Use of sodium metasilicate as silica source and stabilizing agent in two-part metakaolin–H2O2 geopolymer foams

Abstract

The synergistic effects of the SiO2/Al2O3 ratio (2.0, 2.5, and 3.0) and H2O2 content (1.5%, 3.0%, and 6.0%) were evaluated in metakaolin-based geopolymer foams using sodium metasilicate pentahydrate as a complementary silica source. Sodium metasilicate helped to stabilize the pores in foams with SiO2/Al2O3 molar ratios of up to 2.5 cured at 50 °C without stabilizing additives. The optimum porous system for insulation cores was obtained using a SiO2/Al2O3 ratio of 2.5 and H2O2 content of 6%. Furthermore, a SiO2/Al2O3 molar ratio of 3.0 reduced pore formation as the increased geopolymerization and viscosity served as a barrier to bubble diffusion.