Abstract:
The influences of inorganic mineral on the properties of waterborne fluorocarbon coating were studied, and the variation in adhesion of fluorocarbon composite coatings under the salt freezing environment was studied, and the influence of fluorocarbon composite coatings on the amount of spalling per unit area of concrete was analyzed, by surface hydrophobic property test, mechanical property test, interface bonding property test and salt freezing test of concrete. The improvement mechanism of salt freezing resistance of concrete was analyzed, combining the changes of microscopic appearance and pore structure. The results show that the water contact angle of the fluorocarbon composite coating with single doped silica sol increases by 10.2%, compared with fluorocarbon coating, and the pencil hardness is up to 3 H. The pencil hardness of the fluorocarbon composite coating with triple adding of silica sol, sepiolite powder and iron tailing powder is up to 3 H, and the adhesion increases by 44.2%. The properties of the fluorocarbon composite coating with double adding of silica sol and sepiolite powder lie between both coatings. The residual adhesion of the fluorocarbon composite coating with single doped silica sol is the largest. Inorganic mineral fluorocarbon composite coatings can significantly improve the exfoliation resistance of concrete, but the improvement effect is not significant compared with fluorocarbon coating. Some micropores are generated in the waterborne fluorocarbon coating under the salt freezing environment, and the pore structure is coarsened. However, the microstructure of the fluorocarbon composite coating with single doped silica sol is still denser, and the most probable pore diameter increases slightly, and the coating is only slightly damaged. The microstructure of concrete under the protection of the fluorocarbon composite coating with single doped silica sol is denser, and the spalling amount per unit area decreases by 81.2%, compared with that without protection. Research results provide experimental and theoretical bases for the design of concrete protective coating under the salt freezing environment in cold areas.