A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses

A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO-Al2O3-SiO2 system at 1500 °C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H2, NH3, CH4, H2S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al2O3 ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62 GPa and the linear thermal expansion coefficient, α, varied between (62 and 139) × 10−7 K−1. Several glasses showed a high hydrolytic resistance in deionised water at 98 °C.