Abstract The greatest and noblest challenge of mining engineering for the present and the future of iron ore treatment could be considered as the pursuit of optimizing the use of mineral resources. The use of mining tailings, in the mineral sector itself, or in another industrial branch, meets the needs of circular economy as it increases the useful service life of this material. In order to investigate this scenario, a technological characterization of a sample from a tailings dam was carried out along with magnetic concentration tests in a Wet High-Intensity Magnetic Separator (WHIMS) to propose a possible concentration route. In relation to the characterization itself, the results demonstrated a relative density of 3.04 x 103 Kg/m3and an average superficial specific area of 3.75 cm3/g. The granulometric analysis classified the material as fine, with d90 of 0.110 mm and d50 ≅ 0.049 mm. Quartz, hematite, goethite, kaolinite and manganese oxide were identified in the sample. The test which presented the best results (66.83% Fe and 1.74% SiO2) consisted of the Rougher, Cleaner and Recleaner phases, using a 1.5 mm grooved GAP matrix, a 7,000 Gauss magnetic field, 30% solids, and water pressure at 0.5 kgf/cm2 (49.0 x 103 Pa). Finally, the conclusive results indicate that the studied material can be concentrated through magnetic concentration, keeping in mind the specifications concerning the pellet feed fines commercial product. Besides the financial gain, the activity prolongs the durability of the tailings dam and reduces the environmental impacts associated with these structures.

Abstract Soil-cement bricks are earth construction materials that have been gaining prominence due to their environmental advantages. The Brazilian Technical Standard NBR 8491 establishes physical and mechanical procedures to characterize these bricks. However, the thermal characterization is an important assessment, since it is related to the building’s thermal performance. The objective of this study is to thermally characterize a panel of soil-cement bricks produced with mining tailings. For such, its absorptance (α) was evaluated using the ALTA II spectrometer, and its thermal transmittance (U) and thermal resistance (RT) through the hot box method (ISO 9869). The results enabled the calculation of the thermal capacity (CT), thermal lag (φ) and solar factor (FSO) of the panel, which were compared to the Brazilian Technical Standards NBR 15575-4 and NBR 15220 for Bioclimatic Zone 8. As a result, the soil-cement body panel showed values of α = 0.71, U = 2.47 Wm-2K-1, CT = 273.4 kJm-2K-1, φ = 6.02 h and FSO = 6.81%, meeting the requirements established in the first standard, but failing to attend the second. To comply with the Brazilians specifications, it is suggested to paint bricks with lighter colors focusing on decreasing its absorptance value. Thus, soil-cement bricks may be an environmental alternative to dispose of the waste generated during the mining process, contributing to sustainability.

RESUMO A economia circular na mineração, com a utilização de rejeitos para geração de novos produtos, destaca-se como forma potencial de mitigar o passivo ambiental da atividade mineral. Este trabalho avaliou a utilização de rejeito da mineração de ouro, como matéria-prima principal, na composição de tijolos tipo solo-cimento. Para tal, foram preparadas misturas com traços cimento CPII-Z-32 (1): rejeito (5-10): solo (0-5) e submetidas à caracterização física (distribuição granulométrica pela NBR 7181, massa específica por picnometria a gás hélio e área superficial específica por BET), química (fluorescência de raios-X), mineralógica (difração de raios-X), geotécnica (limites de consistência) e ensaios de compactação (NBR 12023), sendo este último ensaio determinador do teor de umidade ótimo utilizado na produção dos tijolos para cada mistura. Os parâmetros mecânicos dos tijolos foram caracterizados segundo a NBR 8491 e a avaliação ambiental foi realizada através da NBR 10004. Os tijolos com traço 1:5:5 alcançaram resistência a compressão de 3,1 MPa e absorção de água de 17,0%, compatíveis com a exigência da norma. A NBR 10004 classificou estes tijolos como um produto não perigoso e não inerte devido à solubilização de alumínio superior ao limite estabelecido. A liberação de alumínio está associada a composição química natural das matérias-primas. Por outro lado, contaminantes do rejeito, como o cianeto, foram imobilizados pela mistura cimento, rejeito e solo através das fases de hidratação do cimento (C-S-H e C-A-S-H). Portanto, os estudos demonstraram que o rejeito da mineração de ouro estudada, até então considerado passivo ambiental, apresenta potencial para produção de tijolos tipo solo-cimento atendendo as especificações técnicas e ambientais.

ABSTRACT The use of mining tailings meets the needs of circular economy as it increases the useful service life of this material. The present work evaluated the use of gold mining tailings (main raw material) in the production of soil-cement bricks formed by cement, tailings and soil. Mixtures were prepared with traces of cement CPII-Z-32 (1): tailings (5-10): soil (0-5) and subjected to physical characterization (particle size distribution - NBR 7181, specific mass by picnometry - helium gas, and specific surface area - BET), chemical (X-ray fluorescence), mineralogical (X-ray diffraction), geotechnical (consistency limits) and compaction tests (NBR 12023), the latter being used to determine the optimum moisture content used in the production of the bricks for each mixture. The mechanical parameters of the bricks were characterized according to NBR 8491 and the environmental assessment was carried out using NBR 10004. The soil-cement brick with the addition of 50% of soil reached values of ft = 3.1 MPa and A = 17.0%. However, even if it meets the specifications of NBR 8491, each mining tailing has unique characteristics of hazardousness. Therefore, the brick with 50% of soil was evaluated according to NBR 10004 in which it was classified as non-dangerous, but not inert due to the high content of aluminum. The higher the soil content, the closer these parameters are to the maximum allowed by the standard. The chemical evaluation showed phases of cement hydration that are related to the stabilization of contaminants such as cyanide. Finally, the tailing studied demonstrated their potential use as a raw material in the manufacture of soil-cement bricks by meeting the Brazilian’s specifications. It is suggested that new bricks with higher proportions of soil be evaluated.