Strategic and carbon footprint assessment of Brazil's iron mining wastes for construction

This study investigates the reuse potential of three iron mining wastes from Brazil’s Iron Quadrangle: iron ore tailings (IOT), iron ore sandy tailings (IOST), and iron waste rock (IWR). The materials were characterised through physical, chemical, mineralogical, and thermogravimetric analyses, combined with a CPQvA-based qualitative assessment and a carbon footprint analysis for concrete mixtures incorporating mining wastes. IOT presented chemical and physical characteristics compatible with supplementary cementitious materials (SCMs), although X-ray diffraction analysis indicates high crystallinity, suggesting a predominantly filler effect in cement-based composites. IOST, composed primarily of quartz, presents characteristics favourable for use as fine aggregate. IWR exhibited suitable properties for applications such as roller-compacted concrete dams and pavement layers. The qualitative assessment identified IOST as the most promising material, followed by IWR. Carbon footprint analysis indicated that replacing conventional aggregates with IOST and IWR, combined, or substituting 5% of Portland cement with IOT, can reduce carbon dioxide (CO2) emissions from raw material production and transportation for concrete by up to 5%, while these combined strategies can reduce the carbon footprint by approximately 10%, with the magnitude varying by concrete class and cement type. The results highlight the need to integrate legal, environmental, technical, and logistical aspects into waste reuse strategies.