Metamorphic rocks for manufactured sand and coarse aggregate for concrete and mortar

Building Materials

The present study determined the most applicable high-grade metamorphic rocks as the sources for manufactured sand and coarse aggregates production to apply in the construction industry. As the first stage of this study, representative samples of the most common ten types of metamorphic rock were collected and tested for mineralogical and chemical compositions to select the favorable rock types in concrete and mortar production. XRD diffraction patterns and quantitative analysis results of XRF were referred for identifying the mineral and chemical contents respectively. Secondly, among the favorable rock types, based on the geology, the area contribution by each rock was calculated and few abundantly available rocks were considered for further investigation. Finally, the compatibility of rocks was checked by analyzing the physical, mechanical, and durability characteristics. As the physical parameters, the specific gravity, water absorption, loose and packing density, and water content were checked. Mechanical properties of rocks were determined by investigating compressive and tensile strength, impact resistance, abrasion resistance, and crushing value. The durability of rocks against weather fluctuations was probed through the slake durability indexes. Results from the first stage revealed that Charnockite, Hornblende-Gneiss, Intrusive Charnockite, and Granitic-Gneiss were favorable rocks rich with concrete and mortar friendly minerals such as albite, k-feldspar, and quartz. Among the above four rocks, Charnockite contributed around 40% and Hornblende-Gneiss covered approximately 9.5% of the area, which were then considered for the next stage of the investigation. Charnockite and Hornblende-Gneiss showed similar porosities and water absorption in the range of 0.25–0.26%. Each mechanical property of both rocks complied with the requirements provided by the standards; moreover, they manifested excellent durability performance against cyclic wetting and drying as well.