification were carried out on it and applied to the mortar matrix and concrete matrix. Lithium-based protective coating (PC1, PC2), nano-modified coating (NC1, NC2) and organic-inorganic composite coating (OL1) were prepared. The salt erosion resistance of the mortar matrix and concrete matrix was tested, compared with the blank group and the market. The test results found that the organic-inorganic modified OL1 and LC1 coatings have the greatest influence on the chloride penetration resistance of the mortar matrix, in which the chloride penetration depth of 28 days is reduced by 73.03% and 63.83%, respectively, compared with the blank group. The rate of mass change of the blank group, PC1 and PC2 coatings, and NL1 and NL2 coatings were 0.17%, 0.08%, and 0.03%, respectively. The result demonstrated that the lithium-based coating could effectively delay the penetration rate of chloride ions and sulfates into the mortar, and the nano-modified properties could improve the salt resistance. The scanning electron microscopy (SEM) showed that coating treatment would promote the secondary hydration of cement-based materials, by reducing the content of Ca(OH)2 in hydration products of cement-based materials and producing C-S-H gel, which is conducive to strength enhancement and pore refinement. The nano-component would promote the reaction degree, while the organic-inorganic coating would have the respective advantages of the two components.