Mechanically stable and superhydrophobic nano-SiO2@silane/silicate coating for enhanced impermeability of mortar

The superhydrophobic coating can effectively inhibit the intrusion and adhesion of water-corrosive media on the surface of concrete. However, the poor mechanical stability and expensive materials significantly restricts its application in concrete engineering. Thus, superhydrophobic nano-SiO 2 @silane/silicate coating are successfully prepared by simply spraying nano-SiO 2 @silane on the surface of mortar pretreated by silicate. The pretreated silicate can enable the surface of mortar to enhance flatness and compactness, offering an optimal substrate for spraying nano-SiO 2 @silane hydrolysate. Further, the low surface energy of silane and the micro-nanostructure formed by nano-SiO 2 synergistically make the composite coating possess excellent superhydrophobic properties, with a contact angle of 154° and a slide angle of 5°. Notably, compared with original mortar, the water absorption rate, water vapor transmission rate, and chloride ion penetration depth are reduced by 86.4 %, 67.3 % and 87.9 %, respectively, exhibiting outstanding impermeability. In addition, the coated mortar possesses excellent self-cleaning properties and resistance to rain erosion. Meanwhile, the coated mortar also exhibits excellent resistance to mechanical wear (>200 cycles of abrasions) and resistance to UV radiation (>100 h). Such outstanding comprehensive performance can guarantee concrete to long-term apply in outdoors. This work provides a simple, feasible, economical, and effective research idea for developing superhydrophobic coatings on concrete.