Ultra-lightweight cement composites with excellent flexural strength, thermal insulation and water resistance achieved by establishing interpenetrating network

This research aims at developing the ultra-lightweight cement composites (ULCC) with high flexural strength, good thermal insulation, and great water resistance by incorporating the acrylamide. Polyacrylamide (PAM) is formed by in-situ free-radical polymerization during the hydration of cement. The physico-mechanical properties, thermal performance, interactions between hydrated cement and PAM, microstructure and water absorption of the composites are characterized in detail. Fly ash cenospheres (FAC) is used to fabricate the ULCC with a density and thermal conductivity of approximately 1250 kg/m³ and 0.3 W/m K, respectively. The flexural strength is impressively improved by adding PAM, where the composites with 3% PAM have the highest flexural strength while still maintain sufficient compressive strength. The physical and chemical interactions between PAM and hydrated products are found to dominate the flexural strength and toughness of the composites. PAM-modified ULCC displays much higher resistance against water in comparison to the neat mixture as well.