Incorporation of granite cutting sludge in industrial porcelain tile formulations

Granite wastes in the form of sludge, obtained from granite cutting industry, were incorporated in the batch formulations of porcelain tiles. The maximum possible substitution of sludge for feldspar was investigated. Samples of different formulations, in the form of pellets or extruded bars, were produced at both laboratory and pilot-plant scales and characterized throughout all the stages of the production process. The experimental results and their theoretical interpretation show that suitable incorporation of granite sludge can result in porcelain tiles with superior properties, in terms of water absorption (0.07%) and bending strength (>50 MPa). Sludge incorporation had negligible effect on density, shrinkage and plasticity during all stages of tile-production process, anticipating no modifications in the industrial production line.