Preparation of ester-modified nano-SiO2/silicate coatings and its application in the impermeability of concrete

Surface treatment protective technology is a cost-effective approach to prevent harmful ions from infiltrating concrete, avoiding the deterioration of performance and increasing longevity. Here, a novel coupling agent with ester group (MA-KH-550) is synthesized from γ-aminopropyltriethoxysilane (KH-550) and methyl acrylate (MA) to modify nano-SiO 2 particles. Subsequently, the ester-modified nano-SiO 2 can be successfully dispersed in alkaline composite silicate solutions to fabricate nano-SiO 2 /silicate coatings, improving the impermeability of concrete. The incorporation of nano-SiO 2 particles can fill microscopic pores in cementitious materials, which improves the compactness of the concrete. Furthermore, nano-SiO 2 particles can also accelerate secondary hydration of cement and synergistically generate more calcium silicate hydrate gel with silicates to further boost the compactness of the concrete. High-compactness coatings reduce the penetration of the medium, thereby enhancing the impermeability performance of the concrete. When the nano-SiO 2 particle content is 1.0 wt%, the optimal performance of concrete is achieved. Compared with the original C30 concrete, the C30 concrete treated with the nano-SiO 2 /composite silicate (nano-SiO 2 /CSC) shows a 31.1 % decrease in chloride ion resistance, a 35.5 % reduction in carbonization resistance, a loss rate of 1.08 % for anti-freezing quality. This work charts a new course for designing and developing high-performance composite silicate coatings for concrete.