VITRIFICATION OF FLY-ASH FROM THERMAL POWER-STATIONS

Samples of fly ash from Spanish thermal power plants were vitrified af ter mixing with other inorganic wastes such as dolomite slag and glass cullet. The relative viscosity and crystallisation behaviour of the g lasses obtained were investigated by hot stage microscopy (HSM) and di fferential thermal analysis, from which reheating schedules were chose n for recrystallisation. X-ray diffraction analysis (XRD) showed that diopside (augite) and/or wollastonite could be crystallised from these glasses, giving rise to dendritic and/or acicular microstructures whi ch were observed and analysed by scanning electron microscopy (SEM/EDX ). It was shown that the glass ceramics so obtained had improved mecha nical properties compared with the untreated glasses, with Vickers mic rohardness (H-v) = 5-6.9 GPa, elasticity modulus (E) = 59-101 GPa and toughness (K-1C) = 1.7-1.8 MPa m(1/2) maximum ranges from glass cerami cs products showing better properties.