Sustainable one-part geopolymer foams with glass fines versus sand as aggregates

The ever increasing demand for high-quality river sand in construction, which poses economic and environmental concerns, highlights the necessity for finding suitable alternatives. Waste glass has a very low impact tolerance, which makes it very easy to grind and use as a fine aggregate in the construction of lightweight building elements. In this study, glass fines are used as a replacement for fine sand in manufacturing geopolymer foams. The thermal and mechanical properties of the two systems with different densities are investigated and compared with a control sample of geopolymer foam with no aggregates. The geopolymer paste with sand aggregates has a density that was approximately 100 kg/m3 higher than the paste with glass aggregates. The heavier samples with sand aggregates required a higher degree of foaming to drop the density to a similar range, which negatively affects their strength. For a density of 1000 kg/m3, the geopolymer foams with glass aggregates are 25% stronger than the foams with sand aggregates. The strength improves further by 31% and 77% as the density drops down to 800 kg/m3 and 600 kg/m3, respectively. The shape of the bubbles in geopolymer foams with glass aggregates is more regular with less interconnectivity between pores, especially at lower densities. This pore characteristic enhances the insulation capacity of lightweight foams with glass aggregates where thermal conductivity of 0.15 W/mK was achieved in the sample with 600 kg/m3 density.