GLASS-CERAMIC FROM FLY-ASH WITH ADDED MGO AND TIO2

The effects of the addition of MgO and TiO2 to fly ash on the nucleati on and crystal growth mechanisms of the derived glass are investigated with the aid of differential thermal analysis, dilatometry, X-ray dif fraction and scanning electron microscopy (SEM). Phase separation occu rs on heating the investigated glass. The glass-ceramic materials obta ined contain anorthite (CaOAl2O3(2)SiO2) and cordierite (2MgO2Al2O3(5) SiO2) as the main crystalline phases. The morphology of the glass-cera mic material was investigated by SEM and it was consistent with the do uble-framework structure of the phase-separated glass and it was const ituted by a low viscosity phase almost completely crystallised and hig h viscosity phase scarcely or not crystallised, depending on the heat- treatment.