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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29 resultados
Resultados da Pesquisa
Item Quartzite tailings in civil construction materials : a systematic review.(2023) Martins, Letícia Matias; Peixoto, Ricardo André Fiorotti; Mendes, Júlia CastroThe inadequate management of waste from the mining industry can lead to several environmental problems. For instance, the extraction of quartzite, an ornamental stone, generates quartzite waste (or residues or tailings) (QTZ), which is commonly deposited in the environment, causing landscape degradation, contamination by dust, and silting of rivers. To mitigate this scenario and stimulate the circular economy, this literature review focuses on the use of quartzite tailings in construction materials. A systematic search was carried out in the Scopus, Web of Science, and Google Scholar databases, including articles in English and Portuguese published between 2007 and 2022. The results showed that the use of QTZ as aggregate in cement-based composites is viable, as this waste has physical, chemical, mineralogical, and microstructural characteristics similar to conventional natural aggregate. Quartzite waste has been successfully adopted in precast concrete, cladding, and laying mortars, soil–cement bricks, and interlocking pavements. Many works brought the physical and mechanical characterization of the proposed construction materials, with gaps being observed mainly in terms of durability and performance. In conclusion, the use of QTZ in construction materials is a promising alternative, especially in cement-based composites. An important advantage is that this material requires little or no prior processing. However, the reuse of quartzite tailings is still limited, showing that more academic studies, private initiatives, and public policies are required.Item Educação empreendedora para mulheres : estudo de caso do curso online “Empreenda como uma Mulher”.(2023) Fiuza, Nayara das Mercês Lúcio; Umbelino, Dulcineia Gomes; Marquetti, Isabela Toffolo; Cunha, Letícia Teixeira Matos; Barbosa, Lucas Silva; Hermenegildo, Nicolas Gomides; Silveira, Stella Cristine Ferraz; Amaral, Tanise Florentino Costa; Silva, André Luis; Mendes, Júlia CastroO crescimento do empreendedorismo feminino favorece a economia do país, aumenta o número de mulheres em cargos de liderança e incentiva a sua realização pessoal. Entretanto, muitas mulheres empreendem por necessidade, sem instrução formal, enquanto lidam com a dupla jornada de trabalho. Assim, o curso “Empreenda como uma Mulher”, foi lançado visando capacitar empreendedoras em todo o Brasil. Como metodologia, as cursistas foram divididas em 2 grupos de WhatsApp com 20 empreendedoras cada. Nos grupos, a equipe lançou diariamente videoaulas de até 15 minutos, que abordavam aspectos fundamentais de empreendedorismo, como plano de negócios, gestão financeira, gestão de vendas, marketing, precificação, entre outros. Também foram realizadas mentorias e trocas de experiências. O projeto recebeu 133 inscrições de empreendedoras de todo o Brasil, das quais 40 foram selecionadas por critérios socioeconômicos. Dessas, somente 13 (32%) o finalizaram, com as demais alegando que “não tinham tempo”. As cursistas que preencheram o formulário de feedback destacaram o quanto o curso foi fundamental para a melhoria da gestão de seus negócios. Assim, o presente projeto proporcionou aos alunos-membros uma formação holística e socialmente contextualizada, além de contribuir com o aperfeiçoamento de empreendimentos gerenciados por mulheres. Foi possível observar o quão proeminente é a necessidade de capacitação entre mulheres empreendedoras e o quanto o cansaço resultante de suas longas jornadas de trabalho interfere no acesso a essas capacitações.Item Residues in cement-based composites : occurrence mapping in Brazil.(2023) Lopes, Carolina de Melo Nunes; Mendes, Vítor Freitas; Garcia, Danielle Rios; Mendes, Júlia CastroScientific articles related to the incorporation of residues in civil construction materials are growing worldwide, although their practical application is still incipient. In this scenario, this paper produced an occurrence map of the most studied residues in Brazil when incorporated in cement-based composites. Initially, the most relevant residues were identified through a bibliometric analysis on the Scopus database, using the software VOSviewer. This analysis included scientific papers from Brazilian institutions published from 2001 to 2022 regarding the development of cement-based composites using residues, wastes, or