Predesigning matrix-directed super-hydrophobization and hierarchical strengthening of cement foam

The thermodynamically unstable nature of aqueous foam is a challenging problem for fabrication of ultra-lightweight foamed cement-based materials. Such materials are also facing many durability problems due to their hydrophilic property and porous microstructure. In this study, a matrix superhydrophobic cement foam with high specific strength was developed by a one-step process. The rational tomographic and chemical properties of the border-air interfaces of cement foam were simultaneously modified by a nanohybrid method, in which the nano silica was grafted with water repellent functional group, promoting the adsorption of nano silica onto the air-liquid interfaces. The joint effect of increased multi-scale roughness and hydrophilization of the interfaces produced bulk superhydrophobic cement foam, which revealed excellent mechanical robustness even upon major surface damage. Such foamed cement is of great importance for industrial thermal insulation applications, and potentially provide a solution to the long-standing durability problems of cement based porous materials.