Synthesis of foaming geopolymers based on glass waste with borax and MgCO3 additives

Geopolymer materials are widely used in building construction due to their low carbon dioxide emissions, mechanical and thermal characteristics, and substantial heat storage capacity. Low-density geopolymer foams can reduce structural load and enhance acoustic and thermal insulation. This study aims to produce foaming materials from municipal glass waste without/with borax and MgCO3 additives at various temperatures. The foaming behavior of geopolymer materials, i.e., the ability to swell when exposed to temperatures, was studied under the influence of several parameters such as alkali activator concentration (3, 6, and 9) M, dosage and type of additives (10 and 15) wt.% of Borax and MgCO3 as a replacement from glass powder and heat treatment temperatures (450, 550, 650, 750, and 850) °C. Furthermore, cement paste was prepared as a standard reference for comparison. An investigation involves analysis of the microstructure’s, physical and mechanical properties. The results show the compressive strength value after heat treatment 650°C to 850°C for geopolymer specimens without additives less than 10.5 MPa was recorded, commonly identified as foaming materials. Additionally, an increase in volume was observed for geopolymer formulations due to the swelling phenomenon at the same temperature. In contrast, the compressive strength and weight loss decreased with increased volume (foaming behavior) for glass-based-geopolymer pastes with both additives starting at 450 °C for most specimens. A higher increase in volume was recorded at about134.76% and 702.75% for specimens with 10% and 15% borax at 450°C and 750°C, respectively, While about 501.39% and 139.92% for specimens with 10% and 15% MgCO3 at temperatures of 450°C and 850°C respectively. Moreover, the weight loss percentage for geopolymer paste increases with higher heat treatment temperatures. The higher weight loss (23.2-26.4) % was recorded for pastes with a 15%wt. MgCO3.