Recycling quartz from silicon alloy processing as high-performance aggregate for civil construction

Quartz is a key mineral in metal alloy production. Brazil holds 95% of the world's quartz reserves, according to the National Mining Agency. However, its extraction generates considerable environmental impacts. In this study, the reuse potential of recycling quartz from silicon alloy processing as an alternative fine aggregate for civil construction applications was evaluated. Recycled quartz sand (RQS) with an optimum particle size distribution was produced and characterised chemically, physically and mineralogically using standard aggregate tests, X-ray fluorescence, scanning electron microscopy and X-ray diffraction techniques. The properties of the RQS were compared with those of natural river sand (NRS) and crushed gneiss sand (CGS). To evaluate the mechanical performance of the tested sands, three classes of concretes (20, 30 and 40 MPa) were subjected to physical, mechanical and durability tests. The RQS aggregate exhibited high purity, consisting primarily of quartz, with physical properties comparable to those of NRS and CGS aggregates. The RQS concretes presented compressive and tensile strengths comparable to or superior to those of conventional concretes. The durability results also showed the RQS's stability and improved performance. Thus, recycling quartz from silicon alloy processing represents a sustainable alternative for producing cement-based composites, reducing environmental impacts while maintaining or enhancing concrete properties.