Preparation of glass ceramic foams for thermal insulation applications from coal fly ash and waste glass

Glass ceramic foams were prepared by direct foaming method, using coal fly ash and waste glass as the main materials, borax and calcium carbonate as fluxing agent and foaming agent, respectively. The effects of coal fly ash additions, foaming time, heating rate and sintering temperature on the bulk density, porosity, mechanical properties and thermal conductivity were systematically investigated. The optimum parameters to prepare the glass ceramic foams were obtained at 800 °C for 45 min with 40 wt.% coal fly ash, 60 wt.% waste glass, 30 wt.% borax and 0.5 wt.% calcium carbonate. The specimens prepared this way have a low bulk density (as low as 0.46 g/cm3), exhibiting considerable compressive strength (exceeding 5 MPa) and low thermal conductivity (about 0.36 (W/m K)). The energy saving effect using glass ceramic foams was evaluated by EnergyPlus software, indicating that the prepared glass ceramic foams show good energy conservation effect for building thermal insulation materials. The preparation of glass ceramic foams using solid wastes may provide a promising way to prepare thermal insulation material, considering the advantages in both economic and environmental aspects.