Influence of mechanical treatment and magnetic separation on the performance of iron ore tailings as supplementary cementitious material

Despite the great importance of iron mining in the Brazilian economy, significant volumes of tailings with high iron content are generated in the ore beneficiation process. Even with high crystallinity, studies show that the iron ore tailings (IOT) can be used as a supplementary cementitious material (SCM). In this context, this work analyzes the influence of primary (PMT) and secondary (SMT) mechanical treatment and magnetic separation (MS) on the performance of IOT as SCM. To this end, the performance of cementitious composites (pastes and mortars for structural purposes) produced with and without 15% cement replacement by IOT under different treatment conditions was evaluated. The feasibility of reprocessing the iron-rich waste material (IRW) from MS was analyzed. The results showed that, even with SMT, the tailings did not show pozzolanic activity. The tailings with MS and SMT influenced the heat of hydration of the pastes, due to the greater nucleation effect, compared to the other tailings. For this sample, higher compressive strength was achieved among the samples with IOT. The IRW, when submitted to a flotation process, produced a material that still has economic viability. •Mechanical treatment and magnetic separation do not induce the reactivity of the iron ore tailings.•The iron ore tailings acted as a filler and nucleating agent for the hydration reactions.•Finest iron ore tailings with magnetic separation increase the potential for use as a replacement for cement.•The product from the magnetic separation reached levels of mass and metallic recovery with stable economic viability.