EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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2 resultados
Resultados da Pesquisa
Item Influence of high-charge and low-charge PCE-based superplasticizers on Portland cement pastes containing particle-size designed recycled mineral admixtures.(2020) Carvalho, José Maria Franco de; Schmidt, Wolfram; Kühne, Hans-Carsten; Peixoto, Ricardo André FiorottiDesign: and use of engineered recycled mineral ad mixtures obtained from industrial and mineral waste are promising strategies to increase the range of materials suit able for use in cement - based composites. In this work, Portland cement - blended pastes con taining mineral ad mixtures designed for improving particle packing were evaluated in the presence of low - and high - charge poly car boxy late - based super plasticizers. The powders were obtained from basic oxy gen furnace slag, iron ore tailings, quartz mining tailings, and quartzite mining tailings. The zeta - potentials of the particles were obtained via electrophoretic mobility. The flow properties were evaluated by rheological tests per formed in a Couette type rheometer. The hydration kinetics was evaluated by isothermal calorimetry and an adapted method based on the Vicat needle test. The high - charge PCE and the finer mineral ad mixtures produced more stable blends. Coarser mineral ad mixtures led to increased flowability and delayed hydration compared to finer ones. Steel slag powders presented the most significant plasticizer effects, but also the largest set ting de lays and segregation tendency. Quartz – rich superfines reduced the set ting de lays caused by the super plasticizers. In summary, both super plasticizers were effective in improving flow prop er ties, but the high - charge PCE was effective in pre venting segregation in pastes con training mineral ad mixtures coarser and heavier than cement.Item Reduction of acid rock drainage using steel slag in cover systems over sulfide rock waste piles.(2015) Almeida, Rodrigo Pereira de; Leite, Adilson do Lago; Soares, Anderson BorghettiThe extraction of gold, coal, nickel, uranium, copper and other earth-moving activities almost always leads to environmental damage. In metal and coal extraction, exposure of sulfide minerals to the atmosphere leads to generation of acid rock drainage (ARD) and in underground mining to acid mine drainage (AMD) due to contamination of infiltrating groundwater. This study proposes to develop a reactive cover system that inhibits infiltration of oxygen and also releases alkalinity to increase the pH of generated ARD and attenuate metal contaminants at the same time. The reactive cover system is constructed using steel slag, a waste product generated from steel industries. This study shows that this type of cover system has the potential to reduce some of the adverse effects of sulfide mine waste disposal on land. Geochemical and geotechnical characterization tests were carried out. Different proportions of sulfide mine waste and steel slag were studied in leachate extraction tests. The best proportion was 33% of steel slag in dry weight. Other tests were conducted as follows: soil consolidation, saturated permeability and soil water characteristic curve. The cover system was numerically modeled through unsaturated flux analysis using Vadose/w. The solution proposed is an oxygen transport barrier that allows rain water percolation to treat the ARD in the waste rock pile. The results showed that the waste pile slope is an important factor and the cover system must have 5 m thickness to achieve an acceptable effectiveness.