Utilization of waste glass with natural pozzolan in the production of self-glazed glass-ceramic materials

Abstract

Significant self-glazed glass-ceramic was obtained from a natural pozzolan and external glass cullet. Natural pozzolan with/without glass cullet was fused to glass melt that quenched in water to glass frits. The dried glass frits were pulverized (<0.083 mm) and then shaped in a stainless mold. The thermal behavior of the glasses shows a widening of the crystallization temperature with the incorporation of the glass cullet between ∼800 and 950°C. Sintering of the shaped glass powder at 1,050°C/2 h lead to the crystallization of augite, enstatite, cristobalite, and hematite. The microcrystalline structure shows massive texture with pores in-between; however, at high magnification regular euhedral to subhedral crystals in submicron to nearly submicron size was developed in the glassy matrix and their microanalysis indicates the dominant augite. The density of the glass-ceramic samples decreases from 2,706 to 2,539 kg/m3 with the incorporation of glass wastes. The sample surfaces show, through force electron microscopy, the fineness and smoothness of the grains with the incorporation of the glassy portion. The microhardness values were between 6.43 and 6.11 GPa. The coefficient of thermal expansion increased from 32.87 (25–300°C) to 66.89 (25–500°C) × 10−7°C−1. The chemical resistance of samples in water (0.0002–0.0016) is better than in an acidic medium (0.0011–0.0017). These glass-ceramic enjoy good density, hardness, and thermal expansion and can be used in the ceramic industry and cladding walls and floors.