Formulation and improved properties of three-dimensional superhydrophobic ultra-lightweight fly ash cement foams with C-S-H nanoparticles-stabilized waterproof emulsion

Ultra-lightweight foamed cement (ULFC) is characterized by the super low-density (<= 200 kg/m3), excellent thermal-insulation and fire-resistant performance, however, it can inevitably absorb huge amount of water from the surroundings. In this work, a novel three-dimensional superhydrophobic ULFC with apparent density lower than 160 kg/m3 was innovatively achieved by using the bio-inspired design method and C-S-H-nanoparticlesstabilized waterproof emulsion. The results revealed that the water contact angle of ULFC samples can reach up to 154.6 degrees, and the corresponding 24 h volumetric water absorption can be reduced from 8.7 % to 4.1 %. The lowenergy organic group of waterproof agents grafted with the surface of hierarchical rough structure in hardened ULFC, which enhanced the hydrophobicity of cement foams.