Investigation of composite silane emulsion modified by in-situ functionalized graphene oxide for cement-based materials

Abstract

Silane coatings were ubiquitously utilized to protect the structure concrete against water and aggressive ions in marine environment. In this paper, a novel design method for silane-based nanocomposite is proposed to enhance the water repellence for silane coatings. The graphene oxide sheets (GO) were first functionalized by in-situ polymerization of dopamine (DA), and then isobutyltriethoxysilane emulsion coatings were fabricated by sol–gel method with incorporation of rGO-PDA. The PDA molecules, bridging the GO sheets and silane molecules by forming chemical bonds of –NH, CO-NH, and Si-O-C, construct amorphous and dense network structure in the emulsion. The laser particle size analysis shows that GO sheets modified by PDA were dispersed better in silane emulsion. Furthermore, the newly developed silane emulsions were sprayed on the concrete surface, while the water and ions resistance were tested to evaluate the effectiveness of coating materials. The silane emulsions modified by rGO-PDA generate higher hydrophobic effects on concrete surface. The surface contact angles can reach as high as 140° and the capillary absorption rate for water is reduced by 90%. In particular, as the rGO-PDA content is 0.2%, the modified silane emulsions exhibit the highest hydrophobicity. Additionally, the long-term sulfate attack and chloride penetration tests also confirm that as compared with coating without modification, rGO-PDA modified silane emulsions can effectively reduce transport rate of chloride and sulphate ion in concrete by nearly 70%, and alleviate concrete degradation in great extent. This paper presents new ideas for the research of nano-modification of composite silane coatings and provides technical guidance for the surface protection against concrete structures in marine regions.