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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Filtros

2012 - 201992020 - 20222

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Autor: search.filters.author.Bezerra, Augusto Cesar da SilvaTem arquivos: Sim

Resultados da Pesquisa

Agora exibindo 1 - 10 de 11
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    Alkali-activated materials produced using high-calcium, high-carbon biomass ash.
    (2022) Silva, Thiago Henrique; Lara, Luis Felipe dos Santos; Silva, Guilherme Jorge Brigolini; Provis, John Lloyd; Bezerra, Augusto Cesar da Silva
    Eucalyptus ash (EA) was used in this study as a high calcium ash (HCA) precursor for alkali-activated binders. The EA used also has high carbon unburned (High loss on ignition). This type of ash is one of the waste products from biomass-fuelled thermoelectric plants, and annually thousands of tons are discarded as a by-product of the energy generation process in Brasil, but it is rich in unburnt carbon which means that it is challenging to use in cementitious systems. Eucalyptus is a biomass that removes CO2 from the atmosphere by photosynthesis and part of this carbon content remains in the ashes, generating CO2 capture when EA is incorporated in the production of alkali-activated binders. The objective of the present study was to evaluate the properties of the material obtained by the alkali-activation of the high-calcium high-carbon biomass ash to generate a cementitious binder, with different pastes proportions of EA and silica fume (SF), activated by sodium hydroxide. With the different pastes, mortars were produced using standardized sand. The results obtained from the pastes and mortars were satisfactory in several aspects. The mechanical results of the alkali-activated mortars were comparable those of Portland cement mortars. Mortars degraded methylene blue more efficiently in illuminated conditions, even after high adsorption for 24 h in the dark. The content of leached ions in the remaining solutions met potability standards.
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    Influence of cooling methods on the residual mechanical behavior of fire-exposed concrete : an experimental study.
    (2019) Carvalho, Espedito Felipe Teixeira de; Silva Neto, João Trajano da; Soares Junior, Paulo Roberto Ribeiro; Maciel, Priscila de Souza; Fransozo, Helder Luis; Bezerra, Augusto Cesar da Silva; Gouveia, Antônio Maria Claret de
    This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 ◦C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.
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    Influence of cooling methods on the residual mechanical behavior of fire-exposed concrete : an experimental study.
    (2019) Carvalho, Espedito Felipe Teixeira de; Silva Neto, João Trajano da; Soares Junior, Paulo Roberto Ribeiro; Maciel, Priscila de Souza; Fransozo, Hélder Luís; Bezerra, Augusto Cesar da Silva; Gouveia, Antônio Maria Claret de
    This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 ◦C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.
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    Iron ore tailings as a supplementary cementitious material in the production of pigmented cements.
    (2020) Magalhães, Luciano Fernandes de; França, Sâmara; Oliveira, Michelly dos Santos; Peixoto, Ricardo André Fiorotti; Bessa, Sofia Araújo Lima; Bezerra, Augusto Cesar da Silva
    In this paper, the characterisation of iron ore tailings (IOT) was carried out to examine its use as a supplementary cementitious material (SCM) to produce coloured composite cements. The IOT was heat treated, and ten different mixtures were prepared, substituting Portland cement for 10, 20 and 30 wt%. The IOT presented the sum of oxides of silicon, aluminium and iron higher than the minimum prescribed in Brazilian and international standards to be considered a pozzolanic material. The grain size of the IOT was smaller than the grain size of the Portland reference cement and met the standards used. The electrical conductivity indicated that all IOTs are pozzolans, and the index of pozzolanic activity indicated that the heat treatment at 750 C transformed the IOT into pozzolan. The heat treatment changed the colour of the IOT, and that influenced the colour of the composite cement with IOT and in turn, the colour of the produced mortars. In the IOT without thermal treatment, the presence of the kaolinite mineral was identified, and the thermal treatment led to the non-identification of this mineral, probably transforming it into an amorphous phase. The thermogravimetric analysis confirmed the transformation of kaolinite into metakaolinite. The compressive strength presented by IOT composite cement was adequate for several commercial cements provided for in Brazilian and in international standards. Cement with IOT showed lower values de loss of mass and microstructure with less damage under acid attack, and this behaviour was optimized with increases in the percentage and temperature of IOT heat treatment. Finally, the synergy between milling and heat treatment optimized the use of IOT as a pozzolan capable of changing the colour of the final cementitious product, as well as its use as an SCM.
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    Influence of cooling methods on the residual mechanical behavior of fire-exposed concrete : an experimental study.
    (2019) Carvalho, Espedito Felipe Teixeira de; Silva Neto, João Trajano da; Soares Junior, Paulo Roberto Ribeiro; Maciel, Priscila de Souza; Fransozo, Hélder Luís; Bezerra, Augusto Cesar da Silva; Gouveia, Alberto Frederico Vieira de Sousa
