Upcycling Waste Glass into Ceramic Tiles: Eco-Design for a Circular Manufacturing Route

Abstract

Ceramic tile manufacturing faces increasing pressure to cut energy use and reliance on virgin raw materials. Here, soda-lime waste glass was evaluated as a partial replacement for feldspar flux in tile bodies under industrially relevant processing. Five formulations containing 0–20 wt.% waste glass were produced via wet milling, granulation, two-stage uniaxial pressing, and fast firing in an industrial roller kiln (peak 1177°C; total 53 min). Thermal behavior, phase evolution, microstructure, and properties were assessed by DTA/TG, XRD, SEM/EDS, and standardized tests. Waste glass promoted earlier liquid-phase formation, increased vitrification, and lowered porosity under fast-firing conditions. The optimal composition was 15 wt.% glass, leading to the best densification balance with low water absorption (2.83%), reduced open porosity (4.97%), controlled linear shrinkage (7.99%), and high flexural strength (∼61 MPa). XRD showed decreasing crystallinity with increasing glass and albite formation, attributed to sodium diffusion from the glassy phase, consistent with the denser microstructure. This study demonstrates waste-glass fluxing in an industrial fast-firing roller kiln, defines a practical composition-property window at fixed firing temperature, and connects thermal, phase, microstructural, and performance changes. Soda-lime waste glass is therefore a scalable flux for energy-efficient, circular-economy ceramic tile production.