The properties of hydrophobic concrete prepared by biomimetic mineralization method

Abstract

In this study, the calcium hydroxide, an inherent product of cement hydration, was treated using biomimetic carbonation method of incorporating stearic acid to generate the hydrophobic calcium carbonate on concrete surface. Carbonation reaction was carried out at various CO2 pressure and temperatures and utilizing the Scanning Electron Microscope (SEM), chloride-ion penetration test apparatus, and compression test machine to investigate the hydrophobicity, durability, and mechanical properties of the synthesized products. Experimental results indicate that the calcium stearate may change the surface property of concrete from hydrophilicity to hydrophobicity. Increasing reaction temperature can change the particles from irregular shapes to needle-rod structures with increased shear stress and thus favorable to hydrophobicity and microhardness. The contact angle against water for the concrete surface was found to increase with increasing CO2 pressure and temperature, and reached to an optimum value at around 90oC. The maximum static water contact angle of 128.7 degree was obtained at the CO2 pressure of 2 atm and temperature of 90oC . It was also found that biomimetic carbonation increased the permeability, acid resistance and chloride-ion permeability of the concrete material. These unique results demonstrate that the needle-rod structures of CaCO3 synthetized on concrete surface could enhance hydrophobicity, durability, and mechanical properties of concrete.