The effect of the composition on the crystallization behavior of sintered glass-ceramics from blast furnace slag

Glass-ceramics manufacturing has been considered as a very effective method for recycling and utilizing different types of industrial wastes. The purpose of this paper was to investigate the crystallization process of sintered glass-ceramics prepared from vitrified mixtures which were composed on blast furnace slag (68-80 %(mass)), kaolin, Al2O3 and TiO2. First the parent glasses were prepared. Then the glass-ceramics were obtained by one-step heat treating at 1000 degrees C from pressed glass powders. The crystallization behavior was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystalline phases were identified to be melilite, anorthite and pyroxene. The ratio between crystalline phases depends on chemical composition of the parent glasses. The examined microstructures were in accordance with the surface mechanism for crystal nucleation. The enhanced nucleation activity of fine glass powders caused crystallization, which led to good mechanical properties of glass-ceramics.