Abstract
In this article, the protective properties of modified nano silica and cement-based osmotic crystallization composite coating were studied. The results showed that there was a chemical bond between nano silica and silane coupling agent, and hydrophobic alkyl groups were grafted onto the surface of nano silica. It not only improves the hydrophobicity of nanoparticles, but also improves their dispersibility in the organic film-forming coatings. The permeability of the composite coating is significantly improved, effectively resisting the intrusion of chloride ions.