Using marble and granite rejects to enhance the processing of clay products

This work shows the changes in properties of an industrial red-clay-based mixture, already in use in the production of floor tiles, due to additions of an ornamental stone cutting reject (marble and granite). Samples containing up to 30 wt.% reject were uniaxially pressed and sintered in air in an electric furnace (1100-1150 °C, for 2 h). The results obtained (X-ray diffraction and fluorescence, thermal analysis, firing shrinkage, water absorption and mechanical strength), explain the effect that the marble and granite reject additions have on the clay mixture behaviour and show how the properties of the sintered red-clay products can be improved, with the possibility of using lower firing temperatures.