EFFECT OF ALUMINA ADDITION ON THE PROPERTIES OF GLASS-CERAMICS DERIVED FROM WASTE WINDOW GLASS VIA SINTERCRYSTALLIZATION

Abstract

This study investigates the development of glass-ceramics from waste window glass using the sinter-crystallisation technique. Waste glass was ground, sieved through a $100$ $\mu$m mesh, and analysed by the X-ray fluorescence (XRF), which revealed a soda-lime-silica composition with $\text{SiO}_2$ ($59.80$ wt%) as the dominant oxide, followed by $\text{Na}_2\text{O}$ ($23.03$ wt%) and $\text{CaO}$ ($10.09$ wt%). Compacts were prepared with alumina additions ranging from $0$ to $8$ wt% in $2$ wt% increments, pressed at $15$ kN, air-dried for $24$ hours, and sintered at $900^{\circ}\text{C}$ with a heating rate of $5^{\circ}\text{C}/\text{min}$ and a $1$-hour hold to promote the formation of crystalline phases within the residual glass matrix. The X-ray Diffraction (XRD) analysis revealed wollastonite, quartz, and albite as the main crystalline phases. Increasing alumina content promoted wollastonite crystallization, which improved mechanical strength and chemical durability. For example, $\text{GC}-1$ ($0$ wt% $\text{Al}_2\text{O}_3$) contained $72.5$ wt% wollastonite and $25.3$ wt% quartz, while $\text{GC}-3$ ($4$ wt% $\text{Al}_2\text{O}_3$) exhibited higher crystallinity with $80.5$ wt% wollastonite and $17.5$ wt% quartz. The sample with the highest alumina content, $\text{GC}-5$ ($8$ wt% $\text{Al}_2\text{O}_3$), demonstrated superior hardness and resistance to sulfuric acid. These results confirm that alumina enhances the crystallization behavior of waste glass, enabling the production of durable glass-ceramic materials suitable for tiling applications.