tailings. Subsequently, to map the occurrence of these materials in each Brazilian state, we used public and private data on the country’s industrial production and waste disposal. From 1272 articles analyzed, we identified 49 residues with at least 2 citations. Among the most cited residues in Brazilian publications are construction and demolition waste, rice husk, glass waste, sugarcane bagasse, and tire rubber residue. The authors noticed the heterogeneity of the occurrence of the residues across the large Brazilian territory and found gaps on research trends involving them. These and other observations facilitate the decision-making process regarding logistics and investments related to the reuse and recycling of these materials.Item A review on the evolution of Portland cement and chemical admixtures in Brazil.(2021) Natalli, Juliana Fadini; Thomaz, Eduardo Christo Silveira; Mendes, Júlia Castro; Peixoto, Ricardo André FiorottiOver the years, Portland cement concretes have undergone increasing demands for constructability, cost, quality, and environmental impact. These demands were met, mainly, through changes in the cement composition and the introduction of chemical admixtures. In this sense, through a literature review, the authors sought to create a collection of information on the evolution of these materials and their standards from 1937 to 2020 in Brazil . This work is part of a research project that aims to elaborate a dating protocol for Brazilian concretes. From the review conducted, the authors observed that the absence of systematic records in the Brazilian civil construction sector hinders the attempt to create a chronology of the development of concrete in the country. In addition, we concluded that the knowledge of the evolution of Portland cement and chemical admixtures is relevant information that can assist in concrete dating processes. The reliable comparison data, posteriorly combined with microstructural characterisation techniques, may lay the basis for an effective dating methodology.Item Mapping and recycling proposal for the construction and demolition waste generated in the Brazilian Amazon.(2022) Souza, Fernando da Silva; Mendes, Júlia Castro; Morais, Lya Júlia Barbosa; Silva, Jônatas Santos; Peixoto, Ricardo André FiorottiDue to the scarcity of aggregate deposits in the region of the Brazilian Amazon, cities such as Rio Branco (state of Acre) rely on complex logistical operations to guarantee their supply. These operations substantially raise the cost of natural aggregates and, together with their environmental impact, justify the recycling of construction and demolition waste (C&DW) in the region. Therefore, the present study investigates the quantity and composition of the C&DW generated in the urban area of Rio Branco and proposes a recycling plant for the city. Periodic and systematic visits to construction sites were carried out to formulate representative indexes for the generation and composition of the C&DW. These indexes supported an economic feasibility analysis for the recycling plant, as well as a discussion of the environmental impact of this plant on the inert landfill currently used in Rio Branco. As a result, a C&DW generation index per constructed area of 0.22 t/m2 was found for new construction works and 0.41 t/m2 for renovation works, with unit weight of 0.98 t/m3 and 0.92 t/m3 , respec- tively. According to its composition, 100% of C&DW was deemed reusable and/or recyclable. In the last 20 years (1999 - 2018), 3.2 million tonnes of C&DW were generated in the city, averaging 517 kg/(inhab•year). Economic indicators show feasibility for the installation of a recycling plant with a processing capacity of 90 t/h, improving the environmental, economic, and social aspects of the construction sector in the area.Item Comparison of machine learning techniques to predict the compressive strength of concrete and considerations on model generalization.