Preparation and Characterization of Glass-ceramic Composites from South African Coal Fly Ash: A Recent Study

Though fly ash in South Africa has mainly been utilized in the construction industry, a large portion of it is still discarded. Production of glass-ceramic composites through fly ash devitrification has gradually become one of the applications being examined internationally. This study reports the investigation of producing glass-ceramic composites from fly ash and varying quantities of beverage waste glass and magnesium oxide as main raw materials. Glasses were obtained by melting fly ash and its additives using an arc furnace. Based on their behaviour when subjected to differential thermal analysis, the glasses were then crystallised through a double-staged thermal treatment to form glass-ceramic composites. The composition and behaviour of the glass-ceramic composites were investigated using X-ray diffraction, Scanning Electron Microscopy, mechanical and chemical assessments. The crystal content in the glass-ceramic composites increased as the magnesium oxide content was increased. The desired diopside phase decreased with an increased magnesium oxide content and ultimately resulted in the formation of forsterite and anorthite as the major and second major phases respectively. The glass-ceramic composites with lesser amounts of magnesium oxide were chemically and thermally resistant and they also demonstrated high cold compressive strength.