EFFECT OF HEAT TREATMENT ON GLASSES MADE FROM TWO THAI BOTTOM ASHES

Silicate-rich industrial wastes such as bottom ash are attractive for the production of glass products used in construction and other industrial areas. The properties of these glasses can often be improved by converting them to glass-ceramics using controlled heat treatments. The effect of heat treatment on the properties of glasses made from two different bottom ashes was investigated. A lignite bottom ash from Lampang (BL) and a municipal solid waste bottom ash from Phuket (BP) were melted at 1300 to 1500℃ to produce opaque, black glasses, which were then heat treated at 600 or 900℃. For 600℃ is was found that BL and BP glasses remained amorphous but phase separated and saw limited changes to the density, refractive index and Vickers hardness. For 900℃, the BP glass remained amorphous and was heavily deformed, while the BL glass was found to contain augite crystals with a submicron particle size. The melting temperature of the starting BL glass appeared to influence the augite crystallization and resulting properties. The average density (3.18 vs 2.88 g/cm³), refractive index (1.69 vs. 1.64) and Vickers hardness (8.95 vs. 6.29 GPa) of the BL glass-ceramic were significantly increased compared to the BL glass. These findings show the viability of producing glass-ceramics from domestic waste bottom ashes.