This research investigated the possible use of high boron oxide (B2O3) bearing solid waste, obtained during the enrichment of colemanite mineral (Ca2B6O11.5H2O), as an alternative sintering agent to Na-feldspar (NaAlSi3O8) in porcelain tile production. The chemical composition, mineralogical properties and behaviour under the heat treatment of solid colemanite waste were characterized in detail by the use of inductive coupled plasma (ICP), X-ray diffraction (XRD) and differential thermal analysis (DTA) / thermo-gravimetric analysis (TG). Physical-mechanical properties of standard and waste-added porcelain tile bodies obtained by sintering at 1210 oC (under factory conditions) such as green strength, dry strength, fired strength and water absorption were determined as a function of waste replacement for Na-feldspar. The sintering behaviour of waste-added porcelain tile bodies under fast firing conditions was also determined by an optical dilatometer and compared with that of standard porcelain tiles. The phases obtained in standard and waste-added porcelain tile bodies after sintering were determined by XRD analysis. The effect of these phases on microstructure and the relationships between physical-mechanical properties and the microstructure were also investigated through a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectrometery. After detailed phase studies and microstructural analysis together with the characterization of behaviour under heat treatment, it was discovered that colemanite waste had a high fluxing character and decreased the sintering temperature when used in porcelain tile recipes to replace Na-feldspar. It was also determined that factories using colemanite waste should work at lower sintering temperatures in order to obtain better physical-mechanical properties for porcelain tiles and to reduce energy costs.

Keywords: Characterization, Colemanite wastes, Sintering agent, Porcelain tiles.