Incorporation of wastes from granite rock cutting and polishing industries to produce roof tiles

The present work aimed at studying the incorporation of wastes from natural rock cutting and polishing to produce roof tiles. The sintered products incorporating the sludge were targeted to have similar or even enhanced properties in comparison to those made of a standard reference paste industrially used to fabricate concurrent products available in the market. Firstly, the raw materials, including the sludge, were characterised by particle size distribution, density, X-ray diffraction (XRD), thermal properties and loss on ignition. Different formulations were prepared to evaluate the effects of each component on plasticity of pastes, drying and firing processes, and on the final properties of the tiles. Finally, the most promising formulations were selected and characterised for sintered density, water absorption, and flexural bending strength. The results obtained made it possible to conclude about the possibility of producing roof tiles incorporating 10% of granite wastes having excellent properties (water absorption <6%, lower pyroplastic deformation index, and bending strength values of about 14 MPa and 38 MPa for the green and sintered products, respectively). Therefore, the sludge derived from the granite cutting and polishing industries can be classified as a by-product suitable to replace natural non-plastic raw material in traditional ceramic formulations. This will contribute to preserve non-renewable natural resources, while it allows minimization of the negative environmental impact due to its disposal.