(2022) Paixão, Rafael Christian Fonseca da; Penido, Rúben El-Katib; Cury, Alexandre Abrahão; Mendes, Júlia CastroThe compressive strength of concrete is an essential property to ensure the safety of a concrete structure. However, estimating this value is usually a laborious and uncertain process since the mix design is based on empirical methods and its confirmation in the laboratory demands time and resources. In this context, this work aims to evaluate Machine Learning (ML) models to predict the compressive strength of concrete from its constituents. For this purpose, a dataset from the literature was used as input to four ML models: Extreme Gradient Boosting (XGBoost), Support Vector Regression (SVR), Artificial Neural Networks (ANN) and Gaussian Process Regression (GPR). The accuracy of the models was evaluated through 10-fold cross-validation, and quantified by R2 , Mean Absolute Error (MAE), and Root-Mean-Square Error (RMSE) metrics. Subsequently, a new dataset was put together with mixtures from the literature and used to validate the previous models. In the model creation step, all algorithms obtained similar and positive results, with MAE between 1.96-2.26 MPa and R2 varying from 0.79 to 0.83. However, in the validation step, the accuracy of the models dropped sharply, with MAE growing to 3.04-4.04 MPa and R2 decreasing to 0.37-0.59. ANN and GPR showed the best results, while SVR had the worst predictions. This work showed that ML tools are promising techniques to predict the compressive strength of concrete. However, care must be taken with the input data to guarantee that models are not overfitted to a given region, set of materials, or type of concrete.Item Sensitivity analysis of coating mortars according to their specific heat, specific gravity, thermal conductivity, and thickness in contribution to the global thermal performance of buildings.(2022) Mendes, Vítor Freitas; Fardin, Welington; Barreto, Rodrigo Rony; Caetano, Lucas Fonseca; Mendes, Júlia CastroAlthough coating (plastering) mortars are an important element of masonry systems, their impact on the building's overall thermal performance is still unclear. In this sense, the present work performed a sensitivity analysis on the influence of the thermophysical properties of coating mortars on the internal temperature and thermal load of two buildings. The authors aimed to fill the gap between the mortars' properties, their manufacturing specifications, and the actual effect of their application on the building's total energy perfor- mance. The methodology included energy simulations on EnergyPlus considering all Brazilian bioclimatic zones. We varied the mortars' specific heat, specific gravity, thermal conductivity, and thickness from 25% to 200% from baseline values. We also analysed the results through Decision Tree technique (XGBoost). The thermal conductivity (proportional to the specific gravity) was the less significant property, whereas the thickness and the specific heat were the most influential ones. The differences between the best and worst mortars reached 356 ◦C and 224 kWh/year for the house, and 736 ◦C and 45 kWh/year for the commercial building. The results showed that the optimal combination of the tested properties is a function of the bioclimatic characteristics of the region, the building layout, and the existence and schedule of the HVAC system. The simulations also evidenced that the strategy of solely decreasing the thermal conductivity without considerations for the thermal capacity, which is often used in the manufacturing of conventional insulating mortars, is ineffective. Therefore, assertively adjusting the mortars' thermophysical properties can be a promising complementary strategy for improving the thermal performance of buildings.Item Provocações empreendedoras 4 : desafio nas empresas juniores.(Editora Paco Editorial, 2021) Silva, André Luís; Mendes, Júlia Castro; Milanez, Felipe ComarelaItem Provocações empreendedoras 2 : desafios cotidianos.(Cia do eBook, 2020) Silva, André Luís; Mendes, Júlia CastroItem Reverse logistics system applied to the reuse of iron ore tailings.(2020) Araújo, Samantha Rodrigues de; Rodrigues, Lásara Fabrícia; Mendes, Júlia Castro; Peixoto, Ricardo André FiorottiIron ore tailings (IOT) from tailings dams cause significant environmental, economic, and social impacts, which has motivated the search for reuse alternatives. In this scenario, the present work uses reverse logistics to size the resources required to reuse the IOT for road infrastructure. A reverse logistics system was modelled to transport the IOT from the tailings dam to a processing plant and then to the construction site of a road. Resource capacity constraints and operational limitations were considered, and the economic feasibility of the system was analysed. Two scenarios for tailings transportation on the dam/plant route were simulated aiming at a cost less than R$ 25 (US$ 6.13) per tonne: (1) trucks; and (2) conveyor belts. The economic feasibility of both scenarios was proven, with scenario 1 presenting the most promising results – a transport distance of 290km within the established price limit. This methodology can thus be applied to encourage the large-scale reuse of IOT.
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