The influence of compositional variability of dimension stone residues on the properties of rustic porous ceramic tiles

This study analyzed how the compositional variability of dimension stone residues influences the characteristics of rustic porous ceramic tiles. The specimens were prepared by adding 20 wt% of dimension stone residue to the clay and sintered at 1000 °C for 1 h. The testing assays performed were physical properties and structural analysis through scanning electron microscopy. The results indicate that water absorption was lower (~9% to 14%) in samples containing silicate residues compared to carbonate residues (~16%). Apparent porosity of ~21% to 25% and shrinkage of 0.5% to 1.6% were measured in silicate samples while higher apparent porosity of ~30% and expansion of -0.04% were found in carbonate samples. Flexural strength and modulus of rupture were similar, ~16 MPa and ~330 N, respectively, for both sample sets. The samples containing silicate residues whose SiO₂ content was between 48% and 58% and the sum of alkaline and alkaline earth oxides was less than 18% were suitable for manufacturing rustic porous ceramic tile, while residues with high SiO₂ or carbonate contents impaired the properties of the ceramic bodies. Therefore, it is recommended that the dimension stone residues intended for use in ceramic tiles be previously separated according to chemical and mineralogical characteristics. (author)