Developing cost-effective ceramics using weathered feldspar: Effects of firing and composition on ceramic tile performance and microstructure

The study focuses on evaluating the weathered feldspar sands from Wadi El-Falig, El-Yatima and El-Tuleia in the Central Eastern Desert of Egypt as an alternative source for locally available fluxing materials for ceramic tiles. Feldspars are chemically analyzed through X-ray fluorescence method and included in wall and floor tiles, producing formulations and then fired at temperatures of 1130 °C, 1180 °C, and 1215 °C under industrial conditions. The analyzed feldspars have a combined content of Na 2 O + K 2 O of 7.18–8.88 wt%. This confirms that they exhibit a good fluxing capacity. Increasing firing temperature promotes densification and, therefore, reduces apparent porosity and water absorption due to the fact that vitrification takes place. This leads to increased strength of the produced materials. X-ray diffraction analysis (XRD) showed mullite, quartz, and albite to be the dominant phases in the floor-tile bodies; however, the wall-tile recipes involved quartz, albite and hematite. The presence of mullite in the floor tiles baked at 1180 °C and the more compact microstructure noticed by the scanning electron microscope (SEM) resulted in the improved mechanical properties of the products. In conclusion, the results make it clear that weathered feldspar sands from the Central Eastern Desert can serve as a viable technical alternative to commercial feldspar, which reduces dependence on imports.