Clayey Quarry Sludges: Thermal Transformation, Microstructure and Technological Properties

The disposal of clayey quarry sludges generated during aggregate washing process, represents significant environmental impacts and additional economic burden for the aggregate production industry. In this paper three different quarry sludges were sintered and investigated at the range 900–1100 °C using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Blends of the considered quarry sludges were studied and their physical properties (density, shrinkage, water absorption and compressive strength) were assessed. The effect of firing temperature on these properties was estimated and linked to the microstructure changes during heat treatment. The results revealed that anorthite, hematite, portlandite and lime were the neoformed phases. Breakdown products of clay minerals and carbonates contributed to the formation of some of these phases. The measured properties were strongly influenced by the firing temperature. Considering the measured technological properties, ceramic bodies with good mechanical performances (70 MPa) could be manufactured in the aforementioned conditions.