Robust superhydrophobic cementitious composites with ex-situ carbonation: Performance and mechanism

Superhydrophobic surfaces have attracted significant attention due to their ability to enhance the durability of concrete by preventing water and aggressive agent penetration. However, traditional superhydrophobic materials have limitations, being poorly durable and prone to wear. In this study, we propose a novel design for robust superhydrophobic cementitious composites: nano-CaCO₃ is grown ex-situ on fly ash particles to ensure the complete leaching of Ca²⁺ from carbide slag during carbonation, which also allows nano-CaCO₃ to be uniformly introduced into the composite through a carrier effect of carbonated fly ash. In addition, fluoroalkylsilane was incorporated into the carbon-sequestered composite to further reduce surface energy and achieve superhydrophobicity. The results demonstrate that the hydrophobicity of the composites is closely tied to the carbonation process, with a contact angle of 163.0° which signifies a superhydrophobic condition. This study provides valuable insights into the innovative design and production of carbon-sequestered, robust superhydrophobic cement-based materials.