Effective utilisation of quartz sandstone mining wastes: A technical note on its thermal resistance

Sandstones are a sedimentary type of rock which is composed of quartz, feldspar and other minerals. Since quartz and feldspar are the most common minerals in the Earth's crust, they are found in most of the sandstones irrespective of the region they occur. The formation of sandstone results by sedimentation through air or wind followed by the compacting pressure of overlying deposits and cementation by precipitation of minerals. Rajasthan, being the largest state by area in India, is the major sandstone producing region. Although sandstones from the area are extensively used as roofing, flooring and paving material, the process of mining them generates an enormous amount of sandstone wastes. These sandstone wastes with quartz-dominated elemental framework were utilised in an M30 grade concrete with water to cement ratio of 0.35 to overcome the landfilling problems and to reduce the use of depleting conventional coarse aggregates in the Vindhyan regions of Northern India. The concrete samples were investigated by scanning electron microscopy and thermogravimetry. The microscopic study revealed the presence of increased void fractions in the concrete samples containing quartz sandstone aggregates. These void fractions were found to enhance the thermal resistance of concrete based on the reduced weight loss upon heating them and also assumed to improve insulation properties by hindering the heat transfer in the material. The efficient utilisation of these quartz sandstone wastes in concrete can reduce the substantial amount of landfill that is used for dumping them and also provide a valuable source of supplementary aggregate used in the production of cement concrete contributing to the overall sustainability.