    This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 °C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.
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    A relational concept of fire : an innovative strategy for fire safety design.
    (2018) Gouveia, Antônio Maria Claret de; Bezerra, Augusto Cesar da Silva; Silva Neto, João Trajano da; Castanheira, Luciana Gomes; Villas Boas, Paola de Macedo Gomes Dias; Guimarães, Elaine Mártiles Ferreira
    The authors believe that there is a misguided concept regarding high risk fire in many countries. The classic concept of fire is that it is uncontrolled combustion. A new relational concept of fire is proposed herein, where fire is defined as the result of an interactive process between the fire, the building and the occupants. In addition, two design principles are proposed: the initial ignition is fully probabilistic, and the three elements of a fire may be fully designed. The authors discuss the role of design and the genetics of building safety. Conclusions point out that there has been a bad concept of fire during decades of prescriptive design practice. Authors emphasize that this relational concept of fire is a basis for an innovative design for fire safety.
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    Substituição parcial do cimento Portland pela cinza de bagaço de cana-de-açúcar em habitações de interesse social.
    (2017) Rezende, Mariana Felicetti; Machado, Fernando Carlos Scheffer; Gouveia, Antônio Maria Claret de; Bezerra, Augusto Cesar da Silva; Grillo, Rodolfo Henrique Freitas; Ortigara, Yuri Vilas Boas
    Este trabalho apresenta uma simulação das possíveis reduções de emissões de gases de efeito estufa geradas pela substituição parcial de cimento Portland por cinza de bagaço de cana-de-açúcar (CBCA) em habitações de interesse social. Para isso, foi analisado o uso da CBCA nas construções do Programa “Minha Casa Minha Vida” em Minas Gerais e foram mensuradas as reduções pelo Método QE-CO2. As emissões de CO2 de dois cenários hipotéticos foram avaliadas com base na metodologia QE-CO2, nível básico. Os resultados demonstram que a substituição do cimento Portland pela CBCA pode gerar reduções de custos e, sobretudo, dos patamares de emissões de CO2, em ambos os cenários, evidenciando, dessa forma, a possibilidade de utilização da cinza de bagaço da cana-de-açúcar em habitações de interesse social.
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    Resíduo ferroso da indústria mineradora de fosfatados como agregado miúdo em compósitos cimentícios.
    (2013) Silva, Áureo de Alencar; Resende, Domingos Sávio de; Silva Neto, João Trajano da; Bezerra, Augusto Cesar da Silva; Gouveia, Antônio Maria Claret de
    Neste estudo foi investigado o comportamento mecânico de compósitos cimenticios confeccionado com a substituição do agregado miúdo quartzoso natural de rio por um resíduo ferroso com predominância de magnetita (Fe3O4) oriundo da extração de rochas fosfáticas (minério de apatita). O minério de apatita é usado na produção de fosfato para a fabricação de fertilizantes na Mesorregião do Alto Paranaíba e Triangulo Mineiro. O resíduo foi caracterizado fisicamente e para avaliar a utilização como agregado miúdo foram confeccionadas argamassas com substituições de 0, 25, 50, 75 e 100%, e concretos com substituições de 0, 25, 50, 100%. Os compósitos tiveram suas propriedades físicas e mecânicas avaliadas. De forma geral, as propriedades dos compósitos foram melhoradas com o aumento da substituição, principalmente no requisito resistência à compressão.
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    Eucalyptus chip ashes in cementitious composites.
    (2014) Resende, Domingos Sávio de; Radispiel Filho, Herbet; Keles, José Genário; Bezerra, Augusto Cesar da Silva; Aguilar, Maria Teresa Paulino de; Gouveia, Antônio Maria Claret de
    The Alto Paranaiba and Triângulo Mineiro mesoregion in the state of Minas Gerais and the State of São Paulo have a number of industries with eucalyptus chip fired boilers that produce great amounts of ash. Since thermoelectric ashes generally have good pozzolanic activity, this paper studied the mechanical behavior of cementitious composites made with raw eucalyptus chip ash as a partial replacement for Portland cement and processed under two different conditions. The mechanical behavior of the composites was measured from tests on specimens for their compressive strength, tensile strength to diametral stress and to bending. Results show ashes could be used as mineral additives.
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    Sterile clay pozzolans from phosphate mining.
    (2015) Matos Neto, José Afonso de; Resende, Domingos Sávio de; Silva Neto, João Trajano da; Gouveia, Antônio Maria Claret de; Aguilar, Maria Teresa Paulino de; Bezerra, Augusto Cesar da Silva
    The work presents the characterization of clays from sterile mining of the concentrated phosphatic materials of Araxá in Minas Gerais as pozzolanic materials. Three clays of distinct tones, namely, yellow (YC), red (RC), and intermediate (IC) clays, were used at different levels of excavation depth. The clays were calcined at three temperatures (680, 760, and 840 °C) in a muffle-type electric oven. The pozzolanic activity levels of the calcined clays was measured through the conductivity change in saturated Ca(OH)2 solutions and also from the result of the compressive failure load achieved by mortars with 35% of the Portland cement replaced with the calcined material. The results indicated that the calcined clays showed a high level of pozzolanic activity and can be used as a partial substitute for Portland cement, thus suggesting the possibility of recovering this sterile material.