Determination of the expansion potential and processes of the sandstone (greywacke)-shale wastes.

Materials with grain sizes of less than 63 μm from the quarries (Cebeci, Cendere and Arnavutköy) in Istanbul (Turkey) are considered as waste and cannot be utilised in any area. In this study, we aimed to determine the expansion potential of the wastes and the factors that trigger the expansion. The grain sizes of the sandstone-shale wastes from the Cebeci (CB), Cendere (CN) and Arnavutköy (AR) quarries range between 2 and 71 µm, 2 and 56 µm and 2 and 77 µm, respectively. The mineral paragenesis of the wastes from the investigated regions is the same and consists of quartz, albite, muscovite, chlorite and calcite. Expansion tests show that quarry waste samples expanded at temperatures between 1200 and 1210 °C. The wastes were subjected to expansion tests in the range of 2–8 min, and their expansion rates were determined every minute. It was determined that the expansion rate of the quarry wastes in the Cendere region is higher than those of the Cebeci and Arnavutköy regions. Thermal analysis results indicate that the OH‾ release (dehydroxylation) of chlorite and muscovite minerals in waste samples occurred at approximately 560 °C. As a result of dehydroxylation, the wastes undergo partial melting and thus form a viscous structure that can trap gases and provide expansion in the samples. With the formation of a viscous structure, H2O and CO2 gases released from chlorite, muscovite, calcite minerals and organic matter in the range of 1200–1210 °C were trapped in the samples and allowed them to expand. [ABSTRACT FROM AUTHOR]