Glass ceramic foams from coal ash and waste glass: production and characterisation

Lightweight glass ceramic foams have been produced from a mixture of silicate wastes, namely 20 wt-% coal pond ash and 80 wt-% bottle glass cullet. A powder sintering route with the incorporation of 2 wt-%SiC as foaming agent was used. The pore morphology achieved under different sintering conditions was investigated in detail using X-ray microtomography. The apparent density of the foams ranged from 0·2 to 0·4 g cm−3, and the porosity ranged from 70 to 90%. Other variables, such as pore wall thickness, pore size and roundness, all behaved consistently with sintering temperature. The optimum sintering temperature was found to be in the range 1000–1050°C, at which porosity was about 75% and was the most uniform. Foams produced under this condition exhibit satisfactory compressive strength of about 1·5 MPa and show relatively high thermal shock resistance, with compressive strength gradually decreasing as quenching temperature increases.