Resumo em Inglês:

Abstract The extraction of iron ore has a fundamental role in the Brazilian economy. However, such activity generates considerable volumes of waste whose disposal, even if regulated and licensed, has a significant environmental impact. The worldwide concern for sustainable practices along with the urgency for measures to mitigate environmental damage, justifies research on its use in other activities. Therefore, the present study aims to analyze the test results of laboratory versus field of mixtures composed of mining waste. The field studies were made on the execution of an experimental section on the BR 040 highway, in Minas Gerais - Brazil. According to the validation of the laboratory results, the mixtures composed of 35% Tailings + 15% Waste Rock + 50% Canga of Ore and 35% Tailings + 20% Gravel 1 + 45% Gravel 0 were used in the base and sub-base layers of the experimental section, respectively. The field technological control showed that the mixtures had an anomalous behavior from the one observed in the laboratory, mainly regarding strength and deformability.

Resumo em Inglês:

Abstract The present article presents the study of three laterites from the Triãngulo Mineiro and Alto Paranaíba region, aiming to use it as a pavement base. The methodology used consisted of carrying out the tests prescribed by the DNIT 098/2007 standard and, as a complementary methodology, linear contraction, MCT classification, modulus of resilience and X-ray diffractometry were introduced. Four mixtures of laterite with sand were prepared aiming to correct the plasticity of the materials. Three samples of laterites and three of the four mixtures with sand showed sand equivalent values lower than 30%, showing that this is a characteristic of laterites in the region. Only the mixture LatJ3+A4 (70x30) presented a sand equivalent greater than 30%, but this sample presented the worst plasticity indicators in relation to the other mixtures. These results showed the need for further studies on the use of the sand equivalent of laterites. The linear contraction associated with the liquidity limit proved to be more accurate and efficient for the control of plasticity characteristics than the plasticity index together with the liquidity limit and the sand equivalent.

Resumo em Inglês:

Abstract This study aims to develop a pressed concrete roofing tile from powder technology containing basalt powder in substitution of fine sand (aggregate) for application in building covers. Specimens were submitted to technological and toxicological characterization. Hence, pressed specimens based on cement and basalt powder were analyzed. In the bending strength test, the pressed samples containing a cement:basalt mass ratio of 1:6, water content of 5% and specific pressure of 25 MPa revealed a value of 3.82 ±0.46 MPa at 28 days of curing, while the molded samples (reference) with cement:sand mass ratio of 1:5 and 15% water content revealed 1.72 ±0.86 MPa. This composition, containing cement and basalt powder, is not toxic, confirming the possibility for total replacement of sand by basalt powder. Thus, it was demonstrated that the technical viability for the proposed process and the use of basalt powder to obtain pressed flat concrete roof tile meets technical requirements and standards, compared to conventional concrete roofing tiles.

Resumo em Inglês:

Abstract The effect of three reducing agents (sulphur dioxide, pyrite and carbon) on tungsten extraction from a scheelite-wolframite concentrate with chlorine gas was assessed. A low-grade ore (0.9% w/w WO3) was collected in the San Martín department, San Luis Province, Argentina, and subsequently enriched by physical means (65.73% w/w WO3). The minerals identified and their reactivities with chlorine were: scheelite (reactive), wolframite (reactive), pyrite (reactive), quartz (inert) and feldspars (inert). The metal recovered as WO2Cl2, with the different reagent combinations, was in increasing order: Cl2 + N2 < Cl2 + SO2 < pyrite + Cl2 + N2 < pyrite +Cl2 + SO2 < carbon + Cl2 + N2. It was proved that, according to its content, the pyrite initially present in the ore improves chlorination performance. At the same time, the non-volatile reaction products formed - CaCl2 and/or CaSO4 - and the manner of removing the nascent (desorbed) oxygen change depending on the reducing agent tested.

Resumo em Inglês:

Abstract Water galleries are mines that seek to supply drinkable and irrigation water from the aquifer, in order to meet the demand for water in the Canary Islands. This sort of work entails a series of health risks in the form of gases. This document compiles three different studies on the gases that can be found in water galleries in the Canary Islands, having divided the document as follows: 1) the presence of carbon dioxide in 13 galleries in operation on the island of Tenerife; 2) the presence of radon gas in galleries on the islands of Tenerife, El Hierro and La Palma; and 3) the incidence of gases that are harmful to health in a thermal water gallery on La Palma. The results have shown that, in general, the water galleries contain concentrations of gases which are toxic to human health, such as radon, where average radon values measured with both passive detectors are from less than 800 Bq/m3 to around 10,200 Bq/m3. Therefore, it is important to protect the health of the workers who undertake the maintenance of these installations.

