Influence of Waste Glass and Silica Fume Additives on the Properties and Microstructure of Clay-Based Ceramic Materials

This study investigates the effects of waste glass (GL) and silica fume (SF) on the physical, mechanical, and microstructural properties of clay-based ceramic materials produced from low-grade calcite-rich clay loam. Waste glass and silica fume were incorporated at 10–20 wt.%, and the specimens were fired at temperatures ranging from 1050 to 1150 °C. The average density, water absorption, compressive strength, phase composition (XRD), and microstructure (SEM) were evaluated. The results showed that waste glass significantly enhanced the sintering behavior of the ceramic body through liquid-phase formation at elevated temperatures. The average density increased from approximately 1650 to 2200 kg/m3, while water absorption decreased from 6.5% to 3.2%. The optimum firing temperature was 1125 °C, at which the ceramic compositions containing 10 wt.% and 15 wt.% waste glass exhibited no visible deformation and achieved compressive strengths of 32–36 MPa. In contrast, silica fume was less effective as a fluxing additive, resulting in lower strength, increased deformation, and cracking at temperatures above 1100 °C. SEM observations confirmed the formation of a denser, more homogeneous microstructure in the waste glass-modified specimens, while XRD analysis revealed a reduction in quartz content, accompanied by enhanced formation of the diopside and anorthite phases. Among all investigated compositions, the ceramic material containing 10 wt.% waste glass and fired at 1125 °C exhibited the most balanced combination of density, water absorption, and compressive strength, demonstrating its potential for producing high-performance clay-based ceramic materials.