Eco-Friendly Synthesis of Geopolymer Foams from Natural Zeolite Tuffs and Silica Fume: Effects of H₂O₂ and Calcium Stearate on Foam Properties

Eco-friendly geopolymer foams are developed from silica fume, natural zeolite, and H₂O₂. The addition of a stabilizer produces smaller and more homogeneous pore sizes. The technical properties highly depend on porosity and pore size distribution. The samples produced showed good compressive strength and low thermal conductivity. These foams could be a sustainable substitute for thermal insulation. Highlights: The need for environmentally friendly and energy-efficient building materials has increased significantly. This study synthesizes geopolymer foams with enhanced thermal insulation properties using silica fume and natural zeolite tuff. Zeolite’s porous structure and active sites improve polymerization and strengthen the foam, while silica fume reacts with NaOH to release sodium silicate, forming a durable geopolymer matrix. Foam porosity is introduced by generating oxygen gas from H₂O₂ and NaOH, with calcium stearate stabilizing the foam structure. Comparative analysis of the compressive strength, bulk density, porosity, and thermal conductivity shows that incorporating H₂O₂ and calcium stearate significantly reduces thermal conductivity (from 0.19 to 0.06 W/m·K) while ensuring a highly porous system (66–82.6% porosity) with adequate mechanical strength (1.6–3.39 MPa). These findings highlight the potential of the developed geopolymer foam for sustainable insulation applications.