Crystal nucleation and growth in glasses from inorganic wastes from urban incineration

This paper reports the results of a study of the feasibility of recycling the fly ashes from domiciliary waste incineration by producing glasses and glass–ceramics. The major components of the fly ashes, Tyseley (F+L) and Tyseley (F), which were from a British domiciliary incinerator, were CaO, SiO 2 and Al 2O 3 but nucleating agents, such as TiO 2, P 2O 5 and Fe 2O 3, were also present in reasonable amounts. Tyseley (F+L) was similar to a waste ( Tirme F + L) studied previously by the authors and hence glass and glass-ceramic development concentrated on Tyseley (F). It was found that a glass (designated TYS100) of suitable viscosity could be obtained from the waste without the need for any additives. The properties of this glass were similar to those of other glasses made from incinerator waste. The heat treatment required to crystallise the TYS100 glass was nucleation at 560°C for 55 min followed by crystal growth at 1050°C for 15 min. The main crystalline phase in the resulting glass–ceramic was akermanite (Ca 2MgSi 2O 7) with some TiO and TiSi 2 forming in the later stages of heat treatment. The akermanite existed in a thin surface layer and also as spherulites in the bulk; the TiO and TiSi 2 crystals were associated with the spherulites. The mechanical properties and erosion resistance were superior to the glass and acceptable for applications such as tiles for the building industry and those requiring erosion resistance.