3D superhydrophobic lightweight foam concrete designed via in-situ foaming and self-assembled silicone microfilms

The poor durability of lightweight foam concrete, stemming from its highly porous and hydrophilic nature, is a major limitation for its wider application. Designing a superhydrophobic structure would be an effective approach to improving the durability of foam concrete. In this study, a facile strategy was developed to produce 3D superhydrophobic foam concrete using Poly(methyl hydrogen)siloxane (PMHS) by means of in-situ foaming and low surface energy characteristic. Results show that PMHS could be hydrolyzed and released hydrogen gas by reacting with the hydration product of Ca(OH)2. The resulting self-foaming lightweight concrete exhibits controllable average pore sizes ranging from 229 to 430 μm, with a density between 610 and 1177 kg/m3. The hydrolyzed PMHS self-assembles on the foam films, and the micrometer pores are carried with gel-like silicone microfilms through PMHS liquid–solid phase transition after 90℃ steam curing. With the synergetic effect of the dense silicone films and the particular pore frame, the superhydrophobic foam concrete demonstrates good fundamental properties, including thermal insulation and sound absorption, mechanical robustness, chemical durability, and weathering resistance. This study provides a practical solution for developing superhydrophobic lightweight concrete, which substantially enhances the durability of porous cement-based materials.