Resumo em Inglês:

Abstract Geopolymers are amorphous silicate polymers that have been extensively studied due to their applications, scientific and technical relevance, and their potential as cement in substitution to Portland. Much of the focus has been in the use of precursors and aggregates that are rarely pure and homogeneous with the use of tailings being very common. The presence of these impurities complicates the interpretation of some spectral methods, mainly infrared spectrometry. Therefore, this research focuses on the use of a nearly pure kaolin main precursor, having only a trace of iron and titanium, along with other almost pure reagents, to achieve an ideal geopolymer. It was possible to produce metakaolinite, resulting in a material with a good size particle (8.24µm) and surface specific area (6.57m2/g). The XRD result shows that the calcination process resulted in 100% of amorphous material. FTIR data revealed the presence of H2O and NaCO3 in the geopolymer. More important, the Si-Al-O various bands located between 1100 and 500cm-1 validate the polymerization reaction effectiveness. SEM-EDS analyses have demonstrated that the reaction with Na2SiO3 and NaOH were nearly complete, concerning the finer metakaolinite particles that comprised the material’s matrix. However, the coarser metakaolinite lamellae, in the 15-35µm range, did not react completely; a thin border layer was enriched with sodium and most of the interior material maintained its Si-Al-O composition. The presence of traces of iron and titanium did not influence in the polymerization reaction. Compressive strength values of the geopolymer have presented good values in the range of 25 to 35 MPa.

Resumo em Inglês:

Abstract A carbonate-silicate low weathering phosphate ore from an igneous origin deposit in Southeastern Brazil presents a challenge mainly for apatite flotation from its gangue minerals, calcite and dolomite, plus the presence of phlogopite, diopside, magnetite, richterite, ilmenite, vermiculite, quartz and many other minor impurities. Recently, selectivity has been greatly enhanced by using CO2 instead of air, so in this study a variant process was used. In a first stage, carbonate minerals were floated with the use of CO2 as bubble gas; the collector was a saponified fatty acid, medium hydrocarbon chain. Then, the depressed minerals were floated using a sulfosuccinate collector and air as the froth gas. A significant improvement in the apatite concentration has been achieved: the initial 5.28% P2O5 tenor was raised to 21.58%. The overall P2O5 recovery was 61.8% and 12.0% of the global mass recovery. However, the amount of impurities was still significant with the presence of carbonates, phlogopite and minor magnetite. Therefore, the processing route presented herein is quite viable, but further research is necessary to improve the whole method.

Resumo em Inglês:

Abstract A characterization study was performed to verify the more relevant physicochemical properties for quartz flocculation with polyacrylamide, as well as to define which variables should be further investigated regarding this flocculation system. Polyacrylamide was evaluated through molecular weight, radius of gyration, and infrared spectrometry. A natural quartz sample was investigated regarding its particle size distribution, specific surface area, mineralogical and chemical composition. The zeta potential of quartz with flocculant and surfactant was also analyzed. The results indicated that the quartz had high purity and particle sizes between 38 and 10 µm, which was within the intended particle size range; the flocculant presented a suitable molecular weight for the proposed flocculation system. Based on literature, nine variables were chosen to be investigated in Part II of this study: flocculant and surfactant concentration, flocculant and surfactant conditioning time, flocculation addition time, agitation intensity, pH of the suspension, flocculation time, and solid concentration.

Resumo em Inglês:

Abstract Sinergy is the interaction of two or more agents to produce a combined effect greater than the sum of their separate effects. Etherdiamine yields superior results for quartz floatability in a Hallimond tube and higher selectivity in the reverse bench scale cationic flotation of an iron ore, when compared to ethermonoamine. Blending these collectors yields better results than each one used individually characterizing a synergistic effect. This work evaluated the effects of the collectors ethermonoamine, etherdiamine and the mixture of these at the ratio 1:1 on the flotation of the quartz through the microflotation and bench flotation tests with a typical Brazilian iron ore. The results demonstrated the occurrence of synergistic effects in tests performed at concentrations of 1 and 3 mg/L and pH 10.5, in the absence of a depressant. In the presence of a depressant, the synergy was not observed under the same tested conditions, due to the collector-depressant interaction. On other hand, the bench flotation tests indicated the occurrence of synergy regarding silica content in the concentrate while an additive effect was observed for the iron recovery and Selectivity Index index demonstrating that a feasibility of using collector mixtures in this process, was not clearly achieved on the tested ratio 1:1.

Resumo em Inglês:

Abstract In underground mines, stability problems can cause unplanned dilution, increasing the costs of mining operations, such as loading, transport, crushing and grinding. This is usually dealt with by simply increasing investments with support. However, the design geometry of stopes and drifts also has a great effect on a stope’s stability. The use of empirical stability methods is a very common practice, however because of their few input parameters, it cannot predict the actual performance related to each stope and drift design. This study has as main goals a back analysis of the actual dilution, using the Equivalent Linear Overbreak Slough (ELOS) method and analysis in the drift developments at the hanging wall contact, using numerical models. The case study is an underground hard rock gold mine, with a pillar-less Transversal Stope method. The hanging wall failure was quantified using a database from 19 stopes measured by the Cavity Monitoring System (CMS). Numerical finite elements models (FEM) were used, and 5 primary stopes were selected to calibrate models. The volumes of actual dilution showed a good correlation with the volumes of the relaxation zones produced by the models. Then, new optimized drift geometry layouts at the hanging wall contact were proposed, showing a decrease in 2.35 times in the relaxation zone of the numerical models, therefore justifying the use of these models as a dilution optimization tool. This methodology also proved to be useful in the definition of cable bolt length.