Application of polymer modified cementitious coatings (PCCs) for impermeability enhancement of concrete

The impermeability of concrete is closely related to its durability in humid and marine environments. In this study, polyacrylic acid (PA) emulsion and white Portland cement were selected as the main raw materials to prepare highly flexible PCCs, then the dispersibility of ultrafine SiO2 powders and its influences on the basic, tensile properties and durability of PCCs were deeply investigated. Excitingly, hexamethyldisilazane (HMDS) successfully dispersed SiO2 powders based on the change of surface charge number. It was found the PCCs with 4 wt% HMDS modified SiO2 powders had fewer micro-defects and more compactness, thus the tensile properties and durability under different conditions, such as water, acid, alkali, heat and artificial aging, were significantly improved. The water absorption and chloride ion permeability coefficient of concrete coated by the PCCs with 4 wt% well-dispersed SiO2 powders were also decreased.