Influência do tratamento mecânico e da separação magnética no desempenho do rejeito da mineração de ferro como material cimentício suplementar

Abstract

Despite the great importance of iron mining in the Brazilian economy and the optimization of production processes, significant volumes of tailings with high iron content are generated in the ore processing. This tailing, composed mostly of iron and silicon and with a finer grain size than natural river sand, has been used for the production of materials for civil construction. Even with its high crystallinity, studies show that iron ore tailing (IOT) can be used as a supplementary cementitious material (SCM). The literature also shows that particle size reduction can increase the reactivity of a material. In this context, this work analyzes the influence of mechanical treatment and magnetic separation on the performance of IOT as SCM. The performance of cementitious compounds (pastes and mortars for structural purposes) produced with and without replacement of 15% of cement by IOT was evaluated. In natura tailings (as collected) and tailings submitted to magnetic separation and/or mechanical treatment were used, which were characterized in each condition, in relation to their physical, chemical and mineralogical properties. Cementitious pastes were molded for thermal analysis by isothermal conduction calorimetry and thermogravimetry. The performance of the mortars was evaluated regarding workability, open porosity and water absorption by immersion, electrical resistivity and compressive strength at 28 and 91 days. The feasibility of reprocessing the iron-rich waste material originated from magnetic separation was also analyzed. The results showed that, even with secondary grinding, the tailings did not show pozzolanic activity. In general, in the workability, open porosity and water absorption, the influence of the tailings after mechanical treatment and/or magnetic separation was similar to the in natura tailings. The tainling with magnetic separation and secondary grinding influenced the heat of hydration, due to the greater nucleation effect, compared to other tailings. For this sample, greater compressive strength was achieved among the samples produced with IOT. The iron-rich waste material, when subjected to a flotation process, produced a material with economically interesting characteristics.